1 /*
2 * Copyright (c) 2000, 2023, 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 "precompiled.hpp"
26 #include "classfile/classLoaderDataGraph.hpp"
27 #include "classfile/stringTable.hpp"
28 #include "classfile/symbolTable.hpp"
29 #include "classfile/vmSymbols.hpp"
30 #include "code/codeCache.hpp"
31 #include "code/icBuffer.hpp"
32 #include "compiler/oopMap.hpp"
33 #include "gc/serial/cardTableRS.hpp"
34 #include "gc/serial/defNewGeneration.hpp"
35 #include "gc/serial/genMarkSweep.hpp"
36 #include "gc/serial/markSweep.hpp"
37 #include "gc/shared/adaptiveSizePolicy.hpp"
38 #include "gc/shared/cardTableBarrierSet.hpp"
39 #include "gc/shared/classUnloadingContext.hpp"
40 #include "gc/shared/collectedHeap.inline.hpp"
41 #include "gc/shared/collectorCounters.hpp"
42 #include "gc/shared/continuationGCSupport.inline.hpp"
43 #include "gc/shared/gcId.hpp"
44 #include "gc/shared/gcInitLogger.hpp"
45 #include "gc/shared/gcLocker.hpp"
46 #include "gc/shared/gcPolicyCounters.hpp"
47 #include "gc/shared/gcTrace.hpp"
48 #include "gc/shared/gcTraceTime.inline.hpp"
49 #include "gc/shared/gcVMOperations.hpp"
50 #include "gc/shared/genArguments.hpp"
51 #include "gc/shared/genCollectedHeap.hpp"
52 #include "gc/shared/generationSpec.hpp"
53 #include "gc/shared/locationPrinter.inline.hpp"
54 #include "gc/shared/oopStorage.inline.hpp"
55 #include "gc/shared/oopStorageParState.inline.hpp"
56 #include "gc/shared/oopStorageSet.inline.hpp"
57 #include "gc/shared/scavengableNMethods.hpp"
58 #include "gc/shared/slidingForwarding.hpp"
59 #include "gc/shared/space.hpp"
60 #include "gc/shared/strongRootsScope.hpp"
61 #include "gc/shared/weakProcessor.hpp"
62 #include "gc/shared/workerThread.hpp"
63 #include "memory/iterator.hpp"
64 #include "memory/metaspaceCounters.hpp"
65 #include "memory/metaspaceUtils.hpp"
66 #include "memory/resourceArea.hpp"
67 #include "memory/universe.hpp"
68 #include "oops/oop.inline.hpp"
69 #include "runtime/handles.hpp"
70 #include "runtime/handles.inline.hpp"
71 #include "runtime/java.hpp"
72 #include "runtime/threads.hpp"
73 #include "runtime/vmThread.hpp"
74 #include "services/memoryService.hpp"
75 #include "utilities/autoRestore.hpp"
76 #include "utilities/debug.hpp"
77 #include "utilities/formatBuffer.hpp"
78 #include "utilities/macros.hpp"
79 #include "utilities/stack.inline.hpp"
80 #include "utilities/vmError.hpp"
81 #if INCLUDE_JVMCI
82 #include "jvmci/jvmci.hpp"
83 #endif
84
85 GenCollectedHeap::GenCollectedHeap(Generation::Name young,
86 Generation::Name old,
87 const char* policy_counters_name) :
88 CollectedHeap(),
89 _young_gen(nullptr),
90 _old_gen(nullptr),
91 _young_gen_spec(new GenerationSpec(young,
92 NewSize,
93 MaxNewSize,
94 GenAlignment)),
95 _old_gen_spec(new GenerationSpec(old,
96 OldSize,
97 MaxOldSize,
98 GenAlignment)),
99 _rem_set(nullptr),
100 _soft_ref_gen_policy(),
101 _size_policy(nullptr),
102 _gc_policy_counters(new GCPolicyCounters(policy_counters_name, 2, 2)),
103 _incremental_collection_failed(false),
104 _full_collections_completed(0),
105 _young_manager(nullptr),
106 _old_manager(nullptr) {
107 }
108
109 jint GenCollectedHeap::initialize() {
110 // Allocate space for the heap.
111
112 ReservedHeapSpace heap_rs = allocate(HeapAlignment);
113
114 if (!heap_rs.is_reserved()) {
115 vm_shutdown_during_initialization(
116 "Could not reserve enough space for object heap");
117 return JNI_ENOMEM;
118 }
119
120 initialize_reserved_region(heap_rs);
121
122 ReservedSpace young_rs = heap_rs.first_part(_young_gen_spec->max_size());
123 ReservedSpace old_rs = heap_rs.last_part(_young_gen_spec->max_size());
124
125 _rem_set = create_rem_set(heap_rs.region());
126 _rem_set->initialize(young_rs.base(), old_rs.base());
127
128 CardTableBarrierSet *bs = new CardTableBarrierSet(_rem_set);
129 bs->initialize();
130 BarrierSet::set_barrier_set(bs);
131
132 _young_gen = _young_gen_spec->init(young_rs, rem_set());
133 _old_gen = _old_gen_spec->init(old_rs, rem_set());
134
135 GCInitLogger::print();
136
137 SlidingForwarding::initialize(_reserved, SpaceAlignment / HeapWordSize);
138
139 return JNI_OK;
140 }
141
142 CardTableRS* GenCollectedHeap::create_rem_set(const MemRegion& reserved_region) {
143 return new CardTableRS(reserved_region);
144 }
145
146 void GenCollectedHeap::initialize_size_policy(size_t init_eden_size,
147 size_t init_promo_size,
148 size_t init_survivor_size) {
149 const double max_gc_pause_sec = ((double) MaxGCPauseMillis) / 1000.0;
150 _size_policy = new AdaptiveSizePolicy(init_eden_size,
151 init_promo_size,
152 init_survivor_size,
153 max_gc_pause_sec,
154 GCTimeRatio);
155 }
156
157 ReservedHeapSpace GenCollectedHeap::allocate(size_t alignment) {
158 // Now figure out the total size.
159 const size_t pageSize = UseLargePages ? os::large_page_size() : os::vm_page_size();
160 assert(alignment % pageSize == 0, "Must be");
161
162 // Check for overflow.
163 size_t total_reserved = _young_gen_spec->max_size() + _old_gen_spec->max_size();
164 if (total_reserved < _young_gen_spec->max_size()) {
165 vm_exit_during_initialization("The size of the object heap + VM data exceeds "
166 "the maximum representable size");
167 }
168 assert(total_reserved % alignment == 0,
169 "Gen size; total_reserved=" SIZE_FORMAT ", alignment="
170 SIZE_FORMAT, total_reserved, alignment);
171
172 ReservedHeapSpace heap_rs = Universe::reserve_heap(total_reserved, alignment);
173 size_t used_page_size = heap_rs.page_size();
174
175 os::trace_page_sizes("Heap",
176 MinHeapSize,
177 total_reserved,
178 used_page_size,
179 heap_rs.base(),
180 heap_rs.size());
181
182 return heap_rs;
183 }
184
185 class GenIsScavengable : public BoolObjectClosure {
186 public:
187 bool do_object_b(oop obj) {
188 return GenCollectedHeap::heap()->is_in_young(obj);
189 }
190 };
191
192 static GenIsScavengable _is_scavengable;
193
194 void GenCollectedHeap::post_initialize() {
195 CollectedHeap::post_initialize();
196
197 DefNewGeneration* def_new_gen = (DefNewGeneration*)_young_gen;
198
199 def_new_gen->ref_processor_init();
200
201 initialize_size_policy(def_new_gen->eden()->capacity(),
202 _old_gen->capacity(),
203 def_new_gen->from()->capacity());
204
205 MarkSweep::initialize();
206
207 ScavengableNMethods::initialize(&_is_scavengable);
208 }
209
210 PreGenGCValues GenCollectedHeap::get_pre_gc_values() const {
211 const DefNewGeneration* const def_new_gen = (DefNewGeneration*) young_gen();
212
213 return PreGenGCValues(def_new_gen->used(),
214 def_new_gen->capacity(),
215 def_new_gen->eden()->used(),
216 def_new_gen->eden()->capacity(),
217 def_new_gen->from()->used(),
218 def_new_gen->from()->capacity(),
219 old_gen()->used(),
220 old_gen()->capacity());
221 }
222
223 GenerationSpec* GenCollectedHeap::young_gen_spec() const {
224 return _young_gen_spec;
225 }
226
227 GenerationSpec* GenCollectedHeap::old_gen_spec() const {
228 return _old_gen_spec;
229 }
230
231 size_t GenCollectedHeap::capacity() const {
232 return _young_gen->capacity() + _old_gen->capacity();
233 }
234
235 size_t GenCollectedHeap::used() const {
236 return _young_gen->used() + _old_gen->used();
237 }
238
239 void GenCollectedHeap::save_used_regions() {
240 _old_gen->save_used_region();
241 _young_gen->save_used_region();
242 }
243
244 size_t GenCollectedHeap::max_capacity() const {
245 return _young_gen->max_capacity() + _old_gen->max_capacity();
246 }
247
248 // Update the _full_collections_completed counter
249 // at the end of a stop-world full GC.
250 unsigned int GenCollectedHeap::update_full_collections_completed() {
251 assert(_full_collections_completed <= _total_full_collections,
252 "Can't complete more collections than were started");
253 _full_collections_completed = _total_full_collections;
254 return _full_collections_completed;
255 }
256
257 // Return true if any of the following is true:
258 // . the allocation won't fit into the current young gen heap
259 // . gc locker is occupied (jni critical section)
260 // . heap memory is tight -- the most recent previous collection
261 // was a full collection because a partial collection (would
262 // have) failed and is likely to fail again
263 bool GenCollectedHeap::should_try_older_generation_allocation(size_t word_size) const {
264 size_t young_capacity = _young_gen->capacity_before_gc();
265 return (word_size > heap_word_size(young_capacity))
266 || GCLocker::is_active_and_needs_gc()
267 || incremental_collection_failed();
268 }
269
270 HeapWord* GenCollectedHeap::expand_heap_and_allocate(size_t size, bool is_tlab) {
271 HeapWord* result = nullptr;
272 if (_old_gen->should_allocate(size, is_tlab)) {
273 result = _old_gen->expand_and_allocate(size, is_tlab);
274 }
275 if (result == nullptr) {
276 if (_young_gen->should_allocate(size, is_tlab)) {
277 result = _young_gen->expand_and_allocate(size, is_tlab);
278 }
279 }
280 assert(result == nullptr || is_in_reserved(result), "result not in heap");
281 return result;
282 }
283
284 HeapWord* GenCollectedHeap::mem_allocate_work(size_t size,
285 bool is_tlab) {
286
287 HeapWord* result = nullptr;
288
289 // Loop until the allocation is satisfied, or unsatisfied after GC.
290 for (uint try_count = 1, gclocker_stalled_count = 0; /* return or throw */; try_count += 1) {
291
292 // First allocation attempt is lock-free.
293 Generation *young = _young_gen;
294 if (young->should_allocate(size, is_tlab)) {
295 result = young->par_allocate(size, is_tlab);
296 if (result != nullptr) {
297 assert(is_in_reserved(result), "result not in heap");
298 return result;
299 }
300 }
301 uint gc_count_before; // Read inside the Heap_lock locked region.
302 {
303 MutexLocker ml(Heap_lock);
304 log_trace(gc, alloc)("GenCollectedHeap::mem_allocate_work: attempting locked slow path allocation");
305 // Note that only large objects get a shot at being
306 // allocated in later generations.
307 bool first_only = !should_try_older_generation_allocation(size);
308
309 result = attempt_allocation(size, is_tlab, first_only);
310 if (result != nullptr) {
311 assert(is_in_reserved(result), "result not in heap");
312 return result;
313 }
314
315 if (GCLocker::is_active_and_needs_gc()) {
316 if (is_tlab) {
317 return nullptr; // Caller will retry allocating individual object.
318 }
319 if (!is_maximal_no_gc()) {
320 // Try and expand heap to satisfy request.
321 result = expand_heap_and_allocate(size, is_tlab);
322 // Result could be null if we are out of space.
323 if (result != nullptr) {
324 return result;
325 }
326 }
327
328 if (gclocker_stalled_count > GCLockerRetryAllocationCount) {
329 return nullptr; // We didn't get to do a GC and we didn't get any memory.
330 }
331
332 // If this thread is not in a jni critical section, we stall
333 // the requestor until the critical section has cleared and
334 // GC allowed. When the critical section clears, a GC is
335 // initiated by the last thread exiting the critical section; so
336 // we retry the allocation sequence from the beginning of the loop,
337 // rather than causing more, now probably unnecessary, GC attempts.
338 JavaThread* jthr = JavaThread::current();
339 if (!jthr->in_critical()) {
340 MutexUnlocker mul(Heap_lock);
341 // Wait for JNI critical section to be exited
342 GCLocker::stall_until_clear();
343 gclocker_stalled_count += 1;
344 continue;
345 } else {
346 if (CheckJNICalls) {
347 fatal("Possible deadlock due to allocating while"
348 " in jni critical section");
349 }
350 return nullptr;
351 }
352 }
353
354 // Read the gc count while the heap lock is held.
355 gc_count_before = total_collections();
356 }
357
358 VM_GenCollectForAllocation op(size, is_tlab, gc_count_before);
359 VMThread::execute(&op);
360 if (op.prologue_succeeded()) {
361 result = op.result();
362 if (op.gc_locked()) {
363 assert(result == nullptr, "must be null if gc_locked() is true");
364 continue; // Retry and/or stall as necessary.
365 }
366
367 assert(result == nullptr || is_in_reserved(result),
368 "result not in heap");
369 return result;
370 }
371
372 // Give a warning if we seem to be looping forever.
373 if ((QueuedAllocationWarningCount > 0) &&
374 (try_count % QueuedAllocationWarningCount == 0)) {
375 log_warning(gc, ergo)("GenCollectedHeap::mem_allocate_work retries %d times,"
376 " size=" SIZE_FORMAT " %s", try_count, size, is_tlab ? "(TLAB)" : "");
377 }
378 }
379 }
380
381 HeapWord* GenCollectedHeap::attempt_allocation(size_t size,
382 bool is_tlab,
383 bool first_only) {
384 HeapWord* res = nullptr;
385
386 if (_young_gen->should_allocate(size, is_tlab)) {
387 res = _young_gen->allocate(size, is_tlab);
388 if (res != nullptr || first_only) {
389 return res;
390 }
391 }
392
393 if (_old_gen->should_allocate(size, is_tlab)) {
394 res = _old_gen->allocate(size, is_tlab);
395 }
396
397 return res;
398 }
399
400 HeapWord* GenCollectedHeap::mem_allocate(size_t size,
401 bool* gc_overhead_limit_was_exceeded) {
402 return mem_allocate_work(size,
403 false /* is_tlab */);
404 }
405
406 bool GenCollectedHeap::must_clear_all_soft_refs() {
407 return _gc_cause == GCCause::_metadata_GC_clear_soft_refs ||
408 _gc_cause == GCCause::_wb_full_gc;
409 }
410
411 void GenCollectedHeap::collect_generation(Generation* gen, bool full, size_t size,
412 bool is_tlab, bool run_verification, bool clear_soft_refs) {
413 FormatBuffer<> title("Collect gen: %s", gen->short_name());
414 GCTraceTime(Trace, gc, phases) t1(title);
415 TraceCollectorStats tcs(gen->counters());
416 TraceMemoryManagerStats tmms(gen->gc_manager(), gc_cause(), heap()->is_young_gen(gen) ? "end of minor GC" : "end of major GC");
417
418 gen->stat_record()->invocations++;
419 gen->stat_record()->accumulated_time.start();
420
421 // Must be done anew before each collection because
422 // a previous collection will do mangling and will
423 // change top of some spaces.
424 record_gen_tops_before_GC();
425
426 log_trace(gc)("%s invoke=%d size=" SIZE_FORMAT, heap()->is_young_gen(gen) ? "Young" : "Old", gen->stat_record()->invocations, size * HeapWordSize);
427
428 if (run_verification && VerifyBeforeGC) {
429 Universe::verify("Before GC");
430 }
431 COMPILER2_OR_JVMCI_PRESENT(DerivedPointerTable::clear());
432
433 // Do collection work
434 {
435 save_marks(); // save marks for all gens
436
437 gen->collect(full, clear_soft_refs, size, is_tlab);
438 }
439
440 COMPILER2_OR_JVMCI_PRESENT(DerivedPointerTable::update_pointers());
441
442 gen->stat_record()->accumulated_time.stop();
443
444 update_gc_stats(gen, full);
445
446 if (run_verification && VerifyAfterGC) {
447 Universe::verify("After GC");
448 }
449 }
450
451 void GenCollectedHeap::do_collection(bool full,
452 bool clear_all_soft_refs,
453 size_t size,
454 bool is_tlab,
455 GenerationType max_generation) {
456 ResourceMark rm;
457 DEBUG_ONLY(Thread* my_thread = Thread::current();)
458
459 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
460 assert(my_thread->is_VM_thread(), "only VM thread");
461 assert(Heap_lock->is_locked(),
462 "the requesting thread should have the Heap_lock");
463 guarantee(!is_stw_gc_active(), "collection is not reentrant");
464
465 if (GCLocker::check_active_before_gc()) {
466 return; // GC is disabled (e.g. JNI GetXXXCritical operation)
467 }
468
469 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
470 soft_ref_policy()->should_clear_all_soft_refs();
471
472 ClearedAllSoftRefs casr(do_clear_all_soft_refs, soft_ref_policy());
473
474 AutoModifyRestore<bool> temporarily(_is_stw_gc_active, true);
475
476 bool complete = full && (max_generation == OldGen);
477 bool old_collects_young = complete && !ScavengeBeforeFullGC;
478 bool do_young_collection = !old_collects_young && _young_gen->should_collect(full, size, is_tlab);
479
480 const PreGenGCValues pre_gc_values = get_pre_gc_values();
481
482 bool run_verification = total_collections() >= VerifyGCStartAt;
483 bool prepared_for_verification = false;
484 bool do_full_collection = false;
485
486 if (do_young_collection) {
487 GCIdMark gc_id_mark;
488 GCTraceCPUTime tcpu(((DefNewGeneration*)_young_gen)->gc_tracer());
489 GCTraceTime(Info, gc) t("Pause Young", nullptr, gc_cause(), true);
490
491 print_heap_before_gc();
492
493 if (run_verification && VerifyGCLevel <= 0 && VerifyBeforeGC) {
494 prepare_for_verify();
495 prepared_for_verification = true;
496 }
497
498 gc_prologue(complete);
499 increment_total_collections(complete);
500
501 collect_generation(_young_gen,
502 full,
503 size,
504 is_tlab,
505 run_verification && VerifyGCLevel <= 0,
506 do_clear_all_soft_refs);
507
508 if (size > 0 && (!is_tlab || _young_gen->supports_tlab_allocation()) &&
509 size * HeapWordSize <= _young_gen->unsafe_max_alloc_nogc()) {
510 // Allocation request was met by young GC.
511 size = 0;
512 }
513
514 // Ask if young collection is enough. If so, do the final steps for young collection,
515 // and fallthrough to the end.
516 do_full_collection = should_do_full_collection(size, full, is_tlab, max_generation);
517 if (!do_full_collection) {
518 // Adjust generation sizes.
519 _young_gen->compute_new_size();
520
521 print_heap_change(pre_gc_values);
522
523 // Track memory usage and detect low memory after GC finishes
524 MemoryService::track_memory_usage();
525
526 gc_epilogue(complete);
527 }
528
529 print_heap_after_gc();
530
531 } else {
532 // No young collection, ask if we need to perform Full collection.
533 do_full_collection = should_do_full_collection(size, full, is_tlab, max_generation);
534 }
535
536 if (do_full_collection) {
537 GCIdMark gc_id_mark;
538 GCTraceCPUTime tcpu(GenMarkSweep::gc_tracer());
539 GCTraceTime(Info, gc) t("Pause Full", nullptr, gc_cause(), true);
540
541 print_heap_before_gc();
542
543 if (!prepared_for_verification && run_verification &&
544 VerifyGCLevel <= 1 && VerifyBeforeGC) {
545 prepare_for_verify();
546 }
547
548 if (!do_young_collection) {
549 gc_prologue(complete);
550 increment_total_collections(complete);
551 }
552
553 // Accounting quirk: total full collections would be incremented when "complete"
554 // is set, by calling increment_total_collections above. However, we also need to
555 // account Full collections that had "complete" unset.
556 if (!complete) {
557 increment_total_full_collections();
558 }
559
560 CodeCache::on_gc_marking_cycle_start();
561
562 ClassUnloadingContext ctx(1 /* num_nmethod_unlink_workers */,
563 false /* unregister_nmethods_during_purge */,
564 false /* lock_codeblob_free_separately */);
565
566 collect_generation(_old_gen,
567 full,
568 size,
569 is_tlab,
570 run_verification && VerifyGCLevel <= 1,
571 do_clear_all_soft_refs);
572
573 CodeCache::on_gc_marking_cycle_finish();
574 CodeCache::arm_all_nmethods();
575
576 // Adjust generation sizes.
577 _old_gen->compute_new_size();
578 _young_gen->compute_new_size();
579
580 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
581 ClassLoaderDataGraph::purge(true /* at_safepoint */);
582 DEBUG_ONLY(MetaspaceUtils::verify();)
583
584 // Need to clear claim bits for the next mark.
585 ClassLoaderDataGraph::clear_claimed_marks();
586
587 // Resize the metaspace capacity after full collections
588 MetaspaceGC::compute_new_size();
589 update_full_collections_completed();
590
591 print_heap_change(pre_gc_values);
592
593 // Track memory usage and detect low memory after GC finishes
594 MemoryService::track_memory_usage();
595
596 // Need to tell the epilogue code we are done with Full GC, regardless what was
597 // the initial value for "complete" flag.
598 gc_epilogue(true);
599
600 print_heap_after_gc();
601 }
602 }
603
604 bool GenCollectedHeap::should_do_full_collection(size_t size, bool full, bool is_tlab,
605 GenCollectedHeap::GenerationType max_gen) const {
606 return max_gen == OldGen && _old_gen->should_collect(full, size, is_tlab);
607 }
608
609 void GenCollectedHeap::register_nmethod(nmethod* nm) {
610 ScavengableNMethods::register_nmethod(nm);
611 }
612
613 void GenCollectedHeap::unregister_nmethod(nmethod* nm) {
614 ScavengableNMethods::unregister_nmethod(nm);
615 }
616
617 void GenCollectedHeap::verify_nmethod(nmethod* nm) {
618 ScavengableNMethods::verify_nmethod(nm);
619 }
620
621 void GenCollectedHeap::prune_scavengable_nmethods() {
622 ScavengableNMethods::prune_nmethods_not_into_young();
623 }
624
625 void GenCollectedHeap::prune_unlinked_nmethods() {
626 ScavengableNMethods::prune_unlinked_nmethods();
627 }
628
629 HeapWord* GenCollectedHeap::satisfy_failed_allocation(size_t size, bool is_tlab) {
630 GCCauseSetter x(this, GCCause::_allocation_failure);
631 HeapWord* result = nullptr;
632
633 assert(size != 0, "Precondition violated");
634 if (GCLocker::is_active_and_needs_gc()) {
635 // GC locker is active; instead of a collection we will attempt
636 // to expand the heap, if there's room for expansion.
637 if (!is_maximal_no_gc()) {
638 result = expand_heap_and_allocate(size, is_tlab);
639 }
640 return result; // Could be null if we are out of space.
641 } else if (!incremental_collection_will_fail(false /* don't consult_young */)) {
642 // Do an incremental collection.
643 do_collection(false, // full
644 false, // clear_all_soft_refs
645 size, // size
646 is_tlab, // is_tlab
647 GenCollectedHeap::OldGen); // max_generation
648 } else {
649 log_trace(gc)(" :: Trying full because partial may fail :: ");
650 // Try a full collection; see delta for bug id 6266275
651 // for the original code and why this has been simplified
652 // with from-space allocation criteria modified and
653 // such allocation moved out of the safepoint path.
654 do_collection(true, // full
655 false, // clear_all_soft_refs
656 size, // size
657 is_tlab, // is_tlab
658 GenCollectedHeap::OldGen); // max_generation
659 }
660
661 result = attempt_allocation(size, is_tlab, false /*first_only*/);
662
663 if (result != nullptr) {
664 assert(is_in_reserved(result), "result not in heap");
665 return result;
666 }
667
668 // OK, collection failed, try expansion.
669 result = expand_heap_and_allocate(size, is_tlab);
670 if (result != nullptr) {
671 return result;
672 }
673
674 // If we reach this point, we're really out of memory. Try every trick
675 // we can to reclaim memory. Force collection of soft references. Force
676 // a complete compaction of the heap. Any additional methods for finding
677 // free memory should be here, especially if they are expensive. If this
678 // attempt fails, an OOM exception will be thrown.
679 {
680 UIntFlagSetting flag_change(MarkSweepAlwaysCompactCount, 1); // Make sure the heap is fully compacted
681
682 do_collection(true, // full
683 true, // clear_all_soft_refs
684 size, // size
685 is_tlab, // is_tlab
686 GenCollectedHeap::OldGen); // max_generation
687 }
688
689 result = attempt_allocation(size, is_tlab, false /* first_only */);
690 if (result != nullptr) {
691 assert(is_in_reserved(result), "result not in heap");
692 return result;
693 }
694
695 assert(!soft_ref_policy()->should_clear_all_soft_refs(),
696 "Flag should have been handled and cleared prior to this point");
697
698 // What else? We might try synchronous finalization later. If the total
699 // space available is large enough for the allocation, then a more
700 // complete compaction phase than we've tried so far might be
701 // appropriate.
702 return nullptr;
703 }
704
705 #ifdef ASSERT
706 class AssertNonScavengableClosure: public OopClosure {
707 public:
708 virtual void do_oop(oop* p) {
709 assert(!GenCollectedHeap::heap()->is_in_partial_collection(*p),
710 "Referent should not be scavengable."); }
711 virtual void do_oop(narrowOop* p) { ShouldNotReachHere(); }
712 };
713 static AssertNonScavengableClosure assert_is_non_scavengable_closure;
714 #endif
715
716 void GenCollectedHeap::process_roots(ScanningOption so,
717 OopClosure* strong_roots,
718 CLDClosure* strong_cld_closure,
719 CLDClosure* weak_cld_closure,
720 CodeBlobToOopClosure* code_roots) {
721 // General roots.
722 assert(code_roots != nullptr, "code root closure should always be set");
723
724 ClassLoaderDataGraph::roots_cld_do(strong_cld_closure, weak_cld_closure);
725
726 // Only process code roots from thread stacks if we aren't visiting the entire CodeCache anyway
727 CodeBlobToOopClosure* roots_from_code_p = (so & SO_AllCodeCache) ? nullptr : code_roots;
728
729 Threads::oops_do(strong_roots, roots_from_code_p);
730
731 OopStorageSet::strong_oops_do(strong_roots);
732
733 if (so & SO_ScavengeCodeCache) {
734 assert(code_roots != nullptr, "must supply closure for code cache");
735
736 // We only visit parts of the CodeCache when scavenging.
737 ScavengableNMethods::nmethods_do(code_roots);
738 }
739 if (so & SO_AllCodeCache) {
740 assert(code_roots != nullptr, "must supply closure for code cache");
741
742 // CMSCollector uses this to do intermediate-strength collections.
743 // We scan the entire code cache, since CodeCache::do_unloading is not called.
744 CodeCache::blobs_do(code_roots);
745 }
746 // Verify that the code cache contents are not subject to
747 // movement by a scavenging collection.
748 DEBUG_ONLY(CodeBlobToOopClosure assert_code_is_non_scavengable(&assert_is_non_scavengable_closure, !CodeBlobToOopClosure::FixRelocations));
749 DEBUG_ONLY(ScavengableNMethods::asserted_non_scavengable_nmethods_do(&assert_code_is_non_scavengable));
750 }
751
752 void GenCollectedHeap::gen_process_weak_roots(OopClosure* root_closure) {
753 WeakProcessor::oops_do(root_closure);
754 }
755
756 bool GenCollectedHeap::no_allocs_since_save_marks() {
757 return _young_gen->no_allocs_since_save_marks() &&
758 _old_gen->no_allocs_since_save_marks();
759 }
760
761 // public collection interfaces
762 void GenCollectedHeap::collect(GCCause::Cause cause) {
763 // The caller doesn't have the Heap_lock
764 assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
765
766 unsigned int gc_count_before;
767 unsigned int full_gc_count_before;
768
769 {
770 MutexLocker ml(Heap_lock);
771 // Read the GC count while holding the Heap_lock
772 gc_count_before = total_collections();
773 full_gc_count_before = total_full_collections();
774 }
775
776 if (GCLocker::should_discard(cause, gc_count_before)) {
777 return;
778 }
779
780 bool should_run_young_gc = (cause == GCCause::_wb_young_gc)
781 || (cause == GCCause::_gc_locker)
782 DEBUG_ONLY(|| (cause == GCCause::_scavenge_alot));
783
784 const GenerationType max_generation = should_run_young_gc
785 ? YoungGen
786 : OldGen;
787
788 while (true) {
789 VM_GenCollectFull op(gc_count_before, full_gc_count_before,
790 cause, max_generation);
791 VMThread::execute(&op);
792
793 if (!GCCause::is_explicit_full_gc(cause)) {
794 return;
795 }
796
797 {
798 MutexLocker ml(Heap_lock);
799 // Read the GC count while holding the Heap_lock
800 if (full_gc_count_before != total_full_collections()) {
801 return;
802 }
803 }
804
805 if (GCLocker::is_active_and_needs_gc()) {
806 // If GCLocker is active, wait until clear before retrying.
807 GCLocker::stall_until_clear();
808 }
809 }
810 }
811
812 void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs) {
813 do_full_collection(clear_all_soft_refs, OldGen);
814 }
815
816 void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs,
817 GenerationType last_generation) {
818 do_collection(true, // full
819 clear_all_soft_refs, // clear_all_soft_refs
820 0, // size
821 false, // is_tlab
822 last_generation); // last_generation
823 // Hack XXX FIX ME !!!
824 // A scavenge may not have been attempted, or may have
825 // been attempted and failed, because the old gen was too full
826 if (gc_cause() == GCCause::_gc_locker && incremental_collection_failed()) {
827 log_debug(gc, jni)("GC locker: Trying a full collection because scavenge failed");
828 // This time allow the old gen to be collected as well
829 do_collection(true, // full
830 clear_all_soft_refs, // clear_all_soft_refs
831 0, // size
832 false, // is_tlab
833 OldGen); // last_generation
834 }
835 }
836
837 bool GenCollectedHeap::is_in_young(const void* p) const {
838 bool result = p < _old_gen->reserved().start();
839 assert(result == _young_gen->is_in_reserved(p),
840 "incorrect test - result=%d, p=" PTR_FORMAT, result, p2i(p));
841 return result;
842 }
843
844 bool GenCollectedHeap::requires_barriers(stackChunkOop obj) const {
845 return !is_in_young(obj);
846 }
847
848 // Returns "TRUE" iff "p" points into the committed areas of the heap.
849 bool GenCollectedHeap::is_in(const void* p) const {
850 return _young_gen->is_in(p) || _old_gen->is_in(p);
851 }
852
853 #ifdef ASSERT
854 // Don't implement this by using is_in_young(). This method is used
855 // in some cases to check that is_in_young() is correct.
856 bool GenCollectedHeap::is_in_partial_collection(const void* p) {
857 assert(is_in_reserved(p) || p == nullptr,
858 "Does not work if address is non-null and outside of the heap");
859 return p < _young_gen->reserved().end() && p != nullptr;
860 }
861 #endif
862
863 void GenCollectedHeap::oop_iterate(OopIterateClosure* cl) {
864 _young_gen->oop_iterate(cl);
865 _old_gen->oop_iterate(cl);
866 }
867
868 void GenCollectedHeap::object_iterate(ObjectClosure* cl) {
869 _young_gen->object_iterate(cl);
870 _old_gen->object_iterate(cl);
871 }
872
873 Space* GenCollectedHeap::space_containing(const void* addr) const {
874 Space* res = _young_gen->space_containing(addr);
875 if (res != nullptr) {
876 return res;
877 }
878 res = _old_gen->space_containing(addr);
879 assert(res != nullptr, "Could not find containing space");
880 return res;
881 }
882
883 HeapWord* GenCollectedHeap::block_start(const void* addr) const {
884 assert(is_in_reserved(addr), "block_start of address outside of heap");
885 if (_young_gen->is_in_reserved(addr)) {
886 assert(_young_gen->is_in(addr), "addr should be in allocated part of generation");
887 return _young_gen->block_start(addr);
888 }
889
890 assert(_old_gen->is_in_reserved(addr), "Some generation should contain the address");
891 assert(_old_gen->is_in(addr), "addr should be in allocated part of generation");
892 return _old_gen->block_start(addr);
893 }
894
895 bool GenCollectedHeap::block_is_obj(const HeapWord* addr) const {
896 assert(is_in_reserved(addr), "block_is_obj of address outside of heap");
897 assert(block_start(addr) == addr, "addr must be a block start");
898 if (_young_gen->is_in_reserved(addr)) {
899 return _young_gen->block_is_obj(addr);
900 }
901
902 assert(_old_gen->is_in_reserved(addr), "Some generation should contain the address");
903 return _old_gen->block_is_obj(addr);
904 }
905
906 size_t GenCollectedHeap::tlab_capacity(Thread* thr) const {
907 assert(!_old_gen->supports_tlab_allocation(), "Old gen supports TLAB allocation?!");
908 assert(_young_gen->supports_tlab_allocation(), "Young gen doesn't support TLAB allocation?!");
909 return _young_gen->tlab_capacity();
910 }
911
912 size_t GenCollectedHeap::tlab_used(Thread* thr) const {
913 assert(!_old_gen->supports_tlab_allocation(), "Old gen supports TLAB allocation?!");
914 assert(_young_gen->supports_tlab_allocation(), "Young gen doesn't support TLAB allocation?!");
915 return _young_gen->tlab_used();
916 }
917
918 size_t GenCollectedHeap::unsafe_max_tlab_alloc(Thread* thr) const {
919 assert(!_old_gen->supports_tlab_allocation(), "Old gen supports TLAB allocation?!");
920 assert(_young_gen->supports_tlab_allocation(), "Young gen doesn't support TLAB allocation?!");
921 return _young_gen->unsafe_max_tlab_alloc();
922 }
923
924 HeapWord* GenCollectedHeap::allocate_new_tlab(size_t min_size,
925 size_t requested_size,
926 size_t* actual_size) {
927 HeapWord* result = mem_allocate_work(requested_size /* size */,
928 true /* is_tlab */);
929 if (result != nullptr) {
930 *actual_size = requested_size;
931 }
932
933 return result;
934 }
935
936 // Requires "*prev_ptr" to be non-null. Deletes and a block of minimal size
937 // from the list headed by "*prev_ptr".
938 static ScratchBlock *removeSmallestScratch(ScratchBlock **prev_ptr) {
939 bool first = true;
940 size_t min_size = 0; // "first" makes this conceptually infinite.
941 ScratchBlock **smallest_ptr, *smallest;
942 ScratchBlock *cur = *prev_ptr;
943 while (cur) {
944 assert(*prev_ptr == cur, "just checking");
945 if (first || cur->num_words < min_size) {
946 smallest_ptr = prev_ptr;
947 smallest = cur;
948 min_size = smallest->num_words;
949 first = false;
950 }
951 prev_ptr = &cur->next;
952 cur = cur->next;
953 }
954 smallest = *smallest_ptr;
955 *smallest_ptr = smallest->next;
956 return smallest;
957 }
958
959 // Sort the scratch block list headed by res into decreasing size order,
960 // and set "res" to the result.
961 static void sort_scratch_list(ScratchBlock*& list) {
962 ScratchBlock* sorted = nullptr;
963 ScratchBlock* unsorted = list;
964 while (unsorted) {
965 ScratchBlock *smallest = removeSmallestScratch(&unsorted);
966 smallest->next = sorted;
967 sorted = smallest;
968 }
969 list = sorted;
970 }
971
972 ScratchBlock* GenCollectedHeap::gather_scratch(Generation* requestor,
973 size_t max_alloc_words) {
974 ScratchBlock* res = nullptr;
975 _young_gen->contribute_scratch(res, requestor, max_alloc_words);
976 _old_gen->contribute_scratch(res, requestor, max_alloc_words);
977 sort_scratch_list(res);
978 return res;
979 }
980
981 void GenCollectedHeap::release_scratch() {
982 _young_gen->reset_scratch();
983 _old_gen->reset_scratch();
984 }
985
986 void GenCollectedHeap::prepare_for_verify() {
987 ensure_parsability(false); // no need to retire TLABs
988 }
989
990 void GenCollectedHeap::generation_iterate(GenClosure* cl,
991 bool old_to_young) {
992 if (old_to_young) {
993 cl->do_generation(_old_gen);
994 cl->do_generation(_young_gen);
995 } else {
996 cl->do_generation(_young_gen);
997 cl->do_generation(_old_gen);
998 }
999 }
1000
1001 bool GenCollectedHeap::is_maximal_no_gc() const {
1002 return _young_gen->is_maximal_no_gc() && _old_gen->is_maximal_no_gc();
1003 }
1004
1005 void GenCollectedHeap::save_marks() {
1006 _young_gen->save_marks();
1007 _old_gen->save_marks();
1008 }
1009
1010 GenCollectedHeap* GenCollectedHeap::heap() {
1011 // SerialHeap is the only subtype of GenCollectedHeap.
1012 return named_heap<GenCollectedHeap>(CollectedHeap::Serial);
1013 }
1014
1015 #if INCLUDE_SERIALGC
1016 void GenCollectedHeap::prepare_for_compaction() {
1017 // Start by compacting into same gen.
1018 CompactPoint cp(_old_gen);
1019 _old_gen->prepare_for_compaction(&cp);
1020 _young_gen->prepare_for_compaction(&cp);
1021 }
1022 #endif // INCLUDE_SERIALGC
1023
1024 void GenCollectedHeap::verify(VerifyOption option /* ignored */) {
1025 log_debug(gc, verify)("%s", _old_gen->name());
1026 _old_gen->verify();
1027
1028 log_debug(gc, verify)("%s", _young_gen->name());
1029 _young_gen->verify();
1030
1031 log_debug(gc, verify)("RemSet");
1032 rem_set()->verify();
1033 }
1034
1035 void GenCollectedHeap::print_on(outputStream* st) const {
1036 if (_young_gen != nullptr) {
1037 _young_gen->print_on(st);
1038 }
1039 if (_old_gen != nullptr) {
1040 _old_gen->print_on(st);
1041 }
1042 MetaspaceUtils::print_on(st);
1043 }
1044
1045 void GenCollectedHeap::gc_threads_do(ThreadClosure* tc) const {
1046 }
1047
1048 bool GenCollectedHeap::print_location(outputStream* st, void* addr) const {
1049 return BlockLocationPrinter<GenCollectedHeap>::print_location(st, addr);
1050 }
1051
1052 void GenCollectedHeap::print_tracing_info() const {
1053 if (log_is_enabled(Debug, gc, heap, exit)) {
1054 LogStreamHandle(Debug, gc, heap, exit) lsh;
1055 _young_gen->print_summary_info_on(&lsh);
1056 _old_gen->print_summary_info_on(&lsh);
1057 }
1058 }
1059
1060 void GenCollectedHeap::print_heap_change(const PreGenGCValues& pre_gc_values) const {
1061 const DefNewGeneration* const def_new_gen = (DefNewGeneration*) young_gen();
1062
1063 log_info(gc, heap)(HEAP_CHANGE_FORMAT" "
1064 HEAP_CHANGE_FORMAT" "
1065 HEAP_CHANGE_FORMAT,
1066 HEAP_CHANGE_FORMAT_ARGS(def_new_gen->short_name(),
1067 pre_gc_values.young_gen_used(),
1068 pre_gc_values.young_gen_capacity(),
1069 def_new_gen->used(),
1070 def_new_gen->capacity()),
1071 HEAP_CHANGE_FORMAT_ARGS("Eden",
1072 pre_gc_values.eden_used(),
1073 pre_gc_values.eden_capacity(),
1074 def_new_gen->eden()->used(),
1075 def_new_gen->eden()->capacity()),
1076 HEAP_CHANGE_FORMAT_ARGS("From",
1077 pre_gc_values.from_used(),
1078 pre_gc_values.from_capacity(),
1079 def_new_gen->from()->used(),
1080 def_new_gen->from()->capacity()));
1081 log_info(gc, heap)(HEAP_CHANGE_FORMAT,
1082 HEAP_CHANGE_FORMAT_ARGS(old_gen()->short_name(),
1083 pre_gc_values.old_gen_used(),
1084 pre_gc_values.old_gen_capacity(),
1085 old_gen()->used(),
1086 old_gen()->capacity()));
1087 MetaspaceUtils::print_metaspace_change(pre_gc_values.metaspace_sizes());
1088 }
1089
1090 class GenGCPrologueClosure: public GenCollectedHeap::GenClosure {
1091 private:
1092 bool _full;
1093 public:
1094 void do_generation(Generation* gen) {
1095 gen->gc_prologue(_full);
1096 }
1097 GenGCPrologueClosure(bool full) : _full(full) {};
1098 };
1099
1100 void GenCollectedHeap::gc_prologue(bool full) {
1101 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
1102
1103 // Fill TLAB's and such
1104 ensure_parsability(true); // retire TLABs
1105
1106 // Walk generations
1107 GenGCPrologueClosure blk(full);
1108 generation_iterate(&blk, false); // not old-to-young.
1109 };
1110
1111 class GenGCEpilogueClosure: public GenCollectedHeap::GenClosure {
1112 private:
1113 bool _full;
1114 public:
1115 void do_generation(Generation* gen) {
1116 gen->gc_epilogue(_full);
1117 }
1118 GenGCEpilogueClosure(bool full) : _full(full) {};
1119 };
1120
1121 void GenCollectedHeap::gc_epilogue(bool full) {
1122 #if COMPILER2_OR_JVMCI
1123 assert(DerivedPointerTable::is_empty(), "derived pointer present");
1124 #endif // COMPILER2_OR_JVMCI
1125
1126 resize_all_tlabs();
1127
1128 GenGCEpilogueClosure blk(full);
1129 generation_iterate(&blk, false); // not old-to-young.
1130
1131 MetaspaceCounters::update_performance_counters();
1132 };
1133
1134 #ifndef PRODUCT
1135 class GenGCSaveTopsBeforeGCClosure: public GenCollectedHeap::GenClosure {
1136 private:
1137 public:
1138 void do_generation(Generation* gen) {
1139 gen->record_spaces_top();
1140 }
1141 };
1142
1143 void GenCollectedHeap::record_gen_tops_before_GC() {
1144 if (ZapUnusedHeapArea) {
1145 GenGCSaveTopsBeforeGCClosure blk;
1146 generation_iterate(&blk, false); // not old-to-young.
1147 }
1148 }
1149 #endif // not PRODUCT
1150
1151 class GenEnsureParsabilityClosure: public GenCollectedHeap::GenClosure {
1152 public:
1153 void do_generation(Generation* gen) {
1154 gen->ensure_parsability();
1155 }
1156 };
1157
1158 void GenCollectedHeap::ensure_parsability(bool retire_tlabs) {
1159 CollectedHeap::ensure_parsability(retire_tlabs);
1160 GenEnsureParsabilityClosure ep_cl;
1161 generation_iterate(&ep_cl, false);
1162 }