1 /*
2 * Copyright (c) 2001, 2016, 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/bufferingOopClosure.hpp"
32 #include "gc/g1/concurrentG1Refine.hpp"
33 #include "gc/g1/concurrentG1RefineThread.hpp"
34 #include "gc/g1/concurrentMarkThread.inline.hpp"
35 #include "gc/g1/g1Allocator.inline.hpp"
36 #include "gc/g1/g1CollectedHeap.inline.hpp"
37 #include "gc/g1/g1CollectionSet.hpp"
38 #include "gc/g1/g1CollectorPolicy.hpp"
39 #include "gc/g1/g1CollectorState.hpp"
40 #include "gc/g1/g1EvacStats.inline.hpp"
41 #include "gc/g1/g1GCPhaseTimes.hpp"
42 #include "gc/g1/g1HeapSizingPolicy.hpp"
43 #include "gc/g1/g1HeapTransition.hpp"
44 #include "gc/g1/g1HeapVerifier.hpp"
45 #include "gc/g1/g1MarkSweep.hpp"
46 #include "gc/g1/g1OopClosures.inline.hpp"
47 #include "gc/g1/g1ParScanThreadState.inline.hpp"
48 #include "gc/g1/g1Policy.hpp"
49 #include "gc/g1/g1RegionToSpaceMapper.hpp"
50 #include "gc/g1/g1RemSet.inline.hpp"
51 #include "gc/g1/g1RootClosures.hpp"
52 #include "gc/g1/g1RootProcessor.hpp"
53 #include "gc/g1/g1StringDedup.hpp"
54 #include "gc/g1/g1YCTypes.hpp"
55 #include "gc/g1/heapRegion.inline.hpp"
56 #include "gc/g1/heapRegionRemSet.hpp"
57 #include "gc/g1/heapRegionSet.inline.hpp"
58 #include "gc/g1/suspendibleThreadSet.hpp"
59 #include "gc/g1/vm_operations_g1.hpp"
60 #include "gc/shared/gcHeapSummary.hpp"
61 #include "gc/shared/gcId.hpp"
62 #include "gc/shared/gcLocker.inline.hpp"
63 #include "gc/shared/gcTimer.hpp"
64 #include "gc/shared/gcTrace.hpp"
65 #include "gc/shared/gcTraceTime.inline.hpp"
66 #include "gc/shared/generationSpec.hpp"
67 #include "gc/shared/isGCActiveMark.hpp"
68 #include "gc/shared/preservedMarks.inline.hpp"
69 #include "gc/shared/referenceProcessor.inline.hpp"
70 #include "gc/shared/taskqueue.inline.hpp"
71 #include "logging/log.hpp"
72 #include "memory/allocation.hpp"
73 #include "memory/iterator.hpp"
74 #include "memory/resourceArea.hpp"
75 #include "oops/oop.inline.hpp"
76 #include "runtime/atomic.inline.hpp"
77 #include "runtime/init.hpp"
78 #include "runtime/orderAccess.inline.hpp"
79 #include "runtime/vmThread.hpp"
80 #include "utilities/globalDefinitions.hpp"
81 #include "utilities/stack.inline.hpp"
82
83 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
84
85 // INVARIANTS/NOTES
86 //
87 // All allocation activity covered by the G1CollectedHeap interface is
88 // serialized by acquiring the HeapLock. This happens in mem_allocate
89 // and allocate_new_tlab, which are the "entry" points to the
90 // allocation code from the rest of the JVM. (Note that this does not
91 // apply to TLAB allocation, which is not part of this interface: it
92 // is done by clients of this interface.)
93
94 // Local to this file.
95
96 class RefineCardTableEntryClosure: public CardTableEntryClosure {
97 bool _concurrent;
98 public:
99 RefineCardTableEntryClosure() : _concurrent(true) { }
100
101 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
102 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, NULL);
103 // This path is executed by the concurrent refine or mutator threads,
104 // concurrently, and so we do not care if card_ptr contains references
105 // that point into the collection set.
106 assert(!oops_into_cset, "should be");
107
108 if (_concurrent && SuspendibleThreadSet::should_yield()) {
109 // Caller will actually yield.
110 return false;
111 }
112 // Otherwise, we finished successfully; return true.
113 return true;
114 }
115
116 void set_concurrent(bool b) { _concurrent = b; }
117 };
118
119
120 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
121 private:
122 size_t _num_dirtied;
123 G1CollectedHeap* _g1h;
124 G1SATBCardTableLoggingModRefBS* _g1_bs;
125
126 HeapRegion* region_for_card(jbyte* card_ptr) const {
127 return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr));
128 }
129
130 bool will_become_free(HeapRegion* hr) const {
131 // A region will be freed by free_collection_set if the region is in the
132 // collection set and has not had an evacuation failure.
133 return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
134 }
135
136 public:
137 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(),
138 _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { }
139
140 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
141 HeapRegion* hr = region_for_card(card_ptr);
142
143 // Should only dirty cards in regions that won't be freed.
144 if (!will_become_free(hr)) {
145 *card_ptr = CardTableModRefBS::dirty_card_val();
146 _num_dirtied++;
147 }
148
149 return true;
150 }
151
152 size_t num_dirtied() const { return _num_dirtied; }
153 };
154
155
156 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
157 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
158 }
159
160 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
161 // The from card cache is not the memory that is actually committed. So we cannot
162 // take advantage of the zero_filled parameter.
163 reset_from_card_cache(start_idx, num_regions);
164 }
165
166 // Returns true if the reference points to an object that
167 // can move in an incremental collection.
168 bool G1CollectedHeap::is_scavengable(const void* p) {
169 HeapRegion* hr = heap_region_containing(p);
170 return !hr->is_pinned();
171 }
172
173 // Private methods.
174
175 HeapRegion*
176 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
177 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
178 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
179 if (!_secondary_free_list.is_empty()) {
180 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
181 "secondary_free_list has %u entries",
182 _secondary_free_list.length());
183 // It looks as if there are free regions available on the
184 // secondary_free_list. Let's move them to the free_list and try
185 // again to allocate from it.
186 append_secondary_free_list();
187
188 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
189 "empty we should have moved at least one entry to the free_list");
190 HeapRegion* res = _hrm.allocate_free_region(is_old);
191 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
192 "allocated " HR_FORMAT " from secondary_free_list",
193 HR_FORMAT_PARAMS(res));
194 return res;
195 }
196
197 // Wait here until we get notified either when (a) there are no
198 // more free regions coming or (b) some regions have been moved on
199 // the secondary_free_list.
200 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
201 }
202
203 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
204 "could not allocate from secondary_free_list");
205 return NULL;
206 }
207
208 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
209 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
210 "the only time we use this to allocate a humongous region is "
211 "when we are allocating a single humongous region");
212
213 HeapRegion* res;
214 if (G1StressConcRegionFreeing) {
215 if (!_secondary_free_list.is_empty()) {
216 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
217 "forced to look at the secondary_free_list");
218 res = new_region_try_secondary_free_list(is_old);
219 if (res != NULL) {
220 return res;
221 }
222 }
223 }
224
225 res = _hrm.allocate_free_region(is_old);
226
227 if (res == NULL) {
228 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
229 "res == NULL, trying the secondary_free_list");
230 res = new_region_try_secondary_free_list(is_old);
231 }
232 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
233 // Currently, only attempts to allocate GC alloc regions set
234 // do_expand to true. So, we should only reach here during a
235 // safepoint. If this assumption changes we might have to
236 // reconsider the use of _expand_heap_after_alloc_failure.
237 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
238
239 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
240 word_size * HeapWordSize);
241
242 if (expand(word_size * HeapWordSize)) {
243 // Given that expand() succeeded in expanding the heap, and we
244 // always expand the heap by an amount aligned to the heap
245 // region size, the free list should in theory not be empty.
246 // In either case allocate_free_region() will check for NULL.
247 res = _hrm.allocate_free_region(is_old);
248 } else {
249 _expand_heap_after_alloc_failure = false;
250 }
251 }
252 return res;
253 }
254
255 HeapWord*
256 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
257 uint num_regions,
258 size_t word_size,
259 AllocationContext_t context) {
260 assert(first != G1_NO_HRM_INDEX, "pre-condition");
261 assert(is_humongous(word_size), "word_size should be humongous");
262 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
263
264 // Index of last region in the series.
265 uint last = first + num_regions - 1;
266
267 // We need to initialize the region(s) we just discovered. This is
268 // a bit tricky given that it can happen concurrently with
269 // refinement threads refining cards on these regions and
270 // potentially wanting to refine the BOT as they are scanning
271 // those cards (this can happen shortly after a cleanup; see CR
272 // 6991377). So we have to set up the region(s) carefully and in
273 // a specific order.
274
275 // The word size sum of all the regions we will allocate.
276 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
277 assert(word_size <= word_size_sum, "sanity");
278
279 // This will be the "starts humongous" region.
280 HeapRegion* first_hr = region_at(first);
281 // The header of the new object will be placed at the bottom of
282 // the first region.
283 HeapWord* new_obj = first_hr->bottom();
284 // This will be the new top of the new object.
285 HeapWord* obj_top = new_obj + word_size;
286
287 // First, we need to zero the header of the space that we will be
288 // allocating. When we update top further down, some refinement
289 // threads might try to scan the region. By zeroing the header we
290 // ensure that any thread that will try to scan the region will
291 // come across the zero klass word and bail out.
292 //
293 // NOTE: It would not have been correct to have used
294 // CollectedHeap::fill_with_object() and make the space look like
295 // an int array. The thread that is doing the allocation will
296 // later update the object header to a potentially different array
297 // type and, for a very short period of time, the klass and length
298 // fields will be inconsistent. This could cause a refinement
299 // thread to calculate the object size incorrectly.
300 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
301
302 // How many words we use for filler objects.
303 size_t word_fill_size = word_size_sum - word_size;
304
305 // How many words memory we "waste" which cannot hold a filler object.
306 size_t words_not_fillable = 0;
307
308 if (word_fill_size >= min_fill_size()) {
309 fill_with_objects(obj_top, word_fill_size);
310 } else if (word_fill_size > 0) {
311 // We have space to fill, but we cannot fit an object there.
312 words_not_fillable = word_fill_size;
313 word_fill_size = 0;
314 }
315
316 // We will set up the first region as "starts humongous". This
317 // will also update the BOT covering all the regions to reflect
318 // that there is a single object that starts at the bottom of the
319 // first region.
320 first_hr->set_starts_humongous(obj_top, word_fill_size);
321 first_hr->set_allocation_context(context);
322 // Then, if there are any, we will set up the "continues
323 // humongous" regions.
324 HeapRegion* hr = NULL;
325 for (uint i = first + 1; i <= last; ++i) {
326 hr = region_at(i);
327 hr->set_continues_humongous(first_hr);
328 hr->set_allocation_context(context);
329 }
330
331 // Up to this point no concurrent thread would have been able to
332 // do any scanning on any region in this series. All the top
333 // fields still point to bottom, so the intersection between
334 // [bottom,top] and [card_start,card_end] will be empty. Before we
335 // update the top fields, we'll do a storestore to make sure that
336 // no thread sees the update to top before the zeroing of the
337 // object header and the BOT initialization.
338 OrderAccess::storestore();
339
340 // Now, we will update the top fields of the "continues humongous"
341 // regions except the last one.
342 for (uint i = first; i < last; ++i) {
343 hr = region_at(i);
344 hr->set_top(hr->end());
345 }
346
347 hr = region_at(last);
348 // If we cannot fit a filler object, we must set top to the end
349 // of the humongous object, otherwise we cannot iterate the heap
350 // and the BOT will not be complete.
351 hr->set_top(hr->end() - words_not_fillable);
352
353 assert(hr->bottom() < obj_top && obj_top <= hr->end(),
354 "obj_top should be in last region");
355
356 _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
357
358 assert(words_not_fillable == 0 ||
359 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
360 "Miscalculation in humongous allocation");
361
362 increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
363
364 for (uint i = first; i <= last; ++i) {
365 hr = region_at(i);
366 _humongous_set.add(hr);
367 _hr_printer.alloc(hr);
368 }
369
370 return new_obj;
371 }
372
373 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
374 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
375 return align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
376 }
377
378 // If could fit into free regions w/o expansion, try.
379 // Otherwise, if can expand, do so.
380 // Otherwise, if using ex regions might help, try with ex given back.
381 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
382 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
383
384 _verifier->verify_region_sets_optional();
385
386 uint first = G1_NO_HRM_INDEX;
387 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
388
389 if (obj_regions == 1) {
390 // Only one region to allocate, try to use a fast path by directly allocating
391 // from the free lists. Do not try to expand here, we will potentially do that
392 // later.
393 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
394 if (hr != NULL) {
395 first = hr->hrm_index();
396 }
397 } else {
398 // We can't allocate humongous regions spanning more than one region while
399 // cleanupComplete() is running, since some of the regions we find to be
400 // empty might not yet be added to the free list. It is not straightforward
401 // to know in which list they are on so that we can remove them. We only
402 // need to do this if we need to allocate more than one region to satisfy the
403 // current humongous allocation request. If we are only allocating one region
404 // we use the one-region region allocation code (see above), that already
405 // potentially waits for regions from the secondary free list.
406 wait_while_free_regions_coming();
407 append_secondary_free_list_if_not_empty_with_lock();
408
409 // Policy: Try only empty regions (i.e. already committed first). Maybe we
410 // are lucky enough to find some.
411 first = _hrm.find_contiguous_only_empty(obj_regions);
412 if (first != G1_NO_HRM_INDEX) {
413 _hrm.allocate_free_regions_starting_at(first, obj_regions);
414 }
415 }
416
417 if (first == G1_NO_HRM_INDEX) {
418 // Policy: We could not find enough regions for the humongous object in the
419 // free list. Look through the heap to find a mix of free and uncommitted regions.
420 // If so, try expansion.
421 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
422 if (first != G1_NO_HRM_INDEX) {
423 // We found something. Make sure these regions are committed, i.e. expand
424 // the heap. Alternatively we could do a defragmentation GC.
425 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
426 word_size * HeapWordSize);
427
428
429 _hrm.expand_at(first, obj_regions);
430 g1_policy()->record_new_heap_size(num_regions());
431
432 #ifdef ASSERT
433 for (uint i = first; i < first + obj_regions; ++i) {
434 HeapRegion* hr = region_at(i);
435 assert(hr->is_free(), "sanity");
436 assert(hr->is_empty(), "sanity");
437 assert(is_on_master_free_list(hr), "sanity");
438 }
439 #endif
440 _hrm.allocate_free_regions_starting_at(first, obj_regions);
441 } else {
442 // Policy: Potentially trigger a defragmentation GC.
443 }
444 }
445
446 HeapWord* result = NULL;
447 if (first != G1_NO_HRM_INDEX) {
448 result = humongous_obj_allocate_initialize_regions(first, obj_regions,
449 word_size, context);
450 assert(result != NULL, "it should always return a valid result");
451
452 // A successful humongous object allocation changes the used space
453 // information of the old generation so we need to recalculate the
454 // sizes and update the jstat counters here.
455 g1mm()->update_sizes();
456 }
457
458 _verifier->verify_region_sets_optional();
459
460 return result;
461 }
462
463 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
464 assert_heap_not_locked_and_not_at_safepoint();
465 assert(!is_humongous(word_size), "we do not allow humongous TLABs");
466
467 uint dummy_gc_count_before;
468 uint dummy_gclocker_retry_count = 0;
469 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
470 }
471
472 HeapWord*
473 G1CollectedHeap::mem_allocate(size_t word_size,
474 bool* gc_overhead_limit_was_exceeded) {
475 assert_heap_not_locked_and_not_at_safepoint();
476
477 // Loop until the allocation is satisfied, or unsatisfied after GC.
478 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
479 uint gc_count_before;
480
481 HeapWord* result = NULL;
482 if (!is_humongous(word_size)) {
483 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
484 } else {
485 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
486 }
487 if (result != NULL) {
488 return result;
489 }
490
491 // Create the garbage collection operation...
492 VM_G1CollectForAllocation op(gc_count_before, word_size);
493 op.set_allocation_context(AllocationContext::current());
494
495 // ...and get the VM thread to execute it.
496 VMThread::execute(&op);
497
498 if (op.prologue_succeeded() && op.pause_succeeded()) {
499 // If the operation was successful we'll return the result even
500 // if it is NULL. If the allocation attempt failed immediately
501 // after a Full GC, it's unlikely we'll be able to allocate now.
502 HeapWord* result = op.result();
503 if (result != NULL && !is_humongous(word_size)) {
504 // Allocations that take place on VM operations do not do any
505 // card dirtying and we have to do it here. We only have to do
506 // this for non-humongous allocations, though.
507 dirty_young_block(result, word_size);
508 }
509 return result;
510 } else {
511 if (gclocker_retry_count > GCLockerRetryAllocationCount) {
512 return NULL;
513 }
514 assert(op.result() == NULL,
515 "the result should be NULL if the VM op did not succeed");
516 }
517
518 // Give a warning if we seem to be looping forever.
519 if ((QueuedAllocationWarningCount > 0) &&
520 (try_count % QueuedAllocationWarningCount == 0)) {
521 log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count);
522 }
523 }
524
525 ShouldNotReachHere();
526 return NULL;
527 }
528
529 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
530 AllocationContext_t context,
531 uint* gc_count_before_ret,
532 uint* gclocker_retry_count_ret) {
533 // Make sure you read the note in attempt_allocation_humongous().
534
535 assert_heap_not_locked_and_not_at_safepoint();
536 assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
537 "be called for humongous allocation requests");
538
539 // We should only get here after the first-level allocation attempt
540 // (attempt_allocation()) failed to allocate.
541
542 // We will loop until a) we manage to successfully perform the
543 // allocation or b) we successfully schedule a collection which
544 // fails to perform the allocation. b) is the only case when we'll
545 // return NULL.
546 HeapWord* result = NULL;
547 for (int try_count = 1; /* we'll return */; try_count += 1) {
548 bool should_try_gc;
549 uint gc_count_before;
550
551 {
552 MutexLockerEx x(Heap_lock);
553 result = _allocator->attempt_allocation_locked(word_size, context);
554 if (result != NULL) {
555 return result;
556 }
557
558 if (GCLocker::is_active_and_needs_gc()) {
559 if (g1_policy()->can_expand_young_list()) {
560 // No need for an ergo verbose message here,
561 // can_expand_young_list() does this when it returns true.
562 result = _allocator->attempt_allocation_force(word_size, context);
563 if (result != NULL) {
564 return result;
565 }
566 }
567 should_try_gc = false;
568 } else {
569 // The GCLocker may not be active but the GCLocker initiated
570 // GC may not yet have been performed (GCLocker::needs_gc()
571 // returns true). In this case we do not try this GC and
572 // wait until the GCLocker initiated GC is performed, and
573 // then retry the allocation.
574 if (GCLocker::needs_gc()) {
575 should_try_gc = false;
576 } else {
577 // Read the GC count while still holding the Heap_lock.
578 gc_count_before = total_collections();
579 should_try_gc = true;
580 }
581 }
582 }
583
584 if (should_try_gc) {
585 bool succeeded;
586 result = do_collection_pause(word_size, gc_count_before, &succeeded,
587 GCCause::_g1_inc_collection_pause);
588 if (result != NULL) {
589 assert(succeeded, "only way to get back a non-NULL result");
590 return result;
591 }
592
593 if (succeeded) {
594 // If we get here we successfully scheduled a collection which
595 // failed to allocate. No point in trying to allocate
596 // further. We'll just return NULL.
597 MutexLockerEx x(Heap_lock);
598 *gc_count_before_ret = total_collections();
599 return NULL;
600 }
601 } else {
602 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
603 MutexLockerEx x(Heap_lock);
604 *gc_count_before_ret = total_collections();
605 return NULL;
606 }
607 // The GCLocker is either active or the GCLocker initiated
608 // GC has not yet been performed. Stall until it is and
609 // then retry the allocation.
610 GCLocker::stall_until_clear();
611 (*gclocker_retry_count_ret) += 1;
612 }
613
614 // We can reach here if we were unsuccessful in scheduling a
615 // collection (because another thread beat us to it) or if we were
616 // stalled due to the GC locker. In either can we should retry the
617 // allocation attempt in case another thread successfully
618 // performed a collection and reclaimed enough space. We do the
619 // first attempt (without holding the Heap_lock) here and the
620 // follow-on attempt will be at the start of the next loop
621 // iteration (after taking the Heap_lock).
622 result = _allocator->attempt_allocation(word_size, context);
623 if (result != NULL) {
624 return result;
625 }
626
627 // Give a warning if we seem to be looping forever.
628 if ((QueuedAllocationWarningCount > 0) &&
629 (try_count % QueuedAllocationWarningCount == 0)) {
630 log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() "
631 "retries %d times", try_count);
632 }
633 }
634
635 ShouldNotReachHere();
636 return NULL;
637 }
638
639 void G1CollectedHeap::begin_archive_alloc_range() {
640 assert_at_safepoint(true /* should_be_vm_thread */);
641 if (_archive_allocator == NULL) {
642 _archive_allocator = G1ArchiveAllocator::create_allocator(this);
643 }
644 }
645
646 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
647 // Allocations in archive regions cannot be of a size that would be considered
648 // humongous even for a minimum-sized region, because G1 region sizes/boundaries
649 // may be different at archive-restore time.
650 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
651 }
652
653 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
654 assert_at_safepoint(true /* should_be_vm_thread */);
655 assert(_archive_allocator != NULL, "_archive_allocator not initialized");
656 if (is_archive_alloc_too_large(word_size)) {
657 return NULL;
658 }
659 return _archive_allocator->archive_mem_allocate(word_size);
660 }
661
662 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
663 size_t end_alignment_in_bytes) {
664 assert_at_safepoint(true /* should_be_vm_thread */);
665 assert(_archive_allocator != NULL, "_archive_allocator not initialized");
666
667 // Call complete_archive to do the real work, filling in the MemRegion
668 // array with the archive regions.
669 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
670 delete _archive_allocator;
671 _archive_allocator = NULL;
672 }
673
674 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
675 assert(ranges != NULL, "MemRegion array NULL");
676 assert(count != 0, "No MemRegions provided");
677 MemRegion reserved = _hrm.reserved();
678 for (size_t i = 0; i < count; i++) {
679 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
680 return false;
681 }
682 }
683 return true;
684 }
685
686 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, size_t count) {
687 assert(!is_init_completed(), "Expect to be called at JVM init time");
688 assert(ranges != NULL, "MemRegion array NULL");
689 assert(count != 0, "No MemRegions provided");
690 MutexLockerEx x(Heap_lock);
691
692 MemRegion reserved = _hrm.reserved();
693 HeapWord* prev_last_addr = NULL;
694 HeapRegion* prev_last_region = NULL;
695
696 // Temporarily disable pretouching of heap pages. This interface is used
697 // when mmap'ing archived heap data in, so pre-touching is wasted.
698 FlagSetting fs(AlwaysPreTouch, false);
699
700 // Enable archive object checking in G1MarkSweep. We have to let it know
701 // about each archive range, so that objects in those ranges aren't marked.
702 G1MarkSweep::enable_archive_object_check();
703
704 // For each specified MemRegion range, allocate the corresponding G1
705 // regions and mark them as archive regions. We expect the ranges in
706 // ascending starting address order, without overlap.
707 for (size_t i = 0; i < count; i++) {
708 MemRegion curr_range = ranges[i];
709 HeapWord* start_address = curr_range.start();
710 size_t word_size = curr_range.word_size();
711 HeapWord* last_address = curr_range.last();
712 size_t commits = 0;
713
714 guarantee(reserved.contains(start_address) && reserved.contains(last_address),
715 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
716 p2i(start_address), p2i(last_address));
717 guarantee(start_address > prev_last_addr,
718 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
719 p2i(start_address), p2i(prev_last_addr));
720 prev_last_addr = last_address;
721
722 // Check for ranges that start in the same G1 region in which the previous
723 // range ended, and adjust the start address so we don't try to allocate
724 // the same region again. If the current range is entirely within that
725 // region, skip it, just adjusting the recorded top.
726 HeapRegion* start_region = _hrm.addr_to_region(start_address);
727 if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
728 start_address = start_region->end();
729 if (start_address > last_address) {
730 increase_used(word_size * HeapWordSize);
731 start_region->set_top(last_address + 1);
732 continue;
733 }
734 start_region->set_top(start_address);
735 curr_range = MemRegion(start_address, last_address + 1);
736 start_region = _hrm.addr_to_region(start_address);
737 }
738
739 // Perform the actual region allocation, exiting if it fails.
740 // Then note how much new space we have allocated.
741 if (!_hrm.allocate_containing_regions(curr_range, &commits)) {
742 return false;
743 }
744 increase_used(word_size * HeapWordSize);
745 if (commits != 0) {
746 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
747 HeapRegion::GrainWords * HeapWordSize * commits);
748
749 }
750
751 // Mark each G1 region touched by the range as archive, add it to the old set,
752 // and set the allocation context and top.
753 HeapRegion* curr_region = _hrm.addr_to_region(start_address);
754 HeapRegion* last_region = _hrm.addr_to_region(last_address);
755 prev_last_region = last_region;
756
757 while (curr_region != NULL) {
758 assert(curr_region->is_empty() && !curr_region->is_pinned(),
759 "Region already in use (index %u)", curr_region->hrm_index());
760 curr_region->set_allocation_context(AllocationContext::system());
761 curr_region->set_archive();
762 _hr_printer.alloc(curr_region);
763 _old_set.add(curr_region);
764 if (curr_region != last_region) {
765 curr_region->set_top(curr_region->end());
766 curr_region = _hrm.next_region_in_heap(curr_region);
767 } else {
768 curr_region->set_top(last_address + 1);
769 curr_region = NULL;
770 }
771 }
772
773 // Notify mark-sweep of the archive range.
774 G1MarkSweep::set_range_archive(curr_range, true);
775 }
776 return true;
777 }
778
779 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
780 assert(!is_init_completed(), "Expect to be called at JVM init time");
781 assert(ranges != NULL, "MemRegion array NULL");
782 assert(count != 0, "No MemRegions provided");
783 MemRegion reserved = _hrm.reserved();
784 HeapWord *prev_last_addr = NULL;
785 HeapRegion* prev_last_region = NULL;
786
787 // For each MemRegion, create filler objects, if needed, in the G1 regions
788 // that contain the address range. The address range actually within the
789 // MemRegion will not be modified. That is assumed to have been initialized
790 // elsewhere, probably via an mmap of archived heap data.
791 MutexLockerEx x(Heap_lock);
792 for (size_t i = 0; i < count; i++) {
793 HeapWord* start_address = ranges[i].start();
794 HeapWord* last_address = ranges[i].last();
795
796 assert(reserved.contains(start_address) && reserved.contains(last_address),
797 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
798 p2i(start_address), p2i(last_address));
799 assert(start_address > prev_last_addr,
800 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
801 p2i(start_address), p2i(prev_last_addr));
802
803 HeapRegion* start_region = _hrm.addr_to_region(start_address);
804 HeapRegion* last_region = _hrm.addr_to_region(last_address);
805 HeapWord* bottom_address = start_region->bottom();
806
807 // Check for a range beginning in the same region in which the
808 // previous one ended.
809 if (start_region == prev_last_region) {
810 bottom_address = prev_last_addr + 1;
811 }
812
813 // Verify that the regions were all marked as archive regions by
814 // alloc_archive_regions.
815 HeapRegion* curr_region = start_region;
816 while (curr_region != NULL) {
817 guarantee(curr_region->is_archive(),
818 "Expected archive region at index %u", curr_region->hrm_index());
819 if (curr_region != last_region) {
820 curr_region = _hrm.next_region_in_heap(curr_region);
821 } else {
822 curr_region = NULL;
823 }
824 }
825
826 prev_last_addr = last_address;
827 prev_last_region = last_region;
828
829 // Fill the memory below the allocated range with dummy object(s),
830 // if the region bottom does not match the range start, or if the previous
831 // range ended within the same G1 region, and there is a gap.
832 if (start_address != bottom_address) {
833 size_t fill_size = pointer_delta(start_address, bottom_address);
834 G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
835 increase_used(fill_size * HeapWordSize);
836 }
837 }
838 }
839
840 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size,
841 uint* gc_count_before_ret,
842 uint* gclocker_retry_count_ret) {
843 assert_heap_not_locked_and_not_at_safepoint();
844 assert(!is_humongous(word_size), "attempt_allocation() should not "
845 "be called for humongous allocation requests");
846
847 AllocationContext_t context = AllocationContext::current();
848 HeapWord* result = _allocator->attempt_allocation(word_size, context);
849
850 if (result == NULL) {
851 result = attempt_allocation_slow(word_size,
852 context,
853 gc_count_before_ret,
854 gclocker_retry_count_ret);
855 }
856 assert_heap_not_locked();
857 if (result != NULL) {
858 dirty_young_block(result, word_size);
859 }
860 return result;
861 }
862
863 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
864 assert(!is_init_completed(), "Expect to be called at JVM init time");
865 assert(ranges != NULL, "MemRegion array NULL");
866 assert(count != 0, "No MemRegions provided");
867 MemRegion reserved = _hrm.reserved();
868 HeapWord* prev_last_addr = NULL;
869 HeapRegion* prev_last_region = NULL;
870 size_t size_used = 0;
871 size_t uncommitted_regions = 0;
872
873 // For each Memregion, free the G1 regions that constitute it, and
874 // notify mark-sweep that the range is no longer to be considered 'archive.'
875 MutexLockerEx x(Heap_lock);
876 for (size_t i = 0; i < count; i++) {
877 HeapWord* start_address = ranges[i].start();
878 HeapWord* last_address = ranges[i].last();
879
880 assert(reserved.contains(start_address) && reserved.contains(last_address),
881 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
882 p2i(start_address), p2i(last_address));
883 assert(start_address > prev_last_addr,
884 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
885 p2i(start_address), p2i(prev_last_addr));
886 size_used += ranges[i].byte_size();
887 prev_last_addr = last_address;
888
889 HeapRegion* start_region = _hrm.addr_to_region(start_address);
890 HeapRegion* last_region = _hrm.addr_to_region(last_address);
891
892 // Check for ranges that start in the same G1 region in which the previous
893 // range ended, and adjust the start address so we don't try to free
894 // the same region again. If the current range is entirely within that
895 // region, skip it.
896 if (start_region == prev_last_region) {
897 start_address = start_region->end();
898 if (start_address > last_address) {
899 continue;
900 }
901 start_region = _hrm.addr_to_region(start_address);
902 }
903 prev_last_region = last_region;
904
905 // After verifying that each region was marked as an archive region by
906 // alloc_archive_regions, set it free and empty and uncommit it.
907 HeapRegion* curr_region = start_region;
908 while (curr_region != NULL) {
909 guarantee(curr_region->is_archive(),
910 "Expected archive region at index %u", curr_region->hrm_index());
911 uint curr_index = curr_region->hrm_index();
912 _old_set.remove(curr_region);
913 curr_region->set_free();
914 curr_region->set_top(curr_region->bottom());
915 if (curr_region != last_region) {
916 curr_region = _hrm.next_region_in_heap(curr_region);
917 } else {
918 curr_region = NULL;
919 }
920 _hrm.shrink_at(curr_index, 1);
921 uncommitted_regions++;
922 }
923
924 // Notify mark-sweep that this is no longer an archive range.
925 G1MarkSweep::set_range_archive(ranges[i], false);
926 }
927
928 if (uncommitted_regions != 0) {
929 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
930 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
931 }
932 decrease_used(size_used);
933 }
934
935 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
936 uint* gc_count_before_ret,
937 uint* gclocker_retry_count_ret) {
938 // The structure of this method has a lot of similarities to
939 // attempt_allocation_slow(). The reason these two were not merged
940 // into a single one is that such a method would require several "if
941 // allocation is not humongous do this, otherwise do that"
942 // conditional paths which would obscure its flow. In fact, an early
943 // version of this code did use a unified method which was harder to
944 // follow and, as a result, it had subtle bugs that were hard to
945 // track down. So keeping these two methods separate allows each to
946 // be more readable. It will be good to keep these two in sync as
947 // much as possible.
948
949 assert_heap_not_locked_and_not_at_safepoint();
950 assert(is_humongous(word_size), "attempt_allocation_humongous() "
951 "should only be called for humongous allocations");
952
953 // Humongous objects can exhaust the heap quickly, so we should check if we
954 // need to start a marking cycle at each humongous object allocation. We do
955 // the check before we do the actual allocation. The reason for doing it
956 // before the allocation is that we avoid having to keep track of the newly
957 // allocated memory while we do a GC.
958 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
959 word_size)) {
960 collect(GCCause::_g1_humongous_allocation);
961 }
962
963 // We will loop until a) we manage to successfully perform the
964 // allocation or b) we successfully schedule a collection which
965 // fails to perform the allocation. b) is the only case when we'll
966 // return NULL.
967 HeapWord* result = NULL;
968 for (int try_count = 1; /* we'll return */; try_count += 1) {
969 bool should_try_gc;
970 uint gc_count_before;
971
972 {
973 MutexLockerEx x(Heap_lock);
974
975 // Given that humongous objects are not allocated in young
976 // regions, we'll first try to do the allocation without doing a
977 // collection hoping that there's enough space in the heap.
978 result = humongous_obj_allocate(word_size, AllocationContext::current());
979 if (result != NULL) {
980 size_t size_in_regions = humongous_obj_size_in_regions(word_size);
981 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
982 return result;
983 }
984
985 if (GCLocker::is_active_and_needs_gc()) {
986 should_try_gc = false;
987 } else {
988 // The GCLocker may not be active but the GCLocker initiated
989 // GC may not yet have been performed (GCLocker::needs_gc()
990 // returns true). In this case we do not try this GC and
991 // wait until the GCLocker initiated GC is performed, and
992 // then retry the allocation.
993 if (GCLocker::needs_gc()) {
994 should_try_gc = false;
995 } else {
996 // Read the GC count while still holding the Heap_lock.
997 gc_count_before = total_collections();
998 should_try_gc = true;
999 }
1000 }
1001 }
1002
1003 if (should_try_gc) {
1004 // If we failed to allocate the humongous object, we should try to
1005 // do a collection pause (if we're allowed) in case it reclaims
1006 // enough space for the allocation to succeed after the pause.
1007
1008 bool succeeded;
1009 result = do_collection_pause(word_size, gc_count_before, &succeeded,
1010 GCCause::_g1_humongous_allocation);
1011 if (result != NULL) {
1012 assert(succeeded, "only way to get back a non-NULL result");
1013 return result;
1014 }
1015
1016 if (succeeded) {
1017 // If we get here we successfully scheduled a collection which
1018 // failed to allocate. No point in trying to allocate
1019 // further. We'll just return NULL.
1020 MutexLockerEx x(Heap_lock);
1021 *gc_count_before_ret = total_collections();
1022 return NULL;
1023 }
1024 } else {
1025 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1026 MutexLockerEx x(Heap_lock);
1027 *gc_count_before_ret = total_collections();
1028 return NULL;
1029 }
1030 // The GCLocker is either active or the GCLocker initiated
1031 // GC has not yet been performed. Stall until it is and
1032 // then retry the allocation.
1033 GCLocker::stall_until_clear();
1034 (*gclocker_retry_count_ret) += 1;
1035 }
1036
1037 // We can reach here if we were unsuccessful in scheduling a
1038 // collection (because another thread beat us to it) or if we were
1039 // stalled due to the GC locker. In either can we should retry the
1040 // allocation attempt in case another thread successfully
1041 // performed a collection and reclaimed enough space. Give a
1042 // warning if we seem to be looping forever.
1043
1044 if ((QueuedAllocationWarningCount > 0) &&
1045 (try_count % QueuedAllocationWarningCount == 0)) {
1046 log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() "
1047 "retries %d times", try_count);
1048 }
1049 }
1050
1051 ShouldNotReachHere();
1052 return NULL;
1053 }
1054
1055 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1056 AllocationContext_t context,
1057 bool expect_null_mutator_alloc_region) {
1058 assert_at_safepoint(true /* should_be_vm_thread */);
1059 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region,
1060 "the current alloc region was unexpectedly found to be non-NULL");
1061
1062 if (!is_humongous(word_size)) {
1063 return _allocator->attempt_allocation_locked(word_size, context);
1064 } else {
1065 HeapWord* result = humongous_obj_allocate(word_size, context);
1066 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1067 collector_state()->set_initiate_conc_mark_if_possible(true);
1068 }
1069 return result;
1070 }
1071
1072 ShouldNotReachHere();
1073 }
1074
1075 class PostMCRemSetClearClosure: public HeapRegionClosure {
1076 G1CollectedHeap* _g1h;
1077 ModRefBarrierSet* _mr_bs;
1078 public:
1079 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1080 _g1h(g1h), _mr_bs(mr_bs) {}
1081
1082 bool doHeapRegion(HeapRegion* r) {
1083 HeapRegionRemSet* hrrs = r->rem_set();
1084
1085 _g1h->reset_gc_time_stamps(r);
1086
1087 if (r->is_continues_humongous()) {
1088 // We'll assert that the strong code root list and RSet is empty
1089 assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1090 assert(hrrs->occupied() == 0, "RSet should be empty");
1091 } else {
1092 hrrs->clear();
1093 }
1094 // You might think here that we could clear just the cards
1095 // corresponding to the used region. But no: if we leave a dirty card
1096 // in a region we might allocate into, then it would prevent that card
1097 // from being enqueued, and cause it to be missed.
1098 // Re: the performance cost: we shouldn't be doing full GC anyway!
1099 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1100
1101 return false;
1102 }
1103 };
1104
1105 void G1CollectedHeap::clear_rsets_post_compaction() {
1106 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1107 heap_region_iterate(&rs_clear);
1108 }
1109
1110 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1111 G1CollectedHeap* _g1h;
1112 UpdateRSOopClosure _cl;
1113 public:
1114 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, uint worker_i = 0) :
1115 _cl(g1->g1_rem_set(), worker_i),
1116 _g1h(g1)
1117 { }
1118
1119 bool doHeapRegion(HeapRegion* r) {
1120 if (!r->is_continues_humongous()) {
1121 _cl.set_from(r);
1122 r->oop_iterate(&_cl);
1123 }
1124 return false;
1125 }
1126 };
1127
1128 class ParRebuildRSTask: public AbstractGangTask {
1129 G1CollectedHeap* _g1;
1130 HeapRegionClaimer _hrclaimer;
1131
1132 public:
1133 ParRebuildRSTask(G1CollectedHeap* g1) :
1134 AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {}
1135
1136 void work(uint worker_id) {
1137 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1138 _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer);
1139 }
1140 };
1141
1142 class PostCompactionPrinterClosure: public HeapRegionClosure {
1143 private:
1144 G1HRPrinter* _hr_printer;
1145 public:
1146 bool doHeapRegion(HeapRegion* hr) {
1147 assert(!hr->is_young(), "not expecting to find young regions");
1148 _hr_printer->post_compaction(hr);
1149 return false;
1150 }
1151
1152 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1153 : _hr_printer(hr_printer) { }
1154 };
1155
1156 void G1CollectedHeap::print_hrm_post_compaction() {
1157 if (_hr_printer.is_active()) {
1158 PostCompactionPrinterClosure cl(hr_printer());
1159 heap_region_iterate(&cl);
1160 }
1161
1162 }
1163
1164 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1165 bool clear_all_soft_refs) {
1166 assert_at_safepoint(true /* should_be_vm_thread */);
1167
1168 if (GCLocker::check_active_before_gc()) {
1169 return false;
1170 }
1171
1172 STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1173 gc_timer->register_gc_start();
1174
1175 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1176 GCIdMark gc_id_mark;
1177 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1178
1179 SvcGCMarker sgcm(SvcGCMarker::FULL);
1180 ResourceMark rm;
1181
1182 print_heap_before_gc();
1183 print_heap_regions();
1184 trace_heap_before_gc(gc_tracer);
1185
1186 size_t metadata_prev_used = MetaspaceAux::used_bytes();
1187
1188 _verifier->verify_region_sets_optional();
1189
1190 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1191 collector_policy()->should_clear_all_soft_refs();
1192
1193 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1194
1195 {
1196 IsGCActiveMark x;
1197
1198 // Timing
1199 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1200 GCTraceCPUTime tcpu;
1201
1202 {
1203 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1204 TraceCollectorStats tcs(g1mm()->full_collection_counters());
1205 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1206
1207 G1HeapTransition heap_transition(this);
1208 g1_policy()->record_full_collection_start();
1209
1210 // Note: When we have a more flexible GC logging framework that
1211 // allows us to add optional attributes to a GC log record we
1212 // could consider timing and reporting how long we wait in the
1213 // following two methods.
1214 wait_while_free_regions_coming();
1215 // If we start the compaction before the CM threads finish
1216 // scanning the root regions we might trip them over as we'll
1217 // be moving objects / updating references. So let's wait until
1218 // they are done. By telling them to abort, they should complete
1219 // early.
1220 _cm->root_regions()->abort();
1221 _cm->root_regions()->wait_until_scan_finished();
1222 append_secondary_free_list_if_not_empty_with_lock();
1223
1224 gc_prologue(true);
1225 increment_total_collections(true /* full gc */);
1226 increment_old_marking_cycles_started();
1227
1228 assert(used() == recalculate_used(), "Should be equal");
1229
1230 _verifier->verify_before_gc();
1231
1232 _verifier->check_bitmaps("Full GC Start");
1233 pre_full_gc_dump(gc_timer);
1234
1235 #if defined(COMPILER2) || INCLUDE_JVMCI
1236 DerivedPointerTable::clear();
1237 #endif
1238
1239 // Disable discovery and empty the discovered lists
1240 // for the CM ref processor.
1241 ref_processor_cm()->disable_discovery();
1242 ref_processor_cm()->abandon_partial_discovery();
1243 ref_processor_cm()->verify_no_references_recorded();
1244
1245 // Abandon current iterations of concurrent marking and concurrent
1246 // refinement, if any are in progress.
1247 concurrent_mark()->abort();
1248
1249 // Make sure we'll choose a new allocation region afterwards.
1250 _allocator->release_mutator_alloc_region();
1251 _allocator->abandon_gc_alloc_regions();
1252 g1_rem_set()->cleanupHRRS();
1253
1254 // We may have added regions to the current incremental collection
1255 // set between the last GC or pause and now. We need to clear the
1256 // incremental collection set and then start rebuilding it afresh
1257 // after this full GC.
1258 abandon_collection_set(collection_set()->inc_head());
1259 collection_set()->clear_incremental();
1260 collection_set()->stop_incremental_building();
1261
1262 tear_down_region_sets(false /* free_list_only */);
1263 collector_state()->set_gcs_are_young(true);
1264
1265 // See the comments in g1CollectedHeap.hpp and
1266 // G1CollectedHeap::ref_processing_init() about
1267 // how reference processing currently works in G1.
1268
1269 // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1270 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1271
1272 // Temporarily clear the STW ref processor's _is_alive_non_header field.
1273 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1274
1275 ref_processor_stw()->enable_discovery();
1276 ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1277
1278 // Do collection work
1279 {
1280 HandleMark hm; // Discard invalid handles created during gc
1281 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1282 }
1283
1284 assert(num_free_regions() == 0, "we should not have added any free regions");
1285 rebuild_region_sets(false /* free_list_only */);
1286
1287 // Enqueue any discovered reference objects that have
1288 // not been removed from the discovered lists.
1289 ref_processor_stw()->enqueue_discovered_references();
1290
1291 #if defined(COMPILER2) || INCLUDE_JVMCI
1292 DerivedPointerTable::update_pointers();
1293 #endif
1294
1295 MemoryService::track_memory_usage();
1296
1297 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1298 ref_processor_stw()->verify_no_references_recorded();
1299
1300 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1301 ClassLoaderDataGraph::purge();
1302 MetaspaceAux::verify_metrics();
1303
1304 // Note: since we've just done a full GC, concurrent
1305 // marking is no longer active. Therefore we need not
1306 // re-enable reference discovery for the CM ref processor.
1307 // That will be done at the start of the next marking cycle.
1308 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1309 ref_processor_cm()->verify_no_references_recorded();
1310
1311 reset_gc_time_stamp();
1312 // Since everything potentially moved, we will clear all remembered
1313 // sets, and clear all cards. Later we will rebuild remembered
1314 // sets. We will also reset the GC time stamps of the regions.
1315 clear_rsets_post_compaction();
1316 check_gc_time_stamps();
1317
1318 resize_if_necessary_after_full_collection();
1319
1320 // We should do this after we potentially resize the heap so
1321 // that all the COMMIT / UNCOMMIT events are generated before
1322 // the compaction events.
1323 print_hrm_post_compaction();
1324
1325 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1326 if (hot_card_cache->use_cache()) {
1327 hot_card_cache->reset_card_counts();
1328 hot_card_cache->reset_hot_cache();
1329 }
1330
1331 // Rebuild remembered sets of all regions.
1332 uint n_workers =
1333 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1334 workers()->active_workers(),
1335 Threads::number_of_non_daemon_threads());
1336 workers()->set_active_workers(n_workers);
1337
1338 ParRebuildRSTask rebuild_rs_task(this);
1339 workers()->run_task(&rebuild_rs_task);
1340
1341 // Rebuild the strong code root lists for each region
1342 rebuild_strong_code_roots();
1343
1344 if (true) { // FIXME
1345 MetaspaceGC::compute_new_size();
1346 }
1347
1348 #ifdef TRACESPINNING
1349 ParallelTaskTerminator::print_termination_counts();
1350 #endif
1351
1352 // Discard all rset updates
1353 JavaThread::dirty_card_queue_set().abandon_logs();
1354 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1355
1356 // At this point there should be no regions in the
1357 // entire heap tagged as young.
1358 assert(check_young_list_empty(true /* check_heap */),
1359 "young list should be empty at this point");
1360
1361 // Update the number of full collections that have been completed.
1362 increment_old_marking_cycles_completed(false /* concurrent */);
1363
1364 _hrm.verify_optional();
1365 _verifier->verify_region_sets_optional();
1366
1367 _verifier->verify_after_gc();
1368
1369 // Clear the previous marking bitmap, if needed for bitmap verification.
1370 // Note we cannot do this when we clear the next marking bitmap in
1371 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1372 // objects marked during a full GC against the previous bitmap.
1373 // But we need to clear it before calling check_bitmaps below since
1374 // the full GC has compacted objects and updated TAMS but not updated
1375 // the prev bitmap.
1376 if (G1VerifyBitmaps) {
1377 GCTraceTime(Debug, gc)("Clear Bitmap for Verification");
1378 _cm->clear_prev_bitmap(workers());
1379 }
1380 _verifier->check_bitmaps("Full GC End");
1381
1382 // Start a new incremental collection set for the next pause
1383 assert(collection_set()->head() == NULL, "must be");
1384 collection_set()->start_incremental_building();
1385
1386 clear_cset_fast_test();
1387
1388 _allocator->init_mutator_alloc_region();
1389
1390 g1_policy()->record_full_collection_end();
1391
1392 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1393 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1394 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1395 // before any GC notifications are raised.
1396 g1mm()->update_sizes();
1397
1398 gc_epilogue(true);
1399
1400 heap_transition.print();
1401
1402 print_heap_after_gc();
1403 print_heap_regions();
1404 trace_heap_after_gc(gc_tracer);
1405
1406 post_full_gc_dump(gc_timer);
1407 }
1408
1409 gc_timer->register_gc_end();
1410 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1411 }
1412
1413 return true;
1414 }
1415
1416 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1417 // Currently, there is no facility in the do_full_collection(bool) API to notify
1418 // the caller that the collection did not succeed (e.g., because it was locked
1419 // out by the GC locker). So, right now, we'll ignore the return value.
1420 bool dummy = do_full_collection(true, /* explicit_gc */
1421 clear_all_soft_refs);
1422 }
1423
1424 void G1CollectedHeap::resize_if_necessary_after_full_collection() {
1425 // Include bytes that will be pre-allocated to support collections, as "used".
1426 const size_t used_after_gc = used();
1427 const size_t capacity_after_gc = capacity();
1428 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1429
1430 // This is enforced in arguments.cpp.
1431 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1432 "otherwise the code below doesn't make sense");
1433
1434 // We don't have floating point command-line arguments
1435 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1436 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1437 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1438 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1439
1440 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1441 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1442
1443 // We have to be careful here as these two calculations can overflow
1444 // 32-bit size_t's.
1445 double used_after_gc_d = (double) used_after_gc;
1446 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1447 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1448
1449 // Let's make sure that they are both under the max heap size, which
1450 // by default will make them fit into a size_t.
1451 double desired_capacity_upper_bound = (double) max_heap_size;
1452 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1453 desired_capacity_upper_bound);
1454 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1455 desired_capacity_upper_bound);
1456
1457 // We can now safely turn them into size_t's.
1458 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1459 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1460
1461 // This assert only makes sense here, before we adjust them
1462 // with respect to the min and max heap size.
1463 assert(minimum_desired_capacity <= maximum_desired_capacity,
1464 "minimum_desired_capacity = " SIZE_FORMAT ", "
1465 "maximum_desired_capacity = " SIZE_FORMAT,
1466 minimum_desired_capacity, maximum_desired_capacity);
1467
1468 // Should not be greater than the heap max size. No need to adjust
1469 // it with respect to the heap min size as it's a lower bound (i.e.,
1470 // we'll try to make the capacity larger than it, not smaller).
1471 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1472 // Should not be less than the heap min size. No need to adjust it
1473 // with respect to the heap max size as it's an upper bound (i.e.,
1474 // we'll try to make the capacity smaller than it, not greater).
1475 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1476
1477 if (capacity_after_gc < minimum_desired_capacity) {
1478 // Don't expand unless it's significant
1479 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1480
1481 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). "
1482 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1483 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio);
1484
1485 expand(expand_bytes);
1486
1487 // No expansion, now see if we want to shrink
1488 } else if (capacity_after_gc > maximum_desired_capacity) {
1489 // Capacity too large, compute shrinking size
1490 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1491
1492 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). "
1493 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1494 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio);
1495
1496 shrink(shrink_bytes);
1497 }
1498 }
1499
1500 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1501 AllocationContext_t context,
1502 bool do_gc,
1503 bool clear_all_soft_refs,
1504 bool expect_null_mutator_alloc_region,
1505 bool* gc_succeeded) {
1506 *gc_succeeded = true;
1507 // Let's attempt the allocation first.
1508 HeapWord* result =
1509 attempt_allocation_at_safepoint(word_size,
1510 context,
1511 expect_null_mutator_alloc_region);
1512 if (result != NULL) {
1513 assert(*gc_succeeded, "sanity");
1514 return result;
1515 }
1516
1517 // In a G1 heap, we're supposed to keep allocation from failing by
1518 // incremental pauses. Therefore, at least for now, we'll favor
1519 // expansion over collection. (This might change in the future if we can
1520 // do something smarter than full collection to satisfy a failed alloc.)
1521 result = expand_and_allocate(word_size, context);
1522 if (result != NULL) {
1523 assert(*gc_succeeded, "sanity");
1524 return result;
1525 }
1526
1527 if (do_gc) {
1528 // Expansion didn't work, we'll try to do a Full GC.
1529 *gc_succeeded = do_full_collection(false, /* explicit_gc */
1530 clear_all_soft_refs);
1531 }
1532
1533 return NULL;
1534 }
1535
1536 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1537 AllocationContext_t context,
1538 bool* succeeded) {
1539 assert_at_safepoint(true /* should_be_vm_thread */);
1540
1541 // Attempts to allocate followed by Full GC.
1542 HeapWord* result =
1543 satisfy_failed_allocation_helper(word_size,
1544 context,
1545 true, /* do_gc */
1546 false, /* clear_all_soft_refs */
1547 false, /* expect_null_mutator_alloc_region */
1548 succeeded);
1549
1550 if (result != NULL || !*succeeded) {
1551 return result;
1552 }
1553
1554 // Attempts to allocate followed by Full GC that will collect all soft references.
1555 result = satisfy_failed_allocation_helper(word_size,
1556 context,
1557 true, /* do_gc */
1558 true, /* clear_all_soft_refs */
1559 true, /* expect_null_mutator_alloc_region */
1560 succeeded);
1561
1562 if (result != NULL || !*succeeded) {
1563 return result;
1564 }
1565
1566 // Attempts to allocate, no GC
1567 result = satisfy_failed_allocation_helper(word_size,
1568 context,
1569 false, /* do_gc */
1570 false, /* clear_all_soft_refs */
1571 true, /* expect_null_mutator_alloc_region */
1572 succeeded);
1573
1574 if (result != NULL) {
1575 assert(*succeeded, "sanity");
1576 return result;
1577 }
1578
1579 assert(!collector_policy()->should_clear_all_soft_refs(),
1580 "Flag should have been handled and cleared prior to this point");
1581
1582 // What else? We might try synchronous finalization later. If the total
1583 // space available is large enough for the allocation, then a more
1584 // complete compaction phase than we've tried so far might be
1585 // appropriate.
1586 assert(*succeeded, "sanity");
1587 return NULL;
1588 }
1589
1590 // Attempting to expand the heap sufficiently
1591 // to support an allocation of the given "word_size". If
1592 // successful, perform the allocation and return the address of the
1593 // allocated block, or else "NULL".
1594
1595 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1596 assert_at_safepoint(true /* should_be_vm_thread */);
1597
1598 _verifier->verify_region_sets_optional();
1599
1600 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1601 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1602 word_size * HeapWordSize);
1603
1604
1605 if (expand(expand_bytes)) {
1606 _hrm.verify_optional();
1607 _verifier->verify_region_sets_optional();
1608 return attempt_allocation_at_safepoint(word_size,
1609 context,
1610 false /* expect_null_mutator_alloc_region */);
1611 }
1612 return NULL;
1613 }
1614
1615 bool G1CollectedHeap::expand(size_t expand_bytes, double* expand_time_ms) {
1616 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1617 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1618 HeapRegion::GrainBytes);
1619
1620 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount:" SIZE_FORMAT "B expansion amount:" SIZE_FORMAT "B",
1621 expand_bytes, aligned_expand_bytes);
1622
1623 if (is_maximal_no_gc()) {
1624 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1625 return false;
1626 }
1627
1628 double expand_heap_start_time_sec = os::elapsedTime();
1629 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1630 assert(regions_to_expand > 0, "Must expand by at least one region");
1631
1632 uint expanded_by = _hrm.expand_by(regions_to_expand);
1633 if (expand_time_ms != NULL) {
1634 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1635 }
1636
1637 if (expanded_by > 0) {
1638 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1639 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1640 g1_policy()->record_new_heap_size(num_regions());
1641 } else {
1642 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1643
1644 // The expansion of the virtual storage space was unsuccessful.
1645 // Let's see if it was because we ran out of swap.
1646 if (G1ExitOnExpansionFailure &&
1647 _hrm.available() >= regions_to_expand) {
1648 // We had head room...
1649 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1650 }
1651 }
1652 return regions_to_expand > 0;
1653 }
1654
1655 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1656 size_t aligned_shrink_bytes =
1657 ReservedSpace::page_align_size_down(shrink_bytes);
1658 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1659 HeapRegion::GrainBytes);
1660 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1661
1662 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1663 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1664
1665
1666 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",
1667 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1668 if (num_regions_removed > 0) {
1669 g1_policy()->record_new_heap_size(num_regions());
1670 } else {
1671 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1672 }
1673 }
1674
1675 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1676 _verifier->verify_region_sets_optional();
1677
1678 // We should only reach here at the end of a Full GC which means we
1679 // should not not be holding to any GC alloc regions. The method
1680 // below will make sure of that and do any remaining clean up.
1681 _allocator->abandon_gc_alloc_regions();
1682
1683 // Instead of tearing down / rebuilding the free lists here, we
1684 // could instead use the remove_all_pending() method on free_list to
1685 // remove only the ones that we need to remove.
1686 tear_down_region_sets(true /* free_list_only */);
1687 shrink_helper(shrink_bytes);
1688 rebuild_region_sets(true /* free_list_only */);
1689
1690 _hrm.verify_optional();
1691 _verifier->verify_region_sets_optional();
1692 }
1693
1694 // Public methods.
1695
1696 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) :
1697 CollectedHeap(),
1698 _collector_policy(collector_policy),
1699 _g1_policy(create_g1_policy()),
1700 _collection_set(this, _g1_policy),
1701 _dirty_card_queue_set(false),
1702 _is_alive_closure_cm(this),
1703 _is_alive_closure_stw(this),
1704 _ref_processor_cm(NULL),
1705 _ref_processor_stw(NULL),
1706 _bot(NULL),
1707 _cg1r(NULL),
1708 _g1mm(NULL),
1709 _refine_cte_cl(NULL),
1710 _preserved_marks_set(true /* in_c_heap */),
1711 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1712 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1713 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1714 _humongous_reclaim_candidates(),
1715 _has_humongous_reclaim_candidates(false),
1716 _archive_allocator(NULL),
1717 _free_regions_coming(false),
1718 _young_list(new YoungList(this)),
1719 _gc_time_stamp(0),
1720 _summary_bytes_used(0),
1721 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1722 _old_evac_stats("Old", OldPLABSize, PLABWeight),
1723 _expand_heap_after_alloc_failure(true),
1724 _old_marking_cycles_started(0),
1725 _old_marking_cycles_completed(0),
1726 _in_cset_fast_test(),
1727 _worker_cset_start_region(NULL),
1728 _worker_cset_start_region_time_stamp(NULL),
1729 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1730 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()) {
1731
1732 _workers = new WorkGang("GC Thread", ParallelGCThreads,
1733 /* are_GC_task_threads */true,
1734 /* are_ConcurrentGC_threads */false);
1735 _workers->initialize_workers();
1736 _verifier = new G1HeapVerifier(this);
1737
1738 _allocator = G1Allocator::create_allocator(this);
1739
1740 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics());
1741
1742 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1743
1744 // Override the default _filler_array_max_size so that no humongous filler
1745 // objects are created.
1746 _filler_array_max_size = _humongous_object_threshold_in_words;
1747
1748 uint n_queues = ParallelGCThreads;
1749 _task_queues = new RefToScanQueueSet(n_queues);
1750
1751 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1752 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(uint, n_queues, mtGC);
1753 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1754
1755 for (uint i = 0; i < n_queues; i++) {
1756 RefToScanQueue* q = new RefToScanQueue();
1757 q->initialize();
1758 _task_queues->register_queue(i, q);
1759 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1760 }
1761 clear_cset_start_regions();
1762
1763 // Initialize the G1EvacuationFailureALot counters and flags.
1764 NOT_PRODUCT(reset_evacuation_should_fail();)
1765
1766 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1767 }
1768
1769 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1770 size_t size,
1771 size_t translation_factor) {
1772 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1773 // Allocate a new reserved space, preferring to use large pages.
1774 ReservedSpace rs(size, preferred_page_size);
1775 G1RegionToSpaceMapper* result =
1776 G1RegionToSpaceMapper::create_mapper(rs,
1777 size,
1778 rs.alignment(),
1779 HeapRegion::GrainBytes,
1780 translation_factor,
1781 mtGC);
1782
1783 os::trace_page_sizes_for_requested_size(description,
1784 size,
1785 preferred_page_size,
1786 rs.alignment(),
1787 rs.base(),
1788 rs.size());
1789
1790 return result;
1791 }
1792
1793 jint G1CollectedHeap::initialize() {
1794 CollectedHeap::pre_initialize();
1795 os::enable_vtime();
1796
1797 // Necessary to satisfy locking discipline assertions.
1798
1799 MutexLocker x(Heap_lock);
1800
1801 // While there are no constraints in the GC code that HeapWordSize
1802 // be any particular value, there are multiple other areas in the
1803 // system which believe this to be true (e.g. oop->object_size in some
1804 // cases incorrectly returns the size in wordSize units rather than
1805 // HeapWordSize).
1806 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1807
1808 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1809 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1810 size_t heap_alignment = collector_policy()->heap_alignment();
1811
1812 // Ensure that the sizes are properly aligned.
1813 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1814 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1815 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1816
1817 _refine_cte_cl = new RefineCardTableEntryClosure();
1818
1819 jint ecode = JNI_OK;
1820 _cg1r = ConcurrentG1Refine::create(this, _refine_cte_cl, &ecode);
1821 if (_cg1r == NULL) {
1822 return ecode;
1823 }
1824
1825 // Reserve the maximum.
1826
1827 // When compressed oops are enabled, the preferred heap base
1828 // is calculated by subtracting the requested size from the
1829 // 32Gb boundary and using the result as the base address for
1830 // heap reservation. If the requested size is not aligned to
1831 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1832 // into the ReservedHeapSpace constructor) then the actual
1833 // base of the reserved heap may end up differing from the
1834 // address that was requested (i.e. the preferred heap base).
1835 // If this happens then we could end up using a non-optimal
1836 // compressed oops mode.
1837
1838 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1839 heap_alignment);
1840
1841 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1842
1843 // Create the barrier set for the entire reserved region.
1844 G1SATBCardTableLoggingModRefBS* bs
1845 = new G1SATBCardTableLoggingModRefBS(reserved_region());
1846 bs->initialize();
1847 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity");
1848 set_barrier_set(bs);
1849
1850 // Also create a G1 rem set.
1851 _g1_rem_set = new G1RemSet(this, g1_barrier_set());
1852
1853 // Carve out the G1 part of the heap.
1854 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1855 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
1856 G1RegionToSpaceMapper* heap_storage =
1857 G1RegionToSpaceMapper::create_mapper(g1_rs,
1858 g1_rs.size(),
1859 page_size,
1860 HeapRegion::GrainBytes,
1861 1,
1862 mtJavaHeap);
1863 os::trace_page_sizes("Heap",
1864 collector_policy()->min_heap_byte_size(),
1865 max_byte_size,
1866 page_size,
1867 heap_rs.base(),
1868 heap_rs.size());
1869 heap_storage->set_mapping_changed_listener(&_listener);
1870
1871 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1872 G1RegionToSpaceMapper* bot_storage =
1873 create_aux_memory_mapper("Block Offset Table",
1874 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1875 G1BlockOffsetTable::heap_map_factor());
1876
1877 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
1878 G1RegionToSpaceMapper* cardtable_storage =
1879 create_aux_memory_mapper("Card Table",
1880 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize),
1881 G1SATBCardTableLoggingModRefBS::heap_map_factor());
1882
1883 G1RegionToSpaceMapper* card_counts_storage =
1884 create_aux_memory_mapper("Card Counts Table",
1885 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1886 G1CardCounts::heap_map_factor());
1887
1888 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1889 G1RegionToSpaceMapper* prev_bitmap_storage =
1890 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1891 G1RegionToSpaceMapper* next_bitmap_storage =
1892 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1893
1894 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1895 g1_barrier_set()->initialize(cardtable_storage);
1896 // Do later initialization work for concurrent refinement.
1897 _cg1r->init(card_counts_storage);
1898
1899 // 6843694 - ensure that the maximum region index can fit
1900 // in the remembered set structures.
1901 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1902 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1903
1904 g1_rem_set()->initialize(max_capacity(), max_regions());
1905
1906 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1907 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1908 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1909 "too many cards per region");
1910
1911 FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1912
1913 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1914
1915 {
1916 HeapWord* start = _hrm.reserved().start();
1917 HeapWord* end = _hrm.reserved().end();
1918 size_t granularity = HeapRegion::GrainBytes;
1919
1920 _in_cset_fast_test.initialize(start, end, granularity);
1921 _humongous_reclaim_candidates.initialize(start, end, granularity);
1922 }
1923
1924 // Create the G1ConcurrentMark data structure and thread.
1925 // (Must do this late, so that "max_regions" is defined.)
1926 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1927 if (_cm == NULL || !_cm->completed_initialization()) {
1928 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
1929 return JNI_ENOMEM;
1930 }
1931 _cmThread = _cm->cmThread();
1932
1933 // Now expand into the initial heap size.
1934 if (!expand(init_byte_size)) {
1935 vm_shutdown_during_initialization("Failed to allocate initial heap.");
1936 return JNI_ENOMEM;
1937 }
1938
1939 // Perform any initialization actions delegated to the policy.
1940 g1_policy()->init(this, &_collection_set);
1941
1942 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1943 SATB_Q_FL_lock,
1944 G1SATBProcessCompletedThreshold,
1945 Shared_SATB_Q_lock);
1946
1947 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
1948 DirtyCardQ_CBL_mon,
1949 DirtyCardQ_FL_lock,
1950 (int)concurrent_g1_refine()->yellow_zone(),
1951 (int)concurrent_g1_refine()->red_zone(),
1952 Shared_DirtyCardQ_lock,
1953 NULL, // fl_owner
1954 true); // init_free_ids
1955
1956 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
1957 DirtyCardQ_CBL_mon,
1958 DirtyCardQ_FL_lock,
1959 -1, // never trigger processing
1960 -1, // no limit on length
1961 Shared_DirtyCardQ_lock,
1962 &JavaThread::dirty_card_queue_set());
1963
1964 // Here we allocate the dummy HeapRegion that is required by the
1965 // G1AllocRegion class.
1966 HeapRegion* dummy_region = _hrm.get_dummy_region();
1967
1968 // We'll re-use the same region whether the alloc region will
1969 // require BOT updates or not and, if it doesn't, then a non-young
1970 // region will complain that it cannot support allocations without
1971 // BOT updates. So we'll tag the dummy region as eden to avoid that.
1972 dummy_region->set_eden();
1973 // Make sure it's full.
1974 dummy_region->set_top(dummy_region->end());
1975 G1AllocRegion::setup(this, dummy_region);
1976
1977 _allocator->init_mutator_alloc_region();
1978
1979 // Do create of the monitoring and management support so that
1980 // values in the heap have been properly initialized.
1981 _g1mm = new G1MonitoringSupport(this);
1982
1983 G1StringDedup::initialize();
1984
1985 _preserved_marks_set.init(ParallelGCThreads);
1986
1987 return JNI_OK;
1988 }
1989
1990 void G1CollectedHeap::stop() {
1991 // Stop all concurrent threads. We do this to make sure these threads
1992 // do not continue to execute and access resources (e.g. logging)
1993 // that are destroyed during shutdown.
1994 _cg1r->stop();
1995 _cmThread->stop();
1996 if (G1StringDedup::is_enabled()) {
1997 G1StringDedup::stop();
1998 }
1999 }
2000
2001 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2002 return HeapRegion::max_region_size();
2003 }
2004
2005 void G1CollectedHeap::post_initialize() {
2006 ref_processing_init();
2007 }
2008
2009 void G1CollectedHeap::ref_processing_init() {
2010 // Reference processing in G1 currently works as follows:
2011 //
2012 // * There are two reference processor instances. One is
2013 // used to record and process discovered references
2014 // during concurrent marking; the other is used to
2015 // record and process references during STW pauses
2016 // (both full and incremental).
2017 // * Both ref processors need to 'span' the entire heap as
2018 // the regions in the collection set may be dotted around.
2019 //
2020 // * For the concurrent marking ref processor:
2021 // * Reference discovery is enabled at initial marking.
2022 // * Reference discovery is disabled and the discovered
2023 // references processed etc during remarking.
2024 // * Reference discovery is MT (see below).
2025 // * Reference discovery requires a barrier (see below).
2026 // * Reference processing may or may not be MT
2027 // (depending on the value of ParallelRefProcEnabled
2028 // and ParallelGCThreads).
2029 // * A full GC disables reference discovery by the CM
2030 // ref processor and abandons any entries on it's
2031 // discovered lists.
2032 //
2033 // * For the STW processor:
2034 // * Non MT discovery is enabled at the start of a full GC.
2035 // * Processing and enqueueing during a full GC is non-MT.
2036 // * During a full GC, references are processed after marking.
2037 //
2038 // * Discovery (may or may not be MT) is enabled at the start
2039 // of an incremental evacuation pause.
2040 // * References are processed near the end of a STW evacuation pause.
2041 // * For both types of GC:
2042 // * Discovery is atomic - i.e. not concurrent.
2043 // * Reference discovery will not need a barrier.
2044
2045 MemRegion mr = reserved_region();
2046
2047 // Concurrent Mark ref processor
2048 _ref_processor_cm =
2049 new ReferenceProcessor(mr, // span
2050 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2051 // mt processing
2052 ParallelGCThreads,
2053 // degree of mt processing
2054 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2055 // mt discovery
2056 MAX2(ParallelGCThreads, ConcGCThreads),
2057 // degree of mt discovery
2058 false,
2059 // Reference discovery is not atomic
2060 &_is_alive_closure_cm);
2061 // is alive closure
2062 // (for efficiency/performance)
2063
2064 // STW ref processor
2065 _ref_processor_stw =
2066 new ReferenceProcessor(mr, // span
2067 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2068 // mt processing
2069 ParallelGCThreads,
2070 // degree of mt processing
2071 (ParallelGCThreads > 1),
2072 // mt discovery
2073 ParallelGCThreads,
2074 // degree of mt discovery
2075 true,
2076 // Reference discovery is atomic
2077 &_is_alive_closure_stw);
2078 // is alive closure
2079 // (for efficiency/performance)
2080 }
2081
2082 CollectorPolicy* G1CollectedHeap::collector_policy() const {
2083 return _collector_policy;
2084 }
2085
2086 size_t G1CollectedHeap::capacity() const {
2087 return _hrm.length() * HeapRegion::GrainBytes;
2088 }
2089
2090 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2091 hr->reset_gc_time_stamp();
2092 }
2093
2094 #ifndef PRODUCT
2095
2096 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2097 private:
2098 unsigned _gc_time_stamp;
2099 bool _failures;
2100
2101 public:
2102 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2103 _gc_time_stamp(gc_time_stamp), _failures(false) { }
2104
2105 virtual bool doHeapRegion(HeapRegion* hr) {
2106 unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2107 if (_gc_time_stamp != region_gc_time_stamp) {
2108 log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr),
2109 region_gc_time_stamp, _gc_time_stamp);
2110 _failures = true;
2111 }
2112 return false;
2113 }
2114
2115 bool failures() { return _failures; }
2116 };
2117
2118 void G1CollectedHeap::check_gc_time_stamps() {
2119 CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2120 heap_region_iterate(&cl);
2121 guarantee(!cl.failures(), "all GC time stamps should have been reset");
2122 }
2123 #endif // PRODUCT
2124
2125 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) {
2126 _cg1r->hot_card_cache()->drain(cl, worker_i);
2127 }
2128
2129 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) {
2130 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2131 size_t n_completed_buffers = 0;
2132 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2133 n_completed_buffers++;
2134 }
2135 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
2136 dcqs.clear_n_completed_buffers();
2137 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2138 }
2139
2140 // Computes the sum of the storage used by the various regions.
2141 size_t G1CollectedHeap::used() const {
2142 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
2143 if (_archive_allocator != NULL) {
2144 result += _archive_allocator->used();
2145 }
2146 return result;
2147 }
2148
2149 size_t G1CollectedHeap::used_unlocked() const {
2150 return _summary_bytes_used;
2151 }
2152
2153 class SumUsedClosure: public HeapRegionClosure {
2154 size_t _used;
2155 public:
2156 SumUsedClosure() : _used(0) {}
2157 bool doHeapRegion(HeapRegion* r) {
2158 _used += r->used();
2159 return false;
2160 }
2161 size_t result() { return _used; }
2162 };
2163
2164 size_t G1CollectedHeap::recalculate_used() const {
2165 double recalculate_used_start = os::elapsedTime();
2166
2167 SumUsedClosure blk;
2168 heap_region_iterate(&blk);
2169
2170 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2171 return blk.result();
2172 }
2173
2174 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
2175 switch (cause) {
2176 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2177 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent;
2178 case GCCause::_update_allocation_context_stats_inc: return true;
2179 case GCCause::_wb_conc_mark: return true;
2180 default : return false;
2181 }
2182 }
2183
2184 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2185 switch (cause) {
2186 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2187 case GCCause::_g1_humongous_allocation: return true;
2188 default: return is_user_requested_concurrent_full_gc(cause);
2189 }
2190 }
2191
2192 #ifndef PRODUCT
2193 void G1CollectedHeap::allocate_dummy_regions() {
2194 // Let's fill up most of the region
2195 size_t word_size = HeapRegion::GrainWords - 1024;
2196 // And as a result the region we'll allocate will be humongous.
2197 guarantee(is_humongous(word_size), "sanity");
2198
2199 // _filler_array_max_size is set to humongous object threshold
2200 // but temporarily change it to use CollectedHeap::fill_with_object().
2201 SizeTFlagSetting fs(_filler_array_max_size, word_size);
2202
2203 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2204 // Let's use the existing mechanism for the allocation
2205 HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2206 AllocationContext::system());
2207 if (dummy_obj != NULL) {
2208 MemRegion mr(dummy_obj, word_size);
2209 CollectedHeap::fill_with_object(mr);
2210 } else {
2211 // If we can't allocate once, we probably cannot allocate
2212 // again. Let's get out of the loop.
2213 break;
2214 }
2215 }
2216 }
2217 #endif // !PRODUCT
2218
2219 void G1CollectedHeap::increment_old_marking_cycles_started() {
2220 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2221 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2222 "Wrong marking cycle count (started: %d, completed: %d)",
2223 _old_marking_cycles_started, _old_marking_cycles_completed);
2224
2225 _old_marking_cycles_started++;
2226 }
2227
2228 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2229 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2230
2231 // We assume that if concurrent == true, then the caller is a
2232 // concurrent thread that was joined the Suspendible Thread
2233 // Set. If there's ever a cheap way to check this, we should add an
2234 // assert here.
2235
2236 // Given that this method is called at the end of a Full GC or of a
2237 // concurrent cycle, and those can be nested (i.e., a Full GC can
2238 // interrupt a concurrent cycle), the number of full collections
2239 // completed should be either one (in the case where there was no
2240 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2241 // behind the number of full collections started.
2242
2243 // This is the case for the inner caller, i.e. a Full GC.
2244 assert(concurrent ||
2245 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2246 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2247 "for inner caller (Full GC): _old_marking_cycles_started = %u "
2248 "is inconsistent with _old_marking_cycles_completed = %u",
2249 _old_marking_cycles_started, _old_marking_cycles_completed);
2250
2251 // This is the case for the outer caller, i.e. the concurrent cycle.
2252 assert(!concurrent ||
2253 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2254 "for outer caller (concurrent cycle): "
2255 "_old_marking_cycles_started = %u "
2256 "is inconsistent with _old_marking_cycles_completed = %u",
2257 _old_marking_cycles_started, _old_marking_cycles_completed);
2258
2259 _old_marking_cycles_completed += 1;
2260
2261 // We need to clear the "in_progress" flag in the CM thread before
2262 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2263 // is set) so that if a waiter requests another System.gc() it doesn't
2264 // incorrectly see that a marking cycle is still in progress.
2265 if (concurrent) {
2266 _cmThread->set_idle();
2267 }
2268
2269 // This notify_all() will ensure that a thread that called
2270 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2271 // and it's waiting for a full GC to finish will be woken up. It is
2272 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2273 FullGCCount_lock->notify_all();
2274 }
2275
2276 void G1CollectedHeap::collect(GCCause::Cause cause) {
2277 assert_heap_not_locked();
2278
2279 uint gc_count_before;
2280 uint old_marking_count_before;
2281 uint full_gc_count_before;
2282 bool retry_gc;
2283
2284 do {
2285 retry_gc = false;
2286
2287 {
2288 MutexLocker ml(Heap_lock);
2289
2290 // Read the GC count while holding the Heap_lock
2291 gc_count_before = total_collections();
2292 full_gc_count_before = total_full_collections();
2293 old_marking_count_before = _old_marking_cycles_started;
2294 }
2295
2296 if (should_do_concurrent_full_gc(cause)) {
2297 // Schedule an initial-mark evacuation pause that will start a
2298 // concurrent cycle. We're setting word_size to 0 which means that
2299 // we are not requesting a post-GC allocation.
2300 VM_G1IncCollectionPause op(gc_count_before,
2301 0, /* word_size */
2302 true, /* should_initiate_conc_mark */
2303 g1_policy()->max_pause_time_ms(),
2304 cause);
2305 op.set_allocation_context(AllocationContext::current());
2306
2307 VMThread::execute(&op);
2308 if (!op.pause_succeeded()) {
2309 if (old_marking_count_before == _old_marking_cycles_started) {
2310 retry_gc = op.should_retry_gc();
2311 } else {
2312 // A Full GC happened while we were trying to schedule the
2313 // initial-mark GC. No point in starting a new cycle given
2314 // that the whole heap was collected anyway.
2315 }
2316
2317 if (retry_gc) {
2318 if (GCLocker::is_active_and_needs_gc()) {
2319 GCLocker::stall_until_clear();
2320 }
2321 }
2322 }
2323 } else {
2324 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2325 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2326
2327 // Schedule a standard evacuation pause. We're setting word_size
2328 // to 0 which means that we are not requesting a post-GC allocation.
2329 VM_G1IncCollectionPause op(gc_count_before,
2330 0, /* word_size */
2331 false, /* should_initiate_conc_mark */
2332 g1_policy()->max_pause_time_ms(),
2333 cause);
2334 VMThread::execute(&op);
2335 } else {
2336 // Schedule a Full GC.
2337 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2338 VMThread::execute(&op);
2339 }
2340 }
2341 } while (retry_gc);
2342 }
2343
2344 bool G1CollectedHeap::is_in(const void* p) const {
2345 if (_hrm.reserved().contains(p)) {
2346 // Given that we know that p is in the reserved space,
2347 // heap_region_containing() should successfully
2348 // return the containing region.
2349 HeapRegion* hr = heap_region_containing(p);
2350 return hr->is_in(p);
2351 } else {
2352 return false;
2353 }
2354 }
2355
2356 #ifdef ASSERT
2357 bool G1CollectedHeap::is_in_exact(const void* p) const {
2358 bool contains = reserved_region().contains(p);
2359 bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2360 if (contains && available) {
2361 return true;
2362 } else {
2363 return false;
2364 }
2365 }
2366 #endif
2367
2368 bool G1CollectedHeap::obj_in_cs(oop obj) {
2369 HeapRegion* r = _hrm.addr_to_region((HeapWord*) obj);
2370 return r != NULL && r->in_collection_set();
2371 }
2372
2373 // Iteration functions.
2374
2375 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion.
2376
2377 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2378 ExtendedOopClosure* _cl;
2379 public:
2380 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {}
2381 bool doHeapRegion(HeapRegion* r) {
2382 if (!r->is_continues_humongous()) {
2383 r->oop_iterate(_cl);
2384 }
2385 return false;
2386 }
2387 };
2388
2389 // Iterates an ObjectClosure over all objects within a HeapRegion.
2390
2391 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2392 ObjectClosure* _cl;
2393 public:
2394 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2395 bool doHeapRegion(HeapRegion* r) {
2396 if (!r->is_continues_humongous()) {
2397 r->object_iterate(_cl);
2398 }
2399 return false;
2400 }
2401 };
2402
2403 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2404 IterateObjectClosureRegionClosure blk(cl);
2405 heap_region_iterate(&blk);
2406 }
2407
2408 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2409 _hrm.iterate(cl);
2410 }
2411
2412 void
2413 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl,
2414 uint worker_id,
2415 HeapRegionClaimer *hrclaimer,
2416 bool concurrent) const {
2417 _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent);
2418 }
2419
2420 // Clear the cached CSet starting regions and (more importantly)
2421 // the time stamps. Called when we reset the GC time stamp.
2422 void G1CollectedHeap::clear_cset_start_regions() {
2423 assert(_worker_cset_start_region != NULL, "sanity");
2424 assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2425
2426 for (uint i = 0; i < ParallelGCThreads; i++) {
2427 _worker_cset_start_region[i] = NULL;
2428 _worker_cset_start_region_time_stamp[i] = 0;
2429 }
2430 }
2431
2432 // Given the id of a worker, obtain or calculate a suitable
2433 // starting region for iterating over the current collection set.
2434 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2435 assert(get_gc_time_stamp() > 0, "should have been updated by now");
2436
2437 HeapRegion* result = NULL;
2438 unsigned gc_time_stamp = get_gc_time_stamp();
2439
2440 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2441 // Cached starting region for current worker was set
2442 // during the current pause - so it's valid.
2443 // Note: the cached starting heap region may be NULL
2444 // (when the collection set is empty).
2445 result = _worker_cset_start_region[worker_i];
2446 assert(result == NULL || result->in_collection_set(), "sanity");
2447 return result;
2448 }
2449
2450 // The cached entry was not valid so let's calculate
2451 // a suitable starting heap region for this worker.
2452
2453 // We want the parallel threads to start their collection
2454 // set iteration at different collection set regions to
2455 // avoid contention.
2456 // If we have:
2457 // n collection set regions
2458 // p threads
2459 // Then thread t will start at region floor ((t * n) / p)
2460
2461 result = collection_set()->head();
2462 uint cs_size = collection_set()->region_length();
2463 uint active_workers = workers()->active_workers();
2464
2465 uint end_ind = (cs_size * worker_i) / active_workers;
2466 uint start_ind = 0;
2467
2468 if (worker_i > 0 &&
2469 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2470 // Previous workers starting region is valid
2471 // so let's iterate from there
2472 start_ind = (cs_size * (worker_i - 1)) / active_workers;
2473 OrderAccess::loadload();
2474 result = _worker_cset_start_region[worker_i - 1];
2475 }
2476
2477 for (uint i = start_ind; i < end_ind; i++) {
2478 result = result->next_in_collection_set();
2479 }
2480
2481 // Note: the calculated starting heap region may be NULL
2482 // (when the collection set is empty).
2483 assert(result == NULL || result->in_collection_set(), "sanity");
2484 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2485 "should be updated only once per pause");
2486 _worker_cset_start_region[worker_i] = result;
2487 OrderAccess::storestore();
2488 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2489 return result;
2490 }
2491
2492 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2493 HeapRegion* r = collection_set()->head();
2494 while (r != NULL) {
2495 HeapRegion* next = r->next_in_collection_set();
2496 if (cl->doHeapRegion(r)) {
2497 cl->incomplete();
2498 return;
2499 }
2500 r = next;
2501 }
2502 }
2503
2504 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2505 HeapRegionClosure *cl) {
2506 if (r == NULL) {
2507 // The CSet is empty so there's nothing to do.
2508 return;
2509 }
2510
2511 assert(r->in_collection_set(),
2512 "Start region must be a member of the collection set.");
2513 HeapRegion* cur = r;
2514 while (cur != NULL) {
2515 HeapRegion* next = cur->next_in_collection_set();
2516 if (cl->doHeapRegion(cur) && false) {
2517 cl->incomplete();
2518 return;
2519 }
2520 cur = next;
2521 }
2522 cur = collection_set()->head();
2523 while (cur != r) {
2524 HeapRegion* next = cur->next_in_collection_set();
2525 if (cl->doHeapRegion(cur) && false) {
2526 cl->incomplete();
2527 return;
2528 }
2529 cur = next;
2530 }
2531 }
2532
2533 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2534 HeapRegion* result = _hrm.next_region_in_heap(from);
2535 while (result != NULL && result->is_pinned()) {
2536 result = _hrm.next_region_in_heap(result);
2537 }
2538 return result;
2539 }
2540
2541 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2542 HeapRegion* hr = heap_region_containing(addr);
2543 return hr->block_start(addr);
2544 }
2545
2546 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2547 HeapRegion* hr = heap_region_containing(addr);
2548 return hr->block_size(addr);
2549 }
2550
2551 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2552 HeapRegion* hr = heap_region_containing(addr);
2553 return hr->block_is_obj(addr);
2554 }
2555
2556 bool G1CollectedHeap::supports_tlab_allocation() const {
2557 return true;
2558 }
2559
2560 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2561 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2562 }
2563
2564 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2565 return young_list()->eden_used_bytes();
2566 }
2567
2568 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2569 // must be equal to the humongous object limit.
2570 size_t G1CollectedHeap::max_tlab_size() const {
2571 return align_size_down(_humongous_object_threshold_in_words, MinObjAlignment);
2572 }
2573
2574 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2575 AllocationContext_t context = AllocationContext::current();
2576 return _allocator->unsafe_max_tlab_alloc(context);
2577 }
2578
2579 size_t G1CollectedHeap::max_capacity() const {
2580 return _hrm.reserved().byte_size();
2581 }
2582
2583 jlong G1CollectedHeap::millis_since_last_gc() {
2584 // assert(false, "NYI");
2585 return 0;
2586 }
2587
2588 void G1CollectedHeap::prepare_for_verify() {
2589 _verifier->prepare_for_verify();
2590 }
2591
2592 void G1CollectedHeap::verify(VerifyOption vo) {
2593 _verifier->verify(vo);
2594 }
2595
2596 class PrintRegionClosure: public HeapRegionClosure {
2597 outputStream* _st;
2598 public:
2599 PrintRegionClosure(outputStream* st) : _st(st) {}
2600 bool doHeapRegion(HeapRegion* r) {
2601 r->print_on(_st);
2602 return false;
2603 }
2604 };
2605
2606 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2607 const HeapRegion* hr,
2608 const VerifyOption vo) const {
2609 switch (vo) {
2610 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2611 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2612 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked() && !hr->is_archive();
2613 default: ShouldNotReachHere();
2614 }
2615 return false; // keep some compilers happy
2616 }
2617
2618 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2619 const VerifyOption vo) const {
2620 switch (vo) {
2621 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2622 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2623 case VerifyOption_G1UseMarkWord: {
2624 HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj);
2625 return !obj->is_gc_marked() && !hr->is_archive();
2626 }
2627 default: ShouldNotReachHere();
2628 }
2629 return false; // keep some compilers happy
2630 }
2631
2632 void G1CollectedHeap::print_heap_regions() const {
2633 Log(gc, heap, region) log;
2634 if (log.is_trace()) {
2635 ResourceMark rm;
2636 print_regions_on(log.trace_stream());
2637 }
2638 }
2639
2640 void G1CollectedHeap::print_on(outputStream* st) const {
2641 st->print(" %-20s", "garbage-first heap");
2642 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2643 capacity()/K, used_unlocked()/K);
2644 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")",
2645 p2i(_hrm.reserved().start()),
2646 p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords),
2647 p2i(_hrm.reserved().end()));
2648 st->cr();
2649 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2650 uint young_regions = _young_list->length();
2651 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2652 (size_t) young_regions * HeapRegion::GrainBytes / K);
2653 uint survivor_regions = _young_list->survivor_length();
2654 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2655 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2656 st->cr();
2657 MetaspaceAux::print_on(st);
2658 }
2659
2660 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2661 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2662 "HS=humongous(starts), HC=humongous(continues), "
2663 "CS=collection set, F=free, A=archive, TS=gc time stamp, "
2664 "AC=allocation context, "
2665 "TAMS=top-at-mark-start (previous, next)");
2666 PrintRegionClosure blk(st);
2667 heap_region_iterate(&blk);
2668 }
2669
2670 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2671 print_on(st);
2672
2673 // Print the per-region information.
2674 print_regions_on(st);
2675 }
2676
2677 void G1CollectedHeap::print_on_error(outputStream* st) const {
2678 this->CollectedHeap::print_on_error(st);
2679
2680 if (_cm != NULL) {
2681 st->cr();
2682 _cm->print_on_error(st);
2683 }
2684 }
2685
2686 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2687 workers()->print_worker_threads_on(st);
2688 _cmThread->print_on(st);
2689 st->cr();
2690 _cm->print_worker_threads_on(st);
2691 _cg1r->print_worker_threads_on(st); // also prints the sample thread
2692 if (G1StringDedup::is_enabled()) {
2693 G1StringDedup::print_worker_threads_on(st);
2694 }
2695 }
2696
2697 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2698 workers()->threads_do(tc);
2699 tc->do_thread(_cmThread);
2700 _cm->threads_do(tc);
2701 _cg1r->threads_do(tc); // also iterates over the sample thread
2702 if (G1StringDedup::is_enabled()) {
2703 G1StringDedup::threads_do(tc);
2704 }
2705 }
2706
2707 void G1CollectedHeap::print_tracing_info() const {
2708 g1_rem_set()->print_summary_info();
2709 concurrent_mark()->print_summary_info();
2710 g1_policy()->print_yg_surv_rate_info();
2711 }
2712
2713 #ifndef PRODUCT
2714 // Helpful for debugging RSet issues.
2715
2716 class PrintRSetsClosure : public HeapRegionClosure {
2717 private:
2718 const char* _msg;
2719 size_t _occupied_sum;
2720
2721 public:
2722 bool doHeapRegion(HeapRegion* r) {
2723 HeapRegionRemSet* hrrs = r->rem_set();
2724 size_t occupied = hrrs->occupied();
2725 _occupied_sum += occupied;
2726
2727 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2728 if (occupied == 0) {
2729 tty->print_cr(" RSet is empty");
2730 } else {
2731 hrrs->print();
2732 }
2733 tty->print_cr("----------");
2734 return false;
2735 }
2736
2737 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2738 tty->cr();
2739 tty->print_cr("========================================");
2740 tty->print_cr("%s", msg);
2741 tty->cr();
2742 }
2743
2744 ~PrintRSetsClosure() {
2745 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2746 tty->print_cr("========================================");
2747 tty->cr();
2748 }
2749 };
2750
2751 void G1CollectedHeap::print_cset_rsets() {
2752 PrintRSetsClosure cl("Printing CSet RSets");
2753 collection_set_iterate(&cl);
2754 }
2755
2756 void G1CollectedHeap::print_all_rsets() {
2757 PrintRSetsClosure cl("Printing All RSets");;
2758 heap_region_iterate(&cl);
2759 }
2760 #endif // PRODUCT
2761
2762 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2763 YoungList* young_list = heap()->young_list();
2764
2765 size_t eden_used_bytes = young_list->eden_used_bytes();
2766 size_t survivor_used_bytes = young_list->survivor_used_bytes();
2767 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2768
2769 size_t eden_capacity_bytes =
2770 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2771
2772 VirtualSpaceSummary heap_summary = create_heap_space_summary();
2773 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2774 eden_capacity_bytes, survivor_used_bytes, num_regions());
2775 }
2776
2777 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2778 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2779 stats->unused(), stats->used(), stats->region_end_waste(),
2780 stats->regions_filled(), stats->direct_allocated(),
2781 stats->failure_used(), stats->failure_waste());
2782 }
2783
2784 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2785 const G1HeapSummary& heap_summary = create_g1_heap_summary();
2786 gc_tracer->report_gc_heap_summary(when, heap_summary);
2787
2788 const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2789 gc_tracer->report_metaspace_summary(when, metaspace_summary);
2790 }
2791
2792 G1CollectedHeap* G1CollectedHeap::heap() {
2793 CollectedHeap* heap = Universe::heap();
2794 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2795 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap");
2796 return (G1CollectedHeap*)heap;
2797 }
2798
2799 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
2800 // always_do_update_barrier = false;
2801 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2802 // Fill TLAB's and such
2803 accumulate_statistics_all_tlabs();
2804 ensure_parsability(true);
2805
2806 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2807 }
2808
2809 void G1CollectedHeap::gc_epilogue(bool full) {
2810 // we are at the end of the GC. Total collections has already been increased.
2811 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2812
2813 // FIXME: what is this about?
2814 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2815 // is set.
2816 #if defined(COMPILER2) || INCLUDE_JVMCI
2817 assert(DerivedPointerTable::is_empty(), "derived pointer present");
2818 #endif
2819 // always_do_update_barrier = true;
2820
2821 resize_all_tlabs();
2822 allocation_context_stats().update(full);
2823
2824 // We have just completed a GC. Update the soft reference
2825 // policy with the new heap occupancy
2826 Universe::update_heap_info_at_gc();
2827 }
2828
2829 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2830 uint gc_count_before,
2831 bool* succeeded,
2832 GCCause::Cause gc_cause) {
2833 assert_heap_not_locked_and_not_at_safepoint();
2834 VM_G1IncCollectionPause op(gc_count_before,
2835 word_size,
2836 false, /* should_initiate_conc_mark */
2837 g1_policy()->max_pause_time_ms(),
2838 gc_cause);
2839
2840 op.set_allocation_context(AllocationContext::current());
2841 VMThread::execute(&op);
2842
2843 HeapWord* result = op.result();
2844 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
2845 assert(result == NULL || ret_succeeded,
2846 "the result should be NULL if the VM did not succeed");
2847 *succeeded = ret_succeeded;
2848
2849 assert_heap_not_locked();
2850 return result;
2851 }
2852
2853 void
2854 G1CollectedHeap::doConcurrentMark() {
2855 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
2856 if (!_cmThread->in_progress()) {
2857 _cmThread->set_started();
2858 CGC_lock->notify();
2859 }
2860 }
2861
2862 size_t G1CollectedHeap::pending_card_num() {
2863 size_t extra_cards = 0;
2864 JavaThread *curr = Threads::first();
2865 while (curr != NULL) {
2866 DirtyCardQueue& dcq = curr->dirty_card_queue();
2867 extra_cards += dcq.size();
2868 curr = curr->next();
2869 }
2870 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2871 size_t buffer_size = dcqs.buffer_size();
2872 size_t buffer_num = dcqs.completed_buffers_num();
2873
2874 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
2875 // in bytes - not the number of 'entries'. We need to convert
2876 // into a number of cards.
2877 return (buffer_size * buffer_num + extra_cards) / oopSize;
2878 }
2879
2880 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
2881 private:
2882 size_t _total_humongous;
2883 size_t _candidate_humongous;
2884
2885 DirtyCardQueue _dcq;
2886
2887 // We don't nominate objects with many remembered set entries, on
2888 // the assumption that such objects are likely still live.
2889 bool is_remset_small(HeapRegion* region) const {
2890 HeapRegionRemSet* const rset = region->rem_set();
2891 return G1EagerReclaimHumongousObjectsWithStaleRefs
2892 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)
2893 : rset->is_empty();
2894 }
2895
2896 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const {
2897 assert(region->is_starts_humongous(), "Must start a humongous object");
2898
2899 oop obj = oop(region->bottom());
2900
2901 // Dead objects cannot be eager reclaim candidates. Due to class
2902 // unloading it is unsafe to query their classes so we return early.
2903 if (heap->is_obj_dead(obj, region)) {
2904 return false;
2905 }
2906
2907 // Candidate selection must satisfy the following constraints
2908 // while concurrent marking is in progress:
2909 //
2910 // * In order to maintain SATB invariants, an object must not be
2911 // reclaimed if it was allocated before the start of marking and
2912 // has not had its references scanned. Such an object must have
2913 // its references (including type metadata) scanned to ensure no
2914 // live objects are missed by the marking process. Objects
2915 // allocated after the start of concurrent marking don't need to
2916 // be scanned.
2917 //
2918 // * An object must not be reclaimed if it is on the concurrent
2919 // mark stack. Objects allocated after the start of concurrent
2920 // marking are never pushed on the mark stack.
2921 //
2922 // Nominating only objects allocated after the start of concurrent
2923 // marking is sufficient to meet both constraints. This may miss
2924 // some objects that satisfy the constraints, but the marking data
2925 // structures don't support efficiently performing the needed
2926 // additional tests or scrubbing of the mark stack.
2927 //
2928 // However, we presently only nominate is_typeArray() objects.
2929 // A humongous object containing references induces remembered
2930 // set entries on other regions. In order to reclaim such an
2931 // object, those remembered sets would need to be cleaned up.
2932 //
2933 // We also treat is_typeArray() objects specially, allowing them
2934 // to be reclaimed even if allocated before the start of
2935 // concurrent mark. For this we rely on mark stack insertion to
2936 // exclude is_typeArray() objects, preventing reclaiming an object
2937 // that is in the mark stack. We also rely on the metadata for
2938 // such objects to be built-in and so ensured to be kept live.
2939 // Frequent allocation and drop of large binary blobs is an
2940 // important use case for eager reclaim, and this special handling
2941 // may reduce needed headroom.
2942
2943 return obj->is_typeArray() && is_remset_small(region);
2944 }
2945
2946 public:
2947 RegisterHumongousWithInCSetFastTestClosure()
2948 : _total_humongous(0),
2949 _candidate_humongous(0),
2950 _dcq(&JavaThread::dirty_card_queue_set()) {
2951 }
2952
2953 virtual bool doHeapRegion(HeapRegion* r) {
2954 if (!r->is_starts_humongous()) {
2955 return false;
2956 }
2957 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2958
2959 bool is_candidate = humongous_region_is_candidate(g1h, r);
2960 uint rindex = r->hrm_index();
2961 g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
2962 if (is_candidate) {
2963 _candidate_humongous++;
2964 g1h->register_humongous_region_with_cset(rindex);
2965 // Is_candidate already filters out humongous object with large remembered sets.
2966 // If we have a humongous object with a few remembered sets, we simply flush these
2967 // remembered set entries into the DCQS. That will result in automatic
2968 // re-evaluation of their remembered set entries during the following evacuation
2969 // phase.
2970 if (!r->rem_set()->is_empty()) {
2971 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
2972 "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
2973 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
2974 HeapRegionRemSetIterator hrrs(r->rem_set());
2975 size_t card_index;
2976 while (hrrs.has_next(card_index)) {
2977 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
2978 // The remembered set might contain references to already freed
2979 // regions. Filter out such entries to avoid failing card table
2980 // verification.
2981 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) {
2982 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
2983 *card_ptr = CardTableModRefBS::dirty_card_val();
2984 _dcq.enqueue(card_ptr);
2985 }
2986 }
2987 }
2988 assert(hrrs.n_yielded() == r->rem_set()->occupied(),
2989 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
2990 hrrs.n_yielded(), r->rem_set()->occupied());
2991 r->rem_set()->clear_locked();
2992 }
2993 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
2994 }
2995 _total_humongous++;
2996
2997 return false;
2998 }
2999
3000 size_t total_humongous() const { return _total_humongous; }
3001 size_t candidate_humongous() const { return _candidate_humongous; }
3002
3003 void flush_rem_set_entries() { _dcq.flush(); }
3004 };
3005
3006 void G1CollectedHeap::register_humongous_regions_with_cset() {
3007 if (!G1EagerReclaimHumongousObjects) {
3008 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
3009 return;
3010 }
3011 double time = os::elapsed_counter();
3012
3013 // Collect reclaim candidate information and register candidates with cset.
3014 RegisterHumongousWithInCSetFastTestClosure cl;
3015 heap_region_iterate(&cl);
3016
3017 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
3018 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
3019 cl.total_humongous(),
3020 cl.candidate_humongous());
3021 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
3022
3023 // Finally flush all remembered set entries to re-check into the global DCQS.
3024 cl.flush_rem_set_entries();
3025 }
3026
3027 class VerifyRegionRemSetClosure : public HeapRegionClosure {
3028 public:
3029 bool doHeapRegion(HeapRegion* hr) {
3030 if (!hr->is_archive() && !hr->is_continues_humongous()) {
3031 hr->verify_rem_set();
3032 }
3033 return false;
3034 }
3035 };
3036
3037 uint G1CollectedHeap::num_task_queues() const {
3038 return _task_queues->size();
3039 }
3040
3041 #if TASKQUEUE_STATS
3042 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3043 st->print_raw_cr("GC Task Stats");
3044 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3045 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3046 }
3047
3048 void G1CollectedHeap::print_taskqueue_stats() const {
3049 if (!log_is_enabled(Trace, gc, task, stats)) {
3050 return;
3051 }
3052 Log(gc, task, stats) log;
3053 ResourceMark rm;
3054 outputStream* st = log.trace_stream();
3055
3056 print_taskqueue_stats_hdr(st);
3057
3058 TaskQueueStats totals;
3059 const uint n = num_task_queues();
3060 for (uint i = 0; i < n; ++i) {
3061 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
3062 totals += task_queue(i)->stats;
3063 }
3064 st->print_raw("tot "); totals.print(st); st->cr();
3065
3066 DEBUG_ONLY(totals.verify());
3067 }
3068
3069 void G1CollectedHeap::reset_taskqueue_stats() {
3070 const uint n = num_task_queues();
3071 for (uint i = 0; i < n; ++i) {
3072 task_queue(i)->stats.reset();
3073 }
3074 }
3075 #endif // TASKQUEUE_STATS
3076
3077 void G1CollectedHeap::wait_for_root_region_scanning() {
3078 double scan_wait_start = os::elapsedTime();
3079 // We have to wait until the CM threads finish scanning the
3080 // root regions as it's the only way to ensure that all the
3081 // objects on them have been correctly scanned before we start
3082 // moving them during the GC.
3083 bool waited = _cm->root_regions()->wait_until_scan_finished();
3084 double wait_time_ms = 0.0;
3085 if (waited) {
3086 double scan_wait_end = os::elapsedTime();
3087 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3088 }
3089 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
3090 }
3091
3092 bool
3093 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3094 assert_at_safepoint(true /* should_be_vm_thread */);
3095 guarantee(!is_gc_active(), "collection is not reentrant");
3096
3097 if (GCLocker::check_active_before_gc()) {
3098 return false;
3099 }
3100
3101 _gc_timer_stw->register_gc_start();
3102
3103 GCIdMark gc_id_mark;
3104 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3105
3106 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3107 ResourceMark rm;
3108
3109 wait_for_root_region_scanning();
3110
3111 print_heap_before_gc();
3112 print_heap_regions();
3113 trace_heap_before_gc(_gc_tracer_stw);
3114
3115 _verifier->verify_region_sets_optional();
3116 _verifier->verify_dirty_young_regions();
3117
3118 // We should not be doing initial mark unless the conc mark thread is running
3119 if (!_cmThread->should_terminate()) {
3120 // This call will decide whether this pause is an initial-mark
3121 // pause. If it is, during_initial_mark_pause() will return true
3122 // for the duration of this pause.
3123 g1_policy()->decide_on_conc_mark_initiation();
3124 }
3125
3126 // We do not allow initial-mark to be piggy-backed on a mixed GC.
3127 assert(!collector_state()->during_initial_mark_pause() ||
3128 collector_state()->gcs_are_young(), "sanity");
3129
3130 // We also do not allow mixed GCs during marking.
3131 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity");
3132
3133 // Record whether this pause is an initial mark. When the current
3134 // thread has completed its logging output and it's safe to signal
3135 // the CM thread, the flag's value in the policy has been reset.
3136 bool should_start_conc_mark = collector_state()->during_initial_mark_pause();
3137
3138 // Inner scope for scope based logging, timers, and stats collection
3139 {
3140 EvacuationInfo evacuation_info;
3141
3142 if (collector_state()->during_initial_mark_pause()) {
3143 // We are about to start a marking cycle, so we increment the
3144 // full collection counter.
3145 increment_old_marking_cycles_started();
3146 _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
3147 }
3148
3149 _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
3150
3151 GCTraceCPUTime tcpu;
3152
3153 FormatBuffer<> gc_string("Pause ");
3154 if (collector_state()->during_initial_mark_pause()) {
3155 gc_string.append("Initial Mark");
3156 } else if (collector_state()->gcs_are_young()) {
3157 gc_string.append("Young");
3158 } else {
3159 gc_string.append("Mixed");
3160 }
3161 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true);
3162
3163 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
3164 workers()->active_workers(),
3165 Threads::number_of_non_daemon_threads());
3166 workers()->set_active_workers(active_workers);
3167
3168 g1_policy()->note_gc_start();
3169
3170 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3171 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3172
3173 // If the secondary_free_list is not empty, append it to the
3174 // free_list. No need to wait for the cleanup operation to finish;
3175 // the region allocation code will check the secondary_free_list
3176 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3177 // set, skip this step so that the region allocation code has to
3178 // get entries from the secondary_free_list.
3179 if (!G1StressConcRegionFreeing) {
3180 append_secondary_free_list_if_not_empty_with_lock();
3181 }
3182
3183 G1HeapTransition heap_transition(this);
3184 size_t heap_used_bytes_before_gc = used();
3185
3186 assert(check_young_list_well_formed(), "young list should be well formed");
3187
3188 // Don't dynamically change the number of GC threads this early. A value of
3189 // 0 is used to indicate serial work. When parallel work is done,
3190 // it will be set.
3191
3192 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3193 IsGCActiveMark x;
3194
3195 gc_prologue(false);
3196 increment_total_collections(false /* full gc */);
3197 increment_gc_time_stamp();
3198
3199 if (VerifyRememberedSets) {
3200 log_info(gc, verify)("[Verifying RemSets before GC]");
3201 VerifyRegionRemSetClosure v_cl;
3202 heap_region_iterate(&v_cl);
3203 }
3204
3205 _verifier->verify_before_gc();
3206
3207 _verifier->check_bitmaps("GC Start");
3208
3209 #if defined(COMPILER2) || INCLUDE_JVMCI
3210 DerivedPointerTable::clear();
3211 #endif
3212
3213 // Please see comment in g1CollectedHeap.hpp and
3214 // G1CollectedHeap::ref_processing_init() to see how
3215 // reference processing currently works in G1.
3216
3217 // Enable discovery in the STW reference processor
3218 if (g1_policy()->should_process_references()) {
3219 ref_processor_stw()->enable_discovery();
3220 } else {
3221 ref_processor_stw()->disable_discovery();
3222 }
3223
3224 {
3225 // We want to temporarily turn off discovery by the
3226 // CM ref processor, if necessary, and turn it back on
3227 // on again later if we do. Using a scoped
3228 // NoRefDiscovery object will do this.
3229 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3230
3231 // Forget the current alloc region (we might even choose it to be part
3232 // of the collection set!).
3233 _allocator->release_mutator_alloc_region();
3234
3235 // This timing is only used by the ergonomics to handle our pause target.
3236 // It is unclear why this should not include the full pause. We will
3237 // investigate this in CR 7178365.
3238 //
3239 // Preserving the old comment here if that helps the investigation:
3240 //
3241 // The elapsed time induced by the start time below deliberately elides
3242 // the possible verification above.
3243 double sample_start_time_sec = os::elapsedTime();
3244
3245 g1_policy()->record_collection_pause_start(sample_start_time_sec);
3246
3247 if (collector_state()->during_initial_mark_pause()) {
3248 concurrent_mark()->checkpointRootsInitialPre();
3249 }
3250
3251 g1_policy()->finalize_collection_set(target_pause_time_ms);
3252
3253 evacuation_info.set_collectionset_regions(collection_set()->region_length());
3254
3255 // Make sure the remembered sets are up to date. This needs to be
3256 // done before register_humongous_regions_with_cset(), because the
3257 // remembered sets are used there to choose eager reclaim candidates.
3258 // If the remembered sets are not up to date we might miss some
3259 // entries that need to be handled.
3260 g1_rem_set()->cleanupHRRS();
3261
3262 register_humongous_regions_with_cset();
3263
3264 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table.");
3265
3266 _cm->note_start_of_gc();
3267 // We call this after finalize_cset() to
3268 // ensure that the CSet has been finalized.
3269 _cm->verify_no_cset_oops();
3270
3271 if (_hr_printer.is_active()) {
3272 HeapRegion* hr = collection_set()->head();
3273 while (hr != NULL) {
3274 _hr_printer.cset(hr);
3275 hr = hr->next_in_collection_set();
3276 }
3277 }
3278
3279 // Initialize the GC alloc regions.
3280 _allocator->init_gc_alloc_regions(evacuation_info);
3281
3282 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length());
3283 pre_evacuate_collection_set();
3284
3285 // Actually do the work...
3286 evacuate_collection_set(evacuation_info, &per_thread_states);
3287
3288 post_evacuate_collection_set(evacuation_info, &per_thread_states);
3289
3290 const size_t* surviving_young_words = per_thread_states.surviving_young_words();
3291 free_collection_set(collection_set()->head(), evacuation_info, surviving_young_words);
3292
3293 eagerly_reclaim_humongous_regions();
3294
3295 collection_set()->clear_head();
3296
3297 record_obj_copy_mem_stats();
3298 _survivor_evac_stats.adjust_desired_plab_sz();
3299 _old_evac_stats.adjust_desired_plab_sz();
3300
3301 // Start a new incremental collection set for the next pause.
3302 collection_set()->start_incremental_building();
3303
3304 clear_cset_fast_test();
3305
3306 // Don't check the whole heap at this point as the
3307 // GC alloc regions from this pause have been tagged
3308 // as survivors and moved on to the survivor list.
3309 // Survivor regions will fail the !is_young() check.
3310 assert(check_young_list_empty(false /* check_heap */),
3311 "young list should be empty");
3312
3313 _young_list->reset_auxilary_lists();
3314
3315 if (evacuation_failed()) {
3316 set_used(recalculate_used());
3317 if (_archive_allocator != NULL) {
3318 _archive_allocator->clear_used();
3319 }
3320 for (uint i = 0; i < ParallelGCThreads; i++) {
3321 if (_evacuation_failed_info_array[i].has_failed()) {
3322 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3323 }
3324 }
3325 } else {
3326 // The "used" of the the collection set have already been subtracted
3327 // when they were freed. Add in the bytes evacuated.
3328 increase_used(g1_policy()->bytes_copied_during_gc());
3329 }
3330
3331 if (collector_state()->during_initial_mark_pause()) {
3332 // We have to do this before we notify the CM threads that
3333 // they can start working to make sure that all the
3334 // appropriate initialization is done on the CM object.
3335 concurrent_mark()->checkpointRootsInitialPost();
3336 collector_state()->set_mark_in_progress(true);
3337 // Note that we don't actually trigger the CM thread at
3338 // this point. We do that later when we're sure that
3339 // the current thread has completed its logging output.
3340 }
3341
3342 allocate_dummy_regions();
3343
3344 _allocator->init_mutator_alloc_region();
3345
3346 {
3347 size_t expand_bytes = _heap_sizing_policy->expansion_amount();
3348 if (expand_bytes > 0) {
3349 size_t bytes_before = capacity();
3350 // No need for an ergo logging here,
3351 // expansion_amount() does this when it returns a value > 0.
3352 double expand_ms;
3353 if (!expand(expand_bytes, &expand_ms)) {
3354 // We failed to expand the heap. Cannot do anything about it.
3355 }
3356 g1_policy()->phase_times()->record_expand_heap_time(expand_ms);
3357 }
3358 }
3359
3360 // We redo the verification but now wrt to the new CSet which
3361 // has just got initialized after the previous CSet was freed.
3362 _cm->verify_no_cset_oops();
3363 _cm->note_end_of_gc();
3364
3365 // This timing is only used by the ergonomics to handle our pause target.
3366 // It is unclear why this should not include the full pause. We will
3367 // investigate this in CR 7178365.
3368 double sample_end_time_sec = os::elapsedTime();
3369 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3370 size_t total_cards_scanned = per_thread_states.total_cards_scanned();
3371 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc);
3372
3373 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
3374 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc());
3375
3376 MemoryService::track_memory_usage();
3377
3378 // In prepare_for_verify() below we'll need to scan the deferred
3379 // update buffers to bring the RSets up-to-date if
3380 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
3381 // the update buffers we'll probably need to scan cards on the
3382 // regions we just allocated to (i.e., the GC alloc
3383 // regions). However, during the last GC we called
3384 // set_saved_mark() on all the GC alloc regions, so card
3385 // scanning might skip the [saved_mark_word()...top()] area of
3386 // those regions (i.e., the area we allocated objects into
3387 // during the last GC). But it shouldn't. Given that
3388 // saved_mark_word() is conditional on whether the GC time stamp
3389 // on the region is current or not, by incrementing the GC time
3390 // stamp here we invalidate all the GC time stamps on all the
3391 // regions and saved_mark_word() will simply return top() for
3392 // all the regions. This is a nicer way of ensuring this rather
3393 // than iterating over the regions and fixing them. In fact, the
3394 // GC time stamp increment here also ensures that
3395 // saved_mark_word() will return top() between pauses, i.e.,
3396 // during concurrent refinement. So we don't need the
3397 // is_gc_active() check to decided which top to use when
3398 // scanning cards (see CR 7039627).
3399 increment_gc_time_stamp();
3400
3401 if (VerifyRememberedSets) {
3402 log_info(gc, verify)("[Verifying RemSets after GC]");
3403 VerifyRegionRemSetClosure v_cl;
3404 heap_region_iterate(&v_cl);
3405 }
3406
3407 _verifier->verify_after_gc();
3408 _verifier->check_bitmaps("GC End");
3409
3410 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3411 ref_processor_stw()->verify_no_references_recorded();
3412
3413 // CM reference discovery will be re-enabled if necessary.
3414 }
3415
3416 #ifdef TRACESPINNING
3417 ParallelTaskTerminator::print_termination_counts();
3418 #endif
3419
3420 gc_epilogue(false);
3421 }
3422
3423 // Print the remainder of the GC log output.
3424 if (evacuation_failed()) {
3425 log_info(gc)("To-space exhausted");
3426 }
3427
3428 g1_policy()->print_phases();
3429 heap_transition.print();
3430
3431 // It is not yet to safe to tell the concurrent mark to
3432 // start as we have some optional output below. We don't want the
3433 // output from the concurrent mark thread interfering with this
3434 // logging output either.
3435
3436 _hrm.verify_optional();
3437 _verifier->verify_region_sets_optional();
3438
3439 TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3440 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3441
3442 print_heap_after_gc();
3443 print_heap_regions();
3444 trace_heap_after_gc(_gc_tracer_stw);
3445
3446 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3447 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3448 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3449 // before any GC notifications are raised.
3450 g1mm()->update_sizes();
3451
3452 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3453 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
3454 _gc_timer_stw->register_gc_end();
3455 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3456 }
3457 // It should now be safe to tell the concurrent mark thread to start
3458 // without its logging output interfering with the logging output
3459 // that came from the pause.
3460
3461 if (should_start_conc_mark) {
3462 // CAUTION: after the doConcurrentMark() call below,
3463 // the concurrent marking thread(s) could be running
3464 // concurrently with us. Make sure that anything after
3465 // this point does not assume that we are the only GC thread
3466 // running. Note: of course, the actual marking work will
3467 // not start until the safepoint itself is released in
3468 // SuspendibleThreadSet::desynchronize().
3469 doConcurrentMark();
3470 }
3471
3472 return true;
3473 }
3474
3475 void G1CollectedHeap::remove_self_forwarding_pointers() {
3476 G1ParRemoveSelfForwardPtrsTask rsfp_task;
3477 workers()->run_task(&rsfp_task);
3478 }
3479
3480 void G1CollectedHeap::restore_after_evac_failure() {
3481 double remove_self_forwards_start = os::elapsedTime();
3482
3483 remove_self_forwarding_pointers();
3484 _preserved_marks_set.restore(workers());
3485
3486 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3487 }
3488
3489 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) {
3490 if (!_evacuation_failed) {
3491 _evacuation_failed = true;
3492 }
3493
3494 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3495 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3496 }
3497
3498 bool G1ParEvacuateFollowersClosure::offer_termination() {
3499 G1ParScanThreadState* const pss = par_scan_state();
3500 start_term_time();
3501 const bool res = terminator()->offer_termination();
3502 end_term_time();
3503 return res;
3504 }
3505
3506 void G1ParEvacuateFollowersClosure::do_void() {
3507 G1ParScanThreadState* const pss = par_scan_state();
3508 pss->trim_queue();
3509 do {
3510 pss->steal_and_trim_queue(queues());
3511 } while (!offer_termination());
3512 }
3513
3514 class G1ParTask : public AbstractGangTask {
3515 protected:
3516 G1CollectedHeap* _g1h;
3517 G1ParScanThreadStateSet* _pss;
3518 RefToScanQueueSet* _queues;
3519 G1RootProcessor* _root_processor;
3520 ParallelTaskTerminator _terminator;
3521 uint _n_workers;
3522
3523 public:
3524 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers)
3525 : AbstractGangTask("G1 collection"),
3526 _g1h(g1h),
3527 _pss(per_thread_states),
3528 _queues(task_queues),
3529 _root_processor(root_processor),
3530 _terminator(n_workers, _queues),
3531 _n_workers(n_workers)
3532 {}
3533
3534 void work(uint worker_id) {
3535 if (worker_id >= _n_workers) return; // no work needed this round
3536
3537 double start_sec = os::elapsedTime();
3538 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec);
3539
3540 {
3541 ResourceMark rm;
3542 HandleMark hm;
3543
3544 ReferenceProcessor* rp = _g1h->ref_processor_stw();
3545
3546 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
3547 pss->set_ref_processor(rp);
3548
3549 double start_strong_roots_sec = os::elapsedTime();
3550
3551 _root_processor->evacuate_roots(pss->closures(), worker_id);
3552
3553 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, pss);
3554
3555 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid
3556 // treating the nmethods visited to act as roots for concurrent marking.
3557 // We only want to make sure that the oops in the nmethods are adjusted with regard to the
3558 // objects copied by the current evacuation.
3559 size_t cards_scanned = _g1h->g1_rem_set()->oops_into_collection_set_do(&push_heap_rs_cl,
3560 pss->closures()->weak_codeblobs(),
3561 worker_id);
3562
3563 _pss->add_cards_scanned(worker_id, cards_scanned);
3564
3565 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec;
3566
3567 double term_sec = 0.0;
3568 size_t evac_term_attempts = 0;
3569 {
3570 double start = os::elapsedTime();
3571 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator);
3572 evac.do_void();
3573
3574 evac_term_attempts = evac.term_attempts();
3575 term_sec = evac.term_time();
3576 double elapsed_sec = os::elapsedTime() - start;
3577 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
3578 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
3579 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts);
3580 }
3581
3582 assert(pss->queue_is_empty(), "should be empty");
3583
3584 if (log_is_enabled(Debug, gc, task, stats)) {
3585 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3586 size_t lab_waste;
3587 size_t lab_undo_waste;
3588 pss->waste(lab_waste, lab_undo_waste);
3589 _g1h->print_termination_stats(worker_id,
3590 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */
3591 strong_roots_sec * 1000.0, /* strong roots time */
3592 term_sec * 1000.0, /* evac term time */
3593 evac_term_attempts, /* evac term attempts */
3594 lab_waste, /* alloc buffer waste */
3595 lab_undo_waste /* undo waste */
3596 );
3597 }
3598
3599 // Close the inner scope so that the ResourceMark and HandleMark
3600 // destructors are executed here and are included as part of the
3601 // "GC Worker Time".
3602 }
3603 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
3604 }
3605 };
3606
3607 void G1CollectedHeap::print_termination_stats_hdr() {
3608 log_debug(gc, task, stats)("GC Termination Stats");
3609 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------");
3610 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo");
3611 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------");
3612 }
3613
3614 void G1CollectedHeap::print_termination_stats(uint worker_id,
3615 double elapsed_ms,
3616 double strong_roots_ms,
3617 double term_ms,
3618 size_t term_attempts,
3619 size_t alloc_buffer_waste,
3620 size_t undo_waste) const {
3621 log_debug(gc, task, stats)
3622 ("%3d %9.2f %9.2f %6.2f "
3623 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
3624 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
3625 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms,
3626 term_ms, term_ms * 100 / elapsed_ms, term_attempts,
3627 (alloc_buffer_waste + undo_waste) * HeapWordSize / K,
3628 alloc_buffer_waste * HeapWordSize / K,
3629 undo_waste * HeapWordSize / K);
3630 }
3631
3632 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
3633 private:
3634 BoolObjectClosure* _is_alive;
3635 int _initial_string_table_size;
3636 int _initial_symbol_table_size;
3637
3638 bool _process_strings;
3639 int _strings_processed;
3640 int _strings_removed;
3641
3642 bool _process_symbols;
3643 int _symbols_processed;
3644 int _symbols_removed;
3645
3646 public:
3647 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
3648 AbstractGangTask("String/Symbol Unlinking"),
3649 _is_alive(is_alive),
3650 _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
3651 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
3652
3653 _initial_string_table_size = StringTable::the_table()->table_size();
3654 _initial_symbol_table_size = SymbolTable::the_table()->table_size();
3655 if (process_strings) {
3656 StringTable::clear_parallel_claimed_index();
3657 }
3658 if (process_symbols) {
3659 SymbolTable::clear_parallel_claimed_index();
3660 }
3661 }
3662
3663 ~G1StringSymbolTableUnlinkTask() {
3664 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
3665 "claim value %d after unlink less than initial string table size %d",
3666 StringTable::parallel_claimed_index(), _initial_string_table_size);
3667 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
3668 "claim value %d after unlink less than initial symbol table size %d",
3669 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size);
3670
3671 log_info(gc, stringtable)(
3672 "Cleaned string and symbol table, "
3673 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, "
3674 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
3675 strings_processed(), strings_removed(),
3676 symbols_processed(), symbols_removed());
3677 }
3678
3679 void work(uint worker_id) {
3680 int strings_processed = 0;
3681 int strings_removed = 0;
3682 int symbols_processed = 0;
3683 int symbols_removed = 0;
3684 if (_process_strings) {
3685 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
3686 Atomic::add(strings_processed, &_strings_processed);
3687 Atomic::add(strings_removed, &_strings_removed);
3688 }
3689 if (_process_symbols) {
3690 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
3691 Atomic::add(symbols_processed, &_symbols_processed);
3692 Atomic::add(symbols_removed, &_symbols_removed);
3693 }
3694 }
3695
3696 size_t strings_processed() const { return (size_t)_strings_processed; }
3697 size_t strings_removed() const { return (size_t)_strings_removed; }
3698
3699 size_t symbols_processed() const { return (size_t)_symbols_processed; }
3700 size_t symbols_removed() const { return (size_t)_symbols_removed; }
3701 };
3702
3703 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
3704 private:
3705 static Monitor* _lock;
3706
3707 BoolObjectClosure* const _is_alive;
3708 const bool _unloading_occurred;
3709 const uint _num_workers;
3710
3711 // Variables used to claim nmethods.
3712 nmethod* _first_nmethod;
3713 volatile nmethod* _claimed_nmethod;
3714
3715 // The list of nmethods that need to be processed by the second pass.
3716 volatile nmethod* _postponed_list;
3717 volatile uint _num_entered_barrier;
3718
3719 public:
3720 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
3721 _is_alive(is_alive),
3722 _unloading_occurred(unloading_occurred),
3723 _num_workers(num_workers),
3724 _first_nmethod(NULL),
3725 _claimed_nmethod(NULL),
3726 _postponed_list(NULL),
3727 _num_entered_barrier(0)
3728 {
3729 nmethod::increase_unloading_clock();
3730 // Get first alive nmethod
3731 NMethodIterator iter = NMethodIterator();
3732 if(iter.next_alive()) {
3733 _first_nmethod = iter.method();
3734 }
3735 _claimed_nmethod = (volatile nmethod*)_first_nmethod;
3736 }
3737
3738 ~G1CodeCacheUnloadingTask() {
3739 CodeCache::verify_clean_inline_caches();
3740
3741 CodeCache::set_needs_cache_clean(false);
3742 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
3743
3744 CodeCache::verify_icholder_relocations();
3745 }
3746
3747 private:
3748 void add_to_postponed_list(nmethod* nm) {
3749 nmethod* old;
3750 do {
3751 old = (nmethod*)_postponed_list;
3752 nm->set_unloading_next(old);
3753 } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
3754 }
3755
3756 void clean_nmethod(nmethod* nm) {
3757 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
3758
3759 if (postponed) {
3760 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
3761 add_to_postponed_list(nm);
3762 }
3763
3764 // Mark that this thread has been cleaned/unloaded.
3765 // After this call, it will be safe to ask if this nmethod was unloaded or not.
3766 nm->set_unloading_clock(nmethod::global_unloading_clock());
3767 }
3768
3769 void clean_nmethod_postponed(nmethod* nm) {
3770 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
3771 }
3772
3773 static const int MaxClaimNmethods = 16;
3774
3775 void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) {
3776 nmethod* first;
3777 NMethodIterator last;
3778
3779 do {
3780 *num_claimed_nmethods = 0;
3781
3782 first = (nmethod*)_claimed_nmethod;
3783 last = NMethodIterator(first);
3784
3785 if (first != NULL) {
3786
3787 for (int i = 0; i < MaxClaimNmethods; i++) {
3788 if (!last.next_alive()) {
3789 break;
3790 }
3791 claimed_nmethods[i] = last.method();
3792 (*num_claimed_nmethods)++;
3793 }
3794 }
3795
3796 } while ((nmethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first);
3797 }
3798
3799 nmethod* claim_postponed_nmethod() {
3800 nmethod* claim;
3801 nmethod* next;
3802
3803 do {
3804 claim = (nmethod*)_postponed_list;
3805 if (claim == NULL) {
3806 return NULL;
3807 }
3808
3809 next = claim->unloading_next();
3810
3811 } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
3812
3813 return claim;
3814 }
3815
3816 public:
3817 // Mark that we're done with the first pass of nmethod cleaning.
3818 void barrier_mark(uint worker_id) {
3819 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3820 _num_entered_barrier++;
3821 if (_num_entered_barrier == _num_workers) {
3822 ml.notify_all();
3823 }
3824 }
3825
3826 // See if we have to wait for the other workers to
3827 // finish their first-pass nmethod cleaning work.
3828 void barrier_wait(uint worker_id) {
3829 if (_num_entered_barrier < _num_workers) {
3830 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3831 while (_num_entered_barrier < _num_workers) {
3832 ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
3833 }
3834 }
3835 }
3836
3837 // Cleaning and unloading of nmethods. Some work has to be postponed
3838 // to the second pass, when we know which nmethods survive.
3839 void work_first_pass(uint worker_id) {
3840 // The first nmethods is claimed by the first worker.
3841 if (worker_id == 0 && _first_nmethod != NULL) {
3842 clean_nmethod(_first_nmethod);
3843 _first_nmethod = NULL;
3844 }
3845
3846 int num_claimed_nmethods;
3847 nmethod* claimed_nmethods[MaxClaimNmethods];
3848
3849 while (true) {
3850 claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
3851
3852 if (num_claimed_nmethods == 0) {
3853 break;
3854 }
3855
3856 for (int i = 0; i < num_claimed_nmethods; i++) {
3857 clean_nmethod(claimed_nmethods[i]);
3858 }
3859 }
3860 }
3861
3862 void work_second_pass(uint worker_id) {
3863 nmethod* nm;
3864 // Take care of postponed nmethods.
3865 while ((nm = claim_postponed_nmethod()) != NULL) {
3866 clean_nmethod_postponed(nm);
3867 }
3868 }
3869 };
3870
3871 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
3872
3873 class G1KlassCleaningTask : public StackObj {
3874 BoolObjectClosure* _is_alive;
3875 volatile jint _clean_klass_tree_claimed;
3876 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
3877
3878 public:
3879 G1KlassCleaningTask(BoolObjectClosure* is_alive) :
3880 _is_alive(is_alive),
3881 _clean_klass_tree_claimed(0),
3882 _klass_iterator() {
3883 }
3884
3885 private:
3886 bool claim_clean_klass_tree_task() {
3887 if (_clean_klass_tree_claimed) {
3888 return false;
3889 }
3890
3891 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
3892 }
3893
3894 InstanceKlass* claim_next_klass() {
3895 Klass* klass;
3896 do {
3897 klass =_klass_iterator.next_klass();
3898 } while (klass != NULL && !klass->is_instance_klass());
3899
3900 // this can be null so don't call InstanceKlass::cast
3901 return static_cast<InstanceKlass*>(klass);
3902 }
3903
3904 public:
3905
3906 void clean_klass(InstanceKlass* ik) {
3907 ik->clean_weak_instanceklass_links(_is_alive);
3908 }
3909
3910 void work() {
3911 ResourceMark rm;
3912
3913 // One worker will clean the subklass/sibling klass tree.
3914 if (claim_clean_klass_tree_task()) {
3915 Klass::clean_subklass_tree(_is_alive);
3916 }
3917
3918 // All workers will help cleaning the classes,
3919 InstanceKlass* klass;
3920 while ((klass = claim_next_klass()) != NULL) {
3921 clean_klass(klass);
3922 }
3923 }
3924 };
3925
3926 // To minimize the remark pause times, the tasks below are done in parallel.
3927 class G1ParallelCleaningTask : public AbstractGangTask {
3928 private:
3929 G1StringSymbolTableUnlinkTask _string_symbol_task;
3930 G1CodeCacheUnloadingTask _code_cache_task;
3931 G1KlassCleaningTask _klass_cleaning_task;
3932
3933 public:
3934 // The constructor is run in the VMThread.
3935 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
3936 AbstractGangTask("Parallel Cleaning"),
3937 _string_symbol_task(is_alive, process_strings, process_symbols),
3938 _code_cache_task(num_workers, is_alive, unloading_occurred),
3939 _klass_cleaning_task(is_alive) {
3940 }
3941
3942 // The parallel work done by all worker threads.
3943 void work(uint worker_id) {
3944 // Do first pass of code cache cleaning.
3945 _code_cache_task.work_first_pass(worker_id);
3946
3947 // Let the threads mark that the first pass is done.
3948 _code_cache_task.barrier_mark(worker_id);
3949
3950 // Clean the Strings and Symbols.
3951 _string_symbol_task.work(worker_id);
3952
3953 // Wait for all workers to finish the first code cache cleaning pass.
3954 _code_cache_task.barrier_wait(worker_id);
3955
3956 // Do the second code cache cleaning work, which realize on
3957 // the liveness information gathered during the first pass.
3958 _code_cache_task.work_second_pass(worker_id);
3959
3960 // Clean all klasses that were not unloaded.
3961 _klass_cleaning_task.work();
3962 }
3963 };
3964
3965
3966 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
3967 bool process_strings,
3968 bool process_symbols,
3969 bool class_unloading_occurred) {
3970 uint n_workers = workers()->active_workers();
3971
3972 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
3973 n_workers, class_unloading_occurred);
3974 workers()->run_task(&g1_unlink_task);
3975 }
3976
3977 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
3978 bool process_strings, bool process_symbols) {
3979 { // Timing scope
3980 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
3981 workers()->run_task(&g1_unlink_task);
3982 }
3983 }
3984
3985 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3986 private:
3987 DirtyCardQueueSet* _queue;
3988 G1CollectedHeap* _g1h;
3989 public:
3990 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"),
3991 _queue(queue), _g1h(g1h) { }
3992
3993 virtual void work(uint worker_id) {
3994 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
3995 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
3996
3997 RedirtyLoggedCardTableEntryClosure cl(_g1h);
3998 _queue->par_apply_closure_to_all_completed_buffers(&cl);
3999
4000 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
4001 }
4002 };
4003
4004 void G1CollectedHeap::redirty_logged_cards() {
4005 double redirty_logged_cards_start = os::elapsedTime();
4006
4007 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this);
4008 dirty_card_queue_set().reset_for_par_iteration();
4009 workers()->run_task(&redirty_task);
4010
4011 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
4012 dcq.merge_bufferlists(&dirty_card_queue_set());
4013 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
4014
4015 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
4016 }
4017
4018 // Weak Reference Processing support
4019
4020 // An always "is_alive" closure that is used to preserve referents.
4021 // If the object is non-null then it's alive. Used in the preservation
4022 // of referent objects that are pointed to by reference objects
4023 // discovered by the CM ref processor.
4024 class G1AlwaysAliveClosure: public BoolObjectClosure {
4025 G1CollectedHeap* _g1;
4026 public:
4027 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4028 bool do_object_b(oop p) {
4029 if (p != NULL) {
4030 return true;
4031 }
4032 return false;
4033 }
4034 };
4035
4036 bool G1STWIsAliveClosure::do_object_b(oop p) {
4037 // An object is reachable if it is outside the collection set,
4038 // or is inside and copied.
4039 return !_g1->is_in_cset(p) || p->is_forwarded();
4040 }
4041
4042 // Non Copying Keep Alive closure
4043 class G1KeepAliveClosure: public OopClosure {
4044 G1CollectedHeap* _g1;
4045 public:
4046 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4047 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
4048 void do_oop(oop* p) {
4049 oop obj = *p;
4050 assert(obj != NULL, "the caller should have filtered out NULL values");
4051
4052 const InCSetState cset_state = _g1->in_cset_state(obj);
4053 if (!cset_state.is_in_cset_or_humongous()) {
4054 return;
4055 }
4056 if (cset_state.is_in_cset()) {
4057 assert( obj->is_forwarded(), "invariant" );
4058 *p = obj->forwardee();
4059 } else {
4060 assert(!obj->is_forwarded(), "invariant" );
4061 assert(cset_state.is_humongous(),
4062 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value());
4063 _g1->set_humongous_is_live(obj);
4064 }
4065 }
4066 };
4067
4068 // Copying Keep Alive closure - can be called from both
4069 // serial and parallel code as long as different worker
4070 // threads utilize different G1ParScanThreadState instances
4071 // and different queues.
4072
4073 class G1CopyingKeepAliveClosure: public OopClosure {
4074 G1CollectedHeap* _g1h;
4075 OopClosure* _copy_non_heap_obj_cl;
4076 G1ParScanThreadState* _par_scan_state;
4077
4078 public:
4079 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
4080 OopClosure* non_heap_obj_cl,
4081 G1ParScanThreadState* pss):
4082 _g1h(g1h),
4083 _copy_non_heap_obj_cl(non_heap_obj_cl),
4084 _par_scan_state(pss)
4085 {}
4086
4087 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
4088 virtual void do_oop( oop* p) { do_oop_work(p); }
4089
4090 template <class T> void do_oop_work(T* p) {
4091 oop obj = oopDesc::load_decode_heap_oop(p);
4092
4093 if (_g1h->is_in_cset_or_humongous(obj)) {
4094 // If the referent object has been forwarded (either copied
4095 // to a new location or to itself in the event of an
4096 // evacuation failure) then we need to update the reference
4097 // field and, if both reference and referent are in the G1
4098 // heap, update the RSet for the referent.
4099 //
4100 // If the referent has not been forwarded then we have to keep
4101 // it alive by policy. Therefore we have copy the referent.
4102 //
4103 // If the reference field is in the G1 heap then we can push
4104 // on the PSS queue. When the queue is drained (after each
4105 // phase of reference processing) the object and it's followers
4106 // will be copied, the reference field set to point to the
4107 // new location, and the RSet updated. Otherwise we need to
4108 // use the the non-heap or metadata closures directly to copy
4109 // the referent object and update the pointer, while avoiding
4110 // updating the RSet.
4111
4112 if (_g1h->is_in_g1_reserved(p)) {
4113 _par_scan_state->push_on_queue(p);
4114 } else {
4115 assert(!Metaspace::contains((const void*)p),
4116 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p));
4117 _copy_non_heap_obj_cl->do_oop(p);
4118 }
4119 }
4120 }
4121 };
4122
4123 // Serial drain queue closure. Called as the 'complete_gc'
4124 // closure for each discovered list in some of the
4125 // reference processing phases.
4126
4127 class G1STWDrainQueueClosure: public VoidClosure {
4128 protected:
4129 G1CollectedHeap* _g1h;
4130 G1ParScanThreadState* _par_scan_state;
4131
4132 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4133
4134 public:
4135 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
4136 _g1h(g1h),
4137 _par_scan_state(pss)
4138 { }
4139
4140 void do_void() {
4141 G1ParScanThreadState* const pss = par_scan_state();
4142 pss->trim_queue();
4143 }
4144 };
4145
4146 // Parallel Reference Processing closures
4147
4148 // Implementation of AbstractRefProcTaskExecutor for parallel reference
4149 // processing during G1 evacuation pauses.
4150
4151 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
4152 private:
4153 G1CollectedHeap* _g1h;
4154 G1ParScanThreadStateSet* _pss;
4155 RefToScanQueueSet* _queues;
4156 WorkGang* _workers;
4157 uint _active_workers;
4158
4159 public:
4160 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
4161 G1ParScanThreadStateSet* per_thread_states,
4162 WorkGang* workers,
4163 RefToScanQueueSet *task_queues,
4164 uint n_workers) :
4165 _g1h(g1h),
4166 _pss(per_thread_states),
4167 _queues(task_queues),
4168 _workers(workers),
4169 _active_workers(n_workers)
4170 {
4171 g1h->ref_processor_stw()->set_active_mt_degree(n_workers);
4172 }
4173
4174 // Executes the given task using concurrent marking worker threads.
4175 virtual void execute(ProcessTask& task);
4176 virtual void execute(EnqueueTask& task);
4177 };
4178
4179 // Gang task for possibly parallel reference processing
4180
4181 class G1STWRefProcTaskProxy: public AbstractGangTask {
4182 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
4183 ProcessTask& _proc_task;
4184 G1CollectedHeap* _g1h;
4185 G1ParScanThreadStateSet* _pss;
4186 RefToScanQueueSet* _task_queues;
4187 ParallelTaskTerminator* _terminator;
4188
4189 public:
4190 G1STWRefProcTaskProxy(ProcessTask& proc_task,
4191 G1CollectedHeap* g1h,
4192 G1ParScanThreadStateSet* per_thread_states,
4193 RefToScanQueueSet *task_queues,
4194 ParallelTaskTerminator* terminator) :
4195 AbstractGangTask("Process reference objects in parallel"),
4196 _proc_task(proc_task),
4197 _g1h(g1h),
4198 _pss(per_thread_states),
4199 _task_queues(task_queues),
4200 _terminator(terminator)
4201 {}
4202
4203 virtual void work(uint worker_id) {
4204 // The reference processing task executed by a single worker.
4205 ResourceMark rm;
4206 HandleMark hm;
4207
4208 G1STWIsAliveClosure is_alive(_g1h);
4209
4210 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
4211 pss->set_ref_processor(NULL);
4212
4213 // Keep alive closure.
4214 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4215
4216 // Complete GC closure
4217 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator);
4218
4219 // Call the reference processing task's work routine.
4220 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
4221
4222 // Note we cannot assert that the refs array is empty here as not all
4223 // of the processing tasks (specifically phase2 - pp2_work) execute
4224 // the complete_gc closure (which ordinarily would drain the queue) so
4225 // the queue may not be empty.
4226 }
4227 };
4228
4229 // Driver routine for parallel reference processing.
4230 // Creates an instance of the ref processing gang
4231 // task and has the worker threads execute it.
4232 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
4233 assert(_workers != NULL, "Need parallel worker threads.");
4234
4235 ParallelTaskTerminator terminator(_active_workers, _queues);
4236 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
4237
4238 _workers->run_task(&proc_task_proxy);
4239 }
4240
4241 // Gang task for parallel reference enqueueing.
4242
4243 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
4244 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
4245 EnqueueTask& _enq_task;
4246
4247 public:
4248 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
4249 AbstractGangTask("Enqueue reference objects in parallel"),
4250 _enq_task(enq_task)
4251 { }
4252
4253 virtual void work(uint worker_id) {
4254 _enq_task.work(worker_id);
4255 }
4256 };
4257
4258 // Driver routine for parallel reference enqueueing.
4259 // Creates an instance of the ref enqueueing gang
4260 // task and has the worker threads execute it.
4261
4262 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
4263 assert(_workers != NULL, "Need parallel worker threads.");
4264
4265 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
4266
4267 _workers->run_task(&enq_task_proxy);
4268 }
4269
4270 // End of weak reference support closures
4271
4272 // Abstract task used to preserve (i.e. copy) any referent objects
4273 // that are in the collection set and are pointed to by reference
4274 // objects discovered by the CM ref processor.
4275
4276 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
4277 protected:
4278 G1CollectedHeap* _g1h;
4279 G1ParScanThreadStateSet* _pss;
4280 RefToScanQueueSet* _queues;
4281 ParallelTaskTerminator _terminator;
4282 uint _n_workers;
4283
4284 public:
4285 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) :
4286 AbstractGangTask("ParPreserveCMReferents"),
4287 _g1h(g1h),
4288 _pss(per_thread_states),
4289 _queues(task_queues),
4290 _terminator(workers, _queues),
4291 _n_workers(workers)
4292 {
4293 g1h->ref_processor_cm()->set_active_mt_degree(workers);
4294 }
4295
4296 void work(uint worker_id) {
4297 G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id);
4298
4299 ResourceMark rm;
4300 HandleMark hm;
4301
4302 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
4303 pss->set_ref_processor(NULL);
4304 assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4305
4306 // Is alive closure
4307 G1AlwaysAliveClosure always_alive(_g1h);
4308
4309 // Copying keep alive closure. Applied to referent objects that need
4310 // to be copied.
4311 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4312
4313 ReferenceProcessor* rp = _g1h->ref_processor_cm();
4314
4315 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
4316 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
4317
4318 // limit is set using max_num_q() - which was set using ParallelGCThreads.
4319 // So this must be true - but assert just in case someone decides to
4320 // change the worker ids.
4321 assert(worker_id < limit, "sanity");
4322 assert(!rp->discovery_is_atomic(), "check this code");
4323
4324 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
4325 for (uint idx = worker_id; idx < limit; idx += stride) {
4326 DiscoveredList& ref_list = rp->discovered_refs()[idx];
4327
4328 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
4329 while (iter.has_next()) {
4330 // Since discovery is not atomic for the CM ref processor, we
4331 // can see some null referent objects.
4332 iter.load_ptrs(DEBUG_ONLY(true));
4333 oop ref = iter.obj();
4334
4335 // This will filter nulls.
4336 if (iter.is_referent_alive()) {
4337 iter.make_referent_alive();
4338 }
4339 iter.move_to_next();
4340 }
4341 }
4342
4343 // Drain the queue - which may cause stealing
4344 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator);
4345 drain_queue.do_void();
4346 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
4347 assert(pss->queue_is_empty(), "should be");
4348 }
4349 };
4350
4351 void G1CollectedHeap::process_weak_jni_handles() {
4352 double ref_proc_start = os::elapsedTime();
4353
4354 G1STWIsAliveClosure is_alive(this);
4355 G1KeepAliveClosure keep_alive(this);
4356 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
4357
4358 double ref_proc_time = os::elapsedTime() - ref_proc_start;
4359 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4360 }
4361
4362 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) {
4363 // Any reference objects, in the collection set, that were 'discovered'
4364 // by the CM ref processor should have already been copied (either by
4365 // applying the external root copy closure to the discovered lists, or
4366 // by following an RSet entry).
4367 //
4368 // But some of the referents, that are in the collection set, that these
4369 // reference objects point to may not have been copied: the STW ref
4370 // processor would have seen that the reference object had already
4371 // been 'discovered' and would have skipped discovering the reference,
4372 // but would not have treated the reference object as a regular oop.
4373 // As a result the copy closure would not have been applied to the
4374 // referent object.
4375 //
4376 // We need to explicitly copy these referent objects - the references
4377 // will be processed at the end of remarking.
4378 //
4379 // We also need to do this copying before we process the reference
4380 // objects discovered by the STW ref processor in case one of these
4381 // referents points to another object which is also referenced by an
4382 // object discovered by the STW ref processor.
4383 double preserve_cm_referents_time = 0.0;
4384
4385 // To avoid spawning task when there is no work to do, check that
4386 // a concurrent cycle is active and that some references have been
4387 // discovered.
4388 if (concurrent_mark()->cmThread()->during_cycle() &&
4389 ref_processor_cm()->has_discovered_references()) {
4390 double preserve_cm_referents_start = os::elapsedTime();
4391 uint no_of_gc_workers = workers()->active_workers();
4392 G1ParPreserveCMReferentsTask keep_cm_referents(this,
4393 per_thread_states,
4394 no_of_gc_workers,
4395 _task_queues);
4396 workers()->run_task(&keep_cm_referents);
4397 preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start;
4398 }
4399
4400 g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0);
4401 }
4402
4403 // Weak Reference processing during an evacuation pause (part 1).
4404 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4405 double ref_proc_start = os::elapsedTime();
4406
4407 ReferenceProcessor* rp = _ref_processor_stw;
4408 assert(rp->discovery_enabled(), "should have been enabled");
4409
4410 // Closure to test whether a referent is alive.
4411 G1STWIsAliveClosure is_alive(this);
4412
4413 // Even when parallel reference processing is enabled, the processing
4414 // of JNI refs is serial and performed serially by the current thread
4415 // rather than by a worker. The following PSS will be used for processing
4416 // JNI refs.
4417
4418 // Use only a single queue for this PSS.
4419 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0);
4420 pss->set_ref_processor(NULL);
4421 assert(pss->queue_is_empty(), "pre-condition");
4422
4423 // Keep alive closure.
4424 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss);
4425
4426 // Serial Complete GC closure
4427 G1STWDrainQueueClosure drain_queue(this, pss);
4428
4429 // Setup the soft refs policy...
4430 rp->setup_policy(false);
4431
4432 ReferenceProcessorStats stats;
4433 if (!rp->processing_is_mt()) {
4434 // Serial reference processing...
4435 stats = rp->process_discovered_references(&is_alive,
4436 &keep_alive,
4437 &drain_queue,
4438 NULL,
4439 _gc_timer_stw);
4440 } else {
4441 uint no_of_gc_workers = workers()->active_workers();
4442
4443 // Parallel reference processing
4444 assert(no_of_gc_workers <= rp->max_num_q(),
4445 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4446 no_of_gc_workers, rp->max_num_q());
4447
4448 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers);
4449 stats = rp->process_discovered_references(&is_alive,
4450 &keep_alive,
4451 &drain_queue,
4452 &par_task_executor,
4453 _gc_timer_stw);
4454 }
4455
4456 _gc_tracer_stw->report_gc_reference_stats(stats);
4457
4458 // We have completed copying any necessary live referent objects.
4459 assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4460
4461 double ref_proc_time = os::elapsedTime() - ref_proc_start;
4462 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4463 }
4464
4465 // Weak Reference processing during an evacuation pause (part 2).
4466 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4467 double ref_enq_start = os::elapsedTime();
4468
4469 ReferenceProcessor* rp = _ref_processor_stw;
4470 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
4471
4472 // Now enqueue any remaining on the discovered lists on to
4473 // the pending list.
4474 if (!rp->processing_is_mt()) {
4475 // Serial reference processing...
4476 rp->enqueue_discovered_references();
4477 } else {
4478 // Parallel reference enqueueing
4479
4480 uint n_workers = workers()->active_workers();
4481
4482 assert(n_workers <= rp->max_num_q(),
4483 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4484 n_workers, rp->max_num_q());
4485
4486 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers);
4487 rp->enqueue_discovered_references(&par_task_executor);
4488 }
4489
4490 rp->verify_no_references_recorded();
4491 assert(!rp->discovery_enabled(), "should have been disabled");
4492
4493 // FIXME
4494 // CM's reference processing also cleans up the string and symbol tables.
4495 // Should we do that here also? We could, but it is a serial operation
4496 // and could significantly increase the pause time.
4497
4498 double ref_enq_time = os::elapsedTime() - ref_enq_start;
4499 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
4500 }
4501
4502 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
4503 double merge_pss_time_start = os::elapsedTime();
4504 per_thread_states->flush();
4505 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0);
4506 }
4507
4508 void G1CollectedHeap::pre_evacuate_collection_set() {
4509 _expand_heap_after_alloc_failure = true;
4510 _evacuation_failed = false;
4511
4512 // Disable the hot card cache.
4513 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
4514 hot_card_cache->reset_hot_cache_claimed_index();
4515 hot_card_cache->set_use_cache(false);
4516
4517 g1_rem_set()->prepare_for_oops_into_collection_set_do();
4518 _preserved_marks_set.assert_empty();
4519 }
4520
4521 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4522 // Should G1EvacuationFailureALot be in effect for this GC?
4523 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
4524
4525 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
4526 double start_par_time_sec = os::elapsedTime();
4527 double end_par_time_sec;
4528
4529 {
4530 const uint n_workers = workers()->active_workers();
4531 G1RootProcessor root_processor(this, n_workers);
4532 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers);
4533 // InitialMark needs claim bits to keep track of the marked-through CLDs.
4534 if (collector_state()->during_initial_mark_pause()) {
4535 ClassLoaderDataGraph::clear_claimed_marks();
4536 }
4537
4538 print_termination_stats_hdr();
4539
4540 workers()->run_task(&g1_par_task);
4541 end_par_time_sec = os::elapsedTime();
4542
4543 // Closing the inner scope will execute the destructor
4544 // for the G1RootProcessor object. We record the current
4545 // elapsed time before closing the scope so that time
4546 // taken for the destructor is NOT included in the
4547 // reported parallel time.
4548 }
4549
4550 G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4551
4552 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
4553 phase_times->record_par_time(par_time_ms);
4554
4555 double code_root_fixup_time_ms =
4556 (os::elapsedTime() - end_par_time_sec) * 1000.0;
4557 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
4558 }
4559
4560 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4561 // Process any discovered reference objects - we have
4562 // to do this _before_ we retire the GC alloc regions
4563 // as we may have to copy some 'reachable' referent
4564 // objects (and their reachable sub-graphs) that were
4565 // not copied during the pause.
4566 if (g1_policy()->should_process_references()) {
4567 preserve_cm_referents(per_thread_states);
4568 process_discovered_references(per_thread_states);
4569 } else {
4570 ref_processor_stw()->verify_no_references_recorded();
4571 process_weak_jni_handles();
4572 }
4573
4574 if (G1StringDedup::is_enabled()) {
4575 double fixup_start = os::elapsedTime();
4576
4577 G1STWIsAliveClosure is_alive(this);
4578 G1KeepAliveClosure keep_alive(this);
4579 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times());
4580
4581 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
4582 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
4583 }
4584
4585 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4586
4587 if (evacuation_failed()) {
4588 restore_after_evac_failure();
4589
4590 // Reset the G1EvacuationFailureALot counters and flags
4591 // Note: the values are reset only when an actual
4592 // evacuation failure occurs.
4593 NOT_PRODUCT(reset_evacuation_should_fail();)
4594 }
4595
4596 _preserved_marks_set.assert_empty();
4597
4598 // Enqueue any remaining references remaining on the STW
4599 // reference processor's discovered lists. We need to do
4600 // this after the card table is cleaned (and verified) as
4601 // the act of enqueueing entries on to the pending list
4602 // will log these updates (and dirty their associated
4603 // cards). We need these updates logged to update any
4604 // RSets.
4605 if (g1_policy()->should_process_references()) {
4606 enqueue_discovered_references(per_thread_states);
4607 } else {
4608 g1_policy()->phase_times()->record_ref_enq_time(0);
4609 }
4610
4611 _allocator->release_gc_alloc_regions(evacuation_info);
4612
4613 merge_per_thread_state_info(per_thread_states);
4614
4615 // Reset and re-enable the hot card cache.
4616 // Note the counts for the cards in the regions in the
4617 // collection set are reset when the collection set is freed.
4618 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
4619 hot_card_cache->reset_hot_cache();
4620 hot_card_cache->set_use_cache(true);
4621
4622 purge_code_root_memory();
4623
4624 redirty_logged_cards();
4625 #if defined(COMPILER2) || INCLUDE_JVMCI
4626 DerivedPointerTable::update_pointers();
4627 #endif
4628 }
4629
4630 void G1CollectedHeap::record_obj_copy_mem_stats() {
4631 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4632
4633 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4634 create_g1_evac_summary(&_old_evac_stats));
4635 }
4636
4637 void G1CollectedHeap::free_region(HeapRegion* hr,
4638 FreeRegionList* free_list,
4639 bool par,
4640 bool locked) {
4641 assert(!hr->is_free(), "the region should not be free");
4642 assert(!hr->is_empty(), "the region should not be empty");
4643 assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
4644 assert(free_list != NULL, "pre-condition");
4645
4646 if (G1VerifyBitmaps) {
4647 MemRegion mr(hr->bottom(), hr->end());
4648 concurrent_mark()->clearRangePrevBitmap(mr);
4649 }
4650
4651 // Clear the card counts for this region.
4652 // Note: we only need to do this if the region is not young
4653 // (since we don't refine cards in young regions).
4654 if (!hr->is_young()) {
4655 _cg1r->hot_card_cache()->reset_card_counts(hr);
4656 }
4657 hr->hr_clear(par, true /* clear_space */, locked /* locked */);
4658 free_list->add_ordered(hr);
4659 }
4660
4661 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4662 FreeRegionList* free_list,
4663 bool par) {
4664 assert(hr->is_humongous(), "this is only for humongous regions");
4665 assert(free_list != NULL, "pre-condition");
4666 hr->clear_humongous();
4667 free_region(hr, free_list, par);
4668 }
4669
4670 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4671 const uint humongous_regions_removed) {
4672 if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4673 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4674 _old_set.bulk_remove(old_regions_removed);
4675 _humongous_set.bulk_remove(humongous_regions_removed);
4676 }
4677
4678 }
4679
4680 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4681 assert(list != NULL, "list can't be null");
4682 if (!list->is_empty()) {
4683 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4684 _hrm.insert_list_into_free_list(list);
4685 }
4686 }
4687
4688 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4689 decrease_used(bytes);
4690 }
4691
4692 class G1ParScrubRemSetTask: public AbstractGangTask {
4693 protected:
4694 G1RemSet* _g1rs;
4695 HeapRegionClaimer _hrclaimer;
4696
4697 public:
4698 G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) :
4699 AbstractGangTask("G1 ScrubRS"),
4700 _g1rs(g1_rs),
4701 _hrclaimer(num_workers) {
4702 }
4703
4704 void work(uint worker_id) {
4705 _g1rs->scrub(worker_id, &_hrclaimer);
4706 }
4707 };
4708
4709 void G1CollectedHeap::scrub_rem_set() {
4710 uint num_workers = workers()->active_workers();
4711 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers);
4712 workers()->run_task(&g1_par_scrub_rs_task);
4713 }
4714
4715 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4716 size_t pre_used = 0;
4717 FreeRegionList local_free_list("Local List for CSet Freeing");
4718
4719 double young_time_ms = 0.0;
4720 double non_young_time_ms = 0.0;
4721
4722 // Since the collection set is a superset of the the young list,
4723 // all we need to do to clear the young list is clear its
4724 // head and length, and unlink any young regions in the code below
4725 _young_list->clear();
4726
4727 G1Policy* policy = g1_policy();
4728
4729 double start_sec = os::elapsedTime();
4730 bool non_young = true;
4731
4732 HeapRegion* cur = cs_head;
4733 int age_bound = -1;
4734 size_t rs_lengths = 0;
4735
4736 while (cur != NULL) {
4737 assert(!is_on_master_free_list(cur), "sanity");
4738 if (non_young) {
4739 if (cur->is_young()) {
4740 double end_sec = os::elapsedTime();
4741 double elapsed_ms = (end_sec - start_sec) * 1000.0;
4742 non_young_time_ms += elapsed_ms;
4743
4744 start_sec = os::elapsedTime();
4745 non_young = false;
4746 }
4747 } else {
4748 if (!cur->is_young()) {
4749 double end_sec = os::elapsedTime();
4750 double elapsed_ms = (end_sec - start_sec) * 1000.0;
4751 young_time_ms += elapsed_ms;
4752
4753 start_sec = os::elapsedTime();
4754 non_young = true;
4755 }
4756 }
4757
4758 rs_lengths += cur->rem_set()->occupied_locked();
4759
4760 HeapRegion* next = cur->next_in_collection_set();
4761 assert(cur->in_collection_set(), "bad CS");
4762 cur->set_next_in_collection_set(NULL);
4763 clear_in_cset(cur);
4764
4765 if (cur->is_young()) {
4766 int index = cur->young_index_in_cset();
4767 assert(index != -1, "invariant");
4768 assert((uint) index < collection_set()->young_region_length(), "invariant");
4769 size_t words_survived = surviving_young_words[index];
4770 cur->record_surv_words_in_group(words_survived);
4771
4772 // At this point the we have 'popped' cur from the collection set
4773 // (linked via next_in_collection_set()) but it is still in the
4774 // young list (linked via next_young_region()). Clear the
4775 // _next_young_region field.
4776 cur->set_next_young_region(NULL);
4777 } else {
4778 int index = cur->young_index_in_cset();
4779 assert(index == -1, "invariant");
4780 }
4781
4782 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
4783 (!cur->is_young() && cur->young_index_in_cset() == -1),
4784 "invariant" );
4785
4786 if (!cur->evacuation_failed()) {
4787 MemRegion used_mr = cur->used_region();
4788
4789 // And the region is empty.
4790 assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
4791 pre_used += cur->used();
4792 free_region(cur, &local_free_list, false /* par */, true /* locked */);
4793 } else {
4794 cur->uninstall_surv_rate_group();
4795 if (cur->is_young()) {
4796 cur->set_young_index_in_cset(-1);
4797 }
4798 cur->set_evacuation_failed(false);
4799 // When moving a young gen region to old gen, we "allocate" that whole region
4800 // there. This is in addition to any already evacuated objects. Notify the
4801 // policy about that.
4802 // Old gen regions do not cause an additional allocation: both the objects
4803 // still in the region and the ones already moved are accounted for elsewhere.
4804 if (cur->is_young()) {
4805 policy->add_bytes_allocated_in_old_since_last_gc(HeapRegion::GrainBytes);
4806 }
4807 // The region is now considered to be old.
4808 cur->set_old();
4809 // Do some allocation statistics accounting. Regions that failed evacuation
4810 // are always made old, so there is no need to update anything in the young
4811 // gen statistics, but we need to update old gen statistics.
4812 size_t used_words = cur->marked_bytes() / HeapWordSize;
4813 _old_evac_stats.add_failure_used_and_waste(used_words, HeapRegion::GrainWords - used_words);
4814 _old_set.add(cur);
4815 evacuation_info.increment_collectionset_used_after(cur->used());
4816 }
4817 cur = next;
4818 }
4819
4820 evacuation_info.set_regions_freed(local_free_list.length());
4821 policy->record_max_rs_lengths(rs_lengths);
4822 policy->cset_regions_freed();
4823
4824 double end_sec = os::elapsedTime();
4825 double elapsed_ms = (end_sec - start_sec) * 1000.0;
4826
4827 if (non_young) {
4828 non_young_time_ms += elapsed_ms;
4829 } else {
4830 young_time_ms += elapsed_ms;
4831 }
4832
4833 prepend_to_freelist(&local_free_list);
4834 decrement_summary_bytes(pre_used);
4835 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
4836 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
4837 }
4838
4839 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4840 private:
4841 FreeRegionList* _free_region_list;
4842 HeapRegionSet* _proxy_set;
4843 uint _humongous_regions_removed;
4844 size_t _freed_bytes;
4845 public:
4846
4847 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4848 _free_region_list(free_region_list), _humongous_regions_removed(0), _freed_bytes(0) {
4849 }
4850
4851 virtual bool doHeapRegion(HeapRegion* r) {
4852 if (!r->is_starts_humongous()) {
4853 return false;
4854 }
4855
4856 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4857
4858 oop obj = (oop)r->bottom();
4859 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
4860
4861 // The following checks whether the humongous object is live are sufficient.
4862 // The main additional check (in addition to having a reference from the roots
4863 // or the young gen) is whether the humongous object has a remembered set entry.
4864 //
4865 // A humongous object cannot be live if there is no remembered set for it
4866 // because:
4867 // - there can be no references from within humongous starts regions referencing
4868 // the object because we never allocate other objects into them.
4869 // (I.e. there are no intra-region references that may be missed by the
4870 // remembered set)
4871 // - as soon there is a remembered set entry to the humongous starts region
4872 // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4873 // until the end of a concurrent mark.
4874 //
4875 // It is not required to check whether the object has been found dead by marking
4876 // or not, in fact it would prevent reclamation within a concurrent cycle, as
4877 // all objects allocated during that time are considered live.
4878 // SATB marking is even more conservative than the remembered set.
4879 // So if at this point in the collection there is no remembered set entry,
4880 // nobody has a reference to it.
4881 // At the start of collection we flush all refinement logs, and remembered sets
4882 // are completely up-to-date wrt to references to the humongous object.
4883 //
4884 // Other implementation considerations:
4885 // - never consider object arrays at this time because they would pose
4886 // considerable effort for cleaning up the the remembered sets. This is
4887 // required because stale remembered sets might reference locations that
4888 // are currently allocated into.
4889 uint region_idx = r->hrm_index();
4890 if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4891 !r->rem_set()->is_empty()) {
4892 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",
4893 region_idx,
4894 (size_t)obj->size() * HeapWordSize,
4895 p2i(r->bottom()),
4896 r->rem_set()->occupied(),
4897 r->rem_set()->strong_code_roots_list_length(),
4898 next_bitmap->isMarked(r->bottom()),
4899 g1h->is_humongous_reclaim_candidate(region_idx),
4900 obj->is_typeArray()
4901 );
4902 return false;
4903 }
4904
4905 guarantee(obj->is_typeArray(),
4906 "Only eagerly reclaiming type arrays is supported, but the object "
4907 PTR_FORMAT " is not.", p2i(r->bottom()));
4908
4909 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",
4910 region_idx,
4911 (size_t)obj->size() * HeapWordSize,
4912 p2i(r->bottom()),
4913 r->rem_set()->occupied(),
4914 r->rem_set()->strong_code_roots_list_length(),
4915 next_bitmap->isMarked(r->bottom()),
4916 g1h->is_humongous_reclaim_candidate(region_idx),
4917 obj->is_typeArray()
4918 );
4919
4920 // Need to clear mark bit of the humongous object if already set.
4921 if (next_bitmap->isMarked(r->bottom())) {
4922 next_bitmap->clear(r->bottom());
4923 }
4924 do {
4925 HeapRegion* next = g1h->next_region_in_humongous(r);
4926 _freed_bytes += r->used();
4927 r->set_containing_set(NULL);
4928 _humongous_regions_removed++;
4929 g1h->free_humongous_region(r, _free_region_list, false);
4930 r = next;
4931 } while (r != NULL);
4932
4933 return false;
4934 }
4935
4936 uint humongous_free_count() {
4937 return _humongous_regions_removed;
4938 }
4939
4940 size_t bytes_freed() const {
4941 return _freed_bytes;
4942 }
4943 };
4944
4945 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4946 assert_at_safepoint(true);
4947
4948 if (!G1EagerReclaimHumongousObjects ||
4949 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
4950 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
4951 return;
4952 }
4953
4954 double start_time = os::elapsedTime();
4955
4956 FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
4957
4958 G1FreeHumongousRegionClosure cl(&local_cleanup_list);
4959 heap_region_iterate(&cl);
4960
4961 remove_from_old_sets(0, cl.humongous_free_count());
4962
4963 G1HRPrinter* hrp = hr_printer();
4964 if (hrp->is_active()) {
4965 FreeRegionListIterator iter(&local_cleanup_list);
4966 while (iter.more_available()) {
4967 HeapRegion* hr = iter.get_next();
4968 hrp->cleanup(hr);
4969 }
4970 }
4971
4972 prepend_to_freelist(&local_cleanup_list);
4973 decrement_summary_bytes(cl.bytes_freed());
4974
4975 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
4976 cl.humongous_free_count());
4977 }
4978
4979 // This routine is similar to the above but does not record
4980 // any policy statistics or update free lists; we are abandoning
4981 // the current incremental collection set in preparation of a
4982 // full collection. After the full GC we will start to build up
4983 // the incremental collection set again.
4984 // This is only called when we're doing a full collection
4985 // and is immediately followed by the tearing down of the young list.
4986
4987 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
4988 HeapRegion* cur = cs_head;
4989
4990 while (cur != NULL) {
4991 HeapRegion* next = cur->next_in_collection_set();
4992 assert(cur->in_collection_set(), "bad CS");
4993 cur->set_next_in_collection_set(NULL);
4994 clear_in_cset(cur);
4995 cur->set_young_index_in_cset(-1);
4996 cur = next;
4997 }
4998 }
4999
5000 void G1CollectedHeap::set_free_regions_coming() {
5001 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming");
5002
5003 assert(!free_regions_coming(), "pre-condition");
5004 _free_regions_coming = true;
5005 }
5006
5007 void G1CollectedHeap::reset_free_regions_coming() {
5008 assert(free_regions_coming(), "pre-condition");
5009
5010 {
5011 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5012 _free_regions_coming = false;
5013 SecondaryFreeList_lock->notify_all();
5014 }
5015
5016 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming");
5017 }
5018
5019 void G1CollectedHeap::wait_while_free_regions_coming() {
5020 // Most of the time we won't have to wait, so let's do a quick test
5021 // first before we take the lock.
5022 if (!free_regions_coming()) {
5023 return;
5024 }
5025
5026 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions");
5027
5028 {
5029 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5030 while (free_regions_coming()) {
5031 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
5032 }
5033 }
5034
5035 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions");
5036 }
5037
5038 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
5039 return _allocator->is_retained_old_region(hr);
5040 }
5041
5042 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
5043 _young_list->push_region(hr);
5044 }
5045
5046 class NoYoungRegionsClosure: public HeapRegionClosure {
5047 private:
5048 bool _success;
5049 public:
5050 NoYoungRegionsClosure() : _success(true) { }
5051 bool doHeapRegion(HeapRegion* r) {
5052 if (r->is_young()) {
5053 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
5054 p2i(r->bottom()), p2i(r->end()));
5055 _success = false;
5056 }
5057 return false;
5058 }
5059 bool success() { return _success; }
5060 };
5061
5062 bool G1CollectedHeap::check_young_list_empty(bool check_heap) {
5063 bool ret = _young_list->check_list_empty();
5064
5065 if (check_heap) {
5066 NoYoungRegionsClosure closure;
5067 heap_region_iterate(&closure);
5068 ret = ret && closure.success();
5069 }
5070
5071 return ret;
5072 }
5073
5074 class TearDownRegionSetsClosure : public HeapRegionClosure {
5075 private:
5076 HeapRegionSet *_old_set;
5077
5078 public:
5079 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
5080
5081 bool doHeapRegion(HeapRegion* r) {
5082 if (r->is_old()) {
5083 _old_set->remove(r);
5084 } else {
5085 // We ignore free regions, we'll empty the free list afterwards.
5086 // We ignore young regions, we'll empty the young list afterwards.
5087 // We ignore humongous regions, we're not tearing down the
5088 // humongous regions set.
5089 assert(r->is_free() || r->is_young() || r->is_humongous(),
5090 "it cannot be another type");
5091 }
5092 return false;
5093 }
5094
5095 ~TearDownRegionSetsClosure() {
5096 assert(_old_set->is_empty(), "post-condition");
5097 }
5098 };
5099
5100 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
5101 assert_at_safepoint(true /* should_be_vm_thread */);
5102
5103 if (!free_list_only) {
5104 TearDownRegionSetsClosure cl(&_old_set);
5105 heap_region_iterate(&cl);
5106
5107 // Note that emptying the _young_list is postponed and instead done as
5108 // the first step when rebuilding the regions sets again. The reason for
5109 // this is that during a full GC string deduplication needs to know if
5110 // a collected region was young or old when the full GC was initiated.
5111 }
5112 _hrm.remove_all_free_regions();
5113 }
5114
5115 void G1CollectedHeap::increase_used(size_t bytes) {
5116 _summary_bytes_used += bytes;
5117 }
5118
5119 void G1CollectedHeap::decrease_used(size_t bytes) {
5120 assert(_summary_bytes_used >= bytes,
5121 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
5122 _summary_bytes_used, bytes);
5123 _summary_bytes_used -= bytes;
5124 }
5125
5126 void G1CollectedHeap::set_used(size_t bytes) {
5127 _summary_bytes_used = bytes;
5128 }
5129
5130 class RebuildRegionSetsClosure : public HeapRegionClosure {
5131 private:
5132 bool _free_list_only;
5133 HeapRegionSet* _old_set;
5134 HeapRegionManager* _hrm;
5135 size_t _total_used;
5136
5137 public:
5138 RebuildRegionSetsClosure(bool free_list_only,
5139 HeapRegionSet* old_set, HeapRegionManager* hrm) :
5140 _free_list_only(free_list_only),
5141 _old_set(old_set), _hrm(hrm), _total_used(0) {
5142 assert(_hrm->num_free_regions() == 0, "pre-condition");
5143 if (!free_list_only) {
5144 assert(_old_set->is_empty(), "pre-condition");
5145 }
5146 }
5147
5148 bool doHeapRegion(HeapRegion* r) {
5149 if (r->is_empty()) {
5150 // Add free regions to the free list
5151 r->set_free();
5152 r->set_allocation_context(AllocationContext::system());
5153 _hrm->insert_into_free_list(r);
5154 } else if (!_free_list_only) {
5155 assert(!r->is_young(), "we should not come across young regions");
5156
5157 if (r->is_humongous()) {
5158 // We ignore humongous regions. We left the humongous set unchanged.
5159 } else {
5160 // Objects that were compacted would have ended up on regions
5161 // that were previously old or free. Archive regions (which are
5162 // old) will not have been touched.
5163 assert(r->is_free() || r->is_old(), "invariant");
5164 // We now consider them old, so register as such. Leave
5165 // archive regions set that way, however, while still adding
5166 // them to the old set.
5167 if (!r->is_archive()) {
5168 r->set_old();
5169 }
5170 _old_set->add(r);
5171 }
5172 _total_used += r->used();
5173 }
5174
5175 return false;
5176 }
5177
5178 size_t total_used() {
5179 return _total_used;
5180 }
5181 };
5182
5183 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
5184 assert_at_safepoint(true /* should_be_vm_thread */);
5185
5186 if (!free_list_only) {
5187 _young_list->empty_list();
5188 }
5189
5190 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
5191 heap_region_iterate(&cl);
5192
5193 if (!free_list_only) {
5194 set_used(cl.total_used());
5195 if (_archive_allocator != NULL) {
5196 _archive_allocator->clear_used();
5197 }
5198 }
5199 assert(used_unlocked() == recalculate_used(),
5200 "inconsistent used_unlocked(), "
5201 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT,
5202 used_unlocked(), recalculate_used());
5203 }
5204
5205 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
5206 _refine_cte_cl->set_concurrent(concurrent);
5207 }
5208
5209 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
5210 HeapRegion* hr = heap_region_containing(p);
5211 return hr->is_in(p);
5212 }
5213
5214 // Methods for the mutator alloc region
5215
5216 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
5217 bool force) {
5218 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5219 assert(!force || g1_policy()->can_expand_young_list(),
5220 "if force is true we should be able to expand the young list");
5221 bool should_allocate = g1_policy()->should_allocate_mutator_region();
5222 if (force || should_allocate) {
5223 HeapRegion* new_alloc_region = new_region(word_size,
5224 false /* is_old */,
5225 false /* do_expand */);
5226 if (new_alloc_region != NULL) {
5227 set_region_short_lived_locked(new_alloc_region);
5228 _hr_printer.alloc(new_alloc_region, !should_allocate);
5229 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
5230 return new_alloc_region;
5231 }
5232 }
5233 return NULL;
5234 }
5235
5236 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
5237 size_t allocated_bytes) {
5238 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5239 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
5240
5241 collection_set()->add_eden_region(alloc_region);
5242 increase_used(allocated_bytes);
5243 _hr_printer.retire(alloc_region);
5244 // We update the eden sizes here, when the region is retired,
5245 // instead of when it's allocated, since this is the point that its
5246 // used space has been recored in _summary_bytes_used.
5247 g1mm()->update_eden_size();
5248 }
5249
5250 // Methods for the GC alloc regions
5251
5252 bool G1CollectedHeap::has_more_regions(InCSetState dest) {
5253 if (dest.is_old()) {
5254 return true;
5255 } else {
5256 return young_list()->survivor_length() < g1_policy()->max_survivor_regions();
5257 }
5258 }
5259
5260 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) {
5261 assert(FreeList_lock->owned_by_self(), "pre-condition");
5262
5263 if (!has_more_regions(dest)) {
5264 return NULL;
5265 }
5266
5267 const bool is_survivor = dest.is_young();
5268
5269 HeapRegion* new_alloc_region = new_region(word_size,
5270 !is_survivor,
5271 true /* do_expand */);
5272 if (new_alloc_region != NULL) {
5273 // We really only need to do this for old regions given that we
5274 // should never scan survivors. But it doesn't hurt to do it
5275 // for survivors too.
5276 new_alloc_region->record_timestamp();
5277 if (is_survivor) {
5278 new_alloc_region->set_survivor();
5279 young_list()->add_survivor_region(new_alloc_region);
5280 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
5281 } else {
5282 new_alloc_region->set_old();
5283 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
5284 }
5285 _hr_printer.alloc(new_alloc_region);
5286 bool during_im = collector_state()->during_initial_mark_pause();
5287 new_alloc_region->note_start_of_copying(during_im);
5288 return new_alloc_region;
5289 }
5290 return NULL;
5291 }
5292
5293 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
5294 size_t allocated_bytes,
5295 InCSetState dest) {
5296 bool during_im = collector_state()->during_initial_mark_pause();
5297 alloc_region->note_end_of_copying(during_im);
5298 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
5299 if (dest.is_old()) {
5300 _old_set.add(alloc_region);
5301 }
5302 _hr_printer.retire(alloc_region);
5303 }
5304
5305 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
5306 bool expanded = false;
5307 uint index = _hrm.find_highest_free(&expanded);
5308
5309 if (index != G1_NO_HRM_INDEX) {
5310 if (expanded) {
5311 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
5312 HeapRegion::GrainWords * HeapWordSize);
5313 }
5314 _hrm.allocate_free_regions_starting_at(index, 1);
5315 return region_at(index);
5316 }
5317 return NULL;
5318 }
5319
5320 // Optimized nmethod scanning
5321
5322 class RegisterNMethodOopClosure: public OopClosure {
5323 G1CollectedHeap* _g1h;
5324 nmethod* _nm;
5325
5326 template <class T> void do_oop_work(T* p) {
5327 T heap_oop = oopDesc::load_heap_oop(p);
5328 if (!oopDesc::is_null(heap_oop)) {
5329 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5330 HeapRegion* hr = _g1h->heap_region_containing(obj);
5331 assert(!hr->is_continues_humongous(),
5332 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5333 " starting at " HR_FORMAT,
5334 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5335
5336 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
5337 hr->add_strong_code_root_locked(_nm);
5338 }
5339 }
5340
5341 public:
5342 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5343 _g1h(g1h), _nm(nm) {}
5344
5345 void do_oop(oop* p) { do_oop_work(p); }
5346 void do_oop(narrowOop* p) { do_oop_work(p); }
5347 };
5348
5349 class UnregisterNMethodOopClosure: public OopClosure {
5350 G1CollectedHeap* _g1h;
5351 nmethod* _nm;
5352
5353 template <class T> void do_oop_work(T* p) {
5354 T heap_oop = oopDesc::load_heap_oop(p);
5355 if (!oopDesc::is_null(heap_oop)) {
5356 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5357 HeapRegion* hr = _g1h->heap_region_containing(obj);
5358 assert(!hr->is_continues_humongous(),
5359 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5360 " starting at " HR_FORMAT,
5361 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5362
5363 hr->remove_strong_code_root(_nm);
5364 }
5365 }
5366
5367 public:
5368 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5369 _g1h(g1h), _nm(nm) {}
5370
5371 void do_oop(oop* p) { do_oop_work(p); }
5372 void do_oop(narrowOop* p) { do_oop_work(p); }
5373 };
5374
5375 void G1CollectedHeap::register_nmethod(nmethod* nm) {
5376 CollectedHeap::register_nmethod(nm);
5377
5378 guarantee(nm != NULL, "sanity");
5379 RegisterNMethodOopClosure reg_cl(this, nm);
5380 nm->oops_do(®_cl);
5381 }
5382
5383 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
5384 CollectedHeap::unregister_nmethod(nm);
5385
5386 guarantee(nm != NULL, "sanity");
5387 UnregisterNMethodOopClosure reg_cl(this, nm);
5388 nm->oops_do(®_cl, true);
5389 }
5390
5391 void G1CollectedHeap::purge_code_root_memory() {
5392 double purge_start = os::elapsedTime();
5393 G1CodeRootSet::purge();
5394 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
5395 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
5396 }
5397
5398 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
5399 G1CollectedHeap* _g1h;
5400
5401 public:
5402 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
5403 _g1h(g1h) {}
5404
5405 void do_code_blob(CodeBlob* cb) {
5406 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
5407 if (nm == NULL) {
5408 return;
5409 }
5410
5411 if (ScavengeRootsInCode) {
5412 _g1h->register_nmethod(nm);
5413 }
5414 }
5415 };
5416
5417 void G1CollectedHeap::rebuild_strong_code_roots() {
5418 RebuildStrongCodeRootClosure blob_cl(this);
5419 CodeCache::blobs_do(&blob_cl);
5420 }