--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/share/vm/memory/genCollectedHeap.cpp	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,1368 @@
+/*
+ * Copyright 2000-2007 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/_genCollectedHeap.cpp.incl"
+
+GenCollectedHeap* GenCollectedHeap::_gch;
+NOT_PRODUCT(size_t GenCollectedHeap::_skip_header_HeapWords = 0;)
+
+// The set of potentially parallel tasks in strong root scanning.
+enum GCH_process_strong_roots_tasks {
+  // We probably want to parallelize both of these internally, but for now...
+  GCH_PS_younger_gens,
+  // Leave this one last.
+  GCH_PS_NumElements
+};
+
+GenCollectedHeap::GenCollectedHeap(GenCollectorPolicy *policy) :
+  SharedHeap(policy),
+  _gen_policy(policy),
+  _gen_process_strong_tasks(new SubTasksDone(GCH_PS_NumElements)),
+  _full_collections_completed(0)
+{
+  if (_gen_process_strong_tasks == NULL ||
+      !_gen_process_strong_tasks->valid()) {
+    vm_exit_during_initialization("Failed necessary allocation.");
+  }
+  assert(policy != NULL, "Sanity check");
+  _preloading_shared_classes = false;
+}
+
+jint GenCollectedHeap::initialize() {
+  int i;
+  _n_gens = gen_policy()->number_of_generations();
+
+  // While there are no constraints in the GC code that HeapWordSize
+  // be any particular value, there are multiple other areas in the
+  // system which believe this to be true (e.g. oop->object_size in some
+  // cases incorrectly returns the size in wordSize units rather than
+  // HeapWordSize).
+  guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
+
+  // The heap must be at least as aligned as generations.
+  size_t alignment = Generation::GenGrain;
+
+  _gen_specs = gen_policy()->generations();
+  PermanentGenerationSpec *perm_gen_spec =
+                                collector_policy()->permanent_generation();
+
+  // Make sure the sizes are all aligned.
+  for (i = 0; i < _n_gens; i++) {
+    _gen_specs[i]->align(alignment);
+  }
+  perm_gen_spec->align(alignment);
+
+  // If we are dumping the heap, then allocate a wasted block of address
+  // space in order to push the heap to a lower address.  This extra
+  // address range allows for other (or larger) libraries to be loaded
+  // without them occupying the space required for the shared spaces.
+
+  if (DumpSharedSpaces) {
+    uintx reserved = 0;
+    uintx block_size = 64*1024*1024;
+    while (reserved < SharedDummyBlockSize) {
+      char* dummy = os::reserve_memory(block_size);
+      reserved += block_size;
+    }
+  }
+
+  // Allocate space for the heap.
+
+  char* heap_address;
+  size_t total_reserved = 0;
+  int n_covered_regions = 0;
+  ReservedSpace heap_rs(0);
+
+  heap_address = allocate(alignment, perm_gen_spec, &total_reserved,
+                          &n_covered_regions, &heap_rs);
+
+  if (UseSharedSpaces) {
+    if (!heap_rs.is_reserved() || heap_address != heap_rs.base()) {
+      if (heap_rs.is_reserved()) {
+        heap_rs.release();
+      }
+      FileMapInfo* mapinfo = FileMapInfo::current_info();
+      mapinfo->fail_continue("Unable to reserve shared region.");
+      allocate(alignment, perm_gen_spec, &total_reserved, &n_covered_regions,
+               &heap_rs);
+    }
+  }
+
+  if (!heap_rs.is_reserved()) {
+    vm_shutdown_during_initialization(
+      "Could not reserve enough space for object heap");
+    return JNI_ENOMEM;
+  }
+
+  _reserved = MemRegion((HeapWord*)heap_rs.base(),
+                        (HeapWord*)(heap_rs.base() + heap_rs.size()));
+
+  // It is important to do this in a way such that concurrent readers can't
+  // temporarily think somethings in the heap.  (Seen this happen in asserts.)
+  _reserved.set_word_size(0);
+  _reserved.set_start((HeapWord*)heap_rs.base());
+  size_t actual_heap_size = heap_rs.size() - perm_gen_spec->misc_data_size()
+                                           - perm_gen_spec->misc_code_size();
+  _reserved.set_end((HeapWord*)(heap_rs.base() + actual_heap_size));
+
+  _rem_set = collector_policy()->create_rem_set(_reserved, n_covered_regions);
+  set_barrier_set(rem_set()->bs());
+  _gch = this;
+
+  for (i = 0; i < _n_gens; i++) {
+    ReservedSpace this_rs = heap_rs.first_part(_gen_specs[i]->max_size(),
+                                              UseSharedSpaces, UseSharedSpaces);
+    _gens[i] = _gen_specs[i]->init(this_rs, i, rem_set());
+    heap_rs = heap_rs.last_part(_gen_specs[i]->max_size());
+  }
+  _perm_gen = perm_gen_spec->init(heap_rs, PermSize, rem_set());
+
+  clear_incremental_collection_will_fail();
+  clear_last_incremental_collection_failed();
+
+#ifndef SERIALGC
+  // If we are running CMS, create the collector responsible
+  // for collecting the CMS generations.
+  if (collector_policy()->is_concurrent_mark_sweep_policy()) {
+    bool success = create_cms_collector();
+    if (!success) return JNI_ENOMEM;
+  }
+#endif // SERIALGC
+
+  return JNI_OK;
+}
+
+
+char* GenCollectedHeap::allocate(size_t alignment,
+                                 PermanentGenerationSpec* perm_gen_spec,
+                                 size_t* _total_reserved,
+                                 int* _n_covered_regions,
+                                 ReservedSpace* heap_rs){
+  const char overflow_msg[] = "The size of the object heap + VM data exceeds "
+    "the maximum representable size";
+
+  // Now figure out the total size.
+  size_t total_reserved = 0;
+  int n_covered_regions = 0;
+  const size_t pageSize = UseLargePages ?
+      os::large_page_size() : os::vm_page_size();
+
+  for (int i = 0; i < _n_gens; i++) {
+    total_reserved += _gen_specs[i]->max_size();
+    if (total_reserved < _gen_specs[i]->max_size()) {
+      vm_exit_during_initialization(overflow_msg);
+    }
+    n_covered_regions += _gen_specs[i]->n_covered_regions();
+  }
+  assert(total_reserved % pageSize == 0, "Gen size");
+  total_reserved += perm_gen_spec->max_size();
+  assert(total_reserved % pageSize == 0, "Perm Gen size");
+
+  if (total_reserved < perm_gen_spec->max_size()) {
+    vm_exit_during_initialization(overflow_msg);
+  }
+  n_covered_regions += perm_gen_spec->n_covered_regions();
+
+  // Add the size of the data area which shares the same reserved area
+  // as the heap, but which is not actually part of the heap.
+  size_t s = perm_gen_spec->misc_data_size() + perm_gen_spec->misc_code_size();
+
+  total_reserved += s;
+  if (total_reserved < s) {
+    vm_exit_during_initialization(overflow_msg);
+  }
+
+  if (UseLargePages) {
+    assert(total_reserved != 0, "total_reserved cannot be 0");
+    total_reserved = round_to(total_reserved, os::large_page_size());
+    if (total_reserved < os::large_page_size()) {
+      vm_exit_during_initialization(overflow_msg);
+    }
+  }
+
+  // Calculate the address at which the heap must reside in order for
+  // the shared data to be at the required address.
+
+  char* heap_address;
+  if (UseSharedSpaces) {
+
+    // Calculate the address of the first word beyond the heap.
+    FileMapInfo* mapinfo = FileMapInfo::current_info();
+    int lr = CompactingPermGenGen::n_regions - 1;
+    size_t capacity = align_size_up(mapinfo->space_capacity(lr), alignment);
+    heap_address = mapinfo->region_base(lr) + capacity;
+
+    // Calculate the address of the first word of the heap.
+    heap_address -= total_reserved;
+  } else {
+    heap_address = NULL;  // any address will do.
+  }
+
+  *_total_reserved = total_reserved;
+  *_n_covered_regions = n_covered_regions;
+  *heap_rs = ReservedSpace(total_reserved, alignment,
+                           UseLargePages, heap_address);
+
+  return heap_address;
+}
+
+
+void GenCollectedHeap::post_initialize() {
+  SharedHeap::post_initialize();
+  TwoGenerationCollectorPolicy *policy =
+    (TwoGenerationCollectorPolicy *)collector_policy();
+  guarantee(policy->is_two_generation_policy(), "Illegal policy type");
+  DefNewGeneration* def_new_gen = (DefNewGeneration*) get_gen(0);
+  assert(def_new_gen->kind() == Generation::DefNew ||
+         def_new_gen->kind() == Generation::ParNew ||
+         def_new_gen->kind() == Generation::ASParNew,
+         "Wrong generation kind");
+
+  Generation* old_gen = get_gen(1);
+  assert(old_gen->kind() == Generation::ConcurrentMarkSweep ||
+         old_gen->kind() == Generation::ASConcurrentMarkSweep ||
+         old_gen->kind() == Generation::MarkSweepCompact,
+    "Wrong generation kind");
+
+  policy->initialize_size_policy(def_new_gen->eden()->capacity(),
+                                 old_gen->capacity(),
+                                 def_new_gen->from()->capacity());
+  policy->initialize_gc_policy_counters();
+}
+
+void GenCollectedHeap::ref_processing_init() {
+  SharedHeap::ref_processing_init();
+  for (int i = 0; i < _n_gens; i++) {
+    _gens[i]->ref_processor_init();
+  }
+}
+
+size_t GenCollectedHeap::capacity() const {
+  size_t res = 0;
+  for (int i = 0; i < _n_gens; i++) {
+    res += _gens[i]->capacity();
+  }
+  return res;
+}
+
+size_t GenCollectedHeap::used() const {
+  size_t res = 0;
+  for (int i = 0; i < _n_gens; i++) {
+    res += _gens[i]->used();
+  }
+  return res;
+}
+
+// Save the "used_region" for generations level and lower,
+// and, if perm is true, for perm gen.
+void GenCollectedHeap::save_used_regions(int level, bool perm) {
+  assert(level < _n_gens, "Illegal level parameter");
+  for (int i = level; i >= 0; i--) {
+    _gens[i]->save_used_region();
+  }
+  if (perm) {
+    perm_gen()->save_used_region();
+  }
+}
+
+size_t GenCollectedHeap::max_capacity() const {
+  size_t res = 0;
+  for (int i = 0; i < _n_gens; i++) {
+    res += _gens[i]->max_capacity();
+  }
+  return res;
+}
+
+// Update the _full_collections_completed counter
+// at the end of a stop-world full GC.
+unsigned int GenCollectedHeap::update_full_collections_completed() {
+  MonitorLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
+  assert(_full_collections_completed <= _total_full_collections,
+         "Can't complete more collections than were started");
+  _full_collections_completed = _total_full_collections;
+  ml.notify_all();
+  return _full_collections_completed;
+}
+
+// Update the _full_collections_completed counter, as appropriate,
+// at the end of a concurrent GC cycle. Note the conditional update
+// below to allow this method to be called by a concurrent collector
+// without synchronizing in any manner with the VM thread (which
+// may already have initiated a STW full collection "concurrently").
+unsigned int GenCollectedHeap::update_full_collections_completed(unsigned int count) {
+  MonitorLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
+  assert((_full_collections_completed <= _total_full_collections) &&
+         (count <= _total_full_collections),
+         "Can't complete more collections than were started");
+  if (count > _full_collections_completed) {
+    _full_collections_completed = count;
+    ml.notify_all();
+  }
+  return _full_collections_completed;
+}
+
+
+#ifndef PRODUCT
+// Override of memory state checking method in CollectedHeap:
+// Some collectors (CMS for example) can't have badHeapWordVal written
+// in the first two words of an object. (For instance , in the case of
+// CMS these words hold state used to synchronize between certain
+// (concurrent) GC steps and direct allocating mutators.)
+// The skip_header_HeapWords() method below, allows us to skip
+// over the requisite number of HeapWord's. Note that (for
+// generational collectors) this means that those many words are
+// skipped in each object, irrespective of the generation in which
+// that object lives. The resultant loss of precision seems to be
+// harmless and the pain of avoiding that imprecision appears somewhat
+// higher than we are prepared to pay for such rudimentary debugging
+// support.
+void GenCollectedHeap::check_for_non_bad_heap_word_value(HeapWord* addr,
+                                                         size_t size) {
+  if (CheckMemoryInitialization && ZapUnusedHeapArea) {
+    // We are asked to check a size in HeapWords,
+    // but the memory is mangled in juint words.
+    juint* start = (juint*) (addr + skip_header_HeapWords());
+    juint* end   = (juint*) (addr + size);
+    for (juint* slot = start; slot < end; slot += 1) {
+      assert(*slot == badHeapWordVal,
+             "Found non badHeapWordValue in pre-allocation check");
+    }
+  }
+}
+#endif
+
+HeapWord* GenCollectedHeap::attempt_allocation(size_t size,
+                                               bool is_tlab,
+                                               bool first_only) {
+  HeapWord* res;
+  for (int i = 0; i < _n_gens; i++) {
+    if (_gens[i]->should_allocate(size, is_tlab)) {
+      res = _gens[i]->allocate(size, is_tlab);
+      if (res != NULL) return res;
+      else if (first_only) break;
+    }
+  }
+  // Otherwise...
+  return NULL;
+}
+
+HeapWord* GenCollectedHeap::mem_allocate(size_t size,
+                                         bool is_large_noref,
+                                         bool is_tlab,
+                                         bool* gc_overhead_limit_was_exceeded) {
+  return collector_policy()->mem_allocate_work(size,
+                                               is_tlab,
+                                               gc_overhead_limit_was_exceeded);
+}
+
+bool GenCollectedHeap::must_clear_all_soft_refs() {
+  return _gc_cause == GCCause::_last_ditch_collection;
+}
+
+bool GenCollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
+  return (cause == GCCause::_java_lang_system_gc ||
+          cause == GCCause::_gc_locker) &&
+         UseConcMarkSweepGC && ExplicitGCInvokesConcurrent;
+}
+
+void GenCollectedHeap::do_collection(bool  full,
+                                     bool   clear_all_soft_refs,
+                                     size_t size,
+                                     bool   is_tlab,
+                                     int    max_level) {
+  bool prepared_for_verification = false;
+  ResourceMark rm;
+  DEBUG_ONLY(Thread* my_thread = Thread::current();)
+
+  assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
+  assert(my_thread->is_VM_thread() ||
+         my_thread->is_ConcurrentGC_thread(),
+         "incorrect thread type capability");
+  assert(Heap_lock->is_locked(), "the requesting thread should have the Heap_lock");
+  guarantee(!is_gc_active(), "collection is not reentrant");
+  assert(max_level < n_gens(), "sanity check");
+
+  if (GC_locker::check_active_before_gc()) {
+    return; // GC is disabled (e.g. JNI GetXXXCritical operation)
+  }
+
+  const size_t perm_prev_used = perm_gen()->used();
+
+  if (PrintHeapAtGC) {
+    Universe::print_heap_before_gc();
+    if (Verbose) {
+      gclog_or_tty->print_cr("GC Cause: %s", GCCause::to_string(gc_cause()));
+    }
+  }
+
+  {
+    FlagSetting fl(_is_gc_active, true);
+
+    bool complete = full && (max_level == (n_gens()-1));
+    const char* gc_cause_str = "GC ";
+    if (complete) {
+      GCCause::Cause cause = gc_cause();
+      if (cause == GCCause::_java_lang_system_gc) {
+        gc_cause_str = "Full GC (System) ";
+      } else {
+        gc_cause_str = "Full GC ";
+      }
+    }
+    gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
+    TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
+    TraceTime t(gc_cause_str, PrintGCDetails, false, gclog_or_tty);
+
+    gc_prologue(complete);
+    increment_total_collections(complete);
+
+    size_t gch_prev_used = used();
+
+    int starting_level = 0;
+    if (full) {
+      // Search for the oldest generation which will collect all younger
+      // generations, and start collection loop there.
+      for (int i = max_level; i >= 0; i--) {
+        if (_gens[i]->full_collects_younger_generations()) {
+          starting_level = i;
+          break;
+        }
+      }
+    }
+
+    bool must_restore_marks_for_biased_locking = false;
+
+    int max_level_collected = starting_level;
+    for (int i = starting_level; i <= max_level; i++) {
+      if (_gens[i]->should_collect(full, size, is_tlab)) {
+        // Timer for individual generations. Last argument is false: no CR
+        TraceTime t1(_gens[i]->short_name(), PrintGCDetails, false, gclog_or_tty);
+        TraceCollectorStats tcs(_gens[i]->counters());
+        TraceMemoryManagerStats tmms(_gens[i]->kind());
+
+        size_t prev_used = _gens[i]->used();
+        _gens[i]->stat_record()->invocations++;
+        _gens[i]->stat_record()->accumulated_time.start();
+
+        if (PrintGC && Verbose) {
+          gclog_or_tty->print("level=%d invoke=%d size=" SIZE_FORMAT,
+                     i,
+                     _gens[i]->stat_record()->invocations,
+                     size*HeapWordSize);
+        }
+
+        if (VerifyBeforeGC && i >= VerifyGCLevel &&
+            total_collections() >= VerifyGCStartAt) {
+          HandleMark hm;  // Discard invalid handles created during verification
+          if (!prepared_for_verification) {
+            prepare_for_verify();
+            prepared_for_verification = true;
+          }
+          gclog_or_tty->print(" VerifyBeforeGC:");
+          Universe::verify(true);
+        }
+        COMPILER2_PRESENT(DerivedPointerTable::clear());
+
+        if (!must_restore_marks_for_biased_locking &&
+            _gens[i]->performs_in_place_marking()) {
+          // We perform this mark word preservation work lazily
+          // because it's only at this point that we know whether we
+          // absolutely have to do it; we want to avoid doing it for
+          // scavenge-only collections where it's unnecessary
+          must_restore_marks_for_biased_locking = true;
+          BiasedLocking::preserve_marks();
+        }
+
+        // Do collection work
+        {
+          // Note on ref discovery: For what appear to be historical reasons,
+          // GCH enables and disabled (by enqueing) refs discovery.
+          // In the future this should be moved into the generation's
+          // collect method so that ref discovery and enqueueing concerns
+          // are local to a generation. The collect method could return
+          // an appropriate indication in the case that notification on
+          // the ref lock was needed. This will make the treatment of
+          // weak refs more uniform (and indeed remove such concerns
+          // from GCH). XXX
+
+          HandleMark hm;  // Discard invalid handles created during gc
+          save_marks();   // save marks for all gens
+          // We want to discover references, but not process them yet.
+          // This mode is disabled in process_discovered_references if the
+          // generation does some collection work, or in
+          // enqueue_discovered_references if the generation returns
+          // without doing any work.
+          ReferenceProcessor* rp = _gens[i]->ref_processor();
+          // If the discovery of ("weak") refs in this generation is
+          // atomic wrt other collectors in this configuration, we
+          // are guaranteed to have empty discovered ref lists.
+          if (rp->discovery_is_atomic()) {
+            rp->verify_no_references_recorded();
+            rp->enable_discovery();
+          } else {
+            // collect() will enable discovery as appropriate
+          }
+          _gens[i]->collect(full, clear_all_soft_refs, size, is_tlab);
+          if (!rp->enqueuing_is_done()) {
+            rp->enqueue_discovered_references();
+          } else {
+            rp->set_enqueuing_is_done(false);
+          }
+          rp->verify_no_references_recorded();
+        }
+        max_level_collected = i;
+
+        // Determine if allocation request was met.
+        if (size > 0) {
+          if (!is_tlab || _gens[i]->supports_tlab_allocation()) {
+            if (size*HeapWordSize <= _gens[i]->unsafe_max_alloc_nogc()) {
+              size = 0;
+            }
+          }
+        }
+
+        COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
+
+        _gens[i]->stat_record()->accumulated_time.stop();
+
+        update_gc_stats(i, full);
+
+        if (VerifyAfterGC && i >= VerifyGCLevel &&
+            total_collections() >= VerifyGCStartAt) {
+          HandleMark hm;  // Discard invalid handles created during verification
+          gclog_or_tty->print(" VerifyAfterGC:");
+          Universe::verify(false);
+        }
+
+        if (PrintGCDetails) {
+          gclog_or_tty->print(":");
+          _gens[i]->print_heap_change(prev_used);
+        }
+      }
+    }
+
+    // Update "complete" boolean wrt what actually transpired --
+    // for instance, a promotion failure could have led to
+    // a whole heap collection.
+    complete = complete || (max_level_collected == n_gens() - 1);
+
+    if (PrintGCDetails) {
+      print_heap_change(gch_prev_used);
+
+      // Print perm gen info for full GC with PrintGCDetails flag.
+      if (complete) {
+        print_perm_heap_change(perm_prev_used);
+      }
+    }
+
+    for (int j = max_level_collected; j >= 0; j -= 1) {
+      // Adjust generation sizes.
+      _gens[j]->compute_new_size();
+    }
+
+    if (complete) {
+      // Ask the permanent generation to adjust size for full collections
+      perm()->compute_new_size();
+      update_full_collections_completed();
+    }
+
+    // Track memory usage and detect low memory after GC finishes
+    MemoryService::track_memory_usage();
+
+    gc_epilogue(complete);
+
+    if (must_restore_marks_for_biased_locking) {
+      BiasedLocking::restore_marks();
+    }
+  }
+
+  AdaptiveSizePolicy* sp = gen_policy()->size_policy();
+  AdaptiveSizePolicyOutput(sp, total_collections());
+
+  if (PrintHeapAtGC) {
+    Universe::print_heap_after_gc();
+  }
+
+  if (ExitAfterGCNum > 0 && total_collections() == ExitAfterGCNum) {
+    tty->print_cr("Stopping after GC #%d", ExitAfterGCNum);
+    vm_exit(-1);
+  }
+}
+
+HeapWord* GenCollectedHeap::satisfy_failed_allocation(size_t size, bool is_tlab) {
+  return collector_policy()->satisfy_failed_allocation(size, is_tlab);
+}
+
+void GenCollectedHeap::set_par_threads(int t) {
+  SharedHeap::set_par_threads(t);
+  _gen_process_strong_tasks->set_par_threads(t);
+}
+
+class AssertIsPermClosure: public OopClosure {
+public:
+  void do_oop(oop* p) {
+    assert((*p) == NULL || (*p)->is_perm(), "Referent should be perm.");
+  }
+};
+static AssertIsPermClosure assert_is_perm_closure;
+
+void GenCollectedHeap::
+gen_process_strong_roots(int level,
+                         bool younger_gens_as_roots,
+                         bool collecting_perm_gen,
+                         SharedHeap::ScanningOption so,
+                         OopsInGenClosure* older_gens,
+                         OopsInGenClosure* not_older_gens) {
+  // General strong roots.
+  SharedHeap::process_strong_roots(collecting_perm_gen, so,
+                                   not_older_gens, older_gens);
+
+  if (younger_gens_as_roots) {
+    if (!_gen_process_strong_tasks->is_task_claimed(GCH_PS_younger_gens)) {
+      for (int i = 0; i < level; i++) {
+        not_older_gens->set_generation(_gens[i]);
+        _gens[i]->oop_iterate(not_older_gens);
+      }
+      not_older_gens->reset_generation();
+    }
+  }
+  // When collection is parallel, all threads get to cooperate to do
+  // older-gen scanning.
+  for (int i = level+1; i < _n_gens; i++) {
+    older_gens->set_generation(_gens[i]);
+    rem_set()->younger_refs_iterate(_gens[i], older_gens);
+    older_gens->reset_generation();
+  }
+
+  _gen_process_strong_tasks->all_tasks_completed();
+}
+
+void GenCollectedHeap::gen_process_weak_roots(OopClosure* root_closure,
+                                              OopClosure* non_root_closure) {
+  SharedHeap::process_weak_roots(root_closure, non_root_closure);
+  // "Local" "weak" refs
+  for (int i = 0; i < _n_gens; i++) {
+    _gens[i]->ref_processor()->weak_oops_do(root_closure);
+  }
+}
+
+#define GCH_SINCE_SAVE_MARKS_ITERATE_DEFN(OopClosureType, nv_suffix)    \
+void GenCollectedHeap::                                                 \
+oop_since_save_marks_iterate(int level,                                 \
+                             OopClosureType* cur,                       \
+                             OopClosureType* older) {                   \
+  _gens[level]->oop_since_save_marks_iterate##nv_suffix(cur);           \
+  for (int i = level+1; i < n_gens(); i++) {                            \
+    _gens[i]->oop_since_save_marks_iterate##nv_suffix(older);           \
+  }                                                                     \
+  perm_gen()->oop_since_save_marks_iterate##nv_suffix(older);           \
+}
+
+ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DEFN)
+
+#undef GCH_SINCE_SAVE_MARKS_ITERATE_DEFN
+
+bool GenCollectedHeap::no_allocs_since_save_marks(int level) {
+  for (int i = level; i < _n_gens; i++) {
+    if (!_gens[i]->no_allocs_since_save_marks()) return false;
+  }
+  return perm_gen()->no_allocs_since_save_marks();
+}
+
+bool GenCollectedHeap::supports_inline_contig_alloc() const {
+  return _gens[0]->supports_inline_contig_alloc();
+}
+
+HeapWord** GenCollectedHeap::top_addr() const {
+  return _gens[0]->top_addr();
+}
+
+HeapWord** GenCollectedHeap::end_addr() const {
+  return _gens[0]->end_addr();
+}
+
+size_t GenCollectedHeap::unsafe_max_alloc() {
+  return _gens[0]->unsafe_max_alloc_nogc();
+}
+
+// public collection interfaces
+
+void GenCollectedHeap::collect(GCCause::Cause cause) {
+  if (should_do_concurrent_full_gc(cause)) {
+#ifndef SERIALGC
+    // mostly concurrent full collection
+    collect_mostly_concurrent(cause);
+#else  // SERIALGC
+    ShouldNotReachHere();
+#endif // SERIALGC
+  } else {
+#ifdef ASSERT
+    if (cause == GCCause::_scavenge_alot) {
+      // minor collection only
+      collect(cause, 0);
+    } else {
+      // Stop-the-world full collection
+      collect(cause, n_gens() - 1);
+    }
+#else
+    // Stop-the-world full collection
+    collect(cause, n_gens() - 1);
+#endif
+  }
+}
+
+void GenCollectedHeap::collect(GCCause::Cause cause, int max_level) {
+  // The caller doesn't have the Heap_lock
+  assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
+  MutexLocker ml(Heap_lock);
+  collect_locked(cause, max_level);
+}
+
+// This interface assumes that it's being called by the
+// vm thread. It collects the heap assuming that the
+// heap lock is already held and that we are executing in
+// the context of the vm thread.
+void GenCollectedHeap::collect_as_vm_thread(GCCause::Cause cause) {
+  assert(Thread::current()->is_VM_thread(), "Precondition#1");
+  assert(Heap_lock->is_locked(), "Precondition#2");
+  GCCauseSetter gcs(this, cause);
+  switch (cause) {
+    case GCCause::_heap_inspection:
+    case GCCause::_heap_dump: {
+      HandleMark hm;
+      do_full_collection(false,         // don't clear all soft refs
+                         n_gens() - 1);
+      break;
+    }
+    default: // XXX FIX ME
+      ShouldNotReachHere(); // Unexpected use of this function
+  }
+}
+
+void GenCollectedHeap::collect_locked(GCCause::Cause cause) {
+  // The caller has the Heap_lock
+  assert(Heap_lock->owned_by_self(), "this thread should own the Heap_lock");
+  collect_locked(cause, n_gens() - 1);
+}
+
+// this is the private collection interface
+// The Heap_lock is expected to be held on entry.
+
+void GenCollectedHeap::collect_locked(GCCause::Cause cause, int max_level) {
+  if (_preloading_shared_classes) {
+    warning("\nThe permanent generation is not large enough to preload "
+            "requested classes.\nUse -XX:PermSize= to increase the initial "
+            "size of the permanent generation.\n");
+    vm_exit(2);
+  }
+  // Read the GC count while holding the Heap_lock
+  unsigned int gc_count_before      = total_collections();
+  unsigned int full_gc_count_before = total_full_collections();
+  {
+    MutexUnlocker mu(Heap_lock);  // give up heap lock, execute gets it back
+    VM_GenCollectFull op(gc_count_before, full_gc_count_before,
+                         cause, max_level);
+    VMThread::execute(&op);
+  }
+}
+
+#ifndef SERIALGC
+bool GenCollectedHeap::create_cms_collector() {
+
+  assert(((_gens[1]->kind() == Generation::ConcurrentMarkSweep) ||
+         (_gens[1]->kind() == Generation::ASConcurrentMarkSweep)) &&
+         _perm_gen->as_gen()->kind() == Generation::ConcurrentMarkSweep,
+         "Unexpected generation kinds");
+  // Skip two header words in the block content verification
+  NOT_PRODUCT(_skip_header_HeapWords = CMSCollector::skip_header_HeapWords();)
+  CMSCollector* collector = new CMSCollector(
+    (ConcurrentMarkSweepGeneration*)_gens[1],
+    (ConcurrentMarkSweepGeneration*)_perm_gen->as_gen(),
+    _rem_set->as_CardTableRS(),
+    (ConcurrentMarkSweepPolicy*) collector_policy());
+
+  if (collector == NULL || !collector->completed_initialization()) {
+    if (collector) {
+      delete collector;  // Be nice in embedded situation
+    }
+    vm_shutdown_during_initialization("Could not create CMS collector");
+    return false;
+  }
+  return true;  // success
+}
+
+void GenCollectedHeap::collect_mostly_concurrent(GCCause::Cause cause) {
+  assert(!Heap_lock->owned_by_self(), "Should not own Heap_lock");
+
+  MutexLocker ml(Heap_lock);
+  // Read the GC counts while holding the Heap_lock
+  unsigned int full_gc_count_before = total_full_collections();
+  unsigned int gc_count_before      = total_collections();
+  {
+    MutexUnlocker mu(Heap_lock);
+    VM_GenCollectFullConcurrent op(gc_count_before, full_gc_count_before, cause);
+    VMThread::execute(&op);
+  }
+}
+#endif // SERIALGC
+
+
+void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs,
+                                          int max_level) {
+  int local_max_level;
+  if (!incremental_collection_will_fail() &&
+      gc_cause() == GCCause::_gc_locker) {
+    local_max_level = 0;
+  } else {
+    local_max_level = max_level;
+  }
+
+  do_collection(true                 /* full */,
+                clear_all_soft_refs  /* clear_all_soft_refs */,
+                0                    /* size */,
+                false                /* is_tlab */,
+                local_max_level      /* max_level */);
+  // Hack XXX FIX ME !!!
+  // A scavenge may not have been attempted, or may have
+  // been attempted and failed, because the old gen was too full
+  if (local_max_level == 0 && gc_cause() == GCCause::_gc_locker &&
+      incremental_collection_will_fail()) {
+    if (PrintGCDetails) {
+      gclog_or_tty->print_cr("GC locker: Trying a full collection "
+                             "because scavenge failed");
+    }
+    // This time allow the old gen to be collected as well
+    do_collection(true                 /* full */,
+                  clear_all_soft_refs  /* clear_all_soft_refs */,
+                  0                    /* size */,
+                  false                /* is_tlab */,
+                  n_gens() - 1         /* max_level */);
+  }
+}
+
+// Returns "TRUE" iff "p" points into the allocated area of the heap.
+bool GenCollectedHeap::is_in(const void* p) const {
+  #ifndef ASSERT
+  guarantee(VerifyBeforeGC   ||
+            VerifyDuringGC   ||
+            VerifyBeforeExit ||
+            VerifyAfterGC, "too expensive");
+  #endif
+  // This might be sped up with a cache of the last generation that
+  // answered yes.
+  for (int i = 0; i < _n_gens; i++) {
+    if (_gens[i]->is_in(p)) return true;
+  }
+  if (_perm_gen->as_gen()->is_in(p)) return true;
+  // Otherwise...
+  return false;
+}
+
+// Returns "TRUE" iff "p" points into the allocated area of the heap.
+bool GenCollectedHeap::is_in_youngest(void* p) {
+  return _gens[0]->is_in(p);
+}
+
+void GenCollectedHeap::oop_iterate(OopClosure* cl) {
+  for (int i = 0; i < _n_gens; i++) {
+    _gens[i]->oop_iterate(cl);
+  }
+}
+
+void GenCollectedHeap::oop_iterate(MemRegion mr, OopClosure* cl) {
+  for (int i = 0; i < _n_gens; i++) {
+    _gens[i]->oop_iterate(mr, cl);
+  }
+}
+
+void GenCollectedHeap::object_iterate(ObjectClosure* cl) {
+  for (int i = 0; i < _n_gens; i++) {
+    _gens[i]->object_iterate(cl);
+  }
+  perm_gen()->object_iterate(cl);
+}
+
+void GenCollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) {
+  for (int i = 0; i < _n_gens; i++) {
+    _gens[i]->object_iterate_since_last_GC(cl);
+  }
+}
+
+Space* GenCollectedHeap::space_containing(const void* addr) const {
+  for (int i = 0; i < _n_gens; i++) {
+    Space* res = _gens[i]->space_containing(addr);
+    if (res != NULL) return res;
+  }
+  Space* res = perm_gen()->space_containing(addr);
+  if (res != NULL) return res;
+  // Otherwise...
+  assert(false, "Could not find containing space");
+  return NULL;
+}
+
+
+HeapWord* GenCollectedHeap::block_start(const void* addr) const {
+  assert(is_in_reserved(addr), "block_start of address outside of heap");
+  for (int i = 0; i < _n_gens; i++) {
+    if (_gens[i]->is_in_reserved(addr)) {
+      assert(_gens[i]->is_in(addr),
+             "addr should be in allocated part of generation");
+      return _gens[i]->block_start(addr);
+    }
+  }
+  if (perm_gen()->is_in_reserved(addr)) {
+    assert(perm_gen()->is_in(addr),
+           "addr should be in allocated part of perm gen");
+    return perm_gen()->block_start(addr);
+  }
+  assert(false, "Some generation should contain the address");
+  return NULL;
+}
+
+size_t GenCollectedHeap::block_size(const HeapWord* addr) const {
+  assert(is_in_reserved(addr), "block_size of address outside of heap");
+  for (int i = 0; i < _n_gens; i++) {
+    if (_gens[i]->is_in_reserved(addr)) {
+      assert(_gens[i]->is_in(addr),
+             "addr should be in allocated part of generation");
+      return _gens[i]->block_size(addr);
+    }
+  }
+  if (perm_gen()->is_in_reserved(addr)) {
+    assert(perm_gen()->is_in(addr),
+           "addr should be in allocated part of perm gen");
+    return perm_gen()->block_size(addr);
+  }
+  assert(false, "Some generation should contain the address");
+  return 0;
+}
+
+bool GenCollectedHeap::block_is_obj(const HeapWord* addr) const {
+  assert(is_in_reserved(addr), "block_is_obj of address outside of heap");
+  assert(block_start(addr) == addr, "addr must be a block start");
+  for (int i = 0; i < _n_gens; i++) {
+    if (_gens[i]->is_in_reserved(addr)) {
+      return _gens[i]->block_is_obj(addr);
+    }
+  }
+  if (perm_gen()->is_in_reserved(addr)) {
+    return perm_gen()->block_is_obj(addr);
+  }
+  assert(false, "Some generation should contain the address");
+  return false;
+}
+
+bool GenCollectedHeap::supports_tlab_allocation() const {
+  for (int i = 0; i < _n_gens; i += 1) {
+    if (_gens[i]->supports_tlab_allocation()) {
+      return true;
+    }
+  }
+  return false;
+}
+
+size_t GenCollectedHeap::tlab_capacity(Thread* thr) const {
+  size_t result = 0;
+  for (int i = 0; i < _n_gens; i += 1) {
+    if (_gens[i]->supports_tlab_allocation()) {
+      result += _gens[i]->tlab_capacity();
+    }
+  }
+  return result;
+}
+
+size_t GenCollectedHeap::unsafe_max_tlab_alloc(Thread* thr) const {
+  size_t result = 0;
+  for (int i = 0; i < _n_gens; i += 1) {
+    if (_gens[i]->supports_tlab_allocation()) {
+      result += _gens[i]->unsafe_max_tlab_alloc();
+    }
+  }
+  return result;
+}
+
+HeapWord* GenCollectedHeap::allocate_new_tlab(size_t size) {
+  bool gc_overhead_limit_was_exceeded;
+  HeapWord* result = mem_allocate(size   /* size */,
+                                  false  /* is_large_noref */,
+                                  true   /* is_tlab */,
+                                  &gc_overhead_limit_was_exceeded);
+  return result;
+}
+
+// Requires "*prev_ptr" to be non-NULL.  Deletes and a block of minimal size
+// from the list headed by "*prev_ptr".
+static ScratchBlock *removeSmallestScratch(ScratchBlock **prev_ptr) {
+  bool first = true;
+  size_t min_size = 0;   // "first" makes this conceptually infinite.
+  ScratchBlock **smallest_ptr, *smallest;
+  ScratchBlock  *cur = *prev_ptr;
+  while (cur) {
+    assert(*prev_ptr == cur, "just checking");
+    if (first || cur->num_words < min_size) {
+      smallest_ptr = prev_ptr;
+      smallest     = cur;
+      min_size     = smallest->num_words;
+      first        = false;
+    }
+    prev_ptr = &cur->next;
+    cur     =  cur->next;
+  }
+  smallest      = *smallest_ptr;
+  *smallest_ptr = smallest->next;
+  return smallest;
+}
+
+// Sort the scratch block list headed by res into decreasing size order,
+// and set "res" to the result.
+static void sort_scratch_list(ScratchBlock*& list) {
+  ScratchBlock* sorted = NULL;
+  ScratchBlock* unsorted = list;
+  while (unsorted) {
+    ScratchBlock *smallest = removeSmallestScratch(&unsorted);
+    smallest->next  = sorted;
+    sorted          = smallest;
+  }
+  list = sorted;
+}
+
+ScratchBlock* GenCollectedHeap::gather_scratch(Generation* requestor,
+                                               size_t max_alloc_words) {
+  ScratchBlock* res = NULL;
+  for (int i = 0; i < _n_gens; i++) {
+    _gens[i]->contribute_scratch(res, requestor, max_alloc_words);
+  }
+  sort_scratch_list(res);
+  return res;
+}
+
+size_t GenCollectedHeap::large_typearray_limit() {
+  return gen_policy()->large_typearray_limit();
+}
+
+class GenPrepareForVerifyClosure: public GenCollectedHeap::GenClosure {
+  void do_generation(Generation* gen) {
+    gen->prepare_for_verify();
+  }
+};
+
+void GenCollectedHeap::prepare_for_verify() {
+  ensure_parsability(false);        // no need to retire TLABs
+  GenPrepareForVerifyClosure blk;
+  generation_iterate(&blk, false);
+  perm_gen()->prepare_for_verify();
+}
+
+
+void GenCollectedHeap::generation_iterate(GenClosure* cl,
+                                          bool old_to_young) {
+  if (old_to_young) {
+    for (int i = _n_gens-1; i >= 0; i--) {
+      cl->do_generation(_gens[i]);
+    }
+  } else {
+    for (int i = 0; i < _n_gens; i++) {
+      cl->do_generation(_gens[i]);
+    }
+  }
+}
+
+void GenCollectedHeap::space_iterate(SpaceClosure* cl) {
+  for (int i = 0; i < _n_gens; i++) {
+    _gens[i]->space_iterate(cl, true);
+  }
+  perm_gen()->space_iterate(cl, true);
+}
+
+bool GenCollectedHeap::is_maximal_no_gc() const {
+  for (int i = 0; i < _n_gens; i++) {  // skip perm gen
+    if (!_gens[i]->is_maximal_no_gc()) {
+      return false;
+    }
+  }
+  return true;
+}
+
+void GenCollectedHeap::save_marks() {
+  for (int i = 0; i < _n_gens; i++) {
+    _gens[i]->save_marks();
+  }
+  perm_gen()->save_marks();
+}
+
+void GenCollectedHeap::compute_new_generation_sizes(int collectedGen) {
+  for (int i = 0; i <= collectedGen; i++) {
+    _gens[i]->compute_new_size();
+  }
+}
+
+GenCollectedHeap* GenCollectedHeap::heap() {
+  assert(_gch != NULL, "Uninitialized access to GenCollectedHeap::heap()");
+  assert(_gch->kind() == CollectedHeap::GenCollectedHeap, "not a generational heap");
+  return _gch;
+}
+
+
+void GenCollectedHeap::prepare_for_compaction() {
+  Generation* scanning_gen = _gens[_n_gens-1];
+  // Start by compacting into same gen.
+  CompactPoint cp(scanning_gen, NULL, NULL);
+  while (scanning_gen != NULL) {
+    scanning_gen->prepare_for_compaction(&cp);
+    scanning_gen = prev_gen(scanning_gen);
+  }
+}
+
+GCStats* GenCollectedHeap::gc_stats(int level) const {
+  return _gens[level]->gc_stats();
+}
+
+void GenCollectedHeap::verify(bool allow_dirty, bool silent) {
+  if (!silent) {
+    gclog_or_tty->print("permgen ");
+  }
+  perm_gen()->verify(allow_dirty);
+  for (int i = _n_gens-1; i >= 0; i--) {
+    Generation* g = _gens[i];
+    if (!silent) {
+      gclog_or_tty->print(g->name());
+      gclog_or_tty->print(" ");
+    }
+    g->verify(allow_dirty);
+  }
+  if (!silent) {
+    gclog_or_tty->print("remset ");
+  }
+  rem_set()->verify();
+  if (!silent) {
+     gclog_or_tty->print("ref_proc ");
+  }
+  ReferenceProcessor::verify();
+}
+
+void GenCollectedHeap::print() const { print_on(tty); }
+void GenCollectedHeap::print_on(outputStream* st) const {
+  for (int i = 0; i < _n_gens; i++) {
+    _gens[i]->print_on(st);
+  }
+  perm_gen()->print_on(st);
+}
+
+void GenCollectedHeap::gc_threads_do(ThreadClosure* tc) const {
+  if (workers() != NULL) {
+    workers()->threads_do(tc);
+  }
+#ifndef SERIALGC
+  if (UseConcMarkSweepGC) {
+    ConcurrentMarkSweepThread::threads_do(tc);
+  }
+#endif // SERIALGC
+}
+
+void GenCollectedHeap::print_gc_threads_on(outputStream* st) const {
+#ifndef SERIALGC
+  if (UseParNewGC) {
+    workers()->print_worker_threads_on(st);
+  }
+  if (UseConcMarkSweepGC) {
+    ConcurrentMarkSweepThread::print_all_on(st);
+  }
+#endif // SERIALGC
+}
+
+void GenCollectedHeap::print_tracing_info() const {
+  if (TraceGen0Time) {
+    get_gen(0)->print_summary_info();
+  }
+  if (TraceGen1Time) {
+    get_gen(1)->print_summary_info();
+  }
+}
+
+void GenCollectedHeap::print_heap_change(size_t prev_used) const {
+  if (PrintGCDetails && Verbose) {
+    gclog_or_tty->print(" "  SIZE_FORMAT
+                        "->" SIZE_FORMAT
+                        "("  SIZE_FORMAT ")",
+                        prev_used, used(), capacity());
+  } else {
+    gclog_or_tty->print(" "  SIZE_FORMAT "K"
+                        "->" SIZE_FORMAT "K"
+                        "("  SIZE_FORMAT "K)",
+                        prev_used / K, used() / K, capacity() / K);
+  }
+}
+
+//New method to print perm gen info with PrintGCDetails flag
+void GenCollectedHeap::print_perm_heap_change(size_t perm_prev_used) const {
+  gclog_or_tty->print(", [%s :", perm_gen()->short_name());
+  perm_gen()->print_heap_change(perm_prev_used);
+  gclog_or_tty->print("]");
+}
+
+class GenGCPrologueClosure: public GenCollectedHeap::GenClosure {
+ private:
+  bool _full;
+ public:
+  void do_generation(Generation* gen) {
+    gen->gc_prologue(_full);
+  }
+  GenGCPrologueClosure(bool full) : _full(full) {};
+};
+
+void GenCollectedHeap::gc_prologue(bool full) {
+  assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
+
+  always_do_update_barrier = false;
+  // Fill TLAB's and such
+  CollectedHeap::accumulate_statistics_all_tlabs();
+  ensure_parsability(true);   // retire TLABs
+
+  // Call allocation profiler
+  AllocationProfiler::iterate_since_last_gc();
+  // Walk generations
+  GenGCPrologueClosure blk(full);
+  generation_iterate(&blk, false);  // not old-to-young.
+  perm_gen()->gc_prologue(full);
+};
+
+class GenGCEpilogueClosure: public GenCollectedHeap::GenClosure {
+ private:
+  bool _full;
+ public:
+  void do_generation(Generation* gen) {
+    gen->gc_epilogue(_full);
+  }
+  GenGCEpilogueClosure(bool full) : _full(full) {};
+};
+
+void GenCollectedHeap::gc_epilogue(bool full) {
+  // Remember if a partial collection of the heap failed, and
+  // we did a complete collection.
+  if (full && incremental_collection_will_fail()) {
+    set_last_incremental_collection_failed();
+  } else {
+    clear_last_incremental_collection_failed();
+  }
+  // Clear the flag, if set; the generation gc_epilogues will set the
+  // flag again if the condition persists despite the collection.
+  clear_incremental_collection_will_fail();
+
+#ifdef COMPILER2
+  assert(DerivedPointerTable::is_empty(), "derived pointer present");
+  size_t actual_gap = pointer_delta((HeapWord*) (max_uintx-3), *(end_addr()));
+  guarantee(actual_gap > (size_t)FastAllocateSizeLimit, "inline allocation wraps");
+#endif /* COMPILER2 */
+
+  resize_all_tlabs();
+
+  GenGCEpilogueClosure blk(full);
+  generation_iterate(&blk, false);  // not old-to-young.
+  perm_gen()->gc_epilogue(full);
+
+  always_do_update_barrier = UseConcMarkSweepGC;
+};
+
+class GenEnsureParsabilityClosure: public GenCollectedHeap::GenClosure {
+ public:
+  void do_generation(Generation* gen) {
+    gen->ensure_parsability();
+  }
+};
+
+void GenCollectedHeap::ensure_parsability(bool retire_tlabs) {
+  CollectedHeap::ensure_parsability(retire_tlabs);
+  GenEnsureParsabilityClosure ep_cl;
+  generation_iterate(&ep_cl, false);
+  perm_gen()->ensure_parsability();
+}
+
+oop GenCollectedHeap::handle_failed_promotion(Generation* gen,
+                                              oop obj,
+                                              size_t obj_size,
+                                              oop* ref) {
+  assert(obj_size == (size_t)obj->size(), "bad obj_size passed in");
+  HeapWord* result = NULL;
+
+  // First give each higher generation a chance to allocate the promoted object.
+  Generation* allocator = next_gen(gen);
+  if (allocator != NULL) {
+    do {
+      result = allocator->allocate(obj_size, false);
+    } while (result == NULL && (allocator = next_gen(allocator)) != NULL);
+  }
+
+  if (result == NULL) {
+    // Then give gen and higher generations a chance to expand and allocate the
+    // object.
+    do {
+      result = gen->expand_and_allocate(obj_size, false);
+    } while (result == NULL && (gen = next_gen(gen)) != NULL);
+  }
+
+  if (result != NULL) {
+    Copy::aligned_disjoint_words((HeapWord*)obj, result, obj_size);
+  }
+  return oop(result);
+}
+
+class GenTimeOfLastGCClosure: public GenCollectedHeap::GenClosure {
+  jlong _time;   // in ms
+  jlong _now;    // in ms
+
+ public:
+  GenTimeOfLastGCClosure(jlong now) : _time(now), _now(now) { }
+
+  jlong time() { return _time; }
+
+  void do_generation(Generation* gen) {
+    _time = MIN2(_time, gen->time_of_last_gc(_now));
+  }
+};
+
+jlong GenCollectedHeap::millis_since_last_gc() {
+  jlong now = os::javaTimeMillis();
+  GenTimeOfLastGCClosure tolgc_cl(now);
+  // iterate over generations getting the oldest
+  // time that a generation was collected
+  generation_iterate(&tolgc_cl, false);
+  tolgc_cl.do_generation(perm_gen());
+  // XXX Despite the assert above, since javaTimeMillis()
+  // doesnot guarantee monotonically increasing return
+  // values (note, i didn't say "strictly monotonic"),
+  // we need to guard against getting back a time
+  // later than now. This should be fixed by basing
+  // on someting like gethrtime() which guarantees
+  // monotonicity. Note that cond_wait() is susceptible
+  // to a similar problem, because its interface is
+  // based on absolute time in the form of the
+  // system time's notion of UCT. See also 4506635
+  // for yet another problem of similar nature. XXX
+  jlong retVal = now - tolgc_cl.time();
+  if (retVal < 0) {
+    NOT_PRODUCT(warning("time warp: %d", retVal);)
+    return 0;
+  }
+  return retVal;
+}