1 /*
2 * Copyright (c) 2002, 2011, 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 "gc_implementation/parallelScavenge/cardTableExtension.hpp"
28 #include "gc_implementation/parallelScavenge/gcTaskManager.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/psParallelCompact.hpp"
34 #include "gc_implementation/parallelScavenge/psScavenge.inline.hpp"
35 #include "gc_implementation/parallelScavenge/psTasks.hpp"
36 #include "gc_implementation/shared/isGCActiveMark.hpp"
37 #include "gc_implementation/shared/spaceDecorator.hpp"
38 #include "gc_interface/gcCause.hpp"
39 #include "memory/collectorPolicy.hpp"
40 #include "memory/gcLocker.inline.hpp"
41 #include "memory/referencePolicy.hpp"
42 #include "memory/referenceProcessor.hpp"
43 #include "memory/resourceArea.hpp"
44 #include "oops/oop.inline.hpp"
45 #include "oops/oop.psgc.inline.hpp"
46 #include "runtime/biasedLocking.hpp"
47 #include "runtime/fprofiler.hpp"
48 #include "runtime/handles.inline.hpp"
49 #include "runtime/threadCritical.hpp"
50 #include "runtime/vmThread.hpp"
51 #include "runtime/vm_operations.hpp"
52 #include "services/memoryService.hpp"
53 #include "utilities/stack.inline.hpp"
54
55
56 HeapWord* PSScavenge::_to_space_top_before_gc = NULL;
57 int PSScavenge::_consecutive_skipped_scavenges = 0;
58 ReferenceProcessor* PSScavenge::_ref_processor = NULL;
59 CardTableExtension* PSScavenge::_card_table = NULL;
60 bool PSScavenge::_survivor_overflow = false;
61 int PSScavenge::_tenuring_threshold = 0;
62 HeapWord* PSScavenge::_young_generation_boundary = NULL;
63 elapsedTimer PSScavenge::_accumulated_time;
64 Stack<markOop> PSScavenge::_preserved_mark_stack;
65 Stack<oop> PSScavenge::_preserved_oop_stack;
66 CollectorCounters* PSScavenge::_counters = NULL;
67 bool PSScavenge::_promotion_failed = false;
68
69 // Define before use
70 class PSIsAliveClosure: public BoolObjectClosure {
71 public:
72 void do_object(oop p) {
73 assert(false, "Do not call.");
74 }
75 bool do_object_b(oop p) {
76 return (!PSScavenge::is_obj_in_young((HeapWord*) p)) || p->is_forwarded();
77 }
78 };
79
80 PSIsAliveClosure PSScavenge::_is_alive_closure;
81
82 class PSKeepAliveClosure: public OopClosure {
83 protected:
84 MutableSpace* _to_space;
85 PSPromotionManager* _promotion_manager;
86
87 public:
88 PSKeepAliveClosure(PSPromotionManager* pm) : _promotion_manager(pm) {
89 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
90 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
91 _to_space = heap->young_gen()->to_space();
92
93 assert(_promotion_manager != NULL, "Sanity");
94 }
95
96 template <class T> void do_oop_work(T* p) {
97 assert (!oopDesc::is_null(*p), "expected non-null ref");
98 assert ((oopDesc::load_decode_heap_oop_not_null(p))->is_oop(),
99 "expected an oop while scanning weak refs");
100
101 // Weak refs may be visited more than once.
102 if (PSScavenge::should_scavenge(p, _to_space)) {
103 PSScavenge::copy_and_push_safe_barrier(_promotion_manager, p);
104 }
105 }
106 virtual void do_oop(oop* p) { PSKeepAliveClosure::do_oop_work(p); }
107 virtual void do_oop(narrowOop* p) { PSKeepAliveClosure::do_oop_work(p); }
108 };
109
110 class PSEvacuateFollowersClosure: public VoidClosure {
111 private:
112 PSPromotionManager* _promotion_manager;
113 public:
114 PSEvacuateFollowersClosure(PSPromotionManager* pm) : _promotion_manager(pm) {}
115
116 virtual void do_void() {
117 assert(_promotion_manager != NULL, "Sanity");
118 _promotion_manager->drain_stacks(true);
119 guarantee(_promotion_manager->stacks_empty(),
120 "stacks should be empty at this point");
121 }
122 };
123
124 class PSPromotionFailedClosure : public ObjectClosure {
125 virtual void do_object(oop obj) {
126 if (obj->is_forwarded()) {
127 obj->init_mark();
128 }
129 }
130 };
131
132 class PSRefProcTaskProxy: public GCTask {
133 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
134 ProcessTask & _rp_task;
135 uint _work_id;
136 public:
137 PSRefProcTaskProxy(ProcessTask & rp_task, uint work_id)
138 : _rp_task(rp_task),
139 _work_id(work_id)
140 { }
141
142 private:
143 virtual char* name() { return (char *)"Process referents by policy in parallel"; }
144 virtual void do_it(GCTaskManager* manager, uint which);
145 };
146
147 void PSRefProcTaskProxy::do_it(GCTaskManager* manager, uint which)
148 {
149 PSPromotionManager* promotion_manager =
150 PSPromotionManager::gc_thread_promotion_manager(which);
151 assert(promotion_manager != NULL, "sanity check");
152 PSKeepAliveClosure keep_alive(promotion_manager);
153 PSEvacuateFollowersClosure evac_followers(promotion_manager);
154 PSIsAliveClosure is_alive;
155 _rp_task.work(_work_id, is_alive, keep_alive, evac_followers);
156 }
157
158 class PSRefEnqueueTaskProxy: public GCTask {
159 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
160 EnqueueTask& _enq_task;
161 uint _work_id;
162
163 public:
164 PSRefEnqueueTaskProxy(EnqueueTask& enq_task, uint work_id)
165 : _enq_task(enq_task),
166 _work_id(work_id)
167 { }
168
169 virtual char* name() { return (char *)"Enqueue reference objects in parallel"; }
170 virtual void do_it(GCTaskManager* manager, uint which)
171 {
172 _enq_task.work(_work_id);
173 }
174 };
175
176 class PSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
177 virtual void execute(ProcessTask& task);
178 virtual void execute(EnqueueTask& task);
179 };
180
181 void PSRefProcTaskExecutor::execute(ProcessTask& task)
182 {
183 GCTaskQueue* q = GCTaskQueue::create();
184 for(uint i=0; i<ParallelGCThreads; i++) {
185 q->enqueue(new PSRefProcTaskProxy(task, i));
186 }
187 ParallelTaskTerminator terminator(
188 ParallelScavengeHeap::gc_task_manager()->workers(),
189 (TaskQueueSetSuper*) PSPromotionManager::stack_array_depth());
190 if (task.marks_oops_alive() && ParallelGCThreads > 1) {
191 for (uint j=0; j<ParallelGCThreads; j++) {
192 q->enqueue(new StealTask(&terminator));
193 }
194 }
195 ParallelScavengeHeap::gc_task_manager()->execute_and_wait(q);
196 }
197
198
199 void PSRefProcTaskExecutor::execute(EnqueueTask& task)
200 {
201 GCTaskQueue* q = GCTaskQueue::create();
202 for(uint i=0; i<ParallelGCThreads; i++) {
203 q->enqueue(new PSRefEnqueueTaskProxy(task, i));
204 }
205 ParallelScavengeHeap::gc_task_manager()->execute_and_wait(q);
206 }
207
208 // This method contains all heap specific policy for invoking scavenge.
209 // PSScavenge::invoke_no_policy() will do nothing but attempt to
210 // scavenge. It will not clean up after failed promotions, bail out if
211 // we've exceeded policy time limits, or any other special behavior.
212 // All such policy should be placed here.
213 //
214 // Note that this method should only be called from the vm_thread while
215 // at a safepoint!
216 void PSScavenge::invoke() {
217 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
218 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
219 assert(!Universe::heap()->is_gc_active(), "not reentrant");
220
221 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
222 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
223
224 PSAdaptiveSizePolicy* policy = heap->size_policy();
225 IsGCActiveMark mark;
226
227 bool scavenge_was_done = PSScavenge::invoke_no_policy();
228
229 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
230 if (UsePerfData)
231 counters->update_full_follows_scavenge(0);
232 if (!scavenge_was_done ||
233 policy->should_full_GC(heap->old_gen()->free_in_bytes())) {
234 if (UsePerfData)
235 counters->update_full_follows_scavenge(full_follows_scavenge);
236 GCCauseSetter gccs(heap, GCCause::_adaptive_size_policy);
237 CollectorPolicy* cp = heap->collector_policy();
238 const bool clear_all_softrefs = cp->should_clear_all_soft_refs();
239
240 if (UseParallelOldGC) {
241 PSParallelCompact::invoke_no_policy(clear_all_softrefs);
242 } else {
243 PSMarkSweep::invoke_no_policy(clear_all_softrefs);
244 }
245 }
246 }
247
248 // This method contains no policy. You should probably
249 // be calling invoke() instead.
250 bool PSScavenge::invoke_no_policy() {
251 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
252 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
253
254 assert(_preserved_mark_stack.is_empty(), "should be empty");
255 assert(_preserved_oop_stack.is_empty(), "should be empty");
256
257 TimeStamp scavenge_entry;
258 TimeStamp scavenge_midpoint;
259 TimeStamp scavenge_exit;
260
261 scavenge_entry.update();
262
263 if (GC_locker::check_active_before_gc()) {
264 return false;
265 }
266
267 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
268 GCCause::Cause gc_cause = heap->gc_cause();
269 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
270
271 // Check for potential problems.
272 if (!should_attempt_scavenge()) {
273 return false;
274 }
275
276 bool promotion_failure_occurred = false;
277
278 PSYoungGen* young_gen = heap->young_gen();
279 PSOldGen* old_gen = heap->old_gen();
280 PSPermGen* perm_gen = heap->perm_gen();
281 PSAdaptiveSizePolicy* size_policy = heap->size_policy();
282 heap->increment_total_collections();
283
284 AdaptiveSizePolicyOutput(size_policy, heap->total_collections());
285
286 if ((gc_cause != GCCause::_java_lang_system_gc) ||
287 UseAdaptiveSizePolicyWithSystemGC) {
288 // Gather the feedback data for eden occupancy.
289 young_gen->eden_space()->accumulate_statistics();
290 }
291
292 if (ZapUnusedHeapArea) {
293 // Save information needed to minimize mangling
294 heap->record_gen_tops_before_GC();
295 }
296
297 if (PrintHeapAtGC) {
298 Universe::print_heap_before_gc();
299 }
300
301 assert(!NeverTenure || _tenuring_threshold == markOopDesc::max_age + 1, "Sanity");
302 assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity");
303
304 size_t prev_used = heap->used();
305 assert(promotion_failed() == false, "Sanity");
306
307 // Fill in TLABs
308 heap->accumulate_statistics_all_tlabs();
309 heap->ensure_parsability(true); // retire TLABs
310
311 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
312 HandleMark hm; // Discard invalid handles created during verification
313 gclog_or_tty->print(" VerifyBeforeGC:");
314 Universe::verify(true);
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("GC", 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 perm_gen->verify_object_start_array();
337 }
338
339 // Verify no unmarked old->young roots
340 if (VerifyRememberedSets) {
341 CardTableExtension::verify_all_young_refs_imprecise();
342 }
343
344 if (!ScavengeWithObjectsInToSpace) {
345 assert(young_gen->to_space()->is_empty(),
346 "Attempt to scavenge with live objects in to_space");
347 young_gen->to_space()->clear(SpaceDecorator::Mangle);
348 } else if (ZapUnusedHeapArea) {
349 young_gen->to_space()->mangle_unused_area();
350 }
351 save_to_space_top_before_gc();
352
353 COMPILER2_PRESENT(DerivedPointerTable::clear());
354
355 reference_processor()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
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 if (!JavaObjectsInPerm) {
443 // Unlink any dead interned Strings
444 StringTable::unlink(&_is_alive_closure);
445 // Process the remaining live ones
446 PSScavengeRootsClosure root_closure(promotion_manager);
447 StringTable::oops_do(&root_closure);
448 }
449
450 // Finally, flush the promotion_manager's labs, and deallocate its stacks.
451 PSPromotionManager::post_scavenge();
452
453 promotion_failure_occurred = promotion_failed();
454 if (promotion_failure_occurred) {
455 clean_up_failed_promotion();
456 if (PrintGC) {
457 gclog_or_tty->print("--");
458 }
459 }
460
461 // Let the size policy know we're done. Note that we count promotion
462 // failure cleanup time as part of the collection (otherwise, we're
463 // implicitly saying it's mutator time).
464 size_policy->minor_collection_end(gc_cause);
465
466 if (!promotion_failure_occurred) {
467 // Swap the survivor spaces.
468
469
470 young_gen->eden_space()->clear(SpaceDecorator::Mangle);
471 young_gen->from_space()->clear(SpaceDecorator::Mangle);
472 young_gen->swap_spaces();
473
474 size_t survived = young_gen->from_space()->used_in_bytes();
475 size_t promoted = old_gen->used_in_bytes() - old_gen_used_before;
476 size_policy->update_averages(_survivor_overflow, survived, promoted);
477
478 // A successful scavenge should restart the GC time limit count which is
479 // for full GC's.
480 size_policy->reset_gc_overhead_limit_count();
481 if (UseAdaptiveSizePolicy) {
482 // Calculate the new survivor size and tenuring threshold
483
484 if (PrintAdaptiveSizePolicy) {
485 gclog_or_tty->print("AdaptiveSizeStart: ");
486 gclog_or_tty->stamp();
487 gclog_or_tty->print_cr(" collection: %d ",
488 heap->total_collections());
489
490 if (Verbose) {
491 gclog_or_tty->print("old_gen_capacity: %d young_gen_capacity: %d"
492 " perm_gen_capacity: %d ",
493 old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes(),
494 perm_gen->capacity_in_bytes());
495 }
496 }
497
498
499 if (UsePerfData) {
500 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
501 counters->update_old_eden_size(
502 size_policy->calculated_eden_size_in_bytes());
503 counters->update_old_promo_size(
504 size_policy->calculated_promo_size_in_bytes());
505 counters->update_old_capacity(old_gen->capacity_in_bytes());
506 counters->update_young_capacity(young_gen->capacity_in_bytes());
507 counters->update_survived(survived);
508 counters->update_promoted(promoted);
509 counters->update_survivor_overflowed(_survivor_overflow);
510 }
511
512 size_t survivor_limit =
513 size_policy->max_survivor_size(young_gen->max_size());
514 _tenuring_threshold =
515 size_policy->compute_survivor_space_size_and_threshold(
516 _survivor_overflow,
517 _tenuring_threshold,
518 survivor_limit);
519
520 if (PrintTenuringDistribution) {
521 gclog_or_tty->cr();
522 gclog_or_tty->print_cr("Desired survivor size %ld bytes, new threshold %d (max %d)",
523 size_policy->calculated_survivor_size_in_bytes(),
524 _tenuring_threshold, MaxTenuringThreshold);
525 }
526
527 if (UsePerfData) {
528 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
529 counters->update_tenuring_threshold(_tenuring_threshold);
530 counters->update_survivor_size_counters();
531 }
532
533 // Do call at minor collections?
534 // Don't check if the size_policy is ready at this
535 // level. Let the size_policy check that internally.
536 if (UseAdaptiveSizePolicy &&
537 UseAdaptiveGenerationSizePolicyAtMinorCollection &&
538 ((gc_cause != GCCause::_java_lang_system_gc) ||
539 UseAdaptiveSizePolicyWithSystemGC)) {
540
541 // Calculate optimial free space amounts
542 assert(young_gen->max_size() >
543 young_gen->from_space()->capacity_in_bytes() +
544 young_gen->to_space()->capacity_in_bytes(),
545 "Sizes of space in young gen are out-of-bounds");
546 size_t max_eden_size = young_gen->max_size() -
547 young_gen->from_space()->capacity_in_bytes() -
548 young_gen->to_space()->capacity_in_bytes();
549 size_policy->compute_generation_free_space(young_gen->used_in_bytes(),
550 young_gen->eden_space()->used_in_bytes(),
551 old_gen->used_in_bytes(),
552 perm_gen->used_in_bytes(),
553 young_gen->eden_space()->capacity_in_bytes(),
554 old_gen->max_gen_size(),
555 max_eden_size,
556 false /* full gc*/,
557 gc_cause,
558 heap->collector_policy());
559
560 }
561 // Resize the young generation at every collection
562 // even if new sizes have not been calculated. This is
563 // to allow resizes that may have been inhibited by the
564 // relative location of the "to" and "from" spaces.
565
566 // Resizing the old gen at minor collects can cause increases
567 // that don't feed back to the generation sizing policy until
568 // a major collection. Don't resize the old gen here.
569
570 heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
571 size_policy->calculated_survivor_size_in_bytes());
572
573 if (PrintAdaptiveSizePolicy) {
574 gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
575 heap->total_collections());
576 }
577 }
578
579 // Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can
580 // cause the change of the heap layout. Make sure eden is reshaped if that's the case.
581 // Also update() will case adaptive NUMA chunk resizing.
582 assert(young_gen->eden_space()->is_empty(), "eden space should be empty now");
583 young_gen->eden_space()->update();
584
585 heap->gc_policy_counters()->update_counters();
586
587 heap->resize_all_tlabs();
588
589 assert(young_gen->to_space()->is_empty(), "to space should be empty now");
590 }
591
592 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
593
594 NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
595
596 // Re-verify object start arrays
597 if (VerifyObjectStartArray &&
598 VerifyAfterGC) {
599 old_gen->verify_object_start_array();
600 perm_gen->verify_object_start_array();
601 }
602
603 // Verify all old -> young cards are now precise
604 if (VerifyRememberedSets) {
605 // Precise verification will give false positives. Until this is fixed,
606 // use imprecise verification.
607 // CardTableExtension::verify_all_young_refs_precise();
608 CardTableExtension::verify_all_young_refs_imprecise();
609 }
610
611 if (TraceGen0Time) accumulated_time()->stop();
612
613 if (PrintGC) {
614 if (PrintGCDetails) {
615 // Don't print a GC timestamp here. This is after the GC so
616 // would be confusing.
617 young_gen->print_used_change(young_gen_used_before);
618 }
619 heap->print_heap_change(prev_used);
620 }
621
622 // Track memory usage and detect low memory
623 MemoryService::track_memory_usage();
624 heap->update_counters();
625 }
626
627 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
628 HandleMark hm; // Discard invalid handles created during verification
629 gclog_or_tty->print(" VerifyAfterGC:");
630 Universe::verify(false);
631 }
632
633 if (PrintHeapAtGC) {
634 Universe::print_heap_after_gc();
635 }
636
637 if (ZapUnusedHeapArea) {
638 young_gen->eden_space()->check_mangled_unused_area_complete();
639 young_gen->from_space()->check_mangled_unused_area_complete();
640 young_gen->to_space()->check_mangled_unused_area_complete();
641 }
642
643 scavenge_exit.update();
644
645 if (PrintGCTaskTimeStamps) {
646 tty->print_cr("VM-Thread " INT64_FORMAT " " INT64_FORMAT " " INT64_FORMAT,
647 scavenge_entry.ticks(), scavenge_midpoint.ticks(),
648 scavenge_exit.ticks());
649 gc_task_manager()->print_task_time_stamps();
650 }
651
652 #ifdef TRACESPINNING
653 ParallelTaskTerminator::print_termination_counts();
654 #endif
655
656 return !promotion_failure_occurred;
657 }
658
659 // This method iterates over all objects in the young generation,
660 // unforwarding markOops. It then restores any preserved mark oops,
661 // and clears the _preserved_mark_stack.
662 void PSScavenge::clean_up_failed_promotion() {
663 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
664 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
665 assert(promotion_failed(), "Sanity");
666
667 PSYoungGen* young_gen = heap->young_gen();
668
669 {
670 ResourceMark rm;
671
672 // Unforward all pointers in the young gen.
673 PSPromotionFailedClosure unforward_closure;
674 young_gen->object_iterate(&unforward_closure);
675
676 if (PrintGC && Verbose) {
677 gclog_or_tty->print_cr("Restoring %d marks", _preserved_oop_stack.size());
678 }
679
680 // Restore any saved marks.
681 while (!_preserved_oop_stack.is_empty()) {
682 oop obj = _preserved_oop_stack.pop();
683 markOop mark = _preserved_mark_stack.pop();
684 obj->set_mark(mark);
685 }
686
687 // Clear the preserved mark and oop stack caches.
688 _preserved_mark_stack.clear(true);
689 _preserved_oop_stack.clear(true);
690 _promotion_failed = false;
691 }
692
693 // Reset the PromotionFailureALot counters.
694 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
695 }
696
697 // This method is called whenever an attempt to promote an object
698 // fails. Some markOops will need preservation, some will not. Note
699 // that the entire eden is traversed after a failed promotion, with
700 // all forwarded headers replaced by the default markOop. This means
701 // it is not neccessary to preserve most markOops.
702 void PSScavenge::oop_promotion_failed(oop obj, markOop obj_mark) {
703 _promotion_failed = true;
704 if (obj_mark->must_be_preserved_for_promotion_failure(obj)) {
705 // Should use per-worker private stakcs hetre rather than
706 // locking a common pair of stacks.
707 ThreadCritical tc;
708 _preserved_oop_stack.push(obj);
709 _preserved_mark_stack.push(obj_mark);
710 }
711 }
712
713 bool PSScavenge::should_attempt_scavenge() {
714 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
715 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
716 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
717
718 if (UsePerfData) {
719 counters->update_scavenge_skipped(not_skipped);
720 }
721
722 PSYoungGen* young_gen = heap->young_gen();
723 PSOldGen* old_gen = heap->old_gen();
724
725 if (!ScavengeWithObjectsInToSpace) {
726 // Do not attempt to promote unless to_space is empty
727 if (!young_gen->to_space()->is_empty()) {
728 _consecutive_skipped_scavenges++;
729 if (UsePerfData) {
730 counters->update_scavenge_skipped(to_space_not_empty);
731 }
732 return false;
733 }
734 }
735
736 // Test to see if the scavenge will likely fail.
737 PSAdaptiveSizePolicy* policy = heap->size_policy();
738
739 // A similar test is done in the policy's should_full_GC(). If this is
740 // changed, decide if that test should also be changed.
741 size_t avg_promoted = (size_t) policy->padded_average_promoted_in_bytes();
742 size_t promotion_estimate = MIN2(avg_promoted, young_gen->used_in_bytes());
743 bool result = promotion_estimate < old_gen->free_in_bytes();
744
745 if (PrintGCDetails && Verbose) {
746 gclog_or_tty->print(result ? " do scavenge: " : " skip scavenge: ");
747 gclog_or_tty->print_cr(" average_promoted " SIZE_FORMAT
748 " padded_average_promoted " SIZE_FORMAT
749 " free in old gen " SIZE_FORMAT,
750 (size_t) policy->average_promoted_in_bytes(),
751 (size_t) policy->padded_average_promoted_in_bytes(),
752 old_gen->free_in_bytes());
753 if (young_gen->used_in_bytes() <
754 (size_t) policy->padded_average_promoted_in_bytes()) {
755 gclog_or_tty->print_cr(" padded_promoted_average is greater"
756 " than maximum promotion = " SIZE_FORMAT, young_gen->used_in_bytes());
757 }
758 }
759
760 if (result) {
761 _consecutive_skipped_scavenges = 0;
762 } else {
763 _consecutive_skipped_scavenges++;
764 if (UsePerfData) {
765 counters->update_scavenge_skipped(promoted_too_large);
766 }
767 }
768 return result;
769 }
770
771 // Used to add tasks
772 GCTaskManager* const PSScavenge::gc_task_manager() {
773 assert(ParallelScavengeHeap::gc_task_manager() != NULL,
774 "shouldn't return NULL");
775 return ParallelScavengeHeap::gc_task_manager();
776 }
777
778 void PSScavenge::initialize() {
779 // Arguments must have been parsed
780
781 if (AlwaysTenure) {
782 _tenuring_threshold = 0;
783 } else if (NeverTenure) {
784 _tenuring_threshold = markOopDesc::max_age + 1;
785 } else {
786 // We want to smooth out our startup times for the AdaptiveSizePolicy
787 _tenuring_threshold = (UseAdaptiveSizePolicy) ? InitialTenuringThreshold :
788 MaxTenuringThreshold;
789 }
790
791 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
792 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
793
794 PSYoungGen* young_gen = heap->young_gen();
795 PSOldGen* old_gen = heap->old_gen();
796 PSPermGen* perm_gen = heap->perm_gen();
797
798 // Set boundary between young_gen and old_gen
799 assert(perm_gen->reserved().end() <= old_gen->object_space()->bottom(),
800 "perm above old");
801 assert(old_gen->reserved().end() <= young_gen->eden_space()->bottom(),
802 "old above young");
803 _young_generation_boundary = young_gen->eden_space()->bottom();
804
805 // Initialize ref handling object for scavenging.
806 MemRegion mr = young_gen->reserved();
807 _ref_processor =
808 new ReferenceProcessor(mr, // span
809 ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
810 (int) ParallelGCThreads, // mt processing degree
811 true, // mt discovery
812 (int) ParallelGCThreads, // mt discovery degree
813 true, // atomic_discovery
814 NULL, // header provides liveness info
815 false); // next field updates do not need write barrier
816
817 // Cache the cardtable
818 BarrierSet* bs = Universe::heap()->barrier_set();
819 assert(bs->kind() == BarrierSet::CardTableModRef, "Wrong barrier set kind");
820 _card_table = (CardTableExtension*)bs;
821
822 _counters = new CollectorCounters("PSScavenge", 0);
823 }