1 /*
2 * Copyright (c) 2002, 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 */
24
25 #include "precompiled.hpp"
26 #include "gc_implementation/parallelScavenge/cardTableExtension.hpp"
27 #include "gc_implementation/parallelScavenge/gcTaskManager.hpp"
28 #include "gc_implementation/parallelScavenge/generationSizer.hpp"
29 #include "gc_implementation/parallelScavenge/parallelScavengeHeap.hpp"
30 #include "gc_implementation/parallelScavenge/psAdaptiveSizePolicy.hpp"
31 #include "gc_implementation/parallelScavenge/psMarkSweep.hpp"
32 #include "gc_implementation/parallelScavenge/psParallelCompact.hpp"
33 #include "gc_implementation/parallelScavenge/psScavenge.inline.hpp"
34 #include "gc_implementation/parallelScavenge/psTasks.hpp"
35 #include "gc_implementation/shared/isGCActiveMark.hpp"
36 #include "gc_implementation/shared/spaceDecorator.hpp"
37 #include "gc_interface/gcCause.hpp"
38 #include "memory/collectorPolicy.hpp"
39 #include "memory/gcLocker.inline.hpp"
40 #include "memory/referencePolicy.hpp"
41 #include "memory/referenceProcessor.hpp"
42 #include "memory/resourceArea.hpp"
43 #include "oops/oop.inline.hpp"
44 #include "oops/oop.psgc.inline.hpp"
45 #include "runtime/biasedLocking.hpp"
46 #include "runtime/fprofiler.hpp"
47 #include "runtime/handles.inline.hpp"
48 #include "runtime/threadCritical.hpp"
49 #include "runtime/vmThread.hpp"
50 #include "runtime/vm_operations.hpp"
51 #include "services/memoryService.hpp"
52 #include "utilities/stack.inline.hpp"
53
54
55 HeapWord* PSScavenge::_to_space_top_before_gc = NULL;
56 int PSScavenge::_consecutive_skipped_scavenges = 0;
57 ReferenceProcessor* PSScavenge::_ref_processor = NULL;
58 CardTableExtension* PSScavenge::_card_table = NULL;
59 bool PSScavenge::_survivor_overflow = false;
60 int PSScavenge::_tenuring_threshold = 0;
61 HeapWord* PSScavenge::_young_generation_boundary = NULL;
62 elapsedTimer PSScavenge::_accumulated_time;
63 Stack<markOop> PSScavenge::_preserved_mark_stack;
64 Stack<oop> PSScavenge::_preserved_oop_stack;
65 CollectorCounters* PSScavenge::_counters = NULL;
66 bool PSScavenge::_promotion_failed = false;
67
68 // Define before use
69 class PSIsAliveClosure: public BoolObjectClosure {
70 public:
71 void do_object(oop p) {
72 assert(false, "Do not call.");
73 }
74 bool do_object_b(oop p) {
75 return (!PSScavenge::is_obj_in_young((HeapWord*) p)) || p->is_forwarded();
76 }
77 };
78
79 PSIsAliveClosure PSScavenge::_is_alive_closure;
80
81 class PSKeepAliveClosure: public OopClosure {
82 protected:
83 MutableSpace* _to_space;
84 PSPromotionManager* _promotion_manager;
85
86 public:
87 PSKeepAliveClosure(PSPromotionManager* pm) : _promotion_manager(pm) {
88 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
89 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
90 _to_space = heap->young_gen()->to_space();
91
92 assert(_promotion_manager != NULL, "Sanity");
93 }
94
95 template <class T> void do_oop_work(T* p) {
96 assert (!oopDesc::is_null(*p), "expected non-null ref");
97 assert ((oopDesc::load_decode_heap_oop_not_null(p))->is_oop(),
98 "expected an oop while scanning weak refs");
99
100 // Weak refs may be visited more than once.
101 if (PSScavenge::should_scavenge(p, _to_space)) {
102 PSScavenge::copy_and_push_safe_barrier(_promotion_manager, p);
103 }
104 }
105 virtual void do_oop(oop* p) { PSKeepAliveClosure::do_oop_work(p); }
106 virtual void do_oop(narrowOop* p) { PSKeepAliveClosure::do_oop_work(p); }
107 };
108
109 class PSEvacuateFollowersClosure: public VoidClosure {
110 private:
111 PSPromotionManager* _promotion_manager;
112 public:
113 PSEvacuateFollowersClosure(PSPromotionManager* pm) : _promotion_manager(pm) {}
114
115 virtual void do_void() {
116 assert(_promotion_manager != NULL, "Sanity");
117 _promotion_manager->drain_stacks(true);
118 guarantee(_promotion_manager->stacks_empty(),
119 "stacks should be empty at this point");
120 }
121 };
122
123 class PSPromotionFailedClosure : public ObjectClosure {
124 virtual void do_object(oop obj) {
125 if (obj->is_forwarded()) {
126 obj->init_mark();
127 }
128 }
129 };
130
131 class PSRefProcTaskProxy: public GCTask {
132 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
133 ProcessTask & _rp_task;
134 uint _work_id;
135 public:
136 PSRefProcTaskProxy(ProcessTask & rp_task, uint work_id)
137 : _rp_task(rp_task),
138 _work_id(work_id)
139 { }
140
141 private:
142 virtual char* name() { return (char *)"Process referents by policy in parallel"; }
143 virtual void do_it(GCTaskManager* manager, uint which);
144 };
145
146 void PSRefProcTaskProxy::do_it(GCTaskManager* manager, uint which)
147 {
148 PSPromotionManager* promotion_manager =
149 PSPromotionManager::gc_thread_promotion_manager(which);
150 assert(promotion_manager != NULL, "sanity check");
151 PSKeepAliveClosure keep_alive(promotion_manager);
152 PSEvacuateFollowersClosure evac_followers(promotion_manager);
153 PSIsAliveClosure is_alive;
154 _rp_task.work(_work_id, is_alive, keep_alive, evac_followers);
155 }
156
157 class PSRefEnqueueTaskProxy: public GCTask {
158 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
159 EnqueueTask& _enq_task;
160 uint _work_id;
161
162 public:
163 PSRefEnqueueTaskProxy(EnqueueTask& enq_task, uint work_id)
164 : _enq_task(enq_task),
165 _work_id(work_id)
166 { }
167
168 virtual char* name() { return (char *)"Enqueue reference objects in parallel"; }
169 virtual void do_it(GCTaskManager* manager, uint which)
170 {
171 _enq_task.work(_work_id);
172 }
173 };
174
175 class PSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
176 virtual void execute(ProcessTask& task);
177 virtual void execute(EnqueueTask& task);
178 };
179
180 void PSRefProcTaskExecutor::execute(ProcessTask& task)
181 {
182 GCTaskQueue* q = GCTaskQueue::create();
183 for(uint i=0; i<ParallelGCThreads; i++) {
184 q->enqueue(new PSRefProcTaskProxy(task, i));
185 }
186 ParallelTaskTerminator terminator(
187 ParallelScavengeHeap::gc_task_manager()->workers(),
188 (TaskQueueSetSuper*) PSPromotionManager::stack_array_depth());
189 if (task.marks_oops_alive() && ParallelGCThreads > 1) {
190 for (uint j=0; j<ParallelGCThreads; j++) {
191 q->enqueue(new StealTask(&terminator));
192 }
193 }
194 ParallelScavengeHeap::gc_task_manager()->execute_and_wait(q);
195 }
196
197
198 void PSRefProcTaskExecutor::execute(EnqueueTask& task)
199 {
200 GCTaskQueue* q = GCTaskQueue::create();
201 for(uint i=0; i<ParallelGCThreads; i++) {
202 q->enqueue(new PSRefEnqueueTaskProxy(task, i));
203 }
204 ParallelScavengeHeap::gc_task_manager()->execute_and_wait(q);
205 }
206
207 // This method contains all heap specific policy for invoking scavenge.
208 // PSScavenge::invoke_no_policy() will do nothing but attempt to
209 // scavenge. It will not clean up after failed promotions, bail out if
210 // we've exceeded policy time limits, or any other special behavior.
211 // All such policy should be placed here.
212 //
213 // Note that this method should only be called from the vm_thread while
214 // at a safepoint!
215 void PSScavenge::invoke() {
216 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
217 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
218 assert(!Universe::heap()->is_gc_active(), "not reentrant");
219
220 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
221 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
222
223 PSAdaptiveSizePolicy* policy = heap->size_policy();
224 IsGCActiveMark mark;
225
226 bool scavenge_was_done = PSScavenge::invoke_no_policy();
227
228 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
229 if (UsePerfData)
230 counters->update_full_follows_scavenge(0);
231 if (!scavenge_was_done ||
232 policy->should_full_GC(heap->old_gen()->free_in_bytes())) {
233 if (UsePerfData)
234 counters->update_full_follows_scavenge(full_follows_scavenge);
235 GCCauseSetter gccs(heap, GCCause::_adaptive_size_policy);
236 CollectorPolicy* cp = heap->collector_policy();
237 const bool clear_all_softrefs = cp->should_clear_all_soft_refs();
238
239 if (UseParallelOldGC) {
240 PSParallelCompact::invoke_no_policy(clear_all_softrefs);
241 } else {
242 PSMarkSweep::invoke_no_policy(clear_all_softrefs);
243 }
244 }
245 }
246
247 // This method contains no policy. You should probably
248 // be calling invoke() instead.
249 bool PSScavenge::invoke_no_policy() {
250 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
251 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
252
253 assert(_preserved_mark_stack.is_empty(), "should be empty");
254 assert(_preserved_oop_stack.is_empty(), "should be empty");
255
256 TimeStamp scavenge_entry;
257 TimeStamp scavenge_midpoint;
258 TimeStamp scavenge_exit;
259
260 scavenge_entry.update();
261
262 if (GC_locker::check_active_before_gc()) {
263 return false;
264 }
265
266 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
267 GCCause::Cause gc_cause = heap->gc_cause();
268 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
269
270 // Check for potential problems.
271 if (!should_attempt_scavenge()) {
272 return false;
273 }
274
275 bool promotion_failure_occurred = false;
276
277 PSYoungGen* young_gen = heap->young_gen();
278 PSOldGen* old_gen = heap->old_gen();
279 PSPermGen* perm_gen = heap->perm_gen();
280 PSAdaptiveSizePolicy* size_policy = heap->size_policy();
281 heap->increment_total_collections();
282
283 AdaptiveSizePolicyOutput(size_policy, heap->total_collections());
284
285 if ((gc_cause != GCCause::_java_lang_system_gc) ||
286 UseAdaptiveSizePolicyWithSystemGC) {
287 // Gather the feedback data for eden occupancy.
288 young_gen->eden_space()->accumulate_statistics();
289 }
290
291 if (ZapUnusedHeapArea) {
292 // Save information needed to minimize mangling
293 heap->record_gen_tops_before_GC();
294 }
295
296 if (PrintHeapAtGC) {
297 Universe::print_heap_before_gc();
298 }
299
300 assert(!NeverTenure || _tenuring_threshold == markOopDesc::max_age + 1, "Sanity");
301 assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity");
302
303 size_t prev_used = heap->used();
304 assert(promotion_failed() == false, "Sanity");
305
306 // Fill in TLABs
307 heap->accumulate_statistics_all_tlabs();
308 heap->ensure_parsability(true); // retire TLABs
309
310 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
311 HandleMark hm; // Discard invalid handles created during verification
312 gclog_or_tty->print(" VerifyBeforeGC:");
313 Universe::verify(true);
314 }
315
316 {
317 ResourceMark rm;
318 HandleMark hm;
319
320 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
321 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
322 TraceTime t1("GC", PrintGC, !PrintGCDetails, gclog_or_tty);
323 TraceCollectorStats tcs(counters());
324 TraceMemoryManagerStats tms(false /* not full GC */);
325
326 if (TraceGen0Time) accumulated_time()->start();
327
328 // Let the size policy know we're starting
329 size_policy->minor_collection_begin();
330
331 // Verify the object start arrays.
332 if (VerifyObjectStartArray &&
333 VerifyBeforeGC) {
334 old_gen->verify_object_start_array();
335 perm_gen->verify_object_start_array();
336 }
337
338 // Verify no unmarked old->young roots
339 if (VerifyRememberedSets) {
340 CardTableExtension::verify_all_young_refs_imprecise();
341 }
342
343 if (!ScavengeWithObjectsInToSpace) {
344 assert(young_gen->to_space()->is_empty(),
345 "Attempt to scavenge with live objects in to_space");
346 young_gen->to_space()->clear(SpaceDecorator::Mangle);
347 } else if (ZapUnusedHeapArea) {
348 young_gen->to_space()->mangle_unused_area();
349 }
350 save_to_space_top_before_gc();
351
352 NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
353 COMPILER2_PRESENT(DerivedPointerTable::clear());
354
355 reference_processor()->enable_discovery();
356 reference_processor()->setup_policy(false);
357
358 // We track how much was promoted to the next generation for
359 // the AdaptiveSizePolicy.
360 size_t old_gen_used_before = old_gen->used_in_bytes();
361
362 // For PrintGCDetails
363 size_t young_gen_used_before = young_gen->used_in_bytes();
364
365 // Reset our survivor overflow.
366 set_survivor_overflow(false);
367
368 // We need to save the old/perm top values before
369 // creating the promotion_manager. We pass the top
370 // values to the card_table, to prevent it from
371 // straying into the promotion labs.
372 HeapWord* old_top = old_gen->object_space()->top();
373 HeapWord* perm_top = perm_gen->object_space()->top();
374
375 // Release all previously held resources
376 gc_task_manager()->release_all_resources();
377
378 PSPromotionManager::pre_scavenge();
379
380 // We'll use the promotion manager again later.
381 PSPromotionManager* promotion_manager = PSPromotionManager::vm_thread_promotion_manager();
382 {
383 // TraceTime("Roots");
384 ParallelScavengeHeap::ParStrongRootsScope psrs;
385
386 GCTaskQueue* q = GCTaskQueue::create();
387
388 for(uint i=0; i<ParallelGCThreads; i++) {
389 q->enqueue(new OldToYoungRootsTask(old_gen, old_top, i));
390 }
391
392 q->enqueue(new SerialOldToYoungRootsTask(perm_gen, perm_top));
393
394 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::universe));
395 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jni_handles));
396 // We scan the thread roots in parallel
397 Threads::create_thread_roots_tasks(q);
398 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::object_synchronizer));
399 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::flat_profiler));
400 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::management));
401 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::system_dictionary));
402 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jvmti));
403 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::code_cache));
404
405 ParallelTaskTerminator terminator(
406 gc_task_manager()->workers(),
407 (TaskQueueSetSuper*) promotion_manager->stack_array_depth());
408 if (ParallelGCThreads>1) {
409 for (uint j=0; j<ParallelGCThreads; j++) {
410 q->enqueue(new StealTask(&terminator));
411 }
412 }
413
414 gc_task_manager()->execute_and_wait(q);
415 }
416
417 scavenge_midpoint.update();
418
419 // Process reference objects discovered during scavenge
420 {
421 reference_processor()->setup_policy(false); // not always_clear
422 PSKeepAliveClosure keep_alive(promotion_manager);
423 PSEvacuateFollowersClosure evac_followers(promotion_manager);
424 if (reference_processor()->processing_is_mt()) {
425 PSRefProcTaskExecutor task_executor;
426 reference_processor()->process_discovered_references(
427 &_is_alive_closure, &keep_alive, &evac_followers, &task_executor);
428 } else {
429 reference_processor()->process_discovered_references(
430 &_is_alive_closure, &keep_alive, &evac_followers, NULL);
431 }
432 }
433
434 // Enqueue reference objects discovered during scavenge.
435 if (reference_processor()->processing_is_mt()) {
436 PSRefProcTaskExecutor task_executor;
437 reference_processor()->enqueue_discovered_references(&task_executor);
438 } else {
439 reference_processor()->enqueue_discovered_references(NULL);
440 }
441
442 // Finally, flush the promotion_manager's labs, and deallocate its stacks.
443 PSPromotionManager::post_scavenge();
444
445 promotion_failure_occurred = promotion_failed();
446 if (promotion_failure_occurred) {
447 clean_up_failed_promotion();
448 if (PrintGC) {
449 gclog_or_tty->print("--");
450 }
451 }
452
453 // Let the size policy know we're done. Note that we count promotion
454 // failure cleanup time as part of the collection (otherwise, we're
455 // implicitly saying it's mutator time).
456 size_policy->minor_collection_end(gc_cause);
457
458 if (!promotion_failure_occurred) {
459 // Swap the survivor spaces.
460
461
462 young_gen->eden_space()->clear(SpaceDecorator::Mangle);
463 young_gen->from_space()->clear(SpaceDecorator::Mangle);
464 young_gen->swap_spaces();
465
466 size_t survived = young_gen->from_space()->used_in_bytes();
467 size_t promoted = old_gen->used_in_bytes() - old_gen_used_before;
468 size_policy->update_averages(_survivor_overflow, survived, promoted);
469
470 // A successful scavenge should restart the GC time limit count which is
471 // for full GC's.
472 size_policy->reset_gc_overhead_limit_count();
473 if (UseAdaptiveSizePolicy) {
474 // Calculate the new survivor size and tenuring threshold
475
476 if (PrintAdaptiveSizePolicy) {
477 gclog_or_tty->print("AdaptiveSizeStart: ");
478 gclog_or_tty->stamp();
479 gclog_or_tty->print_cr(" collection: %d ",
480 heap->total_collections());
481
482 if (Verbose) {
483 gclog_or_tty->print("old_gen_capacity: %d young_gen_capacity: %d"
484 " perm_gen_capacity: %d ",
485 old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes(),
486 perm_gen->capacity_in_bytes());
487 }
488 }
489
490
491 if (UsePerfData) {
492 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
493 counters->update_old_eden_size(
494 size_policy->calculated_eden_size_in_bytes());
495 counters->update_old_promo_size(
496 size_policy->calculated_promo_size_in_bytes());
497 counters->update_old_capacity(old_gen->capacity_in_bytes());
498 counters->update_young_capacity(young_gen->capacity_in_bytes());
499 counters->update_survived(survived);
500 counters->update_promoted(promoted);
501 counters->update_survivor_overflowed(_survivor_overflow);
502 }
503
504 size_t survivor_limit =
505 size_policy->max_survivor_size(young_gen->max_size());
506 _tenuring_threshold =
507 size_policy->compute_survivor_space_size_and_threshold(
508 _survivor_overflow,
509 _tenuring_threshold,
510 survivor_limit);
511
512 if (PrintTenuringDistribution) {
513 gclog_or_tty->cr();
514 gclog_or_tty->print_cr("Desired survivor size %ld bytes, new threshold %d (max %d)",
515 size_policy->calculated_survivor_size_in_bytes(),
516 _tenuring_threshold, MaxTenuringThreshold);
517 }
518
519 if (UsePerfData) {
520 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
521 counters->update_tenuring_threshold(_tenuring_threshold);
522 counters->update_survivor_size_counters();
523 }
524
525 // Do call at minor collections?
526 // Don't check if the size_policy is ready at this
527 // level. Let the size_policy check that internally.
528 if (UseAdaptiveSizePolicy &&
529 UseAdaptiveGenerationSizePolicyAtMinorCollection &&
530 ((gc_cause != GCCause::_java_lang_system_gc) ||
531 UseAdaptiveSizePolicyWithSystemGC)) {
532
533 // Calculate optimial free space amounts
534 assert(young_gen->max_size() >
535 young_gen->from_space()->capacity_in_bytes() +
536 young_gen->to_space()->capacity_in_bytes(),
537 "Sizes of space in young gen are out-of-bounds");
538 size_t max_eden_size = young_gen->max_size() -
539 young_gen->from_space()->capacity_in_bytes() -
540 young_gen->to_space()->capacity_in_bytes();
541 size_policy->compute_generation_free_space(young_gen->used_in_bytes(),
542 young_gen->eden_space()->used_in_bytes(),
543 old_gen->used_in_bytes(),
544 perm_gen->used_in_bytes(),
545 young_gen->eden_space()->capacity_in_bytes(),
546 old_gen->max_gen_size(),
547 max_eden_size,
548 false /* full gc*/,
549 gc_cause,
550 heap->collector_policy());
551
552 }
553 // Resize the young generation at every collection
554 // even if new sizes have not been calculated. This is
555 // to allow resizes that may have been inhibited by the
556 // relative location of the "to" and "from" spaces.
557
558 // Resizing the old gen at minor collects can cause increases
559 // that don't feed back to the generation sizing policy until
560 // a major collection. Don't resize the old gen here.
561
562 heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
563 size_policy->calculated_survivor_size_in_bytes());
564
565 if (PrintAdaptiveSizePolicy) {
566 gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
567 heap->total_collections());
568 }
569 }
570
571 // Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can
572 // cause the change of the heap layout. Make sure eden is reshaped if that's the case.
573 // Also update() will case adaptive NUMA chunk resizing.
574 assert(young_gen->eden_space()->is_empty(), "eden space should be empty now");
575 young_gen->eden_space()->update();
576
577 heap->gc_policy_counters()->update_counters();
578
579 heap->resize_all_tlabs();
580
581 assert(young_gen->to_space()->is_empty(), "to space should be empty now");
582 }
583
584 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
585
586 NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
587
588 // Re-verify object start arrays
589 if (VerifyObjectStartArray &&
590 VerifyAfterGC) {
591 old_gen->verify_object_start_array();
592 perm_gen->verify_object_start_array();
593 }
594
595 // Verify all old -> young cards are now precise
596 if (VerifyRememberedSets) {
597 // Precise verification will give false positives. Until this is fixed,
598 // use imprecise verification.
599 // CardTableExtension::verify_all_young_refs_precise();
600 CardTableExtension::verify_all_young_refs_imprecise();
601 }
602
603 if (TraceGen0Time) accumulated_time()->stop();
604
605 if (PrintGC) {
606 if (PrintGCDetails) {
607 // Don't print a GC timestamp here. This is after the GC so
608 // would be confusing.
609 young_gen->print_used_change(young_gen_used_before);
610 }
611 heap->print_heap_change(prev_used);
612 }
613
614 // Track memory usage and detect low memory
615 MemoryService::track_memory_usage();
616 heap->update_counters();
617 }
618
619 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
620 HandleMark hm; // Discard invalid handles created during verification
621 gclog_or_tty->print(" VerifyAfterGC:");
622 Universe::verify(false);
623 }
624
625 if (PrintHeapAtGC) {
626 Universe::print_heap_after_gc();
627 }
628
629 if (ZapUnusedHeapArea) {
630 young_gen->eden_space()->check_mangled_unused_area_complete();
631 young_gen->from_space()->check_mangled_unused_area_complete();
632 young_gen->to_space()->check_mangled_unused_area_complete();
633 }
634
635 scavenge_exit.update();
636
637 if (PrintGCTaskTimeStamps) {
638 tty->print_cr("VM-Thread " INT64_FORMAT " " INT64_FORMAT " " INT64_FORMAT,
639 scavenge_entry.ticks(), scavenge_midpoint.ticks(),
640 scavenge_exit.ticks());
641 gc_task_manager()->print_task_time_stamps();
642 }
643
644 #ifdef TRACESPINNING
645 ParallelTaskTerminator::print_termination_counts();
646 #endif
647
648 return !promotion_failure_occurred;
649 }
650
651 // This method iterates over all objects in the young generation,
652 // unforwarding markOops. It then restores any preserved mark oops,
653 // and clears the _preserved_mark_stack.
654 void PSScavenge::clean_up_failed_promotion() {
655 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
656 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
657 assert(promotion_failed(), "Sanity");
658
659 PSYoungGen* young_gen = heap->young_gen();
660
661 {
662 ResourceMark rm;
663
664 // Unforward all pointers in the young gen.
665 PSPromotionFailedClosure unforward_closure;
666 young_gen->object_iterate(&unforward_closure);
667
668 if (PrintGC && Verbose) {
669 gclog_or_tty->print_cr("Restoring %d marks", _preserved_oop_stack.size());
670 }
671
672 // Restore any saved marks.
673 while (!_preserved_oop_stack.is_empty()) {
674 oop obj = _preserved_oop_stack.pop();
675 markOop mark = _preserved_mark_stack.pop();
676 obj->set_mark(mark);
677 }
678
679 // Clear the preserved mark and oop stack caches.
680 _preserved_mark_stack.clear(true);
681 _preserved_oop_stack.clear(true);
682 _promotion_failed = false;
683 }
684
685 // Reset the PromotionFailureALot counters.
686 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
687 }
688
689 // This method is called whenever an attempt to promote an object
690 // fails. Some markOops will need preservation, some will not. Note
691 // that the entire eden is traversed after a failed promotion, with
692 // all forwarded headers replaced by the default markOop. This means
693 // it is not neccessary to preserve most markOops.
694 void PSScavenge::oop_promotion_failed(oop obj, markOop obj_mark) {
695 _promotion_failed = true;
696 if (obj_mark->must_be_preserved_for_promotion_failure(obj)) {
697 // Should use per-worker private stakcs hetre rather than
698 // locking a common pair of stacks.
699 ThreadCritical tc;
700 _preserved_oop_stack.push(obj);
701 _preserved_mark_stack.push(obj_mark);
702 }
703 }
704
705 bool PSScavenge::should_attempt_scavenge() {
706 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
707 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
708 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
709
710 if (UsePerfData) {
711 counters->update_scavenge_skipped(not_skipped);
712 }
713
714 PSYoungGen* young_gen = heap->young_gen();
715 PSOldGen* old_gen = heap->old_gen();
716
717 if (!ScavengeWithObjectsInToSpace) {
718 // Do not attempt to promote unless to_space is empty
719 if (!young_gen->to_space()->is_empty()) {
720 _consecutive_skipped_scavenges++;
721 if (UsePerfData) {
722 counters->update_scavenge_skipped(to_space_not_empty);
723 }
724 return false;
725 }
726 }
727
728 // Test to see if the scavenge will likely fail.
729 PSAdaptiveSizePolicy* policy = heap->size_policy();
730
731 // A similar test is done in the policy's should_full_GC(). If this is
732 // changed, decide if that test should also be changed.
733 size_t avg_promoted = (size_t) policy->padded_average_promoted_in_bytes();
734 size_t promotion_estimate = MIN2(avg_promoted, young_gen->used_in_bytes());
735 bool result = promotion_estimate < old_gen->free_in_bytes();
736
737 if (PrintGCDetails && Verbose) {
738 gclog_or_tty->print(result ? " do scavenge: " : " skip scavenge: ");
739 gclog_or_tty->print_cr(" average_promoted " SIZE_FORMAT
740 " padded_average_promoted " SIZE_FORMAT
741 " free in old gen " SIZE_FORMAT,
742 (size_t) policy->average_promoted_in_bytes(),
743 (size_t) policy->padded_average_promoted_in_bytes(),
744 old_gen->free_in_bytes());
745 if (young_gen->used_in_bytes() <
746 (size_t) policy->padded_average_promoted_in_bytes()) {
747 gclog_or_tty->print_cr(" padded_promoted_average is greater"
748 " than maximum promotion = " SIZE_FORMAT, young_gen->used_in_bytes());
749 }
750 }
751
752 if (result) {
753 _consecutive_skipped_scavenges = 0;
754 } else {
755 _consecutive_skipped_scavenges++;
756 if (UsePerfData) {
757 counters->update_scavenge_skipped(promoted_too_large);
758 }
759 }
760 return result;
761 }
762
763 // Used to add tasks
764 GCTaskManager* const PSScavenge::gc_task_manager() {
765 assert(ParallelScavengeHeap::gc_task_manager() != NULL,
766 "shouldn't return NULL");
767 return ParallelScavengeHeap::gc_task_manager();
768 }
769
770 void PSScavenge::initialize() {
771 // Arguments must have been parsed
772
773 if (AlwaysTenure) {
774 _tenuring_threshold = 0;
775 } else if (NeverTenure) {
776 _tenuring_threshold = markOopDesc::max_age + 1;
777 } else {
778 // We want to smooth out our startup times for the AdaptiveSizePolicy
779 _tenuring_threshold = (UseAdaptiveSizePolicy) ? InitialTenuringThreshold :
780 MaxTenuringThreshold;
781 }
782
783 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
784 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
785
786 PSYoungGen* young_gen = heap->young_gen();
787 PSOldGen* old_gen = heap->old_gen();
788 PSPermGen* perm_gen = heap->perm_gen();
789
790 // Set boundary between young_gen and old_gen
791 assert(perm_gen->reserved().end() <= old_gen->object_space()->bottom(),
792 "perm above old");
793 assert(old_gen->reserved().end() <= young_gen->eden_space()->bottom(),
794 "old above young");
795 _young_generation_boundary = young_gen->eden_space()->bottom();
796
797 // Initialize ref handling object for scavenging.
798 MemRegion mr = young_gen->reserved();
799 _ref_processor =
800 new ReferenceProcessor(mr, // span
801 ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
802 ParallelGCThreads, // mt processing degree
803 true, // mt discovery
804 ParallelGCThreads, // mt discovery degree
805 true, // atomic_discovery
806 NULL, // header provides liveness info
807 false); // next field updates do not need write barrier
808
809 // Cache the cardtable
810 BarrierSet* bs = Universe::heap()->barrier_set();
811 assert(bs->kind() == BarrierSet::CardTableModRef, "Wrong barrier set kind");
812 _card_table = (CardTableExtension*)bs;
813
814 _counters = new CollectorCounters("PSScavenge", 0);
815 }