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 if (UseAdaptiveSizePolicy) {
451 // Calculate the new survivor size and tenuring threshold
452
453 if (PrintAdaptiveSizePolicy) {
454 gclog_or_tty->print("AdaptiveSizeStart: ");
455 gclog_or_tty->stamp();
456 gclog_or_tty->print_cr(" collection: %d ",
457 heap->total_collections());
458
459 if (Verbose) {
460 gclog_or_tty->print("old_gen_capacity: %d young_gen_capacity: %d"
461 " perm_gen_capacity: %d ",
462 old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes(),
463 perm_gen->capacity_in_bytes());
464 }
465 }
466
467
468 if (UsePerfData) {
469 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
470 counters->update_old_eden_size(
471 size_policy->calculated_eden_size_in_bytes());
472 counters->update_old_promo_size(
473 size_policy->calculated_promo_size_in_bytes());
474 counters->update_old_capacity(old_gen->capacity_in_bytes());
475 counters->update_young_capacity(young_gen->capacity_in_bytes());
476 counters->update_survived(survived);
477 counters->update_promoted(promoted);
478 counters->update_survivor_overflowed(_survivor_overflow);
479 }
480
481 size_t survivor_limit =
482 size_policy->max_survivor_size(young_gen->max_size());
483 _tenuring_threshold =
484 size_policy->compute_survivor_space_size_and_threshold(
485 _survivor_overflow,
486 _tenuring_threshold,
487 survivor_limit);
488
489 if (PrintTenuringDistribution) {
490 gclog_or_tty->cr();
491 gclog_or_tty->print_cr("Desired survivor size %ld bytes, new threshold %d (max %d)",
492 size_policy->calculated_survivor_size_in_bytes(),
493 _tenuring_threshold, MaxTenuringThreshold);
494 }
495
496 if (UsePerfData) {
497 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
498 counters->update_tenuring_threshold(_tenuring_threshold);
499 counters->update_survivor_size_counters();
500 }
501
502 // Do call at minor collections?
503 // Don't check if the size_policy is ready at this
504 // level. Let the size_policy check that internally.
505 if (UseAdaptiveSizePolicy &&
506 UseAdaptiveGenerationSizePolicyAtMinorCollection &&
507 ((gc_cause != GCCause::_java_lang_system_gc) ||
508 UseAdaptiveSizePolicyWithSystemGC)) {
509
510 // Calculate optimial free space amounts
511 assert(young_gen->max_size() >
512 young_gen->from_space()->capacity_in_bytes() +
513 young_gen->to_space()->capacity_in_bytes(),
514 "Sizes of space in young gen are out-of-bounds");
515 size_t max_eden_size = young_gen->max_size() -
516 young_gen->from_space()->capacity_in_bytes() -
517 young_gen->to_space()->capacity_in_bytes();
518 size_policy->compute_generation_free_space(young_gen->used_in_bytes(),
519 young_gen->eden_space()->used_in_bytes(),
520 old_gen->used_in_bytes(),
521 perm_gen->used_in_bytes(),
522 young_gen->eden_space()->capacity_in_bytes(),
523 old_gen->max_gen_size(),
524 max_eden_size,
525 false /* full gc*/,
526 gc_cause);
527
528 }
529 // Resize the young generation at every collection
530 // even if new sizes have not been calculated. This is
531 // to allow resizes that may have been inhibited by the
532 // relative location of the "to" and "from" spaces.
533
534 // Resizing the old gen at minor collects can cause increases
535 // that don't feed back to the generation sizing policy until
536 // a major collection. Don't resize the old gen here.
537
538 heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
539 size_policy->calculated_survivor_size_in_bytes());
540
541 if (PrintAdaptiveSizePolicy) {
542 gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
543 heap->total_collections());
544 }
545 }
546
547 // Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can
548 // cause the change of the heap layout. Make sure eden is reshaped if that's the case.
549 // Also update() will case adaptive NUMA chunk resizing.
550 assert(young_gen->eden_space()->is_empty(), "eden space should be empty now");
551 young_gen->eden_space()->update();
552
553 heap->gc_policy_counters()->update_counters();
554
555 heap->resize_all_tlabs();
556
557 assert(young_gen->to_space()->is_empty(), "to space should be empty now");
558 }
559
560 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
561
562 NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
563
564 // Re-verify object start arrays
565 if (VerifyObjectStartArray &&
566 VerifyAfterGC) {
567 old_gen->verify_object_start_array();
568 perm_gen->verify_object_start_array();
569 }
570
571 // Verify all old -> young cards are now precise
572 if (VerifyRememberedSets) {
573 // Precise verification will give false positives. Until this is fixed,
574 // use imprecise verification.
575 // CardTableExtension::verify_all_young_refs_precise();
576 CardTableExtension::verify_all_young_refs_imprecise();
577 }
578
579 if (TraceGen0Time) accumulated_time()->stop();
580
581 if (PrintGC) {
582 if (PrintGCDetails) {
583 // Don't print a GC timestamp here. This is after the GC so
584 // would be confusing.
585 young_gen->print_used_change(young_gen_used_before);
586 }
587 heap->print_heap_change(prev_used);
588 }
589
590 // Track memory usage and detect low memory
591 MemoryService::track_memory_usage();
592 heap->update_counters();
593 }
594
595 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
596 HandleMark hm; // Discard invalid handles created during verification
597 gclog_or_tty->print(" VerifyAfterGC:");
598 Universe::verify(false);
599 }
600
601 if (PrintHeapAtGC) {
602 Universe::print_heap_after_gc();
603 }
604
605 if (ZapUnusedHeapArea) {
606 young_gen->eden_space()->check_mangled_unused_area_complete();
607 young_gen->from_space()->check_mangled_unused_area_complete();
608 young_gen->to_space()->check_mangled_unused_area_complete();
609 }
610
611 scavenge_exit.update();
612
613 if (PrintGCTaskTimeStamps) {
614 tty->print_cr("VM-Thread " INT64_FORMAT " " INT64_FORMAT " " INT64_FORMAT,
615 scavenge_entry.ticks(), scavenge_midpoint.ticks(),
616 scavenge_exit.ticks());
617 gc_task_manager()->print_task_time_stamps();
618 }
619
620 #ifdef TRACESPINNING
621 ParallelTaskTerminator::print_termination_counts();
622 #endif
623
624 return !promotion_failure_occurred;
625 }
626
627 // This method iterates over all objects in the young generation,
628 // unforwarding markOops. It then restores any preserved mark oops,
629 // and clears the _preserved_mark_stack.
630 void PSScavenge::clean_up_failed_promotion() {
631 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
632 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
633 assert(promotion_failed(), "Sanity");
634
635 PSYoungGen* young_gen = heap->young_gen();
636
637 {
638 ResourceMark rm;
639
640 // Unforward all pointers in the young gen.
641 PSPromotionFailedClosure unforward_closure;
642 young_gen->object_iterate(&unforward_closure);
643
644 if (PrintGC && Verbose) {
645 gclog_or_tty->print_cr("Restoring %d marks",
646 _preserved_oop_stack->length());
647 }
648
649 // Restore any saved marks.
650 for (int i=0; i < _preserved_oop_stack->length(); i++) {
651 oop obj = _preserved_oop_stack->at(i);
652 markOop mark = _preserved_mark_stack->at(i);
653 obj->set_mark(mark);
654 }
655
656 // Deallocate the preserved mark and oop stacks.
657 // The stacks were allocated as CHeap objects, so
658 // we must call delete to prevent mem leaks.
659 delete _preserved_mark_stack;
660 _preserved_mark_stack = NULL;
661 delete _preserved_oop_stack;
662 _preserved_oop_stack = NULL;
663 }
664
665 // Reset the PromotionFailureALot counters.
666 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
667 }
668
669 // This method is called whenever an attempt to promote an object
670 // fails. Some markOops will need preserving, some will not. Note
671 // that the entire eden is traversed after a failed promotion, with
672 // all forwarded headers replaced by the default markOop. This means
673 // it is not neccessary to preserve most markOops.
674 void PSScavenge::oop_promotion_failed(oop obj, markOop obj_mark) {
675 if (_preserved_mark_stack == NULL) {
676 ThreadCritical tc; // Lock and retest
677 if (_preserved_mark_stack == NULL) {
678 assert(_preserved_oop_stack == NULL, "Sanity");
679 _preserved_mark_stack = new (ResourceObj::C_HEAP) GrowableArray<markOop>(40, true);
680 _preserved_oop_stack = new (ResourceObj::C_HEAP) GrowableArray<oop>(40, true);
681 }
682 }
683
684 // Because we must hold the ThreadCritical lock before using
685 // the stacks, we should be safe from observing partial allocations,
686 // which are also guarded by the ThreadCritical lock.
687 if (obj_mark->must_be_preserved_for_promotion_failure(obj)) {
688 ThreadCritical tc;
689 _preserved_oop_stack->push(obj);
690 _preserved_mark_stack->push(obj_mark);
691 }
692 }
693
694 bool PSScavenge::should_attempt_scavenge() {
695 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
696 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
697 PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
698
699 if (UsePerfData) {
700 counters->update_scavenge_skipped(not_skipped);
701 }
702
703 PSYoungGen* young_gen = heap->young_gen();
704 PSOldGen* old_gen = heap->old_gen();
705
706 if (!ScavengeWithObjectsInToSpace) {
707 // Do not attempt to promote unless to_space is empty
708 if (!young_gen->to_space()->is_empty()) {
709 _consecutive_skipped_scavenges++;
710 if (UsePerfData) {
711 counters->update_scavenge_skipped(to_space_not_empty);
712 }
713 return false;
714 }
715 }
716
717 // Test to see if the scavenge will likely fail.
718 PSAdaptiveSizePolicy* policy = heap->size_policy();
719
720 // A similar test is done in the policy's should_full_GC(). If this is
721 // changed, decide if that test should also be changed.
722 size_t avg_promoted = (size_t) policy->padded_average_promoted_in_bytes();
723 size_t promotion_estimate = MIN2(avg_promoted, young_gen->used_in_bytes());
724 bool result = promotion_estimate < old_gen->free_in_bytes();
725
726 if (PrintGCDetails && Verbose) {
727 gclog_or_tty->print(result ? " do scavenge: " : " skip scavenge: ");
728 gclog_or_tty->print_cr(" average_promoted " SIZE_FORMAT
729 " padded_average_promoted " SIZE_FORMAT
730 " free in old gen " SIZE_FORMAT,
731 (size_t) policy->average_promoted_in_bytes(),
732 (size_t) policy->padded_average_promoted_in_bytes(),
733 old_gen->free_in_bytes());
734 if (young_gen->used_in_bytes() <
735 (size_t) policy->padded_average_promoted_in_bytes()) {
736 gclog_or_tty->print_cr(" padded_promoted_average is greater"
737 " than maximum promotion = " SIZE_FORMAT, young_gen->used_in_bytes());
738 }
739 }
740
741 if (result) {
742 _consecutive_skipped_scavenges = 0;
743 } else {
744 _consecutive_skipped_scavenges++;
745 if (UsePerfData) {
746 counters->update_scavenge_skipped(promoted_too_large);
747 }
748 }
749 return result;
750 }
751
752 // Used to add tasks
753 GCTaskManager* const PSScavenge::gc_task_manager() {
754 assert(ParallelScavengeHeap::gc_task_manager() != NULL,
755 "shouldn't return NULL");
756 return ParallelScavengeHeap::gc_task_manager();
757 }
758
759 void PSScavenge::initialize() {
760 // Arguments must have been parsed
761
762 if (AlwaysTenure) {
763 _tenuring_threshold = 0;
764 } else if (NeverTenure) {
765 _tenuring_threshold = markOopDesc::max_age + 1;
766 } else {
767 // We want to smooth out our startup times for the AdaptiveSizePolicy
768 _tenuring_threshold = (UseAdaptiveSizePolicy) ? InitialTenuringThreshold :
769 MaxTenuringThreshold;
770 }
771
772 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
773 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
774
775 PSYoungGen* young_gen = heap->young_gen();
776 PSOldGen* old_gen = heap->old_gen();
777 PSPermGen* perm_gen = heap->perm_gen();
778
779 // Set boundary between young_gen and old_gen
780 assert(perm_gen->reserved().end() <= old_gen->object_space()->bottom(),
781 "perm above old");
782 assert(old_gen->reserved().end() <= young_gen->eden_space()->bottom(),
783 "old above young");
784 _young_generation_boundary = young_gen->eden_space()->bottom();
785
786 // Initialize ref handling object for scavenging.
787 MemRegion mr = young_gen->reserved();
788 _ref_processor = ReferenceProcessor::create_ref_processor(
789 mr, // span
790 true, // atomic_discovery
791 true, // mt_discovery
792 NULL, // is_alive_non_header
793 ParallelGCThreads,
794 ParallelRefProcEnabled);
795
796 // Cache the cardtable
797 BarrierSet* bs = Universe::heap()->barrier_set();
798 assert(bs->kind() == BarrierSet::CardTableModRef, "Wrong barrier set kind");
799 _card_table = (CardTableExtension*)bs;
800
801 _counters = new CollectorCounters("PSScavenge", 0);
802 }