1 /*
2 * Copyright (c) 2002, 2025, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "classfile/classLoaderDataGraph.hpp"
26 #include "classfile/stringTable.hpp"
27 #include "code/codeCache.hpp"
28 #include "compiler/oopMap.hpp"
29 #include "gc/parallel/parallelScavengeHeap.hpp"
30 #include "gc/parallel/psAdaptiveSizePolicy.hpp"
31 #include "gc/parallel/psClosure.inline.hpp"
32 #include "gc/parallel/psCompactionManager.hpp"
33 #include "gc/parallel/psCompactionManagerNew.hpp"
34 #include "gc/parallel/psParallelCompact.inline.hpp"
35 #include "gc/parallel/psPromotionManager.inline.hpp"
36 #include "gc/parallel/psRootType.hpp"
37 #include "gc/parallel/psScavenge.hpp"
38 #include "gc/shared/gcCause.hpp"
39 #include "gc/shared/gcHeapSummary.hpp"
40 #include "gc/shared/gcId.hpp"
41 #include "gc/shared/gcLocker.hpp"
42 #include "gc/shared/gcTimer.hpp"
43 #include "gc/shared/gcTrace.hpp"
44 #include "gc/shared/gcTraceTime.inline.hpp"
45 #include "gc/shared/gcVMOperations.hpp"
46 #include "gc/shared/isGCActiveMark.hpp"
47 #include "gc/shared/oopStorage.inline.hpp"
48 #include "gc/shared/oopStorageParState.inline.hpp"
49 #include "gc/shared/oopStorageSetParState.inline.hpp"
50 #include "gc/shared/referencePolicy.hpp"
51 #include "gc/shared/referenceProcessor.hpp"
52 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
53 #include "gc/shared/scavengableNMethods.hpp"
54 #include "gc/shared/spaceDecorator.hpp"
55 #include "gc/shared/taskTerminator.hpp"
56 #include "gc/shared/weakProcessor.inline.hpp"
57 #include "gc/shared/workerPolicy.hpp"
58 #include "gc/shared/workerThread.hpp"
59 #include "gc/shared/workerUtils.hpp"
60 #include "logging/log.hpp"
61 #include "memory/iterator.hpp"
62 #include "memory/resourceArea.hpp"
63 #include "memory/universe.hpp"
64 #include "oops/access.inline.hpp"
65 #include "oops/compressedOops.inline.hpp"
66 #include "oops/oop.inline.hpp"
67 #include "runtime/handles.inline.hpp"
68 #include "runtime/threads.hpp"
69 #include "runtime/vmOperations.hpp"
70 #include "runtime/vmThread.hpp"
71 #include "services/memoryService.hpp"
72 #include "utilities/stack.inline.hpp"
73
74 SpanSubjectToDiscoveryClosure PSScavenge::_span_based_discoverer;
75 ReferenceProcessor* PSScavenge::_ref_processor = nullptr;
76 PSCardTable* PSScavenge::_card_table = nullptr;
77 bool PSScavenge::_survivor_overflow = false;
78 uint PSScavenge::_tenuring_threshold = 0;
79 HeapWord* PSScavenge::_young_generation_boundary = nullptr;
80 uintptr_t PSScavenge::_young_generation_boundary_compressed = 0;
81 elapsedTimer PSScavenge::_accumulated_time;
82 STWGCTimer PSScavenge::_gc_timer;
83 ParallelScavengeTracer PSScavenge::_gc_tracer;
84 CollectorCounters* PSScavenge::_counters = nullptr;
85
86 static void scavenge_roots_work(ParallelRootType::Value root_type, uint worker_id) {
87 assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
88
89 PSPromotionManager* pm = PSPromotionManager::gc_thread_promotion_manager(worker_id);
90 PSPromoteRootsClosure roots_to_old_closure(pm);
91
92 switch (root_type) {
93 case ParallelRootType::class_loader_data:
94 {
95 PSScavengeCLDClosure cld_closure(pm);
96 ClassLoaderDataGraph::cld_do(&cld_closure);
97 }
98 break;
99
100 case ParallelRootType::code_cache:
101 {
102 NMethodToOopClosure code_closure(&roots_to_old_closure, NMethodToOopClosure::FixRelocations);
103 ScavengableNMethods::nmethods_do(&code_closure);
104 }
105 break;
106
107 case ParallelRootType::sentinel:
108 DEBUG_ONLY(default:) // DEBUG_ONLY hack will create compile error on release builds (-Wswitch) and runtime check on debug builds
109 fatal("Bad enumeration value: %u", root_type);
110 break;
111 }
112
113 // Do the real work
114 pm->drain_stacks(false);
115 }
116
117 static void steal_work(TaskTerminator& terminator, uint worker_id) {
118 assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
119
120 PSPromotionManager* pm =
121 PSPromotionManager::gc_thread_promotion_manager(worker_id);
122 pm->drain_stacks(true);
123 guarantee(pm->stacks_empty(),
124 "stacks should be empty at this point");
125
126 while (true) {
127 ScannerTask task;
128 if (PSPromotionManager::steal_depth(worker_id, task)) {
129 pm->process_popped_location_depth(task, true);
130 pm->drain_stacks(true);
131 } else {
132 if (terminator.offer_termination()) {
133 break;
134 }
135 }
136 }
137 guarantee(pm->stacks_empty(), "stacks should be empty at this point");
138 }
139
140 // Define before use
141 class PSIsAliveClosure: public BoolObjectClosure {
142 public:
143 bool do_object_b(oop p) {
144 return (!PSScavenge::is_obj_in_young(p)) || p->is_forwarded();
145 }
146 };
147
148 PSIsAliveClosure PSScavenge::_is_alive_closure;
149
150 class PSKeepAliveClosure: public OopClosure {
151 PSPromotionManager* _promotion_manager;
152
153 public:
154 PSKeepAliveClosure(PSPromotionManager* pm) : _promotion_manager(pm) {
155 assert(_promotion_manager != nullptr, "Sanity");
156 }
157
158 template <class T> void do_oop_work(T* p) {
159 #ifdef ASSERT
160 // Referent must be non-null and in from-space
161 oop obj = RawAccess<IS_NOT_NULL>::oop_load(p);
162 assert(oopDesc::is_oop(obj), "referent must be an oop");
163 assert(PSScavenge::is_obj_in_young(obj), "must be in young-gen");
164 assert(!PSScavenge::is_obj_in_to_space(obj), "must be in from-space");
165 #endif
166
167 _promotion_manager->copy_and_push_safe_barrier</*promote_immediately=*/false>(p);
168 }
169 virtual void do_oop(oop* p) { PSKeepAliveClosure::do_oop_work(p); }
170 virtual void do_oop(narrowOop* p) { PSKeepAliveClosure::do_oop_work(p); }
171 };
172
173 class PSEvacuateFollowersClosure: public VoidClosure {
174 private:
175 PSPromotionManager* _promotion_manager;
176 TaskTerminator* _terminator;
177 uint _worker_id;
178
179 public:
180 PSEvacuateFollowersClosure(PSPromotionManager* pm, TaskTerminator* terminator, uint worker_id)
181 : _promotion_manager(pm), _terminator(terminator), _worker_id(worker_id) {}
182
183 virtual void do_void() {
184 assert(_promotion_manager != nullptr, "Sanity");
185 _promotion_manager->drain_stacks(true);
186 guarantee(_promotion_manager->stacks_empty(),
187 "stacks should be empty at this point");
188
189 if (_terminator != nullptr) {
190 steal_work(*_terminator, _worker_id);
191 }
192 }
193 };
194
195 class ParallelScavengeRefProcProxyTask : public RefProcProxyTask {
196 TaskTerminator _terminator;
197
198 public:
199 ParallelScavengeRefProcProxyTask(uint max_workers)
200 : RefProcProxyTask("ParallelScavengeRefProcProxyTask", max_workers),
201 _terminator(max_workers, UseCompactObjectHeaders ? ParCompactionManagerNew::marking_stacks() : ParCompactionManager::marking_stacks()) {}
202
203 void work(uint worker_id) override {
204 assert(worker_id < _max_workers, "sanity");
205 PSPromotionManager* promotion_manager = (_tm == RefProcThreadModel::Single) ? PSPromotionManager::vm_thread_promotion_manager() : PSPromotionManager::gc_thread_promotion_manager(worker_id);
206 PSIsAliveClosure is_alive;
207 PSKeepAliveClosure keep_alive(promotion_manager);
208 BarrierEnqueueDiscoveredFieldClosure enqueue;
209 PSEvacuateFollowersClosure complete_gc(promotion_manager, (_marks_oops_alive && _tm == RefProcThreadModel::Multi) ? &_terminator : nullptr, worker_id);;
210 _rp_task->rp_work(worker_id, &is_alive, &keep_alive, &enqueue, &complete_gc);
211 }
212
213 void prepare_run_task_hook() override {
214 _terminator.reset_for_reuse(_queue_count);
215 }
216 };
217
218 class PSThreadRootsTaskClosure : public ThreadClosure {
219 PSPromotionManager* _pm;
220 public:
221 PSThreadRootsTaskClosure(PSPromotionManager* pm) : _pm(pm) {}
222 virtual void do_thread(Thread* thread) {
223 assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
224
225 PSScavengeRootsClosure roots_closure(_pm);
226
227 // No need to visit nmethods, because they are handled by ScavengableNMethods.
228 thread->oops_do(&roots_closure, nullptr);
229
230 // Do the real work
231 _pm->drain_stacks(false);
232 }
233 };
234
235 class ScavengeRootsTask : public WorkerTask {
236 ThreadsClaimTokenScope _threads_claim_token_scope; // needed for Threads::possibly_parallel_threads_do
237 OopStorageSetStrongParState<false /* concurrent */, false /* is_const */> _oop_storage_strong_par_state;
238 SequentialSubTasksDone _subtasks;
239 PSOldGen* _old_gen;
240 HeapWord* _gen_top;
241 uint _active_workers;
242 bool _is_old_gen_empty;
243 TaskTerminator _terminator;
244
245 public:
246 ScavengeRootsTask(PSOldGen* old_gen,
247 uint active_workers) :
248 WorkerTask("ScavengeRootsTask"),
249 _threads_claim_token_scope(),
250 _subtasks(ParallelRootType::sentinel),
251 _old_gen(old_gen),
252 _gen_top(old_gen->object_space()->top()),
253 _active_workers(active_workers),
254 _is_old_gen_empty(old_gen->object_space()->is_empty()),
255 _terminator(active_workers, PSPromotionManager::vm_thread_promotion_manager()->stack_array_depth()) {
256 if (!_is_old_gen_empty) {
257 PSCardTable* card_table = ParallelScavengeHeap::heap()->card_table();
258 card_table->pre_scavenge(active_workers);
259 }
260 }
261
262 virtual void work(uint worker_id) {
263 assert(worker_id < _active_workers, "Sanity");
264 ResourceMark rm;
265 PSPromotionManager* pm = PSPromotionManager::gc_thread_promotion_manager(worker_id);
266
267 if (!_is_old_gen_empty) {
268 // There are only old-to-young pointers if there are objects
269 // in the old gen.
270 {
271 PSCardTable* card_table = ParallelScavengeHeap::heap()->card_table();
272
273 // The top of the old gen changes during scavenge when objects are promoted.
274 card_table->scavenge_contents_parallel(_old_gen->start_array(),
275 _old_gen->object_space()->bottom(),
276 _gen_top,
277 pm,
278 worker_id,
279 _active_workers);
280
281 // Do the real work
282 pm->drain_stacks(false);
283 }
284 }
285
286 for (uint root_type = 0; _subtasks.try_claim_task(root_type); /* empty */ ) {
287 scavenge_roots_work(static_cast<ParallelRootType::Value>(root_type), worker_id);
288 }
289
290 PSThreadRootsTaskClosure thread_closure(pm);
291 Threads::possibly_parallel_threads_do(_active_workers > 1 /* is_par */, &thread_closure);
292
293 // Scavenge OopStorages
294 {
295 PSScavengeRootsClosure root_closure(pm);
296 _oop_storage_strong_par_state.oops_do(&root_closure);
297
298 // Do the real work
299 pm->drain_stacks(false);
300 }
301
302 // If active_workers can exceed 1, add a steal_work().
303 // PSPromotionManager::drain_stacks_depth() does not fully drain its
304 // stacks and expects a steal_work() to complete the draining if
305 // ParallelGCThreads is > 1.
306
307 if (_active_workers > 1) {
308 steal_work(_terminator, worker_id);
309 }
310 }
311 };
312
313 bool PSScavenge::invoke(bool clear_soft_refs) {
314 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
315 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
316
317 IsSTWGCActiveMark mark;
318
319 _gc_timer.register_gc_start();
320
321 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
322 GCCause::Cause gc_cause = heap->gc_cause();
323
324 SvcGCMarker sgcm(SvcGCMarker::MINOR);
325 GCIdMark gc_id_mark;
326 _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
327
328 bool promotion_failure_occurred = false;
329
330 PSYoungGen* young_gen = heap->young_gen();
331 PSOldGen* old_gen = heap->old_gen();
332 PSAdaptiveSizePolicy* size_policy = heap->size_policy();
333
334 assert(young_gen->to_space()->is_empty(), "precondition");
335
336 heap->increment_total_collections();
337
338 // Gather the feedback data for eden occupancy.
339 young_gen->eden_space()->accumulate_statistics();
340
341 heap->print_before_gc();
342 heap->trace_heap_before_gc(&_gc_tracer);
343
344 assert(!NeverTenure || _tenuring_threshold == markWord::max_age + 1, "Sanity");
345 assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity");
346
347 // Fill in TLABs
348 heap->ensure_parsability(true); // retire TLABs
349
350 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
351 Universe::verify("Before GC");
352 }
353
354 {
355 ResourceMark rm;
356
357 GCTraceCPUTime tcpu(&_gc_tracer);
358 GCTraceTime(Info, gc) tm("Pause Young", nullptr, gc_cause, true);
359 TraceCollectorStats tcs(counters());
360 TraceMemoryManagerStats tms(heap->young_gc_manager(), gc_cause, "end of minor GC");
361
362 if (log_is_enabled(Debug, gc, heap, exit)) {
363 accumulated_time()->start();
364 }
365
366 // Let the size policy know we're starting
367 size_policy->minor_collection_begin();
368
369 #if COMPILER2_OR_JVMCI
370 DerivedPointerTable::clear();
371 #endif
372
373 reference_processor()->start_discovery(clear_soft_refs);
374
375 const PreGenGCValues pre_gc_values = heap->get_pre_gc_values();
376
377 // Reset our survivor overflow.
378 set_survivor_overflow(false);
379
380 const uint active_workers =
381 WorkerPolicy::calc_active_workers(ParallelScavengeHeap::heap()->workers().max_workers(),
382 ParallelScavengeHeap::heap()->workers().active_workers(),
383 Threads::number_of_non_daemon_threads());
384 ParallelScavengeHeap::heap()->workers().set_active_workers(active_workers);
385
386 PSPromotionManager::pre_scavenge();
387
388 {
389 GCTraceTime(Debug, gc, phases) tm("Scavenge", &_gc_timer);
390
391 ScavengeRootsTask task(old_gen, active_workers);
392 ParallelScavengeHeap::heap()->workers().run_task(&task);
393 }
394
395 // Process reference objects discovered during scavenge
396 {
397 GCTraceTime(Debug, gc, phases) tm("Reference Processing", &_gc_timer);
398
399 ReferenceProcessorStats stats;
400 ReferenceProcessorPhaseTimes pt(&_gc_timer, reference_processor()->max_num_queues());
401
402 ParallelScavengeRefProcProxyTask task(reference_processor()->max_num_queues());
403 stats = reference_processor()->process_discovered_references(task, &ParallelScavengeHeap::heap()->workers(), pt);
404
405 _gc_tracer.report_gc_reference_stats(stats);
406 pt.print_all_references();
407 }
408
409 {
410 GCTraceTime(Debug, gc, phases) tm("Weak Processing", &_gc_timer);
411 PSAdjustWeakRootsClosure root_closure;
412 WeakProcessor::weak_oops_do(&heap->workers(), &_is_alive_closure, &root_closure, 1);
413 }
414
415 // Finally, flush the promotion_manager's labs, and deallocate its stacks.
416 promotion_failure_occurred = PSPromotionManager::post_scavenge(_gc_tracer);
417 if (promotion_failure_occurred) {
418 clean_up_failed_promotion();
419 log_info(gc, promotion)("Promotion failed");
420 }
421
422 _gc_tracer.report_tenuring_threshold(tenuring_threshold());
423
424 // This is an underestimate, since it excludes time on auto-resizing. The
425 // most expensive part in auto-resizing is commit/uncommit OS API calls.
426 size_policy->minor_collection_end(young_gen->eden_space()->capacity_in_bytes());
427
428 if (!promotion_failure_occurred) {
429 // Swap the survivor spaces.
430 young_gen->eden_space()->clear(SpaceDecorator::Mangle);
431 young_gen->from_space()->clear(SpaceDecorator::Mangle);
432 young_gen->swap_spaces();
433
434 size_t survived = young_gen->from_space()->used_in_bytes();
435 assert(old_gen->used_in_bytes() >= pre_gc_values.old_gen_used(), "inv");
436 size_t promoted = old_gen->used_in_bytes() - pre_gc_values.old_gen_used();
437 size_policy->update_averages(_survivor_overflow, survived, promoted);
438 size_policy->sample_old_gen_used_bytes(old_gen->used_in_bytes());
439
440 if (UseAdaptiveSizePolicy) {
441 _tenuring_threshold = size_policy->compute_tenuring_threshold(_survivor_overflow,
442 _tenuring_threshold);
443
444 log_debug(gc, age)("New threshold %u (max threshold %u)", _tenuring_threshold, MaxTenuringThreshold);
445
446 if (young_gen->is_from_to_layout()) {
447 size_policy->print_stats(_survivor_overflow);
448 heap->resize_after_young_gc(_survivor_overflow);
449 }
450
451 if (UsePerfData) {
452 GCPolicyCounters* counters = ParallelScavengeHeap::gc_policy_counters();
453 counters->tenuring_threshold()->set_value(_tenuring_threshold);
454 counters->desired_survivor_size()->set_value(young_gen->from_space()->capacity_in_bytes());
455 }
456
457 {
458 // In case the counter overflows
459 uint num_minor_gcs = heap->total_collections() > heap->total_full_collections()
460 ? heap->total_collections() - heap->total_full_collections()
461 : 1;
462 size_policy->decay_supplemental_growth(num_minor_gcs);
463 }
464 }
465
466 // Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can
467 // cause the change of the heap layout. Make sure eden is reshaped if that's the case.
468 // Also update() will case adaptive NUMA chunk resizing.
469 assert(young_gen->eden_space()->is_empty(), "eden space should be empty now");
470 young_gen->eden_space()->update();
471
472 heap->resize_all_tlabs();
473
474 assert(young_gen->to_space()->is_empty(), "to space should be empty now");
475
476 heap->gc_epilogue(false);
477 }
478
479 #if COMPILER2_OR_JVMCI
480 DerivedPointerTable::update_pointers();
481 #endif
482
483 size_policy->record_gc_pause_end_instant();
484
485 if (log_is_enabled(Debug, gc, heap, exit)) {
486 accumulated_time()->stop();
487 }
488
489 heap->print_heap_change(pre_gc_values);
490
491 // Track memory usage and detect low memory
492 MemoryService::track_memory_usage();
493 heap->update_counters();
494 }
495
496 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
497 Universe::verify("After GC");
498 }
499
500 heap->print_after_gc();
501 heap->trace_heap_after_gc(&_gc_tracer);
502
503 _gc_timer.register_gc_end();
504
505 _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
506
507 return !promotion_failure_occurred;
508 }
509
510 void PSScavenge::clean_up_failed_promotion() {
511 PSPromotionManager::restore_preserved_marks();
512
513 // Reset the PromotionFailureALot counters.
514 NOT_PRODUCT(ParallelScavengeHeap::heap()->reset_promotion_should_fail();)
515 }
516
517 // Adaptive size policy support.
518 void PSScavenge::set_young_generation_boundary(HeapWord* v) {
519 _young_generation_boundary = v;
520 if (UseCompressedOops) {
521 _young_generation_boundary_compressed = (uintptr_t)CompressedOops::encode(cast_to_oop(v));
522 }
523 }
524
525 void PSScavenge::initialize() {
526 // Arguments must have been parsed
527
528 if (AlwaysTenure || NeverTenure) {
529 assert(MaxTenuringThreshold == 0 || MaxTenuringThreshold == markWord::max_age + 1,
530 "MaxTenuringThreshold should be 0 or markWord::max_age + 1, but is %d", (int) MaxTenuringThreshold);
531 _tenuring_threshold = MaxTenuringThreshold;
532 } else {
533 // We want to smooth out our startup times for the AdaptiveSizePolicy
534 _tenuring_threshold = (UseAdaptiveSizePolicy) ? InitialTenuringThreshold :
535 MaxTenuringThreshold;
536 }
537
538 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
539 PSYoungGen* young_gen = heap->young_gen();
540 PSOldGen* old_gen = heap->old_gen();
541
542 // Set boundary between young_gen and old_gen
543 assert(old_gen->reserved().end() == young_gen->reserved().start(),
544 "old above young");
545 set_young_generation_boundary(young_gen->reserved().start());
546
547 // Initialize ref handling object for scavenging.
548 _span_based_discoverer.set_span(young_gen->reserved());
549 _ref_processor =
550 new ReferenceProcessor(&_span_based_discoverer,
551 ParallelGCThreads, // mt processing degree
552 ParallelGCThreads, // mt discovery degree
553 false, // concurrent_discovery
554 &_is_alive_closure); // header provides liveness info
555
556 // Cache the cardtable
557 _card_table = heap->card_table();
558
559 _counters = new CollectorCounters("Parallel young collection pauses", 0);
560 }