1 /*
2 * Copyright (c) 2002, 2013, 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 "classfile/symbolTable.hpp"
27 #include "code/codeCache.hpp"
28 #include "gc_implementation/parallelScavenge/cardTableExtension.hpp"
29 #include "gc_implementation/parallelScavenge/gcTaskManager.hpp"
30 #include "gc_implementation/parallelScavenge/generationSizer.hpp"
31 #include "gc_implementation/parallelScavenge/parallelScavengeHeap.hpp"
32 #include "gc_implementation/parallelScavenge/psAdaptiveSizePolicy.hpp"
33 #include "gc_implementation/parallelScavenge/psMarkSweep.hpp"
34 #include "gc_implementation/parallelScavenge/psParallelCompact.hpp"
35 #include "gc_implementation/parallelScavenge/psScavenge.inline.hpp"
36 #include "gc_implementation/parallelScavenge/psTasks.hpp"
37 #include "gc_implementation/shared/isGCActiveMark.hpp"
38 #include "gc_implementation/shared/spaceDecorator.hpp"
39 #include "gc_interface/gcCause.hpp"
40 #include "memory/collectorPolicy.hpp"
41 #include "memory/gcLocker.inline.hpp"
42 #include "memory/referencePolicy.hpp"
43 #include "memory/referenceProcessor.hpp"
44 #include "memory/resourceArea.hpp"
45 #include "oops/oop.inline.hpp"
46 #include "oops/oop.psgc.inline.hpp"
47 #include "runtime/biasedLocking.hpp"
48 #include "runtime/fprofiler.hpp"
49 #include "runtime/handles.inline.hpp"
50 #include "runtime/threadCritical.hpp"
51 #include "runtime/vmThread.hpp"
52 #include "runtime/vm_operations.hpp"
53 #include "services/memoryService.hpp"
54 #include "utilities/stack.inline.hpp"
55
56
57 HeapWord* PSScavenge::_to_space_top_before_gc = NULL;
58 int PSScavenge::_consecutive_skipped_scavenges = 0;
59 ReferenceProcessor* PSScavenge::_ref_processor = NULL;
60 CardTableExtension* PSScavenge::_card_table = NULL;
61 bool PSScavenge::_survivor_overflow = false;
62 uint PSScavenge::_tenuring_threshold = 0;
63 HeapWord* PSScavenge::_young_generation_boundary = NULL;
64 elapsedTimer PSScavenge::_accumulated_time;
65 Stack<markOop, mtGC> PSScavenge::_preserved_mark_stack;
66 Stack<oop, mtGC> PSScavenge::_preserved_oop_stack;
67 CollectorCounters* PSScavenge::_counters = NULL;
68 bool PSScavenge::_promotion_failed = false;
69
70 // Define before use
71 class PSIsAliveClosure: public BoolObjectClosure {
72 public:
73 bool do_object_b(oop p) {
74 return (!PSScavenge::is_obj_in_young((HeapWord*) p)) || p->is_forwarded();
75 }
76 };
77
78 PSIsAliveClosure PSScavenge::_is_alive_closure;
79
80 class PSKeepAliveClosure: public OopClosure {
81 protected:
82 MutableSpace* _to_space;
83 PSPromotionManager* _promotion_manager;
84
85 public:
86 PSKeepAliveClosure(PSPromotionManager* pm) : _promotion_manager(pm) {
87 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
88 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
89 _to_space = heap->young_gen()->to_space();
90
91 assert(_promotion_manager != NULL, "Sanity");
92 }
93
94 template <class T> void do_oop_work(T* p) {
95 assert (!oopDesc::is_null(*p), "expected non-null ref");
96 assert ((oopDesc::load_decode_heap_oop_not_null(p))->is_oop(),
97 "expected an oop while scanning weak refs");
98
99 // Weak refs may be visited more than once.
100 if (PSScavenge::should_scavenge(p, _to_space)) {
101 PSScavenge::copy_and_push_safe_barrier<T, /*promote_immediately=*/false>(_promotion_manager, p);
102 }
103 }
104 virtual void do_oop(oop* p) { PSKeepAliveClosure::do_oop_work(p); }
105 virtual void do_oop(narrowOop* p) { PSKeepAliveClosure::do_oop_work(p); }
106 };
107
108 class PSEvacuateFollowersClosure: public VoidClosure {
109 private:
110 PSPromotionManager* _promotion_manager;
111 public:
112 PSEvacuateFollowersClosure(PSPromotionManager* pm) : _promotion_manager(pm) {}
113
114 virtual void do_void() {
115 assert(_promotion_manager != NULL, "Sanity");
116 _promotion_manager->drain_stacks(true);
117 guarantee(_promotion_manager->stacks_empty(),
118 "stacks should be empty at this point");
119 }
120 };
121
122 class PSPromotionFailedClosure : public ObjectClosure {
123 virtual void do_object(oop obj) {
124 if (obj->is_forwarded()) {
125 obj->init_mark();
126 }
127 }
128 };
129
130 class PSRefProcTaskProxy: public GCTask {
131 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
132 ProcessTask & _rp_task;
133 uint _work_id;
134 public:
135 PSRefProcTaskProxy(ProcessTask & rp_task, uint work_id)
136 : _rp_task(rp_task),
137 _work_id(work_id)
138 { }
139
140 private:
141 virtual char* name() { return (char *)"Process referents by policy in parallel"; }
142 virtual void do_it(GCTaskManager* manager, uint which);
143 };
144
145 void PSRefProcTaskProxy::do_it(GCTaskManager* manager, uint which)
146 {
147 PSPromotionManager* promotion_manager =
148 PSPromotionManager::gc_thread_promotion_manager(which);
149 assert(promotion_manager != NULL, "sanity check");
150 PSKeepAliveClosure keep_alive(promotion_manager);
151 PSEvacuateFollowersClosure evac_followers(promotion_manager);
152 PSIsAliveClosure is_alive;
153 _rp_task.work(_work_id, is_alive, keep_alive, evac_followers);
154 }
155
156 class PSRefEnqueueTaskProxy: public GCTask {
157 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
158 EnqueueTask& _enq_task;
159 uint _work_id;
160
161 public:
162 PSRefEnqueueTaskProxy(EnqueueTask& enq_task, uint work_id)
163 : _enq_task(enq_task),
164 _work_id(work_id)
165 { }
166
167 virtual char* name() { return (char *)"Enqueue reference objects in parallel"; }
168 virtual void do_it(GCTaskManager* manager, uint which)
169 {
170 _enq_task.work(_work_id);
171 }
172 };
173
174 class PSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
175 virtual void execute(ProcessTask& task);
176 virtual void execute(EnqueueTask& task);
177 };
178
179 void PSRefProcTaskExecutor::execute(ProcessTask& task)
180 {
181 GCTaskQueue* q = GCTaskQueue::create();
182 GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager();
183 for(uint i=0; i < manager->active_workers(); i++) {
184 q->enqueue(new PSRefProcTaskProxy(task, i));
185 }
186 ParallelTaskTerminator terminator(manager->active_workers(),
187 (TaskQueueSetSuper*) PSPromotionManager::stack_array_depth());
188 if (task.marks_oops_alive() && manager->active_workers() > 1) {
189 for (uint j = 0; j < manager->active_workers(); j++) {
190 q->enqueue(new StealTask(&terminator));
191 }
192 }
193 manager->execute_and_wait(q);
194 }
195
196
197 void PSRefProcTaskExecutor::execute(EnqueueTask& task)
198 {
199 GCTaskQueue* q = GCTaskQueue::create();
200 GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager();
201 for(uint i=0; i < manager->active_workers(); i++) {
202 q->enqueue(new PSRefEnqueueTaskProxy(task, i));
203 }
204 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 bool 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* const heap = (ParallelScavengeHeap*)Universe::heap();
221 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
222
223 PSAdaptiveSizePolicy* policy = heap->size_policy();
224 IsGCActiveMark mark;
225
226 const bool scavenge_done = PSScavenge::invoke_no_policy();
227 const bool need_full_gc = !scavenge_done ||
228 policy->should_full_GC(heap->old_gen()->free_in_bytes());
229 bool full_gc_done = false;
230
231 if (UsePerfData) {
232 PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
233 const int ffs_val = need_full_gc ? full_follows_scavenge : not_skipped;
234 counters->update_full_follows_scavenge(ffs_val);
235 }
236
237 if (need_full_gc) {
238 GCCauseSetter gccs(heap, GCCause::_adaptive_size_policy);
239 CollectorPolicy* cp = heap->collector_policy();
240 const bool clear_all_softrefs = cp->should_clear_all_soft_refs();
241
242 if (UseParallelOldGC) {
243 full_gc_done = PSParallelCompact::invoke_no_policy(clear_all_softrefs);
244 } else {
245 full_gc_done = PSMarkSweep::invoke_no_policy(clear_all_softrefs);
246 }
247 }
248
249 return full_gc_done;
250 }
251
252 // This method contains no policy. You should probably
253 // be calling invoke() instead.
254 bool PSScavenge::invoke_no_policy() {
255 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
256 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
257
258 assert(_preserved_mark_stack.is_empty(), "should be empty");
259 assert(_preserved_oop_stack.is_empty(), "should be empty");
260
261 TimeStamp scavenge_entry;
262 TimeStamp scavenge_midpoint;
263 TimeStamp scavenge_exit;
264
265 scavenge_entry.update();
266
267 if (GC_locker::check_active_before_gc()) {
268 return false;
269 }
270
271 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
272 GCCause::Cause gc_cause = heap->gc_cause();
273 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
274
275 // Check for potential problems.
276 if (!should_attempt_scavenge()) {
277 return false;
278 }
279
280 bool promotion_failure_occurred = false;
281
282 PSYoungGen* young_gen = heap->young_gen();
283 PSOldGen* old_gen = heap->old_gen();
284 PSAdaptiveSizePolicy* size_policy = heap->size_policy();
285 heap->increment_total_collections();
286
287 AdaptiveSizePolicyOutput(size_policy, heap->total_collections());
288
289 if ((gc_cause != GCCause::_java_lang_system_gc) ||
290 UseAdaptiveSizePolicyWithSystemGC) {
291 // Gather the feedback data for eden occupancy.
292 young_gen->eden_space()->accumulate_statistics();
293 }
294
295 if (ZapUnusedHeapArea) {
296 // Save information needed to minimize mangling
297 heap->record_gen_tops_before_GC();
298 }
299
300 heap->print_heap_before_gc();
301
302 assert(!NeverTenure || _tenuring_threshold == markOopDesc::max_age + 1, "Sanity");
303 assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity");
304
305 size_t prev_used = heap->used();
306 assert(promotion_failed() == false, "Sanity");
307
308 // Fill in TLABs
309 heap->accumulate_statistics_all_tlabs();
310 heap->ensure_parsability(true); // retire TLABs
311
312 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
313 HandleMark hm; // Discard invalid handles created during verification
314 Universe::verify(" VerifyBeforeGC:");
315 }
316
317 {
318 ResourceMark rm;
319 HandleMark hm;
320
321 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
322 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
323 TraceTime t1(GCCauseString("GC", gc_cause), PrintGC, !PrintGCDetails, gclog_or_tty);
324 TraceCollectorStats tcs(counters());
325 TraceMemoryManagerStats tms(false /* not full GC */,gc_cause);
326
327 if (TraceGen0Time) accumulated_time()->start();
328
329 // Let the size policy know we're starting
330 size_policy->minor_collection_begin();
331
332 // Verify the object start arrays.
333 if (VerifyObjectStartArray &&
334 VerifyBeforeGC) {
335 old_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 COMPILER2_PRESENT(DerivedPointerTable::clear());
353
354 reference_processor()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
355 reference_processor()->setup_policy(false);
356
357 // We track how much was promoted to the next generation for
358 // the AdaptiveSizePolicy.
359 size_t old_gen_used_before = old_gen->used_in_bytes();
360
361 // For PrintGCDetails
362 size_t young_gen_used_before = young_gen->used_in_bytes();
363
364 // Reset our survivor overflow.
365 set_survivor_overflow(false);
366
367 // We need to save the old top values before
368 // creating the promotion_manager. We pass the top
369 // values to the card_table, to prevent it from
370 // straying into the promotion labs.
371 HeapWord* old_top = old_gen->object_space()->top();
372
373 // Release all previously held resources
374 gc_task_manager()->release_all_resources();
375
376 // Set the number of GC threads to be used in this collection
377 gc_task_manager()->set_active_gang();
378 gc_task_manager()->task_idle_workers();
379 // Get the active number of workers here and use that value
380 // throughout the methods.
381 uint active_workers = gc_task_manager()->active_workers();
382 heap->set_par_threads(active_workers);
383
384 PSPromotionManager::pre_scavenge();
385
386 // We'll use the promotion manager again later.
387 PSPromotionManager* promotion_manager = PSPromotionManager::vm_thread_promotion_manager();
388 {
389 // TraceTime("Roots");
390 ParallelScavengeHeap::ParStrongRootsScope psrs;
391
392 GCTaskQueue* q = GCTaskQueue::create();
393
394 if (!old_gen->object_space()->is_empty()) {
395 // There are only old-to-young pointers if there are objects
396 // in the old gen.
397 uint stripe_total = active_workers;
398 for(uint i=0; i < stripe_total; i++) {
399 q->enqueue(new OldToYoungRootsTask(old_gen, old_top, i, stripe_total));
400 }
401 }
402
403 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::universe));
404 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jni_handles));
405 // We scan the thread roots in parallel
406 Threads::create_thread_roots_tasks(q);
407 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::object_synchronizer));
408 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::flat_profiler));
409 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::management));
410 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::system_dictionary));
411 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jvmti));
412 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::code_cache));
413
414 ParallelTaskTerminator terminator(
415 active_workers,
416 (TaskQueueSetSuper*) promotion_manager->stack_array_depth());
417 if (active_workers > 1) {
418 for (uint j = 0; j < active_workers; j++) {
419 q->enqueue(new StealTask(&terminator));
420 }
421 }
422
423 gc_task_manager()->execute_and_wait(q);
424 }
425
426 scavenge_midpoint.update();
427
428 // Process reference objects discovered during scavenge
429 {
430 reference_processor()->setup_policy(false); // not always_clear
431 reference_processor()->set_active_mt_degree(active_workers);
432 PSKeepAliveClosure keep_alive(promotion_manager);
433 PSEvacuateFollowersClosure evac_followers(promotion_manager);
434 if (reference_processor()->processing_is_mt()) {
435 PSRefProcTaskExecutor task_executor;
436 reference_processor()->process_discovered_references(
437 &_is_alive_closure, &keep_alive, &evac_followers, &task_executor);
438 } else {
439 reference_processor()->process_discovered_references(
440 &_is_alive_closure, &keep_alive, &evac_followers, NULL);
441 }
442 }
443
444 // Enqueue reference objects discovered during scavenge.
445 if (reference_processor()->processing_is_mt()) {
446 PSRefProcTaskExecutor task_executor;
447 reference_processor()->enqueue_discovered_references(&task_executor);
448 } else {
449 reference_processor()->enqueue_discovered_references(NULL);
450 }
451
452 // Unlink any dead interned Strings
453 StringTable::unlink(&_is_alive_closure);
454 // Process the remaining live ones
455 PSScavengeRootsClosure root_closure(promotion_manager);
456 StringTable::oops_do(&root_closure);
457
458 // Finally, flush the promotion_manager's labs, and deallocate its stacks.
459 PSPromotionManager::post_scavenge();
460
461 promotion_failure_occurred = promotion_failed();
462 if (promotion_failure_occurred) {
463 clean_up_failed_promotion();
464 if (PrintGC) {
465 gclog_or_tty->print("--");
466 }
467 }
468
469 // Let the size policy know we're done. Note that we count promotion
470 // failure cleanup time as part of the collection (otherwise, we're
471 // implicitly saying it's mutator time).
472 size_policy->minor_collection_end(gc_cause);
473
474 if (!promotion_failure_occurred) {
475 // Swap the survivor spaces.
476
477
478 young_gen->eden_space()->clear(SpaceDecorator::Mangle);
479 young_gen->from_space()->clear(SpaceDecorator::Mangle);
480 young_gen->swap_spaces();
481
482 size_t survived = young_gen->from_space()->used_in_bytes();
483 size_t promoted = old_gen->used_in_bytes() - old_gen_used_before;
484 size_policy->update_averages(_survivor_overflow, survived, promoted);
485
486 // A successful scavenge should restart the GC time limit count which is
487 // for full GC's.
488 size_policy->reset_gc_overhead_limit_count();
489 if (UseAdaptiveSizePolicy) {
490 // Calculate the new survivor size and tenuring threshold
491
492 if (PrintAdaptiveSizePolicy) {
493 gclog_or_tty->print("AdaptiveSizeStart: ");
494 gclog_or_tty->stamp();
495 gclog_or_tty->print_cr(" collection: %d ",
496 heap->total_collections());
497
498 if (Verbose) {
499 gclog_or_tty->print("old_gen_capacity: %d young_gen_capacity: %d",
500 old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
501 }
502 }
503
504
505 if (UsePerfData) {
506 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
507 counters->update_old_eden_size(
508 size_policy->calculated_eden_size_in_bytes());
509 counters->update_old_promo_size(
510 size_policy->calculated_promo_size_in_bytes());
511 counters->update_old_capacity(old_gen->capacity_in_bytes());
512 counters->update_young_capacity(young_gen->capacity_in_bytes());
513 counters->update_survived(survived);
514 counters->update_promoted(promoted);
515 counters->update_survivor_overflowed(_survivor_overflow);
516 }
517
518 size_t survivor_limit =
519 size_policy->max_survivor_size(young_gen->max_size());
520 _tenuring_threshold =
521 size_policy->compute_survivor_space_size_and_threshold(
522 _survivor_overflow,
523 _tenuring_threshold,
524 survivor_limit);
525
526 if (PrintTenuringDistribution) {
527 gclog_or_tty->cr();
528 gclog_or_tty->print_cr("Desired survivor size " SIZE_FORMAT " bytes, new threshold %u (max %u)",
529 size_policy->calculated_survivor_size_in_bytes(),
530 _tenuring_threshold, MaxTenuringThreshold);
531 }
532
533 if (UsePerfData) {
534 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
535 counters->update_tenuring_threshold(_tenuring_threshold);
536 counters->update_survivor_size_counters();
537 }
538
539 // Do call at minor collections?
540 // Don't check if the size_policy is ready at this
541 // level. Let the size_policy check that internally.
542 if (UseAdaptiveSizePolicy &&
543 UseAdaptiveGenerationSizePolicyAtMinorCollection &&
544 ((gc_cause != GCCause::_java_lang_system_gc) ||
545 UseAdaptiveSizePolicyWithSystemGC)) {
546
547 // Calculate optimial free space amounts
548 assert(young_gen->max_size() >
549 young_gen->from_space()->capacity_in_bytes() +
550 young_gen->to_space()->capacity_in_bytes(),
551 "Sizes of space in young gen are out-of-bounds");
552
553 size_t young_live = young_gen->used_in_bytes();
554 size_t eden_live = young_gen->eden_space()->used_in_bytes();
555 size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
556 size_t max_old_gen_size = old_gen->max_gen_size();
557 size_t max_eden_size = young_gen->max_size() -
558 young_gen->from_space()->capacity_in_bytes() -
559 young_gen->to_space()->capacity_in_bytes();
560
561 // Used for diagnostics
562 size_policy->clear_generation_free_space_flags();
563
564 size_policy->compute_eden_space_size(young_live,
565 eden_live,
566 cur_eden,
567 max_eden_size,
568 false /* not full gc*/);
569
570 size_policy->check_gc_overhead_limit(young_live,
571 eden_live,
572 max_old_gen_size,
573 max_eden_size,
574 false /* not full gc*/,
575 gc_cause,
576 heap->collector_policy());
577
578 size_policy->decay_supplemental_growth(false /* not full gc*/);
579 }
580 // Resize the young generation at every collection
581 // even if new sizes have not been calculated. This is
582 // to allow resizes that may have been inhibited by the
583 // relative location of the "to" and "from" spaces.
584
585 // Resizing the old gen at minor collects can cause increases
586 // that don't feed back to the generation sizing policy until
587 // a major collection. Don't resize the old gen here.
588
589 heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
590 size_policy->calculated_survivor_size_in_bytes());
591
592 if (PrintAdaptiveSizePolicy) {
593 gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
594 heap->total_collections());
595 }
596 }
597
598 // Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can
599 // cause the change of the heap layout. Make sure eden is reshaped if that's the case.
600 // Also update() will case adaptive NUMA chunk resizing.
601 assert(young_gen->eden_space()->is_empty(), "eden space should be empty now");
602 young_gen->eden_space()->update();
603
604 heap->gc_policy_counters()->update_counters();
605
606 heap->resize_all_tlabs();
607
608 assert(young_gen->to_space()->is_empty(), "to space should be empty now");
609 }
610
611 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
612
613 NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
614
615 CodeCache::prune_scavenge_root_nmethods();
616
617 // Re-verify object start arrays
618 if (VerifyObjectStartArray &&
619 VerifyAfterGC) {
620 old_gen->verify_object_start_array();
621 }
622
623 // Verify all old -> young cards are now precise
624 if (VerifyRememberedSets) {
625 // Precise verification will give false positives. Until this is fixed,
626 // use imprecise verification.
627 // CardTableExtension::verify_all_young_refs_precise();
628 CardTableExtension::verify_all_young_refs_imprecise();
629 }
630
631 if (TraceGen0Time) accumulated_time()->stop();
632
633 if (PrintGC) {
634 if (PrintGCDetails) {
635 // Don't print a GC timestamp here. This is after the GC so
636 // would be confusing.
637 young_gen->print_used_change(young_gen_used_before);
638 }
639 heap->print_heap_change(prev_used);
640 }
641
642 // Track memory usage and detect low memory
643 MemoryService::track_memory_usage();
644 heap->update_counters();
645
646 gc_task_manager()->release_idle_workers();
647 }
648
649 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
650 HandleMark hm; // Discard invalid handles created during verification
651 Universe::verify(" VerifyAfterGC:");
652 }
653
654 heap->print_heap_after_gc();
655
656 if (ZapUnusedHeapArea) {
657 young_gen->eden_space()->check_mangled_unused_area_complete();
658 young_gen->from_space()->check_mangled_unused_area_complete();
659 young_gen->to_space()->check_mangled_unused_area_complete();
660 }
661
662 scavenge_exit.update();
663
664 if (PrintGCTaskTimeStamps) {
665 tty->print_cr("VM-Thread " INT64_FORMAT " " INT64_FORMAT " " INT64_FORMAT,
666 scavenge_entry.ticks(), scavenge_midpoint.ticks(),
667 scavenge_exit.ticks());
668 gc_task_manager()->print_task_time_stamps();
669 }
670
671 #ifdef TRACESPINNING
672 ParallelTaskTerminator::print_termination_counts();
673 #endif
674
675 return !promotion_failure_occurred;
676 }
677
678 // This method iterates over all objects in the young generation,
679 // unforwarding markOops. It then restores any preserved mark oops,
680 // and clears the _preserved_mark_stack.
681 void PSScavenge::clean_up_failed_promotion() {
682 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
683 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
684 assert(promotion_failed(), "Sanity");
685
686 PSYoungGen* young_gen = heap->young_gen();
687
688 {
689 ResourceMark rm;
690
691 // Unforward all pointers in the young gen.
692 PSPromotionFailedClosure unforward_closure;
693 young_gen->object_iterate(&unforward_closure);
694
695 if (PrintGC && Verbose) {
696 gclog_or_tty->print_cr("Restoring %d marks", _preserved_oop_stack.size());
697 }
698
699 // Restore any saved marks.
700 while (!_preserved_oop_stack.is_empty()) {
701 oop obj = _preserved_oop_stack.pop();
702 markOop mark = _preserved_mark_stack.pop();
703 obj->set_mark(mark);
704 }
705
706 // Clear the preserved mark and oop stack caches.
707 _preserved_mark_stack.clear(true);
708 _preserved_oop_stack.clear(true);
709 _promotion_failed = false;
710 }
711
712 // Reset the PromotionFailureALot counters.
713 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
714 }
715
716 // This method is called whenever an attempt to promote an object
717 // fails. Some markOops will need preservation, some will not. Note
718 // that the entire eden is traversed after a failed promotion, with
719 // all forwarded headers replaced by the default markOop. This means
720 // it is not neccessary to preserve most markOops.
721 void PSScavenge::oop_promotion_failed(oop obj, markOop obj_mark) {
722 _promotion_failed = true;
723 if (obj_mark->must_be_preserved_for_promotion_failure(obj)) {
724 // Should use per-worker private stakcs hetre rather than
725 // locking a common pair of stacks.
726 ThreadCritical tc;
727 _preserved_oop_stack.push(obj);
728 _preserved_mark_stack.push(obj_mark);
729 }
730 }
731
732 bool PSScavenge::should_attempt_scavenge() {
733 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
734 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
735 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
736
737 if (UsePerfData) {
738 counters->update_scavenge_skipped(not_skipped);
739 }
740
741 PSYoungGen* young_gen = heap->young_gen();
742 PSOldGen* old_gen = heap->old_gen();
743
744 if (!ScavengeWithObjectsInToSpace) {
745 // Do not attempt to promote unless to_space is empty
746 if (!young_gen->to_space()->is_empty()) {
747 _consecutive_skipped_scavenges++;
748 if (UsePerfData) {
749 counters->update_scavenge_skipped(to_space_not_empty);
750 }
751 return false;
752 }
753 }
754
755 // Test to see if the scavenge will likely fail.
756 PSAdaptiveSizePolicy* policy = heap->size_policy();
757
758 // A similar test is done in the policy's should_full_GC(). If this is
759 // changed, decide if that test should also be changed.
760 size_t avg_promoted = (size_t) policy->padded_average_promoted_in_bytes();
761 size_t promotion_estimate = MIN2(avg_promoted, young_gen->used_in_bytes());
762 bool result = promotion_estimate < old_gen->free_in_bytes();
763
764 if (PrintGCDetails && Verbose) {
765 gclog_or_tty->print(result ? " do scavenge: " : " skip scavenge: ");
766 gclog_or_tty->print_cr(" average_promoted " SIZE_FORMAT
767 " padded_average_promoted " SIZE_FORMAT
768 " free in old gen " SIZE_FORMAT,
769 (size_t) policy->average_promoted_in_bytes(),
770 (size_t) policy->padded_average_promoted_in_bytes(),
771 old_gen->free_in_bytes());
772 if (young_gen->used_in_bytes() <
773 (size_t) policy->padded_average_promoted_in_bytes()) {
774 gclog_or_tty->print_cr(" padded_promoted_average is greater"
775 " than maximum promotion = " SIZE_FORMAT, young_gen->used_in_bytes());
776 }
777 }
778
779 if (result) {
780 _consecutive_skipped_scavenges = 0;
781 } else {
782 _consecutive_skipped_scavenges++;
783 if (UsePerfData) {
784 counters->update_scavenge_skipped(promoted_too_large);
785 }
786 }
787 return result;
788 }
789
790 // Used to add tasks
791 GCTaskManager* const PSScavenge::gc_task_manager() {
792 assert(ParallelScavengeHeap::gc_task_manager() != NULL,
793 "shouldn't return NULL");
794 return ParallelScavengeHeap::gc_task_manager();
795 }
796
797 void PSScavenge::initialize() {
798 // Arguments must have been parsed
799
800 if (AlwaysTenure) {
801 _tenuring_threshold = 0;
802 } else if (NeverTenure) {
803 _tenuring_threshold = markOopDesc::max_age + 1;
804 } else {
805 // We want to smooth out our startup times for the AdaptiveSizePolicy
806 _tenuring_threshold = (UseAdaptiveSizePolicy) ? InitialTenuringThreshold :
807 MaxTenuringThreshold;
808 }
809
810 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
811 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
812
813 PSYoungGen* young_gen = heap->young_gen();
814 PSOldGen* old_gen = heap->old_gen();
815
816 // Set boundary between young_gen and old_gen
817 assert(old_gen->reserved().end() <= young_gen->eden_space()->bottom(),
818 "old above young");
819 _young_generation_boundary = young_gen->eden_space()->bottom();
820
821 // Initialize ref handling object for scavenging.
822 MemRegion mr = young_gen->reserved();
823
824 _ref_processor =
825 new ReferenceProcessor(mr, // span
826 ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
827 (int) ParallelGCThreads, // mt processing degree
828 true, // mt discovery
829 (int) ParallelGCThreads, // mt discovery degree
830 true, // atomic_discovery
831 NULL, // header provides liveness info
832 false); // next field updates do not need write barrier
833
834 // Cache the cardtable
835 BarrierSet* bs = Universe::heap()->barrier_set();
836 assert(bs->kind() == BarrierSet::CardTableModRef, "Wrong barrier set kind");
837 _card_table = (CardTableExtension*)bs;
838
839 _counters = new CollectorCounters("PSScavenge", 0);
840 }