1 /*
2 * Copyright 2002-2010 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
24
25
26 # include "incls/_precompiled.incl"
27 # include "incls/_psScavenge.cpp.incl"
28
29 HeapWord* PSScavenge::_to_space_top_before_gc = NULL;
30 int PSScavenge::_consecutive_skipped_scavenges = 0;
31 ReferenceProcessor* PSScavenge::_ref_processor = NULL;
32 CardTableExtension* PSScavenge::_card_table = NULL;
33 bool PSScavenge::_survivor_overflow = false;
34 int PSScavenge::_tenuring_threshold = 0;
35 HeapWord* PSScavenge::_young_generation_boundary = NULL;
36 elapsedTimer PSScavenge::_accumulated_time;
37 GrowableArray<markOop>* PSScavenge::_preserved_mark_stack = NULL;
38 GrowableArray<oop>* PSScavenge::_preserved_oop_stack = NULL;
39 CollectorCounters* PSScavenge::_counters = NULL;
40
41 // Define before use
42 class PSIsAliveClosure: public BoolObjectClosure {
43 public:
44 void do_object(oop p) {
45 assert(false, "Do not call.");
46 }
47 bool do_object_b(oop p) {
48 return (!PSScavenge::is_obj_in_young((HeapWord*) p)) || p->is_forwarded();
49 }
50 };
51
52 PSIsAliveClosure PSScavenge::_is_alive_closure;
53
54 class PSKeepAliveClosure: public OopClosure {
55 protected:
56 MutableSpace* _to_space;
57 PSPromotionManager* _promotion_manager;
58
59 public:
60 PSKeepAliveClosure(PSPromotionManager* pm) : _promotion_manager(pm) {
61 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
62 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
63 _to_space = heap->young_gen()->to_space();
64
65 assert(_promotion_manager != NULL, "Sanity");
66 }
67
68 template <class T> void do_oop_work(T* p) {
69 assert (!oopDesc::is_null(*p), "expected non-null ref");
70 assert ((oopDesc::load_decode_heap_oop_not_null(p))->is_oop(),
71 "expected an oop while scanning weak refs");
72
73 // Weak refs may be visited more than once.
74 if (PSScavenge::should_scavenge(p, _to_space)) {
75 PSScavenge::copy_and_push_safe_barrier(_promotion_manager, p);
76 }
77 }
78 virtual void do_oop(oop* p) { PSKeepAliveClosure::do_oop_work(p); }
79 virtual void do_oop(narrowOop* p) { PSKeepAliveClosure::do_oop_work(p); }
80 };
81
82 class PSEvacuateFollowersClosure: public VoidClosure {
83 private:
84 PSPromotionManager* _promotion_manager;
85 public:
86 PSEvacuateFollowersClosure(PSPromotionManager* pm) : _promotion_manager(pm) {}
87
88 virtual void do_void() {
89 assert(_promotion_manager != NULL, "Sanity");
90 _promotion_manager->drain_stacks(true);
91 guarantee(_promotion_manager->stacks_empty(),
92 "stacks should be empty at this point");
93 }
94 };
95
96 class PSPromotionFailedClosure : public ObjectClosure {
97 virtual void do_object(oop obj) {
98 if (obj->is_forwarded()) {
99 obj->init_mark();
100 }
101 }
102 };
103
104 class PSRefProcTaskProxy: public GCTask {
105 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
106 ProcessTask & _rp_task;
107 uint _work_id;
108 public:
109 PSRefProcTaskProxy(ProcessTask & rp_task, uint work_id)
110 : _rp_task(rp_task),
111 _work_id(work_id)
112 { }
113
114 private:
115 virtual char* name() { return (char *)"Process referents by policy in parallel"; }
116 virtual void do_it(GCTaskManager* manager, uint which);
117 };
118
119 void PSRefProcTaskProxy::do_it(GCTaskManager* manager, uint which)
120 {
121 PSPromotionManager* promotion_manager =
122 PSPromotionManager::gc_thread_promotion_manager(which);
123 assert(promotion_manager != NULL, "sanity check");
124 PSKeepAliveClosure keep_alive(promotion_manager);
125 PSEvacuateFollowersClosure evac_followers(promotion_manager);
126 PSIsAliveClosure is_alive;
127 _rp_task.work(_work_id, is_alive, keep_alive, evac_followers);
128 }
129
130 class PSRefEnqueueTaskProxy: public GCTask {
131 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
132 EnqueueTask& _enq_task;
133 uint _work_id;
134
135 public:
136 PSRefEnqueueTaskProxy(EnqueueTask& enq_task, uint work_id)
137 : _enq_task(enq_task),
138 _work_id(work_id)
139 { }
140
141 virtual char* name() { return (char *)"Enqueue reference objects in parallel"; }
142 virtual void do_it(GCTaskManager* manager, uint which)
143 {
144 _enq_task.work(_work_id);
145 }
146 };
147
148 class PSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
149 virtual void execute(ProcessTask& task);
150 virtual void execute(EnqueueTask& task);
151 };
152
153 void PSRefProcTaskExecutor::execute(ProcessTask& task)
154 {
155 GCTaskQueue* q = GCTaskQueue::create();
156 for(uint i=0; i<ParallelGCThreads; i++) {
157 q->enqueue(new PSRefProcTaskProxy(task, i));
158 }
159 ParallelTaskTerminator terminator(
160 ParallelScavengeHeap::gc_task_manager()->workers(),
161 UseDepthFirstScavengeOrder ?
162 (TaskQueueSetSuper*) PSPromotionManager::stack_array_depth()
163 : (TaskQueueSetSuper*) PSPromotionManager::stack_array_breadth());
164 if (task.marks_oops_alive() && ParallelGCThreads > 1) {
165 for (uint j=0; j<ParallelGCThreads; j++) {
166 q->enqueue(new StealTask(&terminator));
167 }
168 }
169 ParallelScavengeHeap::gc_task_manager()->execute_and_wait(q);
170 }
171
172
173 void PSRefProcTaskExecutor::execute(EnqueueTask& task)
174 {
175 GCTaskQueue* q = GCTaskQueue::create();
176 for(uint i=0; i<ParallelGCThreads; i++) {
177 q->enqueue(new PSRefEnqueueTaskProxy(task, i));
178 }
179 ParallelScavengeHeap::gc_task_manager()->execute_and_wait(q);
180 }
181
182 // This method contains all heap specific policy for invoking scavenge.
183 // PSScavenge::invoke_no_policy() will do nothing but attempt to
184 // scavenge. It will not clean up after failed promotions, bail out if
185 // we've exceeded policy time limits, or any other special behavior.
186 // All such policy should be placed here.
187 //
188 // Note that this method should only be called from the vm_thread while
189 // at a safepoint!
190 void PSScavenge::invoke() {
191 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
192 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
193 assert(!Universe::heap()->is_gc_active(), "not reentrant");
194
195 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
196 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
197
198 PSAdaptiveSizePolicy* policy = heap->size_policy();
199 IsGCActiveMark mark;
200
201 bool scavenge_was_done = PSScavenge::invoke_no_policy();
202
203 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
204 if (UsePerfData)
205 counters->update_full_follows_scavenge(0);
206 if (!scavenge_was_done ||
207 policy->should_full_GC(heap->old_gen()->free_in_bytes())) {
208 if (UsePerfData)
209 counters->update_full_follows_scavenge(full_follows_scavenge);
210 GCCauseSetter gccs(heap, GCCause::_adaptive_size_policy);
211 CollectorPolicy* cp = heap->collector_policy();
212 const bool clear_all_softrefs = cp->should_clear_all_soft_refs();
213
214 if (UseParallelOldGC) {
215 PSParallelCompact::invoke_no_policy(clear_all_softrefs);
216 } else {
217 PSMarkSweep::invoke_no_policy(clear_all_softrefs);
218 }
219 }
220 }
221
222 // This method contains no policy. You should probably
223 // be calling invoke() instead.
224 bool PSScavenge::invoke_no_policy() {
225 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
226 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
227
228 TimeStamp scavenge_entry;
229 TimeStamp scavenge_midpoint;
230 TimeStamp scavenge_exit;
231
232 scavenge_entry.update();
233
234 if (GC_locker::check_active_before_gc()) {
235 return false;
236 }
237
238 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
239 GCCause::Cause gc_cause = heap->gc_cause();
240 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
241
242 // Check for potential problems.
243 if (!should_attempt_scavenge()) {
244 return false;
245 }
246
247 bool promotion_failure_occurred = false;
248
249 PSYoungGen* young_gen = heap->young_gen();
250 PSOldGen* old_gen = heap->old_gen();
251 PSPermGen* perm_gen = heap->perm_gen();
252 PSAdaptiveSizePolicy* size_policy = heap->size_policy();
253 heap->increment_total_collections();
254
255 AdaptiveSizePolicyOutput(size_policy, heap->total_collections());
256
257 if ((gc_cause != GCCause::_java_lang_system_gc) ||
258 UseAdaptiveSizePolicyWithSystemGC) {
259 // Gather the feedback data for eden occupancy.
260 young_gen->eden_space()->accumulate_statistics();
261 }
262
263 if (ZapUnusedHeapArea) {
264 // Save information needed to minimize mangling
265 heap->record_gen_tops_before_GC();
266 }
267
268 if (PrintHeapAtGC) {
269 Universe::print_heap_before_gc();
270 }
271
272 assert(!NeverTenure || _tenuring_threshold == markOopDesc::max_age + 1, "Sanity");
273 assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity");
274
275 size_t prev_used = heap->used();
276 assert(promotion_failed() == false, "Sanity");
277
278 // Fill in TLABs
279 heap->accumulate_statistics_all_tlabs();
280 heap->ensure_parsability(true); // retire TLABs
281
282 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
283 HandleMark hm; // Discard invalid handles created during verification
284 gclog_or_tty->print(" VerifyBeforeGC:");
285 Universe::verify(true);
286 }
287
288 {
289 ResourceMark rm;
290 HandleMark hm;
291
292 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
293 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
294 TraceTime t1("GC", PrintGC, !PrintGCDetails, gclog_or_tty);
295 TraceCollectorStats tcs(counters());
296 TraceMemoryManagerStats tms(false /* not full GC */);
297
298 if (TraceGen0Time) accumulated_time()->start();
299
300 // Let the size policy know we're starting
301 size_policy->minor_collection_begin();
302
303 // Verify the object start arrays.
304 if (VerifyObjectStartArray &&
305 VerifyBeforeGC) {
306 old_gen->verify_object_start_array();
307 perm_gen->verify_object_start_array();
308 }
309
310 // Verify no unmarked old->young roots
311 if (VerifyRememberedSets) {
312 CardTableExtension::verify_all_young_refs_imprecise();
313 }
314
315 if (!ScavengeWithObjectsInToSpace) {
316 assert(young_gen->to_space()->is_empty(),
317 "Attempt to scavenge with live objects in to_space");
318 young_gen->to_space()->clear(SpaceDecorator::Mangle);
319 } else if (ZapUnusedHeapArea) {
320 young_gen->to_space()->mangle_unused_area();
321 }
322 save_to_space_top_before_gc();
323
324 NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
325 COMPILER2_PRESENT(DerivedPointerTable::clear());
326
327 reference_processor()->enable_discovery();
328 reference_processor()->setup_policy(false);
329
330 // We track how much was promoted to the next generation for
331 // the AdaptiveSizePolicy.
332 size_t old_gen_used_before = old_gen->used_in_bytes();
333
334 // For PrintGCDetails
335 size_t young_gen_used_before = young_gen->used_in_bytes();
336
337 // Reset our survivor overflow.
338 set_survivor_overflow(false);
339
340 // We need to save the old/perm top values before
341 // creating the promotion_manager. We pass the top
342 // values to the card_table, to prevent it from
343 // straying into the promotion labs.
344 HeapWord* old_top = old_gen->object_space()->top();
345 HeapWord* perm_top = perm_gen->object_space()->top();
346
347 // Release all previously held resources
348 gc_task_manager()->release_all_resources();
349
350 PSPromotionManager::pre_scavenge();
351
352 // We'll use the promotion manager again later.
353 PSPromotionManager* promotion_manager = PSPromotionManager::vm_thread_promotion_manager();
354 {
355 // TraceTime("Roots");
356 ParallelScavengeHeap::ParStrongRootsScope psrs;
357
358 GCTaskQueue* q = GCTaskQueue::create();
359
360 for(uint i=0; i<ParallelGCThreads; i++) {
361 q->enqueue(new OldToYoungRootsTask(old_gen, old_top, i));
362 }
363
364 q->enqueue(new SerialOldToYoungRootsTask(perm_gen, perm_top));
365
366 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::universe));
367 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jni_handles));
368 // We scan the thread roots in parallel
369 Threads::create_thread_roots_tasks(q);
370 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::object_synchronizer));
371 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::flat_profiler));
372 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::management));
373 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::system_dictionary));
374 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jvmti));
375 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::code_cache));
376
377 ParallelTaskTerminator terminator(
378 gc_task_manager()->workers(),
379 promotion_manager->depth_first() ?
380 (TaskQueueSetSuper*) promotion_manager->stack_array_depth()
381 : (TaskQueueSetSuper*) promotion_manager->stack_array_breadth());
382 if (ParallelGCThreads>1) {
383 for (uint j=0; j<ParallelGCThreads; j++) {
384 q->enqueue(new StealTask(&terminator));
385 }
386 }
387
388 gc_task_manager()->execute_and_wait(q);
389 }
390
391 scavenge_midpoint.update();
392
393 // Process reference objects discovered during scavenge
394 {
395 reference_processor()->setup_policy(false); // not always_clear
396 PSKeepAliveClosure keep_alive(promotion_manager);
397 PSEvacuateFollowersClosure evac_followers(promotion_manager);
398 if (reference_processor()->processing_is_mt()) {
399 PSRefProcTaskExecutor task_executor;
400 reference_processor()->process_discovered_references(
401 &_is_alive_closure, &keep_alive, &evac_followers, &task_executor);
402 } else {
403 reference_processor()->process_discovered_references(
404 &_is_alive_closure, &keep_alive, &evac_followers, NULL);
405 }
406 }
407
408 // Enqueue reference objects discovered during scavenge.
409 if (reference_processor()->processing_is_mt()) {
410 PSRefProcTaskExecutor task_executor;
411 reference_processor()->enqueue_discovered_references(&task_executor);
412 } else {
413 reference_processor()->enqueue_discovered_references(NULL);
414 }
415
416 // Finally, flush the promotion_manager's labs, and deallocate its stacks.
417 assert(promotion_manager->claimed_stack_empty(), "Sanity");
418 PSPromotionManager::post_scavenge();
419
420 promotion_failure_occurred = promotion_failed();
421 if (promotion_failure_occurred) {
422 clean_up_failed_promotion();
423 if (PrintGC) {
424 gclog_or_tty->print("--");
425 }
426 }
427
428 // Let the size policy know we're done. Note that we count promotion
429 // failure cleanup time as part of the collection (otherwise, we're
430 // implicitly saying it's mutator time).
431 size_policy->minor_collection_end(gc_cause);
432
433 if (!promotion_failure_occurred) {
434 // Swap the survivor spaces.
435
436
437 young_gen->eden_space()->clear(SpaceDecorator::Mangle);
438 young_gen->from_space()->clear(SpaceDecorator::Mangle);
439 young_gen->swap_spaces();
440
441 size_t survived = young_gen->from_space()->used_in_bytes();
442 size_t promoted = old_gen->used_in_bytes() - old_gen_used_before;
443 size_policy->update_averages(_survivor_overflow, survived, promoted);
444
445 // A successful scavenge should restart the GC time limit count which is
446 // for full GC's.
447 size_policy->reset_gc_overhead_limit_count();
448 if (PSResizeByFreeRatioWithSystemGC &&
449 gc_cause == GCCause::_java_lang_system_gc) {
450 ParallelScavengeHeap* heap = (ParallelScavengeHeap*) Universe::heap();
451 heap->resize_by_free_ratio(false);
452
453 } else if (UseAdaptiveSizePolicy) {
454 // Calculate the new survivor size and tenuring threshold
455
456 if (PrintAdaptiveSizePolicy) {
457 gclog_or_tty->print("AdaptiveSizeStart: ");
458 gclog_or_tty->stamp();
459 gclog_or_tty->print_cr(" collection: %d ",
460 heap->total_collections());
461
462 if (Verbose) {
463 gclog_or_tty->print("old_gen_capacity: %d young_gen_capacity: %d"
464 " perm_gen_capacity: %d ",
465 old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes(),
466 perm_gen->capacity_in_bytes());
467 }
468 }
469
470
471 if (UsePerfData) {
472 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
473 counters->update_old_eden_size(
474 size_policy->calculated_eden_size_in_bytes());
475 counters->update_old_promo_size(
476 size_policy->calculated_promo_size_in_bytes());
477 counters->update_old_capacity(old_gen->capacity_in_bytes());
478 counters->update_young_capacity(young_gen->capacity_in_bytes());
479 counters->update_survived(survived);
480 counters->update_promoted(promoted);
481 counters->update_survivor_overflowed(_survivor_overflow);
482 }
483
484 size_t survivor_limit =
485 size_policy->max_survivor_size(young_gen->max_size());
486 _tenuring_threshold =
487 size_policy->compute_survivor_space_size_and_threshold(
488 _survivor_overflow,
489 _tenuring_threshold,
490 survivor_limit);
491
492 if (PrintTenuringDistribution) {
493 gclog_or_tty->cr();
494 gclog_or_tty->print_cr("Desired survivor size %ld bytes, new threshold %d (max %d)",
495 size_policy->calculated_survivor_size_in_bytes(),
496 _tenuring_threshold, MaxTenuringThreshold);
497 }
498
499 if (UsePerfData) {
500 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
501 counters->update_tenuring_threshold(_tenuring_threshold);
502 counters->update_survivor_size_counters();
503 }
504
505 // Do call at minor collections?
506 // Don't check if the size_policy is ready at this
507 // level. Let the size_policy check that internally.
508 if (UseAdaptiveSizePolicy &&
509 UseAdaptiveGenerationSizePolicyAtMinorCollection &&
510 ((gc_cause != GCCause::_java_lang_system_gc) ||
511 UseAdaptiveSizePolicyWithSystemGC)) {
512
513 // Calculate optimial free space amounts
514 assert(young_gen->max_size() >
515 young_gen->from_space()->capacity_in_bytes() +
516 young_gen->to_space()->capacity_in_bytes(),
517 "Sizes of space in young gen are out-of-bounds");
518 size_t max_eden_size = young_gen->max_size() -
519 young_gen->from_space()->capacity_in_bytes() -
520 young_gen->to_space()->capacity_in_bytes();
521 size_policy->compute_generation_free_space(young_gen->used_in_bytes(),
522 young_gen->eden_space()->used_in_bytes(),
523 old_gen->used_in_bytes(),
524 perm_gen->used_in_bytes(),
525 young_gen->eden_space()->capacity_in_bytes(),
526 old_gen->max_gen_size(),
527 max_eden_size,
528 false /* full gc*/,
529 gc_cause,
530 heap->collector_policy());
531
532 }
533 // Resize the young generation at every collection
534 // even if new sizes have not been calculated. This is
535 // to allow resizes that may have been inhibited by the
536 // relative location of the "to" and "from" spaces.
537
538 // Resizing the old gen at minor collects can cause increases
539 // that don't feed back to the generation sizing policy until
540 // a major collection. Don't resize the old gen here.
541
542 heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
543 size_policy->calculated_survivor_size_in_bytes());
544
545 if (PrintAdaptiveSizePolicy) {
546 gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
547 heap->total_collections());
548 }
549 } else {
550 ParallelScavengeHeap* heap = (ParallelScavengeHeap*) Universe::heap();
551 heap->resize_by_free_ratio(false);
552 }
553
554 // Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can
555 // cause the change of the heap layout. Make sure eden is reshaped if that's the case.
556 // Also update() will case adaptive NUMA chunk resizing.
557 assert(young_gen->eden_space()->is_empty(), "eden space should be empty now");
558 young_gen->eden_space()->update();
559
560 heap->gc_policy_counters()->update_counters();
561
562 heap->resize_all_tlabs();
563
564 assert(young_gen->to_space()->is_empty(), "to space should be empty now");
565 }
566
567 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
568
569 NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
570
571 // Re-verify object start arrays
572 if (VerifyObjectStartArray &&
573 VerifyAfterGC) {
574 old_gen->verify_object_start_array();
575 perm_gen->verify_object_start_array();
576 }
577
578 // Verify all old -> young cards are now precise
579 if (VerifyRememberedSets) {
580 // Precise verification will give false positives. Until this is fixed,
581 // use imprecise verification.
582 // CardTableExtension::verify_all_young_refs_precise();
583 CardTableExtension::verify_all_young_refs_imprecise();
584 }
585
586 if (TraceGen0Time) accumulated_time()->stop();
587
588 if (PrintGC) {
589 if (PrintGCDetails) {
590 // Don't print a GC timestamp here. This is after the GC so
591 // would be confusing.
592 young_gen->print_used_change(young_gen_used_before);
593 }
594 heap->print_heap_change(prev_used);
595 }
596
597 // Track memory usage and detect low memory
598 MemoryService::track_memory_usage();
599 heap->update_counters();
600 }
601
602 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
603 HandleMark hm; // Discard invalid handles created during verification
604 gclog_or_tty->print(" VerifyAfterGC:");
605 Universe::verify(false);
606 }
607
608 if (PrintHeapAtGC) {
609 Universe::print_heap_after_gc();
610 }
611
612 if (ZapUnusedHeapArea) {
613 young_gen->eden_space()->check_mangled_unused_area_complete();
614 young_gen->from_space()->check_mangled_unused_area_complete();
615 young_gen->to_space()->check_mangled_unused_area_complete();
616 }
617
618 scavenge_exit.update();
619
620 if (PrintGCTaskTimeStamps) {
621 tty->print_cr("VM-Thread " INT64_FORMAT " " INT64_FORMAT " " INT64_FORMAT,
622 scavenge_entry.ticks(), scavenge_midpoint.ticks(),
623 scavenge_exit.ticks());
624 gc_task_manager()->print_task_time_stamps();
625 }
626
627 #ifdef TRACESPINNING
628 ParallelTaskTerminator::print_termination_counts();
629 #endif
630
631 return !promotion_failure_occurred;
632 }
633
634 // This method iterates over all objects in the young generation,
635 // unforwarding markOops. It then restores any preserved mark oops,
636 // and clears the _preserved_mark_stack.
637 void PSScavenge::clean_up_failed_promotion() {
638 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
639 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
640 assert(promotion_failed(), "Sanity");
641
642 PSYoungGen* young_gen = heap->young_gen();
643
644 {
645 ResourceMark rm;
646
647 // Unforward all pointers in the young gen.
648 PSPromotionFailedClosure unforward_closure;
649 young_gen->object_iterate(&unforward_closure);
650
651 if (PrintGC && Verbose) {
652 gclog_or_tty->print_cr("Restoring %d marks",
653 _preserved_oop_stack->length());
654 }
655
656 // Restore any saved marks.
657 for (int i=0; i < _preserved_oop_stack->length(); i++) {
658 oop obj = _preserved_oop_stack->at(i);
659 markOop mark = _preserved_mark_stack->at(i);
660 obj->set_mark(mark);
661 }
662
663 // Deallocate the preserved mark and oop stacks.
664 // The stacks were allocated as CHeap objects, so
665 // we must call delete to prevent mem leaks.
666 delete _preserved_mark_stack;
667 _preserved_mark_stack = NULL;
668 delete _preserved_oop_stack;
669 _preserved_oop_stack = NULL;
670 }
671
672 // Reset the PromotionFailureALot counters.
673 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
674 }
675
676 // This method is called whenever an attempt to promote an object
677 // fails. Some markOops will need preserving, some will not. Note
678 // that the entire eden is traversed after a failed promotion, with
679 // all forwarded headers replaced by the default markOop. This means
680 // it is not neccessary to preserve most markOops.
681 void PSScavenge::oop_promotion_failed(oop obj, markOop obj_mark) {
682 if (_preserved_mark_stack == NULL) {
683 ThreadCritical tc; // Lock and retest
684 if (_preserved_mark_stack == NULL) {
685 assert(_preserved_oop_stack == NULL, "Sanity");
686 _preserved_mark_stack = new (ResourceObj::C_HEAP) GrowableArray<markOop>(40, true);
687 _preserved_oop_stack = new (ResourceObj::C_HEAP) GrowableArray<oop>(40, true);
688 }
689 }
690
691 // Because we must hold the ThreadCritical lock before using
692 // the stacks, we should be safe from observing partial allocations,
693 // which are also guarded by the ThreadCritical lock.
694 if (obj_mark->must_be_preserved_for_promotion_failure(obj)) {
695 ThreadCritical tc;
696 _preserved_oop_stack->push(obj);
697 _preserved_mark_stack->push(obj_mark);
698 }
699 }
700
701 bool PSScavenge::should_attempt_scavenge() {
702 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
703 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
704 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
705
706 if (UsePerfData) {
707 counters->update_scavenge_skipped(not_skipped);
708 }
709
710 PSYoungGen* young_gen = heap->young_gen();
711 PSOldGen* old_gen = heap->old_gen();
712
713 if (!ScavengeWithObjectsInToSpace) {
714 // Do not attempt to promote unless to_space is empty
715 if (!young_gen->to_space()->is_empty()) {
716 _consecutive_skipped_scavenges++;
717 if (UsePerfData) {
718 counters->update_scavenge_skipped(to_space_not_empty);
719 }
720 return false;
721 }
722 }
723
724 // Test to see if the scavenge will likely fail.
725 PSAdaptiveSizePolicy* policy = heap->size_policy();
726
727 // A similar test is done in the policy's should_full_GC(). If this is
728 // changed, decide if that test should also be changed.
729 size_t avg_promoted = (size_t) policy->padded_average_promoted_in_bytes();
730 size_t promotion_estimate = MIN2(avg_promoted, young_gen->used_in_bytes());
731 bool result = promotion_estimate < old_gen->free_in_bytes();
732
733 if (PrintGCDetails && Verbose) {
734 gclog_or_tty->print(result ? " do scavenge: " : " skip scavenge: ");
735 gclog_or_tty->print_cr(" average_promoted " SIZE_FORMAT
736 " padded_average_promoted " SIZE_FORMAT
737 " free in old gen " SIZE_FORMAT,
738 (size_t) policy->average_promoted_in_bytes(),
739 (size_t) policy->padded_average_promoted_in_bytes(),
740 old_gen->free_in_bytes());
741 if (young_gen->used_in_bytes() <
742 (size_t) policy->padded_average_promoted_in_bytes()) {
743 gclog_or_tty->print_cr(" padded_promoted_average is greater"
744 " than maximum promotion = " SIZE_FORMAT, young_gen->used_in_bytes());
745 }
746 }
747
748 if (result) {
749 _consecutive_skipped_scavenges = 0;
750 } else {
751 _consecutive_skipped_scavenges++;
752 if (UsePerfData) {
753 counters->update_scavenge_skipped(promoted_too_large);
754 }
755 }
756 return result;
757 }
758
759 // Used to add tasks
760 GCTaskManager* const PSScavenge::gc_task_manager() {
761 assert(ParallelScavengeHeap::gc_task_manager() != NULL,
762 "shouldn't return NULL");
763 return ParallelScavengeHeap::gc_task_manager();
764 }
765
766 void PSScavenge::initialize() {
767 // Arguments must have been parsed
768
769 if (AlwaysTenure) {
770 _tenuring_threshold = 0;
771 } else if (NeverTenure) {
772 _tenuring_threshold = markOopDesc::max_age + 1;
773 } else {
774 // We want to smooth out our startup times for the AdaptiveSizePolicy
775 _tenuring_threshold = (UseAdaptiveSizePolicy) ? InitialTenuringThreshold :
776 MaxTenuringThreshold;
777 }
778
779 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
780 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
781
782 PSYoungGen* young_gen = heap->young_gen();
783 PSOldGen* old_gen = heap->old_gen();
784 PSPermGen* perm_gen = heap->perm_gen();
785
786 // Set boundary between young_gen and old_gen
787 assert(perm_gen->reserved().end() <= old_gen->object_space()->bottom(),
788 "perm above old");
789 assert(old_gen->reserved().end() <= young_gen->eden_space()->bottom(),
790 "old above young");
791 _young_generation_boundary = young_gen->eden_space()->bottom();
792
793 // Initialize ref handling object for scavenging.
794 MemRegion mr = young_gen->reserved();
795 _ref_processor = ReferenceProcessor::create_ref_processor(
796 mr, // span
797 true, // atomic_discovery
798 true, // mt_discovery
799 NULL, // is_alive_non_header
800 ParallelGCThreads,
801 ParallelRefProcEnabled);
802
803 // Cache the cardtable
804 BarrierSet* bs = Universe::heap()->barrier_set();
805 assert(bs->kind() == BarrierSet::CardTableModRef, "Wrong barrier set kind");
806 _card_table = (CardTableExtension*)bs;
807
808 _counters = new CollectorCounters("PSScavenge", 0);
809 }