1 /*
2 * Copyright 2002-2009 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 {
192 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
193 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
194 assert(!Universe::heap()->is_gc_active(), "not reentrant");
195
196 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
197 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
198
199 PSAdaptiveSizePolicy* policy = heap->size_policy();
200
201 // Before each allocation/collection attempt, find out from the
202 // policy object if GCs are, on the whole, taking too long. If so,
203 // bail out without attempting a collection.
204 if (!policy->gc_time_limit_exceeded()) {
205 IsGCActiveMark mark;
206
207 bool scavenge_was_done = PSScavenge::invoke_no_policy();
208
209 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
210 if (UsePerfData)
211 counters->update_full_follows_scavenge(0);
212 if (!scavenge_was_done ||
213 policy->should_full_GC(heap->old_gen()->free_in_bytes())) {
214 if (UsePerfData)
215 counters->update_full_follows_scavenge(full_follows_scavenge);
216
217 GCCauseSetter gccs(heap, GCCause::_adaptive_size_policy);
218 if (UseParallelOldGC) {
219 PSParallelCompact::invoke_no_policy(false);
220 } else {
221 PSMarkSweep::invoke_no_policy(false);
222 }
223 }
224 }
225 }
226
227 // This method contains no policy. You should probably
228 // be calling invoke() instead.
229 bool PSScavenge::invoke_no_policy() {
230 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
231 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
232
233 TimeStamp scavenge_entry;
234 TimeStamp scavenge_midpoint;
235 TimeStamp scavenge_exit;
236
237 scavenge_entry.update();
238
239 if (GC_locker::check_active_before_gc()) {
240 return false;
241 }
242
243 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
244 GCCause::Cause gc_cause = heap->gc_cause();
245 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
246
247 // Check for potential problems.
248 if (!should_attempt_scavenge()) {
249 return false;
250 }
251
252 bool promotion_failure_occurred = false;
253
254 PSYoungGen* young_gen = heap->young_gen();
255 PSOldGen* old_gen = heap->old_gen();
256 PSPermGen* perm_gen = heap->perm_gen();
257 PSAdaptiveSizePolicy* size_policy = heap->size_policy();
258 heap->increment_total_collections();
259
260 AdaptiveSizePolicyOutput(size_policy, heap->total_collections());
261
262 if ((gc_cause != GCCause::_java_lang_system_gc) ||
263 UseAdaptiveSizePolicyWithSystemGC) {
264 // Gather the feedback data for eden occupancy.
265 young_gen->eden_space()->accumulate_statistics();
266 }
267
268 if (ZapUnusedHeapArea) {
269 // Save information needed to minimize mangling
270 heap->record_gen_tops_before_GC();
271 }
272
273 if (PrintHeapAtGC) {
274 Universe::print_heap_before_gc();
275 }
276
277 assert(!NeverTenure || _tenuring_threshold == markOopDesc::max_age + 1, "Sanity");
278 assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity");
279
280 size_t prev_used = heap->used();
281 assert(promotion_failed() == false, "Sanity");
282
283 // Fill in TLABs
284 heap->accumulate_statistics_all_tlabs();
285 heap->ensure_parsability(true); // retire TLABs
286
287 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
288 HandleMark hm; // Discard invalid handles created during verification
289 gclog_or_tty->print(" VerifyBeforeGC:");
290 Universe::verify(true);
291 }
292
293 {
294 ResourceMark rm;
295 HandleMark hm;
296
297 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
298 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
299 TraceTime t1("GC", PrintGC, !PrintGCDetails, gclog_or_tty);
300 TraceCollectorStats tcs(counters());
301 TraceMemoryManagerStats tms(false /* not full GC */);
302
303 if (TraceGen0Time) accumulated_time()->start();
304
305 // Let the size policy know we're starting
306 size_policy->minor_collection_begin();
307
308 // Verify the object start arrays.
309 if (VerifyObjectStartArray &&
310 VerifyBeforeGC) {
311 old_gen->verify_object_start_array();
312 perm_gen->verify_object_start_array();
313 }
314
315 // Verify no unmarked old->young roots
316 if (VerifyRememberedSets) {
317 CardTableExtension::verify_all_young_refs_imprecise();
318 }
319
320 if (!ScavengeWithObjectsInToSpace) {
321 assert(young_gen->to_space()->is_empty(),
322 "Attempt to scavenge with live objects in to_space");
323 young_gen->to_space()->clear(SpaceDecorator::Mangle);
324 } else if (ZapUnusedHeapArea) {
325 young_gen->to_space()->mangle_unused_area();
326 }
327 save_to_space_top_before_gc();
328
329 NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
330 COMPILER2_PRESENT(DerivedPointerTable::clear());
331
332 reference_processor()->enable_discovery();
333 reference_processor()->setup_policy(false);
334
335 // We track how much was promoted to the next generation for
336 // the AdaptiveSizePolicy.
337 size_t old_gen_used_before = old_gen->used_in_bytes();
338
339 // For PrintGCDetails
340 size_t young_gen_used_before = young_gen->used_in_bytes();
341
342 // Reset our survivor overflow.
343 set_survivor_overflow(false);
344
345 // We need to save the old/perm top values before
346 // creating the promotion_manager. We pass the top
347 // values to the card_table, to prevent it from
348 // straying into the promotion labs.
349 HeapWord* old_top = old_gen->object_space()->top();
350 HeapWord* perm_top = perm_gen->object_space()->top();
351
352 // Release all previously held resources
353 gc_task_manager()->release_all_resources();
354
355 PSPromotionManager::pre_scavenge();
356
357 // We'll use the promotion manager again later.
358 PSPromotionManager* promotion_manager = PSPromotionManager::vm_thread_promotion_manager();
359 {
360 // TraceTime("Roots");
361 ParallelScavengeHeap::ParStrongRootsScope psrs;
362
363 GCTaskQueue* q = GCTaskQueue::create();
364
365 for(uint i=0; i<ParallelGCThreads; i++) {
366 q->enqueue(new OldToYoungRootsTask(old_gen, old_top, i));
367 }
368
369 q->enqueue(new SerialOldToYoungRootsTask(perm_gen, perm_top));
370
371 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::universe));
372 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jni_handles));
373 // We scan the thread roots in parallel
374 Threads::create_thread_roots_tasks(q);
375 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::object_synchronizer));
376 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::flat_profiler));
377 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::management));
378 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::system_dictionary));
379 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jvmti));
380 q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::code_cache));
381
382 ParallelTaskTerminator terminator(
383 gc_task_manager()->workers(),
384 promotion_manager->depth_first() ?
385 (TaskQueueSetSuper*) promotion_manager->stack_array_depth()
386 : (TaskQueueSetSuper*) promotion_manager->stack_array_breadth());
387 if (ParallelGCThreads>1) {
388 for (uint j=0; j<ParallelGCThreads; j++) {
389 q->enqueue(new StealTask(&terminator));
390 }
391 }
392
393 gc_task_manager()->execute_and_wait(q);
394 }
395
396 scavenge_midpoint.update();
397
398 // Process reference objects discovered during scavenge
399 {
400 reference_processor()->setup_policy(false); // not always_clear
401 PSKeepAliveClosure keep_alive(promotion_manager);
402 PSEvacuateFollowersClosure evac_followers(promotion_manager);
403 if (reference_processor()->processing_is_mt()) {
404 PSRefProcTaskExecutor task_executor;
405 reference_processor()->process_discovered_references(
406 &_is_alive_closure, &keep_alive, &evac_followers, &task_executor);
407 } else {
408 reference_processor()->process_discovered_references(
409 &_is_alive_closure, &keep_alive, &evac_followers, NULL);
410 }
411 }
412
413 // Enqueue reference objects discovered during scavenge.
414 if (reference_processor()->processing_is_mt()) {
415 PSRefProcTaskExecutor task_executor;
416 reference_processor()->enqueue_discovered_references(&task_executor);
417 } else {
418 reference_processor()->enqueue_discovered_references(NULL);
419 }
420
421 // Finally, flush the promotion_manager's labs, and deallocate its stacks.
422 assert(promotion_manager->claimed_stack_empty(), "Sanity");
423 PSPromotionManager::post_scavenge();
424
425 promotion_failure_occurred = promotion_failed();
426 if (promotion_failure_occurred) {
427 clean_up_failed_promotion();
428 if (PrintGC) {
429 gclog_or_tty->print("--");
430 }
431 }
432
433 // Let the size policy know we're done. Note that we count promotion
434 // failure cleanup time as part of the collection (otherwise, we're
435 // implicitly saying it's mutator time).
436 size_policy->minor_collection_end(gc_cause);
437
438 if (!promotion_failure_occurred) {
439 // Swap the survivor spaces.
440
441
442 young_gen->eden_space()->clear(SpaceDecorator::Mangle);
443 young_gen->from_space()->clear(SpaceDecorator::Mangle);
444 young_gen->swap_spaces();
445
446 size_t survived = young_gen->from_space()->used_in_bytes();
447 size_t promoted = old_gen->used_in_bytes() - old_gen_used_before;
448 size_policy->update_averages(_survivor_overflow, survived, promoted);
449
450 bool free_ratio_in_effect = false;
451 if ((UseFreeRatioForParallelGC ||
452 (UseFreeRatioOnlyInSystemGCForParallelGC &&
453 gc_cause == GCCause::_java_lang_system_gc))) {
454 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
455 free_ratio_in_effect = heap->try_to_shrink_by_free_ratio(false);
456 }
457
458 if (!free_ratio_in_effect && UseAdaptiveSizePolicy) {
459 // Calculate the new survivor size and tenuring threshold
460
461 if (PrintAdaptiveSizePolicy) {
462 gclog_or_tty->print("AdaptiveSizeStart: ");
463 gclog_or_tty->stamp();
464 gclog_or_tty->print_cr(" collection: %d ",
465 heap->total_collections());
466
467 if (Verbose) {
468 gclog_or_tty->print("old_gen_capacity: %d young_gen_capacity: %d"
469 " perm_gen_capacity: %d ",
470 old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes(),
471 perm_gen->capacity_in_bytes());
472 }
473 }
474
475
476 if (UsePerfData) {
477 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
478 counters->update_old_eden_size(
479 size_policy->calculated_eden_size_in_bytes());
480 counters->update_old_promo_size(
481 size_policy->calculated_promo_size_in_bytes());
482 counters->update_old_capacity(old_gen->capacity_in_bytes());
483 counters->update_young_capacity(young_gen->capacity_in_bytes());
484 counters->update_survived(survived);
485 counters->update_promoted(promoted);
486 counters->update_survivor_overflowed(_survivor_overflow);
487 }
488
489 size_t survivor_limit =
490 size_policy->max_survivor_size(young_gen->max_size());
491 _tenuring_threshold =
492 size_policy->compute_survivor_space_size_and_threshold(
493 _survivor_overflow,
494 _tenuring_threshold,
495 survivor_limit);
496
497 if (PrintTenuringDistribution) {
498 gclog_or_tty->cr();
499 gclog_or_tty->print_cr("Desired survivor size %ld bytes, new threshold %d (max %d)",
500 size_policy->calculated_survivor_size_in_bytes(),
501 _tenuring_threshold, MaxTenuringThreshold);
502 }
503
504 if (UsePerfData) {
505 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
506 counters->update_tenuring_threshold(_tenuring_threshold);
507 counters->update_survivor_size_counters();
508 }
509
510 // Do call at minor collections?
511 // Don't check if the size_policy is ready at this
512 // level. Let the size_policy check that internally.
513 if (UseAdaptiveSizePolicy &&
514 UseAdaptiveGenerationSizePolicyAtMinorCollection &&
515 ((gc_cause != GCCause::_java_lang_system_gc) ||
516 UseAdaptiveSizePolicyWithSystemGC)) {
517
518 // Calculate optimial free space amounts
519 assert(young_gen->max_size() >
520 young_gen->from_space()->capacity_in_bytes() +
521 young_gen->to_space()->capacity_in_bytes(),
522 "Sizes of space in young gen are out-of-bounds");
523 size_t max_eden_size = young_gen->max_size() -
524 young_gen->from_space()->capacity_in_bytes() -
525 young_gen->to_space()->capacity_in_bytes();
526 size_policy->compute_generation_free_space(young_gen->used_in_bytes(),
527 young_gen->eden_space()->used_in_bytes(),
528 old_gen->used_in_bytes(),
529 perm_gen->used_in_bytes(),
530 young_gen->eden_space()->capacity_in_bytes(),
531 old_gen->max_gen_size(),
532 max_eden_size,
533 false /* full gc*/,
534 gc_cause);
535
536 }
537 // Resize the young generation at every collection
538 // even if new sizes have not been calculated. This is
539 // to allow resizes that may have been inhibited by the
540 // relative location of the "to" and "from" spaces.
541
542 // Resizing the old gen at minor collects can cause increases
543 // that don't feed back to the generation sizing policy until
544 // a major collection. Don't resize the old gen here.
545
546 heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
547 size_policy->calculated_survivor_size_in_bytes());
548
549 if (PrintAdaptiveSizePolicy) {
550 gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
551 heap->total_collections());
552 }
553 }
554
555 // Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can
556 // cause the change of the heap layout. Make sure eden is reshaped if that's the case.
557 // Also update() will case adaptive NUMA chunk resizing.
558 assert(young_gen->eden_space()->is_empty(), "eden space should be empty now");
559 young_gen->eden_space()->update();
560
561 heap->gc_policy_counters()->update_counters();
562
563 heap->resize_all_tlabs();
564
565 assert(young_gen->to_space()->is_empty(), "to space should be empty now");
566 }
567
568 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
569
570 NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
571
572 // Re-verify object start arrays
573 if (VerifyObjectStartArray &&
574 VerifyAfterGC) {
575 old_gen->verify_object_start_array();
576 perm_gen->verify_object_start_array();
577 }
578
579 // Verify all old -> young cards are now precise
580 if (VerifyRememberedSets) {
581 // Precise verification will give false positives. Until this is fixed,
582 // use imprecise verification.
583 // CardTableExtension::verify_all_young_refs_precise();
584 CardTableExtension::verify_all_young_refs_imprecise();
585 }
586
587 if (TraceGen0Time) accumulated_time()->stop();
588
589 if (PrintGC) {
590 if (PrintGCDetails) {
591 // Don't print a GC timestamp here. This is after the GC so
592 // would be confusing.
593 young_gen->print_used_change(young_gen_used_before);
594 }
595 heap->print_heap_change(prev_used);
596 }
597
598 // Track memory usage and detect low memory
599 MemoryService::track_memory_usage();
600 heap->update_counters();
601 }
602
603 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
604 HandleMark hm; // Discard invalid handles created during verification
605 gclog_or_tty->print(" VerifyAfterGC:");
606 Universe::verify(false);
607 }
608
609 if (PrintHeapAtGC) {
610 Universe::print_heap_after_gc();
611 }
612
613 if (ZapUnusedHeapArea) {
614 young_gen->eden_space()->check_mangled_unused_area_complete();
615 young_gen->from_space()->check_mangled_unused_area_complete();
616 young_gen->to_space()->check_mangled_unused_area_complete();
617 }
618
619 scavenge_exit.update();
620
621 if (PrintGCTaskTimeStamps) {
622 tty->print_cr("VM-Thread " INT64_FORMAT " " INT64_FORMAT " " INT64_FORMAT,
623 scavenge_entry.ticks(), scavenge_midpoint.ticks(),
624 scavenge_exit.ticks());
625 gc_task_manager()->print_task_time_stamps();
626 }
627
628 #ifdef TRACESPINNING
629 ParallelTaskTerminator::print_termination_counts();
630 #endif
631
632 return !promotion_failure_occurred;
633 }
634
635 // This method iterates over all objects in the young generation,
636 // unforwarding markOops. It then restores any preserved mark oops,
637 // and clears the _preserved_mark_stack.
638 void PSScavenge::clean_up_failed_promotion() {
639 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
640 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
641 assert(promotion_failed(), "Sanity");
642
643 PSYoungGen* young_gen = heap->young_gen();
644
645 {
646 ResourceMark rm;
647
648 // Unforward all pointers in the young gen.
649 PSPromotionFailedClosure unforward_closure;
650 young_gen->object_iterate(&unforward_closure);
651
652 if (PrintGC && Verbose) {
653 gclog_or_tty->print_cr("Restoring %d marks",
654 _preserved_oop_stack->length());
655 }
656
657 // Restore any saved marks.
658 for (int i=0; i < _preserved_oop_stack->length(); i++) {
659 oop obj = _preserved_oop_stack->at(i);
660 markOop mark = _preserved_mark_stack->at(i);
661 obj->set_mark(mark);
662 }
663
664 // Deallocate the preserved mark and oop stacks.
665 // The stacks were allocated as CHeap objects, so
666 // we must call delete to prevent mem leaks.
667 delete _preserved_mark_stack;
668 _preserved_mark_stack = NULL;
669 delete _preserved_oop_stack;
670 _preserved_oop_stack = NULL;
671 }
672
673 // Reset the PromotionFailureALot counters.
674 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
675 }
676
677 // This method is called whenever an attempt to promote an object
678 // fails. Some markOops will need preserving, some will not. Note
679 // that the entire eden is traversed after a failed promotion, with
680 // all forwarded headers replaced by the default markOop. This means
681 // it is not neccessary to preserve most markOops.
682 void PSScavenge::oop_promotion_failed(oop obj, markOop obj_mark) {
683 if (_preserved_mark_stack == NULL) {
684 ThreadCritical tc; // Lock and retest
685 if (_preserved_mark_stack == NULL) {
686 assert(_preserved_oop_stack == NULL, "Sanity");
687 _preserved_mark_stack = new (ResourceObj::C_HEAP) GrowableArray<markOop>(40, true);
688 _preserved_oop_stack = new (ResourceObj::C_HEAP) GrowableArray<oop>(40, true);
689 }
690 }
691
692 // Because we must hold the ThreadCritical lock before using
693 // the stacks, we should be safe from observing partial allocations,
694 // which are also guarded by the ThreadCritical lock.
695 if (obj_mark->must_be_preserved_for_promotion_failure(obj)) {
696 ThreadCritical tc;
697 _preserved_oop_stack->push(obj);
698 _preserved_mark_stack->push(obj_mark);
699 }
700 }
701
702 bool PSScavenge::should_attempt_scavenge() {
703 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
704 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
705 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
706
707 if (UsePerfData) {
708 counters->update_scavenge_skipped(not_skipped);
709 }
710
711 PSYoungGen* young_gen = heap->young_gen();
712 PSOldGen* old_gen = heap->old_gen();
713
714 if (!ScavengeWithObjectsInToSpace) {
715 // Do not attempt to promote unless to_space is empty
716 if (!young_gen->to_space()->is_empty()) {
717 _consecutive_skipped_scavenges++;
718 if (UsePerfData) {
719 counters->update_scavenge_skipped(to_space_not_empty);
720 }
721 return false;
722 }
723 }
724
725 // Test to see if the scavenge will likely fail.
726 PSAdaptiveSizePolicy* policy = heap->size_policy();
727
728 // A similar test is done in the policy's should_full_GC(). If this is
729 // changed, decide if that test should also be changed.
730 size_t avg_promoted = (size_t) policy->padded_average_promoted_in_bytes();
731 size_t promotion_estimate = MIN2(avg_promoted, young_gen->used_in_bytes());
732 bool result = promotion_estimate < old_gen->free_in_bytes();
733
734 if (PrintGCDetails && Verbose) {
735 gclog_or_tty->print(result ? " do scavenge: " : " skip scavenge: ");
736 gclog_or_tty->print_cr(" average_promoted " SIZE_FORMAT
737 " padded_average_promoted " SIZE_FORMAT
738 " free in old gen " SIZE_FORMAT,
739 (size_t) policy->average_promoted_in_bytes(),
740 (size_t) policy->padded_average_promoted_in_bytes(),
741 old_gen->free_in_bytes());
742 if (young_gen->used_in_bytes() <
743 (size_t) policy->padded_average_promoted_in_bytes()) {
744 gclog_or_tty->print_cr(" padded_promoted_average is greater"
745 " than maximum promotion = " SIZE_FORMAT, young_gen->used_in_bytes());
746 }
747 }
748
749 if (result) {
750 _consecutive_skipped_scavenges = 0;
751 } else {
752 _consecutive_skipped_scavenges++;
753 if (UsePerfData) {
754 counters->update_scavenge_skipped(promoted_too_large);
755 }
756 }
757 return result;
758 }
759
760 // Used to add tasks
761 GCTaskManager* const PSScavenge::gc_task_manager() {
762 assert(ParallelScavengeHeap::gc_task_manager() != NULL,
763 "shouldn't return NULL");
764 return ParallelScavengeHeap::gc_task_manager();
765 }
766
767 void PSScavenge::initialize() {
768 // Arguments must have been parsed
769
770 if (AlwaysTenure) {
771 _tenuring_threshold = 0;
772 } else if (NeverTenure) {
773 _tenuring_threshold = markOopDesc::max_age + 1;
774 } else {
775 // We want to smooth out our startup times for the AdaptiveSizePolicy
776 _tenuring_threshold = (UseAdaptiveSizePolicy) ? InitialTenuringThreshold :
777 MaxTenuringThreshold;
778 }
779
780 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
781 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
782
783 PSYoungGen* young_gen = heap->young_gen();
784 PSOldGen* old_gen = heap->old_gen();
785 PSPermGen* perm_gen = heap->perm_gen();
786
787 // Set boundary between young_gen and old_gen
788 assert(perm_gen->reserved().end() <= old_gen->object_space()->bottom(),
789 "perm above old");
790 assert(old_gen->reserved().end() <= young_gen->eden_space()->bottom(),
791 "old above young");
792 _young_generation_boundary = young_gen->eden_space()->bottom();
793
794 // Initialize ref handling object for scavenging.
795 MemRegion mr = young_gen->reserved();
796 _ref_processor = ReferenceProcessor::create_ref_processor(
797 mr, // span
798 true, // atomic_discovery
799 true, // mt_discovery
800 NULL, // is_alive_non_header
801 ParallelGCThreads,
802 ParallelRefProcEnabled);
803
804 // Cache the cardtable
805 BarrierSet* bs = Universe::heap()->barrier_set();
806 assert(bs->kind() == BarrierSet::CardTableModRef, "Wrong barrier set kind");
807 _card_table = (CardTableExtension*)bs;
808
809 _counters = new CollectorCounters("PSScavenge", 0);
810 }