/* * 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/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 "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/aprofiler.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 methodOops 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 for the permanent generation, since it is // implicitly collected whenever we do a full mark sweep collection. sh->perm_gen()->stat_record()->invocations++; 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(); // We must invalidate the perm-gen rs, so that it gets rebuilt. GenRemSet* rs = sh->rem_set(); rs->invalidate(sh->perm_gen()->used_region(), true /*whole_heap*/); // "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 TraceTime tm("phase 1", G1Log::fine() && Verbose, true, gclog_or_tty); GenMarkSweep::trace(" 1"); SharedHeap* sh = SharedHeap::heap(); sh->process_strong_roots(true, // activeate StrongRootsScope true, // Collecting permanent generation. SharedHeap::SO_SystemClasses, &GenMarkSweep::follow_root_closure, &GenMarkSweep::follow_code_root_closure, &GenMarkSweep::follow_root_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); rp->process_discovered_references(&GenMarkSweep::is_alive, &GenMarkSweep::keep_alive, &GenMarkSweep::follow_stack_closure, NULL); // Follow system dictionary roots and unload classes bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive); assert(GenMarkSweep::_marking_stack.is_empty(), "stack should be empty by now"); // Follow code cache roots (has to be done after system dictionary, // assumes all live klasses are marked) CodeCache::do_unloading(&GenMarkSweep::is_alive, &GenMarkSweep::keep_alive, purged_class); GenMarkSweep::follow_stack(); // Update subklass/sibling/implementor links of live klasses GenMarkSweep::follow_weak_klass_links(); assert(GenMarkSweep::_marking_stack.is_empty(), "stack should be empty by now"); // Visit memoized MDO's and clear any unmarked weak refs GenMarkSweep::follow_mdo_weak_refs(); assert(GenMarkSweep::_marking_stack.is_empty(), "just drained"); // Visit interned string tables and delete unmarked oops StringTable::unlink(&GenMarkSweep::is_alive); // Clean up unreferenced symbols in symbol table. SymbolTable::unlink(); assert(GenMarkSweep::_marking_stack.is_empty(), "stack should be empty by now"); if (VerifyDuringGC) { HandleMark hm; // handle scope COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact); gclog_or_tty->print(" VerifyDuringGC:(full)[Verifying "); 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. Universe::heap()->verify(/* silent */ false, /* option */ VerifyOption_G1UseMarkWord); G1CollectedHeap* g1h = G1CollectedHeap::heap(); gclog_or_tty->print_cr("]"); } } class G1PrepareCompactClosure: public HeapRegionClosure { G1CollectedHeap* _g1h; ModRefBarrierSet* _mrbs; CompactPoint _cp; HumongousRegionSet _humongous_proxy_set; void free_humongous_region(HeapRegion* hr) { HeapWord* end = hr->end(); size_t dummy_pre_used; FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep"); assert(hr->startsHumongous(), "Only the start of a humongous region should be freed."); _g1h->free_humongous_region(hr, &dummy_pre_used, &dummy_free_list, &_humongous_proxy_set, 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(G1CollectedHeap::heap()->mr_bs()), _cp(NULL, cs, cs->initialize_threshold()), _humongous_proxy_set("G1MarkSweep Humongous Proxy Set") { } 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. _g1h->update_sets_after_freeing_regions(0, /* pre_used */ NULL, /* free_list */ NULL, /* old_proxy_set */ &_humongous_proxy_set, false /* par */); } 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 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 klassOop 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 klassOop! // // 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(); Generation* pg = g1h->perm_gen(); TraceTime tm("phase 2", G1Log::fine() && Verbose, true, gclog_or_tty); 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(); CompactPoint perm_cp(pg, NULL, NULL); pg->prepare_for_compaction(&perm_cp); } 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()); debug_only(GenMarkSweep::track_interior_pointers(obj)); // point all the oops to the new location obj->adjust_pointers(); debug_only(GenMarkSweep::check_interior_pointers()); } } else { // This really ought to be "as_CompactibleSpace"... r->adjust_pointers(); } return false; } }; void G1MarkSweep::mark_sweep_phase3() { G1CollectedHeap* g1h = G1CollectedHeap::heap(); Generation* pg = g1h->perm_gen(); // Adjust the pointers to reflect the new locations TraceTime tm("phase 3", G1Log::fine() && Verbose, true, gclog_or_tty); GenMarkSweep::trace("3"); SharedHeap* sh = SharedHeap::heap(); sh->process_strong_roots(true, // activate StrongRootsScope true, // Collecting permanent generation. SharedHeap::SO_AllClasses, &GenMarkSweep::adjust_root_pointer_closure, NULL, // do not touch code cache here &GenMarkSweep::adjust_pointer_closure); assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity"); g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::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.) g1h->g1_process_weak_roots(&GenMarkSweep::adjust_root_pointer_closure, &GenMarkSweep::adjust_pointer_closure); GenMarkSweep::adjust_marks(); G1AdjustPointersClosure blk; g1h->heap_region_iterate(&blk); pg->adjust_pointers(); } 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 // 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 klassOops 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. G1CollectedHeap* g1h = G1CollectedHeap::heap(); Generation* pg = g1h->perm_gen(); TraceTime tm("phase 4", G1Log::fine() && Verbose, true, gclog_or_tty); GenMarkSweep::trace("4"); pg->compact(); G1SpaceCompactClosure blk; g1h->heap_region_iterate(&blk); }