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/g1GCPhaseTimes.hpp"
45 #include "gc/g1/g1HeapSizingPolicy.hpp"
46 #include "gc/g1/g1HeapTransition.hpp"
47 #include "gc/g1/g1HeapVerifier.hpp"
48 #include "gc/g1/g1HotCardCache.hpp"
49 #include "gc/g1/g1MemoryPool.hpp"
50 #include "gc/g1/g1OopClosures.inline.hpp"
51 #include "gc/g1/g1ParallelCleaning.hpp"
52 #include "gc/g1/g1ParScanThreadState.inline.hpp"
53 #include "gc/g1/g1Policy.hpp"
54 #include "gc/g1/g1RedirtyCardsQueue.hpp"
55 #include "gc/g1/g1RegionToSpaceMapper.hpp"
56 #include "gc/g1/g1RemSet.hpp"
57 #include "gc/g1/g1RootClosures.hpp"
58 #include "gc/g1/g1RootProcessor.hpp"
59 #include "gc/g1/g1SATBMarkQueueSet.hpp"
60 #include "gc/g1/g1StringDedup.hpp"
61 #include "gc/g1/g1ThreadLocalData.hpp"
62 #include "gc/g1/g1Trace.hpp"
63 #include "gc/g1/g1YCTypes.hpp"
64 #include "gc/g1/g1YoungRemSetSamplingThread.hpp"
65 #include "gc/g1/g1VMOperations.hpp"
66 #include "gc/g1/heapRegion.inline.hpp"
67 #include "gc/g1/heapRegionRemSet.hpp"
68 #include "gc/g1/heapRegionSet.inline.hpp"
69 #include "gc/shared/concurrentGCBreakpoints.hpp"
70 #include "gc/shared/gcBehaviours.hpp"
71 #include "gc/shared/gcHeapSummary.hpp"
72 #include "gc/shared/gcId.hpp"
73 #include "gc/shared/gcLocker.hpp"
74 #include "gc/shared/gcTimer.hpp"
75 #include "gc/shared/gcTraceTime.inline.hpp"
76 #include "gc/shared/generationSpec.hpp"
77 #include "gc/shared/isGCActiveMark.hpp"
78 #include "gc/shared/locationPrinter.inline.hpp"
79 #include "gc/shared/oopStorageParState.hpp"
80 #include "gc/shared/preservedMarks.inline.hpp"
81 #include "gc/shared/suspendibleThreadSet.hpp"
82 #include "gc/shared/referenceProcessor.inline.hpp"
83 #include "gc/shared/taskTerminator.hpp"
84 #include "gc/shared/taskqueue.inline.hpp"
85 #include "gc/shared/weakProcessor.inline.hpp"
86 #include "gc/shared/workerPolicy.hpp"
87 #include "logging/log.hpp"
88 #include "memory/allocation.hpp"
89 #include "memory/iterator.hpp"
90 #include "memory/heapInspection.hpp"
91 #include "memory/resourceArea.hpp"
92 #include "memory/universe.hpp"
93 #include "oops/access.inline.hpp"
94 #include "oops/compressedOops.inline.hpp"
95 #include "oops/oop.inline.hpp"
96 #include "runtime/atomic.hpp"
97 #include "runtime/flags/flagSetting.hpp"
98 #include "runtime/handles.inline.hpp"
99 #include "runtime/init.hpp"
100 #include "runtime/orderAccess.hpp"
101 #include "runtime/threadSMR.hpp"
102 #include "runtime/vmThread.hpp"
103 #include "utilities/align.hpp"
104 #include "utilities/bitMap.inline.hpp"
105 #include "utilities/globalDefinitions.hpp"
106 #include "utilities/stack.inline.hpp"
107
108 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
109
110 // INVARIANTS/NOTES
111 //
112 // All allocation activity covered by the G1CollectedHeap interface is
113 // serialized by acquiring the HeapLock. This happens in mem_allocate
114 // and allocate_new_tlab, which are the "entry" points to the
115 // allocation code from the rest of the JVM. (Note that this does not
116 // apply to TLAB allocation, which is not part of this interface: it
117 // is done by clients of this interface.)
118
119 class RedirtyLoggedCardTableEntryClosure : public G1CardTableEntryClosure {
120 private:
121 size_t _num_dirtied;
122 G1CollectedHeap* _g1h;
123 G1CardTable* _g1_ct;
124
125 HeapRegion* region_for_card(CardValue* card_ptr) const {
126 return _g1h->heap_region_containing(_g1_ct->addr_for(card_ptr));
127 }
128
129 bool will_become_free(HeapRegion* hr) const {
130 // A region will be freed by free_collection_set if the region is in the
131 // collection set and has not had an evacuation failure.
132 return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
133 }
134
135 public:
136 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : G1CardTableEntryClosure(),
137 _num_dirtied(0), _g1h(g1h), _g1_ct(g1h->card_table()) { }
138
139 void do_card_ptr(CardValue* card_ptr, uint worker_id) {
140 HeapRegion* hr = region_for_card(card_ptr);
141
142 // Should only dirty cards in regions that won't be freed.
143 if (!will_become_free(hr)) {
144 *card_ptr = G1CardTable::dirty_card_val();
145 _num_dirtied++;
146 }
147 }
148
149 size_t num_dirtied() const { return _num_dirtied; }
150 };
151
152
153 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
154 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
155 }
156
157 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
158 // The from card cache is not the memory that is actually committed. So we cannot
159 // take advantage of the zero_filled parameter.
160 reset_from_card_cache(start_idx, num_regions);
161 }
162
163 void G1CollectedHeap::run_task(AbstractGangTask* task) {
164 workers()->run_task(task, workers()->active_workers());
165 }
166
167 Tickspan G1CollectedHeap::run_task_timed(AbstractGangTask* task) {
168 Ticks start = Ticks::now();
169 run_task(task);
170 return Ticks::now() - start;
171 }
172
173 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
174 MemRegion mr) {
175 return new HeapRegion(hrs_index, bot(), mr);
176 }
177
178 // Private methods.
179
180 HeapRegion* G1CollectedHeap::new_region(size_t word_size,
181 HeapRegionType type,
182 bool do_expand,
183 uint node_index) {
184 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
185 "the only time we use this to allocate a humongous region is "
186 "when we are allocating a single humongous region");
187
188 HeapRegion* res = _hrm->allocate_free_region(type, node_index);
189
190 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
191 // Currently, only attempts to allocate GC alloc regions set
192 // do_expand to true. So, we should only reach here during a
193 // safepoint. If this assumption changes we might have to
194 // reconsider the use of _expand_heap_after_alloc_failure.
195 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
196
197 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
198 word_size * HeapWordSize);
199
200 assert(word_size * HeapWordSize < HeapRegion::GrainBytes,
201 "This kind of expansion should never be more than one region. Size: " SIZE_FORMAT,
202 word_size * HeapWordSize);
203 if (expand_single_region(node_index)) {
204 // Given that expand_single_region() succeeded in expanding the heap, and we
205 // always expand the heap by an amount aligned to the heap
206 // region size, the free list should in theory not be empty.
207 // In either case allocate_free_region() will check for NULL.
208 res = _hrm->allocate_free_region(type, node_index);
209 } else {
210 _expand_heap_after_alloc_failure = false;
211 }
212 }
213 return res;
214 }
215
216 HeapWord*
217 G1CollectedHeap::humongous_obj_allocate_initialize_regions(HeapRegion* first_hr,
218 uint num_regions,
219 size_t word_size) {
220 assert(first_hr != NULL, "pre-condition");
221 assert(is_humongous(word_size), "word_size should be humongous");
222 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
223
224 // Index of last region in the series.
225 uint first = first_hr->hrm_index();
226 uint last = first + num_regions - 1;
227
228 // We need to initialize the region(s) we just discovered. This is
229 // a bit tricky given that it can happen concurrently with
230 // refinement threads refining cards on these regions and
231 // potentially wanting to refine the BOT as they are scanning
232 // those cards (this can happen shortly after a cleanup; see CR
233 // 6991377). So we have to set up the region(s) carefully and in
234 // a specific order.
235
236 // The word size sum of all the regions we will allocate.
237 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
238 assert(word_size <= word_size_sum, "sanity");
239
240 // The passed in hr will be the "starts humongous" region. The header
241 // of the new object will be placed at the bottom of this region.
242 HeapWord* new_obj = first_hr->bottom();
243 // This will be the new top of the new object.
244 HeapWord* obj_top = new_obj + word_size;
245
246 // First, we need to zero the header of the space that we will be
247 // allocating. When we update top further down, some refinement
248 // threads might try to scan the region. By zeroing the header we
249 // ensure that any thread that will try to scan the region will
250 // come across the zero klass word and bail out.
251 //
252 // NOTE: It would not have been correct to have used
253 // CollectedHeap::fill_with_object() and make the space look like
254 // an int array. The thread that is doing the allocation will
255 // later update the object header to a potentially different array
256 // type and, for a very short period of time, the klass and length
257 // fields will be inconsistent. This could cause a refinement
258 // thread to calculate the object size incorrectly.
259 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
260
261 // Next, pad out the unused tail of the last region with filler
262 // objects, for improved usage accounting.
263 // How many words we use for filler objects.
264 size_t word_fill_size = word_size_sum - word_size;
265
266 // How many words memory we "waste" which cannot hold a filler object.
267 size_t words_not_fillable = 0;
268
269 if (word_fill_size >= min_fill_size()) {
270 fill_with_objects(obj_top, word_fill_size);
271 } else if (word_fill_size > 0) {
272 // We have space to fill, but we cannot fit an object there.
273 words_not_fillable = word_fill_size;
274 word_fill_size = 0;
275 }
276
277 // We will set up the first region as "starts humongous". This
278 // will also update the BOT covering all the regions to reflect
279 // that there is a single object that starts at the bottom of the
280 // first region.
281 first_hr->set_starts_humongous(obj_top, word_fill_size);
282 _policy->remset_tracker()->update_at_allocate(first_hr);
283 // Then, if there are any, we will set up the "continues
284 // humongous" regions.
285 HeapRegion* hr = NULL;
286 for (uint i = first + 1; i <= last; ++i) {
287 hr = region_at(i);
288 hr->set_continues_humongous(first_hr);
289 _policy->remset_tracker()->update_at_allocate(hr);
290 }
291
292 // Up to this point no concurrent thread would have been able to
293 // do any scanning on any region in this series. All the top
294 // fields still point to bottom, so the intersection between
295 // [bottom,top] and [card_start,card_end] will be empty. Before we
296 // update the top fields, we'll do a storestore to make sure that
297 // no thread sees the update to top before the zeroing of the
298 // object header and the BOT initialization.
299 OrderAccess::storestore();
300
301 // Now, we will update the top fields of the "continues humongous"
302 // regions except the last one.
303 for (uint i = first; i < last; ++i) {
304 hr = region_at(i);
305 hr->set_top(hr->end());
306 }
307
308 hr = region_at(last);
309 // If we cannot fit a filler object, we must set top to the end
310 // of the humongous object, otherwise we cannot iterate the heap
311 // and the BOT will not be complete.
312 hr->set_top(hr->end() - words_not_fillable);
313
314 assert(hr->bottom() < obj_top && obj_top <= hr->end(),
315 "obj_top should be in last region");
316
317 _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
318
319 assert(words_not_fillable == 0 ||
320 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
321 "Miscalculation in humongous allocation");
322
323 increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
324
325 for (uint i = first; i <= last; ++i) {
326 hr = region_at(i);
327 _humongous_set.add(hr);
328 _hr_printer.alloc(hr);
329 }
330
331 return new_obj;
332 }
333
334 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
335 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
336 return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
337 }
338
339 // If could fit into free regions w/o expansion, try.
340 // Otherwise, if can expand, do so.
341 // Otherwise, if using ex regions might help, try with ex given back.
342 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
343 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
344
345 _verifier->verify_region_sets_optional();
346
347 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
348
349 // Policy: First try to allocate a humongous object in the free list.
350 HeapRegion* humongous_start = _hrm->allocate_humongous(obj_regions);
351 if (humongous_start == NULL) {
352 // Policy: We could not find enough regions for the humongous object in the
353 // free list. Look through the heap to find a mix of free and uncommitted regions.
354 // If so, expand the heap and allocate the humongous object.
355 humongous_start = _hrm->expand_and_allocate_humongous(obj_regions);
356 if (humongous_start != NULL) {
357 // We managed to find a region by expanding the heap.
358 log_debug(gc, ergo, heap)("Heap expansion (humongous allocation request). Allocation request: " SIZE_FORMAT "B",
359 word_size * HeapWordSize);
360 policy()->record_new_heap_size(num_regions());
361 } else {
362 // Policy: Potentially trigger a defragmentation GC.
363 }
364 }
365
366 HeapWord* result = NULL;
367 if (humongous_start != NULL) {
368 result = humongous_obj_allocate_initialize_regions(humongous_start, obj_regions, word_size);
369 assert(result != NULL, "it should always return a valid result");
370
371 // A successful humongous object allocation changes the used space
372 // information of the old generation so we need to recalculate the
373 // sizes and update the jstat counters here.
374 g1mm()->update_sizes();
375 }
376
377 _verifier->verify_region_sets_optional();
378
379 return result;
380 }
381
382 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t min_size,
383 size_t requested_size,
384 size_t* actual_size) {
385 assert_heap_not_locked_and_not_at_safepoint();
386 assert(!is_humongous(requested_size), "we do not allow humongous TLABs");
387
388 return attempt_allocation(min_size, requested_size, actual_size);
389 }
390
391 HeapWord*
392 G1CollectedHeap::mem_allocate(size_t word_size,
393 bool* gc_overhead_limit_was_exceeded) {
394 assert_heap_not_locked_and_not_at_safepoint();
395
396 if (is_humongous(word_size)) {
397 return attempt_allocation_humongous(word_size);
398 }
399 size_t dummy = 0;
400 return attempt_allocation(word_size, word_size, &dummy);
401 }
402
403 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size) {
404 ResourceMark rm; // For retrieving the thread names in log messages.
405
406 // Make sure you read the note in attempt_allocation_humongous().
407
408 assert_heap_not_locked_and_not_at_safepoint();
409 assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
410 "be called for humongous allocation requests");
411
412 // We should only get here after the first-level allocation attempt
413 // (attempt_allocation()) failed to allocate.
414
415 // We will loop until a) we manage to successfully perform the
416 // allocation or b) we successfully schedule a collection which
417 // fails to perform the allocation. b) is the only case when we'll
418 // return NULL.
419 HeapWord* result = NULL;
420 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
421 bool should_try_gc;
422 uint gc_count_before;
423
424 {
425 MutexLocker x(Heap_lock);
426 result = _allocator->attempt_allocation_locked(word_size);
427 if (result != NULL) {
428 return result;
429 }
430
431 // If the GCLocker is active and we are bound for a GC, try expanding young gen.
432 // This is different to when only GCLocker::needs_gc() is set: try to avoid
433 // waiting because the GCLocker is active to not wait too long.
434 if (GCLocker::is_active_and_needs_gc() && policy()->can_expand_young_list()) {
435 // No need for an ergo message here, can_expand_young_list() does this when
436 // it returns true.
437 result = _allocator->attempt_allocation_force(word_size);
438 if (result != NULL) {
439 return result;
440 }
441 }
442 // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
443 // the GCLocker initiated GC has been performed and then retry. This includes
444 // the case when the GC Locker is not active but has not been performed.
445 should_try_gc = !GCLocker::needs_gc();
446 // Read the GC count while still holding the Heap_lock.
447 gc_count_before = total_collections();
448 }
449
450 if (should_try_gc) {
451 bool succeeded;
452 result = do_collection_pause(word_size, gc_count_before, &succeeded,
453 GCCause::_g1_inc_collection_pause);
454 if (result != NULL) {
455 assert(succeeded, "only way to get back a non-NULL result");
456 log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
457 Thread::current()->name(), p2i(result));
458 return result;
459 }
460
461 if (succeeded) {
462 // We successfully scheduled a collection which failed to allocate. No
463 // point in trying to allocate further. We'll just return NULL.
464 log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
465 SIZE_FORMAT " words", Thread::current()->name(), word_size);
466 return NULL;
467 }
468 log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT " words",
469 Thread::current()->name(), word_size);
470 } else {
471 // Failed to schedule a collection.
472 if (gclocker_retry_count > GCLockerRetryAllocationCount) {
473 log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
474 SIZE_FORMAT " words", Thread::current()->name(), word_size);
475 return NULL;
476 }
477 log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
478 // The GCLocker is either active or the GCLocker initiated
479 // GC has not yet been performed. Stall until it is and
480 // then retry the allocation.
481 GCLocker::stall_until_clear();
482 gclocker_retry_count += 1;
483 }
484
485 // We can reach here if we were unsuccessful in scheduling a
486 // collection (because another thread beat us to it) or if we were
487 // stalled due to the GC locker. In either can we should retry the
488 // allocation attempt in case another thread successfully
489 // performed a collection and reclaimed enough space. We do the
490 // first attempt (without holding the Heap_lock) here and the
491 // follow-on attempt will be at the start of the next loop
492 // iteration (after taking the Heap_lock).
493 size_t dummy = 0;
494 result = _allocator->attempt_allocation(word_size, word_size, &dummy);
495 if (result != NULL) {
496 return result;
497 }
498
499 // Give a warning if we seem to be looping forever.
500 if ((QueuedAllocationWarningCount > 0) &&
501 (try_count % QueuedAllocationWarningCount == 0)) {
502 log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words",
503 Thread::current()->name(), try_count, word_size);
504 }
505 }
506
507 ShouldNotReachHere();
508 return NULL;
509 }
510
511 void G1CollectedHeap::begin_archive_alloc_range(bool open) {
512 assert_at_safepoint_on_vm_thread();
513 if (_archive_allocator == NULL) {
514 _archive_allocator = G1ArchiveAllocator::create_allocator(this, open);
515 }
516 }
517
518 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
519 // Allocations in archive regions cannot be of a size that would be considered
520 // humongous even for a minimum-sized region, because G1 region sizes/boundaries
521 // may be different at archive-restore time.
522 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
523 }
524
525 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
526 assert_at_safepoint_on_vm_thread();
527 assert(_archive_allocator != NULL, "_archive_allocator not initialized");
528 if (is_archive_alloc_too_large(word_size)) {
529 return NULL;
530 }
531 return _archive_allocator->archive_mem_allocate(word_size);
532 }
533
534 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
535 size_t end_alignment_in_bytes) {
536 assert_at_safepoint_on_vm_thread();
537 assert(_archive_allocator != NULL, "_archive_allocator not initialized");
538
539 // Call complete_archive to do the real work, filling in the MemRegion
540 // array with the archive regions.
541 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
542 delete _archive_allocator;
543 _archive_allocator = NULL;
544 }
545
546 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
547 assert(ranges != NULL, "MemRegion array NULL");
548 assert(count != 0, "No MemRegions provided");
549 MemRegion reserved = _hrm->reserved();
550 for (size_t i = 0; i < count; i++) {
551 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
552 return false;
553 }
554 }
555 return true;
556 }
557
558 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges,
559 size_t count,
560 bool open) {
561 assert(!is_init_completed(), "Expect to be called at JVM init time");
562 assert(ranges != NULL, "MemRegion array NULL");
563 assert(count != 0, "No MemRegions provided");
564 MutexLocker x(Heap_lock);
565
566 MemRegion reserved = _hrm->reserved();
567 HeapWord* prev_last_addr = NULL;
568 HeapRegion* prev_last_region = NULL;
569
570 // Temporarily disable pretouching of heap pages. This interface is used
571 // when mmap'ing archived heap data in, so pre-touching is wasted.
572 FlagSetting fs(AlwaysPreTouch, false);
573
574 // Enable archive object checking used by G1MarkSweep. We have to let it know
575 // about each archive range, so that objects in those ranges aren't marked.
576 G1ArchiveAllocator::enable_archive_object_check();
577
578 // For each specified MemRegion range, allocate the corresponding G1
579 // regions and mark them as archive regions. We expect the ranges
580 // in ascending starting address order, without overlap.
581 for (size_t i = 0; i < count; i++) {
582 MemRegion curr_range = ranges[i];
583 HeapWord* start_address = curr_range.start();
584 size_t word_size = curr_range.word_size();
585 HeapWord* last_address = curr_range.last();
586 size_t commits = 0;
587
588 guarantee(reserved.contains(start_address) && reserved.contains(last_address),
589 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
590 p2i(start_address), p2i(last_address));
591 guarantee(start_address > prev_last_addr,
592 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
593 p2i(start_address), p2i(prev_last_addr));
594 prev_last_addr = last_address;
595
596 // Check for ranges that start in the same G1 region in which the previous
597 // range ended, and adjust the start address so we don't try to allocate
598 // the same region again. If the current range is entirely within that
599 // region, skip it, just adjusting the recorded top.
600 HeapRegion* start_region = _hrm->addr_to_region(start_address);
601 if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
602 start_address = start_region->end();
603 if (start_address > last_address) {
604 increase_used(word_size * HeapWordSize);
605 start_region->set_top(last_address + 1);
606 continue;
607 }
608 start_region->set_top(start_address);
609 curr_range = MemRegion(start_address, last_address + 1);
610 start_region = _hrm->addr_to_region(start_address);
611 }
612
613 // Perform the actual region allocation, exiting if it fails.
614 // Then note how much new space we have allocated.
615 if (!_hrm->allocate_containing_regions(curr_range, &commits, workers())) {
616 return false;
617 }
618 increase_used(word_size * HeapWordSize);
619 if (commits != 0) {
620 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
621 HeapRegion::GrainWords * HeapWordSize * commits);
622
623 }
624
625 // Mark each G1 region touched by the range as archive, add it to
626 // the old set, and set top.
627 HeapRegion* curr_region = _hrm->addr_to_region(start_address);
628 HeapRegion* last_region = _hrm->addr_to_region(last_address);
629 prev_last_region = last_region;
630
631 while (curr_region != NULL) {
632 assert(curr_region->is_empty() && !curr_region->is_pinned(),
633 "Region already in use (index %u)", curr_region->hrm_index());
634 if (open) {
635 curr_region->set_open_archive();
636 } else {
637 curr_region->set_closed_archive();
638 }
639 _hr_printer.alloc(curr_region);
640 _archive_set.add(curr_region);
641 HeapWord* top;
642 HeapRegion* next_region;
643 if (curr_region != last_region) {
644 top = curr_region->end();
645 next_region = _hrm->next_region_in_heap(curr_region);
646 } else {
647 top = last_address + 1;
648 next_region = NULL;
649 }
650 curr_region->set_top(top);
651 curr_region = next_region;
652 }
653
654 // Notify mark-sweep of the archive
655 G1ArchiveAllocator::set_range_archive(curr_range, open);
656 }
657 return true;
658 }
659
660 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
661 assert(!is_init_completed(), "Expect to be called at JVM init time");
662 assert(ranges != NULL, "MemRegion array NULL");
663 assert(count != 0, "No MemRegions provided");
664 MemRegion reserved = _hrm->reserved();
665 HeapWord *prev_last_addr = NULL;
666 HeapRegion* prev_last_region = NULL;
667
668 // For each MemRegion, create filler objects, if needed, in the G1 regions
669 // that contain the address range. The address range actually within the
670 // MemRegion will not be modified. That is assumed to have been initialized
671 // elsewhere, probably via an mmap of archived heap data.
672 MutexLocker x(Heap_lock);
673 for (size_t i = 0; i < count; i++) {
674 HeapWord* start_address = ranges[i].start();
675 HeapWord* last_address = ranges[i].last();
676
677 assert(reserved.contains(start_address) && reserved.contains(last_address),
678 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
679 p2i(start_address), p2i(last_address));
680 assert(start_address > prev_last_addr,
681 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
682 p2i(start_address), p2i(prev_last_addr));
683
684 HeapRegion* start_region = _hrm->addr_to_region(start_address);
685 HeapRegion* last_region = _hrm->addr_to_region(last_address);
686 HeapWord* bottom_address = start_region->bottom();
687
688 // Check for a range beginning in the same region in which the
689 // previous one ended.
690 if (start_region == prev_last_region) {
691 bottom_address = prev_last_addr + 1;
692 }
693
694 // Verify that the regions were all marked as archive regions by
695 // alloc_archive_regions.
696 HeapRegion* curr_region = start_region;
697 while (curr_region != NULL) {
698 guarantee(curr_region->is_archive(),
699 "Expected archive region at index %u", curr_region->hrm_index());
700 if (curr_region != last_region) {
701 curr_region = _hrm->next_region_in_heap(curr_region);
702 } else {
703 curr_region = NULL;
704 }
705 }
706
707 prev_last_addr = last_address;
708 prev_last_region = last_region;
709
710 // Fill the memory below the allocated range with dummy object(s),
711 // if the region bottom does not match the range start, or if the previous
712 // range ended within the same G1 region, and there is a gap.
713 if (start_address != bottom_address) {
714 size_t fill_size = pointer_delta(start_address, bottom_address);
715 G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
716 increase_used(fill_size * HeapWordSize);
717 }
718 }
719 }
720
721 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t min_word_size,
722 size_t desired_word_size,
723 size_t* actual_word_size) {
724 assert_heap_not_locked_and_not_at_safepoint();
725 assert(!is_humongous(desired_word_size), "attempt_allocation() should not "
726 "be called for humongous allocation requests");
727
728 HeapWord* result = _allocator->attempt_allocation(min_word_size, desired_word_size, actual_word_size);
729
730 if (result == NULL) {
731 *actual_word_size = desired_word_size;
732 result = attempt_allocation_slow(desired_word_size);
733 }
734
735 assert_heap_not_locked();
736 if (result != NULL) {
737 assert(*actual_word_size != 0, "Actual size must have been set here");
738 dirty_young_block(result, *actual_word_size);
739 } else {
740 *actual_word_size = 0;
741 }
742
743 return result;
744 }
745
746 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
747 assert(!is_init_completed(), "Expect to be called at JVM init time");
748 assert(ranges != NULL, "MemRegion array NULL");
749 assert(count != 0, "No MemRegions provided");
750 MemRegion reserved = _hrm->reserved();
751 HeapWord* prev_last_addr = NULL;
752 HeapRegion* prev_last_region = NULL;
753 size_t size_used = 0;
754 size_t uncommitted_regions = 0;
755
756 // For each Memregion, free the G1 regions that constitute it, and
757 // notify mark-sweep that the range is no longer to be considered 'archive.'
758 MutexLocker x(Heap_lock);
759 for (size_t i = 0; i < count; i++) {
760 HeapWord* start_address = ranges[i].start();
761 HeapWord* last_address = ranges[i].last();
762
763 assert(reserved.contains(start_address) && reserved.contains(last_address),
764 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
765 p2i(start_address), p2i(last_address));
766 assert(start_address > prev_last_addr,
767 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
768 p2i(start_address), p2i(prev_last_addr));
769 size_used += ranges[i].byte_size();
770 prev_last_addr = last_address;
771
772 HeapRegion* start_region = _hrm->addr_to_region(start_address);
773 HeapRegion* last_region = _hrm->addr_to_region(last_address);
774
775 // Check for ranges that start in the same G1 region in which the previous
776 // range ended, and adjust the start address so we don't try to free
777 // the same region again. If the current range is entirely within that
778 // region, skip it.
779 if (start_region == prev_last_region) {
780 start_address = start_region->end();
781 if (start_address > last_address) {
782 continue;
783 }
784 start_region = _hrm->addr_to_region(start_address);
785 }
786 prev_last_region = last_region;
787
788 // After verifying that each region was marked as an archive region by
789 // alloc_archive_regions, set it free and empty and uncommit it.
790 HeapRegion* curr_region = start_region;
791 while (curr_region != NULL) {
792 guarantee(curr_region->is_archive(),
793 "Expected archive region at index %u", curr_region->hrm_index());
794 uint curr_index = curr_region->hrm_index();
795 _archive_set.remove(curr_region);
796 curr_region->set_free();
797 curr_region->set_top(curr_region->bottom());
798 if (curr_region != last_region) {
799 curr_region = _hrm->next_region_in_heap(curr_region);
800 } else {
801 curr_region = NULL;
802 }
803 _hrm->shrink_at(curr_index, 1);
804 uncommitted_regions++;
805 }
806
807 // Notify mark-sweep that this is no longer an archive range.
808 G1ArchiveAllocator::clear_range_archive(ranges[i]);
809 }
810
811 if (uncommitted_regions != 0) {
812 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
813 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
814 }
815 decrease_used(size_used);
816 }
817
818 oop G1CollectedHeap::materialize_archived_object(oop obj) {
819 assert(obj != NULL, "archived obj is NULL");
820 assert(G1ArchiveAllocator::is_archived_object(obj), "must be archived object");
821
822 // Loading an archived object makes it strongly reachable. If it is
823 // loaded during concurrent marking, it must be enqueued to the SATB
824 // queue, shading the previously white object gray.
825 G1BarrierSet::enqueue(obj);
826
827 return obj;
828 }
829
830 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size) {
831 ResourceMark rm; // For retrieving the thread names in log messages.
832
833 // The structure of this method has a lot of similarities to
834 // attempt_allocation_slow(). The reason these two were not merged
835 // into a single one is that such a method would require several "if
836 // allocation is not humongous do this, otherwise do that"
837 // conditional paths which would obscure its flow. In fact, an early
838 // version of this code did use a unified method which was harder to
839 // follow and, as a result, it had subtle bugs that were hard to
840 // track down. So keeping these two methods separate allows each to
841 // be more readable. It will be good to keep these two in sync as
842 // much as possible.
843
844 assert_heap_not_locked_and_not_at_safepoint();
845 assert(is_humongous(word_size), "attempt_allocation_humongous() "
846 "should only be called for humongous allocations");
847
848 // Humongous objects can exhaust the heap quickly, so we should check if we
849 // need to start a marking cycle at each humongous object allocation. We do
850 // the check before we do the actual allocation. The reason for doing it
851 // before the allocation is that we avoid having to keep track of the newly
852 // allocated memory while we do a GC.
853 if (policy()->need_to_start_conc_mark("concurrent humongous allocation",
854 word_size)) {
855 collect(GCCause::_g1_humongous_allocation);
856 }
857
858 // We will loop until a) we manage to successfully perform the
859 // allocation or b) we successfully schedule a collection which
860 // fails to perform the allocation. b) is the only case when we'll
861 // return NULL.
862 HeapWord* result = NULL;
863 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
864 bool should_try_gc;
865 uint gc_count_before;
866
867
868 {
869 MutexLocker x(Heap_lock);
870
871 // Given that humongous objects are not allocated in young
872 // regions, we'll first try to do the allocation without doing a
873 // collection hoping that there's enough space in the heap.
874 result = humongous_obj_allocate(word_size);
875 if (result != NULL) {
876 size_t size_in_regions = humongous_obj_size_in_regions(word_size);
877 policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
878 return result;
879 }
880
881 // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
882 // the GCLocker initiated GC has been performed and then retry. This includes
883 // the case when the GC Locker is not active but has not been performed.
884 should_try_gc = !GCLocker::needs_gc();
885 // Read the GC count while still holding the Heap_lock.
886 gc_count_before = total_collections();
887 }
888
889 if (should_try_gc) {
890 bool succeeded;
891 result = do_collection_pause(word_size, gc_count_before, &succeeded,
892 GCCause::_g1_humongous_allocation);
893 if (result != NULL) {
894 assert(succeeded, "only way to get back a non-NULL result");
895 log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
896 Thread::current()->name(), p2i(result));
897 return result;
898 }
899
900 if (succeeded) {
901 // We successfully scheduled a collection which failed to allocate. No
902 // point in trying to allocate further. We'll just return NULL.
903 log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
904 SIZE_FORMAT " words", Thread::current()->name(), word_size);
905 return NULL;
906 }
907 log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT "",
908 Thread::current()->name(), word_size);
909 } else {
910 // Failed to schedule a collection.
911 if (gclocker_retry_count > GCLockerRetryAllocationCount) {
912 log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
913 SIZE_FORMAT " words", Thread::current()->name(), word_size);
914 return NULL;
915 }
916 log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
917 // The GCLocker is either active or the GCLocker initiated
918 // GC has not yet been performed. Stall until it is and
919 // then retry the allocation.
920 GCLocker::stall_until_clear();
921 gclocker_retry_count += 1;
922 }
923
924
925 // We can reach here if we were unsuccessful in scheduling a
926 // collection (because another thread beat us to it) or if we were
927 // stalled due to the GC locker. In either can we should retry the
928 // allocation attempt in case another thread successfully
929 // performed a collection and reclaimed enough space.
930 // Humongous object allocation always needs a lock, so we wait for the retry
931 // in the next iteration of the loop, unlike for the regular iteration case.
932 // Give a warning if we seem to be looping forever.
933
934 if ((QueuedAllocationWarningCount > 0) &&
935 (try_count % QueuedAllocationWarningCount == 0)) {
936 log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words",
937 Thread::current()->name(), try_count, word_size);
938 }
939 }
940
941 ShouldNotReachHere();
942 return NULL;
943 }
944
945 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
946 bool expect_null_mutator_alloc_region) {
947 assert_at_safepoint_on_vm_thread();
948 assert(!_allocator->has_mutator_alloc_region() || !expect_null_mutator_alloc_region,
949 "the current alloc region was unexpectedly found to be non-NULL");
950
951 if (!is_humongous(word_size)) {
952 return _allocator->attempt_allocation_locked(word_size);
953 } else {
954 HeapWord* result = humongous_obj_allocate(word_size);
955 if (result != NULL && policy()->need_to_start_conc_mark("STW humongous allocation")) {
956 collector_state()->set_initiate_conc_mark_if_possible(true);
957 }
958 return result;
959 }
960
961 ShouldNotReachHere();
962 }
963
964 class PostCompactionPrinterClosure: public HeapRegionClosure {
965 private:
966 G1HRPrinter* _hr_printer;
967 public:
968 bool do_heap_region(HeapRegion* hr) {
969 assert(!hr->is_young(), "not expecting to find young regions");
970 _hr_printer->post_compaction(hr);
971 return false;
972 }
973
974 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
975 : _hr_printer(hr_printer) { }
976 };
977
978 void G1CollectedHeap::print_hrm_post_compaction() {
979 if (_hr_printer.is_active()) {
980 PostCompactionPrinterClosure cl(hr_printer());
981 heap_region_iterate(&cl);
982 }
983 }
984
985 void G1CollectedHeap::abort_concurrent_cycle() {
986 // If we start the compaction before the CM threads finish
987 // scanning the root regions we might trip them over as we'll
988 // be moving objects / updating references. So let's wait until
989 // they are done. By telling them to abort, they should complete
990 // early.
991 _cm->root_regions()->abort();
992 _cm->root_regions()->wait_until_scan_finished();
993
994 // Disable discovery and empty the discovered lists
995 // for the CM ref processor.
996 _ref_processor_cm->disable_discovery();
997 _ref_processor_cm->abandon_partial_discovery();
998 _ref_processor_cm->verify_no_references_recorded();
999
1000 // Abandon current iterations of concurrent marking and concurrent
1001 // refinement, if any are in progress.
1002 concurrent_mark()->concurrent_cycle_abort();
1003 }
1004
1005 void G1CollectedHeap::prepare_heap_for_full_collection() {
1006 // Make sure we'll choose a new allocation region afterwards.
1007 _allocator->release_mutator_alloc_regions();
1008 _allocator->abandon_gc_alloc_regions();
1009
1010 // We may have added regions to the current incremental collection
1011 // set between the last GC or pause and now. We need to clear the
1012 // incremental collection set and then start rebuilding it afresh
1013 // after this full GC.
1014 abandon_collection_set(collection_set());
1015
1016 tear_down_region_sets(false /* free_list_only */);
1017
1018 hrm()->prepare_for_full_collection_start();
1019 }
1020
1021 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) {
1022 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1023 assert_used_and_recalculate_used_equal(this);
1024 _verifier->verify_region_sets_optional();
1025 _verifier->verify_before_gc(G1HeapVerifier::G1VerifyFull);
1026 _verifier->check_bitmaps("Full GC Start");
1027 }
1028
1029 void G1CollectedHeap::prepare_heap_for_mutators() {
1030 hrm()->prepare_for_full_collection_end();
1031
1032 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1033 ClassLoaderDataGraph::purge();
1034 MetaspaceUtils::verify_metrics();
1035
1036 // Prepare heap for normal collections.
1037 assert(num_free_regions() == 0, "we should not have added any free regions");
1038 rebuild_region_sets(false /* free_list_only */);
1039 abort_refinement();
1040 resize_heap_if_necessary();
1041
1042 // Rebuild the strong code root lists for each region
1043 rebuild_strong_code_roots();
1044
1045 // Purge code root memory
1046 purge_code_root_memory();
1047
1048 // Start a new incremental collection set for the next pause
1049 start_new_collection_set();
1050
1051 _allocator->init_mutator_alloc_regions();
1052
1053 // Post collection state updates.
1054 MetaspaceGC::compute_new_size();
1055 }
1056
1057 void G1CollectedHeap::abort_refinement() {
1058 if (_hot_card_cache->use_cache()) {
1059 _hot_card_cache->reset_hot_cache();
1060 }
1061
1062 // Discard all remembered set updates and reset refinement statistics.
1063 G1BarrierSet::dirty_card_queue_set().abandon_logs();
1064 assert(G1BarrierSet::dirty_card_queue_set().num_cards() == 0,
1065 "DCQS should be empty");
1066 concurrent_refine()->get_and_reset_refinement_stats();
1067 }
1068
1069 void G1CollectedHeap::verify_after_full_collection() {
1070 _hrm->verify_optional();
1071 _verifier->verify_region_sets_optional();
1072 _verifier->verify_after_gc(G1HeapVerifier::G1VerifyFull);
1073 // Clear the previous marking bitmap, if needed for bitmap verification.
1074 // Note we cannot do this when we clear the next marking bitmap in
1075 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1076 // objects marked during a full GC against the previous bitmap.
1077 // But we need to clear it before calling check_bitmaps below since
1078 // the full GC has compacted objects and updated TAMS but not updated
1079 // the prev bitmap.
1080 if (G1VerifyBitmaps) {
1081 GCTraceTime(Debug, gc) tm("Clear Prev Bitmap for Verification");
1082 _cm->clear_prev_bitmap(workers());
1083 }
1084 // This call implicitly verifies that the next bitmap is clear after Full GC.
1085 _verifier->check_bitmaps("Full GC End");
1086
1087 // At this point there should be no regions in the
1088 // entire heap tagged as young.
1089 assert(check_young_list_empty(), "young list should be empty at this point");
1090
1091 // Note: since we've just done a full GC, concurrent
1092 // marking is no longer active. Therefore we need not
1093 // re-enable reference discovery for the CM ref processor.
1094 // That will be done at the start of the next marking cycle.
1095 // We also know that the STW processor should no longer
1096 // discover any new references.
1097 assert(!_ref_processor_stw->discovery_enabled(), "Postcondition");
1098 assert(!_ref_processor_cm->discovery_enabled(), "Postcondition");
1099 _ref_processor_stw->verify_no_references_recorded();
1100 _ref_processor_cm->verify_no_references_recorded();
1101 }
1102
1103 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) {
1104 // Post collection logging.
1105 // We should do this after we potentially resize the heap so
1106 // that all the COMMIT / UNCOMMIT events are generated before
1107 // the compaction events.
1108 print_hrm_post_compaction();
1109 heap_transition->print();
1110 print_heap_after_gc();
1111 print_heap_regions();
1112 }
1113
1114 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1115 bool clear_all_soft_refs) {
1116 assert_at_safepoint_on_vm_thread();
1117
1118 if (GCLocker::check_active_before_gc()) {
1119 // Full GC was not completed.
1120 return false;
1121 }
1122
1123 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1124 soft_ref_policy()->should_clear_all_soft_refs();
1125
1126 G1FullCollector collector(this, explicit_gc, do_clear_all_soft_refs);
1127 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1128
1129 collector.prepare_collection();
1130 collector.collect();
1131 collector.complete_collection();
1132
1133 // Full collection was successfully completed.
1134 return true;
1135 }
1136
1137 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1138 // Currently, there is no facility in the do_full_collection(bool) API to notify
1139 // the caller that the collection did not succeed (e.g., because it was locked
1140 // out by the GC locker). So, right now, we'll ignore the return value.
1141 bool dummy = do_full_collection(true, /* explicit_gc */
1142 clear_all_soft_refs);
1143 }
1144
1145 void G1CollectedHeap::resize_heap_if_necessary() {
1146 assert_at_safepoint_on_vm_thread();
1147
1148 // Capacity, free and used after the GC counted as full regions to
1149 // include the waste in the following calculations.
1150 const size_t capacity_after_gc = capacity();
1151 const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes();
1152
1153 // This is enforced in arguments.cpp.
1154 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1155 "otherwise the code below doesn't make sense");
1156
1157 // We don't have floating point command-line arguments
1158 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1159 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1160 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1161 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1162
1163 // We have to be careful here as these two calculations can overflow
1164 // 32-bit size_t's.
1165 double used_after_gc_d = (double) used_after_gc;
1166 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1167 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1168
1169 // Let's make sure that they are both under the max heap size, which
1170 // by default will make them fit into a size_t.
1171 double desired_capacity_upper_bound = (double) MaxHeapSize;
1172 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1173 desired_capacity_upper_bound);
1174 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1175 desired_capacity_upper_bound);
1176
1177 // We can now safely turn them into size_t's.
1178 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1179 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1180
1181 // This assert only makes sense here, before we adjust them
1182 // with respect to the min and max heap size.
1183 assert(minimum_desired_capacity <= maximum_desired_capacity,
1184 "minimum_desired_capacity = " SIZE_FORMAT ", "
1185 "maximum_desired_capacity = " SIZE_FORMAT,
1186 minimum_desired_capacity, maximum_desired_capacity);
1187
1188 // Should not be greater than the heap max size. No need to adjust
1189 // it with respect to the heap min size as it's a lower bound (i.e.,
1190 // we'll try to make the capacity larger than it, not smaller).
1191 minimum_desired_capacity = MIN2(minimum_desired_capacity, MaxHeapSize);
1192 // Should not be less than the heap min size. No need to adjust it
1193 // with respect to the heap max size as it's an upper bound (i.e.,
1194 // we'll try to make the capacity smaller than it, not greater).
1195 maximum_desired_capacity = MAX2(maximum_desired_capacity, MinHeapSize);
1196
1197 if (capacity_after_gc < minimum_desired_capacity) {
1198 // Don't expand unless it's significant
1199 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1200
1201 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity). "
1202 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1203 "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1204 capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio);
1205
1206 expand(expand_bytes, _workers);
1207
1208 // No expansion, now see if we want to shrink
1209 } else if (capacity_after_gc > maximum_desired_capacity) {
1210 // Capacity too large, compute shrinking size
1211 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1212
1213 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity). "
1214 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1215 "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1216 capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio);
1217
1218 shrink(shrink_bytes);
1219 }
1220 }
1221
1222 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1223 bool do_gc,
1224 bool clear_all_soft_refs,
1225 bool expect_null_mutator_alloc_region,
1226 bool* gc_succeeded) {
1227 *gc_succeeded = true;
1228 // Let's attempt the allocation first.
1229 HeapWord* result =
1230 attempt_allocation_at_safepoint(word_size,
1231 expect_null_mutator_alloc_region);
1232 if (result != NULL) {
1233 return result;
1234 }
1235
1236 // In a G1 heap, we're supposed to keep allocation from failing by
1237 // incremental pauses. Therefore, at least for now, we'll favor
1238 // expansion over collection. (This might change in the future if we can
1239 // do something smarter than full collection to satisfy a failed alloc.)
1240 result = expand_and_allocate(word_size);
1241 if (result != NULL) {
1242 return result;
1243 }
1244
1245 if (do_gc) {
1246 // Expansion didn't work, we'll try to do a Full GC.
1247 *gc_succeeded = do_full_collection(false, /* explicit_gc */
1248 clear_all_soft_refs);
1249 }
1250
1251 return NULL;
1252 }
1253
1254 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1255 bool* succeeded) {
1256 assert_at_safepoint_on_vm_thread();
1257
1258 // Attempts to allocate followed by Full GC.
1259 HeapWord* result =
1260 satisfy_failed_allocation_helper(word_size,
1261 true, /* do_gc */
1262 false, /* clear_all_soft_refs */
1263 false, /* expect_null_mutator_alloc_region */
1264 succeeded);
1265
1266 if (result != NULL || !*succeeded) {
1267 return result;
1268 }
1269
1270 // Attempts to allocate followed by Full GC that will collect all soft references.
1271 result = satisfy_failed_allocation_helper(word_size,
1272 true, /* do_gc */
1273 true, /* clear_all_soft_refs */
1274 true, /* expect_null_mutator_alloc_region */
1275 succeeded);
1276
1277 if (result != NULL || !*succeeded) {
1278 return result;
1279 }
1280
1281 // Attempts to allocate, no GC
1282 result = satisfy_failed_allocation_helper(word_size,
1283 false, /* do_gc */
1284 false, /* clear_all_soft_refs */
1285 true, /* expect_null_mutator_alloc_region */
1286 succeeded);
1287
1288 if (result != NULL) {
1289 return result;
1290 }
1291
1292 assert(!soft_ref_policy()->should_clear_all_soft_refs(),
1293 "Flag should have been handled and cleared prior to this point");
1294
1295 // What else? We might try synchronous finalization later. If the total
1296 // space available is large enough for the allocation, then a more
1297 // complete compaction phase than we've tried so far might be
1298 // appropriate.
1299 return NULL;
1300 }
1301
1302 // Attempting to expand the heap sufficiently
1303 // to support an allocation of the given "word_size". If
1304 // successful, perform the allocation and return the address of the
1305 // allocated block, or else "NULL".
1306
1307 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1308 assert_at_safepoint_on_vm_thread();
1309
1310 _verifier->verify_region_sets_optional();
1311
1312 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1313 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1314 word_size * HeapWordSize);
1315
1316
1317 if (expand(expand_bytes, _workers)) {
1318 _hrm->verify_optional();
1319 _verifier->verify_region_sets_optional();
1320 return attempt_allocation_at_safepoint(word_size,
1321 false /* expect_null_mutator_alloc_region */);
1322 }
1323 return NULL;
1324 }
1325
1326 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) {
1327 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1328 aligned_expand_bytes = align_up(aligned_expand_bytes,
1329 HeapRegion::GrainBytes);
1330
1331 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B",
1332 expand_bytes, aligned_expand_bytes);
1333
1334 if (is_maximal_no_gc()) {
1335 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1336 return false;
1337 }
1338
1339 double expand_heap_start_time_sec = os::elapsedTime();
1340 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1341 assert(regions_to_expand > 0, "Must expand by at least one region");
1342
1343 uint expanded_by = _hrm->expand_by(regions_to_expand, pretouch_workers);
1344 if (expand_time_ms != NULL) {
1345 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1346 }
1347
1348 if (expanded_by > 0) {
1349 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1350 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1351 policy()->record_new_heap_size(num_regions());
1352 } else {
1353 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1354
1355 // The expansion of the virtual storage space was unsuccessful.
1356 // Let's see if it was because we ran out of swap.
1357 if (G1ExitOnExpansionFailure &&
1358 _hrm->available() >= regions_to_expand) {
1359 // We had head room...
1360 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1361 }
1362 }
1363 return regions_to_expand > 0;
1364 }
1365
1366 bool G1CollectedHeap::expand_single_region(uint node_index) {
1367 uint expanded_by = _hrm->expand_on_preferred_node(node_index);
1368
1369 if (expanded_by == 0) {
1370 assert(is_maximal_no_gc(), "Should be no regions left, available: %u", _hrm->available());
1371 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1372 return false;
1373 }
1374
1375 policy()->record_new_heap_size(num_regions());
1376 return true;
1377 }
1378
1379 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1380 size_t aligned_shrink_bytes =
1381 ReservedSpace::page_align_size_down(shrink_bytes);
1382 aligned_shrink_bytes = align_down(aligned_shrink_bytes,
1383 HeapRegion::GrainBytes);
1384 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1385
1386 uint num_regions_removed = _hrm->shrink_by(num_regions_to_remove);
1387 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1388
1389 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",
1390 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1391 if (num_regions_removed > 0) {
1392 policy()->record_new_heap_size(num_regions());
1393 } else {
1394 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1395 }
1396 }
1397
1398 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1399 _verifier->verify_region_sets_optional();
1400
1401 // We should only reach here at the end of a Full GC or during Remark which
1402 // means we should not not be holding to any GC alloc regions. The method
1403 // below will make sure of that and do any remaining clean up.
1404 _allocator->abandon_gc_alloc_regions();
1405
1406 // Instead of tearing down / rebuilding the free lists here, we
1407 // could instead use the remove_all_pending() method on free_list to
1408 // remove only the ones that we need to remove.
1409 tear_down_region_sets(true /* free_list_only */);
1410 shrink_helper(shrink_bytes);
1411 rebuild_region_sets(true /* free_list_only */);
1412
1413 _hrm->verify_optional();
1414 _verifier->verify_region_sets_optional();
1415 }
1416
1417 class OldRegionSetChecker : public HeapRegionSetChecker {
1418 public:
1419 void check_mt_safety() {
1420 // Master Old Set MT safety protocol:
1421 // (a) If we're at a safepoint, operations on the master old set
1422 // should be invoked:
1423 // - by the VM thread (which will serialize them), or
1424 // - by the GC workers while holding the FreeList_lock, if we're
1425 // at a safepoint for an evacuation pause (this lock is taken
1426 // anyway when an GC alloc region is retired so that a new one
1427 // is allocated from the free list), or
1428 // - by the GC workers while holding the OldSets_lock, if we're at a
1429 // safepoint for a cleanup pause.
1430 // (b) If we're not at a safepoint, operations on the master old set
1431 // should be invoked while holding the Heap_lock.
1432
1433 if (SafepointSynchronize::is_at_safepoint()) {
1434 guarantee(Thread::current()->is_VM_thread() ||
1435 FreeList_lock->owned_by_self() || OldSets_lock->owned_by_self(),
1436 "master old set MT safety protocol at a safepoint");
1437 } else {
1438 guarantee(Heap_lock->owned_by_self(), "master old set MT safety protocol outside a safepoint");
1439 }
1440 }
1441 bool is_correct_type(HeapRegion* hr) { return hr->is_old(); }
1442 const char* get_description() { return "Old Regions"; }
1443 };
1444
1445 class ArchiveRegionSetChecker : public HeapRegionSetChecker {
1446 public:
1447 void check_mt_safety() {
1448 guarantee(!Universe::is_fully_initialized() || SafepointSynchronize::is_at_safepoint(),
1449 "May only change archive regions during initialization or safepoint.");
1450 }
1451 bool is_correct_type(HeapRegion* hr) { return hr->is_archive(); }
1452 const char* get_description() { return "Archive Regions"; }
1453 };
1454
1455 class HumongousRegionSetChecker : public HeapRegionSetChecker {
1456 public:
1457 void check_mt_safety() {
1458 // Humongous Set MT safety protocol:
1459 // (a) If we're at a safepoint, operations on the master humongous
1460 // set should be invoked by either the VM thread (which will
1461 // serialize them) or by the GC workers while holding the
1462 // OldSets_lock.
1463 // (b) If we're not at a safepoint, operations on the master
1464 // humongous set should be invoked while holding the Heap_lock.
1465
1466 if (SafepointSynchronize::is_at_safepoint()) {
1467 guarantee(Thread::current()->is_VM_thread() ||
1468 OldSets_lock->owned_by_self(),
1469 "master humongous set MT safety protocol at a safepoint");
1470 } else {
1471 guarantee(Heap_lock->owned_by_self(),
1472 "master humongous set MT safety protocol outside a safepoint");
1473 }
1474 }
1475 bool is_correct_type(HeapRegion* hr) { return hr->is_humongous(); }
1476 const char* get_description() { return "Humongous Regions"; }
1477 };
1478
1479 G1CollectedHeap::G1CollectedHeap() :
1480 CollectedHeap(),
1481 _young_gen_sampling_thread(NULL),
1482 _workers(NULL),
1483 _card_table(NULL),
1484 _soft_ref_policy(),
1485 _old_set("Old Region Set", new OldRegionSetChecker()),
1486 _archive_set("Archive Region Set", new ArchiveRegionSetChecker()),
1487 _humongous_set("Humongous Region Set", new HumongousRegionSetChecker()),
1488 _bot(NULL),
1489 _listener(),
1490 _numa(G1NUMA::create()),
1491 _hrm(NULL),
1492 _allocator(NULL),
1493 _verifier(NULL),
1494 _summary_bytes_used(0),
1495 _bytes_used_during_gc(0),
1496 _archive_allocator(NULL),
1497 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1498 _old_evac_stats("Old", OldPLABSize, PLABWeight),
1499 _expand_heap_after_alloc_failure(true),
1500 _g1mm(NULL),
1501 _humongous_reclaim_candidates(),
1502 _has_humongous_reclaim_candidates(false),
1503 _hr_printer(),
1504 _collector_state(),
1505 _old_marking_cycles_started(0),
1506 _old_marking_cycles_completed(0),
1507 _eden(),
1508 _survivor(),
1509 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1510 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1511 _policy(G1Policy::create_policy(_gc_timer_stw)),
1512 _heap_sizing_policy(NULL),
1513 _collection_set(this, _policy),
1514 _hot_card_cache(NULL),
1515 _rem_set(NULL),
1516 _cm(NULL),
1517 _cm_thread(NULL),
1518 _cr(NULL),
1519 _task_queues(NULL),
1520 _evacuation_failed(false),
1521 _evacuation_failed_info_array(NULL),
1522 _preserved_marks_set(true /* in_c_heap */),
1523 #ifndef PRODUCT
1524 _evacuation_failure_alot_for_current_gc(false),
1525 _evacuation_failure_alot_gc_number(0),
1526 _evacuation_failure_alot_count(0),
1527 #endif
1528 _ref_processor_stw(NULL),
1529 _is_alive_closure_stw(this),
1530 _is_subject_to_discovery_stw(this),
1531 _ref_processor_cm(NULL),
1532 _is_alive_closure_cm(this),
1533 _is_subject_to_discovery_cm(this),
1534 _region_attr() {
1535
1536 _verifier = new G1HeapVerifier(this);
1537
1538 _allocator = new G1Allocator(this);
1539
1540 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _policy->analytics());
1541
1542 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1543
1544 // Override the default _filler_array_max_size so that no humongous filler
1545 // objects are created.
1546 _filler_array_max_size = _humongous_object_threshold_in_words;
1547
1548 uint n_queues = ParallelGCThreads;
1549 _task_queues = new RefToScanQueueSet(n_queues);
1550
1551 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1552
1553 for (uint i = 0; i < n_queues; i++) {
1554 RefToScanQueue* q = new RefToScanQueue();
1555 q->initialize();
1556 _task_queues->register_queue(i, q);
1557 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1558 }
1559
1560 // Initialize the G1EvacuationFailureALot counters and flags.
1561 NOT_PRODUCT(reset_evacuation_should_fail();)
1562 _gc_tracer_stw->initialize();
1563
1564 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1565 }
1566
1567 static size_t actual_reserved_page_size(ReservedSpace rs) {
1568 size_t page_size = os::vm_page_size();
1569 if (UseLargePages) {
1570 // There are two ways to manage large page memory.
1571 // 1. OS supports committing large page memory.
1572 // 2. OS doesn't support committing large page memory so ReservedSpace manages it.
1573 // And ReservedSpace calls it 'special'. If we failed to set 'special',
1574 // we reserved memory without large page.
1575 if (os::can_commit_large_page_memory() || rs.special()) {
1576 // An alignment at ReservedSpace comes from preferred page size or
1577 // heap alignment, and if the alignment came from heap alignment, it could be
1578 // larger than large pages size. So need to cap with the large page size.
1579 page_size = MIN2(rs.alignment(), os::large_page_size());
1580 }
1581 }
1582
1583 return page_size;
1584 }
1585
1586 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1587 size_t size,
1588 size_t translation_factor) {
1589 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1590 // Allocate a new reserved space, preferring to use large pages.
1591 ReservedSpace rs(size, preferred_page_size);
1592 size_t page_size = actual_reserved_page_size(rs);
1593 G1RegionToSpaceMapper* result =
1594 G1RegionToSpaceMapper::create_mapper(rs,
1595 size,
1596 page_size,
1597 HeapRegion::GrainBytes,
1598 translation_factor,
1599 mtGC);
1600
1601 os::trace_page_sizes_for_requested_size(description,
1602 size,
1603 preferred_page_size,
1604 page_size,
1605 rs.base(),
1606 rs.size());
1607
1608 return result;
1609 }
1610
1611 jint G1CollectedHeap::initialize_concurrent_refinement() {
1612 jint ecode = JNI_OK;
1613 _cr = G1ConcurrentRefine::create(&ecode);
1614 return ecode;
1615 }
1616
1617 jint G1CollectedHeap::initialize_young_gen_sampling_thread() {
1618 _young_gen_sampling_thread = new G1YoungRemSetSamplingThread();
1619 if (_young_gen_sampling_thread->osthread() == NULL) {
1620 vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread");
1621 return JNI_ENOMEM;
1622 }
1623 return JNI_OK;
1624 }
1625
1626 jint G1CollectedHeap::initialize() {
1627
1628 // Necessary to satisfy locking discipline assertions.
1629
1630 MutexLocker x(Heap_lock);
1631
1632 // While there are no constraints in the GC code that HeapWordSize
1633 // be any particular value, there are multiple other areas in the
1634 // system which believe this to be true (e.g. oop->object_size in some
1635 // cases incorrectly returns the size in wordSize units rather than
1636 // HeapWordSize).
1637 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1638
1639 size_t init_byte_size = InitialHeapSize;
1640 size_t reserved_byte_size = G1Arguments::heap_reserved_size_bytes();
1641
1642 // Ensure that the sizes are properly aligned.
1643 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1644 Universe::check_alignment(reserved_byte_size, HeapRegion::GrainBytes, "g1 heap");
1645 Universe::check_alignment(reserved_byte_size, HeapAlignment, "g1 heap");
1646
1647 // Reserve the maximum.
1648
1649 // When compressed oops are enabled, the preferred heap base
1650 // is calculated by subtracting the requested size from the
1651 // 32Gb boundary and using the result as the base address for
1652 // heap reservation. If the requested size is not aligned to
1653 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1654 // into the ReservedHeapSpace constructor) then the actual
1655 // base of the reserved heap may end up differing from the
1656 // address that was requested (i.e. the preferred heap base).
1657 // If this happens then we could end up using a non-optimal
1658 // compressed oops mode.
1659
1660 ReservedHeapSpace heap_rs = Universe::reserve_heap(reserved_byte_size,
1661 HeapAlignment);
1662
1663 initialize_reserved_region(heap_rs);
1664
1665 // Create the barrier set for the entire reserved region.
1666 G1CardTable* ct = new G1CardTable(heap_rs.region());
1667 ct->initialize();
1668 G1BarrierSet* bs = new G1BarrierSet(ct);
1669 bs->initialize();
1670 assert(bs->is_a(BarrierSet::G1BarrierSet), "sanity");
1671 BarrierSet::set_barrier_set(bs);
1672 _card_table = ct;
1673
1674 {
1675 G1SATBMarkQueueSet& satbqs = bs->satb_mark_queue_set();
1676 satbqs.set_process_completed_buffers_threshold(G1SATBProcessCompletedThreshold);
1677 satbqs.set_buffer_enqueue_threshold_percentage(G1SATBBufferEnqueueingThresholdPercent);
1678 }
1679
1680 // Create the hot card cache.
1681 _hot_card_cache = new G1HotCardCache(this);
1682
1683 // Carve out the G1 part of the heap.
1684 ReservedSpace g1_rs = heap_rs.first_part(reserved_byte_size);
1685 size_t page_size = actual_reserved_page_size(heap_rs);
1686 G1RegionToSpaceMapper* heap_storage =
1687 G1RegionToSpaceMapper::create_heap_mapper(g1_rs,
1688 g1_rs.size(),
1689 page_size,
1690 HeapRegion::GrainBytes,
1691 1,
1692 mtJavaHeap);
1693 if(heap_storage == NULL) {
1694 vm_shutdown_during_initialization("Could not initialize G1 heap");
1695 return JNI_ERR;
1696 }
1697
1698 os::trace_page_sizes("Heap",
1699 MinHeapSize,
1700 reserved_byte_size,
1701 page_size,
1702 heap_rs.base(),
1703 heap_rs.size());
1704 heap_storage->set_mapping_changed_listener(&_listener);
1705
1706 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1707 G1RegionToSpaceMapper* bot_storage =
1708 create_aux_memory_mapper("Block Offset Table",
1709 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1710 G1BlockOffsetTable::heap_map_factor());
1711
1712 G1RegionToSpaceMapper* cardtable_storage =
1713 create_aux_memory_mapper("Card Table",
1714 G1CardTable::compute_size(g1_rs.size() / HeapWordSize),
1715 G1CardTable::heap_map_factor());
1716
1717 G1RegionToSpaceMapper* card_counts_storage =
1718 create_aux_memory_mapper("Card Counts Table",
1719 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1720 G1CardCounts::heap_map_factor());
1721
1722 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1723 G1RegionToSpaceMapper* prev_bitmap_storage =
1724 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1725 G1RegionToSpaceMapper* next_bitmap_storage =
1726 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1727
1728 _hrm = HeapRegionManager::create_manager(this);
1729
1730 _hrm->initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1731 _card_table->initialize(cardtable_storage);
1732
1733 // Do later initialization work for concurrent refinement.
1734 _hot_card_cache->initialize(card_counts_storage);
1735
1736 // 6843694 - ensure that the maximum region index can fit
1737 // in the remembered set structures.
1738 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1739 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1740
1741 // The G1FromCardCache reserves card with value 0 as "invalid", so the heap must not
1742 // start within the first card.
1743 guarantee(g1_rs.base() >= (char*)G1CardTable::card_size, "Java heap must not start within the first card.");
1744 // Also create a G1 rem set.
1745 _rem_set = new G1RemSet(this, _card_table, _hot_card_cache);
1746 _rem_set->initialize(max_reserved_capacity(), max_regions());
1747
1748 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1749 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1750 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1751 "too many cards per region");
1752
1753 FreeRegionList::set_unrealistically_long_length(max_expandable_regions() + 1);
1754
1755 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1756
1757 {
1758 HeapWord* start = _hrm->reserved().start();
1759 HeapWord* end = _hrm->reserved().end();
1760 size_t granularity = HeapRegion::GrainBytes;
1761
1762 _region_attr.initialize(start, end, granularity);
1763 _humongous_reclaim_candidates.initialize(start, end, granularity);
1764 }
1765
1766 _workers = new WorkGang("GC Thread", ParallelGCThreads,
1767 true /* are_GC_task_threads */,
1768 false /* are_ConcurrentGC_threads */);
1769 if (_workers == NULL) {
1770 return JNI_ENOMEM;
1771 }
1772 _workers->initialize_workers();
1773
1774 _numa->set_region_info(HeapRegion::GrainBytes, page_size);
1775
1776 // Create the G1ConcurrentMark data structure and thread.
1777 // (Must do this late, so that "max_regions" is defined.)
1778 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1779 _cm_thread = _cm->cm_thread();
1780
1781 // Now expand into the initial heap size.
1782 if (!expand(init_byte_size, _workers)) {
1783 vm_shutdown_during_initialization("Failed to allocate initial heap.");
1784 return JNI_ENOMEM;
1785 }
1786
1787 // Perform any initialization actions delegated to the policy.
1788 policy()->init(this, &_collection_set);
1789
1790 jint ecode = initialize_concurrent_refinement();
1791 if (ecode != JNI_OK) {
1792 return ecode;
1793 }
1794
1795 ecode = initialize_young_gen_sampling_thread();
1796 if (ecode != JNI_OK) {
1797 return ecode;
1798 }
1799
1800 {
1801 G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
1802 dcqs.set_process_cards_threshold(concurrent_refine()->yellow_zone());
1803 dcqs.set_max_cards(concurrent_refine()->red_zone());
1804 }
1805
1806 // Here we allocate the dummy HeapRegion that is required by the
1807 // G1AllocRegion class.
1808 HeapRegion* dummy_region = _hrm->get_dummy_region();
1809
1810 // We'll re-use the same region whether the alloc region will
1811 // require BOT updates or not and, if it doesn't, then a non-young
1812 // region will complain that it cannot support allocations without
1813 // BOT updates. So we'll tag the dummy region as eden to avoid that.
1814 dummy_region->set_eden();
1815 // Make sure it's full.
1816 dummy_region->set_top(dummy_region->end());
1817 G1AllocRegion::setup(this, dummy_region);
1818
1819 _allocator->init_mutator_alloc_regions();
1820
1821 // Do create of the monitoring and management support so that
1822 // values in the heap have been properly initialized.
1823 _g1mm = new G1MonitoringSupport(this);
1824
1825 G1StringDedup::initialize();
1826
1827 _preserved_marks_set.init(ParallelGCThreads);
1828
1829 _collection_set.initialize(max_regions());
1830
1831 return JNI_OK;
1832 }
1833
1834 void G1CollectedHeap::stop() {
1835 // Stop all concurrent threads. We do this to make sure these threads
1836 // do not continue to execute and access resources (e.g. logging)
1837 // that are destroyed during shutdown.
1838 _cr->stop();
1839 _young_gen_sampling_thread->stop();
1840 _cm_thread->stop();
1841 if (G1StringDedup::is_enabled()) {
1842 G1StringDedup::stop();
1843 }
1844 }
1845
1846 void G1CollectedHeap::safepoint_synchronize_begin() {
1847 SuspendibleThreadSet::synchronize();
1848 }
1849
1850 void G1CollectedHeap::safepoint_synchronize_end() {
1851 SuspendibleThreadSet::desynchronize();
1852 }
1853
1854 void G1CollectedHeap::post_initialize() {
1855 CollectedHeap::post_initialize();
1856 ref_processing_init();
1857 }
1858
1859 void G1CollectedHeap::ref_processing_init() {
1860 // Reference processing in G1 currently works as follows:
1861 //
1862 // * There are two reference processor instances. One is
1863 // used to record and process discovered references
1864 // during concurrent marking; the other is used to
1865 // record and process references during STW pauses
1866 // (both full and incremental).
1867 // * Both ref processors need to 'span' the entire heap as
1868 // the regions in the collection set may be dotted around.
1869 //
1870 // * For the concurrent marking ref processor:
1871 // * Reference discovery is enabled at initial marking.
1872 // * Reference discovery is disabled and the discovered
1873 // references processed etc during remarking.
1874 // * Reference discovery is MT (see below).
1875 // * Reference discovery requires a barrier (see below).
1876 // * Reference processing may or may not be MT
1877 // (depending on the value of ParallelRefProcEnabled
1878 // and ParallelGCThreads).
1879 // * A full GC disables reference discovery by the CM
1880 // ref processor and abandons any entries on it's
1881 // discovered lists.
1882 //
1883 // * For the STW processor:
1884 // * Non MT discovery is enabled at the start of a full GC.
1885 // * Processing and enqueueing during a full GC is non-MT.
1886 // * During a full GC, references are processed after marking.
1887 //
1888 // * Discovery (may or may not be MT) is enabled at the start
1889 // of an incremental evacuation pause.
1890 // * References are processed near the end of a STW evacuation pause.
1891 // * For both types of GC:
1892 // * Discovery is atomic - i.e. not concurrent.
1893 // * Reference discovery will not need a barrier.
1894
1895 bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1);
1896
1897 // Concurrent Mark ref processor
1898 _ref_processor_cm =
1899 new ReferenceProcessor(&_is_subject_to_discovery_cm,
1900 mt_processing, // mt processing
1901 ParallelGCThreads, // degree of mt processing
1902 (ParallelGCThreads > 1) || (ConcGCThreads > 1), // mt discovery
1903 MAX2(ParallelGCThreads, ConcGCThreads), // degree of mt discovery
1904 false, // Reference discovery is not atomic
1905 &_is_alive_closure_cm, // is alive closure
1906 true); // allow changes to number of processing threads
1907
1908 // STW ref processor
1909 _ref_processor_stw =
1910 new ReferenceProcessor(&_is_subject_to_discovery_stw,
1911 mt_processing, // mt processing
1912 ParallelGCThreads, // degree of mt processing
1913 (ParallelGCThreads > 1), // mt discovery
1914 ParallelGCThreads, // degree of mt discovery
1915 true, // Reference discovery is atomic
1916 &_is_alive_closure_stw, // is alive closure
1917 true); // allow changes to number of processing threads
1918 }
1919
1920 SoftRefPolicy* G1CollectedHeap::soft_ref_policy() {
1921 return &_soft_ref_policy;
1922 }
1923
1924 size_t G1CollectedHeap::capacity() const {
1925 return _hrm->length() * HeapRegion::GrainBytes;
1926 }
1927
1928 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const {
1929 return _hrm->total_free_bytes();
1930 }
1931
1932 void G1CollectedHeap::iterate_hcc_closure(G1CardTableEntryClosure* cl, uint worker_id) {
1933 _hot_card_cache->drain(cl, worker_id);
1934 }
1935
1936 // Computes the sum of the storage used by the various regions.
1937 size_t G1CollectedHeap::used() const {
1938 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
1939 if (_archive_allocator != NULL) {
1940 result += _archive_allocator->used();
1941 }
1942 return result;
1943 }
1944
1945 size_t G1CollectedHeap::used_unlocked() const {
1946 return _summary_bytes_used;
1947 }
1948
1949 class SumUsedClosure: public HeapRegionClosure {
1950 size_t _used;
1951 public:
1952 SumUsedClosure() : _used(0) {}
1953 bool do_heap_region(HeapRegion* r) {
1954 _used += r->used();
1955 return false;
1956 }
1957 size_t result() { return _used; }
1958 };
1959
1960 size_t G1CollectedHeap::recalculate_used() const {
1961 SumUsedClosure blk;
1962 heap_region_iterate(&blk);
1963 return blk.result();
1964 }
1965
1966 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
1967 switch (cause) {
1968 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
1969 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent;
1970 case GCCause::_wb_conc_mark: return true;
1971 default : return false;
1972 }
1973 }
1974
1975 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
1976 switch (cause) {
1977 case GCCause::_g1_humongous_allocation: return true;
1978 case GCCause::_g1_periodic_collection: return G1PeriodicGCInvokesConcurrent;
1979 case GCCause::_wb_breakpoint: return true;
1980 default: return is_user_requested_concurrent_full_gc(cause);
1981 }
1982 }
1983
1984 bool G1CollectedHeap::should_upgrade_to_full_gc(GCCause::Cause cause) {
1985 if (policy()->force_upgrade_to_full()) {
1986 return true;
1987 } else if (should_do_concurrent_full_gc(_gc_cause)) {
1988 return false;
1989 } else if (has_regions_left_for_allocation()) {
1990 return false;
1991 } else {
1992 return true;
1993 }
1994 }
1995
1996 #ifndef PRODUCT
1997 void G1CollectedHeap::allocate_dummy_regions() {
1998 // Let's fill up most of the region
1999 size_t word_size = HeapRegion::GrainWords - 1024;
2000 // And as a result the region we'll allocate will be humongous.
2001 guarantee(is_humongous(word_size), "sanity");
2002
2003 // _filler_array_max_size is set to humongous object threshold
2004 // but temporarily change it to use CollectedHeap::fill_with_object().
2005 SizeTFlagSetting fs(_filler_array_max_size, word_size);
2006
2007 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2008 // Let's use the existing mechanism for the allocation
2009 HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2010 if (dummy_obj != NULL) {
2011 MemRegion mr(dummy_obj, word_size);
2012 CollectedHeap::fill_with_object(mr);
2013 } else {
2014 // If we can't allocate once, we probably cannot allocate
2015 // again. Let's get out of the loop.
2016 break;
2017 }
2018 }
2019 }
2020 #endif // !PRODUCT
2021
2022 void G1CollectedHeap::increment_old_marking_cycles_started() {
2023 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2024 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2025 "Wrong marking cycle count (started: %d, completed: %d)",
2026 _old_marking_cycles_started, _old_marking_cycles_completed);
2027
2028 _old_marking_cycles_started++;
2029 }
2030
2031 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2032 MonitorLocker ml(G1OldGCCount_lock, Mutex::_no_safepoint_check_flag);
2033
2034 // We assume that if concurrent == true, then the caller is a
2035 // concurrent thread that was joined the Suspendible Thread
2036 // Set. If there's ever a cheap way to check this, we should add an
2037 // assert here.
2038
2039 // Given that this method is called at the end of a Full GC or of a
2040 // concurrent cycle, and those can be nested (i.e., a Full GC can
2041 // interrupt a concurrent cycle), the number of full collections
2042 // completed should be either one (in the case where there was no
2043 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2044 // behind the number of full collections started.
2045
2046 // This is the case for the inner caller, i.e. a Full GC.
2047 assert(concurrent ||
2048 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2049 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2050 "for inner caller (Full GC): _old_marking_cycles_started = %u "
2051 "is inconsistent with _old_marking_cycles_completed = %u",
2052 _old_marking_cycles_started, _old_marking_cycles_completed);
2053
2054 // This is the case for the outer caller, i.e. the concurrent cycle.
2055 assert(!concurrent ||
2056 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2057 "for outer caller (concurrent cycle): "
2058 "_old_marking_cycles_started = %u "
2059 "is inconsistent with _old_marking_cycles_completed = %u",
2060 _old_marking_cycles_started, _old_marking_cycles_completed);
2061
2062 _old_marking_cycles_completed += 1;
2063
2064 // We need to clear the "in_progress" flag in the CM thread before
2065 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2066 // is set) so that if a waiter requests another System.gc() it doesn't
2067 // incorrectly see that a marking cycle is still in progress.
2068 if (concurrent) {
2069 _cm_thread->set_idle();
2070 }
2071
2072 // Notify threads waiting in System.gc() (with ExplicitGCInvokesConcurrent)
2073 // for a full GC to finish that their wait is over.
2074 ml.notify_all();
2075 }
2076
2077 void G1CollectedHeap::collect(GCCause::Cause cause) {
2078 try_collect(cause);
2079 }
2080
2081 // Return true if (x < y) with allowance for wraparound.
2082 static bool gc_counter_less_than(uint x, uint y) {
2083 return (x - y) > (UINT_MAX/2);
2084 }
2085
2086 // LOG_COLLECT_CONCURRENTLY(cause, msg, args...)
2087 // Macro so msg printing is format-checked.
2088 #define LOG_COLLECT_CONCURRENTLY(cause, ...) \
2089 do { \
2090 LogTarget(Trace, gc) LOG_COLLECT_CONCURRENTLY_lt; \
2091 if (LOG_COLLECT_CONCURRENTLY_lt.is_enabled()) { \
2092 ResourceMark rm; /* For thread name. */ \
2093 LogStream LOG_COLLECT_CONCURRENTLY_s(&LOG_COLLECT_CONCURRENTLY_lt); \
2094 LOG_COLLECT_CONCURRENTLY_s.print("%s: Try Collect Concurrently (%s): ", \
2095 Thread::current()->name(), \
2096 GCCause::to_string(cause)); \
2097 LOG_COLLECT_CONCURRENTLY_s.print(__VA_ARGS__); \
2098 } \
2099 } while (0)
2100
2101 #define LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, result) \
2102 LOG_COLLECT_CONCURRENTLY(cause, "complete %s", BOOL_TO_STR(result))
2103
2104 bool G1CollectedHeap::try_collect_concurrently(GCCause::Cause cause,
2105 uint gc_counter,
2106 uint old_marking_started_before) {
2107 assert_heap_not_locked();
2108 assert(should_do_concurrent_full_gc(cause),
2109 "Non-concurrent cause %s", GCCause::to_string(cause));
2110
2111 for (uint i = 1; true; ++i) {
2112 // Try to schedule an initial-mark evacuation pause that will
2113 // start a concurrent cycle.
2114 LOG_COLLECT_CONCURRENTLY(cause, "attempt %u", i);
2115 VM_G1TryInitiateConcMark op(gc_counter,
2116 cause,
2117 policy()->max_pause_time_ms());
2118 VMThread::execute(&op);
2119
2120 // Request is trivially finished.
2121 if (cause == GCCause::_g1_periodic_collection) {
2122 LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, op.gc_succeeded());
2123 return op.gc_succeeded();
2124 }
2125
2126 // If VMOp skipped initiating concurrent marking cycle because
2127 // we're terminating, then we're done.
2128 if (op.terminating()) {
2129 LOG_COLLECT_CONCURRENTLY(cause, "skipped: terminating");
2130 return false;
2131 }
2132
2133 // Lock to get consistent set of values.
2134 uint old_marking_started_after;
2135 uint old_marking_completed_after;
2136 {
2137 MutexLocker ml(Heap_lock);
2138 // Update gc_counter for retrying VMOp if needed. Captured here to be
2139 // consistent with the values we use below for termination tests. If
2140 // a retry is needed after a possible wait, and another collection
2141 // occurs in the meantime, it will cause our retry to be skipped and
2142 // we'll recheck for termination with updated conditions from that
2143 // more recent collection. That's what we want, rather than having
2144 // our retry possibly perform an unnecessary collection.
2145 gc_counter = total_collections();
2146 old_marking_started_after = _old_marking_cycles_started;
2147 old_marking_completed_after = _old_marking_cycles_completed;
2148 }
2149
2150 if (cause == GCCause::_wb_breakpoint) {
2151 if (op.gc_succeeded()) {
2152 LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, true);
2153 return true;
2154 }
2155 // When _wb_breakpoint there can't be another cycle or deferred.
2156 assert(!op.cycle_already_in_progress(), "invariant");
2157 assert(!op.whitebox_attached(), "invariant");
2158 // Concurrent cycle attempt might have been cancelled by some other
2159 // collection, so retry. Unlike other cases below, we want to retry
2160 // even if cancelled by a STW full collection, because we really want
2161 // to start a concurrent cycle.
2162 if (old_marking_started_before != old_marking_started_after) {
2163 LOG_COLLECT_CONCURRENTLY(cause, "ignoring STW full GC");
2164 old_marking_started_before = old_marking_started_after;
2165 }
2166 } else if (!GCCause::is_user_requested_gc(cause)) {
2167 // For an "automatic" (not user-requested) collection, we just need to
2168 // ensure that progress is made.
2169 //
2170 // Request is finished if any of
2171 // (1) the VMOp successfully performed a GC,
2172 // (2) a concurrent cycle was already in progress,
2173 // (3) whitebox is controlling concurrent cycles,
2174 // (4) a new cycle was started (by this thread or some other), or
2175 // (5) a Full GC was performed.
2176 // Cases (4) and (5) are detected together by a change to
2177 // _old_marking_cycles_started.
2178 //
2179 // Note that (1) does not imply (4). If we're still in the mixed
2180 // phase of an earlier concurrent collection, the request to make the
2181 // collection an initial-mark won't be honored. If we don't check for
2182 // both conditions we'll spin doing back-to-back collections.
2183 if (op.gc_succeeded() ||
2184 op.cycle_already_in_progress() ||
2185 op.whitebox_attached() ||
2186 (old_marking_started_before != old_marking_started_after)) {
2187 LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, true);
2188 return true;
2189 }
2190 } else { // User-requested GC.
2191 // For a user-requested collection, we want to ensure that a complete
2192 // full collection has been performed before returning, but without
2193 // waiting for more than needed.
2194
2195 // For user-requested GCs (unlike non-UR), a successful VMOp implies a
2196 // new cycle was started. That's good, because it's not clear what we
2197 // should do otherwise. Trying again just does back to back GCs.
2198 // Can't wait for someone else to start a cycle. And returning fails
2199 // to meet the goal of ensuring a full collection was performed.
2200 assert(!op.gc_succeeded() ||
2201 (old_marking_started_before != old_marking_started_after),
2202 "invariant: succeeded %s, started before %u, started after %u",
2203 BOOL_TO_STR(op.gc_succeeded()),
2204 old_marking_started_before, old_marking_started_after);
2205
2206 // Request is finished if a full collection (concurrent or stw)
2207 // was started after this request and has completed, e.g.
2208 // started_before < completed_after.
2209 if (gc_counter_less_than(old_marking_started_before,
2210 old_marking_completed_after)) {
2211 LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, true);
2212 return true;
2213 }
2214
2215 if (old_marking_started_after != old_marking_completed_after) {
2216 // If there is an in-progress cycle (possibly started by us), then
2217 // wait for that cycle to complete, e.g.
2218 // while completed_now < started_after.
2219 LOG_COLLECT_CONCURRENTLY(cause, "wait");
2220 MonitorLocker ml(G1OldGCCount_lock);
2221 while (gc_counter_less_than(_old_marking_cycles_completed,
2222 old_marking_started_after)) {
2223 ml.wait();
2224 }
2225 // Request is finished if the collection we just waited for was
2226 // started after this request.
2227 if (old_marking_started_before != old_marking_started_after) {
2228 LOG_COLLECT_CONCURRENTLY(cause, "complete after wait");
2229 return true;
2230 }
2231 }
2232
2233 // If VMOp was successful then it started a new cycle that the above
2234 // wait &etc should have recognized as finishing this request. This
2235 // differs from a non-user-request, where gc_succeeded does not imply
2236 // a new cycle was started.
2237 assert(!op.gc_succeeded(), "invariant");
2238
2239 if (op.cycle_already_in_progress()) {
2240 // If VMOp failed because a cycle was already in progress, it
2241 // is now complete. But it didn't finish this user-requested
2242 // GC, so try again.
2243 LOG_COLLECT_CONCURRENTLY(cause, "retry after in-progress");
2244 continue;
2245 } else if (op.whitebox_attached()) {
2246 // If WhiteBox wants control, wait for notification of a state
2247 // change in the controller, then try again. Don't wait for
2248 // release of control, since collections may complete while in
2249 // control. Note: This won't recognize a STW full collection
2250 // while waiting; we can't wait on multiple monitors.
2251 LOG_COLLECT_CONCURRENTLY(cause, "whitebox control stall");
2252 MonitorLocker ml(ConcurrentGCBreakpoints::monitor());
2253 if (ConcurrentGCBreakpoints::is_controlled()) {
2254 ml.wait();
2255 }
2256 continue;
2257 }
2258 }
2259
2260 // Collection failed and should be retried.
2261 assert(op.transient_failure(), "invariant");
2262
2263 if (GCLocker::is_active_and_needs_gc()) {
2264 // If GCLocker is active, wait until clear before retrying.
2265 LOG_COLLECT_CONCURRENTLY(cause, "gc-locker stall");
2266 GCLocker::stall_until_clear();
2267 }
2268
2269 LOG_COLLECT_CONCURRENTLY(cause, "retry");
2270 }
2271 }
2272
2273 bool G1CollectedHeap::try_collect(GCCause::Cause cause) {
2274 assert_heap_not_locked();
2275
2276 // Lock to get consistent set of values.
2277 uint gc_count_before;
2278 uint full_gc_count_before;
2279 uint old_marking_started_before;
2280 {
2281 MutexLocker ml(Heap_lock);
2282 gc_count_before = total_collections();
2283 full_gc_count_before = total_full_collections();
2284 old_marking_started_before = _old_marking_cycles_started;
2285 }
2286
2287 if (should_do_concurrent_full_gc(cause)) {
2288 return try_collect_concurrently(cause,
2289 gc_count_before,
2290 old_marking_started_before);
2291 } else if (GCLocker::should_discard(cause, gc_count_before)) {
2292 // Indicate failure to be consistent with VMOp failure due to
2293 // another collection slipping in after our gc_count but before
2294 // our request is processed.
2295 return false;
2296 } else if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2297 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2298
2299 // Schedule a standard evacuation pause. We're setting word_size
2300 // to 0 which means that we are not requesting a post-GC allocation.
2301 VM_G1CollectForAllocation op(0, /* word_size */
2302 gc_count_before,
2303 cause,
2304 policy()->max_pause_time_ms());
2305 VMThread::execute(&op);
2306 return op.gc_succeeded();
2307 } else {
2308 // Schedule a Full GC.
2309 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2310 VMThread::execute(&op);
2311 return op.gc_succeeded();
2312 }
2313 }
2314
2315 bool G1CollectedHeap::is_in(const void* p) const {
2316 if (_hrm->reserved().contains(p)) {
2317 // Given that we know that p is in the reserved space,
2318 // heap_region_containing() should successfully
2319 // return the containing region.
2320 HeapRegion* hr = heap_region_containing(p);
2321 return hr->is_in(p);
2322 } else {
2323 return false;
2324 }
2325 }
2326
2327 #ifdef ASSERT
2328 bool G1CollectedHeap::is_in_exact(const void* p) const {
2329 bool contains = reserved_region().contains(p);
2330 bool available = _hrm->is_available(addr_to_region((HeapWord*)p));
2331 if (contains && available) {
2332 return true;
2333 } else {
2334 return false;
2335 }
2336 }
2337 #endif
2338
2339 // Iteration functions.
2340
2341 // Iterates an ObjectClosure over all objects within a HeapRegion.
2342
2343 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2344 ObjectClosure* _cl;
2345 public:
2346 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2347 bool do_heap_region(HeapRegion* r) {
2348 if (!r->is_continues_humongous()) {
2349 r->object_iterate(_cl);
2350 }
2351 return false;
2352 }
2353 };
2354
2355 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2356 IterateObjectClosureRegionClosure blk(cl);
2357 heap_region_iterate(&blk);
2358 }
2359
2360 void G1CollectedHeap::keep_alive(oop obj) {
2361 G1BarrierSet::enqueue(obj);
2362 }
2363
2364 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2365 _hrm->iterate(cl);
2366 }
2367
2368 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
2369 HeapRegionClaimer *hrclaimer,
2370 uint worker_id) const {
2371 _hrm->par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id));
2372 }
2373
2374 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl,
2375 HeapRegionClaimer *hrclaimer) const {
2376 _hrm->par_iterate(cl, hrclaimer, 0);
2377 }
2378
2379 void G1CollectedHeap::collection_set_iterate_all(HeapRegionClosure* cl) {
2380 _collection_set.iterate(cl);
2381 }
2382
2383 void G1CollectedHeap::collection_set_par_iterate_all(HeapRegionClosure* cl, HeapRegionClaimer* hr_claimer, uint worker_id) {
2384 _collection_set.par_iterate(cl, hr_claimer, worker_id, workers()->active_workers());
2385 }
2386
2387 void G1CollectedHeap::collection_set_iterate_increment_from(HeapRegionClosure *cl, HeapRegionClaimer* hr_claimer, uint worker_id) {
2388 _collection_set.iterate_incremental_part_from(cl, hr_claimer, worker_id, workers()->active_workers());
2389 }
2390
2391 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2392 HeapRegion* hr = heap_region_containing(addr);
2393 return hr->block_start(addr);
2394 }
2395
2396 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2397 HeapRegion* hr = heap_region_containing(addr);
2398 return hr->block_is_obj(addr);
2399 }
2400
2401 bool G1CollectedHeap::supports_tlab_allocation() const {
2402 return true;
2403 }
2404
2405 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2406 return (_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2407 }
2408
2409 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2410 return _eden.length() * HeapRegion::GrainBytes;
2411 }
2412
2413 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2414 // must be equal to the humongous object limit.
2415 size_t G1CollectedHeap::max_tlab_size() const {
2416 return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
2417 }
2418
2419 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2420 return _allocator->unsafe_max_tlab_alloc();
2421 }
2422
2423 size_t G1CollectedHeap::max_capacity() const {
2424 return _hrm->max_expandable_length() * HeapRegion::GrainBytes;
2425 }
2426
2427 size_t G1CollectedHeap::max_reserved_capacity() const {
2428 return _hrm->max_length() * HeapRegion::GrainBytes;
2429 }
2430
2431 jlong G1CollectedHeap::millis_since_last_gc() {
2432 // See the notes in GenCollectedHeap::millis_since_last_gc()
2433 // for more information about the implementation.
2434 jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) -
2435 _policy->collection_pause_end_millis();
2436 if (ret_val < 0) {
2437 log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
2438 ". returning zero instead.", ret_val);
2439 return 0;
2440 }
2441 return ret_val;
2442 }
2443
2444 void G1CollectedHeap::deduplicate_string(oop str) {
2445 assert(java_lang_String::is_instance(str), "invariant");
2446
2447 if (G1StringDedup::is_enabled()) {
2448 G1StringDedup::deduplicate(str);
2449 }
2450 }
2451
2452 void G1CollectedHeap::prepare_for_verify() {
2453 _verifier->prepare_for_verify();
2454 }
2455
2456 void G1CollectedHeap::verify(VerifyOption vo) {
2457 _verifier->verify(vo);
2458 }
2459
2460 bool G1CollectedHeap::supports_concurrent_gc_breakpoints() const {
2461 return true;
2462 }
2463
2464 bool G1CollectedHeap::is_heterogeneous_heap() const {
2465 return G1Arguments::is_heterogeneous_heap();
2466 }
2467
2468 class PrintRegionClosure: public HeapRegionClosure {
2469 outputStream* _st;
2470 public:
2471 PrintRegionClosure(outputStream* st) : _st(st) {}
2472 bool do_heap_region(HeapRegion* r) {
2473 r->print_on(_st);
2474 return false;
2475 }
2476 };
2477
2478 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2479 const HeapRegion* hr,
2480 const VerifyOption vo) const {
2481 switch (vo) {
2482 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2483 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2484 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr);
2485 default: ShouldNotReachHere();
2486 }
2487 return false; // keep some compilers happy
2488 }
2489
2490 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2491 const VerifyOption vo) const {
2492 switch (vo) {
2493 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2494 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2495 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj);
2496 default: ShouldNotReachHere();
2497 }
2498 return false; // keep some compilers happy
2499 }
2500
2501 void G1CollectedHeap::print_heap_regions() const {
2502 LogTarget(Trace, gc, heap, region) lt;
2503 if (lt.is_enabled()) {
2504 LogStream ls(lt);
2505 print_regions_on(&ls);
2506 }
2507 }
2508
2509 void G1CollectedHeap::print_on(outputStream* st) const {
2510 st->print(" %-20s", "garbage-first heap");
2511 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2512 capacity()/K, used_unlocked()/K);
2513 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")",
2514 p2i(_hrm->reserved().start()),
2515 p2i(_hrm->reserved().end()));
2516 st->cr();
2517 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2518 uint young_regions = young_regions_count();
2519 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2520 (size_t) young_regions * HeapRegion::GrainBytes / K);
2521 uint survivor_regions = survivor_regions_count();
2522 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2523 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2524 st->cr();
2525 if (_numa->is_enabled()) {
2526 uint num_nodes = _numa->num_active_nodes();
2527 st->print(" remaining free region(s) on each NUMA node: ");
2528 const int* node_ids = _numa->node_ids();
2529 for (uint node_index = 0; node_index < num_nodes; node_index++) {
2530 st->print("%d=%u ", node_ids[node_index], _hrm->num_free_regions(node_index));
2531 }
2532 st->cr();
2533 }
2534 MetaspaceUtils::print_on(st);
2535 }
2536
2537 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2538 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2539 "HS=humongous(starts), HC=humongous(continues), "
2540 "CS=collection set, F=free, "
2541 "OA=open archive, CA=closed archive, "
2542 "TAMS=top-at-mark-start (previous, next)");
2543 PrintRegionClosure blk(st);
2544 heap_region_iterate(&blk);
2545 }
2546
2547 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2548 print_on(st);
2549
2550 // Print the per-region information.
2551 print_regions_on(st);
2552 }
2553
2554 void G1CollectedHeap::print_on_error(outputStream* st) const {
2555 this->CollectedHeap::print_on_error(st);
2556
2557 if (_cm != NULL) {
2558 st->cr();
2559 _cm->print_on_error(st);
2560 }
2561 }
2562
2563 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2564 workers()->print_worker_threads_on(st);
2565 _cm_thread->print_on(st);
2566 st->cr();
2567 _cm->print_worker_threads_on(st);
2568 _cr->print_threads_on(st);
2569 _young_gen_sampling_thread->print_on(st);
2570 if (G1StringDedup::is_enabled()) {
2571 G1StringDedup::print_worker_threads_on(st);
2572 }
2573 }
2574
2575 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2576 workers()->threads_do(tc);
2577 tc->do_thread(_cm_thread);
2578 _cm->threads_do(tc);
2579 _cr->threads_do(tc);
2580 tc->do_thread(_young_gen_sampling_thread);
2581 if (G1StringDedup::is_enabled()) {
2582 G1StringDedup::threads_do(tc);
2583 }
2584 }
2585
2586 void G1CollectedHeap::print_tracing_info() const {
2587 rem_set()->print_summary_info();
2588 concurrent_mark()->print_summary_info();
2589 }
2590
2591 #ifndef PRODUCT
2592 // Helpful for debugging RSet issues.
2593
2594 class PrintRSetsClosure : public HeapRegionClosure {
2595 private:
2596 const char* _msg;
2597 size_t _occupied_sum;
2598
2599 public:
2600 bool do_heap_region(HeapRegion* r) {
2601 HeapRegionRemSet* hrrs = r->rem_set();
2602 size_t occupied = hrrs->occupied();
2603 _occupied_sum += occupied;
2604
2605 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2606 if (occupied == 0) {
2607 tty->print_cr(" RSet is empty");
2608 } else {
2609 hrrs->print();
2610 }
2611 tty->print_cr("----------");
2612 return false;
2613 }
2614
2615 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2616 tty->cr();
2617 tty->print_cr("========================================");
2618 tty->print_cr("%s", msg);
2619 tty->cr();
2620 }
2621
2622 ~PrintRSetsClosure() {
2623 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2624 tty->print_cr("========================================");
2625 tty->cr();
2626 }
2627 };
2628
2629 void G1CollectedHeap::print_cset_rsets() {
2630 PrintRSetsClosure cl("Printing CSet RSets");
2631 collection_set_iterate_all(&cl);
2632 }
2633
2634 void G1CollectedHeap::print_all_rsets() {
2635 PrintRSetsClosure cl("Printing All RSets");;
2636 heap_region_iterate(&cl);
2637 }
2638 #endif // PRODUCT
2639
2640 bool G1CollectedHeap::print_location(outputStream* st, void* addr) const {
2641 return BlockLocationPrinter<G1CollectedHeap>::print_location(st, addr);
2642 }
2643
2644 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2645
2646 size_t eden_used_bytes = _eden.used_bytes();
2647 size_t survivor_used_bytes = _survivor.used_bytes();
2648 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2649
2650 size_t eden_capacity_bytes =
2651 (policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2652
2653 VirtualSpaceSummary heap_summary = create_heap_space_summary();
2654 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2655 eden_capacity_bytes, survivor_used_bytes, num_regions());
2656 }
2657
2658 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2659 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2660 stats->unused(), stats->used(), stats->region_end_waste(),
2661 stats->regions_filled(), stats->direct_allocated(),
2662 stats->failure_used(), stats->failure_waste());
2663 }
2664
2665 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2666 const G1HeapSummary& heap_summary = create_g1_heap_summary();
2667 gc_tracer->report_gc_heap_summary(when, heap_summary);
2668
2669 const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2670 gc_tracer->report_metaspace_summary(when, metaspace_summary);
2671 }
2672
2673 G1CollectedHeap* G1CollectedHeap::heap() {
2674 CollectedHeap* heap = Universe::heap();
2675 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2676 assert(heap->kind() == CollectedHeap::G1, "Invalid name");
2677 return (G1CollectedHeap*)heap;
2678 }
2679
2680 void G1CollectedHeap::gc_prologue(bool full) {
2681 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2682
2683 // This summary needs to be printed before incrementing total collections.
2684 rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2685
2686 // Update common counters.
2687 increment_total_collections(full /* full gc */);
2688 if (full || collector_state()->in_initial_mark_gc()) {
2689 increment_old_marking_cycles_started();
2690 }
2691
2692 // Fill TLAB's and such
2693 {
2694 Ticks start = Ticks::now();
2695 ensure_parsability(true);
2696 Tickspan dt = Ticks::now() - start;
2697 phase_times()->record_prepare_tlab_time_ms(dt.seconds() * MILLIUNITS);
2698 }
2699
2700 if (!full) {
2701 // Flush dirty card queues to qset, so later phases don't need to account
2702 // for partially filled per-thread queues and such. Not needed for full
2703 // collections, which ignore those logs.
2704 Ticks start = Ticks::now();
2705 G1BarrierSet::dirty_card_queue_set().concatenate_logs();
2706 Tickspan dt = Ticks::now() - start;
2707 phase_times()->record_concatenate_dirty_card_logs_time_ms(dt.seconds() * MILLIUNITS);
2708 }
2709 }
2710
2711 void G1CollectedHeap::gc_epilogue(bool full) {
2712 // Update common counters.
2713 if (full) {
2714 // Update the number of full collections that have been completed.
2715 increment_old_marking_cycles_completed(false /* concurrent */);
2716 }
2717
2718 // We are at the end of the GC. Total collections has already been increased.
2719 rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2720
2721 // FIXME: what is this about?
2722 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2723 // is set.
2724 #if COMPILER2_OR_JVMCI
2725 assert(DerivedPointerTable::is_empty(), "derived pointer present");
2726 #endif
2727
2728 double start = os::elapsedTime();
2729 resize_all_tlabs();
2730 phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2731
2732 MemoryService::track_memory_usage();
2733 // We have just completed a GC. Update the soft reference
2734 // policy with the new heap occupancy
2735 Universe::update_heap_info_at_gc();
2736
2737 // Print NUMA statistics.
2738 _numa->print_statistics();
2739 }
2740
2741 void G1CollectedHeap::verify_numa_regions(const char* desc) {
2742 LogTarget(Trace, gc, heap, verify) lt;
2743
2744 if (lt.is_enabled()) {
2745 LogStream ls(lt);
2746 // Iterate all heap regions to print matching between preferred numa id and actual numa id.
2747 G1NodeIndexCheckClosure cl(desc, _numa, &ls);
2748 heap_region_iterate(&cl);
2749 }
2750 }
2751
2752 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2753 uint gc_count_before,
2754 bool* succeeded,
2755 GCCause::Cause gc_cause) {
2756 assert_heap_not_locked_and_not_at_safepoint();
2757 VM_G1CollectForAllocation op(word_size,
2758 gc_count_before,
2759 gc_cause,
2760 policy()->max_pause_time_ms());
2761 VMThread::execute(&op);
2762
2763 HeapWord* result = op.result();
2764 bool ret_succeeded = op.prologue_succeeded() && op.gc_succeeded();
2765 assert(result == NULL || ret_succeeded,
2766 "the result should be NULL if the VM did not succeed");
2767 *succeeded = ret_succeeded;
2768
2769 assert_heap_not_locked();
2770 return result;
2771 }
2772
2773 void G1CollectedHeap::do_concurrent_mark() {
2774 MutexLocker x(CGC_lock, Mutex::_no_safepoint_check_flag);
2775 if (!_cm_thread->in_progress()) {
2776 _cm_thread->set_started();
2777 CGC_lock->notify();
2778 }
2779 }
2780
2781 bool G1CollectedHeap::is_potential_eager_reclaim_candidate(HeapRegion* r) const {
2782 // We don't nominate objects with many remembered set entries, on
2783 // the assumption that such objects are likely still live.
2784 HeapRegionRemSet* rem_set = r->rem_set();
2785
2786 return G1EagerReclaimHumongousObjectsWithStaleRefs ?
2787 rem_set->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) :
2788 G1EagerReclaimHumongousObjects && rem_set->is_empty();
2789 }
2790
2791 #ifndef PRODUCT
2792 void G1CollectedHeap::verify_region_attr_remset_update() {
2793 class VerifyRegionAttrRemSet : public HeapRegionClosure {
2794 public:
2795 virtual bool do_heap_region(HeapRegion* r) {
2796 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2797 bool const needs_remset_update = g1h->region_attr(r->bottom()).needs_remset_update();
2798 assert(r->rem_set()->is_tracked() == needs_remset_update,
2799 "Region %u remset tracking status (%s) different to region attribute (%s)",
2800 r->hrm_index(), BOOL_TO_STR(r->rem_set()->is_tracked()), BOOL_TO_STR(needs_remset_update));
2801 return false;
2802 }
2803 } cl;
2804 heap_region_iterate(&cl);
2805 }
2806 #endif
2807
2808 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2809 public:
2810 bool do_heap_region(HeapRegion* hr) {
2811 if (!hr->is_archive() && !hr->is_continues_humongous()) {
2812 hr->verify_rem_set();
2813 }
2814 return false;
2815 }
2816 };
2817
2818 uint G1CollectedHeap::num_task_queues() const {
2819 return _task_queues->size();
2820 }
2821
2822 #if TASKQUEUE_STATS
2823 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2824 st->print_raw_cr("GC Task Stats");
2825 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2826 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2827 }
2828
2829 void G1CollectedHeap::print_taskqueue_stats() const {
2830 if (!log_is_enabled(Trace, gc, task, stats)) {
2831 return;
2832 }
2833 Log(gc, task, stats) log;
2834 ResourceMark rm;
2835 LogStream ls(log.trace());
2836 outputStream* st = &ls;
2837
2838 print_taskqueue_stats_hdr(st);
2839
2840 TaskQueueStats totals;
2841 const uint n = num_task_queues();
2842 for (uint i = 0; i < n; ++i) {
2843 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2844 totals += task_queue(i)->stats;
2845 }
2846 st->print_raw("tot "); totals.print(st); st->cr();
2847
2848 DEBUG_ONLY(totals.verify());
2849 }
2850
2851 void G1CollectedHeap::reset_taskqueue_stats() {
2852 const uint n = num_task_queues();
2853 for (uint i = 0; i < n; ++i) {
2854 task_queue(i)->stats.reset();
2855 }
2856 }
2857 #endif // TASKQUEUE_STATS
2858
2859 void G1CollectedHeap::wait_for_root_region_scanning() {
2860 double scan_wait_start = os::elapsedTime();
2861 // We have to wait until the CM threads finish scanning the
2862 // root regions as it's the only way to ensure that all the
2863 // objects on them have been correctly scanned before we start
2864 // moving them during the GC.
2865 bool waited = _cm->root_regions()->wait_until_scan_finished();
2866 double wait_time_ms = 0.0;
2867 if (waited) {
2868 double scan_wait_end = os::elapsedTime();
2869 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2870 }
2871 phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2872 }
2873
2874 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2875 private:
2876 G1HRPrinter* _hr_printer;
2877 public:
2878 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2879
2880 virtual bool do_heap_region(HeapRegion* r) {
2881 _hr_printer->cset(r);
2882 return false;
2883 }
2884 };
2885
2886 void G1CollectedHeap::start_new_collection_set() {
2887 double start = os::elapsedTime();
2888
2889 collection_set()->start_incremental_building();
2890
2891 clear_region_attr();
2892
2893 guarantee(_eden.length() == 0, "eden should have been cleared");
2894 policy()->transfer_survivors_to_cset(survivor());
2895
2896 // We redo the verification but now wrt to the new CSet which
2897 // has just got initialized after the previous CSet was freed.
2898 _cm->verify_no_collection_set_oops();
2899
2900 phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0);
2901 }
2902
2903 void G1CollectedHeap::calculate_collection_set(G1EvacuationInfo& evacuation_info, double target_pause_time_ms) {
2904
2905 _collection_set.finalize_initial_collection_set(target_pause_time_ms, &_survivor);
2906 evacuation_info.set_collectionset_regions(collection_set()->region_length() +
2907 collection_set()->optional_region_length());
2908
2909 _cm->verify_no_collection_set_oops();
2910
2911 if (_hr_printer.is_active()) {
2912 G1PrintCollectionSetClosure cl(&_hr_printer);
2913 _collection_set.iterate(&cl);
2914 _collection_set.iterate_optional(&cl);
2915 }
2916 }
2917
2918 G1HeapVerifier::G1VerifyType G1CollectedHeap::young_collection_verify_type() const {
2919 if (collector_state()->in_initial_mark_gc()) {
2920 return G1HeapVerifier::G1VerifyConcurrentStart;
2921 } else if (collector_state()->in_young_only_phase()) {
2922 return G1HeapVerifier::G1VerifyYoungNormal;
2923 } else {
2924 return G1HeapVerifier::G1VerifyMixed;
2925 }
2926 }
2927
2928 void G1CollectedHeap::verify_before_young_collection(G1HeapVerifier::G1VerifyType type) {
2929 if (VerifyRememberedSets) {
2930 log_info(gc, verify)("[Verifying RemSets before GC]");
2931 VerifyRegionRemSetClosure v_cl;
2932 heap_region_iterate(&v_cl);
2933 }
2934 _verifier->verify_before_gc(type);
2935 _verifier->check_bitmaps("GC Start");
2936 verify_numa_regions("GC Start");
2937 }
2938
2939 void G1CollectedHeap::verify_after_young_collection(G1HeapVerifier::G1VerifyType type) {
2940 if (VerifyRememberedSets) {
2941 log_info(gc, verify)("[Verifying RemSets after GC]");
2942 VerifyRegionRemSetClosure v_cl;
2943 heap_region_iterate(&v_cl);
2944 }
2945 _verifier->verify_after_gc(type);
2946 _verifier->check_bitmaps("GC End");
2947 verify_numa_regions("GC End");
2948 }
2949
2950 void G1CollectedHeap::expand_heap_after_young_collection(){
2951 size_t expand_bytes = _heap_sizing_policy->expansion_amount();
2952 if (expand_bytes > 0) {
2953 // No need for an ergo logging here,
2954 // expansion_amount() does this when it returns a value > 0.
2955 double expand_ms;
2956 if (!expand(expand_bytes, _workers, &expand_ms)) {
2957 // We failed to expand the heap. Cannot do anything about it.
2958 }
2959 phase_times()->record_expand_heap_time(expand_ms);
2960 }
2961 }
2962
2963 const char* G1CollectedHeap::young_gc_name() const {
2964 if (collector_state()->in_initial_mark_gc()) {
2965 return "Pause Young (Concurrent Start)";
2966 } else if (collector_state()->in_young_only_phase()) {
2967 if (collector_state()->in_young_gc_before_mixed()) {
2968 return "Pause Young (Prepare Mixed)";
2969 } else {
2970 return "Pause Young (Normal)";
2971 }
2972 } else {
2973 return "Pause Young (Mixed)";
2974 }
2975 }
2976
2977 bool G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
2978 assert_at_safepoint_on_vm_thread();
2979 guarantee(!is_gc_active(), "collection is not reentrant");
2980
2981 if (GCLocker::check_active_before_gc()) {
2982 return false;
2983 }
2984
2985 do_collection_pause_at_safepoint_helper(target_pause_time_ms);
2986 if (should_upgrade_to_full_gc(gc_cause())) {
2987 log_info(gc, ergo)("Attempting maximally compacting collection");
2988 bool result = do_full_collection(false /* explicit gc */,
2989 true /* clear_all_soft_refs */);
2990 // do_full_collection only fails if blocked by GC locker, but
2991 // we've already checked for that above.
2992 assert(result, "invariant");
2993 }
2994 return true;
2995 }
2996
2997 void G1CollectedHeap::do_collection_pause_at_safepoint_helper(double target_pause_time_ms) {
2998 GCIdMark gc_id_mark;
2999
3000 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3001 ResourceMark rm;
3002
3003 policy()->note_gc_start();
3004
3005 _gc_timer_stw->register_gc_start();
3006 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3007
3008 wait_for_root_region_scanning();
3009
3010 print_heap_before_gc();
3011 print_heap_regions();
3012 trace_heap_before_gc(_gc_tracer_stw);
3013
3014 _verifier->verify_region_sets_optional();
3015 _verifier->verify_dirty_young_regions();
3016
3017 // We should not be doing initial mark unless the conc mark thread is running
3018 if (!_cm_thread->should_terminate()) {
3019 // This call will decide whether this pause is an initial-mark
3020 // pause. If it is, in_initial_mark_gc() will return true
3021 // for the duration of this pause.
3022 policy()->decide_on_conc_mark_initiation();
3023 }
3024
3025 // We do not allow initial-mark to be piggy-backed on a mixed GC.
3026 assert(!collector_state()->in_initial_mark_gc() ||
3027 collector_state()->in_young_only_phase(), "sanity");
3028 // We also do not allow mixed GCs during marking.
3029 assert(!collector_state()->mark_or_rebuild_in_progress() || collector_state()->in_young_only_phase(), "sanity");
3030
3031 // Record whether this pause is an initial mark. When the current
3032 // thread has completed its logging output and it's safe to signal
3033 // the CM thread, the flag's value in the policy has been reset.
3034 bool should_start_conc_mark = collector_state()->in_initial_mark_gc();
3035 if (should_start_conc_mark) {
3036 _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
3037 }
3038
3039 // Inner scope for scope based logging, timers, and stats collection
3040 {
3041 G1EvacuationInfo evacuation_info;
3042
3043 _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
3044
3045 GCTraceCPUTime tcpu;
3046
3047 GCTraceTime(Info, gc) tm(young_gc_name(), NULL, gc_cause(), true);
3048
3049 uint active_workers = WorkerPolicy::calc_active_workers(workers()->total_workers(),
3050 workers()->active_workers(),
3051 Threads::number_of_non_daemon_threads());
3052 active_workers = workers()->update_active_workers(active_workers);
3053 log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
3054
3055 G1MonitoringScope ms(g1mm(),
3056 false /* full_gc */,
3057 collector_state()->yc_type() == Mixed /* all_memory_pools_affected */);
3058
3059 G1HeapTransition heap_transition(this);
3060
3061 {
3062 IsGCActiveMark x;
3063
3064 gc_prologue(false);
3065
3066 G1HeapVerifier::G1VerifyType verify_type = young_collection_verify_type();
3067 verify_before_young_collection(verify_type);
3068
3069 {
3070 // The elapsed time induced by the start time below deliberately elides
3071 // the possible verification above.
3072 double sample_start_time_sec = os::elapsedTime();
3073
3074 // Please see comment in g1CollectedHeap.hpp and
3075 // G1CollectedHeap::ref_processing_init() to see how
3076 // reference processing currently works in G1.
3077 _ref_processor_stw->enable_discovery();
3078
3079 // We want to temporarily turn off discovery by the
3080 // CM ref processor, if necessary, and turn it back on
3081 // on again later if we do. Using a scoped
3082 // NoRefDiscovery object will do this.
3083 NoRefDiscovery no_cm_discovery(_ref_processor_cm);
3084
3085 policy()->record_collection_pause_start(sample_start_time_sec);
3086
3087 // Forget the current allocation region (we might even choose it to be part
3088 // of the collection set!).
3089 _allocator->release_mutator_alloc_regions();
3090
3091 calculate_collection_set(evacuation_info, target_pause_time_ms);
3092
3093 G1RedirtyCardsQueueSet rdcqs(G1BarrierSet::dirty_card_queue_set().allocator());
3094 G1ParScanThreadStateSet per_thread_states(this,
3095 &rdcqs,
3096 workers()->active_workers(),
3097 collection_set()->young_region_length(),
3098 collection_set()->optional_region_length());
3099 pre_evacuate_collection_set(evacuation_info, &per_thread_states);
3100
3101 // Actually do the work...
3102 evacuate_initial_collection_set(&per_thread_states);
3103
3104 if (_collection_set.optional_region_length() != 0) {
3105 evacuate_optional_collection_set(&per_thread_states);
3106 }
3107 post_evacuate_collection_set(evacuation_info, &rdcqs, &per_thread_states);
3108
3109 start_new_collection_set();
3110
3111 _survivor_evac_stats.adjust_desired_plab_sz();
3112 _old_evac_stats.adjust_desired_plab_sz();
3113
3114 if (should_start_conc_mark) {
3115 // We have to do this before we notify the CM threads that
3116 // they can start working to make sure that all the
3117 // appropriate initialization is done on the CM object.
3118 concurrent_mark()->post_initial_mark();
3119 // Note that we don't actually trigger the CM thread at
3120 // this point. We do that later when we're sure that
3121 // the current thread has completed its logging output.
3122 }
3123
3124 allocate_dummy_regions();
3125
3126 _allocator->init_mutator_alloc_regions();
3127
3128 expand_heap_after_young_collection();
3129
3130 double sample_end_time_sec = os::elapsedTime();
3131 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3132 policy()->record_collection_pause_end(pause_time_ms);
3133 }
3134
3135 verify_after_young_collection(verify_type);
3136
3137 gc_epilogue(false);
3138 }
3139
3140 // Print the remainder of the GC log output.
3141 if (evacuation_failed()) {
3142 log_info(gc)("To-space exhausted");
3143 }
3144
3145 policy()->print_phases();
3146 heap_transition.print();
3147
3148 _hrm->verify_optional();
3149 _verifier->verify_region_sets_optional();
3150
3151 TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3152 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3153
3154 print_heap_after_gc();
3155 print_heap_regions();
3156 trace_heap_after_gc(_gc_tracer_stw);
3157
3158 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3159 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3160 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3161 // before any GC notifications are raised.
3162 g1mm()->update_sizes();
3163
3164 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3165 _gc_tracer_stw->report_tenuring_threshold(_policy->tenuring_threshold());
3166 _gc_timer_stw->register_gc_end();
3167 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3168 }
3169 // It should now be safe to tell the concurrent mark thread to start
3170 // without its logging output interfering with the logging output
3171 // that came from the pause.
3172
3173 if (should_start_conc_mark) {
3174 // CAUTION: after the doConcurrentMark() call below, the concurrent marking
3175 // thread(s) could be running concurrently with us. Make sure that anything
3176 // after this point does not assume that we are the only GC thread running.
3177 // Note: of course, the actual marking work will not start until the safepoint
3178 // itself is released in SuspendibleThreadSet::desynchronize().
3179 do_concurrent_mark();
3180 ConcurrentGCBreakpoints::notify_idle_to_active();
3181 }
3182 }
3183
3184 void G1CollectedHeap::remove_self_forwarding_pointers(G1RedirtyCardsQueueSet* rdcqs) {
3185 G1ParRemoveSelfForwardPtrsTask rsfp_task(rdcqs);
3186 workers()->run_task(&rsfp_task);
3187 }
3188
3189 void G1CollectedHeap::restore_after_evac_failure(G1RedirtyCardsQueueSet* rdcqs) {
3190 double remove_self_forwards_start = os::elapsedTime();
3191
3192 remove_self_forwarding_pointers(rdcqs);
3193 _preserved_marks_set.restore(workers());
3194
3195 phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3196 }
3197
3198 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markWord m) {
3199 if (!_evacuation_failed) {
3200 _evacuation_failed = true;
3201 }
3202
3203 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3204 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3205 }
3206
3207 bool G1ParEvacuateFollowersClosure::offer_termination() {
3208 EventGCPhaseParallel event;
3209 G1ParScanThreadState* const pss = par_scan_state();
3210 start_term_time();
3211 const bool res = terminator()->offer_termination();
3212 end_term_time();
3213 event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(G1GCPhaseTimes::Termination));
3214 return res;
3215 }
3216
3217 void G1ParEvacuateFollowersClosure::do_void() {
3218 EventGCPhaseParallel event;
3219 G1ParScanThreadState* const pss = par_scan_state();
3220 pss->trim_queue();
3221 event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(_phase));
3222 do {
3223 EventGCPhaseParallel event;
3224 pss->steal_and_trim_queue(queues());
3225 event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(_phase));
3226 } while (!offer_termination());
3227 }
3228
3229 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
3230 bool class_unloading_occurred) {
3231 uint num_workers = workers()->active_workers();
3232 G1ParallelCleaningTask unlink_task(is_alive, num_workers, class_unloading_occurred, false);
3233 workers()->run_task(&unlink_task);
3234 }
3235
3236 // Clean string dedup data structures.
3237 // Ideally we would prefer to use a StringDedupCleaningTask here, but we want to
3238 // record the durations of the phases. Hence the almost-copy.
3239 class G1StringDedupCleaningTask : public AbstractGangTask {
3240 BoolObjectClosure* _is_alive;
3241 OopClosure* _keep_alive;
3242 G1GCPhaseTimes* _phase_times;
3243
3244 public:
3245 G1StringDedupCleaningTask(BoolObjectClosure* is_alive,
3246 OopClosure* keep_alive,
3247 G1GCPhaseTimes* phase_times) :
3248 AbstractGangTask("Partial Cleaning Task"),
3249 _is_alive(is_alive),
3250 _keep_alive(keep_alive),
3251 _phase_times(phase_times)
3252 {
3253 assert(G1StringDedup::is_enabled(), "String deduplication disabled.");
3254 StringDedup::gc_prologue(true);
3255 }
3256
3257 ~G1StringDedupCleaningTask() {
3258 StringDedup::gc_epilogue();
3259 }
3260
3261 void work(uint worker_id) {
3262 StringDedupUnlinkOrOopsDoClosure cl(_is_alive, _keep_alive);
3263 {
3264 G1GCParPhaseTimesTracker x(_phase_times, G1GCPhaseTimes::StringDedupQueueFixup, worker_id);
3265 StringDedupQueue::unlink_or_oops_do(&cl);
3266 }
3267 {
3268 G1GCParPhaseTimesTracker x(_phase_times, G1GCPhaseTimes::StringDedupTableFixup, worker_id);
3269 StringDedupTable::unlink_or_oops_do(&cl, worker_id);
3270 }
3271 }
3272 };
3273
3274 void G1CollectedHeap::string_dedup_cleaning(BoolObjectClosure* is_alive,
3275 OopClosure* keep_alive,
3276 G1GCPhaseTimes* phase_times) {
3277 G1StringDedupCleaningTask cl(is_alive, keep_alive, phase_times);
3278 workers()->run_task(&cl);
3279 }
3280
3281 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3282 private:
3283 G1RedirtyCardsQueueSet* _qset;
3284 G1CollectedHeap* _g1h;
3285 BufferNode* volatile _nodes;
3286
3287 void par_apply(RedirtyLoggedCardTableEntryClosure* cl, uint worker_id) {
3288 size_t buffer_size = _qset->buffer_size();
3289 BufferNode* next = Atomic::load(&_nodes);
3290 while (next != NULL) {
3291 BufferNode* node = next;
3292 next = Atomic::cmpxchg(&_nodes, node, node->next());
3293 if (next == node) {
3294 cl->apply_to_buffer(node, buffer_size, worker_id);
3295 next = node->next();
3296 }
3297 }
3298 }
3299
3300 public:
3301 G1RedirtyLoggedCardsTask(G1RedirtyCardsQueueSet* qset, G1CollectedHeap* g1h) :
3302 AbstractGangTask("Redirty Cards"),
3303 _qset(qset), _g1h(g1h), _nodes(qset->all_completed_buffers()) { }
3304
3305 virtual void work(uint worker_id) {
3306 G1GCPhaseTimes* p = _g1h->phase_times();
3307 G1GCParPhaseTimesTracker x(p, G1GCPhaseTimes::RedirtyCards, worker_id);
3308
3309 RedirtyLoggedCardTableEntryClosure cl(_g1h);
3310 par_apply(&cl, worker_id);
3311
3312 p->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3313 }
3314 };
3315
3316 void G1CollectedHeap::redirty_logged_cards(G1RedirtyCardsQueueSet* rdcqs) {
3317 double redirty_logged_cards_start = os::elapsedTime();
3318
3319 G1RedirtyLoggedCardsTask redirty_task(rdcqs, this);
3320 workers()->run_task(&redirty_task);
3321
3322 G1DirtyCardQueueSet& dcq = G1BarrierSet::dirty_card_queue_set();
3323 dcq.merge_bufferlists(rdcqs);
3324
3325 phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3326 }
3327
3328 // Weak Reference Processing support
3329
3330 bool G1STWIsAliveClosure::do_object_b(oop p) {
3331 // An object is reachable if it is outside the collection set,
3332 // or is inside and copied.
3333 return !_g1h->is_in_cset(p) || p->is_forwarded();
3334 }
3335
3336 bool G1STWSubjectToDiscoveryClosure::do_object_b(oop obj) {
3337 assert(obj != NULL, "must not be NULL");
3338 assert(_g1h->is_in_reserved(obj), "Trying to discover obj " PTR_FORMAT " not in heap", p2i(obj));
3339 // The areas the CM and STW ref processor manage must be disjoint. The is_in_cset() below
3340 // may falsely indicate that this is not the case here: however the collection set only
3341 // contains old regions when concurrent mark is not running.
3342 return _g1h->is_in_cset(obj) || _g1h->heap_region_containing(obj)->is_survivor();
3343 }
3344
3345 // Non Copying Keep Alive closure
3346 class G1KeepAliveClosure: public OopClosure {
3347 G1CollectedHeap*_g1h;
3348 public:
3349 G1KeepAliveClosure(G1CollectedHeap* g1h) :_g1h(g1h) {}
3350 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3351 void do_oop(oop* p) {
3352 oop obj = *p;
3353 assert(obj != NULL, "the caller should have filtered out NULL values");
3354
3355 const G1HeapRegionAttr region_attr =_g1h->region_attr(obj);
3356 if (!region_attr.is_in_cset_or_humongous()) {
3357 return;
3358 }
3359 if (region_attr.is_in_cset()) {
3360 assert( obj->is_forwarded(), "invariant" );
3361 *p = obj->forwardee();
3362 } else {
3363 assert(!obj->is_forwarded(), "invariant" );
3364 assert(region_attr.is_humongous(),
3365 "Only allowed G1HeapRegionAttr state is IsHumongous, but is %d", region_attr.type());
3366 _g1h->set_humongous_is_live(obj);
3367 }
3368 }
3369 };
3370
3371 // Copying Keep Alive closure - can be called from both
3372 // serial and parallel code as long as different worker
3373 // threads utilize different G1ParScanThreadState instances
3374 // and different queues.
3375
3376 class G1CopyingKeepAliveClosure: public OopClosure {
3377 G1CollectedHeap* _g1h;
3378 G1ParScanThreadState* _par_scan_state;
3379
3380 public:
3381 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3382 G1ParScanThreadState* pss):
3383 _g1h(g1h),
3384 _par_scan_state(pss)
3385 {}
3386
3387 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3388 virtual void do_oop( oop* p) { do_oop_work(p); }
3389
3390 template <class T> void do_oop_work(T* p) {
3391 oop obj = RawAccess<>::oop_load(p);
3392
3393 if (_g1h->is_in_cset_or_humongous(obj)) {
3394 // If the referent object has been forwarded (either copied
3395 // to a new location or to itself in the event of an
3396 // evacuation failure) then we need to update the reference
3397 // field and, if both reference and referent are in the G1
3398 // heap, update the RSet for the referent.
3399 //
3400 // If the referent has not been forwarded then we have to keep
3401 // it alive by policy. Therefore we have copy the referent.
3402 //
3403 // When the queue is drained (after each phase of reference processing)
3404 // the object and it's followers will be copied, the reference field set
3405 // to point to the new location, and the RSet updated.
3406 _par_scan_state->push_on_queue(p);
3407 }
3408 }
3409 };
3410
3411 // Serial drain queue closure. Called as the 'complete_gc'
3412 // closure for each discovered list in some of the
3413 // reference processing phases.
3414
3415 class G1STWDrainQueueClosure: public VoidClosure {
3416 protected:
3417 G1CollectedHeap* _g1h;
3418 G1ParScanThreadState* _par_scan_state;
3419
3420 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
3421
3422 public:
3423 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
3424 _g1h(g1h),
3425 _par_scan_state(pss)
3426 { }
3427
3428 void do_void() {
3429 G1ParScanThreadState* const pss = par_scan_state();
3430 pss->trim_queue();
3431 }
3432 };
3433
3434 // Parallel Reference Processing closures
3435
3436 // Implementation of AbstractRefProcTaskExecutor for parallel reference
3437 // processing during G1 evacuation pauses.
3438
3439 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
3440 private:
3441 G1CollectedHeap* _g1h;
3442 G1ParScanThreadStateSet* _pss;
3443 RefToScanQueueSet* _queues;
3444 WorkGang* _workers;
3445
3446 public:
3447 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
3448 G1ParScanThreadStateSet* per_thread_states,
3449 WorkGang* workers,
3450 RefToScanQueueSet *task_queues) :
3451 _g1h(g1h),
3452 _pss(per_thread_states),
3453 _queues(task_queues),
3454 _workers(workers)
3455 {
3456 g1h->ref_processor_stw()->set_active_mt_degree(workers->active_workers());
3457 }
3458
3459 // Executes the given task using concurrent marking worker threads.
3460 virtual void execute(ProcessTask& task, uint ergo_workers);
3461 };
3462
3463 // Gang task for possibly parallel reference processing
3464
3465 class G1STWRefProcTaskProxy: public AbstractGangTask {
3466 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
3467 ProcessTask& _proc_task;
3468 G1CollectedHeap* _g1h;
3469 G1ParScanThreadStateSet* _pss;
3470 RefToScanQueueSet* _task_queues;
3471 TaskTerminator* _terminator;
3472
3473 public:
3474 G1STWRefProcTaskProxy(ProcessTask& proc_task,
3475 G1CollectedHeap* g1h,
3476 G1ParScanThreadStateSet* per_thread_states,
3477 RefToScanQueueSet *task_queues,
3478 TaskTerminator* terminator) :
3479 AbstractGangTask("Process reference objects in parallel"),
3480 _proc_task(proc_task),
3481 _g1h(g1h),
3482 _pss(per_thread_states),
3483 _task_queues(task_queues),
3484 _terminator(terminator)
3485 {}
3486
3487 virtual void work(uint worker_id) {
3488 // The reference processing task executed by a single worker.
3489 ResourceMark rm;
3490 HandleMark hm;
3491
3492 G1STWIsAliveClosure is_alive(_g1h);
3493
3494 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
3495 pss->set_ref_discoverer(NULL);
3496
3497 // Keep alive closure.
3498 G1CopyingKeepAliveClosure keep_alive(_g1h, pss);
3499
3500 // Complete GC closure
3501 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator, G1GCPhaseTimes::ObjCopy);
3502
3503 // Call the reference processing task's work routine.
3504 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
3505
3506 // Note we cannot assert that the refs array is empty here as not all
3507 // of the processing tasks (specifically phase2 - pp2_work) execute
3508 // the complete_gc closure (which ordinarily would drain the queue) so
3509 // the queue may not be empty.
3510 }
3511 };
3512
3513 // Driver routine for parallel reference processing.
3514 // Creates an instance of the ref processing gang
3515 // task and has the worker threads execute it.
3516 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task, uint ergo_workers) {
3517 assert(_workers != NULL, "Need parallel worker threads.");
3518
3519 assert(_workers->active_workers() >= ergo_workers,
3520 "Ergonomically chosen workers (%u) should be less than or equal to active workers (%u)",
3521 ergo_workers, _workers->active_workers());
3522 TaskTerminator terminator(ergo_workers, _queues);
3523 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
3524
3525 _workers->run_task(&proc_task_proxy, ergo_workers);
3526 }
3527
3528 // End of weak reference support closures
3529
3530 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
3531 double ref_proc_start = os::elapsedTime();
3532
3533 ReferenceProcessor* rp = _ref_processor_stw;
3534 assert(rp->discovery_enabled(), "should have been enabled");
3535
3536 // Closure to test whether a referent is alive.
3537 G1STWIsAliveClosure is_alive(this);
3538
3539 // Even when parallel reference processing is enabled, the processing
3540 // of JNI refs is serial and performed serially by the current thread
3541 // rather than by a worker. The following PSS will be used for processing
3542 // JNI refs.
3543
3544 // Use only a single queue for this PSS.
3545 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0);
3546 pss->set_ref_discoverer(NULL);
3547 assert(pss->queue_is_empty(), "pre-condition");
3548
3549 // Keep alive closure.
3550 G1CopyingKeepAliveClosure keep_alive(this, pss);
3551
3552 // Serial Complete GC closure
3553 G1STWDrainQueueClosure drain_queue(this, pss);
3554
3555 // Setup the soft refs policy...
3556 rp->setup_policy(false);
3557
3558 ReferenceProcessorPhaseTimes* pt = phase_times()->ref_phase_times();
3559
3560 ReferenceProcessorStats stats;
3561 if (!rp->processing_is_mt()) {
3562 // Serial reference processing...
3563 stats = rp->process_discovered_references(&is_alive,
3564 &keep_alive,
3565 &drain_queue,
3566 NULL,
3567 pt);
3568 } else {
3569 uint no_of_gc_workers = workers()->active_workers();
3570
3571 // Parallel reference processing
3572 assert(no_of_gc_workers <= rp->max_num_queues(),
3573 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
3574 no_of_gc_workers, rp->max_num_queues());
3575
3576 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues);
3577 stats = rp->process_discovered_references(&is_alive,
3578 &keep_alive,
3579 &drain_queue,
3580 &par_task_executor,
3581 pt);
3582 }
3583
3584 _gc_tracer_stw->report_gc_reference_stats(stats);
3585
3586 // We have completed copying any necessary live referent objects.
3587 assert(pss->queue_is_empty(), "both queue and overflow should be empty");
3588
3589 make_pending_list_reachable();
3590
3591 assert(!rp->discovery_enabled(), "Postcondition");
3592 rp->verify_no_references_recorded();
3593
3594 double ref_proc_time = os::elapsedTime() - ref_proc_start;
3595 phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
3596 }
3597
3598 void G1CollectedHeap::make_pending_list_reachable() {
3599 if (collector_state()->in_initial_mark_gc()) {
3600 oop pll_head = Universe::reference_pending_list();
3601 if (pll_head != NULL) {
3602 // Any valid worker id is fine here as we are in the VM thread and single-threaded.
3603 _cm->mark_in_next_bitmap(0 /* worker_id */, pll_head);
3604 }
3605 }
3606 }
3607
3608 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
3609 Ticks start = Ticks::now();
3610 per_thread_states->flush();
3611 phase_times()->record_or_add_time_secs(G1GCPhaseTimes::MergePSS, 0 /* worker_id */, (Ticks::now() - start).seconds());
3612 }
3613
3614 class G1PrepareEvacuationTask : public AbstractGangTask {
3615 class G1PrepareRegionsClosure : public HeapRegionClosure {
3616 G1CollectedHeap* _g1h;
3617 G1PrepareEvacuationTask* _parent_task;
3618 size_t _worker_humongous_total;
3619 size_t _worker_humongous_candidates;
3620
3621 bool humongous_region_is_candidate(HeapRegion* region) const {
3622 assert(region->is_starts_humongous(), "Must start a humongous object");
3623
3624 oop obj = oop(region->bottom());
3625
3626 // Dead objects cannot be eager reclaim candidates. Due to class
3627 // unloading it is unsafe to query their classes so we return early.
3628 if (_g1h->is_obj_dead(obj, region)) {
3629 return false;
3630 }
3631
3632 // If we do not have a complete remembered set for the region, then we can
3633 // not be sure that we have all references to it.
3634 if (!region->rem_set()->is_complete()) {
3635 return false;
3636 }
3637 // Candidate selection must satisfy the following constraints
3638 // while concurrent marking is in progress:
3639 //
3640 // * In order to maintain SATB invariants, an object must not be
3641 // reclaimed if it was allocated before the start of marking and
3642 // has not had its references scanned. Such an object must have
3643 // its references (including type metadata) scanned to ensure no
3644 // live objects are missed by the marking process. Objects
3645 // allocated after the start of concurrent marking don't need to
3646 // be scanned.
3647 //
3648 // * An object must not be reclaimed if it is on the concurrent
3649 // mark stack. Objects allocated after the start of concurrent
3650 // marking are never pushed on the mark stack.
3651 //
3652 // Nominating only objects allocated after the start of concurrent
3653 // marking is sufficient to meet both constraints. This may miss
3654 // some objects that satisfy the constraints, but the marking data
3655 // structures don't support efficiently performing the needed
3656 // additional tests or scrubbing of the mark stack.
3657 //
3658 // However, we presently only nominate is_typeArray() objects.
3659 // A humongous object containing references induces remembered
3660 // set entries on other regions. In order to reclaim such an
3661 // object, those remembered sets would need to be cleaned up.
3662 //
3663 // We also treat is_typeArray() objects specially, allowing them
3664 // to be reclaimed even if allocated before the start of
3665 // concurrent mark. For this we rely on mark stack insertion to
3666 // exclude is_typeArray() objects, preventing reclaiming an object
3667 // that is in the mark stack. We also rely on the metadata for
3668 // such objects to be built-in and so ensured to be kept live.
3669 // Frequent allocation and drop of large binary blobs is an
3670 // important use case for eager reclaim, and this special handling
3671 // may reduce needed headroom.
3672
3673 return obj->is_typeArray() &&
3674 _g1h->is_potential_eager_reclaim_candidate(region);
3675 }
3676
3677 public:
3678 G1PrepareRegionsClosure(G1CollectedHeap* g1h, G1PrepareEvacuationTask* parent_task) :
3679 _g1h(g1h),
3680 _parent_task(parent_task),
3681 _worker_humongous_total(0),
3682 _worker_humongous_candidates(0) { }
3683
3684 ~G1PrepareRegionsClosure() {
3685 _parent_task->add_humongous_candidates(_worker_humongous_candidates);
3686 _parent_task->add_humongous_total(_worker_humongous_total);
3687 }
3688
3689 virtual bool do_heap_region(HeapRegion* hr) {
3690 // First prepare the region for scanning
3691 _g1h->rem_set()->prepare_region_for_scan(hr);
3692
3693 // Now check if region is a humongous candidate
3694 if (!hr->is_starts_humongous()) {
3695 _g1h->register_region_with_region_attr(hr);
3696 return false;
3697 }
3698
3699 uint index = hr->hrm_index();
3700 if (humongous_region_is_candidate(hr)) {
3701 _g1h->set_humongous_reclaim_candidate(index, true);
3702 _g1h->register_humongous_region_with_region_attr(index);
3703 _worker_humongous_candidates++;
3704 // We will later handle the remembered sets of these regions.
3705 } else {
3706 _g1h->set_humongous_reclaim_candidate(index, false);
3707 _g1h->register_region_with_region_attr(hr);
3708 }
3709 _worker_humongous_total++;
3710
3711 return false;
3712 }
3713 };
3714
3715 G1CollectedHeap* _g1h;
3716 HeapRegionClaimer _claimer;
3717 volatile size_t _humongous_total;
3718 volatile size_t _humongous_candidates;
3719 public:
3720 G1PrepareEvacuationTask(G1CollectedHeap* g1h) :
3721 AbstractGangTask("Prepare Evacuation"),
3722 _g1h(g1h),
3723 _claimer(_g1h->workers()->active_workers()),
3724 _humongous_total(0),
3725 _humongous_candidates(0) { }
3726
3727 ~G1PrepareEvacuationTask() {
3728 _g1h->set_has_humongous_reclaim_candidate(_humongous_candidates > 0);
3729 }
3730
3731 void work(uint worker_id) {
3732 G1PrepareRegionsClosure cl(_g1h, this);
3733 _g1h->heap_region_par_iterate_from_worker_offset(&cl, &_claimer, worker_id);
3734 }
3735
3736 void add_humongous_candidates(size_t candidates) {
3737 Atomic::add(&_humongous_candidates, candidates);
3738 }
3739
3740 void add_humongous_total(size_t total) {
3741 Atomic::add(&_humongous_total, total);
3742 }
3743
3744 size_t humongous_candidates() {
3745 return _humongous_candidates;
3746 }
3747
3748 size_t humongous_total() {
3749 return _humongous_total;
3750 }
3751 };
3752
3753 void G1CollectedHeap::pre_evacuate_collection_set(G1EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
3754 _bytes_used_during_gc = 0;
3755
3756 _expand_heap_after_alloc_failure = true;
3757 _evacuation_failed = false;
3758
3759 // Disable the hot card cache.
3760 _hot_card_cache->reset_hot_cache_claimed_index();
3761 _hot_card_cache->set_use_cache(false);
3762
3763 // Initialize the GC alloc regions.
3764 _allocator->init_gc_alloc_regions(evacuation_info);
3765
3766 {
3767 Ticks start = Ticks::now();
3768 rem_set()->prepare_for_scan_heap_roots();
3769 phase_times()->record_prepare_heap_roots_time_ms((Ticks::now() - start).seconds() * 1000.0);
3770 }
3771
3772 {
3773 G1PrepareEvacuationTask g1_prep_task(this);
3774 Tickspan task_time = run_task_timed(&g1_prep_task);
3775
3776 phase_times()->record_register_regions(task_time.seconds() * 1000.0,
3777 g1_prep_task.humongous_total(),
3778 g1_prep_task.humongous_candidates());
3779 }
3780
3781 assert(_verifier->check_region_attr_table(), "Inconsistency in the region attributes table.");
3782 _preserved_marks_set.assert_empty();
3783
3784 #if COMPILER2_OR_JVMCI
3785 DerivedPointerTable::clear();
3786 #endif
3787
3788 // InitialMark needs claim bits to keep track of the marked-through CLDs.
3789 if (collector_state()->in_initial_mark_gc()) {
3790 concurrent_mark()->pre_initial_mark();
3791
3792 double start_clear_claimed_marks = os::elapsedTime();
3793
3794 ClassLoaderDataGraph::clear_claimed_marks();
3795
3796 double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
3797 phase_times()->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
3798 }
3799
3800 // Should G1EvacuationFailureALot be in effect for this GC?
3801 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
3802 }
3803
3804 class G1EvacuateRegionsBaseTask : public AbstractGangTask {
3805 protected:
3806 G1CollectedHeap* _g1h;
3807 G1ParScanThreadStateSet* _per_thread_states;
3808 RefToScanQueueSet* _task_queues;
3809 TaskTerminator _terminator;
3810 uint _num_workers;
3811
3812 void evacuate_live_objects(G1ParScanThreadState* pss,
3813 uint worker_id,
3814 G1GCPhaseTimes::GCParPhases objcopy_phase,
3815 G1GCPhaseTimes::GCParPhases termination_phase) {
3816 G1GCPhaseTimes* p = _g1h->phase_times();
3817
3818 Ticks start = Ticks::now();
3819 G1ParEvacuateFollowersClosure cl(_g1h, pss, _task_queues, &_terminator, objcopy_phase);
3820 cl.do_void();
3821
3822 assert(pss->queue_is_empty(), "should be empty");
3823
3824 Tickspan evac_time = (Ticks::now() - start);
3825 p->record_or_add_time_secs(objcopy_phase, worker_id, evac_time.seconds() - cl.term_time());
3826
3827 if (termination_phase == G1GCPhaseTimes::Termination) {
3828 p->record_time_secs(termination_phase, worker_id, cl.term_time());
3829 p->record_thread_work_item(termination_phase, worker_id, cl.term_attempts());
3830 } else {
3831 p->record_or_add_time_secs(termination_phase, worker_id, cl.term_time());
3832 p->record_or_add_thread_work_item(termination_phase, worker_id, cl.term_attempts());
3833 }
3834 assert(pss->trim_ticks().seconds() == 0.0, "Unexpected partial trimming during evacuation");
3835 }
3836
3837 virtual void start_work(uint worker_id) { }
3838
3839 virtual void end_work(uint worker_id) { }
3840
3841 virtual void scan_roots(G1ParScanThreadState* pss, uint worker_id) = 0;
3842
3843 virtual void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) = 0;
3844
3845 public:
3846 G1EvacuateRegionsBaseTask(const char* name, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet* task_queues, uint num_workers) :
3847 AbstractGangTask(name),
3848 _g1h(G1CollectedHeap::heap()),
3849 _per_thread_states(per_thread_states),
3850 _task_queues(task_queues),
3851 _terminator(num_workers, _task_queues),
3852 _num_workers(num_workers)
3853 { }
3854
3855 void work(uint worker_id) {
3856 start_work(worker_id);
3857
3858 {
3859 ResourceMark rm;
3860 HandleMark hm;
3861
3862 G1ParScanThreadState* pss = _per_thread_states->state_for_worker(worker_id);
3863 pss->set_ref_discoverer(_g1h->ref_processor_stw());
3864
3865 scan_roots(pss, worker_id);
3866 evacuate_live_objects(pss, worker_id);
3867 }
3868
3869 end_work(worker_id);
3870 }
3871 };
3872
3873 class G1EvacuateRegionsTask : public G1EvacuateRegionsBaseTask {
3874 G1RootProcessor* _root_processor;
3875
3876 void scan_roots(G1ParScanThreadState* pss, uint worker_id) {
3877 _root_processor->evacuate_roots(pss, worker_id);
3878 _g1h->rem_set()->scan_heap_roots(pss, worker_id, G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::ObjCopy);
3879 _g1h->rem_set()->scan_collection_set_regions(pss, worker_id, G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::CodeRoots, G1GCPhaseTimes::ObjCopy);
3880 }
3881
3882 void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) {
3883 G1EvacuateRegionsBaseTask::evacuate_live_objects(pss, worker_id, G1GCPhaseTimes::ObjCopy, G1GCPhaseTimes::Termination);
3884 }
3885
3886 void start_work(uint worker_id) {
3887 _g1h->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, Ticks::now().seconds());
3888 }
3889
3890 void end_work(uint worker_id) {
3891 _g1h->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, Ticks::now().seconds());
3892 }
3893
3894 public:
3895 G1EvacuateRegionsTask(G1CollectedHeap* g1h,
3896 G1ParScanThreadStateSet* per_thread_states,
3897 RefToScanQueueSet* task_queues,
3898 G1RootProcessor* root_processor,
3899 uint num_workers) :
3900 G1EvacuateRegionsBaseTask("G1 Evacuate Regions", per_thread_states, task_queues, num_workers),
3901 _root_processor(root_processor)
3902 { }
3903 };
3904
3905 void G1CollectedHeap::evacuate_initial_collection_set(G1ParScanThreadStateSet* per_thread_states) {
3906 G1GCPhaseTimes* p = phase_times();
3907
3908 {
3909 Ticks start = Ticks::now();
3910 rem_set()->merge_heap_roots(true /* initial_evacuation */);
3911 p->record_merge_heap_roots_time((Ticks::now() - start).seconds() * 1000.0);
3912 }
3913
3914 Tickspan task_time;
3915 const uint num_workers = workers()->active_workers();
3916
3917 Ticks start_processing = Ticks::now();
3918 {
3919 G1RootProcessor root_processor(this, num_workers);
3920 G1EvacuateRegionsTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, num_workers);
3921 task_time = run_task_timed(&g1_par_task);
3922 // Closing the inner scope will execute the destructor for the G1RootProcessor object.
3923 // To extract its code root fixup time we measure total time of this scope and
3924 // subtract from the time the WorkGang task took.
3925 }
3926 Tickspan total_processing = Ticks::now() - start_processing;
3927
3928 p->record_initial_evac_time(task_time.seconds() * 1000.0);
3929 p->record_or_add_code_root_fixup_time((total_processing - task_time).seconds() * 1000.0);
3930 }
3931
3932 class G1EvacuateOptionalRegionsTask : public G1EvacuateRegionsBaseTask {
3933
3934 void scan_roots(G1ParScanThreadState* pss, uint worker_id) {
3935 _g1h->rem_set()->scan_heap_roots(pss, worker_id, G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::OptObjCopy);
3936 _g1h->rem_set()->scan_collection_set_regions(pss, worker_id, G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::OptCodeRoots, G1GCPhaseTimes::OptObjCopy);
3937 }
3938
3939 void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) {
3940 G1EvacuateRegionsBaseTask::evacuate_live_objects(pss, worker_id, G1GCPhaseTimes::OptObjCopy, G1GCPhaseTimes::OptTermination);
3941 }
3942
3943 public:
3944 G1EvacuateOptionalRegionsTask(G1ParScanThreadStateSet* per_thread_states,
3945 RefToScanQueueSet* queues,
3946 uint num_workers) :
3947 G1EvacuateRegionsBaseTask("G1 Evacuate Optional Regions", per_thread_states, queues, num_workers) {
3948 }
3949 };
3950
3951 void G1CollectedHeap::evacuate_next_optional_regions(G1ParScanThreadStateSet* per_thread_states) {
3952 class G1MarkScope : public MarkScope { };
3953
3954 Tickspan task_time;
3955
3956 Ticks start_processing = Ticks::now();
3957 {
3958 G1MarkScope code_mark_scope;
3959 G1EvacuateOptionalRegionsTask task(per_thread_states, _task_queues, workers()->active_workers());
3960 task_time = run_task_timed(&task);
3961 // See comment in evacuate_collection_set() for the reason of the scope.
3962 }
3963 Tickspan total_processing = Ticks::now() - start_processing;
3964
3965 G1GCPhaseTimes* p = phase_times();
3966 p->record_or_add_code_root_fixup_time((total_processing - task_time).seconds() * 1000.0);
3967 }
3968
3969 void G1CollectedHeap::evacuate_optional_collection_set(G1ParScanThreadStateSet* per_thread_states) {
3970 const double gc_start_time_ms = phase_times()->cur_collection_start_sec() * 1000.0;
3971
3972 while (!evacuation_failed() && _collection_set.optional_region_length() > 0) {
3973
3974 double time_used_ms = os::elapsedTime() * 1000.0 - gc_start_time_ms;
3975 double time_left_ms = MaxGCPauseMillis - time_used_ms;
3976
3977 if (time_left_ms < 0 ||
3978 !_collection_set.finalize_optional_for_evacuation(time_left_ms * policy()->optional_evacuation_fraction())) {
3979 log_trace(gc, ergo, cset)("Skipping evacuation of %u optional regions, no more regions can be evacuated in %.3fms",
3980 _collection_set.optional_region_length(), time_left_ms);
3981 break;
3982 }
3983
3984 {
3985 Ticks start = Ticks::now();
3986 rem_set()->merge_heap_roots(false /* initial_evacuation */);
3987 phase_times()->record_or_add_optional_merge_heap_roots_time((Ticks::now() - start).seconds() * 1000.0);
3988 }
3989
3990 {
3991 Ticks start = Ticks::now();
3992 evacuate_next_optional_regions(per_thread_states);
3993 phase_times()->record_or_add_optional_evac_time((Ticks::now() - start).seconds() * 1000.0);
3994 }
3995 }
3996
3997 _collection_set.abandon_optional_collection_set(per_thread_states);
3998 }
3999
4000 void G1CollectedHeap::post_evacuate_collection_set(G1EvacuationInfo& evacuation_info,
4001 G1RedirtyCardsQueueSet* rdcqs,
4002 G1ParScanThreadStateSet* per_thread_states) {
4003 G1GCPhaseTimes* p = phase_times();
4004
4005 rem_set()->cleanup_after_scan_heap_roots();
4006
4007 // Process any discovered reference objects - we have
4008 // to do this _before_ we retire the GC alloc regions
4009 // as we may have to copy some 'reachable' referent
4010 // objects (and their reachable sub-graphs) that were
4011 // not copied during the pause.
4012 process_discovered_references(per_thread_states);
4013
4014 G1STWIsAliveClosure is_alive(this);
4015 G1KeepAliveClosure keep_alive(this);
4016
4017 WeakProcessor::weak_oops_do(workers(), &is_alive, &keep_alive, p->weak_phase_times());
4018
4019 if (G1StringDedup::is_enabled()) {
4020 double string_dedup_time_ms = os::elapsedTime();
4021
4022 string_dedup_cleaning(&is_alive, &keep_alive, p);
4023
4024 double string_cleanup_time_ms = (os::elapsedTime() - string_dedup_time_ms) * 1000.0;
4025 p->record_string_deduplication_time(string_cleanup_time_ms);
4026 }
4027
4028 _allocator->release_gc_alloc_regions(evacuation_info);
4029
4030 if (evacuation_failed()) {
4031 restore_after_evac_failure(rdcqs);
4032
4033 // Reset the G1EvacuationFailureALot counters and flags
4034 NOT_PRODUCT(reset_evacuation_should_fail();)
4035
4036 double recalculate_used_start = os::elapsedTime();
4037 set_used(recalculate_used());
4038 p->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
4039
4040 if (_archive_allocator != NULL) {
4041 _archive_allocator->clear_used();
4042 }
4043 for (uint i = 0; i < ParallelGCThreads; i++) {
4044 if (_evacuation_failed_info_array[i].has_failed()) {
4045 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
4046 }
4047 }
4048 } else {
4049 // The "used" of the the collection set have already been subtracted
4050 // when they were freed. Add in the bytes used.
4051 increase_used(_bytes_used_during_gc);
4052 }
4053
4054 _preserved_marks_set.assert_empty();
4055
4056 merge_per_thread_state_info(per_thread_states);
4057
4058 // Reset and re-enable the hot card cache.
4059 // Note the counts for the cards in the regions in the
4060 // collection set are reset when the collection set is freed.
4061 _hot_card_cache->reset_hot_cache();
4062 _hot_card_cache->set_use_cache(true);
4063
4064 purge_code_root_memory();
4065
4066 redirty_logged_cards(rdcqs);
4067
4068 free_collection_set(&_collection_set, evacuation_info, per_thread_states->surviving_young_words());
4069
4070 eagerly_reclaim_humongous_regions();
4071
4072 record_obj_copy_mem_stats();
4073
4074 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
4075 evacuation_info.set_bytes_used(_bytes_used_during_gc);
4076
4077 #if COMPILER2_OR_JVMCI
4078 double start = os::elapsedTime();
4079 DerivedPointerTable::update_pointers();
4080 phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0);
4081 #endif
4082 policy()->print_age_table();
4083 }
4084
4085 void G1CollectedHeap::record_obj_copy_mem_stats() {
4086 policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4087
4088 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4089 create_g1_evac_summary(&_old_evac_stats));
4090 }
4091
4092 void G1CollectedHeap::free_region(HeapRegion* hr, FreeRegionList* free_list) {
4093 assert(!hr->is_free(), "the region should not be free");
4094 assert(!hr->is_empty(), "the region should not be empty");
4095 assert(_hrm->is_available(hr->hrm_index()), "region should be committed");
4096
4097 if (G1VerifyBitmaps) {
4098 MemRegion mr(hr->bottom(), hr->end());
4099 concurrent_mark()->clear_range_in_prev_bitmap(mr);
4100 }
4101
4102 // Clear the card counts for this region.
4103 // Note: we only need to do this if the region is not young
4104 // (since we don't refine cards in young regions).
4105 if (!hr->is_young()) {
4106 _hot_card_cache->reset_card_counts(hr);
4107 }
4108
4109 // Reset region metadata to allow reuse.
4110 hr->hr_clear(true /* clear_space */);
4111 _policy->remset_tracker()->update_at_free(hr);
4112
4113 if (free_list != NULL) {
4114 free_list->add_ordered(hr);
4115 }
4116 }
4117
4118 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4119 FreeRegionList* free_list) {
4120 assert(hr->is_humongous(), "this is only for humongous regions");
4121 assert(free_list != NULL, "pre-condition");
4122 hr->clear_humongous();
4123 free_region(hr, free_list);
4124 }
4125
4126 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4127 const uint humongous_regions_removed) {
4128 if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4129 MutexLocker x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4130 _old_set.bulk_remove(old_regions_removed);
4131 _humongous_set.bulk_remove(humongous_regions_removed);
4132 }
4133
4134 }
4135
4136 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4137 assert(list != NULL, "list can't be null");
4138 if (!list->is_empty()) {
4139 MutexLocker x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4140 _hrm->insert_list_into_free_list(list);
4141 }
4142 }
4143
4144 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4145 decrease_used(bytes);
4146 }
4147
4148 class G1FreeCollectionSetTask : public AbstractGangTask {
4149 // Helper class to keep statistics for the collection set freeing
4150 class FreeCSetStats {
4151 size_t _before_used_bytes; // Usage in regions successfully evacutate
4152 size_t _after_used_bytes; // Usage in regions failing evacuation
4153 size_t _bytes_allocated_in_old_since_last_gc; // Size of young regions turned into old
4154 size_t _failure_used_words; // Live size in failed regions
4155 size_t _failure_waste_words; // Wasted size in failed regions
4156 size_t _rs_length; // Remembered set size
4157 uint _regions_freed; // Number of regions freed
4158 public:
4159 FreeCSetStats() :
4160 _before_used_bytes(0),
4161 _after_used_bytes(0),
4162 _bytes_allocated_in_old_since_last_gc(0),
4163 _failure_used_words(0),
4164 _failure_waste_words(0),
4165 _rs_length(0),
4166 _regions_freed(0) { }
4167
4168 void merge_stats(FreeCSetStats* other) {
4169 assert(other != NULL, "invariant");
4170 _before_used_bytes += other->_before_used_bytes;
4171 _after_used_bytes += other->_after_used_bytes;
4172 _bytes_allocated_in_old_since_last_gc += other->_bytes_allocated_in_old_since_last_gc;
4173 _failure_used_words += other->_failure_used_words;
4174 _failure_waste_words += other->_failure_waste_words;
4175 _rs_length += other->_rs_length;
4176 _regions_freed += other->_regions_freed;
4177 }
4178
4179 void report(G1CollectedHeap* g1h, G1EvacuationInfo* evacuation_info) {
4180 evacuation_info->set_regions_freed(_regions_freed);
4181 evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4182
4183 g1h->decrement_summary_bytes(_before_used_bytes);
4184 g1h->alloc_buffer_stats(G1HeapRegionAttr::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4185
4186 G1Policy *policy = g1h->policy();
4187 policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4188 policy->record_rs_length(_rs_length);
4189 policy->cset_regions_freed();
4190 }
4191
4192 void account_failed_region(HeapRegion* r) {
4193 size_t used_words = r->marked_bytes() / HeapWordSize;
4194 _failure_used_words += used_words;
4195 _failure_waste_words += HeapRegion::GrainWords - used_words;
4196 _after_used_bytes += r->used();
4197
4198 // When moving a young gen region to old gen, we "allocate" that whole
4199 // region there. This is in addition to any already evacuated objects.
4200 // Notify the policy about that. Old gen regions do not cause an
4201 // additional allocation: both the objects still in the region and the
4202 // ones already moved are accounted for elsewhere.
4203 if (r->is_young()) {
4204 _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
4205 }
4206 }
4207
4208 void account_evacuated_region(HeapRegion* r) {
4209 _before_used_bytes += r->used();
4210 _regions_freed += 1;
4211 }
4212
4213 void account_rs_length(HeapRegion* r) {
4214 _rs_length += r->rem_set()->occupied();
4215 }
4216 };
4217
4218 // Closure applied to all regions in the collection set.
4219 class FreeCSetClosure : public HeapRegionClosure {
4220 // Helper to send JFR events for regions.
4221 class JFREventForRegion {
4222 EventGCPhaseParallel _event;
4223 public:
4224 JFREventForRegion(HeapRegion* region, uint worker_id) : _event() {
4225 _event.set_gcId(GCId::current());
4226 _event.set_gcWorkerId(worker_id);
4227 if (region->is_young()) {
4228 _event.set_name(G1GCPhaseTimes::phase_name(G1GCPhaseTimes::YoungFreeCSet));
4229 } else {
4230 _event.set_name(G1GCPhaseTimes::phase_name(G1GCPhaseTimes::NonYoungFreeCSet));
4231 }
4232 }
4233
4234 ~JFREventForRegion() {
4235 _event.commit();
4236 }
4237 };
4238
4239 // Helper to do timing for region work.
4240 class TimerForRegion {
4241 Tickspan& _time;
4242 Ticks _start_time;
4243 public:
4244 TimerForRegion(Tickspan& time) : _time(time), _start_time(Ticks::now()) { }
4245 ~TimerForRegion() {
4246 _time += Ticks::now() - _start_time;
4247 }
4248 };
4249
4250 // FreeCSetClosure members
4251 G1CollectedHeap* _g1h;
4252 const size_t* _surviving_young_words;
4253 uint _worker_id;
4254 Tickspan _young_time;
4255 Tickspan _non_young_time;
4256 FreeCSetStats* _stats;
4257
4258 void assert_in_cset(HeapRegion* r) {
4259 assert(r->young_index_in_cset() != 0 &&
4260 (uint)r->young_index_in_cset() <= _g1h->collection_set()->young_region_length(),
4261 "Young index %u is wrong for region %u of type %s with %u young regions",
4262 r->young_index_in_cset(), r->hrm_index(), r->get_type_str(), _g1h->collection_set()->young_region_length());
4263 }
4264
4265 void handle_evacuated_region(HeapRegion* r) {
4266 assert(!r->is_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
4267 stats()->account_evacuated_region(r);
4268
4269 // Free the region and and its remembered set.
4270 _g1h->free_region(r, NULL);
4271 }
4272
4273 void handle_failed_region(HeapRegion* r) {
4274 // Do some allocation statistics accounting. Regions that failed evacuation
4275 // are always made old, so there is no need to update anything in the young
4276 // gen statistics, but we need to update old gen statistics.
4277 stats()->account_failed_region(r);
4278
4279 // Update the region state due to the failed evacuation.
4280 r->handle_evacuation_failure();
4281
4282 // Add region to old set, need to hold lock.
4283 MutexLocker x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4284 _g1h->old_set_add(r);
4285 }
4286
4287 Tickspan& timer_for_region(HeapRegion* r) {
4288 return r->is_young() ? _young_time : _non_young_time;
4289 }
4290
4291 FreeCSetStats* stats() {
4292 return _stats;
4293 }
4294 public:
4295 FreeCSetClosure(const size_t* surviving_young_words,
4296 uint worker_id,
4297 FreeCSetStats* stats) :
4298 HeapRegionClosure(),
4299 _g1h(G1CollectedHeap::heap()),
4300 _surviving_young_words(surviving_young_words),
4301 _worker_id(worker_id),
4302 _young_time(),
4303 _non_young_time(),
4304 _stats(stats) { }
4305
4306 virtual bool do_heap_region(HeapRegion* r) {
4307 assert(r->in_collection_set(), "Invariant: %u missing from CSet", r->hrm_index());
4308 JFREventForRegion event(r, _worker_id);
4309 TimerForRegion timer(timer_for_region(r));
4310
4311 _g1h->clear_region_attr(r);
4312 stats()->account_rs_length(r);
4313
4314 if (r->is_young()) {
4315 assert_in_cset(r);
4316 r->record_surv_words_in_group(_surviving_young_words[r->young_index_in_cset()]);
4317 }
4318
4319 if (r->evacuation_failed()) {
4320 handle_failed_region(r);
4321 } else {
4322 handle_evacuated_region(r);
4323 }
4324 assert(!_g1h->is_on_master_free_list(r), "sanity");
4325
4326 return false;
4327 }
4328
4329 void report_timing(Tickspan parallel_time) {
4330 G1GCPhaseTimes* pt = _g1h->phase_times();
4331 pt->record_time_secs(G1GCPhaseTimes::ParFreeCSet, _worker_id, parallel_time.seconds());
4332 if (_young_time.value() > 0) {
4333 pt->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, _worker_id, _young_time.seconds());
4334 }
4335 if (_non_young_time.value() > 0) {
4336 pt->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, _worker_id, _non_young_time.seconds());
4337 }
4338 }
4339 };
4340
4341 // G1FreeCollectionSetTask members
4342 G1CollectedHeap* _g1h;
4343 G1EvacuationInfo* _evacuation_info;
4344 FreeCSetStats* _worker_stats;
4345 HeapRegionClaimer _claimer;
4346 const size_t* _surviving_young_words;
4347 uint _active_workers;
4348
4349 FreeCSetStats* worker_stats(uint worker) {
4350 return &_worker_stats[worker];
4351 }
4352
4353 void report_statistics() {
4354 // Merge the accounting
4355 FreeCSetStats total_stats;
4356 for (uint worker = 0; worker < _active_workers; worker++) {
4357 total_stats.merge_stats(worker_stats(worker));
4358 }
4359 total_stats.report(_g1h, _evacuation_info);
4360 }
4361
4362 public:
4363 G1FreeCollectionSetTask(G1EvacuationInfo* evacuation_info, const size_t* surviving_young_words, uint active_workers) :
4364 AbstractGangTask("G1 Free Collection Set"),
4365 _g1h(G1CollectedHeap::heap()),
4366 _evacuation_info(evacuation_info),
4367 _worker_stats(NEW_C_HEAP_ARRAY(FreeCSetStats, active_workers, mtGC)),
4368 _claimer(active_workers),
4369 _surviving_young_words(surviving_young_words),
4370 _active_workers(active_workers) {
4371 for (uint worker = 0; worker < active_workers; worker++) {
4372 ::new (&_worker_stats[worker]) FreeCSetStats();
4373 }
4374 }
4375
4376 ~G1FreeCollectionSetTask() {
4377 Ticks serial_time = Ticks::now();
4378 report_statistics();
4379 for (uint worker = 0; worker < _active_workers; worker++) {
4380 _worker_stats[worker].~FreeCSetStats();
4381 }
4382 FREE_C_HEAP_ARRAY(FreeCSetStats, _worker_stats);
4383 _g1h->phase_times()->record_serial_free_cset_time_ms((Ticks::now() - serial_time).seconds() * 1000.0);
4384 }
4385
4386 virtual void work(uint worker_id) {
4387 EventGCPhaseParallel event;
4388 Ticks start = Ticks::now();
4389 FreeCSetClosure cl(_surviving_young_words, worker_id, worker_stats(worker_id));
4390 _g1h->collection_set_par_iterate_all(&cl, &_claimer, worker_id);
4391
4392 // Report the total parallel time along with some more detailed metrics.
4393 cl.report_timing(Ticks::now() - start);
4394 event.commit(GCId::current(), worker_id, G1GCPhaseTimes::phase_name(G1GCPhaseTimes::ParFreeCSet));
4395 }
4396 };
4397
4398 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, G1EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4399 _eden.clear();
4400
4401 // The free collections set is split up in two tasks, the first
4402 // frees the collection set and records what regions are free,
4403 // and the second one rebuilds the free list. This proved to be
4404 // more efficient than adding a sorted list to another.
4405
4406 Ticks free_cset_start_time = Ticks::now();
4407 {
4408 uint const num_cs_regions = _collection_set.region_length();
4409 uint const num_workers = clamp(num_cs_regions, 1u, workers()->active_workers());
4410 G1FreeCollectionSetTask cl(&evacuation_info, surviving_young_words, num_workers);
4411
4412 log_debug(gc, ergo)("Running %s using %u workers for collection set length %u (%u)",
4413 cl.name(), num_workers, num_cs_regions, num_regions());
4414 workers()->run_task(&cl, num_workers);
4415 }
4416
4417 Ticks free_cset_end_time = Ticks::now();
4418 phase_times()->record_total_free_cset_time_ms((free_cset_end_time - free_cset_start_time).seconds() * 1000.0);
4419
4420 // Now rebuild the free region list.
4421 hrm()->rebuild_free_list(workers());
4422 phase_times()->record_total_rebuild_freelist_time_ms((Ticks::now() - free_cset_end_time).seconds() * 1000.0);
4423
4424 collection_set->clear();
4425 }
4426
4427 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4428 private:
4429 FreeRegionList* _free_region_list;
4430 HeapRegionSet* _proxy_set;
4431 uint _humongous_objects_reclaimed;
4432 uint _humongous_regions_reclaimed;
4433 size_t _freed_bytes;
4434 public:
4435
4436 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4437 _free_region_list(free_region_list), _proxy_set(NULL), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) {
4438 }
4439
4440 virtual bool do_heap_region(HeapRegion* r) {
4441 if (!r->is_starts_humongous()) {
4442 return false;
4443 }
4444
4445 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4446
4447 oop obj = (oop)r->bottom();
4448 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap();
4449
4450 // The following checks whether the humongous object is live are sufficient.
4451 // The main additional check (in addition to having a reference from the roots
4452 // or the young gen) is whether the humongous object has a remembered set entry.
4453 //
4454 // A humongous object cannot be live if there is no remembered set for it
4455 // because:
4456 // - there can be no references from within humongous starts regions referencing
4457 // the object because we never allocate other objects into them.
4458 // (I.e. there are no intra-region references that may be missed by the
4459 // remembered set)
4460 // - as soon there is a remembered set entry to the humongous starts region
4461 // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4462 // until the end of a concurrent mark.
4463 //
4464 // It is not required to check whether the object has been found dead by marking
4465 // or not, in fact it would prevent reclamation within a concurrent cycle, as
4466 // all objects allocated during that time are considered live.
4467 // SATB marking is even more conservative than the remembered set.
4468 // So if at this point in the collection there is no remembered set entry,
4469 // nobody has a reference to it.
4470 // At the start of collection we flush all refinement logs, and remembered sets
4471 // are completely up-to-date wrt to references to the humongous object.
4472 //
4473 // Other implementation considerations:
4474 // - never consider object arrays at this time because they would pose
4475 // considerable effort for cleaning up the the remembered sets. This is
4476 // required because stale remembered sets might reference locations that
4477 // are currently allocated into.
4478 uint region_idx = r->hrm_index();
4479 if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4480 !r->rem_set()->is_empty()) {
4481 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",
4482 region_idx,
4483 (size_t)obj->size() * HeapWordSize,
4484 p2i(r->bottom()),
4485 r->rem_set()->occupied(),
4486 r->rem_set()->strong_code_roots_list_length(),
4487 next_bitmap->is_marked(r->bottom()),
4488 g1h->is_humongous_reclaim_candidate(region_idx),
4489 obj->is_typeArray()
4490 );
4491 return false;
4492 }
4493
4494 guarantee(obj->is_typeArray(),
4495 "Only eagerly reclaiming type arrays is supported, but the object "
4496 PTR_FORMAT " is not.", p2i(r->bottom()));
4497
4498 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",
4499 region_idx,
4500 (size_t)obj->size() * HeapWordSize,
4501 p2i(r->bottom()),
4502 r->rem_set()->occupied(),
4503 r->rem_set()->strong_code_roots_list_length(),
4504 next_bitmap->is_marked(r->bottom()),
4505 g1h->is_humongous_reclaim_candidate(region_idx),
4506 obj->is_typeArray()
4507 );
4508
4509 G1ConcurrentMark* const cm = g1h->concurrent_mark();
4510 cm->humongous_object_eagerly_reclaimed(r);
4511 assert(!cm->is_marked_in_prev_bitmap(obj) && !cm->is_marked_in_next_bitmap(obj),
4512 "Eagerly reclaimed humongous region %u should not be marked at all but is in prev %s next %s",
4513 region_idx,
4514 BOOL_TO_STR(cm->is_marked_in_prev_bitmap(obj)),
4515 BOOL_TO_STR(cm->is_marked_in_next_bitmap(obj)));
4516 _humongous_objects_reclaimed++;
4517 do {
4518 HeapRegion* next = g1h->next_region_in_humongous(r);
4519 _freed_bytes += r->used();
4520 r->set_containing_set(NULL);
4521 _humongous_regions_reclaimed++;
4522 g1h->free_humongous_region(r, _free_region_list);
4523 r = next;
4524 } while (r != NULL);
4525
4526 return false;
4527 }
4528
4529 uint humongous_objects_reclaimed() {
4530 return _humongous_objects_reclaimed;
4531 }
4532
4533 uint humongous_regions_reclaimed() {
4534 return _humongous_regions_reclaimed;
4535 }
4536
4537 size_t bytes_freed() const {
4538 return _freed_bytes;
4539 }
4540 };
4541
4542 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4543 assert_at_safepoint_on_vm_thread();
4544
4545 if (!G1EagerReclaimHumongousObjects ||
4546 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
4547 phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
4548 return;
4549 }
4550
4551 double start_time = os::elapsedTime();
4552
4553 FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
4554
4555 G1FreeHumongousRegionClosure cl(&local_cleanup_list);
4556 heap_region_iterate(&cl);
4557
4558 remove_from_old_sets(0, cl.humongous_regions_reclaimed());
4559
4560 G1HRPrinter* hrp = hr_printer();
4561 if (hrp->is_active()) {
4562 FreeRegionListIterator iter(&local_cleanup_list);
4563 while (iter.more_available()) {
4564 HeapRegion* hr = iter.get_next();
4565 hrp->cleanup(hr);
4566 }
4567 }
4568
4569 prepend_to_freelist(&local_cleanup_list);
4570 decrement_summary_bytes(cl.bytes_freed());
4571
4572 phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
4573 cl.humongous_objects_reclaimed());
4574 }
4575
4576 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
4577 public:
4578 virtual bool do_heap_region(HeapRegion* r) {
4579 assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
4580 G1CollectedHeap::heap()->clear_region_attr(r);
4581 r->clear_young_index_in_cset();
4582 return false;
4583 }
4584 };
4585
4586 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
4587 G1AbandonCollectionSetClosure cl;
4588 collection_set_iterate_all(&cl);
4589
4590 collection_set->clear();
4591 collection_set->stop_incremental_building();
4592 }
4593
4594 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
4595 return _allocator->is_retained_old_region(hr);
4596 }
4597
4598 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
4599 _eden.add(hr);
4600 _policy->set_region_eden(hr);
4601 }
4602
4603 #ifdef ASSERT
4604
4605 class NoYoungRegionsClosure: public HeapRegionClosure {
4606 private:
4607 bool _success;
4608 public:
4609 NoYoungRegionsClosure() : _success(true) { }
4610 bool do_heap_region(HeapRegion* r) {
4611 if (r->is_young()) {
4612 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
4613 p2i(r->bottom()), p2i(r->end()));
4614 _success = false;
4615 }
4616 return false;
4617 }
4618 bool success() { return _success; }
4619 };
4620
4621 bool G1CollectedHeap::check_young_list_empty() {
4622 bool ret = (young_regions_count() == 0);
4623
4624 NoYoungRegionsClosure closure;
4625 heap_region_iterate(&closure);
4626 ret = ret && closure.success();
4627
4628 return ret;
4629 }
4630
4631 #endif // ASSERT
4632
4633 class TearDownRegionSetsClosure : public HeapRegionClosure {
4634 HeapRegionSet *_old_set;
4635
4636 public:
4637 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
4638
4639 bool do_heap_region(HeapRegion* r) {
4640 if (r->is_old()) {
4641 _old_set->remove(r);
4642 } else if(r->is_young()) {
4643 r->uninstall_surv_rate_group();
4644 } else {
4645 // We ignore free regions, we'll empty the free list afterwards.
4646 // We ignore humongous and archive regions, we're not tearing down these
4647 // sets.
4648 assert(r->is_archive() || r->is_free() || r->is_humongous(),
4649 "it cannot be another type");
4650 }
4651 return false;
4652 }
4653
4654 ~TearDownRegionSetsClosure() {
4655 assert(_old_set->is_empty(), "post-condition");
4656 }
4657 };
4658
4659 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
4660 assert_at_safepoint_on_vm_thread();
4661
4662 if (!free_list_only) {
4663 TearDownRegionSetsClosure cl(&_old_set);
4664 heap_region_iterate(&cl);
4665
4666 // Note that emptying the _young_list is postponed and instead done as
4667 // the first step when rebuilding the regions sets again. The reason for
4668 // this is that during a full GC string deduplication needs to know if
4669 // a collected region was young or old when the full GC was initiated.
4670 }
4671 _hrm->remove_all_free_regions();
4672 }
4673
4674 void G1CollectedHeap::increase_used(size_t bytes) {
4675 _summary_bytes_used += bytes;
4676 }
4677
4678 void G1CollectedHeap::decrease_used(size_t bytes) {
4679 assert(_summary_bytes_used >= bytes,
4680 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
4681 _summary_bytes_used, bytes);
4682 _summary_bytes_used -= bytes;
4683 }
4684
4685 void G1CollectedHeap::set_used(size_t bytes) {
4686 _summary_bytes_used = bytes;
4687 }
4688
4689 class RebuildRegionSetsClosure : public HeapRegionClosure {
4690 private:
4691 bool _free_list_only;
4692
4693 HeapRegionSet* _old_set;
4694 HeapRegionManager* _hrm;
4695
4696 size_t _total_used;
4697
4698 public:
4699 RebuildRegionSetsClosure(bool free_list_only,
4700 HeapRegionSet* old_set,
4701 HeapRegionManager* hrm) :
4702 _free_list_only(free_list_only),
4703 _old_set(old_set), _hrm(hrm), _total_used(0) {
4704 assert(_hrm->num_free_regions() == 0, "pre-condition");
4705 if (!free_list_only) {
4706 assert(_old_set->is_empty(), "pre-condition");
4707 }
4708 }
4709
4710 bool do_heap_region(HeapRegion* r) {
4711 if (r->is_empty()) {
4712 assert(r->rem_set()->is_empty(), "Empty regions should have empty remembered sets.");
4713 // Add free regions to the free list
4714 r->set_free();
4715 _hrm->insert_into_free_list(r);
4716 } else if (!_free_list_only) {
4717 assert(r->rem_set()->is_empty(), "At this point remembered sets must have been cleared.");
4718
4719 if (r->is_archive() || r->is_humongous()) {
4720 // We ignore archive and humongous regions. We left these sets unchanged.
4721 } else {
4722 assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
4723 // We now move all (non-humongous, non-old, non-archive) regions to old gen, and register them as such.
4724 r->move_to_old();
4725 _old_set->add(r);
4726 }
4727 _total_used += r->used();
4728 }
4729
4730 return false;
4731 }
4732
4733 size_t total_used() {
4734 return _total_used;
4735 }
4736 };
4737
4738 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
4739 assert_at_safepoint_on_vm_thread();
4740
4741 if (!free_list_only) {
4742 _eden.clear();
4743 _survivor.clear();
4744 }
4745
4746 RebuildRegionSetsClosure cl(free_list_only, &_old_set, _hrm);
4747 heap_region_iterate(&cl);
4748
4749 if (!free_list_only) {
4750 set_used(cl.total_used());
4751 if (_archive_allocator != NULL) {
4752 _archive_allocator->clear_used();
4753 }
4754 }
4755 assert_used_and_recalculate_used_equal(this);
4756 }
4757
4758 // Methods for the mutator alloc region
4759
4760 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
4761 bool force,
4762 uint node_index) {
4763 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4764 bool should_allocate = policy()->should_allocate_mutator_region();
4765 if (force || should_allocate) {
4766 HeapRegion* new_alloc_region = new_region(word_size,
4767 HeapRegionType::Eden,
4768 false /* do_expand */,
4769 node_index);
4770 if (new_alloc_region != NULL) {
4771 set_region_short_lived_locked(new_alloc_region);
4772 _hr_printer.alloc(new_alloc_region, !should_allocate);
4773 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
4774 _policy->remset_tracker()->update_at_allocate(new_alloc_region);
4775 return new_alloc_region;
4776 }
4777 }
4778 return NULL;
4779 }
4780
4781 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
4782 size_t allocated_bytes) {
4783 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4784 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
4785
4786 collection_set()->add_eden_region(alloc_region);
4787 increase_used(allocated_bytes);
4788 _eden.add_used_bytes(allocated_bytes);
4789 _hr_printer.retire(alloc_region);
4790
4791 // We update the eden sizes here, when the region is retired,
4792 // instead of when it's allocated, since this is the point that its
4793 // used space has been recorded in _summary_bytes_used.
4794 g1mm()->update_eden_size();
4795 }
4796
4797 // Methods for the GC alloc regions
4798
4799 bool G1CollectedHeap::has_more_regions(G1HeapRegionAttr dest) {
4800 if (dest.is_old()) {
4801 return true;
4802 } else {
4803 return survivor_regions_count() < policy()->max_survivor_regions();
4804 }
4805 }
4806
4807 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, G1HeapRegionAttr dest, uint node_index) {
4808 assert(FreeList_lock->owned_by_self(), "pre-condition");
4809
4810 if (!has_more_regions(dest)) {
4811 return NULL;
4812 }
4813
4814 HeapRegionType type;
4815 if (dest.is_young()) {
4816 type = HeapRegionType::Survivor;
4817 } else {
4818 type = HeapRegionType::Old;
4819 }
4820
4821 HeapRegion* new_alloc_region = new_region(word_size,
4822 type,
4823 true /* do_expand */,
4824 node_index);
4825
4826 if (new_alloc_region != NULL) {
4827 if (type.is_survivor()) {
4828 new_alloc_region->set_survivor();
4829 _survivor.add(new_alloc_region);
4830 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
4831 } else {
4832 new_alloc_region->set_old();
4833 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
4834 }
4835 _policy->remset_tracker()->update_at_allocate(new_alloc_region);
4836 register_region_with_region_attr(new_alloc_region);
4837 _hr_printer.alloc(new_alloc_region);
4838 return new_alloc_region;
4839 }
4840 return NULL;
4841 }
4842
4843 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
4844 size_t allocated_bytes,
4845 G1HeapRegionAttr dest) {
4846 _bytes_used_during_gc += allocated_bytes;
4847 if (dest.is_old()) {
4848 old_set_add(alloc_region);
4849 } else {
4850 assert(dest.is_young(), "Retiring alloc region should be young (%d)", dest.type());
4851 _survivor.add_used_bytes(allocated_bytes);
4852 }
4853
4854 bool const during_im = collector_state()->in_initial_mark_gc();
4855 if (during_im && allocated_bytes > 0) {
4856 _cm->root_regions()->add(alloc_region->next_top_at_mark_start(), alloc_region->top());
4857 }
4858 _hr_printer.retire(alloc_region);
4859 }
4860
4861 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
4862 bool expanded = false;
4863 uint index = _hrm->find_highest_free(&expanded);
4864
4865 if (index != G1_NO_HRM_INDEX) {
4866 if (expanded) {
4867 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
4868 HeapRegion::GrainWords * HeapWordSize);
4869 }
4870 return _hrm->allocate_free_regions_starting_at(index, 1);
4871 }
4872 return NULL;
4873 }
4874
4875 // Optimized nmethod scanning
4876
4877 class RegisterNMethodOopClosure: public OopClosure {
4878 G1CollectedHeap* _g1h;
4879 nmethod* _nm;
4880
4881 template <class T> void do_oop_work(T* p) {
4882 T heap_oop = RawAccess<>::oop_load(p);
4883 if (!CompressedOops::is_null(heap_oop)) {
4884 oop obj = CompressedOops::decode_not_null(heap_oop);
4885 HeapRegion* hr = _g1h->heap_region_containing(obj);
4886 assert(!hr->is_continues_humongous(),
4887 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
4888 " starting at " HR_FORMAT,
4889 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
4890
4891 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
4892 hr->add_strong_code_root_locked(_nm);
4893 }
4894 }
4895
4896 public:
4897 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
4898 _g1h(g1h), _nm(nm) {}
4899
4900 void do_oop(oop* p) { do_oop_work(p); }
4901 void do_oop(narrowOop* p) { do_oop_work(p); }
4902 };
4903
4904 class UnregisterNMethodOopClosure: public OopClosure {
4905 G1CollectedHeap* _g1h;
4906 nmethod* _nm;
4907
4908 template <class T> void do_oop_work(T* p) {
4909 T heap_oop = RawAccess<>::oop_load(p);
4910 if (!CompressedOops::is_null(heap_oop)) {
4911 oop obj = CompressedOops::decode_not_null(heap_oop);
4912 HeapRegion* hr = _g1h->heap_region_containing(obj);
4913 assert(!hr->is_continues_humongous(),
4914 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
4915 " starting at " HR_FORMAT,
4916 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
4917
4918 hr->remove_strong_code_root(_nm);
4919 }
4920 }
4921
4922 public:
4923 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
4924 _g1h(g1h), _nm(nm) {}
4925
4926 void do_oop(oop* p) { do_oop_work(p); }
4927 void do_oop(narrowOop* p) { do_oop_work(p); }
4928 };
4929
4930 void G1CollectedHeap::register_nmethod(nmethod* nm) {
4931 guarantee(nm != NULL, "sanity");
4932 RegisterNMethodOopClosure reg_cl(this, nm);
4933 nm->oops_do(®_cl);
4934 }
4935
4936 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
4937 guarantee(nm != NULL, "sanity");
4938 UnregisterNMethodOopClosure reg_cl(this, nm);
4939 nm->oops_do(®_cl, true);
4940 }
4941
4942 void G1CollectedHeap::purge_code_root_memory() {
4943 double purge_start = os::elapsedTime();
4944 G1CodeRootSet::purge();
4945 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
4946 phase_times()->record_strong_code_root_purge_time(purge_time_ms);
4947 }
4948
4949 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
4950 G1CollectedHeap* _g1h;
4951
4952 public:
4953 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
4954 _g1h(g1h) {}
4955
4956 void do_code_blob(CodeBlob* cb) {
4957 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
4958 if (nm == NULL) {
4959 return;
4960 }
4961
4962 _g1h->register_nmethod(nm);
4963 }
4964 };
4965
4966 void G1CollectedHeap::rebuild_strong_code_roots() {
4967 RebuildStrongCodeRootClosure blob_cl(this);
4968 CodeCache::blobs_do(&blob_cl);
4969 }
4970
4971 void G1CollectedHeap::initialize_serviceability() {
4972 _g1mm->initialize_serviceability();
4973 }
4974
4975 MemoryUsage G1CollectedHeap::memory_usage() {
4976 return _g1mm->memory_usage();
4977 }
4978
4979 GrowableArray<GCMemoryManager*> G1CollectedHeap::memory_managers() {
4980 return _g1mm->memory_managers();
4981 }
4982
4983 GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() {
4984 return _g1mm->memory_pools();
4985 }
4986
4987 class G1ParallelObjectIterator : public ParallelObjectIterator {
4988 private:
4989 G1CollectedHeap* _heap;
4990 HeapRegionClaimer _claimer;
4991
4992 public:
4993 G1ParallelObjectIterator(uint thread_num) :
4994 _heap(G1CollectedHeap::heap()),
4995 _claimer(thread_num == 0 ? G1CollectedHeap::heap()->workers()->active_workers() : thread_num) {}
4996
4997 virtual void object_iterate(ObjectClosure* cl, uint worker_id) {
4998 _heap->object_iterate_parallel(cl, worker_id, &_claimer);
4999 }
5000 };
5001
5002 ParallelObjectIterator* G1CollectedHeap::parallel_object_iterator(uint thread_num) {
5003 return new G1ParallelObjectIterator(thread_num);
5004 }
5005
5006 void G1CollectedHeap::object_iterate_parallel(ObjectClosure* cl, uint worker_id, HeapRegionClaimer* claimer) {
5007 IterateObjectClosureRegionClosure blk(cl);
5008 heap_region_par_iterate_from_worker_offset(&blk, claimer, worker_id);
5009 }