Thu, 27 Jan 2011 16:11:27 -0800
6990754: Use native memory and reference counting to implement SymbolTable
Summary: move symbols from permgen into C heap and reference count them
Reviewed-by: never, acorn, jmasa, stefank
1 /*
2 * Copyright (c) 2001, 2010, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
25 #include "precompiled.hpp"
26 #include "classfile/symbolTable.hpp"
27 #include "classfile/systemDictionary.hpp"
28 #include "code/codeCache.hpp"
29 #include "gc_implementation/parallelScavenge/generationSizer.hpp"
30 #include "gc_implementation/parallelScavenge/parallelScavengeHeap.hpp"
31 #include "gc_implementation/parallelScavenge/psAdaptiveSizePolicy.hpp"
32 #include "gc_implementation/parallelScavenge/psMarkSweep.hpp"
33 #include "gc_implementation/parallelScavenge/psMarkSweepDecorator.hpp"
34 #include "gc_implementation/parallelScavenge/psOldGen.hpp"
35 #include "gc_implementation/parallelScavenge/psPermGen.hpp"
36 #include "gc_implementation/parallelScavenge/psScavenge.hpp"
37 #include "gc_implementation/parallelScavenge/psYoungGen.hpp"
38 #include "gc_implementation/shared/isGCActiveMark.hpp"
39 #include "gc_implementation/shared/spaceDecorator.hpp"
40 #include "gc_interface/gcCause.hpp"
41 #include "memory/gcLocker.inline.hpp"
42 #include "memory/referencePolicy.hpp"
43 #include "memory/referenceProcessor.hpp"
44 #include "oops/oop.inline.hpp"
45 #include "runtime/biasedLocking.hpp"
46 #include "runtime/fprofiler.hpp"
47 #include "runtime/safepoint.hpp"
48 #include "runtime/vmThread.hpp"
49 #include "services/management.hpp"
50 #include "services/memoryService.hpp"
51 #include "utilities/events.hpp"
52 #include "utilities/stack.inline.hpp"
54 elapsedTimer PSMarkSweep::_accumulated_time;
55 unsigned int PSMarkSweep::_total_invocations = 0;
56 jlong PSMarkSweep::_time_of_last_gc = 0;
57 CollectorCounters* PSMarkSweep::_counters = NULL;
59 void PSMarkSweep::initialize() {
60 MemRegion mr = Universe::heap()->reserved_region();
61 _ref_processor = new ReferenceProcessor(mr,
62 true, // atomic_discovery
63 false); // mt_discovery
64 _counters = new CollectorCounters("PSMarkSweep", 1);
65 }
67 // This method contains all heap specific policy for invoking mark sweep.
68 // PSMarkSweep::invoke_no_policy() will only attempt to mark-sweep-compact
69 // the heap. It will do nothing further. If we need to bail out for policy
70 // reasons, scavenge before full gc, or any other specialized behavior, it
71 // needs to be added here.
72 //
73 // Note that this method should only be called from the vm_thread while
74 // at a safepoint!
75 //
76 // Note that the all_soft_refs_clear flag in the collector policy
77 // may be true because this method can be called without intervening
78 // activity. For example when the heap space is tight and full measure
79 // are being taken to free space.
81 void PSMarkSweep::invoke(bool maximum_heap_compaction) {
82 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
83 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
84 assert(!Universe::heap()->is_gc_active(), "not reentrant");
86 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
87 GCCause::Cause gc_cause = heap->gc_cause();
88 PSAdaptiveSizePolicy* policy = heap->size_policy();
89 IsGCActiveMark mark;
91 if (ScavengeBeforeFullGC) {
92 PSScavenge::invoke_no_policy();
93 }
95 const bool clear_all_soft_refs =
96 heap->collector_policy()->should_clear_all_soft_refs();
98 int count = (maximum_heap_compaction)?1:MarkSweepAlwaysCompactCount;
99 IntFlagSetting flag_setting(MarkSweepAlwaysCompactCount, count);
100 PSMarkSweep::invoke_no_policy(clear_all_soft_refs || maximum_heap_compaction);
101 }
103 // This method contains no policy. You should probably
104 // be calling invoke() instead.
105 void PSMarkSweep::invoke_no_policy(bool clear_all_softrefs) {
106 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
107 assert(ref_processor() != NULL, "Sanity");
109 if (GC_locker::check_active_before_gc()) {
110 return;
111 }
113 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
114 GCCause::Cause gc_cause = heap->gc_cause();
115 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
116 PSAdaptiveSizePolicy* size_policy = heap->size_policy();
118 // The scope of casr should end after code that can change
119 // CollectorPolicy::_should_clear_all_soft_refs.
120 ClearedAllSoftRefs casr(clear_all_softrefs, heap->collector_policy());
122 PSYoungGen* young_gen = heap->young_gen();
123 PSOldGen* old_gen = heap->old_gen();
124 PSPermGen* perm_gen = heap->perm_gen();
126 // Increment the invocation count
127 heap->increment_total_collections(true /* full */);
129 // Save information needed to minimize mangling
130 heap->record_gen_tops_before_GC();
132 // We need to track unique mark sweep invocations as well.
133 _total_invocations++;
135 AdaptiveSizePolicyOutput(size_policy, heap->total_collections());
137 if (PrintHeapAtGC) {
138 Universe::print_heap_before_gc();
139 }
141 // Fill in TLABs
142 heap->accumulate_statistics_all_tlabs();
143 heap->ensure_parsability(true); // retire TLABs
145 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
146 HandleMark hm; // Discard invalid handles created during verification
147 gclog_or_tty->print(" VerifyBeforeGC:");
148 Universe::verify(true);
149 }
151 // Verify object start arrays
152 if (VerifyObjectStartArray &&
153 VerifyBeforeGC) {
154 old_gen->verify_object_start_array();
155 perm_gen->verify_object_start_array();
156 }
158 heap->pre_full_gc_dump();
160 // Filled in below to track the state of the young gen after the collection.
161 bool eden_empty;
162 bool survivors_empty;
163 bool young_gen_empty;
165 {
166 HandleMark hm;
167 const bool is_system_gc = gc_cause == GCCause::_java_lang_system_gc;
168 // This is useful for debugging but don't change the output the
169 // the customer sees.
170 const char* gc_cause_str = "Full GC";
171 if (is_system_gc && PrintGCDetails) {
172 gc_cause_str = "Full GC (System)";
173 }
174 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
175 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
176 TraceTime t1(gc_cause_str, PrintGC, !PrintGCDetails, gclog_or_tty);
177 TraceCollectorStats tcs(counters());
178 TraceMemoryManagerStats tms(true /* Full GC */);
180 if (TraceGen1Time) accumulated_time()->start();
182 // Let the size policy know we're starting
183 size_policy->major_collection_begin();
185 // When collecting the permanent generation methodOops may be moving,
186 // so we either have to flush all bcp data or convert it into bci.
187 CodeCache::gc_prologue();
188 Threads::gc_prologue();
189 BiasedLocking::preserve_marks();
191 // Capture heap size before collection for printing.
192 size_t prev_used = heap->used();
194 // Capture perm gen size before collection for sizing.
195 size_t perm_gen_prev_used = perm_gen->used_in_bytes();
197 // For PrintGCDetails
198 size_t old_gen_prev_used = old_gen->used_in_bytes();
199 size_t young_gen_prev_used = young_gen->used_in_bytes();
201 allocate_stacks();
203 NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
204 COMPILER2_PRESENT(DerivedPointerTable::clear());
206 ref_processor()->enable_discovery();
207 ref_processor()->setup_policy(clear_all_softrefs);
209 mark_sweep_phase1(clear_all_softrefs);
211 mark_sweep_phase2();
213 // Don't add any more derived pointers during phase3
214 COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity"));
215 COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
217 mark_sweep_phase3();
219 mark_sweep_phase4();
221 restore_marks();
223 deallocate_stacks();
225 if (ZapUnusedHeapArea) {
226 // Do a complete mangle (top to end) because the usage for
227 // scratch does not maintain a top pointer.
228 young_gen->to_space()->mangle_unused_area_complete();
229 }
231 eden_empty = young_gen->eden_space()->is_empty();
232 if (!eden_empty) {
233 eden_empty = absorb_live_data_from_eden(size_policy, young_gen, old_gen);
234 }
236 // Update heap occupancy information which is used as
237 // input to soft ref clearing policy at the next gc.
238 Universe::update_heap_info_at_gc();
240 survivors_empty = young_gen->from_space()->is_empty() &&
241 young_gen->to_space()->is_empty();
242 young_gen_empty = eden_empty && survivors_empty;
244 BarrierSet* bs = heap->barrier_set();
245 if (bs->is_a(BarrierSet::ModRef)) {
246 ModRefBarrierSet* modBS = (ModRefBarrierSet*)bs;
247 MemRegion old_mr = heap->old_gen()->reserved();
248 MemRegion perm_mr = heap->perm_gen()->reserved();
249 assert(perm_mr.end() <= old_mr.start(), "Generations out of order");
251 if (young_gen_empty) {
252 modBS->clear(MemRegion(perm_mr.start(), old_mr.end()));
253 } else {
254 modBS->invalidate(MemRegion(perm_mr.start(), old_mr.end()));
255 }
256 }
258 BiasedLocking::restore_marks();
259 Threads::gc_epilogue();
260 CodeCache::gc_epilogue();
261 JvmtiExport::gc_epilogue();
263 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
265 ref_processor()->enqueue_discovered_references(NULL);
267 // Update time of last GC
268 reset_millis_since_last_gc();
270 // Let the size policy know we're done
271 size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause);
273 if (UseAdaptiveSizePolicy) {
275 if (PrintAdaptiveSizePolicy) {
276 gclog_or_tty->print("AdaptiveSizeStart: ");
277 gclog_or_tty->stamp();
278 gclog_or_tty->print_cr(" collection: %d ",
279 heap->total_collections());
280 if (Verbose) {
281 gclog_or_tty->print("old_gen_capacity: %d young_gen_capacity: %d"
282 " perm_gen_capacity: %d ",
283 old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes(),
284 perm_gen->capacity_in_bytes());
285 }
286 }
288 // Don't check if the size_policy is ready here. Let
289 // the size_policy check that internally.
290 if (UseAdaptiveGenerationSizePolicyAtMajorCollection &&
291 ((gc_cause != GCCause::_java_lang_system_gc) ||
292 UseAdaptiveSizePolicyWithSystemGC)) {
293 // Calculate optimal free space amounts
294 assert(young_gen->max_size() >
295 young_gen->from_space()->capacity_in_bytes() +
296 young_gen->to_space()->capacity_in_bytes(),
297 "Sizes of space in young gen are out-of-bounds");
298 size_t max_eden_size = young_gen->max_size() -
299 young_gen->from_space()->capacity_in_bytes() -
300 young_gen->to_space()->capacity_in_bytes();
301 size_policy->compute_generation_free_space(young_gen->used_in_bytes(),
302 young_gen->eden_space()->used_in_bytes(),
303 old_gen->used_in_bytes(),
304 perm_gen->used_in_bytes(),
305 young_gen->eden_space()->capacity_in_bytes(),
306 old_gen->max_gen_size(),
307 max_eden_size,
308 true /* full gc*/,
309 gc_cause,
310 heap->collector_policy());
312 heap->resize_old_gen(size_policy->calculated_old_free_size_in_bytes());
314 // Don't resize the young generation at an major collection. A
315 // desired young generation size may have been calculated but
316 // resizing the young generation complicates the code because the
317 // resizing of the old generation may have moved the boundary
318 // between the young generation and the old generation. Let the
319 // young generation resizing happen at the minor collections.
320 }
321 if (PrintAdaptiveSizePolicy) {
322 gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
323 heap->total_collections());
324 }
325 }
327 if (UsePerfData) {
328 heap->gc_policy_counters()->update_counters();
329 heap->gc_policy_counters()->update_old_capacity(
330 old_gen->capacity_in_bytes());
331 heap->gc_policy_counters()->update_young_capacity(
332 young_gen->capacity_in_bytes());
333 }
335 heap->resize_all_tlabs();
337 // We collected the perm gen, so we'll resize it here.
338 perm_gen->compute_new_size(perm_gen_prev_used);
340 if (TraceGen1Time) accumulated_time()->stop();
342 if (PrintGC) {
343 if (PrintGCDetails) {
344 // Don't print a GC timestamp here. This is after the GC so
345 // would be confusing.
346 young_gen->print_used_change(young_gen_prev_used);
347 old_gen->print_used_change(old_gen_prev_used);
348 }
349 heap->print_heap_change(prev_used);
350 // Do perm gen after heap becase prev_used does
351 // not include the perm gen (done this way in the other
352 // collectors).
353 if (PrintGCDetails) {
354 perm_gen->print_used_change(perm_gen_prev_used);
355 }
356 }
358 // Track memory usage and detect low memory
359 MemoryService::track_memory_usage();
360 heap->update_counters();
361 }
363 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
364 HandleMark hm; // Discard invalid handles created during verification
365 gclog_or_tty->print(" VerifyAfterGC:");
366 Universe::verify(false);
367 }
369 // Re-verify object start arrays
370 if (VerifyObjectStartArray &&
371 VerifyAfterGC) {
372 old_gen->verify_object_start_array();
373 perm_gen->verify_object_start_array();
374 }
376 if (ZapUnusedHeapArea) {
377 old_gen->object_space()->check_mangled_unused_area_complete();
378 perm_gen->object_space()->check_mangled_unused_area_complete();
379 }
381 NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
383 if (PrintHeapAtGC) {
384 Universe::print_heap_after_gc();
385 }
387 heap->post_full_gc_dump();
389 #ifdef TRACESPINNING
390 ParallelTaskTerminator::print_termination_counts();
391 #endif
392 }
394 bool PSMarkSweep::absorb_live_data_from_eden(PSAdaptiveSizePolicy* size_policy,
395 PSYoungGen* young_gen,
396 PSOldGen* old_gen) {
397 MutableSpace* const eden_space = young_gen->eden_space();
398 assert(!eden_space->is_empty(), "eden must be non-empty");
399 assert(young_gen->virtual_space()->alignment() ==
400 old_gen->virtual_space()->alignment(), "alignments do not match");
402 if (!(UseAdaptiveSizePolicy && UseAdaptiveGCBoundary)) {
403 return false;
404 }
406 // Both generations must be completely committed.
407 if (young_gen->virtual_space()->uncommitted_size() != 0) {
408 return false;
409 }
410 if (old_gen->virtual_space()->uncommitted_size() != 0) {
411 return false;
412 }
414 // Figure out how much to take from eden. Include the average amount promoted
415 // in the total; otherwise the next young gen GC will simply bail out to a
416 // full GC.
417 const size_t alignment = old_gen->virtual_space()->alignment();
418 const size_t eden_used = eden_space->used_in_bytes();
419 const size_t promoted = (size_t)size_policy->avg_promoted()->padded_average();
420 const size_t absorb_size = align_size_up(eden_used + promoted, alignment);
421 const size_t eden_capacity = eden_space->capacity_in_bytes();
423 if (absorb_size >= eden_capacity) {
424 return false; // Must leave some space in eden.
425 }
427 const size_t new_young_size = young_gen->capacity_in_bytes() - absorb_size;
428 if (new_young_size < young_gen->min_gen_size()) {
429 return false; // Respect young gen minimum size.
430 }
432 if (TraceAdaptiveGCBoundary && Verbose) {
433 gclog_or_tty->print(" absorbing " SIZE_FORMAT "K: "
434 "eden " SIZE_FORMAT "K->" SIZE_FORMAT "K "
435 "from " SIZE_FORMAT "K, to " SIZE_FORMAT "K "
436 "young_gen " SIZE_FORMAT "K->" SIZE_FORMAT "K ",
437 absorb_size / K,
438 eden_capacity / K, (eden_capacity - absorb_size) / K,
439 young_gen->from_space()->used_in_bytes() / K,
440 young_gen->to_space()->used_in_bytes() / K,
441 young_gen->capacity_in_bytes() / K, new_young_size / K);
442 }
444 // Fill the unused part of the old gen.
445 MutableSpace* const old_space = old_gen->object_space();
446 HeapWord* const unused_start = old_space->top();
447 size_t const unused_words = pointer_delta(old_space->end(), unused_start);
449 if (unused_words > 0) {
450 if (unused_words < CollectedHeap::min_fill_size()) {
451 return false; // If the old gen cannot be filled, must give up.
452 }
453 CollectedHeap::fill_with_objects(unused_start, unused_words);
454 }
456 // Take the live data from eden and set both top and end in the old gen to
457 // eden top. (Need to set end because reset_after_change() mangles the region
458 // from end to virtual_space->high() in debug builds).
459 HeapWord* const new_top = eden_space->top();
460 old_gen->virtual_space()->expand_into(young_gen->virtual_space(),
461 absorb_size);
462 young_gen->reset_after_change();
463 old_space->set_top(new_top);
464 old_space->set_end(new_top);
465 old_gen->reset_after_change();
467 // Update the object start array for the filler object and the data from eden.
468 ObjectStartArray* const start_array = old_gen->start_array();
469 for (HeapWord* p = unused_start; p < new_top; p += oop(p)->size()) {
470 start_array->allocate_block(p);
471 }
473 // Could update the promoted average here, but it is not typically updated at
474 // full GCs and the value to use is unclear. Something like
475 //
476 // cur_promoted_avg + absorb_size / number_of_scavenges_since_last_full_gc.
478 size_policy->set_bytes_absorbed_from_eden(absorb_size);
479 return true;
480 }
482 void PSMarkSweep::allocate_stacks() {
483 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
484 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
486 PSYoungGen* young_gen = heap->young_gen();
488 MutableSpace* to_space = young_gen->to_space();
489 _preserved_marks = (PreservedMark*)to_space->top();
490 _preserved_count = 0;
492 // We want to calculate the size in bytes first.
493 _preserved_count_max = pointer_delta(to_space->end(), to_space->top(), sizeof(jbyte));
494 // Now divide by the size of a PreservedMark
495 _preserved_count_max /= sizeof(PreservedMark);
496 }
499 void PSMarkSweep::deallocate_stacks() {
500 _preserved_mark_stack.clear(true);
501 _preserved_oop_stack.clear(true);
502 _marking_stack.clear();
503 _objarray_stack.clear(true);
504 _revisit_klass_stack.clear(true);
505 _revisit_mdo_stack.clear(true);
506 }
508 void PSMarkSweep::mark_sweep_phase1(bool clear_all_softrefs) {
509 // Recursively traverse all live objects and mark them
510 EventMark m("1 mark object");
511 TraceTime tm("phase 1", PrintGCDetails && Verbose, true, gclog_or_tty);
512 trace(" 1");
514 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
515 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
517 // General strong roots.
518 {
519 ParallelScavengeHeap::ParStrongRootsScope psrs;
520 Universe::oops_do(mark_and_push_closure());
521 ReferenceProcessor::oops_do(mark_and_push_closure());
522 JNIHandles::oops_do(mark_and_push_closure()); // Global (strong) JNI handles
523 CodeBlobToOopClosure each_active_code_blob(mark_and_push_closure(), /*do_marking=*/ true);
524 Threads::oops_do(mark_and_push_closure(), &each_active_code_blob);
525 ObjectSynchronizer::oops_do(mark_and_push_closure());
526 FlatProfiler::oops_do(mark_and_push_closure());
527 Management::oops_do(mark_and_push_closure());
528 JvmtiExport::oops_do(mark_and_push_closure());
529 SystemDictionary::always_strong_oops_do(mark_and_push_closure());
530 // Do not treat nmethods as strong roots for mark/sweep, since we can unload them.
531 //CodeCache::scavenge_root_nmethods_do(CodeBlobToOopClosure(mark_and_push_closure()));
532 }
534 // Flush marking stack.
535 follow_stack();
537 // Process reference objects found during marking
538 {
539 ref_processor()->setup_policy(clear_all_softrefs);
540 ref_processor()->process_discovered_references(
541 is_alive_closure(), mark_and_push_closure(), follow_stack_closure(), NULL);
542 }
544 // Follow system dictionary roots and unload classes
545 bool purged_class = SystemDictionary::do_unloading(is_alive_closure());
547 // Follow code cache roots
548 CodeCache::do_unloading(is_alive_closure(), mark_and_push_closure(),
549 purged_class);
550 follow_stack(); // Flush marking stack
552 // Update subklass/sibling/implementor links of live klasses
553 follow_weak_klass_links();
554 assert(_marking_stack.is_empty(), "just drained");
556 // Visit memoized mdo's and clear unmarked weak refs
557 follow_mdo_weak_refs();
558 assert(_marking_stack.is_empty(), "just drained");
560 // Visit interned string tables and delete unmarked oops
561 StringTable::unlink(is_alive_closure());
562 // Clean up unreferenced symbols in symbol table.
563 SymbolTable::unlink();
565 assert(_marking_stack.is_empty(), "stack should be empty by now");
566 }
569 void PSMarkSweep::mark_sweep_phase2() {
570 EventMark m("2 compute new addresses");
571 TraceTime tm("phase 2", PrintGCDetails && Verbose, true, gclog_or_tty);
572 trace("2");
574 // Now all live objects are marked, compute the new object addresses.
576 // It is imperative that we traverse perm_gen LAST. If dead space is
577 // allowed a range of dead object may get overwritten by a dead int
578 // array. If perm_gen is not traversed last a klassOop may get
579 // overwritten. This is fine since it is dead, but if the class has dead
580 // instances we have to skip them, and in order to find their size we
581 // need the klassOop!
582 //
583 // It is not required that we traverse spaces in the same order in
584 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
585 // tracking expects us to do so. See comment under phase4.
587 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
588 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
590 PSOldGen* old_gen = heap->old_gen();
591 PSPermGen* perm_gen = heap->perm_gen();
593 // Begin compacting into the old gen
594 PSMarkSweepDecorator::set_destination_decorator_tenured();
596 // This will also compact the young gen spaces.
597 old_gen->precompact();
599 // Compact the perm gen into the perm gen
600 PSMarkSweepDecorator::set_destination_decorator_perm_gen();
602 perm_gen->precompact();
603 }
605 // This should be moved to the shared markSweep code!
606 class PSAlwaysTrueClosure: public BoolObjectClosure {
607 public:
608 void do_object(oop p) { ShouldNotReachHere(); }
609 bool do_object_b(oop p) { return true; }
610 };
611 static PSAlwaysTrueClosure always_true;
613 void PSMarkSweep::mark_sweep_phase3() {
614 // Adjust the pointers to reflect the new locations
615 EventMark m("3 adjust pointers");
616 TraceTime tm("phase 3", PrintGCDetails && Verbose, true, gclog_or_tty);
617 trace("3");
619 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
620 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
622 PSYoungGen* young_gen = heap->young_gen();
623 PSOldGen* old_gen = heap->old_gen();
624 PSPermGen* perm_gen = heap->perm_gen();
626 // General strong roots.
627 Universe::oops_do(adjust_root_pointer_closure());
628 ReferenceProcessor::oops_do(adjust_root_pointer_closure());
629 JNIHandles::oops_do(adjust_root_pointer_closure()); // Global (strong) JNI handles
630 Threads::oops_do(adjust_root_pointer_closure(), NULL);
631 ObjectSynchronizer::oops_do(adjust_root_pointer_closure());
632 FlatProfiler::oops_do(adjust_root_pointer_closure());
633 Management::oops_do(adjust_root_pointer_closure());
634 JvmtiExport::oops_do(adjust_root_pointer_closure());
635 // SO_AllClasses
636 SystemDictionary::oops_do(adjust_root_pointer_closure());
637 //CodeCache::scavenge_root_nmethods_oops_do(adjust_root_pointer_closure());
639 // Now adjust pointers in remaining weak roots. (All of which should
640 // have been cleared if they pointed to non-surviving objects.)
641 // Global (weak) JNI handles
642 JNIHandles::weak_oops_do(&always_true, adjust_root_pointer_closure());
644 CodeCache::oops_do(adjust_pointer_closure());
645 StringTable::oops_do(adjust_root_pointer_closure());
646 ref_processor()->weak_oops_do(adjust_root_pointer_closure());
647 PSScavenge::reference_processor()->weak_oops_do(adjust_root_pointer_closure());
649 adjust_marks();
651 young_gen->adjust_pointers();
652 old_gen->adjust_pointers();
653 perm_gen->adjust_pointers();
654 }
656 void PSMarkSweep::mark_sweep_phase4() {
657 EventMark m("4 compact heap");
658 TraceTime tm("phase 4", PrintGCDetails && Verbose, true, gclog_or_tty);
659 trace("4");
661 // All pointers are now adjusted, move objects accordingly
663 // It is imperative that we traverse perm_gen first in phase4. All
664 // classes must be allocated earlier than their instances, and traversing
665 // perm_gen first makes sure that all klassOops have moved to their new
666 // location before any instance does a dispatch through it's klass!
667 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
668 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
670 PSYoungGen* young_gen = heap->young_gen();
671 PSOldGen* old_gen = heap->old_gen();
672 PSPermGen* perm_gen = heap->perm_gen();
674 perm_gen->compact();
675 old_gen->compact();
676 young_gen->compact();
677 }
679 jlong PSMarkSweep::millis_since_last_gc() {
680 jlong ret_val = os::javaTimeMillis() - _time_of_last_gc;
681 // XXX See note in genCollectedHeap::millis_since_last_gc().
682 if (ret_val < 0) {
683 NOT_PRODUCT(warning("time warp: %d", ret_val);)
684 return 0;
685 }
686 return ret_val;
687 }
689 void PSMarkSweep::reset_millis_since_last_gc() {
690 _time_of_last_gc = os::javaTimeMillis();
691 }