duke@435: /*
never@3499:  * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved.
duke@435:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@435:  *
duke@435:  * This code is free software; you can redistribute it and/or modify it
duke@435:  * under the terms of the GNU General Public License version 2 only, as
duke@435:  * published by the Free Software Foundation.
duke@435:  *
duke@435:  * This code is distributed in the hope that it will be useful, but WITHOUT
duke@435:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@435:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
duke@435:  * version 2 for more details (a copy is included in the LICENSE file that
duke@435:  * accompanied this code).
duke@435:  *
duke@435:  * You should have received a copy of the GNU General Public License version
duke@435:  * 2 along with this work; if not, write to the Free Software Foundation,
duke@435:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@435:  *
trims@1907:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
trims@1907:  * or visit www.oracle.com if you need additional information or have any
trims@1907:  * questions.
duke@435:  *
duke@435:  */
duke@435: 
stefank@2314: #include "precompiled.hpp"
stefank@2314: #include "classfile/javaClasses.hpp"
stefank@2314: #include "classfile/symbolTable.hpp"
stefank@2314: #include "classfile/systemDictionary.hpp"
stefank@2314: #include "classfile/vmSymbols.hpp"
stefank@2314: #include "code/codeCache.hpp"
stefank@2314: #include "code/icBuffer.hpp"
stefank@2314: #include "gc_interface/collectedHeap.inline.hpp"
stefank@2314: #include "memory/genCollectedHeap.hpp"
stefank@2314: #include "memory/genMarkSweep.hpp"
stefank@2314: #include "memory/genOopClosures.inline.hpp"
stefank@2314: #include "memory/generation.inline.hpp"
stefank@2314: #include "memory/modRefBarrierSet.hpp"
stefank@2314: #include "memory/referencePolicy.hpp"
stefank@2314: #include "memory/space.hpp"
stefank@2314: #include "oops/instanceRefKlass.hpp"
stefank@2314: #include "oops/oop.inline.hpp"
stefank@2314: #include "prims/jvmtiExport.hpp"
stefank@2314: #include "runtime/fprofiler.hpp"
stefank@2314: #include "runtime/handles.inline.hpp"
stefank@2314: #include "runtime/synchronizer.hpp"
stefank@4299: #include "runtime/thread.inline.hpp"
stefank@2314: #include "runtime/vmThread.hpp"
stefank@2314: #include "utilities/copy.hpp"
stefank@2314: #include "utilities/events.hpp"
duke@435: 
duke@435: void GenMarkSweep::invoke_at_safepoint(int level, ReferenceProcessor* rp,
duke@435:   bool clear_all_softrefs) {
duke@435:   assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
duke@435: 
jmasa@1822:   GenCollectedHeap* gch = GenCollectedHeap::heap();
jmasa@1822: #ifdef ASSERT
jmasa@1822:   if (gch->collector_policy()->should_clear_all_soft_refs()) {
jmasa@1822:     assert(clear_all_softrefs, "Policy should have been checked earlier");
jmasa@1822:   }
jmasa@1822: #endif
jmasa@1822: 
duke@435:   // hook up weak ref data so it can be used during Mark-Sweep
duke@435:   assert(ref_processor() == NULL, "no stomping");
ysr@888:   assert(rp != NULL, "should be non-NULL");
duke@435:   _ref_processor = rp;
ysr@892:   rp->setup_policy(clear_all_softrefs);
duke@435: 
brutisso@3767:   TraceTime t1(GCCauseString("Full GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, gclog_or_tty);
duke@435: 
coleenp@4037:   // When collecting the permanent generation Method*s may be moving,
duke@435:   // so we either have to flush all bcp data or convert it into bci.
duke@435:   CodeCache::gc_prologue();
duke@435:   Threads::gc_prologue();
duke@435: 
coleenp@4037:   // Increment the invocation count
coleenp@4037:   _total_invocations++;
duke@435: 
duke@435:   // Capture heap size before collection for printing.
duke@435:   size_t gch_prev_used = gch->used();
duke@435: 
duke@435:   // Some of the card table updates below assume that the perm gen is
duke@435:   // also being collected.
duke@435:   assert(level == gch->n_gens() - 1,
duke@435:          "All generations are being collected, ergo perm gen too.");
duke@435: 
duke@435:   // Capture used regions for each generation that will be
duke@435:   // subject to collection, so that card table adjustments can
duke@435:   // be made intelligently (see clear / invalidate further below).
coleenp@4037:   gch->save_used_regions(level);
duke@435: 
duke@435:   allocate_stacks();
duke@435: 
duke@435:   mark_sweep_phase1(level, clear_all_softrefs);
duke@435: 
duke@435:   mark_sweep_phase2();
duke@435: 
duke@435:   // Don't add any more derived pointers during phase3
duke@435:   COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity"));
duke@435:   COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
duke@435: 
duke@435:   mark_sweep_phase3(level);
duke@435: 
duke@435:   mark_sweep_phase4();
duke@435: 
duke@435:   restore_marks();
duke@435: 
duke@435:   // Set saved marks for allocation profiler (and other things? -- dld)
duke@435:   // (Should this be in general part?)
duke@435:   gch->save_marks();
duke@435: 
duke@435:   deallocate_stacks();
duke@435: 
duke@435:   // If compaction completely evacuated all generations younger than this
duke@435:   // one, then we can clear the card table.  Otherwise, we must invalidate
duke@435:   // it (consider all cards dirty).  In the future, we might consider doing
duke@435:   // compaction within generations only, and doing card-table sliding.
duke@435:   bool all_empty = true;
duke@435:   for (int i = 0; all_empty && i < level; i++) {
duke@435:     Generation* g = gch->get_gen(i);
duke@435:     all_empty = all_empty && gch->get_gen(i)->used() == 0;
duke@435:   }
duke@435:   GenRemSet* rs = gch->rem_set();
duke@435:   // Clear/invalidate below make use of the "prev_used_regions" saved earlier.
duke@435:   if (all_empty) {
duke@435:     // We've evacuated all generations below us.
duke@435:     Generation* g = gch->get_gen(level);
coleenp@4037:     rs->clear_into_younger(g);
duke@435:   } else {
duke@435:     // Invalidate the cards corresponding to the currently used
duke@435:     // region and clear those corresponding to the evacuated region
duke@435:     // of all generations just collected (i.e. level and younger).
duke@435:     rs->invalidate_or_clear(gch->get_gen(level),
coleenp@4037:                             true /* younger */);
duke@435:   }
duke@435: 
duke@435:   Threads::gc_epilogue();
duke@435:   CodeCache::gc_epilogue();
kamg@2467:   JvmtiExport::gc_epilogue();
duke@435: 
duke@435:   if (PrintGC && !PrintGCDetails) {
duke@435:     gch->print_heap_change(gch_prev_used);
duke@435:   }
duke@435: 
duke@435:   // refs processing: clean slate
duke@435:   _ref_processor = NULL;
duke@435: 
duke@435:   // Update heap occupancy information which is used as
duke@435:   // input to soft ref clearing policy at the next gc.
duke@435:   Universe::update_heap_info_at_gc();
duke@435: 
duke@435:   // Update time of last gc for all generations we collected
duke@435:   // (which curently is all the generations in the heap).
johnc@3538:   // We need to use a monotonically non-deccreasing time in ms
johnc@3538:   // or we will see time-warp warnings and os::javaTimeMillis()
johnc@3538:   // does not guarantee monotonicity.
johnc@3538:   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
johnc@3538:   gch->update_time_of_last_gc(now);
duke@435: }
duke@435: 
duke@435: void GenMarkSweep::allocate_stacks() {
duke@435:   GenCollectedHeap* gch = GenCollectedHeap::heap();
duke@435:   // Scratch request on behalf of oldest generation; will do no
duke@435:   // allocation.
duke@435:   ScratchBlock* scratch = gch->gather_scratch(gch->_gens[gch->_n_gens-1], 0);
duke@435: 
duke@435:   // $$$ To cut a corner, we'll only use the first scratch block, and then
duke@435:   // revert to malloc.
duke@435:   if (scratch != NULL) {
duke@435:     _preserved_count_max =
duke@435:       scratch->num_words * HeapWordSize / sizeof(PreservedMark);
duke@435:   } else {
duke@435:     _preserved_count_max = 0;
duke@435:   }
duke@435: 
duke@435:   _preserved_marks = (PreservedMark*)scratch;
duke@435:   _preserved_count = 0;
duke@435: }
duke@435: 
duke@435: 
duke@435: void GenMarkSweep::deallocate_stacks() {
tonyp@791:   if (!UseG1GC) {
tonyp@791:     GenCollectedHeap* gch = GenCollectedHeap::heap();
tonyp@791:     gch->release_scratch();
tonyp@791:   }
jmasa@698: 
jcoomes@2191:   _preserved_mark_stack.clear(true);
jcoomes@2191:   _preserved_oop_stack.clear(true);
jcoomes@2191:   _marking_stack.clear();
jcoomes@2191:   _objarray_stack.clear(true);
duke@435: }
duke@435: 
duke@435: void GenMarkSweep::mark_sweep_phase1(int level,
duke@435:                                   bool clear_all_softrefs) {
duke@435:   // Recursively traverse all live objects and mark them
duke@435:   TraceTime tm("phase 1", PrintGC && Verbose, true, gclog_or_tty);
duke@435:   trace(" 1");
duke@435: 
duke@435:   GenCollectedHeap* gch = GenCollectedHeap::heap();
duke@435: 
duke@435:   // Because follow_root_closure is created statically, cannot
duke@435:   // use OopsInGenClosure constructor which takes a generation,
duke@435:   // as the Universe has not been created when the static constructors
duke@435:   // are run.
duke@435:   follow_root_closure.set_orig_generation(gch->get_gen(level));
duke@435: 
coleenp@4037:   // Need new claim bits before marking starts.
coleenp@4037:   ClassLoaderDataGraph::clear_claimed_marks();
coleenp@4037: 
duke@435:   gch->gen_process_strong_roots(level,
duke@435:                                 false, // Younger gens are not roots.
jrose@1424:                                 true,  // activate StrongRootsScope
coleenp@4037:                                 false, // not scavenging
duke@435:                                 SharedHeap::SO_SystemClasses,
jrose@1424:                                 &follow_root_closure,
jrose@1424:                                 true,   // walk code active on stacks
coleenp@4037:                                 &follow_root_closure,
coleenp@4037:                                 &follow_klass_closure);
duke@435: 
duke@435:   // Process reference objects found during marking
duke@435:   {
ysr@892:     ref_processor()->setup_policy(clear_all_softrefs);
duke@435:     ref_processor()->process_discovered_references(
ysr@888:       &is_alive, &keep_alive, &follow_stack_closure, NULL);
duke@435:   }
duke@435: 
duke@435:   // Follow system dictionary roots and unload classes
duke@435:   bool purged_class = SystemDictionary::do_unloading(&is_alive);
duke@435: 
duke@435:   // Follow code cache roots
brutisso@4098:   CodeCache::do_unloading(&is_alive, purged_class);
duke@435:   follow_stack(); // Flush marking stack
duke@435: 
duke@435:   // Update subklass/sibling/implementor links of live klasses
coleenp@4037:   Klass::clean_weak_klass_links(&is_alive);
jcoomes@2191:   assert(_marking_stack.is_empty(), "just drained");
ysr@1376: 
coleenp@2497:   // Visit interned string tables and delete unmarked oops
duke@435:   StringTable::unlink(&is_alive);
coleenp@2497:   // Clean up unreferenced symbols in symbol table.
coleenp@2497:   SymbolTable::unlink();
duke@435: 
jcoomes@2191:   assert(_marking_stack.is_empty(), "stack should be empty by now");
duke@435: }
duke@435: 
duke@435: 
duke@435: void GenMarkSweep::mark_sweep_phase2() {
duke@435:   // Now all live objects are marked, compute the new object addresses.
duke@435: 
duke@435:   // It is imperative that we traverse perm_gen LAST. If dead space is
duke@435:   // allowed a range of dead object may get overwritten by a dead int
coleenp@4037:   // array. If perm_gen is not traversed last a Klass* may get
duke@435:   // overwritten. This is fine since it is dead, but if the class has dead
duke@435:   // instances we have to skip them, and in order to find their size we
coleenp@4037:   // need the Klass*!
duke@435:   //
duke@435:   // It is not required that we traverse spaces in the same order in
duke@435:   // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
duke@435:   // tracking expects us to do so. See comment under phase4.
duke@435: 
duke@435:   GenCollectedHeap* gch = GenCollectedHeap::heap();
duke@435: 
duke@435:   TraceTime tm("phase 2", PrintGC && Verbose, true, gclog_or_tty);
duke@435:   trace("2");
duke@435: 
duke@435:   gch->prepare_for_compaction();
duke@435: }
duke@435: 
duke@435: class GenAdjustPointersClosure: public GenCollectedHeap::GenClosure {
duke@435: public:
duke@435:   void do_generation(Generation* gen) {
duke@435:     gen->adjust_pointers();
duke@435:   }
duke@435: };
duke@435: 
duke@435: void GenMarkSweep::mark_sweep_phase3(int level) {
duke@435:   GenCollectedHeap* gch = GenCollectedHeap::heap();
duke@435: 
duke@435:   // Adjust the pointers to reflect the new locations
duke@435:   TraceTime tm("phase 3", PrintGC && Verbose, true, gclog_or_tty);
duke@435:   trace("3");
duke@435: 
coleenp@4037:   // Need new claim bits for the pointer adjustment tracing.
coleenp@4037:   ClassLoaderDataGraph::clear_claimed_marks();
duke@435: 
duke@435:   // Because the two closures below are created statically, cannot
duke@435:   // use OopsInGenClosure constructor which takes a generation,
duke@435:   // as the Universe has not been created when the static constructors
duke@435:   // are run.
duke@435:   adjust_root_pointer_closure.set_orig_generation(gch->get_gen(level));
duke@435:   adjust_pointer_closure.set_orig_generation(gch->get_gen(level));
duke@435: 
duke@435:   gch->gen_process_strong_roots(level,
duke@435:                                 false, // Younger gens are not roots.
jrose@1424:                                 true,  // activate StrongRootsScope
coleenp@4037:                                 false, // not scavenging
duke@435:                                 SharedHeap::SO_AllClasses,
duke@435:                                 &adjust_root_pointer_closure,
jrose@1424:                                 false, // do not walk code
coleenp@4037:                                 &adjust_root_pointer_closure,
coleenp@4037:                                 &adjust_klass_closure);
duke@435: 
duke@435:   // Now adjust pointers in remaining weak roots.  (All of which should
duke@435:   // have been cleared if they pointed to non-surviving objects.)
jrose@1424:   CodeBlobToOopClosure adjust_code_pointer_closure(&adjust_pointer_closure,
jrose@1424:                                                    /*do_marking=*/ false);
duke@435:   gch->gen_process_weak_roots(&adjust_root_pointer_closure,
jrose@1424:                               &adjust_code_pointer_closure,
duke@435:                               &adjust_pointer_closure);
duke@435: 
duke@435:   adjust_marks();
duke@435:   GenAdjustPointersClosure blk;
duke@435:   gch->generation_iterate(&blk, true);
duke@435: }
duke@435: 
duke@435: class GenCompactClosure: public GenCollectedHeap::GenClosure {
duke@435: public:
duke@435:   void do_generation(Generation* gen) {
duke@435:     gen->compact();
duke@435:   }
duke@435: };
duke@435: 
duke@435: void GenMarkSweep::mark_sweep_phase4() {
duke@435:   // All pointers are now adjusted, move objects accordingly
duke@435: 
duke@435:   // It is imperative that we traverse perm_gen first in phase4. All
duke@435:   // classes must be allocated earlier than their instances, and traversing
coleenp@4037:   // perm_gen first makes sure that all Klass*s have moved to their new
duke@435:   // location before any instance does a dispatch through it's klass!
duke@435: 
duke@435:   // The ValidateMarkSweep live oops tracking expects us to traverse spaces
duke@435:   // in the same order in phase2, phase3 and phase4. We don't quite do that
duke@435:   // here (perm_gen first rather than last), so we tell the validate code
duke@435:   // to use a higher index (saved from phase2) when verifying perm_gen.
duke@435:   GenCollectedHeap* gch = GenCollectedHeap::heap();
duke@435: 
duke@435:   TraceTime tm("phase 4", PrintGC && Verbose, true, gclog_or_tty);
duke@435:   trace("4");
duke@435: 
duke@435:   GenCompactClosure blk;
duke@435:   gch->generation_iterate(&blk, true);
duke@435: }