/* * 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/g1/g1Log.hpp" #include "gc_implementation/g1/g1MarkSweep.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 "memory/gcLocker.hpp" #include "memory/genCollectedHeap.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/biasedLocking.hpp" #include "runtime/fprofiler.hpp" #include "runtime/synchronizer.hpp" #include "runtime/thread.hpp" #include "runtime/vmThread.hpp" #include "utilities/copy.hpp" #include "utilities/events.hpp" class HeapRegion; void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp, bool clear_all_softrefs) { assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint"); SharedHeap* sh = SharedHeap::heap(); #ifdef ASSERT if (sh->collector_policy()->should_clear_all_soft_refs()) { assert(clear_all_softrefs, "Policy should have been checked earler"); } #endif // hook up weak ref data so it can be used during Mark-Sweep assert(GenMarkSweep::ref_processor() == NULL, "no stomping"); assert(rp != NULL, "should be non-NULL"); assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Precondition"); GenMarkSweep::_ref_processor = rp; rp->setup_policy(clear_all_softrefs); // 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(); bool marked_for_unloading = false; allocate_stacks(); // We should save the marks of the currently locked biased monitors. // The marking doesn't preserve the marks of biased objects. BiasedLocking::preserve_marks(); mark_sweep_phase1(marked_for_unloading, clear_all_softrefs); mark_sweep_phase2(); // Don't add any more derived pointers during phase3 COMPILER2_PRESENT(DerivedPointerTable::set_active(false)); mark_sweep_phase3(); mark_sweep_phase4(); GenMarkSweep::restore_marks(); BiasedLocking::restore_marks(); GenMarkSweep::deallocate_stacks(); // "free at last gc" is calculated from these. // CHF: cheating for now!!! // Universe::set_heap_capacity_at_last_gc(Universe::heap()->capacity()); // Universe::set_heap_used_at_last_gc(Universe::heap()->used()); Threads::gc_epilogue(); CodeCache::gc_epilogue(); JvmtiExport::gc_epilogue(); // refs processing: clean slate GenMarkSweep::_ref_processor = NULL; } void G1MarkSweep::allocate_stacks() { GenMarkSweep::_preserved_count_max = 0; GenMarkSweep::_preserved_marks = NULL; GenMarkSweep::_preserved_count = 0; } void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading, bool clear_all_softrefs) { // Recursively traverse all live objects and mark them GCTraceTime tm("phase 1", G1Log::fine() && Verbose, true, gc_timer()); GenMarkSweep::trace(" 1"); SharedHeap* sh = SharedHeap::heap(); // Need cleared claim bits for the strong roots processing ClassLoaderDataGraph::clear_claimed_marks(); sh->process_strong_roots(true, // activate StrongRootsScope false, // not scavenging. SharedHeap::SO_SystemClasses, &GenMarkSweep::follow_root_closure, &GenMarkSweep::follow_code_root_closure, &GenMarkSweep::follow_klass_closure); // Process reference objects found during marking ReferenceProcessor* rp = GenMarkSweep::ref_processor(); assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Sanity"); rp->setup_policy(clear_all_softrefs); const ReferenceProcessorStats& stats = rp->process_discovered_references(&GenMarkSweep::is_alive, &GenMarkSweep::keep_alive, &GenMarkSweep::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(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed"); // Unload classes and purge the SystemDictionary. bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive); // Unload nmethods. CodeCache::do_unloading(&GenMarkSweep::is_alive, purged_class); // Prune dead klasses from subklass/sibling/implementor lists. Klass::clean_weak_klass_links(&GenMarkSweep::is_alive); // Delete entries for dead interned string and clean up unreferenced symbols in symbol table. G1CollectedHeap::heap()->unlink_string_and_symbol_table(&GenMarkSweep::is_alive); if (VerifyDuringGC) { HandleMark hm; // handle scope COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact); Universe::heap()->prepare_for_verify(); // Note: we can verify only the heap here. When an object is // marked, the previous value of the mark word (including // identity hash values, ages, etc) is preserved, and the mark // word is set to markOop::marked_value - effectively removing // any hash values from the mark word. These hash values are // used when verifying the dictionaries and so removing them // from the mark word can make verification of the dictionaries // fail. At the end of the GC, the orginal mark word values // (including hash values) are restored to the appropriate // objects. if (!VerifySilently) { gclog_or_tty->print(" VerifyDuringGC:(full)[Verifying "); } Universe::heap()->verify(VerifySilently, VerifyOption_G1UseMarkWord); if (!VerifySilently) { gclog_or_tty->print_cr("]"); } } gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive); } class G1PrepareCompactClosure: public HeapRegionClosure { G1CollectedHeap* _g1h; ModRefBarrierSet* _mrbs; CompactPoint _cp; HeapRegionSetCount _humongous_regions_removed; void free_humongous_region(HeapRegion* hr) { HeapWord* end = hr->end(); FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep"); assert(hr->startsHumongous(), "Only the start of a humongous region should be freed."); hr->set_containing_set(NULL); _humongous_regions_removed.increment(1u, hr->capacity()); _g1h->free_humongous_region(hr, &dummy_free_list, false /* par */); hr->prepare_for_compaction(&_cp); // Also clear the part of the card table that will be unused after // compaction. _mrbs->clear(MemRegion(hr->compaction_top(), end)); dummy_free_list.remove_all(); } public: G1PrepareCompactClosure(CompactibleSpace* cs) : _g1h(G1CollectedHeap::heap()), _mrbs(_g1h->g1_barrier_set()), _cp(NULL, cs, cs->initialize_threshold()), _humongous_regions_removed() { } void update_sets() { // We'll recalculate total used bytes and recreate the free list // at the end of the GC, so no point in updating those values here. HeapRegionSetCount empty_set; _g1h->remove_from_old_sets(empty_set, _humongous_regions_removed); } bool doHeapRegion(HeapRegion* hr) { if (hr->isHumongous()) { if (hr->startsHumongous()) { oop obj = oop(hr->bottom()); if (obj->is_gc_marked()) { obj->forward_to(obj); } else { free_humongous_region(hr); } } else { assert(hr->continuesHumongous(), "Invalid humongous."); } } else { hr->prepare_for_compaction(&_cp); // Also clear the part of the card table that will be unused after // compaction. _mrbs->clear(MemRegion(hr->compaction_top(), hr->end())); } return false; } }; void G1MarkSweep::mark_sweep_phase2() { // 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. G1CollectedHeap* g1h = G1CollectedHeap::heap(); GCTraceTime tm("phase 2", G1Log::fine() && Verbose, true, gc_timer()); GenMarkSweep::trace("2"); // find the first region HeapRegion* r = g1h->region_at(0); CompactibleSpace* sp = r; if (r->isHumongous() && oop(r->bottom())->is_gc_marked()) { sp = r->next_compaction_space(); } G1PrepareCompactClosure blk(sp); g1h->heap_region_iterate(&blk); blk.update_sets(); } class G1AdjustPointersClosure: public HeapRegionClosure { public: bool doHeapRegion(HeapRegion* r) { if (r->isHumongous()) { if (r->startsHumongous()) { // We must adjust the pointers on the single H object. oop obj = oop(r->bottom()); // point all the oops to the new location obj->adjust_pointers(); } } else { // This really ought to be "as_CompactibleSpace"... r->adjust_pointers(); } return false; } }; void G1MarkSweep::mark_sweep_phase3() { G1CollectedHeap* g1h = G1CollectedHeap::heap(); // Adjust the pointers to reflect the new locations GCTraceTime tm("phase 3", G1Log::fine() && Verbose, true, gc_timer()); GenMarkSweep::trace("3"); SharedHeap* sh = SharedHeap::heap(); // Need cleared claim bits for the strong roots processing ClassLoaderDataGraph::clear_claimed_marks(); sh->process_strong_roots(true, // activate StrongRootsScope false, // not scavenging. SharedHeap::SO_AllClasses, &GenMarkSweep::adjust_pointer_closure, NULL, // do not touch code cache here &GenMarkSweep::adjust_klass_closure); assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity"); g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure); // Now adjust pointers in remaining weak roots. (All of which should // have been cleared if they pointed to non-surviving objects.) g1h->g1_process_weak_roots(&GenMarkSweep::adjust_pointer_closure); GenMarkSweep::adjust_marks(); G1AdjustPointersClosure blk; g1h->heap_region_iterate(&blk); } class G1SpaceCompactClosure: public HeapRegionClosure { public: G1SpaceCompactClosure() {} bool doHeapRegion(HeapRegion* hr) { if (hr->isHumongous()) { if (hr->startsHumongous()) { oop obj = oop(hr->bottom()); if (obj->is_gc_marked()) { obj->init_mark(); } else { assert(hr->is_empty(), "Should have been cleared in phase 2."); } hr->reset_during_compaction(); } } else { hr->compact(); } return false; } }; void G1MarkSweep::mark_sweep_phase4() { // All pointers are now adjusted, move objects accordingly // 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 (code and comment not fixed for perm removal), so we tell the validate code // to use a higher index (saved from phase2) when verifying perm_gen. G1CollectedHeap* g1h = G1CollectedHeap::heap(); GCTraceTime tm("phase 4", G1Log::fine() && Verbose, true, gc_timer()); GenMarkSweep::trace("4"); G1SpaceCompactClosure blk; g1h->heap_region_iterate(&blk); }