1 /*
2 * Copyright (c) 2001, 2020, 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/metadataOnStackMark.hpp"
28 #include "classfile/stringTable.hpp"
29 #include "code/codeCache.hpp"
30 #include "code/icBuffer.hpp"
31 #include "gc/g1/g1Allocator.inline.hpp"
32 #include "gc/g1/g1Arguments.hpp"
33 #include "gc/g1/g1BarrierSet.hpp"
34 #include "gc/g1/g1CardTableEntryClosure.hpp"
35 #include "gc/g1/g1CollectedHeap.inline.hpp"
36 #include "gc/g1/g1CollectionSet.hpp"
37 #include "gc/g1/g1CollectorState.hpp"
38 #include "gc/g1/g1ConcurrentRefine.hpp"
39 #include "gc/g1/g1ConcurrentRefineThread.hpp"
40 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
41 #include "gc/g1/g1DirtyCardQueue.hpp"
42 #include "gc/g1/g1EvacStats.inline.hpp"
43 #include "gc/g1/g1FullCollector.hpp"
44 #include "gc/g1/g1GCParPhaseTimesTracker.hpp"
45 #include "gc/g1/g1GCPhaseTimes.hpp"
46 #include "gc/g1/g1HeapSizingPolicy.hpp"
47 #include "gc/g1/g1HeapTransition.hpp"
48 #include "gc/g1/g1HeapVerifier.hpp"
49 #include "gc/g1/g1HotCardCache.hpp"
50 #include "gc/g1/g1InitLogger.hpp"
51 #include "gc/g1/g1MemoryPool.hpp"
52 #include "gc/g1/g1OopClosures.inline.hpp"
53 #include "gc/g1/g1ParallelCleaning.hpp"
54 #include "gc/g1/g1ParScanThreadState.inline.hpp"
55 #include "gc/g1/g1Policy.hpp"
56 #include "gc/g1/g1RedirtyCardsQueue.hpp"
57 #include "gc/g1/g1RegionToSpaceMapper.hpp"
58 #include "gc/g1/g1RemSet.hpp"
59 #include "gc/g1/g1RootClosures.hpp"
60 #include "gc/g1/g1RootProcessor.hpp"
61 #include "gc/g1/g1SATBMarkQueueSet.hpp"
62 #include "gc/g1/g1StringDedup.hpp"
63 #include "gc/g1/g1ThreadLocalData.hpp"
64 #include "gc/g1/g1Trace.hpp"
65 #include "gc/g1/g1YCTypes.hpp"
66 #include "gc/g1/g1YoungRemSetSamplingThread.hpp"
67 #include "gc/g1/g1VMOperations.hpp"
68 #include "gc/g1/heapRegion.inline.hpp"
69 #include "gc/g1/heapRegionRemSet.hpp"
70 #include "gc/g1/heapRegionSet.inline.hpp"
71 #include "gc/shared/concurrentGCBreakpoints.hpp"
72 #include "gc/shared/gcBehaviours.hpp"
73 #include "gc/shared/gcHeapSummary.hpp"
74 #include "gc/shared/gcId.hpp"
75 #include "gc/shared/gcLocker.hpp"
76 #include "gc/shared/gcTimer.hpp"
77 #include "gc/shared/gcTraceTime.inline.hpp"
78 #include "gc/shared/generationSpec.hpp"
79 #include "gc/shared/isGCActiveMark.hpp"
80 #include "gc/shared/locationPrinter.inline.hpp"
81 #include "gc/shared/oopStorageParState.hpp"
82 #include "gc/shared/preservedMarks.inline.hpp"
83 #include "gc/shared/suspendibleThreadSet.hpp"
84 #include "gc/shared/referenceProcessor.inline.hpp"
85 #include "gc/shared/taskTerminator.hpp"
86 #include "gc/shared/taskqueue.inline.hpp"
87 #include "gc/shared/weakProcessor.inline.hpp"
88 #include "gc/shared/workerPolicy.hpp"
89 #include "logging/log.hpp"
90 #include "memory/allocation.hpp"
91 #include "memory/iterator.hpp"
92 #include "memory/resourceArea.hpp"
93 #include "memory/universe.hpp"
94 #include "oops/access.inline.hpp"
95 #include "oops/compressedOops.inline.hpp"
96 #include "oops/oop.inline.hpp"
97 #include "runtime/atomic.hpp"
98 #include "runtime/flags/flagSetting.hpp"
99 #include "runtime/handles.inline.hpp"
100 #include "runtime/init.hpp"
101 #include "runtime/orderAccess.hpp"
102 #include "runtime/threadSMR.hpp"
103 #include "runtime/vmThread.hpp"
104 #include "utilities/align.hpp"
105 #include "utilities/bitMap.inline.hpp"
106 #include "utilities/globalDefinitions.hpp"
107 #include "utilities/stack.inline.hpp"
108
109 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
110
111 // INVARIANTS/NOTES
112 //
113 // All allocation activity covered by the G1CollectedHeap interface is
114 // serialized by acquiring the HeapLock. This happens in mem_allocate
115 // and allocate_new_tlab, which are the "entry" points to the
116 // allocation code from the rest of the JVM. (Note that this does not
117 // apply to TLAB allocation, which is not part of this interface: it
118 // is done by clients of this interface.)
119
120 class RedirtyLoggedCardTableEntryClosure : public G1CardTableEntryClosure {
121 private:
122 size_t _num_dirtied;
123 G1CollectedHeap* _g1h;
124 G1CardTable* _g1_ct;
125
126 HeapRegion* region_for_card(CardValue* card_ptr) const {
127 return _g1h->heap_region_containing(_g1_ct->addr_for(card_ptr));
128 }
129
130 bool will_become_free(HeapRegion* hr) const {
131 // A region will be freed by free_collection_set if the region is in the
132 // collection set and has not had an evacuation failure.
133 return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
134 }
135
136 public:
137 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : G1CardTableEntryClosure(),
138 _num_dirtied(0), _g1h(g1h), _g1_ct(g1h->card_table()) { }
139
140 void do_card_ptr(CardValue* card_ptr, uint worker_id) {
141 HeapRegion* hr = region_for_card(card_ptr);
142
143 // Should only dirty cards in regions that won't be freed.
144 if (!will_become_free(hr)) {
145 *card_ptr = G1CardTable::dirty_card_val();
146 _num_dirtied++;
147 }
148 }
149
150 size_t num_dirtied() const { return _num_dirtied; }
151 };
152
153
154 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
155 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
156 }
157
158 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
159 // The from card cache is not the memory that is actually committed. So we cannot
160 // take advantage of the zero_filled parameter.
161 reset_from_card_cache(start_idx, num_regions);
162 }
163
164 Tickspan G1CollectedHeap::run_task(AbstractGangTask* task) {
165 Ticks start = Ticks::now();
166 workers()->run_task(task, workers()->active_workers());
167 return Ticks::now() - start;
168 }
169
170 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
171 MemRegion mr) {
172 return new HeapRegion(hrs_index, bot(), mr);
173 }
174
175 // Private methods.
176
177 HeapRegion* G1CollectedHeap::new_region(size_t word_size,
178 HeapRegionType type,
179 bool do_expand,
180 uint node_index) {
181 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
182 "the only time we use this to allocate a humongous region is "
183 "when we are allocating a single humongous region");
184
185 HeapRegion* res = _hrm->allocate_free_region(type, node_index);
186
187 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
188 // Currently, only attempts to allocate GC alloc regions set
189 // do_expand to true. So, we should only reach here during a
190 // safepoint. If this assumption changes we might have to
191 // reconsider the use of _expand_heap_after_alloc_failure.
192 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
193
194 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
195 word_size * HeapWordSize);
196
197 assert(word_size * HeapWordSize < HeapRegion::GrainBytes,
198 "This kind of expansion should never be more than one region. Size: " SIZE_FORMAT,
199 word_size * HeapWordSize);
200 if (expand_single_region(node_index)) {
201 // Given that expand_single_region() succeeded in expanding the heap, and we
202 // always expand the heap by an amount aligned to the heap
203 // region size, the free list should in theory not be empty.
204 // In either case allocate_free_region() will check for NULL.
205 res = _hrm->allocate_free_region(type, node_index);
206 } else {
207 _expand_heap_after_alloc_failure = false;
208 }
209 }
210 return res;
211 }
212
213 HeapWord*
214 G1CollectedHeap::humongous_obj_allocate_initialize_regions(HeapRegion* first_hr,
215 uint num_regions,
216 size_t word_size) {
217 assert(first_hr != NULL, "pre-condition");
218 assert(is_humongous(word_size), "word_size should be humongous");
219 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
220
221 // Index of last region in the series.
222 uint first = first_hr->hrm_index();
223 uint last = first + num_regions - 1;
224
225 // We need to initialize the region(s) we just discovered. This is
226 // a bit tricky given that it can happen concurrently with
227 // refinement threads refining cards on these regions and
228 // potentially wanting to refine the BOT as they are scanning
229 // those cards (this can happen shortly after a cleanup; see CR
230 // 6991377). So we have to set up the region(s) carefully and in
231 // a specific order.
232
233 // The word size sum of all the regions we will allocate.
234 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
235 assert(word_size <= word_size_sum, "sanity");
236
237 // The passed in hr will be the "starts humongous" region. The header
238 // of the new object will be placed at the bottom of this region.
239 HeapWord* new_obj = first_hr->bottom();
240 // This will be the new top of the new object.
241 HeapWord* obj_top = new_obj + word_size;
242
243 // First, we need to zero the header of the space that we will be
244 // allocating. When we update top further down, some refinement
245 // threads might try to scan the region. By zeroing the header we
246 // ensure that any thread that will try to scan the region will
247 // come across the zero klass word and bail out.
248 //
249 // NOTE: It would not have been correct to have used
250 // CollectedHeap::fill_with_object() and make the space look like
251 // an int array. The thread that is doing the allocation will
252 // later update the object header to a potentially different array
253 // type and, for a very short period of time, the klass and length
254 // fields will be inconsistent. This could cause a refinement
255 // thread to calculate the object size incorrectly.
256 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
257
258 // Next, pad out the unused tail of the last region with filler
259 // objects, for improved usage accounting.
260 // How many words we use for filler objects.
261 size_t word_fill_size = word_size_sum - word_size;
262
263 // How many words memory we "waste" which cannot hold a filler object.
264 size_t words_not_fillable = 0;
265
266 if (word_fill_size >= min_fill_size()) {
267 fill_with_objects(obj_top, word_fill_size);
268 } else if (word_fill_size > 0) {
269 // We have space to fill, but we cannot fit an object there.
270 words_not_fillable = word_fill_size;
271 word_fill_size = 0;
272 }
273
274 // We will set up the first region as "starts humongous". This
275 // will also update the BOT covering all the regions to reflect
276 // that there is a single object that starts at the bottom of the
277 // first region.
278 first_hr->set_starts_humongous(obj_top, word_fill_size);
279 _policy->remset_tracker()->update_at_allocate(first_hr);
280 // Then, if there are any, we will set up the "continues
281 // humongous" regions.
282 HeapRegion* hr = NULL;
283 for (uint i = first + 1; i <= last; ++i) {
284 hr = region_at(i);
285 hr->set_continues_humongous(first_hr);
286 _policy->remset_tracker()->update_at_allocate(hr);
287 }
288
289 // Up to this point no concurrent thread would have been able to
290 // do any scanning on any region in this series. All the top
291 // fields still point to bottom, so the intersection between
292 // [bottom,top] and [card_start,card_end] will be empty. Before we
293 // update the top fields, we'll do a storestore to make sure that
294 // no thread sees the update to top before the zeroing of the
295 // object header and the BOT initialization.
296 OrderAccess::storestore();
297
298 // Now, we will update the top fields of the "continues humongous"
299 // regions except the last one.
300 for (uint i = first; i < last; ++i) {
301 hr = region_at(i);
302 hr->set_top(hr->end());
303 }
304
305 hr = region_at(last);
306 // If we cannot fit a filler object, we must set top to the end
307 // of the humongous object, otherwise we cannot iterate the heap
308 // and the BOT will not be complete.
309 hr->set_top(hr->end() - words_not_fillable);
310
311 assert(hr->bottom() < obj_top && obj_top <= hr->end(),
312 "obj_top should be in last region");
313
314 _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
315
316 assert(words_not_fillable == 0 ||
317 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
318 "Miscalculation in humongous allocation");
319
320 increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
321
322 for (uint i = first; i <= last; ++i) {
323 hr = region_at(i);
324 _humongous_set.add(hr);
325 _hr_printer.alloc(hr);
326 }
327
328 return new_obj;
329 }
330
331 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
332 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
333 return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
334 }
335
336 // If could fit into free regions w/o expansion, try.
337 // Otherwise, if can expand, do so.
338 // Otherwise, if using ex regions might help, try with ex given back.
339 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
340 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
341
342 _verifier->verify_region_sets_optional();
343
344 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
345
346 // Policy: First try to allocate a humongous object in the free list.
347 HeapRegion* humongous_start = _hrm->allocate_humongous(obj_regions);
348 if (humongous_start == NULL) {
349 // Policy: We could not find enough regions for the humongous object in the
350 // free list. Look through the heap to find a mix of free and uncommitted regions.
351 // If so, expand the heap and allocate the humongous object.
352 humongous_start = _hrm->expand_and_allocate_humongous(obj_regions);
353 if (humongous_start != NULL) {
354 // We managed to find a region by expanding the heap.
355 log_debug(gc, ergo, heap)("Heap expansion (humongous allocation request). Allocation request: " SIZE_FORMAT "B",
356 word_size * HeapWordSize);
357 policy()->record_new_heap_size(num_regions());
358 } else {
359 // Policy: Potentially trigger a defragmentation GC.
360 }
361 }
362
363 HeapWord* result = NULL;
364 if (humongous_start != NULL) {
365 result = humongous_obj_allocate_initialize_regions(humongous_start, obj_regions, word_size);
366 assert(result != NULL, "it should always return a valid result");
367
368 // A successful humongous object allocation changes the used space
369 // information of the old generation so we need to recalculate the
370 // sizes and update the jstat counters here.
371 g1mm()->update_sizes();
372 }
373
374 _verifier->verify_region_sets_optional();
375
376 return result;
377 }
378
379 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t min_size,
380 size_t requested_size,
381 size_t* actual_size) {
382 assert_heap_not_locked_and_not_at_safepoint();
383 assert(!is_humongous(requested_size), "we do not allow humongous TLABs");
384
385 return attempt_allocation(min_size, requested_size, actual_size);
386 }
387
388 HeapWord*
389 G1CollectedHeap::mem_allocate(size_t word_size,
390 bool* gc_overhead_limit_was_exceeded) {
391 assert_heap_not_locked_and_not_at_safepoint();
392
393 if (is_humongous(word_size)) {
394 return attempt_allocation_humongous(word_size);
395 }
396 size_t dummy = 0;
397 return attempt_allocation(word_size, word_size, &dummy);
398 }
399
400 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size) {
401 ResourceMark rm; // For retrieving the thread names in log messages.
402
403 // Make sure you read the note in attempt_allocation_humongous().
404
405 assert_heap_not_locked_and_not_at_safepoint();
406 assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
407 "be called for humongous allocation requests");
408
409 // We should only get here after the first-level allocation attempt
410 // (attempt_allocation()) failed to allocate.
411
412 // We will loop until a) we manage to successfully perform the
413 // allocation or b) we successfully schedule a collection which
414 // fails to perform the allocation. b) is the only case when we'll
415 // return NULL.
416 HeapWord* result = NULL;
417 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
418 bool should_try_gc;
419 uint gc_count_before;
420
421 {
422 MutexLocker x(Heap_lock);
423 result = _allocator->attempt_allocation_locked(word_size);
424 if (result != NULL) {
425 return result;
426 }
427
428 // If the GCLocker is active and we are bound for a GC, try expanding young gen.
429 // This is different to when only GCLocker::needs_gc() is set: try to avoid
430 // waiting because the GCLocker is active to not wait too long.
431 if (GCLocker::is_active_and_needs_gc() && policy()->can_expand_young_list()) {
432 // No need for an ergo message here, can_expand_young_list() does this when
433 // it returns true.
434 result = _allocator->attempt_allocation_force(word_size);
435 if (result != NULL) {
436 return result;
437 }
438 }
439 // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
440 // the GCLocker initiated GC has been performed and then retry. This includes
441 // the case when the GC Locker is not active but has not been performed.
442 should_try_gc = !GCLocker::needs_gc();
443 // Read the GC count while still holding the Heap_lock.
444 gc_count_before = total_collections();
445 }
446
447 if (should_try_gc) {
448 bool succeeded;
449 result = do_collection_pause(word_size, gc_count_before, &succeeded,
450 GCCause::_g1_inc_collection_pause);
451 if (result != NULL) {
452 assert(succeeded, "only way to get back a non-NULL result");
453 log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
454 Thread::current()->name(), p2i(result));
455 return result;
456 }
457
458 if (succeeded) {
459 // We successfully scheduled a collection which failed to allocate. No
460 // point in trying to allocate further. We'll just return NULL.
461 log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
462 SIZE_FORMAT " words", Thread::current()->name(), word_size);
463 return NULL;
464 }
465 log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT " words",
466 Thread::current()->name(), word_size);
467 } else {
468 // Failed to schedule a collection.
469 if (gclocker_retry_count > GCLockerRetryAllocationCount) {
470 log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
471 SIZE_FORMAT " words", Thread::current()->name(), word_size);
472 return NULL;
473 }
474 log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
475 // The GCLocker is either active or the GCLocker initiated
476 // GC has not yet been performed. Stall until it is and
477 // then retry the allocation.
478 GCLocker::stall_until_clear();
479 gclocker_retry_count += 1;
480 }
481
482 // We can reach here if we were unsuccessful in scheduling a
483 // collection (because another thread beat us to it) or if we were
484 // stalled due to the GC locker. In either can we should retry the
485 // allocation attempt in case another thread successfully
486 // performed a collection and reclaimed enough space. We do the
487 // first attempt (without holding the Heap_lock) here and the
488 // follow-on attempt will be at the start of the next loop
489 // iteration (after taking the Heap_lock).
490 size_t dummy = 0;
491 result = _allocator->attempt_allocation(word_size, word_size, &dummy);
492 if (result != NULL) {
493 return result;
494 }
495
496 // Give a warning if we seem to be looping forever.
497 if ((QueuedAllocationWarningCount > 0) &&
498 (try_count % QueuedAllocationWarningCount == 0)) {
499 log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words",
500 Thread::current()->name(), try_count, word_size);
501 }
502 }
503
504 ShouldNotReachHere();
505 return NULL;
506 }
507
508 void G1CollectedHeap::begin_archive_alloc_range(bool open) {
509 assert_at_safepoint_on_vm_thread();
510 if (_archive_allocator == NULL) {
511 _archive_allocator = G1ArchiveAllocator::create_allocator(this, open);
512 }
513 }
514
515 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
516 // Allocations in archive regions cannot be of a size that would be considered
517 // humongous even for a minimum-sized region, because G1 region sizes/boundaries
518 // may be different at archive-restore time.
519 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
520 }
521
522 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
523 assert_at_safepoint_on_vm_thread();
524 assert(_archive_allocator != NULL, "_archive_allocator not initialized");
525 if (is_archive_alloc_too_large(word_size)) {
526 return NULL;
527 }
528 return _archive_allocator->archive_mem_allocate(word_size);
529 }
530
531 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
532 size_t end_alignment_in_bytes) {
533 assert_at_safepoint_on_vm_thread();
534 assert(_archive_allocator != NULL, "_archive_allocator not initialized");
535
536 // Call complete_archive to do the real work, filling in the MemRegion
537 // array with the archive regions.
538 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
539 delete _archive_allocator;
540 _archive_allocator = NULL;
541 }
542
543 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
544 assert(ranges != NULL, "MemRegion array NULL");
545 assert(count != 0, "No MemRegions provided");
546 MemRegion reserved = _hrm->reserved();
547 for (size_t i = 0; i < count; i++) {
548 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
549 return false;
550 }
551 }
552 return true;
553 }
554
555 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges,
556 size_t count,
557 bool open) {
558 assert(!is_init_completed(), "Expect to be called at JVM init time");
559 assert(ranges != NULL, "MemRegion array NULL");
560 assert(count != 0, "No MemRegions provided");
561 MutexLocker x(Heap_lock);
562
563 MemRegion reserved = _hrm->reserved();
564 HeapWord* prev_last_addr = NULL;
565 HeapRegion* prev_last_region = NULL;
566
567 // Temporarily disable pretouching of heap pages. This interface is used
568 // when mmap'ing archived heap data in, so pre-touching is wasted.
569 FlagSetting fs(AlwaysPreTouch, false);
570
571 // Enable archive object checking used by G1MarkSweep. We have to let it know
572 // about each archive range, so that objects in those ranges aren't marked.
573 G1ArchiveAllocator::enable_archive_object_check();
574
575 // For each specified MemRegion range, allocate the corresponding G1
576 // regions and mark them as archive regions. We expect the ranges
577 // in ascending starting address order, without overlap.
578 for (size_t i = 0; i < count; i++) {
579 MemRegion curr_range = ranges[i];
580 HeapWord* start_address = curr_range.start();
581 size_t word_size = curr_range.word_size();
582 HeapWord* last_address = curr_range.last();
583 size_t commits = 0;
584
585 guarantee(reserved.contains(start_address) && reserved.contains(last_address),
586 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
587 p2i(start_address), p2i(last_address));
588 guarantee(start_address > prev_last_addr,
589 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
590 p2i(start_address), p2i(prev_last_addr));
591 prev_last_addr = last_address;
592
593 // Check for ranges that start in the same G1 region in which the previous
594 // range ended, and adjust the start address so we don't try to allocate
595 // the same region again. If the current range is entirely within that
596 // region, skip it, just adjusting the recorded top.
597 HeapRegion* start_region = _hrm->addr_to_region(start_address);
598 if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
599 start_address = start_region->end();
600 if (start_address > last_address) {
601 increase_used(word_size * HeapWordSize);
602 start_region->set_top(last_address + 1);
603 continue;
604 }
605 start_region->set_top(start_address);
606 curr_range = MemRegion(start_address, last_address + 1);
607 start_region = _hrm->addr_to_region(start_address);
608 }
609
610 // Perform the actual region allocation, exiting if it fails.
611 // Then note how much new space we have allocated.
612 if (!_hrm->allocate_containing_regions(curr_range, &commits, workers())) {
613 return false;
614 }
615 increase_used(word_size * HeapWordSize);
616 if (commits != 0) {
617 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
618 HeapRegion::GrainWords * HeapWordSize * commits);
619
620 }
621
622 // Mark each G1 region touched by the range as archive, add it to
623 // the old set, and set top.
624 HeapRegion* curr_region = _hrm->addr_to_region(start_address);
625 HeapRegion* last_region = _hrm->addr_to_region(last_address);
626 prev_last_region = last_region;
627
628 while (curr_region != NULL) {
629 assert(curr_region->is_empty() && !curr_region->is_pinned(),
630 "Region already in use (index %u)", curr_region->hrm_index());
631 if (open) {
632 curr_region->set_open_archive();
633 } else {
634 curr_region->set_closed_archive();
635 }
636 _hr_printer.alloc(curr_region);
637 _archive_set.add(curr_region);
638 HeapWord* top;
639 HeapRegion* next_region;
640 if (curr_region != last_region) {
641 top = curr_region->end();
642 next_region = _hrm->next_region_in_heap(curr_region);
643 } else {
644 top = last_address + 1;
645 next_region = NULL;
646 }
647 curr_region->set_top(top);
648 curr_region = next_region;
649 }
650
651 // Notify mark-sweep of the archive
652 G1ArchiveAllocator::set_range_archive(curr_range, open);
653 }
654 return true;
655 }
656
657 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
658 assert(!is_init_completed(), "Expect to be called at JVM init time");
659 assert(ranges != NULL, "MemRegion array NULL");
660 assert(count != 0, "No MemRegions provided");
661 MemRegion reserved = _hrm->reserved();
662 HeapWord *prev_last_addr = NULL;
663 HeapRegion* prev_last_region = NULL;
664
665 // For each MemRegion, create filler objects, if needed, in the G1 regions
666 // that contain the address range. The address range actually within the
667 // MemRegion will not be modified. That is assumed to have been initialized
668 // elsewhere, probably via an mmap of archived heap data.
669 MutexLocker x(Heap_lock);
670 for (size_t i = 0; i < count; i++) {
671 HeapWord* start_address = ranges[i].start();
672 HeapWord* last_address = ranges[i].last();
673
674 assert(reserved.contains(start_address) && reserved.contains(last_address),
675 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
676 p2i(start_address), p2i(last_address));
677 assert(start_address > prev_last_addr,
678 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
679 p2i(start_address), p2i(prev_last_addr));
680
681 HeapRegion* start_region = _hrm->addr_to_region(start_address);
682 HeapRegion* last_region = _hrm->addr_to_region(last_address);
683 HeapWord* bottom_address = start_region->bottom();
684
685 // Check for a range beginning in the same region in which the
686 // previous one ended.
687 if (start_region == prev_last_region) {
688 bottom_address = prev_last_addr + 1;
689 }
690
691 // Verify that the regions were all marked as archive regions by
692 // alloc_archive_regions.
693 HeapRegion* curr_region = start_region;
694 while (curr_region != NULL) {
695 guarantee(curr_region->is_archive(),
696 "Expected archive region at index %u", curr_region->hrm_index());
697 if (curr_region != last_region) {
698 curr_region = _hrm->next_region_in_heap(curr_region);
699 } else {
700 curr_region = NULL;
701 }
702 }
703
704 prev_last_addr = last_address;
705 prev_last_region = last_region;
706
707 // Fill the memory below the allocated range with dummy object(s),
708 // if the region bottom does not match the range start, or if the previous
709 // range ended within the same G1 region, and there is a gap.
710 if (start_address != bottom_address) {
711 size_t fill_size = pointer_delta(start_address, bottom_address);
712 G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
713 increase_used(fill_size * HeapWordSize);
714 }
715 }
716 }
717
718 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t min_word_size,
719 size_t desired_word_size,
720 size_t* actual_word_size) {
721 assert_heap_not_locked_and_not_at_safepoint();
722 assert(!is_humongous(desired_word_size), "attempt_allocation() should not "
723 "be called for humongous allocation requests");
724
725 HeapWord* result = _allocator->attempt_allocation(min_word_size, desired_word_size, actual_word_size);
726
727 if (result == NULL) {
728 *actual_word_size = desired_word_size;
729 result = attempt_allocation_slow(desired_word_size);
730 }
731
732 assert_heap_not_locked();
733 if (result != NULL) {
734 assert(*actual_word_size != 0, "Actual size must have been set here");
735 dirty_young_block(result, *actual_word_size);
736 } else {
737 *actual_word_size = 0;
738 }
739
740 return result;
741 }
742
743 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
744 assert(!is_init_completed(), "Expect to be called at JVM init time");
745 assert(ranges != NULL, "MemRegion array NULL");
746 assert(count != 0, "No MemRegions provided");
747 MemRegion reserved = _hrm->reserved();
748 HeapWord* prev_last_addr = NULL;
749 HeapRegion* prev_last_region = NULL;
750 size_t size_used = 0;
751 size_t uncommitted_regions = 0;
752
753 // For each Memregion, free the G1 regions that constitute it, and
754 // notify mark-sweep that the range is no longer to be considered 'archive.'
755 MutexLocker x(Heap_lock);
756 for (size_t i = 0; i < count; i++) {
757 HeapWord* start_address = ranges[i].start();
758 HeapWord* last_address = ranges[i].last();
759
760 assert(reserved.contains(start_address) && reserved.contains(last_address),
761 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
762 p2i(start_address), p2i(last_address));
763 assert(start_address > prev_last_addr,
764 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
765 p2i(start_address), p2i(prev_last_addr));
766 size_used += ranges[i].byte_size();
767 prev_last_addr = last_address;
768
769 HeapRegion* start_region = _hrm->addr_to_region(start_address);
770 HeapRegion* last_region = _hrm->addr_to_region(last_address);
771
772 // Check for ranges that start in the same G1 region in which the previous
773 // range ended, and adjust the start address so we don't try to free
774 // the same region again. If the current range is entirely within that
775 // region, skip it.
776 if (start_region == prev_last_region) {
777 start_address = start_region->end();
778 if (start_address > last_address) {
779 continue;
780 }
781 start_region = _hrm->addr_to_region(start_address);
782 }
783 prev_last_region = last_region;
784
785 // After verifying that each region was marked as an archive region by
786 // alloc_archive_regions, set it free and empty and uncommit it.
787 HeapRegion* curr_region = start_region;
788 while (curr_region != NULL) {
789 guarantee(curr_region->is_archive(),
790 "Expected archive region at index %u", curr_region->hrm_index());
791 uint curr_index = curr_region->hrm_index();
792 _archive_set.remove(curr_region);
793 curr_region->set_free();
794 curr_region->set_top(curr_region->bottom());
795 if (curr_region != last_region) {
796 curr_region = _hrm->next_region_in_heap(curr_region);
797 } else {
798 curr_region = NULL;
799 }
800 _hrm->shrink_at(curr_index, 1);
801 uncommitted_regions++;
802 }
803
804 // Notify mark-sweep that this is no longer an archive range.
805 G1ArchiveAllocator::clear_range_archive(ranges[i]);
806 }
807
808 if (uncommitted_regions != 0) {
809 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
810 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
811 }
812 decrease_used(size_used);
813 }
814
815 oop G1CollectedHeap::materialize_archived_object(oop obj) {
816 assert(obj != NULL, "archived obj is NULL");
817 assert(G1ArchiveAllocator::is_archived_object(obj), "must be archived object");
818
819 // Loading an archived object makes it strongly reachable. If it is
820 // loaded during concurrent marking, it must be enqueued to the SATB
821 // queue, shading the previously white object gray.
822 G1BarrierSet::enqueue(obj);
823
824 return obj;
825 }
826
827 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size) {
828 ResourceMark rm; // For retrieving the thread names in log messages.
829
830 // The structure of this method has a lot of similarities to
831 // attempt_allocation_slow(). The reason these two were not merged
832 // into a single one is that such a method would require several "if
833 // allocation is not humongous do this, otherwise do that"
834 // conditional paths which would obscure its flow. In fact, an early
835 // version of this code did use a unified method which was harder to
836 // follow and, as a result, it had subtle bugs that were hard to
837 // track down. So keeping these two methods separate allows each to
838 // be more readable. It will be good to keep these two in sync as
839 // much as possible.
840
841 assert_heap_not_locked_and_not_at_safepoint();
842 assert(is_humongous(word_size), "attempt_allocation_humongous() "
843 "should only be called for humongous allocations");
844
845 // Humongous objects can exhaust the heap quickly, so we should check if we
846 // need to start a marking cycle at each humongous object allocation. We do
847 // the check before we do the actual allocation. The reason for doing it
848 // before the allocation is that we avoid having to keep track of the newly
849 // allocated memory while we do a GC.
850 if (policy()->need_to_start_conc_mark("concurrent humongous allocation",
851 word_size)) {
852 collect(GCCause::_g1_humongous_allocation);
853 }
854
855 // We will loop until a) we manage to successfully perform the
856 // allocation or b) we successfully schedule a collection which
857 // fails to perform the allocation. b) is the only case when we'll
858 // return NULL.
859 HeapWord* result = NULL;
860 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
861 bool should_try_gc;
862 uint gc_count_before;
863
864
865 {
866 MutexLocker x(Heap_lock);
867
868 // Given that humongous objects are not allocated in young
869 // regions, we'll first try to do the allocation without doing a
870 // collection hoping that there's enough space in the heap.
871 result = humongous_obj_allocate(word_size);
872 if (result != NULL) {
873 size_t size_in_regions = humongous_obj_size_in_regions(word_size);
874 policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
875 return result;
876 }
877
878 // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
879 // the GCLocker initiated GC has been performed and then retry. This includes
880 // the case when the GC Locker is not active but has not been performed.
881 should_try_gc = !GCLocker::needs_gc();
882 // Read the GC count while still holding the Heap_lock.
883 gc_count_before = total_collections();
884 }
885
886 if (should_try_gc) {
887 bool succeeded;
888 result = do_collection_pause(word_size, gc_count_before, &succeeded,
889 GCCause::_g1_humongous_allocation);
890 if (result != NULL) {
891 assert(succeeded, "only way to get back a non-NULL result");
892 log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
893 Thread::current()->name(), p2i(result));
894 return result;
895 }
896
897 if (succeeded) {
898 // We successfully scheduled a collection which failed to allocate. No
899 // point in trying to allocate further. We'll just return NULL.
900 log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
901 SIZE_FORMAT " words", Thread::current()->name(), word_size);
902 return NULL;
903 }
904 log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT "",
905 Thread::current()->name(), word_size);
906 } else {
907 // Failed to schedule a collection.
908 if (gclocker_retry_count > GCLockerRetryAllocationCount) {
909 log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
910 SIZE_FORMAT " words", Thread::current()->name(), word_size);
911 return NULL;
912 }
913 log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
914 // The GCLocker is either active or the GCLocker initiated
915 // GC has not yet been performed. Stall until it is and
916 // then retry the allocation.
917 GCLocker::stall_until_clear();
918 gclocker_retry_count += 1;
919 }
920
921
922 // We can reach here if we were unsuccessful in scheduling a
923 // collection (because another thread beat us to it) or if we were
924 // stalled due to the GC locker. In either can we should retry the
925 // allocation attempt in case another thread successfully
926 // performed a collection and reclaimed enough space.
927 // Humongous object allocation always needs a lock, so we wait for the retry
928 // in the next iteration of the loop, unlike for the regular iteration case.
929 // Give a warning if we seem to be looping forever.
930
931 if ((QueuedAllocationWarningCount > 0) &&
932 (try_count % QueuedAllocationWarningCount == 0)) {
933 log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words",
934 Thread::current()->name(), try_count, word_size);
935 }
936 }
937
938 ShouldNotReachHere();
939 return NULL;
940 }
941
942 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
943 bool expect_null_mutator_alloc_region) {
944 assert_at_safepoint_on_vm_thread();
945 assert(!_allocator->has_mutator_alloc_region() || !expect_null_mutator_alloc_region,
946 "the current alloc region was unexpectedly found to be non-NULL");
947
948 if (!is_humongous(word_size)) {
949 return _allocator->attempt_allocation_locked(word_size);
950 } else {
951 HeapWord* result = humongous_obj_allocate(word_size);
952 if (result != NULL && policy()->need_to_start_conc_mark("STW humongous allocation")) {
953 collector_state()->set_initiate_conc_mark_if_possible(true);
954 }
955 return result;
956 }
957
958 ShouldNotReachHere();
959 }
960
961 class PostCompactionPrinterClosure: public HeapRegionClosure {
962 private:
963 G1HRPrinter* _hr_printer;
964 public:
965 bool do_heap_region(HeapRegion* hr) {
966 assert(!hr->is_young(), "not expecting to find young regions");
967 _hr_printer->post_compaction(hr);
968 return false;
969 }
970
971 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
972 : _hr_printer(hr_printer) { }
973 };
974
975 void G1CollectedHeap::print_hrm_post_compaction() {
976 if (_hr_printer.is_active()) {
977 PostCompactionPrinterClosure cl(hr_printer());
978 heap_region_iterate(&cl);
979 }
980 }
981
982 void G1CollectedHeap::abort_concurrent_cycle() {
983 // If we start the compaction before the CM threads finish
984 // scanning the root regions we might trip them over as we'll
985 // be moving objects / updating references. So let's wait until
986 // they are done. By telling them to abort, they should complete
987 // early.
988 _cm->root_regions()->abort();
989 _cm->root_regions()->wait_until_scan_finished();
990
991 // Disable discovery and empty the discovered lists
992 // for the CM ref processor.
993 _ref_processor_cm->disable_discovery();
994 _ref_processor_cm->abandon_partial_discovery();
995 _ref_processor_cm->verify_no_references_recorded();
996
997 // Abandon current iterations of concurrent marking and concurrent
998 // refinement, if any are in progress.
999 concurrent_mark()->concurrent_cycle_abort();
1000 }
1001
1002 void G1CollectedHeap::prepare_heap_for_full_collection() {
1003 // Make sure we'll choose a new allocation region afterwards.
1004 _allocator->release_mutator_alloc_regions();
1005 _allocator->abandon_gc_alloc_regions();
1006
1007 // We may have added regions to the current incremental collection
1008 // set between the last GC or pause and now. We need to clear the
1009 // incremental collection set and then start rebuilding it afresh
1010 // after this full GC.
1011 abandon_collection_set(collection_set());
1012
1013 tear_down_region_sets(false /* free_list_only */);
1014
1015 hrm()->prepare_for_full_collection_start();
1016 }
1017
1018 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) {
1019 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1020 assert_used_and_recalculate_used_equal(this);
1021 _verifier->verify_region_sets_optional();
1022 _verifier->verify_before_gc(G1HeapVerifier::G1VerifyFull);
1023 _verifier->check_bitmaps("Full GC Start");
1024 }
1025
1026 void G1CollectedHeap::prepare_heap_for_mutators() {
1027 hrm()->prepare_for_full_collection_end();
1028
1029 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1030 ClassLoaderDataGraph::purge();
1031 MetaspaceUtils::verify_metrics();
1032
1033 // Prepare heap for normal collections.
1034 assert(num_free_regions() == 0, "we should not have added any free regions");
1035 rebuild_region_sets(false /* free_list_only */);
1036 abort_refinement();
1037 resize_heap_if_necessary();
1038
1039 // Rebuild the strong code root lists for each region
1040 rebuild_strong_code_roots();
1041
1042 // Purge code root memory
1043 purge_code_root_memory();
1044
1045 // Start a new incremental collection set for the next pause
1046 start_new_collection_set();
1047
1048 _allocator->init_mutator_alloc_regions();
1049
1050 // Post collection state updates.
1051 MetaspaceGC::compute_new_size();
1052 }
1053
1054 void G1CollectedHeap::abort_refinement() {
1055 if (_hot_card_cache->use_cache()) {
1056 _hot_card_cache->reset_hot_cache();
1057 }
1058
1059 // Discard all remembered set updates and reset refinement statistics.
1060 G1BarrierSet::dirty_card_queue_set().abandon_logs();
1061 assert(G1BarrierSet::dirty_card_queue_set().num_cards() == 0,
1062 "DCQS should be empty");
1063 concurrent_refine()->get_and_reset_refinement_stats();
1064 }
1065
1066 void G1CollectedHeap::verify_after_full_collection() {
1067 _hrm->verify_optional();
1068 _verifier->verify_region_sets_optional();
1069 _verifier->verify_after_gc(G1HeapVerifier::G1VerifyFull);
1070 // Clear the previous marking bitmap, if needed for bitmap verification.
1071 // Note we cannot do this when we clear the next marking bitmap in
1072 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1073 // objects marked during a full GC against the previous bitmap.
1074 // But we need to clear it before calling check_bitmaps below since
1075 // the full GC has compacted objects and updated TAMS but not updated
1076 // the prev bitmap.
1077 if (G1VerifyBitmaps) {
1078 GCTraceTime(Debug, gc) tm("Clear Prev Bitmap for Verification");
1079 _cm->clear_prev_bitmap(workers());
1080 }
1081 // This call implicitly verifies that the next bitmap is clear after Full GC.
1082 _verifier->check_bitmaps("Full GC End");
1083
1084 // At this point there should be no regions in the
1085 // entire heap tagged as young.
1086 assert(check_young_list_empty(), "young list should be empty at this point");
1087
1088 // Note: since we've just done a full GC, concurrent
1089 // marking is no longer active. Therefore we need not
1090 // re-enable reference discovery for the CM ref processor.
1091 // That will be done at the start of the next marking cycle.
1092 // We also know that the STW processor should no longer
1093 // discover any new references.
1094 assert(!_ref_processor_stw->discovery_enabled(), "Postcondition");
1095 assert(!_ref_processor_cm->discovery_enabled(), "Postcondition");
1096 _ref_processor_stw->verify_no_references_recorded();
1097 _ref_processor_cm->verify_no_references_recorded();
1098 }
1099
1100 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) {
1101 // Post collection logging.
1102 // We should do this after we potentially resize the heap so
1103 // that all the COMMIT / UNCOMMIT events are generated before
1104 // the compaction events.
1105 print_hrm_post_compaction();
1106 heap_transition->print();
1107 print_heap_after_gc();
1108 print_heap_regions();
1109 }
1110
1111 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1112 bool clear_all_soft_refs) {
1113 assert_at_safepoint_on_vm_thread();
1114
1115 if (GCLocker::check_active_before_gc()) {
1116 // Full GC was not completed.
1117 return false;
1118 }
1119
1120 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1121 soft_ref_policy()->should_clear_all_soft_refs();
1122
1123 G1FullCollector collector(this, explicit_gc, do_clear_all_soft_refs);
1124 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1125
1126 collector.prepare_collection();
1127 collector.collect();
1128 collector.complete_collection();
1129
1130 // Full collection was successfully completed.
1131 return true;
1132 }
1133
1134 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1135 // Currently, there is no facility in the do_full_collection(bool) API to notify
1136 // the caller that the collection did not succeed (e.g., because it was locked
1137 // out by the GC locker). So, right now, we'll ignore the return value.
1138 bool dummy = do_full_collection(true, /* explicit_gc */
1139 clear_all_soft_refs);
1140 }
1141
1142 void G1CollectedHeap::resize_heap_if_necessary() {
1143 assert_at_safepoint_on_vm_thread();
1144
1145 // Capacity, free and used after the GC counted as full regions to
1146 // include the waste in the following calculations.
1147 const size_t capacity_after_gc = capacity();
1148 const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes();
1149
1150 // This is enforced in arguments.cpp.
1151 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1152 "otherwise the code below doesn't make sense");
1153
1154 // We don't have floating point command-line arguments
1155 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1156 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1157 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1158 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1159
1160 // We have to be careful here as these two calculations can overflow
1161 // 32-bit size_t's.
1162 double used_after_gc_d = (double) used_after_gc;
1163 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1164 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1165
1166 // Let's make sure that they are both under the max heap size, which
1167 // by default will make them fit into a size_t.
1168 double desired_capacity_upper_bound = (double) MaxHeapSize;
1169 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1170 desired_capacity_upper_bound);
1171 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1172 desired_capacity_upper_bound);
1173
1174 // We can now safely turn them into size_t's.
1175 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1176 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1177
1178 // This assert only makes sense here, before we adjust them
1179 // with respect to the min and max heap size.
1180 assert(minimum_desired_capacity <= maximum_desired_capacity,
1181 "minimum_desired_capacity = " SIZE_FORMAT ", "
1182 "maximum_desired_capacity = " SIZE_FORMAT,
1183 minimum_desired_capacity, maximum_desired_capacity);
1184
1185 // Should not be greater than the heap max size. No need to adjust
1186 // it with respect to the heap min size as it's a lower bound (i.e.,
1187 // we'll try to make the capacity larger than it, not smaller).
1188 minimum_desired_capacity = MIN2(minimum_desired_capacity, MaxHeapSize);
1189 // Should not be less than the heap min size. No need to adjust it
1190 // with respect to the heap max size as it's an upper bound (i.e.,
1191 // we'll try to make the capacity smaller than it, not greater).
1192 maximum_desired_capacity = MAX2(maximum_desired_capacity, MinHeapSize);
1193
1194 if (capacity_after_gc < minimum_desired_capacity) {
1195 // Don't expand unless it's significant
1196 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1197
1198 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity). "
1199 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1200 "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1201 capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio);
1202
1203 expand(expand_bytes, _workers);
1204
1205 // No expansion, now see if we want to shrink
1206 } else if (capacity_after_gc > maximum_desired_capacity) {
1207 // Capacity too large, compute shrinking size
1208 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1209
1210 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity). "
1211 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1212 "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1213 capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio);
1214
1215 shrink(shrink_bytes);
1216 }
1217 }
1218
1219 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1220 bool do_gc,
1221 bool clear_all_soft_refs,
1222 bool expect_null_mutator_alloc_region,
1223 bool* gc_succeeded) {
1224 *gc_succeeded = true;
1225 // Let's attempt the allocation first.
1226 HeapWord* result =
1227 attempt_allocation_at_safepoint(word_size,
1228 expect_null_mutator_alloc_region);
1229 if (result != NULL) {
1230 return result;
1231 }
1232
1233 // In a G1 heap, we're supposed to keep allocation from failing by
1234 // incremental pauses. Therefore, at least for now, we'll favor
1235 // expansion over collection. (This might change in the future if we can
1236 // do something smarter than full collection to satisfy a failed alloc.)
1237 result = expand_and_allocate(word_size);
1238 if (result != NULL) {
1239 return result;
1240 }
1241
1242 if (do_gc) {
1243 // Expansion didn't work, we'll try to do a Full GC.
1244 *gc_succeeded = do_full_collection(false, /* explicit_gc */
1245 clear_all_soft_refs);
1246 }
1247
1248 return NULL;
1249 }
1250
1251 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1252 bool* succeeded) {
1253 assert_at_safepoint_on_vm_thread();
1254
1255 // Attempts to allocate followed by Full GC.
1256 HeapWord* result =
1257 satisfy_failed_allocation_helper(word_size,
1258 true, /* do_gc */
1259 false, /* clear_all_soft_refs */
1260 false, /* expect_null_mutator_alloc_region */
1261 succeeded);
1262
1263 if (result != NULL || !*succeeded) {
1264 return result;
1265 }
1266
1267 // Attempts to allocate followed by Full GC that will collect all soft references.
1268 result = satisfy_failed_allocation_helper(word_size,
1269 true, /* do_gc */
1270 true, /* clear_all_soft_refs */
1271 true, /* expect_null_mutator_alloc_region */
1272 succeeded);
1273
1274 if (result != NULL || !*succeeded) {
1275 return result;
1276 }
1277
1278 // Attempts to allocate, no GC
1279 result = satisfy_failed_allocation_helper(word_size,
1280 false, /* do_gc */
1281 false, /* clear_all_soft_refs */
1282 true, /* expect_null_mutator_alloc_region */
1283 succeeded);
1284
1285 if (result != NULL) {
1286 return result;
1287 }
1288
1289 assert(!soft_ref_policy()->should_clear_all_soft_refs(),
1290 "Flag should have been handled and cleared prior to this point");
1291
1292 // What else? We might try synchronous finalization later. If the total
1293 // space available is large enough for the allocation, then a more
1294 // complete compaction phase than we've tried so far might be
1295 // appropriate.
1296 return NULL;
1297 }
1298
1299 // Attempting to expand the heap sufficiently
1300 // to support an allocation of the given "word_size". If
1301 // successful, perform the allocation and return the address of the
1302 // allocated block, or else "NULL".
1303
1304 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1305 assert_at_safepoint_on_vm_thread();
1306
1307 _verifier->verify_region_sets_optional();
1308
1309 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1310 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1311 word_size * HeapWordSize);
1312
1313
1314 if (expand(expand_bytes, _workers)) {
1315 _hrm->verify_optional();
1316 _verifier->verify_region_sets_optional();
1317 return attempt_allocation_at_safepoint(word_size,
1318 false /* expect_null_mutator_alloc_region */);
1319 }
1320 return NULL;
1321 }
1322
1323 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) {
1324 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1325 aligned_expand_bytes = align_up(aligned_expand_bytes,
1326 HeapRegion::GrainBytes);
1327
1328 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B",
1329 expand_bytes, aligned_expand_bytes);
1330
1331 if (is_maximal_no_gc()) {
1332 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1333 return false;
1334 }
1335
1336 double expand_heap_start_time_sec = os::elapsedTime();
1337 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1338 assert(regions_to_expand > 0, "Must expand by at least one region");
1339
1340 uint expanded_by = _hrm->expand_by(regions_to_expand, pretouch_workers);
1341 if (expand_time_ms != NULL) {
1342 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1343 }
1344
1345 if (expanded_by > 0) {
1346 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1347 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1348 policy()->record_new_heap_size(num_regions());
1349 } else {
1350 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1351
1352 // The expansion of the virtual storage space was unsuccessful.
1353 // Let's see if it was because we ran out of swap.
1354 if (G1ExitOnExpansionFailure &&
1355 _hrm->available() >= regions_to_expand) {
1356 // We had head room...
1357 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1358 }
1359 }
1360 return regions_to_expand > 0;
1361 }
1362
1363 bool G1CollectedHeap::expand_single_region(uint node_index) {
1364 uint expanded_by = _hrm->expand_on_preferred_node(node_index);
1365
1366 if (expanded_by == 0) {
1367 assert(is_maximal_no_gc(), "Should be no regions left, available: %u", _hrm->available());
1368 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1369 return false;
1370 }
1371
1372 policy()->record_new_heap_size(num_regions());
1373 return true;
1374 }
1375
1376 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1377 size_t aligned_shrink_bytes =
1378 ReservedSpace::page_align_size_down(shrink_bytes);
1379 aligned_shrink_bytes = align_down(aligned_shrink_bytes,
1380 HeapRegion::GrainBytes);
1381 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1382
1383 uint num_regions_removed = _hrm->shrink_by(num_regions_to_remove);
1384 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1385
1386 log_debug(gc, ergo, heap)("Shrink the heap. requested shrinking amount: " SIZE_FORMAT "B aligned shrinking amount: " SIZE_FORMAT "B attempted shrinking amount: " SIZE_FORMAT "B",
1387 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1388 if (num_regions_removed > 0) {
1389 policy()->record_new_heap_size(num_regions());
1390 } else {
1391 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1392 }
1393 }
1394
1395 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1396 _verifier->verify_region_sets_optional();
1397
1398 // We should only reach here at the end of a Full GC or during Remark which
1399 // means we should not not be holding to any GC alloc regions. The method
1400 // below will make sure of that and do any remaining clean up.
1401 _allocator->abandon_gc_alloc_regions();
1402
1403 // Instead of tearing down / rebuilding the free lists here, we
1404 // could instead use the remove_all_pending() method on free_list to
1405 // remove only the ones that we need to remove.
1406 tear_down_region_sets(true /* free_list_only */);
1407 shrink_helper(shrink_bytes);
1408 rebuild_region_sets(true /* free_list_only */);
1409
1410 _hrm->verify_optional();
1411 _verifier->verify_region_sets_optional();
1412 }
1413
1414 class OldRegionSetChecker : public HeapRegionSetChecker {
1415 public:
1416 void check_mt_safety() {
1417 // Master Old Set MT safety protocol:
1418 // (a) If we're at a safepoint, operations on the master old set
1419 // should be invoked:
1420 // - by the VM thread (which will serialize them), or
1421 // - by the GC workers while holding the FreeList_lock, if we're
1422 // at a safepoint for an evacuation pause (this lock is taken
1423 // anyway when an GC alloc region is retired so that a new one
1424 // is allocated from the free list), or
1425 // - by the GC workers while holding the OldSets_lock, if we're at a
1426 // safepoint for a cleanup pause.
1427 // (b) If we're not at a safepoint, operations on the master old set
1428 // should be invoked while holding the Heap_lock.
1429
1430 if (SafepointSynchronize::is_at_safepoint()) {
1431 guarantee(Thread::current()->is_VM_thread() ||
1432 FreeList_lock->owned_by_self() || OldSets_lock->owned_by_self(),
1433 "master old set MT safety protocol at a safepoint");
1434 } else {
1435 guarantee(Heap_lock->owned_by_self(), "master old set MT safety protocol outside a safepoint");
1436 }
1437 }
1438 bool is_correct_type(HeapRegion* hr) { return hr->is_old(); }
1439 const char* get_description() { return "Old Regions"; }
1440 };
1441
1442 class ArchiveRegionSetChecker : public HeapRegionSetChecker {
1443 public:
1444 void check_mt_safety() {
1445 guarantee(!Universe::is_fully_initialized() || SafepointSynchronize::is_at_safepoint(),
1446 "May only change archive regions during initialization or safepoint.");
1447 }
1448 bool is_correct_type(HeapRegion* hr) { return hr->is_archive(); }
1449 const char* get_description() { return "Archive Regions"; }
1450 };
1451
1452 class HumongousRegionSetChecker : public HeapRegionSetChecker {
1453 public:
1454 void check_mt_safety() {
1455 // Humongous Set MT safety protocol:
1456 // (a) If we're at a safepoint, operations on the master humongous
1457 // set should be invoked by either the VM thread (which will
1458 // serialize them) or by the GC workers while holding the
1459 // OldSets_lock.
1460 // (b) If we're not at a safepoint, operations on the master
1461 // humongous set should be invoked while holding the Heap_lock.
1462
1463 if (SafepointSynchronize::is_at_safepoint()) {
1464 guarantee(Thread::current()->is_VM_thread() ||
1465 OldSets_lock->owned_by_self(),
1466 "master humongous set MT safety protocol at a safepoint");
1467 } else {
1468 guarantee(Heap_lock->owned_by_self(),
1469 "master humongous set MT safety protocol outside a safepoint");
1470 }
1471 }
1472 bool is_correct_type(HeapRegion* hr) { return hr->is_humongous(); }
1473 const char* get_description() { return "Humongous Regions"; }
1474 };
1475
1476 G1CollectedHeap::G1CollectedHeap() :
1477 CollectedHeap(),
1478 _young_gen_sampling_thread(NULL),
1479 _workers(NULL),
1480 _card_table(NULL),
1481 _soft_ref_policy(),
1482 _old_set("Old Region Set", new OldRegionSetChecker()),
1483 _archive_set("Archive Region Set", new ArchiveRegionSetChecker()),
1484 _humongous_set("Humongous Region Set", new HumongousRegionSetChecker()),
1485 _bot(NULL),
1486 _listener(),
1487 _numa(G1NUMA::create()),
1488 _hrm(NULL),
1489 _allocator(NULL),
1490 _verifier(NULL),
1491 _summary_bytes_used(0),
1492 _bytes_used_during_gc(0),
1493 _archive_allocator(NULL),
1494 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1495 _old_evac_stats("Old", OldPLABSize, PLABWeight),
1496 _expand_heap_after_alloc_failure(true),
1497 _g1mm(NULL),
1498 _humongous_reclaim_candidates(),
1499 _has_humongous_reclaim_candidates(false),
1500 _hr_printer(),
1501 _collector_state(),
1502 _old_marking_cycles_started(0),
1503 _old_marking_cycles_completed(0),
1504 _eden(),
1505 _survivor(),
1506 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1507 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1508 _policy(G1Policy::create_policy(_gc_timer_stw)),
1509 _heap_sizing_policy(NULL),
1510 _collection_set(this, _policy),
1511 _hot_card_cache(NULL),
1512 _rem_set(NULL),
1513 _cm(NULL),
1514 _cm_thread(NULL),
1515 _cr(NULL),
1516 _task_queues(NULL),
1517 _evacuation_failed(false),
1518 _evacuation_failed_info_array(NULL),
1519 _preserved_marks_set(true /* in_c_heap */),
1520 #ifndef PRODUCT
1521 _evacuation_failure_alot_for_current_gc(false),
1522 _evacuation_failure_alot_gc_number(0),
1523 _evacuation_failure_alot_count(0),
1524 #endif
1525 _ref_processor_stw(NULL),
1526 _is_alive_closure_stw(this),
1527 _is_subject_to_discovery_stw(this),
1528 _ref_processor_cm(NULL),
1529 _is_alive_closure_cm(this),
1530 _is_subject_to_discovery_cm(this),
1531 _region_attr() {
1532
1533 _verifier = new G1HeapVerifier(this);
1534
1535 _allocator = new G1Allocator(this);
1536
1537 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _policy->analytics());
1538
1539 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1540
1541 // Override the default _filler_array_max_size so that no humongous filler
1542 // objects are created.
1543 _filler_array_max_size = _humongous_object_threshold_in_words;
1544
1545 uint n_queues = ParallelGCThreads;
1546 _task_queues = new ScannerTasksQueueSet(n_queues);
1547
1548 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1549
1550 for (uint i = 0; i < n_queues; i++) {
1551 ScannerTasksQueue* q = new ScannerTasksQueue();
1552 q->initialize();
1553 _task_queues->register_queue(i, q);
1554 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1555 }
1556
1557 // Initialize the G1EvacuationFailureALot counters and flags.
1558 NOT_PRODUCT(reset_evacuation_should_fail();)
1559 _gc_tracer_stw->initialize();
1560
1561 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1562 }
1563
1564 static size_t actual_reserved_page_size(ReservedSpace rs) {
1565 size_t page_size = os::vm_page_size();
1566 if (UseLargePages) {
1567 // There are two ways to manage large page memory.
1568 // 1. OS supports committing large page memory.
1569 // 2. OS doesn't support committing large page memory so ReservedSpace manages it.
1570 // And ReservedSpace calls it 'special'. If we failed to set 'special',
1571 // we reserved memory without large page.
1572 if (os::can_commit_large_page_memory() || rs.special()) {
1573 // An alignment at ReservedSpace comes from preferred page size or
1574 // heap alignment, and if the alignment came from heap alignment, it could be
1575 // larger than large pages size. So need to cap with the large page size.
1576 page_size = MIN2(rs.alignment(), os::large_page_size());
1577 }
1578 }
1579
1580 return page_size;
1581 }
1582
1583 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1584 size_t size,
1585 size_t translation_factor) {
1586 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1587 // Allocate a new reserved space, preferring to use large pages.
1588 ReservedSpace rs(size, preferred_page_size);
1589 size_t page_size = actual_reserved_page_size(rs);
1590 G1RegionToSpaceMapper* result =
1591 G1RegionToSpaceMapper::create_mapper(rs,
1592 size,
1593 page_size,
1594 HeapRegion::GrainBytes,
1595 translation_factor,
1596 mtGC);
1597
1598 os::trace_page_sizes_for_requested_size(description,
1599 size,
1600 preferred_page_size,
1601 page_size,
1602 rs.base(),
1603 rs.size());
1604
1605 return result;
1606 }
1607
1608 jint G1CollectedHeap::initialize_concurrent_refinement() {
1609 jint ecode = JNI_OK;
1610 _cr = G1ConcurrentRefine::create(&ecode);
1611 return ecode;
1612 }
1613
1614 jint G1CollectedHeap::initialize_young_gen_sampling_thread() {
1615 _young_gen_sampling_thread = new G1YoungRemSetSamplingThread();
1616 if (_young_gen_sampling_thread->osthread() == NULL) {
1617 vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread");
1618 return JNI_ENOMEM;
1619 }
1620 return JNI_OK;
1621 }
1622
1623 jint G1CollectedHeap::initialize() {
1624
1625 // Necessary to satisfy locking discipline assertions.
1626
1627 MutexLocker x(Heap_lock);
1628
1629 // While there are no constraints in the GC code that HeapWordSize
1630 // be any particular value, there are multiple other areas in the
1631 // system which believe this to be true (e.g. oop->object_size in some
1632 // cases incorrectly returns the size in wordSize units rather than
1633 // HeapWordSize).
1634 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1635
1636 size_t init_byte_size = InitialHeapSize;
1637 size_t reserved_byte_size = G1Arguments::heap_reserved_size_bytes();
1638
1639 // Ensure that the sizes are properly aligned.
1640 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1641 Universe::check_alignment(reserved_byte_size, HeapRegion::GrainBytes, "g1 heap");
1642 Universe::check_alignment(reserved_byte_size, HeapAlignment, "g1 heap");
1643
1644 // Reserve the maximum.
1645
1646 // When compressed oops are enabled, the preferred heap base
1647 // is calculated by subtracting the requested size from the
1648 // 32Gb boundary and using the result as the base address for
1649 // heap reservation. If the requested size is not aligned to
1650 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1651 // into the ReservedHeapSpace constructor) then the actual
1652 // base of the reserved heap may end up differing from the
1653 // address that was requested (i.e. the preferred heap base).
1654 // If this happens then we could end up using a non-optimal
1655 // compressed oops mode.
1656
1657 ReservedHeapSpace heap_rs = Universe::reserve_heap(reserved_byte_size,
1658 HeapAlignment);
1659
1660 initialize_reserved_region(heap_rs);
1661
1662 // Create the barrier set for the entire reserved region.
1663 G1CardTable* ct = new G1CardTable(heap_rs.region());
1664 ct->initialize();
1665 G1BarrierSet* bs = new G1BarrierSet(ct);
1666 bs->initialize();
1667 assert(bs->is_a(BarrierSet::G1BarrierSet), "sanity");
1668 BarrierSet::set_barrier_set(bs);
1669 _card_table = ct;
1670
1671 {
1672 G1SATBMarkQueueSet& satbqs = bs->satb_mark_queue_set();
1673 satbqs.set_process_completed_buffers_threshold(G1SATBProcessCompletedThreshold);
1674 satbqs.set_buffer_enqueue_threshold_percentage(G1SATBBufferEnqueueingThresholdPercent);
1675 }
1676
1677 // Create the hot card cache.
1678 _hot_card_cache = new G1HotCardCache(this);
1679
1680 // Carve out the G1 part of the heap.
1681 ReservedSpace g1_rs = heap_rs.first_part(reserved_byte_size);
1682 size_t page_size = actual_reserved_page_size(heap_rs);
1683 G1RegionToSpaceMapper* heap_storage =
1684 G1RegionToSpaceMapper::create_heap_mapper(g1_rs,
1685 g1_rs.size(),
1686 page_size,
1687 HeapRegion::GrainBytes,
1688 1,
1689 mtJavaHeap);
1690 if(heap_storage == NULL) {
1691 vm_shutdown_during_initialization("Could not initialize G1 heap");
1692 return JNI_ERR;
1693 }
1694
1695 os::trace_page_sizes("Heap",
1696 MinHeapSize,
1697 reserved_byte_size,
1698 page_size,
1699 heap_rs.base(),
1700 heap_rs.size());
1701 heap_storage->set_mapping_changed_listener(&_listener);
1702
1703 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1704 G1RegionToSpaceMapper* bot_storage =
1705 create_aux_memory_mapper("Block Offset Table",
1706 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1707 G1BlockOffsetTable::heap_map_factor());
1708
1709 G1RegionToSpaceMapper* cardtable_storage =
1710 create_aux_memory_mapper("Card Table",
1711 G1CardTable::compute_size(g1_rs.size() / HeapWordSize),
1712 G1CardTable::heap_map_factor());
1713
1714 G1RegionToSpaceMapper* card_counts_storage =
1715 create_aux_memory_mapper("Card Counts Table",
1716 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1717 G1CardCounts::heap_map_factor());
1718
1719 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1720 G1RegionToSpaceMapper* prev_bitmap_storage =
1721 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1722 G1RegionToSpaceMapper* next_bitmap_storage =
1723 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1724
1725 _hrm = HeapRegionManager::create_manager(this);
1726
1727 _hrm->initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1728 _card_table->initialize(cardtable_storage);
1729
1730 // Do later initialization work for concurrent refinement.
1731 _hot_card_cache->initialize(card_counts_storage);
1732
1733 // 6843694 - ensure that the maximum region index can fit
1734 // in the remembered set structures.
1735 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1736 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1737
1738 // The G1FromCardCache reserves card with value 0 as "invalid", so the heap must not
1739 // start within the first card.
1740 guarantee(g1_rs.base() >= (char*)G1CardTable::card_size, "Java heap must not start within the first card.");
1741 // Also create a G1 rem set.
1742 _rem_set = new G1RemSet(this, _card_table, _hot_card_cache);
1743 _rem_set->initialize(max_reserved_capacity(), max_regions());
1744
1745 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1746 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1747 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1748 "too many cards per region");
1749
1750 FreeRegionList::set_unrealistically_long_length(max_expandable_regions() + 1);
1751
1752 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1753
1754 {
1755 HeapWord* start = _hrm->reserved().start();
1756 HeapWord* end = _hrm->reserved().end();
1757 size_t granularity = HeapRegion::GrainBytes;
1758
1759 _region_attr.initialize(start, end, granularity);
1760 _humongous_reclaim_candidates.initialize(start, end, granularity);
1761 }
1762
1763 _workers = new WorkGang("GC Thread", ParallelGCThreads,
1764 true /* are_GC_task_threads */,
1765 false /* are_ConcurrentGC_threads */);
1766 if (_workers == NULL) {
1767 return JNI_ENOMEM;
1768 }
1769 _workers->initialize_workers();
1770
1771 _numa->set_region_info(HeapRegion::GrainBytes, page_size);
1772
1773 // Create the G1ConcurrentMark data structure and thread.
1774 // (Must do this late, so that "max_regions" is defined.)
1775 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1776 _cm_thread = _cm->cm_thread();
1777
1778 // Now expand into the initial heap size.
1779 if (!expand(init_byte_size, _workers)) {
1780 vm_shutdown_during_initialization("Failed to allocate initial heap.");
1781 return JNI_ENOMEM;
1782 }
1783
1784 // Perform any initialization actions delegated to the policy.
1785 policy()->init(this, &_collection_set);
1786
1787 jint ecode = initialize_concurrent_refinement();
1788 if (ecode != JNI_OK) {
1789 return ecode;
1790 }
1791
1792 ecode = initialize_young_gen_sampling_thread();
1793 if (ecode != JNI_OK) {
1794 return ecode;
1795 }
1796
1797 {
1798 G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
1799 dcqs.set_process_cards_threshold(concurrent_refine()->yellow_zone());
1800 dcqs.set_max_cards(concurrent_refine()->red_zone());
1801 }
1802
1803 // Here we allocate the dummy HeapRegion that is required by the
1804 // G1AllocRegion class.
1805 HeapRegion* dummy_region = _hrm->get_dummy_region();
1806
1807 // We'll re-use the same region whether the alloc region will
1808 // require BOT updates or not and, if it doesn't, then a non-young
1809 // region will complain that it cannot support allocations without
1810 // BOT updates. So we'll tag the dummy region as eden to avoid that.
1811 dummy_region->set_eden();
1812 // Make sure it's full.
1813 dummy_region->set_top(dummy_region->end());
1814 G1AllocRegion::setup(this, dummy_region);
1815
1816 _allocator->init_mutator_alloc_regions();
1817
1818 // Do create of the monitoring and management support so that
1819 // values in the heap have been properly initialized.
1820 _g1mm = new G1MonitoringSupport(this);
1821
1822 G1StringDedup::initialize();
1823
1824 _preserved_marks_set.init(ParallelGCThreads);
1825
1826 _collection_set.initialize(max_regions());
1827
1828 G1InitLogger::print();
1829
1830 return JNI_OK;
1831 }
1832
1833 void G1CollectedHeap::stop() {
1834 // Stop all concurrent threads. We do this to make sure these threads
1835 // do not continue to execute and access resources (e.g. logging)
1836 // that are destroyed during shutdown.
1837 _cr->stop();
1838 _young_gen_sampling_thread->stop();
1839 _cm_thread->stop();
1840 if (G1StringDedup::is_enabled()) {
1841 G1StringDedup::stop();
1842 }
1843 }
1844
1845 void G1CollectedHeap::safepoint_synchronize_begin() {
1846 SuspendibleThreadSet::synchronize();
1847 }
1848
1849 void G1CollectedHeap::safepoint_synchronize_end() {
1850 SuspendibleThreadSet::desynchronize();
1851 }
1852
1853 void G1CollectedHeap::post_initialize() {
1854 CollectedHeap::post_initialize();
1855 ref_processing_init();
1856 }
1857
1858 void G1CollectedHeap::ref_processing_init() {
1859 // Reference processing in G1 currently works as follows:
1860 //
1861 // * There are two reference processor instances. One is
1862 // used to record and process discovered references
1863 // during concurrent marking; the other is used to
1864 // record and process references during STW pauses
1865 // (both full and incremental).
1866 // * Both ref processors need to 'span' the entire heap as
1867 // the regions in the collection set may be dotted around.
1868 //
1869 // * For the concurrent marking ref processor:
1870 // * Reference discovery is enabled at initial marking.
1871 // * Reference discovery is disabled and the discovered
1872 // references processed etc during remarking.
1873 // * Reference discovery is MT (see below).
1874 // * Reference discovery requires a barrier (see below).
1875 // * Reference processing may or may not be MT
1876 // (depending on the value of ParallelRefProcEnabled
1877 // and ParallelGCThreads).
1878 // * A full GC disables reference discovery by the CM
1879 // ref processor and abandons any entries on it's
1880 // discovered lists.
1881 //
1882 // * For the STW processor:
1883 // * Non MT discovery is enabled at the start of a full GC.
1884 // * Processing and enqueueing during a full GC is non-MT.
1885 // * During a full GC, references are processed after marking.
1886 //
1887 // * Discovery (may or may not be MT) is enabled at the start
1888 // of an incremental evacuation pause.
1889 // * References are processed near the end of a STW evacuation pause.
1890 // * For both types of GC:
1891 // * Discovery is atomic - i.e. not concurrent.
1892 // * Reference discovery will not need a barrier.
1893
1894 bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1);
1895
1896 // Concurrent Mark ref processor
1897 _ref_processor_cm =
1898 new ReferenceProcessor(&_is_subject_to_discovery_cm,
1899 mt_processing, // mt processing
1900 ParallelGCThreads, // degree of mt processing
1901 (ParallelGCThreads > 1) || (ConcGCThreads > 1), // mt discovery
1902 MAX2(ParallelGCThreads, ConcGCThreads), // degree of mt discovery
1903 false, // Reference discovery is not atomic
1904 &_is_alive_closure_cm, // is alive closure
1905 true); // allow changes to number of processing threads
1906
1907 // STW ref processor
1908 _ref_processor_stw =
1909 new ReferenceProcessor(&_is_subject_to_discovery_stw,
1910 mt_processing, // mt processing
1911 ParallelGCThreads, // degree of mt processing
1912 (ParallelGCThreads > 1), // mt discovery
1913 ParallelGCThreads, // degree of mt discovery
1914 true, // Reference discovery is atomic
1915 &_is_alive_closure_stw, // is alive closure
1916 true); // allow changes to number of processing threads
1917 }
1918
1919 SoftRefPolicy* G1CollectedHeap::soft_ref_policy() {
1920 return &_soft_ref_policy;
1921 }
1922
1923 size_t G1CollectedHeap::capacity() const {
1924 return _hrm->length() * HeapRegion::GrainBytes;
1925 }
1926
1927 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const {
1928 return _hrm->total_free_bytes();
1929 }
1930
1931 void G1CollectedHeap::iterate_hcc_closure(G1CardTableEntryClosure* cl, uint worker_id) {
1932 _hot_card_cache->drain(cl, worker_id);
1933 }
1934
1935 // Computes the sum of the storage used by the various regions.
1936 size_t G1CollectedHeap::used() const {
1937 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
1938 if (_archive_allocator != NULL) {
1939 result += _archive_allocator->used();
1940 }
1941 return result;
1942 }
1943
1944 size_t G1CollectedHeap::used_unlocked() const {
1945 return _summary_bytes_used;
1946 }
1947
1948 class SumUsedClosure: public HeapRegionClosure {
1949 size_t _used;
1950 public:
1951 SumUsedClosure() : _used(0) {}
1952 bool do_heap_region(HeapRegion* r) {
1953 _used += r->used();
1954 return false;
1955 }
1956 size_t result() { return _used; }
1957 };
1958
1959 size_t G1CollectedHeap::recalculate_used() const {
1960 SumUsedClosure blk;
1961 heap_region_iterate(&blk);
1962 return blk.result();
1963 }
1964
1965 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
1966 switch (cause) {
1967 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
1968 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent;
1969 case GCCause::_wb_conc_mark: return true;
1970 default : return false;
1971 }
1972 }
1973
1974 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
1975 switch (cause) {
1976 case GCCause::_g1_humongous_allocation: return true;
1977 case GCCause::_g1_periodic_collection: return G1PeriodicGCInvokesConcurrent;
1978 case GCCause::_wb_breakpoint: return true;
1979 default: return is_user_requested_concurrent_full_gc(cause);
1980 }
1981 }
1982
1983 bool G1CollectedHeap::should_upgrade_to_full_gc(GCCause::Cause cause) {
1984 if (policy()->force_upgrade_to_full()) {
1985 return true;
1986 } else if (should_do_concurrent_full_gc(_gc_cause)) {
1987 return false;
1988 } else if (has_regions_left_for_allocation()) {
1989 return false;
1990 } else {
1991 return true;
1992 }
1993 }
1994
1995 #ifndef PRODUCT
1996 void G1CollectedHeap::allocate_dummy_regions() {
1997 // Let's fill up most of the region
1998 size_t word_size = HeapRegion::GrainWords - 1024;
1999 // And as a result the region we'll allocate will be humongous.
2000 guarantee(is_humongous(word_size), "sanity");
2001
2002 // _filler_array_max_size is set to humongous object threshold
2003 // but temporarily change it to use CollectedHeap::fill_with_object().
2004 SizeTFlagSetting fs(_filler_array_max_size, word_size);
2005
2006 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2007 // Let's use the existing mechanism for the allocation
2008 HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2009 if (dummy_obj != NULL) {
2010 MemRegion mr(dummy_obj, word_size);
2011 CollectedHeap::fill_with_object(mr);
2012 } else {
2013 // If we can't allocate once, we probably cannot allocate
2014 // again. Let's get out of the loop.
2015 break;
2016 }
2017 }
2018 }
2019 #endif // !PRODUCT
2020
2021 void G1CollectedHeap::increment_old_marking_cycles_started() {
2022 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2023 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2024 "Wrong marking cycle count (started: %d, completed: %d)",
2025 _old_marking_cycles_started, _old_marking_cycles_completed);
2026
2027 _old_marking_cycles_started++;
2028 }
2029
2030 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2031 MonitorLocker ml(G1OldGCCount_lock, Mutex::_no_safepoint_check_flag);
2032
2033 // We assume that if concurrent == true, then the caller is a
2034 // concurrent thread that was joined the Suspendible Thread
2035 // Set. If there's ever a cheap way to check this, we should add an
2036 // assert here.
2037
2038 // Given that this method is called at the end of a Full GC or of a
2039 // concurrent cycle, and those can be nested (i.e., a Full GC can
2040 // interrupt a concurrent cycle), the number of full collections
2041 // completed should be either one (in the case where there was no
2042 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2043 // behind the number of full collections started.
2044
2045 // This is the case for the inner caller, i.e. a Full GC.
2046 assert(concurrent ||
2047 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2048 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2049 "for inner caller (Full GC): _old_marking_cycles_started = %u "
2050 "is inconsistent with _old_marking_cycles_completed = %u",
2051 _old_marking_cycles_started, _old_marking_cycles_completed);
2052
2053 // This is the case for the outer caller, i.e. the concurrent cycle.
2054 assert(!concurrent ||
2055 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2056 "for outer caller (concurrent cycle): "
2057 "_old_marking_cycles_started = %u "
2058 "is inconsistent with _old_marking_cycles_completed = %u",
2059 _old_marking_cycles_started, _old_marking_cycles_completed);
2060
2061 _old_marking_cycles_completed += 1;
2062
2063 // We need to clear the "in_progress" flag in the CM thread before
2064 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2065 // is set) so that if a waiter requests another System.gc() it doesn't
2066 // incorrectly see that a marking cycle is still in progress.
2067 if (concurrent) {
2068 _cm_thread->set_idle();
2069 }
2070
2071 // Notify threads waiting in System.gc() (with ExplicitGCInvokesConcurrent)
2072 // for a full GC to finish that their wait is over.
2073 ml.notify_all();
2074 }
2075
2076 void G1CollectedHeap::collect(GCCause::Cause cause) {
2077 try_collect(cause);
2078 }
2079
2080 // Return true if (x < y) with allowance for wraparound.
2081 static bool gc_counter_less_than(uint x, uint y) {
2082 return (x - y) > (UINT_MAX/2);
2083 }
2084
2085 // LOG_COLLECT_CONCURRENTLY(cause, msg, args...)
2086 // Macro so msg printing is format-checked.
2087 #define LOG_COLLECT_CONCURRENTLY(cause, ...) \
2088 do { \
2089 LogTarget(Trace, gc) LOG_COLLECT_CONCURRENTLY_lt; \
2090 if (LOG_COLLECT_CONCURRENTLY_lt.is_enabled()) { \
2091 ResourceMark rm; /* For thread name. */ \
2092 LogStream LOG_COLLECT_CONCURRENTLY_s(&LOG_COLLECT_CONCURRENTLY_lt); \
2093 LOG_COLLECT_CONCURRENTLY_s.print("%s: Try Collect Concurrently (%s): ", \
2094 Thread::current()->name(), \
2095 GCCause::to_string(cause)); \
2096 LOG_COLLECT_CONCURRENTLY_s.print(__VA_ARGS__); \
2097 } \
2098 } while (0)
2099
2100 #define LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, result) \
2101 LOG_COLLECT_CONCURRENTLY(cause, "complete %s", BOOL_TO_STR(result))
2102
2103 bool G1CollectedHeap::try_collect_concurrently(GCCause::Cause cause,
2104 uint gc_counter,
2105 uint old_marking_started_before) {
2106 assert_heap_not_locked();
2107 assert(should_do_concurrent_full_gc(cause),
2108 "Non-concurrent cause %s", GCCause::to_string(cause));
2109
2110 for (uint i = 1; true; ++i) {
2111 // Try to schedule an initial-mark evacuation pause that will
2112 // start a concurrent cycle.
2113 LOG_COLLECT_CONCURRENTLY(cause, "attempt %u", i);
2114 VM_G1TryInitiateConcMark op(gc_counter,
2115 cause,
2116 policy()->max_pause_time_ms());
2117 VMThread::execute(&op);
2118
2119 // Request is trivially finished.
2120 if (cause == GCCause::_g1_periodic_collection) {
2121 LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, op.gc_succeeded());
2122 return op.gc_succeeded();
2123 }
2124
2125 // If VMOp skipped initiating concurrent marking cycle because
2126 // we're terminating, then we're done.
2127 if (op.terminating()) {
2128 LOG_COLLECT_CONCURRENTLY(cause, "skipped: terminating");
2129 return false;
2130 }
2131
2132 // Lock to get consistent set of values.
2133 uint old_marking_started_after;
2134 uint old_marking_completed_after;
2135 {
2136 MutexLocker ml(Heap_lock);
2137 // Update gc_counter for retrying VMOp if needed. Captured here to be
2138 // consistent with the values we use below for termination tests. If
2139 // a retry is needed after a possible wait, and another collection
2140 // occurs in the meantime, it will cause our retry to be skipped and
2141 // we'll recheck for termination with updated conditions from that
2142 // more recent collection. That's what we want, rather than having
2143 // our retry possibly perform an unnecessary collection.
2144 gc_counter = total_collections();
2145 old_marking_started_after = _old_marking_cycles_started;
2146 old_marking_completed_after = _old_marking_cycles_completed;
2147 }
2148
2149 if (cause == GCCause::_wb_breakpoint) {
2150 if (op.gc_succeeded()) {
2151 LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, true);
2152 return true;
2153 }
2154 // When _wb_breakpoint there can't be another cycle or deferred.
2155 assert(!op.cycle_already_in_progress(), "invariant");
2156 assert(!op.whitebox_attached(), "invariant");
2157 // Concurrent cycle attempt might have been cancelled by some other
2158 // collection, so retry. Unlike other cases below, we want to retry
2159 // even if cancelled by a STW full collection, because we really want
2160 // to start a concurrent cycle.
2161 if (old_marking_started_before != old_marking_started_after) {
2162 LOG_COLLECT_CONCURRENTLY(cause, "ignoring STW full GC");
2163 old_marking_started_before = old_marking_started_after;
2164 }
2165 } else if (!GCCause::is_user_requested_gc(cause)) {
2166 // For an "automatic" (not user-requested) collection, we just need to
2167 // ensure that progress is made.
2168 //
2169 // Request is finished if any of
2170 // (1) the VMOp successfully performed a GC,
2171 // (2) a concurrent cycle was already in progress,
2172 // (3) whitebox is controlling concurrent cycles,
2173 // (4) a new cycle was started (by this thread or some other), or
2174 // (5) a Full GC was performed.
2175 // Cases (4) and (5) are detected together by a change to
2176 // _old_marking_cycles_started.
2177 //
2178 // Note that (1) does not imply (4). If we're still in the mixed
2179 // phase of an earlier concurrent collection, the request to make the
2180 // collection an initial-mark won't be honored. If we don't check for
2181 // both conditions we'll spin doing back-to-back collections.
2182 if (op.gc_succeeded() ||
2183 op.cycle_already_in_progress() ||
2184 op.whitebox_attached() ||
2185 (old_marking_started_before != old_marking_started_after)) {
2186 LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, true);
2187 return true;
2188 }
2189 } else { // User-requested GC.
2190 // For a user-requested collection, we want to ensure that a complete
2191 // full collection has been performed before returning, but without
2192 // waiting for more than needed.
2193
2194 // For user-requested GCs (unlike non-UR), a successful VMOp implies a
2195 // new cycle was started. That's good, because it's not clear what we
2196 // should do otherwise. Trying again just does back to back GCs.
2197 // Can't wait for someone else to start a cycle. And returning fails
2198 // to meet the goal of ensuring a full collection was performed.
2199 assert(!op.gc_succeeded() ||
2200 (old_marking_started_before != old_marking_started_after),
2201 "invariant: succeeded %s, started before %u, started after %u",
2202 BOOL_TO_STR(op.gc_succeeded()),
2203 old_marking_started_before, old_marking_started_after);
2204
2205 // Request is finished if a full collection (concurrent or stw)
2206 // was started after this request and has completed, e.g.
2207 // started_before < completed_after.
2208 if (gc_counter_less_than(old_marking_started_before,
2209 old_marking_completed_after)) {
2210 LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, true);
2211 return true;
2212 }
2213
2214 if (old_marking_started_after != old_marking_completed_after) {
2215 // If there is an in-progress cycle (possibly started by us), then
2216 // wait for that cycle to complete, e.g.
2217 // while completed_now < started_after.
2218 LOG_COLLECT_CONCURRENTLY(cause, "wait");
2219 MonitorLocker ml(G1OldGCCount_lock);
2220 while (gc_counter_less_than(_old_marking_cycles_completed,
2221 old_marking_started_after)) {
2222 ml.wait();
2223 }
2224 // Request is finished if the collection we just waited for was
2225 // started after this request.
2226 if (old_marking_started_before != old_marking_started_after) {
2227 LOG_COLLECT_CONCURRENTLY(cause, "complete after wait");
2228 return true;
2229 }
2230 }
2231
2232 // If VMOp was successful then it started a new cycle that the above
2233 // wait &etc should have recognized as finishing this request. This
2234 // differs from a non-user-request, where gc_succeeded does not imply
2235 // a new cycle was started.
2236 assert(!op.gc_succeeded(), "invariant");
2237
2238 if (op.cycle_already_in_progress()) {
2239 // If VMOp failed because a cycle was already in progress, it
2240 // is now complete. But it didn't finish this user-requested
2241 // GC, so try again.
2242 LOG_COLLECT_CONCURRENTLY(cause, "retry after in-progress");
2243 continue;
2244 } else if (op.whitebox_attached()) {
2245 // If WhiteBox wants control, wait for notification of a state
2246 // change in the controller, then try again. Don't wait for
2247 // release of control, since collections may complete while in
2248 // control. Note: This won't recognize a STW full collection
2249 // while waiting; we can't wait on multiple monitors.
2250 LOG_COLLECT_CONCURRENTLY(cause, "whitebox control stall");
2251 MonitorLocker ml(ConcurrentGCBreakpoints::monitor());
2252 if (ConcurrentGCBreakpoints::is_controlled()) {
2253 ml.wait();
2254 }
2255 continue;
2256 }
2257 }
2258
2259 // Collection failed and should be retried.
2260 assert(op.transient_failure(), "invariant");
2261
2262 if (GCLocker::is_active_and_needs_gc()) {
2263 // If GCLocker is active, wait until clear before retrying.
2264 LOG_COLLECT_CONCURRENTLY(cause, "gc-locker stall");
2265 GCLocker::stall_until_clear();
2266 }
2267
2268 LOG_COLLECT_CONCURRENTLY(cause, "retry");
2269 }
2270 }
2271
2272 bool G1CollectedHeap::try_collect(GCCause::Cause cause) {
2273 assert_heap_not_locked();
2274
2275 // Lock to get consistent set of values.
2276 uint gc_count_before;
2277 uint full_gc_count_before;
2278 uint old_marking_started_before;
2279 {
2280 MutexLocker ml(Heap_lock);
2281 gc_count_before = total_collections();
2282 full_gc_count_before = total_full_collections();
2283 old_marking_started_before = _old_marking_cycles_started;
2284 }
2285
2286 if (should_do_concurrent_full_gc(cause)) {
2287 return try_collect_concurrently(cause,
2288 gc_count_before,
2289 old_marking_started_before);
2290 } else if (GCLocker::should_discard(cause, gc_count_before)) {
2291 // Indicate failure to be consistent with VMOp failure due to
2292 // another collection slipping in after our gc_count but before
2293 // our request is processed.
2294 return false;
2295 } else if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2296 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2297
2298 // Schedule a standard evacuation pause. We're setting word_size
2299 // to 0 which means that we are not requesting a post-GC allocation.
2300 VM_G1CollectForAllocation op(0, /* word_size */
2301 gc_count_before,
2302 cause,
2303 policy()->max_pause_time_ms());
2304 VMThread::execute(&op);
2305 return op.gc_succeeded();
2306 } else {
2307 // Schedule a Full GC.
2308 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2309 VMThread::execute(&op);
2310 return op.gc_succeeded();
2311 }
2312 }
2313
2314 bool G1CollectedHeap::is_in(const void* p) const {
2315 if (_hrm->reserved().contains(p)) {
2316 // Given that we know that p is in the reserved space,
2317 // heap_region_containing() should successfully
2318 // return the containing region.
2319 HeapRegion* hr = heap_region_containing(p);
2320 return hr->is_in(p);
2321 } else {
2322 return false;
2323 }
2324 }
2325
2326 #ifdef ASSERT
2327 bool G1CollectedHeap::is_in_exact(const void* p) const {
2328 bool contains = reserved_region().contains(p);
2329 bool available = _hrm->is_available(addr_to_region((HeapWord*)p));
2330 if (contains && available) {
2331 return true;
2332 } else {
2333 return false;
2334 }
2335 }
2336 #endif
2337
2338 // Iteration functions.
2339
2340 // Iterates an ObjectClosure over all objects within a HeapRegion.
2341
2342 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2343 ObjectClosure* _cl;
2344 public:
2345 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2346 bool do_heap_region(HeapRegion* r) {
2347 if (!r->is_continues_humongous()) {
2348 r->object_iterate(_cl);
2349 }
2350 return false;
2351 }
2352 };
2353
2354 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2355 IterateObjectClosureRegionClosure blk(cl);
2356 heap_region_iterate(&blk);
2357 }
2358
2359 void G1CollectedHeap::keep_alive(oop obj) {
2360 G1BarrierSet::enqueue(obj);
2361 }
2362
2363 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2364 _hrm->iterate(cl);
2365 }
2366
2367 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
2368 HeapRegionClaimer *hrclaimer,
2369 uint worker_id) const {
2370 _hrm->par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id));
2371 }
2372
2373 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl,
2374 HeapRegionClaimer *hrclaimer) const {
2375 _hrm->par_iterate(cl, hrclaimer, 0);
2376 }
2377
2378 void G1CollectedHeap::collection_set_iterate_all(HeapRegionClosure* cl) {
2379 _collection_set.iterate(cl);
2380 }
2381
2382 void G1CollectedHeap::collection_set_par_iterate_all(HeapRegionClosure* cl, HeapRegionClaimer* hr_claimer, uint worker_id) {
2383 _collection_set.par_iterate(cl, hr_claimer, worker_id, workers()->active_workers());
2384 }
2385
2386 void G1CollectedHeap::collection_set_iterate_increment_from(HeapRegionClosure *cl, HeapRegionClaimer* hr_claimer, uint worker_id) {
2387 _collection_set.iterate_incremental_part_from(cl, hr_claimer, worker_id, workers()->active_workers());
2388 }
2389
2390 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2391 HeapRegion* hr = heap_region_containing(addr);
2392 return hr->block_start(addr);
2393 }
2394
2395 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2396 HeapRegion* hr = heap_region_containing(addr);
2397 return hr->block_is_obj(addr);
2398 }
2399
2400 bool G1CollectedHeap::supports_tlab_allocation() const {
2401 return true;
2402 }
2403
2404 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2405 return (_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2406 }
2407
2408 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2409 return _eden.length() * HeapRegion::GrainBytes;
2410 }
2411
2412 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2413 // must be equal to the humongous object limit.
2414 size_t G1CollectedHeap::max_tlab_size() const {
2415 return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
2416 }
2417
2418 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2419 return _allocator->unsafe_max_tlab_alloc();
2420 }
2421
2422 size_t G1CollectedHeap::max_capacity() const {
2423 return _hrm->max_expandable_length() * HeapRegion::GrainBytes;
2424 }
2425
2426 size_t G1CollectedHeap::max_reserved_capacity() const {
2427 return _hrm->max_length() * HeapRegion::GrainBytes;
2428 }
2429
2430 jlong G1CollectedHeap::millis_since_last_gc() {
2431 // See the notes in GenCollectedHeap::millis_since_last_gc()
2432 // for more information about the implementation.
2433 jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) -
2434 _policy->collection_pause_end_millis();
2435 if (ret_val < 0) {
2436 log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
2437 ". returning zero instead.", ret_val);
2438 return 0;
2439 }
2440 return ret_val;
2441 }
2442
2443 void G1CollectedHeap::deduplicate_string(oop str) {
2444 assert(java_lang_String::is_instance(str), "invariant");
2445
2446 if (G1StringDedup::is_enabled()) {
2447 G1StringDedup::deduplicate(str);
2448 }
2449 }
2450
2451 void G1CollectedHeap::prepare_for_verify() {
2452 _verifier->prepare_for_verify();
2453 }
2454
2455 void G1CollectedHeap::verify(VerifyOption vo) {
2456 _verifier->verify(vo);
2457 }
2458
2459 bool G1CollectedHeap::supports_concurrent_gc_breakpoints() const {
2460 return true;
2461 }
2462
2463 bool G1CollectedHeap::is_heterogeneous_heap() const {
2464 return G1Arguments::is_heterogeneous_heap();
2465 }
2466
2467 class PrintRegionClosure: public HeapRegionClosure {
2468 outputStream* _st;
2469 public:
2470 PrintRegionClosure(outputStream* st) : _st(st) {}
2471 bool do_heap_region(HeapRegion* r) {
2472 r->print_on(_st);
2473 return false;
2474 }
2475 };
2476
2477 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2478 const HeapRegion* hr,
2479 const VerifyOption vo) const {
2480 switch (vo) {
2481 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2482 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2483 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr);
2484 default: ShouldNotReachHere();
2485 }
2486 return false; // keep some compilers happy
2487 }
2488
2489 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2490 const VerifyOption vo) const {
2491 switch (vo) {
2492 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2493 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2494 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj);
2495 default: ShouldNotReachHere();
2496 }
2497 return false; // keep some compilers happy
2498 }
2499
2500 void G1CollectedHeap::print_heap_regions() const {
2501 LogTarget(Trace, gc, heap, region) lt;
2502 if (lt.is_enabled()) {
2503 LogStream ls(lt);
2504 print_regions_on(&ls);
2505 }
2506 }
2507
2508 void G1CollectedHeap::print_on(outputStream* st) const {
2509 st->print(" %-20s", "garbage-first heap");
2510 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2511 capacity()/K, used_unlocked()/K);
2512 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")",
2513 p2i(_hrm->reserved().start()),
2514 p2i(_hrm->reserved().end()));
2515 st->cr();
2516 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2517 uint young_regions = young_regions_count();
2518 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2519 (size_t) young_regions * HeapRegion::GrainBytes / K);
2520 uint survivor_regions = survivor_regions_count();
2521 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2522 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2523 st->cr();
2524 if (_numa->is_enabled()) {
2525 uint num_nodes = _numa->num_active_nodes();
2526 st->print(" remaining free region(s) on each NUMA node: ");
2527 const int* node_ids = _numa->node_ids();
2528 for (uint node_index = 0; node_index < num_nodes; node_index++) {
2529 st->print("%d=%u ", node_ids[node_index], _hrm->num_free_regions(node_index));
2530 }
2531 st->cr();
2532 }
2533 MetaspaceUtils::print_on(st);
2534 }
2535
2536 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2537 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2538 "HS=humongous(starts), HC=humongous(continues), "
2539 "CS=collection set, F=free, "
2540 "OA=open archive, CA=closed archive, "
2541 "TAMS=top-at-mark-start (previous, next)");
2542 PrintRegionClosure blk(st);
2543 heap_region_iterate(&blk);
2544 }
2545
2546 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2547 print_on(st);
2548
2549 // Print the per-region information.
2550 print_regions_on(st);
2551 }
2552
2553 void G1CollectedHeap::print_on_error(outputStream* st) const {
2554 this->CollectedHeap::print_on_error(st);
2555
2556 if (_cm != NULL) {
2557 st->cr();
2558 _cm->print_on_error(st);
2559 }
2560 }
2561
2562 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2563 workers()->print_worker_threads_on(st);
2564 _cm_thread->print_on(st);
2565 st->cr();
2566 _cm->print_worker_threads_on(st);
2567 _cr->print_threads_on(st);
2568 _young_gen_sampling_thread->print_on(st);
2569 if (G1StringDedup::is_enabled()) {
2570 G1StringDedup::print_worker_threads_on(st);
2571 }
2572 }
2573
2574 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2575 workers()->threads_do(tc);
2576 tc->do_thread(_cm_thread);
2577 _cm->threads_do(tc);
2578 _cr->threads_do(tc);
2579 tc->do_thread(_young_gen_sampling_thread);
2580 if (G1StringDedup::is_enabled()) {
2581 G1StringDedup::threads_do(tc);
2582 }
2583 }
2584
2585 void G1CollectedHeap::print_tracing_info() const {
2586 rem_set()->print_summary_info();
2587 concurrent_mark()->print_summary_info();
2588 }
2589
2590 #ifndef PRODUCT
2591 // Helpful for debugging RSet issues.
2592
2593 class PrintRSetsClosure : public HeapRegionClosure {
2594 private:
2595 const char* _msg;
2596 size_t _occupied_sum;
2597
2598 public:
2599 bool do_heap_region(HeapRegion* r) {
2600 HeapRegionRemSet* hrrs = r->rem_set();
2601 size_t occupied = hrrs->occupied();
2602 _occupied_sum += occupied;
2603
2604 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2605 if (occupied == 0) {
2606 tty->print_cr(" RSet is empty");
2607 } else {
2608 hrrs->print();
2609 }
2610 tty->print_cr("----------");
2611 return false;
2612 }
2613
2614 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2615 tty->cr();
2616 tty->print_cr("========================================");
2617 tty->print_cr("%s", msg);
2618 tty->cr();
2619 }
2620
2621 ~PrintRSetsClosure() {
2622 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2623 tty->print_cr("========================================");
2624 tty->cr();
2625 }
2626 };
2627
2628 void G1CollectedHeap::print_cset_rsets() {
2629 PrintRSetsClosure cl("Printing CSet RSets");
2630 collection_set_iterate_all(&cl);
2631 }
2632
2633 void G1CollectedHeap::print_all_rsets() {
2634 PrintRSetsClosure cl("Printing All RSets");;
2635 heap_region_iterate(&cl);
2636 }
2637 #endif // PRODUCT
2638
2639 bool G1CollectedHeap::print_location(outputStream* st, void* addr) const {
2640 return BlockLocationPrinter<G1CollectedHeap>::print_location(st, addr);
2641 }
2642
2643 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2644
2645 size_t eden_used_bytes = _eden.used_bytes();
2646 size_t survivor_used_bytes = _survivor.used_bytes();
2647 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2648
2649 size_t eden_capacity_bytes =
2650 (policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2651
2652 VirtualSpaceSummary heap_summary = create_heap_space_summary();
2653 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2654 eden_capacity_bytes, survivor_used_bytes, num_regions());
2655 }
2656
2657 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2658 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2659 stats->unused(), stats->used(), stats->region_end_waste(),
2660 stats->regions_filled(), stats->direct_allocated(),
2661 stats->failure_used(), stats->failure_waste());
2662 }
2663
2664 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2665 const G1HeapSummary& heap_summary = create_g1_heap_summary();
2666 gc_tracer->report_gc_heap_summary(when, heap_summary);
2667
2668 const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2669 gc_tracer->report_metaspace_summary(when, metaspace_summary);
2670 }
2671
2672 G1CollectedHeap* G1CollectedHeap::heap() {
2673 CollectedHeap* heap = Universe::heap();
2674 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2675 assert(heap->kind() == CollectedHeap::G1, "Invalid name");
2676 return (G1CollectedHeap*)heap;
2677 }
2678
2679 void G1CollectedHeap::gc_prologue(bool full) {
2680 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2681
2682 // This summary needs to be printed before incrementing total collections.
2683 rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2684
2685 // Update common counters.
2686 increment_total_collections(full /* full gc */);
2687 if (full || collector_state()->in_initial_mark_gc()) {
2688 increment_old_marking_cycles_started();
2689 }
2690
2691 // Fill TLAB's and such
2692 {
2693 Ticks start = Ticks::now();
2694 ensure_parsability(true);
2695 Tickspan dt = Ticks::now() - start;
2696 phase_times()->record_prepare_tlab_time_ms(dt.seconds() * MILLIUNITS);
2697 }
2698
2699 if (!full) {
2700 // Flush dirty card queues to qset, so later phases don't need to account
2701 // for partially filled per-thread queues and such. Not needed for full
2702 // collections, which ignore those logs.
2703 Ticks start = Ticks::now();
2704 G1BarrierSet::dirty_card_queue_set().concatenate_logs();
2705 Tickspan dt = Ticks::now() - start;
2706 phase_times()->record_concatenate_dirty_card_logs_time_ms(dt.seconds() * MILLIUNITS);
2707 }
2708 }
2709
2710 void G1CollectedHeap::gc_epilogue(bool full) {
2711 // Update common counters.
2712 if (full) {
2713 // Update the number of full collections that have been completed.
2714 increment_old_marking_cycles_completed(false /* concurrent */);
2715 }
2716
2717 // We are at the end of the GC. Total collections has already been increased.
2718 rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2719
2720 // FIXME: what is this about?
2721 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2722 // is set.
2723 #if COMPILER2_OR_JVMCI
2724 assert(DerivedPointerTable::is_empty(), "derived pointer present");
2725 #endif
2726
2727 double start = os::elapsedTime();
2728 resize_all_tlabs();
2729 phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2730
2731 MemoryService::track_memory_usage();
2732 // We have just completed a GC. Update the soft reference
2733 // policy with the new heap occupancy
2734 Universe::update_heap_info_at_gc();
2735
2736 // Print NUMA statistics.
2737 _numa->print_statistics();
2738 }
2739
2740 void G1CollectedHeap::verify_numa_regions(const char* desc) {
2741 LogTarget(Trace, gc, heap, verify) lt;
2742
2743 if (lt.is_enabled()) {
2744 LogStream ls(lt);
2745 // Iterate all heap regions to print matching between preferred numa id and actual numa id.
2746 G1NodeIndexCheckClosure cl(desc, _numa, &ls);
2747 heap_region_iterate(&cl);
2748 }
2749 }
2750
2751 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2752 uint gc_count_before,
2753 bool* succeeded,
2754 GCCause::Cause gc_cause) {
2755 assert_heap_not_locked_and_not_at_safepoint();
2756 VM_G1CollectForAllocation op(word_size,
2757 gc_count_before,
2758 gc_cause,
2759 policy()->max_pause_time_ms());
2760 VMThread::execute(&op);
2761
2762 HeapWord* result = op.result();
2763 bool ret_succeeded = op.prologue_succeeded() && op.gc_succeeded();
2764 assert(result == NULL || ret_succeeded,
2765 "the result should be NULL if the VM did not succeed");
2766 *succeeded = ret_succeeded;
2767
2768 assert_heap_not_locked();
2769 return result;
2770 }
2771
2772 void G1CollectedHeap::do_concurrent_mark() {
2773 MutexLocker x(CGC_lock, Mutex::_no_safepoint_check_flag);
2774 if (!_cm_thread->in_progress()) {
2775 _cm_thread->set_started();
2776 CGC_lock->notify();
2777 }
2778 }
2779
2780 bool G1CollectedHeap::is_potential_eager_reclaim_candidate(HeapRegion* r) const {
2781 // We don't nominate objects with many remembered set entries, on
2782 // the assumption that such objects are likely still live.
2783 HeapRegionRemSet* rem_set = r->rem_set();
2784
2785 return G1EagerReclaimHumongousObjectsWithStaleRefs ?
2786 rem_set->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) :
2787 G1EagerReclaimHumongousObjects && rem_set->is_empty();
2788 }
2789
2790 #ifndef PRODUCT
2791 void G1CollectedHeap::verify_region_attr_remset_update() {
2792 class VerifyRegionAttrRemSet : public HeapRegionClosure {
2793 public:
2794 virtual bool do_heap_region(HeapRegion* r) {
2795 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2796 bool const needs_remset_update = g1h->region_attr(r->bottom()).needs_remset_update();
2797 assert(r->rem_set()->is_tracked() == needs_remset_update,
2798 "Region %u remset tracking status (%s) different to region attribute (%s)",
2799 r->hrm_index(), BOOL_TO_STR(r->rem_set()->is_tracked()), BOOL_TO_STR(needs_remset_update));
2800 return false;
2801 }
2802 } cl;
2803 heap_region_iterate(&cl);
2804 }
2805 #endif
2806
2807 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2808 public:
2809 bool do_heap_region(HeapRegion* hr) {
2810 if (!hr->is_archive() && !hr->is_continues_humongous()) {
2811 hr->verify_rem_set();
2812 }
2813 return false;
2814 }
2815 };
2816
2817 uint G1CollectedHeap::num_task_queues() const {
2818 return _task_queues->size();
2819 }
2820
2821 #if TASKQUEUE_STATS
2822 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2823 st->print_raw_cr("GC Task Stats");
2824 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2825 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2826 }
2827
2828 void G1CollectedHeap::print_taskqueue_stats() const {
2829 if (!log_is_enabled(Trace, gc, task, stats)) {
2830 return;
2831 }
2832 Log(gc, task, stats) log;
2833 ResourceMark rm;
2834 LogStream ls(log.trace());
2835 outputStream* st = &ls;
2836
2837 print_taskqueue_stats_hdr(st);
2838
2839 TaskQueueStats totals;
2840 const uint n = num_task_queues();
2841 for (uint i = 0; i < n; ++i) {
2842 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2843 totals += task_queue(i)->stats;
2844 }
2845 st->print_raw("tot "); totals.print(st); st->cr();
2846
2847 DEBUG_ONLY(totals.verify());
2848 }
2849
2850 void G1CollectedHeap::reset_taskqueue_stats() {
2851 const uint n = num_task_queues();
2852 for (uint i = 0; i < n; ++i) {
2853 task_queue(i)->stats.reset();
2854 }
2855 }
2856 #endif // TASKQUEUE_STATS
2857
2858 void G1CollectedHeap::wait_for_root_region_scanning() {
2859 double scan_wait_start = os::elapsedTime();
2860 // We have to wait until the CM threads finish scanning the
2861 // root regions as it's the only way to ensure that all the
2862 // objects on them have been correctly scanned before we start
2863 // moving them during the GC.
2864 bool waited = _cm->root_regions()->wait_until_scan_finished();
2865 double wait_time_ms = 0.0;
2866 if (waited) {
2867 double scan_wait_end = os::elapsedTime();
2868 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2869 }
2870 phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2871 }
2872
2873 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2874 private:
2875 G1HRPrinter* _hr_printer;
2876 public:
2877 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2878
2879 virtual bool do_heap_region(HeapRegion* r) {
2880 _hr_printer->cset(r);
2881 return false;
2882 }
2883 };
2884
2885 void G1CollectedHeap::start_new_collection_set() {
2886 double start = os::elapsedTime();
2887
2888 collection_set()->start_incremental_building();
2889
2890 clear_region_attr();
2891
2892 guarantee(_eden.length() == 0, "eden should have been cleared");
2893 policy()->transfer_survivors_to_cset(survivor());
2894
2895 // We redo the verification but now wrt to the new CSet which
2896 // has just got initialized after the previous CSet was freed.
2897 _cm->verify_no_collection_set_oops();
2898
2899 phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0);
2900 }
2901
2902 void G1CollectedHeap::calculate_collection_set(G1EvacuationInfo& evacuation_info, double target_pause_time_ms) {
2903
2904 _collection_set.finalize_initial_collection_set(target_pause_time_ms, &_survivor);
2905 evacuation_info.set_collectionset_regions(collection_set()->region_length() +
2906 collection_set()->optional_region_length());
2907
2908 _cm->verify_no_collection_set_oops();
2909
2910 if (_hr_printer.is_active()) {
2911 G1PrintCollectionSetClosure cl(&_hr_printer);
2912 _collection_set.iterate(&cl);
2913 _collection_set.iterate_optional(&cl);
2914 }
2915 }
2916
2917 G1HeapVerifier::G1VerifyType G1CollectedHeap::young_collection_verify_type() const {
2918 if (collector_state()->in_initial_mark_gc()) {
2919 return G1HeapVerifier::G1VerifyConcurrentStart;
2920 } else if (collector_state()->in_young_only_phase()) {
2921 return G1HeapVerifier::G1VerifyYoungNormal;
2922 } else {
2923 return G1HeapVerifier::G1VerifyMixed;
2924 }
2925 }
2926
2927 void G1CollectedHeap::verify_before_young_collection(G1HeapVerifier::G1VerifyType type) {
2928 if (VerifyRememberedSets) {
2929 log_info(gc, verify)("[Verifying RemSets before GC]");
2930 VerifyRegionRemSetClosure v_cl;
2931 heap_region_iterate(&v_cl);
2932 }
2933 _verifier->verify_before_gc(type);
2934 _verifier->check_bitmaps("GC Start");
2935 verify_numa_regions("GC Start");
2936 }
2937
2938 void G1CollectedHeap::verify_after_young_collection(G1HeapVerifier::G1VerifyType type) {
2939 if (VerifyRememberedSets) {
2940 log_info(gc, verify)("[Verifying RemSets after GC]");
2941 VerifyRegionRemSetClosure v_cl;
2942 heap_region_iterate(&v_cl);
2943 }
2944 _verifier->verify_after_gc(type);
2945 _verifier->check_bitmaps("GC End");
2946 verify_numa_regions("GC End");
2947 }
2948
2949 void G1CollectedHeap::expand_heap_after_young_collection(){
2950 size_t expand_bytes = _heap_sizing_policy->expansion_amount();
2951 if (expand_bytes > 0) {
2952 // No need for an ergo logging here,
2953 // expansion_amount() does this when it returns a value > 0.
2954 double expand_ms;
2955 if (!expand(expand_bytes, _workers, &expand_ms)) {
2956 // We failed to expand the heap. Cannot do anything about it.
2957 }
2958 phase_times()->record_expand_heap_time(expand_ms);
2959 }
2960 }
2961
2962 const char* G1CollectedHeap::young_gc_name() const {
2963 if (collector_state()->in_initial_mark_gc()) {
2964 return "Pause Young (Concurrent Start)";
2965 } else if (collector_state()->in_young_only_phase()) {
2966 if (collector_state()->in_young_gc_before_mixed()) {
2967 return "Pause Young (Prepare Mixed)";
2968 } else {
2969 return "Pause Young (Normal)";
2970 }
2971 } else {
2972 return "Pause Young (Mixed)";
2973 }
2974 }
2975
2976 bool G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
2977 assert_at_safepoint_on_vm_thread();
2978 guarantee(!is_gc_active(), "collection is not reentrant");
2979
2980 if (GCLocker::check_active_before_gc()) {
2981 return false;
2982 }
2983
2984 do_collection_pause_at_safepoint_helper(target_pause_time_ms);
2985 if (should_upgrade_to_full_gc(gc_cause())) {
2986 log_info(gc, ergo)("Attempting maximally compacting collection");
2987 bool result = do_full_collection(false /* explicit gc */,
2988 true /* clear_all_soft_refs */);
2989 // do_full_collection only fails if blocked by GC locker, but
2990 // we've already checked for that above.
2991 assert(result, "invariant");
2992 }
2993 return true;
2994 }
2995
2996 void G1CollectedHeap::do_collection_pause_at_safepoint_helper(double target_pause_time_ms) {
2997 GCIdMark gc_id_mark;
2998
2999 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3000 ResourceMark rm;
3001
3002 policy()->note_gc_start();
3003
3004 _gc_timer_stw->register_gc_start();
3005 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3006
3007 wait_for_root_region_scanning();
3008
3009 print_heap_before_gc();
3010 print_heap_regions();
3011 trace_heap_before_gc(_gc_tracer_stw);
3012
3013 _verifier->verify_region_sets_optional();
3014 _verifier->verify_dirty_young_regions();
3015
3016 // We should not be doing initial mark unless the conc mark thread is running
3017 if (!_cm_thread->should_terminate()) {
3018 // This call will decide whether this pause is an initial-mark
3019 // pause. If it is, in_initial_mark_gc() will return true
3020 // for the duration of this pause.
3021 policy()->decide_on_conc_mark_initiation();
3022 }
3023
3024 // We do not allow initial-mark to be piggy-backed on a mixed GC.
3025 assert(!collector_state()->in_initial_mark_gc() ||
3026 collector_state()->in_young_only_phase(), "sanity");
3027 // We also do not allow mixed GCs during marking.
3028 assert(!collector_state()->mark_or_rebuild_in_progress() || collector_state()->in_young_only_phase(), "sanity");
3029
3030 // Record whether this pause is an initial mark. When the current
3031 // thread has completed its logging output and it's safe to signal
3032 // the CM thread, the flag's value in the policy has been reset.
3033 bool should_start_conc_mark = collector_state()->in_initial_mark_gc();
3034 if (should_start_conc_mark) {
3035 _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
3036 }
3037
3038 // Inner scope for scope based logging, timers, and stats collection
3039 {
3040 G1EvacuationInfo evacuation_info;
3041
3042 _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
3043
3044 GCTraceCPUTime tcpu;
3045
3046 GCTraceTime(Info, gc) tm(young_gc_name(), NULL, gc_cause(), true);
3047
3048 uint active_workers = WorkerPolicy::calc_active_workers(workers()->total_workers(),
3049 workers()->active_workers(),
3050 Threads::number_of_non_daemon_threads());
3051 active_workers = workers()->update_active_workers(active_workers);
3052 log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
3053
3054 G1MonitoringScope ms(g1mm(),
3055 false /* full_gc */,
3056 collector_state()->yc_type() == Mixed /* all_memory_pools_affected */);
3057
3058 G1HeapTransition heap_transition(this);
3059
3060 {
3061 IsGCActiveMark x;
3062
3063 gc_prologue(false);
3064
3065 G1HeapVerifier::G1VerifyType verify_type = young_collection_verify_type();
3066 verify_before_young_collection(verify_type);
3067
3068 {
3069 // The elapsed time induced by the start time below deliberately elides
3070 // the possible verification above.
3071 double sample_start_time_sec = os::elapsedTime();
3072
3073 // Please see comment in g1CollectedHeap.hpp and
3074 // G1CollectedHeap::ref_processing_init() to see how
3075 // reference processing currently works in G1.
3076 _ref_processor_stw->enable_discovery();
3077
3078 // We want to temporarily turn off discovery by the
3079 // CM ref processor, if necessary, and turn it back on
3080 // on again later if we do. Using a scoped
3081 // NoRefDiscovery object will do this.
3082 NoRefDiscovery no_cm_discovery(_ref_processor_cm);
3083
3084 policy()->record_collection_pause_start(sample_start_time_sec);
3085
3086 // Forget the current allocation region (we might even choose it to be part
3087 // of the collection set!).
3088 _allocator->release_mutator_alloc_regions();
3089
3090 calculate_collection_set(evacuation_info, target_pause_time_ms);
3091
3092 G1RedirtyCardsQueueSet rdcqs(G1BarrierSet::dirty_card_queue_set().allocator());
3093 G1ParScanThreadStateSet per_thread_states(this,
3094 &rdcqs,
3095 workers()->active_workers(),
3096 collection_set()->young_region_length(),
3097 collection_set()->optional_region_length());
3098 pre_evacuate_collection_set(evacuation_info, &per_thread_states);
3099
3100 // Actually do the work...
3101 evacuate_initial_collection_set(&per_thread_states);
3102
3103 if (_collection_set.optional_region_length() != 0) {
3104 evacuate_optional_collection_set(&per_thread_states);
3105 }
3106 post_evacuate_collection_set(evacuation_info, &rdcqs, &per_thread_states);
3107
3108 start_new_collection_set();
3109
3110 _survivor_evac_stats.adjust_desired_plab_sz();
3111 _old_evac_stats.adjust_desired_plab_sz();
3112
3113 if (should_start_conc_mark) {
3114 // We have to do this before we notify the CM threads that
3115 // they can start working to make sure that all the
3116 // appropriate initialization is done on the CM object.
3117 concurrent_mark()->post_initial_mark();
3118 // Note that we don't actually trigger the CM thread at
3119 // this point. We do that later when we're sure that
3120 // the current thread has completed its logging output.
3121 }
3122
3123 allocate_dummy_regions();
3124
3125 _allocator->init_mutator_alloc_regions();
3126
3127 expand_heap_after_young_collection();
3128
3129 double sample_end_time_sec = os::elapsedTime();
3130 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3131 policy()->record_collection_pause_end(pause_time_ms);
3132 }
3133
3134 verify_after_young_collection(verify_type);
3135
3136 gc_epilogue(false);
3137 }
3138
3139 // Print the remainder of the GC log output.
3140 if (evacuation_failed()) {
3141 log_info(gc)("To-space exhausted");
3142 }
3143
3144 policy()->print_phases();
3145 heap_transition.print();
3146
3147 _hrm->verify_optional();
3148 _verifier->verify_region_sets_optional();
3149
3150 TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3151 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3152
3153 print_heap_after_gc();
3154 print_heap_regions();
3155 trace_heap_after_gc(_gc_tracer_stw);
3156
3157 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3158 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3159 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3160 // before any GC notifications are raised.
3161 g1mm()->update_sizes();
3162
3163 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3164 _gc_tracer_stw->report_tenuring_threshold(_policy->tenuring_threshold());
3165 _gc_timer_stw->register_gc_end();
3166 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3167 }
3168 // It should now be safe to tell the concurrent mark thread to start
3169 // without its logging output interfering with the logging output
3170 // that came from the pause.
3171
3172 if (should_start_conc_mark) {
3173 // CAUTION: after the doConcurrentMark() call below, the concurrent marking
3174 // thread(s) could be running concurrently with us. Make sure that anything
3175 // after this point does not assume that we are the only GC thread running.
3176 // Note: of course, the actual marking work will not start until the safepoint
3177 // itself is released in SuspendibleThreadSet::desynchronize().
3178 do_concurrent_mark();
3179 ConcurrentGCBreakpoints::notify_idle_to_active();
3180 }
3181 }
3182
3183 void G1CollectedHeap::remove_self_forwarding_pointers(G1RedirtyCardsQueueSet* rdcqs) {
3184 G1ParRemoveSelfForwardPtrsTask rsfp_task(rdcqs);
3185 workers()->run_task(&rsfp_task);
3186 }
3187
3188 void G1CollectedHeap::restore_after_evac_failure(G1RedirtyCardsQueueSet* rdcqs) {
3189 double remove_self_forwards_start = os::elapsedTime();
3190
3191 remove_self_forwarding_pointers(rdcqs);
3192 _preserved_marks_set.restore(workers());
3193
3194 phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3195 }
3196
3197 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markWord m) {
3198 if (!_evacuation_failed) {
3199 _evacuation_failed = true;
3200 }
3201
3202 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3203 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3204 }
3205
3206 bool G1ParEvacuateFollowersClosure::offer_termination() {
3207 EventGCPhaseParallel event;
3208 G1ParScanThreadState* const pss = par_scan_state();
3209 start_term_time();
3210 const bool res = terminator()->offer_termination();
3211 end_term_time();
3212 event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(G1GCPhaseTimes::Termination));
3213 return res;
3214 }
3215
3216 void G1ParEvacuateFollowersClosure::do_void() {
3217 EventGCPhaseParallel event;
3218 G1ParScanThreadState* const pss = par_scan_state();
3219 pss->trim_queue();
3220 event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(_phase));
3221 do {
3222 EventGCPhaseParallel event;
3223 pss->steal_and_trim_queue(queues());
3224 event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(_phase));
3225 } while (!offer_termination());
3226 }
3227
3228 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
3229 bool class_unloading_occurred) {
3230 uint num_workers = workers()->active_workers();
3231 G1ParallelCleaningTask unlink_task(is_alive, num_workers, class_unloading_occurred, false);
3232 workers()->run_task(&unlink_task);
3233 }
3234
3235 // Clean string dedup data structures.
3236 // Ideally we would prefer to use a StringDedupCleaningTask here, but we want to
3237 // record the durations of the phases. Hence the almost-copy.
3238 class G1StringDedupCleaningTask : public AbstractGangTask {
3239 BoolObjectClosure* _is_alive;
3240 OopClosure* _keep_alive;
3241 G1GCPhaseTimes* _phase_times;
3242
3243 public:
3244 G1StringDedupCleaningTask(BoolObjectClosure* is_alive,
3245 OopClosure* keep_alive,
3246 G1GCPhaseTimes* phase_times) :
3247 AbstractGangTask("Partial Cleaning Task"),
3248 _is_alive(is_alive),
3249 _keep_alive(keep_alive),
3250 _phase_times(phase_times)
3251 {
3252 assert(G1StringDedup::is_enabled(), "String deduplication disabled.");
3253 StringDedup::gc_prologue(true);
3254 }
3255
3256 ~G1StringDedupCleaningTask() {
3257 StringDedup::gc_epilogue();
3258 }
3259
3260 void work(uint worker_id) {
3261 StringDedupUnlinkOrOopsDoClosure cl(_is_alive, _keep_alive);
3262 {
3263 G1GCParPhaseTimesTracker x(_phase_times, G1GCPhaseTimes::StringDedupQueueFixup, worker_id);
3264 StringDedupQueue::unlink_or_oops_do(&cl);
3265 }
3266 {
3267 G1GCParPhaseTimesTracker x(_phase_times, G1GCPhaseTimes::StringDedupTableFixup, worker_id);
3268 StringDedupTable::unlink_or_oops_do(&cl, worker_id);
3269 }
3270 }
3271 };
3272
3273 void G1CollectedHeap::string_dedup_cleaning(BoolObjectClosure* is_alive,
3274 OopClosure* keep_alive,
3275 G1GCPhaseTimes* phase_times) {
3276 G1StringDedupCleaningTask cl(is_alive, keep_alive, phase_times);
3277 workers()->run_task(&cl);
3278 }
3279
3280 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3281 private:
3282 G1RedirtyCardsQueueSet* _qset;
3283 G1CollectedHeap* _g1h;
3284 BufferNode* volatile _nodes;
3285
3286 void par_apply(RedirtyLoggedCardTableEntryClosure* cl, uint worker_id) {
3287 size_t buffer_size = _qset->buffer_size();
3288 BufferNode* next = Atomic::load(&_nodes);
3289 while (next != NULL) {
3290 BufferNode* node = next;
3291 next = Atomic::cmpxchg(&_nodes, node, node->next());
3292 if (next == node) {
3293 cl->apply_to_buffer(node, buffer_size, worker_id);
3294 next = node->next();
3295 }
3296 }
3297 }
3298
3299 public:
3300 G1RedirtyLoggedCardsTask(G1RedirtyCardsQueueSet* qset, G1CollectedHeap* g1h) :
3301 AbstractGangTask("Redirty Cards"),
3302 _qset(qset), _g1h(g1h), _nodes(qset->all_completed_buffers()) { }
3303
3304 virtual void work(uint worker_id) {
3305 G1GCPhaseTimes* p = _g1h->phase_times();
3306 G1GCParPhaseTimesTracker x(p, G1GCPhaseTimes::RedirtyCards, worker_id);
3307
3308 RedirtyLoggedCardTableEntryClosure cl(_g1h);
3309 par_apply(&cl, worker_id);
3310
3311 p->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3312 }
3313 };
3314
3315 void G1CollectedHeap::redirty_logged_cards(G1RedirtyCardsQueueSet* rdcqs) {
3316 double redirty_logged_cards_start = os::elapsedTime();
3317
3318 G1RedirtyLoggedCardsTask redirty_task(rdcqs, this);
3319 workers()->run_task(&redirty_task);
3320
3321 G1DirtyCardQueueSet& dcq = G1BarrierSet::dirty_card_queue_set();
3322 dcq.merge_bufferlists(rdcqs);
3323
3324 phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3325 }
3326
3327 // Weak Reference Processing support
3328
3329 bool G1STWIsAliveClosure::do_object_b(oop p) {
3330 // An object is reachable if it is outside the collection set,
3331 // or is inside and copied.
3332 return !_g1h->is_in_cset(p) || p->is_forwarded();
3333 }
3334
3335 bool G1STWSubjectToDiscoveryClosure::do_object_b(oop obj) {
3336 assert(obj != NULL, "must not be NULL");
3337 assert(_g1h->is_in_reserved(obj), "Trying to discover obj " PTR_FORMAT " not in heap", p2i(obj));
3338 // The areas the CM and STW ref processor manage must be disjoint. The is_in_cset() below
3339 // may falsely indicate that this is not the case here: however the collection set only
3340 // contains old regions when concurrent mark is not running.
3341 return _g1h->is_in_cset(obj) || _g1h->heap_region_containing(obj)->is_survivor();
3342 }
3343
3344 // Non Copying Keep Alive closure
3345 class G1KeepAliveClosure: public OopClosure {
3346 G1CollectedHeap*_g1h;
3347 public:
3348 G1KeepAliveClosure(G1CollectedHeap* g1h) :_g1h(g1h) {}
3349 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3350 void do_oop(oop* p) {
3351 oop obj = *p;
3352 assert(obj != NULL, "the caller should have filtered out NULL values");
3353
3354 const G1HeapRegionAttr region_attr =_g1h->region_attr(obj);
3355 if (!region_attr.is_in_cset_or_humongous()) {
3356 return;
3357 }
3358 if (region_attr.is_in_cset()) {
3359 assert( obj->is_forwarded(), "invariant" );
3360 *p = obj->forwardee();
3361 } else {
3362 assert(!obj->is_forwarded(), "invariant" );
3363 assert(region_attr.is_humongous(),
3364 "Only allowed G1HeapRegionAttr state is IsHumongous, but is %d", region_attr.type());
3365 _g1h->set_humongous_is_live(obj);
3366 }
3367 }
3368 };
3369
3370 // Copying Keep Alive closure - can be called from both
3371 // serial and parallel code as long as different worker
3372 // threads utilize different G1ParScanThreadState instances
3373 // and different queues.
3374
3375 class G1CopyingKeepAliveClosure: public OopClosure {
3376 G1CollectedHeap* _g1h;
3377 G1ParScanThreadState* _par_scan_state;
3378
3379 public:
3380 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3381 G1ParScanThreadState* pss):
3382 _g1h(g1h),
3383 _par_scan_state(pss)
3384 {}
3385
3386 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3387 virtual void do_oop( oop* p) { do_oop_work(p); }
3388
3389 template <class T> void do_oop_work(T* p) {
3390 oop obj = RawAccess<>::oop_load(p);
3391
3392 if (_g1h->is_in_cset_or_humongous(obj)) {
3393 // If the referent object has been forwarded (either copied
3394 // to a new location or to itself in the event of an
3395 // evacuation failure) then we need to update the reference
3396 // field and, if both reference and referent are in the G1
3397 // heap, update the RSet for the referent.
3398 //
3399 // If the referent has not been forwarded then we have to keep
3400 // it alive by policy. Therefore we have copy the referent.
3401 //
3402 // When the queue is drained (after each phase of reference processing)
3403 // the object and it's followers will be copied, the reference field set
3404 // to point to the new location, and the RSet updated.
3405 _par_scan_state->push_on_queue(ScannerTask(p));
3406 }
3407 }
3408 };
3409
3410 // Serial drain queue closure. Called as the 'complete_gc'
3411 // closure for each discovered list in some of the
3412 // reference processing phases.
3413
3414 class G1STWDrainQueueClosure: public VoidClosure {
3415 protected:
3416 G1CollectedHeap* _g1h;
3417 G1ParScanThreadState* _par_scan_state;
3418
3419 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
3420
3421 public:
3422 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
3423 _g1h(g1h),
3424 _par_scan_state(pss)
3425 { }
3426
3427 void do_void() {
3428 G1ParScanThreadState* const pss = par_scan_state();
3429 pss->trim_queue();
3430 }
3431 };
3432
3433 // Parallel Reference Processing closures
3434
3435 // Implementation of AbstractRefProcTaskExecutor for parallel reference
3436 // processing during G1 evacuation pauses.
3437
3438 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
3439 private:
3440 G1CollectedHeap* _g1h;
3441 G1ParScanThreadStateSet* _pss;
3442 ScannerTasksQueueSet* _queues;
3443 WorkGang* _workers;
3444
3445 public:
3446 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
3447 G1ParScanThreadStateSet* per_thread_states,
3448 WorkGang* workers,
3449 ScannerTasksQueueSet *task_queues) :
3450 _g1h(g1h),
3451 _pss(per_thread_states),
3452 _queues(task_queues),
3453 _workers(workers)
3454 {
3455 g1h->ref_processor_stw()->set_active_mt_degree(workers->active_workers());
3456 }
3457
3458 // Executes the given task using concurrent marking worker threads.
3459 virtual void execute(ProcessTask& task, uint ergo_workers);
3460 };
3461
3462 // Gang task for possibly parallel reference processing
3463
3464 class G1STWRefProcTaskProxy: public AbstractGangTask {
3465 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
3466 ProcessTask& _proc_task;
3467 G1CollectedHeap* _g1h;
3468 G1ParScanThreadStateSet* _pss;
3469 ScannerTasksQueueSet* _task_queues;
3470 TaskTerminator* _terminator;
3471
3472 public:
3473 G1STWRefProcTaskProxy(ProcessTask& proc_task,
3474 G1CollectedHeap* g1h,
3475 G1ParScanThreadStateSet* per_thread_states,
3476 ScannerTasksQueueSet *task_queues,
3477 TaskTerminator* terminator) :
3478 AbstractGangTask("Process reference objects in parallel"),
3479 _proc_task(proc_task),
3480 _g1h(g1h),
3481 _pss(per_thread_states),
3482 _task_queues(task_queues),
3483 _terminator(terminator)
3484 {}
3485
3486 virtual void work(uint worker_id) {
3487 // The reference processing task executed by a single worker.
3488 ResourceMark rm;
3489 HandleMark hm;
3490
3491 G1STWIsAliveClosure is_alive(_g1h);
3492
3493 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
3494 pss->set_ref_discoverer(NULL);
3495
3496 // Keep alive closure.
3497 G1CopyingKeepAliveClosure keep_alive(_g1h, pss);
3498
3499 // Complete GC closure
3500 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator, G1GCPhaseTimes::ObjCopy);
3501
3502 // Call the reference processing task's work routine.
3503 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
3504
3505 // Note we cannot assert that the refs array is empty here as not all
3506 // of the processing tasks (specifically phase2 - pp2_work) execute
3507 // the complete_gc closure (which ordinarily would drain the queue) so
3508 // the queue may not be empty.
3509 }
3510 };
3511
3512 // Driver routine for parallel reference processing.
3513 // Creates an instance of the ref processing gang
3514 // task and has the worker threads execute it.
3515 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task, uint ergo_workers) {
3516 assert(_workers != NULL, "Need parallel worker threads.");
3517
3518 assert(_workers->active_workers() >= ergo_workers,
3519 "Ergonomically chosen workers (%u) should be less than or equal to active workers (%u)",
3520 ergo_workers, _workers->active_workers());
3521 TaskTerminator terminator(ergo_workers, _queues);
3522 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
3523
3524 _workers->run_task(&proc_task_proxy, ergo_workers);
3525 }
3526
3527 // End of weak reference support closures
3528
3529 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
3530 double ref_proc_start = os::elapsedTime();
3531
3532 ReferenceProcessor* rp = _ref_processor_stw;
3533 assert(rp->discovery_enabled(), "should have been enabled");
3534
3535 // Closure to test whether a referent is alive.
3536 G1STWIsAliveClosure is_alive(this);
3537
3538 // Even when parallel reference processing is enabled, the processing
3539 // of JNI refs is serial and performed serially by the current thread
3540 // rather than by a worker. The following PSS will be used for processing
3541 // JNI refs.
3542
3543 // Use only a single queue for this PSS.
3544 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0);
3545 pss->set_ref_discoverer(NULL);
3546 assert(pss->queue_is_empty(), "pre-condition");
3547
3548 // Keep alive closure.
3549 G1CopyingKeepAliveClosure keep_alive(this, pss);
3550
3551 // Serial Complete GC closure
3552 G1STWDrainQueueClosure drain_queue(this, pss);
3553
3554 // Setup the soft refs policy...
3555 rp->setup_policy(false);
3556
3557 ReferenceProcessorPhaseTimes* pt = phase_times()->ref_phase_times();
3558
3559 ReferenceProcessorStats stats;
3560 if (!rp->processing_is_mt()) {
3561 // Serial reference processing...
3562 stats = rp->process_discovered_references(&is_alive,
3563 &keep_alive,
3564 &drain_queue,
3565 NULL,
3566 pt);
3567 } else {
3568 uint no_of_gc_workers = workers()->active_workers();
3569
3570 // Parallel reference processing
3571 assert(no_of_gc_workers <= rp->max_num_queues(),
3572 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
3573 no_of_gc_workers, rp->max_num_queues());
3574
3575 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues);
3576 stats = rp->process_discovered_references(&is_alive,
3577 &keep_alive,
3578 &drain_queue,
3579 &par_task_executor,
3580 pt);
3581 }
3582
3583 _gc_tracer_stw->report_gc_reference_stats(stats);
3584
3585 // We have completed copying any necessary live referent objects.
3586 assert(pss->queue_is_empty(), "both queue and overflow should be empty");
3587
3588 make_pending_list_reachable();
3589
3590 assert(!rp->discovery_enabled(), "Postcondition");
3591 rp->verify_no_references_recorded();
3592
3593 double ref_proc_time = os::elapsedTime() - ref_proc_start;
3594 phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
3595 }
3596
3597 void G1CollectedHeap::make_pending_list_reachable() {
3598 if (collector_state()->in_initial_mark_gc()) {
3599 oop pll_head = Universe::reference_pending_list();
3600 if (pll_head != NULL) {
3601 // Any valid worker id is fine here as we are in the VM thread and single-threaded.
3602 _cm->mark_in_next_bitmap(0 /* worker_id */, pll_head);
3603 }
3604 }
3605 }
3606
3607 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
3608 Ticks start = Ticks::now();
3609 per_thread_states->flush();
3610 phase_times()->record_or_add_time_secs(G1GCPhaseTimes::MergePSS, 0 /* worker_id */, (Ticks::now() - start).seconds());
3611 }
3612
3613 class G1PrepareEvacuationTask : public AbstractGangTask {
3614 class G1PrepareRegionsClosure : public HeapRegionClosure {
3615 G1CollectedHeap* _g1h;
3616 G1PrepareEvacuationTask* _parent_task;
3617 size_t _worker_humongous_total;
3618 size_t _worker_humongous_candidates;
3619
3620 bool humongous_region_is_candidate(HeapRegion* region) const {
3621 assert(region->is_starts_humongous(), "Must start a humongous object");
3622
3623 oop obj = oop(region->bottom());
3624
3625 // Dead objects cannot be eager reclaim candidates. Due to class
3626 // unloading it is unsafe to query their classes so we return early.
3627 if (_g1h->is_obj_dead(obj, region)) {
3628 return false;
3629 }
3630
3631 // If we do not have a complete remembered set for the region, then we can
3632 // not be sure that we have all references to it.
3633 if (!region->rem_set()->is_complete()) {
3634 return false;
3635 }
3636 // Candidate selection must satisfy the following constraints
3637 // while concurrent marking is in progress:
3638 //
3639 // * In order to maintain SATB invariants, an object must not be
3640 // reclaimed if it was allocated before the start of marking and
3641 // has not had its references scanned. Such an object must have
3642 // its references (including type metadata) scanned to ensure no
3643 // live objects are missed by the marking process. Objects
3644 // allocated after the start of concurrent marking don't need to
3645 // be scanned.
3646 //
3647 // * An object must not be reclaimed if it is on the concurrent
3648 // mark stack. Objects allocated after the start of concurrent
3649 // marking are never pushed on the mark stack.
3650 //
3651 // Nominating only objects allocated after the start of concurrent
3652 // marking is sufficient to meet both constraints. This may miss
3653 // some objects that satisfy the constraints, but the marking data
3654 // structures don't support efficiently performing the needed
3655 // additional tests or scrubbing of the mark stack.
3656 //
3657 // However, we presently only nominate is_typeArray() objects.
3658 // A humongous object containing references induces remembered
3659 // set entries on other regions. In order to reclaim such an
3660 // object, those remembered sets would need to be cleaned up.
3661 //
3662 // We also treat is_typeArray() objects specially, allowing them
3663 // to be reclaimed even if allocated before the start of
3664 // concurrent mark. For this we rely on mark stack insertion to
3665 // exclude is_typeArray() objects, preventing reclaiming an object
3666 // that is in the mark stack. We also rely on the metadata for
3667 // such objects to be built-in and so ensured to be kept live.
3668 // Frequent allocation and drop of large binary blobs is an
3669 // important use case for eager reclaim, and this special handling
3670 // may reduce needed headroom.
3671
3672 return obj->is_typeArray() &&
3673 _g1h->is_potential_eager_reclaim_candidate(region);
3674 }
3675
3676 public:
3677 G1PrepareRegionsClosure(G1CollectedHeap* g1h, G1PrepareEvacuationTask* parent_task) :
3678 _g1h(g1h),
3679 _parent_task(parent_task),
3680 _worker_humongous_total(0),
3681 _worker_humongous_candidates(0) { }
3682
3683 ~G1PrepareRegionsClosure() {
3684 _parent_task->add_humongous_candidates(_worker_humongous_candidates);
3685 _parent_task->add_humongous_total(_worker_humongous_total);
3686 }
3687
3688 virtual bool do_heap_region(HeapRegion* hr) {
3689 // First prepare the region for scanning
3690 _g1h->rem_set()->prepare_region_for_scan(hr);
3691
3692 // Now check if region is a humongous candidate
3693 if (!hr->is_starts_humongous()) {
3694 _g1h->register_region_with_region_attr(hr);
3695 return false;
3696 }
3697
3698 uint index = hr->hrm_index();
3699 if (humongous_region_is_candidate(hr)) {
3700 _g1h->set_humongous_reclaim_candidate(index, true);
3701 _g1h->register_humongous_region_with_region_attr(index);
3702 _worker_humongous_candidates++;
3703 // We will later handle the remembered sets of these regions.
3704 } else {
3705 _g1h->set_humongous_reclaim_candidate(index, false);
3706 _g1h->register_region_with_region_attr(hr);
3707 }
3708 _worker_humongous_total++;
3709
3710 return false;
3711 }
3712 };
3713
3714 G1CollectedHeap* _g1h;
3715 HeapRegionClaimer _claimer;
3716 volatile size_t _humongous_total;
3717 volatile size_t _humongous_candidates;
3718 public:
3719 G1PrepareEvacuationTask(G1CollectedHeap* g1h) :
3720 AbstractGangTask("Prepare Evacuation"),
3721 _g1h(g1h),
3722 _claimer(_g1h->workers()->active_workers()),
3723 _humongous_total(0),
3724 _humongous_candidates(0) { }
3725
3726 ~G1PrepareEvacuationTask() {
3727 _g1h->set_has_humongous_reclaim_candidate(_humongous_candidates > 0);
3728 }
3729
3730 void work(uint worker_id) {
3731 G1PrepareRegionsClosure cl(_g1h, this);
3732 _g1h->heap_region_par_iterate_from_worker_offset(&cl, &_claimer, worker_id);
3733 }
3734
3735 void add_humongous_candidates(size_t candidates) {
3736 Atomic::add(&_humongous_candidates, candidates);
3737 }
3738
3739 void add_humongous_total(size_t total) {
3740 Atomic::add(&_humongous_total, total);
3741 }
3742
3743 size_t humongous_candidates() {
3744 return _humongous_candidates;
3745 }
3746
3747 size_t humongous_total() {
3748 return _humongous_total;
3749 }
3750 };
3751
3752 void G1CollectedHeap::pre_evacuate_collection_set(G1EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
3753 _bytes_used_during_gc = 0;
3754
3755 _expand_heap_after_alloc_failure = true;
3756 _evacuation_failed = false;
3757
3758 // Disable the hot card cache.
3759 _hot_card_cache->reset_hot_cache_claimed_index();
3760 _hot_card_cache->set_use_cache(false);
3761
3762 // Initialize the GC alloc regions.
3763 _allocator->init_gc_alloc_regions(evacuation_info);
3764
3765 {
3766 Ticks start = Ticks::now();
3767 rem_set()->prepare_for_scan_heap_roots();
3768 phase_times()->record_prepare_heap_roots_time_ms((Ticks::now() - start).seconds() * 1000.0);
3769 }
3770
3771 {
3772 G1PrepareEvacuationTask g1_prep_task(this);
3773 Tickspan task_time = run_task(&g1_prep_task);
3774
3775 phase_times()->record_register_regions(task_time.seconds() * 1000.0,
3776 g1_prep_task.humongous_total(),
3777 g1_prep_task.humongous_candidates());
3778 }
3779
3780 assert(_verifier->check_region_attr_table(), "Inconsistency in the region attributes table.");
3781 _preserved_marks_set.assert_empty();
3782
3783 #if COMPILER2_OR_JVMCI
3784 DerivedPointerTable::clear();
3785 #endif
3786
3787 // InitialMark needs claim bits to keep track of the marked-through CLDs.
3788 if (collector_state()->in_initial_mark_gc()) {
3789 concurrent_mark()->pre_initial_mark();
3790
3791 double start_clear_claimed_marks = os::elapsedTime();
3792
3793 ClassLoaderDataGraph::clear_claimed_marks();
3794
3795 double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
3796 phase_times()->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
3797 }
3798
3799 // Should G1EvacuationFailureALot be in effect for this GC?
3800 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
3801 }
3802
3803 class G1EvacuateRegionsBaseTask : public AbstractGangTask {
3804 protected:
3805 G1CollectedHeap* _g1h;
3806 G1ParScanThreadStateSet* _per_thread_states;
3807 ScannerTasksQueueSet* _task_queues;
3808 TaskTerminator _terminator;
3809 uint _num_workers;
3810
3811 void evacuate_live_objects(G1ParScanThreadState* pss,
3812 uint worker_id,
3813 G1GCPhaseTimes::GCParPhases objcopy_phase,
3814 G1GCPhaseTimes::GCParPhases termination_phase) {
3815 G1GCPhaseTimes* p = _g1h->phase_times();
3816
3817 Ticks start = Ticks::now();
3818 G1ParEvacuateFollowersClosure cl(_g1h, pss, _task_queues, &_terminator, objcopy_phase);
3819 cl.do_void();
3820
3821 assert(pss->queue_is_empty(), "should be empty");
3822
3823 Tickspan evac_time = (Ticks::now() - start);
3824 p->record_or_add_time_secs(objcopy_phase, worker_id, evac_time.seconds() - cl.term_time());
3825
3826 if (termination_phase == G1GCPhaseTimes::Termination) {
3827 p->record_time_secs(termination_phase, worker_id, cl.term_time());
3828 p->record_thread_work_item(termination_phase, worker_id, cl.term_attempts());
3829 } else {
3830 p->record_or_add_time_secs(termination_phase, worker_id, cl.term_time());
3831 p->record_or_add_thread_work_item(termination_phase, worker_id, cl.term_attempts());
3832 }
3833 assert(pss->trim_ticks().seconds() == 0.0, "Unexpected partial trimming during evacuation");
3834 }
3835
3836 virtual void start_work(uint worker_id) { }
3837
3838 virtual void end_work(uint worker_id) { }
3839
3840 virtual void scan_roots(G1ParScanThreadState* pss, uint worker_id) = 0;
3841
3842 virtual void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) = 0;
3843
3844 public:
3845 G1EvacuateRegionsBaseTask(const char* name,
3846 G1ParScanThreadStateSet* per_thread_states,
3847 ScannerTasksQueueSet* task_queues,
3848 uint num_workers) :
3849 AbstractGangTask(name),
3850 _g1h(G1CollectedHeap::heap()),
3851 _per_thread_states(per_thread_states),
3852 _task_queues(task_queues),
3853 _terminator(num_workers, _task_queues),
3854 _num_workers(num_workers)
3855 { }
3856
3857 void work(uint worker_id) {
3858 start_work(worker_id);
3859
3860 {
3861 ResourceMark rm;
3862 HandleMark hm;
3863
3864 G1ParScanThreadState* pss = _per_thread_states->state_for_worker(worker_id);
3865 pss->set_ref_discoverer(_g1h->ref_processor_stw());
3866
3867 scan_roots(pss, worker_id);
3868 evacuate_live_objects(pss, worker_id);
3869 }
3870
3871 end_work(worker_id);
3872 }
3873 };
3874
3875 class G1EvacuateRegionsTask : public G1EvacuateRegionsBaseTask {
3876 G1RootProcessor* _root_processor;
3877
3878 void scan_roots(G1ParScanThreadState* pss, uint worker_id) {
3879 _root_processor->evacuate_roots(pss, worker_id);
3880 _g1h->rem_set()->scan_heap_roots(pss, worker_id, G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::ObjCopy);
3881 _g1h->rem_set()->scan_collection_set_regions(pss, worker_id, G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::CodeRoots, G1GCPhaseTimes::ObjCopy);
3882 }
3883
3884 void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) {
3885 G1EvacuateRegionsBaseTask::evacuate_live_objects(pss, worker_id, G1GCPhaseTimes::ObjCopy, G1GCPhaseTimes::Termination);
3886 }
3887
3888 void start_work(uint worker_id) {
3889 _g1h->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, Ticks::now().seconds());
3890 }
3891
3892 void end_work(uint worker_id) {
3893 _g1h->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, Ticks::now().seconds());
3894 }
3895
3896 public:
3897 G1EvacuateRegionsTask(G1CollectedHeap* g1h,
3898 G1ParScanThreadStateSet* per_thread_states,
3899 ScannerTasksQueueSet* task_queues,
3900 G1RootProcessor* root_processor,
3901 uint num_workers) :
3902 G1EvacuateRegionsBaseTask("G1 Evacuate Regions", per_thread_states, task_queues, num_workers),
3903 _root_processor(root_processor)
3904 { }
3905 };
3906
3907 void G1CollectedHeap::evacuate_initial_collection_set(G1ParScanThreadStateSet* per_thread_states) {
3908 G1GCPhaseTimes* p = phase_times();
3909
3910 {
3911 Ticks start = Ticks::now();
3912 rem_set()->merge_heap_roots(true /* initial_evacuation */);
3913 p->record_merge_heap_roots_time((Ticks::now() - start).seconds() * 1000.0);
3914 }
3915
3916 Tickspan task_time;
3917 const uint num_workers = workers()->active_workers();
3918
3919 Ticks start_processing = Ticks::now();
3920 {
3921 G1RootProcessor root_processor(this, num_workers);
3922 G1EvacuateRegionsTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, num_workers);
3923 task_time = run_task(&g1_par_task);
3924 // Closing the inner scope will execute the destructor for the G1RootProcessor object.
3925 // To extract its code root fixup time we measure total time of this scope and
3926 // subtract from the time the WorkGang task took.
3927 }
3928 Tickspan total_processing = Ticks::now() - start_processing;
3929
3930 p->record_initial_evac_time(task_time.seconds() * 1000.0);
3931 p->record_or_add_code_root_fixup_time((total_processing - task_time).seconds() * 1000.0);
3932 }
3933
3934 class G1EvacuateOptionalRegionsTask : public G1EvacuateRegionsBaseTask {
3935
3936 void scan_roots(G1ParScanThreadState* pss, uint worker_id) {
3937 _g1h->rem_set()->scan_heap_roots(pss, worker_id, G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::OptObjCopy);
3938 _g1h->rem_set()->scan_collection_set_regions(pss, worker_id, G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::OptCodeRoots, G1GCPhaseTimes::OptObjCopy);
3939 }
3940
3941 void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) {
3942 G1EvacuateRegionsBaseTask::evacuate_live_objects(pss, worker_id, G1GCPhaseTimes::OptObjCopy, G1GCPhaseTimes::OptTermination);
3943 }
3944
3945 public:
3946 G1EvacuateOptionalRegionsTask(G1ParScanThreadStateSet* per_thread_states,
3947 ScannerTasksQueueSet* queues,
3948 uint num_workers) :
3949 G1EvacuateRegionsBaseTask("G1 Evacuate Optional Regions", per_thread_states, queues, num_workers) {
3950 }
3951 };
3952
3953 void G1CollectedHeap::evacuate_next_optional_regions(G1ParScanThreadStateSet* per_thread_states) {
3954 class G1MarkScope : public MarkScope { };
3955
3956 Tickspan task_time;
3957
3958 Ticks start_processing = Ticks::now();
3959 {
3960 G1MarkScope code_mark_scope;
3961 G1EvacuateOptionalRegionsTask task(per_thread_states, _task_queues, workers()->active_workers());
3962 task_time = run_task(&task);
3963 // See comment in evacuate_collection_set() for the reason of the scope.
3964 }
3965 Tickspan total_processing = Ticks::now() - start_processing;
3966
3967 G1GCPhaseTimes* p = phase_times();
3968 p->record_or_add_code_root_fixup_time((total_processing - task_time).seconds() * 1000.0);
3969 }
3970
3971 void G1CollectedHeap::evacuate_optional_collection_set(G1ParScanThreadStateSet* per_thread_states) {
3972 const double gc_start_time_ms = phase_times()->cur_collection_start_sec() * 1000.0;
3973
3974 while (!evacuation_failed() && _collection_set.optional_region_length() > 0) {
3975
3976 double time_used_ms = os::elapsedTime() * 1000.0 - gc_start_time_ms;
3977 double time_left_ms = MaxGCPauseMillis - time_used_ms;
3978
3979 if (time_left_ms < 0 ||
3980 !_collection_set.finalize_optional_for_evacuation(time_left_ms * policy()->optional_evacuation_fraction())) {
3981 log_trace(gc, ergo, cset)("Skipping evacuation of %u optional regions, no more regions can be evacuated in %.3fms",
3982 _collection_set.optional_region_length(), time_left_ms);
3983 break;
3984 }
3985
3986 {
3987 Ticks start = Ticks::now();
3988 rem_set()->merge_heap_roots(false /* initial_evacuation */);
3989 phase_times()->record_or_add_optional_merge_heap_roots_time((Ticks::now() - start).seconds() * 1000.0);
3990 }
3991
3992 {
3993 Ticks start = Ticks::now();
3994 evacuate_next_optional_regions(per_thread_states);
3995 phase_times()->record_or_add_optional_evac_time((Ticks::now() - start).seconds() * 1000.0);
3996 }
3997 }
3998
3999 _collection_set.abandon_optional_collection_set(per_thread_states);
4000 }
4001
4002 void G1CollectedHeap::post_evacuate_collection_set(G1EvacuationInfo& evacuation_info,
4003 G1RedirtyCardsQueueSet* rdcqs,
4004 G1ParScanThreadStateSet* per_thread_states) {
4005 G1GCPhaseTimes* p = phase_times();
4006
4007 rem_set()->cleanup_after_scan_heap_roots();
4008
4009 // Process any discovered reference objects - we have
4010 // to do this _before_ we retire the GC alloc regions
4011 // as we may have to copy some 'reachable' referent
4012 // objects (and their reachable sub-graphs) that were
4013 // not copied during the pause.
4014 process_discovered_references(per_thread_states);
4015
4016 G1STWIsAliveClosure is_alive(this);
4017 G1KeepAliveClosure keep_alive(this);
4018
4019 WeakProcessor::weak_oops_do(workers(), &is_alive, &keep_alive, p->weak_phase_times());
4020
4021 if (G1StringDedup::is_enabled()) {
4022 double string_dedup_time_ms = os::elapsedTime();
4023
4024 string_dedup_cleaning(&is_alive, &keep_alive, p);
4025
4026 double string_cleanup_time_ms = (os::elapsedTime() - string_dedup_time_ms) * 1000.0;
4027 p->record_string_deduplication_time(string_cleanup_time_ms);
4028 }
4029
4030 _allocator->release_gc_alloc_regions(evacuation_info);
4031
4032 if (evacuation_failed()) {
4033 restore_after_evac_failure(rdcqs);
4034
4035 // Reset the G1EvacuationFailureALot counters and flags
4036 NOT_PRODUCT(reset_evacuation_should_fail();)
4037
4038 double recalculate_used_start = os::elapsedTime();
4039 set_used(recalculate_used());
4040 p->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
4041
4042 if (_archive_allocator != NULL) {
4043 _archive_allocator->clear_used();
4044 }
4045 for (uint i = 0; i < ParallelGCThreads; i++) {
4046 if (_evacuation_failed_info_array[i].has_failed()) {
4047 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
4048 }
4049 }
4050 } else {
4051 // The "used" of the the collection set have already been subtracted
4052 // when they were freed. Add in the bytes used.
4053 increase_used(_bytes_used_during_gc);
4054 }
4055
4056 _preserved_marks_set.assert_empty();
4057
4058 merge_per_thread_state_info(per_thread_states);
4059
4060 // Reset and re-enable the hot card cache.
4061 // Note the counts for the cards in the regions in the
4062 // collection set are reset when the collection set is freed.
4063 _hot_card_cache->reset_hot_cache();
4064 _hot_card_cache->set_use_cache(true);
4065
4066 purge_code_root_memory();
4067
4068 redirty_logged_cards(rdcqs);
4069
4070 free_collection_set(&_collection_set, evacuation_info, per_thread_states->surviving_young_words());
4071
4072 eagerly_reclaim_humongous_regions();
4073
4074 record_obj_copy_mem_stats();
4075
4076 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
4077 evacuation_info.set_bytes_used(_bytes_used_during_gc);
4078
4079 #if COMPILER2_OR_JVMCI
4080 double start = os::elapsedTime();
4081 DerivedPointerTable::update_pointers();
4082 phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0);
4083 #endif
4084 policy()->print_age_table();
4085 }
4086
4087 void G1CollectedHeap::record_obj_copy_mem_stats() {
4088 policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4089
4090 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4091 create_g1_evac_summary(&_old_evac_stats));
4092 }
4093
4094 void G1CollectedHeap::free_region(HeapRegion* hr, FreeRegionList* free_list) {
4095 assert(!hr->is_free(), "the region should not be free");
4096 assert(!hr->is_empty(), "the region should not be empty");
4097 assert(_hrm->is_available(hr->hrm_index()), "region should be committed");
4098
4099 if (G1VerifyBitmaps) {
4100 MemRegion mr(hr->bottom(), hr->end());
4101 concurrent_mark()->clear_range_in_prev_bitmap(mr);
4102 }
4103
4104 // Clear the card counts for this region.
4105 // Note: we only need to do this if the region is not young
4106 // (since we don't refine cards in young regions).
4107 if (!hr->is_young()) {
4108 _hot_card_cache->reset_card_counts(hr);
4109 }
4110
4111 // Reset region metadata to allow reuse.
4112 hr->hr_clear(true /* clear_space */);
4113 _policy->remset_tracker()->update_at_free(hr);
4114
4115 if (free_list != NULL) {
4116 free_list->add_ordered(hr);
4117 }
4118 }
4119
4120 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4121 FreeRegionList* free_list) {
4122 assert(hr->is_humongous(), "this is only for humongous regions");
4123 assert(free_list != NULL, "pre-condition");
4124 hr->clear_humongous();
4125 free_region(hr, free_list);
4126 }
4127
4128 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4129 const uint humongous_regions_removed) {
4130 if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4131 MutexLocker x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4132 _old_set.bulk_remove(old_regions_removed);
4133 _humongous_set.bulk_remove(humongous_regions_removed);
4134 }
4135
4136 }
4137
4138 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4139 assert(list != NULL, "list can't be null");
4140 if (!list->is_empty()) {
4141 MutexLocker x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4142 _hrm->insert_list_into_free_list(list);
4143 }
4144 }
4145
4146 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4147 decrease_used(bytes);
4148 }
4149
4150 class G1FreeCollectionSetTask : public AbstractGangTask {
4151 // Helper class to keep statistics for the collection set freeing
4152 class FreeCSetStats {
4153 size_t _before_used_bytes; // Usage in regions successfully evacutate
4154 size_t _after_used_bytes; // Usage in regions failing evacuation
4155 size_t _bytes_allocated_in_old_since_last_gc; // Size of young regions turned into old
4156 size_t _failure_used_words; // Live size in failed regions
4157 size_t _failure_waste_words; // Wasted size in failed regions
4158 size_t _rs_length; // Remembered set size
4159 uint _regions_freed; // Number of regions freed
4160 public:
4161 FreeCSetStats() :
4162 _before_used_bytes(0),
4163 _after_used_bytes(0),
4164 _bytes_allocated_in_old_since_last_gc(0),
4165 _failure_used_words(0),
4166 _failure_waste_words(0),
4167 _rs_length(0),
4168 _regions_freed(0) { }
4169
4170 void merge_stats(FreeCSetStats* other) {
4171 assert(other != NULL, "invariant");
4172 _before_used_bytes += other->_before_used_bytes;
4173 _after_used_bytes += other->_after_used_bytes;
4174 _bytes_allocated_in_old_since_last_gc += other->_bytes_allocated_in_old_since_last_gc;
4175 _failure_used_words += other->_failure_used_words;
4176 _failure_waste_words += other->_failure_waste_words;
4177 _rs_length += other->_rs_length;
4178 _regions_freed += other->_regions_freed;
4179 }
4180
4181 void report(G1CollectedHeap* g1h, G1EvacuationInfo* evacuation_info) {
4182 evacuation_info->set_regions_freed(_regions_freed);
4183 evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4184
4185 g1h->decrement_summary_bytes(_before_used_bytes);
4186 g1h->alloc_buffer_stats(G1HeapRegionAttr::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4187
4188 G1Policy *policy = g1h->policy();
4189 policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4190 policy->record_rs_length(_rs_length);
4191 policy->cset_regions_freed();
4192 }
4193
4194 void account_failed_region(HeapRegion* r) {
4195 size_t used_words = r->marked_bytes() / HeapWordSize;
4196 _failure_used_words += used_words;
4197 _failure_waste_words += HeapRegion::GrainWords - used_words;
4198 _after_used_bytes += r->used();
4199
4200 // When moving a young gen region to old gen, we "allocate" that whole
4201 // region there. This is in addition to any already evacuated objects.
4202 // Notify the policy about that. Old gen regions do not cause an
4203 // additional allocation: both the objects still in the region and the
4204 // ones already moved are accounted for elsewhere.
4205 if (r->is_young()) {
4206 _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
4207 }
4208 }
4209
4210 void account_evacuated_region(HeapRegion* r) {
4211 _before_used_bytes += r->used();
4212 _regions_freed += 1;
4213 }
4214
4215 void account_rs_length(HeapRegion* r) {
4216 _rs_length += r->rem_set()->occupied();
4217 }
4218 };
4219
4220 // Closure applied to all regions in the collection set.
4221 class FreeCSetClosure : public HeapRegionClosure {
4222 // Helper to send JFR events for regions.
4223 class JFREventForRegion {
4224 EventGCPhaseParallel _event;
4225 public:
4226 JFREventForRegion(HeapRegion* region, uint worker_id) : _event() {
4227 _event.set_gcId(GCId::current());
4228 _event.set_gcWorkerId(worker_id);
4229 if (region->is_young()) {
4230 _event.set_name(G1GCPhaseTimes::phase_name(G1GCPhaseTimes::YoungFreeCSet));
4231 } else {
4232 _event.set_name(G1GCPhaseTimes::phase_name(G1GCPhaseTimes::NonYoungFreeCSet));
4233 }
4234 }
4235
4236 ~JFREventForRegion() {
4237 _event.commit();
4238 }
4239 };
4240
4241 // Helper to do timing for region work.
4242 class TimerForRegion {
4243 Tickspan& _time;
4244 Ticks _start_time;
4245 public:
4246 TimerForRegion(Tickspan& time) : _time(time), _start_time(Ticks::now()) { }
4247 ~TimerForRegion() {
4248 _time += Ticks::now() - _start_time;
4249 }
4250 };
4251
4252 // FreeCSetClosure members
4253 G1CollectedHeap* _g1h;
4254 const size_t* _surviving_young_words;
4255 uint _worker_id;
4256 Tickspan _young_time;
4257 Tickspan _non_young_time;
4258 FreeCSetStats* _stats;
4259
4260 void assert_in_cset(HeapRegion* r) {
4261 assert(r->young_index_in_cset() != 0 &&
4262 (uint)r->young_index_in_cset() <= _g1h->collection_set()->young_region_length(),
4263 "Young index %u is wrong for region %u of type %s with %u young regions",
4264 r->young_index_in_cset(), r->hrm_index(), r->get_type_str(), _g1h->collection_set()->young_region_length());
4265 }
4266
4267 void handle_evacuated_region(HeapRegion* r) {
4268 assert(!r->is_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
4269 stats()->account_evacuated_region(r);
4270
4271 // Free the region and and its remembered set.
4272 _g1h->free_region(r, NULL);
4273 }
4274
4275 void handle_failed_region(HeapRegion* r) {
4276 // Do some allocation statistics accounting. Regions that failed evacuation
4277 // are always made old, so there is no need to update anything in the young
4278 // gen statistics, but we need to update old gen statistics.
4279 stats()->account_failed_region(r);
4280
4281 // Update the region state due to the failed evacuation.
4282 r->handle_evacuation_failure();
4283
4284 // Add region to old set, need to hold lock.
4285 MutexLocker x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4286 _g1h->old_set_add(r);
4287 }
4288
4289 Tickspan& timer_for_region(HeapRegion* r) {
4290 return r->is_young() ? _young_time : _non_young_time;
4291 }
4292
4293 FreeCSetStats* stats() {
4294 return _stats;
4295 }
4296 public:
4297 FreeCSetClosure(const size_t* surviving_young_words,
4298 uint worker_id,
4299 FreeCSetStats* stats) :
4300 HeapRegionClosure(),
4301 _g1h(G1CollectedHeap::heap()),
4302 _surviving_young_words(surviving_young_words),
4303 _worker_id(worker_id),
4304 _young_time(),
4305 _non_young_time(),
4306 _stats(stats) { }
4307
4308 virtual bool do_heap_region(HeapRegion* r) {
4309 assert(r->in_collection_set(), "Invariant: %u missing from CSet", r->hrm_index());
4310 JFREventForRegion event(r, _worker_id);
4311 TimerForRegion timer(timer_for_region(r));
4312
4313 _g1h->clear_region_attr(r);
4314 stats()->account_rs_length(r);
4315
4316 if (r->is_young()) {
4317 assert_in_cset(r);
4318 r->record_surv_words_in_group(_surviving_young_words[r->young_index_in_cset()]);
4319 }
4320
4321 if (r->evacuation_failed()) {
4322 handle_failed_region(r);
4323 } else {
4324 handle_evacuated_region(r);
4325 }
4326 assert(!_g1h->is_on_master_free_list(r), "sanity");
4327
4328 return false;
4329 }
4330
4331 void report_timing(Tickspan parallel_time) {
4332 G1GCPhaseTimes* pt = _g1h->phase_times();
4333 pt->record_time_secs(G1GCPhaseTimes::ParFreeCSet, _worker_id, parallel_time.seconds());
4334 if (_young_time.value() > 0) {
4335 pt->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, _worker_id, _young_time.seconds());
4336 }
4337 if (_non_young_time.value() > 0) {
4338 pt->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, _worker_id, _non_young_time.seconds());
4339 }
4340 }
4341 };
4342
4343 // G1FreeCollectionSetTask members
4344 G1CollectedHeap* _g1h;
4345 G1EvacuationInfo* _evacuation_info;
4346 FreeCSetStats* _worker_stats;
4347 HeapRegionClaimer _claimer;
4348 const size_t* _surviving_young_words;
4349 uint _active_workers;
4350
4351 FreeCSetStats* worker_stats(uint worker) {
4352 return &_worker_stats[worker];
4353 }
4354
4355 void report_statistics() {
4356 // Merge the accounting
4357 FreeCSetStats total_stats;
4358 for (uint worker = 0; worker < _active_workers; worker++) {
4359 total_stats.merge_stats(worker_stats(worker));
4360 }
4361 total_stats.report(_g1h, _evacuation_info);
4362 }
4363
4364 public:
4365 G1FreeCollectionSetTask(G1EvacuationInfo* evacuation_info, const size_t* surviving_young_words, uint active_workers) :
4366 AbstractGangTask("G1 Free Collection Set"),
4367 _g1h(G1CollectedHeap::heap()),
4368 _evacuation_info(evacuation_info),
4369 _worker_stats(NEW_C_HEAP_ARRAY(FreeCSetStats, active_workers, mtGC)),
4370 _claimer(active_workers),
4371 _surviving_young_words(surviving_young_words),
4372 _active_workers(active_workers) {
4373 for (uint worker = 0; worker < active_workers; worker++) {
4374 ::new (&_worker_stats[worker]) FreeCSetStats();
4375 }
4376 }
4377
4378 ~G1FreeCollectionSetTask() {
4379 Ticks serial_time = Ticks::now();
4380 report_statistics();
4381 for (uint worker = 0; worker < _active_workers; worker++) {
4382 _worker_stats[worker].~FreeCSetStats();
4383 }
4384 FREE_C_HEAP_ARRAY(FreeCSetStats, _worker_stats);
4385 _g1h->phase_times()->record_serial_free_cset_time_ms((Ticks::now() - serial_time).seconds() * 1000.0);
4386 }
4387
4388 virtual void work(uint worker_id) {
4389 EventGCPhaseParallel event;
4390 Ticks start = Ticks::now();
4391 FreeCSetClosure cl(_surviving_young_words, worker_id, worker_stats(worker_id));
4392 _g1h->collection_set_par_iterate_all(&cl, &_claimer, worker_id);
4393
4394 // Report the total parallel time along with some more detailed metrics.
4395 cl.report_timing(Ticks::now() - start);
4396 event.commit(GCId::current(), worker_id, G1GCPhaseTimes::phase_name(G1GCPhaseTimes::ParFreeCSet));
4397 }
4398 };
4399
4400 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, G1EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4401 _eden.clear();
4402
4403 // The free collections set is split up in two tasks, the first
4404 // frees the collection set and records what regions are free,
4405 // and the second one rebuilds the free list. This proved to be
4406 // more efficient than adding a sorted list to another.
4407
4408 Ticks free_cset_start_time = Ticks::now();
4409 {
4410 uint const num_cs_regions = _collection_set.region_length();
4411 uint const num_workers = clamp(num_cs_regions, 1u, workers()->active_workers());
4412 G1FreeCollectionSetTask cl(&evacuation_info, surviving_young_words, num_workers);
4413
4414 log_debug(gc, ergo)("Running %s using %u workers for collection set length %u (%u)",
4415 cl.name(), num_workers, num_cs_regions, num_regions());
4416 workers()->run_task(&cl, num_workers);
4417 }
4418
4419 Ticks free_cset_end_time = Ticks::now();
4420 phase_times()->record_total_free_cset_time_ms((free_cset_end_time - free_cset_start_time).seconds() * 1000.0);
4421
4422 // Now rebuild the free region list.
4423 hrm()->rebuild_free_list(workers());
4424 phase_times()->record_total_rebuild_freelist_time_ms((Ticks::now() - free_cset_end_time).seconds() * 1000.0);
4425
4426 collection_set->clear();
4427 }
4428
4429 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4430 private:
4431 FreeRegionList* _free_region_list;
4432 HeapRegionSet* _proxy_set;
4433 uint _humongous_objects_reclaimed;
4434 uint _humongous_regions_reclaimed;
4435 size_t _freed_bytes;
4436 public:
4437
4438 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4439 _free_region_list(free_region_list), _proxy_set(NULL), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) {
4440 }
4441
4442 virtual bool do_heap_region(HeapRegion* r) {
4443 if (!r->is_starts_humongous()) {
4444 return false;
4445 }
4446
4447 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4448
4449 oop obj = (oop)r->bottom();
4450 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap();
4451
4452 // The following checks whether the humongous object is live are sufficient.
4453 // The main additional check (in addition to having a reference from the roots
4454 // or the young gen) is whether the humongous object has a remembered set entry.
4455 //
4456 // A humongous object cannot be live if there is no remembered set for it
4457 // because:
4458 // - there can be no references from within humongous starts regions referencing
4459 // the object because we never allocate other objects into them.
4460 // (I.e. there are no intra-region references that may be missed by the
4461 // remembered set)
4462 // - as soon there is a remembered set entry to the humongous starts region
4463 // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4464 // until the end of a concurrent mark.
4465 //
4466 // It is not required to check whether the object has been found dead by marking
4467 // or not, in fact it would prevent reclamation within a concurrent cycle, as
4468 // all objects allocated during that time are considered live.
4469 // SATB marking is even more conservative than the remembered set.
4470 // So if at this point in the collection there is no remembered set entry,
4471 // nobody has a reference to it.
4472 // At the start of collection we flush all refinement logs, and remembered sets
4473 // are completely up-to-date wrt to references to the humongous object.
4474 //
4475 // Other implementation considerations:
4476 // - never consider object arrays at this time because they would pose
4477 // considerable effort for cleaning up the the remembered sets. This is
4478 // required because stale remembered sets might reference locations that
4479 // are currently allocated into.
4480 uint region_idx = r->hrm_index();
4481 if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4482 !r->rem_set()->is_empty()) {
4483 log_debug(gc, humongous)("Live humongous region %u object size " SIZE_FORMAT " start " PTR_FORMAT " with remset " SIZE_FORMAT " code roots " SIZE_FORMAT " is marked %d reclaim candidate %d type array %d",
4484 region_idx,
4485 (size_t)obj->size() * HeapWordSize,
4486 p2i(r->bottom()),
4487 r->rem_set()->occupied(),
4488 r->rem_set()->strong_code_roots_list_length(),
4489 next_bitmap->is_marked(r->bottom()),
4490 g1h->is_humongous_reclaim_candidate(region_idx),
4491 obj->is_typeArray()
4492 );
4493 return false;
4494 }
4495
4496 guarantee(obj->is_typeArray(),
4497 "Only eagerly reclaiming type arrays is supported, but the object "
4498 PTR_FORMAT " is not.", p2i(r->bottom()));
4499
4500 log_debug(gc, humongous)("Dead humongous region %u object size " SIZE_FORMAT " start " PTR_FORMAT " with remset " SIZE_FORMAT " code roots " SIZE_FORMAT " is marked %d reclaim candidate %d type array %d",
4501 region_idx,
4502 (size_t)obj->size() * HeapWordSize,
4503 p2i(r->bottom()),
4504 r->rem_set()->occupied(),
4505 r->rem_set()->strong_code_roots_list_length(),
4506 next_bitmap->is_marked(r->bottom()),
4507 g1h->is_humongous_reclaim_candidate(region_idx),
4508 obj->is_typeArray()
4509 );
4510
4511 G1ConcurrentMark* const cm = g1h->concurrent_mark();
4512 cm->humongous_object_eagerly_reclaimed(r);
4513 assert(!cm->is_marked_in_prev_bitmap(obj) && !cm->is_marked_in_next_bitmap(obj),
4514 "Eagerly reclaimed humongous region %u should not be marked at all but is in prev %s next %s",
4515 region_idx,
4516 BOOL_TO_STR(cm->is_marked_in_prev_bitmap(obj)),
4517 BOOL_TO_STR(cm->is_marked_in_next_bitmap(obj)));
4518 _humongous_objects_reclaimed++;
4519 do {
4520 HeapRegion* next = g1h->next_region_in_humongous(r);
4521 _freed_bytes += r->used();
4522 r->set_containing_set(NULL);
4523 _humongous_regions_reclaimed++;
4524 g1h->free_humongous_region(r, _free_region_list);
4525 r = next;
4526 } while (r != NULL);
4527
4528 return false;
4529 }
4530
4531 uint humongous_objects_reclaimed() {
4532 return _humongous_objects_reclaimed;
4533 }
4534
4535 uint humongous_regions_reclaimed() {
4536 return _humongous_regions_reclaimed;
4537 }
4538
4539 size_t bytes_freed() const {
4540 return _freed_bytes;
4541 }
4542 };
4543
4544 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4545 assert_at_safepoint_on_vm_thread();
4546
4547 if (!G1EagerReclaimHumongousObjects ||
4548 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
4549 phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
4550 return;
4551 }
4552
4553 double start_time = os::elapsedTime();
4554
4555 FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
4556
4557 G1FreeHumongousRegionClosure cl(&local_cleanup_list);
4558 heap_region_iterate(&cl);
4559
4560 remove_from_old_sets(0, cl.humongous_regions_reclaimed());
4561
4562 G1HRPrinter* hrp = hr_printer();
4563 if (hrp->is_active()) {
4564 FreeRegionListIterator iter(&local_cleanup_list);
4565 while (iter.more_available()) {
4566 HeapRegion* hr = iter.get_next();
4567 hrp->cleanup(hr);
4568 }
4569 }
4570
4571 prepend_to_freelist(&local_cleanup_list);
4572 decrement_summary_bytes(cl.bytes_freed());
4573
4574 phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
4575 cl.humongous_objects_reclaimed());
4576 }
4577
4578 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
4579 public:
4580 virtual bool do_heap_region(HeapRegion* r) {
4581 assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
4582 G1CollectedHeap::heap()->clear_region_attr(r);
4583 r->clear_young_index_in_cset();
4584 return false;
4585 }
4586 };
4587
4588 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
4589 G1AbandonCollectionSetClosure cl;
4590 collection_set_iterate_all(&cl);
4591
4592 collection_set->clear();
4593 collection_set->stop_incremental_building();
4594 }
4595
4596 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
4597 return _allocator->is_retained_old_region(hr);
4598 }
4599
4600 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
4601 _eden.add(hr);
4602 _policy->set_region_eden(hr);
4603 }
4604
4605 #ifdef ASSERT
4606
4607 class NoYoungRegionsClosure: public HeapRegionClosure {
4608 private:
4609 bool _success;
4610 public:
4611 NoYoungRegionsClosure() : _success(true) { }
4612 bool do_heap_region(HeapRegion* r) {
4613 if (r->is_young()) {
4614 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
4615 p2i(r->bottom()), p2i(r->end()));
4616 _success = false;
4617 }
4618 return false;
4619 }
4620 bool success() { return _success; }
4621 };
4622
4623 bool G1CollectedHeap::check_young_list_empty() {
4624 bool ret = (young_regions_count() == 0);
4625
4626 NoYoungRegionsClosure closure;
4627 heap_region_iterate(&closure);
4628 ret = ret && closure.success();
4629
4630 return ret;
4631 }
4632
4633 #endif // ASSERT
4634
4635 class TearDownRegionSetsClosure : public HeapRegionClosure {
4636 HeapRegionSet *_old_set;
4637
4638 public:
4639 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
4640
4641 bool do_heap_region(HeapRegion* r) {
4642 if (r->is_old()) {
4643 _old_set->remove(r);
4644 } else if(r->is_young()) {
4645 r->uninstall_surv_rate_group();
4646 } else {
4647 // We ignore free regions, we'll empty the free list afterwards.
4648 // We ignore humongous and archive regions, we're not tearing down these
4649 // sets.
4650 assert(r->is_archive() || r->is_free() || r->is_humongous(),
4651 "it cannot be another type");
4652 }
4653 return false;
4654 }
4655
4656 ~TearDownRegionSetsClosure() {
4657 assert(_old_set->is_empty(), "post-condition");
4658 }
4659 };
4660
4661 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
4662 assert_at_safepoint_on_vm_thread();
4663
4664 if (!free_list_only) {
4665 TearDownRegionSetsClosure cl(&_old_set);
4666 heap_region_iterate(&cl);
4667
4668 // Note that emptying the _young_list is postponed and instead done as
4669 // the first step when rebuilding the regions sets again. The reason for
4670 // this is that during a full GC string deduplication needs to know if
4671 // a collected region was young or old when the full GC was initiated.
4672 }
4673 _hrm->remove_all_free_regions();
4674 }
4675
4676 void G1CollectedHeap::increase_used(size_t bytes) {
4677 _summary_bytes_used += bytes;
4678 }
4679
4680 void G1CollectedHeap::decrease_used(size_t bytes) {
4681 assert(_summary_bytes_used >= bytes,
4682 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
4683 _summary_bytes_used, bytes);
4684 _summary_bytes_used -= bytes;
4685 }
4686
4687 void G1CollectedHeap::set_used(size_t bytes) {
4688 _summary_bytes_used = bytes;
4689 }
4690
4691 class RebuildRegionSetsClosure : public HeapRegionClosure {
4692 private:
4693 bool _free_list_only;
4694
4695 HeapRegionSet* _old_set;
4696 HeapRegionManager* _hrm;
4697
4698 size_t _total_used;
4699
4700 public:
4701 RebuildRegionSetsClosure(bool free_list_only,
4702 HeapRegionSet* old_set,
4703 HeapRegionManager* hrm) :
4704 _free_list_only(free_list_only),
4705 _old_set(old_set), _hrm(hrm), _total_used(0) {
4706 assert(_hrm->num_free_regions() == 0, "pre-condition");
4707 if (!free_list_only) {
4708 assert(_old_set->is_empty(), "pre-condition");
4709 }
4710 }
4711
4712 bool do_heap_region(HeapRegion* r) {
4713 if (r->is_empty()) {
4714 assert(r->rem_set()->is_empty(), "Empty regions should have empty remembered sets.");
4715 // Add free regions to the free list
4716 r->set_free();
4717 _hrm->insert_into_free_list(r);
4718 } else if (!_free_list_only) {
4719 assert(r->rem_set()->is_empty(), "At this point remembered sets must have been cleared.");
4720
4721 if (r->is_archive() || r->is_humongous()) {
4722 // We ignore archive and humongous regions. We left these sets unchanged.
4723 } else {
4724 assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
4725 // We now move all (non-humongous, non-old, non-archive) regions to old gen, and register them as such.
4726 r->move_to_old();
4727 _old_set->add(r);
4728 }
4729 _total_used += r->used();
4730 }
4731
4732 return false;
4733 }
4734
4735 size_t total_used() {
4736 return _total_used;
4737 }
4738 };
4739
4740 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
4741 assert_at_safepoint_on_vm_thread();
4742
4743 if (!free_list_only) {
4744 _eden.clear();
4745 _survivor.clear();
4746 }
4747
4748 RebuildRegionSetsClosure cl(free_list_only, &_old_set, _hrm);
4749 heap_region_iterate(&cl);
4750
4751 if (!free_list_only) {
4752 set_used(cl.total_used());
4753 if (_archive_allocator != NULL) {
4754 _archive_allocator->clear_used();
4755 }
4756 }
4757 assert_used_and_recalculate_used_equal(this);
4758 }
4759
4760 // Methods for the mutator alloc region
4761
4762 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
4763 bool force,
4764 uint node_index) {
4765 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4766 bool should_allocate = policy()->should_allocate_mutator_region();
4767 if (force || should_allocate) {
4768 HeapRegion* new_alloc_region = new_region(word_size,
4769 HeapRegionType::Eden,
4770 false /* do_expand */,
4771 node_index);
4772 if (new_alloc_region != NULL) {
4773 set_region_short_lived_locked(new_alloc_region);
4774 _hr_printer.alloc(new_alloc_region, !should_allocate);
4775 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
4776 _policy->remset_tracker()->update_at_allocate(new_alloc_region);
4777 return new_alloc_region;
4778 }
4779 }
4780 return NULL;
4781 }
4782
4783 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
4784 size_t allocated_bytes) {
4785 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4786 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
4787
4788 collection_set()->add_eden_region(alloc_region);
4789 increase_used(allocated_bytes);
4790 _eden.add_used_bytes(allocated_bytes);
4791 _hr_printer.retire(alloc_region);
4792
4793 // We update the eden sizes here, when the region is retired,
4794 // instead of when it's allocated, since this is the point that its
4795 // used space has been recorded in _summary_bytes_used.
4796 g1mm()->update_eden_size();
4797 }
4798
4799 // Methods for the GC alloc regions
4800
4801 bool G1CollectedHeap::has_more_regions(G1HeapRegionAttr dest) {
4802 if (dest.is_old()) {
4803 return true;
4804 } else {
4805 return survivor_regions_count() < policy()->max_survivor_regions();
4806 }
4807 }
4808
4809 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, G1HeapRegionAttr dest, uint node_index) {
4810 assert(FreeList_lock->owned_by_self(), "pre-condition");
4811
4812 if (!has_more_regions(dest)) {
4813 return NULL;
4814 }
4815
4816 HeapRegionType type;
4817 if (dest.is_young()) {
4818 type = HeapRegionType::Survivor;
4819 } else {
4820 type = HeapRegionType::Old;
4821 }
4822
4823 HeapRegion* new_alloc_region = new_region(word_size,
4824 type,
4825 true /* do_expand */,
4826 node_index);
4827
4828 if (new_alloc_region != NULL) {
4829 if (type.is_survivor()) {
4830 new_alloc_region->set_survivor();
4831 _survivor.add(new_alloc_region);
4832 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
4833 } else {
4834 new_alloc_region->set_old();
4835 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
4836 }
4837 _policy->remset_tracker()->update_at_allocate(new_alloc_region);
4838 register_region_with_region_attr(new_alloc_region);
4839 _hr_printer.alloc(new_alloc_region);
4840 return new_alloc_region;
4841 }
4842 return NULL;
4843 }
4844
4845 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
4846 size_t allocated_bytes,
4847 G1HeapRegionAttr dest) {
4848 _bytes_used_during_gc += allocated_bytes;
4849 if (dest.is_old()) {
4850 old_set_add(alloc_region);
4851 } else {
4852 assert(dest.is_young(), "Retiring alloc region should be young (%d)", dest.type());
4853 _survivor.add_used_bytes(allocated_bytes);
4854 }
4855
4856 bool const during_im = collector_state()->in_initial_mark_gc();
4857 if (during_im && allocated_bytes > 0) {
4858 _cm->root_regions()->add(alloc_region->next_top_at_mark_start(), alloc_region->top());
4859 }
4860 _hr_printer.retire(alloc_region);
4861 }
4862
4863 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
4864 bool expanded = false;
4865 uint index = _hrm->find_highest_free(&expanded);
4866
4867 if (index != G1_NO_HRM_INDEX) {
4868 if (expanded) {
4869 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
4870 HeapRegion::GrainWords * HeapWordSize);
4871 }
4872 return _hrm->allocate_free_regions_starting_at(index, 1);
4873 }
4874 return NULL;
4875 }
4876
4877 // Optimized nmethod scanning
4878
4879 class RegisterNMethodOopClosure: public OopClosure {
4880 G1CollectedHeap* _g1h;
4881 nmethod* _nm;
4882
4883 template <class T> void do_oop_work(T* p) {
4884 T heap_oop = RawAccess<>::oop_load(p);
4885 if (!CompressedOops::is_null(heap_oop)) {
4886 oop obj = CompressedOops::decode_not_null(heap_oop);
4887 HeapRegion* hr = _g1h->heap_region_containing(obj);
4888 assert(!hr->is_continues_humongous(),
4889 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
4890 " starting at " HR_FORMAT,
4891 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
4892
4893 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
4894 hr->add_strong_code_root_locked(_nm);
4895 }
4896 }
4897
4898 public:
4899 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
4900 _g1h(g1h), _nm(nm) {}
4901
4902 void do_oop(oop* p) { do_oop_work(p); }
4903 void do_oop(narrowOop* p) { do_oop_work(p); }
4904 };
4905
4906 class UnregisterNMethodOopClosure: public OopClosure {
4907 G1CollectedHeap* _g1h;
4908 nmethod* _nm;
4909
4910 template <class T> void do_oop_work(T* p) {
4911 T heap_oop = RawAccess<>::oop_load(p);
4912 if (!CompressedOops::is_null(heap_oop)) {
4913 oop obj = CompressedOops::decode_not_null(heap_oop);
4914 HeapRegion* hr = _g1h->heap_region_containing(obj);
4915 assert(!hr->is_continues_humongous(),
4916 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
4917 " starting at " HR_FORMAT,
4918 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
4919
4920 hr->remove_strong_code_root(_nm);
4921 }
4922 }
4923
4924 public:
4925 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
4926 _g1h(g1h), _nm(nm) {}
4927
4928 void do_oop(oop* p) { do_oop_work(p); }
4929 void do_oop(narrowOop* p) { do_oop_work(p); }
4930 };
4931
4932 void G1CollectedHeap::register_nmethod(nmethod* nm) {
4933 guarantee(nm != NULL, "sanity");
4934 RegisterNMethodOopClosure reg_cl(this, nm);
4935 nm->oops_do(®_cl);
4936 }
4937
4938 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
4939 guarantee(nm != NULL, "sanity");
4940 UnregisterNMethodOopClosure reg_cl(this, nm);
4941 nm->oops_do(®_cl, true);
4942 }
4943
4944 void G1CollectedHeap::purge_code_root_memory() {
4945 double purge_start = os::elapsedTime();
4946 G1CodeRootSet::purge();
4947 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
4948 phase_times()->record_strong_code_root_purge_time(purge_time_ms);
4949 }
4950
4951 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
4952 G1CollectedHeap* _g1h;
4953
4954 public:
4955 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
4956 _g1h(g1h) {}
4957
4958 void do_code_blob(CodeBlob* cb) {
4959 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
4960 if (nm == NULL) {
4961 return;
4962 }
4963
4964 _g1h->register_nmethod(nm);
4965 }
4966 };
4967
4968 void G1CollectedHeap::rebuild_strong_code_roots() {
4969 RebuildStrongCodeRootClosure blob_cl(this);
4970 CodeCache::blobs_do(&blob_cl);
4971 }
4972
4973 void G1CollectedHeap::initialize_serviceability() {
4974 _g1mm->initialize_serviceability();
4975 }
4976
4977 MemoryUsage G1CollectedHeap::memory_usage() {
4978 return _g1mm->memory_usage();
4979 }
4980
4981 GrowableArray<GCMemoryManager*> G1CollectedHeap::memory_managers() {
4982 return _g1mm->memory_managers();
4983 }
4984
4985 GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() {
4986 return _g1mm->memory_pools();
4987 }