1 /*
2 * Copyright (c) 2002, 2026, 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->trim_stacks();
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 guarantee(pm->stacks_empty(), "precondition");
123
124 while (true) {
125 ScannerTask task;
126 if (PSPromotionManager::steal_depth(worker_id, task)) {
127 pm->process_popped_location_depth(task, true);
128 pm->drain_stacks();
129 } else {
130 if (terminator.offer_termination()) {
131 break;
132 }
133 }
134 }
135 guarantee(pm->stacks_empty(), "stacks should be empty at this point");
136 }
137
138 // Define before use
139 class PSIsAliveClosure: public BoolObjectClosure {
140 public:
141 bool do_object_b(oop p) {
142 return (!PSScavenge::is_obj_in_young(p)) || p->is_forwarded();
143 }
144 };
145
146 PSIsAliveClosure PSScavenge::_is_alive_closure;
147
148 class PSKeepAliveClosure: public OopClosure {
149 PSPromotionManager* _promotion_manager;
150
151 public:
152 PSKeepAliveClosure(PSPromotionManager* pm) : _promotion_manager(pm) {
153 assert(_promotion_manager != nullptr, "Sanity");
154 }
155
156 template <class T> void do_oop_work(T* p) {
157 #ifdef ASSERT
158 // Referent must be non-null and in from-space
159 oop obj = RawAccess<IS_NOT_NULL>::oop_load(p);
160 assert(oopDesc::is_oop(obj), "referent must be an oop");
161 assert(PSScavenge::is_obj_in_young(obj), "must be in young-gen");
162 assert(!PSScavenge::is_obj_in_to_space(obj), "must be in from-space");
163 #endif
164
165 _promotion_manager->copy_and_push_safe_barrier</*promote_immediately=*/false>(p);
166 }
167 virtual void do_oop(oop* p) { PSKeepAliveClosure::do_oop_work(p); }
168 virtual void do_oop(narrowOop* p) { PSKeepAliveClosure::do_oop_work(p); }
169 };
170
171 class PSEvacuateFollowersClosure: public VoidClosure {
172 private:
173 PSPromotionManager* _promotion_manager;
174 TaskTerminator* _terminator;
175 uint _worker_id;
176
177 public:
178 PSEvacuateFollowersClosure(PSPromotionManager* pm, TaskTerminator* terminator, uint worker_id)
179 : _promotion_manager(pm), _terminator(terminator), _worker_id(worker_id) {}
180
181 virtual void do_void() {
182 assert(_promotion_manager != nullptr, "Sanity");
183 _promotion_manager->drain_stacks();
184
185 if (_terminator != nullptr) {
186 steal_work(*_terminator, _worker_id);
187 }
188 }
189 };
190
191 class ParallelScavengeRefProcProxyTask : public RefProcProxyTask {
192 TaskTerminator _terminator;
193
194 public:
195 ParallelScavengeRefProcProxyTask(uint max_workers)
196 : RefProcProxyTask("ParallelScavengeRefProcProxyTask", max_workers),
197 _terminator(max_workers, UseCompactObjectHeaders ? ParCompactionManagerNew::marking_stacks() : ParCompactionManager::marking_stacks()) {}
198
199 void work(uint worker_id) override {
200 assert(worker_id < _max_workers, "sanity");
201 PSPromotionManager* promotion_manager = (_tm == RefProcThreadModel::Single) ? PSPromotionManager::vm_thread_promotion_manager() : PSPromotionManager::gc_thread_promotion_manager(worker_id);
202 PSIsAliveClosure is_alive;
203 PSKeepAliveClosure keep_alive(promotion_manager);
204 BarrierEnqueueDiscoveredFieldClosure enqueue;
205 PSEvacuateFollowersClosure complete_gc(promotion_manager, (_marks_oops_alive && _tm == RefProcThreadModel::Multi) ? &_terminator : nullptr, worker_id);;
206 _rp_task->rp_work(worker_id, &is_alive, &keep_alive, &enqueue, &complete_gc);
207 }
208
209 void prepare_run_task_hook() override {
210 _terminator.reset_for_reuse(_queue_count);
211 }
212 };
213
214 class PSThreadRootsTaskClosure : public ThreadClosure {
215 PSPromotionManager* _pm;
216 public:
217 PSThreadRootsTaskClosure(PSPromotionManager* pm) : _pm(pm) {}
218 virtual void do_thread(Thread* thread) {
219 assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
220
221 PSScavengeRootsClosure roots_closure(_pm);
222
223 // No need to visit nmethods, because they are handled by ScavengableNMethods.
224 thread->oops_do(&roots_closure, nullptr);
225
226 // Do the real work
227 _pm->trim_stacks();
228 }
229 };
230
231 class ScavengeRootsTask : public WorkerTask {
232 ThreadsClaimTokenScope _threads_claim_token_scope; // needed for Threads::possibly_parallel_threads_do
233 OopStorageSetStrongParState<false /* concurrent */, false /* is_const */> _oop_storage_strong_par_state;
234 SequentialSubTasksDone _subtasks;
235 PSOldGen* _old_gen;
236 HeapWord* _gen_top;
237 uint _active_workers;
238 bool _is_old_gen_empty;
239 TaskTerminator _terminator;
240
241 public:
242 ScavengeRootsTask(PSOldGen* old_gen,
243 uint active_workers) :
244 WorkerTask("ScavengeRootsTask"),
245 _threads_claim_token_scope(),
246 _subtasks(ParallelRootType::sentinel),
247 _old_gen(old_gen),
248 _gen_top(old_gen->object_space()->top()),
249 _active_workers(active_workers),
250 _is_old_gen_empty(old_gen->object_space()->is_empty()),
251 _terminator(active_workers, PSPromotionManager::vm_thread_promotion_manager()->stack_array_depth()) {
252 if (!_is_old_gen_empty) {
253 PSCardTable* card_table = ParallelScavengeHeap::heap()->card_table();
254 card_table->pre_scavenge(active_workers);
255 }
256 }
257
258 virtual void work(uint worker_id) {
259 assert(worker_id < _active_workers, "Sanity");
260 ResourceMark rm;
261 PSPromotionManager* pm = PSPromotionManager::gc_thread_promotion_manager(worker_id);
262
263 if (!_is_old_gen_empty) {
264 // There are only old-to-young pointers if there are objects
265 // in the old gen.
266 {
267 PSCardTable* card_table = ParallelScavengeHeap::heap()->card_table();
268
269 // The top of the old gen changes during scavenge when objects are promoted.
270 card_table->scavenge_contents_parallel(_old_gen->start_array(),
271 _old_gen->object_space()->bottom(),
272 _gen_top,
273 pm,
274 worker_id,
275 _active_workers);
276
277 // Do the real work
278 pm->trim_stacks();
279 }
280 }
281
282 for (uint root_type = 0; _subtasks.try_claim_task(root_type); /* empty */ ) {
283 scavenge_roots_work(static_cast<ParallelRootType::Value>(root_type), worker_id);
284 }
285
286 PSThreadRootsTaskClosure thread_closure(pm);
287 Threads::possibly_parallel_threads_do(_active_workers > 1 /* is_par */, &thread_closure);
288
289 // Scavenge OopStorages
290 {
291 PSScavengeRootsClosure root_closure(pm);
292 _oop_storage_strong_par_state.oops_do(&root_closure);
293
294 // Do the real work
295 pm->trim_stacks();
296 }
297
298 // Drain worker local stacks and perform work stealing if more than one worker.
299 pm->drain_stacks();
300 if (_active_workers > 1) {
301 steal_work(_terminator, worker_id);
302 }
303 }
304 };
305
306 bool PSScavenge::invoke(bool clear_soft_refs) {
307 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
308 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
309
310 IsSTWGCActiveMark mark;
311
312 _gc_timer.register_gc_start();
313
314 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
315 GCCause::Cause gc_cause = heap->gc_cause();
316
317 SvcGCMarker sgcm(SvcGCMarker::MINOR);
318 GCIdMark gc_id_mark;
319 _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
320
321 bool promotion_failure_occurred = false;
322
323 PSYoungGen* young_gen = heap->young_gen();
324 PSOldGen* old_gen = heap->old_gen();
325 PSAdaptiveSizePolicy* size_policy = heap->size_policy();
326
327 assert(young_gen->to_space()->is_empty(), "precondition");
328
329 heap->increment_total_collections();
330
331 // Gather the feedback data for eden occupancy.
332 young_gen->eden_space()->accumulate_statistics();
333
334 heap->print_before_gc();
335 heap->trace_heap_before_gc(&_gc_tracer);
336
337 // Fill in TLABs
338 heap->ensure_parsability(true); // retire TLABs
339
340 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
341 Universe::verify("Before GC");
342 }
343
344 {
345 ResourceMark rm;
346
347 GCTraceCPUTime tcpu(&_gc_tracer);
348 GCTraceTime(Info, gc) tm("Pause Young", nullptr, gc_cause, true);
349 TraceCollectorStats tcs(counters());
350 TraceMemoryManagerStats tms(heap->young_gc_manager(), gc_cause, "end of minor GC");
351
352 if (log_is_enabled(Debug, gc, heap, exit)) {
353 accumulated_time()->start();
354 }
355
356 // Let the size policy know we're starting
357 size_policy->minor_collection_begin();
358
359 #ifdef COMPILER2
360 DerivedPointerTable::clear();
361 #endif // COMPILER2
362
363 reference_processor()->start_discovery(clear_soft_refs);
364
365 const PreGenGCValues pre_gc_values = heap->get_pre_gc_values();
366
367 // Reset our survivor overflow.
368 set_survivor_overflow(false);
369
370 const uint active_workers =
371 WorkerPolicy::calc_active_workers(ParallelScavengeHeap::heap()->workers().max_workers(),
372 ParallelScavengeHeap::heap()->workers().active_workers(),
373 Threads::number_of_non_daemon_threads());
374 ParallelScavengeHeap::heap()->workers().set_active_workers(active_workers);
375
376 PSPromotionManager::pre_scavenge();
377
378 {
379 GCTraceTime(Debug, gc, phases) tm("Scavenge", &_gc_timer);
380
381 ScavengeRootsTask task(old_gen, active_workers);
382 ParallelScavengeHeap::heap()->workers().run_task(&task);
383 }
384
385 // Process reference objects discovered during scavenge
386 {
387 GCTraceTime(Debug, gc, phases) tm("Reference Processing", &_gc_timer);
388
389 ReferenceProcessorStats stats;
390 ReferenceProcessorPhaseTimes pt(&_gc_timer, reference_processor()->max_num_queues());
391
392 ParallelScavengeRefProcProxyTask task(reference_processor()->max_num_queues());
393 stats = reference_processor()->process_discovered_references(task, &ParallelScavengeHeap::heap()->workers(), pt);
394
395 _gc_tracer.report_gc_reference_stats(stats);
396 pt.print_all_references();
397 }
398
399 {
400 GCTraceTime(Debug, gc, phases) tm("Weak Processing", &_gc_timer);
401 PSAdjustWeakRootsClosure root_closure;
402 WeakProcessor::weak_oops_do(&heap->workers(), &_is_alive_closure, &root_closure, 1);
403 }
404
405 // Finally, flush the promotion_manager's labs, and deallocate its stacks.
406 promotion_failure_occurred = PSPromotionManager::post_scavenge(_gc_tracer);
407 if (promotion_failure_occurred) {
408 clean_up_failed_promotion();
409 log_info(gc, promotion)("Promotion failed");
410 }
411
412 _gc_tracer.report_tenuring_threshold(tenuring_threshold());
413
414 // This is an underestimate, since it excludes time on auto-resizing. The
415 // most expensive part in auto-resizing is commit/uncommit OS API calls.
416 size_policy->minor_collection_end(young_gen->eden_space()->capacity_in_bytes());
417
418 if (!promotion_failure_occurred) {
419 // Swap the survivor spaces.
420 young_gen->eden_space()->clear(SpaceDecorator::Mangle);
421 young_gen->from_space()->clear(SpaceDecorator::Mangle);
422 young_gen->swap_spaces();
423
424 size_t survived = young_gen->from_space()->used_in_bytes();
425 assert(old_gen->used_in_bytes() >= pre_gc_values.old_gen_used(), "inv");
426 size_t promoted = old_gen->used_in_bytes() - pre_gc_values.old_gen_used();
427 size_policy->update_averages(_survivor_overflow, survived, promoted);
428 size_policy->sample_old_gen_used_bytes(old_gen->used_in_bytes());
429
430 if (UseAdaptiveSizePolicy) {
431 if (young_gen->is_from_to_layout()) {
432 size_policy->print_stats(_survivor_overflow);
433 heap->resize_after_young_gc(_survivor_overflow);
434 _tenuring_threshold = size_policy->compute_tenuring_threshold(young_gen->sizing_state(),
435 _tenuring_threshold);
436 }
437
438 if (UsePerfData) {
439 GCPolicyCounters* counters = ParallelScavengeHeap::gc_policy_counters();
440 counters->tenuring_threshold()->set_value(_tenuring_threshold);
441 counters->desired_survivor_size()->set_value(young_gen->from_space()->capacity_in_bytes());
442 }
443
444 {
445 // In case the counter overflows
446 uint num_minor_gcs = heap->total_collections() > heap->total_full_collections()
447 ? heap->total_collections() - heap->total_full_collections()
448 : 1;
449 size_policy->decay_supplemental_growth(num_minor_gcs);
450 }
451 }
452
453 // Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can
454 // cause the change of the heap layout. Make sure eden is reshaped if that's the case.
455 // Also update() will case adaptive NUMA chunk resizing.
456 assert(young_gen->eden_space()->is_empty(), "eden space should be empty now");
457 young_gen->eden_space()->update();
458
459 heap->resize_all_tlabs();
460
461 assert(young_gen->to_space()->is_empty(), "to space should be empty now");
462
463 heap->gc_epilogue(false);
464 }
465
466 #ifdef COMPILER2
467 DerivedPointerTable::update_pointers();
468 #endif // COMPILER2
469
470 size_policy->record_gc_pause_end_instant();
471
472 if (log_is_enabled(Debug, gc, heap, exit)) {
473 accumulated_time()->stop();
474 }
475
476 heap->print_heap_change(pre_gc_values);
477
478 // Track memory usage and detect low memory
479 MemoryService::track_memory_usage();
480 heap->update_counters();
481 }
482
483 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
484 Universe::verify("After GC");
485 }
486
487 heap->print_after_gc();
488 heap->trace_heap_after_gc(&_gc_tracer);
489
490 _gc_timer.register_gc_end();
491
492 _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
493
494 return !promotion_failure_occurred;
495 }
496
497 void PSScavenge::clean_up_failed_promotion() {
498 PSPromotionManager::restore_preserved_marks();
499
500 // Reset the PromotionFailureALot counters.
501 NOT_PRODUCT(ParallelScavengeHeap::heap()->reset_promotion_should_fail();)
502 }
503
504 // Adaptive size policy support.
505 void PSScavenge::set_young_generation_boundary(HeapWord* v) {
506 _young_generation_boundary = v;
507 if (UseCompressedOops) {
508 _young_generation_boundary_compressed = (uintptr_t)CompressedOops::encode(cast_to_oop(v));
509 }
510 }
511
512 void PSScavenge::initialize() {
513 // Arguments must have been parsed
514
515 if (AlwaysTenure || NeverTenure) {
516 assert(MaxTenuringThreshold == 0 || MaxTenuringThreshold == markWord::max_age + 1,
517 "MaxTenuringThreshold should be 0 or markWord::max_age + 1, but is %d", (int) MaxTenuringThreshold);
518 _tenuring_threshold = MaxTenuringThreshold;
519 } else {
520 // We want to smooth out startup times for AdaptiveSizePolicy.
521 _tenuring_threshold = UseAdaptiveSizePolicy ? InitialTenuringThreshold
522 : MaxTenuringThreshold;
523 }
524
525 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
526 PSYoungGen* young_gen = heap->young_gen();
527 PSOldGen* old_gen = heap->old_gen();
528
529 // Set boundary between young_gen and old_gen
530 assert(old_gen->reserved().end() == young_gen->reserved().start(),
531 "old above young");
532 set_young_generation_boundary(young_gen->reserved().start());
533
534 // Initialize ref handling object for scavenging.
535 _span_based_discoverer.set_span(young_gen->reserved());
536 _ref_processor =
537 new ReferenceProcessor(&_span_based_discoverer,
538 ParallelGCThreads, // mt processing degree
539 ParallelGCThreads, // mt discovery degree
540 false, // concurrent_discovery
541 &_is_alive_closure); // header provides liveness info
542
543 // Cache the cardtable
544 _card_table = heap->card_table();
545
546 _counters = new CollectorCounters("Parallel young collection pauses", 0);
547 }