truffle: src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.cpp comparison

comparison src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.cpp @ 0:a61af66fc99e jdk7-b24

Initial load

author	duke
date	Sat, 01 Dec 2007 00:00:00 +0000
parents
children	2faf283ce688

comparison

equal deleted inserted replaced

--1:000000000000
+:a61af66fc99e
+/*
+* Copyright 2001-2007 Sun Microsystems, Inc.  All Rights Reserved.
+* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+*
+* This code is free software; you can redistribute it and/or modify it
+* under the terms of the GNU General Public License version 2 only, as
+* published by the Free Software Foundation.
+*
+* This code is distributed in the hope that it will be useful, but WITHOUT
+* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+* FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+* version 2 for more details (a copy is included in the LICENSE file that
+* accompanied this code).
+*
+* You should have received a copy of the GNU General Public License version
+* 2 along with this work; if not, write to the Free Software Foundation,
+* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+*
+* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+* CA 95054 USA or visit www.sun.com if you need additional information or
+* have any questions.
+*
+*/
+# include "incls/_precompiled.incl"
+# include "incls/_concurrentMarkSweepGeneration.cpp.incl"
+// statics
+CMSCollector* ConcurrentMarkSweepGeneration::_collector = NULL;
+bool          CMSCollector::_full_gc_requested          = false;
+//////////////////////////////////////////////////////////////////
+// In support of CMS/VM thread synchronization
+//////////////////////////////////////////////////////////////////
+// We split use of the CGC_lock into 2 "levels".
+// The low-level locking is of the usual CGC_lock monitor. We introduce
+// a higher level "token" (hereafter "CMS token") built on top of the
+// low level monitor (hereafter "CGC lock").
+// The token-passing protocol gives priority to the VM thread. The
+// CMS-lock doesn't provide any fairness guarantees, but clients
+// should ensure that it is only held for very short, bounded
+// durations.
+//
+// When either of the CMS thread or the VM thread is involved in
+// collection operations during which it does not want the other
+// thread to interfere, it obtains the CMS token.
+//
+// If either thread tries to get the token while the other has
+// it, that thread waits. However, if the VM thread and CMS thread
+// both want the token, then the VM thread gets priority while the
+// CMS thread waits. This ensures, for instance, that the "concurrent"
+// phases of the CMS thread's work do not block out the VM thread
+// for long periods of time as the CMS thread continues to hog
+// the token. (See bug 4616232).
+//
+// The baton-passing functions are, however, controlled by the
+// flags _foregroundGCShouldWait and _foregroundGCIsActive,
+// and here the low-level CMS lock, not the high level token,
+// ensures mutual exclusion.
+//
+// Two important conditions that we have to satisfy:
+// 1. if a thread does a low-level wait on the CMS lock, then it
+//    relinquishes the CMS token if it were holding that token
+//    when it acquired the low-level CMS lock.
+// 2. any low-level notifications on the low-level lock
+//    should only be sent when a thread has relinquished the token.
+//
+// In the absence of either property, we'd have potential deadlock.
+//
+// We protect each of the CMS (concurrent and sequential) phases
+// with the CMS _token_, not the CMS _lock_.
+//
+// The only code protected by CMS lock is the token acquisition code
+// itself, see ConcurrentMarkSweepThread::[de]synchronize(), and the
+// baton-passing code.
+//
+// Unfortunately, i couldn't come up with a good abstraction to factor and
+// hide the naked CGC_lock manipulation in the baton-passing code
+// further below. That's something we should try to do. Also, the proof
+// of correctness of this 2-level locking scheme is far from obvious,
+// and potentially quite slippery. We have an uneasy supsicion, for instance,
+// that there may be a theoretical possibility of delay/starvation in the
+// low-level lock/wait/notify scheme used for the baton-passing because of
+// potential intereference with the priority scheme embodied in the
+// CMS-token-passing protocol. See related comments at a CGC_lock->wait()
+// invocation further below and marked with "XXX 20011219YSR".
+// Indeed, as we note elsewhere, this may become yet more slippery
+// in the presence of multiple CMS and/or multiple VM threads. XXX
+class CMSTokenSync: public StackObj {
+private:
+bool _is_cms_thread;
+public:
+CMSTokenSync(bool is_cms_thread):
+_is_cms_thread(is_cms_thread) {
+assert(is_cms_thread == Thread::current()->is_ConcurrentGC_thread(),
+"Incorrect argument to constructor");
+ConcurrentMarkSweepThread::synchronize(_is_cms_thread);
+}
+~CMSTokenSync() {
+assert(_is_cms_thread ?
+ConcurrentMarkSweepThread::cms_thread_has_cms_token() :
+ConcurrentMarkSweepThread::vm_thread_has_cms_token(),
+"Incorrect state");
+ConcurrentMarkSweepThread::desynchronize(_is_cms_thread);
+}
+};
+// Convenience class that does a CMSTokenSync, and then acquires
+// upto three locks.
+class CMSTokenSyncWithLocks: public CMSTokenSync {
+private:
+// Note: locks are acquired in textual declaration order
+// and released in the opposite order
+MutexLockerEx _locker1, _locker2, _locker3;
+public:
+CMSTokenSyncWithLocks(bool is_cms_thread, Mutex* mutex1,
+Mutex* mutex2 = NULL, Mutex* mutex3 = NULL):
+CMSTokenSync(is_cms_thread),
+_locker1(mutex1, Mutex::_no_safepoint_check_flag),
+_locker2(mutex2, Mutex::_no_safepoint_check_flag),
+_locker3(mutex3, Mutex::_no_safepoint_check_flag)
+{ }
+};
+// Wrapper class to temporarily disable icms during a foreground cms collection.
+class ICMSDisabler: public StackObj {
+public:
+// The ctor disables icms and wakes up the thread so it notices the change;
+// the dtor re-enables icms.  Note that the CMSCollector methods will check
+// CMSIncrementalMode.
+ICMSDisabler()  { CMSCollector::disable_icms(); CMSCollector::start_icms(); }
+~ICMSDisabler() { CMSCollector::enable_icms(); }
+};
+//////////////////////////////////////////////////////////////////
+//  Concurrent Mark-Sweep Generation /////////////////////////////
+//////////////////////////////////////////////////////////////////
+NOT_PRODUCT(CompactibleFreeListSpace* debug_cms_space;)
+// This struct contains per-thread things necessary to support parallel
+// young-gen collection.
+class CMSParGCThreadState: public CHeapObj {
+public:
+CFLS_LAB lab;
+PromotionInfo promo;
+// Constructor.
+CMSParGCThreadState(CompactibleFreeListSpace* cfls) : lab(cfls) {
+promo.setSpace(cfls);
+}
+};
+ConcurrentMarkSweepGeneration::ConcurrentMarkSweepGeneration(
+ReservedSpace rs, size_t initial_byte_size, int level,
+CardTableRS* ct, bool use_adaptive_freelists,
+FreeBlockDictionary::DictionaryChoice dictionaryChoice) :
+CardGeneration(rs, initial_byte_size, level, ct),
+_dilatation_factor(((double)MinChunkSize)/((double)(oopDesc::header_size()))),
+_debug_collection_type(Concurrent_collection_type)
+{
+HeapWord* bottom = (HeapWord*) _virtual_space.low();
+HeapWord* end    = (HeapWord*) _virtual_space.high();
+_direct_allocated_words = 0;
+NOT_PRODUCT(
+_numObjectsPromoted = 0;
+_numWordsPromoted = 0;
+_numObjectsAllocated = 0;
+_numWordsAllocated = 0;
+)
+_cmsSpace = new CompactibleFreeListSpace(_bts, MemRegion(bottom, end),
+use_adaptive_freelists,
+dictionaryChoice);
+NOT_PRODUCT(debug_cms_space = _cmsSpace;)
+if (_cmsSpace == NULL) {
+vm_exit_during_initialization(
+"CompactibleFreeListSpace allocation failure");
+}
+_cmsSpace->_gen = this;
+_gc_stats = new CMSGCStats();
+// Verify the assumption that FreeChunk::_prev and OopDesc::_klass
+// offsets match. The ability to tell free chunks from objects
+// depends on this property.
+debug_only(
+FreeChunk* junk = NULL;
+assert(junk->prev_addr() == (void*)(oop(junk)->klass_addr()),
+"Offset of FreeChunk::_prev within FreeChunk must match"
+"  that of OopDesc::_klass within OopDesc");
+)
+if (ParallelGCThreads > 0) {
+typedef CMSParGCThreadState* CMSParGCThreadStatePtr;
+_par_gc_thread_states =
+NEW_C_HEAP_ARRAY(CMSParGCThreadStatePtr, ParallelGCThreads);
+if (_par_gc_thread_states == NULL) {
+vm_exit_during_initialization("Could not allocate par gc structs");
+}
+for (uint i = 0; i < ParallelGCThreads; i++) {
+_par_gc_thread_states[i] = new CMSParGCThreadState(cmsSpace());
+if (_par_gc_thread_states[i] == NULL) {
+vm_exit_during_initialization("Could not allocate par gc structs");
+}
+}
+} else {
+_par_gc_thread_states = NULL;
+}
+_incremental_collection_failed = false;
+// The "dilatation_factor" is the expansion that can occur on
+// account of the fact that the minimum object size in the CMS
+// generation may be larger than that in, say, a contiguous young
+//  generation.
+// Ideally, in the calculation below, we'd compute the dilatation
+// factor as: MinChunkSize/(promoting_gen's min object size)
+// Since we do not have such a general query interface for the
+// promoting generation, we'll instead just use the mimimum
+// object size (which today is a header's worth of space);
+// note that all arithmetic is in units of HeapWords.
+assert(MinChunkSize >= oopDesc::header_size(), "just checking");
+assert(_dilatation_factor >= 1.0, "from previous assert");
+}
+void ConcurrentMarkSweepGeneration::ref_processor_init() {
+assert(collector() != NULL, "no collector");
+collector()->ref_processor_init();
+}
+void CMSCollector::ref_processor_init() {
+if (_ref_processor == NULL) {
+// Allocate and initialize a reference processor
+_ref_processor = ReferenceProcessor::create_ref_processor(
+_span,                               // span
+_cmsGen->refs_discovery_is_atomic(), // atomic_discovery
+_cmsGen->refs_discovery_is_mt(),     // mt_discovery
+&_is_alive_closure,
+ParallelGCThreads,
+ParallelRefProcEnabled);
+// Initialize the _ref_processor field of CMSGen
+_cmsGen->set_ref_processor(_ref_processor);
+// Allocate a dummy ref processor for perm gen.
+ReferenceProcessor* rp2 = new ReferenceProcessor();
+if (rp2 == NULL) {
+vm_exit_during_initialization("Could not allocate ReferenceProcessor object");
+}
+_permGen->set_ref_processor(rp2);
+}
+}
+CMSAdaptiveSizePolicy* CMSCollector::size_policy() {
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+assert(gch->kind() == CollectedHeap::GenCollectedHeap,
+"Wrong type of heap");
+CMSAdaptiveSizePolicy* sp = (CMSAdaptiveSizePolicy*)
+gch->gen_policy()->size_policy();
+assert(sp->is_gc_cms_adaptive_size_policy(),
+"Wrong type of size policy");
+return sp;
+}
+CMSGCAdaptivePolicyCounters* CMSCollector::gc_adaptive_policy_counters() {
+CMSGCAdaptivePolicyCounters* results =
+(CMSGCAdaptivePolicyCounters*) collector_policy()->counters();
+assert(
+results->kind() == GCPolicyCounters::CMSGCAdaptivePolicyCountersKind,
+"Wrong gc policy counter kind");
+return results;
+}
+void ConcurrentMarkSweepGeneration::initialize_performance_counters() {
+const char* gen_name = "old";
+// Generation Counters - generation 1, 1 subspace
+_gen_counters = new GenerationCounters(gen_name, 1, 1, &_virtual_space);
+_space_counters = new GSpaceCounters(gen_name, 0,
+_virtual_space.reserved_size(),
+this, _gen_counters);
+}
+CMSStats::CMSStats(ConcurrentMarkSweepGeneration* cms_gen, unsigned int alpha):
+_cms_gen(cms_gen)
+{
+assert(alpha <= 100, "bad value");
+_saved_alpha = alpha;
+// Initialize the alphas to the bootstrap value of 100.
+_gc0_alpha = _cms_alpha = 100;
+_cms_begin_time.update();
+_cms_end_time.update();
+_gc0_duration = 0.0;
+_gc0_period = 0.0;
+_gc0_promoted = 0;
+_cms_duration = 0.0;
+_cms_period = 0.0;
+_cms_allocated = 0;
+_cms_used_at_gc0_begin = 0;
+_cms_used_at_gc0_end = 0;
+_allow_duty_cycle_reduction = false;
+_valid_bits = 0;
+_icms_duty_cycle = CMSIncrementalDutyCycle;
+}
+// If promotion failure handling is on use
+// the padded average size of the promotion for each
+// young generation collection.
+double CMSStats::time_until_cms_gen_full() const {
+size_t cms_free = _cms_gen->cmsSpace()->free();
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+size_t expected_promotion = gch->get_gen(0)->capacity();
+if (HandlePromotionFailure) {
+expected_promotion = MIN2(
+(size_t) _cms_gen->gc_stats()->avg_promoted()->padded_average(),
+expected_promotion);
+}
+if (cms_free > expected_promotion) {
+// Start a cms collection if there isn't enough space to promote
+// for the next minor collection.  Use the padded average as
+// a safety factor.
+cms_free -= expected_promotion;
+// Adjust by the safety factor.
+double cms_free_dbl = (double)cms_free;
+cms_free_dbl = cms_free_dbl * (100.0 - CMSIncrementalSafetyFactor) / 100.0;
+if (PrintGCDetails && Verbose) {
+gclog_or_tty->print_cr("CMSStats::time_until_cms_gen_full: cms_free "
+SIZE_FORMAT " expected_promotion " SIZE_FORMAT,
+cms_free, expected_promotion);
+gclog_or_tty->print_cr("  cms_free_dbl %f cms_consumption_rate %f",
+cms_free_dbl, cms_consumption_rate() + 1.0);
+}
+// Add 1 in case the consumption rate goes to zero.
+return cms_free_dbl / (cms_consumption_rate() + 1.0);
+}
+return 0.0;
+}
+// Compare the duration of the cms collection to the
+// time remaining before the cms generation is empty.
+// Note that the time from the start of the cms collection
+// to the start of the cms sweep (less than the total
+// duration of the cms collection) can be used.  This
+// has been tried and some applications experienced
+// promotion failures early in execution.  This was
+// possibly because the averages were not accurate
+// enough at the beginning.
+double CMSStats::time_until_cms_start() const {
+// We add "gc0_period" to the "work" calculation
+// below because this query is done (mostly) at the
+// end of a scavenge, so we need to conservatively
+// account for that much possible delay
+// in the query so as to avoid concurrent mode failures
+// due to starting the collection just a wee bit too
+// late.
+double work = cms_duration() + gc0_period();
+double deadline = time_until_cms_gen_full();
+if (work > deadline) {
+if (Verbose && PrintGCDetails) {
+gclog_or_tty->print(
+" CMSCollector: collect because of anticipated promotion "
+"before full %3.7f + %3.7f > %3.7f ", cms_duration(),
+gc0_period(), time_until_cms_gen_full());
+}
+return 0.0;
+}
+return work - deadline;
+}
+// Return a duty cycle based on old_duty_cycle and new_duty_cycle, limiting the
+// amount of change to prevent wild oscillation.
+unsigned int CMSStats::icms_damped_duty_cycle(unsigned int old_duty_cycle,
+unsigned int new_duty_cycle) {
+assert(old_duty_cycle <= 100, "bad input value");
+assert(new_duty_cycle <= 100, "bad input value");
+// Note:  use subtraction with caution since it may underflow (values are
+// unsigned).  Addition is safe since we're in the range 0-100.
+unsigned int damped_duty_cycle = new_duty_cycle;
+if (new_duty_cycle < old_duty_cycle) {
+const unsigned int largest_delta = MAX2(old_duty_cycle / 4, 5U);
+if (new_duty_cycle + largest_delta < old_duty_cycle) {
+damped_duty_cycle = old_duty_cycle - largest_delta;
+}
+} else if (new_duty_cycle > old_duty_cycle) {
+const unsigned int largest_delta = MAX2(old_duty_cycle / 4, 15U);
+if (new_duty_cycle > old_duty_cycle + largest_delta) {
+damped_duty_cycle = MIN2(old_duty_cycle + largest_delta, 100U);
+}
+}
+assert(damped_duty_cycle <= 100, "invalid duty cycle computed");
+if (CMSTraceIncrementalPacing) {
+gclog_or_tty->print(" [icms_damped_duty_cycle(%d,%d) = %d] ",
+old_duty_cycle, new_duty_cycle, damped_duty_cycle);
+}
+return damped_duty_cycle;
+}
+unsigned int CMSStats::icms_update_duty_cycle_impl() {
+assert(CMSIncrementalPacing && valid(),
+"should be handled in icms_update_duty_cycle()");
+double cms_time_so_far = cms_timer().seconds();
+double scaled_duration = cms_duration_per_mb() * _cms_used_at_gc0_end / M;
+double scaled_duration_remaining = fabsd(scaled_duration - cms_time_so_far);
+// Avoid division by 0.
+double time_until_full = MAX2(time_until_cms_gen_full(), 0.01);
+double duty_cycle_dbl = 100.0 * scaled_duration_remaining / time_until_full;
+unsigned int new_duty_cycle = MIN2((unsigned int)duty_cycle_dbl, 100U);
+if (new_duty_cycle > _icms_duty_cycle) {
+// Avoid very small duty cycles (1 or 2); 0 is allowed.
+if (new_duty_cycle > 2) {
+_icms_duty_cycle = icms_damped_duty_cycle(_icms_duty_cycle,
+new_duty_cycle);
+}
+} else if (_allow_duty_cycle_reduction) {
+// The duty cycle is reduced only once per cms cycle (see record_cms_end()).
+new_duty_cycle = icms_damped_duty_cycle(_icms_duty_cycle, new_duty_cycle);
+// Respect the minimum duty cycle.
+unsigned int min_duty_cycle = (unsigned int)CMSIncrementalDutyCycleMin;
+_icms_duty_cycle = MAX2(new_duty_cycle, min_duty_cycle);
+}
+if (PrintGCDetails || CMSTraceIncrementalPacing) {
+gclog_or_tty->print(" icms_dc=%d ", _icms_duty_cycle);
+}
+_allow_duty_cycle_reduction = false;
+return _icms_duty_cycle;
+}
+#ifndef PRODUCT
+void CMSStats::print_on(outputStream *st) const {
+st->print(" gc0_alpha=%d,cms_alpha=%d", _gc0_alpha, _cms_alpha);
+st->print(",gc0_dur=%g,gc0_per=%g,gc0_promo=" SIZE_FORMAT,
+gc0_duration(), gc0_period(), gc0_promoted());
+st->print(",cms_dur=%g,cms_dur_per_mb=%g,cms_per=%g,cms_alloc=" SIZE_FORMAT,
+cms_duration(), cms_duration_per_mb(),
+cms_period(), cms_allocated());
+st->print(",cms_since_beg=%g,cms_since_end=%g",
+cms_time_since_begin(), cms_time_since_end());
+st->print(",cms_used_beg=" SIZE_FORMAT ",cms_used_end=" SIZE_FORMAT,
+_cms_used_at_gc0_begin, _cms_used_at_gc0_end);
+if (CMSIncrementalMode) {
+st->print(",dc=%d", icms_duty_cycle());
+}
+if (valid()) {
+st->print(",promo_rate=%g,cms_alloc_rate=%g",
+promotion_rate(), cms_allocation_rate());
+st->print(",cms_consumption_rate=%g,time_until_full=%g",
+cms_consumption_rate(), time_until_cms_gen_full());
+}
+st->print(" ");
+}
+#endif // #ifndef PRODUCT
+CMSCollector::CollectorState CMSCollector::_collectorState =
+CMSCollector::Idling;
+bool CMSCollector::_foregroundGCIsActive = false;
+bool CMSCollector::_foregroundGCShouldWait = false;
+CMSCollector::CMSCollector(ConcurrentMarkSweepGeneration* cmsGen,
+ConcurrentMarkSweepGeneration* permGen,
+CardTableRS*                   ct,
+ConcurrentMarkSweepPolicy*     cp):
+_cmsGen(cmsGen),
+_permGen(permGen),
+_ct(ct),
+_ref_processor(NULL),    // will be set later
+_conc_workers(NULL),     // may be set later
+_abort_preclean(false),
+_start_sampling(false),
+_between_prologue_and_epilogue(false),
+_markBitMap(0, Mutex::leaf + 1, "CMS_markBitMap_lock"),
+_perm_gen_verify_bit_map(0, -1 /* no mutex */, "No_lock"),
+_modUnionTable((CardTableModRefBS::card_shift - LogHeapWordSize),
+-1 /* lock-free */, "No_lock" /* dummy */),
+_modUnionClosure(&_modUnionTable),
+_modUnionClosurePar(&_modUnionTable),
+_is_alive_closure(&_markBitMap),
+_restart_addr(NULL),
+_overflow_list(NULL),
+_preserved_oop_stack(NULL),
+_preserved_mark_stack(NULL),
+_stats(cmsGen),
+_eden_chunk_array(NULL),     // may be set in ctor body
+_eden_chunk_capacity(0),     // -- ditto --
+_eden_chunk_index(0),        // -- ditto --
+_survivor_plab_array(NULL),  // -- ditto --
+_survivor_chunk_array(NULL), // -- ditto --
+_survivor_chunk_capacity(0), // -- ditto --
+_survivor_chunk_index(0),    // -- ditto --
+_ser_pmc_preclean_ovflw(0),
+_ser_pmc_remark_ovflw(0),
+_par_pmc_remark_ovflw(0),
+_ser_kac_ovflw(0),
+_par_kac_ovflw(0),
+#ifndef PRODUCT
+_num_par_pushes(0),
+#endif
+_collection_count_start(0),
+_verifying(false),
+_icms_start_limit(NULL),
+_icms_stop_limit(NULL),
+_verification_mark_bm(0, Mutex::leaf + 1, "CMS_verification_mark_bm_lock"),
+_completed_initialization(false),
+_collector_policy(cp),
+_unload_classes(false),
+_unloaded_classes_last_cycle(false),
+_sweep_estimate(CMS_SweepWeight, CMS_SweepPadding)
+{
+if (ExplicitGCInvokesConcurrentAndUnloadsClasses) {
+ExplicitGCInvokesConcurrent = true;
+}
+// Now expand the span and allocate the collection support structures
+// (MUT, marking bit map etc.) to cover both generations subject to
+// collection.
+// First check that _permGen is adjacent to _cmsGen and above it.
+assert(   _cmsGen->reserved().word_size()  > 0
+&& _permGen->reserved().word_size() > 0,
+"generations should not be of zero size");
+assert(_cmsGen->reserved().intersection(_permGen->reserved()).is_empty(),
+"_cmsGen and _permGen should not overlap");
+assert(_cmsGen->reserved().end() == _permGen->reserved().start(),
+"_cmsGen->end() different from _permGen->start()");
+// For use by dirty card to oop closures.
+_cmsGen->cmsSpace()->set_collector(this);
+_permGen->cmsSpace()->set_collector(this);
+// Adjust my span to cover old (cms) gen and perm gen
+_span = _cmsGen->reserved()._union(_permGen->reserved());
+// Initialize the span of is_alive_closure
+_is_alive_closure.set_span(_span);
+// Allocate MUT and marking bit map
+{
+MutexLockerEx x(_markBitMap.lock(), Mutex::_no_safepoint_check_flag);
+if (!_markBitMap.allocate(_span)) {
+warning("Failed to allocate CMS Bit Map");
+return;
+}
+assert(_markBitMap.covers(_span), "_markBitMap inconsistency?");
+}
+{
+_modUnionTable.allocate(_span);
+assert(_modUnionTable.covers(_span), "_modUnionTable inconsistency?");
+}
+if (!_markStack.allocate(CMSMarkStackSize)) {
+warning("Failed to allocate CMS Marking Stack");
+return;
+}
+if (!_revisitStack.allocate(CMSRevisitStackSize)) {
+warning("Failed to allocate CMS Revisit Stack");
+return;
+}
+// Support for multi-threaded concurrent phases
+if (ParallelGCThreads > 0 && CMSConcurrentMTEnabled) {
+if (FLAG_IS_DEFAULT(ParallelCMSThreads)) {
+// just for now
+FLAG_SET_DEFAULT(ParallelCMSThreads, (ParallelGCThreads + 3)/4);
+}
+if (ParallelCMSThreads > 1) {
+_conc_workers = new YieldingFlexibleWorkGang("Parallel CMS Threads",
+ParallelCMSThreads, true);
+if (_conc_workers == NULL) {
+warning("GC/CMS: _conc_workers allocation failure: "
+"forcing -CMSConcurrentMTEnabled");
+CMSConcurrentMTEnabled = false;
+}
+} else {
+CMSConcurrentMTEnabled = false;
+}
+}
+if (!CMSConcurrentMTEnabled) {
+ParallelCMSThreads = 0;
+} else {
+// Turn off CMSCleanOnEnter optimization temporarily for
+// the MT case where it's not fixed yet; see 6178663.
+CMSCleanOnEnter = false;
+}
+assert((_conc_workers != NULL) == (ParallelCMSThreads > 1),
+"Inconsistency");
+// Parallel task queues; these are shared for the
+// concurrent and stop-world phases of CMS, but
+// are not shared with parallel scavenge (ParNew).
+{
+uint i;
+uint num_queues = (uint) MAX2(ParallelGCThreads, ParallelCMSThreads);
+if ((CMSParallelRemarkEnabled || CMSConcurrentMTEnabled
+|| ParallelRefProcEnabled)
+&& num_queues > 0) {
+_task_queues = new OopTaskQueueSet(num_queues);
+if (_task_queues == NULL) {
+warning("task_queues allocation failure.");
+return;
+}
+_hash_seed = NEW_C_HEAP_ARRAY(int, num_queues);
+if (_hash_seed == NULL) {
+warning("_hash_seed array allocation failure");
+return;
+}
+// XXX use a global constant instead of 64!
+typedef struct OopTaskQueuePadded {
+OopTaskQueue work_queue;
+char pad[64 - sizeof(OopTaskQueue)];  // prevent false sharing
+} OopTaskQueuePadded;
+for (i = 0; i < num_queues; i++) {
+OopTaskQueuePadded *q_padded = new OopTaskQueuePadded();
+if (q_padded == NULL) {
+warning("work_queue allocation failure.");
+return;
+}
+_task_queues->register_queue(i, &q_padded->work_queue);
+}
+for (i = 0; i < num_queues; i++) {
+_task_queues->queue(i)->initialize();
+_hash_seed[i] = 17;  // copied from ParNew
+}
+}
+}
+// "initiatingOccupancy" is the occupancy ratio at which we trigger
+// a new collection cycle.  Unless explicitly specified via
+// CMSTriggerRatio, it is calculated by:
+//   Let "f" be MinHeapFreeRatio in
+//
+//    intiatingOccupancy = 100-f +
+//                         f * (CMSTriggerRatio/100)
+// That is, if we assume the heap is at its desired maximum occupancy at the
+// end of a collection, we let CMSTriggerRatio of the (purported) free
+// space be allocated before initiating a new collection cycle.
+if (CMSInitiatingOccupancyFraction > 0) {
+_initiatingOccupancy = (double)CMSInitiatingOccupancyFraction / 100.0;
+} else {
+_initiatingOccupancy = ((100 - MinHeapFreeRatio) +
+(double)(CMSTriggerRatio *
+MinHeapFreeRatio) / 100.0)
+/ 100.0;
+}
+// Clip CMSBootstrapOccupancy between 0 and 100.
+_bootstrap_occupancy = ((double)MIN2((intx)100, MAX2((intx)0, CMSBootstrapOccupancy)))
+/(double)100;
+_full_gcs_since_conc_gc = 0;
+// Now tell CMS generations the identity of their collector
+ConcurrentMarkSweepGeneration::set_collector(this);
+// Create & start a CMS thread for this CMS collector
+_cmsThread = ConcurrentMarkSweepThread::start(this);
+assert(cmsThread() != NULL, "CMS Thread should have been created");
+assert(cmsThread()->collector() == this,
+"CMS Thread should refer to this gen");
+assert(CGC_lock != NULL, "Where's the CGC_lock?");
+// Support for parallelizing young gen rescan
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+_young_gen = gch->prev_gen(_cmsGen);
+if (gch->supports_inline_contig_alloc()) {
+_top_addr = gch->top_addr();
+_end_addr = gch->end_addr();
+assert(_young_gen != NULL, "no _young_gen");
+_eden_chunk_index = 0;
+_eden_chunk_capacity = (_young_gen->max_capacity()+CMSSamplingGrain)/CMSSamplingGrain;
+_eden_chunk_array = NEW_C_HEAP_ARRAY(HeapWord*, _eden_chunk_capacity);
+if (_eden_chunk_array == NULL) {
+_eden_chunk_capacity = 0;
+warning("GC/CMS: _eden_chunk_array allocation failure");
+}
+}
+assert(_eden_chunk_array != NULL || _eden_chunk_capacity == 0, "Error");
+// Support for parallelizing survivor space rescan
+if (CMSParallelRemarkEnabled && CMSParallelSurvivorRemarkEnabled) {
+size_t max_plab_samples = MaxNewSize/((SurvivorRatio+2)*MinTLABSize);
+_survivor_plab_array  = NEW_C_HEAP_ARRAY(ChunkArray, ParallelGCThreads);
+_survivor_chunk_array = NEW_C_HEAP_ARRAY(HeapWord*, 2*max_plab_samples);
+_cursor               = NEW_C_HEAP_ARRAY(size_t, ParallelGCThreads);
+if (_survivor_plab_array == NULL || _survivor_chunk_array == NULL
+|| _cursor == NULL) {
+warning("Failed to allocate survivor plab/chunk array");
+if (_survivor_plab_array  != NULL) {
+FREE_C_HEAP_ARRAY(ChunkArray, _survivor_plab_array);
+_survivor_plab_array = NULL;
+}
+if (_survivor_chunk_array != NULL) {
+FREE_C_HEAP_ARRAY(HeapWord*, _survivor_chunk_array);
+_survivor_chunk_array = NULL;
+}
+if (_cursor != NULL) {
+FREE_C_HEAP_ARRAY(size_t, _cursor);
+_cursor = NULL;
+}
+} else {
+_survivor_chunk_capacity = 2*max_plab_samples;
+for (uint i = 0; i < ParallelGCThreads; i++) {
+HeapWord** vec = NEW_C_HEAP_ARRAY(HeapWord*, max_plab_samples);
+if (vec == NULL) {
+warning("Failed to allocate survivor plab array");
+for (int j = i; j > 0; j--) {
+FREE_C_HEAP_ARRAY(HeapWord*, _survivor_plab_array[j-1].array());
+}
+FREE_C_HEAP_ARRAY(ChunkArray, _survivor_plab_array);
+FREE_C_HEAP_ARRAY(HeapWord*, _survivor_chunk_array);
+_survivor_plab_array = NULL;
+_survivor_chunk_array = NULL;
+_survivor_chunk_capacity = 0;
+break;
+} else {
+ChunkArray* cur =
+::new (&_survivor_plab_array[i]) ChunkArray(vec,
+max_plab_samples);
+assert(cur->end() == 0, "Should be 0");
+assert(cur->array() == vec, "Should be vec");
+assert(cur->capacity() == max_plab_samples, "Error");
+}
+}
+}
+}
+assert(   (   _survivor_plab_array  != NULL
+&& _survivor_chunk_array != NULL)
+|| (   _survivor_chunk_capacity == 0
+&& _survivor_chunk_index == 0),
+"Error");
+// Choose what strong roots should be scanned depending on verification options
+// and perm gen collection mode.
+if (!CMSClassUnloadingEnabled) {
+// If class unloading is disabled we want to include all classes into the root set.
+add_root_scanning_option(SharedHeap::SO_AllClasses);
+} else {
+add_root_scanning_option(SharedHeap::SO_SystemClasses);
+}
+NOT_PRODUCT(_overflow_counter = CMSMarkStackOverflowInterval;)
+_gc_counters = new CollectorCounters("CMS", 1);
+_completed_initialization = true;
+_sweep_timer.start();  // start of time
+}
+const char* ConcurrentMarkSweepGeneration::name() const {
+return "concurrent mark-sweep generation";
+}
+void ConcurrentMarkSweepGeneration::update_counters() {
+if (UsePerfData) {
+_space_counters->update_all();
+_gen_counters->update_all();
+}
+}
+// this is an optimized version of update_counters(). it takes the
+// used value as a parameter rather than computing it.
+//
+void ConcurrentMarkSweepGeneration::update_counters(size_t used) {
+if (UsePerfData) {
+_space_counters->update_used(used);
+_space_counters->update_capacity();
+_gen_counters->update_all();
+}
+}
+void ConcurrentMarkSweepGeneration::print() const {
+Generation::print();
+cmsSpace()->print();
+}
+#ifndef PRODUCT
+void ConcurrentMarkSweepGeneration::print_statistics() {
+cmsSpace()->printFLCensus(0);
+}
+#endif
+void ConcurrentMarkSweepGeneration::printOccupancy(const char *s) {
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+if (PrintGCDetails) {
+if (Verbose) {
+gclog_or_tty->print(" [%d %s-%s: "SIZE_FORMAT"("SIZE_FORMAT")]",
+level(), short_name(), s, used(), capacity());
+} else {
+gclog_or_tty->print(" [%d %s-%s: "SIZE_FORMAT"K("SIZE_FORMAT"K)]",
+level(), short_name(), s, used() / K, capacity() / K);
+}
+}
+if (Verbose) {
+gclog_or_tty->print(" "SIZE_FORMAT"("SIZE_FORMAT")",
+gch->used(), gch->capacity());
+} else {
+gclog_or_tty->print(" "SIZE_FORMAT"K("SIZE_FORMAT"K)",
+gch->used() / K, gch->capacity() / K);
+}
+}
+size_t
+ConcurrentMarkSweepGeneration::contiguous_available() const {
+// dld proposes an improvement in precision here. If the committed
+// part of the space ends in a free block we should add that to
+// uncommitted size in the calculation below. Will make this
+// change later, staying with the approximation below for the
+// time being. -- ysr.
+return MAX2(_virtual_space.uncommitted_size(), unsafe_max_alloc_nogc());
+}
+size_t
+ConcurrentMarkSweepGeneration::unsafe_max_alloc_nogc() const {
+return _cmsSpace->max_alloc_in_words() * HeapWordSize;
+}
+size_t ConcurrentMarkSweepGeneration::max_available() const {
+return free() + _virtual_space.uncommitted_size();
+}
+bool ConcurrentMarkSweepGeneration::promotion_attempt_is_safe(
+size_t max_promotion_in_bytes,
+bool younger_handles_promotion_failure) const {
+// This is the most conservative test.  Full promotion is
+// guaranteed if this is used. The multiplicative factor is to
+// account for the worst case "dilatation".
+double adjusted_max_promo_bytes = _dilatation_factor * max_promotion_in_bytes;
+if (adjusted_max_promo_bytes > (double)max_uintx) { // larger than size_t
+adjusted_max_promo_bytes = (double)max_uintx;
+}
+bool result = (max_contiguous_available() >= (size_t)adjusted_max_promo_bytes);
+if (younger_handles_promotion_failure && !result) {
+// Full promotion is not guaranteed because fragmentation
+// of the cms generation can prevent the full promotion.
+result = (max_available() >= (size_t)adjusted_max_promo_bytes);
+if (!result) {
+// With promotion failure handling the test for the ability
+// to support the promotion does not have to be guaranteed.
+// Use an average of the amount promoted.
+result = max_available() >= (size_t)
+gc_stats()->avg_promoted()->padded_average();
+if (PrintGC && Verbose && result) {
+gclog_or_tty->print_cr(
+"\nConcurrentMarkSweepGeneration::promotion_attempt_is_safe"
+" max_available: " SIZE_FORMAT
+" avg_promoted: " SIZE_FORMAT,
+max_available(), (size_t)
+gc_stats()->avg_promoted()->padded_average());
+}
+} else {
+if (PrintGC && Verbose) {
+gclog_or_tty->print_cr(
+"\nConcurrentMarkSweepGeneration::promotion_attempt_is_safe"
+" max_available: " SIZE_FORMAT
+" adj_max_promo_bytes: " SIZE_FORMAT,
+max_available(), (size_t)adjusted_max_promo_bytes);
+}
+}
+} else {
+if (PrintGC && Verbose) {
+gclog_or_tty->print_cr(
+"\nConcurrentMarkSweepGeneration::promotion_attempt_is_safe"
+" contiguous_available: " SIZE_FORMAT
+" adj_max_promo_bytes: " SIZE_FORMAT,
+max_contiguous_available(), (size_t)adjusted_max_promo_bytes);
+}
+}
+return result;
+}
+CompactibleSpace*
+ConcurrentMarkSweepGeneration::first_compaction_space() const {
+return _cmsSpace;
+}
+void ConcurrentMarkSweepGeneration::reset_after_compaction() {
+// Clear the promotion information.  These pointers can be adjusted
+// along with all the other pointers into the heap but
+// compaction is expected to be a rare event with
+// a heap using cms so don't do it without seeing the need.
+if (ParallelGCThreads > 0) {
+for (uint i = 0; i < ParallelGCThreads; i++) {
+_par_gc_thread_states[i]->promo.reset();
+}
+}
+}
+void ConcurrentMarkSweepGeneration::space_iterate(SpaceClosure* blk, bool usedOnly) {
+blk->do_space(_cmsSpace);
+}
+void ConcurrentMarkSweepGeneration::compute_new_size() {
+assert_locked_or_safepoint(Heap_lock);
+// If incremental collection failed, we just want to expand
+// to the limit.
+if (incremental_collection_failed()) {
+clear_incremental_collection_failed();
+grow_to_reserved();
+return;
+}
+size_t expand_bytes = 0;
+double free_percentage = ((double) free()) / capacity();
+double desired_free_percentage = (double) MinHeapFreeRatio / 100;
+double maximum_free_percentage = (double) MaxHeapFreeRatio / 100;
+// compute expansion delta needed for reaching desired free percentage
+if (free_percentage < desired_free_percentage) {
+size_t desired_capacity = (size_t)(used() / ((double) 1 - desired_free_percentage));
+assert(desired_capacity >= capacity(), "invalid expansion size");
+expand_bytes = MAX2(desired_capacity - capacity(), MinHeapDeltaBytes);
+}
+if (expand_bytes > 0) {
+if (PrintGCDetails && Verbose) {
+size_t desired_capacity = (size_t)(used() / ((double) 1 - desired_free_percentage));
+gclog_or_tty->print_cr("\nFrom compute_new_size: ");
+gclog_or_tty->print_cr("  Free fraction %f", free_percentage);
+gclog_or_tty->print_cr("  Desired free fraction %f",
+desired_free_percentage);
+gclog_or_tty->print_cr("  Maximum free fraction %f",
+maximum_free_percentage);
+gclog_or_tty->print_cr("  Capactiy "SIZE_FORMAT, capacity()/1000);
+gclog_or_tty->print_cr("  Desired capacity "SIZE_FORMAT,
+desired_capacity/1000);
+int prev_level = level() - 1;
+if (prev_level >= 0) {
+size_t prev_size = 0;
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+Generation* prev_gen = gch->_gens[prev_level];
+prev_size = prev_gen->capacity();
+gclog_or_tty->print_cr("  Younger gen size "SIZE_FORMAT,
+prev_size/1000);
+}
+gclog_or_tty->print_cr("  unsafe_max_alloc_nogc "SIZE_FORMAT,
+unsafe_max_alloc_nogc()/1000);
+gclog_or_tty->print_cr("  contiguous available "SIZE_FORMAT,
+contiguous_available()/1000);
+gclog_or_tty->print_cr("  Expand by "SIZE_FORMAT" (bytes)",
+expand_bytes);
+}
+// safe if expansion fails
+expand(expand_bytes, 0, CMSExpansionCause::_satisfy_free_ratio);
+if (PrintGCDetails && Verbose) {
+gclog_or_tty->print_cr("  Expanded free fraction %f",
+((double) free()) / capacity());
+}
+}
+}
+Mutex* ConcurrentMarkSweepGeneration::freelistLock() const {
+return cmsSpace()->freelistLock();
+}
+HeapWord* ConcurrentMarkSweepGeneration::allocate(size_t size,
+bool   tlab) {
+CMSSynchronousYieldRequest yr;
+MutexLockerEx x(freelistLock(),
+Mutex::_no_safepoint_check_flag);
+return have_lock_and_allocate(size, tlab);
+}
+HeapWord* ConcurrentMarkSweepGeneration::have_lock_and_allocate(size_t size,
+bool   tlab) {
+assert_lock_strong(freelistLock());
+size_t adjustedSize = CompactibleFreeListSpace::adjustObjectSize(size);
+HeapWord* res = cmsSpace()->allocate(adjustedSize);
+// Allocate the object live (grey) if the background collector has
+// started marking. This is necessary because the marker may
+// have passed this address and consequently this object will
+// not otherwise be greyed and would be incorrectly swept up.
+// Note that if this object contains references, the writing
+// of those references will dirty the card containing this object
+// allowing the object to be blackened (and its references scanned)
+// either during a preclean phase or at the final checkpoint.
+if (res != NULL) {
+collector()->direct_allocated(res, adjustedSize);
+_direct_allocated_words += adjustedSize;
+// allocation counters
+NOT_PRODUCT(
+_numObjectsAllocated++;
+_numWordsAllocated += (int)adjustedSize;
+)
+}
+return res;
+}
+// In the case of direct allocation by mutators in a generation that
+// is being concurrently collected, the object must be allocated
+// live (grey) if the background collector has started marking.
+// This is necessary because the marker may
+// have passed this address and consequently this object will
+// not otherwise be greyed and would be incorrectly swept up.
+// Note that if this object contains references, the writing
+// of those references will dirty the card containing this object
+// allowing the object to be blackened (and its references scanned)
+// either during a preclean phase or at the final checkpoint.
+void CMSCollector::direct_allocated(HeapWord* start, size_t size) {
+assert(_markBitMap.covers(start, size), "Out of bounds");
+if (_collectorState >= Marking) {
+MutexLockerEx y(_markBitMap.lock(),
+Mutex::_no_safepoint_check_flag);
+// [see comments preceding SweepClosure::do_blk() below for details]
+// 1. need to mark the object as live so it isn't collected
+// 2. need to mark the 2nd bit to indicate the object may be uninitialized
+// 3. need to mark the end of the object so sweeper can skip over it
+//    if it's uninitialized when the sweeper reaches it.
+_markBitMap.mark(start);          // object is live
+_markBitMap.mark(start + 1);      // object is potentially uninitialized?
+_markBitMap.mark(start + size - 1);
+// mark end of object
+}
+// check that oop looks uninitialized
+assert(oop(start)->klass() == NULL, "_klass should be NULL");
+}
+void CMSCollector::promoted(bool par, HeapWord* start,
+bool is_obj_array, size_t obj_size) {
+assert(_markBitMap.covers(start), "Out of bounds");
+// See comment in direct_allocated() about when objects should
+// be allocated live.
+if (_collectorState >= Marking) {
+// we already hold the marking bit map lock, taken in
+// the prologue
+if (par) {
+_markBitMap.par_mark(start);
+} else {
+_markBitMap.mark(start);
+}
+// We don't need to mark the object as uninitialized (as
+// in direct_allocated above) because this is being done with the
+// world stopped and the object will be initialized by the
+// time the sweeper gets to look at it.
+assert(SafepointSynchronize::is_at_safepoint(),
+"expect promotion only at safepoints");
+if (_collectorState < Sweeping) {
+// Mark the appropriate cards in the modUnionTable, so that
+// this object gets scanned before the sweep. If this is
+// not done, CMS generation references in the object might
+// not get marked.
+// For the case of arrays, which are otherwise precisely
+// marked, we need to dirty the entire array, not just its head.
+if (is_obj_array) {
+// The [par_]mark_range() method expects mr.end() below to
+// be aligned to the granularity of a bit's representation
+// in the heap. In the case of the MUT below, that's a
+// card size.
+MemRegion mr(start,
+(HeapWord*)round_to((intptr_t)(start + obj_size),
+CardTableModRefBS::card_size /* bytes */));
+if (par) {
+_modUnionTable.par_mark_range(mr);
+} else {
+_modUnionTable.mark_range(mr);
+}
+} else {  // not an obj array; we can just mark the head
+if (par) {
+_modUnionTable.par_mark(start);
+} else {
+_modUnionTable.mark(start);
+}
+}
+}
+}
+}
+static inline size_t percent_of_space(Space* space, HeapWord* addr)
+{
+size_t delta = pointer_delta(addr, space->bottom());
+return (size_t)(delta * 100.0 / (space->capacity() / HeapWordSize));
+}
+void CMSCollector::icms_update_allocation_limits()
+{
+Generation* gen0 = GenCollectedHeap::heap()->get_gen(0);
+EdenSpace* eden = gen0->as_DefNewGeneration()->eden();
+const unsigned int duty_cycle = stats().icms_update_duty_cycle();
+if (CMSTraceIncrementalPacing) {
+stats().print();
+}
+assert(duty_cycle <= 100, "invalid duty cycle");
+if (duty_cycle != 0) {
+// The duty_cycle is a percentage between 0 and 100; convert to words and
+// then compute the offset from the endpoints of the space.
+size_t free_words = eden->free() / HeapWordSize;
+double free_words_dbl = (double)free_words;
+size_t duty_cycle_words = (size_t)(free_words_dbl * duty_cycle / 100.0);
+size_t offset_words = (free_words - duty_cycle_words) / 2;
+_icms_start_limit = eden->top() + offset_words;
+_icms_stop_limit = eden->end() - offset_words;
+// The limits may be adjusted (shifted to the right) by
+// CMSIncrementalOffset, to allow the application more mutator time after a
+// young gen gc (when all mutators were stopped) and before CMS starts and
+// takes away one or more cpus.
+if (CMSIncrementalOffset != 0) {
+double adjustment_dbl = free_words_dbl * CMSIncrementalOffset / 100.0;
+size_t adjustment = (size_t)adjustment_dbl;
+HeapWord* tmp_stop = _icms_stop_limit + adjustment;
+if (tmp_stop > _icms_stop_limit && tmp_stop < eden->end()) {
+_icms_start_limit += adjustment;
+_icms_stop_limit = tmp_stop;
+}
+}
+}
+if (duty_cycle == 0 || (_icms_start_limit == _icms_stop_limit)) {
+_icms_start_limit = _icms_stop_limit = eden->end();
+}
+// Install the new start limit.
+eden->set_soft_end(_icms_start_limit);
+if (CMSTraceIncrementalMode) {
+gclog_or_tty->print(" icms alloc limits:  "
+PTR_FORMAT "," PTR_FORMAT
+" (" SIZE_FORMAT "%%," SIZE_FORMAT "%%) ",
+_icms_start_limit, _icms_stop_limit,
+percent_of_space(eden, _icms_start_limit),
+percent_of_space(eden, _icms_stop_limit));
+if (Verbose) {
+gclog_or_tty->print("eden:  ");
+eden->print_on(gclog_or_tty);
+}
+}
+}
+// Any changes here should try to maintain the invariant
+// that if this method is called with _icms_start_limit
+// and _icms_stop_limit both NULL, then it should return NULL
+// and not notify the icms thread.
+HeapWord*
+CMSCollector::allocation_limit_reached(Space* space, HeapWord* top,
+size_t word_size)
+{
+// A start_limit equal to end() means the duty cycle is 0, so treat that as a
+// nop.
+if (CMSIncrementalMode && _icms_start_limit != space->end()) {
+if (top <= _icms_start_limit) {
+if (CMSTraceIncrementalMode) {
+space->print_on(gclog_or_tty);
+gclog_or_tty->stamp();
+gclog_or_tty->print_cr(" start limit top=" PTR_FORMAT
+", new limit=" PTR_FORMAT
+" (" SIZE_FORMAT "%%)",
+top, _icms_stop_limit,
+percent_of_space(space, _icms_stop_limit));
+}
+ConcurrentMarkSweepThread::start_icms();
+assert(top < _icms_stop_limit, "Tautology");
+if (word_size < pointer_delta(_icms_stop_limit, top)) {
+return _icms_stop_limit;
+}
+// The allocation will cross both the _start and _stop limits, so do the
+// stop notification also and return end().
+if (CMSTraceIncrementalMode) {
+space->print_on(gclog_or_tty);
+gclog_or_tty->stamp();
+gclog_or_tty->print_cr(" +stop limit top=" PTR_FORMAT
+", new limit=" PTR_FORMAT
+" (" SIZE_FORMAT "%%)",
+top, space->end(),
+percent_of_space(space, space->end()));
+}
+ConcurrentMarkSweepThread::stop_icms();
+return space->end();
+}
+if (top <= _icms_stop_limit) {
+if (CMSTraceIncrementalMode) {
+space->print_on(gclog_or_tty);
+gclog_or_tty->stamp();
+gclog_or_tty->print_cr(" stop limit top=" PTR_FORMAT
+", new limit=" PTR_FORMAT
+" (" SIZE_FORMAT "%%)",
+top, space->end(),
+percent_of_space(space, space->end()));
+}
+ConcurrentMarkSweepThread::stop_icms();
+return space->end();
+}
+if (CMSTraceIncrementalMode) {
+space->print_on(gclog_or_tty);
+gclog_or_tty->stamp();
+gclog_or_tty->print_cr(" end limit top=" PTR_FORMAT
+", new limit=" PTR_FORMAT,
+top, NULL);
+}
+}
+return NULL;
+}
+oop ConcurrentMarkSweepGeneration::promote(oop obj, size_t obj_size, oop* ref) {
+assert(obj_size == (size_t)obj->size(), "bad obj_size passed in");
+// allocate, copy and if necessary update promoinfo --
+// delegate to underlying space.
+assert_lock_strong(freelistLock());
+#ifndef PRODUCT
+if (Universe::heap()->promotion_should_fail()) {
+return NULL;
+}
+#endif  // #ifndef PRODUCT
+oop res = _cmsSpace->promote(obj, obj_size, ref);
+if (res == NULL) {
+// expand and retry
+size_t s = _cmsSpace->expansionSpaceRequired(obj_size);  // HeapWords
+expand(s*HeapWordSize, MinHeapDeltaBytes,
+CMSExpansionCause::_satisfy_promotion);
+// Since there's currently no next generation, we don't try to promote
+// into a more senior generation.
+assert(next_gen() == NULL, "assumption, based upon which no attempt "
+"is made to pass on a possibly failing "
+"promotion to next generation");
+res = _cmsSpace->promote(obj, obj_size, ref);
+}
+if (res != NULL) {
+// See comment in allocate() about when objects should
+// be allocated live.
+assert(obj->is_oop(), "Will dereference klass pointer below");
+collector()->promoted(false,           // Not parallel
+(HeapWord*)res, obj->is_objArray(), obj_size);
+// promotion counters
+NOT_PRODUCT(
+_numObjectsPromoted++;
+_numWordsPromoted +=
+(int)(CompactibleFreeListSpace::adjustObjectSize(obj->size()));
+)
+}
+return res;
+}
+HeapWord*
+ConcurrentMarkSweepGeneration::allocation_limit_reached(Space* space,
+HeapWord* top,
+size_t word_sz)
+{
+return collector()->allocation_limit_reached(space, top, word_sz);
+}
+// Things to support parallel young-gen collection.
+oop
+ConcurrentMarkSweepGeneration::par_promote(int thread_num,
+oop old, markOop m,
+size_t word_sz) {
+#ifndef PRODUCT
+if (Universe::heap()->promotion_should_fail()) {
+return NULL;
+}
+#endif  // #ifndef PRODUCT
+CMSParGCThreadState* ps = _par_gc_thread_states[thread_num];
+PromotionInfo* promoInfo = &ps->promo;
+// if we are tracking promotions, then first ensure space for
+// promotion (including spooling space for saving header if necessary).
+// then allocate and copy, then track promoted info if needed.
+// When tracking (see PromotionInfo::track()), the mark word may
+// be displaced and in this case restoration of the mark word
+// occurs in the (oop_since_save_marks_)iterate phase.
+if (promoInfo->tracking() && !promoInfo->ensure_spooling_space()) {
+// Out of space for allocating spooling buffers;
+// try expanding and allocating spooling buffers.
+if (!expand_and_ensure_spooling_space(promoInfo)) {
+return NULL;
+}
+}
+assert(promoInfo->has_spooling_space(), "Control point invariant");
+HeapWord* obj_ptr = ps->lab.alloc(word_sz);
+if (obj_ptr == NULL) {
+obj_ptr = expand_and_par_lab_allocate(ps, word_sz);
+if (obj_ptr == NULL) {
+return NULL;
+}
+}
+oop obj = oop(obj_ptr);
+assert(obj->klass() == NULL, "Object should be uninitialized here.");
+// Otherwise, copy the object.  Here we must be careful to insert the
+// klass pointer last, since this marks the block as an allocated object.
+HeapWord* old_ptr = (HeapWord*)old;
+if (word_sz > (size_t)oopDesc::header_size()) {
+Copy::aligned_disjoint_words(old_ptr + oopDesc::header_size(),
+obj_ptr + oopDesc::header_size(),
+word_sz - oopDesc::header_size());
+}
+// Restore the mark word copied above.
+obj->set_mark(m);
+// Now we can track the promoted object, if necessary.  We take care
+// To delay the transition from uninitialized to full object
+// (i.e., insertion of klass pointer) until after, so that it
+// atomically becomes a promoted object.
+if (promoInfo->tracking()) {
+promoInfo->track((PromotedObject*)obj, old->klass());
+}
+// Finally, install the klass pointer.
+obj->set_klass(old->klass());
+assert(old->is_oop(), "Will dereference klass ptr below");
+collector()->promoted(true,          // parallel
+obj_ptr, old->is_objArray(), word_sz);
+NOT_PRODUCT(
+Atomic::inc(&_numObjectsPromoted);
+Atomic::add((jint)CompactibleFreeListSpace::adjustObjectSize(obj->size()),
+&_numWordsPromoted);
+)
+return obj;
+}
+void
+ConcurrentMarkSweepGeneration::
+par_promote_alloc_undo(int thread_num,
+HeapWord* obj, size_t word_sz) {
+// CMS does not support promotion undo.
+ShouldNotReachHere();
+}
+void
+ConcurrentMarkSweepGeneration::
+par_promote_alloc_done(int thread_num) {
+CMSParGCThreadState* ps = _par_gc_thread_states[thread_num];
+ps->lab.retire();
+#if CFLS_LAB_REFILL_STATS
+if (thread_num == 0) {
+_cmsSpace->print_par_alloc_stats();
+}
+#endif
+}
+void
+ConcurrentMarkSweepGeneration::
+par_oop_since_save_marks_iterate_done(int thread_num) {
+CMSParGCThreadState* ps = _par_gc_thread_states[thread_num];
+ParScanWithoutBarrierClosure* dummy_cl = NULL;
+ps->promo.promoted_oops_iterate_nv(dummy_cl);
+}
+// XXXPERM
+bool ConcurrentMarkSweepGeneration::should_collect(bool   full,
+size_t size,
+bool   tlab)
+{
+// We allow a STW collection only if a full
+// collection was requested.
+return full || should_allocate(size, tlab); // FIX ME !!!
+// This and promotion failure handling are connected at the
+// hip and should be fixed by untying them.
+}
+bool CMSCollector::shouldConcurrentCollect() {
+if (_full_gc_requested) {
+assert(ExplicitGCInvokesConcurrent, "Unexpected state");
+if (Verbose && PrintGCDetails) {
+gclog_or_tty->print_cr("CMSCollector: collect because of explicit "
+" gc request");
+}
+return true;
+}
+// For debugging purposes, change the type of collection.
+// If the rotation is not on the concurrent collection
+// type, don't start a concurrent collection.
+NOT_PRODUCT(
+if (RotateCMSCollectionTypes &&
+(_cmsGen->debug_collection_type() !=
+ConcurrentMarkSweepGeneration::Concurrent_collection_type)) {
+assert(_cmsGen->debug_collection_type() !=
+ConcurrentMarkSweepGeneration::Unknown_collection_type,
+"Bad cms collection type");
+return false;
+}
+)
+FreelistLocker x(this);
+// ------------------------------------------------------------------
+// Print out lots of information which affects the initiation of
+// a collection.
+if (PrintCMSInitiationStatistics && stats().valid()) {
+gclog_or_tty->print("CMSCollector shouldConcurrentCollect: ");
+gclog_or_tty->stamp();
+gclog_or_tty->print_cr("");
+stats().print_on(gclog_or_tty);
+gclog_or_tty->print_cr("time_until_cms_gen_full %3.7f",
+stats().time_until_cms_gen_full());
+gclog_or_tty->print_cr("free="SIZE_FORMAT, _cmsGen->free());
+gclog_or_tty->print_cr("contiguous_available="SIZE_FORMAT,
+_cmsGen->contiguous_available());
+gclog_or_tty->print_cr("promotion_rate=%g", stats().promotion_rate());
+gclog_or_tty->print_cr("cms_allocation_rate=%g", stats().cms_allocation_rate());
+gclog_or_tty->print_cr("occupancy=%3.7f", _cmsGen->occupancy());
+gclog_or_tty->print_cr("initiatingOccupancy=%3.7f", initiatingOccupancy());
+}
+// ------------------------------------------------------------------
+// If the estimated time to complete a cms collection (cms_duration())
+// is less than the estimated time remaining until the cms generation
+// is full, start a collection.
+if (!UseCMSInitiatingOccupancyOnly) {
+if (stats().valid()) {
+if (stats().time_until_cms_start() == 0.0) {
+return true;
+}
+} else {
+// We want to conservatively collect somewhat early in order
+// to try and "bootstrap" our CMS/promotion statistics;
+// this branch will not fire after the first successful CMS
+// collection because the stats should then be valid.
+if (_cmsGen->occupancy() >= _bootstrap_occupancy) {
+if (Verbose && PrintGCDetails) {
+gclog_or_tty->print_cr(
+" CMSCollector: collect for bootstrapping statistics:"
+" occupancy = %f, boot occupancy = %f", _cmsGen->occupancy(),
+_bootstrap_occupancy);
+}
+return true;
+}
+}
+}
+// Otherwise, we start a collection cycle if either the perm gen or
+// old gen want a collection cycle started. Each may use
+// an appropriate criterion for making this decision.
+// XXX We need to make sure that the gen expansion
+// criterion dovetails well with this.
+if (_cmsGen->shouldConcurrentCollect(initiatingOccupancy())) {
+if (Verbose && PrintGCDetails) {
+gclog_or_tty->print_cr("CMS old gen initiated");
+}
+return true;
+}
+if (cms_should_unload_classes() &&
+_permGen->shouldConcurrentCollect(initiatingOccupancy())) {
+if (Verbose && PrintGCDetails) {
+gclog_or_tty->print_cr("CMS perm gen initiated");
+}
+return true;
+}
+return false;
+}
+// Clear _expansion_cause fields of constituent generations
+void CMSCollector::clear_expansion_cause() {
+_cmsGen->clear_expansion_cause();
+_permGen->clear_expansion_cause();
+}
+bool ConcurrentMarkSweepGeneration::shouldConcurrentCollect(
+double initiatingOccupancy) {
+// We should be conservative in starting a collection cycle.  To
+// start too eagerly runs the risk of collecting too often in the
+// extreme.  To collect too rarely falls back on full collections,
+// which works, even if not optimum in terms of concurrent work.
+// As a work around for too eagerly collecting, use the flag
+// UseCMSInitiatingOccupancyOnly.  This also has the advantage of
+// giving the user an easily understandable way of controlling the
+// collections.
+// We want to start a new collection cycle if any of the following
+// conditions hold:
+// . our current occupancy exceeds the initiating occupancy, or
+// . we recently needed to expand and have not since that expansion,
+//   collected, or
+// . we are not using adaptive free lists and linear allocation is
+//   going to fail, or
+// . (for old gen) incremental collection has already failed or
+//   may soon fail in the near future as we may not be able to absorb
+//   promotions.
+assert_lock_strong(freelistLock());
+if (occupancy() > initiatingOccupancy) {
+if (PrintGCDetails && Verbose) {
+gclog_or_tty->print(" %s: collect because of occupancy %f / %f  ",
+short_name(), occupancy(), initiatingOccupancy);
+}
+return true;
+}
+if (UseCMSInitiatingOccupancyOnly) {
+return false;
+}
+if (expansion_cause() == CMSExpansionCause::_satisfy_allocation) {
+if (PrintGCDetails && Verbose) {
+gclog_or_tty->print(" %s: collect because expanded for allocation ",
+short_name());
+}
+return true;
+}
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+assert(gch->collector_policy()->is_two_generation_policy(),
+"You may want to check the correctness of the following");
+if (gch->incremental_collection_will_fail()) {
+if (PrintGCDetails && Verbose) {
+gclog_or_tty->print(" %s: collect because incremental collection will fail ",
+short_name());
+}
+return true;
+}
+if (!_cmsSpace->adaptive_freelists() &&
+_cmsSpace->linearAllocationWouldFail()) {
+if (PrintGCDetails && Verbose) {
+gclog_or_tty->print(" %s: collect because of linAB ",
+short_name());
+}
+return true;
+}
+return false;
+}
+void ConcurrentMarkSweepGeneration::collect(bool   full,
+bool   clear_all_soft_refs,
+size_t size,
+bool   tlab)
+{
+collector()->collect(full, clear_all_soft_refs, size, tlab);
+}
+void CMSCollector::collect(bool   full,
+bool   clear_all_soft_refs,
+size_t size,
+bool   tlab)
+{
+if (!UseCMSCollectionPassing && _collectorState > Idling) {
+// For debugging purposes skip the collection if the state
+// is not currently idle
+if (TraceCMSState) {
+gclog_or_tty->print_cr("Thread " INTPTR_FORMAT " skipped full:%d CMS state %d",
+Thread::current(), full, _collectorState);
+}
+return;
+}
+// The following "if" branch is present for defensive reasons.
+// In the current uses of this interface, it can be replaced with:
+// assert(!GC_locker.is_active(), "Can't be called otherwise");
+// But I am not placing that assert here to allow future
+// generality in invoking this interface.
+if (GC_locker::is_active()) {
+// A consistency test for GC_locker
+assert(GC_locker::needs_gc(), "Should have been set already");
+// Skip this foreground collection, instead
+// expanding the heap if necessary.
+// Need the free list locks for the call to free() in compute_new_size()
+compute_new_size();
+return;
+}
+acquire_control_and_collect(full, clear_all_soft_refs);
+_full_gcs_since_conc_gc++;
+}
+void CMSCollector::request_full_gc(unsigned int full_gc_count) {
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+unsigned int gc_count = gch->total_full_collections();
+if (gc_count == full_gc_count) {
+MutexLockerEx y(CGC_lock, Mutex::_no_safepoint_check_flag);
+_full_gc_requested = true;
+CGC_lock->notify();   // nudge CMS thread
+}
+}
+// The foreground and background collectors need to coordinate in order
+// to make sure that they do not mutually interfere with CMS collections.
+// When a background collection is active,
+// the foreground collector may need to take over (preempt) and
+// synchronously complete an ongoing collection. Depending on the
+// frequency of the background collections and the heap usage
+// of the application, this preemption can be seldom or frequent.
+// There are only certain
+// points in the background collection that the "collection-baton"
+// can be passed to the foreground collector.
+//
+// The foreground collector will wait for the baton before
+// starting any part of the collection.  The foreground collector
+// will only wait at one location.
+//
+// The background collector will yield the baton before starting a new
+// phase of the collection (e.g., before initial marking, marking from roots,
+// precleaning, final re-mark, sweep etc.)  This is normally done at the head
+// of the loop which switches the phases. The background collector does some
+// of the phases (initial mark, final re-mark) with the world stopped.
+// Because of locking involved in stopping the world,
+// the foreground collector should not block waiting for the background
+// collector when it is doing a stop-the-world phase.  The background
+// collector will yield the baton at an additional point just before
+// it enters a stop-the-world phase.  Once the world is stopped, the
+// background collector checks the phase of the collection.  If the
+// phase has not changed, it proceeds with the collection.  If the
+// phase has changed, it skips that phase of the collection.  See
+// the comments on the use of the Heap_lock in collect_in_background().
+//
+// Variable used in baton passing.
+//   _foregroundGCIsActive - Set to true by the foreground collector when
+//      it wants the baton.  The foreground clears it when it has finished
+//      the collection.
+//   _foregroundGCShouldWait - Set to true by the background collector
+//        when it is running.  The foreground collector waits while
+//      _foregroundGCShouldWait is true.
+//  CGC_lock - monitor used to protect access to the above variables
+//      and to notify the foreground and background collectors.
+//  _collectorState - current state of the CMS collection.
+//
+// The foreground collector
+//   acquires the CGC_lock
+//   sets _foregroundGCIsActive
+//   waits on the CGC_lock for _foregroundGCShouldWait to be false
+//     various locks acquired in preparation for the collection
+//     are released so as not to block the background collector
+//     that is in the midst of a collection
+//   proceeds with the collection
+//   clears _foregroundGCIsActive
+//   returns
+//
+// The background collector in a loop iterating on the phases of the
+//      collection
+//   acquires the CGC_lock
+//   sets _foregroundGCShouldWait
+//   if _foregroundGCIsActive is set
+//     clears _foregroundGCShouldWait, notifies _CGC_lock
+//     waits on _CGC_lock for _foregroundGCIsActive to become false
+//     and exits the loop.
+//   otherwise
+//     proceed with that phase of the collection
+//     if the phase is a stop-the-world phase,
+//       yield the baton once more just before enqueueing
+//       the stop-world CMS operation (executed by the VM thread).
+//   returns after all phases of the collection are done
+//
+void CMSCollector::acquire_control_and_collect(bool full,
+bool clear_all_soft_refs) {
+assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
+assert(!Thread::current()->is_ConcurrentGC_thread(),
+"shouldn't try to acquire control from self!");
+// Start the protocol for acquiring control of the
+// collection from the background collector (aka CMS thread).
+assert(ConcurrentMarkSweepThread::vm_thread_has_cms_token(),
+"VM thread should have CMS token");
+// Remember the possibly interrupted state of an ongoing
+// concurrent collection
+CollectorState first_state = _collectorState;
+// Signal to a possibly ongoing concurrent collection that
+// we want to do a foreground collection.
+_foregroundGCIsActive = true;
+// Disable incremental mode during a foreground collection.
+ICMSDisabler icms_disabler;
+// release locks and wait for a notify from the background collector
+// releasing the locks in only necessary for phases which
+// do yields to improve the granularity of the collection.
+assert_lock_strong(bitMapLock());
+// We need to lock the Free list lock for the space that we are
+// currently collecting.
+assert(haveFreelistLocks(), "Must be holding free list locks");
+bitMapLock()->unlock();
+releaseFreelistLocks();
+{
+MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
+if (_foregroundGCShouldWait) {
+// We are going to be waiting for action for the CMS thread;
+// it had better not be gone (for instance at shutdown)!
+assert(ConcurrentMarkSweepThread::cmst() != NULL,
+"CMS thread must be running");
+// Wait here until the background collector gives us the go-ahead
+ConcurrentMarkSweepThread::clear_CMS_flag(
+ConcurrentMarkSweepThread::CMS_vm_has_token);  // release token
+// Get a possibly blocked CMS thread going:
+//   Note that we set _foregroundGCIsActive true above,
+//   without protection of the CGC_lock.
+CGC_lock->notify();
+assert(!ConcurrentMarkSweepThread::vm_thread_wants_cms_token(),
+"Possible deadlock");
+while (_foregroundGCShouldWait) {
+// wait for notification
+CGC_lock->wait(Mutex::_no_safepoint_check_flag);
+// Possibility of delay/starvation here, since CMS token does
+// not know to give priority to VM thread? Actually, i think
+// there wouldn't be any delay/starvation, but the proof of
+// that "fact" (?) appears non-trivial. XXX 20011219YSR
+}
+ConcurrentMarkSweepThread::set_CMS_flag(
+ConcurrentMarkSweepThread::CMS_vm_has_token);
+}
+}
+// The CMS_token is already held.  Get back the other locks.
+assert(ConcurrentMarkSweepThread::vm_thread_has_cms_token(),
+"VM thread should have CMS token");
+getFreelistLocks();
+bitMapLock()->lock_without_safepoint_check();
+if (TraceCMSState) {
+gclog_or_tty->print_cr("CMS foreground collector has asked for control "
+INTPTR_FORMAT " with first state %d", Thread::current(), first_state);
+gclog_or_tty->print_cr("    gets control with state %d", _collectorState);
+}
+// Check if we need to do a compaction, or if not, whether
+// we need to start the mark-sweep from scratch.
+bool should_compact    = false;
+bool should_start_over = false;
+decide_foreground_collection_type(clear_all_soft_refs,
+&should_compact, &should_start_over);
+NOT_PRODUCT(
+if (RotateCMSCollectionTypes) {
+if (_cmsGen->debug_collection_type() ==
+ConcurrentMarkSweepGeneration::MSC_foreground_collection_type) {
+should_compact = true;
+} else if (_cmsGen->debug_collection_type() ==
+ConcurrentMarkSweepGeneration::MS_foreground_collection_type) {
+should_compact = false;
+}
+}
+)
+if (PrintGCDetails && first_state > Idling) {
+GCCause::Cause cause = GenCollectedHeap::heap()->gc_cause();
+if (GCCause::is_user_requested_gc(cause) ||
+GCCause::is_serviceability_requested_gc(cause)) {
+gclog_or_tty->print(" (concurrent mode interrupted)");
+} else {
+gclog_or_tty->print(" (concurrent mode failure)");
+}
+}
+if (should_compact) {
+// If the collection is being acquired from the background
+// collector, there may be references on the discovered
+// references lists that have NULL referents (being those
+// that were concurrently cleared by a mutator) or
+// that are no longer active (having been enqueued concurrently
+// by the mutator).
+// Scrub the list of those references because Mark-Sweep-Compact
+// code assumes referents are not NULL and that all discovered
+// Reference objects are active.
+ref_processor()->clean_up_discovered_references();
+do_compaction_work(clear_all_soft_refs);
+// Has the GC time limit been exceeded?
+check_gc_time_limit();
+} else {
+do_mark_sweep_work(clear_all_soft_refs, first_state,
+should_start_over);
+}
+// Reset the expansion cause, now that we just completed
+// a collection cycle.
+clear_expansion_cause();
+_foregroundGCIsActive = false;
+return;
+}
+void CMSCollector::check_gc_time_limit() {
+// Ignore explicit GC's.  Exiting here does not set the flag and
+// does not reset the count.  Updating of the averages for system
+// GC's is still controlled by UseAdaptiveSizePolicyWithSystemGC.
+GCCause::Cause gc_cause = GenCollectedHeap::heap()->gc_cause();
+if (GCCause::is_user_requested_gc(gc_cause) ||
+GCCause::is_serviceability_requested_gc(gc_cause)) {
+return;
+}
+// Calculate the fraction of the CMS generation was freed during
+// the last collection.
+// Only consider the STW compacting cost for now.
+//
+// Note that the gc time limit test only works for the collections
+// of the young gen + tenured gen and not for collections of the
+// permanent gen.  That is because the calculation of the space
+// freed by the collection is the free space in the young gen +
+// tenured gen.
+double fraction_free =
+((double)_cmsGen->free())/((double)_cmsGen->max_capacity());
+if ((100.0 * size_policy()->compacting_gc_cost()) >
+((double) GCTimeLimit) &&
+((fraction_free * 100) < GCHeapFreeLimit)) {
+size_policy()->inc_gc_time_limit_count();
+if (UseGCOverheadLimit &&
+(size_policy()->gc_time_limit_count() >
+AdaptiveSizePolicyGCTimeLimitThreshold)) {
+size_policy()->set_gc_time_limit_exceeded(true);
+// Avoid consecutive OOM due to the gc time limit by resetting
+// the counter.
+size_policy()->reset_gc_time_limit_count();
+if (PrintGCDetails) {
+gclog_or_tty->print_cr("      GC is exceeding overhead limit "
+"of %d%%", GCTimeLimit);
+}
+} else {
+if (PrintGCDetails) {
+gclog_or_tty->print_cr("      GC would exceed overhead limit "
+"of %d%%", GCTimeLimit);
+}
+}
+} else {
+size_policy()->reset_gc_time_limit_count();
+}
+}
+// Resize the perm generation and the tenured generation
+// after obtaining the free list locks for the
+// two generations.
+void CMSCollector::compute_new_size() {
+assert_locked_or_safepoint(Heap_lock);
+FreelistLocker z(this);
+_permGen->compute_new_size();
+_cmsGen->compute_new_size();
+}
+// A work method used by foreground collection to determine
+// what type of collection (compacting or not, continuing or fresh)
+// it should do.
+// NOTE: the intent is to make UseCMSCompactAtFullCollection
+// and CMSCompactWhenClearAllSoftRefs the default in the future
+// and do away with the flags after a suitable period.
+void CMSCollector::decide_foreground_collection_type(
+bool clear_all_soft_refs, bool* should_compact,
+bool* should_start_over) {
+// Normally, we'll compact only if the UseCMSCompactAtFullCollection
+// flag is set, and we have either requested a System.gc() or
+// the number of full gc's since the last concurrent cycle
+// has exceeded the threshold set by CMSFullGCsBeforeCompaction,
+// or if an incremental collection has failed
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+assert(gch->collector_policy()->is_two_generation_policy(),
+"You may want to check the correctness of the following");
+// Inform cms gen if this was due to partial collection failing.
+// The CMS gen may use this fact to determine its expansion policy.
+if (gch->incremental_collection_will_fail()) {
+assert(!_cmsGen->incremental_collection_failed(),
+"Should have been noticed, reacted to and cleared");
+_cmsGen->set_incremental_collection_failed();
+}
+*should_compact =
+UseCMSCompactAtFullCollection &&
+((_full_gcs_since_conc_gc >= CMSFullGCsBeforeCompaction) ||
+GCCause::is_user_requested_gc(gch->gc_cause()) ||
+gch->incremental_collection_will_fail());
+*should_start_over = false;
+if (clear_all_soft_refs && !*should_compact) {
+// We are about to do a last ditch collection attempt
+// so it would normally make sense to do a compaction
+// to reclaim as much space as possible.
+if (CMSCompactWhenClearAllSoftRefs) {
+// Default: The rationale is that in this case either
+// we are past the final marking phase, in which case
+// we'd have to start over, or so little has been done
+// that there's little point in saving that work. Compaction
+// appears to be the sensible choice in either case.
+*should_compact = true;
+} else {
+// We have been asked to clear all soft refs, but not to
+// compact. Make sure that we aren't past the final checkpoint
+// phase, for that is where we process soft refs. If we are already
+// past that phase, we'll need to redo the refs discovery phase and
+// if necessary clear soft refs that weren't previously
+// cleared. We do so by remembering the phase in which
+// we came in, and if we are past the refs processing
+// phase, we'll choose to just redo the mark-sweep
+// collection from scratch.
+if (_collectorState > FinalMarking) {
+// We are past the refs processing phase;
+// start over and do a fresh synchronous CMS cycle
+_collectorState = Resetting; // skip to reset to start new cycle
+reset(false /* == !asynch */);
+*should_start_over = true;
+} // else we can continue a possibly ongoing current cycle
+}
+}
+}
+// A work method used by the foreground collector to do
+// a mark-sweep-compact.
+void CMSCollector::do_compaction_work(bool clear_all_soft_refs) {
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+TraceTime t("CMS:MSC ", PrintGCDetails && Verbose, true, gclog_or_tty);
+if (PrintGC && Verbose && !(GCCause::is_user_requested_gc(gch->gc_cause()))) {
+gclog_or_tty->print_cr("Compact ConcurrentMarkSweepGeneration after %d "
+"collections passed to foreground collector", _full_gcs_since_conc_gc);
+}
+// Sample collection interval time and reset for collection pause.
+if (UseAdaptiveSizePolicy) {
+size_policy()->msc_collection_begin();
+}
+// Temporarily widen the span of the weak reference processing to
+// the entire heap.
+MemRegion new_span(GenCollectedHeap::heap()->reserved_region());
+ReferenceProcessorSpanMutator x(ref_processor(), new_span);
+// Temporarily, clear the "is_alive_non_header" field of the
+// reference processor.
+ReferenceProcessorIsAliveMutator y(ref_processor(), NULL);
+// Temporarily make reference _processing_ single threaded (non-MT).
+ReferenceProcessorMTProcMutator z(ref_processor(), false);
+// Temporarily make refs discovery atomic
+ReferenceProcessorAtomicMutator w(ref_processor(), true);
+ref_processor()->set_enqueuing_is_done(false);
+ref_processor()->enable_discovery();
+// If an asynchronous collection finishes, the _modUnionTable is
+// all clear.  If we are assuming the collection from an asynchronous
+// collection, clear the _modUnionTable.
+assert(_collectorState != Idling || _modUnionTable.isAllClear(),
+"_modUnionTable should be clear if the baton was not passed");
+_modUnionTable.clear_all();
+// We must adjust the allocation statistics being maintained
+// in the free list space. We do so by reading and clearing
+// the sweep timer and updating the block flux rate estimates below.
+assert(_sweep_timer.is_active(), "We should never see the timer inactive");
+_sweep_timer.stop();
+// Note that we do not use this sample to update the _sweep_estimate.
+_cmsGen->cmsSpace()->beginSweepFLCensus((float)(_sweep_timer.seconds()),
+_sweep_estimate.padded_average());
+GenMarkSweep::invoke_at_safepoint(_cmsGen->level(),
+ref_processor(), clear_all_soft_refs);
+#ifdef ASSERT
+CompactibleFreeListSpace* cms_space = _cmsGen->cmsSpace();
+size_t free_size = cms_space->free();
+assert(free_size ==
+pointer_delta(cms_space->end(), cms_space->compaction_top())
+* HeapWordSize,
+"All the free space should be compacted into one chunk at top");
+assert(cms_space->dictionary()->totalChunkSize(
+debug_only(cms_space->freelistLock())) == 0 ||
+cms_space->totalSizeInIndexedFreeLists() == 0,
+"All the free space should be in a single chunk");
+size_t num = cms_space->totalCount();
+assert((free_size == 0 && num == 0) ||
+(free_size > 0  && (num == 1 || num == 2)),
+"There should be at most 2 free chunks after compaction");
+#endif // ASSERT
+_collectorState = Resetting;
+assert(_restart_addr == NULL,
+"Should have been NULL'd before baton was passed");
+reset(false /* == !asynch */);
+_cmsGen->reset_after_compaction();
+if (verifying() && !cms_should_unload_classes()) {
+perm_gen_verify_bit_map()->clear_all();
+}
+// Clear any data recorded in the PLAB chunk arrays.
+if (_survivor_plab_array != NULL) {
+reset_survivor_plab_arrays();
+}
+// Adjust the per-size allocation stats for the next epoch.
+_cmsGen->cmsSpace()->endSweepFLCensus(sweepCount() /* fake */);
+// Restart the "sweep timer" for next epoch.
+_sweep_timer.reset();
+_sweep_timer.start();
+// Sample collection pause time and reset for collection interval.
+if (UseAdaptiveSizePolicy) {
+size_policy()->msc_collection_end(gch->gc_cause());
+}
+// For a mark-sweep-compact, compute_new_size() will be called
+// in the heap's do_collection() method.
+}
+// A work method used by the foreground collector to do
+// a mark-sweep, after taking over from a possibly on-going
+// concurrent mark-sweep collection.
+void CMSCollector::do_mark_sweep_work(bool clear_all_soft_refs,
+CollectorState first_state, bool should_start_over) {
+if (PrintGC && Verbose) {
+gclog_or_tty->print_cr("Pass concurrent collection to foreground "
+"collector with count %d",
+_full_gcs_since_conc_gc);
+}
+switch (_collectorState) {
+case Idling:
+if (first_state == Idling || should_start_over) {
+// The background GC was not active, or should
+// restarted from scratch;  start the cycle.
+_collectorState = InitialMarking;
+}
+// If first_state was not Idling, then a background GC
+// was in progress and has now finished.  No need to do it
+// again.  Leave the state as Idling.
+break;
+case Precleaning:
+// In the foreground case don't do the precleaning since
+// it is not done concurrently and there is extra work
+// required.
+_collectorState = FinalMarking;
+}
+if (PrintGCDetails &&
+(_collectorState > Idling ||
+!GCCause::is_user_requested_gc(GenCollectedHeap::heap()->gc_cause()))) {
+gclog_or_tty->print(" (concurrent mode failure)");
+}
+collect_in_foreground(clear_all_soft_refs);
+// For a mark-sweep, compute_new_size() will be called
+// in the heap's do_collection() method.
+}
+void CMSCollector::getFreelistLocks() const {
+// Get locks for all free lists in all generations that this
+// collector is responsible for
+_cmsGen->freelistLock()->lock_without_safepoint_check();
+_permGen->freelistLock()->lock_without_safepoint_check();
+}
+void CMSCollector::releaseFreelistLocks() const {
+// Release locks for all free lists in all generations that this
+// collector is responsible for
+_cmsGen->freelistLock()->unlock();
+_permGen->freelistLock()->unlock();
+}
+bool CMSCollector::haveFreelistLocks() const {
+// Check locks for all free lists in all generations that this
+// collector is responsible for
+assert_lock_strong(_cmsGen->freelistLock());
+assert_lock_strong(_permGen->freelistLock());
+PRODUCT_ONLY(ShouldNotReachHere());
+return true;
+}
+// A utility class that is used by the CMS collector to
+// temporarily "release" the foreground collector from its
+// usual obligation to wait for the background collector to
+// complete an ongoing phase before proceeding.
+class ReleaseForegroundGC: public StackObj {
+private:
+CMSCollector* _c;
+public:
+ReleaseForegroundGC(CMSCollector* c) : _c(c) {
+assert(_c->_foregroundGCShouldWait, "Else should not need to call");
+MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
+// allow a potentially blocked foreground collector to proceed
+_c->_foregroundGCShouldWait = false;
+if (_c->_foregroundGCIsActive) {
+CGC_lock->notify();
+}
+assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
+"Possible deadlock");
+}
+~ReleaseForegroundGC() {
+assert(!_c->_foregroundGCShouldWait, "Usage protocol violation?");
+MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
+_c->_foregroundGCShouldWait = true;
+}
+};
+// There are separate collect_in_background and collect_in_foreground because of
+// the different locking requirements of the background collector and the
+// foreground collector.  There was originally an attempt to share
+// one "collect" method between the background collector and the foreground
+// collector but the if-then-else required made it cleaner to have
+// separate methods.
+void CMSCollector::collect_in_background(bool clear_all_soft_refs) {
+assert(Thread::current()->is_ConcurrentGC_thread(),
+"A CMS asynchronous collection is only allowed on a CMS thread.");
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+{
+bool safepoint_check = Mutex::_no_safepoint_check_flag;
+MutexLockerEx hl(Heap_lock, safepoint_check);
+MutexLockerEx x(CGC_lock, safepoint_check);
+if (_foregroundGCIsActive || !UseAsyncConcMarkSweepGC) {
+// The foreground collector is active or we're
+// not using asynchronous collections.  Skip this
+// background collection.
+assert(!_foregroundGCShouldWait, "Should be clear");
+return;
+} else {
+assert(_collectorState == Idling, "Should be idling before start.");
+_collectorState = InitialMarking;
+// Reset the expansion cause, now that we are about to begin
+// a new cycle.
+clear_expansion_cause();
+}
+_unloaded_classes_last_cycle = cms_should_unload_classes(); // ... from last cycle
+// This controls class unloading in response to an explicit gc request.
+// If ExplicitGCInvokesConcurrentAndUnloadsClasses is set, then
+// we will unload classes even if CMSClassUnloadingEnabled is not set.
+// See CR 6541037 and related CRs.
+_unload_classes = _full_gc_requested                      // ... for this cycle
+&& ExplicitGCInvokesConcurrentAndUnloadsClasses;
+_full_gc_requested = false;           // acks all outstanding full gc requests
+// Signal that we are about to start a collection
+gch->increment_total_full_collections();  // ... starting a collection cycle
+_collection_count_start = gch->total_full_collections();
+}
+// Used for PrintGC
+size_t prev_used;
+if (PrintGC && Verbose) {
+prev_used = _cmsGen->used(); // XXXPERM
+}
+// The change of the collection state is normally done at this level;
+// the exceptions are phases that are executed while the world is
+// stopped.  For those phases the change of state is done while the
+// world is stopped.  For baton passing purposes this allows the
+// background collector to finish the phase and change state atomically.
+// The foreground collector cannot wait on a phase that is done
+// while the world is stopped because the foreground collector already
+// has the world stopped and would deadlock.
+while (_collectorState != Idling) {
+if (TraceCMSState) {
+gclog_or_tty->print_cr("Thread " INTPTR_FORMAT " in CMS state %d",
+Thread::current(), _collectorState);
+}
+// The foreground collector
+//   holds the Heap_lock throughout its collection.
+//   holds the CMS token (but not the lock)
+//     except while it is waiting for the background collector to yield.
+//
+// The foreground collector should be blocked (not for long)
+//   if the background collector is about to start a phase
+//   executed with world stopped.  If the background
+//   collector has already started such a phase, the
+//   foreground collector is blocked waiting for the
+//   Heap_lock.  The stop-world phases (InitialMarking and FinalMarking)
+//   are executed in the VM thread.
+//
+// The locking order is
+//   PendingListLock (PLL)  -- if applicable (FinalMarking)
+//   Heap_lock  (both this & PLL locked in VM_CMS_Operation::prologue())
+//   CMS token  (claimed in
+//                stop_world_and_do() -->
+//                  safepoint_synchronize() -->
+//                    CMSThread::synchronize())
+{
+// Check if the FG collector wants us to yield.
+CMSTokenSync x(true); // is cms thread
+if (waitForForegroundGC()) {
+// We yielded to a foreground GC, nothing more to be
+// done this round.
+assert(_foregroundGCShouldWait == false, "We set it to false in "
+"waitForForegroundGC()");
+if (TraceCMSState) {
+gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT
+" exiting collection CMS state %d",
+Thread::current(), _collectorState);
+}
+return;
+} else {
+// The background collector can run but check to see if the
+// foreground collector has done a collection while the
+// background collector was waiting to get the CGC_lock
+// above.  If yes, break so that _foregroundGCShouldWait
+// is cleared before returning.
+if (_collectorState == Idling) {
+break;
+}
+}
+}
+assert(_foregroundGCShouldWait, "Foreground collector, if active, "
+"should be waiting");
+switch (_collectorState) {
+case InitialMarking:
+{
+ReleaseForegroundGC x(this);
+stats().record_cms_begin();
+VM_CMS_Initial_Mark initial_mark_op(this);
+VMThread::execute(&initial_mark_op);
+}
+// The collector state may be any legal state at this point
+// since the background collector may have yielded to the
+// foreground collector.
+break;
+case Marking:
+// initial marking in checkpointRootsInitialWork has been completed
+if (markFromRoots(true)) { // we were successful
+assert(_collectorState == Precleaning, "Collector state should "
+"have changed");
+} else {
+assert(_foregroundGCIsActive, "Internal state inconsistency");
+}
+break;
+case Precleaning:
+if (UseAdaptiveSizePolicy) {
+size_policy()->concurrent_precleaning_begin();
+}
+// marking from roots in markFromRoots has been completed
+preclean();
+if (UseAdaptiveSizePolicy) {
+size_policy()->concurrent_precleaning_end();
+}
+assert(_collectorState == AbortablePreclean ||
+_collectorState == FinalMarking,
+"Collector state should have changed");
+break;
+case AbortablePreclean:
+if (UseAdaptiveSizePolicy) {
+size_policy()->concurrent_phases_resume();
+}
+abortable_preclean();
+if (UseAdaptiveSizePolicy) {
+size_policy()->concurrent_precleaning_end();
+}
+assert(_collectorState == FinalMarking, "Collector state should "
+"have changed");
+break;
+case FinalMarking:
+{
+ReleaseForegroundGC x(this);
+VM_CMS_Final_Remark final_remark_op(this);
+VMThread::execute(&final_remark_op);
+}
+assert(_foregroundGCShouldWait, "block post-condition");
+break;
+case Sweeping:
+if (UseAdaptiveSizePolicy) {
+size_policy()->concurrent_sweeping_begin();
+}
+// final marking in checkpointRootsFinal has been completed
+sweep(true);
+assert(_collectorState == Resizing, "Collector state change "
+"to Resizing must be done under the free_list_lock");
+_full_gcs_since_conc_gc = 0;
+// Stop the timers for adaptive size policy for the concurrent phases
+if (UseAdaptiveSizePolicy) {
+size_policy()->concurrent_sweeping_end();
+size_policy()->concurrent_phases_end(gch->gc_cause(),
+gch->prev_gen(_cmsGen)->capacity(),
+_cmsGen->free());
+}
+case Resizing: {
+// Sweeping has been completed...
+// At this point the background collection has completed.
+// Don't move the call to compute_new_size() down
+// into code that might be executed if the background
+// collection was preempted.
+{
+ReleaseForegroundGC x(this);   // unblock FG collection
+MutexLockerEx       y(Heap_lock, Mutex::_no_safepoint_check_flag);
+CMSTokenSync        z(true);   // not strictly needed.
+if (_collectorState == Resizing) {
+compute_new_size();
+_collectorState = Resetting;
+} else {
+assert(_collectorState == Idling, "The state should only change"
+" because the foreground collector has finished the collection");
+}
+}
+break;
+}
+case Resetting:
+// CMS heap resizing has been completed
+reset(true);
+assert(_collectorState == Idling, "Collector state should "
+"have changed");
+stats().record_cms_end();
+// Don't move the concurrent_phases_end() and compute_new_size()
+// calls to here because a preempted background collection
+// has it's state set to "Resetting".
+break;
+case Idling:
+default:
+ShouldNotReachHere();
+break;
+}
+if (TraceCMSState) {
+gclog_or_tty->print_cr("  Thread " INTPTR_FORMAT " done - next CMS state %d",
+Thread::current(), _collectorState);
+}
+assert(_foregroundGCShouldWait, "block post-condition");
+}
+// Should this be in gc_epilogue?
+collector_policy()->counters()->update_counters();
+{
+// Clear _foregroundGCShouldWait and, in the event that the
+// foreground collector is waiting, notify it, before
+// returning.
+MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
+_foregroundGCShouldWait = false;
+if (_foregroundGCIsActive) {
+CGC_lock->notify();
+}
+assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
+"Possible deadlock");
+}
+if (TraceCMSState) {
+gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT
+" exiting collection CMS state %d",
+Thread::current(), _collectorState);
+}
+if (PrintGC && Verbose) {
+_cmsGen->print_heap_change(prev_used);
+}
+}
+void CMSCollector::collect_in_foreground(bool clear_all_soft_refs) {
+assert(_foregroundGCIsActive && !_foregroundGCShouldWait,
+"Foreground collector should be waiting, not executing");
+assert(Thread::current()->is_VM_thread(), "A foreground collection"
+"may only be done by the VM Thread with the world stopped");
+assert(ConcurrentMarkSweepThread::vm_thread_has_cms_token(),
+"VM thread should have CMS token");
+NOT_PRODUCT(TraceTime t("CMS:MS (foreground) ", PrintGCDetails && Verbose,
+true, gclog_or_tty);)
+if (UseAdaptiveSizePolicy) {
+size_policy()->ms_collection_begin();
+}
+COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact);
+HandleMark hm;  // Discard invalid handles created during verification
+if (VerifyBeforeGC &&
+GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
+Universe::verify(true);
+}
+bool init_mark_was_synchronous = false; // until proven otherwise
+while (_collectorState != Idling) {
+if (TraceCMSState) {
+gclog_or_tty->print_cr("Thread " INTPTR_FORMAT " in CMS state %d",
+Thread::current(), _collectorState);
+}
+switch (_collectorState) {
+case InitialMarking:
+init_mark_was_synchronous = true;  // fact to be exploited in re-mark
+checkpointRootsInitial(false);
+assert(_collectorState == Marking, "Collector state should have changed"
+" within checkpointRootsInitial()");
+break;
+case Marking:
+// initial marking in checkpointRootsInitialWork has been completed
+if (VerifyDuringGC &&
+GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
+gclog_or_tty->print("Verify before initial mark: ");
+Universe::verify(true);
+}
+{
+bool res = markFromRoots(false);
+assert(res && _collectorState == FinalMarking, "Collector state should "
+"have changed");
+break;
+}
+case FinalMarking:
+if (VerifyDuringGC &&
+GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
+gclog_or_tty->print("Verify before re-mark: ");
+Universe::verify(true);
+}
+checkpointRootsFinal(false, clear_all_soft_refs,
+init_mark_was_synchronous);
+assert(_collectorState == Sweeping, "Collector state should not "
+"have changed within checkpointRootsFinal()");
+break;
+case Sweeping:
+// final marking in checkpointRootsFinal has been completed
+if (VerifyDuringGC &&
+GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
+gclog_or_tty->print("Verify before sweep: ");
+Universe::verify(true);
+}
+sweep(false);
+assert(_collectorState == Resizing, "Incorrect state");
+break;
+case Resizing: {
+// Sweeping has been completed; the actual resize in this case
+// is done separately; nothing to be done in this state.
+_collectorState = Resetting;
+break;
+}
+case Resetting:
+// The heap has been resized.
+if (VerifyDuringGC &&
+GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
+gclog_or_tty->print("Verify before reset: ");
+Universe::verify(true);
+}
+reset(false);
+assert(_collectorState == Idling, "Collector state should "
+"have changed");
+break;
+case Precleaning:
+case AbortablePreclean:
+// Elide the preclean phase
+_collectorState = FinalMarking;
+break;
+default:
+ShouldNotReachHere();
+}
+if (TraceCMSState) {
+gclog_or_tty->print_cr("  Thread " INTPTR_FORMAT " done - next CMS state %d",
+Thread::current(), _collectorState);
+}
+}
+if (UseAdaptiveSizePolicy) {
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+size_policy()->ms_collection_end(gch->gc_cause());
+}
+if (VerifyAfterGC &&
+GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
+Universe::verify(true);
+}
+if (TraceCMSState) {
+gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT
+" exiting collection CMS state %d",
+Thread::current(), _collectorState);
+}
+}
+bool CMSCollector::waitForForegroundGC() {
+bool res = false;
+assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
+"CMS thread should have CMS token");
+// Block the foreground collector until the
+// background collectors decides whether to
+// yield.
+MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
+_foregroundGCShouldWait = true;
+if (_foregroundGCIsActive) {
+// The background collector yields to the
+// foreground collector and returns a value
+// indicating that it has yielded.  The foreground
+// collector can proceed.
+res = true;
+_foregroundGCShouldWait = false;
+ConcurrentMarkSweepThread::clear_CMS_flag(
+ConcurrentMarkSweepThread::CMS_cms_has_token);
+ConcurrentMarkSweepThread::set_CMS_flag(
+ConcurrentMarkSweepThread::CMS_cms_wants_token);
+// Get a possibly blocked foreground thread going
+CGC_lock->notify();
+if (TraceCMSState) {
+gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT " waiting at CMS state %d",
+Thread::current(), _collectorState);
+}
+while (_foregroundGCIsActive) {
+CGC_lock->wait(Mutex::_no_safepoint_check_flag);
+}
+ConcurrentMarkSweepThread::set_CMS_flag(
+ConcurrentMarkSweepThread::CMS_cms_has_token);
+ConcurrentMarkSweepThread::clear_CMS_flag(
+ConcurrentMarkSweepThread::CMS_cms_wants_token);
+}
+if (TraceCMSState) {
+gclog_or_tty->print_cr("CMS Thread " INTPTR_FORMAT " continuing at CMS state %d",
+Thread::current(), _collectorState);
+}
+return res;
+}
+// Because of the need to lock the free lists and other structures in
+// the collector, common to all the generations that the collector is
+// collecting, we need the gc_prologues of individual CMS generations
+// delegate to their collector. It may have been simpler had the
+// current infrastructure allowed one to call a prologue on a
+// collector. In the absence of that we have the generation's
+// prologue delegate to the collector, which delegates back
+// some "local" work to a worker method in the individual generations
+// that it's responsible for collecting, while itself doing any
+// work common to all generations it's responsible for. A similar
+// comment applies to the  gc_epilogue()'s.
+// The role of the varaible _between_prologue_and_epilogue is to
+// enforce the invocation protocol.
+void CMSCollector::gc_prologue(bool full) {
+// Call gc_prologue_work() for each CMSGen and PermGen that
+// we are responsible for.
+// The following locking discipline assumes that we are only called
+// when the world is stopped.
+assert(SafepointSynchronize::is_at_safepoint(), "world is stopped assumption");
+// The CMSCollector prologue must call the gc_prologues for the
+// "generations" (including PermGen if any) that it's responsible
+// for.
+assert(   Thread::current()->is_VM_thread()
+|| (   CMSScavengeBeforeRemark
+&& Thread::current()->is_ConcurrentGC_thread()),
+"Incorrect thread type for prologue execution");
+if (_between_prologue_and_epilogue) {
+// We have already been invoked; this is a gc_prologue delegation
+// from yet another CMS generation that we are responsible for, just
+// ignore it since all relevant work has already been done.
+return;
+}
+// set a bit saying prologue has been called; cleared in epilogue
+_between_prologue_and_epilogue = true;
+// Claim locks for common data structures, then call gc_prologue_work()
+// for each CMSGen and PermGen that we are responsible for.
+getFreelistLocks();   // gets free list locks on constituent spaces
+bitMapLock()->lock_without_safepoint_check();
+// Should call gc_prologue_work() for all cms gens we are responsible for
+bool registerClosure =    _collectorState >= Marking
+&& _collectorState < Sweeping;
+ModUnionClosure* muc = ParallelGCThreads > 0 ? &_modUnionClosurePar
+: &_modUnionClosure;
+_cmsGen->gc_prologue_work(full, registerClosure, muc);
+_permGen->gc_prologue_work(full, registerClosure, muc);
+if (!full) {
+stats().record_gc0_begin();
+}
+}
+void ConcurrentMarkSweepGeneration::gc_prologue(bool full) {
+// Delegate to CMScollector which knows how to coordinate between
+// this and any other CMS generations that it is responsible for
+// collecting.
+collector()->gc_prologue(full);
+}
+// This is a "private" interface for use by this generation's CMSCollector.
+// Not to be called directly by any other entity (for instance,
+// GenCollectedHeap, which calls the "public" gc_prologue method above).
+void ConcurrentMarkSweepGeneration::gc_prologue_work(bool full,
+bool registerClosure, ModUnionClosure* modUnionClosure) {
+assert(!incremental_collection_failed(), "Shouldn't be set yet");
+assert(cmsSpace()->preconsumptionDirtyCardClosure() == NULL,
+"Should be NULL");
+if (registerClosure) {
+cmsSpace()->setPreconsumptionDirtyCardClosure(modUnionClosure);
+}
+cmsSpace()->gc_prologue();
+// Clear stat counters
+NOT_PRODUCT(
+assert(_numObjectsPromoted == 0, "check");
+assert(_numWordsPromoted   == 0, "check");
+if (Verbose && PrintGC) {
+gclog_or_tty->print("Allocated "SIZE_FORMAT" objects, "
+SIZE_FORMAT" bytes concurrently",
+_numObjectsAllocated, _numWordsAllocated*sizeof(HeapWord));
+}
+_numObjectsAllocated = 0;
+_numWordsAllocated   = 0;
+)
+}
+void CMSCollector::gc_epilogue(bool full) {
+// The following locking discipline assumes that we are only called
+// when the world is stopped.
+assert(SafepointSynchronize::is_at_safepoint(),
+"world is stopped assumption");
+// Currently the CMS epilogue (see CompactibleFreeListSpace) merely checks
+// if linear allocation blocks need to be appropriately marked to allow the
+// the blocks to be parsable. We also check here whether we need to nudge the
+// CMS collector thread to start a new cycle (if it's not already active).
+assert(   Thread::current()->is_VM_thread()
+|| (   CMSScavengeBeforeRemark
+&& Thread::current()->is_ConcurrentGC_thread()),
+"Incorrect thread type for epilogue execution");
+if (!_between_prologue_and_epilogue) {
+// We have already been invoked; this is a gc_epilogue delegation
+// from yet another CMS generation that we are responsible for, just
+// ignore it since all relevant work has already been done.
+return;
+}
+assert(haveFreelistLocks(), "must have freelist locks");
+assert_lock_strong(bitMapLock());
+_cmsGen->gc_epilogue_work(full);
+_permGen->gc_epilogue_work(full);
+if (_collectorState == AbortablePreclean || _collectorState == Precleaning) {
+// in case sampling was not already enabled, enable it
+_start_sampling = true;
+}
+// reset _eden_chunk_array so sampling starts afresh
+_eden_chunk_index = 0;
+size_t cms_used   = _cmsGen->cmsSpace()->used();
+size_t perm_used  = _permGen->cmsSpace()->used();
+// update performance counters - this uses a special version of
+// update_counters() that allows the utilization to be passed as a
+// parameter, avoiding multiple calls to used().
+//
+_cmsGen->update_counters(cms_used);
+_permGen->update_counters(perm_used);
+if (CMSIncrementalMode) {
+icms_update_allocation_limits();
+}
+bitMapLock()->unlock();
+releaseFreelistLocks();
+_between_prologue_and_epilogue = false;  // ready for next cycle
+}
+void ConcurrentMarkSweepGeneration::gc_epilogue(bool full) {
+collector()->gc_epilogue(full);
+// Also reset promotion tracking in par gc thread states.
+if (ParallelGCThreads > 0) {
+for (uint i = 0; i < ParallelGCThreads; i++) {
+_par_gc_thread_states[i]->promo.stopTrackingPromotions();
+}
+}
+}
+void ConcurrentMarkSweepGeneration::gc_epilogue_work(bool full) {
+assert(!incremental_collection_failed(), "Should have been cleared");
+cmsSpace()->setPreconsumptionDirtyCardClosure(NULL);
+cmsSpace()->gc_epilogue();
+// Print stat counters
+NOT_PRODUCT(
+assert(_numObjectsAllocated == 0, "check");
+assert(_numWordsAllocated == 0, "check");
+if (Verbose && PrintGC) {
+gclog_or_tty->print("Promoted "SIZE_FORMAT" objects, "
+SIZE_FORMAT" bytes",
+_numObjectsPromoted, _numWordsPromoted*sizeof(HeapWord));
+}
+_numObjectsPromoted = 0;
+_numWordsPromoted   = 0;
+)
+if (PrintGC && Verbose) {
+// Call down the chain in contiguous_available needs the freelistLock
+// so print this out before releasing the freeListLock.
+gclog_or_tty->print(" Contiguous available "SIZE_FORMAT" bytes ",
+contiguous_available());
+}
+}
+#ifndef PRODUCT
+bool CMSCollector::have_cms_token() {
+Thread* thr = Thread::current();
+if (thr->is_VM_thread()) {
+return ConcurrentMarkSweepThread::vm_thread_has_cms_token();
+} else if (thr->is_ConcurrentGC_thread()) {
+return ConcurrentMarkSweepThread::cms_thread_has_cms_token();
+} else if (thr->is_GC_task_thread()) {
+return ConcurrentMarkSweepThread::vm_thread_has_cms_token() &&
+ParGCRareEvent_lock->owned_by_self();
+}
+return false;
+}
+#endif
+// Check reachability of the given heap address in CMS generation,
+// treating all other generations as roots.
+bool CMSCollector::is_cms_reachable(HeapWord* addr) {
+// We could "guarantee" below, rather than assert, but i'll
+// leave these as "asserts" so that an adventurous debugger
+// could try this in the product build provided some subset of
+// the conditions were met, provided they were intersted in the
+// results and knew that the computation below wouldn't interfere
+// with other concurrent computations mutating the structures
+// being read or written.
+assert(SafepointSynchronize::is_at_safepoint(),
+"Else mutations in object graph will make answer suspect");
+assert(have_cms_token(), "Should hold cms token");
+assert(haveFreelistLocks(), "must hold free list locks");
+assert_lock_strong(bitMapLock());
+// Clear the marking bit map array before starting, but, just
+// for kicks, first report if the given address is already marked
+gclog_or_tty->print_cr("Start: Address 0x%x is%s marked", addr,
+_markBitMap.isMarked(addr) ? "" : " not");
+if (verify_after_remark()) {
+MutexLockerEx x(verification_mark_bm()->lock(), Mutex::_no_safepoint_check_flag);
+bool result = verification_mark_bm()->isMarked(addr);
+gclog_or_tty->print_cr("TransitiveMark: Address 0x%x %s marked", addr,
+result ? "IS" : "is NOT");
+return result;
+} else {
+gclog_or_tty->print_cr("Could not compute result");
+return false;
+}
+}
+////////////////////////////////////////////////////////
+// CMS Verification Support
+////////////////////////////////////////////////////////
+// Following the remark phase, the following invariant
+// should hold -- each object in the CMS heap which is
+// marked in markBitMap() should be marked in the verification_mark_bm().
+class VerifyMarkedClosure: public BitMapClosure {
+CMSBitMap* _marks;
+bool       _failed;
+public:
+VerifyMarkedClosure(CMSBitMap* bm): _marks(bm), _failed(false) {}
+void do_bit(size_t offset) {
+HeapWord* addr = _marks->offsetToHeapWord(offset);
+if (!_marks->isMarked(addr)) {
+oop(addr)->print();
+gclog_or_tty->print_cr(" ("INTPTR_FORMAT" should have been marked)", addr);
+_failed = true;
+}
+}
+bool failed() { return _failed; }
+};
+bool CMSCollector::verify_after_remark() {
+gclog_or_tty->print(" [Verifying CMS Marking... ");
+MutexLockerEx ml(verification_mark_bm()->lock(), Mutex::_no_safepoint_check_flag);
+static bool init = false;
+assert(SafepointSynchronize::is_at_safepoint(),
+"Else mutations in object graph will make answer suspect");
+assert(have_cms_token(),
+"Else there may be mutual interference in use of "
+" verification data structures");
+assert(_collectorState > Marking && _collectorState <= Sweeping,
+"Else marking info checked here may be obsolete");
+assert(haveFreelistLocks(), "must hold free list locks");
+assert_lock_strong(bitMapLock());
+// Allocate marking bit map if not already allocated
+if (!init) { // first time
+if (!verification_mark_bm()->allocate(_span)) {
+return false;
+}
+init = true;
+}
+assert(verification_mark_stack()->isEmpty(), "Should be empty");
+// Turn off refs discovery -- so we will be tracing through refs.
+// This is as intended, because by this time
+// GC must already have cleared any refs that need to be cleared,
+// and traced those that need to be marked; moreover,
+// the marking done here is not going to intefere in any
+// way with the marking information used by GC.
+NoRefDiscovery no_discovery(ref_processor());
+COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact;)
+// Clear any marks from a previous round
+verification_mark_bm()->clear_all();
+assert(verification_mark_stack()->isEmpty(), "markStack should be empty");
+assert(overflow_list_is_empty(), "overflow list should be empty");
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+gch->ensure_parsability(false);  // fill TLABs, but no need to retire them
+// Update the saved marks which may affect the root scans.
+gch->save_marks();
+if (CMSRemarkVerifyVariant == 1) {
+// In this first variant of verification, we complete
+// all marking, then check if the new marks-verctor is
+// a subset of the CMS marks-vector.
+verify_after_remark_work_1();
+} else if (CMSRemarkVerifyVariant == 2) {
+// In this second variant of verification, we flag an error
+// (i.e. an object reachable in the new marks-vector not reachable
+// in the CMS marks-vector) immediately, also indicating the
+// identify of an object (A) that references the unmarked object (B) --
+// presumably, a mutation to A failed to be picked up by preclean/remark?
+verify_after_remark_work_2();
+} else {
+warning("Unrecognized value %d for CMSRemarkVerifyVariant",
+CMSRemarkVerifyVariant);
+}
+gclog_or_tty->print(" done] ");
+return true;
+}
+void CMSCollector::verify_after_remark_work_1() {
+ResourceMark rm;
+HandleMark  hm;
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+// Mark from roots one level into CMS
+MarkRefsIntoClosure notOlder(_span, verification_mark_bm(), true /* nmethods */);
+gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel.
+gch->gen_process_strong_roots(_cmsGen->level(),
+true,   // younger gens are roots
+true,   // collecting perm gen
+SharedHeap::ScanningOption(roots_scanning_options()),
+NULL, &notOlder);
+// Now mark from the roots
+assert(_revisitStack.isEmpty(), "Should be empty");
+MarkFromRootsClosure markFromRootsClosure(this, _span,
+verification_mark_bm(), verification_mark_stack(), &_revisitStack,
+false /* don't yield */, true /* verifying */);
+assert(_restart_addr == NULL, "Expected pre-condition");
+verification_mark_bm()->iterate(&markFromRootsClosure);
+while (_restart_addr != NULL) {
+// Deal with stack overflow: by restarting at the indicated
+// address.
+HeapWord* ra = _restart_addr;
+markFromRootsClosure.reset(ra);
+_restart_addr = NULL;
+verification_mark_bm()->iterate(&markFromRootsClosure, ra, _span.end());
+}
+assert(verification_mark_stack()->isEmpty(), "Should have been drained");
+verify_work_stacks_empty();
+// Should reset the revisit stack above, since no class tree
+// surgery is forthcoming.
+_revisitStack.reset(); // throwing away all contents
+// Marking completed -- now verify that each bit marked in
+// verification_mark_bm() is also marked in markBitMap(); flag all
+// errors by printing corresponding objects.
+VerifyMarkedClosure vcl(markBitMap());
+verification_mark_bm()->iterate(&vcl);
+if (vcl.failed()) {
+gclog_or_tty->print("Verification failed");
+Universe::heap()->print();
+fatal(" ... aborting");
+}
+}
+void CMSCollector::verify_after_remark_work_2() {
+ResourceMark rm;
+HandleMark  hm;
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+// Mark from roots one level into CMS
+MarkRefsIntoVerifyClosure notOlder(_span, verification_mark_bm(),
+markBitMap(), true /* nmethods */);
+gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel.
+gch->gen_process_strong_roots(_cmsGen->level(),
+true,   // younger gens are roots
+true,   // collecting perm gen
+SharedHeap::ScanningOption(roots_scanning_options()),
+NULL, &notOlder);
+// Now mark from the roots
+assert(_revisitStack.isEmpty(), "Should be empty");
+MarkFromRootsVerifyClosure markFromRootsClosure(this, _span,
+verification_mark_bm(), markBitMap(), verification_mark_stack());
+assert(_restart_addr == NULL, "Expected pre-condition");
+verification_mark_bm()->iterate(&markFromRootsClosure);
+while (_restart_addr != NULL) {
+// Deal with stack overflow: by restarting at the indicated
+// address.
+HeapWord* ra = _restart_addr;
+markFromRootsClosure.reset(ra);
+_restart_addr = NULL;
+verification_mark_bm()->iterate(&markFromRootsClosure, ra, _span.end());
+}
+assert(verification_mark_stack()->isEmpty(), "Should have been drained");
+verify_work_stacks_empty();
+// Should reset the revisit stack above, since no class tree
+// surgery is forthcoming.
+_revisitStack.reset(); // throwing away all contents
+// Marking completed -- now verify that each bit marked in
+// verification_mark_bm() is also marked in markBitMap(); flag all
+// errors by printing corresponding objects.
+VerifyMarkedClosure vcl(markBitMap());
+verification_mark_bm()->iterate(&vcl);
+assert(!vcl.failed(), "Else verification above should not have succeeded");
+}
+void ConcurrentMarkSweepGeneration::save_marks() {
+// delegate to CMS space
+cmsSpace()->save_marks();
+for (uint i = 0; i < ParallelGCThreads; i++) {
+_par_gc_thread_states[i]->promo.startTrackingPromotions();
+}
+}
+bool ConcurrentMarkSweepGeneration::no_allocs_since_save_marks() {
+return cmsSpace()->no_allocs_since_save_marks();
+}
+#define CMS_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix)    \
+\
+void ConcurrentMarkSweepGeneration::                            \
+oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) {   \
+cl->set_generation(this);                                     \
+cmsSpace()->oop_since_save_marks_iterate##nv_suffix(cl);      \
+cl->reset_generation();                                       \
+save_marks();                                                 \
+}
+ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DEFN)
+void
+ConcurrentMarkSweepGeneration::object_iterate_since_last_GC(ObjectClosure* blk)
+{
+// Not currently implemented; need to do the following. -- ysr.
+// dld -- I think that is used for some sort of allocation profiler.  So it
+// really means the objects allocated by the mutator since the last
+// GC.  We could potentially implement this cheaply by recording only
+// the direct allocations in a side data structure.
+//
+// I think we probably ought not to be required to support these
+// iterations at any arbitrary point; I think there ought to be some
+// call to enable/disable allocation profiling in a generation/space,
+// and the iterator ought to return the objects allocated in the
+// gen/space since the enable call, or the last iterator call (which
+// will probably be at a GC.)  That way, for gens like CM&S that would
+// require some extra data structure to support this, we only pay the
+// cost when it's in use...
+cmsSpace()->object_iterate_since_last_GC(blk);
+}
+void
+ConcurrentMarkSweepGeneration::younger_refs_iterate(OopsInGenClosure* cl) {
+cl->set_generation(this);
+younger_refs_in_space_iterate(_cmsSpace, cl);
+cl->reset_generation();
+}
+void
+ConcurrentMarkSweepGeneration::oop_iterate(MemRegion mr, OopClosure* cl) {
+if (freelistLock()->owned_by_self()) {
+Generation::oop_iterate(mr, cl);
+} else {
+MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag);
+Generation::oop_iterate(mr, cl);
+}
+}
+void
+ConcurrentMarkSweepGeneration::oop_iterate(OopClosure* cl) {
+if (freelistLock()->owned_by_self()) {
+Generation::oop_iterate(cl);
+} else {
+MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag);
+Generation::oop_iterate(cl);
+}
+}
+void
+ConcurrentMarkSweepGeneration::object_iterate(ObjectClosure* cl) {
+if (freelistLock()->owned_by_self()) {
+Generation::object_iterate(cl);
+} else {
+MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag);
+Generation::object_iterate(cl);
+}
+}
+void
+ConcurrentMarkSweepGeneration::pre_adjust_pointers() {
+}
+void
+ConcurrentMarkSweepGeneration::post_compact() {
+}
+void
+ConcurrentMarkSweepGeneration::prepare_for_verify() {
+// Fix the linear allocation blocks to look like free blocks.
+// Locks are normally acquired/released in gc_prologue/gc_epilogue, but those
+// are not called when the heap is verified during universe initialization and
+// at vm shutdown.
+if (freelistLock()->owned_by_self()) {
+cmsSpace()->prepare_for_verify();
+} else {
+MutexLockerEx fll(freelistLock(), Mutex::_no_safepoint_check_flag);
+cmsSpace()->prepare_for_verify();
+}
+}
+void
+ConcurrentMarkSweepGeneration::verify(bool allow_dirty /* ignored */) {
+// Locks are normally acquired/released in gc_prologue/gc_epilogue, but those
+// are not called when the heap is verified during universe initialization and
+// at vm shutdown.
+if (freelistLock()->owned_by_self()) {
+cmsSpace()->verify(false /* ignored */);
+} else {
+MutexLockerEx fll(freelistLock(), Mutex::_no_safepoint_check_flag);
+cmsSpace()->verify(false /* ignored */);
+}
+}
+void CMSCollector::verify(bool allow_dirty /* ignored */) {
+_cmsGen->verify(allow_dirty);
+_permGen->verify(allow_dirty);
+}
+#ifndef PRODUCT
+bool CMSCollector::overflow_list_is_empty() const {
+assert(_num_par_pushes >= 0, "Inconsistency");
+if (_overflow_list == NULL) {
+assert(_num_par_pushes == 0, "Inconsistency");
+}
+return _overflow_list == NULL;
+}
+// The methods verify_work_stacks_empty() and verify_overflow_empty()
+// merely consolidate assertion checks that appear to occur together frequently.
+void CMSCollector::verify_work_stacks_empty() const {
+assert(_markStack.isEmpty(), "Marking stack should be empty");
+assert(overflow_list_is_empty(), "Overflow list should be empty");
+}
+void CMSCollector::verify_overflow_empty() const {
+assert(overflow_list_is_empty(), "Overflow list should be empty");
+assert(no_preserved_marks(), "No preserved marks");
+}
+#endif // PRODUCT
+void CMSCollector::setup_cms_unloading_and_verification_state() {
+const  bool should_verify =    VerifyBeforeGC || VerifyAfterGC || VerifyDuringGC
+|| VerifyBeforeExit;
+const  int  rso           =    SharedHeap::SO_Symbols | SharedHeap::SO_Strings
+|   SharedHeap::SO_CodeCache;
+if (cms_should_unload_classes()) {   // Should unload classes this cycle
+remove_root_scanning_option(rso);  // Shrink the root set appropriately
+set_verifying(should_verify);    // Set verification state for this cycle
+return;                            // Nothing else needs to be done at this time
+}
+// Not unloading classes this cycle
+assert(!cms_should_unload_classes(), "Inconsitency!");
+if ((!verifying() || cms_unloaded_classes_last_cycle()) && should_verify) {
+// We were not verifying, or we _were_ unloading classes in the last cycle,
+// AND some verification options are enabled this cycle; in this case,
+// we must make sure that the deadness map is allocated if not already so,
+// and cleared (if already allocated previously --
+// CMSBitMap::sizeInBits() is used to determine if it's allocated).
+if (perm_gen_verify_bit_map()->sizeInBits() == 0) {
+if (!perm_gen_verify_bit_map()->allocate(_permGen->reserved())) {
+warning("Failed to allocate permanent generation verification CMS Bit Map;\n"
+"permanent generation verification disabled");
+return;  // Note that we leave verification disabled, so we'll retry this
+// allocation next cycle. We _could_ remember this failure
+// and skip further attempts and permanently disable verification
+// attempts if that is considered more desirable.
+}
+assert(perm_gen_verify_bit_map()->covers(_permGen->reserved()),
+"_perm_gen_ver_bit_map inconsistency?");
+} else {
+perm_gen_verify_bit_map()->clear_all();
+}
+// Include symbols, strings and code cache elements to prevent their resurrection.
+add_root_scanning_option(rso);
+set_verifying(true);
+} else if (verifying() && !should_verify) {
+// We were verifying, but some verification flags got disabled.
+set_verifying(false);
+// Exclude symbols, strings and code cache elements from root scanning to
+// reduce IM and RM pauses.
+remove_root_scanning_option(rso);
+}
+}
+#ifndef PRODUCT
+HeapWord* CMSCollector::block_start(const void* p) const {
+const HeapWord* addr = (HeapWord*)p;
+if (_span.contains(p)) {
+if (_cmsGen->cmsSpace()->is_in_reserved(addr)) {
+return _cmsGen->cmsSpace()->block_start(p);
+} else {
+assert(_permGen->cmsSpace()->is_in_reserved(addr),
+"Inconsistent _span?");
+return _permGen->cmsSpace()->block_start(p);
+}
+}
+return NULL;
+}
+#endif
+HeapWord*
+ConcurrentMarkSweepGeneration::expand_and_allocate(size_t word_size,
+bool   tlab,
+bool   parallel) {
+assert(!tlab, "Can't deal with TLAB allocation");
+MutexLockerEx x(freelistLock(), Mutex::_no_safepoint_check_flag);
+expand(word_size*HeapWordSize, MinHeapDeltaBytes,
+CMSExpansionCause::_satisfy_allocation);
+if (GCExpandToAllocateDelayMillis > 0) {
+os::sleep(Thread::current(), GCExpandToAllocateDelayMillis, false);
+}
+size_t adj_word_sz = CompactibleFreeListSpace::adjustObjectSize(word_size);
+if (parallel) {
+return cmsSpace()->par_allocate(adj_word_sz);
+} else {
+return cmsSpace()->allocate(adj_word_sz);
+}
+}
+// YSR: All of this generation expansion/shrinking stuff is an exact copy of
+// OneContigSpaceCardGeneration, which makes me wonder if we should move this
+// to CardGeneration and share it...
+void ConcurrentMarkSweepGeneration::expand(size_t bytes, size_t expand_bytes,
+CMSExpansionCause::Cause cause)
+{
+assert_locked_or_safepoint(Heap_lock);
+size_t aligned_bytes  = ReservedSpace::page_align_size_up(bytes);
+size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
+bool success = false;
+if (aligned_expand_bytes > aligned_bytes) {
+success = grow_by(aligned_expand_bytes);
+}
+if (!success) {
+success = grow_by(aligned_bytes);
+}
+if (!success) {
+size_t remaining_bytes = _virtual_space.uncommitted_size();
+if (remaining_bytes > 0) {
+success = grow_by(remaining_bytes);
+}
+}
+if (GC_locker::is_active()) {
+if (PrintGC && Verbose) {
+gclog_or_tty->print_cr("Garbage collection disabled, expanded heap instead");
+}
+}
+// remember why we expanded; this information is used
+// by shouldConcurrentCollect() when making decisions on whether to start
+// a new CMS cycle.
+if (success) {
+set_expansion_cause(cause);
+if (PrintGCDetails && Verbose) {
+gclog_or_tty->print_cr("Expanded CMS gen for %s",
+CMSExpansionCause::to_string(cause));
+}
+}
+}
+HeapWord* ConcurrentMarkSweepGeneration::expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz) {
+HeapWord* res = NULL;
+MutexLocker x(ParGCRareEvent_lock);
+while (true) {
+// Expansion by some other thread might make alloc OK now:
+res = ps->lab.alloc(word_sz);
+if (res != NULL) return res;
+// If there's not enough expansion space available, give up.
+if (_virtual_space.uncommitted_size() < (word_sz * HeapWordSize)) {
+return NULL;
+}
+// Otherwise, we try expansion.
+expand(word_sz*HeapWordSize, MinHeapDeltaBytes,
+CMSExpansionCause::_allocate_par_lab);
+// Now go around the loop and try alloc again;
+// A competing par_promote might beat us to the expansion space,
+// so we may go around the loop again if promotion fails agaion.
+if (GCExpandToAllocateDelayMillis > 0) {
+os::sleep(Thread::current(), GCExpandToAllocateDelayMillis, false);
+}
+}
+}
+bool ConcurrentMarkSweepGeneration::expand_and_ensure_spooling_space(
+PromotionInfo* promo) {
+MutexLocker x(ParGCRareEvent_lock);
+size_t refill_size_bytes = promo->refillSize() * HeapWordSize;
+while (true) {
+// Expansion by some other thread might make alloc OK now:
+if (promo->ensure_spooling_space()) {
+assert(promo->has_spooling_space(),
+"Post-condition of successful ensure_spooling_space()");
+return true;
+}
+// If there's not enough expansion space available, give up.
+if (_virtual_space.uncommitted_size() < refill_size_bytes) {
+return false;
+}
+// Otherwise, we try expansion.
+expand(refill_size_bytes, MinHeapDeltaBytes,
+CMSExpansionCause::_allocate_par_spooling_space);
+// Now go around the loop and try alloc again;
+// A competing allocation might beat us to the expansion space,
+// so we may go around the loop again if allocation fails again.
+if (GCExpandToAllocateDelayMillis > 0) {
+os::sleep(Thread::current(), GCExpandToAllocateDelayMillis, false);
+}
+}
+}
+void ConcurrentMarkSweepGeneration::shrink(size_t bytes) {
+assert_locked_or_safepoint(Heap_lock);
+size_t size = ReservedSpace::page_align_size_down(bytes);
+if (size > 0) {
+shrink_by(size);
+}
+}
+bool ConcurrentMarkSweepGeneration::grow_by(size_t bytes) {
+assert_locked_or_safepoint(Heap_lock);
+bool result = _virtual_space.expand_by(bytes);
+if (result) {
+HeapWord* old_end = _cmsSpace->end();
+size_t new_word_size =
+heap_word_size(_virtual_space.committed_size());
+MemRegion mr(_cmsSpace->bottom(), new_word_size);
+_bts->resize(new_word_size);  // resize the block offset shared array
+Universe::heap()->barrier_set()->resize_covered_region(mr);
+// Hmmmm... why doesn't CFLS::set_end verify locking?
+// This is quite ugly; FIX ME XXX
+_cmsSpace->assert_locked();
+_cmsSpace->set_end((HeapWord*)_virtual_space.high());
+// update the space and generation capacity counters
+if (UsePerfData) {
+_space_counters->update_capacity();
+_gen_counters->update_all();
+}
+if (Verbose && PrintGC) {
+size_t new_mem_size = _virtual_space.committed_size();
+size_t old_mem_size = new_mem_size - bytes;
+gclog_or_tty->print_cr("Expanding %s from %ldK by %ldK to %ldK",
+name(), old_mem_size/K, bytes/K, new_mem_size/K);
+}
+}
+return result;
+}
+bool ConcurrentMarkSweepGeneration::grow_to_reserved() {
+assert_locked_or_safepoint(Heap_lock);
+bool success = true;
+const size_t remaining_bytes = _virtual_space.uncommitted_size();
+if (remaining_bytes > 0) {
+success = grow_by(remaining_bytes);
+DEBUG_ONLY(if (!success) warning("grow to reserved failed");)
+}
+return success;
+}
+void ConcurrentMarkSweepGeneration::shrink_by(size_t bytes) {
+assert_locked_or_safepoint(Heap_lock);
+assert_lock_strong(freelistLock());
+// XXX Fix when compaction is implemented.
+warning("Shrinking of CMS not yet implemented");
+return;
+}
+// Simple ctor/dtor wrapper for accounting & timer chores around concurrent
+// phases.
+class CMSPhaseAccounting: public StackObj {
+public:
+CMSPhaseAccounting(CMSCollector *collector,
+const char *phase,
+bool print_cr = true);
+~CMSPhaseAccounting();
+private:
+CMSCollector *_collector;
+const char *_phase;
+elapsedTimer _wallclock;
+bool _print_cr;
+public:
+// Not MT-safe; so do not pass around these StackObj's
+// where they may be accessed by other threads.
+jlong wallclock_millis() {
+assert(_wallclock.is_active(), "Wall clock should not stop");
+_wallclock.stop();  // to record time
+jlong ret = _wallclock.milliseconds();
+_wallclock.start(); // restart
+return ret;
+}
+};
+CMSPhaseAccounting::CMSPhaseAccounting(CMSCollector *collector,
+const char *phase,
+bool print_cr) :
+_collector(collector), _phase(phase), _print_cr(print_cr) {
+if (PrintCMSStatistics != 0) {
+_collector->resetYields();
+}
+if (PrintGCDetails && PrintGCTimeStamps) {
+gclog_or_tty->date_stamp(PrintGCDateStamps);
+gclog_or_tty->stamp();
+gclog_or_tty->print_cr(": [%s-concurrent-%s-start]",
+_collector->cmsGen()->short_name(), _phase);
+}
+_collector->resetTimer();
+_wallclock.start();
+_collector->startTimer();
+}
+CMSPhaseAccounting::~CMSPhaseAccounting() {
+assert(_wallclock.is_active(), "Wall clock should not have stopped");
+_collector->stopTimer();
+_wallclock.stop();
+if (PrintGCDetails) {
+gclog_or_tty->date_stamp(PrintGCDateStamps);
+if (PrintGCTimeStamps) {
+gclog_or_tty->stamp();
+gclog_or_tty->print(": ");
+}
+gclog_or_tty->print("[%s-concurrent-%s: %3.3f/%3.3f secs]",
+_collector->cmsGen()->short_name(),
+_phase, _collector->timerValue(), _wallclock.seconds());
+if (_print_cr) {
+gclog_or_tty->print_cr("");
+}
+if (PrintCMSStatistics != 0) {
+gclog_or_tty->print_cr(" (CMS-concurrent-%s yielded %d times)", _phase,
+_collector->yields());
+}
+}
+}
+// CMS work
+// Checkpoint the roots into this generation from outside
+// this generation. [Note this initial checkpoint need only
+// be approximate -- we'll do a catch up phase subsequently.]
+void CMSCollector::checkpointRootsInitial(bool asynch) {
+assert(_collectorState == InitialMarking, "Wrong collector state");
+check_correct_thread_executing();
+ReferenceProcessor* rp = ref_processor();
+SpecializationStats::clear();
+assert(_restart_addr == NULL, "Control point invariant");
+if (asynch) {
+// acquire locks for subsequent manipulations
+MutexLockerEx x(bitMapLock(),
+Mutex::_no_safepoint_check_flag);
+checkpointRootsInitialWork(asynch);
+rp->verify_no_references_recorded();
+rp->enable_discovery(); // enable ("weak") refs discovery
+_collectorState = Marking;
+} else {
+// (Weak) Refs discovery: this is controlled from genCollectedHeap::do_collection
+// which recognizes if we are a CMS generation, and doesn't try to turn on
+// discovery; verify that they aren't meddling.
+assert(!rp->discovery_is_atomic(),
+"incorrect setting of discovery predicate");
+assert(!rp->discovery_enabled(), "genCollectedHeap shouldn't control "
+"ref discovery for this generation kind");
+// already have locks
+checkpointRootsInitialWork(asynch);
+rp->enable_discovery(); // now enable ("weak") refs discovery
+_collectorState = Marking;
+}
+SpecializationStats::print();
+}
+void CMSCollector::checkpointRootsInitialWork(bool asynch) {
+assert(SafepointSynchronize::is_at_safepoint(), "world should be stopped");
+assert(_collectorState == InitialMarking, "just checking");
+// If there has not been a GC[n-1] since last GC[n] cycle completed,
+// precede our marking with a collection of all
+// younger generations to keep floating garbage to a minimum.
+// XXX: we won't do this for now -- it's an optimization to be done later.
+// already have locks
+assert_lock_strong(bitMapLock());
+assert(_markBitMap.isAllClear(), "was reset at end of previous cycle");
+// Setup the verification and class unloading state for this
+// CMS collection cycle.
+setup_cms_unloading_and_verification_state();
+NOT_PRODUCT(TraceTime t("\ncheckpointRootsInitialWork",
+PrintGCDetails && Verbose, true, gclog_or_tty);)
+if (UseAdaptiveSizePolicy) {
+size_policy()->checkpoint_roots_initial_begin();
+}
+// Reset all the PLAB chunk arrays if necessary.
+if (_survivor_plab_array != NULL && !CMSPLABRecordAlways) {
+reset_survivor_plab_arrays();
+}
+ResourceMark rm;
+HandleMark  hm;
+FalseClosure falseClosure;
+// In the case of a synchronous collection, we will elide the
+// remark step, so it's important to catch all the nmethod oops
+// in this step; hence the last argument to the constrcutor below.
+MarkRefsIntoClosure notOlder(_span, &_markBitMap, !asynch /* nmethods */);
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+verify_work_stacks_empty();
+verify_overflow_empty();
+gch->ensure_parsability(false);  // fill TLABs, but no need to retire them
+// Update the saved marks which may affect the root scans.
+gch->save_marks();
+// weak reference processing has not started yet.
+ref_processor()->set_enqueuing_is_done(false);
+{
+COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact;)
+gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel.
+gch->gen_process_strong_roots(_cmsGen->level(),
+true,   // younger gens are roots
+true,   // collecting perm gen
+SharedHeap::ScanningOption(roots_scanning_options()),
+NULL, &notOlder);
+}
+// Clear mod-union table; it will be dirtied in the prologue of
+// CMS generation per each younger generation collection.
+assert(_modUnionTable.isAllClear(),
+"Was cleared in most recent final checkpoint phase"
+" or no bits are set in the gc_prologue before the start of the next "
+"subsequent marking phase.");
+// Temporarily disabled, since pre/post-consumption closures don't
+// care about precleaned cards
+#if 0
+{
+MemRegion mr = MemRegion((HeapWord*)_virtual_space.low(),
+(HeapWord*)_virtual_space.high());
+_ct->ct_bs()->preclean_dirty_cards(mr);
+}
+#endif
+// Save the end of the used_region of the constituent generations
+// to be used to limit the extent of sweep in each generation.
+save_sweep_limits();
+if (UseAdaptiveSizePolicy) {
+size_policy()->checkpoint_roots_initial_end(gch->gc_cause());
+}
+verify_overflow_empty();
+}
+bool CMSCollector::markFromRoots(bool asynch) {
+// we might be tempted to assert that:
+// assert(asynch == !SafepointSynchronize::is_at_safepoint(),
+//        "inconsistent argument?");
+// However that wouldn't be right, because it's possible that
+// a safepoint is indeed in progress as a younger generation
+// stop-the-world GC happens even as we mark in this generation.
+assert(_collectorState == Marking, "inconsistent state?");
+check_correct_thread_executing();
+verify_overflow_empty();
+bool res;
+if (asynch) {
+// Start the timers for adaptive size policy for the concurrent phases
+// Do it here so that the foreground MS can use the concurrent
+// timer since a foreground MS might has the sweep done concurrently
+// or STW.
+if (UseAdaptiveSizePolicy) {
+size_policy()->concurrent_marking_begin();
+}
+// Weak ref discovery note: We may be discovering weak
+// refs in this generation concurrent (but interleaved) with
+// weak ref discovery by a younger generation collector.
+CMSTokenSyncWithLocks ts(true, bitMapLock());
+TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
+CMSPhaseAccounting pa(this, "mark", !PrintGCDetails);
+res = markFromRootsWork(asynch);
+if (res) {
+_collectorState = Precleaning;
+} else { // We failed and a foreground collection wants to take over
+assert(_foregroundGCIsActive, "internal state inconsistency");
+assert(_restart_addr == NULL,  "foreground will restart from scratch");
+if (PrintGCDetails) {
+gclog_or_tty->print_cr("bailing out to foreground collection");
+}
+}
+if (UseAdaptiveSizePolicy) {
+size_policy()->concurrent_marking_end();
+}
+} else {
+assert(SafepointSynchronize::is_at_safepoint(),
+"inconsistent with asynch == false");
+if (UseAdaptiveSizePolicy) {
+size_policy()->ms_collection_marking_begin();
+}
+// already have locks
+res = markFromRootsWork(asynch);
+_collectorState = FinalMarking;
+if (UseAdaptiveSizePolicy) {
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+size_policy()->ms_collection_marking_end(gch->gc_cause());
+}
+}
+verify_overflow_empty();
+return res;
+}
+bool CMSCollector::markFromRootsWork(bool asynch) {
+// iterate over marked bits in bit map, doing a full scan and mark
+// from these roots using the following algorithm:
+// . if oop is to the right of the current scan pointer,
+//   mark corresponding bit (we'll process it later)
+// . else (oop is to left of current scan pointer)
+//   push oop on marking stack
+// . drain the marking stack
+// Note that when we do a marking step we need to hold the
+// bit map lock -- recall that direct allocation (by mutators)
+// and promotion (by younger generation collectors) is also
+// marking the bit map. [the so-called allocate live policy.]
+// Because the implementation of bit map marking is not
+// robust wrt simultaneous marking of bits in the same word,
+// we need to make sure that there is no such interference
+// between concurrent such updates.
+// already have locks
+assert_lock_strong(bitMapLock());
+// Clear the revisit stack, just in case there are any
+// obsolete contents from a short-circuited previous CMS cycle.
+_revisitStack.reset();
+verify_work_stacks_empty();
+verify_overflow_empty();
+assert(_revisitStack.isEmpty(), "tabula rasa");
+bool result = false;
+if (CMSConcurrentMTEnabled && ParallelCMSThreads > 0) {
+result = do_marking_mt(asynch);
+} else {
+result = do_marking_st(asynch);
+}
+return result;
+}
+// Forward decl
+class CMSConcMarkingTask;
+class CMSConcMarkingTerminator: public ParallelTaskTerminator {
+CMSCollector*       _collector;
+CMSConcMarkingTask* _task;
+bool _yield;
+protected:
+virtual void yield();
+public:
+// "n_threads" is the number of threads to be terminated.
+// "queue_set" is a set of work queues of other threads.
+// "collector" is the CMS collector associated with this task terminator.
+// "yield" indicates whether we need the gang as a whole to yield.
+CMSConcMarkingTerminator(int n_threads, TaskQueueSetSuper* queue_set,
+CMSCollector* collector, bool yield) :
+ParallelTaskTerminator(n_threads, queue_set),
+_collector(collector),
+_yield(yield) { }
+void set_task(CMSConcMarkingTask* task) {
+_task = task;
+}
+};
+// MT Concurrent Marking Task
+class CMSConcMarkingTask: public YieldingFlexibleGangTask {
+CMSCollector* _collector;
+YieldingFlexibleWorkGang* _workers;        // the whole gang
+int           _n_workers;                  // requested/desired # workers
+bool          _asynch;
+bool          _result;
+CompactibleFreeListSpace*  _cms_space;
+CompactibleFreeListSpace* _perm_space;
+HeapWord*     _global_finger;
+//  Exposed here for yielding support
+Mutex* const _bit_map_lock;
+// The per thread work queues, available here for stealing
+OopTaskQueueSet*  _task_queues;
+CMSConcMarkingTerminator _term;
+public:
+CMSConcMarkingTask(CMSCollector* collector,
+CompactibleFreeListSpace* cms_space,
+CompactibleFreeListSpace* perm_space,
+bool asynch, int n_workers,
+YieldingFlexibleWorkGang* workers,
+OopTaskQueueSet* task_queues):
+YieldingFlexibleGangTask("Concurrent marking done multi-threaded"),
+_collector(collector),
+_cms_space(cms_space),
+_perm_space(perm_space),
+_asynch(asynch), _n_workers(n_workers), _result(true),
+_workers(workers), _task_queues(task_queues),
+_term(n_workers, task_queues, _collector, asynch),
+_bit_map_lock(collector->bitMapLock())
+{
+assert(n_workers <= workers->total_workers(),
+"Else termination won't work correctly today"); // XXX FIX ME!
+_requested_size = n_workers;
+_term.set_task(this);
+assert(_cms_space->bottom() < _perm_space->bottom(),
+"Finger incorrectly initialized below");
+_global_finger = _cms_space->bottom();
+}
+OopTaskQueueSet* task_queues()  { return _task_queues; }
+OopTaskQueue* work_queue(int i) { return task_queues()->queue(i); }
+HeapWord** global_finger_addr() { return &_global_finger; }
+CMSConcMarkingTerminator* terminator() { return &_term; }
+void work(int i);
+virtual void coordinator_yield();  // stuff done by coordinator
+bool result() { return _result; }
+void reset(HeapWord* ra) {
+_term.reset_for_reuse();
+}
+static bool get_work_from_overflow_stack(CMSMarkStack* ovflw_stk,
+OopTaskQueue* work_q);
+private:
+void do_scan_and_mark(int i, CompactibleFreeListSpace* sp);
+void do_work_steal(int i);
+void bump_global_finger(HeapWord* f);
+};
+void CMSConcMarkingTerminator::yield() {
+if (ConcurrentMarkSweepThread::should_yield() &&
+!_collector->foregroundGCIsActive() &&
+_yield) {
+_task->yield();
+} else {
+ParallelTaskTerminator::yield();
+}
+}
+////////////////////////////////////////////////////////////////
+// Concurrent Marking Algorithm Sketch
+////////////////////////////////////////////////////////////////
+// Until all tasks exhausted (both spaces):
+// -- claim next available chunk
+// -- bump global finger via CAS
+// -- find first object that starts in this chunk
+//    and start scanning bitmap from that position
+// -- scan marked objects for oops
+// -- CAS-mark target, and if successful:
+//    . if target oop is above global finger (volatile read)
+//      nothing to do
+//    . if target oop is in chunk and above local finger
+//        then nothing to do
+//    . else push on work-queue
+// -- Deal with possible overflow issues:
+//    . local work-queue overflow causes stuff to be pushed on
+//      global (common) overflow queue
+//    . always first empty local work queue
+//    . then get a batch of oops from global work queue if any
+//    . then do work stealing
+// -- When all tasks claimed (both spaces)
+//    and local work queue empty,
+//    then in a loop do:
+//    . check global overflow stack; steal a batch of oops and trace
+//    . try to steal from other threads oif GOS is empty
+//    . if neither is available, offer termination
+// -- Terminate and return result
+//
+void CMSConcMarkingTask::work(int i) {
+elapsedTimer _timer;
+ResourceMark rm;
+HandleMark hm;
+DEBUG_ONLY(_collector->verify_overflow_empty();)
+// Before we begin work, our work queue should be empty
+assert(work_queue(i)->size() == 0, "Expected to be empty");
+// Scan the bitmap covering _cms_space, tracing through grey objects.
+_timer.start();
+do_scan_and_mark(i, _cms_space);
+_timer.stop();
+if (PrintCMSStatistics != 0) {
+gclog_or_tty->print_cr("Finished cms space scanning in %dth thread: %3.3f sec",
+i, _timer.seconds()); // XXX: need xxx/xxx type of notation, two timers
+}
+// ... do the same for the _perm_space
+_timer.reset();
+_timer.start();
+do_scan_and_mark(i, _perm_space);
+_timer.stop();
+if (PrintCMSStatistics != 0) {
+gclog_or_tty->print_cr("Finished perm space scanning in %dth thread: %3.3f sec",
+i, _timer.seconds()); // XXX: need xxx/xxx type of notation, two timers
+}
+// ... do work stealing
+_timer.reset();
+_timer.start();
+do_work_steal(i);
+_timer.stop();
+if (PrintCMSStatistics != 0) {
+gclog_or_tty->print_cr("Finished work stealing in %dth thread: %3.3f sec",
+i, _timer.seconds()); // XXX: need xxx/xxx type of notation, two timers
+}
+assert(_collector->_markStack.isEmpty(), "Should have been emptied");
+assert(work_queue(i)->size() == 0, "Should have been emptied");
+// Note that under the current task protocol, the
+// following assertion is true even of the spaces
+// expanded since the completion of the concurrent
+// marking. XXX This will likely change under a strict
+// ABORT semantics.
+assert(_global_finger >  _cms_space->end() &&
+_global_finger >= _perm_space->end(),
+"All tasks have been completed");
+DEBUG_ONLY(_collector->verify_overflow_empty();)
+}
+void CMSConcMarkingTask::bump_global_finger(HeapWord* f) {
+HeapWord* read = _global_finger;
+HeapWord* cur  = read;
+while (f > read) {
+cur = read;
+read = (HeapWord*) Atomic::cmpxchg_ptr(f, &_global_finger, cur);
+if (cur == read) {
+// our cas succeeded
+assert(_global_finger >= f, "protocol consistency");
+break;
+}
+}
+}
+// This is really inefficient, and should be redone by
+// using (not yet available) block-read and -write interfaces to the
+// stack and the work_queue. XXX FIX ME !!!
+bool CMSConcMarkingTask::get_work_from_overflow_stack(CMSMarkStack* ovflw_stk,
+OopTaskQueue* work_q) {
+// Fast lock-free check
+if (ovflw_stk->length() == 0) {
+return false;
+}
+assert(work_q->size() == 0, "Shouldn't steal");
+MutexLockerEx ml(ovflw_stk->par_lock(),
+Mutex::_no_safepoint_check_flag);
+// Grab up to 1/4 the size of the work queue
+size_t num = MIN2((size_t)work_q->max_elems()/4,
+(size_t)ParGCDesiredObjsFromOverflowList);
+num = MIN2(num, ovflw_stk->length());
+for (int i = (int) num; i > 0; i--) {
+oop cur = ovflw_stk->pop();
+assert(cur != NULL, "Counted wrong?");
+work_q->push(cur);
+}
+return num > 0;
+}
+void CMSConcMarkingTask::do_scan_and_mark(int i, CompactibleFreeListSpace* sp) {
+SequentialSubTasksDone* pst = sp->conc_par_seq_tasks();
+int n_tasks = pst->n_tasks();
+// We allow that there may be no tasks to do here because
+// we are restarting after a stack overflow.
+assert(pst->valid() || n_tasks == 0, "Uninitializd use?");
+int nth_task = 0;
+HeapWord* start = sp->bottom();
+size_t chunk_size = sp->marking_task_size();
+while (!pst->is_task_claimed(/* reference */ nth_task)) {
+// Having claimed the nth task in this space,
+// compute the chunk that it corresponds to:
+MemRegion span = MemRegion(start + nth_task*chunk_size,
+start + (nth_task+1)*chunk_size);
+// Try and bump the global finger via a CAS;
+// note that we need to do the global finger bump
+// _before_ taking the intersection below, because
+// the task corresponding to that region will be
+// deemed done even if the used_region() expands
+// because of allocation -- as it almost certainly will
+// during start-up while the threads yield in the
+// closure below.
+HeapWord* finger = span.end();
+bump_global_finger(finger);   // atomically
+// There are null tasks here corresponding to chunks
+// beyond the "top" address of the space.
+span = span.intersection(sp->used_region());
+if (!span.is_empty()) {  // Non-null task
+// We want to skip the first object because
+// the protocol is to scan any object in its entirety
+// that _starts_ in this span; a fortiori, any
+// object starting in an earlier span is scanned
+// as part of an earlier claimed task.
+// Below we use the "careful" version of block_start
+// so we do not try to navigate uninitialized objects.
+HeapWord* prev_obj = sp->block_start_careful(span.start());
+// Below we use a variant of block_size that uses the
+// Printezis bits to avoid waiting for allocated
+// objects to become initialized/parsable.
+while (prev_obj < span.start()) {
+size_t sz = sp->block_size_no_stall(prev_obj, _collector);
+if (sz > 0) {
+prev_obj += sz;
+} else {
+// In this case we may end up doing a bit of redundant
+// scanning, but that appears unavoidable, short of
+// locking the free list locks; see bug 6324141.
+break;
+}
+}
+if (prev_obj < span.end()) {
+MemRegion my_span = MemRegion(prev_obj, span.end());
+// Do the marking work within a non-empty span --
+// the last argument to the constructor indicates whether the
+// iteration should be incremental with periodic yields.
+Par_MarkFromRootsClosure cl(this, _collector, my_span,
+&_collector->_markBitMap,
+work_queue(i),
+&_collector->_markStack,
+&_collector->_revisitStack,
+_asynch);
+_collector->_markBitMap.iterate(&cl, my_span.start(), my_span.end());
+} // else nothing to do for this task
+}   // else nothing to do for this task
+}
+// We'd be tempted to assert here that since there are no
+// more tasks left to claim in this space, the global_finger
+// must exceed space->top() and a fortiori space->end(). However,
+// that would not quite be correct because the bumping of
+// global_finger occurs strictly after the claiming of a task,
+// so by the time we reach here the global finger may not yet
+// have been bumped up by the thread that claimed the last
+// task.
+pst->all_tasks_completed();
+}
+class Par_ConcMarkingClosure: public OopClosure {
+CMSCollector* _collector;
+MemRegion     _span;
+CMSBitMap*    _bit_map;
+CMSMarkStack* _overflow_stack;
+CMSMarkStack* _revisit_stack;     // XXXXXX Check proper use
+OopTaskQueue* _work_queue;
+public:
+Par_ConcMarkingClosure(CMSCollector* collector, OopTaskQueue* work_queue,
+CMSBitMap* bit_map, CMSMarkStack* overflow_stack):
+_collector(collector),
+_span(_collector->_span),
+_work_queue(work_queue),
+_bit_map(bit_map),
+_overflow_stack(overflow_stack) { }   // need to initialize revisit stack etc.
+void do_oop(oop* p);
+void trim_queue(size_t max);
+void handle_stack_overflow(HeapWord* lost);
+};
+// Grey object rescan during work stealing phase --
+// the salient assumption here is that stolen oops must
+// always be initialized, so we do not need to check for
+// uninitialized objects before scanning here.
+void Par_ConcMarkingClosure::do_oop(oop* p) {
+oop    this_oop = *p;
+assert(this_oop->is_oop_or_null(),
+"expected an oop or NULL");
+HeapWord* addr = (HeapWord*)this_oop;
+// Check if oop points into the CMS generation
+// and is not marked
+if (_span.contains(addr) && !_bit_map->isMarked(addr)) {
+// a white object ...
+// If we manage to "claim" the object, by being the
+// first thread to mark it, then we push it on our
+// marking stack
+if (_bit_map->par_mark(addr)) {     // ... now grey
+// push on work queue (grey set)
+bool simulate_overflow = false;
+NOT_PRODUCT(
+if (CMSMarkStackOverflowALot &&
+_collector->simulate_overflow()) {
+// simulate a stack overflow
+simulate_overflow = true;
+}
+)
+if (simulate_overflow ||
+!(_work_queue->push(this_oop) || _overflow_stack->par_push(this_oop))) {
+// stack overflow
+if (PrintCMSStatistics != 0) {
+gclog_or_tty->print_cr("CMS marking stack overflow (benign) at "
+SIZE_FORMAT, _overflow_stack->capacity());
+}
+// We cannot assert that the overflow stack is full because
+// it may have been emptied since.
+assert(simulate_overflow ||
+_work_queue->size() == _work_queue->max_elems(),
+"Else push should have succeeded");
+handle_stack_overflow(addr);
+}
+} // Else, some other thread got there first
+}
+}
+void Par_ConcMarkingClosure::trim_queue(size_t max) {
+while (_work_queue->size() > max) {
+oop new_oop;
+if (_work_queue->pop_local(new_oop)) {
+assert(new_oop->is_oop(), "Should be an oop");
+assert(_bit_map->isMarked((HeapWord*)new_oop), "Grey object");
+assert(_span.contains((HeapWord*)new_oop), "Not in span");
+assert(new_oop->is_parsable(), "Should be parsable");
+new_oop->oop_iterate(this);  // do_oop() above
+}
+}
+}
+// Upon stack overflow, we discard (part of) the stack,
+// remembering the least address amongst those discarded
+// in CMSCollector's _restart_address.
+void Par_ConcMarkingClosure::handle_stack_overflow(HeapWord* lost) {
+// We need to do this under a mutex to prevent other
+// workers from interfering with the expansion below.
+MutexLockerEx ml(_overflow_stack->par_lock(),
+Mutex::_no_safepoint_check_flag);
+// Remember the least grey address discarded
+HeapWord* ra = (HeapWord*)_overflow_stack->least_value(lost);
+_collector->lower_restart_addr(ra);
+_overflow_stack->reset();  // discard stack contents
+_overflow_stack->expand(); // expand the stack if possible
+}
+void CMSConcMarkingTask::do_work_steal(int i) {
+OopTaskQueue* work_q = work_queue(i);
+oop obj_to_scan;
+CMSBitMap* bm = &(_collector->_markBitMap);
+CMSMarkStack* ovflw = &(_collector->_markStack);
+int* seed = _collector->hash_seed(i);
+Par_ConcMarkingClosure cl(_collector, work_q, bm, ovflw);
+while (true) {
+cl.trim_queue(0);
+assert(work_q->size() == 0, "Should have been emptied above");
+if (get_work_from_overflow_stack(ovflw, work_q)) {
+// Can't assert below because the work obtained from the
+// overflow stack may already have been stolen from us.
+// assert(work_q->size() > 0, "Work from overflow stack");
+continue;
+} else if (task_queues()->steal(i, seed, /* reference */ obj_to_scan)) {
+assert(obj_to_scan->is_oop(), "Should be an oop");
+assert(bm->isMarked((HeapWord*)obj_to_scan), "Grey object");
+obj_to_scan->oop_iterate(&cl);
+} else if (terminator()->offer_termination()) {
+assert(work_q->size() == 0, "Impossible!");
+break;
+}
+}
+}
+// This is run by the CMS (coordinator) thread.
+void CMSConcMarkingTask::coordinator_yield() {
+assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
+"CMS thread should hold CMS token");
+// First give up the locks, then yield, then re-lock
+// We should probably use a constructor/destructor idiom to
+// do this unlock/lock or modify the MutexUnlocker class to
+// serve our purpose. XXX
+assert_lock_strong(_bit_map_lock);
+_bit_map_lock->unlock();
+ConcurrentMarkSweepThread::desynchronize(true);
+ConcurrentMarkSweepThread::acknowledge_yield_request();
+_collector->stopTimer();
+if (PrintCMSStatistics != 0) {
+_collector->incrementYields();
+}
+_collector->icms_wait();
+// It is possible for whichever thread initiated the yield request
+// not to get a chance to wake up and take the bitmap lock between
+// this thread releasing it and reacquiring it. So, while the
+// should_yield() flag is on, let's sleep for a bit to give the
+// other thread a chance to wake up. The limit imposed on the number
+// of iterations is defensive, to avoid any unforseen circumstances
+// putting us into an infinite loop. Since it's always been this
+// (coordinator_yield()) method that was observed to cause the
+// problem, we are using a parameter (CMSCoordinatorYieldSleepCount)
+// which is by default non-zero. For the other seven methods that
+// also perform the yield operation, as are using a different
+// parameter (CMSYieldSleepCount) which is by default zero. This way we
+// can enable the sleeping for those methods too, if necessary.
+// See 6442774.
+//
+// We really need to reconsider the synchronization between the GC
+// thread and the yield-requesting threads in the future and we
+// should really use wait/notify, which is the recommended
+// way of doing this type of interaction. Additionally, we should
+// consolidate the eight methods that do the yield operation and they
+// are almost identical into one for better maintenability and
+// readability. See 6445193.
+//
+// Tony 2006.06.29
+for (unsigned i = 0; i < CMSCoordinatorYieldSleepCount &&
+ConcurrentMarkSweepThread::should_yield() &&
+!CMSCollector::foregroundGCIsActive(); ++i) {
+os::sleep(Thread::current(), 1, false);
+ConcurrentMarkSweepThread::acknowledge_yield_request();
+}
+ConcurrentMarkSweepThread::synchronize(true);
+_bit_map_lock->lock_without_safepoint_check();
+_collector->startTimer();
+}
+bool CMSCollector::do_marking_mt(bool asynch) {
+assert(ParallelCMSThreads > 0 && conc_workers() != NULL, "precondition");
+// In the future this would be determined ergonomically, based
+// on #cpu's, # active mutator threads (and load), and mutation rate.
+int num_workers = ParallelCMSThreads;
+CompactibleFreeListSpace* cms_space  = _cmsGen->cmsSpace();
+CompactibleFreeListSpace* perm_space = _permGen->cmsSpace();
+CMSConcMarkingTask tsk(this, cms_space, perm_space,
+asynch, num_workers /* number requested XXX */,
+conc_workers(), task_queues());
+// Since the actual number of workers we get may be different
+// from the number we requested above, do we need to do anything different
+// below? In particular, may be we need to subclass the SequantialSubTasksDone
+// class?? XXX
+cms_space ->initialize_sequential_subtasks_for_marking(num_workers);
+perm_space->initialize_sequential_subtasks_for_marking(num_workers);
+// Refs discovery is already non-atomic.
+assert(!ref_processor()->discovery_is_atomic(), "Should be non-atomic");
+// Mutate the Refs discovery so it is MT during the
+// multi-threaded marking phase.
+ReferenceProcessorMTMutator mt(ref_processor(), num_workers > 1);
+conc_workers()->start_task(&tsk);
+while (tsk.yielded()) {
+tsk.coordinator_yield();
+conc_workers()->continue_task(&tsk);
+}
+// If the task was aborted, _restart_addr will be non-NULL
+assert(tsk.completed() || _restart_addr != NULL, "Inconsistency");
+while (_restart_addr != NULL) {
+// XXX For now we do not make use of ABORTED state and have not
+// yet implemented the right abort semantics (even in the original
+// single-threaded CMS case). That needs some more investigation
+// and is deferred for now; see CR# TBF. 07252005YSR. XXX
+assert(!CMSAbortSemantics || tsk.aborted(), "Inconsistency");
+// If _restart_addr is non-NULL, a marking stack overflow
+// occured; we need to do a fresh marking iteration from the
+// indicated restart address.
+if (_foregroundGCIsActive && asynch) {
+// We may be running into repeated stack overflows, having
+// reached the limit of the stack size, while making very
+// slow forward progress. It may be best to bail out and
+// let the foreground collector do its job.
+// Clear _restart_addr, so that foreground GC
+// works from scratch. This avoids the headache of
+// a "rescan" which would otherwise be needed because
+// of the dirty mod union table & card table.
+_restart_addr = NULL;
+return false;
+}
+// Adjust the task to restart from _restart_addr
+tsk.reset(_restart_addr);
+cms_space ->initialize_sequential_subtasks_for_marking(num_workers,
+_restart_addr);
+perm_space->initialize_sequential_subtasks_for_marking(num_workers,
+_restart_addr);
+_restart_addr = NULL;
+// Get the workers going again
+conc_workers()->start_task(&tsk);
+while (tsk.yielded()) {
+tsk.coordinator_yield();
+conc_workers()->continue_task(&tsk);
+}
+}
+assert(tsk.completed(), "Inconsistency");
+assert(tsk.result() == true, "Inconsistency");
+return true;
+}
+bool CMSCollector::do_marking_st(bool asynch) {
+ResourceMark rm;
+HandleMark   hm;
+MarkFromRootsClosure markFromRootsClosure(this, _span, &_markBitMap,
+&_markStack, &_revisitStack, CMSYield && asynch);
+// the last argument to iterate indicates whether the iteration
+// should be incremental with periodic yields.
+_markBitMap.iterate(&markFromRootsClosure);
+// If _restart_addr is non-NULL, a marking stack overflow
+// occured; we need to do a fresh iteration from the
+// indicated restart address.
+while (_restart_addr != NULL) {
+if (_foregroundGCIsActive && asynch) {
+// We may be running into repeated stack overflows, having
+// reached the limit of the stack size, while making very
+// slow forward progress. It may be best to bail out and
+// let the foreground collector do its job.
+// Clear _restart_addr, so that foreground GC
+// works from scratch. This avoids the headache of
+// a "rescan" which would otherwise be needed because
+// of the dirty mod union table & card table.
+_restart_addr = NULL;
+return false;  // indicating failure to complete marking
+}
+// Deal with stack overflow:
+// we restart marking from _restart_addr
+HeapWord* ra = _restart_addr;
+markFromRootsClosure.reset(ra);
+_restart_addr = NULL;
+_markBitMap.iterate(&markFromRootsClosure, ra, _span.end());
+}
+return true;
+}
+void CMSCollector::preclean() {
+check_correct_thread_executing();
+assert(Thread::current()->is_ConcurrentGC_thread(), "Wrong thread");
+verify_work_stacks_empty();
+verify_overflow_empty();
+_abort_preclean = false;
+if (CMSPrecleaningEnabled) {
+_eden_chunk_index = 0;
+size_t used = get_eden_used();
+size_t capacity = get_eden_capacity();
+// Don't start sampling unless we will get sufficiently
+// many samples.
+if (used < (capacity/(CMSScheduleRemarkSamplingRatio * 100)
+* CMSScheduleRemarkEdenPenetration)) {
+_start_sampling = true;
+} else {
+_start_sampling = false;
+}
+TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
+CMSPhaseAccounting pa(this, "preclean", !PrintGCDetails);
+preclean_work(CMSPrecleanRefLists1, CMSPrecleanSurvivors1);
+}
+CMSTokenSync x(true); // is cms thread
+if (CMSPrecleaningEnabled) {
+sample_eden();
+_collectorState = AbortablePreclean;
+} else {
+_collectorState = FinalMarking;
+}
+verify_work_stacks_empty();
+verify_overflow_empty();
+}
+// Try and schedule the remark such that young gen
+// occupancy is CMSScheduleRemarkEdenPenetration %.
+void CMSCollector::abortable_preclean() {
+check_correct_thread_executing();
+assert(CMSPrecleaningEnabled,  "Inconsistent control state");
+assert(_collectorState == AbortablePreclean, "Inconsistent control state");
+// If Eden's current occupancy is below this threshold,
+// immediately schedule the remark; else preclean
+// past the next scavenge in an effort to
+// schedule the pause as described avove. By choosing
+// CMSScheduleRemarkEdenSizeThreshold >= max eden size
+// we will never do an actual abortable preclean cycle.
+if (get_eden_used() > CMSScheduleRemarkEdenSizeThreshold) {
+TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
+CMSPhaseAccounting pa(this, "abortable-preclean", !PrintGCDetails);
+// We need more smarts in the abortable preclean
+// loop below to deal with cases where allocation
+// in young gen is very very slow, and our precleaning
+// is running a losing race against a horde of
+// mutators intent on flooding us with CMS updates
+// (dirty cards).
+// One, admittedly dumb, strategy is to give up
+// after a certain number of abortable precleaning loops
+// or after a certain maximum time. We want to make
+// this smarter in the next iteration.
+// XXX FIX ME!!! YSR
+size_t loops = 0, workdone = 0, cumworkdone = 0, waited = 0;
+while (!(should_abort_preclean() ||
+ConcurrentMarkSweepThread::should_terminate())) {
+workdone = preclean_work(CMSPrecleanRefLists2, CMSPrecleanSurvivors2);
+cumworkdone += workdone;
+loops++;
+// Voluntarily terminate abortable preclean phase if we have
+// been at it for too long.
+if ((CMSMaxAbortablePrecleanLoops != 0) &&
+loops >= CMSMaxAbortablePrecleanLoops) {
+if (PrintGCDetails) {
+gclog_or_tty->print(" CMS: abort preclean due to loops ");
+}
+break;
+}
+if (pa.wallclock_millis() > CMSMaxAbortablePrecleanTime) {
+if (PrintGCDetails) {
+gclog_or_tty->print(" CMS: abort preclean due to time ");
+}
+break;
+}
+// If we are doing little work each iteration, we should
+// take a short break.
+if (workdone < CMSAbortablePrecleanMinWorkPerIteration) {
+// Sleep for some time, waiting for work to accumulate
+stopTimer();
+cmsThread()->wait_on_cms_lock(CMSAbortablePrecleanWaitMillis);
+startTimer();
+waited++;
+}
+}
+if (PrintCMSStatistics > 0) {
+gclog_or_tty->print(" [%d iterations, %d waits, %d cards)] ",
+loops, waited, cumworkdone);
+}
+}
+CMSTokenSync x(true); // is cms thread
+if (_collectorState != Idling) {
+assert(_collectorState == AbortablePreclean,
+"Spontaneous state transition?");
+_collectorState = FinalMarking;
+} // Else, a foreground collection completed this CMS cycle.
+return;
+}
+// Respond to an Eden sampling opportunity
+void CMSCollector::sample_eden() {
+// Make sure a young gc cannot sneak in between our
+// reading and recording of a sample.
+assert(Thread::current()->is_ConcurrentGC_thread(),
+"Only the cms thread may collect Eden samples");
+assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
+"Should collect samples while holding CMS token");
+if (!_start_sampling) {
+return;
+}
+if (_eden_chunk_array) {
+if (_eden_chunk_index < _eden_chunk_capacity) {
+_eden_chunk_array[_eden_chunk_index] = *_top_addr;   // take sample
+assert(_eden_chunk_array[_eden_chunk_index] <= *_end_addr,
+"Unexpected state of Eden");
+// We'd like to check that what we just sampled is an oop-start address;
+// however, we cannot do that here since the object may not yet have been
+// initialized. So we'll instead do the check when we _use_ this sample
+// later.
+if (_eden_chunk_index == 0 ||
+(pointer_delta(_eden_chunk_array[_eden_chunk_index],
+_eden_chunk_array[_eden_chunk_index-1])
+>= CMSSamplingGrain)) {
+_eden_chunk_index++;  // commit sample
+}
+}
+}
+if ((_collectorState == AbortablePreclean) && !_abort_preclean) {
+size_t used = get_eden_used();
+size_t capacity = get_eden_capacity();
+assert(used <= capacity, "Unexpected state of Eden");
+if (used >  (capacity/100 * CMSScheduleRemarkEdenPenetration)) {
+_abort_preclean = true;
+}
+}
+}
+size_t CMSCollector::preclean_work(bool clean_refs, bool clean_survivor) {
+assert(_collectorState == Precleaning ||
+_collectorState == AbortablePreclean, "incorrect state");
+ResourceMark rm;
+HandleMark   hm;
+// Do one pass of scrubbing the discovered reference lists
+// to remove any reference objects with strongly-reachable
+// referents.
+if (clean_refs) {
+ReferenceProcessor* rp = ref_processor();
+CMSPrecleanRefsYieldClosure yield_cl(this);
+assert(rp->span().equals(_span), "Spans should be equal");
+CMSKeepAliveClosure keep_alive(this, _span, &_markBitMap,
+&_markStack);
+CMSDrainMarkingStackClosure complete_trace(this,
+_span, &_markBitMap, &_markStack,
+&keep_alive);
+// We don't want this step to interfere with a young
+// collection because we don't want to take CPU
+// or memory bandwidth away from the young GC threads
+// (which may be as many as there are CPUs).
+// Note that we don't need to protect ourselves from
+// interference with mutators because they can't
+// manipulate the discovered reference lists nor affect
+// the computed reachability of the referents, the
+// only properties manipulated by the precleaning
+// of these reference lists.
+stopTimer();
+CMSTokenSyncWithLocks x(true /* is cms thread */,
+bitMapLock());
+startTimer();
+sample_eden();
+// The following will yield to allow foreground
+// collection to proceed promptly. XXX YSR:
+// The code in this method may need further
+// tweaking for better performance and some restructuring
+// for cleaner interfaces.
+rp->preclean_discovered_references(
+rp->is_alive_non_header(), &keep_alive, &complete_trace,
+&yield_cl);
+}
+if (clean_survivor) {  // preclean the active survivor space(s)
+assert(_young_gen->kind() == Generation::DefNew ||
+_young_gen->kind() == Generation::ParNew ||
+_young_gen->kind() == Generation::ASParNew,
+"incorrect type for cast");
+DefNewGeneration* dng = (DefNewGeneration*)_young_gen;
+PushAndMarkClosure pam_cl(this, _span, ref_processor(),
+&_markBitMap, &_modUnionTable,
+&_markStack, &_revisitStack,
+true /* precleaning phase */);
+stopTimer();
+CMSTokenSyncWithLocks ts(true /* is cms thread */,
+bitMapLock());
+startTimer();
+unsigned int before_count =
+GenCollectedHeap::heap()->total_collections();
+SurvivorSpacePrecleanClosure
+sss_cl(this, _span, &_markBitMap, &_markStack,
+&pam_cl, before_count, CMSYield);
+dng->from()->object_iterate_careful(&sss_cl);
+dng->to()->object_iterate_careful(&sss_cl);
+}
+MarkRefsIntoAndScanClosure
+mrias_cl(_span, ref_processor(), &_markBitMap, &_modUnionTable,
+&_markStack, &_revisitStack, this, CMSYield,
+true /* precleaning phase */);
+// CAUTION: The following closure has persistent state that may need to
+// be reset upon a decrease in the sequence of addresses it
+// processes.
+ScanMarkedObjectsAgainCarefullyClosure
+smoac_cl(this, _span,
+&_markBitMap, &_markStack, &_revisitStack, &mrias_cl, CMSYield);
+// Preclean dirty cards in ModUnionTable and CardTable using
+// appropriate convergence criterion;
+// repeat CMSPrecleanIter times unless we find that
+// we are losing.
+assert(CMSPrecleanIter < 10, "CMSPrecleanIter is too large");
+assert(CMSPrecleanNumerator < CMSPrecleanDenominator,
+"Bad convergence multiplier");
+assert(CMSPrecleanThreshold >= 100,
+"Unreasonably low CMSPrecleanThreshold");
+size_t numIter, cumNumCards, lastNumCards, curNumCards;
+for (numIter = 0, cumNumCards = lastNumCards = curNumCards = 0;
+numIter < CMSPrecleanIter;
+numIter++, lastNumCards = curNumCards, cumNumCards += curNumCards) {
+curNumCards  = preclean_mod_union_table(_cmsGen, &smoac_cl);
+if (CMSPermGenPrecleaningEnabled) {
+curNumCards  += preclean_mod_union_table(_permGen, &smoac_cl);
+}
+if (Verbose && PrintGCDetails) {
+gclog_or_tty->print(" (modUnionTable: %d cards)", curNumCards);
+}
+// Either there are very few dirty cards, so re-mark
+// pause will be small anyway, or our pre-cleaning isn't
+// that much faster than the rate at which cards are being
+// dirtied, so we might as well stop and re-mark since
+// precleaning won't improve our re-mark time by much.
+if (curNumCards <= CMSPrecleanThreshold ||
+(numIter > 0 &&
+(curNumCards * CMSPrecleanDenominator >
+lastNumCards * CMSPrecleanNumerator))) {
+numIter++;
+cumNumCards += curNumCards;
+break;
+}
+}
+curNumCards = preclean_card_table(_cmsGen, &smoac_cl);
+if (CMSPermGenPrecleaningEnabled) {
+curNumCards += preclean_card_table(_permGen, &smoac_cl);
+}
+cumNumCards += curNumCards;
+if (PrintGCDetails && PrintCMSStatistics != 0) {
+gclog_or_tty->print_cr(" (cardTable: %d cards, re-scanned %d cards, %d iterations)",
+curNumCards, cumNumCards, numIter);
+}
+return cumNumCards;   // as a measure of useful work done
+}
+// PRECLEANING NOTES:
+// Precleaning involves:
+// . reading the bits of the modUnionTable and clearing the set bits.
+// . For the cards corresponding to the set bits, we scan the
+//   objects on those cards. This means we need the free_list_lock
+//   so that we can safely iterate over the CMS space when scanning
+//   for oops.
+// . When we scan the objects, we'll be both reading and setting
+//   marks in the marking bit map, so we'll need the marking bit map.
+// . For protecting _collector_state transitions, we take the CGC_lock.
+//   Note that any races in the reading of of card table entries by the
+//   CMS thread on the one hand and the clearing of those entries by the
+//   VM thread or the setting of those entries by the mutator threads on the
+//   other are quite benign. However, for efficiency it makes sense to keep
+//   the VM thread from racing with the CMS thread while the latter is
+//   dirty card info to the modUnionTable. We therefore also use the
+//   CGC_lock to protect the reading of the card table and the mod union
+//   table by the CM thread.
+// . We run concurrently with mutator updates, so scanning
+//   needs to be done carefully  -- we should not try to scan
+//   potentially uninitialized objects.
+//
+// Locking strategy: While holding the CGC_lock, we scan over and
+// reset a maximal dirty range of the mod union / card tables, then lock
+// the free_list_lock and bitmap lock to do a full marking, then
+// release these locks; and repeat the cycle. This allows for a
+// certain amount of fairness in the sharing of these locks between
+// the CMS collector on the one hand, and the VM thread and the
+// mutators on the other.
+// NOTE: preclean_mod_union_table() and preclean_card_table()
+// further below are largely identical; if you need to modify
+// one of these methods, please check the other method too.
+size_t CMSCollector::preclean_mod_union_table(
+ConcurrentMarkSweepGeneration* gen,
+ScanMarkedObjectsAgainCarefullyClosure* cl) {
+verify_work_stacks_empty();
+verify_overflow_empty();
+// strategy: starting with the first card, accumulate contiguous
+// ranges of dirty cards; clear these cards, then scan the region
+// covered by these cards.
+// Since all of the MUT is committed ahead, we can just use
+// that, in case the generations expand while we are precleaning.
+// It might also be fine to just use the committed part of the
+// generation, but we might potentially miss cards when the
+// generation is rapidly expanding while we are in the midst
+// of precleaning.
+HeapWord* startAddr = gen->reserved().start();
+HeapWord* endAddr   = gen->reserved().end();
+cl->setFreelistLock(gen->freelistLock());   // needed for yielding
+size_t numDirtyCards, cumNumDirtyCards;
+HeapWord *nextAddr, *lastAddr;
+for (cumNumDirtyCards = numDirtyCards = 0,
+nextAddr = lastAddr = startAddr;
+nextAddr < endAddr;
+nextAddr = lastAddr, cumNumDirtyCards += numDirtyCards) {
+ResourceMark rm;
+HandleMark   hm;
+MemRegion dirtyRegion;
+{
+stopTimer();
+CMSTokenSync ts(true);
+startTimer();
+sample_eden();
+// Get dirty region starting at nextOffset (inclusive),
+// simultaneously clearing it.
+dirtyRegion =
+_modUnionTable.getAndClearMarkedRegion(nextAddr, endAddr);
+assert(dirtyRegion.start() >= nextAddr,
+"returned region inconsistent?");
+}
+// Remember where the next search should begin.
+// The returned region (if non-empty) is a right open interval,
+// so lastOffset is obtained from the right end of that
+// interval.
+lastAddr = dirtyRegion.end();
+// Should do something more transparent and less hacky XXX
+numDirtyCards =
+_modUnionTable.heapWordDiffToOffsetDiff(dirtyRegion.word_size());
+// We'll scan the cards in the dirty region (with periodic
+// yields for foreground GC as needed).
+if (!dirtyRegion.is_empty()) {
+assert(numDirtyCards > 0, "consistency check");
+HeapWord* stop_point = NULL;
+{
+stopTimer();
+CMSTokenSyncWithLocks ts(true, gen->freelistLock(),
+bitMapLock());
+startTimer();
+verify_work_stacks_empty();
+verify_overflow_empty();
+sample_eden();
+stop_point =
+gen->cmsSpace()->object_iterate_careful_m(dirtyRegion, cl);
+}
+if (stop_point != NULL) {
+// The careful iteration stopped early either because it found an
+// uninitialized object, or because we were in the midst of an
+// "abortable preclean", which should now be aborted. Redirty
+// the bits corresponding to the partially-scanned or unscanned
+// cards. We'll either restart at the next block boundary or
+// abort the preclean.
+assert((CMSPermGenPrecleaningEnabled && (gen == _permGen)) ||
+(_collectorState == AbortablePreclean && should_abort_preclean()),
+"Unparsable objects should only be in perm gen.");
+stopTimer();
+CMSTokenSyncWithLocks ts(true, bitMapLock());
+startTimer();
+_modUnionTable.mark_range(MemRegion(stop_point, dirtyRegion.end()));
+if (should_abort_preclean()) {
+break; // out of preclean loop
+} else {
+// Compute the next address at which preclean should pick up;
+// might need bitMapLock in order to read P-bits.
+lastAddr = next_card_start_after_block(stop_point);
+}
+}
+} else {
+assert(lastAddr == endAddr, "consistency check");
+assert(numDirtyCards == 0, "consistency check");
+break;
+}
+}
+verify_work_stacks_empty();
+verify_overflow_empty();
+return cumNumDirtyCards;
+}
+// NOTE: preclean_mod_union_table() above and preclean_card_table()
+// below are largely identical; if you need to modify
+// one of these methods, please check the other method too.
+size_t CMSCollector::preclean_card_table(ConcurrentMarkSweepGeneration* gen,
+ScanMarkedObjectsAgainCarefullyClosure* cl) {
+// strategy: it's similar to precleamModUnionTable above, in that
+// we accumulate contiguous ranges of dirty cards, mark these cards
+// precleaned, then scan the region covered by these cards.
+HeapWord* endAddr   = (HeapWord*)(gen->_virtual_space.high());
+HeapWord* startAddr = (HeapWord*)(gen->_virtual_space.low());
+cl->setFreelistLock(gen->freelistLock());   // needed for yielding
+size_t numDirtyCards, cumNumDirtyCards;
+HeapWord *lastAddr, *nextAddr;
+for (cumNumDirtyCards = numDirtyCards = 0,
+nextAddr = lastAddr = startAddr;
+nextAddr < endAddr;
+nextAddr = lastAddr, cumNumDirtyCards += numDirtyCards) {
+ResourceMark rm;
+HandleMark   hm;
+MemRegion dirtyRegion;
+{
+// See comments in "Precleaning notes" above on why we
+// do this locking. XXX Could the locking overheads be
+// too high when dirty cards are sparse? [I don't think so.]
+stopTimer();
+CMSTokenSync x(true); // is cms thread
+startTimer();
+sample_eden();
+// Get and clear dirty region from card table
+dirtyRegion = _ct->ct_bs()->dirty_card_range_after_preclean(
+MemRegion(nextAddr, endAddr));
+assert(dirtyRegion.start() >= nextAddr,
+"returned region inconsistent?");
+}
+lastAddr = dirtyRegion.end();
+numDirtyCards =
+dirtyRegion.word_size()/CardTableModRefBS::card_size_in_words;
+if (!dirtyRegion.is_empty()) {
+stopTimer();
+CMSTokenSyncWithLocks ts(true, gen->freelistLock(), bitMapLock());
+startTimer();
+sample_eden();
+verify_work_stacks_empty();
+verify_overflow_empty();
+HeapWord* stop_point =
+gen->cmsSpace()->object_iterate_careful_m(dirtyRegion, cl);
+if (stop_point != NULL) {
+// The careful iteration stopped early because it found an
+// uninitialized object.  Redirty the bits corresponding to the
+// partially-scanned or unscanned cards, and start again at the
+// next block boundary.
+assert(CMSPermGenPrecleaningEnabled ||
+(_collectorState == AbortablePreclean && should_abort_preclean()),
+"Unparsable objects should only be in perm gen.");
+_ct->ct_bs()->invalidate(MemRegion(stop_point, dirtyRegion.end()));
+if (should_abort_preclean()) {
+break; // out of preclean loop
+} else {
+// Compute the next address at which preclean should pick up.
+lastAddr = next_card_start_after_block(stop_point);
+}
+}
+} else {
+break;
+}
+}
+verify_work_stacks_empty();
+verify_overflow_empty();
+return cumNumDirtyCards;
+}
+void CMSCollector::checkpointRootsFinal(bool asynch,
+bool clear_all_soft_refs, bool init_mark_was_synchronous) {
+assert(_collectorState == FinalMarking, "incorrect state transition?");
+check_correct_thread_executing();
+// world is stopped at this checkpoint
+assert(SafepointSynchronize::is_at_safepoint(),
+"world should be stopped");
+verify_work_stacks_empty();
+verify_overflow_empty();
+SpecializationStats::clear();
+if (PrintGCDetails) {
+gclog_or_tty->print("[YG occupancy: "SIZE_FORMAT" K ("SIZE_FORMAT" K)]",
+_young_gen->used() / K,
+_young_gen->capacity() / K);
+}
+if (asynch) {
+if (CMSScavengeBeforeRemark) {
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+// Temporarily set flag to false, GCH->do_collection will
+// expect it to be false and set to true
+FlagSetting fl(gch->_is_gc_active, false);
+NOT_PRODUCT(TraceTime t("Scavenge-Before-Remark",
+PrintGCDetails && Verbose, true, gclog_or_tty);)
+int level = _cmsGen->level() - 1;
+if (level >= 0) {
+gch->do_collection(true,        // full (i.e. force, see below)
+false,       // !clear_all_soft_refs
+0,           // size
+false,       // is_tlab
+level        // max_level
+);
+}
+}
+FreelistLocker x(this);
+MutexLockerEx y(bitMapLock(),
+Mutex::_no_safepoint_check_flag);
+assert(!init_mark_was_synchronous, "but that's impossible!");
+checkpointRootsFinalWork(asynch, clear_all_soft_refs, false);
+} else {
+// already have all the locks
+checkpointRootsFinalWork(asynch, clear_all_soft_refs,
+init_mark_was_synchronous);
+}
+verify_work_stacks_empty();
+verify_overflow_empty();
+SpecializationStats::print();
+}
+void CMSCollector::checkpointRootsFinalWork(bool asynch,
+bool clear_all_soft_refs, bool init_mark_was_synchronous) {
+NOT_PRODUCT(TraceTime tr("checkpointRootsFinalWork", PrintGCDetails, false, gclog_or_tty);)
+assert(haveFreelistLocks(), "must have free list locks");
+assert_lock_strong(bitMapLock());
+if (UseAdaptiveSizePolicy) {
+size_policy()->checkpoint_roots_final_begin();
+}
+ResourceMark rm;
+HandleMark   hm;
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+if (cms_should_unload_classes()) {
+CodeCache::gc_prologue();
+}
+assert(haveFreelistLocks(), "must have free list locks");
+assert_lock_strong(bitMapLock());
+if (!init_mark_was_synchronous) {
+// We might assume that we need not fill TLAB's when
+// CMSScavengeBeforeRemark is set, because we may have just done
+// a scavenge which would have filled all TLAB's -- and besides
+// Eden would be empty. This however may not always be the case --
+// for instance although we asked for a scavenge, it may not have
+// happened because of a JNI critical section. We probably need
+// a policy for deciding whether we can in that case wait until
+// the critical section releases and then do the remark following
+// the scavenge, and skip it here. In the absence of that policy,
+// or of an indication of whether the scavenge did indeed occur,
+// we cannot rely on TLAB's having been filled and must do
+// so here just in case a scavenge did not happen.
+gch->ensure_parsability(false);  // fill TLAB's, but no need to retire them
+// Update the saved marks which may affect the root scans.
+gch->save_marks();
+{
+COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact;)
+// Note on the role of the mod union table:
+// Since the marker in "markFromRoots" marks concurrently with
+// mutators, it is possible for some reachable objects not to have been
+// scanned. For instance, an only reference to an object A was
+// placed in object B after the marker scanned B. Unless B is rescanned,
+// A would be collected. Such updates to references in marked objects
+// are detected via the mod union table which is the set of all cards
+// dirtied since the first checkpoint in this GC cycle and prior to
+// the most recent young generation GC, minus those cleaned up by the
+// concurrent precleaning.
+if (CMSParallelRemarkEnabled && ParallelGCThreads > 0) {
+TraceTime t("Rescan (parallel) ", PrintGCDetails, false, gclog_or_tty);
+do_remark_parallel();
+} else {
+TraceTime t("Rescan (non-parallel) ", PrintGCDetails, false,
+gclog_or_tty);
+do_remark_non_parallel();
+}
+}
+} else {
+assert(!asynch, "Can't have init_mark_was_synchronous in asynch mode");
+// The initial mark was stop-world, so there's no rescanning to
+// do; go straight on to the next step below.
+}
+verify_work_stacks_empty();
+verify_overflow_empty();
+{
+NOT_PRODUCT(TraceTime ts("refProcessingWork", PrintGCDetails, false, gclog_or_tty);)
+refProcessingWork(asynch, clear_all_soft_refs);
+}
+verify_work_stacks_empty();
+verify_overflow_empty();
+if (cms_should_unload_classes()) {
+CodeCache::gc_epilogue();
+}
+// If we encountered any (marking stack / work queue) overflow
+// events during the current CMS cycle, take appropriate
+// remedial measures, where possible, so as to try and avoid
+// recurrence of that condition.
+assert(_markStack.isEmpty(), "No grey objects");
+size_t ser_ovflw = _ser_pmc_remark_ovflw + _ser_pmc_preclean_ovflw +
+_ser_kac_ovflw;
+if (ser_ovflw > 0) {
+if (PrintCMSStatistics != 0) {
+gclog_or_tty->print_cr("Marking stack overflow (benign) "
+"(pmc_pc="SIZE_FORMAT", pmc_rm="SIZE_FORMAT", kac="SIZE_FORMAT")",
+_ser_pmc_preclean_ovflw, _ser_pmc_remark_ovflw,
+_ser_kac_ovflw);
+}
+_markStack.expand();
+_ser_pmc_remark_ovflw = 0;
+_ser_pmc_preclean_ovflw = 0;
+_ser_kac_ovflw = 0;
+}
+if (_par_pmc_remark_ovflw > 0 || _par_kac_ovflw > 0) {
+if (PrintCMSStatistics != 0) {
+gclog_or_tty->print_cr("Work queue overflow (benign) "
+"(pmc_rm="SIZE_FORMAT", kac="SIZE_FORMAT")",
+_par_pmc_remark_ovflw, _par_kac_ovflw);
+}
+_par_pmc_remark_ovflw = 0;
+_par_kac_ovflw = 0;
+}
+if (PrintCMSStatistics != 0) {
+if (_markStack._hit_limit > 0) {
+gclog_or_tty->print_cr(" (benign) Hit max stack size limit ("SIZE_FORMAT")",
+_markStack._hit_limit);
+}
+if (_markStack._failed_double > 0) {
+gclog_or_tty->print_cr(" (benign) Failed stack doubling ("SIZE_FORMAT"),"
+" current capacity "SIZE_FORMAT,
+_markStack._failed_double,
+_markStack.capacity());
+}
+}
+_markStack._hit_limit = 0;
+_markStack._failed_double = 0;
+if ((VerifyAfterGC || VerifyDuringGC) &&
+GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
+verify_after_remark();
+}
+// Change under the freelistLocks.
+_collectorState = Sweeping;
+// Call isAllClear() under bitMapLock
+assert(_modUnionTable.isAllClear(), "Should be clear by end of the"
+" final marking");
+if (UseAdaptiveSizePolicy) {
+size_policy()->checkpoint_roots_final_end(gch->gc_cause());
+}
+}
+// Parallel remark task
+class CMSParRemarkTask: public AbstractGangTask {
+CMSCollector* _collector;
+WorkGang*     _workers;
+int           _n_workers;
+CompactibleFreeListSpace* _cms_space;
+CompactibleFreeListSpace* _perm_space;
+// The per-thread work queues, available here for stealing.
+OopTaskQueueSet*       _task_queues;
+ParallelTaskTerminator _term;
+public:
+CMSParRemarkTask(CMSCollector* collector,
+CompactibleFreeListSpace* cms_space,
+CompactibleFreeListSpace* perm_space,
+int n_workers, WorkGang* workers,
+OopTaskQueueSet* task_queues):
+AbstractGangTask("Rescan roots and grey objects in parallel"),
+_collector(collector),
+_cms_space(cms_space), _perm_space(perm_space),
+_n_workers(n_workers),
+_workers(workers),
+_task_queues(task_queues),
+_term(workers->total_workers(), task_queues) { }
+OopTaskQueueSet* task_queues() { return _task_queues; }
+OopTaskQueue* work_queue(int i) { return task_queues()->queue(i); }
+ParallelTaskTerminator* terminator() { return &_term; }
+void work(int i);
+private:
+// Work method in support of parallel rescan ... of young gen spaces
+void do_young_space_rescan(int i, Par_MarkRefsIntoAndScanClosure* cl,
+ContiguousSpace* space,
+HeapWord** chunk_array, size_t chunk_top);
+// ... of  dirty cards in old space
+void do_dirty_card_rescan_tasks(CompactibleFreeListSpace* sp, int i,
+Par_MarkRefsIntoAndScanClosure* cl);
+// ... work stealing for the above
+void do_work_steal(int i, Par_MarkRefsIntoAndScanClosure* cl, int* seed);
+};
+void CMSParRemarkTask::work(int i) {
+elapsedTimer _timer;
+ResourceMark rm;
+HandleMark   hm;
+// ---------- rescan from roots --------------
+_timer.start();
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+Par_MarkRefsIntoAndScanClosure par_mrias_cl(_collector,
+_collector->_span, _collector->ref_processor(),
+&(_collector->_markBitMap),
+work_queue(i), &(_collector->_revisitStack));
+// Rescan young gen roots first since these are likely
+// coarsely partitioned and may, on that account, constitute
+// the critical path; thus, it's best to start off that
+// work first.
+// ---------- young gen roots --------------
+{
+DefNewGeneration* dng = _collector->_young_gen->as_DefNewGeneration();
+EdenSpace* eden_space = dng->eden();
+ContiguousSpace* from_space = dng->from();
+ContiguousSpace* to_space   = dng->to();
+HeapWord** eca = _collector->_eden_chunk_array;
+size_t     ect = _collector->_eden_chunk_index;
+HeapWord** sca = _collector->_survivor_chunk_array;
+size_t     sct = _collector->_survivor_chunk_index;
+assert(ect <= _collector->_eden_chunk_capacity, "out of bounds");
+assert(sct <= _collector->_survivor_chunk_capacity, "out of bounds");
+do_young_space_rescan(i, &par_mrias_cl, to_space, NULL, 0);
+do_young_space_rescan(i, &par_mrias_cl, from_space, sca, sct);
+do_young_space_rescan(i, &par_mrias_cl, eden_space, eca, ect);
+_timer.stop();
+if (PrintCMSStatistics != 0) {
+gclog_or_tty->print_cr(
+"Finished young gen rescan work in %dth thread: %3.3f sec",
+i, _timer.seconds());
+}
+}
+// ---------- remaining roots --------------
+_timer.reset();
+_timer.start();
+gch->gen_process_strong_roots(_collector->_cmsGen->level(),
+false,     // yg was scanned above
+true,      // collecting perm gen
+SharedHeap::ScanningOption(_collector->CMSCollector::roots_scanning_options()),
+NULL, &par_mrias_cl);
+_timer.stop();
+if (PrintCMSStatistics != 0) {
+gclog_or_tty->print_cr(
+"Finished remaining root rescan work in %dth thread: %3.3f sec",
+i, _timer.seconds());
+}
+// ---------- rescan dirty cards ------------
+_timer.reset();
+_timer.start();
+// Do the rescan tasks for each of the two spaces
+// (cms_space and perm_space) in turn.
+do_dirty_card_rescan_tasks(_cms_space, i, &par_mrias_cl);
+do_dirty_card_rescan_tasks(_perm_space, i, &par_mrias_cl);
+_timer.stop();
+if (PrintCMSStatistics != 0) {
+gclog_or_tty->print_cr(
+"Finished dirty card rescan work in %dth thread: %3.3f sec",
+i, _timer.seconds());
+}
+// ---------- steal work from other threads ...
+// ---------- ... and drain overflow list.
+_timer.reset();
+_timer.start();
+do_work_steal(i, &par_mrias_cl, _collector->hash_seed(i));
+_timer.stop();
+if (PrintCMSStatistics != 0) {
+gclog_or_tty->print_cr(
+"Finished work stealing in %dth thread: %3.3f sec",
+i, _timer.seconds());
+}
+}
+void
+CMSParRemarkTask::do_young_space_rescan(int i,
+Par_MarkRefsIntoAndScanClosure* cl, ContiguousSpace* space,
+HeapWord** chunk_array, size_t chunk_top) {
+// Until all tasks completed:
+// . claim an unclaimed task
+// . compute region boundaries corresponding to task claimed
+//   using chunk_array
+// . par_oop_iterate(cl) over that region
+ResourceMark rm;
+HandleMark   hm;
+SequentialSubTasksDone* pst = space->par_seq_tasks();
+assert(pst->valid(), "Uninitialized use?");
+int nth_task = 0;
+int n_tasks  = pst->n_tasks();
+HeapWord *start, *end;
+while (!pst->is_task_claimed(/* reference */ nth_task)) {
+// We claimed task # nth_task; compute its boundaries.
+if (chunk_top == 0) {  // no samples were taken
+assert(nth_task == 0 && n_tasks == 1, "Can have only 1 EdenSpace task");
+start = space->bottom();
+end   = space->top();
+} else if (nth_task == 0) {
+start = space->bottom();
+end   = chunk_array[nth_task];
+} else if (nth_task < (jint)chunk_top) {
+assert(nth_task >= 1, "Control point invariant");
+start = chunk_array[nth_task - 1];
+end   = chunk_array[nth_task];
+} else {
+assert(nth_task == (jint)chunk_top, "Control point invariant");
+start = chunk_array[chunk_top - 1];
+end   = space->top();
+}
+MemRegion mr(start, end);
+// Verify that mr is in space
+assert(mr.is_empty() || space->used_region().contains(mr),
+"Should be in space");
+// Verify that "start" is an object boundary
+assert(mr.is_empty() || oop(mr.start())->is_oop(),
+"Should be an oop");
+space->par_oop_iterate(mr, cl);
+}
+pst->all_tasks_completed();
+}
+void
+CMSParRemarkTask::do_dirty_card_rescan_tasks(
+CompactibleFreeListSpace* sp, int i,
+Par_MarkRefsIntoAndScanClosure* cl) {
+// Until all tasks completed:
+// . claim an unclaimed task
+// . compute region boundaries corresponding to task claimed
+// . transfer dirty bits ct->mut for that region
+// . apply rescanclosure to dirty mut bits for that region
+ResourceMark rm;
+HandleMark   hm;
+OopTaskQueue* work_q = work_queue(i);
+ModUnionClosure modUnionClosure(&(_collector->_modUnionTable));
+// CAUTION! CAUTION! CAUTION! CAUTION! CAUTION! CAUTION! CAUTION!
+// CAUTION: This closure has state that persists across calls to
+// the work method dirty_range_iterate_clear() in that it has
+// imbedded in it a (subtype of) UpwardsObjectClosure. The
+// use of that state in the imbedded UpwardsObjectClosure instance
+// assumes that the cards are always iterated (even if in parallel
+// by several threads) in monotonically increasing order per each
+// thread. This is true of the implementation below which picks
+// card ranges (chunks) in monotonically increasing order globally
+// and, a-fortiori, in monotonically increasing order per thread
+// (the latter order being a subsequence of the former).
+// If the work code below is ever reorganized into a more chaotic
+// work-partitioning form than the current "sequential tasks"
+// paradigm, the use of that persistent state will have to be
+// revisited and modified appropriately. See also related
+// bug 4756801 work on which should examine this code to make
+// sure that the changes there do not run counter to the
+// assumptions made here and necessary for correctness and
+// efficiency. Note also that this code might yield inefficient
+// behaviour in the case of very large objects that span one or
+// more work chunks. Such objects would potentially be scanned
+// several times redundantly. Work on 4756801 should try and
+// address that performance anomaly if at all possible. XXX
+MemRegion  full_span  = _collector->_span;
+CMSBitMap* bm    = &(_collector->_markBitMap);     // shared
+CMSMarkStack* rs = &(_collector->_revisitStack);   // shared
+MarkFromDirtyCardsClosure
+greyRescanClosure(_collector, full_span, // entire span of interest
+sp, bm, work_q, rs, cl);
+SequentialSubTasksDone* pst = sp->conc_par_seq_tasks();
+assert(pst->valid(), "Uninitialized use?");
+int nth_task = 0;
+const int alignment = CardTableModRefBS::card_size * BitsPerWord;
+MemRegion span = sp->used_region();
+HeapWord* start_addr = span.start();
+HeapWord* end_addr = (HeapWord*)round_to((intptr_t)span.end(),
+alignment);
+const size_t chunk_size = sp->rescan_task_size(); // in HeapWord units
+assert((HeapWord*)round_to((intptr_t)start_addr, alignment) ==
+start_addr, "Check alignment");
+assert((size_t)round_to((intptr_t)chunk_size, alignment) ==
+chunk_size, "Check alignment");
+while (!pst->is_task_claimed(/* reference */ nth_task)) {
+// Having claimed the nth_task, compute corresponding mem-region,
+// which is a-fortiori aligned correctly (i.e. at a MUT bopundary).
+// The alignment restriction ensures that we do not need any
+// synchronization with other gang-workers while setting or
+// clearing bits in thus chunk of the MUT.
+MemRegion this_span = MemRegion(start_addr + nth_task*chunk_size,
+start_addr + (nth_task+1)*chunk_size);
+// The last chunk's end might be way beyond end of the
+// used region. In that case pull back appropriately.
+if (this_span.end() > end_addr) {
+this_span.set_end(end_addr);
+assert(!this_span.is_empty(), "Program logic (calculation of n_tasks)");
+}
+// Iterate over the dirty cards covering this chunk, marking them
+// precleaned, and setting the corresponding bits in the mod union
+// table. Since we have been careful to partition at Card and MUT-word
+// boundaries no synchronization is needed between parallel threads.
+_collector->_ct->ct_bs()->dirty_card_iterate(this_span,
+&modUnionClosure);
+// Having transferred these marks into the modUnionTable,
+// rescan the marked objects on the dirty cards in the modUnionTable.
+// Even if this is at a synchronous collection, the initial marking
+// may have been done during an asynchronous collection so there
+// may be dirty bits in the mod-union table.
+_collector->_modUnionTable.dirty_range_iterate_clear(
+this_span, &greyRescanClosure);
+_collector->_modUnionTable.verifyNoOneBitsInRange(
+this_span.start(),
+this_span.end());
+}
+pst->all_tasks_completed();  // declare that i am done
+}
+// . see if we can share work_queues with ParNew? XXX
+void
+CMSParRemarkTask::do_work_steal(int i, Par_MarkRefsIntoAndScanClosure* cl,
+int* seed) {
+OopTaskQueue* work_q = work_queue(i);
+NOT_PRODUCT(int num_steals = 0;)
+oop obj_to_scan;
+CMSBitMap* bm = &(_collector->_markBitMap);
+size_t num_from_overflow_list =
+MIN2((size_t)work_q->max_elems()/4,
+(size_t)ParGCDesiredObjsFromOverflowList);
+while (true) {
+// Completely finish any left over work from (an) earlier round(s)
+cl->trim_queue(0);
+// Now check if there's any work in the overflow list
+if (_collector->par_take_from_overflow_list(num_from_overflow_list,
+work_q)) {
+// found something in global overflow list;
+// not yet ready to go stealing work from others.
+// We'd like to assert(work_q->size() != 0, ...)
+// because we just took work from the overflow list,
+// but of course we can't since all of that could have
+// been already stolen from us.
+// "He giveth and He taketh away."
+continue;
+}
+// Verify that we have no work before we resort to stealing
+assert(work_q->size() == 0, "Have work, shouldn't steal");
+// Try to steal from other queues that have work
+if (task_queues()->steal(i, seed, /* reference */ obj_to_scan)) {
+NOT_PRODUCT(num_steals++;)
+assert(obj_to_scan->is_oop(), "Oops, not an oop!");
+assert(bm->isMarked((HeapWord*)obj_to_scan), "Stole an unmarked oop?");
+// Do scanning work
+obj_to_scan->oop_iterate(cl);
+// Loop around, finish this work, and try to steal some more
+} else if (terminator()->offer_termination()) {
+break;  // nirvana from the infinite cycle
+}
+}
+NOT_PRODUCT(
+if (PrintCMSStatistics != 0) {
+gclog_or_tty->print("\n\t(%d: stole %d oops)", i, num_steals);
+}
+)
+assert(work_q->size() == 0 && _collector->overflow_list_is_empty(),
+"Else our work is not yet done");
+}
+// Return a thread-local PLAB recording array, as appropriate.
+void* CMSCollector::get_data_recorder(int thr_num) {
+if (_survivor_plab_array != NULL &&
+(CMSPLABRecordAlways ||
+(_collectorState > Marking && _collectorState < FinalMarking))) {
+assert(thr_num < (int)ParallelGCThreads, "thr_num is out of bounds");
+ChunkArray* ca = &_survivor_plab_array[thr_num];
+ca->reset();   // clear it so that fresh data is recorded
+return (void*) ca;
+} else {
+return NULL;
+}
+}
+// Reset all the thread-local PLAB recording arrays
+void CMSCollector::reset_survivor_plab_arrays() {
+for (uint i = 0; i < ParallelGCThreads; i++) {
+_survivor_plab_array[i].reset();
+}
+}
+// Merge the per-thread plab arrays into the global survivor chunk
+// array which will provide the partitioning of the survivor space
+// for CMS rescan.
+void CMSCollector::merge_survivor_plab_arrays(ContiguousSpace* surv) {
+assert(_survivor_plab_array  != NULL, "Error");
+assert(_survivor_chunk_array != NULL, "Error");
+assert(_collectorState == FinalMarking, "Error");
+for (uint j = 0; j < ParallelGCThreads; j++) {
+_cursor[j] = 0;
+}
+HeapWord* top = surv->top();
+size_t i;
+for (i = 0; i < _survivor_chunk_capacity; i++) {  // all sca entries
+HeapWord* min_val = top;          // Higher than any PLAB address
+uint      min_tid = 0;            // position of min_val this round
+for (uint j = 0; j < ParallelGCThreads; j++) {
+ChunkArray* cur_sca = &_survivor_plab_array[j];
+if (_cursor[j] == cur_sca->end()) {
+continue;
+}
+assert(_cursor[j] < cur_sca->end(), "ctl pt invariant");
+HeapWord* cur_val = cur_sca->nth(_cursor[j]);
+assert(surv->used_region().contains(cur_val), "Out of bounds value");
+if (cur_val < min_val) {
+min_tid = j;
+min_val = cur_val;
+} else {
+assert(cur_val < top, "All recorded addresses should be less");
+}
+}
+// At this point min_val and min_tid are respectively
+// the least address in _survivor_plab_array[j]->nth(_cursor[j])
+// and the thread (j) that witnesses that address.
+// We record this address in the _survivor_chunk_array[i]
+// and increment _cursor[min_tid] prior to the next round i.
+if (min_val == top) {
+break;
+}
+_survivor_chunk_array[i] = min_val;
+_cursor[min_tid]++;
+}
+// We are all done; record the size of the _survivor_chunk_array
+_survivor_chunk_index = i; // exclusive: [0, i)
+if (PrintCMSStatistics > 0) {
+gclog_or_tty->print(" (Survivor:" SIZE_FORMAT "chunks) ", i);
+}
+// Verify that we used up all the recorded entries
+#ifdef ASSERT
+size_t total = 0;
+for (uint j = 0; j < ParallelGCThreads; j++) {
+assert(_cursor[j] == _survivor_plab_array[j].end(), "Ctl pt invariant");
+total += _cursor[j];
+}
+assert(total == _survivor_chunk_index, "Ctl Pt Invariant");
+// Check that the merged array is in sorted order
+if (total > 0) {
+for (size_t i = 0; i < total - 1; i++) {
+if (PrintCMSStatistics > 0) {
+gclog_or_tty->print(" (chunk" SIZE_FORMAT ":" INTPTR_FORMAT ") ",
+i, _survivor_chunk_array[i]);
+}
+assert(_survivor_chunk_array[i] < _survivor_chunk_array[i+1],
+"Not sorted");
+}
+}
+#endif // ASSERT
+}
+// Set up the space's par_seq_tasks structure for work claiming
+// for parallel rescan of young gen.
+// See ParRescanTask where this is currently used.
+void
+CMSCollector::
+initialize_sequential_subtasks_for_young_gen_rescan(int n_threads) {
+assert(n_threads > 0, "Unexpected n_threads argument");
+DefNewGeneration* dng = (DefNewGeneration*)_young_gen;
+// Eden space
+{
+SequentialSubTasksDone* pst = dng->eden()->par_seq_tasks();
+assert(!pst->valid(), "Clobbering existing data?");
+// Each valid entry in [0, _eden_chunk_index) represents a task.
+size_t n_tasks = _eden_chunk_index + 1;
+assert(n_tasks == 1 || _eden_chunk_array != NULL, "Error");
+pst->set_par_threads(n_threads);
+pst->set_n_tasks((int)n_tasks);
+}
+// Merge the survivor plab arrays into _survivor_chunk_array
+if (_survivor_plab_array != NULL) {
+merge_survivor_plab_arrays(dng->from());
+} else {
+assert(_survivor_chunk_index == 0, "Error");
+}
+// To space
+{
+SequentialSubTasksDone* pst = dng->to()->par_seq_tasks();
+assert(!pst->valid(), "Clobbering existing data?");
+pst->set_par_threads(n_threads);
+pst->set_n_tasks(1);
+assert(pst->valid(), "Error");
+}
+// From space
+{
+SequentialSubTasksDone* pst = dng->from()->par_seq_tasks();
+assert(!pst->valid(), "Clobbering existing data?");
+size_t n_tasks = _survivor_chunk_index + 1;
+assert(n_tasks == 1 || _survivor_chunk_array != NULL, "Error");
+pst->set_par_threads(n_threads);
+pst->set_n_tasks((int)n_tasks);
+assert(pst->valid(), "Error");
+}
+}
+// Parallel version of remark
+void CMSCollector::do_remark_parallel() {
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+WorkGang* workers = gch->workers();
+assert(workers != NULL, "Need parallel worker threads.");
+int n_workers = workers->total_workers();
+CompactibleFreeListSpace* cms_space  = _cmsGen->cmsSpace();
+CompactibleFreeListSpace* perm_space = _permGen->cmsSpace();
+CMSParRemarkTask tsk(this,
+cms_space, perm_space,
+n_workers, workers, task_queues());
+// Set up for parallel process_strong_roots work.
+gch->set_par_threads(n_workers);
+gch->change_strong_roots_parity();
+// We won't be iterating over the cards in the card table updating
+// the younger_gen cards, so we shouldn't call the following else
+// the verification code as well as subsequent younger_refs_iterate
+// code would get confused. XXX
+// gch->rem_set()->prepare_for_younger_refs_iterate(true); // parallel
+// The young gen rescan work will not be done as part of
+// process_strong_roots (which currently doesn't knw how to
+// parallelize such a scan), but rather will be broken up into
+// a set of parallel tasks (via the sampling that the [abortable]
+// preclean phase did of EdenSpace, plus the [two] tasks of
+// scanning the [two] survivor spaces. Further fine-grain
+// parallelization of the scanning of the survivor spaces
+// themselves, and of precleaning of the younger gen itself
+// is deferred to the future.
+initialize_sequential_subtasks_for_young_gen_rescan(n_workers);
+// The dirty card rescan work is broken up into a "sequence"
+// of parallel tasks (per constituent space) that are dynamically
+// claimed by the parallel threads.
+cms_space->initialize_sequential_subtasks_for_rescan(n_workers);
+perm_space->initialize_sequential_subtasks_for_rescan(n_workers);
+// It turns out that even when we're using 1 thread, doing the work in a
+// separate thread causes wide variance in run times.  We can't help this
+// in the multi-threaded case, but we special-case n=1 here to get
+// repeatable measurements of the 1-thread overhead of the parallel code.
+if (n_workers > 1) {
+// Make refs discovery MT-safe
+ReferenceProcessorMTMutator mt(ref_processor(), true);
+workers->run_task(&tsk);
+} else {
+tsk.work(0);
+}
+gch->set_par_threads(0);  // 0 ==> non-parallel.
+// restore, single-threaded for now, any preserved marks
+// as a result of work_q overflow
+restore_preserved_marks_if_any();
+}
+// Non-parallel version of remark
+void CMSCollector::do_remark_non_parallel() {
+ResourceMark rm;
+HandleMark   hm;
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+MarkRefsIntoAndScanClosure
+mrias_cl(_span, ref_processor(), &_markBitMap, &_modUnionTable,
+&_markStack, &_revisitStack, this,
+false /* should_yield */, false /* not precleaning */);
+MarkFromDirtyCardsClosure
+markFromDirtyCardsClosure(this, _span,
+NULL,  // space is set further below
+&_markBitMap, &_markStack, &_revisitStack,
+&mrias_cl);
+{
+TraceTime t("grey object rescan", PrintGCDetails, false, gclog_or_tty);
+// Iterate over the dirty cards, marking them precleaned, and
+// setting the corresponding bits in the mod union table.
+{
+ModUnionClosure modUnionClosure(&_modUnionTable);
+_ct->ct_bs()->dirty_card_iterate(
+_cmsGen->used_region(),
+&modUnionClosure);
+_ct->ct_bs()->dirty_card_iterate(
+_permGen->used_region(),
+&modUnionClosure);
+}
+// Having transferred these marks into the modUnionTable, we just need
+// to rescan the marked objects on the dirty cards in the modUnionTable.
+// The initial marking may have been done during an asynchronous
+// collection so there may be dirty bits in the mod-union table.
+const int alignment =
+CardTableModRefBS::card_size * BitsPerWord;
+{
+// ... First handle dirty cards in CMS gen
+markFromDirtyCardsClosure.set_space(_cmsGen->cmsSpace());
+MemRegion ur = _cmsGen->used_region();
+HeapWord* lb = ur.start();
+HeapWord* ub = (HeapWord*)round_to((intptr_t)ur.end(), alignment);
+MemRegion cms_span(lb, ub);
+_modUnionTable.dirty_range_iterate_clear(cms_span,
+&markFromDirtyCardsClosure);
+verify_work_stacks_empty();
+if (PrintCMSStatistics != 0) {
+gclog_or_tty->print(" (re-scanned "SIZE_FORMAT" dirty cards in cms gen) ",
+markFromDirtyCardsClosure.num_dirty_cards());
+}
+}
+{
+// .. and then repeat for dirty cards in perm gen
+markFromDirtyCardsClosure.set_space(_permGen->cmsSpace());
+MemRegion ur = _permGen->used_region();
+HeapWord* lb = ur.start();
+HeapWord* ub = (HeapWord*)round_to((intptr_t)ur.end(), alignment);
+MemRegion perm_span(lb, ub);
+_modUnionTable.dirty_range_iterate_clear(perm_span,
+&markFromDirtyCardsClosure);
+verify_work_stacks_empty();
+if (PrintCMSStatistics != 0) {
+gclog_or_tty->print(" (re-scanned "SIZE_FORMAT" dirty cards in perm gen) ",
+markFromDirtyCardsClosure.num_dirty_cards());
+}
+}
+}
+if (VerifyDuringGC &&
+GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
+HandleMark hm;  // Discard invalid handles created during verification
+Universe::verify(true);
+}
+{
+TraceTime t("root rescan", PrintGCDetails, false, gclog_or_tty);
+verify_work_stacks_empty();
+gch->rem_set()->prepare_for_younger_refs_iterate(false); // Not parallel.
+gch->gen_process_strong_roots(_cmsGen->level(),
+true,  // younger gens as roots
+true,  // collecting perm gen
+SharedHeap::ScanningOption(roots_scanning_options()),
+NULL, &mrias_cl);
+}
+verify_work_stacks_empty();
+// Restore evacuated mark words, if any, used for overflow list links
+if (!CMSOverflowEarlyRestoration) {
+restore_preserved_marks_if_any();
+}
+verify_overflow_empty();
+}
+////////////////////////////////////////////////////////
+// Parallel Reference Processing Task Proxy Class
+////////////////////////////////////////////////////////
+class CMSRefProcTaskProxy: public AbstractGangTask {
+typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
+CMSCollector*          _collector;
+CMSBitMap*             _mark_bit_map;
+MemRegion              _span;
+OopTaskQueueSet*       _task_queues;
+ParallelTaskTerminator _term;
+ProcessTask&           _task;
+public:
+CMSRefProcTaskProxy(ProcessTask&     task,
+CMSCollector*    collector,
+const MemRegion& span,
+CMSBitMap*       mark_bit_map,
+int              total_workers,
+OopTaskQueueSet* task_queues):
+AbstractGangTask("Process referents by policy in parallel"),
+_task(task),
+_collector(collector), _span(span), _mark_bit_map(mark_bit_map),
+_task_queues(task_queues),
+_term(total_workers, task_queues)
+{ }
+OopTaskQueueSet* task_queues() { return _task_queues; }
+OopTaskQueue* work_queue(int i) { return task_queues()->queue(i); }
+ParallelTaskTerminator* terminator() { return &_term; }
+void do_work_steal(int i,
+CMSParDrainMarkingStackClosure* drain,
+CMSParKeepAliveClosure* keep_alive,
+int* seed);
+virtual void work(int i);
+};
+void CMSRefProcTaskProxy::work(int i) {
+CMSParKeepAliveClosure par_keep_alive(_collector, _span,
+_mark_bit_map, work_queue(i));
+CMSParDrainMarkingStackClosure par_drain_stack(_collector, _span,
+_mark_bit_map, work_queue(i));
+CMSIsAliveClosure is_alive_closure(_mark_bit_map);
+_task.work(i, is_alive_closure, par_keep_alive, par_drain_stack);
+if (_task.marks_oops_alive()) {
+do_work_steal(i, &par_drain_stack, &par_keep_alive,
+_collector->hash_seed(i));
+}
+assert(work_queue(i)->size() == 0, "work_queue should be empty");
+assert(_collector->_overflow_list == NULL, "non-empty _overflow_list");
+}
+class CMSRefEnqueueTaskProxy: public AbstractGangTask {
+typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
+EnqueueTask& _task;
+public:
+CMSRefEnqueueTaskProxy(EnqueueTask& task)
+: AbstractGangTask("Enqueue reference objects in parallel"),
+_task(task)
+{ }
+virtual void work(int i)
+{
+_task.work(i);
+}
+};
+CMSParKeepAliveClosure::CMSParKeepAliveClosure(CMSCollector* collector,
+MemRegion span, CMSBitMap* bit_map, OopTaskQueue* work_queue):
+_collector(collector),
+_span(span),
+_bit_map(bit_map),
+_work_queue(work_queue),
+_mark_and_push(collector, span, bit_map, work_queue),
+_low_water_mark(MIN2((uint)(work_queue->max_elems()/4),
+(uint)(CMSWorkQueueDrainThreshold * ParallelGCThreads)))
+{ }
+// . see if we can share work_queues with ParNew? XXX
+void CMSRefProcTaskProxy::do_work_steal(int i,
+CMSParDrainMarkingStackClosure* drain,
+CMSParKeepAliveClosure* keep_alive,
+int* seed) {
+OopTaskQueue* work_q = work_queue(i);
+NOT_PRODUCT(int num_steals = 0;)
+oop obj_to_scan;
+size_t num_from_overflow_list =
+MIN2((size_t)work_q->max_elems()/4,
+(size_t)ParGCDesiredObjsFromOverflowList);
+while (true) {
+// Completely finish any left over work from (an) earlier round(s)
+drain->trim_queue(0);
+// Now check if there's any work in the overflow list
+if (_collector->par_take_from_overflow_list(num_from_overflow_list,
+work_q)) {
+// Found something in global overflow list;
+// not yet ready to go stealing work from others.
+// We'd like to assert(work_q->size() != 0, ...)
+// because we just took work from the overflow list,
+// but of course we can't, since all of that might have
+// been already stolen from us.
+continue;
+}
+// Verify that we have no work before we resort to stealing
+assert(work_q->size() == 0, "Have work, shouldn't steal");
+// Try to steal from other queues that have work
+if (task_queues()->steal(i, seed, /* reference */ obj_to_scan)) {
+NOT_PRODUCT(num_steals++;)
+assert(obj_to_scan->is_oop(), "Oops, not an oop!");
+assert(_mark_bit_map->isMarked((HeapWord*)obj_to_scan), "Stole an unmarked oop?");
+// Do scanning work
+obj_to_scan->oop_iterate(keep_alive);
+// Loop around, finish this work, and try to steal some more
+} else if (terminator()->offer_termination()) {
+break;  // nirvana from the infinite cycle
+}
+}
+NOT_PRODUCT(
+if (PrintCMSStatistics != 0) {
+gclog_or_tty->print("\n\t(%d: stole %d oops)", i, num_steals);
+}
+)
+}
+void CMSRefProcTaskExecutor::execute(ProcessTask& task)
+{
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+WorkGang* workers = gch->workers();
+assert(workers != NULL, "Need parallel worker threads.");
+int n_workers = workers->total_workers();
+CMSRefProcTaskProxy rp_task(task, &_collector,
+_collector.ref_processor()->span(),
+_collector.markBitMap(),
+n_workers, _collector.task_queues());
+workers->run_task(&rp_task);
+}
+void CMSRefProcTaskExecutor::execute(EnqueueTask& task)
+{
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+WorkGang* workers = gch->workers();
+assert(workers != NULL, "Need parallel worker threads.");
+CMSRefEnqueueTaskProxy enq_task(task);
+workers->run_task(&enq_task);
+}
+void CMSCollector::refProcessingWork(bool asynch, bool clear_all_soft_refs) {
+ResourceMark rm;
+HandleMark   hm;
+ReferencePolicy* soft_ref_policy;
+assert(!ref_processor()->enqueuing_is_done(), "Enqueuing should not be complete");
+// Process weak references.
+if (clear_all_soft_refs) {
+soft_ref_policy = new AlwaysClearPolicy();
+} else {
+#ifdef COMPILER2
+soft_ref_policy = new LRUMaxHeapPolicy();
+#else
+soft_ref_policy = new LRUCurrentHeapPolicy();
+#endif // COMPILER2
+}
+verify_work_stacks_empty();
+ReferenceProcessor* rp = ref_processor();
+assert(rp->span().equals(_span), "Spans should be equal");
+CMSKeepAliveClosure cmsKeepAliveClosure(this, _span, &_markBitMap,
+&_markStack);
+CMSDrainMarkingStackClosure cmsDrainMarkingStackClosure(this,
+_span, &_markBitMap, &_markStack,
+&cmsKeepAliveClosure);
+{
+TraceTime t("weak refs processing", PrintGCDetails, false, gclog_or_tty);
+if (rp->processing_is_mt()) {
+CMSRefProcTaskExecutor task_executor(*this);
+rp->process_discovered_references(soft_ref_policy,
+&_is_alive_closure,
+&cmsKeepAliveClosure,
+&cmsDrainMarkingStackClosure,
+&task_executor);
+} else {
+rp->process_discovered_references(soft_ref_policy,
+&_is_alive_closure,
+&cmsKeepAliveClosure,
+&cmsDrainMarkingStackClosure,
+NULL);
+}
+verify_work_stacks_empty();
+}
+if (cms_should_unload_classes()) {
+{
+TraceTime t("class unloading", PrintGCDetails, false, gclog_or_tty);
+// Follow SystemDictionary roots and unload classes
+bool purged_class = SystemDictionary::do_unloading(&_is_alive_closure);
+// Follow CodeCache roots and unload any methods marked for unloading
+CodeCache::do_unloading(&_is_alive_closure,
+&cmsKeepAliveClosure,
+purged_class);
+cmsDrainMarkingStackClosure.do_void();
+verify_work_stacks_empty();
+// Update subklass/sibling/implementor links in KlassKlass descendants
+assert(!_revisitStack.isEmpty(), "revisit stack should not be empty");
+oop k;
+while ((k = _revisitStack.pop()) != NULL) {
+((Klass*)(oopDesc*)k)->follow_weak_klass_links(
+&_is_alive_closure,
+&cmsKeepAliveClosure);
+}
+assert(!ClassUnloading ||
+(_markStack.isEmpty() && overflow_list_is_empty()),
+"Should not have found new reachable objects");
+assert(_revisitStack.isEmpty(), "revisit stack should have been drained");
+cmsDrainMarkingStackClosure.do_void();
+verify_work_stacks_empty();
+}
+{
+TraceTime t("scrub symbol & string tables", PrintGCDetails, false, gclog_or_tty);
+// Now clean up stale oops in SymbolTable and StringTable
+SymbolTable::unlink(&_is_alive_closure);
+StringTable::unlink(&_is_alive_closure);
+}
+}
+verify_work_stacks_empty();
+// Restore any preserved marks as a result of mark stack or
+// work queue overflow
+restore_preserved_marks_if_any();  // done single-threaded for now
+rp->set_enqueuing_is_done(true);
+if (rp->processing_is_mt()) {
+CMSRefProcTaskExecutor task_executor(*this);
+rp->enqueue_discovered_references(&task_executor);
+} else {
+rp->enqueue_discovered_references(NULL);
+}
+rp->verify_no_references_recorded();
+assert(!rp->discovery_enabled(), "should have been disabled");
+// JVMTI object tagging is based on JNI weak refs. If any of these
+// refs were cleared then JVMTI needs to update its maps and
+// maybe post ObjectFrees to agents.
+JvmtiExport::cms_ref_processing_epilogue();
+}
+#ifndef PRODUCT
+void CMSCollector::check_correct_thread_executing() {
+Thread* t = Thread::current();
+// Only the VM thread or the CMS thread should be here.
+assert(t->is_ConcurrentGC_thread() || t->is_VM_thread(),
+"Unexpected thread type");
+// If this is the vm thread, the foreground process
+// should not be waiting.  Note that _foregroundGCIsActive is
+// true while the foreground collector is waiting.
+if (_foregroundGCShouldWait) {
+// We cannot be the VM thread
+assert(t->is_ConcurrentGC_thread(),
+"Should be CMS thread");
+} else {
+// We can be the CMS thread only if we are in a stop-world
+// phase of CMS collection.
+if (t->is_ConcurrentGC_thread()) {
+assert(_collectorState == InitialMarking ||
+_collectorState == FinalMarking,
+"Should be a stop-world phase");
+// The CMS thread should be holding the CMS_token.
+assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
+"Potential interference with concurrently "
+"executing VM thread");
+}
+}
+}
+#endif
+void CMSCollector::sweep(bool asynch) {
+assert(_collectorState == Sweeping, "just checking");
+check_correct_thread_executing();
+verify_work_stacks_empty();
+verify_overflow_empty();
+incrementSweepCount();
+_sweep_timer.stop();
+_sweep_estimate.sample(_sweep_timer.seconds());
+size_policy()->avg_cms_free_at_sweep()->sample(_cmsGen->free());
+// PermGen verification support: If perm gen sweeping is disabled in
+// this cycle, we preserve the perm gen object "deadness" information
+// in the perm_gen_verify_bit_map. In order to do that we traverse
+// all blocks in perm gen and mark all dead objects.
+if (verifying() && !cms_should_unload_classes()) {
+CMSTokenSyncWithLocks ts(true, _permGen->freelistLock(),
+bitMapLock());
+assert(perm_gen_verify_bit_map()->sizeInBits() != 0,
+"Should have already been allocated");
+MarkDeadObjectsClosure mdo(this, _permGen->cmsSpace(),
+markBitMap(), perm_gen_verify_bit_map());
+_permGen->cmsSpace()->blk_iterate(&mdo);
+}
+if (asynch) {
+TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
+CMSPhaseAccounting pa(this, "sweep", !PrintGCDetails);
+// First sweep the old gen then the perm gen
+{
+CMSTokenSyncWithLocks ts(true, _cmsGen->freelistLock(),
+bitMapLock());
+sweepWork(_cmsGen, asynch);
+}
+// Now repeat for perm gen
+if (cms_should_unload_classes()) {
+CMSTokenSyncWithLocks ts(true, _permGen->freelistLock(),
+bitMapLock());
+sweepWork(_permGen, asynch);
+}
+// Update Universe::_heap_*_at_gc figures.
+// We need all the free list locks to make the abstract state
+// transition from Sweeping to Resetting. See detailed note
+// further below.
+{
+CMSTokenSyncWithLocks ts(true, _cmsGen->freelistLock(),
+_permGen->freelistLock());
+// Update heap occupancy information which is used as
+// input to soft ref clearing policy at the next gc.
+Universe::update_heap_info_at_gc();
+_collectorState = Resizing;
+}
+} else {
+// already have needed locks
+sweepWork(_cmsGen,  asynch);
+if (cms_should_unload_classes()) {
+sweepWork(_permGen, asynch);
+}
+// Update heap occupancy information which is used as
+// input to soft ref clearing policy at the next gc.
+Universe::update_heap_info_at_gc();
+_collectorState = Resizing;
+}
+verify_work_stacks_empty();
+verify_overflow_empty();
+_sweep_timer.reset();
+_sweep_timer.start();
+update_time_of_last_gc(os::javaTimeMillis());
+// NOTE on abstract state transitions:
+// Mutators allocate-live and/or mark the mod-union table dirty
+// based on the state of the collection.  The former is done in
+// the interval [Marking, Sweeping] and the latter in the interval
+// [Marking, Sweeping).  Thus the transitions into the Marking state
+// and out of the Sweeping state must be synchronously visible
+// globally to the mutators.
+// The transition into the Marking state happens with the world
+// stopped so the mutators will globally see it.  Sweeping is
+// done asynchronously by the background collector so the transition
+// from the Sweeping state to the Resizing state must be done
+// under the freelistLock (as is the check for whether to
+// allocate-live and whether to dirty the mod-union table).
+assert(_collectorState == Resizing, "Change of collector state to"
+" Resizing must be done under the freelistLocks (plural)");
+// Now that sweeping has been completed, if the GCH's
+// incremental_collection_will_fail flag is set, clear it,
+// thus inviting a younger gen collection to promote into
+// this generation. If such a promotion may still fail,
+// the flag will be set again when a young collection is
+// attempted.
+// I think the incremental_collection_will_fail flag's use
+// is specific to a 2 generation collection policy, so i'll
+// assert that that's the configuration we are operating within.
+// The use of the flag can and should be generalized appropriately
+// in the future to deal with a general n-generation system.
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+assert(gch->collector_policy()->is_two_generation_policy(),
+"Resetting of incremental_collection_will_fail flag"
+" may be incorrect otherwise");
+gch->clear_incremental_collection_will_fail();
+gch->update_full_collections_completed(_collection_count_start);
+}
+// FIX ME!!! Looks like this belongs in CFLSpace, with
+// CMSGen merely delegating to it.
+void ConcurrentMarkSweepGeneration::setNearLargestChunk() {
+double nearLargestPercent = 0.999;
+HeapWord*  minAddr        = _cmsSpace->bottom();
+HeapWord*  largestAddr    =
+(HeapWord*) _cmsSpace->dictionary()->findLargestDict();
+if (largestAddr == 0) {
+// The dictionary appears to be empty.  In this case
+// try to coalesce at the end of the heap.
+largestAddr = _cmsSpace->end();
+}
+size_t largestOffset     = pointer_delta(largestAddr, minAddr);
+size_t nearLargestOffset =
+(size_t)((double)largestOffset * nearLargestPercent) - MinChunkSize;
+_cmsSpace->set_nearLargestChunk(minAddr + nearLargestOffset);
+}
+bool ConcurrentMarkSweepGeneration::isNearLargestChunk(HeapWord* addr) {
+return addr >= _cmsSpace->nearLargestChunk();
+}
+FreeChunk* ConcurrentMarkSweepGeneration::find_chunk_at_end() {
+return _cmsSpace->find_chunk_at_end();
+}
+void ConcurrentMarkSweepGeneration::update_gc_stats(int current_level,
+bool full) {
+// The next lower level has been collected.  Gather any statistics
+// that are of interest at this point.
+if (!full && (current_level + 1) == level()) {
+// Gather statistics on the young generation collection.
+collector()->stats().record_gc0_end(used());
+}
+}
+CMSAdaptiveSizePolicy* ConcurrentMarkSweepGeneration::size_policy() {
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+assert(gch->kind() == CollectedHeap::GenCollectedHeap,
+"Wrong type of heap");
+CMSAdaptiveSizePolicy* sp = (CMSAdaptiveSizePolicy*)
+gch->gen_policy()->size_policy();
+assert(sp->is_gc_cms_adaptive_size_policy(),
+"Wrong type of size policy");
+return sp;
+}
+void ConcurrentMarkSweepGeneration::rotate_debug_collection_type() {
+if (PrintGCDetails && Verbose) {
+gclog_or_tty->print("Rotate from %d ", _debug_collection_type);
+}
+_debug_collection_type = (CollectionTypes) (_debug_collection_type + 1);
+_debug_collection_type =
+(CollectionTypes) (_debug_collection_type % Unknown_collection_type);
+if (PrintGCDetails && Verbose) {
+gclog_or_tty->print_cr("to %d ", _debug_collection_type);
+}
+}
+void CMSCollector::sweepWork(ConcurrentMarkSweepGeneration* gen,
+bool asynch) {
+// We iterate over the space(s) underlying this generation,
+// checking the mark bit map to see if the bits corresponding
+// to specific blocks are marked or not. Blocks that are
+// marked are live and are not swept up. All remaining blocks
+// are swept up, with coalescing on-the-fly as we sweep up
+// contiguous free and/or garbage blocks:
+// We need to ensure that the sweeper synchronizes with allocators
+// and stop-the-world collectors. In particular, the following
+// locks are used:
+// . CMS token: if this is held, a stop the world collection cannot occur
+// . freelistLock: if this is held no allocation can occur from this
+//                 generation by another thread
+// . bitMapLock: if this is held, no other thread can access or update
+//
+// Note that we need to hold the freelistLock if we use
+// block iterate below; else the iterator might go awry if
+// a mutator (or promotion) causes block contents to change
+// (for instance if the allocator divvies up a block).
+// If we hold the free list lock, for all practical purposes
+// young generation GC's can't occur (they'll usually need to
+// promote), so we might as well prevent all young generation
+// GC's while we do a sweeping step. For the same reason, we might
+// as well take the bit map lock for the entire duration
+// check that we hold the requisite locks
+assert(have_cms_token(), "Should hold cms token");
+assert(   (asynch && ConcurrentMarkSweepThread::cms_thread_has_cms_token())
+|| (!asynch && ConcurrentMarkSweepThread::vm_thread_has_cms_token()),
+"Should possess CMS token to sweep");
+assert_lock_strong(gen->freelistLock());
+assert_lock_strong(bitMapLock());
+assert(!_sweep_timer.is_active(), "Was switched off in an outer context");
+gen->cmsSpace()->beginSweepFLCensus((float)(_sweep_timer.seconds()),
+_sweep_estimate.padded_average());
+gen->setNearLargestChunk();
+{
+SweepClosure sweepClosure(this, gen, &_markBitMap,
+CMSYield && asynch);
+gen->cmsSpace()->blk_iterate_careful(&sweepClosure);
+// We need to free-up/coalesce garbage/blocks from a
+// co-terminal free run. This is done in the SweepClosure
+// destructor; so, do not remove this scope, else the
+// end-of-sweep-census below will be off by a little bit.
+}
+gen->cmsSpace()->sweep_completed();
+gen->cmsSpace()->endSweepFLCensus(sweepCount());
+}
+// Reset CMS data structures (for now just the marking bit map)
+// preparatory for the next cycle.
+void CMSCollector::reset(bool asynch) {
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+CMSAdaptiveSizePolicy* sp = size_policy();
+AdaptiveSizePolicyOutput(sp, gch->total_collections());
+if (asynch) {
+CMSTokenSyncWithLocks ts(true, bitMapLock());
+// If the state is not "Resetting", the foreground  thread
+// has done a collection and the resetting.
+if (_collectorState != Resetting) {
+assert(_collectorState == Idling, "The state should only change"
+" because the foreground collector has finished the collection");
+return;
+}
+// Clear the mark bitmap (no grey objects to start with)
+// for the next cycle.
+TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
+CMSPhaseAccounting cmspa(this, "reset", !PrintGCDetails);
+HeapWord* curAddr = _markBitMap.startWord();
+while (curAddr < _markBitMap.endWord()) {
+size_t remaining  = pointer_delta(_markBitMap.endWord(), curAddr);
+MemRegion chunk(curAddr, MIN2(CMSBitMapYieldQuantum, remaining));
+_markBitMap.clear_large_range(chunk);
+if (ConcurrentMarkSweepThread::should_yield() &&
+!foregroundGCIsActive() &&
+CMSYield) {
+assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
+"CMS thread should hold CMS token");
+assert_lock_strong(bitMapLock());
+bitMapLock()->unlock();
+ConcurrentMarkSweepThread::desynchronize(true);
+ConcurrentMarkSweepThread::acknowledge_yield_request();
+stopTimer();
+if (PrintCMSStatistics != 0) {
+incrementYields();
+}
+icms_wait();
+// See the comment in coordinator_yield()
+for (unsigned i = 0; i < CMSYieldSleepCount &&
+ConcurrentMarkSweepThread::should_yield() &&
+!CMSCollector::foregroundGCIsActive(); ++i) {
+os::sleep(Thread::current(), 1, false);
+ConcurrentMarkSweepThread::acknowledge_yield_request();
+}
+ConcurrentMarkSweepThread::synchronize(true);
+bitMapLock()->lock_without_safepoint_check();
+startTimer();
+}
+curAddr = chunk.end();
+}
+_collectorState = Idling;
+} else {
+// already have the lock
+assert(_collectorState == Resetting, "just checking");
+assert_lock_strong(bitMapLock());
+_markBitMap.clear_all();
+_collectorState = Idling;
+}
+// Stop incremental mode after a cycle completes, so that any future cycles
+// are triggered by allocation.
+stop_icms();
+NOT_PRODUCT(
+if (RotateCMSCollectionTypes) {
+_cmsGen->rotate_debug_collection_type();
+}
+)
+}
+void CMSCollector::do_CMS_operation(CMS_op_type op) {
+gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
+TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
+TraceTime t("GC", PrintGC, !PrintGCDetails, gclog_or_tty);
+TraceCollectorStats tcs(counters());
+switch (op) {
+case CMS_op_checkpointRootsInitial: {
+checkpointRootsInitial(true);       // asynch
+if (PrintGC) {
+_cmsGen->printOccupancy("initial-mark");
+}
+break;
+}
+case CMS_op_checkpointRootsFinal: {
+checkpointRootsFinal(true,    // asynch
+false,   // !clear_all_soft_refs
+false);  // !init_mark_was_synchronous
+if (PrintGC) {
+_cmsGen->printOccupancy("remark");
+}
+break;
+}
+default:
+fatal("No such CMS_op");
+}
+}
+#ifndef PRODUCT
+size_t const CMSCollector::skip_header_HeapWords() {
+return FreeChunk::header_size();
+}
+// Try and collect here conditions that should hold when
+// CMS thread is exiting. The idea is that the foreground GC
+// thread should not be blocked if it wants to terminate
+// the CMS thread and yet continue to run the VM for a while
+// after that.
+void CMSCollector::verify_ok_to_terminate() const {
+assert(Thread::current()->is_ConcurrentGC_thread(),
+"should be called by CMS thread");
+assert(!_foregroundGCShouldWait, "should be false");
+// We could check here that all the various low-level locks
+// are not held by the CMS thread, but that is overkill; see
+// also CMSThread::verify_ok_to_terminate() where the CGC_lock
+// is checked.
+}
+#endif
+size_t CMSCollector::block_size_using_printezis_bits(HeapWord* addr) const {
+assert(_markBitMap.isMarked(addr) && _markBitMap.isMarked(addr + 1),
+"missing Printezis mark?");
+HeapWord* nextOneAddr = _markBitMap.getNextMarkedWordAddress(addr + 2);
+size_t size = pointer_delta(nextOneAddr + 1, addr);
+assert(size == CompactibleFreeListSpace::adjustObjectSize(size),
+"alignment problem");
+assert(size >= 3, "Necessary for Printezis marks to work");
+return size;
+}
+// A variant of the above (block_size_using_printezis_bits()) except
+// that we return 0 if the P-bits are not yet set.
+size_t CMSCollector::block_size_if_printezis_bits(HeapWord* addr) const {
+if (_markBitMap.isMarked(addr)) {
+assert(_markBitMap.isMarked(addr + 1), "Missing Printezis bit?");
+HeapWord* nextOneAddr = _markBitMap.getNextMarkedWordAddress(addr + 2);
+size_t size = pointer_delta(nextOneAddr + 1, addr);
+assert(size == CompactibleFreeListSpace::adjustObjectSize(size),
+"alignment problem");
+assert(size >= 3, "Necessary for Printezis marks to work");
+return size;
+} else {
+assert(!_markBitMap.isMarked(addr + 1), "Bit map inconsistency?");
+return 0;
+}
+}
+HeapWord* CMSCollector::next_card_start_after_block(HeapWord* addr) const {
+size_t sz = 0;
+oop p = (oop)addr;
+if (p->klass() != NULL && p->is_parsable()) {
+sz = CompactibleFreeListSpace::adjustObjectSize(p->size());
+} else {
+sz = block_size_using_printezis_bits(addr);
+}
+assert(sz > 0, "size must be nonzero");
+HeapWord* next_block = addr + sz;
+HeapWord* next_card  = (HeapWord*)round_to((uintptr_t)next_block,
+CardTableModRefBS::card_size);
+assert(round_down((uintptr_t)addr,      CardTableModRefBS::card_size) <
+round_down((uintptr_t)next_card, CardTableModRefBS::card_size),
+"must be different cards");
+return next_card;
+}
+// CMS Bit Map Wrapper /////////////////////////////////////////
+// Construct a CMS bit map infrastructure, but don't create the
+// bit vector itself. That is done by a separate call CMSBitMap::allocate()
+// further below.
+CMSBitMap::CMSBitMap(int shifter, int mutex_rank, const char* mutex_name):
+_bm(NULL,0),
+_shifter(shifter),
+_lock(mutex_rank >= 0 ? new Mutex(mutex_rank, mutex_name, true) : NULL)
+{
+_bmStartWord = 0;
+_bmWordSize  = 0;
+}
+bool CMSBitMap::allocate(MemRegion mr) {
+_bmStartWord = mr.start();
+_bmWordSize  = mr.word_size();
+ReservedSpace brs(ReservedSpace::allocation_align_size_up(
+(_bmWordSize >> (_shifter + LogBitsPerByte)) + 1));
+if (!brs.is_reserved()) {
+warning("CMS bit map allocation failure");
+return false;
+}
+// For now we'll just commit all of the bit map up fromt.
+// Later on we'll try to be more parsimonious with swap.
+if (!_virtual_space.initialize(brs, brs.size())) {
+warning("CMS bit map backing store failure");
+return false;
+}
+assert(_virtual_space.committed_size() == brs.size(),
+"didn't reserve backing store for all of CMS bit map?");
+_bm.set_map((uintptr_t*)_virtual_space.low());
+assert(_virtual_space.committed_size() << (_shifter + LogBitsPerByte) >=
+_bmWordSize, "inconsistency in bit map sizing");
+_bm.set_size(_bmWordSize >> _shifter);
+// bm.clear(); // can we rely on getting zero'd memory? verify below
+assert(isAllClear(),
+"Expected zero'd memory from ReservedSpace constructor");
+assert(_bm.size() == heapWordDiffToOffsetDiff(sizeInWords()),
+"consistency check");
+return true;
+}
+void CMSBitMap::dirty_range_iterate_clear(MemRegion mr, MemRegionClosure* cl) {
+HeapWord *next_addr, *end_addr, *last_addr;
+assert_locked();
+assert(covers(mr), "out-of-range error");
+// XXX assert that start and end are appropriately aligned
+for (next_addr = mr.start(), end_addr = mr.end();
+next_addr < end_addr; next_addr = last_addr) {
+MemRegion dirty_region = getAndClearMarkedRegion(next_addr, end_addr);
+last_addr = dirty_region.end();
+if (!dirty_region.is_empty()) {
+cl->do_MemRegion(dirty_region);
+} else {
+assert(last_addr == end_addr, "program logic");
+return;
+}
+}
+}
+#ifndef PRODUCT
+void CMSBitMap::assert_locked() const {
+CMSLockVerifier::assert_locked(lock());
+}
+bool CMSBitMap::covers(MemRegion mr) const {
+// assert(_bm.map() == _virtual_space.low(), "map inconsistency");
+assert((size_t)_bm.size() == (_bmWordSize >> _shifter),
+"size inconsistency");
+return (mr.start() >= _bmStartWord) &&
+(mr.end()   <= endWord());
+}
+bool CMSBitMap::covers(HeapWord* start, size_t size) const {
+return (start >= _bmStartWord && (start + size) <= endWord());
+}
+void CMSBitMap::verifyNoOneBitsInRange(HeapWord* left, HeapWord* right) {
+// verify that there are no 1 bits in the interval [left, right)
+FalseBitMapClosure falseBitMapClosure;
+iterate(&falseBitMapClosure, left, right);
+}
+void CMSBitMap::region_invariant(MemRegion mr)
+{
+assert_locked();
+// mr = mr.intersection(MemRegion(_bmStartWord, _bmWordSize));
+assert(!mr.is_empty(), "unexpected empty region");
+assert(covers(mr), "mr should be covered by bit map");
+// convert address range into offset range
+size_t start_ofs = heapWordToOffset(mr.start());
+// Make sure that end() is appropriately aligned
+assert(mr.end() == (HeapWord*)round_to((intptr_t)mr.end(),
+(1 << (_shifter+LogHeapWordSize))),
+"Misaligned mr.end()");
+size_t end_ofs   = heapWordToOffset(mr.end());
+assert(end_ofs > start_ofs, "Should mark at least one bit");
+}
+#endif
+bool CMSMarkStack::allocate(size_t size) {
+// allocate a stack of the requisite depth
+ReservedSpace rs(ReservedSpace::allocation_align_size_up(
+size * sizeof(oop)));
+if (!rs.is_reserved()) {
+warning("CMSMarkStack allocation failure");
+return false;
+}
+if (!_virtual_space.initialize(rs, rs.size())) {
+warning("CMSMarkStack backing store failure");
+return false;
+}
+assert(_virtual_space.committed_size() == rs.size(),
+"didn't reserve backing store for all of CMS stack?");
+_base = (oop*)(_virtual_space.low());
+_index = 0;
+_capacity = size;
+NOT_PRODUCT(_max_depth = 0);
+return true;
+}
+// XXX FIX ME !!! In the MT case we come in here holding a
+// leaf lock. For printing we need to take a further lock
+// which has lower rank. We need to recallibrate the two
+// lock-ranks involved in order to be able to rpint the
+// messages below. (Or defer the printing to the caller.
+// For now we take the expedient path of just disabling the
+// messages for the problematic case.)
+void CMSMarkStack::expand() {
+assert(_capacity <= CMSMarkStackSizeMax, "stack bigger than permitted");
+if (_capacity == CMSMarkStackSizeMax) {
+if (_hit_limit++ == 0 && !CMSConcurrentMTEnabled && PrintGCDetails) {
+// We print a warning message only once per CMS cycle.
+gclog_or_tty->print_cr(" (benign) Hit CMSMarkStack max size limit");
+}
+return;
+}
+// Double capacity if possible
+size_t new_capacity = MIN2(_capacity*2, CMSMarkStackSizeMax);
+// Do not give up existing stack until we have managed to
+// get the double capacity that we desired.
+ReservedSpace rs(ReservedSpace::allocation_align_size_up(
+new_capacity * sizeof(oop)));
+if (rs.is_reserved()) {
+// Release the backing store associated with old stack
+_virtual_space.release();
+// Reinitialize virtual space for new stack
+if (!_virtual_space.initialize(rs, rs.size())) {
+fatal("Not enough swap for expanded marking stack");
+}
+_base = (oop*)(_virtual_space.low());
+_index = 0;
+_capacity = new_capacity;
+} else if (_failed_double++ == 0 && !CMSConcurrentMTEnabled && PrintGCDetails) {
+// Failed to double capacity, continue;
+// we print a detail message only once per CMS cycle.
+gclog_or_tty->print(" (benign) Failed to expand marking stack from "SIZE_FORMAT"K to "
+SIZE_FORMAT"K",
+_capacity / K, new_capacity / K);
+}
+}
+// Closures
+// XXX: there seems to be a lot of code  duplication here;
+// should refactor and consolidate common code.
+// This closure is used to mark refs into the CMS generation in
+// the CMS bit map. Called at the first checkpoint. This closure
+// assumes that we do not need to re-mark dirty cards; if the CMS
+// generation on which this is used is not an oldest (modulo perm gen)
+// generation then this will lose younger_gen cards!
+MarkRefsIntoClosure::MarkRefsIntoClosure(
+MemRegion span, CMSBitMap* bitMap, bool should_do_nmethods):
+_span(span),
+_bitMap(bitMap),
+_should_do_nmethods(should_do_nmethods)
+{
+assert(_ref_processor == NULL, "deliberately left NULL");
+assert(_bitMap->covers(_span), "_bitMap/_span mismatch");
+}
+void MarkRefsIntoClosure::do_oop(oop* p) {
+// if p points into _span, then mark corresponding bit in _markBitMap
+oop thisOop = *p;
+if (thisOop != NULL) {
+assert(thisOop->is_oop(), "expected an oop");
+HeapWord* addr = (HeapWord*)thisOop;
+if (_span.contains(addr)) {
+// this should be made more efficient
+_bitMap->mark(addr);
+}
+}
+}
+// A variant of the above, used for CMS marking verification.
+MarkRefsIntoVerifyClosure::MarkRefsIntoVerifyClosure(
+MemRegion span, CMSBitMap* verification_bm, CMSBitMap* cms_bm,
+bool should_do_nmethods):
+_span(span),
+_verification_bm(verification_bm),
+_cms_bm(cms_bm),
+_should_do_nmethods(should_do_nmethods) {
+assert(_ref_processor == NULL, "deliberately left NULL");
+assert(_verification_bm->covers(_span), "_verification_bm/_span mismatch");
+}
+void MarkRefsIntoVerifyClosure::do_oop(oop* p) {
+// if p points into _span, then mark corresponding bit in _markBitMap
+oop this_oop = *p;
+if (this_oop != NULL) {
+assert(this_oop->is_oop(), "expected an oop");
+HeapWord* addr = (HeapWord*)this_oop;
+if (_span.contains(addr)) {
+_verification_bm->mark(addr);
+if (!_cms_bm->isMarked(addr)) {
+oop(addr)->print();
+gclog_or_tty->print_cr(" ("INTPTR_FORMAT" should have been marked)", addr);
+fatal("... aborting");
+}
+}
+}
+}
+//////////////////////////////////////////////////
+// MarkRefsIntoAndScanClosure
+//////////////////////////////////////////////////
+MarkRefsIntoAndScanClosure::MarkRefsIntoAndScanClosure(MemRegion span,
+ReferenceProcessor* rp,
+CMSBitMap* bit_map,
+CMSBitMap* mod_union_table,
+CMSMarkStack*  mark_stack,
+CMSMarkStack*  revisit_stack,
+CMSCollector* collector,
+bool should_yield,
+bool concurrent_precleaning):
+_collector(collector),
+_span(span),
+_bit_map(bit_map),
+_mark_stack(mark_stack),
+_pushAndMarkClosure(collector, span, rp, bit_map, mod_union_table,
+mark_stack, revisit_stack, concurrent_precleaning),
+_yield(should_yield),
+_concurrent_precleaning(concurrent_precleaning),
+_freelistLock(NULL)
+{
+_ref_processor = rp;
+assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL");
+}
+// This closure is used to mark refs into the CMS generation at the
+// second (final) checkpoint, and to scan and transitively follow
+// the unmarked oops. It is also used during the concurrent precleaning
+// phase while scanning objects on dirty cards in the CMS generation.
+// The marks are made in the marking bit map and the marking stack is
+// used for keeping the (newly) grey objects during the scan.
+// The parallel version (Par_...) appears further below.
+void MarkRefsIntoAndScanClosure::do_oop(oop* p) {
+oop this_oop = *p;
+if (this_oop != NULL) {
+assert(this_oop->is_oop(), "expected an oop");
+HeapWord* addr = (HeapWord*)this_oop;
+assert(_mark_stack->isEmpty(), "post-condition (eager drainage)");
+assert(_collector->overflow_list_is_empty(), "should be empty");
+if (_span.contains(addr) &&
+!_bit_map->isMarked(addr)) {
+// mark bit map (object is now grey)
+_bit_map->mark(addr);
+// push on marking stack (stack should be empty), and drain the
+// stack by applying this closure to the oops in the oops popped
+// from the stack (i.e. blacken the grey objects)
+bool res = _mark_stack->push(this_oop);
+assert(res, "Should have space to push on empty stack");
+do {
+oop new_oop = _mark_stack->pop();
+assert(new_oop != NULL && new_oop->is_oop(), "Expected an oop");
+assert(new_oop->is_parsable(), "Found unparsable oop");
+assert(_bit_map->isMarked((HeapWord*)new_oop),
+"only grey objects on this stack");
+// iterate over the oops in this oop, marking and pushing
+// the ones in CMS heap (i.e. in _span).
+new_oop->oop_iterate(&_pushAndMarkClosure);
+// check if it's time to yield
+do_yield_check();
+} while (!_mark_stack->isEmpty() ||
+(!_concurrent_precleaning && take_from_overflow_list()));
+// if marking stack is empty, and we are not doing this
+// during precleaning, then check the overflow list
+}
+assert(_mark_stack->isEmpty(), "post-condition (eager drainage)");
+assert(_collector->overflow_list_is_empty(),
+"overflow list was drained above");
+// We could restore evacuated mark words, if any, used for
+// overflow list links here because the overflow list is
+// provably empty here. That would reduce the maximum
+// size requirements for preserved_{oop,mark}_stack.
+// But we'll just postpone it until we are all done
+// so we can just stream through.
+if (!_concurrent_precleaning && CMSOverflowEarlyRestoration) {
+_collector->restore_preserved_marks_if_any();
+assert(_collector->no_preserved_marks(), "No preserved marks");
+}
+assert(!CMSOverflowEarlyRestoration || _collector->no_preserved_marks(),
+"All preserved marks should have been restored above");
+}
+}
+void MarkRefsIntoAndScanClosure::do_yield_work() {
+assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
+"CMS thread should hold CMS token");
+assert_lock_strong(_freelistLock);
+assert_lock_strong(_bit_map->lock());
+// relinquish the free_list_lock and bitMaplock()
+_bit_map->lock()->unlock();
+_freelistLock->unlock();
+ConcurrentMarkSweepThread::desynchronize(true);
+ConcurrentMarkSweepThread::acknowledge_yield_request();
+_collector->stopTimer();
+GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr());
+if (PrintCMSStatistics != 0) {
+_collector->incrementYields();
+}
+_collector->icms_wait();
+// See the comment in coordinator_yield()
+for (unsigned i = 0; i < CMSYieldSleepCount &&
+ConcurrentMarkSweepThread::should_yield() &&
+!CMSCollector::foregroundGCIsActive(); ++i) {
+os::sleep(Thread::current(), 1, false);
+ConcurrentMarkSweepThread::acknowledge_yield_request();
+}
+ConcurrentMarkSweepThread::synchronize(true);
+_freelistLock->lock_without_safepoint_check();
+_bit_map->lock()->lock_without_safepoint_check();
+_collector->startTimer();
+}
+///////////////////////////////////////////////////////////
+// Par_MarkRefsIntoAndScanClosure: a parallel version of
+//                                 MarkRefsIntoAndScanClosure
+///////////////////////////////////////////////////////////
+Par_MarkRefsIntoAndScanClosure::Par_MarkRefsIntoAndScanClosure(
+CMSCollector* collector, MemRegion span, ReferenceProcessor* rp,
+CMSBitMap* bit_map, OopTaskQueue* work_queue, CMSMarkStack*  revisit_stack):
+_span(span),
+_bit_map(bit_map),
+_work_queue(work_queue),
+_low_water_mark(MIN2((uint)(work_queue->max_elems()/4),
+(uint)(CMSWorkQueueDrainThreshold * ParallelGCThreads))),
+_par_pushAndMarkClosure(collector, span, rp, bit_map, work_queue,
+revisit_stack)
+{
+_ref_processor = rp;
+assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL");
+}
+// This closure is used to mark refs into the CMS generation at the
+// second (final) checkpoint, and to scan and transitively follow
+// the unmarked oops. The marks are made in the marking bit map and
+// the work_queue is used for keeping the (newly) grey objects during
+// the scan phase whence they are also available for stealing by parallel
+// threads. Since the marking bit map is shared, updates are
+// synchronized (via CAS).
+void Par_MarkRefsIntoAndScanClosure::do_oop(oop* p) {
+oop this_oop = *p;
+if (this_oop != NULL) {
+// Ignore mark word because this could be an already marked oop
+// that may be chained at the end of the overflow list.
+assert(this_oop->is_oop(true /* ignore mark word */), "expected an oop");
+HeapWord* addr = (HeapWord*)this_oop;
+if (_span.contains(addr) &&
+!_bit_map->isMarked(addr)) {
+// mark bit map (object will become grey):
+// It is possible for several threads to be
+// trying to "claim" this object concurrently;
+// the unique thread that succeeds in marking the
+// object first will do the subsequent push on
+// to the work queue (or overflow list).
+if (_bit_map->par_mark(addr)) {
+// push on work_queue (which may not be empty), and trim the
+// queue to an appropriate length by applying this closure to
+// the oops in the oops popped from the stack (i.e. blacken the
+// grey objects)
+bool res = _work_queue->push(this_oop);
+assert(res, "Low water mark should be less than capacity?");
+trim_queue(_low_water_mark);
+} // Else, another thread claimed the object
+}
+}
+}
+// This closure is used to rescan the marked objects on the dirty cards
+// in the mod union table and the card table proper.
+size_t ScanMarkedObjectsAgainCarefullyClosure::do_object_careful_m(
+oop p, MemRegion mr) {
+size_t size = 0;
+HeapWord* addr = (HeapWord*)p;
+DEBUG_ONLY(_collector->verify_work_stacks_empty();)
+assert(_span.contains(addr), "we are scanning the CMS generation");
+// check if it's time to yield
+if (do_yield_check()) {
+// We yielded for some foreground stop-world work,
+// and we have been asked to abort this ongoing preclean cycle.
+return 0;
+}
+if (_bitMap->isMarked(addr)) {
+// it's marked; is it potentially uninitialized?
+if (p->klass() != NULL) {
+if (CMSPermGenPrecleaningEnabled && !p->is_parsable()) {
+// Signal precleaning to redirty the card since
+// the klass pointer is already installed.
+assert(size == 0, "Initial value");
+} else {
+assert(p->is_parsable(), "must be parsable.");
+// an initialized object; ignore mark word in verification below
+// since we are running concurrent with mutators
+assert(p->is_oop(true), "should be an oop");
+if (p->is_objArray()) {
+// objArrays are precisely marked; restrict scanning
+// to dirty cards only.
+size = p->oop_iterate(_scanningClosure, mr);
+assert(size == CompactibleFreeListSpace::adjustObjectSize(size),
+"adjustObjectSize should be the identity for array sizes, "
+"which are necessarily larger than minimum object size of "
+"two heap words");
+} else {
+// A non-array may have been imprecisely marked; we need
+// to scan object in its entirety.
+size = CompactibleFreeListSpace::adjustObjectSize(
+p->oop_iterate(_scanningClosure));
+}
+#ifdef DEBUG
+size_t direct_size =
+CompactibleFreeListSpace::adjustObjectSize(p->size());
+assert(size == direct_size, "Inconsistency in size");
+assert(size >= 3, "Necessary for Printezis marks to work");
+if (!_bitMap->isMarked(addr+1)) {
+_bitMap->verifyNoOneBitsInRange(addr+2, addr+size);
+} else {
+_bitMap->verifyNoOneBitsInRange(addr+2, addr+size-1);
+assert(_bitMap->isMarked(addr+size-1),
+"inconsistent Printezis mark");
+}
+#endif // DEBUG
+}
+} else {
+// an unitialized object
+assert(_bitMap->isMarked(addr+1), "missing Printezis mark?");
+HeapWord* nextOneAddr = _bitMap->getNextMarkedWordAddress(addr + 2);
+size = pointer_delta(nextOneAddr + 1, addr);
+assert(size == CompactibleFreeListSpace::adjustObjectSize(size),
+"alignment problem");
+// Note that pre-cleaning needn't redirty the card. OopDesc::set_klass()
+// will dirty the card when the klass pointer is installed in the
+// object (signalling the completion of initialization).
+}
+} else {
+// Either a not yet marked object or an uninitialized object
+if (p->klass() == NULL || !p->is_parsable()) {
+// An uninitialized object, skip to the next card, since
+// we may not be able to read its P-bits yet.
+assert(size == 0, "Initial value");
+} else {
+// An object not (yet) reached by marking: we merely need to
+// compute its size so as to go look at the next block.
+assert(p->is_oop(true), "should be an oop");
+size = CompactibleFreeListSpace::adjustObjectSize(p->size());
+}
+}
+DEBUG_ONLY(_collector->verify_work_stacks_empty();)
+return size;
+}
+void ScanMarkedObjectsAgainCarefullyClosure::do_yield_work() {
+assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
+"CMS thread should hold CMS token");
+assert_lock_strong(_freelistLock);
+assert_lock_strong(_bitMap->lock());
+// relinquish the free_list_lock and bitMaplock()
+_bitMap->lock()->unlock();
+_freelistLock->unlock();
+ConcurrentMarkSweepThread::desynchronize(true);
+ConcurrentMarkSweepThread::acknowledge_yield_request();
+_collector->stopTimer();
+GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr());
+if (PrintCMSStatistics != 0) {
+_collector->incrementYields();
+}
+_collector->icms_wait();
+// See the comment in coordinator_yield()
+for (unsigned i = 0; i < CMSYieldSleepCount &&
+ConcurrentMarkSweepThread::should_yield() &&
+!CMSCollector::foregroundGCIsActive(); ++i) {
+os::sleep(Thread::current(), 1, false);
+ConcurrentMarkSweepThread::acknowledge_yield_request();
+}
+ConcurrentMarkSweepThread::synchronize(true);
+_freelistLock->lock_without_safepoint_check();
+_bitMap->lock()->lock_without_safepoint_check();
+_collector->startTimer();
+}
+//////////////////////////////////////////////////////////////////
+// SurvivorSpacePrecleanClosure
+//////////////////////////////////////////////////////////////////
+// This (single-threaded) closure is used to preclean the oops in
+// the survivor spaces.
+size_t SurvivorSpacePrecleanClosure::do_object_careful(oop p) {
+HeapWord* addr = (HeapWord*)p;
+DEBUG_ONLY(_collector->verify_work_stacks_empty();)
+assert(!_span.contains(addr), "we are scanning the survivor spaces");
+assert(p->klass() != NULL, "object should be initializd");
+assert(p->is_parsable(), "must be parsable.");
+// an initialized object; ignore mark word in verification below
+// since we are running concurrent with mutators
+assert(p->is_oop(true), "should be an oop");
+// Note that we do not yield while we iterate over
+// the interior oops of p, pushing the relevant ones
+// on our marking stack.
+size_t size = p->oop_iterate(_scanning_closure);
+do_yield_check();
+// Observe that below, we do not abandon the preclean
+// phase as soon as we should; rather we empty the
+// marking stack before returning. This is to satisfy
+// some existing assertions. In general, it may be a
+// good idea to abort immediately and complete the marking
+// from the grey objects at a later time.
+while (!_mark_stack->isEmpty()) {
+oop new_oop = _mark_stack->pop();
+assert(new_oop != NULL && new_oop->is_oop(), "Expected an oop");
+assert(new_oop->is_parsable(), "Found unparsable oop");
+assert(_bit_map->isMarked((HeapWord*)new_oop),
+"only grey objects on this stack");
+// iterate over the oops in this oop, marking and pushing
+// the ones in CMS heap (i.e. in _span).
+new_oop->oop_iterate(_scanning_closure);
+// check if it's time to yield
+do_yield_check();
+}
+unsigned int after_count =
+GenCollectedHeap::heap()->total_collections();
+bool abort = (_before_count != after_count) ||
+_collector->should_abort_preclean();
+return abort ? 0 : size;
+}
+void SurvivorSpacePrecleanClosure::do_yield_work() {
+assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
+"CMS thread should hold CMS token");
+assert_lock_strong(_bit_map->lock());
+// Relinquish the bit map lock
+_bit_map->lock()->unlock();
+ConcurrentMarkSweepThread::desynchronize(true);
+ConcurrentMarkSweepThread::acknowledge_yield_request();
+_collector->stopTimer();
+GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr());
+if (PrintCMSStatistics != 0) {
+_collector->incrementYields();
+}
+_collector->icms_wait();
+// See the comment in coordinator_yield()
+for (unsigned i = 0; i < CMSYieldSleepCount &&
+ConcurrentMarkSweepThread::should_yield() &&
+!CMSCollector::foregroundGCIsActive(); ++i) {
+os::sleep(Thread::current(), 1, false);
+ConcurrentMarkSweepThread::acknowledge_yield_request();
+}
+ConcurrentMarkSweepThread::synchronize(true);
+_bit_map->lock()->lock_without_safepoint_check();
+_collector->startTimer();
+}
+// This closure is used to rescan the marked objects on the dirty cards
+// in the mod union table and the card table proper. In the parallel
+// case, although the bitMap is shared, we do a single read so the
+// isMarked() query is "safe".
+bool ScanMarkedObjectsAgainClosure::do_object_bm(oop p, MemRegion mr) {
+// Ignore mark word because we are running concurrent with mutators
+assert(p->is_oop_or_null(true), "expected an oop or null");
+HeapWord* addr = (HeapWord*)p;
+assert(_span.contains(addr), "we are scanning the CMS generation");
+bool is_obj_array = false;
+#ifdef DEBUG
+if (!_parallel) {
+assert(_mark_stack->isEmpty(), "pre-condition (eager drainage)");
+assert(_collector->overflow_list_is_empty(),
+"overflow list should be empty");
+}
+#endif // DEBUG
+if (_bit_map->isMarked(addr)) {
+// Obj arrays are precisely marked, non-arrays are not;
+// so we scan objArrays precisely and non-arrays in their
+// entirety.
+if (p->is_objArray()) {
+is_obj_array = true;
+if (_parallel) {
+p->oop_iterate(_par_scan_closure, mr);
+} else {
+p->oop_iterate(_scan_closure, mr);
+}
+} else {
+if (_parallel) {
+p->oop_iterate(_par_scan_closure);
+} else {
+p->oop_iterate(_scan_closure);
+}
+}
+}
+#ifdef DEBUG
+if (!_parallel) {
+assert(_mark_stack->isEmpty(), "post-condition (eager drainage)");
+assert(_collector->overflow_list_is_empty(),
+"overflow list should be empty");
+}
+#endif // DEBUG
+return is_obj_array;
+}
+MarkFromRootsClosure::MarkFromRootsClosure(CMSCollector* collector,
+MemRegion span,
+CMSBitMap* bitMap, CMSMarkStack*  markStack,
+CMSMarkStack*  revisitStack,
+bool should_yield, bool verifying):
+_collector(collector),
+_span(span),
+_bitMap(bitMap),
+_mut(&collector->_modUnionTable),
+_markStack(markStack),
+_revisitStack(revisitStack),
+_yield(should_yield),
+_skipBits(0)
+{
+assert(_markStack->isEmpty(), "stack should be empty");
+_finger = _bitMap->startWord();
+_threshold = _finger;
+assert(_collector->_restart_addr == NULL, "Sanity check");
+assert(_span.contains(_finger), "Out of bounds _finger?");
+DEBUG_ONLY(_verifying = verifying;)
+}
+void MarkFromRootsClosure::reset(HeapWord* addr) {
+assert(_markStack->isEmpty(), "would cause duplicates on stack");
+assert(_span.contains(addr), "Out of bounds _finger?");
+_finger = addr;
+_threshold = (HeapWord*)round_to(
+(intptr_t)_finger, CardTableModRefBS::card_size);
+}
+// Should revisit to see if this should be restructured for
+// greater efficiency.
+void MarkFromRootsClosure::do_bit(size_t offset) {
+if (_skipBits > 0) {
+_skipBits--;
+return;
+}
+// convert offset into a HeapWord*
+HeapWord* addr = _bitMap->startWord() + offset;
+assert(_bitMap->endWord() && addr < _bitMap->endWord(),
+"address out of range");
+assert(_bitMap->isMarked(addr), "tautology");
+if (_bitMap->isMarked(addr+1)) {
+// this is an allocated but not yet initialized object
+assert(_skipBits == 0, "tautology");
+_skipBits = 2;  // skip next two marked bits ("Printezis-marks")
+oop p = oop(addr);
+if (p->klass() == NULL || !p->is_parsable()) {
+DEBUG_ONLY(if (!_verifying) {)
+// We re-dirty the cards on which this object lies and increase
+// the _threshold so that we'll come back to scan this object
+// during the preclean or remark phase. (CMSCleanOnEnter)
+if (CMSCleanOnEnter) {
+size_t sz = _collector->block_size_using_printezis_bits(addr);
+HeapWord* start_card_addr = (HeapWord*)round_down(
+(intptr_t)addr, CardTableModRefBS::card_size);
+HeapWord* end_card_addr   = (HeapWord*)round_to(
+(intptr_t)(addr+sz), CardTableModRefBS::card_size);
+MemRegion redirty_range = MemRegion(start_card_addr, end_card_addr);
+assert(!redirty_range.is_empty(), "Arithmetical tautology");
+// Bump _threshold to end_card_addr; note that
+// _threshold cannot possibly exceed end_card_addr, anyhow.
+// This prevents future clearing of the card as the scan proceeds
+// to the right.
+assert(_threshold <= end_card_addr,
+"Because we are just scanning into this object");
+if (_threshold < end_card_addr) {
+_threshold = end_card_addr;
+}
+if (p->klass() != NULL) {
+// Redirty the range of cards...
+_mut->mark_range(redirty_range);
+} // ...else the setting of klass will dirty the card anyway.
+}
+DEBUG_ONLY(})
+return;
+}
+}
+scanOopsInOop(addr);
+}
+// We take a break if we've been at this for a while,
+// so as to avoid monopolizing the locks involved.
+void MarkFromRootsClosure::do_yield_work() {
+// First give up the locks, then yield, then re-lock
+// We should probably use a constructor/destructor idiom to
+// do this unlock/lock or modify the MutexUnlocker class to
+// serve our purpose. XXX
+assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
+"CMS thread should hold CMS token");
+assert_lock_strong(_bitMap->lock());
+_bitMap->lock()->unlock();
+ConcurrentMarkSweepThread::desynchronize(true);
+ConcurrentMarkSweepThread::acknowledge_yield_request();
+_collector->stopTimer();
+GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr());
+if (PrintCMSStatistics != 0) {
+_collector->incrementYields();
+}
+_collector->icms_wait();
+// See the comment in coordinator_yield()
+for (unsigned i = 0; i < CMSYieldSleepCount &&
+ConcurrentMarkSweepThread::should_yield() &&
+!CMSCollector::foregroundGCIsActive(); ++i) {
+os::sleep(Thread::current(), 1, false);
+ConcurrentMarkSweepThread::acknowledge_yield_request();
+}
+ConcurrentMarkSweepThread::synchronize(true);
+_bitMap->lock()->lock_without_safepoint_check();
+_collector->startTimer();
+}
+void MarkFromRootsClosure::scanOopsInOop(HeapWord* ptr) {
+assert(_bitMap->isMarked(ptr), "expected bit to be set");
+assert(_markStack->isEmpty(),
+"should drain stack to limit stack usage");
+// convert ptr to an oop preparatory to scanning
+oop this_oop = oop(ptr);
+// Ignore mark word in verification below, since we
+// may be running concurrent with mutators.
+assert(this_oop->is_oop(true), "should be an oop");
+assert(_finger <= ptr, "_finger runneth ahead");
+// advance the finger to right end of this object
+_finger = ptr + this_oop->size();
+assert(_finger > ptr, "we just incremented it above");
+// On large heaps, it may take us some time to get through
+// the marking phase (especially if running iCMS). During
+// this time it's possible that a lot of mutations have
+// accumulated in the card table and the mod union table --
+// these mutation records are redundant until we have
+// actually traced into the corresponding card.
+// Here, we check whether advancing the finger would make
+// us cross into a new card, and if so clear corresponding
+// cards in the MUT (preclean them in the card-table in the
+// future).
+DEBUG_ONLY(if (!_verifying) {)
+// The clean-on-enter optimization is disabled by default,
+// until we fix 6178663.
+if (CMSCleanOnEnter && (_finger > _threshold)) {
+// [_threshold, _finger) represents the interval
+// of cards to be cleared  in MUT (or precleaned in card table).
+// The set of cards to be cleared is all those that overlap
+// with the interval [_threshold, _finger); note that
+// _threshold is always kept card-aligned but _finger isn't
+// always card-aligned.
+HeapWord* old_threshold = _threshold;
+assert(old_threshold == (HeapWord*)round_to(
+(intptr_t)old_threshold, CardTableModRefBS::card_size),
+"_threshold should always be card-aligned");
+_threshold = (HeapWord*)round_to(
+(intptr_t)_finger, CardTableModRefBS::card_size);
+MemRegion mr(old_threshold, _threshold);
+assert(!mr.is_empty(), "Control point invariant");
+assert(_span.contains(mr), "Should clear within span");
+// XXX When _finger crosses from old gen into perm gen
+// we may be doing unnecessary cleaning; do better in the
+// future by detecting that condition and clearing fewer
+// MUT/CT entries.
+_mut->clear_range(mr);
+}
+DEBUG_ONLY(})
+// Note: the finger doesn't advance while we drain
+// the stack below.
+PushOrMarkClosure pushOrMarkClosure(_collector,
+_span, _bitMap, _markStack,
+_revisitStack,
+_finger, this);
+bool res = _markStack->push(this_oop);
+assert(res, "Empty non-zero size stack should have space for single push");
+while (!_markStack->isEmpty()) {
+oop new_oop = _markStack->pop();
+// Skip verifying header mark word below because we are
+// running concurrent with mutators.
+assert(new_oop->is_oop(true), "Oops! expected to pop an oop");
+// now scan this oop's oops
+new_oop->oop_iterate(&pushOrMarkClosure);
+do_yield_check();
+}
+assert(_markStack->isEmpty(), "tautology, emphasizing post-condition");
+}
+Par_MarkFromRootsClosure::Par_MarkFromRootsClosure(CMSConcMarkingTask* task,
+CMSCollector* collector, MemRegion span,
+CMSBitMap* bit_map,
+OopTaskQueue* work_queue,
+CMSMarkStack*  overflow_stack,
+CMSMarkStack*  revisit_stack,
+bool should_yield):
+_collector(collector),
+_whole_span(collector->_span),
+_span(span),
+_bit_map(bit_map),
+_mut(&collector->_modUnionTable),
+_work_queue(work_queue),
+_overflow_stack(overflow_stack),
+_revisit_stack(revisit_stack),
+_yield(should_yield),
+_skip_bits(0),
+_task(task)
+{
+assert(_work_queue->size() == 0, "work_queue should be empty");
+_finger = span.start();
+_threshold = _finger;     // XXX Defer clear-on-enter optimization for now
+assert(_span.contains(_finger), "Out of bounds _finger?");
+}
+// Should revisit to see if this should be restructured for
+// greater efficiency.
+void Par_MarkFromRootsClosure::do_bit(size_t offset) {
+if (_skip_bits > 0) {
+_skip_bits--;
+return;
+}
+// convert offset into a HeapWord*
+HeapWord* addr = _bit_map->startWord() + offset;
+assert(_bit_map->endWord() && addr < _bit_map->endWord(),
+"address out of range");
+assert(_bit_map->isMarked(addr), "tautology");
+if (_bit_map->isMarked(addr+1)) {
+// this is an allocated object that might not yet be initialized
+assert(_skip_bits == 0, "tautology");
+_skip_bits = 2;  // skip next two marked bits ("Printezis-marks")
+oop p = oop(addr);
+if (p->klass() == NULL || !p->is_parsable()) {
+// in the case of Clean-on-Enter optimization, redirty card
+// and avoid clearing card by increasing  the threshold.
+return;
+}
+}
+scan_oops_in_oop(addr);
+}
+void Par_MarkFromRootsClosure::scan_oops_in_oop(HeapWord* ptr) {
+assert(_bit_map->isMarked(ptr), "expected bit to be set");
+// Should we assert that our work queue is empty or
+// below some drain limit?
+assert(_work_queue->size() == 0,
+"should drain stack to limit stack usage");
+// convert ptr to an oop preparatory to scanning
+oop this_oop = oop(ptr);
+// Ignore mark word in verification below, since we
+// may be running concurrent with mutators.
+assert(this_oop->is_oop(true), "should be an oop");
+assert(_finger <= ptr, "_finger runneth ahead");
+// advance the finger to right end of this object
+_finger = ptr + this_oop->size();
+assert(_finger > ptr, "we just incremented it above");
+// On large heaps, it may take us some time to get through
+// the marking phase (especially if running iCMS). During
+// this time it's possible that a lot of mutations have
+// accumulated in the card table and the mod union table --
+// these mutation records are redundant until we have
+// actually traced into the corresponding card.
+// Here, we check whether advancing the finger would make
+// us cross into a new card, and if so clear corresponding
+// cards in the MUT (preclean them in the card-table in the
+// future).
+// The clean-on-enter optimization is disabled by default,
+// until we fix 6178663.
+if (CMSCleanOnEnter && (_finger > _threshold)) {
+// [_threshold, _finger) represents the interval
+// of cards to be cleared  in MUT (or precleaned in card table).
+// The set of cards to be cleared is all those that overlap
+// with the interval [_threshold, _finger); note that
+// _threshold is always kept card-aligned but _finger isn't
+// always card-aligned.
+HeapWord* old_threshold = _threshold;
+assert(old_threshold == (HeapWord*)round_to(
+(intptr_t)old_threshold, CardTableModRefBS::card_size),
+"_threshold should always be card-aligned");
+_threshold = (HeapWord*)round_to(
+(intptr_t)_finger, CardTableModRefBS::card_size);
+MemRegion mr(old_threshold, _threshold);
+assert(!mr.is_empty(), "Control point invariant");
+assert(_span.contains(mr), "Should clear within span"); // _whole_span ??
+// XXX When _finger crosses from old gen into perm gen
+// we may be doing unnecessary cleaning; do better in the
+// future by detecting that condition and clearing fewer
+// MUT/CT entries.
+_mut->clear_range(mr);
+}
+// Note: the local finger doesn't advance while we drain
+// the stack below, but the global finger sure can and will.
+HeapWord** gfa = _task->global_finger_addr();
+Par_PushOrMarkClosure pushOrMarkClosure(_collector,
+_span, _bit_map,
+_work_queue,
+_overflow_stack,
+_revisit_stack,
+_finger,
+gfa, this);
+bool res = _work_queue->push(this_oop);   // overflow could occur here
+assert(res, "Will hold once we use workqueues");
+while (true) {
+oop new_oop;
+if (!_work_queue->pop_local(new_oop)) {
+// We emptied our work_queue; check if there's stuff that can
+// be gotten from the overflow stack.
+if (CMSConcMarkingTask::get_work_from_overflow_stack(
+_overflow_stack, _work_queue)) {
+do_yield_check();
+continue;
+} else {  // done
+break;
+}
+}
+// Skip verifying header mark word below because we are
+// running concurrent with mutators.
+assert(new_oop->is_oop(true), "Oops! expected to pop an oop");
+// now scan this oop's oops
+new_oop->oop_iterate(&pushOrMarkClosure);
+do_yield_check();
+}
+assert(_work_queue->size() == 0, "tautology, emphasizing post-condition");
+}
+// Yield in response to a request from VM Thread or
+// from mutators.
+void Par_MarkFromRootsClosure::do_yield_work() {
+assert(_task != NULL, "sanity");
+_task->yield();
+}
+// A variant of the above used for verifying CMS marking work.
+MarkFromRootsVerifyClosure::MarkFromRootsVerifyClosure(CMSCollector* collector,
+MemRegion span,
+CMSBitMap* verification_bm, CMSBitMap* cms_bm,
+CMSMarkStack*  mark_stack):
+_collector(collector),
+_span(span),
+_verification_bm(verification_bm),
+_cms_bm(cms_bm),
+_mark_stack(mark_stack),
+_pam_verify_closure(collector, span, verification_bm, cms_bm,
+mark_stack)
+{
+assert(_mark_stack->isEmpty(), "stack should be empty");
+_finger = _verification_bm->startWord();
+assert(_collector->_restart_addr == NULL, "Sanity check");
+assert(_span.contains(_finger), "Out of bounds _finger?");
+}
+void MarkFromRootsVerifyClosure::reset(HeapWord* addr) {
+assert(_mark_stack->isEmpty(), "would cause duplicates on stack");
+assert(_span.contains(addr), "Out of bounds _finger?");
+_finger = addr;
+}
+// Should revisit to see if this should be restructured for
+// greater efficiency.
+void MarkFromRootsVerifyClosure::do_bit(size_t offset) {
+// convert offset into a HeapWord*
+HeapWord* addr = _verification_bm->startWord() + offset;
+assert(_verification_bm->endWord() && addr < _verification_bm->endWord(),
+"address out of range");
+assert(_verification_bm->isMarked(addr), "tautology");
+assert(_cms_bm->isMarked(addr), "tautology");
+assert(_mark_stack->isEmpty(),
+"should drain stack to limit stack usage");
+// convert addr to an oop preparatory to scanning
+oop this_oop = oop(addr);
+assert(this_oop->is_oop(), "should be an oop");
+assert(_finger <= addr, "_finger runneth ahead");
+// advance the finger to right end of this object
+_finger = addr + this_oop->size();
+assert(_finger > addr, "we just incremented it above");
+// Note: the finger doesn't advance while we drain
+// the stack below.
+bool res = _mark_stack->push(this_oop);
+assert(res, "Empty non-zero size stack should have space for single push");
+while (!_mark_stack->isEmpty()) {
+oop new_oop = _mark_stack->pop();
+assert(new_oop->is_oop(), "Oops! expected to pop an oop");
+// now scan this oop's oops
+new_oop->oop_iterate(&_pam_verify_closure);
+}
+assert(_mark_stack->isEmpty(), "tautology, emphasizing post-condition");
+}
+PushAndMarkVerifyClosure::PushAndMarkVerifyClosure(
+CMSCollector* collector, MemRegion span,
+CMSBitMap* verification_bm, CMSBitMap* cms_bm,
+CMSMarkStack*  mark_stack):
+OopClosure(collector->ref_processor()),
+_collector(collector),
+_span(span),
+_verification_bm(verification_bm),
+_cms_bm(cms_bm),
+_mark_stack(mark_stack)
+{ }
+// Upon stack overflow, we discard (part of) the stack,
+// remembering the least address amongst those discarded
+// in CMSCollector's _restart_address.
+void PushAndMarkVerifyClosure::handle_stack_overflow(HeapWord* lost) {
+// Remember the least grey address discarded
+HeapWord* ra = (HeapWord*)_mark_stack->least_value(lost);
+_collector->lower_restart_addr(ra);
+_mark_stack->reset();  // discard stack contents
+_mark_stack->expand(); // expand the stack if possible
+}
+void PushAndMarkVerifyClosure::do_oop(oop* p) {
+oop    this_oop = *p;
+assert(this_oop->is_oop_or_null(), "expected an oop or NULL");
+HeapWord* addr = (HeapWord*)this_oop;
+if (_span.contains(addr) && !_verification_bm->isMarked(addr)) {
+// Oop lies in _span and isn't yet grey or black
+_verification_bm->mark(addr);            // now grey
+if (!_cms_bm->isMarked(addr)) {
+oop(addr)->print();
+gclog_or_tty->print_cr(" ("INTPTR_FORMAT" should have been marked)", addr);
+fatal("... aborting");
+}
+if (!_mark_stack->push(this_oop)) { // stack overflow
+if (PrintCMSStatistics != 0) {
+gclog_or_tty->print_cr("CMS marking stack overflow (benign) at "
+SIZE_FORMAT, _mark_stack->capacity());
+}
+assert(_mark_stack->isFull(), "Else push should have succeeded");
+handle_stack_overflow(addr);
+}
+// anything including and to the right of _finger
+// will be scanned as we iterate over the remainder of the
+// bit map
+}
+}
+PushOrMarkClosure::PushOrMarkClosure(CMSCollector* collector,
+MemRegion span,
+CMSBitMap* bitMap, CMSMarkStack*  markStack,
+CMSMarkStack*  revisitStack,
+HeapWord* finger, MarkFromRootsClosure* parent) :
+OopClosure(collector->ref_processor()),
+_collector(collector),
+_span(span),
+_bitMap(bitMap),
+_markStack(markStack),
+_revisitStack(revisitStack),
+_finger(finger),
+_parent(parent),
+_should_remember_klasses(collector->cms_should_unload_classes())
+{ }
+Par_PushOrMarkClosure::Par_PushOrMarkClosure(CMSCollector* collector,
+MemRegion span,
+CMSBitMap* bit_map,
+OopTaskQueue* work_queue,
+CMSMarkStack*  overflow_stack,
+CMSMarkStack*  revisit_stack,
+HeapWord* finger,
+HeapWord** global_finger_addr,
+Par_MarkFromRootsClosure* parent) :
+OopClosure(collector->ref_processor()),
+_collector(collector),
+_whole_span(collector->_span),
+_span(span),
+_bit_map(bit_map),
+_work_queue(work_queue),
+_overflow_stack(overflow_stack),
+_revisit_stack(revisit_stack),
+_finger(finger),
+_global_finger_addr(global_finger_addr),
+_parent(parent),
+_should_remember_klasses(collector->cms_should_unload_classes())
+{ }
+void CMSCollector::lower_restart_addr(HeapWord* low) {
+assert(_span.contains(low), "Out of bounds addr");
+if (_restart_addr == NULL) {
+_restart_addr = low;
+} else {
+_restart_addr = MIN2(_restart_addr, low);
+}
+}
+// Upon stack overflow, we discard (part of) the stack,
+// remembering the least address amongst those discarded
+// in CMSCollector's _restart_address.
+void PushOrMarkClosure::handle_stack_overflow(HeapWord* lost) {
+// Remember the least grey address discarded
+HeapWord* ra = (HeapWord*)_markStack->least_value(lost);
+_collector->lower_restart_addr(ra);
+_markStack->reset();  // discard stack contents
+_markStack->expand(); // expand the stack if possible
+}
+// Upon stack overflow, we discard (part of) the stack,
+// remembering the least address amongst those discarded
+// in CMSCollector's _restart_address.
+void Par_PushOrMarkClosure::handle_stack_overflow(HeapWord* lost) {
+// We need to do this under a mutex to prevent other
+// workers from interfering with the expansion below.
+MutexLockerEx ml(_overflow_stack->par_lock(),
+Mutex::_no_safepoint_check_flag);
+// Remember the least grey address discarded
+HeapWord* ra = (HeapWord*)_overflow_stack->least_value(lost);
+_collector->lower_restart_addr(ra);
+_overflow_stack->reset();  // discard stack contents
+_overflow_stack->expand(); // expand the stack if possible
+}
+void PushOrMarkClosure::do_oop(oop* p) {
+oop    thisOop = *p;
+// Ignore mark word because we are running concurrent with mutators.
+assert(thisOop->is_oop_or_null(true), "expected an oop or NULL");
+HeapWord* addr = (HeapWord*)thisOop;
+if (_span.contains(addr) && !_bitMap->isMarked(addr)) {
+// Oop lies in _span and isn't yet grey or black
+_bitMap->mark(addr);            // now grey
+if (addr < _finger) {
+// the bit map iteration has already either passed, or
+// sampled, this bit in the bit map; we'll need to
+// use the marking stack to scan this oop's oops.
+bool simulate_overflow = false;
+NOT_PRODUCT(
+if (CMSMarkStackOverflowALot &&
+_collector->simulate_overflow()) {
+// simulate a stack overflow
+simulate_overflow = true;
+}
+)
+if (simulate_overflow || !_markStack->push(thisOop)) { // stack overflow
+if (PrintCMSStatistics != 0) {
+gclog_or_tty->print_cr("CMS marking stack overflow (benign) at "
+SIZE_FORMAT, _markStack->capacity());
+}
+assert(simulate_overflow || _markStack->isFull(), "Else push should have succeeded");
+handle_stack_overflow(addr);
+}
+}
+// anything including and to the right of _finger
+// will be scanned as we iterate over the remainder of the
+// bit map
+do_yield_check();
+}
+}
+void Par_PushOrMarkClosure::do_oop(oop* p) {
+oop    this_oop = *p;
+// Ignore mark word because we are running concurrent with mutators.
+assert(this_oop->is_oop_or_null(true), "expected an oop or NULL");
+HeapWord* addr = (HeapWord*)this_oop;
+if (_whole_span.contains(addr) && !_bit_map->isMarked(addr)) {
+// Oop lies in _span and isn't yet grey or black
+// We read the global_finger (volatile read) strictly after marking oop
+bool res = _bit_map->par_mark(addr);    // now grey
+volatile HeapWord** gfa = (volatile HeapWord**)_global_finger_addr;
+// Should we push this marked oop on our stack?
+// -- if someone else marked it, nothing to do
+// -- if target oop is above global finger nothing to do
+// -- if target oop is in chunk and above local finger
+//      then nothing to do
+// -- else push on work queue
+if (   !res       // someone else marked it, they will deal with it
+|| (addr >= *gfa)  // will be scanned in a later task
+|| (_span.contains(addr) && addr >= _finger)) { // later in this chunk
+return;
+}
+// the bit map iteration has already either passed, or
+// sampled, this bit in the bit map; we'll need to
+// use the marking stack to scan this oop's oops.
+bool simulate_overflow = false;
+NOT_PRODUCT(
+if (CMSMarkStackOverflowALot &&
+_collector->simulate_overflow()) {
+// simulate a stack overflow
+simulate_overflow = true;
+}
+)
+if (simulate_overflow ||
+!(_work_queue->push(this_oop) || _overflow_stack->par_push(this_oop))) {
+// stack overflow
+if (PrintCMSStatistics != 0) {
+gclog_or_tty->print_cr("CMS marking stack overflow (benign) at "
+SIZE_FORMAT, _overflow_stack->capacity());
+}
+// We cannot assert that the overflow stack is full because
+// it may have been emptied since.
+assert(simulate_overflow ||
+_work_queue->size() == _work_queue->max_elems(),
+"Else push should have succeeded");
+handle_stack_overflow(addr);
+}
+do_yield_check();
+}
+}
+PushAndMarkClosure::PushAndMarkClosure(CMSCollector* collector,
+MemRegion span,
+ReferenceProcessor* rp,
+CMSBitMap* bit_map,
+CMSBitMap* mod_union_table,
+CMSMarkStack*  mark_stack,
+CMSMarkStack*  revisit_stack,
+bool           concurrent_precleaning):
+OopClosure(rp),
+_collector(collector),
+_span(span),
+_bit_map(bit_map),
+_mod_union_table(mod_union_table),
+_mark_stack(mark_stack),
+_revisit_stack(revisit_stack),
+_concurrent_precleaning(concurrent_precleaning),
+_should_remember_klasses(collector->cms_should_unload_classes())
+{
+assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL");
+}
+// Grey object rescan during pre-cleaning and second checkpoint phases --
+// the non-parallel version (the parallel version appears further below.)
+void PushAndMarkClosure::do_oop(oop* p) {
+oop    this_oop = *p;
+// Ignore mark word verification. If during concurrent precleaning
+// the object monitor may be locked. If during the checkpoint
+// phases, the object may already have been reached by a  different
+// path and may be at the end of the global overflow list (so
+// the mark word may be NULL).
+assert(this_oop->is_oop_or_null(true/* ignore mark word */),
+"expected an oop or NULL");
+HeapWord* addr = (HeapWord*)this_oop;
+// Check if oop points into the CMS generation
+// and is not marked
+if (_span.contains(addr) && !_bit_map->isMarked(addr)) {
+// a white object ...
+_bit_map->mark(addr);         // ... now grey
+// push on the marking stack (grey set)
+bool simulate_overflow = false;
+NOT_PRODUCT(
+if (CMSMarkStackOverflowALot &&
+_collector->simulate_overflow()) {
+// simulate a stack overflow
+simulate_overflow = true;
+}
+)
+if (simulate_overflow || !_mark_stack->push(this_oop)) {
+if (_concurrent_precleaning) {
+// During precleaning we can just dirty the appropriate card
+// in the mod union table, thus ensuring that the object remains
+// in the grey set  and continue. Note that no one can be intefering
+// with us in this action of dirtying the mod union table, so
+// no locking is required.
+_mod_union_table->mark(addr);
+_collector->_ser_pmc_preclean_ovflw++;
+} else {
+// During the remark phase, we need to remember this oop
+// in the overflow list.
+_collector->push_on_overflow_list(this_oop);
+_collector->_ser_pmc_remark_ovflw++;
+}
+}
+}
+}
+Par_PushAndMarkClosure::Par_PushAndMarkClosure(CMSCollector* collector,
+MemRegion span,
+ReferenceProcessor* rp,
+CMSBitMap* bit_map,
+OopTaskQueue* work_queue,
+CMSMarkStack* revisit_stack):
+OopClosure(rp),
+_collector(collector),
+_span(span),
+_bit_map(bit_map),
+_work_queue(work_queue),
+_revisit_stack(revisit_stack),
+_should_remember_klasses(collector->cms_should_unload_classes())
+{
+assert(_ref_processor != NULL, "_ref_processor shouldn't be NULL");
+}
+// Grey object rescan during second checkpoint phase --
+// the parallel version.
+void Par_PushAndMarkClosure::do_oop(oop* p) {
+oop    this_oop = *p;
+// In the assert below, we ignore the mark word because
+// this oop may point to an already visited object that is
+// on the overflow stack (in which case the mark word has
+// been hijacked for chaining into the overflow stack --
+// if this is the last object in the overflow stack then
+// its mark word will be NULL). Because this object may
+// have been subsequently popped off the global overflow
+// stack, and the mark word possibly restored to the prototypical
+// value, by the time we get to examined this failing assert in
+// the debugger, is_oop_or_null(false) may subsequently start
+// to hold.
+assert(this_oop->is_oop_or_null(true),
+"expected an oop or NULL");
+HeapWord* addr = (HeapWord*)this_oop;
+// Check if oop points into the CMS generation
+// and is not marked
+if (_span.contains(addr) && !_bit_map->isMarked(addr)) {
+// a white object ...
+// If we manage to "claim" the object, by being the
+// first thread to mark it, then we push it on our
+// marking stack
+if (_bit_map->par_mark(addr)) {     // ... now grey
+// push on work queue (grey set)
+bool simulate_overflow = false;
+NOT_PRODUCT(
+if (CMSMarkStackOverflowALot &&
+_collector->par_simulate_overflow()) {
+// simulate a stack overflow
+simulate_overflow = true;
+}
+)
+if (simulate_overflow || !_work_queue->push(this_oop)) {
+_collector->par_push_on_overflow_list(this_oop);
+_collector->_par_pmc_remark_ovflw++; //  imprecise OK: no need to CAS
+}
+} // Else, some other thread got there first
+}
+}
+void PushAndMarkClosure::remember_klass(Klass* k) {
+if (!_revisit_stack->push(oop(k))) {
+fatal("Revisit stack overflowed in PushAndMarkClosure");
+}
+}
+void Par_PushAndMarkClosure::remember_klass(Klass* k) {
+if (!_revisit_stack->par_push(oop(k))) {
+fatal("Revist stack overflowed in Par_PushAndMarkClosure");
+}
+}
+void CMSPrecleanRefsYieldClosure::do_yield_work() {
+Mutex* bml = _collector->bitMapLock();
+assert_lock_strong(bml);
+assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
+"CMS thread should hold CMS token");
+bml->unlock();
+ConcurrentMarkSweepThread::desynchronize(true);
+ConcurrentMarkSweepThread::acknowledge_yield_request();
+_collector->stopTimer();
+GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr());
+if (PrintCMSStatistics != 0) {
+_collector->incrementYields();
+}
+_collector->icms_wait();
+// See the comment in coordinator_yield()
+for (unsigned i = 0; i < CMSYieldSleepCount &&
+ConcurrentMarkSweepThread::should_yield() &&
+!CMSCollector::foregroundGCIsActive(); ++i) {
+os::sleep(Thread::current(), 1, false);
+ConcurrentMarkSweepThread::acknowledge_yield_request();
+}
+ConcurrentMarkSweepThread::synchronize(true);
+bml->lock();
+_collector->startTimer();
+}
+bool CMSPrecleanRefsYieldClosure::should_return() {
+if (ConcurrentMarkSweepThread::should_yield()) {
+do_yield_work();
+}
+return _collector->foregroundGCIsActive();
+}
+void MarkFromDirtyCardsClosure::do_MemRegion(MemRegion mr) {
+assert(((size_t)mr.start())%CardTableModRefBS::card_size_in_words == 0,
+"mr should be aligned to start at a card boundary");
+// We'd like to assert:
+// assert(mr.word_size()%CardTableModRefBS::card_size_in_words == 0,
+//        "mr should be a range of cards");
+// However, that would be too strong in one case -- the last
+// partition ends at _unallocated_block which, in general, can be
+// an arbitrary boundary, not necessarily card aligned.
+if (PrintCMSStatistics != 0) {
+_num_dirty_cards +=
+mr.word_size()/CardTableModRefBS::card_size_in_words;
+}
+_space->object_iterate_mem(mr, &_scan_cl);
+}
+SweepClosure::SweepClosure(CMSCollector* collector,
+ConcurrentMarkSweepGeneration* g,
+CMSBitMap* bitMap, bool should_yield) :
+_collector(collector),
+_g(g),
+_sp(g->cmsSpace()),
+_limit(_sp->sweep_limit()),
+_freelistLock(_sp->freelistLock()),
+_bitMap(bitMap),
+_yield(should_yield),
+_inFreeRange(false),           // No free range at beginning of sweep
+_freeRangeInFreeLists(false),  // No free range at beginning of sweep
+_lastFreeRangeCoalesced(false),
+_freeFinger(g->used_region().start())
+{
+NOT_PRODUCT(
+_numObjectsFreed = 0;
+_numWordsFreed   = 0;
+_numObjectsLive = 0;
+_numWordsLive = 0;
+_numObjectsAlreadyFree = 0;
+_numWordsAlreadyFree = 0;
+_last_fc = NULL;
+_sp->initializeIndexedFreeListArrayReturnedBytes();
+_sp->dictionary()->initializeDictReturnedBytes();
+)
+assert(_limit >= _sp->bottom() && _limit <= _sp->end(),
+"sweep _limit out of bounds");
+if (CMSTraceSweeper) {
+gclog_or_tty->print("\n====================\nStarting new sweep\n");
+}
+}
+// We need this destructor to reclaim any space at the end
+// of the space, which do_blk below may not have added back to
+// the free lists. [basically dealing with the "fringe effect"]
+SweepClosure::~SweepClosure() {
+assert_lock_strong(_freelistLock);
+// this should be treated as the end of a free run if any
+// The current free range should be returned to the free lists
+// as one coalesced chunk.
+if (inFreeRange()) {
+flushCurFreeChunk(freeFinger(),
+pointer_delta(_limit, freeFinger()));
+assert(freeFinger() < _limit, "the finger pointeth off base");
+if (CMSTraceSweeper) {
+gclog_or_tty->print("destructor:");
+gclog_or_tty->print("Sweep:put_free_blk 0x%x ("SIZE_FORMAT") "
+"[coalesced:"SIZE_FORMAT"]\n",
+freeFinger(), pointer_delta(_limit, freeFinger()),
+lastFreeRangeCoalesced());
+}
+}
+NOT_PRODUCT(
+if (Verbose && PrintGC) {
+gclog_or_tty->print("Collected "SIZE_FORMAT" objects, "
+SIZE_FORMAT " bytes",
+_numObjectsFreed, _numWordsFreed*sizeof(HeapWord));
+gclog_or_tty->print_cr("\nLive "SIZE_FORMAT" objects,  "
+SIZE_FORMAT" bytes  "
+"Already free "SIZE_FORMAT" objects, "SIZE_FORMAT" bytes",
+_numObjectsLive, _numWordsLive*sizeof(HeapWord),
+_numObjectsAlreadyFree, _numWordsAlreadyFree*sizeof(HeapWord));
+size_t totalBytes = (_numWordsFreed + _numWordsLive + _numWordsAlreadyFree) *
+sizeof(HeapWord);
+gclog_or_tty->print_cr("Total sweep: "SIZE_FORMAT" bytes", totalBytes);
+if (PrintCMSStatistics && CMSVerifyReturnedBytes) {
+size_t indexListReturnedBytes = _sp->sumIndexedFreeListArrayReturnedBytes();
+size_t dictReturnedBytes = _sp->dictionary()->sumDictReturnedBytes();
+size_t returnedBytes = indexListReturnedBytes + dictReturnedBytes;
+gclog_or_tty->print("Returned "SIZE_FORMAT" bytes", returnedBytes);
+gclog_or_tty->print("   Indexed List Returned "SIZE_FORMAT" bytes",
+indexListReturnedBytes);
+gclog_or_tty->print_cr("        Dictionary Returned "SIZE_FORMAT" bytes",
+dictReturnedBytes);
+}
+}
+)
+// Now, in debug mode, just null out the sweep_limit
+NOT_PRODUCT(_sp->clear_sweep_limit();)
+if (CMSTraceSweeper) {
+gclog_or_tty->print("end of sweep\n================\n");
+}
+}
+void SweepClosure::initialize_free_range(HeapWord* freeFinger,
+bool freeRangeInFreeLists) {
+if (CMSTraceSweeper) {
+gclog_or_tty->print("---- Start free range 0x%x with free block [%d] (%d)\n",
+freeFinger, _sp->block_size(freeFinger),
+freeRangeInFreeLists);
+}
+assert(!inFreeRange(), "Trampling existing free range");
+set_inFreeRange(true);
+set_lastFreeRangeCoalesced(false);
+set_freeFinger(freeFinger);
+set_freeRangeInFreeLists(freeRangeInFreeLists);
+if (CMSTestInFreeList) {
+if (freeRangeInFreeLists) {
+FreeChunk* fc = (FreeChunk*) freeFinger;
+assert(fc->isFree(), "A chunk on the free list should be free.");
+assert(fc->size() > 0, "Free range should have a size");
+assert(_sp->verifyChunkInFreeLists(fc), "Chunk is not in free lists");
+}
+}
+}
+// Note that the sweeper runs concurrently with mutators. Thus,
+// it is possible for direct allocation in this generation to happen
+// in the middle of the sweep. Note that the sweeper also coalesces
+// contiguous free blocks. Thus, unless the sweeper and the allocator
+// synchronize appropriately freshly allocated blocks may get swept up.
+// This is accomplished by the sweeper locking the free lists while
+// it is sweeping. Thus blocks that are determined to be free are
+// indeed free. There is however one additional complication:
+// blocks that have been allocated since the final checkpoint and
+// mark, will not have been marked and so would be treated as
+// unreachable and swept up. To prevent this, the allocator marks
+// the bit map when allocating during the sweep phase. This leads,
+// however, to a further complication -- objects may have been allocated
+// but not yet initialized -- in the sense that the header isn't yet
+// installed. The sweeper can not then determine the size of the block
+// in order to skip over it. To deal with this case, we use a technique
+// (due to Printezis) to encode such uninitialized block sizes in the
+// bit map. Since the bit map uses a bit per every HeapWord, but the
+// CMS generation has a minimum object size of 3 HeapWords, it follows
+// that "normal marks" won't be adjacent in the bit map (there will
+// always be at least two 0 bits between successive 1 bits). We make use
+// of these "unused" bits to represent uninitialized blocks -- the bit
+// corresponding to the start of the uninitialized object and the next
+// bit are both set. Finally, a 1 bit marks the end of the object that
+// started with the two consecutive 1 bits to indicate its potentially
+// uninitialized state.
+size_t SweepClosure::do_blk_careful(HeapWord* addr) {
+FreeChunk* fc = (FreeChunk*)addr;
+size_t res;
+// check if we are done sweepinrg
+if (addr == _limit) { // we have swept up to the limit, do nothing more
+assert(_limit >= _sp->bottom() && _limit <= _sp->end(),
+"sweep _limit out of bounds");
+// help the closure application finish
+return pointer_delta(_sp->end(), _limit);
+}
+assert(addr <= _limit, "sweep invariant");
+// check if we should yield
+do_yield_check(addr);
+if (fc->isFree()) {
+// Chunk that is already free
+res = fc->size();
+doAlreadyFreeChunk(fc);
+debug_only(_sp->verifyFreeLists());
+assert(res == fc->size(), "Don't expect the size to change");
+NOT_PRODUCT(
+_numObjectsAlreadyFree++;
+_numWordsAlreadyFree += res;
+)
+NOT_PRODUCT(_last_fc = fc;)
+} else if (!_bitMap->isMarked(addr)) {
+// Chunk is fresh garbage
+res = doGarbageChunk(fc);
+debug_only(_sp->verifyFreeLists());
+NOT_PRODUCT(
+_numObjectsFreed++;
+_numWordsFreed += res;
+)
+} else {
+// Chunk that is alive.
+res = doLiveChunk(fc);
+debug_only(_sp->verifyFreeLists());
+NOT_PRODUCT(
+_numObjectsLive++;
+_numWordsLive += res;
+)
+}
+return res;
+}
+// For the smart allocation, record following
+//  split deaths - a free chunk is removed from its free list because
+//      it is being split into two or more chunks.
+//  split birth - a free chunk is being added to its free list because
+//      a larger free chunk has been split and resulted in this free chunk.
+//  coal death - a free chunk is being removed from its free list because
+//      it is being coalesced into a large free chunk.
+//  coal birth - a free chunk is being added to its free list because
+//      it was created when two or more free chunks where coalesced into
+//      this free chunk.
+//
+// These statistics are used to determine the desired number of free
+// chunks of a given size.  The desired number is chosen to be relative
+// to the end of a CMS sweep.  The desired number at the end of a sweep
+// is the
+//      count-at-end-of-previous-sweep (an amount that was enough)
+//              - count-at-beginning-of-current-sweep  (the excess)
+//              + split-births  (gains in this size during interval)
+//              - split-deaths  (demands on this size during interval)
+// where the interval is from the end of one sweep to the end of the
+// next.
+//
+// When sweeping the sweeper maintains an accumulated chunk which is
+// the chunk that is made up of chunks that have been coalesced.  That
+// will be termed the left-hand chunk.  A new chunk of garbage that
+// is being considered for coalescing will be referred to as the
+// right-hand chunk.
+//
+// When making a decision on whether to coalesce a right-hand chunk with
+// the current left-hand chunk, the current count vs. the desired count
+// of the left-hand chunk is considered.  Also if the right-hand chunk
+// is near the large chunk at the end of the heap (see
+// ConcurrentMarkSweepGeneration::isNearLargestChunk()), then the
+// left-hand chunk is coalesced.
+//
+// When making a decision about whether to split a chunk, the desired count
+// vs. the current count of the candidate to be split is also considered.
+// If the candidate is underpopulated (currently fewer chunks than desired)
+// a chunk of an overpopulated (currently more chunks than desired) size may
+// be chosen.  The "hint" associated with a free list, if non-null, points
+// to a free list which may be overpopulated.
+//
+void SweepClosure::doAlreadyFreeChunk(FreeChunk* fc) {
+size_t size = fc->size();
+// Chunks that cannot be coalesced are not in the
+// free lists.
+if (CMSTestInFreeList && !fc->cantCoalesce()) {
+assert(_sp->verifyChunkInFreeLists(fc),
+"free chunk should be in free lists");
+}
+// a chunk that is already free, should not have been
+// marked in the bit map
+HeapWord* addr = (HeapWord*) fc;
+assert(!_bitMap->isMarked(addr), "free chunk should be unmarked");
+// Verify that the bit map has no bits marked between
+// addr and purported end of this block.
+_bitMap->verifyNoOneBitsInRange(addr + 1, addr + size);
+// Some chunks cannot be coalesced in under any circumstances.
+// See the definition of cantCoalesce().
+if (!fc->cantCoalesce()) {
+// This chunk can potentially be coalesced.
+if (_sp->adaptive_freelists()) {
+// All the work is done in
+doPostIsFreeOrGarbageChunk(fc, size);
+} else {  // Not adaptive free lists
+// this is a free chunk that can potentially be coalesced by the sweeper;
+if (!inFreeRange()) {
+// if the next chunk is a free block that can't be coalesced
+// it doesn't make sense to remove this chunk from the free lists
+FreeChunk* nextChunk = (FreeChunk*)(addr + size);
+assert((HeapWord*)nextChunk <= _limit, "sweep invariant");
+if ((HeapWord*)nextChunk < _limit  &&    // there's a next chunk...
+nextChunk->isFree()    &&            // which is free...
+nextChunk->cantCoalesce()) {         // ... but cant be coalesced
+// nothing to do
+} else {
+// Potentially the start of a new free range:
+// Don't eagerly remove it from the free lists.
+// No need to remove it if it will just be put
+// back again.  (Also from a pragmatic point of view
+// if it is a free block in a region that is beyond
+// any allocated blocks, an assertion will fail)
+// Remember the start of a free run.
+initialize_free_range(addr, true);
+// end - can coalesce with next chunk
+}
+} else {
+// the midst of a free range, we are coalescing
+debug_only(record_free_block_coalesced(fc);)
+if (CMSTraceSweeper) {
+gclog_or_tty->print("  -- pick up free block 0x%x (%d)\n", fc, size);
+}
+// remove it from the free lists
+_sp->removeFreeChunkFromFreeLists(fc);
+set_lastFreeRangeCoalesced(true);
+// If the chunk is being coalesced and the current free range is
+// in the free lists, remove the current free range so that it
+// will be returned to the free lists in its entirety - all
+// the coalesced pieces included.
+if (freeRangeInFreeLists()) {
+FreeChunk* ffc = (FreeChunk*) freeFinger();
+assert(ffc->size() == pointer_delta(addr, freeFinger()),
+"Size of free range is inconsistent with chunk size.");
+if (CMSTestInFreeList) {
+assert(_sp->verifyChunkInFreeLists(ffc),
+"free range is not in free lists");
+}
+_sp->removeFreeChunkFromFreeLists(ffc);
+set_freeRangeInFreeLists(false);
+}
+}
+}
+} else {
+// Code path common to both original and adaptive free lists.
+// cant coalesce with previous block; this should be treated
+// as the end of a free run if any
+if (inFreeRange()) {
+// we kicked some butt; time to pick up the garbage
+assert(freeFinger() < addr, "the finger pointeth off base");
+flushCurFreeChunk(freeFinger(), pointer_delta(addr, freeFinger()));
+}
+// else, nothing to do, just continue
+}
+}
+size_t SweepClosure::doGarbageChunk(FreeChunk* fc) {
+// This is a chunk of garbage.  It is not in any free list.
+// Add it to a free list or let it possibly be coalesced into
+// a larger chunk.
+HeapWord* addr = (HeapWord*) fc;
+size_t size = CompactibleFreeListSpace::adjustObjectSize(oop(addr)->size());
+if (_sp->adaptive_freelists()) {
+// Verify that the bit map has no bits marked between
+// addr and purported end of just dead object.
+_bitMap->verifyNoOneBitsInRange(addr + 1, addr + size);
+doPostIsFreeOrGarbageChunk(fc, size);
+} else {
+if (!inFreeRange()) {
+// start of a new free range
+assert(size > 0, "A free range should have a size");
+initialize_free_range(addr, false);
+} else {
+// this will be swept up when we hit the end of the
+// free range
+if (CMSTraceSweeper) {
+gclog_or_tty->print("  -- pick up garbage 0x%x (%d) \n", fc, size);
+}
+// If the chunk is being coalesced and the current free range is
+// in the free lists, remove the current free range so that it
+// will be returned to the free lists in its entirety - all
+// the coalesced pieces included.
+if (freeRangeInFreeLists()) {
+FreeChunk* ffc = (FreeChunk*)freeFinger();
+assert(ffc->size() == pointer_delta(addr, freeFinger()),
+"Size of free range is inconsistent with chunk size.");
+if (CMSTestInFreeList) {
+assert(_sp->verifyChunkInFreeLists(ffc),
+"free range is not in free lists");
+}
+_sp->removeFreeChunkFromFreeLists(ffc);
+set_freeRangeInFreeLists(false);
+}
+set_lastFreeRangeCoalesced(true);
+}
+// this will be swept up when we hit the end of the free range
+// Verify that the bit map has no bits marked between
+// addr and purported end of just dead object.
+_bitMap->verifyNoOneBitsInRange(addr + 1, addr + size);
+}
+return size;
+}
+size_t SweepClosure::doLiveChunk(FreeChunk* fc) {
+HeapWord* addr = (HeapWord*) fc;
+// The sweeper has just found a live object. Return any accumulated
+// left hand chunk to the free lists.
+if (inFreeRange()) {
+if (_sp->adaptive_freelists()) {
+flushCurFreeChunk(freeFinger(),
+pointer_delta(addr, freeFinger()));
+} else { // not adaptive freelists
+set_inFreeRange(false);
+// Add the free range back to the free list if it is not already
+// there.
+if (!freeRangeInFreeLists()) {
+assert(freeFinger() < addr, "the finger pointeth off base");
+if (CMSTraceSweeper) {
+gclog_or_tty->print("Sweep:put_free_blk 0x%x (%d) "
+"[coalesced:%d]\n",
+freeFinger(), pointer_delta(addr, freeFinger()),
+lastFreeRangeCoalesced());
+}
+_sp->addChunkAndRepairOffsetTable(freeFinger(),
+pointer_delta(addr, freeFinger()), lastFreeRangeCoalesced());
+}
+}
+}
+// Common code path for original and adaptive free lists.
+// this object is live: we'd normally expect this to be
+// an oop, and like to assert the following:
+// assert(oop(addr)->is_oop(), "live block should be an oop");
+// However, as we commented above, this may be an object whose
+// header hasn't yet been initialized.
+size_t size;
+assert(_bitMap->isMarked(addr), "Tautology for this control point");
+if (_bitMap->isMarked(addr + 1)) {
+// Determine the size from the bit map, rather than trying to
+// compute it from the object header.
+HeapWord* nextOneAddr = _bitMap->getNextMarkedWordAddress(addr + 2);
+size = pointer_delta(nextOneAddr + 1, addr);
+assert(size == CompactibleFreeListSpace::adjustObjectSize(size),
+"alignment problem");
+#ifdef DEBUG
+if (oop(addr)->klass() != NULL &&
+(   !_collector->cms_should_unload_classes()
+|| oop(addr)->is_parsable())) {
+// Ignore mark word because we are running concurrent with mutators
+assert(oop(addr)->is_oop(true), "live block should be an oop");
+assert(size ==
+CompactibleFreeListSpace::adjustObjectSize(oop(addr)->size()),
+"P-mark and computed size do not agree");
+}
+#endif
+} else {
+// This should be an initialized object that's alive.
+assert(oop(addr)->klass() != NULL &&
+(!_collector->cms_should_unload_classes()
+|| oop(addr)->is_parsable()),
+"Should be an initialized object");
+// Ignore mark word because we are running concurrent with mutators
+assert(oop(addr)->is_oop(true), "live block should be an oop");
+// Verify that the bit map has no bits marked between
+// addr and purported end of this block.
+size = CompactibleFreeListSpace::adjustObjectSize(oop(addr)->size());
+assert(size >= 3, "Necessary for Printezis marks to work");
+assert(!_bitMap->isMarked(addr+1), "Tautology for this control point");
+DEBUG_ONLY(_bitMap->verifyNoOneBitsInRange(addr+2, addr+size);)
+}
+return size;
+}
+void SweepClosure::doPostIsFreeOrGarbageChunk(FreeChunk* fc,
+size_t chunkSize) {
+// doPostIsFreeOrGarbageChunk() should only be called in the smart allocation
+// scheme.
+bool fcInFreeLists = fc->isFree();
+assert(_sp->adaptive_freelists(), "Should only be used in this case.");
+assert((HeapWord*)fc <= _limit, "sweep invariant");
+if (CMSTestInFreeList && fcInFreeLists) {
+assert(_sp->verifyChunkInFreeLists(fc),
+"free chunk is not in free lists");
+}
+if (CMSTraceSweeper) {
+gclog_or_tty->print_cr("  -- pick up another chunk at 0x%x (%d)", fc, chunkSize);
+}
+HeapWord* addr = (HeapWord*) fc;
+bool coalesce;
+size_t left  = pointer_delta(addr, freeFinger());
+size_t right = chunkSize;
+switch (FLSCoalescePolicy) {
+// numeric value forms a coalition aggressiveness metric
+case 0:  { // never coalesce
+coalesce = false;
+break;
+}
+case 1: { // coalesce if left & right chunks on overpopulated lists
+coalesce = _sp->coalOverPopulated(left) &&
+_sp->coalOverPopulated(right);
+break;
+}
+case 2: { // coalesce if left chunk on overpopulated list (default)
+coalesce = _sp->coalOverPopulated(left);
+break;
+}
+case 3: { // coalesce if left OR right chunk on overpopulated list
+coalesce = _sp->coalOverPopulated(left) ||
+_sp->coalOverPopulated(right);
+break;
+}
+case 4: { // always coalesce
+coalesce = true;
+break;
+}
+default:
+ShouldNotReachHere();
+}
+// Should the current free range be coalesced?
+// If the chunk is in a free range and either we decided to coalesce above
+// or the chunk is near the large block at the end of the heap
+// (isNearLargestChunk() returns true), then coalesce this chunk.
+bool doCoalesce = inFreeRange() &&
+(coalesce || _g->isNearLargestChunk((HeapWord*)fc));
+if (doCoalesce) {
+// Coalesce the current free range on the left with the new
+// chunk on the right.  If either is on a free list,
+// it must be removed from the list and stashed in the closure.
+if (freeRangeInFreeLists()) {
+FreeChunk* ffc = (FreeChunk*)freeFinger();
+assert(ffc->size() == pointer_delta(addr, freeFinger()),
+"Size of free range is inconsistent with chunk size.");
+if (CMSTestInFreeList) {
+assert(_sp->verifyChunkInFreeLists(ffc),
+"Chunk is not in free lists");
+}
+_sp->coalDeath(ffc->size());
+_sp->removeFreeChunkFromFreeLists(ffc);
+set_freeRangeInFreeLists(false);
+}
+if (fcInFreeLists) {
+_sp->coalDeath(chunkSize);
+assert(fc->size() == chunkSize,
+"The chunk has the wrong size or is not in the free lists");
+_sp->removeFreeChunkFromFreeLists(fc);
+}
+set_lastFreeRangeCoalesced(true);
+} else {  // not in a free range and/or should not coalesce
+// Return the current free range and start a new one.
+if (inFreeRange()) {
+// In a free range but cannot coalesce with the right hand chunk.
+// Put the current free range into the free lists.
+flushCurFreeChunk(freeFinger(),
+pointer_delta(addr, freeFinger()));
+}
+// Set up for new free range.  Pass along whether the right hand
+// chunk is in the free lists.
+initialize_free_range((HeapWord*)fc, fcInFreeLists);
+}
+}
+void SweepClosure::flushCurFreeChunk(HeapWord* chunk, size_t size) {
+assert(inFreeRange(), "Should only be called if currently in a free range.");
+assert(size > 0,
+"A zero sized chunk cannot be added to the free lists.");
+if (!freeRangeInFreeLists()) {
+if(CMSTestInFreeList) {
+FreeChunk* fc = (FreeChunk*) chunk;
+fc->setSize(size);
+assert(!_sp->verifyChunkInFreeLists(fc),
+"chunk should not be in free lists yet");
+}
+if (CMSTraceSweeper) {
+gclog_or_tty->print_cr(" -- add free block 0x%x (%d) to free lists",
+chunk, size);
+}
+// A new free range is going to be starting.  The current
+// free range has not been added to the free lists yet or
+// was removed so add it back.
+// If the current free range was coalesced, then the death
+// of the free range was recorded.  Record a birth now.
+if (lastFreeRangeCoalesced()) {
+_sp->coalBirth(size);
+}
+_sp->addChunkAndRepairOffsetTable(chunk, size,
+lastFreeRangeCoalesced());
+}
+set_inFreeRange(false);
+set_freeRangeInFreeLists(false);
+}
+// We take a break if we've been at this for a while,
+// so as to avoid monopolizing the locks involved.
+void SweepClosure::do_yield_work(HeapWord* addr) {
+// Return current free chunk being used for coalescing (if any)
+// to the appropriate freelist.  After yielding, the next
+// free block encountered will start a coalescing range of
+// free blocks.  If the next free block is adjacent to the
+// chunk just flushed, they will need to wait for the next
+// sweep to be coalesced.
+if (inFreeRange()) {
+flushCurFreeChunk(freeFinger(), pointer_delta(addr, freeFinger()));
+}
+// First give up the locks, then yield, then re-lock.
+// We should probably use a constructor/destructor idiom to
+// do this unlock/lock or modify the MutexUnlocker class to
+// serve our purpose. XXX
+assert_lock_strong(_bitMap->lock());
+assert_lock_strong(_freelistLock);
+assert(ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
+"CMS thread should hold CMS token");
+_bitMap->lock()->unlock();
+_freelistLock->unlock();
+ConcurrentMarkSweepThread::desynchronize(true);
+ConcurrentMarkSweepThread::acknowledge_yield_request();
+_collector->stopTimer();
+GCPauseTimer p(_collector->size_policy()->concurrent_timer_ptr());
+if (PrintCMSStatistics != 0) {
+_collector->incrementYields();
+}
+_collector->icms_wait();
+// See the comment in coordinator_yield()
+for (unsigned i = 0; i < CMSYieldSleepCount &&
+ConcurrentMarkSweepThread::should_yield() &&
+!CMSCollector::foregroundGCIsActive(); ++i) {
+os::sleep(Thread::current(), 1, false);
+ConcurrentMarkSweepThread::acknowledge_yield_request();
+}
+ConcurrentMarkSweepThread::synchronize(true);
+_freelistLock->lock();
+_bitMap->lock()->lock_without_safepoint_check();
+_collector->startTimer();
+}
+#ifndef PRODUCT
+// This is actually very useful in a product build if it can
+// be called from the debugger.  Compile it into the product
+// as needed.
+bool debug_verifyChunkInFreeLists(FreeChunk* fc) {
+return debug_cms_space->verifyChunkInFreeLists(fc);
+}
+void SweepClosure::record_free_block_coalesced(FreeChunk* fc) const {
+if (CMSTraceSweeper) {
+gclog_or_tty->print("Sweep:coal_free_blk 0x%x (%d)\n", fc, fc->size());
+}
+}
+#endif
+// CMSIsAliveClosure
+bool CMSIsAliveClosure::do_object_b(oop obj) {
+HeapWord* addr = (HeapWord*)obj;
+return addr != NULL &&
+(!_span.contains(addr) || _bit_map->isMarked(addr));
+}
+// CMSKeepAliveClosure: the serial version
+void CMSKeepAliveClosure::do_oop(oop* p) {
+oop this_oop = *p;
+HeapWord* addr = (HeapWord*)this_oop;
+if (_span.contains(addr) &&
+!_bit_map->isMarked(addr)) {
+_bit_map->mark(addr);
+bool simulate_overflow = false;
+NOT_PRODUCT(
+if (CMSMarkStackOverflowALot &&
+_collector->simulate_overflow()) {
+// simulate a stack overflow
+simulate_overflow = true;
+}
+)
+if (simulate_overflow || !_mark_stack->push(this_oop)) {
+_collector->push_on_overflow_list(this_oop);
+_collector->_ser_kac_ovflw++;
+}
+}
+}
+// CMSParKeepAliveClosure: a parallel version of the above.
+// The work queues are private to each closure (thread),
+// but (may be) available for stealing by other threads.
+void CMSParKeepAliveClosure::do_oop(oop* p) {
+oop this_oop = *p;
+HeapWord* addr = (HeapWord*)this_oop;
+if (_span.contains(addr) &&
+!_bit_map->isMarked(addr)) {
+// In general, during recursive tracing, several threads
+// may be concurrently getting here; the first one to
+// "tag" it, claims it.
+if (_bit_map->par_mark(addr)) {
+bool res = _work_queue->push(this_oop);
+assert(res, "Low water mark should be much less than capacity");
+// Do a recursive trim in the hope that this will keep
+// stack usage lower, but leave some oops for potential stealers
+trim_queue(_low_water_mark);
+} // Else, another thread got there first
+}
+}
+void CMSParKeepAliveClosure::trim_queue(uint max) {
+while (_work_queue->size() > max) {
+oop new_oop;
+if (_work_queue->pop_local(new_oop)) {
+assert(new_oop != NULL && new_oop->is_oop(), "Expected an oop");
+assert(_bit_map->isMarked((HeapWord*)new_oop),
+"no white objects on this stack!");
+assert(_span.contains((HeapWord*)new_oop), "Out of bounds oop");
+// iterate over the oops in this oop, marking and pushing
+// the ones in CMS heap (i.e. in _span).
+new_oop->oop_iterate(&_mark_and_push);
+}
+}
+}
+void CMSInnerParMarkAndPushClosure::do_oop(oop* p) {
+oop this_oop = *p;
+HeapWord* addr = (HeapWord*)this_oop;
+if (_span.contains(addr) &&
+!_bit_map->isMarked(addr)) {
+if (_bit_map->par_mark(addr)) {
+bool simulate_overflow = false;
+NOT_PRODUCT(
+if (CMSMarkStackOverflowALot &&
+_collector->par_simulate_overflow()) {
+// simulate a stack overflow
+simulate_overflow = true;
+}
+)
+if (simulate_overflow || !_work_queue->push(this_oop)) {
+_collector->par_push_on_overflow_list(this_oop);
+_collector->_par_kac_ovflw++;
+}
+} // Else another thread got there already
+}
+}
+//////////////////////////////////////////////////////////////////
+//  CMSExpansionCause                /////////////////////////////
+//////////////////////////////////////////////////////////////////
+const char* CMSExpansionCause::to_string(CMSExpansionCause::Cause cause) {
+switch (cause) {
+case _no_expansion:
+return "No expansion";
+case _satisfy_free_ratio:
+return "Free ratio";
+case _satisfy_promotion:
+return "Satisfy promotion";
+case _satisfy_allocation:
+return "allocation";
+case _allocate_par_lab:
+return "Par LAB";
+case _allocate_par_spooling_space:
+return "Par Spooling Space";
+case _adaptive_size_policy:
+return "Ergonomics";
+default:
+return "unknown";
+}
+}
+void CMSDrainMarkingStackClosure::do_void() {
+// the max number to take from overflow list at a time
+const size_t num = _mark_stack->capacity()/4;
+while (!_mark_stack->isEmpty() ||
+// if stack is empty, check the overflow list
+_collector->take_from_overflow_list(num, _mark_stack)) {
+oop this_oop = _mark_stack->pop();
+HeapWord* addr = (HeapWord*)this_oop;
+assert(_span.contains(addr), "Should be within span");
+assert(_bit_map->isMarked(addr), "Should be marked");
+assert(this_oop->is_oop(), "Should be an oop");
+this_oop->oop_iterate(_keep_alive);
+}
+}
+void CMSParDrainMarkingStackClosure::do_void() {
+// drain queue
+trim_queue(0);
+}
+// Trim our work_queue so its length is below max at return
+void CMSParDrainMarkingStackClosure::trim_queue(uint max) {
+while (_work_queue->size() > max) {
+oop new_oop;
+if (_work_queue->pop_local(new_oop)) {
+assert(new_oop->is_oop(), "Expected an oop");
+assert(_bit_map->isMarked((HeapWord*)new_oop),
+"no white objects on this stack!");
+assert(_span.contains((HeapWord*)new_oop), "Out of bounds oop");
+// iterate over the oops in this oop, marking and pushing
+// the ones in CMS heap (i.e. in _span).
+new_oop->oop_iterate(&_mark_and_push);
+}
+}
+}
+////////////////////////////////////////////////////////////////////
+// Support for Marking Stack Overflow list handling and related code
+////////////////////////////////////////////////////////////////////
+// Much of the following code is similar in shape and spirit to the
+// code used in ParNewGC. We should try and share that code
+// as much as possible in the future.
+#ifndef PRODUCT
+// Debugging support for CMSStackOverflowALot
+// It's OK to call this multi-threaded;  the worst thing
+// that can happen is that we'll get a bunch of closely
+// spaced simulated oveflows, but that's OK, in fact
+// probably good as it would exercise the overflow code
+// under contention.
+bool CMSCollector::simulate_overflow() {
+if (_overflow_counter-- <= 0) { // just being defensive
+_overflow_counter = CMSMarkStackOverflowInterval;
+return true;
+} else {
+return false;
+}
+}
+bool CMSCollector::par_simulate_overflow() {
+return simulate_overflow();
+}
+#endif
+// Single-threaded
+bool CMSCollector::take_from_overflow_list(size_t num, CMSMarkStack* stack) {
+assert(stack->isEmpty(), "Expected precondition");
+assert(stack->capacity() > num, "Shouldn't bite more than can chew");
+size_t i = num;
+oop  cur = _overflow_list;
+const markOop proto = markOopDesc::prototype();
+NOT_PRODUCT(size_t n = 0;)
+for (oop next; i > 0 && cur != NULL; cur = next, i--) {
+next = oop(cur->mark());
+cur->set_mark(proto);   // until proven otherwise
+assert(cur->is_oop(), "Should be an oop");
+bool res = stack->push(cur);
+assert(res, "Bit off more than can chew?");
+NOT_PRODUCT(n++;)
+}
+_overflow_list = cur;
+#ifndef PRODUCT
+assert(_num_par_pushes >= n, "Too many pops?");
+_num_par_pushes -=n;
+#endif
+return !stack->isEmpty();
+}
+// Multi-threaded; use CAS to break off a prefix
+bool CMSCollector::par_take_from_overflow_list(size_t num,
+OopTaskQueue* work_q) {
+assert(work_q->size() == 0, "That's the current policy");
+assert(num < work_q->max_elems(), "Can't bite more than we can chew");
+if (_overflow_list == NULL) {
+return false;
+}
+// Grab the entire list; we'll put back a suffix
+oop prefix = (oop)Atomic::xchg_ptr(NULL, &_overflow_list);
+if (prefix == NULL) {  // someone grabbed it before we did ...
+// ... we could spin for a short while, but for now we don't
+return false;
+}
+size_t i = num;
+oop cur = prefix;
+for (; i > 1 && cur->mark() != NULL; cur = oop(cur->mark()), i--);
+if (cur->mark() != NULL) {
+oop suffix_head = cur->mark(); // suffix will be put back on global list
+cur->set_mark(NULL);           // break off suffix
+// Find tail of suffix so we can prepend suffix to global list
+for (cur = suffix_head; cur->mark() != NULL; cur = (oop)(cur->mark()));
+oop suffix_tail = cur;
+assert(suffix_tail != NULL && suffix_tail->mark() == NULL,
+"Tautology");
+oop observed_overflow_list = _overflow_list;
+do {
+cur = observed_overflow_list;
+suffix_tail->set_mark(markOop(cur));
+observed_overflow_list =
+(oop) Atomic::cmpxchg_ptr(suffix_head, &_overflow_list, cur);
+} while (cur != observed_overflow_list);
+}
+// Push the prefix elements on work_q
+assert(prefix != NULL, "control point invariant");
+const markOop proto = markOopDesc::prototype();
+oop next;
+NOT_PRODUCT(size_t n = 0;)
+for (cur = prefix; cur != NULL; cur = next) {
+next = oop(cur->mark());
+cur->set_mark(proto);   // until proven otherwise
+assert(cur->is_oop(), "Should be an oop");
+bool res = work_q->push(cur);
+assert(res, "Bit off more than we can chew?");
+NOT_PRODUCT(n++;)
+}
+#ifndef PRODUCT
+assert(_num_par_pushes >= n, "Too many pops?");
+Atomic::add_ptr(-(intptr_t)n, &_num_par_pushes);
+#endif
+return true;
+}
+// Single-threaded
+void CMSCollector::push_on_overflow_list(oop p) {
+NOT_PRODUCT(_num_par_pushes++;)
+assert(p->is_oop(), "Not an oop");
+preserve_mark_if_necessary(p);
+p->set_mark((markOop)_overflow_list);
+_overflow_list = p;
+}
+// Multi-threaded; use CAS to prepend to overflow list
+void CMSCollector::par_push_on_overflow_list(oop p) {
+NOT_PRODUCT(Atomic::inc_ptr(&_num_par_pushes);)
+assert(p->is_oop(), "Not an oop");
+par_preserve_mark_if_necessary(p);
+oop observed_overflow_list = _overflow_list;
+oop cur_overflow_list;
+do {
+cur_overflow_list = observed_overflow_list;
+p->set_mark(markOop(cur_overflow_list));
+observed_overflow_list =
+(oop) Atomic::cmpxchg_ptr(p, &_overflow_list, cur_overflow_list);
+} while (cur_overflow_list != observed_overflow_list);
+}
+// Single threaded
+// General Note on GrowableArray: pushes may silently fail
+// because we are (temporarily) out of C-heap for expanding
+// the stack. The problem is quite ubiquitous and affects
+// a lot of code in the JVM. The prudent thing for GrowableArray
+// to do (for now) is to exit with an error. However, that may
+// be too draconian in some cases because the caller may be
+// able to recover without much harm. For suych cases, we
+// should probably introduce a "soft_push" method which returns
+// an indication of success or failure with the assumption that
+// the caller may be able to recover from a failure; code in
+// the VM can then be changed, incrementally, to deal with such
+// failures where possible, thus, incrementally hardening the VM
+// in such low resource situations.
+void CMSCollector::preserve_mark_work(oop p, markOop m) {
+int PreserveMarkStackSize = 128;
+if (_preserved_oop_stack == NULL) {
+assert(_preserved_mark_stack == NULL,
+"bijection with preserved_oop_stack");
+// Allocate the stacks
+_preserved_oop_stack  = new (ResourceObj::C_HEAP)
+GrowableArray<oop>(PreserveMarkStackSize, true);
+_preserved_mark_stack = new (ResourceObj::C_HEAP)
+GrowableArray<markOop>(PreserveMarkStackSize, true);
+if (_preserved_oop_stack == NULL || _preserved_mark_stack == NULL) {
+vm_exit_out_of_memory(2* PreserveMarkStackSize * sizeof(oop) /* punt */,
+"Preserved Mark/Oop Stack for CMS (C-heap)");
+}
+}
+_preserved_oop_stack->push(p);
+_preserved_mark_stack->push(m);
+assert(m == p->mark(), "Mark word changed");
+assert(_preserved_oop_stack->length() == _preserved_mark_stack->length(),
+"bijection");
+}
+// Single threaded
+void CMSCollector::preserve_mark_if_necessary(oop p) {
+markOop m = p->mark();
+if (m->must_be_preserved(p)) {
+preserve_mark_work(p, m);
+}
+}
+void CMSCollector::par_preserve_mark_if_necessary(oop p) {
+markOop m = p->mark();
+if (m->must_be_preserved(p)) {
+MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
+// Even though we read the mark word without holding
+// the lock, we are assured that it will not change
+// because we "own" this oop, so no other thread can
+// be trying to push it on the overflow list; see
+// the assertion in preserve_mark_work() that checks
+// that m == p->mark().
+preserve_mark_work(p, m);
+}
+}
+// We should be able to do this multi-threaded,
+// a chunk of stack being a task (this is
+// correct because each oop only ever appears
+// once in the overflow list. However, it's
+// not very easy to completely overlap this with
+// other operations, so will generally not be done
+// until all work's been completed. Because we
+// expect the preserved oop stack (set) to be small,
+// it's probably fine to do this single-threaded.
+// We can explore cleverer concurrent/overlapped/parallel
+// processing of preserved marks if we feel the
+// need for this in the future. Stack overflow should
+// be so rare in practice and, when it happens, its
+// effect on performance so great that this will
+// likely just be in the noise anyway.
+void CMSCollector::restore_preserved_marks_if_any() {
+if (_preserved_oop_stack == NULL) {
+assert(_preserved_mark_stack == NULL,
+"bijection with preserved_oop_stack");
+return;
+}
+assert(SafepointSynchronize::is_at_safepoint(),
+"world should be stopped");
+assert(Thread::current()->is_ConcurrentGC_thread() ||
+Thread::current()->is_VM_thread(),
+"should be single-threaded");
+int length = _preserved_oop_stack->length();
+assert(_preserved_mark_stack->length() == length, "bijection");
+for (int i = 0; i < length; i++) {
+oop p = _preserved_oop_stack->at(i);
+assert(p->is_oop(), "Should be an oop");
+assert(_span.contains(p), "oop should be in _span");
+assert(p->mark() == markOopDesc::prototype(),
+"Set when taken from overflow list");
+markOop m = _preserved_mark_stack->at(i);
+p->set_mark(m);
+}
+_preserved_mark_stack->clear();
+_preserved_oop_stack->clear();
+assert(_preserved_mark_stack->is_empty() &&
+_preserved_oop_stack->is_empty(),
+"stacks were cleared above");
+}
+#ifndef PRODUCT
+bool CMSCollector::no_preserved_marks() const {
+return (   (   _preserved_mark_stack == NULL
+&& _preserved_oop_stack == NULL)
+|| (   _preserved_mark_stack->is_empty()
+&& _preserved_oop_stack->is_empty()));
+}
+#endif
+CMSAdaptiveSizePolicy* ASConcurrentMarkSweepGeneration::cms_size_policy() const
+{
+GenCollectedHeap* gch = (GenCollectedHeap*) GenCollectedHeap::heap();
+CMSAdaptiveSizePolicy* size_policy =
+(CMSAdaptiveSizePolicy*) gch->gen_policy()->size_policy();
+assert(size_policy->is_gc_cms_adaptive_size_policy(),
+"Wrong type for size policy");
+return size_policy;
+}
+void ASConcurrentMarkSweepGeneration::resize(size_t cur_promo_size,
+size_t desired_promo_size) {
+if (cur_promo_size < desired_promo_size) {
+size_t expand_bytes = desired_promo_size - cur_promo_size;
+if (PrintAdaptiveSizePolicy && Verbose) {
+gclog_or_tty->print_cr(" ASConcurrentMarkSweepGeneration::resize "
+"Expanding tenured generation by " SIZE_FORMAT " (bytes)",
+expand_bytes);
+}
+expand(expand_bytes,
+MinHeapDeltaBytes,
+CMSExpansionCause::_adaptive_size_policy);
+} else if (desired_promo_size < cur_promo_size) {
+size_t shrink_bytes = cur_promo_size - desired_promo_size;
+if (PrintAdaptiveSizePolicy && Verbose) {
+gclog_or_tty->print_cr(" ASConcurrentMarkSweepGeneration::resize "
+"Shrinking tenured generation by " SIZE_FORMAT " (bytes)",
+shrink_bytes);
+}
+shrink(shrink_bytes);
+}
+}
+CMSGCAdaptivePolicyCounters* ASConcurrentMarkSweepGeneration::gc_adaptive_policy_counters() {
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+CMSGCAdaptivePolicyCounters* counters =
+(CMSGCAdaptivePolicyCounters*) gch->collector_policy()->counters();
+assert(counters->kind() == GCPolicyCounters::CMSGCAdaptivePolicyCountersKind,
+"Wrong kind of counters");
+return counters;
+}
+void ASConcurrentMarkSweepGeneration::update_counters() {
+if (UsePerfData) {
+_space_counters->update_all();
+_gen_counters->update_all();
+CMSGCAdaptivePolicyCounters* counters = gc_adaptive_policy_counters();
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+CMSGCStats* gc_stats_l = (CMSGCStats*) gc_stats();
+assert(gc_stats_l->kind() == GCStats::CMSGCStatsKind,
+"Wrong gc statistics type");
+counters->update_counters(gc_stats_l);
+}
+}
+void ASConcurrentMarkSweepGeneration::update_counters(size_t used) {
+if (UsePerfData) {
+_space_counters->update_used(used);
+_space_counters->update_capacity();
+_gen_counters->update_all();
+CMSGCAdaptivePolicyCounters* counters = gc_adaptive_policy_counters();
+GenCollectedHeap* gch = GenCollectedHeap::heap();
+CMSGCStats* gc_stats_l = (CMSGCStats*) gc_stats();
+assert(gc_stats_l->kind() == GCStats::CMSGCStatsKind,
+"Wrong gc statistics type");
+counters->update_counters(gc_stats_l);
+}
+}
+// The desired expansion delta is computed so that:
+// . desired free percentage or greater is used
+void ASConcurrentMarkSweepGeneration::compute_new_size() {
+assert_locked_or_safepoint(Heap_lock);
+GenCollectedHeap* gch = (GenCollectedHeap*) GenCollectedHeap::heap();
+// If incremental collection failed, we just want to expand
+// to the limit.
+if (incremental_collection_failed()) {
+clear_incremental_collection_failed();
+grow_to_reserved();
+return;
+}
+assert(UseAdaptiveSizePolicy, "Should be using adaptive sizing");
+assert(gch->kind() == CollectedHeap::GenCollectedHeap,
+"Wrong type of heap");
+int prev_level = level() - 1;
+assert(prev_level >= 0, "The cms generation is the lowest generation");
+Generation* prev_gen = gch->get_gen(prev_level);
+assert(prev_gen->kind() == Generation::ASParNew,
+"Wrong type of young generation");
+ParNewGeneration* younger_gen = (ParNewGeneration*) prev_gen;
+size_t cur_eden = younger_gen->eden()->capacity();
+CMSAdaptiveSizePolicy* size_policy = cms_size_policy();
+size_t cur_promo = free();
+size_policy->compute_tenured_generation_free_space(cur_promo,
+max_available(),
+cur_eden);
+resize(cur_promo, size_policy->promo_size());
+// Record the new size of the space in the cms generation
+// that is available for promotions.  This is temporary.
+// It should be the desired promo size.
+size_policy->avg_cms_promo()->sample(free());
+size_policy->avg_old_live()->sample(used());
+if (UsePerfData) {
+CMSGCAdaptivePolicyCounters* counters = gc_adaptive_policy_counters();
+counters->update_cms_capacity_counter(capacity());
+}
+}
+void ASConcurrentMarkSweepGeneration::shrink_by(size_t desired_bytes) {
+assert_locked_or_safepoint(Heap_lock);
+assert_lock_strong(freelistLock());
+HeapWord* old_end = _cmsSpace->end();
+HeapWord* unallocated_start = _cmsSpace->unallocated_block();
+assert(old_end >= unallocated_start, "Miscalculation of unallocated_start");
+FreeChunk* chunk_at_end = find_chunk_at_end();
+if (chunk_at_end == NULL) {
+// No room to shrink
+if (PrintGCDetails && Verbose) {
+gclog_or_tty->print_cr("No room to shrink: old_end  "
+PTR_FORMAT "  unallocated_start  " PTR_FORMAT
+" chunk_at_end  " PTR_FORMAT,
+old_end, unallocated_start, chunk_at_end);
+}
+return;
+} else {
+// Find the chunk at the end of the space and determine
+// how much it can be shrunk.
+size_t shrinkable_size_in_bytes = chunk_at_end->size();
+size_t aligned_shrinkable_size_in_bytes =
+align_size_down(shrinkable_size_in_bytes, os::vm_page_size());
+assert(unallocated_start <= chunk_at_end->end(),
+"Inconsistent chunk at end of space");
+size_t bytes = MIN2(desired_bytes, aligned_shrinkable_size_in_bytes);
+size_t word_size_before = heap_word_size(_virtual_space.committed_size());
+// Shrink the underlying space
+_virtual_space.shrink_by(bytes);
+if (PrintGCDetails && Verbose) {
+gclog_or_tty->print_cr("ConcurrentMarkSweepGeneration::shrink_by:"
+" desired_bytes " SIZE_FORMAT
+" shrinkable_size_in_bytes " SIZE_FORMAT
+" aligned_shrinkable_size_in_bytes " SIZE_FORMAT
+"  bytes  " SIZE_FORMAT,
+desired_bytes, shrinkable_size_in_bytes,
+aligned_shrinkable_size_in_bytes, bytes);
+gclog_or_tty->print_cr("          old_end  " SIZE_FORMAT
+"  unallocated_start  " SIZE_FORMAT,
+old_end, unallocated_start);
+}
+// If the space did shrink (shrinking is not guaranteed),
+// shrink the chunk at the end by the appropriate amount.
+if (((HeapWord*)_virtual_space.high()) < old_end) {
+size_t new_word_size =
+heap_word_size(_virtual_space.committed_size());
+// Have to remove the chunk from the dictionary because it is changing
+// size and might be someplace elsewhere in the dictionary.
+// Get the chunk at end, shrink it, and put it
+// back.
+_cmsSpace->removeChunkFromDictionary(chunk_at_end);
+size_t word_size_change = word_size_before - new_word_size;
+size_t chunk_at_end_old_size = chunk_at_end->size();
+assert(chunk_at_end_old_size >= word_size_change,
+"Shrink is too large");
+chunk_at_end->setSize(chunk_at_end_old_size -
+word_size_change);
+_cmsSpace->freed((HeapWord*) chunk_at_end->end(),
+word_size_change);
+_cmsSpace->returnChunkToDictionary(chunk_at_end);
+MemRegion mr(_cmsSpace->bottom(), new_word_size);
+_bts->resize(new_word_size);  // resize the block offset shared array
+Universe::heap()->barrier_set()->resize_covered_region(mr);
+_cmsSpace->assert_locked();
+_cmsSpace->set_end((HeapWord*)_virtual_space.high());
+NOT_PRODUCT(_cmsSpace->dictionary()->verify());
+// update the space and generation capacity counters
+if (UsePerfData) {
+_space_counters->update_capacity();
+_gen_counters->update_all();
+}
+if (Verbose && PrintGCDetails) {
+size_t new_mem_size = _virtual_space.committed_size();
+size_t old_mem_size = new_mem_size + bytes;
+gclog_or_tty->print_cr("Shrinking %s from %ldK by %ldK to %ldK",
+name(), old_mem_size/K, bytes/K, new_mem_size/K);
+}
+}
+assert(_cmsSpace->unallocated_block() <= _cmsSpace->end(),
+"Inconsistency at end of space");
+assert(chunk_at_end->end() == _cmsSpace->end(),
+"Shrinking is inconsistent");
+return;
+}
+}
+// Transfer some number of overflown objects to usual marking
+// stack. Return true if some objects were transferred.
+bool MarkRefsIntoAndScanClosure::take_from_overflow_list() {
+size_t num = MIN2((size_t)_mark_stack->capacity()/4,
+(size_t)ParGCDesiredObjsFromOverflowList);
+bool res = _collector->take_from_overflow_list(num, _mark_stack);
+assert(_collector->overflow_list_is_empty() || res,
+"If list is not empty, we should have taken something");
+assert(!res || !_mark_stack->isEmpty(),
+"If we took something, it should now be on our stack");
+return res;
+}
+size_t MarkDeadObjectsClosure::do_blk(HeapWord* addr) {
+size_t res = _sp->block_size_no_stall(addr, _collector);
+assert(res != 0, "Should always be able to compute a size");
+if (_sp->block_is_obj(addr)) {
+if (_live_bit_map->isMarked(addr)) {
+// It can't have been dead in a previous cycle
+guarantee(!_dead_bit_map->isMarked(addr), "No resurrection!");
+} else {
+_dead_bit_map->mark(addr);      // mark the dead object
+}
+}
+return res;
+}

Mercurial > hg > truffle

comparison src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.cpp @ 0:a61af66fc99e jdk7-b24