/* * Copyright (c) 2001, 2012, 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 "classfile/symbolTable.hpp" #include "classfile/systemDictionary.hpp" #include "code/codeCache.hpp" #include "gc_implementation/parallelScavenge/generationSizer.hpp" #include "gc_implementation/parallelScavenge/parallelScavengeHeap.hpp" #include "gc_implementation/parallelScavenge/psAdaptiveSizePolicy.hpp" #include "gc_implementation/parallelScavenge/psMarkSweep.hpp" #include "gc_implementation/parallelScavenge/psMarkSweepDecorator.hpp" #include "gc_implementation/parallelScavenge/psOldGen.hpp" #include "gc_implementation/parallelScavenge/psScavenge.hpp" #include "gc_implementation/parallelScavenge/psYoungGen.hpp" #include "gc_implementation/shared/isGCActiveMark.hpp" #include "gc_implementation/shared/markSweep.hpp" #include "gc_implementation/shared/spaceDecorator.hpp" #include "gc_interface/gcCause.hpp" #include "memory/gcLocker.inline.hpp" #include "memory/referencePolicy.hpp" #include "memory/referenceProcessor.hpp" #include "oops/oop.inline.hpp" #include "runtime/biasedLocking.hpp" #include "runtime/fprofiler.hpp" #include "runtime/safepoint.hpp" #include "runtime/vmThread.hpp" #include "services/management.hpp" #include "services/memoryService.hpp" #include "utilities/events.hpp" #include "utilities/stack.inline.hpp" elapsedTimer PSMarkSweep::_accumulated_time; jlong PSMarkSweep::_time_of_last_gc = 0; CollectorCounters* PSMarkSweep::_counters = NULL; void PSMarkSweep::initialize() { MemRegion mr = Universe::heap()->reserved_region(); _ref_processor = new ReferenceProcessor(mr); // a vanilla ref proc _counters = new CollectorCounters("PSMarkSweep", 1); } // This method contains all heap specific policy for invoking mark sweep. // PSMarkSweep::invoke_no_policy() will only attempt to mark-sweep-compact // the heap. It will do nothing further. If we need to bail out for policy // reasons, scavenge before full gc, or any other specialized behavior, it // needs to be added here. // // Note that this method should only be called from the vm_thread while // at a safepoint! // // Note that the all_soft_refs_clear flag in the collector policy // may be true because this method can be called without intervening // activity. For example when the heap space is tight and full measure // are being taken to free space. void PSMarkSweep::invoke(bool maximum_heap_compaction) { assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint"); assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread"); assert(!Universe::heap()->is_gc_active(), "not reentrant"); ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); GCCause::Cause gc_cause = heap->gc_cause(); PSAdaptiveSizePolicy* policy = heap->size_policy(); IsGCActiveMark mark; if (ScavengeBeforeFullGC) { PSScavenge::invoke_no_policy(); } const bool clear_all_soft_refs = heap->collector_policy()->should_clear_all_soft_refs(); int count = (maximum_heap_compaction)?1:MarkSweepAlwaysCompactCount; IntFlagSetting flag_setting(MarkSweepAlwaysCompactCount, count); PSMarkSweep::invoke_no_policy(clear_all_soft_refs || maximum_heap_compaction); } // This method contains no policy. You should probably // be calling invoke() instead. bool PSMarkSweep::invoke_no_policy(bool clear_all_softrefs) { assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint"); assert(ref_processor() != NULL, "Sanity"); if (GC_locker::check_active_before_gc()) { return false; } ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); GCCause::Cause gc_cause = heap->gc_cause(); assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); PSAdaptiveSizePolicy* size_policy = heap->size_policy(); // The scope of casr should end after code that can change // CollectorPolicy::_should_clear_all_soft_refs. ClearedAllSoftRefs casr(clear_all_softrefs, heap->collector_policy()); PSYoungGen* young_gen = heap->young_gen(); PSOldGen* old_gen = heap->old_gen(); // Increment the invocation count heap->increment_total_collections(true /* full */); // Save information needed to minimize mangling heap->record_gen_tops_before_GC(); // We need to track unique mark sweep invocations as well. _total_invocations++; AdaptiveSizePolicyOutput(size_policy, heap->total_collections()); heap->print_heap_before_gc(); // Fill in TLABs heap->accumulate_statistics_all_tlabs(); heap->ensure_parsability(true); // retire TLABs if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) { HandleMark hm; // Discard invalid handles created during verification gclog_or_tty->print(" VerifyBeforeGC:"); Universe::verify(); } // Verify object start arrays if (VerifyObjectStartArray && VerifyBeforeGC) { old_gen->verify_object_start_array(); } heap->pre_full_gc_dump(); // Filled in below to track the state of the young gen after the collection. bool eden_empty; bool survivors_empty; bool young_gen_empty; { HandleMark hm; gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps); TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty); TraceTime t1(GCCauseString("Full GC", gc_cause), PrintGC, !PrintGCDetails, gclog_or_tty); TraceCollectorStats tcs(counters()); TraceMemoryManagerStats tms(true /* Full GC */,gc_cause); if (TraceGen1Time) accumulated_time()->start(); // Let the size policy know we're starting size_policy->major_collection_begin(); CodeCache::gc_prologue(); Threads::gc_prologue(); BiasedLocking::preserve_marks(); // Capture heap size before collection for printing. size_t prev_used = heap->used(); // Capture metadata size before collection for sizing. size_t metadata_prev_used = MetaspaceAux::used_in_bytes(); // For PrintGCDetails size_t old_gen_prev_used = old_gen->used_in_bytes(); size_t young_gen_prev_used = young_gen->used_in_bytes(); allocate_stacks(); COMPILER2_PRESENT(DerivedPointerTable::clear()); ref_processor()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/); ref_processor()->setup_policy(clear_all_softrefs); mark_sweep_phase1(clear_all_softrefs); mark_sweep_phase2(); // Don't add any more derived pointers during phase3 COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity")); COMPILER2_PRESENT(DerivedPointerTable::set_active(false)); mark_sweep_phase3(); mark_sweep_phase4(); restore_marks(); deallocate_stacks(); if (ZapUnusedHeapArea) { // Do a complete mangle (top to end) because the usage for // scratch does not maintain a top pointer. young_gen->to_space()->mangle_unused_area_complete(); } eden_empty = young_gen->eden_space()->is_empty(); if (!eden_empty) { eden_empty = absorb_live_data_from_eden(size_policy, young_gen, old_gen); } // Update heap occupancy information which is used as // input to soft ref clearing policy at the next gc. Universe::update_heap_info_at_gc(); survivors_empty = young_gen->from_space()->is_empty() && young_gen->to_space()->is_empty(); young_gen_empty = eden_empty && survivors_empty; BarrierSet* bs = heap->barrier_set(); if (bs->is_a(BarrierSet::ModRef)) { ModRefBarrierSet* modBS = (ModRefBarrierSet*)bs; MemRegion old_mr = heap->old_gen()->reserved(); if (young_gen_empty) { modBS->clear(MemRegion(old_mr.start(), old_mr.end())); } else { modBS->invalidate(MemRegion(old_mr.start(), old_mr.end())); } } // Delete metaspaces for unloaded class loaders and clean up loader_data graph ClassLoaderDataGraph::purge(); BiasedLocking::restore_marks(); Threads::gc_epilogue(); CodeCache::gc_epilogue(); JvmtiExport::gc_epilogue(); COMPILER2_PRESENT(DerivedPointerTable::update_pointers()); ref_processor()->enqueue_discovered_references(NULL); // Update time of last GC reset_millis_since_last_gc(); // Let the size policy know we're done size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause); if (UseAdaptiveSizePolicy) { if (PrintAdaptiveSizePolicy) { gclog_or_tty->print("AdaptiveSizeStart: "); gclog_or_tty->stamp(); gclog_or_tty->print_cr(" collection: %d ", heap->total_collections()); if (Verbose) { gclog_or_tty->print("old_gen_capacity: %d young_gen_capacity: %d", old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes()); } } // Don't check if the size_policy is ready here. Let // the size_policy check that internally. if (UseAdaptiveGenerationSizePolicyAtMajorCollection && ((gc_cause != GCCause::_java_lang_system_gc) || UseAdaptiveSizePolicyWithSystemGC)) { // Calculate optimal free space amounts assert(young_gen->max_size() > young_gen->from_space()->capacity_in_bytes() + young_gen->to_space()->capacity_in_bytes(), "Sizes of space in young gen are out-of-bounds"); size_t max_eden_size = young_gen->max_size() - young_gen->from_space()->capacity_in_bytes() - young_gen->to_space()->capacity_in_bytes(); size_policy->compute_generation_free_space(young_gen->used_in_bytes(), young_gen->eden_space()->used_in_bytes(), old_gen->used_in_bytes(), young_gen->eden_space()->capacity_in_bytes(), old_gen->max_gen_size(), max_eden_size, true /* full gc*/, gc_cause, heap->collector_policy()); heap->resize_old_gen(size_policy->calculated_old_free_size_in_bytes()); // Don't resize the young generation at an major collection. A // desired young generation size may have been calculated but // resizing the young generation complicates the code because the // resizing of the old generation may have moved the boundary // between the young generation and the old generation. Let the // young generation resizing happen at the minor collections. } if (PrintAdaptiveSizePolicy) { gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ", heap->total_collections()); } } if (UsePerfData) { heap->gc_policy_counters()->update_counters(); heap->gc_policy_counters()->update_old_capacity( old_gen->capacity_in_bytes()); heap->gc_policy_counters()->update_young_capacity( young_gen->capacity_in_bytes()); } heap->resize_all_tlabs(); // We collected the heap, recalculate the metaspace capacity MetaspaceGC::compute_new_size(); if (TraceGen1Time) accumulated_time()->stop(); if (PrintGC) { if (PrintGCDetails) { // Don't print a GC timestamp here. This is after the GC so // would be confusing. young_gen->print_used_change(young_gen_prev_used); old_gen->print_used_change(old_gen_prev_used); } heap->print_heap_change(prev_used); if (PrintGCDetails) { MetaspaceAux::print_metaspace_change(metadata_prev_used); } } // Track memory usage and detect low memory MemoryService::track_memory_usage(); heap->update_counters(); } if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) { HandleMark hm; // Discard invalid handles created during verification gclog_or_tty->print(" VerifyAfterGC:"); Universe::verify(); } // Re-verify object start arrays if (VerifyObjectStartArray && VerifyAfterGC) { old_gen->verify_object_start_array(); } if (ZapUnusedHeapArea) { old_gen->object_space()->check_mangled_unused_area_complete(); } NOT_PRODUCT(ref_processor()->verify_no_references_recorded()); heap->print_heap_after_gc(); heap->post_full_gc_dump(); #ifdef TRACESPINNING ParallelTaskTerminator::print_termination_counts(); #endif return true; } bool PSMarkSweep::absorb_live_data_from_eden(PSAdaptiveSizePolicy* size_policy, PSYoungGen* young_gen, PSOldGen* old_gen) { MutableSpace* const eden_space = young_gen->eden_space(); assert(!eden_space->is_empty(), "eden must be non-empty"); assert(young_gen->virtual_space()->alignment() == old_gen->virtual_space()->alignment(), "alignments do not match"); if (!(UseAdaptiveSizePolicy && UseAdaptiveGCBoundary)) { return false; } // Both generations must be completely committed. if (young_gen->virtual_space()->uncommitted_size() != 0) { return false; } if (old_gen->virtual_space()->uncommitted_size() != 0) { return false; } // Figure out how much to take from eden. Include the average amount promoted // in the total; otherwise the next young gen GC will simply bail out to a // full GC. const size_t alignment = old_gen->virtual_space()->alignment(); const size_t eden_used = eden_space->used_in_bytes(); const size_t promoted = (size_t)size_policy->avg_promoted()->padded_average(); const size_t absorb_size = align_size_up(eden_used + promoted, alignment); const size_t eden_capacity = eden_space->capacity_in_bytes(); if (absorb_size >= eden_capacity) { return false; // Must leave some space in eden. } const size_t new_young_size = young_gen->capacity_in_bytes() - absorb_size; if (new_young_size < young_gen->min_gen_size()) { return false; // Respect young gen minimum size. } if (TraceAdaptiveGCBoundary && Verbose) { gclog_or_tty->print(" absorbing " SIZE_FORMAT "K: " "eden " SIZE_FORMAT "K->" SIZE_FORMAT "K " "from " SIZE_FORMAT "K, to " SIZE_FORMAT "K " "young_gen " SIZE_FORMAT "K->" SIZE_FORMAT "K ", absorb_size / K, eden_capacity / K, (eden_capacity - absorb_size) / K, young_gen->from_space()->used_in_bytes() / K, young_gen->to_space()->used_in_bytes() / K, young_gen->capacity_in_bytes() / K, new_young_size / K); } // Fill the unused part of the old gen. MutableSpace* const old_space = old_gen->object_space(); HeapWord* const unused_start = old_space->top(); size_t const unused_words = pointer_delta(old_space->end(), unused_start); if (unused_words > 0) { if (unused_words < CollectedHeap::min_fill_size()) { return false; // If the old gen cannot be filled, must give up. } CollectedHeap::fill_with_objects(unused_start, unused_words); } // Take the live data from eden and set both top and end in the old gen to // eden top. (Need to set end because reset_after_change() mangles the region // from end to virtual_space->high() in debug builds). HeapWord* const new_top = eden_space->top(); old_gen->virtual_space()->expand_into(young_gen->virtual_space(), absorb_size); young_gen->reset_after_change(); old_space->set_top(new_top); old_space->set_end(new_top); old_gen->reset_after_change(); // Update the object start array for the filler object and the data from eden. ObjectStartArray* const start_array = old_gen->start_array(); for (HeapWord* p = unused_start; p < new_top; p += oop(p)->size()) { start_array->allocate_block(p); } // Could update the promoted average here, but it is not typically updated at // full GCs and the value to use is unclear. Something like // // cur_promoted_avg + absorb_size / number_of_scavenges_since_last_full_gc. size_policy->set_bytes_absorbed_from_eden(absorb_size); return true; } void PSMarkSweep::allocate_stacks() { ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); PSYoungGen* young_gen = heap->young_gen(); MutableSpace* to_space = young_gen->to_space(); _preserved_marks = (PreservedMark*)to_space->top(); _preserved_count = 0; // We want to calculate the size in bytes first. _preserved_count_max = pointer_delta(to_space->end(), to_space->top(), sizeof(jbyte)); // Now divide by the size of a PreservedMark _preserved_count_max /= sizeof(PreservedMark); } void PSMarkSweep::deallocate_stacks() { _preserved_mark_stack.clear(true); _preserved_oop_stack.clear(true); _marking_stack.clear(); _objarray_stack.clear(true); } void PSMarkSweep::mark_sweep_phase1(bool clear_all_softrefs) { // Recursively traverse all live objects and mark them TraceTime tm("phase 1", PrintGCDetails && Verbose, true, gclog_or_tty); trace(" 1"); ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); // Need to clear claim bits before the tracing starts. ClassLoaderDataGraph::clear_claimed_marks(); // General strong roots. { ParallelScavengeHeap::ParStrongRootsScope psrs; Universe::oops_do(mark_and_push_closure()); JNIHandles::oops_do(mark_and_push_closure()); // Global (strong) JNI handles CLDToOopClosure mark_and_push_from_cld(mark_and_push_closure()); CodeBlobToOopClosure each_active_code_blob(mark_and_push_closure(), /*do_marking=*/ true); Threads::oops_do(mark_and_push_closure(), &mark_and_push_from_cld, &each_active_code_blob); ObjectSynchronizer::oops_do(mark_and_push_closure()); FlatProfiler::oops_do(mark_and_push_closure()); Management::oops_do(mark_and_push_closure()); JvmtiExport::oops_do(mark_and_push_closure()); SystemDictionary::always_strong_oops_do(mark_and_push_closure()); ClassLoaderDataGraph::always_strong_oops_do(mark_and_push_closure(), follow_klass_closure(), true); // Do not treat nmethods as strong roots for mark/sweep, since we can unload them. //CodeCache::scavenge_root_nmethods_do(CodeBlobToOopClosure(mark_and_push_closure())); } // Flush marking stack. follow_stack(); // Process reference objects found during marking { ref_processor()->setup_policy(clear_all_softrefs); ref_processor()->process_discovered_references( is_alive_closure(), mark_and_push_closure(), follow_stack_closure(), NULL); } // Follow system dictionary roots and unload classes bool purged_class = SystemDictionary::do_unloading(is_alive_closure()); // Follow code cache roots CodeCache::do_unloading(is_alive_closure(), purged_class); follow_stack(); // Flush marking stack // Update subklass/sibling/implementor links of live klasses Klass::clean_weak_klass_links(&is_alive); assert(_marking_stack.is_empty(), "just drained"); // Visit interned string tables and delete unmarked oops StringTable::unlink(is_alive_closure()); // Clean up unreferenced symbols in symbol table. SymbolTable::unlink(); assert(_marking_stack.is_empty(), "stack should be empty by now"); } void PSMarkSweep::mark_sweep_phase2() { TraceTime tm("phase 2", PrintGCDetails && Verbose, true, gclog_or_tty); trace("2"); // Now all live objects are marked, compute the new object addresses. // It is not required that we traverse spaces in the same order in // phase2, phase3 and phase4, but the ValidateMarkSweep live oops // tracking expects us to do so. See comment under phase4. ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); PSOldGen* old_gen = heap->old_gen(); // Begin compacting into the old gen PSMarkSweepDecorator::set_destination_decorator_tenured(); // This will also compact the young gen spaces. old_gen->precompact(); } // This should be moved to the shared markSweep code! class PSAlwaysTrueClosure: public BoolObjectClosure { public: void do_object(oop p) { ShouldNotReachHere(); } bool do_object_b(oop p) { return true; } }; static PSAlwaysTrueClosure always_true; void PSMarkSweep::mark_sweep_phase3() { // Adjust the pointers to reflect the new locations TraceTime tm("phase 3", PrintGCDetails && Verbose, true, gclog_or_tty); trace("3"); ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); PSYoungGen* young_gen = heap->young_gen(); PSOldGen* old_gen = heap->old_gen(); // Need to clear claim bits before the tracing starts. ClassLoaderDataGraph::clear_claimed_marks(); // General strong roots. Universe::oops_do(adjust_root_pointer_closure()); JNIHandles::oops_do(adjust_root_pointer_closure()); // Global (strong) JNI handles CLDToOopClosure adjust_from_cld(adjust_root_pointer_closure()); Threads::oops_do(adjust_root_pointer_closure(), &adjust_from_cld, NULL); ObjectSynchronizer::oops_do(adjust_root_pointer_closure()); FlatProfiler::oops_do(adjust_root_pointer_closure()); Management::oops_do(adjust_root_pointer_closure()); JvmtiExport::oops_do(adjust_root_pointer_closure()); // SO_AllClasses SystemDictionary::oops_do(adjust_root_pointer_closure()); ClassLoaderDataGraph::oops_do(adjust_root_pointer_closure(), adjust_klass_closure(), true); //CodeCache::scavenge_root_nmethods_oops_do(adjust_root_pointer_closure()); // Now adjust pointers in remaining weak roots. (All of which should // have been cleared if they pointed to non-surviving objects.) // Global (weak) JNI handles JNIHandles::weak_oops_do(&always_true, adjust_root_pointer_closure()); CodeCache::oops_do(adjust_pointer_closure()); StringTable::oops_do(adjust_root_pointer_closure()); ref_processor()->weak_oops_do(adjust_root_pointer_closure()); PSScavenge::reference_processor()->weak_oops_do(adjust_root_pointer_closure()); adjust_marks(); young_gen->adjust_pointers(); old_gen->adjust_pointers(); } void PSMarkSweep::mark_sweep_phase4() { EventMark m("4 compact heap"); TraceTime tm("phase 4", PrintGCDetails && Verbose, true, gclog_or_tty); trace("4"); // All pointers are now adjusted, move objects accordingly ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); PSYoungGen* young_gen = heap->young_gen(); PSOldGen* old_gen = heap->old_gen(); old_gen->compact(); young_gen->compact(); } jlong PSMarkSweep::millis_since_last_gc() { // We need a monotonically non-deccreasing time in ms but // os::javaTimeMillis() does not guarantee monotonicity. jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; jlong ret_val = now - _time_of_last_gc; // XXX See note in genCollectedHeap::millis_since_last_gc(). if (ret_val < 0) { NOT_PRODUCT(warning("time warp: "INT64_FORMAT, ret_val);) return 0; } return ret_val; } void PSMarkSweep::reset_millis_since_last_gc() { // We need a monotonically non-deccreasing time in ms but // os::javaTimeMillis() does not guarantee monotonicity. _time_of_last_gc = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; }