diff -r 000000000000 -r a61af66fc99e src/share/vm/memory/genMarkSweep.cpp --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/share/vm/memory/genMarkSweep.cpp Sat Dec 01 00:00:00 2007 +0000 @@ -0,0 +1,392 @@ +/* + * Copyright 2001-2007 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, + * CA 95054 USA or visit www.sun.com if you need additional information or + * have any questions. + * + */ + +#include "incls/_precompiled.incl" +#include "incls/_genMarkSweep.cpp.incl" + +void GenMarkSweep::invoke_at_safepoint(int level, ReferenceProcessor* rp, + bool clear_all_softrefs) { + assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint"); + + // hook up weak ref data so it can be used during Mark-Sweep + assert(ref_processor() == NULL, "no stomping"); + _ref_processor = rp; + assert(rp != NULL, "should be non-NULL"); + + TraceTime t1("Full GC", PrintGC && !PrintGCDetails, true, gclog_or_tty); + + // 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. + GenCollectedHeap* gch = GenCollectedHeap::heap(); + gch->perm_gen()->stat_record()->invocations++; + + // Capture heap size before collection for printing. + size_t gch_prev_used = gch->used(); + + // Some of the card table updates below assume that the perm gen is + // also being collected. + assert(level == gch->n_gens() - 1, + "All generations are being collected, ergo perm gen too."); + + // 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, true /* perm */); + + 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); + + VALIDATE_MARK_SWEEP_ONLY( + if (ValidateMarkSweep) { + guarantee(_root_refs_stack->length() == 0, + "should be empty by now"); + } + ) + + mark_sweep_phase4(); + + VALIDATE_MARK_SWEEP_ONLY( + if (ValidateMarkSweep) { + guarantee(_live_oops->length() == _live_oops_moved_to->length(), + "should be the same size"); + } + ) + + 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(); + // Clear/invalidate below make use of the "prev_used_regions" saved earlier. + if (all_empty) { + // We've evacuated all generations below us. + Generation* g = gch->get_gen(level); + rs->clear_into_younger(g, true /* perm */); + } else { + // Invalidate the cards corresponding to the currently used + // region and clear those corresponding to the evacuated region + // of all generations just collected (i.e. level and younger). + rs->invalidate_or_clear(gch->get_gen(level), + true /* younger */, + true /* perm */); + } + + Threads::gc_epilogue(); + CodeCache::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). + gch->update_time_of_last_gc(os::javaTimeMillis()); +} + +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; + _preserved_mark_stack = NULL; + _preserved_oop_stack = NULL; + + _marking_stack = new (ResourceObj::C_HEAP) GrowableArray(4000, true); + + int size = SystemDictionary::number_of_classes() * 2; + _revisit_klass_stack = new (ResourceObj::C_HEAP) GrowableArray(size, true); + +#ifdef VALIDATE_MARK_SWEEP + if (ValidateMarkSweep) { + _root_refs_stack = new (ResourceObj::C_HEAP) GrowableArray(100, true); + _other_refs_stack = new (ResourceObj::C_HEAP) GrowableArray(100, true); + _adjusted_pointers = new (ResourceObj::C_HEAP) GrowableArray(100, true); + _live_oops = new (ResourceObj::C_HEAP) GrowableArray(100, true); + _live_oops_moved_to = new (ResourceObj::C_HEAP) GrowableArray(100, true); + _live_oops_size = new (ResourceObj::C_HEAP) GrowableArray(100, true); + } + if (RecordMarkSweepCompaction) { + if (_cur_gc_live_oops == NULL) { + _cur_gc_live_oops = new(ResourceObj::C_HEAP) GrowableArray(100, true); + _cur_gc_live_oops_moved_to = new(ResourceObj::C_HEAP) GrowableArray(100, true); + _cur_gc_live_oops_size = new(ResourceObj::C_HEAP) GrowableArray(100, true); + _last_gc_live_oops = new(ResourceObj::C_HEAP) GrowableArray(100, true); + _last_gc_live_oops_moved_to = new(ResourceObj::C_HEAP) GrowableArray(100, true); + _last_gc_live_oops_size = new(ResourceObj::C_HEAP) GrowableArray(100, true); + } else { + _cur_gc_live_oops->clear(); + _cur_gc_live_oops_moved_to->clear(); + _cur_gc_live_oops_size->clear(); + } + } +#endif +} + + +void GenMarkSweep::deallocate_stacks() { + if (_preserved_oop_stack) { + delete _preserved_mark_stack; + _preserved_mark_stack = NULL; + delete _preserved_oop_stack; + _preserved_oop_stack = NULL; + } + + delete _marking_stack; + delete _revisit_klass_stack; + +#ifdef VALIDATE_MARK_SWEEP + if (ValidateMarkSweep) { + delete _root_refs_stack; + delete _other_refs_stack; + delete _adjusted_pointers; + delete _live_oops; + delete _live_oops_size; + delete _live_oops_moved_to; + _live_oops_index = 0; + _live_oops_index_at_perm = 0; + } +#endif +} + +void GenMarkSweep::mark_sweep_phase1(int level, + bool clear_all_softrefs) { + // Recursively traverse all live objects and mark them + EventMark m("1 mark object"); + TraceTime tm("phase 1", PrintGC && Verbose, true, gclog_or_tty); + trace(" 1"); + + VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false)); + + 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)); + + gch->gen_process_strong_roots(level, + false, // Younger gens are not roots. + true, // Collecting permanent generation. + SharedHeap::SO_SystemClasses, + &follow_root_closure, &follow_root_closure); + + // Process reference objects found during marking + { + ReferencePolicy *soft_ref_policy; + if (clear_all_softrefs) { + soft_ref_policy = new AlwaysClearPolicy(); + } else { +#ifdef COMPILER2 + soft_ref_policy = new LRUMaxHeapPolicy(); +#else + soft_ref_policy = new LRUCurrentHeapPolicy(); +#endif // COMPILER2 + } + assert(soft_ref_policy != NULL,"No soft reference policy"); + ref_processor()->process_discovered_references( + soft_ref_policy, &is_alive, &keep_alive, + &follow_stack_closure, NULL); + } + + // Follow system dictionary roots and unload classes + bool purged_class = SystemDictionary::do_unloading(&is_alive); + + // Follow code cache roots + CodeCache::do_unloading(&is_alive, &keep_alive, purged_class); + follow_stack(); // Flush marking stack + + // Update subklass/sibling/implementor links of live klasses + follow_weak_klass_links(); + assert(_marking_stack->is_empty(), "just drained"); + + // Visit symbol and interned string tables and delete unmarked oops + SymbolTable::unlink(&is_alive); + StringTable::unlink(&is_alive); + + assert(_marking_stack->is_empty(), "stack should be empty by now"); +} + + +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 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. + + GenCollectedHeap* gch = GenCollectedHeap::heap(); + Generation* pg = gch->perm_gen(); + + EventMark m("2 compute new addresses"); + TraceTime tm("phase 2", PrintGC && Verbose, true, gclog_or_tty); + trace("2"); + + VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false)); + + gch->prepare_for_compaction(); + + VALIDATE_MARK_SWEEP_ONLY(_live_oops_index_at_perm = _live_oops_index); + CompactPoint perm_cp(pg, NULL, NULL); + pg->prepare_for_compaction(&perm_cp); +} + +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(); + Generation* pg = gch->perm_gen(); + + // Adjust the pointers to reflect the new locations + EventMark m("3 adjust pointers"); + TraceTime tm("phase 3", PrintGC && Verbose, true, gclog_or_tty); + trace("3"); + + VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false)); + + // Needs to be done before the system dictionary is adjusted. + pg->pre_adjust_pointers(); + + // Because the two closures below are created statically, cannot + // use OopsInGenClosure constructor which takes a generation, + // as the Universe has not been created when the static constructors + // are run. + adjust_root_pointer_closure.set_orig_generation(gch->get_gen(level)); + adjust_pointer_closure.set_orig_generation(gch->get_gen(level)); + + gch->gen_process_strong_roots(level, + false, // Younger gens are not roots. + true, // Collecting permanent generation. + SharedHeap::SO_AllClasses, + &adjust_root_pointer_closure, + &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.) + gch->gen_process_weak_roots(&adjust_root_pointer_closure, + &adjust_pointer_closure); + + adjust_marks(); + GenAdjustPointersClosure blk; + gch->generation_iterate(&blk, true); + pg->adjust_pointers(); +} + +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 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. + GenCollectedHeap* gch = GenCollectedHeap::heap(); + Generation* pg = gch->perm_gen(); + + EventMark m("4 compact heap"); + TraceTime tm("phase 4", PrintGC && Verbose, true, gclog_or_tty); + trace("4"); + + VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(true)); + + pg->compact(); + + VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false)); + + GenCompactClosure blk; + gch->generation_iterate(&blk, true); + + VALIDATE_MARK_SWEEP_ONLY(compaction_complete()); + + pg->post_compact(); // Shared spaces verification. +}