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