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view src/share/vm/runtime/sweeper.cpp @ 16017:8d8c6a40d8e2
Backed out changeset: a1b9340534bf
author | Doug Simon <doug.simon@oracle.com> |
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date | Wed, 04 Jun 2014 19:17:22 +0200 |
parents | 4ca6dc0799b6 |
children | 52b4284cb496 |
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/* * Copyright (c) 1997, 2013, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. * */ #include "precompiled.hpp" #include "code/codeCache.hpp" #include "code/compiledIC.hpp" #include "code/icBuffer.hpp" #include "code/nmethod.hpp" #include "compiler/compileBroker.hpp" #include "memory/resourceArea.hpp" #include "oops/method.hpp" #include "runtime/atomic.hpp" #include "runtime/compilationPolicy.hpp" #include "runtime/mutexLocker.hpp" #include "runtime/os.hpp" #include "runtime/sweeper.hpp" #include "runtime/vm_operations.hpp" #include "trace/tracing.hpp" #include "utilities/events.hpp" #include "utilities/ticks.inline.hpp" #include "utilities/xmlstream.hpp" #ifdef ASSERT #define SWEEP(nm) record_sweep(nm, __LINE__) // Sweeper logging code class SweeperRecord { public: int traversal; int invocation; int compile_id; long traversal_mark; int state; const char* kind; address vep; address uep; int line; void print() { tty->print_cr("traversal = %d invocation = %d compile_id = %d %s uep = " PTR_FORMAT " vep = " PTR_FORMAT " state = %d traversal_mark %d line = %d", traversal, invocation, compile_id, kind == NULL ? "" : kind, uep, vep, state, traversal_mark, line); } }; static int _sweep_index = 0; static SweeperRecord* _records = NULL; void NMethodSweeper::report_events(int id, address entry) { if (_records != NULL) { for (int i = _sweep_index; i < SweeperLogEntries; i++) { if (_records[i].uep == entry || _records[i].vep == entry || _records[i].compile_id == id) { _records[i].print(); } } for (int i = 0; i < _sweep_index; i++) { if (_records[i].uep == entry || _records[i].vep == entry || _records[i].compile_id == id) { _records[i].print(); } } } } void NMethodSweeper::report_events() { if (_records != NULL) { for (int i = _sweep_index; i < SweeperLogEntries; i++) { // skip empty records if (_records[i].vep == NULL) continue; _records[i].print(); } for (int i = 0; i < _sweep_index; i++) { // skip empty records if (_records[i].vep == NULL) continue; _records[i].print(); } } } void NMethodSweeper::record_sweep(nmethod* nm, int line) { if (_records != NULL) { _records[_sweep_index].traversal = _traversals; _records[_sweep_index].traversal_mark = nm->_stack_traversal_mark; _records[_sweep_index].invocation = _sweep_fractions_left; _records[_sweep_index].compile_id = nm->compile_id(); _records[_sweep_index].kind = nm->compile_kind(); _records[_sweep_index].state = nm->_state; _records[_sweep_index].vep = nm->verified_entry_point(); _records[_sweep_index].uep = nm->entry_point(); _records[_sweep_index].line = line; _sweep_index = (_sweep_index + 1) % SweeperLogEntries; } } #else #define SWEEP(nm) #endif nmethod* NMethodSweeper::_current = NULL; // Current nmethod long NMethodSweeper::_traversals = 0; // Stack scan count, also sweep ID. long NMethodSweeper::_time_counter = 0; // Virtual time used to periodically invoke sweeper long NMethodSweeper::_last_sweep = 0; // Value of _time_counter when the last sweep happened int NMethodSweeper::_seen = 0; // Nof. nmethod we have currently processed in current pass of CodeCache int NMethodSweeper::_flushed_count = 0; // Nof. nmethods flushed in current sweep int NMethodSweeper::_zombified_count = 0; // Nof. nmethods made zombie in current sweep int NMethodSweeper::_marked_for_reclamation_count = 0; // Nof. nmethods marked for reclaim in current sweep volatile bool NMethodSweeper::_should_sweep = true; // Indicates if we should invoke the sweeper volatile int NMethodSweeper::_sweep_fractions_left = 0; // Nof. invocations left until we are completed with this pass volatile int NMethodSweeper::_sweep_started = 0; // Flag to control conc sweeper volatile int NMethodSweeper::_bytes_changed = 0; // Counts the total nmethod size if the nmethod changed from: // 1) alive -> not_entrant // 2) not_entrant -> zombie // 3) zombie -> marked_for_reclamation int NMethodSweeper::_total_nof_methods_reclaimed = 0; // Accumulated nof methods flushed Tickspan NMethodSweeper::_total_time_sweeping; // Accumulated time sweeping Tickspan NMethodSweeper::_total_time_this_sweep; // Total time this sweep Tickspan NMethodSweeper::_peak_sweep_time; // Peak time for a full sweep Tickspan NMethodSweeper::_peak_sweep_fraction_time; // Peak time sweeping one fraction int NMethodSweeper::_hotness_counter_reset_val = 0; class MarkActivationClosure: public CodeBlobClosure { public: virtual void do_code_blob(CodeBlob* cb) { if (cb->is_nmethod()) { nmethod* nm = (nmethod*)cb; nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val()); // If we see an activation belonging to a non_entrant nmethod, we mark it. if (nm->is_not_entrant()) { nm->mark_as_seen_on_stack(); } } } }; static MarkActivationClosure mark_activation_closure; class SetHotnessClosure: public CodeBlobClosure { public: virtual void do_code_blob(CodeBlob* cb) { if (cb->is_nmethod()) { nmethod* nm = (nmethod*)cb; nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val()); } } }; static SetHotnessClosure set_hotness_closure; int NMethodSweeper::hotness_counter_reset_val() { if (_hotness_counter_reset_val == 0) { _hotness_counter_reset_val = (ReservedCodeCacheSize < M) ? 1 : (ReservedCodeCacheSize / M) * 2; } return _hotness_counter_reset_val; } bool NMethodSweeper::sweep_in_progress() { return (_current != NULL); } // Scans the stacks of all Java threads and marks activations of not-entrant methods. // No need to synchronize access, since 'mark_active_nmethods' is always executed at a // safepoint. void NMethodSweeper::mark_active_nmethods() { assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint"); // If we do not want to reclaim not-entrant or zombie methods there is no need // to scan stacks if (!MethodFlushing) { return; } // Increase time so that we can estimate when to invoke the sweeper again. _time_counter++; // Check for restart assert(CodeCache::find_blob_unsafe(_current) == _current, "Sweeper nmethod cached state invalid"); if (!sweep_in_progress()) { _seen = 0; _sweep_fractions_left = NmethodSweepFraction; _current = CodeCache::first_nmethod(); _traversals += 1; _total_time_this_sweep = Tickspan(); if (PrintMethodFlushing) { tty->print_cr("### Sweep: stack traversal %d", _traversals); } Threads::nmethods_do(&mark_activation_closure); } else { // Only set hotness counter Threads::nmethods_do(&set_hotness_closure); } OrderAccess::storestore(); } /** * This function invokes the sweeper if at least one of the three conditions is met: * (1) The code cache is getting full * (2) There are sufficient state changes in/since the last sweep. * (3) We have not been sweeping for 'some time' */ void NMethodSweeper::possibly_sweep() { assert(JavaThread::current()->thread_state() == _thread_in_vm, "must run in vm mode"); // Only compiler threads are allowed to sweep if (!MethodFlushing || !sweep_in_progress() NOT_GRAAL(|| !Thread::current()->is_Compiler_thread()) GRAAL_ONLY(|| !Thread::current()->is_Java_thread())) { return; } // If there was no state change while nmethod sweeping, 'should_sweep' will be false. // This is one of the two places where should_sweep can be set to true. The general // idea is as follows: If there is enough free space in the code cache, there is no // need to invoke the sweeper. The following formula (which determines whether to invoke // the sweeper or not) depends on the assumption that for larger ReservedCodeCacheSizes // we need less frequent sweeps than for smaller ReservedCodecCacheSizes. Furthermore, // the formula considers how much space in the code cache is currently used. Here are // some examples that will (hopefully) help in understanding. // // Small ReservedCodeCacheSizes: (e.g., < 16M) We invoke the sweeper every time, since // the result of the division is 0. This // keeps the used code cache size small // (important for embedded Java) // Large ReservedCodeCacheSize : (e.g., 256M + code cache is 10% full). The formula // computes: (256 / 16) - 1 = 15 // As a result, we invoke the sweeper after // 15 invocations of 'mark_active_nmethods. // Large ReservedCodeCacheSize: (e.g., 256M + code Cache is 90% full). The formula // computes: (256 / 16) - 10 = 6. if (!_should_sweep) { int time_since_last_sweep = _time_counter - _last_sweep; double wait_until_next_sweep = (ReservedCodeCacheSize / (16 * M)) - time_since_last_sweep - CodeCache::reverse_free_ratio(); if ((wait_until_next_sweep <= 0.0) || !CompileBroker::should_compile_new_jobs()) { _should_sweep = true; } } if (_should_sweep && _sweep_fractions_left > 0) { // Only one thread at a time will sweep jint old = Atomic::cmpxchg( 1, &_sweep_started, 0 ); if (old != 0) { return; } #ifdef ASSERT if (LogSweeper && _records == NULL) { // Create the ring buffer for the logging code _records = NEW_C_HEAP_ARRAY(SweeperRecord, SweeperLogEntries, mtGC); memset(_records, 0, sizeof(SweeperRecord) * SweeperLogEntries); } #endif if (_sweep_fractions_left > 0) { sweep_code_cache(); _sweep_fractions_left--; } // We are done with sweeping the code cache once. if (_sweep_fractions_left == 0) { _last_sweep = _time_counter; // Reset flag; temporarily disables sweeper _should_sweep = false; // If there was enough state change, 'possibly_enable_sweeper()' // sets '_should_sweep' to true possibly_enable_sweeper(); // Reset _bytes_changed only if there was enough state change. _bytes_changed // can further increase by calls to 'report_state_change'. if (_should_sweep) { _bytes_changed = 0; } } _sweep_started = 0; } } void NMethodSweeper::sweep_code_cache() { Ticks sweep_start_counter = Ticks::now(); _flushed_count = 0; _zombified_count = 0; _marked_for_reclamation_count = 0; if (PrintMethodFlushing && Verbose) { tty->print_cr("### Sweep at %d out of %d. Invocations left: %d", _seen, CodeCache::nof_nmethods(), _sweep_fractions_left); } if (!CompileBroker::should_compile_new_jobs()) { // If we have turned off compilations we might as well do full sweeps // in order to reach the clean state faster. Otherwise the sleeping compiler // threads will slow down sweeping. _sweep_fractions_left = 1; } // We want to visit all nmethods after NmethodSweepFraction // invocations so divide the remaining number of nmethods by the // remaining number of invocations. This is only an estimate since // the number of nmethods changes during the sweep so the final // stage must iterate until it there are no more nmethods. int todo = (CodeCache::nof_nmethods() - _seen) / _sweep_fractions_left; int swept_count = 0; assert(!SafepointSynchronize::is_at_safepoint(), "should not be in safepoint when we get here"); assert(!CodeCache_lock->owned_by_self(), "just checking"); int freed_memory = 0; { MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); // The last invocation iterates until there are no more nmethods for (int i = 0; (i < todo || _sweep_fractions_left == 1) && _current != NULL; i++) { swept_count++; if (SafepointSynchronize::is_synchronizing()) { // Safepoint request if (PrintMethodFlushing && Verbose) { tty->print_cr("### Sweep at %d out of %d, invocation: %d, yielding to safepoint", _seen, CodeCache::nof_nmethods(), _sweep_fractions_left); } MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); assert(Thread::current()->is_Java_thread(), "should be java thread"); JavaThread* thread = (JavaThread*)Thread::current(); ThreadBlockInVM tbivm(thread); thread->java_suspend_self(); } // Since we will give up the CodeCache_lock, always skip ahead // to the next nmethod. Other blobs can be deleted by other // threads but nmethods are only reclaimed by the sweeper. nmethod* next = CodeCache::next_nmethod(_current); // Now ready to process nmethod and give up CodeCache_lock { MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); freed_memory += process_nmethod(_current); } _seen++; _current = next; } } assert(_sweep_fractions_left > 1 || _current == NULL, "must have scanned the whole cache"); const Ticks sweep_end_counter = Ticks::now(); const Tickspan sweep_time = sweep_end_counter - sweep_start_counter; _total_time_sweeping += sweep_time; _total_time_this_sweep += sweep_time; _peak_sweep_fraction_time = MAX2(sweep_time, _peak_sweep_fraction_time); _total_nof_methods_reclaimed += _flushed_count; EventSweepCodeCache event(UNTIMED); if (event.should_commit()) { event.set_starttime(sweep_start_counter); event.set_endtime(sweep_end_counter); event.set_sweepIndex(_traversals); event.set_sweepFractionIndex(NmethodSweepFraction - _sweep_fractions_left + 1); event.set_sweptCount(swept_count); event.set_flushedCount(_flushed_count); event.set_markedCount(_marked_for_reclamation_count); event.set_zombifiedCount(_zombified_count); event.commit(); } #ifdef ASSERT if(PrintMethodFlushing) { tty->print_cr("### sweeper: sweep time(%d): " INT64_FORMAT, _sweep_fractions_left, (jlong)sweep_time.value()); } #endif if (_sweep_fractions_left == 1) { _peak_sweep_time = MAX2(_peak_sweep_time, _total_time_this_sweep); log_sweep("finished"); } // Sweeper is the only case where memory is released, check here if it // is time to restart the compiler. Only checking if there is a certain // amount of free memory in the code cache might lead to re-enabling // compilation although no memory has been released. For example, there are // cases when compilation was disabled although there is 4MB (or more) free // memory in the code cache. The reason is code cache fragmentation. Therefore, // it only makes sense to re-enable compilation if we have actually freed memory. // Note that typically several kB are released for sweeping 16MB of the code // cache. As a result, 'freed_memory' > 0 to restart the compiler. if (!CompileBroker::should_compile_new_jobs() && (freed_memory > 0)) { CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation); log_sweep("restart_compiler"); } } /** * This function updates the sweeper statistics that keep track of nmethods * state changes. If there is 'enough' state change, the sweeper is invoked * as soon as possible. There can be data races on _bytes_changed. The data * races are benign, since it does not matter if we loose a couple of bytes. * In the worst case we call the sweeper a little later. Also, we are guaranteed * to invoke the sweeper if the code cache gets full. */ void NMethodSweeper::report_state_change(nmethod* nm) { _bytes_changed += nm->total_size(); possibly_enable_sweeper(); } /** * Function determines if there was 'enough' state change in the code cache to invoke * the sweeper again. Currently, we determine 'enough' as more than 1% state change in * the code cache since the last sweep. */ void NMethodSweeper::possibly_enable_sweeper() { double percent_changed = ((double)_bytes_changed / (double)ReservedCodeCacheSize) * 100; if (percent_changed > 1.0) { _should_sweep = true; } } class NMethodMarker: public StackObj { private: #ifdef GRAAL JavaThread* _thread; #else CompilerThread* _thread; #endif public: NMethodMarker(nmethod* nm) { #ifdef GRAAL _thread = JavaThread::current(); #else _thread = CompilerThread::current(); #endif if (!nm->is_zombie() && !nm->is_unloaded()) { // Only expose live nmethods for scanning _thread->set_scanned_nmethod(nm); } } ~NMethodMarker() { _thread->set_scanned_nmethod(NULL); } }; void NMethodSweeper::release_nmethod(nmethod *nm) { // Clean up any CompiledICHolders { ResourceMark rm; MutexLocker ml_patch(CompiledIC_lock); RelocIterator iter(nm); while (iter.next()) { if (iter.type() == relocInfo::virtual_call_type) { CompiledIC::cleanup_call_site(iter.virtual_call_reloc()); } } } MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); nm->flush(); } int NMethodSweeper::process_nmethod(nmethod *nm) { assert(!CodeCache_lock->owned_by_self(), "just checking"); int freed_memory = 0; // Make sure this nmethod doesn't get unloaded during the scan, // since safepoints may happen during acquired below locks. NMethodMarker nmm(nm); SWEEP(nm); // Skip methods that are currently referenced by the VM if (nm->is_locked_by_vm()) { // But still remember to clean-up inline caches for alive nmethods if (nm->is_alive()) { // Clean inline caches that point to zombie/non-entrant methods MutexLocker cl(CompiledIC_lock); nm->cleanup_inline_caches(); SWEEP(nm); } return freed_memory; } if (nm->is_zombie()) { // If it is the first time we see nmethod then we mark it. Otherwise, // we reclaim it. When we have seen a zombie method twice, we know that // there are no inline caches that refer to it. if (nm->is_marked_for_reclamation()) { assert(!nm->is_locked_by_vm(), "must not flush locked nmethods"); if (PrintMethodFlushing && Verbose) { tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (marked for reclamation) being flushed", nm->compile_id(), nm); } freed_memory = nm->total_size(); release_nmethod(nm); _flushed_count++; } else { if (PrintMethodFlushing && Verbose) { tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (zombie) being marked for reclamation", nm->compile_id(), nm); } nm->mark_for_reclamation(); // Keep track of code cache state change _bytes_changed += nm->total_size(); _marked_for_reclamation_count++; SWEEP(nm); } } else if (nm->is_not_entrant()) { // If there are no current activations of this method on the // stack we can safely convert it to a zombie method if (nm->can_not_entrant_be_converted()) { if (PrintMethodFlushing && Verbose) { tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (not entrant) being made zombie", nm->compile_id(), nm); } // Code cache state change is tracked in make_zombie() nm->make_zombie(); _zombified_count++; SWEEP(nm); } else { // Still alive, clean up its inline caches MutexLocker cl(CompiledIC_lock); nm->cleanup_inline_caches(); SWEEP(nm); } } else if (nm->is_unloaded()) { // Unloaded code, just make it a zombie if (PrintMethodFlushing && Verbose) { tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (unloaded) being made zombie", nm->compile_id(), nm); } if (nm->is_osr_method()) { SWEEP(nm); // No inline caches will ever point to osr methods, so we can just remove it freed_memory = nm->total_size(); release_nmethod(nm); _flushed_count++; } else { // Code cache state change is tracked in make_zombie() nm->make_zombie(); _zombified_count++; SWEEP(nm); } } else { if (UseCodeCacheFlushing) { if (!nm->is_locked_by_vm() && !nm->is_osr_method() && !nm->is_native_method()) { // Do not make native methods and OSR-methods not-entrant nm->dec_hotness_counter(); // Get the initial value of the hotness counter. This value depends on the // ReservedCodeCacheSize int reset_val = hotness_counter_reset_val(); int time_since_reset = reset_val - nm->hotness_counter(); double threshold = -reset_val + (CodeCache::reverse_free_ratio() * NmethodSweepActivity); // The less free space in the code cache we have - the bigger reverse_free_ratio() is. // I.e., 'threshold' increases with lower available space in the code cache and a higher // NmethodSweepActivity. If the current hotness counter - which decreases from its initial // value until it is reset by stack walking - is smaller than the computed threshold, the // corresponding nmethod is considered for removal. if ((NmethodSweepActivity > 0) && (nm->hotness_counter() < threshold) && (time_since_reset > 10)) { // A method is marked as not-entrant if the method is // 1) 'old enough': nm->hotness_counter() < threshold // 2) The method was in_use for a minimum amount of time: (time_since_reset > 10) // The second condition is necessary if we are dealing with very small code cache // sizes (e.g., <10m) and the code cache size is too small to hold all hot methods. // The second condition ensures that methods are not immediately made not-entrant // after compilation. nm->make_not_entrant(); // Code cache state change is tracked in make_not_entrant() if (PrintMethodFlushing && Verbose) { tty->print_cr("### Nmethod %d/" PTR_FORMAT "made not-entrant: hotness counter %d/%d threshold %f", nm->compile_id(), nm, nm->hotness_counter(), reset_val, threshold); } } } } // Clean-up all inline caches that point to zombie/non-reentrant methods MutexLocker cl(CompiledIC_lock); nm->cleanup_inline_caches(); SWEEP(nm); } return freed_memory; } // Print out some state information about the current sweep and the // state of the code cache if it's requested. void NMethodSweeper::log_sweep(const char* msg, const char* format, ...) { if (PrintMethodFlushing) { stringStream s; // Dump code cache state into a buffer before locking the tty, // because log_state() will use locks causing lock conflicts. CodeCache::log_state(&s); ttyLocker ttyl; tty->print("### sweeper: %s ", msg); if (format != NULL) { va_list ap; va_start(ap, format); tty->vprint(format, ap); va_end(ap); } tty->print_cr(s.as_string()); } if (LogCompilation && (xtty != NULL)) { stringStream s; // Dump code cache state into a buffer before locking the tty, // because log_state() will use locks causing lock conflicts. CodeCache::log_state(&s); ttyLocker ttyl; xtty->begin_elem("sweeper state='%s' traversals='" INTX_FORMAT "' ", msg, (intx)traversal_count()); if (format != NULL) { va_list ap; va_start(ap, format); xtty->vprint(format, ap); va_end(ap); } xtty->print(s.as_string()); xtty->stamp(); xtty->end_elem(); } }