Thu, 01 Jul 2010 21:40:45 -0700
6957084: simplify TaskQueue overflow handling
Reviewed-by: ysr, jmasa
1 /*
2 * Copyright (c) 2002, 2010, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
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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.
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23 */
26 # include "incls/_precompiled.incl"
27 # include "incls/_psScavenge.cpp.incl"
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;
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 };
52 PSIsAliveClosure PSScavenge::_is_alive_closure;
54 class PSKeepAliveClosure: public OopClosure {
55 protected:
56 MutableSpace* _to_space;
57 PSPromotionManager* _promotion_manager;
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();
65 assert(_promotion_manager != NULL, "Sanity");
66 }
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");
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 };
82 class PSEvacuateFollowersClosure: public VoidClosure {
83 private:
84 PSPromotionManager* _promotion_manager;
85 public:
86 PSEvacuateFollowersClosure(PSPromotionManager* pm) : _promotion_manager(pm) {}
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 };
96 class PSPromotionFailedClosure : public ObjectClosure {
97 virtual void do_object(oop obj) {
98 if (obj->is_forwarded()) {
99 obj->init_mark();
100 }
101 }
102 };
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 { }
114 private:
115 virtual char* name() { return (char *)"Process referents by policy in parallel"; }
116 virtual void do_it(GCTaskManager* manager, uint which);
117 };
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 }
130 class PSRefEnqueueTaskProxy: public GCTask {
131 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
132 EnqueueTask& _enq_task;
133 uint _work_id;
135 public:
136 PSRefEnqueueTaskProxy(EnqueueTask& enq_task, uint work_id)
137 : _enq_task(enq_task),
138 _work_id(work_id)
139 { }
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 };
148 class PSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
149 virtual void execute(ProcessTask& task);
150 virtual void execute(EnqueueTask& task);
151 };
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 }
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 }
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");
195 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
196 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
198 PSAdaptiveSizePolicy* policy = heap->size_policy();
199 IsGCActiveMark mark;
201 bool scavenge_was_done = PSScavenge::invoke_no_policy();
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();
214 if (UseParallelOldGC) {
215 PSParallelCompact::invoke_no_policy(clear_all_softrefs);
216 } else {
217 PSMarkSweep::invoke_no_policy(clear_all_softrefs);
218 }
219 }
220 }
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");
228 TimeStamp scavenge_entry;
229 TimeStamp scavenge_midpoint;
230 TimeStamp scavenge_exit;
232 scavenge_entry.update();
234 if (GC_locker::check_active_before_gc()) {
235 return false;
236 }
238 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
239 GCCause::Cause gc_cause = heap->gc_cause();
240 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
242 // Check for potential problems.
243 if (!should_attempt_scavenge()) {
244 return false;
245 }
247 bool promotion_failure_occurred = false;
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();
255 AdaptiveSizePolicyOutput(size_policy, heap->total_collections());
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 }
263 if (ZapUnusedHeapArea) {
264 // Save information needed to minimize mangling
265 heap->record_gen_tops_before_GC();
266 }
268 if (PrintHeapAtGC) {
269 Universe::print_heap_before_gc();
270 }
272 assert(!NeverTenure || _tenuring_threshold == markOopDesc::max_age + 1, "Sanity");
273 assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity");
275 size_t prev_used = heap->used();
276 assert(promotion_failed() == false, "Sanity");
278 // Fill in TLABs
279 heap->accumulate_statistics_all_tlabs();
280 heap->ensure_parsability(true); // retire TLABs
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 }
288 {
289 ResourceMark rm;
290 HandleMark hm;
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 */);
298 if (TraceGen0Time) accumulated_time()->start();
300 // Let the size policy know we're starting
301 size_policy->minor_collection_begin();
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 }
310 // Verify no unmarked old->young roots
311 if (VerifyRememberedSets) {
312 CardTableExtension::verify_all_young_refs_imprecise();
313 }
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();
324 NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
325 COMPILER2_PRESENT(DerivedPointerTable::clear());
327 reference_processor()->enable_discovery();
328 reference_processor()->setup_policy(false);
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();
334 // For PrintGCDetails
335 size_t young_gen_used_before = young_gen->used_in_bytes();
337 // Reset our survivor overflow.
338 set_survivor_overflow(false);
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();
347 // Release all previously held resources
348 gc_task_manager()->release_all_resources();
350 PSPromotionManager::pre_scavenge();
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;
358 GCTaskQueue* q = GCTaskQueue::create();
360 for(uint i=0; i<ParallelGCThreads; i++) {
361 q->enqueue(new OldToYoungRootsTask(old_gen, old_top, i));
362 }
364 q->enqueue(new SerialOldToYoungRootsTask(perm_gen, perm_top));
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));
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 }
388 gc_task_manager()->execute_and_wait(q);
389 }
391 scavenge_midpoint.update();
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 }
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 }
416 // Finally, flush the promotion_manager's labs, and deallocate its stacks.
417 PSPromotionManager::post_scavenge();
419 promotion_failure_occurred = promotion_failed();
420 if (promotion_failure_occurred) {
421 clean_up_failed_promotion();
422 if (PrintGC) {
423 gclog_or_tty->print("--");
424 }
425 }
427 // Let the size policy know we're done. Note that we count promotion
428 // failure cleanup time as part of the collection (otherwise, we're
429 // implicitly saying it's mutator time).
430 size_policy->minor_collection_end(gc_cause);
432 if (!promotion_failure_occurred) {
433 // Swap the survivor spaces.
436 young_gen->eden_space()->clear(SpaceDecorator::Mangle);
437 young_gen->from_space()->clear(SpaceDecorator::Mangle);
438 young_gen->swap_spaces();
440 size_t survived = young_gen->from_space()->used_in_bytes();
441 size_t promoted = old_gen->used_in_bytes() - old_gen_used_before;
442 size_policy->update_averages(_survivor_overflow, survived, promoted);
444 // A successful scavenge should restart the GC time limit count which is
445 // for full GC's.
446 size_policy->reset_gc_overhead_limit_count();
447 if (UseAdaptiveSizePolicy) {
448 // Calculate the new survivor size and tenuring threshold
450 if (PrintAdaptiveSizePolicy) {
451 gclog_or_tty->print("AdaptiveSizeStart: ");
452 gclog_or_tty->stamp();
453 gclog_or_tty->print_cr(" collection: %d ",
454 heap->total_collections());
456 if (Verbose) {
457 gclog_or_tty->print("old_gen_capacity: %d young_gen_capacity: %d"
458 " perm_gen_capacity: %d ",
459 old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes(),
460 perm_gen->capacity_in_bytes());
461 }
462 }
465 if (UsePerfData) {
466 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
467 counters->update_old_eden_size(
468 size_policy->calculated_eden_size_in_bytes());
469 counters->update_old_promo_size(
470 size_policy->calculated_promo_size_in_bytes());
471 counters->update_old_capacity(old_gen->capacity_in_bytes());
472 counters->update_young_capacity(young_gen->capacity_in_bytes());
473 counters->update_survived(survived);
474 counters->update_promoted(promoted);
475 counters->update_survivor_overflowed(_survivor_overflow);
476 }
478 size_t survivor_limit =
479 size_policy->max_survivor_size(young_gen->max_size());
480 _tenuring_threshold =
481 size_policy->compute_survivor_space_size_and_threshold(
482 _survivor_overflow,
483 _tenuring_threshold,
484 survivor_limit);
486 if (PrintTenuringDistribution) {
487 gclog_or_tty->cr();
488 gclog_or_tty->print_cr("Desired survivor size %ld bytes, new threshold %d (max %d)",
489 size_policy->calculated_survivor_size_in_bytes(),
490 _tenuring_threshold, MaxTenuringThreshold);
491 }
493 if (UsePerfData) {
494 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
495 counters->update_tenuring_threshold(_tenuring_threshold);
496 counters->update_survivor_size_counters();
497 }
499 // Do call at minor collections?
500 // Don't check if the size_policy is ready at this
501 // level. Let the size_policy check that internally.
502 if (UseAdaptiveSizePolicy &&
503 UseAdaptiveGenerationSizePolicyAtMinorCollection &&
504 ((gc_cause != GCCause::_java_lang_system_gc) ||
505 UseAdaptiveSizePolicyWithSystemGC)) {
507 // Calculate optimial free space amounts
508 assert(young_gen->max_size() >
509 young_gen->from_space()->capacity_in_bytes() +
510 young_gen->to_space()->capacity_in_bytes(),
511 "Sizes of space in young gen are out-of-bounds");
512 size_t max_eden_size = young_gen->max_size() -
513 young_gen->from_space()->capacity_in_bytes() -
514 young_gen->to_space()->capacity_in_bytes();
515 size_policy->compute_generation_free_space(young_gen->used_in_bytes(),
516 young_gen->eden_space()->used_in_bytes(),
517 old_gen->used_in_bytes(),
518 perm_gen->used_in_bytes(),
519 young_gen->eden_space()->capacity_in_bytes(),
520 old_gen->max_gen_size(),
521 max_eden_size,
522 false /* full gc*/,
523 gc_cause,
524 heap->collector_policy());
526 }
527 // Resize the young generation at every collection
528 // even if new sizes have not been calculated. This is
529 // to allow resizes that may have been inhibited by the
530 // relative location of the "to" and "from" spaces.
532 // Resizing the old gen at minor collects can cause increases
533 // that don't feed back to the generation sizing policy until
534 // a major collection. Don't resize the old gen here.
536 heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
537 size_policy->calculated_survivor_size_in_bytes());
539 if (PrintAdaptiveSizePolicy) {
540 gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
541 heap->total_collections());
542 }
543 }
545 // Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can
546 // cause the change of the heap layout. Make sure eden is reshaped if that's the case.
547 // Also update() will case adaptive NUMA chunk resizing.
548 assert(young_gen->eden_space()->is_empty(), "eden space should be empty now");
549 young_gen->eden_space()->update();
551 heap->gc_policy_counters()->update_counters();
553 heap->resize_all_tlabs();
555 assert(young_gen->to_space()->is_empty(), "to space should be empty now");
556 }
558 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
560 NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
562 // Re-verify object start arrays
563 if (VerifyObjectStartArray &&
564 VerifyAfterGC) {
565 old_gen->verify_object_start_array();
566 perm_gen->verify_object_start_array();
567 }
569 // Verify all old -> young cards are now precise
570 if (VerifyRememberedSets) {
571 // Precise verification will give false positives. Until this is fixed,
572 // use imprecise verification.
573 // CardTableExtension::verify_all_young_refs_precise();
574 CardTableExtension::verify_all_young_refs_imprecise();
575 }
577 if (TraceGen0Time) accumulated_time()->stop();
579 if (PrintGC) {
580 if (PrintGCDetails) {
581 // Don't print a GC timestamp here. This is after the GC so
582 // would be confusing.
583 young_gen->print_used_change(young_gen_used_before);
584 }
585 heap->print_heap_change(prev_used);
586 }
588 // Track memory usage and detect low memory
589 MemoryService::track_memory_usage();
590 heap->update_counters();
591 }
593 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
594 HandleMark hm; // Discard invalid handles created during verification
595 gclog_or_tty->print(" VerifyAfterGC:");
596 Universe::verify(false);
597 }
599 if (PrintHeapAtGC) {
600 Universe::print_heap_after_gc();
601 }
603 if (ZapUnusedHeapArea) {
604 young_gen->eden_space()->check_mangled_unused_area_complete();
605 young_gen->from_space()->check_mangled_unused_area_complete();
606 young_gen->to_space()->check_mangled_unused_area_complete();
607 }
609 scavenge_exit.update();
611 if (PrintGCTaskTimeStamps) {
612 tty->print_cr("VM-Thread " INT64_FORMAT " " INT64_FORMAT " " INT64_FORMAT,
613 scavenge_entry.ticks(), scavenge_midpoint.ticks(),
614 scavenge_exit.ticks());
615 gc_task_manager()->print_task_time_stamps();
616 }
618 #ifdef TRACESPINNING
619 ParallelTaskTerminator::print_termination_counts();
620 #endif
622 return !promotion_failure_occurred;
623 }
625 // This method iterates over all objects in the young generation,
626 // unforwarding markOops. It then restores any preserved mark oops,
627 // and clears the _preserved_mark_stack.
628 void PSScavenge::clean_up_failed_promotion() {
629 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
630 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
631 assert(promotion_failed(), "Sanity");
633 PSYoungGen* young_gen = heap->young_gen();
635 {
636 ResourceMark rm;
638 // Unforward all pointers in the young gen.
639 PSPromotionFailedClosure unforward_closure;
640 young_gen->object_iterate(&unforward_closure);
642 if (PrintGC && Verbose) {
643 gclog_or_tty->print_cr("Restoring %d marks",
644 _preserved_oop_stack->length());
645 }
647 // Restore any saved marks.
648 for (int i=0; i < _preserved_oop_stack->length(); i++) {
649 oop obj = _preserved_oop_stack->at(i);
650 markOop mark = _preserved_mark_stack->at(i);
651 obj->set_mark(mark);
652 }
654 // Deallocate the preserved mark and oop stacks.
655 // The stacks were allocated as CHeap objects, so
656 // we must call delete to prevent mem leaks.
657 delete _preserved_mark_stack;
658 _preserved_mark_stack = NULL;
659 delete _preserved_oop_stack;
660 _preserved_oop_stack = NULL;
661 }
663 // Reset the PromotionFailureALot counters.
664 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
665 }
667 // This method is called whenever an attempt to promote an object
668 // fails. Some markOops will need preserving, some will not. Note
669 // that the entire eden is traversed after a failed promotion, with
670 // all forwarded headers replaced by the default markOop. This means
671 // it is not neccessary to preserve most markOops.
672 void PSScavenge::oop_promotion_failed(oop obj, markOop obj_mark) {
673 if (_preserved_mark_stack == NULL) {
674 ThreadCritical tc; // Lock and retest
675 if (_preserved_mark_stack == NULL) {
676 assert(_preserved_oop_stack == NULL, "Sanity");
677 _preserved_mark_stack = new (ResourceObj::C_HEAP) GrowableArray<markOop>(40, true);
678 _preserved_oop_stack = new (ResourceObj::C_HEAP) GrowableArray<oop>(40, true);
679 }
680 }
682 // Because we must hold the ThreadCritical lock before using
683 // the stacks, we should be safe from observing partial allocations,
684 // which are also guarded by the ThreadCritical lock.
685 if (obj_mark->must_be_preserved_for_promotion_failure(obj)) {
686 ThreadCritical tc;
687 _preserved_oop_stack->push(obj);
688 _preserved_mark_stack->push(obj_mark);
689 }
690 }
692 bool PSScavenge::should_attempt_scavenge() {
693 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
694 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
695 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
697 if (UsePerfData) {
698 counters->update_scavenge_skipped(not_skipped);
699 }
701 PSYoungGen* young_gen = heap->young_gen();
702 PSOldGen* old_gen = heap->old_gen();
704 if (!ScavengeWithObjectsInToSpace) {
705 // Do not attempt to promote unless to_space is empty
706 if (!young_gen->to_space()->is_empty()) {
707 _consecutive_skipped_scavenges++;
708 if (UsePerfData) {
709 counters->update_scavenge_skipped(to_space_not_empty);
710 }
711 return false;
712 }
713 }
715 // Test to see if the scavenge will likely fail.
716 PSAdaptiveSizePolicy* policy = heap->size_policy();
718 // A similar test is done in the policy's should_full_GC(). If this is
719 // changed, decide if that test should also be changed.
720 size_t avg_promoted = (size_t) policy->padded_average_promoted_in_bytes();
721 size_t promotion_estimate = MIN2(avg_promoted, young_gen->used_in_bytes());
722 bool result = promotion_estimate < old_gen->free_in_bytes();
724 if (PrintGCDetails && Verbose) {
725 gclog_or_tty->print(result ? " do scavenge: " : " skip scavenge: ");
726 gclog_or_tty->print_cr(" average_promoted " SIZE_FORMAT
727 " padded_average_promoted " SIZE_FORMAT
728 " free in old gen " SIZE_FORMAT,
729 (size_t) policy->average_promoted_in_bytes(),
730 (size_t) policy->padded_average_promoted_in_bytes(),
731 old_gen->free_in_bytes());
732 if (young_gen->used_in_bytes() <
733 (size_t) policy->padded_average_promoted_in_bytes()) {
734 gclog_or_tty->print_cr(" padded_promoted_average is greater"
735 " than maximum promotion = " SIZE_FORMAT, young_gen->used_in_bytes());
736 }
737 }
739 if (result) {
740 _consecutive_skipped_scavenges = 0;
741 } else {
742 _consecutive_skipped_scavenges++;
743 if (UsePerfData) {
744 counters->update_scavenge_skipped(promoted_too_large);
745 }
746 }
747 return result;
748 }
750 // Used to add tasks
751 GCTaskManager* const PSScavenge::gc_task_manager() {
752 assert(ParallelScavengeHeap::gc_task_manager() != NULL,
753 "shouldn't return NULL");
754 return ParallelScavengeHeap::gc_task_manager();
755 }
757 void PSScavenge::initialize() {
758 // Arguments must have been parsed
760 if (AlwaysTenure) {
761 _tenuring_threshold = 0;
762 } else if (NeverTenure) {
763 _tenuring_threshold = markOopDesc::max_age + 1;
764 } else {
765 // We want to smooth out our startup times for the AdaptiveSizePolicy
766 _tenuring_threshold = (UseAdaptiveSizePolicy) ? InitialTenuringThreshold :
767 MaxTenuringThreshold;
768 }
770 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
771 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
773 PSYoungGen* young_gen = heap->young_gen();
774 PSOldGen* old_gen = heap->old_gen();
775 PSPermGen* perm_gen = heap->perm_gen();
777 // Set boundary between young_gen and old_gen
778 assert(perm_gen->reserved().end() <= old_gen->object_space()->bottom(),
779 "perm above old");
780 assert(old_gen->reserved().end() <= young_gen->eden_space()->bottom(),
781 "old above young");
782 _young_generation_boundary = young_gen->eden_space()->bottom();
784 // Initialize ref handling object for scavenging.
785 MemRegion mr = young_gen->reserved();
786 _ref_processor = ReferenceProcessor::create_ref_processor(
787 mr, // span
788 true, // atomic_discovery
789 true, // mt_discovery
790 NULL, // is_alive_non_header
791 ParallelGCThreads,
792 ParallelRefProcEnabled);
794 // Cache the cardtable
795 BarrierSet* bs = Universe::heap()->barrier_set();
796 assert(bs->kind() == BarrierSet::CardTableModRef, "Wrong barrier set kind");
797 _card_table = (CardTableExtension*)bs;
799 _counters = new CollectorCounters("PSScavenge", 0);
800 }