diff -r 000000000000 -r f90c822e73f8 src/share/vm/memory/genMarkSweep.cpp --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/share/vm/memory/genMarkSweep.cpp Wed Apr 27 01:25:04 2016 +0800 @@ -0,0 +1,344 @@ +/* + * Copyright (c) 2001, 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 "classfile/javaClasses.hpp" +#include "classfile/symbolTable.hpp" +#include "classfile/systemDictionary.hpp" +#include "classfile/vmSymbols.hpp" +#include "code/codeCache.hpp" +#include "code/icBuffer.hpp" +#include "gc_implementation/shared/gcHeapSummary.hpp" +#include "gc_implementation/shared/gcTimer.hpp" +#include "gc_implementation/shared/gcTrace.hpp" +#include "gc_implementation/shared/gcTraceTime.hpp" +#include "gc_interface/collectedHeap.inline.hpp" +#include "memory/genCollectedHeap.hpp" +#include "memory/genMarkSweep.hpp" +#include "memory/genOopClosures.inline.hpp" +#include "memory/generation.inline.hpp" +#include "memory/modRefBarrierSet.hpp" +#include "memory/referencePolicy.hpp" +#include "memory/space.hpp" +#include "oops/instanceRefKlass.hpp" +#include "oops/oop.inline.hpp" +#include "prims/jvmtiExport.hpp" +#include "runtime/fprofiler.hpp" +#include "runtime/handles.inline.hpp" +#include "runtime/synchronizer.hpp" +#include "runtime/thread.inline.hpp" +#include "runtime/vmThread.hpp" +#include "utilities/copy.hpp" +#include "utilities/events.hpp" + +void GenMarkSweep::invoke_at_safepoint(int level, ReferenceProcessor* rp, bool clear_all_softrefs) { + guarantee(level == 1, "We always collect both old and young."); + assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint"); + + GenCollectedHeap* gch = GenCollectedHeap::heap(); +#ifdef ASSERT + if (gch->collector_policy()->should_clear_all_soft_refs()) { + assert(clear_all_softrefs, "Policy should have been checked earlier"); + } +#endif + + // hook up weak ref data so it can be used during Mark-Sweep + assert(ref_processor() == NULL, "no stomping"); + assert(rp != NULL, "should be non-NULL"); + _ref_processor = rp; + rp->setup_policy(clear_all_softrefs); + + GCTraceTime t1(GCCauseString("Full GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, NULL); + + gch->trace_heap_before_gc(_gc_tracer); + + // When collecting the permanent generation Method*s may be moving, + // so we either have to flush all bcp data or convert it into bci. + CodeCache::gc_prologue(); + Threads::gc_prologue(); + + // Increment the invocation count + _total_invocations++; + + // Capture heap size before collection for printing. + size_t gch_prev_used = gch->used(); + + // Capture used regions for each generation that will be + // subject to collection, so that card table adjustments can + // be made intelligently (see clear / invalidate further below). + gch->save_used_regions(level); + + allocate_stacks(); + + mark_sweep_phase1(level, 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(level); + + mark_sweep_phase4(); + + restore_marks(); + + // Set saved marks for allocation profiler (and other things? -- dld) + // (Should this be in general part?) + gch->save_marks(); + + deallocate_stacks(); + + // If compaction completely evacuated all generations younger than this + // one, then we can clear the card table. Otherwise, we must invalidate + // it (consider all cards dirty). In the future, we might consider doing + // compaction within generations only, and doing card-table sliding. + bool all_empty = true; + for (int i = 0; all_empty && i < level; i++) { + Generation* g = gch->get_gen(i); + all_empty = all_empty && gch->get_gen(i)->used() == 0; + } + GenRemSet* rs = gch->rem_set(); + Generation* old_gen = gch->get_gen(level); + // Clear/invalidate below make use of the "prev_used_regions" saved earlier. + if (all_empty) { + // We've evacuated all generations below us. + rs->clear_into_younger(old_gen); + } else { + // Invalidate the cards corresponding to the currently used + // region and clear those corresponding to the evacuated region. + rs->invalidate_or_clear(old_gen); + } + + Threads::gc_epilogue(); + CodeCache::gc_epilogue(); + JvmtiExport::gc_epilogue(); + + if (PrintGC && !PrintGCDetails) { + gch->print_heap_change(gch_prev_used); + } + + // refs processing: clean slate + _ref_processor = NULL; + + // Update heap occupancy information which is used as + // input to soft ref clearing policy at the next gc. + Universe::update_heap_info_at_gc(); + + // Update time of last gc for all generations we collected + // (which curently is all the generations in the heap). + // We need to use a monotonically non-deccreasing time in ms + // or we will see time-warp warnings and os::javaTimeMillis() + // does not guarantee monotonicity. + jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; + gch->update_time_of_last_gc(now); + + gch->trace_heap_after_gc(_gc_tracer); +} + +void GenMarkSweep::allocate_stacks() { + GenCollectedHeap* gch = GenCollectedHeap::heap(); + // Scratch request on behalf of oldest generation; will do no + // allocation. + ScratchBlock* scratch = gch->gather_scratch(gch->_gens[gch->_n_gens-1], 0); + + // $$$ To cut a corner, we'll only use the first scratch block, and then + // revert to malloc. + if (scratch != NULL) { + _preserved_count_max = + scratch->num_words * HeapWordSize / sizeof(PreservedMark); + } else { + _preserved_count_max = 0; + } + + _preserved_marks = (PreservedMark*)scratch; + _preserved_count = 0; +} + + +void GenMarkSweep::deallocate_stacks() { + if (!UseG1GC) { + GenCollectedHeap* gch = GenCollectedHeap::heap(); + gch->release_scratch(); + } + + _preserved_mark_stack.clear(true); + _preserved_oop_stack.clear(true); + _marking_stack.clear(); + _objarray_stack.clear(true); +} + +void GenMarkSweep::mark_sweep_phase1(int level, + bool clear_all_softrefs) { + // Recursively traverse all live objects and mark them + GCTraceTime tm("phase 1", PrintGC && Verbose, true, _gc_timer); + trace(" 1"); + + GenCollectedHeap* gch = GenCollectedHeap::heap(); + + // Because follow_root_closure is created statically, cannot + // use OopsInGenClosure constructor which takes a generation, + // as the Universe has not been created when the static constructors + // are run. + follow_root_closure.set_orig_generation(gch->get_gen(level)); + + // Need new claim bits before marking starts. + ClassLoaderDataGraph::clear_claimed_marks(); + + gch->gen_process_strong_roots(level, + false, // Younger gens are not roots. + true, // activate StrongRootsScope + false, // not scavenging + SharedHeap::SO_SystemClasses, + &follow_root_closure, + true, // walk code active on stacks + &follow_root_closure, + &follow_klass_closure); + + // Process reference objects found during marking + { + ref_processor()->setup_policy(clear_all_softrefs); + const ReferenceProcessorStats& stats = + ref_processor()->process_discovered_references( + &is_alive, &keep_alive, &follow_stack_closure, NULL, _gc_timer); + gc_tracer()->report_gc_reference_stats(stats); + } + + // This is the point where the entire marking should have completed. + assert(_marking_stack.is_empty(), "Marking should have completed"); + + // Unload classes and purge the SystemDictionary. + bool purged_class = SystemDictionary::do_unloading(&is_alive); + + // Unload nmethods. + CodeCache::do_unloading(&is_alive, purged_class); + + // Prune dead klasses from subklass/sibling/implementor lists. + Klass::clean_weak_klass_links(&is_alive); + + // Delete entries for dead interned strings. + StringTable::unlink(&is_alive); + + // Clean up unreferenced symbols in symbol table. + SymbolTable::unlink(); + + gc_tracer()->report_object_count_after_gc(&is_alive); +} + + +void GenMarkSweep::mark_sweep_phase2() { + // Now all live objects are marked, compute the new object addresses. + + // It is imperative that we traverse perm_gen LAST. If dead space is + // allowed a range of dead object may get overwritten by a dead int + // array. If perm_gen is not traversed last a Klass* may get + // overwritten. This is fine since it is dead, but if the class has dead + // instances we have to skip them, and in order to find their size we + // need the Klass*! + // + // 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. + + GenCollectedHeap* gch = GenCollectedHeap::heap(); + + GCTraceTime tm("phase 2", PrintGC && Verbose, true, _gc_timer); + trace("2"); + + gch->prepare_for_compaction(); +} + +class GenAdjustPointersClosure: public GenCollectedHeap::GenClosure { +public: + void do_generation(Generation* gen) { + gen->adjust_pointers(); + } +}; + +void GenMarkSweep::mark_sweep_phase3(int level) { + GenCollectedHeap* gch = GenCollectedHeap::heap(); + + // Adjust the pointers to reflect the new locations + GCTraceTime tm("phase 3", PrintGC && Verbose, true, _gc_timer); + trace("3"); + + // Need new claim bits for the pointer adjustment tracing. + ClassLoaderDataGraph::clear_claimed_marks(); + + // Because the closure below is created statically, we cannot + // use OopsInGenClosure constructor which takes a generation, + // as the Universe has not been created when the static constructors + // are run. + adjust_pointer_closure.set_orig_generation(gch->get_gen(level)); + + gch->gen_process_strong_roots(level, + false, // Younger gens are not roots. + true, // activate StrongRootsScope + false, // not scavenging + SharedHeap::SO_AllClasses, + &adjust_pointer_closure, + false, // do not walk code + &adjust_pointer_closure, + &adjust_klass_closure); + + // Now adjust pointers in remaining weak roots. (All of which should + // have been cleared if they pointed to non-surviving objects.) + CodeBlobToOopClosure adjust_code_pointer_closure(&adjust_pointer_closure, + /*do_marking=*/ false); + gch->gen_process_weak_roots(&adjust_pointer_closure, + &adjust_code_pointer_closure); + + adjust_marks(); + GenAdjustPointersClosure blk; + gch->generation_iterate(&blk, true); +} + +class GenCompactClosure: public GenCollectedHeap::GenClosure { +public: + void do_generation(Generation* gen) { + gen->compact(); + } +}; + +void GenMarkSweep::mark_sweep_phase4() { + // All pointers are now adjusted, move objects accordingly + + // It is imperative that we traverse perm_gen first in phase4. All + // classes must be allocated earlier than their instances, and traversing + // perm_gen first makes sure that all Klass*s have moved to their new + // location before any instance does a dispatch through it's klass! + + // The ValidateMarkSweep live oops tracking expects us to traverse spaces + // in the same order in phase2, phase3 and phase4. We don't quite do that + // here (perm_gen first rather than last), so we tell the validate code + // to use a higher index (saved from phase2) when verifying perm_gen. + GenCollectedHeap* gch = GenCollectedHeap::heap(); + + GCTraceTime tm("phase 4", PrintGC && Verbose, true, _gc_timer); + trace("4"); + + GenCompactClosure blk; + gch->generation_iterate(&blk, true); +}