Mercurial > hg > graal-jvmci-8
view src/share/vm/memory/genMarkSweep.cpp @ 20304:a22acf6d7598
8048112: G1 Full GC needs to support the case when the very first region is not available
Summary: Refactor preparation for compaction during Full GC so that it lazily initializes the first compaction point. This also avoids problems later when the first region may not be committed. Also reviewed by K. Barrett.
Reviewed-by: brutisso
author | tschatzl |
---|---|
date | Mon, 21 Jul 2014 10:00:31 +0200 |
parents | 2c6ef90f030a |
children | 7848fc12602b 38d6febe66af |
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/* * 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, _gc_tracer->gc_id()); 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, _gc_tracer->gc_id()); 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_roots(level, false, // Younger gens are not roots. true, // activate StrongRootsScope SharedHeap::SO_None, GenCollectedHeap::StrongRootsOnly, &follow_root_closure, &follow_root_closure, &follow_cld_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->gc_id()); 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, _gc_tracer->gc_id()); 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, _gc_tracer->gc_id()); 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_roots(level, false, // Younger gens are not roots. true, // activate StrongRootsScope SharedHeap::SO_AllCodeCache, GenCollectedHeap::StrongAndWeakRoots, &adjust_pointer_closure, &adjust_pointer_closure, &adjust_cld_closure); gch->gen_process_weak_roots(&adjust_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, _gc_tracer->gc_id()); trace("4"); GenCompactClosure blk; gch->generation_iterate(&blk, true); }