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/*
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* Copyright 2001-2007 Sun Microsystems, Inc. All Rights Reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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* CA 95054 USA or visit www.sun.com if you need additional information or
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* have any questions.
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*
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*/
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#include "incls/_precompiled.incl"
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#include "incls/_genMarkSweep.cpp.incl"
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void GenMarkSweep::invoke_at_safepoint(int level, ReferenceProcessor* rp,
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bool clear_all_softrefs) {
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assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
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// hook up weak ref data so it can be used during Mark-Sweep
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assert(ref_processor() == NULL, "no stomping");
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_ref_processor = rp;
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assert(rp != NULL, "should be non-NULL");
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TraceTime t1("Full GC", PrintGC && !PrintGCDetails, true, gclog_or_tty);
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// When collecting the permanent generation methodOops may be moving,
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// so we either have to flush all bcp data or convert it into bci.
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CodeCache::gc_prologue();
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Threads::gc_prologue();
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// Increment the invocation count for the permanent generation, since it is
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// implicitly collected whenever we do a full mark sweep collection.
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GenCollectedHeap* gch = GenCollectedHeap::heap();
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gch->perm_gen()->stat_record()->invocations++;
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// Capture heap size before collection for printing.
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size_t gch_prev_used = gch->used();
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// Some of the card table updates below assume that the perm gen is
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// also being collected.
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assert(level == gch->n_gens() - 1,
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"All generations are being collected, ergo perm gen too.");
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// Capture used regions for each generation that will be
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// subject to collection, so that card table adjustments can
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// be made intelligently (see clear / invalidate further below).
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gch->save_used_regions(level, true /* perm */);
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allocate_stacks();
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mark_sweep_phase1(level, clear_all_softrefs);
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mark_sweep_phase2();
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// Don't add any more derived pointers during phase3
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COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity"));
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COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
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mark_sweep_phase3(level);
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VALIDATE_MARK_SWEEP_ONLY(
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if (ValidateMarkSweep) {
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guarantee(_root_refs_stack->length() == 0,
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"should be empty by now");
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}
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)
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mark_sweep_phase4();
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VALIDATE_MARK_SWEEP_ONLY(
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if (ValidateMarkSweep) {
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guarantee(_live_oops->length() == _live_oops_moved_to->length(),
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"should be the same size");
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}
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)
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restore_marks();
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// Set saved marks for allocation profiler (and other things? -- dld)
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// (Should this be in general part?)
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gch->save_marks();
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deallocate_stacks();
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// If compaction completely evacuated all generations younger than this
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// one, then we can clear the card table. Otherwise, we must invalidate
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// it (consider all cards dirty). In the future, we might consider doing
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// compaction within generations only, and doing card-table sliding.
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bool all_empty = true;
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for (int i = 0; all_empty && i < level; i++) {
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Generation* g = gch->get_gen(i);
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all_empty = all_empty && gch->get_gen(i)->used() == 0;
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}
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GenRemSet* rs = gch->rem_set();
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// Clear/invalidate below make use of the "prev_used_regions" saved earlier.
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if (all_empty) {
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// We've evacuated all generations below us.
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Generation* g = gch->get_gen(level);
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rs->clear_into_younger(g, true /* perm */);
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} else {
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// Invalidate the cards corresponding to the currently used
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// region and clear those corresponding to the evacuated region
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// of all generations just collected (i.e. level and younger).
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rs->invalidate_or_clear(gch->get_gen(level),
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true /* younger */,
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true /* perm */);
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}
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Threads::gc_epilogue();
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CodeCache::gc_epilogue();
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if (PrintGC && !PrintGCDetails) {
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gch->print_heap_change(gch_prev_used);
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}
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// refs processing: clean slate
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_ref_processor = NULL;
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// Update heap occupancy information which is used as
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// input to soft ref clearing policy at the next gc.
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Universe::update_heap_info_at_gc();
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// Update time of last gc for all generations we collected
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// (which curently is all the generations in the heap).
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gch->update_time_of_last_gc(os::javaTimeMillis());
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}
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void GenMarkSweep::allocate_stacks() {
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GenCollectedHeap* gch = GenCollectedHeap::heap();
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// Scratch request on behalf of oldest generation; will do no
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// allocation.
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ScratchBlock* scratch = gch->gather_scratch(gch->_gens[gch->_n_gens-1], 0);
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// $$$ To cut a corner, we'll only use the first scratch block, and then
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// revert to malloc.
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if (scratch != NULL) {
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_preserved_count_max =
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scratch->num_words * HeapWordSize / sizeof(PreservedMark);
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} else {
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_preserved_count_max = 0;
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}
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_preserved_marks = (PreservedMark*)scratch;
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_preserved_count = 0;
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_preserved_mark_stack = NULL;
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_preserved_oop_stack = NULL;
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_marking_stack = new (ResourceObj::C_HEAP) GrowableArray<oop>(4000, true);
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int size = SystemDictionary::number_of_classes() * 2;
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_revisit_klass_stack = new (ResourceObj::C_HEAP) GrowableArray<Klass*>(size, true);
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#ifdef VALIDATE_MARK_SWEEP
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if (ValidateMarkSweep) {
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_root_refs_stack = new (ResourceObj::C_HEAP) GrowableArray<oop*>(100, true);
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_other_refs_stack = new (ResourceObj::C_HEAP) GrowableArray<oop*>(100, true);
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_adjusted_pointers = new (ResourceObj::C_HEAP) GrowableArray<oop*>(100, true);
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_live_oops = new (ResourceObj::C_HEAP) GrowableArray<oop>(100, true);
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_live_oops_moved_to = new (ResourceObj::C_HEAP) GrowableArray<oop>(100, true);
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_live_oops_size = new (ResourceObj::C_HEAP) GrowableArray<size_t>(100, true);
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}
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if (RecordMarkSweepCompaction) {
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if (_cur_gc_live_oops == NULL) {
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_cur_gc_live_oops = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);
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_cur_gc_live_oops_moved_to = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);
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_cur_gc_live_oops_size = new(ResourceObj::C_HEAP) GrowableArray<size_t>(100, true);
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_last_gc_live_oops = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);
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_last_gc_live_oops_moved_to = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);
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_last_gc_live_oops_size = new(ResourceObj::C_HEAP) GrowableArray<size_t>(100, true);
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} else {
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_cur_gc_live_oops->clear();
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_cur_gc_live_oops_moved_to->clear();
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_cur_gc_live_oops_size->clear();
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}
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}
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#endif
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}
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void GenMarkSweep::deallocate_stacks() {
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if (_preserved_oop_stack) {
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delete _preserved_mark_stack;
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_preserved_mark_stack = NULL;
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delete _preserved_oop_stack;
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_preserved_oop_stack = NULL;
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}
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delete _marking_stack;
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delete _revisit_klass_stack;
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#ifdef VALIDATE_MARK_SWEEP
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if (ValidateMarkSweep) {
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delete _root_refs_stack;
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delete _other_refs_stack;
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delete _adjusted_pointers;
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delete _live_oops;
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delete _live_oops_size;
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delete _live_oops_moved_to;
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_live_oops_index = 0;
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_live_oops_index_at_perm = 0;
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}
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#endif
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}
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void GenMarkSweep::mark_sweep_phase1(int level,
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bool clear_all_softrefs) {
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// Recursively traverse all live objects and mark them
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EventMark m("1 mark object");
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TraceTime tm("phase 1", PrintGC && Verbose, true, gclog_or_tty);
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trace(" 1");
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VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));
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GenCollectedHeap* gch = GenCollectedHeap::heap();
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// Because follow_root_closure is created statically, cannot
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// use OopsInGenClosure constructor which takes a generation,
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// as the Universe has not been created when the static constructors
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// are run.
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follow_root_closure.set_orig_generation(gch->get_gen(level));
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gch->gen_process_strong_roots(level,
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false, // Younger gens are not roots.
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true, // Collecting permanent generation.
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SharedHeap::SO_SystemClasses,
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&follow_root_closure, &follow_root_closure);
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// Process reference objects found during marking
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{
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ReferencePolicy *soft_ref_policy;
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if (clear_all_softrefs) {
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soft_ref_policy = new AlwaysClearPolicy();
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} else {
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#ifdef COMPILER2
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soft_ref_policy = new LRUMaxHeapPolicy();
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#else
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soft_ref_policy = new LRUCurrentHeapPolicy();
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#endif // COMPILER2
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}
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assert(soft_ref_policy != NULL,"No soft reference policy");
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ref_processor()->process_discovered_references(
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soft_ref_policy, &is_alive, &keep_alive,
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&follow_stack_closure, NULL);
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}
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// Follow system dictionary roots and unload classes
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bool purged_class = SystemDictionary::do_unloading(&is_alive);
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// Follow code cache roots
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CodeCache::do_unloading(&is_alive, &keep_alive, purged_class);
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follow_stack(); // Flush marking stack
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// Update subklass/sibling/implementor links of live klasses
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follow_weak_klass_links();
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assert(_marking_stack->is_empty(), "just drained");
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// Visit symbol and interned string tables and delete unmarked oops
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SymbolTable::unlink(&is_alive);
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StringTable::unlink(&is_alive);
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assert(_marking_stack->is_empty(), "stack should be empty by now");
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}
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void GenMarkSweep::mark_sweep_phase2() {
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// Now all live objects are marked, compute the new object addresses.
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// It is imperative that we traverse perm_gen LAST. If dead space is
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// allowed a range of dead object may get overwritten by a dead int
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// array. If perm_gen is not traversed last a klassOop may get
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// overwritten. This is fine since it is dead, but if the class has dead
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// instances we have to skip them, and in order to find their size we
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// need the klassOop!
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//
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// It is not required that we traverse spaces in the same order in
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// phase2, phase3 and phase4, but the ValidateMarkSweep live oops
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// tracking expects us to do so. See comment under phase4.
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GenCollectedHeap* gch = GenCollectedHeap::heap();
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Generation* pg = gch->perm_gen();
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EventMark m("2 compute new addresses");
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TraceTime tm("phase 2", PrintGC && Verbose, true, gclog_or_tty);
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trace("2");
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VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));
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gch->prepare_for_compaction();
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VALIDATE_MARK_SWEEP_ONLY(_live_oops_index_at_perm = _live_oops_index);
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CompactPoint perm_cp(pg, NULL, NULL);
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pg->prepare_for_compaction(&perm_cp);
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}
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class GenAdjustPointersClosure: public GenCollectedHeap::GenClosure {
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public:
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void do_generation(Generation* gen) {
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gen->adjust_pointers();
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}
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};
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void GenMarkSweep::mark_sweep_phase3(int level) {
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GenCollectedHeap* gch = GenCollectedHeap::heap();
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Generation* pg = gch->perm_gen();
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// Adjust the pointers to reflect the new locations
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EventMark m("3 adjust pointers");
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TraceTime tm("phase 3", PrintGC && Verbose, true, gclog_or_tty);
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trace("3");
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VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));
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// Needs to be done before the system dictionary is adjusted.
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pg->pre_adjust_pointers();
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// Because the two closures below are created statically, cannot
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// use OopsInGenClosure constructor which takes a generation,
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// as the Universe has not been created when the static constructors
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// are run.
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adjust_root_pointer_closure.set_orig_generation(gch->get_gen(level));
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adjust_pointer_closure.set_orig_generation(gch->get_gen(level));
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gch->gen_process_strong_roots(level,
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false, // Younger gens are not roots.
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true, // Collecting permanent generation.
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SharedHeap::SO_AllClasses,
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&adjust_root_pointer_closure,
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&adjust_root_pointer_closure);
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// Now adjust pointers in remaining weak roots. (All of which should
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// have been cleared if they pointed to non-surviving objects.)
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gch->gen_process_weak_roots(&adjust_root_pointer_closure,
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&adjust_pointer_closure);
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adjust_marks();
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GenAdjustPointersClosure blk;
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gch->generation_iterate(&blk, true);
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pg->adjust_pointers();
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}
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class GenCompactClosure: public GenCollectedHeap::GenClosure {
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public:
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void do_generation(Generation* gen) {
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gen->compact();
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}
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};
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void GenMarkSweep::mark_sweep_phase4() {
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// All pointers are now adjusted, move objects accordingly
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// It is imperative that we traverse perm_gen first in phase4. All
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// classes must be allocated earlier than their instances, and traversing
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// perm_gen first makes sure that all klassOops have moved to their new
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// location before any instance does a dispatch through it's klass!
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// The ValidateMarkSweep live oops tracking expects us to traverse spaces
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// in the same order in phase2, phase3 and phase4. We don't quite do that
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// here (perm_gen first rather than last), so we tell the validate code
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// to use a higher index (saved from phase2) when verifying perm_gen.
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GenCollectedHeap* gch = GenCollectedHeap::heap();
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Generation* pg = gch->perm_gen();
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EventMark m("4 compact heap");
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TraceTime tm("phase 4", PrintGC && Verbose, true, gclog_or_tty);
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trace("4");
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VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(true));
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pg->compact();
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383 |
|
|
384 |
VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));
|
|
385 |
|
|
386 |
GenCompactClosure blk;
|
|
387 |
gch->generation_iterate(&blk, true);
|
|
388 |
|
|
389 |
VALIDATE_MARK_SWEEP_ONLY(compaction_complete());
|
|
390 |
|
|
391 |
pg->post_compact(); // Shared spaces verification.
|
|
392 |
}
|