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/psParallelCompact.inline.hpp"
34 #include "gc/parallel/psPromotionManager.inline.hpp"
35 #include "gc/parallel/psRootType.hpp"
36 #include "gc/parallel/psScavenge.hpp"
37 #include "gc/shared/gcCause.hpp"
38 #include "gc/shared/gcHeapSummary.hpp"
39 #include "gc/shared/gcId.hpp"
40 #include "gc/shared/gcLocker.hpp"
41 #include "gc/shared/gcTimer.hpp"
42 #include "gc/shared/gcTrace.hpp"
43 #include "gc/shared/gcTraceTime.inline.hpp"
44 #include "gc/shared/gcVMOperations.hpp"
45 #include "gc/shared/isGCActiveMark.hpp"
46 #include "gc/shared/oopStorage.inline.hpp"
47 #include "gc/shared/oopStorageParState.inline.hpp"
48 #include "gc/shared/oopStorageSetParState.inline.hpp"
49 #include "gc/shared/referencePolicy.hpp"
50 #include "gc/shared/referenceProcessor.hpp"
51 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
52 #include "gc/shared/scavengableNMethods.hpp"
53 #include "gc/shared/spaceDecorator.hpp"
54 #include "gc/shared/taskTerminator.hpp"
55 #include "gc/shared/weakProcessor.inline.hpp"
56 #include "gc/shared/workerPolicy.hpp"
57 #include "gc/shared/workerThread.hpp"
58 #include "gc/shared/workerUtils.hpp"
59 #include "logging/log.hpp"
60 #include "memory/iterator.hpp"
61 #include "memory/resourceArea.hpp"
62 #include "memory/universe.hpp"
63 #include "oops/access.inline.hpp"
64 #include "oops/compressedOops.inline.hpp"
65 #include "oops/oop.inline.hpp"
66 #include "runtime/handles.inline.hpp"
67 #include "runtime/threads.hpp"
68 #include "runtime/vmOperations.hpp"
69 #include "runtime/vmThread.hpp"
70 #include "services/memoryService.hpp"
71 #include "utilities/stack.inline.hpp"
72
73 SpanSubjectToDiscoveryClosure PSScavenge::_span_based_discoverer;
74 ReferenceProcessor* PSScavenge::_ref_processor = nullptr;
75 PSCardTable* PSScavenge::_card_table = nullptr;
76 bool PSScavenge::_survivor_overflow = false;
77 uint PSScavenge::_tenuring_threshold = 0;
78 HeapWord* PSScavenge::_young_generation_boundary = nullptr;
79 uintptr_t PSScavenge::_young_generation_boundary_compressed = 0;
80 elapsedTimer PSScavenge::_accumulated_time;
81 STWGCTimer PSScavenge::_gc_timer;
82 ParallelScavengeTracer PSScavenge::_gc_tracer;
83 CollectorCounters* PSScavenge::_counters = nullptr;
84
85 static void scavenge_roots_work(ParallelRootType::Value root_type, uint worker_id) {
86 assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
87
88 PSPromotionManager* pm = PSPromotionManager::gc_thread_promotion_manager(worker_id);
89 PSPromoteRootsClosure roots_to_old_closure(pm);
90
91 switch (root_type) {
92 case ParallelRootType::class_loader_data:
93 {
94 PSScavengeCLDClosure cld_closure(pm);
95 ClassLoaderDataGraph::cld_do(&cld_closure);
96 }
97 break;
98
99 case ParallelRootType::code_cache:
100 {
101 NMethodToOopClosure code_closure(&roots_to_old_closure, NMethodToOopClosure::FixRelocations);
102 ScavengableNMethods::nmethods_do(&code_closure);
103 }
104 break;
105
106 case ParallelRootType::sentinel:
107 DEBUG_ONLY(default:) // DEBUG_ONLY hack will create compile error on release builds (-Wswitch) and runtime check on debug builds
108 fatal("Bad enumeration value: %u", root_type);
109 break;
110 }
111
112 // Do the real work
113 pm->trim_stacks();
114 }
115
116 static void steal_work(TaskTerminator& terminator, uint worker_id) {
117 assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
118
119 PSPromotionManager* pm =
120 PSPromotionManager::gc_thread_promotion_manager(worker_id);
121 guarantee(pm->stacks_empty(), "precondition");
122
123 while (true) {
124 ScannerTask task;
125 if (PSPromotionManager::steal_depth(worker_id, task)) {
126 pm->process_popped_location_depth(task, true);
127 pm->drain_stacks();
128 } else {
129 if (terminator.offer_termination()) {
130 break;
131 }
132 }
133 }
134 guarantee(pm->stacks_empty(), "stacks should be empty at this point");
135 }
136
137 // Define before use
138 class PSIsAliveClosure: public BoolObjectClosure {
139 public:
140 bool do_object_b(oop p) {
141 return (!PSScavenge::is_obj_in_young(p)) || p->is_forwarded();
142 }
143 };
144
145 PSIsAliveClosure PSScavenge::_is_alive_closure;
146
147 class PSKeepAliveClosure: public OopClosure {
148 PSPromotionManager* _promotion_manager;
149
150 public:
151 PSKeepAliveClosure(PSPromotionManager* pm) : _promotion_manager(pm) {
152 assert(_promotion_manager != nullptr, "Sanity");
153 }
154
155 template <class T> void do_oop_work(T* p) {
156 #ifdef ASSERT
157 // Referent must be non-null and in from-space
158 oop obj = RawAccess<IS_NOT_NULL>::oop_load(p);
159 assert(oopDesc::is_oop(obj), "referent must be an oop");
160 assert(PSScavenge::is_obj_in_young(obj), "must be in young-gen");
161 assert(!PSScavenge::is_obj_in_to_space(obj), "must be in from-space");
162 #endif
163
164 _promotion_manager->copy_and_push_safe_barrier</*promote_immediately=*/false>(p);
165 }
166 virtual void do_oop(oop* p) { PSKeepAliveClosure::do_oop_work(p); }
167 virtual void do_oop(narrowOop* p) { PSKeepAliveClosure::do_oop_work(p); }
168 };
169
170 class PSEvacuateFollowersClosure: public VoidClosure {
171 private:
172 PSPromotionManager* _promotion_manager;
173 TaskTerminator* _terminator;
174 uint _worker_id;
175
176 public:
177 PSEvacuateFollowersClosure(PSPromotionManager* pm, TaskTerminator* terminator, uint worker_id)
178 : _promotion_manager(pm), _terminator(terminator), _worker_id(worker_id) {}
179
180 virtual void do_void() {
181 assert(_promotion_manager != nullptr, "Sanity");
182 _promotion_manager->drain_stacks();
183
184 if (_terminator != nullptr) {
185 steal_work(*_terminator, _worker_id);
186 }
187 }
188 };
189
190 class ParallelScavengeRefProcProxyTask : public RefProcProxyTask {
191 TaskTerminator _terminator;
192
193 public:
194 ParallelScavengeRefProcProxyTask(uint max_workers)
195 : RefProcProxyTask("ParallelScavengeRefProcProxyTask", max_workers),
196 _terminator(max_workers, ParCompactionManager::marking_stacks()) {}
197
198 void work(uint worker_id) override {
199 assert(worker_id < _max_workers, "sanity");
200 PSPromotionManager* promotion_manager = (_tm == RefProcThreadModel::Single) ? PSPromotionManager::vm_thread_promotion_manager() : PSPromotionManager::gc_thread_promotion_manager(worker_id);
201 PSIsAliveClosure is_alive;
202 PSKeepAliveClosure keep_alive(promotion_manager);
203 BarrierEnqueueDiscoveredFieldClosure enqueue;
204 PSEvacuateFollowersClosure complete_gc(promotion_manager, (_marks_oops_alive && _tm == RefProcThreadModel::Multi) ? &_terminator : nullptr, worker_id);;
205 _rp_task->rp_work(worker_id, &is_alive, &keep_alive, &enqueue, &complete_gc);
206 }
207
208 void prepare_run_task_hook() override {
209 _terminator.reset_for_reuse(_queue_count);
210 }
211 };
212
213 class PSThreadRootsTaskClosure : public ThreadClosure {
214 PSPromotionManager* _pm;
215 public:
216 PSThreadRootsTaskClosure(PSPromotionManager* pm) : _pm(pm) {}
217 virtual void do_thread(Thread* thread) {
218 assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
219
220 PSScavengeRootsClosure roots_closure(_pm);
221
222 // No need to visit nmethods, because they are handled by ScavengableNMethods.
223 thread->oops_do(&roots_closure, nullptr);
224
225 // Do the real work
226 _pm->trim_stacks();
227 }
228 };
229
230 class ScavengeRootsTask : public WorkerTask {
231 ThreadsClaimTokenScope _threads_claim_token_scope; // needed for Threads::possibly_parallel_threads_do
232 OopStorageSetStrongParState<false /* concurrent */, false /* is_const */> _oop_storage_strong_par_state;
233 SequentialSubTasksDone _subtasks;
234 PSOldGen* _old_gen;
235 HeapWord* _gen_top;
236 uint _active_workers;
237 bool _is_old_gen_empty;
238 TaskTerminator _terminator;
239
240 public:
241 ScavengeRootsTask(PSOldGen* old_gen,
242 uint active_workers) :
243 WorkerTask("ScavengeRootsTask"),
244 _threads_claim_token_scope(),
245 _subtasks(ParallelRootType::sentinel),
246 _old_gen(old_gen),
247 _gen_top(old_gen->object_space()->top()),
248 _active_workers(active_workers),
249 _is_old_gen_empty(old_gen->object_space()->is_empty()),
250 _terminator(active_workers, PSPromotionManager::vm_thread_promotion_manager()->stack_array_depth()) {
251 if (!_is_old_gen_empty) {
252 PSCardTable* card_table = ParallelScavengeHeap::heap()->card_table();
253 card_table->pre_scavenge(active_workers);
254 }
255 }
256
257 virtual void work(uint worker_id) {
258 assert(worker_id < _active_workers, "Sanity");
259 ResourceMark rm;
260 PSPromotionManager* pm = PSPromotionManager::gc_thread_promotion_manager(worker_id);
261
262 if (!_is_old_gen_empty) {
263 // There are only old-to-young pointers if there are objects
264 // in the old gen.
265 {
266 PSCardTable* card_table = ParallelScavengeHeap::heap()->card_table();
267
268 // The top of the old gen changes during scavenge when objects are promoted.
269 card_table->scavenge_contents_parallel(_old_gen->start_array(),
270 _old_gen->object_space()->bottom(),
271 _gen_top,
272 pm,
273 worker_id,
274 _active_workers);
275
276 // Do the real work
277 pm->trim_stacks();
278 }
279 }
280
281 for (uint root_type = 0; _subtasks.try_claim_task(root_type); /* empty */ ) {
282 scavenge_roots_work(static_cast<ParallelRootType::Value>(root_type), worker_id);
283 }
284
285 PSThreadRootsTaskClosure thread_closure(pm);
286 Threads::possibly_parallel_threads_do(_active_workers > 1 /* is_par */, &thread_closure);
287
288 // Scavenge OopStorages
289 {
290 PSScavengeRootsClosure root_closure(pm);
291 _oop_storage_strong_par_state.oops_do(&root_closure);
292
293 // Do the real work
294 pm->trim_stacks();
295 }
296
297 // Drain worker local stacks and perform work stealing if more than one worker.
298 pm->drain_stacks();
299 if (_active_workers > 1) {
300 steal_work(_terminator, worker_id);
301 }
302 }
303 };
304
305 bool PSScavenge::invoke(bool clear_soft_refs) {
306 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
307 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
308
309 IsSTWGCActiveMark mark;
310
311 _gc_timer.register_gc_start();
312
313 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
314 GCCause::Cause gc_cause = heap->gc_cause();
315
316 SvcGCMarker sgcm(SvcGCMarker::MINOR);
317 GCIdMark gc_id_mark;
318 _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
319
320 bool promotion_failure_occurred = false;
321
322 PSYoungGen* young_gen = heap->young_gen();
323 PSOldGen* old_gen = heap->old_gen();
324 PSAdaptiveSizePolicy* size_policy = heap->size_policy();
325
326 assert(young_gen->to_space()->is_empty(), "precondition");
327
328 heap->increment_total_collections();
329
330 // Gather the feedback data for eden occupancy.
331 young_gen->eden_space()->accumulate_statistics();
332
333 heap->print_before_gc();
334 heap->trace_heap_before_gc(&_gc_tracer);
335
336 // Fill in TLABs
337 heap->ensure_parsability(true); // retire TLABs
338
339 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
340 Universe::verify("Before GC");
341 }
342
343 {
344 ResourceMark rm;
345
346 GCTraceCPUTime tcpu(&_gc_tracer);
347 GCTraceTime(Info, gc) tm("Pause Young", nullptr, gc_cause, true);
348 TraceCollectorStats tcs(counters());
349 TraceMemoryManagerStats tms(heap->young_gc_manager(), gc_cause, "end of minor GC");
350
351 if (log_is_enabled(Debug, gc, heap, exit)) {
352 accumulated_time()->start();
353 }
354
355 // Let the size policy know we're starting
356 size_policy->minor_collection_begin();
357
358 #ifdef COMPILER2
359 DerivedPointerTable::clear();
360 #endif // COMPILER2
361
362 reference_processor()->start_discovery(clear_soft_refs);
363
364 const PreGenGCValues pre_gc_values = heap->get_pre_gc_values();
365
366 // Reset our survivor overflow.
367 set_survivor_overflow(false);
368
369 const uint active_workers =
370 WorkerPolicy::calc_active_workers(ParallelScavengeHeap::heap()->workers().max_workers(),
371 ParallelScavengeHeap::heap()->workers().active_workers(),
372 Threads::number_of_non_daemon_threads());
373 ParallelScavengeHeap::heap()->workers().set_active_workers(active_workers);
374
375 PSPromotionManager::pre_scavenge();
376
377 {
378 GCTraceTime(Debug, gc, phases) tm("Scavenge", &_gc_timer);
379
380 ScavengeRootsTask task(old_gen, active_workers);
381 ParallelScavengeHeap::heap()->workers().run_task(&task);
382 }
383
384 // Process reference objects discovered during scavenge
385 {
386 GCTraceTime(Debug, gc, phases) tm("Reference Processing", &_gc_timer);
387
388 ReferenceProcessorStats stats;
389 ReferenceProcessorPhaseTimes pt(&_gc_timer, reference_processor()->max_num_queues());
390
391 ParallelScavengeRefProcProxyTask task(reference_processor()->max_num_queues());
392 stats = reference_processor()->process_discovered_references(task, &ParallelScavengeHeap::heap()->workers(), pt);
393
394 _gc_tracer.report_gc_reference_stats(stats);
395 pt.print_all_references();
396 }
397
398 {
399 GCTraceTime(Debug, gc, phases) tm("Weak Processing", &_gc_timer);
400 PSAdjustWeakRootsClosure root_closure;
401 WeakProcessor::weak_oops_do(&heap->workers(), &_is_alive_closure, &root_closure, 1);
402 }
403
404 // Finally, flush the promotion_manager's labs, and deallocate its stacks.
405 promotion_failure_occurred = PSPromotionManager::post_scavenge(_gc_tracer);
406 if (promotion_failure_occurred) {
407 clean_up_failed_promotion();
408 log_info(gc, promotion)("Promotion failed");
409 }
410
411 _gc_tracer.report_tenuring_threshold(tenuring_threshold());
412
413 // This is an underestimate, since it excludes time on auto-resizing. The
414 // most expensive part in auto-resizing is commit/uncommit OS API calls.
415 size_policy->minor_collection_end(young_gen->eden_space()->capacity_in_bytes());
416
417 if (!promotion_failure_occurred) {
418 // Swap the survivor spaces.
419 young_gen->eden_space()->clear(SpaceDecorator::Mangle);
420 young_gen->from_space()->clear(SpaceDecorator::Mangle);
421 young_gen->swap_spaces();
422
423 size_t survived = young_gen->from_space()->used_in_bytes();
424 assert(old_gen->used_in_bytes() >= pre_gc_values.old_gen_used(), "inv");
425 size_t promoted = old_gen->used_in_bytes() - pre_gc_values.old_gen_used();
426 size_policy->update_averages(_survivor_overflow, survived, promoted);
427 size_policy->sample_old_gen_used_bytes(old_gen->used_in_bytes());
428
429 if (UseAdaptiveSizePolicy) {
430 if (young_gen->is_from_to_layout()) {
431 size_policy->print_stats(_survivor_overflow);
432 heap->resize_after_young_gc(_survivor_overflow);
433 _tenuring_threshold = size_policy->compute_tenuring_threshold(young_gen->sizing_state(),
434 _tenuring_threshold);
435 }
436
437 if (UsePerfData) {
438 GCPolicyCounters* counters = ParallelScavengeHeap::gc_policy_counters();
439 counters->tenuring_threshold()->set_value(_tenuring_threshold);
440 counters->desired_survivor_size()->set_value(young_gen->from_space()->capacity_in_bytes());
441 }
442
443 {
444 // In case the counter overflows
445 uint num_minor_gcs = heap->total_collections() > heap->total_full_collections()
446 ? heap->total_collections() - heap->total_full_collections()
447 : 1;
448 size_policy->decay_supplemental_growth(num_minor_gcs);
449 }
450 }
451
452 // Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can
453 // cause the change of the heap layout. Make sure eden is reshaped if that's the case.
454 // Also update() will case adaptive NUMA chunk resizing.
455 assert(young_gen->eden_space()->is_empty(), "eden space should be empty now");
456 young_gen->eden_space()->update();
457
458 heap->resize_all_tlabs();
459
460 assert(young_gen->to_space()->is_empty(), "to space should be empty now");
461
462 heap->gc_epilogue(false);
463 }
464
465 #ifdef COMPILER2
466 DerivedPointerTable::update_pointers();
467 #endif // COMPILER2
468
469 size_policy->record_gc_pause_end_instant();
470
471 if (log_is_enabled(Debug, gc, heap, exit)) {
472 accumulated_time()->stop();
473 }
474
475 heap->print_heap_change(pre_gc_values);
476
477 // Track memory usage and detect low memory
478 MemoryService::track_memory_usage();
479 heap->update_counters();
480 }
481
482 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
483 Universe::verify("After GC");
484 }
485
486 heap->print_after_gc();
487 heap->trace_heap_after_gc(&_gc_tracer);
488
489 _gc_timer.register_gc_end();
490
491 _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
492
493 return !promotion_failure_occurred;
494 }
495
496 void PSScavenge::clean_up_failed_promotion() {
497 PSPromotionManager::restore_preserved_marks();
498
499 // Reset the PromotionFailureALot counters.
500 NOT_PRODUCT(ParallelScavengeHeap::heap()->reset_promotion_should_fail();)
501 }
502
503 // Adaptive size policy support.
504 void PSScavenge::set_young_generation_boundary(HeapWord* v) {
505 _young_generation_boundary = v;
506 if (UseCompressedOops) {
507 _young_generation_boundary_compressed = (uintptr_t)CompressedOops::encode(cast_to_oop(v));
508 }
509 }
510
511 void PSScavenge::initialize() {
512 // Arguments must have been parsed
513
514 if (AlwaysTenure || NeverTenure) {
515 assert(MaxTenuringThreshold == 0 || MaxTenuringThreshold == markWord::max_age + 1,
516 "MaxTenuringThreshold should be 0 or markWord::max_age + 1, but is %d", (int) MaxTenuringThreshold);
517 _tenuring_threshold = MaxTenuringThreshold;
518 } else {
519 // We want to smooth out startup times for AdaptiveSizePolicy.
520 _tenuring_threshold = UseAdaptiveSizePolicy ? InitialTenuringThreshold
521 : MaxTenuringThreshold;
522 }
523
524 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
525 PSYoungGen* young_gen = heap->young_gen();
526 PSOldGen* old_gen = heap->old_gen();
527
528 // Set boundary between young_gen and old_gen
529 assert(old_gen->reserved().end() == young_gen->reserved().start(),
530 "old above young");
531 set_young_generation_boundary(young_gen->reserved().start());
532
533 // Initialize ref handling object for scavenging.
534 _span_based_discoverer.set_span(young_gen->reserved());
535 _ref_processor =
536 new ReferenceProcessor(&_span_based_discoverer,
537 ParallelGCThreads, // mt processing degree
538 ParallelGCThreads, // mt discovery degree
539 false, // concurrent_discovery
540 &_is_alive_closure); // header provides liveness info
541
542 // Cache the cardtable
543 _card_table = heap->card_table();
544
545 _counters = new CollectorCounters("Parallel young collection pauses", 0);
546 }