1 /*
2 * Copyright (c) 2001, 2018, 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/metadataOnStackMark.hpp"
27 #include "classfile/stringTable.hpp"
28 #include "classfile/symbolTable.hpp"
29 #include "code/codeCache.hpp"
30 #include "code/icBuffer.hpp"
31 #include "gc/g1/g1Allocator.inline.hpp"
32 #include "gc/g1/g1BarrierSet.hpp"
33 #include "gc/g1/g1CollectedHeap.inline.hpp"
34 #include "gc/g1/g1CollectionSet.hpp"
35 #include "gc/g1/g1CollectorPolicy.hpp"
36 #include "gc/g1/g1CollectorState.hpp"
37 #include "gc/g1/g1ConcurrentRefine.hpp"
38 #include "gc/g1/g1ConcurrentRefineThread.hpp"
39 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
40 #include "gc/g1/g1EvacStats.inline.hpp"
41 #include "gc/g1/g1FullCollector.hpp"
42 #include "gc/g1/g1GCPhaseTimes.hpp"
43 #include "gc/g1/g1HeapSizingPolicy.hpp"
44 #include "gc/g1/g1HeapTransition.hpp"
45 #include "gc/g1/g1HeapVerifier.hpp"
46 #include "gc/g1/g1HotCardCache.hpp"
47 #include "gc/g1/g1MemoryPool.hpp"
48 #include "gc/g1/g1OopClosures.inline.hpp"
49 #include "gc/g1/g1ParScanThreadState.inline.hpp"
50 #include "gc/g1/g1Policy.hpp"
51 #include "gc/g1/g1RegionToSpaceMapper.hpp"
52 #include "gc/g1/g1RemSet.hpp"
53 #include "gc/g1/g1RootClosures.hpp"
54 #include "gc/g1/g1RootProcessor.hpp"
55 #include "gc/g1/g1StringDedup.hpp"
56 #include "gc/g1/g1ThreadLocalData.hpp"
57 #include "gc/g1/g1YCTypes.hpp"
58 #include "gc/g1/g1YoungRemSetSamplingThread.hpp"
59 #include "gc/g1/heapRegion.inline.hpp"
60 #include "gc/g1/heapRegionRemSet.hpp"
61 #include "gc/g1/heapRegionSet.inline.hpp"
62 #include "gc/g1/vm_operations_g1.hpp"
63 #include "gc/shared/adaptiveSizePolicy.hpp"
64 #include "gc/shared/gcHeapSummary.hpp"
65 #include "gc/shared/gcId.hpp"
66 #include "gc/shared/gcLocker.hpp"
67 #include "gc/shared/gcTimer.hpp"
68 #include "gc/shared/gcTrace.hpp"
69 #include "gc/shared/gcTraceTime.inline.hpp"
70 #include "gc/shared/generationSpec.hpp"
71 #include "gc/shared/isGCActiveMark.hpp"
72 #include "gc/shared/oopStorageParState.hpp"
73 #include "gc/shared/preservedMarks.inline.hpp"
74 #include "gc/shared/suspendibleThreadSet.hpp"
75 #include "gc/shared/referenceProcessor.inline.hpp"
76 #include "gc/shared/taskqueue.inline.hpp"
77 #include "gc/shared/weakProcessor.hpp"
78 #include "logging/log.hpp"
79 #include "memory/allocation.hpp"
80 #include "memory/iterator.hpp"
81 #include "memory/metaspaceShared.hpp"
82 #include "memory/resourceArea.hpp"
83 #include "oops/access.inline.hpp"
84 #include "oops/compressedOops.inline.hpp"
85 #include "oops/oop.inline.hpp"
86 #include "prims/resolvedMethodTable.hpp"
87 #include "runtime/atomic.hpp"
88 #include "runtime/flags/flagSetting.hpp"
89 #include "runtime/handles.inline.hpp"
90 #include "runtime/init.hpp"
91 #include "runtime/orderAccess.hpp"
92 #include "runtime/threadSMR.hpp"
93 #include "runtime/vmThread.hpp"
94 #include "utilities/align.hpp"
95 #include "utilities/globalDefinitions.hpp"
96 #include "utilities/stack.inline.hpp"
97
98 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
99
100 // INVARIANTS/NOTES
101 //
102 // All allocation activity covered by the G1CollectedHeap interface is
103 // serialized by acquiring the HeapLock. This happens in mem_allocate
104 // and allocate_new_tlab, which are the "entry" points to the
105 // allocation code from the rest of the JVM. (Note that this does not
106 // apply to TLAB allocation, which is not part of this interface: it
107 // is done by clients of this interface.)
108
109 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
110 private:
111 size_t _num_dirtied;
112 G1CollectedHeap* _g1h;
113 G1CardTable* _g1_ct;
114
115 HeapRegion* region_for_card(jbyte* card_ptr) const {
116 return _g1h->heap_region_containing(_g1_ct->addr_for(card_ptr));
117 }
118
119 bool will_become_free(HeapRegion* hr) const {
120 // A region will be freed by free_collection_set if the region is in the
121 // collection set and has not had an evacuation failure.
122 return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
123 }
124
125 public:
126 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(),
127 _num_dirtied(0), _g1h(g1h), _g1_ct(g1h->card_table()) { }
128
129 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
130 HeapRegion* hr = region_for_card(card_ptr);
131
132 // Should only dirty cards in regions that won't be freed.
133 if (!will_become_free(hr)) {
134 *card_ptr = G1CardTable::dirty_card_val();
135 _num_dirtied++;
136 }
137
138 return true;
139 }
140
141 size_t num_dirtied() const { return _num_dirtied; }
142 };
143
144
145 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
146 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
147 }
148
149 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
150 // The from card cache is not the memory that is actually committed. So we cannot
151 // take advantage of the zero_filled parameter.
152 reset_from_card_cache(start_idx, num_regions);
153 }
154
155
156 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
157 MemRegion mr) {
158 return new HeapRegion(hrs_index, bot(), mr);
159 }
160
161 // Private methods.
162
163 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
164 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
165 "the only time we use this to allocate a humongous region is "
166 "when we are allocating a single humongous region");
167
168 HeapRegion* res = _hrm.allocate_free_region(is_old);
169
170 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
171 // Currently, only attempts to allocate GC alloc regions set
172 // do_expand to true. So, we should only reach here during a
173 // safepoint. If this assumption changes we might have to
174 // reconsider the use of _expand_heap_after_alloc_failure.
175 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
176
177 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
178 word_size * HeapWordSize);
179
180 if (expand(word_size * HeapWordSize)) {
181 // Given that expand() succeeded in expanding the heap, and we
182 // always expand the heap by an amount aligned to the heap
183 // region size, the free list should in theory not be empty.
184 // In either case allocate_free_region() will check for NULL.
185 res = _hrm.allocate_free_region(is_old);
186 } else {
187 _expand_heap_after_alloc_failure = false;
188 }
189 }
190 return res;
191 }
192
193 HeapWord*
194 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
195 uint num_regions,
196 size_t word_size) {
197 assert(first != G1_NO_HRM_INDEX, "pre-condition");
198 assert(is_humongous(word_size), "word_size should be humongous");
199 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
200
201 // Index of last region in the series.
202 uint last = first + num_regions - 1;
203
204 // We need to initialize the region(s) we just discovered. This is
205 // a bit tricky given that it can happen concurrently with
206 // refinement threads refining cards on these regions and
207 // potentially wanting to refine the BOT as they are scanning
208 // those cards (this can happen shortly after a cleanup; see CR
209 // 6991377). So we have to set up the region(s) carefully and in
210 // a specific order.
211
212 // The word size sum of all the regions we will allocate.
213 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
214 assert(word_size <= word_size_sum, "sanity");
215
216 // This will be the "starts humongous" region.
217 HeapRegion* first_hr = region_at(first);
218 // The header of the new object will be placed at the bottom of
219 // the first region.
220 HeapWord* new_obj = first_hr->bottom();
221 // This will be the new top of the new object.
222 HeapWord* obj_top = new_obj + word_size;
223
224 // First, we need to zero the header of the space that we will be
225 // allocating. When we update top further down, some refinement
226 // threads might try to scan the region. By zeroing the header we
227 // ensure that any thread that will try to scan the region will
228 // come across the zero klass word and bail out.
229 //
230 // NOTE: It would not have been correct to have used
231 // CollectedHeap::fill_with_object() and make the space look like
232 // an int array. The thread that is doing the allocation will
233 // later update the object header to a potentially different array
234 // type and, for a very short period of time, the klass and length
235 // fields will be inconsistent. This could cause a refinement
236 // thread to calculate the object size incorrectly.
237 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
238
239 // Next, pad out the unused tail of the last region with filler
240 // objects, for improved usage accounting.
241 // How many words we use for filler objects.
242 size_t word_fill_size = word_size_sum - word_size;
243
244 // How many words memory we "waste" which cannot hold a filler object.
245 size_t words_not_fillable = 0;
246
247 if (word_fill_size >= min_fill_size()) {
248 fill_with_objects(obj_top, word_fill_size);
249 } else if (word_fill_size > 0) {
250 // We have space to fill, but we cannot fit an object there.
251 words_not_fillable = word_fill_size;
252 word_fill_size = 0;
253 }
254
255 // We will set up the first region as "starts humongous". This
256 // will also update the BOT covering all the regions to reflect
257 // that there is a single object that starts at the bottom of the
258 // first region.
259 first_hr->set_starts_humongous(obj_top, word_fill_size);
260 _g1_policy->remset_tracker()->update_at_allocate(first_hr);
261 // Then, if there are any, we will set up the "continues
262 // humongous" regions.
263 HeapRegion* hr = NULL;
264 for (uint i = first + 1; i <= last; ++i) {
265 hr = region_at(i);
266 hr->set_continues_humongous(first_hr);
267 _g1_policy->remset_tracker()->update_at_allocate(hr);
268 }
269
270 // Up to this point no concurrent thread would have been able to
271 // do any scanning on any region in this series. All the top
272 // fields still point to bottom, so the intersection between
273 // [bottom,top] and [card_start,card_end] will be empty. Before we
274 // update the top fields, we'll do a storestore to make sure that
275 // no thread sees the update to top before the zeroing of the
276 // object header and the BOT initialization.
277 OrderAccess::storestore();
278
279 // Now, we will update the top fields of the "continues humongous"
280 // regions except the last one.
281 for (uint i = first; i < last; ++i) {
282 hr = region_at(i);
283 hr->set_top(hr->end());
284 }
285
286 hr = region_at(last);
287 // If we cannot fit a filler object, we must set top to the end
288 // of the humongous object, otherwise we cannot iterate the heap
289 // and the BOT will not be complete.
290 hr->set_top(hr->end() - words_not_fillable);
291
292 assert(hr->bottom() < obj_top && obj_top <= hr->end(),
293 "obj_top should be in last region");
294
295 _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
296
297 assert(words_not_fillable == 0 ||
298 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
299 "Miscalculation in humongous allocation");
300
301 increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
302
303 for (uint i = first; i <= last; ++i) {
304 hr = region_at(i);
305 _humongous_set.add(hr);
306 _hr_printer.alloc(hr);
307 }
308
309 return new_obj;
310 }
311
312 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
313 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
314 return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
315 }
316
317 // If could fit into free regions w/o expansion, try.
318 // Otherwise, if can expand, do so.
319 // Otherwise, if using ex regions might help, try with ex given back.
320 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
321 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
322
323 _verifier->verify_region_sets_optional();
324
325 uint first = G1_NO_HRM_INDEX;
326 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
327
328 if (obj_regions == 1) {
329 // Only one region to allocate, try to use a fast path by directly allocating
330 // from the free lists. Do not try to expand here, we will potentially do that
331 // later.
332 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
333 if (hr != NULL) {
334 first = hr->hrm_index();
335 }
336 } else {
337 // Policy: Try only empty regions (i.e. already committed first). Maybe we
338 // are lucky enough to find some.
339 first = _hrm.find_contiguous_only_empty(obj_regions);
340 if (first != G1_NO_HRM_INDEX) {
341 _hrm.allocate_free_regions_starting_at(first, obj_regions);
342 }
343 }
344
345 if (first == G1_NO_HRM_INDEX) {
346 // Policy: We could not find enough regions for the humongous object in the
347 // free list. Look through the heap to find a mix of free and uncommitted regions.
348 // If so, try expansion.
349 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
350 if (first != G1_NO_HRM_INDEX) {
351 // We found something. Make sure these regions are committed, i.e. expand
352 // the heap. Alternatively we could do a defragmentation GC.
353 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
354 word_size * HeapWordSize);
355
356 _hrm.expand_at(first, obj_regions, workers());
357 g1_policy()->record_new_heap_size(num_regions());
358
359 #ifdef ASSERT
360 for (uint i = first; i < first + obj_regions; ++i) {
361 HeapRegion* hr = region_at(i);
362 assert(hr->is_free(), "sanity");
363 assert(hr->is_empty(), "sanity");
364 assert(is_on_master_free_list(hr), "sanity");
365 }
366 #endif
367 _hrm.allocate_free_regions_starting_at(first, obj_regions);
368 } else {
369 // Policy: Potentially trigger a defragmentation GC.
370 }
371 }
372
373 HeapWord* result = NULL;
374 if (first != G1_NO_HRM_INDEX) {
375 result = humongous_obj_allocate_initialize_regions(first, obj_regions, word_size);
376 assert(result != NULL, "it should always return a valid result");
377
378 // A successful humongous object allocation changes the used space
379 // information of the old generation so we need to recalculate the
380 // sizes and update the jstat counters here.
381 g1mm()->update_sizes();
382 }
383
384 _verifier->verify_region_sets_optional();
385
386 return result;
387 }
388
389 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t min_size,
390 size_t requested_size,
391 size_t* actual_size) {
392 assert_heap_not_locked_and_not_at_safepoint();
393 assert(!is_humongous(requested_size), "we do not allow humongous TLABs");
394
395 return attempt_allocation(min_size, requested_size, actual_size);
396 }
397
398 HeapWord*
399 G1CollectedHeap::mem_allocate(size_t word_size,
400 bool* gc_overhead_limit_was_exceeded) {
401 assert_heap_not_locked_and_not_at_safepoint();
402
403 if (is_humongous(word_size)) {
404 return attempt_allocation_humongous(word_size);
405 }
406 size_t dummy = 0;
407 return attempt_allocation(word_size, word_size, &dummy);
408 }
409
410 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size) {
411 ResourceMark rm; // For retrieving the thread names in log messages.
412
413 // Make sure you read the note in attempt_allocation_humongous().
414
415 assert_heap_not_locked_and_not_at_safepoint();
416 assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
417 "be called for humongous allocation requests");
418
419 // We should only get here after the first-level allocation attempt
420 // (attempt_allocation()) failed to allocate.
421
422 // We will loop until a) we manage to successfully perform the
423 // allocation or b) we successfully schedule a collection which
424 // fails to perform the allocation. b) is the only case when we'll
425 // return NULL.
426 HeapWord* result = NULL;
427 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
428 bool should_try_gc;
429 uint gc_count_before;
430
431 {
432 MutexLockerEx x(Heap_lock);
433 result = _allocator->attempt_allocation_locked(word_size);
434 if (result != NULL) {
435 return result;
436 }
437
438 // If the GCLocker is active and we are bound for a GC, try expanding young gen.
439 // This is different to when only GCLocker::needs_gc() is set: try to avoid
440 // waiting because the GCLocker is active to not wait too long.
441 if (GCLocker::is_active_and_needs_gc() && g1_policy()->can_expand_young_list()) {
442 // No need for an ergo message here, can_expand_young_list() does this when
443 // it returns true.
444 result = _allocator->attempt_allocation_force(word_size);
445 if (result != NULL) {
446 return result;
447 }
448 }
449 // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
450 // the GCLocker initiated GC has been performed and then retry. This includes
451 // the case when the GC Locker is not active but has not been performed.
452 should_try_gc = !GCLocker::needs_gc();
453 // Read the GC count while still holding the Heap_lock.
454 gc_count_before = total_collections();
455 }
456
457 if (should_try_gc) {
458 bool succeeded;
459 result = do_collection_pause(word_size, gc_count_before, &succeeded,
460 GCCause::_g1_inc_collection_pause);
461 if (result != NULL) {
462 assert(succeeded, "only way to get back a non-NULL result");
463 log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
464 Thread::current()->name(), p2i(result));
465 return result;
466 }
467
468 if (succeeded) {
469 // We successfully scheduled a collection which failed to allocate. No
470 // point in trying to allocate further. We'll just return NULL.
471 log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
472 SIZE_FORMAT " words", Thread::current()->name(), word_size);
473 return NULL;
474 }
475 log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT " words",
476 Thread::current()->name(), word_size);
477 } else {
478 // Failed to schedule a collection.
479 if (gclocker_retry_count > GCLockerRetryAllocationCount) {
480 log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
481 SIZE_FORMAT " words", Thread::current()->name(), word_size);
482 return NULL;
483 }
484 log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
485 // The GCLocker is either active or the GCLocker initiated
486 // GC has not yet been performed. Stall until it is and
487 // then retry the allocation.
488 GCLocker::stall_until_clear();
489 gclocker_retry_count += 1;
490 }
491
492 // We can reach here if we were unsuccessful in scheduling a
493 // collection (because another thread beat us to it) or if we were
494 // stalled due to the GC locker. In either can we should retry the
495 // allocation attempt in case another thread successfully
496 // performed a collection and reclaimed enough space. We do the
497 // first attempt (without holding the Heap_lock) here and the
498 // follow-on attempt will be at the start of the next loop
499 // iteration (after taking the Heap_lock).
500 size_t dummy = 0;
501 result = _allocator->attempt_allocation(word_size, word_size, &dummy);
502 if (result != NULL) {
503 return result;
504 }
505
506 // Give a warning if we seem to be looping forever.
507 if ((QueuedAllocationWarningCount > 0) &&
508 (try_count % QueuedAllocationWarningCount == 0)) {
509 log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words",
510 Thread::current()->name(), try_count, word_size);
511 }
512 }
513
514 ShouldNotReachHere();
515 return NULL;
516 }
517
518 void G1CollectedHeap::begin_archive_alloc_range(bool open) {
519 assert_at_safepoint_on_vm_thread();
520 if (_archive_allocator == NULL) {
521 _archive_allocator = G1ArchiveAllocator::create_allocator(this, open);
522 }
523 }
524
525 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
526 // Allocations in archive regions cannot be of a size that would be considered
527 // humongous even for a minimum-sized region, because G1 region sizes/boundaries
528 // may be different at archive-restore time.
529 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
530 }
531
532 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
533 assert_at_safepoint_on_vm_thread();
534 assert(_archive_allocator != NULL, "_archive_allocator not initialized");
535 if (is_archive_alloc_too_large(word_size)) {
536 return NULL;
537 }
538 return _archive_allocator->archive_mem_allocate(word_size);
539 }
540
541 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
542 size_t end_alignment_in_bytes) {
543 assert_at_safepoint_on_vm_thread();
544 assert(_archive_allocator != NULL, "_archive_allocator not initialized");
545
546 // Call complete_archive to do the real work, filling in the MemRegion
547 // array with the archive regions.
548 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
549 delete _archive_allocator;
550 _archive_allocator = NULL;
551 }
552
553 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
554 assert(ranges != NULL, "MemRegion array NULL");
555 assert(count != 0, "No MemRegions provided");
556 MemRegion reserved = _hrm.reserved();
557 for (size_t i = 0; i < count; i++) {
558 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
559 return false;
560 }
561 }
562 return true;
563 }
564
565 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges,
566 size_t count,
567 bool open) {
568 assert(!is_init_completed(), "Expect to be called at JVM init time");
569 assert(ranges != NULL, "MemRegion array NULL");
570 assert(count != 0, "No MemRegions provided");
571 MutexLockerEx x(Heap_lock);
572
573 MemRegion reserved = _hrm.reserved();
574 HeapWord* prev_last_addr = NULL;
575 HeapRegion* prev_last_region = NULL;
576
577 // Temporarily disable pretouching of heap pages. This interface is used
578 // when mmap'ing archived heap data in, so pre-touching is wasted.
579 FlagSetting fs(AlwaysPreTouch, false);
580
581 // Enable archive object checking used by G1MarkSweep. We have to let it know
582 // about each archive range, so that objects in those ranges aren't marked.
583 G1ArchiveAllocator::enable_archive_object_check();
584
585 // For each specified MemRegion range, allocate the corresponding G1
586 // regions and mark them as archive regions. We expect the ranges
587 // in ascending starting address order, without overlap.
588 for (size_t i = 0; i < count; i++) {
589 MemRegion curr_range = ranges[i];
590 HeapWord* start_address = curr_range.start();
591 size_t word_size = curr_range.word_size();
592 HeapWord* last_address = curr_range.last();
593 size_t commits = 0;
594
595 guarantee(reserved.contains(start_address) && reserved.contains(last_address),
596 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
597 p2i(start_address), p2i(last_address));
598 guarantee(start_address > prev_last_addr,
599 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
600 p2i(start_address), p2i(prev_last_addr));
601 prev_last_addr = last_address;
602
603 // Check for ranges that start in the same G1 region in which the previous
604 // range ended, and adjust the start address so we don't try to allocate
605 // the same region again. If the current range is entirely within that
606 // region, skip it, just adjusting the recorded top.
607 HeapRegion* start_region = _hrm.addr_to_region(start_address);
608 if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
609 start_address = start_region->end();
610 if (start_address > last_address) {
611 increase_used(word_size * HeapWordSize);
612 start_region->set_top(last_address + 1);
613 continue;
614 }
615 start_region->set_top(start_address);
616 curr_range = MemRegion(start_address, last_address + 1);
617 start_region = _hrm.addr_to_region(start_address);
618 }
619
620 // Perform the actual region allocation, exiting if it fails.
621 // Then note how much new space we have allocated.
622 if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) {
623 return false;
624 }
625 increase_used(word_size * HeapWordSize);
626 if (commits != 0) {
627 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
628 HeapRegion::GrainWords * HeapWordSize * commits);
629
630 }
631
632 // Mark each G1 region touched by the range as archive, add it to
633 // the old set, and set top.
634 HeapRegion* curr_region = _hrm.addr_to_region(start_address);
635 HeapRegion* last_region = _hrm.addr_to_region(last_address);
636 prev_last_region = last_region;
637
638 while (curr_region != NULL) {
639 assert(curr_region->is_empty() && !curr_region->is_pinned(),
640 "Region already in use (index %u)", curr_region->hrm_index());
641 if (open) {
642 curr_region->set_open_archive();
643 } else {
644 curr_region->set_closed_archive();
645 }
646 _hr_printer.alloc(curr_region);
647 _old_set.add(curr_region);
648 HeapWord* top;
649 HeapRegion* next_region;
650 if (curr_region != last_region) {
651 top = curr_region->end();
652 next_region = _hrm.next_region_in_heap(curr_region);
653 } else {
654 top = last_address + 1;
655 next_region = NULL;
656 }
657 curr_region->set_top(top);
658 curr_region->set_first_dead(top);
659 curr_region->set_end_of_live(top);
660 curr_region = next_region;
661 }
662
663 // Notify mark-sweep of the archive
664 G1ArchiveAllocator::set_range_archive(curr_range, open);
665 }
666 return true;
667 }
668
669 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
670 assert(!is_init_completed(), "Expect to be called at JVM init time");
671 assert(ranges != NULL, "MemRegion array NULL");
672 assert(count != 0, "No MemRegions provided");
673 MemRegion reserved = _hrm.reserved();
674 HeapWord *prev_last_addr = NULL;
675 HeapRegion* prev_last_region = NULL;
676
677 // For each MemRegion, create filler objects, if needed, in the G1 regions
678 // that contain the address range. The address range actually within the
679 // MemRegion will not be modified. That is assumed to have been initialized
680 // elsewhere, probably via an mmap of archived heap data.
681 MutexLockerEx x(Heap_lock);
682 for (size_t i = 0; i < count; i++) {
683 HeapWord* start_address = ranges[i].start();
684 HeapWord* last_address = ranges[i].last();
685
686 assert(reserved.contains(start_address) && reserved.contains(last_address),
687 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
688 p2i(start_address), p2i(last_address));
689 assert(start_address > prev_last_addr,
690 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
691 p2i(start_address), p2i(prev_last_addr));
692
693 HeapRegion* start_region = _hrm.addr_to_region(start_address);
694 HeapRegion* last_region = _hrm.addr_to_region(last_address);
695 HeapWord* bottom_address = start_region->bottom();
696
697 // Check for a range beginning in the same region in which the
698 // previous one ended.
699 if (start_region == prev_last_region) {
700 bottom_address = prev_last_addr + 1;
701 }
702
703 // Verify that the regions were all marked as archive regions by
704 // alloc_archive_regions.
705 HeapRegion* curr_region = start_region;
706 while (curr_region != NULL) {
707 guarantee(curr_region->is_archive(),
708 "Expected archive region at index %u", curr_region->hrm_index());
709 if (curr_region != last_region) {
710 curr_region = _hrm.next_region_in_heap(curr_region);
711 } else {
712 curr_region = NULL;
713 }
714 }
715
716 prev_last_addr = last_address;
717 prev_last_region = last_region;
718
719 // Fill the memory below the allocated range with dummy object(s),
720 // if the region bottom does not match the range start, or if the previous
721 // range ended within the same G1 region, and there is a gap.
722 if (start_address != bottom_address) {
723 size_t fill_size = pointer_delta(start_address, bottom_address);
724 G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
725 increase_used(fill_size * HeapWordSize);
726 }
727 }
728 }
729
730 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t min_word_size,
731 size_t desired_word_size,
732 size_t* actual_word_size) {
733 assert_heap_not_locked_and_not_at_safepoint();
734 assert(!is_humongous(desired_word_size), "attempt_allocation() should not "
735 "be called for humongous allocation requests");
736
737 HeapWord* result = _allocator->attempt_allocation(min_word_size, desired_word_size, actual_word_size);
738
739 if (result == NULL) {
740 *actual_word_size = desired_word_size;
741 result = attempt_allocation_slow(desired_word_size);
742 }
743
744 assert_heap_not_locked();
745 if (result != NULL) {
746 assert(*actual_word_size != 0, "Actual size must have been set here");
747 dirty_young_block(result, *actual_word_size);
748 } else {
749 *actual_word_size = 0;
750 }
751
752 return result;
753 }
754
755 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
756 assert(!is_init_completed(), "Expect to be called at JVM init time");
757 assert(ranges != NULL, "MemRegion array NULL");
758 assert(count != 0, "No MemRegions provided");
759 MemRegion reserved = _hrm.reserved();
760 HeapWord* prev_last_addr = NULL;
761 HeapRegion* prev_last_region = NULL;
762 size_t size_used = 0;
763 size_t uncommitted_regions = 0;
764
765 // For each Memregion, free the G1 regions that constitute it, and
766 // notify mark-sweep that the range is no longer to be considered 'archive.'
767 MutexLockerEx x(Heap_lock);
768 for (size_t i = 0; i < count; i++) {
769 HeapWord* start_address = ranges[i].start();
770 HeapWord* last_address = ranges[i].last();
771
772 assert(reserved.contains(start_address) && reserved.contains(last_address),
773 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
774 p2i(start_address), p2i(last_address));
775 assert(start_address > prev_last_addr,
776 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
777 p2i(start_address), p2i(prev_last_addr));
778 size_used += ranges[i].byte_size();
779 prev_last_addr = last_address;
780
781 HeapRegion* start_region = _hrm.addr_to_region(start_address);
782 HeapRegion* last_region = _hrm.addr_to_region(last_address);
783
784 // Check for ranges that start in the same G1 region in which the previous
785 // range ended, and adjust the start address so we don't try to free
786 // the same region again. If the current range is entirely within that
787 // region, skip it.
788 if (start_region == prev_last_region) {
789 start_address = start_region->end();
790 if (start_address > last_address) {
791 continue;
792 }
793 start_region = _hrm.addr_to_region(start_address);
794 }
795 prev_last_region = last_region;
796
797 // After verifying that each region was marked as an archive region by
798 // alloc_archive_regions, set it free and empty and uncommit it.
799 HeapRegion* curr_region = start_region;
800 while (curr_region != NULL) {
801 guarantee(curr_region->is_archive(),
802 "Expected archive region at index %u", curr_region->hrm_index());
803 uint curr_index = curr_region->hrm_index();
804 _old_set.remove(curr_region);
805 curr_region->set_free();
806 curr_region->set_top(curr_region->bottom());
807 if (curr_region != last_region) {
808 curr_region = _hrm.next_region_in_heap(curr_region);
809 } else {
810 curr_region = NULL;
811 }
812 _hrm.shrink_at(curr_index, 1);
813 uncommitted_regions++;
814 }
815
816 // Notify mark-sweep that this is no longer an archive range.
817 G1ArchiveAllocator::set_range_archive(ranges[i], false);
818 }
819
820 if (uncommitted_regions != 0) {
821 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
822 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
823 }
824 decrease_used(size_used);
825 }
826
827 oop G1CollectedHeap::materialize_archived_object(oop obj) {
828 assert(obj != NULL, "archived obj is NULL");
829 assert(MetaspaceShared::is_archive_object(obj), "must be archived object");
830
831 // Loading an archived object makes it strongly reachable. If it is
832 // loaded during concurrent marking, it must be enqueued to the SATB
833 // queue, shading the previously white object gray.
834 G1BarrierSet::enqueue(obj);
835
836 return obj;
837 }
838
839 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size) {
840 ResourceMark rm; // For retrieving the thread names in log messages.
841
842 // The structure of this method has a lot of similarities to
843 // attempt_allocation_slow(). The reason these two were not merged
844 // into a single one is that such a method would require several "if
845 // allocation is not humongous do this, otherwise do that"
846 // conditional paths which would obscure its flow. In fact, an early
847 // version of this code did use a unified method which was harder to
848 // follow and, as a result, it had subtle bugs that were hard to
849 // track down. So keeping these two methods separate allows each to
850 // be more readable. It will be good to keep these two in sync as
851 // much as possible.
852
853 assert_heap_not_locked_and_not_at_safepoint();
854 assert(is_humongous(word_size), "attempt_allocation_humongous() "
855 "should only be called for humongous allocations");
856
857 // Humongous objects can exhaust the heap quickly, so we should check if we
858 // need to start a marking cycle at each humongous object allocation. We do
859 // the check before we do the actual allocation. The reason for doing it
860 // before the allocation is that we avoid having to keep track of the newly
861 // allocated memory while we do a GC.
862 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
863 word_size)) {
864 collect(GCCause::_g1_humongous_allocation);
865 }
866
867 // We will loop until a) we manage to successfully perform the
868 // allocation or b) we successfully schedule a collection which
869 // fails to perform the allocation. b) is the only case when we'll
870 // return NULL.
871 HeapWord* result = NULL;
872 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
873 bool should_try_gc;
874 uint gc_count_before;
875
876
877 {
878 MutexLockerEx x(Heap_lock);
879
880 // Given that humongous objects are not allocated in young
881 // regions, we'll first try to do the allocation without doing a
882 // collection hoping that there's enough space in the heap.
883 result = humongous_obj_allocate(word_size);
884 if (result != NULL) {
885 size_t size_in_regions = humongous_obj_size_in_regions(word_size);
886 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
887 return result;
888 }
889
890 // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
891 // the GCLocker initiated GC has been performed and then retry. This includes
892 // the case when the GC Locker is not active but has not been performed.
893 should_try_gc = !GCLocker::needs_gc();
894 // Read the GC count while still holding the Heap_lock.
895 gc_count_before = total_collections();
896 }
897
898 if (should_try_gc) {
899 bool succeeded;
900 result = do_collection_pause(word_size, gc_count_before, &succeeded,
901 GCCause::_g1_humongous_allocation);
902 if (result != NULL) {
903 assert(succeeded, "only way to get back a non-NULL result");
904 log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
905 Thread::current()->name(), p2i(result));
906 return result;
907 }
908
909 if (succeeded) {
910 // We successfully scheduled a collection which failed to allocate. No
911 // point in trying to allocate further. We'll just return NULL.
912 log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
913 SIZE_FORMAT " words", Thread::current()->name(), word_size);
914 return NULL;
915 }
916 log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT "",
917 Thread::current()->name(), word_size);
918 } else {
919 // Failed to schedule a collection.
920 if (gclocker_retry_count > GCLockerRetryAllocationCount) {
921 log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
922 SIZE_FORMAT " words", Thread::current()->name(), word_size);
923 return NULL;
924 }
925 log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
926 // The GCLocker is either active or the GCLocker initiated
927 // GC has not yet been performed. Stall until it is and
928 // then retry the allocation.
929 GCLocker::stall_until_clear();
930 gclocker_retry_count += 1;
931 }
932
933
934 // We can reach here if we were unsuccessful in scheduling a
935 // collection (because another thread beat us to it) or if we were
936 // stalled due to the GC locker. In either can we should retry the
937 // allocation attempt in case another thread successfully
938 // performed a collection and reclaimed enough space.
939 // Humongous object allocation always needs a lock, so we wait for the retry
940 // in the next iteration of the loop, unlike for the regular iteration case.
941 // Give a warning if we seem to be looping forever.
942
943 if ((QueuedAllocationWarningCount > 0) &&
944 (try_count % QueuedAllocationWarningCount == 0)) {
945 log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words",
946 Thread::current()->name(), try_count, word_size);
947 }
948 }
949
950 ShouldNotReachHere();
951 return NULL;
952 }
953
954 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
955 bool expect_null_mutator_alloc_region) {
956 assert_at_safepoint_on_vm_thread();
957 assert(!_allocator->has_mutator_alloc_region() || !expect_null_mutator_alloc_region,
958 "the current alloc region was unexpectedly found to be non-NULL");
959
960 if (!is_humongous(word_size)) {
961 return _allocator->attempt_allocation_locked(word_size);
962 } else {
963 HeapWord* result = humongous_obj_allocate(word_size);
964 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
965 collector_state()->set_initiate_conc_mark_if_possible(true);
966 }
967 return result;
968 }
969
970 ShouldNotReachHere();
971 }
972
973 class PostCompactionPrinterClosure: public HeapRegionClosure {
974 private:
975 G1HRPrinter* _hr_printer;
976 public:
977 bool do_heap_region(HeapRegion* hr) {
978 assert(!hr->is_young(), "not expecting to find young regions");
979 _hr_printer->post_compaction(hr);
980 return false;
981 }
982
983 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
984 : _hr_printer(hr_printer) { }
985 };
986
987 void G1CollectedHeap::print_hrm_post_compaction() {
988 if (_hr_printer.is_active()) {
989 PostCompactionPrinterClosure cl(hr_printer());
990 heap_region_iterate(&cl);
991 }
992 }
993
994 void G1CollectedHeap::abort_concurrent_cycle() {
995 // If we start the compaction before the CM threads finish
996 // scanning the root regions we might trip them over as we'll
997 // be moving objects / updating references. So let's wait until
998 // they are done. By telling them to abort, they should complete
999 // early.
1000 _cm->root_regions()->abort();
1001 _cm->root_regions()->wait_until_scan_finished();
1002
1003 // Disable discovery and empty the discovered lists
1004 // for the CM ref processor.
1005 _ref_processor_cm->disable_discovery();
1006 _ref_processor_cm->abandon_partial_discovery();
1007 _ref_processor_cm->verify_no_references_recorded();
1008
1009 // Abandon current iterations of concurrent marking and concurrent
1010 // refinement, if any are in progress.
1011 concurrent_mark()->concurrent_cycle_abort();
1012 }
1013
1014 void G1CollectedHeap::prepare_heap_for_full_collection() {
1015 // Make sure we'll choose a new allocation region afterwards.
1016 _allocator->release_mutator_alloc_region();
1017 _allocator->abandon_gc_alloc_regions();
1018 g1_rem_set()->cleanupHRRS();
1019
1020 // We may have added regions to the current incremental collection
1021 // set between the last GC or pause and now. We need to clear the
1022 // incremental collection set and then start rebuilding it afresh
1023 // after this full GC.
1024 abandon_collection_set(collection_set());
1025
1026 tear_down_region_sets(false /* free_list_only */);
1027 }
1028
1029 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) {
1030 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1031 assert(used() == recalculate_used(), "Should be equal");
1032 _verifier->verify_region_sets_optional();
1033 _verifier->verify_before_gc(G1HeapVerifier::G1VerifyFull);
1034 _verifier->check_bitmaps("Full GC Start");
1035 }
1036
1037 void G1CollectedHeap::prepare_heap_for_mutators() {
1038 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1039 ClassLoaderDataGraph::purge();
1040 MetaspaceUtils::verify_metrics();
1041
1042 // Prepare heap for normal collections.
1043 assert(num_free_regions() == 0, "we should not have added any free regions");
1044 rebuild_region_sets(false /* free_list_only */);
1045 abort_refinement();
1046 resize_if_necessary_after_full_collection();
1047
1048 // Rebuild the strong code root lists for each region
1049 rebuild_strong_code_roots();
1050
1051 // Start a new incremental collection set for the next pause
1052 start_new_collection_set();
1053
1054 _allocator->init_mutator_alloc_region();
1055
1056 // Post collection state updates.
1057 MetaspaceGC::compute_new_size();
1058 }
1059
1060 void G1CollectedHeap::abort_refinement() {
1061 if (_hot_card_cache->use_cache()) {
1062 _hot_card_cache->reset_hot_cache();
1063 }
1064
1065 // Discard all remembered set updates.
1066 G1BarrierSet::dirty_card_queue_set().abandon_logs();
1067 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1068 }
1069
1070 void G1CollectedHeap::verify_after_full_collection() {
1071 _hrm.verify_optional();
1072 _verifier->verify_region_sets_optional();
1073 _verifier->verify_after_gc(G1HeapVerifier::G1VerifyFull);
1074 // Clear the previous marking bitmap, if needed for bitmap verification.
1075 // Note we cannot do this when we clear the next marking bitmap in
1076 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1077 // objects marked during a full GC against the previous bitmap.
1078 // But we need to clear it before calling check_bitmaps below since
1079 // the full GC has compacted objects and updated TAMS but not updated
1080 // the prev bitmap.
1081 if (G1VerifyBitmaps) {
1082 GCTraceTime(Debug, gc)("Clear Bitmap for Verification");
1083 _cm->clear_prev_bitmap(workers());
1084 }
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 #ifdef TRACESPINNING
1113 ParallelTaskTerminator::print_termination_counts();
1114 #endif
1115 }
1116
1117 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1118 bool clear_all_soft_refs) {
1119 assert_at_safepoint_on_vm_thread();
1120
1121 if (GCLocker::check_active_before_gc()) {
1122 // Full GC was not completed.
1123 return false;
1124 }
1125
1126 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1127 soft_ref_policy()->should_clear_all_soft_refs();
1128
1129 G1FullCollector collector(this, &_full_gc_memory_manager, explicit_gc, do_clear_all_soft_refs);
1130 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1131
1132 collector.prepare_collection();
1133 collector.collect();
1134 collector.complete_collection();
1135
1136 // Full collection was successfully completed.
1137 return true;
1138 }
1139
1140 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1141 // Currently, there is no facility in the do_full_collection(bool) API to notify
1142 // the caller that the collection did not succeed (e.g., because it was locked
1143 // out by the GC locker). So, right now, we'll ignore the return value.
1144 bool dummy = do_full_collection(true, /* explicit_gc */
1145 clear_all_soft_refs);
1146 }
1147
1148 void G1CollectedHeap::resize_if_necessary_after_full_collection() {
1149 // Capacity, free and used after the GC counted as full regions to
1150 // include the waste in the following calculations.
1151 const size_t capacity_after_gc = capacity();
1152 const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes();
1153
1154 // This is enforced in arguments.cpp.
1155 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1156 "otherwise the code below doesn't make sense");
1157
1158 // We don't have floating point command-line arguments
1159 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1160 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1161 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1162 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1163
1164 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1165 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1166
1167 // We have to be careful here as these two calculations can overflow
1168 // 32-bit size_t's.
1169 double used_after_gc_d = (double) used_after_gc;
1170 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1171 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1172
1173 // Let's make sure that they are both under the max heap size, which
1174 // by default will make them fit into a size_t.
1175 double desired_capacity_upper_bound = (double) max_heap_size;
1176 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1177 desired_capacity_upper_bound);
1178 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1179 desired_capacity_upper_bound);
1180
1181 // We can now safely turn them into size_t's.
1182 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1183 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1184
1185 // This assert only makes sense here, before we adjust them
1186 // with respect to the min and max heap size.
1187 assert(minimum_desired_capacity <= maximum_desired_capacity,
1188 "minimum_desired_capacity = " SIZE_FORMAT ", "
1189 "maximum_desired_capacity = " SIZE_FORMAT,
1190 minimum_desired_capacity, maximum_desired_capacity);
1191
1192 // Should not be greater than the heap max size. No need to adjust
1193 // it with respect to the heap min size as it's a lower bound (i.e.,
1194 // we'll try to make the capacity larger than it, not smaller).
1195 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1196 // Should not be less than the heap min size. No need to adjust it
1197 // with respect to the heap max size as it's an upper bound (i.e.,
1198 // we'll try to make the capacity smaller than it, not greater).
1199 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1200
1201 if (capacity_after_gc < minimum_desired_capacity) {
1202 // Don't expand unless it's significant
1203 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1204
1205 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). "
1206 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1207 "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1208 capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio);
1209
1210 expand(expand_bytes, _workers);
1211
1212 // No expansion, now see if we want to shrink
1213 } else if (capacity_after_gc > maximum_desired_capacity) {
1214 // Capacity too large, compute shrinking size
1215 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1216
1217 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). "
1218 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1219 "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1220 capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio);
1221
1222 shrink(shrink_bytes);
1223 }
1224 }
1225
1226 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1227 bool do_gc,
1228 bool clear_all_soft_refs,
1229 bool expect_null_mutator_alloc_region,
1230 bool* gc_succeeded) {
1231 *gc_succeeded = true;
1232 // Let's attempt the allocation first.
1233 HeapWord* result =
1234 attempt_allocation_at_safepoint(word_size,
1235 expect_null_mutator_alloc_region);
1236 if (result != NULL) {
1237 return result;
1238 }
1239
1240 // In a G1 heap, we're supposed to keep allocation from failing by
1241 // incremental pauses. Therefore, at least for now, we'll favor
1242 // expansion over collection. (This might change in the future if we can
1243 // do something smarter than full collection to satisfy a failed alloc.)
1244 result = expand_and_allocate(word_size);
1245 if (result != NULL) {
1246 return result;
1247 }
1248
1249 if (do_gc) {
1250 // Expansion didn't work, we'll try to do a Full GC.
1251 *gc_succeeded = do_full_collection(false, /* explicit_gc */
1252 clear_all_soft_refs);
1253 }
1254
1255 return NULL;
1256 }
1257
1258 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1259 bool* succeeded) {
1260 assert_at_safepoint_on_vm_thread();
1261
1262 // Attempts to allocate followed by Full GC.
1263 HeapWord* result =
1264 satisfy_failed_allocation_helper(word_size,
1265 true, /* do_gc */
1266 false, /* clear_all_soft_refs */
1267 false, /* expect_null_mutator_alloc_region */
1268 succeeded);
1269
1270 if (result != NULL || !*succeeded) {
1271 return result;
1272 }
1273
1274 // Attempts to allocate followed by Full GC that will collect all soft references.
1275 result = satisfy_failed_allocation_helper(word_size,
1276 true, /* do_gc */
1277 true, /* clear_all_soft_refs */
1278 true, /* expect_null_mutator_alloc_region */
1279 succeeded);
1280
1281 if (result != NULL || !*succeeded) {
1282 return result;
1283 }
1284
1285 // Attempts to allocate, no GC
1286 result = satisfy_failed_allocation_helper(word_size,
1287 false, /* do_gc */
1288 false, /* clear_all_soft_refs */
1289 true, /* expect_null_mutator_alloc_region */
1290 succeeded);
1291
1292 if (result != NULL) {
1293 return result;
1294 }
1295
1296 assert(!soft_ref_policy()->should_clear_all_soft_refs(),
1297 "Flag should have been handled and cleared prior to this point");
1298
1299 // What else? We might try synchronous finalization later. If the total
1300 // space available is large enough for the allocation, then a more
1301 // complete compaction phase than we've tried so far might be
1302 // appropriate.
1303 return NULL;
1304 }
1305
1306 // Attempting to expand the heap sufficiently
1307 // to support an allocation of the given "word_size". If
1308 // successful, perform the allocation and return the address of the
1309 // allocated block, or else "NULL".
1310
1311 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1312 assert_at_safepoint_on_vm_thread();
1313
1314 _verifier->verify_region_sets_optional();
1315
1316 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1317 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1318 word_size * HeapWordSize);
1319
1320
1321 if (expand(expand_bytes, _workers)) {
1322 _hrm.verify_optional();
1323 _verifier->verify_region_sets_optional();
1324 return attempt_allocation_at_safepoint(word_size,
1325 false /* expect_null_mutator_alloc_region */);
1326 }
1327 return NULL;
1328 }
1329
1330 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) {
1331 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1332 aligned_expand_bytes = align_up(aligned_expand_bytes,
1333 HeapRegion::GrainBytes);
1334
1335 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B",
1336 expand_bytes, aligned_expand_bytes);
1337
1338 if (is_maximal_no_gc()) {
1339 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1340 return false;
1341 }
1342
1343 double expand_heap_start_time_sec = os::elapsedTime();
1344 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1345 assert(regions_to_expand > 0, "Must expand by at least one region");
1346
1347 uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers);
1348 if (expand_time_ms != NULL) {
1349 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1350 }
1351
1352 if (expanded_by > 0) {
1353 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1354 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1355 g1_policy()->record_new_heap_size(num_regions());
1356 } else {
1357 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1358
1359 // The expansion of the virtual storage space was unsuccessful.
1360 // Let's see if it was because we ran out of swap.
1361 if (G1ExitOnExpansionFailure &&
1362 _hrm.available() >= regions_to_expand) {
1363 // We had head room...
1364 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1365 }
1366 }
1367 return regions_to_expand > 0;
1368 }
1369
1370 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1371 size_t aligned_shrink_bytes =
1372 ReservedSpace::page_align_size_down(shrink_bytes);
1373 aligned_shrink_bytes = align_down(aligned_shrink_bytes,
1374 HeapRegion::GrainBytes);
1375 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1376
1377 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1378 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1379
1380
1381 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",
1382 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1383 if (num_regions_removed > 0) {
1384 g1_policy()->record_new_heap_size(num_regions());
1385 } else {
1386 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1387 }
1388 }
1389
1390 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1391 _verifier->verify_region_sets_optional();
1392
1393 // We should only reach here at the end of a Full GC which means we
1394 // should not not be holding to any GC alloc regions. The method
1395 // below will make sure of that and do any remaining clean up.
1396 _allocator->abandon_gc_alloc_regions();
1397
1398 // Instead of tearing down / rebuilding the free lists here, we
1399 // could instead use the remove_all_pending() method on free_list to
1400 // remove only the ones that we need to remove.
1401 tear_down_region_sets(true /* free_list_only */);
1402 shrink_helper(shrink_bytes);
1403 rebuild_region_sets(true /* free_list_only */);
1404
1405 _hrm.verify_optional();
1406 _verifier->verify_region_sets_optional();
1407 }
1408
1409 // Public methods.
1410
1411 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) :
1412 CollectedHeap(),
1413 _young_gen_sampling_thread(NULL),
1414 _collector_policy(collector_policy),
1415 _soft_ref_policy(),
1416 _card_table(NULL),
1417 _memory_manager("G1 Young Generation", "end of minor GC"),
1418 _full_gc_memory_manager("G1 Old Generation", "end of major GC"),
1419 _eden_pool(NULL),
1420 _survivor_pool(NULL),
1421 _old_pool(NULL),
1422 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1423 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1424 _g1_policy(new G1Policy(_gc_timer_stw)),
1425 _collection_set(this, _g1_policy),
1426 _dirty_card_queue_set(false),
1427 _ref_processor_stw(NULL),
1428 _is_alive_closure_stw(this),
1429 _is_subject_to_discovery_stw(this),
1430 _ref_processor_cm(NULL),
1431 _is_alive_closure_cm(this),
1432 _is_subject_to_discovery_cm(this),
1433 _bot(NULL),
1434 _hot_card_cache(NULL),
1435 _g1_rem_set(NULL),
1436 _cr(NULL),
1437 _g1mm(NULL),
1438 _preserved_marks_set(true /* in_c_heap */),
1439 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1440 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1441 _humongous_reclaim_candidates(),
1442 _has_humongous_reclaim_candidates(false),
1443 _archive_allocator(NULL),
1444 _summary_bytes_used(0),
1445 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1446 _old_evac_stats("Old", OldPLABSize, PLABWeight),
1447 _expand_heap_after_alloc_failure(true),
1448 _old_marking_cycles_started(0),
1449 _old_marking_cycles_completed(0),
1450 _in_cset_fast_test() {
1451
1452 _workers = new WorkGang("GC Thread", ParallelGCThreads,
1453 /* are_GC_task_threads */true,
1454 /* are_ConcurrentGC_threads */false);
1455 _workers->initialize_workers();
1456 _verifier = new G1HeapVerifier(this);
1457
1458 _allocator = new G1Allocator(this);
1459
1460 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics());
1461
1462 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1463
1464 // Override the default _filler_array_max_size so that no humongous filler
1465 // objects are created.
1466 _filler_array_max_size = _humongous_object_threshold_in_words;
1467
1468 uint n_queues = ParallelGCThreads;
1469 _task_queues = new RefToScanQueueSet(n_queues);
1470
1471 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1472
1473 for (uint i = 0; i < n_queues; i++) {
1474 RefToScanQueue* q = new RefToScanQueue();
1475 q->initialize();
1476 _task_queues->register_queue(i, q);
1477 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1478 }
1479
1480 // Initialize the G1EvacuationFailureALot counters and flags.
1481 NOT_PRODUCT(reset_evacuation_should_fail();)
1482
1483 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1484 }
1485
1486 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1487 size_t size,
1488 size_t translation_factor) {
1489 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1490 // Allocate a new reserved space, preferring to use large pages.
1491 ReservedSpace rs(size, preferred_page_size);
1492 G1RegionToSpaceMapper* result =
1493 G1RegionToSpaceMapper::create_mapper(rs,
1494 size,
1495 rs.alignment(),
1496 HeapRegion::GrainBytes,
1497 translation_factor,
1498 mtGC);
1499
1500 os::trace_page_sizes_for_requested_size(description,
1501 size,
1502 preferred_page_size,
1503 rs.alignment(),
1504 rs.base(),
1505 rs.size());
1506
1507 return result;
1508 }
1509
1510 jint G1CollectedHeap::initialize_concurrent_refinement() {
1511 jint ecode = JNI_OK;
1512 _cr = G1ConcurrentRefine::create(&ecode);
1513 return ecode;
1514 }
1515
1516 jint G1CollectedHeap::initialize_young_gen_sampling_thread() {
1517 _young_gen_sampling_thread = new G1YoungRemSetSamplingThread();
1518 if (_young_gen_sampling_thread->osthread() == NULL) {
1519 vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread");
1520 return JNI_ENOMEM;
1521 }
1522 return JNI_OK;
1523 }
1524
1525 jint G1CollectedHeap::initialize() {
1526 os::enable_vtime();
1527
1528 // Necessary to satisfy locking discipline assertions.
1529
1530 MutexLocker x(Heap_lock);
1531
1532 // While there are no constraints in the GC code that HeapWordSize
1533 // be any particular value, there are multiple other areas in the
1534 // system which believe this to be true (e.g. oop->object_size in some
1535 // cases incorrectly returns the size in wordSize units rather than
1536 // HeapWordSize).
1537 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1538
1539 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1540 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1541 size_t heap_alignment = collector_policy()->heap_alignment();
1542
1543 // Ensure that the sizes are properly aligned.
1544 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1545 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1546 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1547
1548 // Reserve the maximum.
1549
1550 // When compressed oops are enabled, the preferred heap base
1551 // is calculated by subtracting the requested size from the
1552 // 32Gb boundary and using the result as the base address for
1553 // heap reservation. If the requested size is not aligned to
1554 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1555 // into the ReservedHeapSpace constructor) then the actual
1556 // base of the reserved heap may end up differing from the
1557 // address that was requested (i.e. the preferred heap base).
1558 // If this happens then we could end up using a non-optimal
1559 // compressed oops mode.
1560
1561 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1562 heap_alignment);
1563
1564 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1565
1566 // Create the barrier set for the entire reserved region.
1567 G1CardTable* ct = new G1CardTable(reserved_region());
1568 ct->initialize();
1569 G1BarrierSet* bs = new G1BarrierSet(ct);
1570 bs->initialize();
1571 assert(bs->is_a(BarrierSet::G1BarrierSet), "sanity");
1572 BarrierSet::set_barrier_set(bs);
1573 _card_table = ct;
1574
1575 // Create the hot card cache.
1576 _hot_card_cache = new G1HotCardCache(this);
1577
1578 // Carve out the G1 part of the heap.
1579 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1580 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
1581 G1RegionToSpaceMapper* heap_storage =
1582 G1RegionToSpaceMapper::create_mapper(g1_rs,
1583 g1_rs.size(),
1584 page_size,
1585 HeapRegion::GrainBytes,
1586 1,
1587 mtJavaHeap);
1588 os::trace_page_sizes("Heap",
1589 collector_policy()->min_heap_byte_size(),
1590 max_byte_size,
1591 page_size,
1592 heap_rs.base(),
1593 heap_rs.size());
1594 heap_storage->set_mapping_changed_listener(&_listener);
1595
1596 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1597 G1RegionToSpaceMapper* bot_storage =
1598 create_aux_memory_mapper("Block Offset Table",
1599 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1600 G1BlockOffsetTable::heap_map_factor());
1601
1602 G1RegionToSpaceMapper* cardtable_storage =
1603 create_aux_memory_mapper("Card Table",
1604 G1CardTable::compute_size(g1_rs.size() / HeapWordSize),
1605 G1CardTable::heap_map_factor());
1606
1607 G1RegionToSpaceMapper* card_counts_storage =
1608 create_aux_memory_mapper("Card Counts Table",
1609 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1610 G1CardCounts::heap_map_factor());
1611
1612 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1613 G1RegionToSpaceMapper* prev_bitmap_storage =
1614 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1615 G1RegionToSpaceMapper* next_bitmap_storage =
1616 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1617
1618 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1619 _card_table->initialize(cardtable_storage);
1620 // Do later initialization work for concurrent refinement.
1621 _hot_card_cache->initialize(card_counts_storage);
1622
1623 // 6843694 - ensure that the maximum region index can fit
1624 // in the remembered set structures.
1625 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1626 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1627
1628 // The G1FromCardCache reserves card with value 0 as "invalid", so the heap must not
1629 // start within the first card.
1630 guarantee(g1_rs.base() >= (char*)G1CardTable::card_size, "Java heap must not start within the first card.");
1631 // Also create a G1 rem set.
1632 _g1_rem_set = new G1RemSet(this, _card_table, _hot_card_cache);
1633 _g1_rem_set->initialize(max_capacity(), max_regions());
1634
1635 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1636 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1637 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1638 "too many cards per region");
1639
1640 FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1641
1642 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1643
1644 {
1645 HeapWord* start = _hrm.reserved().start();
1646 HeapWord* end = _hrm.reserved().end();
1647 size_t granularity = HeapRegion::GrainBytes;
1648
1649 _in_cset_fast_test.initialize(start, end, granularity);
1650 _humongous_reclaim_candidates.initialize(start, end, granularity);
1651 }
1652
1653 // Create the G1ConcurrentMark data structure and thread.
1654 // (Must do this late, so that "max_regions" is defined.)
1655 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1656 if (_cm == NULL || !_cm->completed_initialization()) {
1657 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
1658 return JNI_ENOMEM;
1659 }
1660 _cm_thread = _cm->cm_thread();
1661
1662 // Now expand into the initial heap size.
1663 if (!expand(init_byte_size, _workers)) {
1664 vm_shutdown_during_initialization("Failed to allocate initial heap.");
1665 return JNI_ENOMEM;
1666 }
1667
1668 // Perform any initialization actions delegated to the policy.
1669 g1_policy()->init(this, &_collection_set);
1670
1671 G1BarrierSet::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1672 SATB_Q_FL_lock,
1673 G1SATBProcessCompletedThreshold,
1674 Shared_SATB_Q_lock);
1675
1676 jint ecode = initialize_concurrent_refinement();
1677 if (ecode != JNI_OK) {
1678 return ecode;
1679 }
1680
1681 ecode = initialize_young_gen_sampling_thread();
1682 if (ecode != JNI_OK) {
1683 return ecode;
1684 }
1685
1686 G1BarrierSet::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1687 DirtyCardQ_FL_lock,
1688 (int)concurrent_refine()->yellow_zone(),
1689 (int)concurrent_refine()->red_zone(),
1690 Shared_DirtyCardQ_lock,
1691 NULL, // fl_owner
1692 true); // init_free_ids
1693
1694 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1695 DirtyCardQ_FL_lock,
1696 -1, // never trigger processing
1697 -1, // no limit on length
1698 Shared_DirtyCardQ_lock,
1699 &G1BarrierSet::dirty_card_queue_set());
1700
1701 // Here we allocate the dummy HeapRegion that is required by the
1702 // G1AllocRegion class.
1703 HeapRegion* dummy_region = _hrm.get_dummy_region();
1704
1705 // We'll re-use the same region whether the alloc region will
1706 // require BOT updates or not and, if it doesn't, then a non-young
1707 // region will complain that it cannot support allocations without
1708 // BOT updates. So we'll tag the dummy region as eden to avoid that.
1709 dummy_region->set_eden();
1710 // Make sure it's full.
1711 dummy_region->set_top(dummy_region->end());
1712 G1AllocRegion::setup(this, dummy_region);
1713
1714 _allocator->init_mutator_alloc_region();
1715
1716 // Do create of the monitoring and management support so that
1717 // values in the heap have been properly initialized.
1718 _g1mm = new G1MonitoringSupport(this);
1719
1720 G1StringDedup::initialize();
1721
1722 _preserved_marks_set.init(ParallelGCThreads);
1723
1724 _collection_set.initialize(max_regions());
1725
1726 return JNI_OK;
1727 }
1728
1729 void G1CollectedHeap::initialize_serviceability() {
1730 _eden_pool = new G1EdenPool(this);
1731 _survivor_pool = new G1SurvivorPool(this);
1732 _old_pool = new G1OldGenPool(this);
1733
1734 _full_gc_memory_manager.add_pool(_eden_pool);
1735 _full_gc_memory_manager.add_pool(_survivor_pool);
1736 _full_gc_memory_manager.add_pool(_old_pool);
1737
1738 _memory_manager.add_pool(_eden_pool);
1739 _memory_manager.add_pool(_survivor_pool);
1740
1741 }
1742
1743 void G1CollectedHeap::stop() {
1744 // Stop all concurrent threads. We do this to make sure these threads
1745 // do not continue to execute and access resources (e.g. logging)
1746 // that are destroyed during shutdown.
1747 _cr->stop();
1748 _young_gen_sampling_thread->stop();
1749 _cm_thread->stop();
1750 if (G1StringDedup::is_enabled()) {
1751 G1StringDedup::stop();
1752 }
1753 }
1754
1755 void G1CollectedHeap::safepoint_synchronize_begin() {
1756 SuspendibleThreadSet::synchronize();
1757 }
1758
1759 void G1CollectedHeap::safepoint_synchronize_end() {
1760 SuspendibleThreadSet::desynchronize();
1761 }
1762
1763 size_t G1CollectedHeap::conservative_max_heap_alignment() {
1764 return HeapRegion::max_region_size();
1765 }
1766
1767 void G1CollectedHeap::post_initialize() {
1768 CollectedHeap::post_initialize();
1769 ref_processing_init();
1770 }
1771
1772 void G1CollectedHeap::ref_processing_init() {
1773 // Reference processing in G1 currently works as follows:
1774 //
1775 // * There are two reference processor instances. One is
1776 // used to record and process discovered references
1777 // during concurrent marking; the other is used to
1778 // record and process references during STW pauses
1779 // (both full and incremental).
1780 // * Both ref processors need to 'span' the entire heap as
1781 // the regions in the collection set may be dotted around.
1782 //
1783 // * For the concurrent marking ref processor:
1784 // * Reference discovery is enabled at initial marking.
1785 // * Reference discovery is disabled and the discovered
1786 // references processed etc during remarking.
1787 // * Reference discovery is MT (see below).
1788 // * Reference discovery requires a barrier (see below).
1789 // * Reference processing may or may not be MT
1790 // (depending on the value of ParallelRefProcEnabled
1791 // and ParallelGCThreads).
1792 // * A full GC disables reference discovery by the CM
1793 // ref processor and abandons any entries on it's
1794 // discovered lists.
1795 //
1796 // * For the STW processor:
1797 // * Non MT discovery is enabled at the start of a full GC.
1798 // * Processing and enqueueing during a full GC is non-MT.
1799 // * During a full GC, references are processed after marking.
1800 //
1801 // * Discovery (may or may not be MT) is enabled at the start
1802 // of an incremental evacuation pause.
1803 // * References are processed near the end of a STW evacuation pause.
1804 // * For both types of GC:
1805 // * Discovery is atomic - i.e. not concurrent.
1806 // * Reference discovery will not need a barrier.
1807
1808 bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1);
1809
1810 // Concurrent Mark ref processor
1811 _ref_processor_cm =
1812 new ReferenceProcessor(&_is_subject_to_discovery_cm,
1813 mt_processing, // mt processing
1814 ParallelGCThreads, // degree of mt processing
1815 (ParallelGCThreads > 1) || (ConcGCThreads > 1), // mt discovery
1816 MAX2(ParallelGCThreads, ConcGCThreads), // degree of mt discovery
1817 false, // Reference discovery is not atomic
1818 &_is_alive_closure_cm); // is alive closure
1819
1820 // STW ref processor
1821 _ref_processor_stw =
1822 new ReferenceProcessor(&_is_subject_to_discovery_stw,
1823 mt_processing, // mt processing
1824 ParallelGCThreads, // degree of mt processing
1825 (ParallelGCThreads > 1), // mt discovery
1826 ParallelGCThreads, // degree of mt discovery
1827 true, // Reference discovery is atomic
1828 &_is_alive_closure_stw); // is alive closure
1829 }
1830
1831 CollectorPolicy* G1CollectedHeap::collector_policy() const {
1832 return _collector_policy;
1833 }
1834
1835 SoftRefPolicy* G1CollectedHeap::soft_ref_policy() {
1836 return &_soft_ref_policy;
1837 }
1838
1839 size_t G1CollectedHeap::capacity() const {
1840 return _hrm.length() * HeapRegion::GrainBytes;
1841 }
1842
1843 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const {
1844 return _hrm.total_free_bytes();
1845 }
1846
1847 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) {
1848 _hot_card_cache->drain(cl, worker_i);
1849 }
1850
1851 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) {
1852 DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
1853 size_t n_completed_buffers = 0;
1854 while (dcqs.apply_closure_during_gc(cl, worker_i)) {
1855 n_completed_buffers++;
1856 }
1857 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers, G1GCPhaseTimes::UpdateRSProcessedBuffers);
1858 dcqs.clear_n_completed_buffers();
1859 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
1860 }
1861
1862 // Computes the sum of the storage used by the various regions.
1863 size_t G1CollectedHeap::used() const {
1864 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
1865 if (_archive_allocator != NULL) {
1866 result += _archive_allocator->used();
1867 }
1868 return result;
1869 }
1870
1871 size_t G1CollectedHeap::used_unlocked() const {
1872 return _summary_bytes_used;
1873 }
1874
1875 class SumUsedClosure: public HeapRegionClosure {
1876 size_t _used;
1877 public:
1878 SumUsedClosure() : _used(0) {}
1879 bool do_heap_region(HeapRegion* r) {
1880 _used += r->used();
1881 return false;
1882 }
1883 size_t result() { return _used; }
1884 };
1885
1886 size_t G1CollectedHeap::recalculate_used() const {
1887 double recalculate_used_start = os::elapsedTime();
1888
1889 SumUsedClosure blk;
1890 heap_region_iterate(&blk);
1891
1892 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
1893 return blk.result();
1894 }
1895
1896 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
1897 switch (cause) {
1898 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
1899 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent;
1900 case GCCause::_wb_conc_mark: return true;
1901 default : return false;
1902 }
1903 }
1904
1905 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
1906 switch (cause) {
1907 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
1908 case GCCause::_g1_humongous_allocation: return true;
1909 default: return is_user_requested_concurrent_full_gc(cause);
1910 }
1911 }
1912
1913 #ifndef PRODUCT
1914 void G1CollectedHeap::allocate_dummy_regions() {
1915 // Let's fill up most of the region
1916 size_t word_size = HeapRegion::GrainWords - 1024;
1917 // And as a result the region we'll allocate will be humongous.
1918 guarantee(is_humongous(word_size), "sanity");
1919
1920 // _filler_array_max_size is set to humongous object threshold
1921 // but temporarily change it to use CollectedHeap::fill_with_object().
1922 SizeTFlagSetting fs(_filler_array_max_size, word_size);
1923
1924 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
1925 // Let's use the existing mechanism for the allocation
1926 HeapWord* dummy_obj = humongous_obj_allocate(word_size);
1927 if (dummy_obj != NULL) {
1928 MemRegion mr(dummy_obj, word_size);
1929 CollectedHeap::fill_with_object(mr);
1930 } else {
1931 // If we can't allocate once, we probably cannot allocate
1932 // again. Let's get out of the loop.
1933 break;
1934 }
1935 }
1936 }
1937 #endif // !PRODUCT
1938
1939 void G1CollectedHeap::increment_old_marking_cycles_started() {
1940 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
1941 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
1942 "Wrong marking cycle count (started: %d, completed: %d)",
1943 _old_marking_cycles_started, _old_marking_cycles_completed);
1944
1945 _old_marking_cycles_started++;
1946 }
1947
1948 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
1949 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
1950
1951 // We assume that if concurrent == true, then the caller is a
1952 // concurrent thread that was joined the Suspendible Thread
1953 // Set. If there's ever a cheap way to check this, we should add an
1954 // assert here.
1955
1956 // Given that this method is called at the end of a Full GC or of a
1957 // concurrent cycle, and those can be nested (i.e., a Full GC can
1958 // interrupt a concurrent cycle), the number of full collections
1959 // completed should be either one (in the case where there was no
1960 // nesting) or two (when a Full GC interrupted a concurrent cycle)
1961 // behind the number of full collections started.
1962
1963 // This is the case for the inner caller, i.e. a Full GC.
1964 assert(concurrent ||
1965 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
1966 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
1967 "for inner caller (Full GC): _old_marking_cycles_started = %u "
1968 "is inconsistent with _old_marking_cycles_completed = %u",
1969 _old_marking_cycles_started, _old_marking_cycles_completed);
1970
1971 // This is the case for the outer caller, i.e. the concurrent cycle.
1972 assert(!concurrent ||
1973 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
1974 "for outer caller (concurrent cycle): "
1975 "_old_marking_cycles_started = %u "
1976 "is inconsistent with _old_marking_cycles_completed = %u",
1977 _old_marking_cycles_started, _old_marking_cycles_completed);
1978
1979 _old_marking_cycles_completed += 1;
1980
1981 // We need to clear the "in_progress" flag in the CM thread before
1982 // we wake up any waiters (especially when ExplicitInvokesConcurrent
1983 // is set) so that if a waiter requests another System.gc() it doesn't
1984 // incorrectly see that a marking cycle is still in progress.
1985 if (concurrent) {
1986 _cm_thread->set_idle();
1987 }
1988
1989 // This notify_all() will ensure that a thread that called
1990 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
1991 // and it's waiting for a full GC to finish will be woken up. It is
1992 // waiting in VM_G1CollectForAllocation::doit_epilogue().
1993 FullGCCount_lock->notify_all();
1994 }
1995
1996 void G1CollectedHeap::collect(GCCause::Cause cause) {
1997 assert_heap_not_locked();
1998
1999 uint gc_count_before;
2000 uint old_marking_count_before;
2001 uint full_gc_count_before;
2002 bool retry_gc;
2003
2004 do {
2005 retry_gc = false;
2006
2007 {
2008 MutexLocker ml(Heap_lock);
2009
2010 // Read the GC count while holding the Heap_lock
2011 gc_count_before = total_collections();
2012 full_gc_count_before = total_full_collections();
2013 old_marking_count_before = _old_marking_cycles_started;
2014 }
2015
2016 if (should_do_concurrent_full_gc(cause)) {
2017 // Schedule an initial-mark evacuation pause that will start a
2018 // concurrent cycle. We're setting word_size to 0 which means that
2019 // we are not requesting a post-GC allocation.
2020 VM_G1CollectForAllocation op(0, /* word_size */
2021 gc_count_before,
2022 cause,
2023 true, /* should_initiate_conc_mark */
2024 g1_policy()->max_pause_time_ms());
2025 VMThread::execute(&op);
2026 if (!op.pause_succeeded()) {
2027 if (old_marking_count_before == _old_marking_cycles_started) {
2028 retry_gc = op.should_retry_gc();
2029 } else {
2030 // A Full GC happened while we were trying to schedule the
2031 // initial-mark GC. No point in starting a new cycle given
2032 // that the whole heap was collected anyway.
2033 }
2034
2035 if (retry_gc) {
2036 if (GCLocker::is_active_and_needs_gc()) {
2037 GCLocker::stall_until_clear();
2038 }
2039 }
2040 }
2041 } else {
2042 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2043 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2044
2045 // Schedule a standard evacuation pause. We're setting word_size
2046 // to 0 which means that we are not requesting a post-GC allocation.
2047 VM_G1CollectForAllocation op(0, /* word_size */
2048 gc_count_before,
2049 cause,
2050 false, /* should_initiate_conc_mark */
2051 g1_policy()->max_pause_time_ms());
2052 VMThread::execute(&op);
2053 } else {
2054 // Schedule a Full GC.
2055 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2056 VMThread::execute(&op);
2057 }
2058 }
2059 } while (retry_gc);
2060 }
2061
2062 bool G1CollectedHeap::is_in(const void* p) const {
2063 if (_hrm.reserved().contains(p)) {
2064 // Given that we know that p is in the reserved space,
2065 // heap_region_containing() should successfully
2066 // return the containing region.
2067 HeapRegion* hr = heap_region_containing(p);
2068 return hr->is_in(p);
2069 } else {
2070 return false;
2071 }
2072 }
2073
2074 #ifdef ASSERT
2075 bool G1CollectedHeap::is_in_exact(const void* p) const {
2076 bool contains = reserved_region().contains(p);
2077 bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2078 if (contains && available) {
2079 return true;
2080 } else {
2081 return false;
2082 }
2083 }
2084 #endif
2085
2086 // Iteration functions.
2087
2088 // Iterates an ObjectClosure over all objects within a HeapRegion.
2089
2090 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2091 ObjectClosure* _cl;
2092 public:
2093 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2094 bool do_heap_region(HeapRegion* r) {
2095 if (!r->is_continues_humongous()) {
2096 r->object_iterate(_cl);
2097 }
2098 return false;
2099 }
2100 };
2101
2102 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2103 IterateObjectClosureRegionClosure blk(cl);
2104 heap_region_iterate(&blk);
2105 }
2106
2107 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2108 _hrm.iterate(cl);
2109 }
2110
2111 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
2112 HeapRegionClaimer *hrclaimer,
2113 uint worker_id) const {
2114 _hrm.par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id));
2115 }
2116
2117 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl,
2118 HeapRegionClaimer *hrclaimer) const {
2119 _hrm.par_iterate(cl, hrclaimer, 0);
2120 }
2121
2122 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2123 _collection_set.iterate(cl);
2124 }
2125
2126 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) {
2127 _collection_set.iterate_from(cl, worker_id, workers()->active_workers());
2128 }
2129
2130 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2131 HeapRegion* hr = heap_region_containing(addr);
2132 return hr->block_start(addr);
2133 }
2134
2135 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2136 HeapRegion* hr = heap_region_containing(addr);
2137 return hr->block_size(addr);
2138 }
2139
2140 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2141 HeapRegion* hr = heap_region_containing(addr);
2142 return hr->block_is_obj(addr);
2143 }
2144
2145 bool G1CollectedHeap::supports_tlab_allocation() const {
2146 return true;
2147 }
2148
2149 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2150 return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2151 }
2152
2153 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2154 return _eden.length() * HeapRegion::GrainBytes;
2155 }
2156
2157 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2158 // must be equal to the humongous object limit.
2159 size_t G1CollectedHeap::max_tlab_size() const {
2160 return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
2161 }
2162
2163 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2164 return _allocator->unsafe_max_tlab_alloc();
2165 }
2166
2167 size_t G1CollectedHeap::max_capacity() const {
2168 return _hrm.reserved().byte_size();
2169 }
2170
2171 jlong G1CollectedHeap::millis_since_last_gc() {
2172 // See the notes in GenCollectedHeap::millis_since_last_gc()
2173 // for more information about the implementation.
2174 jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) -
2175 _g1_policy->collection_pause_end_millis();
2176 if (ret_val < 0) {
2177 log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
2178 ". returning zero instead.", ret_val);
2179 return 0;
2180 }
2181 return ret_val;
2182 }
2183
2184 void G1CollectedHeap::deduplicate_string(oop str) {
2185 assert(java_lang_String::is_instance(str), "invariant");
2186
2187 if (G1StringDedup::is_enabled()) {
2188 G1StringDedup::deduplicate(str);
2189 }
2190 }
2191
2192 void G1CollectedHeap::prepare_for_verify() {
2193 _verifier->prepare_for_verify();
2194 }
2195
2196 void G1CollectedHeap::verify(VerifyOption vo) {
2197 _verifier->verify(vo);
2198 }
2199
2200 bool G1CollectedHeap::supports_concurrent_phase_control() const {
2201 return true;
2202 }
2203
2204 const char* const* G1CollectedHeap::concurrent_phases() const {
2205 return _cm_thread->concurrent_phases();
2206 }
2207
2208 bool G1CollectedHeap::request_concurrent_phase(const char* phase) {
2209 return _cm_thread->request_concurrent_phase(phase);
2210 }
2211
2212 class PrintRegionClosure: public HeapRegionClosure {
2213 outputStream* _st;
2214 public:
2215 PrintRegionClosure(outputStream* st) : _st(st) {}
2216 bool do_heap_region(HeapRegion* r) {
2217 r->print_on(_st);
2218 return false;
2219 }
2220 };
2221
2222 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2223 const HeapRegion* hr,
2224 const VerifyOption vo) const {
2225 switch (vo) {
2226 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2227 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2228 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr);
2229 default: ShouldNotReachHere();
2230 }
2231 return false; // keep some compilers happy
2232 }
2233
2234 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2235 const VerifyOption vo) const {
2236 switch (vo) {
2237 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2238 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2239 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj);
2240 default: ShouldNotReachHere();
2241 }
2242 return false; // keep some compilers happy
2243 }
2244
2245 void G1CollectedHeap::print_heap_regions() const {
2246 LogTarget(Trace, gc, heap, region) lt;
2247 if (lt.is_enabled()) {
2248 LogStream ls(lt);
2249 print_regions_on(&ls);
2250 }
2251 }
2252
2253 void G1CollectedHeap::print_on(outputStream* st) const {
2254 st->print(" %-20s", "garbage-first heap");
2255 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2256 capacity()/K, used_unlocked()/K);
2257 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")",
2258 p2i(_hrm.reserved().start()),
2259 p2i(_hrm.reserved().end()));
2260 st->cr();
2261 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2262 uint young_regions = young_regions_count();
2263 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2264 (size_t) young_regions * HeapRegion::GrainBytes / K);
2265 uint survivor_regions = survivor_regions_count();
2266 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2267 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2268 st->cr();
2269 MetaspaceUtils::print_on(st);
2270 }
2271
2272 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2273 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2274 "HS=humongous(starts), HC=humongous(continues), "
2275 "CS=collection set, F=free, A=archive, "
2276 "TAMS=top-at-mark-start (previous, next)");
2277 PrintRegionClosure blk(st);
2278 heap_region_iterate(&blk);
2279 }
2280
2281 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2282 print_on(st);
2283
2284 // Print the per-region information.
2285 print_regions_on(st);
2286 }
2287
2288 void G1CollectedHeap::print_on_error(outputStream* st) const {
2289 this->CollectedHeap::print_on_error(st);
2290
2291 if (_cm != NULL) {
2292 st->cr();
2293 _cm->print_on_error(st);
2294 }
2295 }
2296
2297 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2298 workers()->print_worker_threads_on(st);
2299 _cm_thread->print_on(st);
2300 st->cr();
2301 _cm->print_worker_threads_on(st);
2302 _cr->print_threads_on(st);
2303 _young_gen_sampling_thread->print_on(st);
2304 if (G1StringDedup::is_enabled()) {
2305 G1StringDedup::print_worker_threads_on(st);
2306 }
2307 }
2308
2309 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2310 workers()->threads_do(tc);
2311 tc->do_thread(_cm_thread);
2312 _cm->threads_do(tc);
2313 _cr->threads_do(tc);
2314 tc->do_thread(_young_gen_sampling_thread);
2315 if (G1StringDedup::is_enabled()) {
2316 G1StringDedup::threads_do(tc);
2317 }
2318 }
2319
2320 void G1CollectedHeap::print_tracing_info() const {
2321 g1_rem_set()->print_summary_info();
2322 concurrent_mark()->print_summary_info();
2323 }
2324
2325 #ifndef PRODUCT
2326 // Helpful for debugging RSet issues.
2327
2328 class PrintRSetsClosure : public HeapRegionClosure {
2329 private:
2330 const char* _msg;
2331 size_t _occupied_sum;
2332
2333 public:
2334 bool do_heap_region(HeapRegion* r) {
2335 HeapRegionRemSet* hrrs = r->rem_set();
2336 size_t occupied = hrrs->occupied();
2337 _occupied_sum += occupied;
2338
2339 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2340 if (occupied == 0) {
2341 tty->print_cr(" RSet is empty");
2342 } else {
2343 hrrs->print();
2344 }
2345 tty->print_cr("----------");
2346 return false;
2347 }
2348
2349 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2350 tty->cr();
2351 tty->print_cr("========================================");
2352 tty->print_cr("%s", msg);
2353 tty->cr();
2354 }
2355
2356 ~PrintRSetsClosure() {
2357 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2358 tty->print_cr("========================================");
2359 tty->cr();
2360 }
2361 };
2362
2363 void G1CollectedHeap::print_cset_rsets() {
2364 PrintRSetsClosure cl("Printing CSet RSets");
2365 collection_set_iterate(&cl);
2366 }
2367
2368 void G1CollectedHeap::print_all_rsets() {
2369 PrintRSetsClosure cl("Printing All RSets");;
2370 heap_region_iterate(&cl);
2371 }
2372 #endif // PRODUCT
2373
2374 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2375
2376 size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes;
2377 size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes;
2378 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2379
2380 size_t eden_capacity_bytes =
2381 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2382
2383 VirtualSpaceSummary heap_summary = create_heap_space_summary();
2384 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2385 eden_capacity_bytes, survivor_used_bytes, num_regions());
2386 }
2387
2388 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2389 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2390 stats->unused(), stats->used(), stats->region_end_waste(),
2391 stats->regions_filled(), stats->direct_allocated(),
2392 stats->failure_used(), stats->failure_waste());
2393 }
2394
2395 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2396 const G1HeapSummary& heap_summary = create_g1_heap_summary();
2397 gc_tracer->report_gc_heap_summary(when, heap_summary);
2398
2399 const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2400 gc_tracer->report_metaspace_summary(when, metaspace_summary);
2401 }
2402
2403 G1CollectedHeap* G1CollectedHeap::heap() {
2404 CollectedHeap* heap = Universe::heap();
2405 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2406 assert(heap->kind() == CollectedHeap::G1, "Invalid name");
2407 return (G1CollectedHeap*)heap;
2408 }
2409
2410 void G1CollectedHeap::gc_prologue(bool full) {
2411 // always_do_update_barrier = false;
2412 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2413
2414 // This summary needs to be printed before incrementing total collections.
2415 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2416
2417 // Update common counters.
2418 increment_total_collections(full /* full gc */);
2419 if (full) {
2420 increment_old_marking_cycles_started();
2421 }
2422
2423 // Fill TLAB's and such
2424 double start = os::elapsedTime();
2425 accumulate_statistics_all_tlabs();
2426 ensure_parsability(true);
2427 g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2428 }
2429
2430 void G1CollectedHeap::gc_epilogue(bool full) {
2431 // Update common counters.
2432 if (full) {
2433 // Update the number of full collections that have been completed.
2434 increment_old_marking_cycles_completed(false /* concurrent */);
2435 }
2436
2437 // We are at the end of the GC. Total collections has already been increased.
2438 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2439
2440 // FIXME: what is this about?
2441 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2442 // is set.
2443 #if COMPILER2_OR_JVMCI
2444 assert(DerivedPointerTable::is_empty(), "derived pointer present");
2445 #endif
2446 // always_do_update_barrier = true;
2447
2448 double start = os::elapsedTime();
2449 resize_all_tlabs();
2450 g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2451
2452 MemoryService::track_memory_usage();
2453 // We have just completed a GC. Update the soft reference
2454 // policy with the new heap occupancy
2455 Universe::update_heap_info_at_gc();
2456 }
2457
2458 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2459 uint gc_count_before,
2460 bool* succeeded,
2461 GCCause::Cause gc_cause) {
2462 assert_heap_not_locked_and_not_at_safepoint();
2463 VM_G1CollectForAllocation op(word_size,
2464 gc_count_before,
2465 gc_cause,
2466 false, /* should_initiate_conc_mark */
2467 g1_policy()->max_pause_time_ms());
2468 VMThread::execute(&op);
2469
2470 HeapWord* result = op.result();
2471 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
2472 assert(result == NULL || ret_succeeded,
2473 "the result should be NULL if the VM did not succeed");
2474 *succeeded = ret_succeeded;
2475
2476 assert_heap_not_locked();
2477 return result;
2478 }
2479
2480 void G1CollectedHeap::do_concurrent_mark() {
2481 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
2482 if (!_cm_thread->in_progress()) {
2483 _cm_thread->set_started();
2484 CGC_lock->notify();
2485 }
2486 }
2487
2488 size_t G1CollectedHeap::pending_card_num() {
2489 size_t extra_cards = 0;
2490 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *curr = jtiwh.next(); ) {
2491 DirtyCardQueue& dcq = G1ThreadLocalData::dirty_card_queue(curr);
2492 extra_cards += dcq.size();
2493 }
2494 DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
2495 size_t buffer_size = dcqs.buffer_size();
2496 size_t buffer_num = dcqs.completed_buffers_num();
2497
2498 return buffer_size * buffer_num + extra_cards;
2499 }
2500
2501 bool G1CollectedHeap::is_potential_eager_reclaim_candidate(HeapRegion* r) const {
2502 // We don't nominate objects with many remembered set entries, on
2503 // the assumption that such objects are likely still live.
2504 HeapRegionRemSet* rem_set = r->rem_set();
2505
2506 return G1EagerReclaimHumongousObjectsWithStaleRefs ?
2507 rem_set->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) :
2508 G1EagerReclaimHumongousObjects && rem_set->is_empty();
2509 }
2510
2511 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
2512 private:
2513 size_t _total_humongous;
2514 size_t _candidate_humongous;
2515
2516 DirtyCardQueue _dcq;
2517
2518 bool humongous_region_is_candidate(G1CollectedHeap* g1h, HeapRegion* region) const {
2519 assert(region->is_starts_humongous(), "Must start a humongous object");
2520
2521 oop obj = oop(region->bottom());
2522
2523 // Dead objects cannot be eager reclaim candidates. Due to class
2524 // unloading it is unsafe to query their classes so we return early.
2525 if (g1h->is_obj_dead(obj, region)) {
2526 return false;
2527 }
2528
2529 // If we do not have a complete remembered set for the region, then we can
2530 // not be sure that we have all references to it.
2531 if (!region->rem_set()->is_complete()) {
2532 return false;
2533 }
2534 // Candidate selection must satisfy the following constraints
2535 // while concurrent marking is in progress:
2536 //
2537 // * In order to maintain SATB invariants, an object must not be
2538 // reclaimed if it was allocated before the start of marking and
2539 // has not had its references scanned. Such an object must have
2540 // its references (including type metadata) scanned to ensure no
2541 // live objects are missed by the marking process. Objects
2542 // allocated after the start of concurrent marking don't need to
2543 // be scanned.
2544 //
2545 // * An object must not be reclaimed if it is on the concurrent
2546 // mark stack. Objects allocated after the start of concurrent
2547 // marking are never pushed on the mark stack.
2548 //
2549 // Nominating only objects allocated after the start of concurrent
2550 // marking is sufficient to meet both constraints. This may miss
2551 // some objects that satisfy the constraints, but the marking data
2552 // structures don't support efficiently performing the needed
2553 // additional tests or scrubbing of the mark stack.
2554 //
2555 // However, we presently only nominate is_typeArray() objects.
2556 // A humongous object containing references induces remembered
2557 // set entries on other regions. In order to reclaim such an
2558 // object, those remembered sets would need to be cleaned up.
2559 //
2560 // We also treat is_typeArray() objects specially, allowing them
2561 // to be reclaimed even if allocated before the start of
2562 // concurrent mark. For this we rely on mark stack insertion to
2563 // exclude is_typeArray() objects, preventing reclaiming an object
2564 // that is in the mark stack. We also rely on the metadata for
2565 // such objects to be built-in and so ensured to be kept live.
2566 // Frequent allocation and drop of large binary blobs is an
2567 // important use case for eager reclaim, and this special handling
2568 // may reduce needed headroom.
2569
2570 return obj->is_typeArray() &&
2571 g1h->is_potential_eager_reclaim_candidate(region);
2572 }
2573
2574 public:
2575 RegisterHumongousWithInCSetFastTestClosure()
2576 : _total_humongous(0),
2577 _candidate_humongous(0),
2578 _dcq(&G1BarrierSet::dirty_card_queue_set()) {
2579 }
2580
2581 virtual bool do_heap_region(HeapRegion* r) {
2582 if (!r->is_starts_humongous()) {
2583 return false;
2584 }
2585 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2586
2587 bool is_candidate = humongous_region_is_candidate(g1h, r);
2588 uint rindex = r->hrm_index();
2589 g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
2590 if (is_candidate) {
2591 _candidate_humongous++;
2592 g1h->register_humongous_region_with_cset(rindex);
2593 // Is_candidate already filters out humongous object with large remembered sets.
2594 // If we have a humongous object with a few remembered sets, we simply flush these
2595 // remembered set entries into the DCQS. That will result in automatic
2596 // re-evaluation of their remembered set entries during the following evacuation
2597 // phase.
2598 if (!r->rem_set()->is_empty()) {
2599 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
2600 "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
2601 G1CardTable* ct = g1h->card_table();
2602 HeapRegionRemSetIterator hrrs(r->rem_set());
2603 size_t card_index;
2604 while (hrrs.has_next(card_index)) {
2605 jbyte* card_ptr = (jbyte*)ct->byte_for_index(card_index);
2606 // The remembered set might contain references to already freed
2607 // regions. Filter out such entries to avoid failing card table
2608 // verification.
2609 if (g1h->is_in_closed_subset(ct->addr_for(card_ptr))) {
2610 if (*card_ptr != G1CardTable::dirty_card_val()) {
2611 *card_ptr = G1CardTable::dirty_card_val();
2612 _dcq.enqueue(card_ptr);
2613 }
2614 }
2615 }
2616 assert(hrrs.n_yielded() == r->rem_set()->occupied(),
2617 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
2618 hrrs.n_yielded(), r->rem_set()->occupied());
2619 // We should only clear the card based remembered set here as we will not
2620 // implicitly rebuild anything else during eager reclaim. Note that at the moment
2621 // (and probably never) we do not enter this path if there are other kind of
2622 // remembered sets for this region.
2623 r->rem_set()->clear_locked(true /* only_cardset */);
2624 // Clear_locked() above sets the state to Empty. However we want to continue
2625 // collecting remembered set entries for humongous regions that were not
2626 // reclaimed.
2627 r->rem_set()->set_state_complete();
2628 }
2629 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
2630 }
2631 _total_humongous++;
2632
2633 return false;
2634 }
2635
2636 size_t total_humongous() const { return _total_humongous; }
2637 size_t candidate_humongous() const { return _candidate_humongous; }
2638
2639 void flush_rem_set_entries() { _dcq.flush(); }
2640 };
2641
2642 void G1CollectedHeap::register_humongous_regions_with_cset() {
2643 if (!G1EagerReclaimHumongousObjects) {
2644 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
2645 return;
2646 }
2647 double time = os::elapsed_counter();
2648
2649 // Collect reclaim candidate information and register candidates with cset.
2650 RegisterHumongousWithInCSetFastTestClosure cl;
2651 heap_region_iterate(&cl);
2652
2653 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
2654 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
2655 cl.total_humongous(),
2656 cl.candidate_humongous());
2657 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
2658
2659 // Finally flush all remembered set entries to re-check into the global DCQS.
2660 cl.flush_rem_set_entries();
2661 }
2662
2663 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2664 public:
2665 bool do_heap_region(HeapRegion* hr) {
2666 if (!hr->is_archive() && !hr->is_continues_humongous()) {
2667 hr->verify_rem_set();
2668 }
2669 return false;
2670 }
2671 };
2672
2673 uint G1CollectedHeap::num_task_queues() const {
2674 return _task_queues->size();
2675 }
2676
2677 #if TASKQUEUE_STATS
2678 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2679 st->print_raw_cr("GC Task Stats");
2680 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2681 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2682 }
2683
2684 void G1CollectedHeap::print_taskqueue_stats() const {
2685 if (!log_is_enabled(Trace, gc, task, stats)) {
2686 return;
2687 }
2688 Log(gc, task, stats) log;
2689 ResourceMark rm;
2690 LogStream ls(log.trace());
2691 outputStream* st = &ls;
2692
2693 print_taskqueue_stats_hdr(st);
2694
2695 TaskQueueStats totals;
2696 const uint n = num_task_queues();
2697 for (uint i = 0; i < n; ++i) {
2698 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2699 totals += task_queue(i)->stats;
2700 }
2701 st->print_raw("tot "); totals.print(st); st->cr();
2702
2703 DEBUG_ONLY(totals.verify());
2704 }
2705
2706 void G1CollectedHeap::reset_taskqueue_stats() {
2707 const uint n = num_task_queues();
2708 for (uint i = 0; i < n; ++i) {
2709 task_queue(i)->stats.reset();
2710 }
2711 }
2712 #endif // TASKQUEUE_STATS
2713
2714 void G1CollectedHeap::wait_for_root_region_scanning() {
2715 double scan_wait_start = os::elapsedTime();
2716 // We have to wait until the CM threads finish scanning the
2717 // root regions as it's the only way to ensure that all the
2718 // objects on them have been correctly scanned before we start
2719 // moving them during the GC.
2720 bool waited = _cm->root_regions()->wait_until_scan_finished();
2721 double wait_time_ms = 0.0;
2722 if (waited) {
2723 double scan_wait_end = os::elapsedTime();
2724 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2725 }
2726 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2727 }
2728
2729 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2730 private:
2731 G1HRPrinter* _hr_printer;
2732 public:
2733 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2734
2735 virtual bool do_heap_region(HeapRegion* r) {
2736 _hr_printer->cset(r);
2737 return false;
2738 }
2739 };
2740
2741 void G1CollectedHeap::start_new_collection_set() {
2742 collection_set()->start_incremental_building();
2743
2744 clear_cset_fast_test();
2745
2746 guarantee(_eden.length() == 0, "eden should have been cleared");
2747 g1_policy()->transfer_survivors_to_cset(survivor());
2748 }
2749
2750 bool
2751 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
2752 assert_at_safepoint_on_vm_thread();
2753 guarantee(!is_gc_active(), "collection is not reentrant");
2754
2755 if (GCLocker::check_active_before_gc()) {
2756 return false;
2757 }
2758
2759 _gc_timer_stw->register_gc_start();
2760
2761 GCIdMark gc_id_mark;
2762 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
2763
2764 SvcGCMarker sgcm(SvcGCMarker::MINOR);
2765 ResourceMark rm;
2766
2767 g1_policy()->note_gc_start();
2768
2769 wait_for_root_region_scanning();
2770
2771 print_heap_before_gc();
2772 print_heap_regions();
2773 trace_heap_before_gc(_gc_tracer_stw);
2774
2775 _verifier->verify_region_sets_optional();
2776 _verifier->verify_dirty_young_regions();
2777
2778 // We should not be doing initial mark unless the conc mark thread is running
2779 if (!_cm_thread->should_terminate()) {
2780 // This call will decide whether this pause is an initial-mark
2781 // pause. If it is, in_initial_mark_gc() will return true
2782 // for the duration of this pause.
2783 g1_policy()->decide_on_conc_mark_initiation();
2784 }
2785
2786 // We do not allow initial-mark to be piggy-backed on a mixed GC.
2787 assert(!collector_state()->in_initial_mark_gc() ||
2788 collector_state()->in_young_only_phase(), "sanity");
2789
2790 // We also do not allow mixed GCs during marking.
2791 assert(!collector_state()->mark_or_rebuild_in_progress() || collector_state()->in_young_only_phase(), "sanity");
2792
2793 // Record whether this pause is an initial mark. When the current
2794 // thread has completed its logging output and it's safe to signal
2795 // the CM thread, the flag's value in the policy has been reset.
2796 bool should_start_conc_mark = collector_state()->in_initial_mark_gc();
2797
2798 // Inner scope for scope based logging, timers, and stats collection
2799 {
2800 EvacuationInfo evacuation_info;
2801
2802 if (collector_state()->in_initial_mark_gc()) {
2803 // We are about to start a marking cycle, so we increment the
2804 // full collection counter.
2805 increment_old_marking_cycles_started();
2806 _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
2807 }
2808
2809 _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
2810
2811 GCTraceCPUTime tcpu;
2812
2813 G1HeapVerifier::G1VerifyType verify_type;
2814 FormatBuffer<> gc_string("Pause ");
2815 if (collector_state()->in_initial_mark_gc()) {
2816 gc_string.append("Initial Mark");
2817 verify_type = G1HeapVerifier::G1VerifyInitialMark;
2818 } else if (collector_state()->in_young_only_phase()) {
2819 gc_string.append("Young");
2820 verify_type = G1HeapVerifier::G1VerifyYoungOnly;
2821 } else {
2822 gc_string.append("Mixed");
2823 verify_type = G1HeapVerifier::G1VerifyMixed;
2824 }
2825 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true);
2826
2827 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
2828 workers()->active_workers(),
2829 Threads::number_of_non_daemon_threads());
2830 active_workers = workers()->update_active_workers(active_workers);
2831 log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
2832
2833 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
2834 TraceMemoryManagerStats tms(&_memory_manager, gc_cause());
2835
2836 G1HeapTransition heap_transition(this);
2837 size_t heap_used_bytes_before_gc = used();
2838
2839 // Don't dynamically change the number of GC threads this early. A value of
2840 // 0 is used to indicate serial work. When parallel work is done,
2841 // it will be set.
2842
2843 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
2844 IsGCActiveMark x;
2845
2846 gc_prologue(false);
2847
2848 if (VerifyRememberedSets) {
2849 log_info(gc, verify)("[Verifying RemSets before GC]");
2850 VerifyRegionRemSetClosure v_cl;
2851 heap_region_iterate(&v_cl);
2852 }
2853
2854 _verifier->verify_before_gc(verify_type);
2855
2856 _verifier->check_bitmaps("GC Start");
2857
2858 #if COMPILER2_OR_JVMCI
2859 DerivedPointerTable::clear();
2860 #endif
2861
2862 // Please see comment in g1CollectedHeap.hpp and
2863 // G1CollectedHeap::ref_processing_init() to see how
2864 // reference processing currently works in G1.
2865
2866 // Enable discovery in the STW reference processor
2867 _ref_processor_stw->enable_discovery();
2868
2869 {
2870 // We want to temporarily turn off discovery by the
2871 // CM ref processor, if necessary, and turn it back on
2872 // on again later if we do. Using a scoped
2873 // NoRefDiscovery object will do this.
2874 NoRefDiscovery no_cm_discovery(_ref_processor_cm);
2875
2876 // Forget the current alloc region (we might even choose it to be part
2877 // of the collection set!).
2878 _allocator->release_mutator_alloc_region();
2879
2880 // This timing is only used by the ergonomics to handle our pause target.
2881 // It is unclear why this should not include the full pause. We will
2882 // investigate this in CR 7178365.
2883 //
2884 // Preserving the old comment here if that helps the investigation:
2885 //
2886 // The elapsed time induced by the start time below deliberately elides
2887 // the possible verification above.
2888 double sample_start_time_sec = os::elapsedTime();
2889
2890 g1_policy()->record_collection_pause_start(sample_start_time_sec);
2891
2892 if (collector_state()->in_initial_mark_gc()) {
2893 concurrent_mark()->pre_initial_mark();
2894 }
2895
2896 g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor);
2897
2898 evacuation_info.set_collectionset_regions(collection_set()->region_length());
2899
2900 // Make sure the remembered sets are up to date. This needs to be
2901 // done before register_humongous_regions_with_cset(), because the
2902 // remembered sets are used there to choose eager reclaim candidates.
2903 // If the remembered sets are not up to date we might miss some
2904 // entries that need to be handled.
2905 g1_rem_set()->cleanupHRRS();
2906
2907 register_humongous_regions_with_cset();
2908
2909 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table.");
2910
2911 // We call this after finalize_cset() to
2912 // ensure that the CSet has been finalized.
2913 _cm->verify_no_cset_oops();
2914
2915 if (_hr_printer.is_active()) {
2916 G1PrintCollectionSetClosure cl(&_hr_printer);
2917 _collection_set.iterate(&cl);
2918 }
2919
2920 // Initialize the GC alloc regions.
2921 _allocator->init_gc_alloc_regions(evacuation_info);
2922
2923 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length());
2924 pre_evacuate_collection_set();
2925
2926 // Actually do the work...
2927 evacuate_collection_set(&per_thread_states);
2928
2929 post_evacuate_collection_set(evacuation_info, &per_thread_states);
2930
2931 const size_t* surviving_young_words = per_thread_states.surviving_young_words();
2932 free_collection_set(&_collection_set, evacuation_info, surviving_young_words);
2933
2934 eagerly_reclaim_humongous_regions();
2935
2936 record_obj_copy_mem_stats();
2937 _survivor_evac_stats.adjust_desired_plab_sz();
2938 _old_evac_stats.adjust_desired_plab_sz();
2939
2940 double start = os::elapsedTime();
2941 start_new_collection_set();
2942 g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0);
2943
2944 if (evacuation_failed()) {
2945 set_used(recalculate_used());
2946 if (_archive_allocator != NULL) {
2947 _archive_allocator->clear_used();
2948 }
2949 for (uint i = 0; i < ParallelGCThreads; i++) {
2950 if (_evacuation_failed_info_array[i].has_failed()) {
2951 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
2952 }
2953 }
2954 } else {
2955 // The "used" of the the collection set have already been subtracted
2956 // when they were freed. Add in the bytes evacuated.
2957 increase_used(g1_policy()->bytes_copied_during_gc());
2958 }
2959
2960 if (collector_state()->in_initial_mark_gc()) {
2961 // We have to do this before we notify the CM threads that
2962 // they can start working to make sure that all the
2963 // appropriate initialization is done on the CM object.
2964 concurrent_mark()->post_initial_mark();
2965 // Note that we don't actually trigger the CM thread at
2966 // this point. We do that later when we're sure that
2967 // the current thread has completed its logging output.
2968 }
2969
2970 allocate_dummy_regions();
2971
2972 _allocator->init_mutator_alloc_region();
2973
2974 {
2975 size_t expand_bytes = _heap_sizing_policy->expansion_amount();
2976 if (expand_bytes > 0) {
2977 size_t bytes_before = capacity();
2978 // No need for an ergo logging here,
2979 // expansion_amount() does this when it returns a value > 0.
2980 double expand_ms;
2981 if (!expand(expand_bytes, _workers, &expand_ms)) {
2982 // We failed to expand the heap. Cannot do anything about it.
2983 }
2984 g1_policy()->phase_times()->record_expand_heap_time(expand_ms);
2985 }
2986 }
2987
2988 // We redo the verification but now wrt to the new CSet which
2989 // has just got initialized after the previous CSet was freed.
2990 _cm->verify_no_cset_oops();
2991
2992 // This timing is only used by the ergonomics to handle our pause target.
2993 // It is unclear why this should not include the full pause. We will
2994 // investigate this in CR 7178365.
2995 double sample_end_time_sec = os::elapsedTime();
2996 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
2997 size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards);
2998 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc);
2999
3000 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
3001 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc());
3002
3003 if (VerifyRememberedSets) {
3004 log_info(gc, verify)("[Verifying RemSets after GC]");
3005 VerifyRegionRemSetClosure v_cl;
3006 heap_region_iterate(&v_cl);
3007 }
3008
3009 _verifier->verify_after_gc(verify_type);
3010 _verifier->check_bitmaps("GC End");
3011
3012 assert(!_ref_processor_stw->discovery_enabled(), "Postcondition");
3013 _ref_processor_stw->verify_no_references_recorded();
3014
3015 // CM reference discovery will be re-enabled if necessary.
3016 }
3017
3018 #ifdef TRACESPINNING
3019 ParallelTaskTerminator::print_termination_counts();
3020 #endif
3021
3022 gc_epilogue(false);
3023 }
3024
3025 // Print the remainder of the GC log output.
3026 if (evacuation_failed()) {
3027 log_info(gc)("To-space exhausted");
3028 }
3029
3030 g1_policy()->print_phases();
3031 heap_transition.print();
3032
3033 // It is not yet to safe to tell the concurrent mark to
3034 // start as we have some optional output below. We don't want the
3035 // output from the concurrent mark thread interfering with this
3036 // logging output either.
3037
3038 _hrm.verify_optional();
3039 _verifier->verify_region_sets_optional();
3040
3041 TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3042 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3043
3044 print_heap_after_gc();
3045 print_heap_regions();
3046 trace_heap_after_gc(_gc_tracer_stw);
3047
3048 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3049 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3050 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3051 // before any GC notifications are raised.
3052 g1mm()->update_sizes();
3053
3054 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3055 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
3056 _gc_timer_stw->register_gc_end();
3057 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3058 }
3059 // It should now be safe to tell the concurrent mark thread to start
3060 // without its logging output interfering with the logging output
3061 // that came from the pause.
3062
3063 if (should_start_conc_mark) {
3064 // CAUTION: after the doConcurrentMark() call below,
3065 // the concurrent marking thread(s) could be running
3066 // concurrently with us. Make sure that anything after
3067 // this point does not assume that we are the only GC thread
3068 // running. Note: of course, the actual marking work will
3069 // not start until the safepoint itself is released in
3070 // SuspendibleThreadSet::desynchronize().
3071 do_concurrent_mark();
3072 }
3073
3074 return true;
3075 }
3076
3077 void G1CollectedHeap::remove_self_forwarding_pointers() {
3078 G1ParRemoveSelfForwardPtrsTask rsfp_task;
3079 workers()->run_task(&rsfp_task);
3080 }
3081
3082 void G1CollectedHeap::restore_after_evac_failure() {
3083 double remove_self_forwards_start = os::elapsedTime();
3084
3085 remove_self_forwarding_pointers();
3086 SharedRestorePreservedMarksTaskExecutor task_executor(workers());
3087 _preserved_marks_set.restore(&task_executor);
3088
3089 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3090 }
3091
3092 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) {
3093 if (!_evacuation_failed) {
3094 _evacuation_failed = true;
3095 }
3096
3097 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3098 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3099 }
3100
3101 bool G1ParEvacuateFollowersClosure::offer_termination() {
3102 G1ParScanThreadState* const pss = par_scan_state();
3103 start_term_time();
3104 const bool res = terminator()->offer_termination();
3105 end_term_time();
3106 return res;
3107 }
3108
3109 void G1ParEvacuateFollowersClosure::do_void() {
3110 G1ParScanThreadState* const pss = par_scan_state();
3111 pss->trim_queue();
3112 do {
3113 pss->steal_and_trim_queue(queues());
3114 } while (!offer_termination());
3115 }
3116
3117 class G1ParTask : public AbstractGangTask {
3118 protected:
3119 G1CollectedHeap* _g1h;
3120 G1ParScanThreadStateSet* _pss;
3121 RefToScanQueueSet* _queues;
3122 G1RootProcessor* _root_processor;
3123 ParallelTaskTerminator _terminator;
3124 uint _n_workers;
3125
3126 public:
3127 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers)
3128 : AbstractGangTask("G1 collection"),
3129 _g1h(g1h),
3130 _pss(per_thread_states),
3131 _queues(task_queues),
3132 _root_processor(root_processor),
3133 _terminator(n_workers, _queues),
3134 _n_workers(n_workers)
3135 {}
3136
3137 void work(uint worker_id) {
3138 if (worker_id >= _n_workers) return; // no work needed this round
3139
3140 double start_sec = os::elapsedTime();
3141 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec);
3142
3143 {
3144 ResourceMark rm;
3145 HandleMark hm;
3146
3147 ReferenceProcessor* rp = _g1h->ref_processor_stw();
3148
3149 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
3150 pss->set_ref_discoverer(rp);
3151
3152 double start_strong_roots_sec = os::elapsedTime();
3153
3154 _root_processor->evacuate_roots(pss, worker_id);
3155
3156 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid
3157 // treating the nmethods visited to act as roots for concurrent marking.
3158 // We only want to make sure that the oops in the nmethods are adjusted with regard to the
3159 // objects copied by the current evacuation.
3160 _g1h->g1_rem_set()->oops_into_collection_set_do(pss, worker_id);
3161
3162 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec;
3163
3164 double term_sec = 0.0;
3165 size_t evac_term_attempts = 0;
3166 {
3167 double start = os::elapsedTime();
3168 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator);
3169 evac.do_void();
3170
3171 evac_term_attempts = evac.term_attempts();
3172 term_sec = evac.term_time();
3173 double elapsed_sec = os::elapsedTime() - start;
3174
3175 G1GCPhaseTimes* p = _g1h->g1_policy()->phase_times();
3176 p->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
3177 p->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
3178 p->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts);
3179 }
3180
3181 assert(pss->queue_is_empty(), "should be empty");
3182
3183 if (log_is_enabled(Debug, gc, task, stats)) {
3184 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3185 size_t lab_waste;
3186 size_t lab_undo_waste;
3187 pss->waste(lab_waste, lab_undo_waste);
3188 _g1h->print_termination_stats(worker_id,
3189 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */
3190 strong_roots_sec * 1000.0, /* strong roots time */
3191 term_sec * 1000.0, /* evac term time */
3192 evac_term_attempts, /* evac term attempts */
3193 lab_waste, /* alloc buffer waste */
3194 lab_undo_waste /* undo waste */
3195 );
3196 }
3197
3198 // Close the inner scope so that the ResourceMark and HandleMark
3199 // destructors are executed here and are included as part of the
3200 // "GC Worker Time".
3201 }
3202 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
3203 }
3204 };
3205
3206 void G1CollectedHeap::print_termination_stats_hdr() {
3207 log_debug(gc, task, stats)("GC Termination Stats");
3208 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------");
3209 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo");
3210 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------");
3211 }
3212
3213 void G1CollectedHeap::print_termination_stats(uint worker_id,
3214 double elapsed_ms,
3215 double strong_roots_ms,
3216 double term_ms,
3217 size_t term_attempts,
3218 size_t alloc_buffer_waste,
3219 size_t undo_waste) const {
3220 log_debug(gc, task, stats)
3221 ("%3d %9.2f %9.2f %6.2f "
3222 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
3223 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
3224 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms,
3225 term_ms, term_ms * 100 / elapsed_ms, term_attempts,
3226 (alloc_buffer_waste + undo_waste) * HeapWordSize / K,
3227 alloc_buffer_waste * HeapWordSize / K,
3228 undo_waste * HeapWordSize / K);
3229 }
3230
3231 class G1StringAndSymbolCleaningTask : public AbstractGangTask {
3232 private:
3233 BoolObjectClosure* _is_alive;
3234 G1StringDedupUnlinkOrOopsDoClosure _dedup_closure;
3235 OopStorage::ParState<false /* concurrent */, false /* const */> _par_state_string;
3236
3237 int _initial_string_table_size;
3238 int _initial_symbol_table_size;
3239
3240 bool _process_strings;
3241 int _strings_processed;
3242 int _strings_removed;
3243
3244 bool _process_symbols;
3245 int _symbols_processed;
3246 int _symbols_removed;
3247
3248 bool _process_string_dedup;
3249
3250 public:
3251 G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) :
3252 AbstractGangTask("String/Symbol Unlinking"),
3253 _is_alive(is_alive),
3254 _dedup_closure(is_alive, NULL, false),
3255 _par_state_string(StringTable::weak_storage()),
3256 _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
3257 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0),
3258 _process_string_dedup(process_string_dedup) {
3259
3260 _initial_string_table_size = (int) StringTable::the_table()->table_size();
3261 _initial_symbol_table_size = SymbolTable::the_table()->table_size();
3262 if (process_symbols) {
3263 SymbolTable::clear_parallel_claimed_index();
3264 }
3265 if (process_strings) {
3266 StringTable::reset_dead_counter();
3267 }
3268 }
3269
3270 ~G1StringAndSymbolCleaningTask() {
3271 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
3272 "claim value %d after unlink less than initial symbol table size %d",
3273 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size);
3274
3275 log_info(gc, stringtable)(
3276 "Cleaned string and symbol table, "
3277 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, "
3278 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
3279 strings_processed(), strings_removed(),
3280 symbols_processed(), symbols_removed());
3281 if (_process_strings) {
3282 StringTable::finish_dead_counter();
3283 }
3284 }
3285
3286 void work(uint worker_id) {
3287 int strings_processed = 0;
3288 int strings_removed = 0;
3289 int symbols_processed = 0;
3290 int symbols_removed = 0;
3291 if (_process_strings) {
3292 StringTable::possibly_parallel_unlink(&_par_state_string, _is_alive, &strings_processed, &strings_removed);
3293 Atomic::add(strings_processed, &_strings_processed);
3294 Atomic::add(strings_removed, &_strings_removed);
3295 }
3296 if (_process_symbols) {
3297 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
3298 Atomic::add(symbols_processed, &_symbols_processed);
3299 Atomic::add(symbols_removed, &_symbols_removed);
3300 }
3301 if (_process_string_dedup) {
3302 G1StringDedup::parallel_unlink(&_dedup_closure, worker_id);
3303 }
3304 }
3305
3306 size_t strings_processed() const { return (size_t)_strings_processed; }
3307 size_t strings_removed() const { return (size_t)_strings_removed; }
3308
3309 size_t symbols_processed() const { return (size_t)_symbols_processed; }
3310 size_t symbols_removed() const { return (size_t)_symbols_removed; }
3311 };
3312
3313 class G1CodeCacheUnloadingTask {
3314 private:
3315 static Monitor* _lock;
3316
3317 BoolObjectClosure* const _is_alive;
3318 const bool _unloading_occurred;
3319 const uint _num_workers;
3320
3321 // Variables used to claim nmethods.
3322 CompiledMethod* _first_nmethod;
3323 CompiledMethod* volatile _claimed_nmethod;
3324
3325 // The list of nmethods that need to be processed by the second pass.
3326 CompiledMethod* volatile _postponed_list;
3327 volatile uint _num_entered_barrier;
3328
3329 public:
3330 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
3331 _is_alive(is_alive),
3332 _unloading_occurred(unloading_occurred),
3333 _num_workers(num_workers),
3334 _first_nmethod(NULL),
3335 _claimed_nmethod(NULL),
3336 _postponed_list(NULL),
3337 _num_entered_barrier(0)
3338 {
3339 CompiledMethod::increase_unloading_clock();
3340 // Get first alive nmethod
3341 CompiledMethodIterator iter = CompiledMethodIterator();
3342 if(iter.next_alive()) {
3343 _first_nmethod = iter.method();
3344 }
3345 _claimed_nmethod = _first_nmethod;
3346 }
3347
3348 ~G1CodeCacheUnloadingTask() {
3349 CodeCache::verify_clean_inline_caches();
3350
3351 CodeCache::set_needs_cache_clean(false);
3352 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
3353
3354 CodeCache::verify_icholder_relocations();
3355 }
3356
3357 private:
3358 void add_to_postponed_list(CompiledMethod* nm) {
3359 CompiledMethod* old;
3360 do {
3361 old = _postponed_list;
3362 nm->set_unloading_next(old);
3363 } while (Atomic::cmpxchg(nm, &_postponed_list, old) != old);
3364 }
3365
3366 void clean_nmethod(CompiledMethod* nm) {
3367 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
3368
3369 if (postponed) {
3370 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
3371 add_to_postponed_list(nm);
3372 }
3373
3374 // Mark that this nmethod has been cleaned/unloaded.
3375 // After this call, it will be safe to ask if this nmethod was unloaded or not.
3376 nm->set_unloading_clock(CompiledMethod::global_unloading_clock());
3377 }
3378
3379 void clean_nmethod_postponed(CompiledMethod* nm) {
3380 nm->do_unloading_parallel_postponed();
3381 }
3382
3383 static const int MaxClaimNmethods = 16;
3384
3385 void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) {
3386 CompiledMethod* first;
3387 CompiledMethodIterator last;
3388
3389 do {
3390 *num_claimed_nmethods = 0;
3391
3392 first = _claimed_nmethod;
3393 last = CompiledMethodIterator(first);
3394
3395 if (first != NULL) {
3396
3397 for (int i = 0; i < MaxClaimNmethods; i++) {
3398 if (!last.next_alive()) {
3399 break;
3400 }
3401 claimed_nmethods[i] = last.method();
3402 (*num_claimed_nmethods)++;
3403 }
3404 }
3405
3406 } while (Atomic::cmpxchg(last.method(), &_claimed_nmethod, first) != first);
3407 }
3408
3409 CompiledMethod* claim_postponed_nmethod() {
3410 CompiledMethod* claim;
3411 CompiledMethod* next;
3412
3413 do {
3414 claim = _postponed_list;
3415 if (claim == NULL) {
3416 return NULL;
3417 }
3418
3419 next = claim->unloading_next();
3420
3421 } while (Atomic::cmpxchg(next, &_postponed_list, claim) != claim);
3422
3423 return claim;
3424 }
3425
3426 public:
3427 // Mark that we're done with the first pass of nmethod cleaning.
3428 void barrier_mark(uint worker_id) {
3429 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3430 _num_entered_barrier++;
3431 if (_num_entered_barrier == _num_workers) {
3432 ml.notify_all();
3433 }
3434 }
3435
3436 // See if we have to wait for the other workers to
3437 // finish their first-pass nmethod cleaning work.
3438 void barrier_wait(uint worker_id) {
3439 if (_num_entered_barrier < _num_workers) {
3440 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3441 while (_num_entered_barrier < _num_workers) {
3442 ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
3443 }
3444 }
3445 }
3446
3447 // Cleaning and unloading of nmethods. Some work has to be postponed
3448 // to the second pass, when we know which nmethods survive.
3449 void work_first_pass(uint worker_id) {
3450 // The first nmethods is claimed by the first worker.
3451 if (worker_id == 0 && _first_nmethod != NULL) {
3452 clean_nmethod(_first_nmethod);
3453 _first_nmethod = NULL;
3454 }
3455
3456 int num_claimed_nmethods;
3457 CompiledMethod* claimed_nmethods[MaxClaimNmethods];
3458
3459 while (true) {
3460 claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
3461
3462 if (num_claimed_nmethods == 0) {
3463 break;
3464 }
3465
3466 for (int i = 0; i < num_claimed_nmethods; i++) {
3467 clean_nmethod(claimed_nmethods[i]);
3468 }
3469 }
3470 }
3471
3472 void work_second_pass(uint worker_id) {
3473 CompiledMethod* nm;
3474 // Take care of postponed nmethods.
3475 while ((nm = claim_postponed_nmethod()) != NULL) {
3476 clean_nmethod_postponed(nm);
3477 }
3478 }
3479 };
3480
3481 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
3482
3483 class G1KlassCleaningTask : public StackObj {
3484 volatile int _clean_klass_tree_claimed;
3485 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
3486
3487 public:
3488 G1KlassCleaningTask() :
3489 _clean_klass_tree_claimed(0),
3490 _klass_iterator() {
3491 }
3492
3493 private:
3494 bool claim_clean_klass_tree_task() {
3495 if (_clean_klass_tree_claimed) {
3496 return false;
3497 }
3498
3499 return Atomic::cmpxchg(1, &_clean_klass_tree_claimed, 0) == 0;
3500 }
3501
3502 InstanceKlass* claim_next_klass() {
3503 Klass* klass;
3504 do {
3505 klass =_klass_iterator.next_klass();
3506 } while (klass != NULL && !klass->is_instance_klass());
3507
3508 // this can be null so don't call InstanceKlass::cast
3509 return static_cast<InstanceKlass*>(klass);
3510 }
3511
3512 public:
3513
3514 void clean_klass(InstanceKlass* ik) {
3515 ik->clean_weak_instanceklass_links();
3516 }
3517
3518 void work() {
3519 ResourceMark rm;
3520
3521 // One worker will clean the subklass/sibling klass tree.
3522 if (claim_clean_klass_tree_task()) {
3523 Klass::clean_subklass_tree();
3524 }
3525
3526 // All workers will help cleaning the classes,
3527 InstanceKlass* klass;
3528 while ((klass = claim_next_klass()) != NULL) {
3529 clean_klass(klass);
3530 }
3531 }
3532 };
3533
3534 class G1ResolvedMethodCleaningTask : public StackObj {
3535 volatile int _resolved_method_task_claimed;
3536 public:
3537 G1ResolvedMethodCleaningTask() :
3538 _resolved_method_task_claimed(0) {}
3539
3540 bool claim_resolved_method_task() {
3541 if (_resolved_method_task_claimed) {
3542 return false;
3543 }
3544 return Atomic::cmpxchg(1, &_resolved_method_task_claimed, 0) == 0;
3545 }
3546
3547 // These aren't big, one thread can do it all.
3548 void work() {
3549 if (claim_resolved_method_task()) {
3550 ResolvedMethodTable::unlink();
3551 }
3552 }
3553 };
3554
3555
3556 // To minimize the remark pause times, the tasks below are done in parallel.
3557 class G1ParallelCleaningTask : public AbstractGangTask {
3558 private:
3559 bool _unloading_occurred;
3560 G1StringAndSymbolCleaningTask _string_symbol_task;
3561 G1CodeCacheUnloadingTask _code_cache_task;
3562 G1KlassCleaningTask _klass_cleaning_task;
3563 G1ResolvedMethodCleaningTask _resolved_method_cleaning_task;
3564
3565 public:
3566 // The constructor is run in the VMThread.
3567 G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) :
3568 AbstractGangTask("Parallel Cleaning"),
3569 _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()),
3570 _code_cache_task(num_workers, is_alive, unloading_occurred),
3571 _klass_cleaning_task(),
3572 _unloading_occurred(unloading_occurred),
3573 _resolved_method_cleaning_task() {
3574 }
3575
3576 // The parallel work done by all worker threads.
3577 void work(uint worker_id) {
3578 // Do first pass of code cache cleaning.
3579 _code_cache_task.work_first_pass(worker_id);
3580
3581 // Let the threads mark that the first pass is done.
3582 _code_cache_task.barrier_mark(worker_id);
3583
3584 // Clean the Strings and Symbols.
3585 _string_symbol_task.work(worker_id);
3586
3587 // Clean unreferenced things in the ResolvedMethodTable
3588 _resolved_method_cleaning_task.work();
3589
3590 // Wait for all workers to finish the first code cache cleaning pass.
3591 _code_cache_task.barrier_wait(worker_id);
3592
3593 // Do the second code cache cleaning work, which realize on
3594 // the liveness information gathered during the first pass.
3595 _code_cache_task.work_second_pass(worker_id);
3596
3597 // Clean all klasses that were not unloaded.
3598 // The weak metadata in klass doesn't need to be
3599 // processed if there was no unloading.
3600 if (_unloading_occurred) {
3601 _klass_cleaning_task.work();
3602 }
3603 }
3604 };
3605
3606
3607 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
3608 bool class_unloading_occurred) {
3609 uint n_workers = workers()->active_workers();
3610
3611 G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred);
3612 workers()->run_task(&g1_unlink_task);
3613 }
3614
3615 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive,
3616 bool process_strings,
3617 bool process_symbols,
3618 bool process_string_dedup) {
3619 if (!process_strings && !process_symbols && !process_string_dedup) {
3620 // Nothing to clean.
3621 return;
3622 }
3623
3624 G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup);
3625 workers()->run_task(&g1_unlink_task);
3626
3627 }
3628
3629 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3630 private:
3631 DirtyCardQueueSet* _queue;
3632 G1CollectedHeap* _g1h;
3633 public:
3634 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"),
3635 _queue(queue), _g1h(g1h) { }
3636
3637 virtual void work(uint worker_id) {
3638 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
3639 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
3640
3641 RedirtyLoggedCardTableEntryClosure cl(_g1h);
3642 _queue->par_apply_closure_to_all_completed_buffers(&cl);
3643
3644 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3645 }
3646 };
3647
3648 void G1CollectedHeap::redirty_logged_cards() {
3649 double redirty_logged_cards_start = os::elapsedTime();
3650
3651 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this);
3652 dirty_card_queue_set().reset_for_par_iteration();
3653 workers()->run_task(&redirty_task);
3654
3655 DirtyCardQueueSet& dcq = G1BarrierSet::dirty_card_queue_set();
3656 dcq.merge_bufferlists(&dirty_card_queue_set());
3657 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
3658
3659 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3660 }
3661
3662 // Weak Reference Processing support
3663
3664 bool G1STWIsAliveClosure::do_object_b(oop p) {
3665 // An object is reachable if it is outside the collection set,
3666 // or is inside and copied.
3667 return !_g1h->is_in_cset(p) || p->is_forwarded();
3668 }
3669
3670 bool G1STWSubjectToDiscoveryClosure::do_object_b(oop obj) {
3671 assert(obj != NULL, "must not be NULL");
3672 assert(_g1h->is_in_reserved(obj), "Trying to discover obj " PTR_FORMAT " not in heap", p2i(obj));
3673 // The areas the CM and STW ref processor manage must be disjoint. The is_in_cset() below
3674 // may falsely indicate that this is not the case here: however the collection set only
3675 // contains old regions when concurrent mark is not running.
3676 return _g1h->is_in_cset(obj) || _g1h->heap_region_containing(obj)->is_survivor();
3677 }
3678
3679 // Non Copying Keep Alive closure
3680 class G1KeepAliveClosure: public OopClosure {
3681 G1CollectedHeap*_g1h;
3682 public:
3683 G1KeepAliveClosure(G1CollectedHeap* g1h) :_g1h(g1h) {}
3684 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3685 void do_oop(oop* p) {
3686 oop obj = *p;
3687 assert(obj != NULL, "the caller should have filtered out NULL values");
3688
3689 const InCSetState cset_state =_g1h->in_cset_state(obj);
3690 if (!cset_state.is_in_cset_or_humongous()) {
3691 return;
3692 }
3693 if (cset_state.is_in_cset()) {
3694 assert( obj->is_forwarded(), "invariant" );
3695 *p = obj->forwardee();
3696 } else {
3697 assert(!obj->is_forwarded(), "invariant" );
3698 assert(cset_state.is_humongous(),
3699 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value());
3700 _g1h->set_humongous_is_live(obj);
3701 }
3702 }
3703 };
3704
3705 // Copying Keep Alive closure - can be called from both
3706 // serial and parallel code as long as different worker
3707 // threads utilize different G1ParScanThreadState instances
3708 // and different queues.
3709
3710 class G1CopyingKeepAliveClosure: public OopClosure {
3711 G1CollectedHeap* _g1h;
3712 OopClosure* _copy_non_heap_obj_cl;
3713 G1ParScanThreadState* _par_scan_state;
3714
3715 public:
3716 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3717 OopClosure* non_heap_obj_cl,
3718 G1ParScanThreadState* pss):
3719 _g1h(g1h),
3720 _copy_non_heap_obj_cl(non_heap_obj_cl),
3721 _par_scan_state(pss)
3722 {}
3723
3724 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3725 virtual void do_oop( oop* p) { do_oop_work(p); }
3726
3727 template <class T> void do_oop_work(T* p) {
3728 oop obj = RawAccess<>::oop_load(p);
3729
3730 if (_g1h->is_in_cset_or_humongous(obj)) {
3731 // If the referent object has been forwarded (either copied
3732 // to a new location or to itself in the event of an
3733 // evacuation failure) then we need to update the reference
3734 // field and, if both reference and referent are in the G1
3735 // heap, update the RSet for the referent.
3736 //
3737 // If the referent has not been forwarded then we have to keep
3738 // it alive by policy. Therefore we have copy the referent.
3739 //
3740 // If the reference field is in the G1 heap then we can push
3741 // on the PSS queue. When the queue is drained (after each
3742 // phase of reference processing) the object and it's followers
3743 // will be copied, the reference field set to point to the
3744 // new location, and the RSet updated. Otherwise we need to
3745 // use the the non-heap or metadata closures directly to copy
3746 // the referent object and update the pointer, while avoiding
3747 // updating the RSet.
3748
3749 if (_g1h->is_in_g1_reserved(p)) {
3750 _par_scan_state->push_on_queue(p);
3751 } else {
3752 assert(!Metaspace::contains((const void*)p),
3753 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p));
3754 _copy_non_heap_obj_cl->do_oop(p);
3755 }
3756 }
3757 }
3758 };
3759
3760 // Serial drain queue closure. Called as the 'complete_gc'
3761 // closure for each discovered list in some of the
3762 // reference processing phases.
3763
3764 class G1STWDrainQueueClosure: public VoidClosure {
3765 protected:
3766 G1CollectedHeap* _g1h;
3767 G1ParScanThreadState* _par_scan_state;
3768
3769 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
3770
3771 public:
3772 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
3773 _g1h(g1h),
3774 _par_scan_state(pss)
3775 { }
3776
3777 void do_void() {
3778 G1ParScanThreadState* const pss = par_scan_state();
3779 pss->trim_queue();
3780 }
3781 };
3782
3783 // Parallel Reference Processing closures
3784
3785 // Implementation of AbstractRefProcTaskExecutor for parallel reference
3786 // processing during G1 evacuation pauses.
3787
3788 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
3789 private:
3790 G1CollectedHeap* _g1h;
3791 G1ParScanThreadStateSet* _pss;
3792 RefToScanQueueSet* _queues;
3793 WorkGang* _workers;
3794 uint _active_workers;
3795
3796 public:
3797 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
3798 G1ParScanThreadStateSet* per_thread_states,
3799 WorkGang* workers,
3800 RefToScanQueueSet *task_queues,
3801 uint n_workers) :
3802 _g1h(g1h),
3803 _pss(per_thread_states),
3804 _queues(task_queues),
3805 _workers(workers),
3806 _active_workers(n_workers)
3807 {
3808 g1h->ref_processor_stw()->set_active_mt_degree(n_workers);
3809 }
3810
3811 // Executes the given task using concurrent marking worker threads.
3812 virtual void execute(ProcessTask& task);
3813 };
3814
3815 // Gang task for possibly parallel reference processing
3816
3817 class G1STWRefProcTaskProxy: public AbstractGangTask {
3818 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
3819 ProcessTask& _proc_task;
3820 G1CollectedHeap* _g1h;
3821 G1ParScanThreadStateSet* _pss;
3822 RefToScanQueueSet* _task_queues;
3823 ParallelTaskTerminator* _terminator;
3824
3825 public:
3826 G1STWRefProcTaskProxy(ProcessTask& proc_task,
3827 G1CollectedHeap* g1h,
3828 G1ParScanThreadStateSet* per_thread_states,
3829 RefToScanQueueSet *task_queues,
3830 ParallelTaskTerminator* terminator) :
3831 AbstractGangTask("Process reference objects in parallel"),
3832 _proc_task(proc_task),
3833 _g1h(g1h),
3834 _pss(per_thread_states),
3835 _task_queues(task_queues),
3836 _terminator(terminator)
3837 {}
3838
3839 virtual void work(uint worker_id) {
3840 // The reference processing task executed by a single worker.
3841 ResourceMark rm;
3842 HandleMark hm;
3843
3844 G1STWIsAliveClosure is_alive(_g1h);
3845
3846 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
3847 pss->set_ref_discoverer(NULL);
3848
3849 // Keep alive closure.
3850 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
3851
3852 // Complete GC closure
3853 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator);
3854
3855 // Call the reference processing task's work routine.
3856 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
3857
3858 // Note we cannot assert that the refs array is empty here as not all
3859 // of the processing tasks (specifically phase2 - pp2_work) execute
3860 // the complete_gc closure (which ordinarily would drain the queue) so
3861 // the queue may not be empty.
3862 }
3863 };
3864
3865 // Driver routine for parallel reference processing.
3866 // Creates an instance of the ref processing gang
3867 // task and has the worker threads execute it.
3868 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
3869 assert(_workers != NULL, "Need parallel worker threads.");
3870
3871 ParallelTaskTerminator terminator(_active_workers, _queues);
3872 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
3873
3874 _workers->run_task(&proc_task_proxy);
3875 }
3876
3877 // End of weak reference support closures
3878
3879 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
3880 double ref_proc_start = os::elapsedTime();
3881
3882 ReferenceProcessor* rp = _ref_processor_stw;
3883 assert(rp->discovery_enabled(), "should have been enabled");
3884
3885 // Closure to test whether a referent is alive.
3886 G1STWIsAliveClosure is_alive(this);
3887
3888 // Even when parallel reference processing is enabled, the processing
3889 // of JNI refs is serial and performed serially by the current thread
3890 // rather than by a worker. The following PSS will be used for processing
3891 // JNI refs.
3892
3893 // Use only a single queue for this PSS.
3894 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0);
3895 pss->set_ref_discoverer(NULL);
3896 assert(pss->queue_is_empty(), "pre-condition");
3897
3898 // Keep alive closure.
3899 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss);
3900
3901 // Serial Complete GC closure
3902 G1STWDrainQueueClosure drain_queue(this, pss);
3903
3904 // Setup the soft refs policy...
3905 rp->setup_policy(false);
3906
3907 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times();
3908
3909 ReferenceProcessorStats stats;
3910 if (!rp->processing_is_mt()) {
3911 // Serial reference processing...
3912 stats = rp->process_discovered_references(&is_alive,
3913 &keep_alive,
3914 &drain_queue,
3915 NULL,
3916 pt);
3917 } else {
3918 uint no_of_gc_workers = workers()->active_workers();
3919
3920 // Parallel reference processing
3921 assert(no_of_gc_workers <= rp->max_num_queues(),
3922 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
3923 no_of_gc_workers, rp->max_num_queues());
3924
3925 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers);
3926 stats = rp->process_discovered_references(&is_alive,
3927 &keep_alive,
3928 &drain_queue,
3929 &par_task_executor,
3930 pt);
3931 }
3932
3933 _gc_tracer_stw->report_gc_reference_stats(stats);
3934
3935 // We have completed copying any necessary live referent objects.
3936 assert(pss->queue_is_empty(), "both queue and overflow should be empty");
3937
3938 make_pending_list_reachable();
3939
3940 rp->verify_no_references_recorded();
3941
3942 double ref_proc_time = os::elapsedTime() - ref_proc_start;
3943 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
3944 }
3945
3946 void G1CollectedHeap::make_pending_list_reachable() {
3947 if (collector_state()->in_initial_mark_gc()) {
3948 oop pll_head = Universe::reference_pending_list();
3949 if (pll_head != NULL) {
3950 // Any valid worker id is fine here as we are in the VM thread and single-threaded.
3951 _cm->mark_in_next_bitmap(0 /* worker_id */, pll_head);
3952 }
3953 }
3954 }
3955
3956 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
3957 double merge_pss_time_start = os::elapsedTime();
3958 per_thread_states->flush();
3959 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0);
3960 }
3961
3962 void G1CollectedHeap::pre_evacuate_collection_set() {
3963 _expand_heap_after_alloc_failure = true;
3964 _evacuation_failed = false;
3965
3966 // Disable the hot card cache.
3967 _hot_card_cache->reset_hot_cache_claimed_index();
3968 _hot_card_cache->set_use_cache(false);
3969
3970 g1_rem_set()->prepare_for_oops_into_collection_set_do();
3971 _preserved_marks_set.assert_empty();
3972
3973 G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
3974
3975 // InitialMark needs claim bits to keep track of the marked-through CLDs.
3976 if (collector_state()->in_initial_mark_gc()) {
3977 double start_clear_claimed_marks = os::elapsedTime();
3978
3979 ClassLoaderDataGraph::clear_claimed_marks();
3980
3981 double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
3982 phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
3983 }
3984 }
3985
3986 void G1CollectedHeap::evacuate_collection_set(G1ParScanThreadStateSet* per_thread_states) {
3987 // Should G1EvacuationFailureALot be in effect for this GC?
3988 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
3989
3990 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
3991
3992 G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
3993
3994 double start_par_time_sec = os::elapsedTime();
3995 double end_par_time_sec;
3996
3997 {
3998 const uint n_workers = workers()->active_workers();
3999 G1RootProcessor root_processor(this, n_workers);
4000 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers);
4001
4002 print_termination_stats_hdr();
4003
4004 workers()->run_task(&g1_par_task);
4005 end_par_time_sec = os::elapsedTime();
4006
4007 // Closing the inner scope will execute the destructor
4008 // for the G1RootProcessor object. We record the current
4009 // elapsed time before closing the scope so that time
4010 // taken for the destructor is NOT included in the
4011 // reported parallel time.
4012 }
4013
4014 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
4015 phase_times->record_par_time(par_time_ms);
4016
4017 double code_root_fixup_time_ms =
4018 (os::elapsedTime() - end_par_time_sec) * 1000.0;
4019 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
4020 }
4021
4022 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4023 // Also cleans the card table from temporary duplicate detection information used
4024 // during UpdateRS/ScanRS.
4025 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4026
4027 // Process any discovered reference objects - we have
4028 // to do this _before_ we retire the GC alloc regions
4029 // as we may have to copy some 'reachable' referent
4030 // objects (and their reachable sub-graphs) that were
4031 // not copied during the pause.
4032 process_discovered_references(per_thread_states);
4033
4034 // FIXME
4035 // CM's reference processing also cleans up the string and symbol tables.
4036 // Should we do that here also? We could, but it is a serial operation
4037 // and could significantly increase the pause time.
4038
4039 G1STWIsAliveClosure is_alive(this);
4040 G1KeepAliveClosure keep_alive(this);
4041
4042 {
4043 double start = os::elapsedTime();
4044
4045 WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
4046
4047 double time_ms = (os::elapsedTime() - start) * 1000.0;
4048 g1_policy()->phase_times()->record_weak_ref_proc_time(time_ms);
4049 }
4050
4051 if (G1StringDedup::is_enabled()) {
4052 double fixup_start = os::elapsedTime();
4053
4054 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times());
4055
4056 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
4057 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
4058 }
4059
4060 if (evacuation_failed()) {
4061 restore_after_evac_failure();
4062
4063 // Reset the G1EvacuationFailureALot counters and flags
4064 // Note: the values are reset only when an actual
4065 // evacuation failure occurs.
4066 NOT_PRODUCT(reset_evacuation_should_fail();)
4067 }
4068
4069 _preserved_marks_set.assert_empty();
4070
4071 _allocator->release_gc_alloc_regions(evacuation_info);
4072
4073 merge_per_thread_state_info(per_thread_states);
4074
4075 // Reset and re-enable the hot card cache.
4076 // Note the counts for the cards in the regions in the
4077 // collection set are reset when the collection set is freed.
4078 _hot_card_cache->reset_hot_cache();
4079 _hot_card_cache->set_use_cache(true);
4080
4081 purge_code_root_memory();
4082
4083 redirty_logged_cards();
4084 #if COMPILER2_OR_JVMCI
4085 double start = os::elapsedTime();
4086 DerivedPointerTable::update_pointers();
4087 g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0);
4088 #endif
4089 g1_policy()->print_age_table();
4090 }
4091
4092 void G1CollectedHeap::record_obj_copy_mem_stats() {
4093 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4094
4095 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4096 create_g1_evac_summary(&_old_evac_stats));
4097 }
4098
4099 void G1CollectedHeap::free_region(HeapRegion* hr,
4100 FreeRegionList* free_list,
4101 bool skip_remset,
4102 bool skip_hot_card_cache,
4103 bool locked) {
4104 assert(!hr->is_free(), "the region should not be free");
4105 assert(!hr->is_empty(), "the region should not be empty");
4106 assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
4107 assert(free_list != NULL, "pre-condition");
4108
4109 if (G1VerifyBitmaps) {
4110 MemRegion mr(hr->bottom(), hr->end());
4111 concurrent_mark()->clear_range_in_prev_bitmap(mr);
4112 }
4113
4114 // Clear the card counts for this region.
4115 // Note: we only need to do this if the region is not young
4116 // (since we don't refine cards in young regions).
4117 if (!skip_hot_card_cache && !hr->is_young()) {
4118 _hot_card_cache->reset_card_counts(hr);
4119 }
4120 hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */);
4121 _g1_policy->remset_tracker()->update_at_free(hr);
4122 free_list->add_ordered(hr);
4123 }
4124
4125 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4126 FreeRegionList* free_list) {
4127 assert(hr->is_humongous(), "this is only for humongous regions");
4128 assert(free_list != NULL, "pre-condition");
4129 hr->clear_humongous();
4130 free_region(hr, free_list, false /* skip_remset */, false /* skip_hcc */, true /* locked */);
4131 }
4132
4133 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4134 const uint humongous_regions_removed) {
4135 if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4136 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4137 _old_set.bulk_remove(old_regions_removed);
4138 _humongous_set.bulk_remove(humongous_regions_removed);
4139 }
4140
4141 }
4142
4143 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4144 assert(list != NULL, "list can't be null");
4145 if (!list->is_empty()) {
4146 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4147 _hrm.insert_list_into_free_list(list);
4148 }
4149 }
4150
4151 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4152 decrease_used(bytes);
4153 }
4154
4155 class G1FreeCollectionSetTask : public AbstractGangTask {
4156 private:
4157
4158 // Closure applied to all regions in the collection set to do work that needs to
4159 // be done serially in a single thread.
4160 class G1SerialFreeCollectionSetClosure : public HeapRegionClosure {
4161 private:
4162 EvacuationInfo* _evacuation_info;
4163 const size_t* _surviving_young_words;
4164
4165 // Bytes used in successfully evacuated regions before the evacuation.
4166 size_t _before_used_bytes;
4167 // Bytes used in unsucessfully evacuated regions before the evacuation
4168 size_t _after_used_bytes;
4169
4170 size_t _bytes_allocated_in_old_since_last_gc;
4171
4172 size_t _failure_used_words;
4173 size_t _failure_waste_words;
4174
4175 FreeRegionList _local_free_list;
4176 public:
4177 G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4178 HeapRegionClosure(),
4179 _evacuation_info(evacuation_info),
4180 _surviving_young_words(surviving_young_words),
4181 _before_used_bytes(0),
4182 _after_used_bytes(0),
4183 _bytes_allocated_in_old_since_last_gc(0),
4184 _failure_used_words(0),
4185 _failure_waste_words(0),
4186 _local_free_list("Local Region List for CSet Freeing") {
4187 }
4188
4189 virtual bool do_heap_region(HeapRegion* r) {
4190 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4191
4192 assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index());
4193 g1h->clear_in_cset(r);
4194
4195 if (r->is_young()) {
4196 assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(),
4197 "Young index %d is wrong for region %u of type %s with %u young regions",
4198 r->young_index_in_cset(),
4199 r->hrm_index(),
4200 r->get_type_str(),
4201 g1h->collection_set()->young_region_length());
4202 size_t words_survived = _surviving_young_words[r->young_index_in_cset()];
4203 r->record_surv_words_in_group(words_survived);
4204 }
4205
4206 if (!r->evacuation_failed()) {
4207 assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
4208 _before_used_bytes += r->used();
4209 g1h->free_region(r,
4210 &_local_free_list,
4211 true, /* skip_remset */
4212 true, /* skip_hot_card_cache */
4213 true /* locked */);
4214 } else {
4215 r->uninstall_surv_rate_group();
4216 r->set_young_index_in_cset(-1);
4217 r->set_evacuation_failed(false);
4218 // When moving a young gen region to old gen, we "allocate" that whole region
4219 // there. This is in addition to any already evacuated objects. Notify the
4220 // policy about that.
4221 // Old gen regions do not cause an additional allocation: both the objects
4222 // still in the region and the ones already moved are accounted for elsewhere.
4223 if (r->is_young()) {
4224 _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
4225 }
4226 // The region is now considered to be old.
4227 r->set_old();
4228 // Do some allocation statistics accounting. Regions that failed evacuation
4229 // are always made old, so there is no need to update anything in the young
4230 // gen statistics, but we need to update old gen statistics.
4231 size_t used_words = r->marked_bytes() / HeapWordSize;
4232
4233 _failure_used_words += used_words;
4234 _failure_waste_words += HeapRegion::GrainWords - used_words;
4235
4236 g1h->old_set_add(r);
4237 _after_used_bytes += r->used();
4238 }
4239 return false;
4240 }
4241
4242 void complete_work() {
4243 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4244
4245 _evacuation_info->set_regions_freed(_local_free_list.length());
4246 _evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4247
4248 g1h->prepend_to_freelist(&_local_free_list);
4249 g1h->decrement_summary_bytes(_before_used_bytes);
4250
4251 G1Policy* policy = g1h->g1_policy();
4252 policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4253
4254 g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4255 }
4256 };
4257
4258 G1CollectionSet* _collection_set;
4259 G1SerialFreeCollectionSetClosure _cl;
4260 const size_t* _surviving_young_words;
4261
4262 size_t _rs_lengths;
4263
4264 volatile jint _serial_work_claim;
4265
4266 struct WorkItem {
4267 uint region_idx;
4268 bool is_young;
4269 bool evacuation_failed;
4270
4271 WorkItem(HeapRegion* r) {
4272 region_idx = r->hrm_index();
4273 is_young = r->is_young();
4274 evacuation_failed = r->evacuation_failed();
4275 }
4276 };
4277
4278 volatile size_t _parallel_work_claim;
4279 size_t _num_work_items;
4280 WorkItem* _work_items;
4281
4282 void do_serial_work() {
4283 // Need to grab the lock to be allowed to modify the old region list.
4284 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4285 _collection_set->iterate(&_cl);
4286 }
4287
4288 void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) {
4289 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4290
4291 HeapRegion* r = g1h->region_at(region_idx);
4292 assert(!g1h->is_on_master_free_list(r), "sanity");
4293
4294 Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths);
4295
4296 if (!is_young) {
4297 g1h->_hot_card_cache->reset_card_counts(r);
4298 }
4299
4300 if (!evacuation_failed) {
4301 r->rem_set()->clear_locked();
4302 }
4303 }
4304
4305 class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure {
4306 private:
4307 size_t _cur_idx;
4308 WorkItem* _work_items;
4309 public:
4310 G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { }
4311
4312 virtual bool do_heap_region(HeapRegion* r) {
4313 _work_items[_cur_idx++] = WorkItem(r);
4314 return false;
4315 }
4316 };
4317
4318 void prepare_work() {
4319 G1PrepareFreeCollectionSetClosure cl(_work_items);
4320 _collection_set->iterate(&cl);
4321 }
4322
4323 void complete_work() {
4324 _cl.complete_work();
4325
4326 G1Policy* policy = G1CollectedHeap::heap()->g1_policy();
4327 policy->record_max_rs_lengths(_rs_lengths);
4328 policy->cset_regions_freed();
4329 }
4330 public:
4331 G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4332 AbstractGangTask("G1 Free Collection Set"),
4333 _cl(evacuation_info, surviving_young_words),
4334 _collection_set(collection_set),
4335 _surviving_young_words(surviving_young_words),
4336 _serial_work_claim(0),
4337 _rs_lengths(0),
4338 _parallel_work_claim(0),
4339 _num_work_items(collection_set->region_length()),
4340 _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) {
4341 prepare_work();
4342 }
4343
4344 ~G1FreeCollectionSetTask() {
4345 complete_work();
4346 FREE_C_HEAP_ARRAY(WorkItem, _work_items);
4347 }
4348
4349 // Chunk size for work distribution. The chosen value has been determined experimentally
4350 // to be a good tradeoff between overhead and achievable parallelism.
4351 static uint chunk_size() { return 32; }
4352
4353 virtual void work(uint worker_id) {
4354 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
4355
4356 // Claim serial work.
4357 if (_serial_work_claim == 0) {
4358 jint value = Atomic::add(1, &_serial_work_claim) - 1;
4359 if (value == 0) {
4360 double serial_time = os::elapsedTime();
4361 do_serial_work();
4362 timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0);
4363 }
4364 }
4365
4366 // Start parallel work.
4367 double young_time = 0.0;
4368 bool has_young_time = false;
4369 double non_young_time = 0.0;
4370 bool has_non_young_time = false;
4371
4372 while (true) {
4373 size_t end = Atomic::add(chunk_size(), &_parallel_work_claim);
4374 size_t cur = end - chunk_size();
4375
4376 if (cur >= _num_work_items) {
4377 break;
4378 }
4379
4380 double start_time = os::elapsedTime();
4381
4382 end = MIN2(end, _num_work_items);
4383
4384 for (; cur < end; cur++) {
4385 bool is_young = _work_items[cur].is_young;
4386
4387 do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed);
4388
4389 double end_time = os::elapsedTime();
4390 double time_taken = end_time - start_time;
4391 if (is_young) {
4392 young_time += time_taken;
4393 has_young_time = true;
4394 } else {
4395 non_young_time += time_taken;
4396 has_non_young_time = true;
4397 }
4398 start_time = end_time;
4399 }
4400 }
4401
4402 if (has_young_time) {
4403 timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time);
4404 }
4405 if (has_non_young_time) {
4406 timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, non_young_time);
4407 }
4408 }
4409 };
4410
4411 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4412 _eden.clear();
4413
4414 double free_cset_start_time = os::elapsedTime();
4415
4416 {
4417 uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U);
4418 uint const num_workers = MIN2(workers()->active_workers(), num_chunks);
4419
4420 G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words);
4421
4422 log_debug(gc, ergo)("Running %s using %u workers for collection set length %u",
4423 cl.name(),
4424 num_workers,
4425 _collection_set.region_length());
4426 workers()->run_task(&cl, num_workers);
4427 }
4428 g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0);
4429
4430 collection_set->clear();
4431 }
4432
4433 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4434 private:
4435 FreeRegionList* _free_region_list;
4436 HeapRegionSet* _proxy_set;
4437 uint _humongous_objects_reclaimed;
4438 uint _humongous_regions_reclaimed;
4439 size_t _freed_bytes;
4440 public:
4441
4442 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4443 _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) {
4444 }
4445
4446 virtual bool do_heap_region(HeapRegion* r) {
4447 if (!r->is_starts_humongous()) {
4448 return false;
4449 }
4450
4451 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4452
4453 oop obj = (oop)r->bottom();
4454 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap();
4455
4456 // The following checks whether the humongous object is live are sufficient.
4457 // The main additional check (in addition to having a reference from the roots
4458 // or the young gen) is whether the humongous object has a remembered set entry.
4459 //
4460 // A humongous object cannot be live if there is no remembered set for it
4461 // because:
4462 // - there can be no references from within humongous starts regions referencing
4463 // the object because we never allocate other objects into them.
4464 // (I.e. there are no intra-region references that may be missed by the
4465 // remembered set)
4466 // - as soon there is a remembered set entry to the humongous starts region
4467 // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4468 // until the end of a concurrent mark.
4469 //
4470 // It is not required to check whether the object has been found dead by marking
4471 // or not, in fact it would prevent reclamation within a concurrent cycle, as
4472 // all objects allocated during that time are considered live.
4473 // SATB marking is even more conservative than the remembered set.
4474 // So if at this point in the collection there is no remembered set entry,
4475 // nobody has a reference to it.
4476 // At the start of collection we flush all refinement logs, and remembered sets
4477 // are completely up-to-date wrt to references to the humongous object.
4478 //
4479 // Other implementation considerations:
4480 // - never consider object arrays at this time because they would pose
4481 // considerable effort for cleaning up the the remembered sets. This is
4482 // required because stale remembered sets might reference locations that
4483 // are currently allocated into.
4484 uint region_idx = r->hrm_index();
4485 if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4486 !r->rem_set()->is_empty()) {
4487 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",
4488 region_idx,
4489 (size_t)obj->size() * HeapWordSize,
4490 p2i(r->bottom()),
4491 r->rem_set()->occupied(),
4492 r->rem_set()->strong_code_roots_list_length(),
4493 next_bitmap->is_marked(r->bottom()),
4494 g1h->is_humongous_reclaim_candidate(region_idx),
4495 obj->is_typeArray()
4496 );
4497 return false;
4498 }
4499
4500 guarantee(obj->is_typeArray(),
4501 "Only eagerly reclaiming type arrays is supported, but the object "
4502 PTR_FORMAT " is not.", p2i(r->bottom()));
4503
4504 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",
4505 region_idx,
4506 (size_t)obj->size() * HeapWordSize,
4507 p2i(r->bottom()),
4508 r->rem_set()->occupied(),
4509 r->rem_set()->strong_code_roots_list_length(),
4510 next_bitmap->is_marked(r->bottom()),
4511 g1h->is_humongous_reclaim_candidate(region_idx),
4512 obj->is_typeArray()
4513 );
4514
4515 G1ConcurrentMark* const cm = g1h->concurrent_mark();
4516 cm->humongous_object_eagerly_reclaimed(r);
4517 assert(!cm->is_marked_in_prev_bitmap(obj) && !cm->is_marked_in_next_bitmap(obj),
4518 "Eagerly reclaimed humongous region %u should not be marked at all but is in prev %s next %s",
4519 region_idx,
4520 BOOL_TO_STR(cm->is_marked_in_prev_bitmap(obj)),
4521 BOOL_TO_STR(cm->is_marked_in_next_bitmap(obj)));
4522 _humongous_objects_reclaimed++;
4523 do {
4524 HeapRegion* next = g1h->next_region_in_humongous(r);
4525 _freed_bytes += r->used();
4526 r->set_containing_set(NULL);
4527 _humongous_regions_reclaimed++;
4528 g1h->free_humongous_region(r, _free_region_list);
4529 r = next;
4530 } while (r != NULL);
4531
4532 return false;
4533 }
4534
4535 uint humongous_objects_reclaimed() {
4536 return _humongous_objects_reclaimed;
4537 }
4538
4539 uint humongous_regions_reclaimed() {
4540 return _humongous_regions_reclaimed;
4541 }
4542
4543 size_t bytes_freed() const {
4544 return _freed_bytes;
4545 }
4546 };
4547
4548 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4549 assert_at_safepoint_on_vm_thread();
4550
4551 if (!G1EagerReclaimHumongousObjects ||
4552 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
4553 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
4554 return;
4555 }
4556
4557 double start_time = os::elapsedTime();
4558
4559 FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
4560
4561 G1FreeHumongousRegionClosure cl(&local_cleanup_list);
4562 heap_region_iterate(&cl);
4563
4564 remove_from_old_sets(0, cl.humongous_regions_reclaimed());
4565
4566 G1HRPrinter* hrp = hr_printer();
4567 if (hrp->is_active()) {
4568 FreeRegionListIterator iter(&local_cleanup_list);
4569 while (iter.more_available()) {
4570 HeapRegion* hr = iter.get_next();
4571 hrp->cleanup(hr);
4572 }
4573 }
4574
4575 prepend_to_freelist(&local_cleanup_list);
4576 decrement_summary_bytes(cl.bytes_freed());
4577
4578 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
4579 cl.humongous_objects_reclaimed());
4580 }
4581
4582 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
4583 public:
4584 virtual bool do_heap_region(HeapRegion* r) {
4585 assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
4586 G1CollectedHeap::heap()->clear_in_cset(r);
4587 r->set_young_index_in_cset(-1);
4588 return false;
4589 }
4590 };
4591
4592 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
4593 G1AbandonCollectionSetClosure cl;
4594 collection_set->iterate(&cl);
4595
4596 collection_set->clear();
4597 collection_set->stop_incremental_building();
4598 }
4599
4600 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
4601 return _allocator->is_retained_old_region(hr);
4602 }
4603
4604 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
4605 _eden.add(hr);
4606 _g1_policy->set_region_eden(hr);
4607 }
4608
4609 #ifdef ASSERT
4610
4611 class NoYoungRegionsClosure: public HeapRegionClosure {
4612 private:
4613 bool _success;
4614 public:
4615 NoYoungRegionsClosure() : _success(true) { }
4616 bool do_heap_region(HeapRegion* r) {
4617 if (r->is_young()) {
4618 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
4619 p2i(r->bottom()), p2i(r->end()));
4620 _success = false;
4621 }
4622 return false;
4623 }
4624 bool success() { return _success; }
4625 };
4626
4627 bool G1CollectedHeap::check_young_list_empty() {
4628 bool ret = (young_regions_count() == 0);
4629
4630 NoYoungRegionsClosure closure;
4631 heap_region_iterate(&closure);
4632 ret = ret && closure.success();
4633
4634 return ret;
4635 }
4636
4637 #endif // ASSERT
4638
4639 class TearDownRegionSetsClosure : public HeapRegionClosure {
4640 private:
4641 HeapRegionSet *_old_set;
4642
4643 public:
4644 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
4645
4646 bool do_heap_region(HeapRegion* r) {
4647 if (r->is_old()) {
4648 _old_set->remove(r);
4649 } else if(r->is_young()) {
4650 r->uninstall_surv_rate_group();
4651 } else {
4652 // We ignore free regions, we'll empty the free list afterwards.
4653 // We ignore humongous regions, we're not tearing down the
4654 // humongous regions set.
4655 assert(r->is_free() || r->is_humongous(),
4656 "it cannot be another type");
4657 }
4658 return false;
4659 }
4660
4661 ~TearDownRegionSetsClosure() {
4662 assert(_old_set->is_empty(), "post-condition");
4663 }
4664 };
4665
4666 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
4667 assert_at_safepoint_on_vm_thread();
4668
4669 if (!free_list_only) {
4670 TearDownRegionSetsClosure cl(&_old_set);
4671 heap_region_iterate(&cl);
4672
4673 // Note that emptying the _young_list is postponed and instead done as
4674 // the first step when rebuilding the regions sets again. The reason for
4675 // this is that during a full GC string deduplication needs to know if
4676 // a collected region was young or old when the full GC was initiated.
4677 }
4678 _hrm.remove_all_free_regions();
4679 }
4680
4681 void G1CollectedHeap::increase_used(size_t bytes) {
4682 _summary_bytes_used += bytes;
4683 }
4684
4685 void G1CollectedHeap::decrease_used(size_t bytes) {
4686 assert(_summary_bytes_used >= bytes,
4687 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
4688 _summary_bytes_used, bytes);
4689 _summary_bytes_used -= bytes;
4690 }
4691
4692 void G1CollectedHeap::set_used(size_t bytes) {
4693 _summary_bytes_used = bytes;
4694 }
4695
4696 class RebuildRegionSetsClosure : public HeapRegionClosure {
4697 private:
4698 bool _free_list_only;
4699 HeapRegionSet* _old_set;
4700 HeapRegionManager* _hrm;
4701 size_t _total_used;
4702
4703 public:
4704 RebuildRegionSetsClosure(bool free_list_only,
4705 HeapRegionSet* old_set, HeapRegionManager* hrm) :
4706 _free_list_only(free_list_only),
4707 _old_set(old_set), _hrm(hrm), _total_used(0) {
4708 assert(_hrm->num_free_regions() == 0, "pre-condition");
4709 if (!free_list_only) {
4710 assert(_old_set->is_empty(), "pre-condition");
4711 }
4712 }
4713
4714 bool do_heap_region(HeapRegion* r) {
4715 // After full GC, no region should have a remembered set.
4716 r->rem_set()->clear(true);
4717 if (r->is_empty()) {
4718 // Add free regions to the free list
4719 r->set_free();
4720 _hrm->insert_into_free_list(r);
4721 } else if (!_free_list_only) {
4722
4723 if (r->is_humongous()) {
4724 // We ignore humongous regions. We left the humongous set unchanged.
4725 } else {
4726 assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
4727 // We now move all (non-humongous, non-old) regions to old gen, and register them as such.
4728 r->move_to_old();
4729 _old_set->add(r);
4730 }
4731 _total_used += r->used();
4732 }
4733
4734 return false;
4735 }
4736
4737 size_t total_used() {
4738 return _total_used;
4739 }
4740 };
4741
4742 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
4743 assert_at_safepoint_on_vm_thread();
4744
4745 if (!free_list_only) {
4746 _eden.clear();
4747 _survivor.clear();
4748 }
4749
4750 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
4751 heap_region_iterate(&cl);
4752
4753 if (!free_list_only) {
4754 set_used(cl.total_used());
4755 if (_archive_allocator != NULL) {
4756 _archive_allocator->clear_used();
4757 }
4758 }
4759 assert(used_unlocked() == recalculate_used(),
4760 "inconsistent used_unlocked(), "
4761 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT,
4762 used_unlocked(), recalculate_used());
4763 }
4764
4765 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
4766 HeapRegion* hr = heap_region_containing(p);
4767 return hr->is_in(p);
4768 }
4769
4770 // Methods for the mutator alloc region
4771
4772 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
4773 bool force) {
4774 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4775 bool should_allocate = g1_policy()->should_allocate_mutator_region();
4776 if (force || should_allocate) {
4777 HeapRegion* new_alloc_region = new_region(word_size,
4778 false /* is_old */,
4779 false /* do_expand */);
4780 if (new_alloc_region != NULL) {
4781 set_region_short_lived_locked(new_alloc_region);
4782 _hr_printer.alloc(new_alloc_region, !should_allocate);
4783 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
4784 _g1_policy->remset_tracker()->update_at_allocate(new_alloc_region);
4785 return new_alloc_region;
4786 }
4787 }
4788 return NULL;
4789 }
4790
4791 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
4792 size_t allocated_bytes) {
4793 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4794 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
4795
4796 collection_set()->add_eden_region(alloc_region);
4797 increase_used(allocated_bytes);
4798 _hr_printer.retire(alloc_region);
4799 // We update the eden sizes here, when the region is retired,
4800 // instead of when it's allocated, since this is the point that its
4801 // used space has been recored in _summary_bytes_used.
4802 g1mm()->update_eden_size();
4803 }
4804
4805 // Methods for the GC alloc regions
4806
4807 bool G1CollectedHeap::has_more_regions(InCSetState dest) {
4808 if (dest.is_old()) {
4809 return true;
4810 } else {
4811 return survivor_regions_count() < g1_policy()->max_survivor_regions();
4812 }
4813 }
4814
4815 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) {
4816 assert(FreeList_lock->owned_by_self(), "pre-condition");
4817
4818 if (!has_more_regions(dest)) {
4819 return NULL;
4820 }
4821
4822 const bool is_survivor = dest.is_young();
4823
4824 HeapRegion* new_alloc_region = new_region(word_size,
4825 !is_survivor,
4826 true /* do_expand */);
4827 if (new_alloc_region != NULL) {
4828 if (is_survivor) {
4829 new_alloc_region->set_survivor();
4830 _survivor.add(new_alloc_region);
4831 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
4832 } else {
4833 new_alloc_region->set_old();
4834 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
4835 }
4836 _g1_policy->remset_tracker()->update_at_allocate(new_alloc_region);
4837 _hr_printer.alloc(new_alloc_region);
4838 bool during_im = collector_state()->in_initial_mark_gc();
4839 new_alloc_region->note_start_of_copying(during_im);
4840 return new_alloc_region;
4841 }
4842 return NULL;
4843 }
4844
4845 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
4846 size_t allocated_bytes,
4847 InCSetState dest) {
4848 bool during_im = collector_state()->in_initial_mark_gc();
4849 alloc_region->note_end_of_copying(during_im);
4850 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
4851 if (dest.is_old()) {
4852 _old_set.add(alloc_region);
4853 }
4854 _hr_printer.retire(alloc_region);
4855 }
4856
4857 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
4858 bool expanded = false;
4859 uint index = _hrm.find_highest_free(&expanded);
4860
4861 if (index != G1_NO_HRM_INDEX) {
4862 if (expanded) {
4863 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
4864 HeapRegion::GrainWords * HeapWordSize);
4865 }
4866 _hrm.allocate_free_regions_starting_at(index, 1);
4867 return region_at(index);
4868 }
4869 return NULL;
4870 }
4871
4872 // Optimized nmethod scanning
4873
4874 class RegisterNMethodOopClosure: public OopClosure {
4875 G1CollectedHeap* _g1h;
4876 nmethod* _nm;
4877
4878 template <class T> void do_oop_work(T* p) {
4879 T heap_oop = RawAccess<>::oop_load(p);
4880 if (!CompressedOops::is_null(heap_oop)) {
4881 oop obj = CompressedOops::decode_not_null(heap_oop);
4882 HeapRegion* hr = _g1h->heap_region_containing(obj);
4883 assert(!hr->is_continues_humongous(),
4884 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
4885 " starting at " HR_FORMAT,
4886 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
4887
4888 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
4889 hr->add_strong_code_root_locked(_nm);
4890 }
4891 }
4892
4893 public:
4894 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
4895 _g1h(g1h), _nm(nm) {}
4896
4897 void do_oop(oop* p) { do_oop_work(p); }
4898 void do_oop(narrowOop* p) { do_oop_work(p); }
4899 };
4900
4901 class UnregisterNMethodOopClosure: public OopClosure {
4902 G1CollectedHeap* _g1h;
4903 nmethod* _nm;
4904
4905 template <class T> void do_oop_work(T* p) {
4906 T heap_oop = RawAccess<>::oop_load(p);
4907 if (!CompressedOops::is_null(heap_oop)) {
4908 oop obj = CompressedOops::decode_not_null(heap_oop);
4909 HeapRegion* hr = _g1h->heap_region_containing(obj);
4910 assert(!hr->is_continues_humongous(),
4911 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
4912 " starting at " HR_FORMAT,
4913 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
4914
4915 hr->remove_strong_code_root(_nm);
4916 }
4917 }
4918
4919 public:
4920 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
4921 _g1h(g1h), _nm(nm) {}
4922
4923 void do_oop(oop* p) { do_oop_work(p); }
4924 void do_oop(narrowOop* p) { do_oop_work(p); }
4925 };
4926
4927 // Returns true if the reference points to an object that
4928 // can move in an incremental collection.
4929 bool G1CollectedHeap::is_scavengable(oop obj) {
4930 HeapRegion* hr = heap_region_containing(obj);
4931 return !hr->is_pinned();
4932 }
4933
4934 void G1CollectedHeap::register_nmethod(nmethod* nm) {
4935 guarantee(nm != NULL, "sanity");
4936 RegisterNMethodOopClosure reg_cl(this, nm);
4937 nm->oops_do(®_cl);
4938 }
4939
4940 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
4941 guarantee(nm != NULL, "sanity");
4942 UnregisterNMethodOopClosure reg_cl(this, nm);
4943 nm->oops_do(®_cl, true);
4944 }
4945
4946 void G1CollectedHeap::purge_code_root_memory() {
4947 double purge_start = os::elapsedTime();
4948 G1CodeRootSet::purge();
4949 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
4950 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
4951 }
4952
4953 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
4954 G1CollectedHeap* _g1h;
4955
4956 public:
4957 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
4958 _g1h(g1h) {}
4959
4960 void do_code_blob(CodeBlob* cb) {
4961 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
4962 if (nm == NULL) {
4963 return;
4964 }
4965
4966 if (ScavengeRootsInCode) {
4967 _g1h->register_nmethod(nm);
4968 }
4969 }
4970 };
4971
4972 void G1CollectedHeap::rebuild_strong_code_roots() {
4973 RebuildStrongCodeRootClosure blob_cl(this);
4974 CodeCache::blobs_do(&blob_cl);
4975 }
4976
4977 GrowableArray<GCMemoryManager*> G1CollectedHeap::memory_managers() {
4978 GrowableArray<GCMemoryManager*> memory_managers(2);
4979 memory_managers.append(&_memory_manager);
4980 memory_managers.append(&_full_gc_memory_manager);
4981 return memory_managers;
4982 }
4983
4984 GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() {
4985 GrowableArray<MemoryPool*> memory_pools(3);
4986 memory_pools.append(_eden_pool);
4987 memory_pools.append(_survivor_pool);
4988 memory_pools.append(_old_pool);
4989 return memory_pools;
4990 }