1 /*
2 * Copyright (c) 2001, 2017, 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/concurrentMarkThread.inline.hpp"
33 #include "gc/g1/g1Allocator.inline.hpp"
34 #include "gc/g1/g1CollectedHeap.inline.hpp"
35 #include "gc/g1/g1CollectionSet.hpp"
36 #include "gc/g1/g1CollectorPolicy.hpp"
37 #include "gc/g1/g1CollectorState.hpp"
38 #include "gc/g1/g1ConcurrentRefine.hpp"
39 #include "gc/g1/g1ConcurrentRefineThread.hpp"
40 #include "gc/g1/g1EvacStats.inline.hpp"
41 #include "gc/g1/g1FullCollector.hpp"
42 #include "gc/g1/g1GCPhaseTimes.hpp"
43 #include "gc/g1/g1HeapSizingPolicy.hpp"
44 #include "gc/g1/g1HeapTransition.hpp"
45 #include "gc/g1/g1HeapVerifier.hpp"
46 #include "gc/g1/g1HotCardCache.hpp"
47 #include "gc/g1/g1OopClosures.inline.hpp"
48 #include "gc/g1/g1ParScanThreadState.inline.hpp"
49 #include "gc/g1/g1Policy.hpp"
50 #include "gc/g1/g1RegionToSpaceMapper.hpp"
51 #include "gc/g1/g1RemSet.hpp"
52 #include "gc/g1/g1RootClosures.hpp"
53 #include "gc/g1/g1RootProcessor.hpp"
54 #include "gc/g1/g1StringDedup.hpp"
55 #include "gc/g1/g1YCTypes.hpp"
56 #include "gc/g1/g1YoungRemSetSamplingThread.hpp"
57 #include "gc/g1/heapRegion.inline.hpp"
58 #include "gc/g1/heapRegionRemSet.hpp"
59 #include "gc/g1/heapRegionSet.inline.hpp"
60 #include "gc/g1/vm_operations_g1.hpp"
61 #include "gc/shared/gcHeapSummary.hpp"
62 #include "gc/shared/gcId.hpp"
63 #include "gc/shared/gcLocker.inline.hpp"
64 #include "gc/shared/gcTimer.hpp"
65 #include "gc/shared/gcTrace.hpp"
66 #include "gc/shared/gcTraceTime.inline.hpp"
67 #include "gc/shared/generationSpec.hpp"
68 #include "gc/shared/isGCActiveMark.hpp"
69 #include "gc/shared/preservedMarks.inline.hpp"
70 #include "gc/shared/suspendibleThreadSet.hpp"
71 #include "gc/shared/referenceProcessor.inline.hpp"
72 #include "gc/shared/taskqueue.inline.hpp"
73 #include "gc/shared/weakProcessor.hpp"
74 #include "logging/log.hpp"
75 #include "memory/allocation.hpp"
76 #include "memory/iterator.hpp"
77 #include "memory/resourceArea.hpp"
78 #include "oops/oop.inline.hpp"
79 #include "prims/resolvedMethodTable.hpp"
80 #include "runtime/atomic.hpp"
81 #include "runtime/init.hpp"
82 #include "runtime/orderAccess.inline.hpp"
83 #include "runtime/threadSMR.hpp"
84 #include "runtime/vmThread.hpp"
85 #include "utilities/align.hpp"
86 #include "utilities/globalDefinitions.hpp"
87 #include "utilities/stack.inline.hpp"
88
89 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
90
91 // INVARIANTS/NOTES
92 //
93 // All allocation activity covered by the G1CollectedHeap interface is
94 // serialized by acquiring the HeapLock. This happens in mem_allocate
95 // and allocate_new_tlab, which are the "entry" points to the
96 // allocation code from the rest of the JVM. (Note that this does not
97 // apply to TLAB allocation, which is not part of this interface: it
98 // is done by clients of this interface.)
99
100 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
101 private:
102 size_t _num_dirtied;
103 G1CollectedHeap* _g1h;
104 G1SATBCardTableLoggingModRefBS* _g1_bs;
105
106 HeapRegion* region_for_card(jbyte* card_ptr) const {
107 return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr));
108 }
109
110 bool will_become_free(HeapRegion* hr) const {
111 // A region will be freed by free_collection_set if the region is in the
112 // collection set and has not had an evacuation failure.
113 return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
114 }
115
116 public:
117 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(),
118 _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { }
119
120 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
121 HeapRegion* hr = region_for_card(card_ptr);
122
123 // Should only dirty cards in regions that won't be freed.
124 if (!will_become_free(hr)) {
125 *card_ptr = CardTableModRefBS::dirty_card_val();
126 _num_dirtied++;
127 }
128
129 return true;
130 }
131
132 size_t num_dirtied() const { return _num_dirtied; }
133 };
134
135
136 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
137 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
138 }
139
140 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
141 // The from card cache is not the memory that is actually committed. So we cannot
142 // take advantage of the zero_filled parameter.
143 reset_from_card_cache(start_idx, num_regions);
144 }
145
146
147 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
148 MemRegion mr) {
149 return new HeapRegion(hrs_index, bot(), mr);
150 }
151
152 // Private methods.
153
154 HeapRegion*
155 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
156 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
157 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
158 if (!_secondary_free_list.is_empty()) {
159 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
160 "secondary_free_list has %u entries",
161 _secondary_free_list.length());
162 // It looks as if there are free regions available on the
163 // secondary_free_list. Let's move them to the free_list and try
164 // again to allocate from it.
165 append_secondary_free_list();
166
167 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
168 "empty we should have moved at least one entry to the free_list");
169 HeapRegion* res = _hrm.allocate_free_region(is_old);
170 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
171 "allocated " HR_FORMAT " from secondary_free_list",
172 HR_FORMAT_PARAMS(res));
173 return res;
174 }
175
176 // Wait here until we get notified either when (a) there are no
177 // more free regions coming or (b) some regions have been moved on
178 // the secondary_free_list.
179 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
180 }
181
182 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
183 "could not allocate from secondary_free_list");
184 return NULL;
185 }
186
187 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
188 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
189 "the only time we use this to allocate a humongous region is "
190 "when we are allocating a single humongous region");
191
192 HeapRegion* res;
193 if (G1StressConcRegionFreeing) {
194 if (!_secondary_free_list.is_empty()) {
195 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
196 "forced to look at the secondary_free_list");
197 res = new_region_try_secondary_free_list(is_old);
198 if (res != NULL) {
199 return res;
200 }
201 }
202 }
203
204 res = _hrm.allocate_free_region(is_old);
205
206 if (res == NULL) {
207 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
208 "res == NULL, trying the secondary_free_list");
209 res = new_region_try_secondary_free_list(is_old);
210 }
211 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
212 // Currently, only attempts to allocate GC alloc regions set
213 // do_expand to true. So, we should only reach here during a
214 // safepoint. If this assumption changes we might have to
215 // reconsider the use of _expand_heap_after_alloc_failure.
216 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
217
218 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
219 word_size * HeapWordSize);
220
221 if (expand(word_size * HeapWordSize)) {
222 // Given that expand() succeeded in expanding the heap, and we
223 // always expand the heap by an amount aligned to the heap
224 // region size, the free list should in theory not be empty.
225 // In either case allocate_free_region() will check for NULL.
226 res = _hrm.allocate_free_region(is_old);
227 } else {
228 _expand_heap_after_alloc_failure = false;
229 }
230 }
231 return res;
232 }
233
234 HeapWord*
235 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
236 uint num_regions,
237 size_t word_size,
238 AllocationContext_t context) {
239 assert(first != G1_NO_HRM_INDEX, "pre-condition");
240 assert(is_humongous(word_size), "word_size should be humongous");
241 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
242
243 // Index of last region in the series.
244 uint last = first + num_regions - 1;
245
246 // We need to initialize the region(s) we just discovered. This is
247 // a bit tricky given that it can happen concurrently with
248 // refinement threads refining cards on these regions and
249 // potentially wanting to refine the BOT as they are scanning
250 // those cards (this can happen shortly after a cleanup; see CR
251 // 6991377). So we have to set up the region(s) carefully and in
252 // a specific order.
253
254 // The word size sum of all the regions we will allocate.
255 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
256 assert(word_size <= word_size_sum, "sanity");
257
258 // This will be the "starts humongous" region.
259 HeapRegion* first_hr = region_at(first);
260 // The header of the new object will be placed at the bottom of
261 // the first region.
262 HeapWord* new_obj = first_hr->bottom();
263 // This will be the new top of the new object.
264 HeapWord* obj_top = new_obj + word_size;
265
266 // First, we need to zero the header of the space that we will be
267 // allocating. When we update top further down, some refinement
268 // threads might try to scan the region. By zeroing the header we
269 // ensure that any thread that will try to scan the region will
270 // come across the zero klass word and bail out.
271 //
272 // NOTE: It would not have been correct to have used
273 // CollectedHeap::fill_with_object() and make the space look like
274 // an int array. The thread that is doing the allocation will
275 // later update the object header to a potentially different array
276 // type and, for a very short period of time, the klass and length
277 // fields will be inconsistent. This could cause a refinement
278 // thread to calculate the object size incorrectly.
279 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
280
281 // Next, pad out the unused tail of the last region with filler
282 // objects, for improved usage accounting.
283 // How many words we use for filler objects.
284 size_t word_fill_size = word_size_sum - word_size;
285
286 // How many words memory we "waste" which cannot hold a filler object.
287 size_t words_not_fillable = 0;
288
289 if (word_fill_size >= min_fill_size()) {
290 fill_with_objects(obj_top, word_fill_size);
291 } else if (word_fill_size > 0) {
292 // We have space to fill, but we cannot fit an object there.
293 words_not_fillable = word_fill_size;
294 word_fill_size = 0;
295 }
296
297 // We will set up the first region as "starts humongous". This
298 // will also update the BOT covering all the regions to reflect
299 // that there is a single object that starts at the bottom of the
300 // first region.
301 first_hr->set_starts_humongous(obj_top, word_fill_size);
302 first_hr->set_allocation_context(context);
303 // Then, if there are any, we will set up the "continues
304 // humongous" regions.
305 HeapRegion* hr = NULL;
306 for (uint i = first + 1; i <= last; ++i) {
307 hr = region_at(i);
308 hr->set_continues_humongous(first_hr);
309 hr->set_allocation_context(context);
310 }
311
312 // Up to this point no concurrent thread would have been able to
313 // do any scanning on any region in this series. All the top
314 // fields still point to bottom, so the intersection between
315 // [bottom,top] and [card_start,card_end] will be empty. Before we
316 // update the top fields, we'll do a storestore to make sure that
317 // no thread sees the update to top before the zeroing of the
318 // object header and the BOT initialization.
319 OrderAccess::storestore();
320
321 // Now, we will update the top fields of the "continues humongous"
322 // regions except the last one.
323 for (uint i = first; i < last; ++i) {
324 hr = region_at(i);
325 hr->set_top(hr->end());
326 }
327
328 hr = region_at(last);
329 // If we cannot fit a filler object, we must set top to the end
330 // of the humongous object, otherwise we cannot iterate the heap
331 // and the BOT will not be complete.
332 hr->set_top(hr->end() - words_not_fillable);
333
334 assert(hr->bottom() < obj_top && obj_top <= hr->end(),
335 "obj_top should be in last region");
336
337 _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
338
339 assert(words_not_fillable == 0 ||
340 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
341 "Miscalculation in humongous allocation");
342
343 increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
344
345 for (uint i = first; i <= last; ++i) {
346 hr = region_at(i);
347 _humongous_set.add(hr);
348 _hr_printer.alloc(hr);
349 }
350
351 return new_obj;
352 }
353
354 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
355 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
356 return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
357 }
358
359 // If could fit into free regions w/o expansion, try.
360 // Otherwise, if can expand, do so.
361 // Otherwise, if using ex regions might help, try with ex given back.
362 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
363 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
364
365 _verifier->verify_region_sets_optional();
366
367 uint first = G1_NO_HRM_INDEX;
368 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
369
370 if (obj_regions == 1) {
371 // Only one region to allocate, try to use a fast path by directly allocating
372 // from the free lists. Do not try to expand here, we will potentially do that
373 // later.
374 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
375 if (hr != NULL) {
376 first = hr->hrm_index();
377 }
378 } else {
379 // We can't allocate humongous regions spanning more than one region while
380 // cleanupComplete() is running, since some of the regions we find to be
381 // empty might not yet be added to the free list. It is not straightforward
382 // to know in which list they are on so that we can remove them. We only
383 // need to do this if we need to allocate more than one region to satisfy the
384 // current humongous allocation request. If we are only allocating one region
385 // we use the one-region region allocation code (see above), that already
386 // potentially waits for regions from the secondary free list.
387 wait_while_free_regions_coming();
388 append_secondary_free_list_if_not_empty_with_lock();
389
390 // Policy: Try only empty regions (i.e. already committed first). Maybe we
391 // are lucky enough to find some.
392 first = _hrm.find_contiguous_only_empty(obj_regions);
393 if (first != G1_NO_HRM_INDEX) {
394 _hrm.allocate_free_regions_starting_at(first, obj_regions);
395 }
396 }
397
398 if (first == G1_NO_HRM_INDEX) {
399 // Policy: We could not find enough regions for the humongous object in the
400 // free list. Look through the heap to find a mix of free and uncommitted regions.
401 // If so, try expansion.
402 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
403 if (first != G1_NO_HRM_INDEX) {
404 // We found something. Make sure these regions are committed, i.e. expand
405 // the heap. Alternatively we could do a defragmentation GC.
406 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
407 word_size * HeapWordSize);
408
409 _hrm.expand_at(first, obj_regions, workers());
410 g1_policy()->record_new_heap_size(num_regions());
411
412 #ifdef ASSERT
413 for (uint i = first; i < first + obj_regions; ++i) {
414 HeapRegion* hr = region_at(i);
415 assert(hr->is_free(), "sanity");
416 assert(hr->is_empty(), "sanity");
417 assert(is_on_master_free_list(hr), "sanity");
418 }
419 #endif
420 _hrm.allocate_free_regions_starting_at(first, obj_regions);
421 } else {
422 // Policy: Potentially trigger a defragmentation GC.
423 }
424 }
425
426 HeapWord* result = NULL;
427 if (first != G1_NO_HRM_INDEX) {
428 result = humongous_obj_allocate_initialize_regions(first, obj_regions,
429 word_size, context);
430 assert(result != NULL, "it should always return a valid result");
431
432 // A successful humongous object allocation changes the used space
433 // information of the old generation so we need to recalculate the
434 // sizes and update the jstat counters here.
435 g1mm()->update_sizes();
436 }
437
438 _verifier->verify_region_sets_optional();
439
440 return result;
441 }
442
443 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
444 assert_heap_not_locked_and_not_at_safepoint();
445 assert(!is_humongous(word_size), "we do not allow humongous TLABs");
446
447 uint dummy_gc_count_before;
448 uint dummy_gclocker_retry_count = 0;
449 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
450 }
451
452 HeapWord*
453 G1CollectedHeap::mem_allocate(size_t word_size,
454 bool* gc_overhead_limit_was_exceeded) {
455 assert_heap_not_locked_and_not_at_safepoint();
456
457 // Loop until the allocation is satisfied, or unsatisfied after GC.
458 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
459 uint gc_count_before;
460
461 HeapWord* result = NULL;
462 if (!is_humongous(word_size)) {
463 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
464 } else {
465 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
466 }
467 if (result != NULL) {
468 return result;
469 }
470
471 // Create the garbage collection operation...
472 VM_G1CollectForAllocation op(gc_count_before, word_size);
473 op.set_allocation_context(AllocationContext::current());
474
475 // ...and get the VM thread to execute it.
476 VMThread::execute(&op);
477
478 if (op.prologue_succeeded() && op.pause_succeeded()) {
479 // If the operation was successful we'll return the result even
480 // if it is NULL. If the allocation attempt failed immediately
481 // after a Full GC, it's unlikely we'll be able to allocate now.
482 HeapWord* result = op.result();
483 if (result != NULL && !is_humongous(word_size)) {
484 // Allocations that take place on VM operations do not do any
485 // card dirtying and we have to do it here. We only have to do
486 // this for non-humongous allocations, though.
487 dirty_young_block(result, word_size);
488 }
489 return result;
490 } else {
491 if (gclocker_retry_count > GCLockerRetryAllocationCount) {
492 return NULL;
493 }
494 assert(op.result() == NULL,
495 "the result should be NULL if the VM op did not succeed");
496 }
497
498 // Give a warning if we seem to be looping forever.
499 if ((QueuedAllocationWarningCount > 0) &&
500 (try_count % QueuedAllocationWarningCount == 0)) {
501 log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count);
502 }
503 }
504
505 ShouldNotReachHere();
506 return NULL;
507 }
508
509 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
510 AllocationContext_t context,
511 uint* gc_count_before_ret,
512 uint* gclocker_retry_count_ret) {
513 // Make sure you read the note in attempt_allocation_humongous().
514
515 assert_heap_not_locked_and_not_at_safepoint();
516 assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
517 "be called for humongous allocation requests");
518
519 // We should only get here after the first-level allocation attempt
520 // (attempt_allocation()) failed to allocate.
521
522 // We will loop until a) we manage to successfully perform the
523 // allocation or b) we successfully schedule a collection which
524 // fails to perform the allocation. b) is the only case when we'll
525 // return NULL.
526 HeapWord* result = NULL;
527 for (int try_count = 1; /* we'll return */; try_count += 1) {
528 bool should_try_gc;
529 uint gc_count_before;
530
531 {
532 MutexLockerEx x(Heap_lock);
533 result = _allocator->attempt_allocation_locked(word_size, context);
534 if (result != NULL) {
535 return result;
536 }
537
538 if (GCLocker::is_active_and_needs_gc()) {
539 if (g1_policy()->can_expand_young_list()) {
540 // No need for an ergo verbose message here,
541 // can_expand_young_list() does this when it returns true.
542 result = _allocator->attempt_allocation_force(word_size, context);
543 if (result != NULL) {
544 return result;
545 }
546 }
547 should_try_gc = false;
548 } else {
549 // The GCLocker may not be active but the GCLocker initiated
550 // GC may not yet have been performed (GCLocker::needs_gc()
551 // returns true). In this case we do not try this GC and
552 // wait until the GCLocker initiated GC is performed, and
553 // then retry the allocation.
554 if (GCLocker::needs_gc()) {
555 should_try_gc = false;
556 } else {
557 // Read the GC count while still holding the Heap_lock.
558 gc_count_before = total_collections();
559 should_try_gc = true;
560 }
561 }
562 }
563
564 if (should_try_gc) {
565 bool succeeded;
566 result = do_collection_pause(word_size, gc_count_before, &succeeded,
567 GCCause::_g1_inc_collection_pause);
568 if (result != NULL) {
569 assert(succeeded, "only way to get back a non-NULL result");
570 return result;
571 }
572
573 if (succeeded) {
574 // If we get here we successfully scheduled a collection which
575 // failed to allocate. No point in trying to allocate
576 // further. We'll just return NULL.
577 MutexLockerEx x(Heap_lock);
578 *gc_count_before_ret = total_collections();
579 return NULL;
580 }
581 } else {
582 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
583 MutexLockerEx x(Heap_lock);
584 *gc_count_before_ret = total_collections();
585 return NULL;
586 }
587 // The GCLocker is either active or the GCLocker initiated
588 // GC has not yet been performed. Stall until it is and
589 // then retry the allocation.
590 GCLocker::stall_until_clear();
591 (*gclocker_retry_count_ret) += 1;
592 }
593
594 // We can reach here if we were unsuccessful in scheduling a
595 // collection (because another thread beat us to it) or if we were
596 // stalled due to the GC locker. In either can we should retry the
597 // allocation attempt in case another thread successfully
598 // performed a collection and reclaimed enough space. We do the
599 // first attempt (without holding the Heap_lock) here and the
600 // follow-on attempt will be at the start of the next loop
601 // iteration (after taking the Heap_lock).
602 result = _allocator->attempt_allocation(word_size, context);
603 if (result != NULL) {
604 return result;
605 }
606
607 // Give a warning if we seem to be looping forever.
608 if ((QueuedAllocationWarningCount > 0) &&
609 (try_count % QueuedAllocationWarningCount == 0)) {
610 log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() "
611 "retries %d times", try_count);
612 }
613 }
614
615 ShouldNotReachHere();
616 return NULL;
617 }
618
619 void G1CollectedHeap::begin_archive_alloc_range(bool open) {
620 assert_at_safepoint(true /* should_be_vm_thread */);
621 if (_archive_allocator == NULL) {
622 _archive_allocator = G1ArchiveAllocator::create_allocator(this, open);
623 }
624 }
625
626 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
627 // Allocations in archive regions cannot be of a size that would be considered
628 // humongous even for a minimum-sized region, because G1 region sizes/boundaries
629 // may be different at archive-restore time.
630 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
631 }
632
633 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
634 assert_at_safepoint(true /* should_be_vm_thread */);
635 assert(_archive_allocator != NULL, "_archive_allocator not initialized");
636 if (is_archive_alloc_too_large(word_size)) {
637 return NULL;
638 }
639 return _archive_allocator->archive_mem_allocate(word_size);
640 }
641
642 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
643 size_t end_alignment_in_bytes) {
644 assert_at_safepoint(true /* should_be_vm_thread */);
645 assert(_archive_allocator != NULL, "_archive_allocator not initialized");
646
647 // Call complete_archive to do the real work, filling in the MemRegion
648 // array with the archive regions.
649 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
650 delete _archive_allocator;
651 _archive_allocator = NULL;
652 }
653
654 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
655 assert(ranges != NULL, "MemRegion array NULL");
656 assert(count != 0, "No MemRegions provided");
657 MemRegion reserved = _hrm.reserved();
658 for (size_t i = 0; i < count; i++) {
659 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
660 return false;
661 }
662 }
663 return true;
664 }
665
666 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges,
667 size_t count,
668 bool open) {
669 assert(!is_init_completed(), "Expect to be called at JVM init time");
670 assert(ranges != NULL, "MemRegion array NULL");
671 assert(count != 0, "No MemRegions provided");
672 MutexLockerEx x(Heap_lock);
673
674 MemRegion reserved = _hrm.reserved();
675 HeapWord* prev_last_addr = NULL;
676 HeapRegion* prev_last_region = NULL;
677
678 // Temporarily disable pretouching of heap pages. This interface is used
679 // when mmap'ing archived heap data in, so pre-touching is wasted.
680 FlagSetting fs(AlwaysPreTouch, false);
681
682 // Enable archive object checking used by G1MarkSweep. We have to let it know
683 // about each archive range, so that objects in those ranges aren't marked.
684 G1ArchiveAllocator::enable_archive_object_check();
685
686 // For each specified MemRegion range, allocate the corresponding G1
687 // regions and mark them as archive regions. We expect the ranges
688 // in ascending starting address order, without overlap.
689 for (size_t i = 0; i < count; i++) {
690 MemRegion curr_range = ranges[i];
691 HeapWord* start_address = curr_range.start();
692 size_t word_size = curr_range.word_size();
693 HeapWord* last_address = curr_range.last();
694 size_t commits = 0;
695
696 guarantee(reserved.contains(start_address) && reserved.contains(last_address),
697 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
698 p2i(start_address), p2i(last_address));
699 guarantee(start_address > prev_last_addr,
700 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
701 p2i(start_address), p2i(prev_last_addr));
702 prev_last_addr = last_address;
703
704 // Check for ranges that start in the same G1 region in which the previous
705 // range ended, and adjust the start address so we don't try to allocate
706 // the same region again. If the current range is entirely within that
707 // region, skip it, just adjusting the recorded top.
708 HeapRegion* start_region = _hrm.addr_to_region(start_address);
709 if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
710 start_address = start_region->end();
711 if (start_address > last_address) {
712 increase_used(word_size * HeapWordSize);
713 start_region->set_top(last_address + 1);
714 continue;
715 }
716 start_region->set_top(start_address);
717 curr_range = MemRegion(start_address, last_address + 1);
718 start_region = _hrm.addr_to_region(start_address);
719 }
720
721 // Perform the actual region allocation, exiting if it fails.
722 // Then note how much new space we have allocated.
723 if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) {
724 return false;
725 }
726 increase_used(word_size * HeapWordSize);
727 if (commits != 0) {
728 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
729 HeapRegion::GrainWords * HeapWordSize * commits);
730
731 }
732
733 // Mark each G1 region touched by the range as archive, add it to
734 // the old set, and set the allocation context and top.
735 HeapRegion* curr_region = _hrm.addr_to_region(start_address);
736 HeapRegion* last_region = _hrm.addr_to_region(last_address);
737 prev_last_region = last_region;
738
739 while (curr_region != NULL) {
740 assert(curr_region->is_empty() && !curr_region->is_pinned(),
741 "Region already in use (index %u)", curr_region->hrm_index());
742 curr_region->set_allocation_context(AllocationContext::system());
743 if (open) {
744 curr_region->set_open_archive();
745 } else {
746 curr_region->set_closed_archive();
747 }
748 _hr_printer.alloc(curr_region);
749 _old_set.add(curr_region);
750 HeapWord* top;
751 HeapRegion* next_region;
752 if (curr_region != last_region) {
753 top = curr_region->end();
754 next_region = _hrm.next_region_in_heap(curr_region);
755 } else {
756 top = last_address + 1;
757 next_region = NULL;
758 }
759 curr_region->set_top(top);
760 curr_region->set_first_dead(top);
761 curr_region->set_end_of_live(top);
762 curr_region = next_region;
763 }
764
765 // Notify mark-sweep of the archive
766 G1ArchiveAllocator::set_range_archive(curr_range, open);
767 }
768 return true;
769 }
770
771 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
772 assert(!is_init_completed(), "Expect to be called at JVM init time");
773 assert(ranges != NULL, "MemRegion array NULL");
774 assert(count != 0, "No MemRegions provided");
775 MemRegion reserved = _hrm.reserved();
776 HeapWord *prev_last_addr = NULL;
777 HeapRegion* prev_last_region = NULL;
778
779 // For each MemRegion, create filler objects, if needed, in the G1 regions
780 // that contain the address range. The address range actually within the
781 // MemRegion will not be modified. That is assumed to have been initialized
782 // elsewhere, probably via an mmap of archived heap data.
783 MutexLockerEx x(Heap_lock);
784 for (size_t i = 0; i < count; i++) {
785 HeapWord* start_address = ranges[i].start();
786 HeapWord* last_address = ranges[i].last();
787
788 assert(reserved.contains(start_address) && reserved.contains(last_address),
789 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
790 p2i(start_address), p2i(last_address));
791 assert(start_address > prev_last_addr,
792 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
793 p2i(start_address), p2i(prev_last_addr));
794
795 HeapRegion* start_region = _hrm.addr_to_region(start_address);
796 HeapRegion* last_region = _hrm.addr_to_region(last_address);
797 HeapWord* bottom_address = start_region->bottom();
798
799 // Check for a range beginning in the same region in which the
800 // previous one ended.
801 if (start_region == prev_last_region) {
802 bottom_address = prev_last_addr + 1;
803 }
804
805 // Verify that the regions were all marked as archive regions by
806 // alloc_archive_regions.
807 HeapRegion* curr_region = start_region;
808 while (curr_region != NULL) {
809 guarantee(curr_region->is_archive(),
810 "Expected archive region at index %u", curr_region->hrm_index());
811 if (curr_region != last_region) {
812 curr_region = _hrm.next_region_in_heap(curr_region);
813 } else {
814 curr_region = NULL;
815 }
816 }
817
818 prev_last_addr = last_address;
819 prev_last_region = last_region;
820
821 // Fill the memory below the allocated range with dummy object(s),
822 // if the region bottom does not match the range start, or if the previous
823 // range ended within the same G1 region, and there is a gap.
824 if (start_address != bottom_address) {
825 size_t fill_size = pointer_delta(start_address, bottom_address);
826 G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
827 increase_used(fill_size * HeapWordSize);
828 }
829 }
830 }
831
832 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size,
833 uint* gc_count_before_ret,
834 uint* gclocker_retry_count_ret) {
835 assert_heap_not_locked_and_not_at_safepoint();
836 assert(!is_humongous(word_size), "attempt_allocation() should not "
837 "be called for humongous allocation requests");
838
839 AllocationContext_t context = AllocationContext::current();
840 HeapWord* result = _allocator->attempt_allocation(word_size, context);
841
842 if (result == NULL) {
843 result = attempt_allocation_slow(word_size,
844 context,
845 gc_count_before_ret,
846 gclocker_retry_count_ret);
847 }
848 assert_heap_not_locked();
849 if (result != NULL) {
850 dirty_young_block(result, word_size);
851 }
852 return result;
853 }
854
855 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
856 assert(!is_init_completed(), "Expect to be called at JVM init time");
857 assert(ranges != NULL, "MemRegion array NULL");
858 assert(count != 0, "No MemRegions provided");
859 MemRegion reserved = _hrm.reserved();
860 HeapWord* prev_last_addr = NULL;
861 HeapRegion* prev_last_region = NULL;
862 size_t size_used = 0;
863 size_t uncommitted_regions = 0;
864
865 // For each Memregion, free the G1 regions that constitute it, and
866 // notify mark-sweep that the range is no longer to be considered 'archive.'
867 MutexLockerEx x(Heap_lock);
868 for (size_t i = 0; i < count; i++) {
869 HeapWord* start_address = ranges[i].start();
870 HeapWord* last_address = ranges[i].last();
871
872 assert(reserved.contains(start_address) && reserved.contains(last_address),
873 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
874 p2i(start_address), p2i(last_address));
875 assert(start_address > prev_last_addr,
876 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
877 p2i(start_address), p2i(prev_last_addr));
878 size_used += ranges[i].byte_size();
879 prev_last_addr = last_address;
880
881 HeapRegion* start_region = _hrm.addr_to_region(start_address);
882 HeapRegion* last_region = _hrm.addr_to_region(last_address);
883
884 // Check for ranges that start in the same G1 region in which the previous
885 // range ended, and adjust the start address so we don't try to free
886 // the same region again. If the current range is entirely within that
887 // region, skip it.
888 if (start_region == prev_last_region) {
889 start_address = start_region->end();
890 if (start_address > last_address) {
891 continue;
892 }
893 start_region = _hrm.addr_to_region(start_address);
894 }
895 prev_last_region = last_region;
896
897 // After verifying that each region was marked as an archive region by
898 // alloc_archive_regions, set it free and empty and uncommit it.
899 HeapRegion* curr_region = start_region;
900 while (curr_region != NULL) {
901 guarantee(curr_region->is_archive(),
902 "Expected archive region at index %u", curr_region->hrm_index());
903 uint curr_index = curr_region->hrm_index();
904 _old_set.remove(curr_region);
905 curr_region->set_free();
906 curr_region->set_top(curr_region->bottom());
907 if (curr_region != last_region) {
908 curr_region = _hrm.next_region_in_heap(curr_region);
909 } else {
910 curr_region = NULL;
911 }
912 _hrm.shrink_at(curr_index, 1);
913 uncommitted_regions++;
914 }
915
916 // Notify mark-sweep that this is no longer an archive range.
917 G1ArchiveAllocator::set_range_archive(ranges[i], false);
918 }
919
920 if (uncommitted_regions != 0) {
921 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
922 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
923 }
924 decrease_used(size_used);
925 }
926
927 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
928 uint* gc_count_before_ret,
929 uint* gclocker_retry_count_ret) {
930 // The structure of this method has a lot of similarities to
931 // attempt_allocation_slow(). The reason these two were not merged
932 // into a single one is that such a method would require several "if
933 // allocation is not humongous do this, otherwise do that"
934 // conditional paths which would obscure its flow. In fact, an early
935 // version of this code did use a unified method which was harder to
936 // follow and, as a result, it had subtle bugs that were hard to
937 // track down. So keeping these two methods separate allows each to
938 // be more readable. It will be good to keep these two in sync as
939 // much as possible.
940
941 assert_heap_not_locked_and_not_at_safepoint();
942 assert(is_humongous(word_size), "attempt_allocation_humongous() "
943 "should only be called for humongous allocations");
944
945 // Humongous objects can exhaust the heap quickly, so we should check if we
946 // need to start a marking cycle at each humongous object allocation. We do
947 // the check before we do the actual allocation. The reason for doing it
948 // before the allocation is that we avoid having to keep track of the newly
949 // allocated memory while we do a GC.
950 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
951 word_size)) {
952 collect(GCCause::_g1_humongous_allocation);
953 }
954
955 // We will loop until a) we manage to successfully perform the
956 // allocation or b) we successfully schedule a collection which
957 // fails to perform the allocation. b) is the only case when we'll
958 // return NULL.
959 HeapWord* result = NULL;
960 for (int try_count = 1; /* we'll return */; try_count += 1) {
961 bool should_try_gc;
962 uint gc_count_before;
963
964 {
965 MutexLockerEx x(Heap_lock);
966
967 // Given that humongous objects are not allocated in young
968 // regions, we'll first try to do the allocation without doing a
969 // collection hoping that there's enough space in the heap.
970 result = humongous_obj_allocate(word_size, AllocationContext::current());
971 if (result != NULL) {
972 size_t size_in_regions = humongous_obj_size_in_regions(word_size);
973 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
974 return result;
975 }
976
977 if (GCLocker::is_active_and_needs_gc()) {
978 should_try_gc = false;
979 } else {
980 // The GCLocker may not be active but the GCLocker initiated
981 // GC may not yet have been performed (GCLocker::needs_gc()
982 // returns true). In this case we do not try this GC and
983 // wait until the GCLocker initiated GC is performed, and
984 // then retry the allocation.
985 if (GCLocker::needs_gc()) {
986 should_try_gc = false;
987 } else {
988 // Read the GC count while still holding the Heap_lock.
989 gc_count_before = total_collections();
990 should_try_gc = true;
991 }
992 }
993 }
994
995 if (should_try_gc) {
996 // If we failed to allocate the humongous object, we should try to
997 // do a collection pause (if we're allowed) in case it reclaims
998 // enough space for the allocation to succeed after the pause.
999
1000 bool succeeded;
1001 result = do_collection_pause(word_size, gc_count_before, &succeeded,
1002 GCCause::_g1_humongous_allocation);
1003 if (result != NULL) {
1004 assert(succeeded, "only way to get back a non-NULL result");
1005 return result;
1006 }
1007
1008 if (succeeded) {
1009 // If we get here we successfully scheduled a collection which
1010 // failed to allocate. No point in trying to allocate
1011 // further. We'll just return NULL.
1012 MutexLockerEx x(Heap_lock);
1013 *gc_count_before_ret = total_collections();
1014 return NULL;
1015 }
1016 } else {
1017 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1018 MutexLockerEx x(Heap_lock);
1019 *gc_count_before_ret = total_collections();
1020 return NULL;
1021 }
1022 // The GCLocker is either active or the GCLocker initiated
1023 // GC has not yet been performed. Stall until it is and
1024 // then retry the allocation.
1025 GCLocker::stall_until_clear();
1026 (*gclocker_retry_count_ret) += 1;
1027 }
1028
1029 // We can reach here if we were unsuccessful in scheduling a
1030 // collection (because another thread beat us to it) or if we were
1031 // stalled due to the GC locker. In either can we should retry the
1032 // allocation attempt in case another thread successfully
1033 // performed a collection and reclaimed enough space. Give a
1034 // warning if we seem to be looping forever.
1035
1036 if ((QueuedAllocationWarningCount > 0) &&
1037 (try_count % QueuedAllocationWarningCount == 0)) {
1038 log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() "
1039 "retries %d times", try_count);
1040 }
1041 }
1042
1043 ShouldNotReachHere();
1044 return NULL;
1045 }
1046
1047 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1048 AllocationContext_t context,
1049 bool expect_null_mutator_alloc_region) {
1050 assert_at_safepoint(true /* should_be_vm_thread */);
1051 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region,
1052 "the current alloc region was unexpectedly found to be non-NULL");
1053
1054 if (!is_humongous(word_size)) {
1055 return _allocator->attempt_allocation_locked(word_size, context);
1056 } else {
1057 HeapWord* result = humongous_obj_allocate(word_size, context);
1058 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1059 collector_state()->set_initiate_conc_mark_if_possible(true);
1060 }
1061 return result;
1062 }
1063
1064 ShouldNotReachHere();
1065 }
1066
1067 class PostCompactionPrinterClosure: public HeapRegionClosure {
1068 private:
1069 G1HRPrinter* _hr_printer;
1070 public:
1071 bool doHeapRegion(HeapRegion* hr) {
1072 assert(!hr->is_young(), "not expecting to find young regions");
1073 _hr_printer->post_compaction(hr);
1074 return false;
1075 }
1076
1077 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1078 : _hr_printer(hr_printer) { }
1079 };
1080
1081 void G1CollectedHeap::print_hrm_post_compaction() {
1082 if (_hr_printer.is_active()) {
1083 PostCompactionPrinterClosure cl(hr_printer());
1084 heap_region_iterate(&cl);
1085 }
1086
1087 }
1088
1089 void G1CollectedHeap::abort_concurrent_cycle() {
1090 // Note: When we have a more flexible GC logging framework that
1091 // allows us to add optional attributes to a GC log record we
1092 // could consider timing and reporting how long we wait in the
1093 // following two methods.
1094 wait_while_free_regions_coming();
1095 // If we start the compaction before the CM threads finish
1096 // scanning the root regions we might trip them over as we'll
1097 // be moving objects / updating references. So let's wait until
1098 // they are done. By telling them to abort, they should complete
1099 // early.
1100 _cm->root_regions()->abort();
1101 _cm->root_regions()->wait_until_scan_finished();
1102 append_secondary_free_list_if_not_empty_with_lock();
1103
1104 // Disable discovery and empty the discovered lists
1105 // for the CM ref processor.
1106 ref_processor_cm()->disable_discovery();
1107 ref_processor_cm()->abandon_partial_discovery();
1108 ref_processor_cm()->verify_no_references_recorded();
1109
1110 // Abandon current iterations of concurrent marking and concurrent
1111 // refinement, if any are in progress.
1112 concurrent_mark()->abort();
1113 }
1114
1115 void G1CollectedHeap::prepare_heap_for_full_collection() {
1116 // Make sure we'll choose a new allocation region afterwards.
1117 _allocator->release_mutator_alloc_region();
1118 _allocator->abandon_gc_alloc_regions();
1119 g1_rem_set()->cleanupHRRS();
1120
1121 // We may have added regions to the current incremental collection
1122 // set between the last GC or pause and now. We need to clear the
1123 // incremental collection set and then start rebuilding it afresh
1124 // after this full GC.
1125 abandon_collection_set(collection_set());
1126
1127 tear_down_region_sets(false /* free_list_only */);
1128 collector_state()->set_gcs_are_young(true);
1129 }
1130
1131 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) {
1132 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1133 assert(used() == recalculate_used(), "Should be equal");
1134 _verifier->verify_region_sets_optional();
1135 _verifier->verify_before_gc();
1136 _verifier->check_bitmaps("Full GC Start");
1137 }
1138
1139 void G1CollectedHeap::prepare_heap_for_mutators() {
1140 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1141 ClassLoaderDataGraph::purge();
1142 MetaspaceAux::verify_metrics();
1143
1144 // Prepare heap for normal collections.
1145 assert(num_free_regions() == 0, "we should not have added any free regions");
1146 rebuild_region_sets(false /* free_list_only */);
1147 abort_refinement();
1148 resize_if_necessary_after_full_collection();
1149
1150 // Rebuild the strong code root lists for each region
1151 rebuild_strong_code_roots();
1152
1153 // Start a new incremental collection set for the next pause
1154 start_new_collection_set();
1155
1156 _allocator->init_mutator_alloc_region();
1157
1158 // Post collection state updates.
1159 MetaspaceGC::compute_new_size();
1160 }
1161
1162 void G1CollectedHeap::abort_refinement() {
1163 if (_hot_card_cache->use_cache()) {
1164 _hot_card_cache->reset_hot_cache();
1165 }
1166
1167 // Discard all remembered set updates.
1168 JavaThread::dirty_card_queue_set().abandon_logs();
1169 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1170 }
1171
1172 void G1CollectedHeap::verify_after_full_collection() {
1173 check_gc_time_stamps();
1174 _hrm.verify_optional();
1175 _verifier->verify_region_sets_optional();
1176 _verifier->verify_after_gc();
1177 // Clear the previous marking bitmap, if needed for bitmap verification.
1178 // Note we cannot do this when we clear the next marking bitmap in
1179 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1180 // objects marked during a full GC against the previous bitmap.
1181 // But we need to clear it before calling check_bitmaps below since
1182 // the full GC has compacted objects and updated TAMS but not updated
1183 // the prev bitmap.
1184 if (G1VerifyBitmaps) {
1185 GCTraceTime(Debug, gc)("Clear Bitmap for Verification");
1186 _cm->clear_prev_bitmap(workers());
1187 }
1188 _verifier->check_bitmaps("Full GC End");
1189
1190 // At this point there should be no regions in the
1191 // entire heap tagged as young.
1192 assert(check_young_list_empty(), "young list should be empty at this point");
1193
1194 // Note: since we've just done a full GC, concurrent
1195 // marking is no longer active. Therefore we need not
1196 // re-enable reference discovery for the CM ref processor.
1197 // That will be done at the start of the next marking cycle.
1198 // We also know that the STW processor should no longer
1199 // discover any new references.
1200 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1201 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1202 ref_processor_stw()->verify_no_references_recorded();
1203 ref_processor_cm()->verify_no_references_recorded();
1204 }
1205
1206 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) {
1207 // Post collection logging.
1208 // We should do this after we potentially resize the heap so
1209 // that all the COMMIT / UNCOMMIT events are generated before
1210 // the compaction events.
1211 print_hrm_post_compaction();
1212 heap_transition->print();
1213 print_heap_after_gc();
1214 print_heap_regions();
1215 #ifdef TRACESPINNING
1216 ParallelTaskTerminator::print_termination_counts();
1217 #endif
1218 }
1219
1220 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1221 bool clear_all_soft_refs) {
1222 assert_at_safepoint(true /* should_be_vm_thread */);
1223
1224 if (GCLocker::check_active_before_gc()) {
1225 // Full GC was not completed.
1226 return false;
1227 }
1228
1229 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1230 collector_policy()->should_clear_all_soft_refs();
1231
1232 G1FullCollector collector(this, explicit_gc, do_clear_all_soft_refs);
1233 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1234
1235 collector.prepare_collection();
1236 collector.collect();
1237 collector.complete_collection();
1238
1239 // Full collection was successfully completed.
1240 return true;
1241 }
1242
1243 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1244 // Currently, there is no facility in the do_full_collection(bool) API to notify
1245 // the caller that the collection did not succeed (e.g., because it was locked
1246 // out by the GC locker). So, right now, we'll ignore the return value.
1247 bool dummy = do_full_collection(true, /* explicit_gc */
1248 clear_all_soft_refs);
1249 }
1250
1251 void G1CollectedHeap::resize_if_necessary_after_full_collection() {
1252 // Capacity, free and used after the GC counted as full regions to
1253 // include the waste in the following calculations.
1254 const size_t capacity_after_gc = capacity();
1255 const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes();
1256
1257 // This is enforced in arguments.cpp.
1258 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1259 "otherwise the code below doesn't make sense");
1260
1261 // We don't have floating point command-line arguments
1262 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1263 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1264 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1265 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1266
1267 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1268 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1269
1270 // We have to be careful here as these two calculations can overflow
1271 // 32-bit size_t's.
1272 double used_after_gc_d = (double) used_after_gc;
1273 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1274 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1275
1276 // Let's make sure that they are both under the max heap size, which
1277 // by default will make them fit into a size_t.
1278 double desired_capacity_upper_bound = (double) max_heap_size;
1279 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1280 desired_capacity_upper_bound);
1281 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1282 desired_capacity_upper_bound);
1283
1284 // We can now safely turn them into size_t's.
1285 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1286 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1287
1288 // This assert only makes sense here, before we adjust them
1289 // with respect to the min and max heap size.
1290 assert(minimum_desired_capacity <= maximum_desired_capacity,
1291 "minimum_desired_capacity = " SIZE_FORMAT ", "
1292 "maximum_desired_capacity = " SIZE_FORMAT,
1293 minimum_desired_capacity, maximum_desired_capacity);
1294
1295 // Should not be greater than the heap max size. No need to adjust
1296 // it with respect to the heap min size as it's a lower bound (i.e.,
1297 // we'll try to make the capacity larger than it, not smaller).
1298 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1299 // Should not be less than the heap min size. No need to adjust it
1300 // with respect to the heap max size as it's an upper bound (i.e.,
1301 // we'll try to make the capacity smaller than it, not greater).
1302 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1303
1304 if (capacity_after_gc < minimum_desired_capacity) {
1305 // Don't expand unless it's significant
1306 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1307
1308 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). "
1309 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1310 "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1311 capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio);
1312
1313 expand(expand_bytes, _workers);
1314
1315 // No expansion, now see if we want to shrink
1316 } else if (capacity_after_gc > maximum_desired_capacity) {
1317 // Capacity too large, compute shrinking size
1318 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1319
1320 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). "
1321 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1322 "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1323 capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio);
1324
1325 shrink(shrink_bytes);
1326 }
1327 }
1328
1329 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1330 AllocationContext_t context,
1331 bool do_gc,
1332 bool clear_all_soft_refs,
1333 bool expect_null_mutator_alloc_region,
1334 bool* gc_succeeded) {
1335 *gc_succeeded = true;
1336 // Let's attempt the allocation first.
1337 HeapWord* result =
1338 attempt_allocation_at_safepoint(word_size,
1339 context,
1340 expect_null_mutator_alloc_region);
1341 if (result != NULL) {
1342 assert(*gc_succeeded, "sanity");
1343 return result;
1344 }
1345
1346 // In a G1 heap, we're supposed to keep allocation from failing by
1347 // incremental pauses. Therefore, at least for now, we'll favor
1348 // expansion over collection. (This might change in the future if we can
1349 // do something smarter than full collection to satisfy a failed alloc.)
1350 result = expand_and_allocate(word_size, context);
1351 if (result != NULL) {
1352 assert(*gc_succeeded, "sanity");
1353 return result;
1354 }
1355
1356 if (do_gc) {
1357 // Expansion didn't work, we'll try to do a Full GC.
1358 *gc_succeeded = do_full_collection(false, /* explicit_gc */
1359 clear_all_soft_refs);
1360 }
1361
1362 return NULL;
1363 }
1364
1365 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1366 AllocationContext_t context,
1367 bool* succeeded) {
1368 assert_at_safepoint(true /* should_be_vm_thread */);
1369
1370 // Attempts to allocate followed by Full GC.
1371 HeapWord* result =
1372 satisfy_failed_allocation_helper(word_size,
1373 context,
1374 true, /* do_gc */
1375 false, /* clear_all_soft_refs */
1376 false, /* expect_null_mutator_alloc_region */
1377 succeeded);
1378
1379 if (result != NULL || !*succeeded) {
1380 return result;
1381 }
1382
1383 // Attempts to allocate followed by Full GC that will collect all soft references.
1384 result = satisfy_failed_allocation_helper(word_size,
1385 context,
1386 true, /* do_gc */
1387 true, /* clear_all_soft_refs */
1388 true, /* expect_null_mutator_alloc_region */
1389 succeeded);
1390
1391 if (result != NULL || !*succeeded) {
1392 return result;
1393 }
1394
1395 // Attempts to allocate, no GC
1396 result = satisfy_failed_allocation_helper(word_size,
1397 context,
1398 false, /* do_gc */
1399 false, /* clear_all_soft_refs */
1400 true, /* expect_null_mutator_alloc_region */
1401 succeeded);
1402
1403 if (result != NULL) {
1404 assert(*succeeded, "sanity");
1405 return result;
1406 }
1407
1408 assert(!collector_policy()->should_clear_all_soft_refs(),
1409 "Flag should have been handled and cleared prior to this point");
1410
1411 // What else? We might try synchronous finalization later. If the total
1412 // space available is large enough for the allocation, then a more
1413 // complete compaction phase than we've tried so far might be
1414 // appropriate.
1415 assert(*succeeded, "sanity");
1416 return NULL;
1417 }
1418
1419 // Attempting to expand the heap sufficiently
1420 // to support an allocation of the given "word_size". If
1421 // successful, perform the allocation and return the address of the
1422 // allocated block, or else "NULL".
1423
1424 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1425 assert_at_safepoint(true /* should_be_vm_thread */);
1426
1427 _verifier->verify_region_sets_optional();
1428
1429 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1430 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1431 word_size * HeapWordSize);
1432
1433
1434 if (expand(expand_bytes, _workers)) {
1435 _hrm.verify_optional();
1436 _verifier->verify_region_sets_optional();
1437 return attempt_allocation_at_safepoint(word_size,
1438 context,
1439 false /* expect_null_mutator_alloc_region */);
1440 }
1441 return NULL;
1442 }
1443
1444 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) {
1445 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1446 aligned_expand_bytes = align_up(aligned_expand_bytes,
1447 HeapRegion::GrainBytes);
1448
1449 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B",
1450 expand_bytes, aligned_expand_bytes);
1451
1452 if (is_maximal_no_gc()) {
1453 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1454 return false;
1455 }
1456
1457 double expand_heap_start_time_sec = os::elapsedTime();
1458 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1459 assert(regions_to_expand > 0, "Must expand by at least one region");
1460
1461 uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers);
1462 if (expand_time_ms != NULL) {
1463 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1464 }
1465
1466 if (expanded_by > 0) {
1467 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1468 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1469 g1_policy()->record_new_heap_size(num_regions());
1470 } else {
1471 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1472
1473 // The expansion of the virtual storage space was unsuccessful.
1474 // Let's see if it was because we ran out of swap.
1475 if (G1ExitOnExpansionFailure &&
1476 _hrm.available() >= regions_to_expand) {
1477 // We had head room...
1478 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1479 }
1480 }
1481 return regions_to_expand > 0;
1482 }
1483
1484 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1485 size_t aligned_shrink_bytes =
1486 ReservedSpace::page_align_size_down(shrink_bytes);
1487 aligned_shrink_bytes = align_down(aligned_shrink_bytes,
1488 HeapRegion::GrainBytes);
1489 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1490
1491 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1492 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1493
1494
1495 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",
1496 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1497 if (num_regions_removed > 0) {
1498 g1_policy()->record_new_heap_size(num_regions());
1499 } else {
1500 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1501 }
1502 }
1503
1504 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1505 _verifier->verify_region_sets_optional();
1506
1507 // We should only reach here at the end of a Full GC which means we
1508 // should not not be holding to any GC alloc regions. The method
1509 // below will make sure of that and do any remaining clean up.
1510 _allocator->abandon_gc_alloc_regions();
1511
1512 // Instead of tearing down / rebuilding the free lists here, we
1513 // could instead use the remove_all_pending() method on free_list to
1514 // remove only the ones that we need to remove.
1515 tear_down_region_sets(true /* free_list_only */);
1516 shrink_helper(shrink_bytes);
1517 rebuild_region_sets(true /* free_list_only */);
1518
1519 _hrm.verify_optional();
1520 _verifier->verify_region_sets_optional();
1521 }
1522
1523 // Public methods.
1524
1525 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) :
1526 CollectedHeap(),
1527 _young_gen_sampling_thread(NULL),
1528 _collector_policy(collector_policy),
1529 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1530 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1531 _g1_policy(create_g1_policy(_gc_timer_stw)),
1532 _collection_set(this, _g1_policy),
1533 _dirty_card_queue_set(false),
1534 _is_alive_closure_cm(this),
1535 _is_alive_closure_stw(this),
1536 _ref_processor_cm(NULL),
1537 _ref_processor_stw(NULL),
1538 _bot(NULL),
1539 _hot_card_cache(NULL),
1540 _g1_rem_set(NULL),
1541 _cr(NULL),
1542 _g1mm(NULL),
1543 _preserved_marks_set(true /* in_c_heap */),
1544 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1545 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1546 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1547 _humongous_reclaim_candidates(),
1548 _has_humongous_reclaim_candidates(false),
1549 _archive_allocator(NULL),
1550 _free_regions_coming(false),
1551 _gc_time_stamp(0),
1552 _summary_bytes_used(0),
1553 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1554 _old_evac_stats("Old", OldPLABSize, PLABWeight),
1555 _expand_heap_after_alloc_failure(true),
1556 _old_marking_cycles_started(0),
1557 _old_marking_cycles_completed(0),
1558 _in_cset_fast_test() {
1559
1560 _workers = new WorkGang("GC Thread", ParallelGCThreads,
1561 /* are_GC_task_threads */true,
1562 /* are_ConcurrentGC_threads */false);
1563 _workers->initialize_workers();
1564 _verifier = new G1HeapVerifier(this);
1565
1566 _allocator = G1Allocator::create_allocator(this);
1567
1568 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics());
1569
1570 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1571
1572 // Override the default _filler_array_max_size so that no humongous filler
1573 // objects are created.
1574 _filler_array_max_size = _humongous_object_threshold_in_words;
1575
1576 uint n_queues = ParallelGCThreads;
1577 _task_queues = new RefToScanQueueSet(n_queues);
1578
1579 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1580
1581 for (uint i = 0; i < n_queues; i++) {
1582 RefToScanQueue* q = new RefToScanQueue();
1583 q->initialize();
1584 _task_queues->register_queue(i, q);
1585 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1586 }
1587
1588 // Initialize the G1EvacuationFailureALot counters and flags.
1589 NOT_PRODUCT(reset_evacuation_should_fail();)
1590
1591 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1592 }
1593
1594 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1595 size_t size,
1596 size_t translation_factor) {
1597 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1598 // Allocate a new reserved space, preferring to use large pages.
1599 ReservedSpace rs(size, preferred_page_size);
1600 G1RegionToSpaceMapper* result =
1601 G1RegionToSpaceMapper::create_mapper(rs,
1602 size,
1603 rs.alignment(),
1604 HeapRegion::GrainBytes,
1605 translation_factor,
1606 mtGC);
1607
1608 os::trace_page_sizes_for_requested_size(description,
1609 size,
1610 preferred_page_size,
1611 rs.alignment(),
1612 rs.base(),
1613 rs.size());
1614
1615 return result;
1616 }
1617
1618 jint G1CollectedHeap::initialize_concurrent_refinement() {
1619 jint ecode = JNI_OK;
1620 _cr = G1ConcurrentRefine::create(&ecode);
1621 return ecode;
1622 }
1623
1624 jint G1CollectedHeap::initialize_young_gen_sampling_thread() {
1625 _young_gen_sampling_thread = new G1YoungRemSetSamplingThread();
1626 if (_young_gen_sampling_thread->osthread() == NULL) {
1627 vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread");
1628 return JNI_ENOMEM;
1629 }
1630 return JNI_OK;
1631 }
1632
1633 jint G1CollectedHeap::initialize() {
1634 CollectedHeap::pre_initialize();
1635 os::enable_vtime();
1636
1637 // Necessary to satisfy locking discipline assertions.
1638
1639 MutexLocker x(Heap_lock);
1640
1641 // While there are no constraints in the GC code that HeapWordSize
1642 // be any particular value, there are multiple other areas in the
1643 // system which believe this to be true (e.g. oop->object_size in some
1644 // cases incorrectly returns the size in wordSize units rather than
1645 // HeapWordSize).
1646 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1647
1648 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1649 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1650 size_t heap_alignment = collector_policy()->heap_alignment();
1651
1652 // Ensure that the sizes are properly aligned.
1653 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1654 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1655 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1656
1657 // Reserve the maximum.
1658
1659 // When compressed oops are enabled, the preferred heap base
1660 // is calculated by subtracting the requested size from the
1661 // 32Gb boundary and using the result as the base address for
1662 // heap reservation. If the requested size is not aligned to
1663 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1664 // into the ReservedHeapSpace constructor) then the actual
1665 // base of the reserved heap may end up differing from the
1666 // address that was requested (i.e. the preferred heap base).
1667 // If this happens then we could end up using a non-optimal
1668 // compressed oops mode.
1669
1670 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1671 heap_alignment);
1672
1673 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1674
1675 // Create the barrier set for the entire reserved region.
1676 G1SATBCardTableLoggingModRefBS* bs
1677 = new G1SATBCardTableLoggingModRefBS(reserved_region());
1678 bs->initialize();
1679 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity");
1680 set_barrier_set(bs);
1681
1682 // Create the hot card cache.
1683 _hot_card_cache = new G1HotCardCache(this);
1684
1685 // Carve out the G1 part of the heap.
1686 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1687 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
1688 G1RegionToSpaceMapper* heap_storage =
1689 G1RegionToSpaceMapper::create_mapper(g1_rs,
1690 g1_rs.size(),
1691 page_size,
1692 HeapRegion::GrainBytes,
1693 1,
1694 mtJavaHeap);
1695 os::trace_page_sizes("Heap",
1696 collector_policy()->min_heap_byte_size(),
1697 max_byte_size,
1698 page_size,
1699 heap_rs.base(),
1700 heap_rs.size());
1701 heap_storage->set_mapping_changed_listener(&_listener);
1702
1703 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1704 G1RegionToSpaceMapper* bot_storage =
1705 create_aux_memory_mapper("Block Offset Table",
1706 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1707 G1BlockOffsetTable::heap_map_factor());
1708
1709 G1RegionToSpaceMapper* cardtable_storage =
1710 create_aux_memory_mapper("Card Table",
1711 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize),
1712 G1SATBCardTableLoggingModRefBS::heap_map_factor());
1713
1714 G1RegionToSpaceMapper* card_counts_storage =
1715 create_aux_memory_mapper("Card Counts Table",
1716 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1717 G1CardCounts::heap_map_factor());
1718
1719 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1720 G1RegionToSpaceMapper* prev_bitmap_storage =
1721 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1722 G1RegionToSpaceMapper* next_bitmap_storage =
1723 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1724
1725 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1726 g1_barrier_set()->initialize(cardtable_storage);
1727 // Do later initialization work for concurrent refinement.
1728 _hot_card_cache->initialize(card_counts_storage);
1729
1730 // 6843694 - ensure that the maximum region index can fit
1731 // in the remembered set structures.
1732 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1733 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1734
1735 // Also create a G1 rem set.
1736 _g1_rem_set = new G1RemSet(this, g1_barrier_set(), _hot_card_cache);
1737 _g1_rem_set->initialize(max_capacity(), max_regions());
1738
1739 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1740 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1741 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1742 "too many cards per region");
1743
1744 FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1745
1746 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1747
1748 {
1749 HeapWord* start = _hrm.reserved().start();
1750 HeapWord* end = _hrm.reserved().end();
1751 size_t granularity = HeapRegion::GrainBytes;
1752
1753 _in_cset_fast_test.initialize(start, end, granularity);
1754 _humongous_reclaim_candidates.initialize(start, end, granularity);
1755 }
1756
1757 // Create the G1ConcurrentMark data structure and thread.
1758 // (Must do this late, so that "max_regions" is defined.)
1759 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1760 if (_cm == NULL || !_cm->completed_initialization()) {
1761 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
1762 return JNI_ENOMEM;
1763 }
1764 _cmThread = _cm->cm_thread();
1765
1766 // Now expand into the initial heap size.
1767 if (!expand(init_byte_size, _workers)) {
1768 vm_shutdown_during_initialization("Failed to allocate initial heap.");
1769 return JNI_ENOMEM;
1770 }
1771
1772 // Perform any initialization actions delegated to the policy.
1773 g1_policy()->init(this, &_collection_set);
1774
1775 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1776 SATB_Q_FL_lock,
1777 G1SATBProcessCompletedThreshold,
1778 Shared_SATB_Q_lock);
1779
1780 jint ecode = initialize_concurrent_refinement();
1781 if (ecode != JNI_OK) {
1782 return ecode;
1783 }
1784
1785 ecode = initialize_young_gen_sampling_thread();
1786 if (ecode != JNI_OK) {
1787 return ecode;
1788 }
1789
1790 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1791 DirtyCardQ_FL_lock,
1792 (int)concurrent_refine()->yellow_zone(),
1793 (int)concurrent_refine()->red_zone(),
1794 Shared_DirtyCardQ_lock,
1795 NULL, // fl_owner
1796 true); // init_free_ids
1797
1798 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1799 DirtyCardQ_FL_lock,
1800 -1, // never trigger processing
1801 -1, // no limit on length
1802 Shared_DirtyCardQ_lock,
1803 &JavaThread::dirty_card_queue_set());
1804
1805 // Here we allocate the dummy HeapRegion that is required by the
1806 // G1AllocRegion class.
1807 HeapRegion* dummy_region = _hrm.get_dummy_region();
1808
1809 // We'll re-use the same region whether the alloc region will
1810 // require BOT updates or not and, if it doesn't, then a non-young
1811 // region will complain that it cannot support allocations without
1812 // BOT updates. So we'll tag the dummy region as eden to avoid that.
1813 dummy_region->set_eden();
1814 // Make sure it's full.
1815 dummy_region->set_top(dummy_region->end());
1816 G1AllocRegion::setup(this, dummy_region);
1817
1818 _allocator->init_mutator_alloc_region();
1819
1820 // Do create of the monitoring and management support so that
1821 // values in the heap have been properly initialized.
1822 _g1mm = new G1MonitoringSupport(this);
1823
1824 G1StringDedup::initialize();
1825
1826 _preserved_marks_set.init(ParallelGCThreads);
1827
1828 _collection_set.initialize(max_regions());
1829
1830 return JNI_OK;
1831 }
1832
1833 void G1CollectedHeap::stop() {
1834 // Stop all concurrent threads. We do this to make sure these threads
1835 // do not continue to execute and access resources (e.g. logging)
1836 // that are destroyed during shutdown.
1837 _cr->stop();
1838 _young_gen_sampling_thread->stop();
1839 _cmThread->stop();
1840 if (G1StringDedup::is_enabled()) {
1841 G1StringDedup::stop();
1842 }
1843 }
1844
1845 void G1CollectedHeap::safepoint_synchronize_begin() {
1846 SuspendibleThreadSet::synchronize();
1847 }
1848
1849 void G1CollectedHeap::safepoint_synchronize_end() {
1850 SuspendibleThreadSet::desynchronize();
1851 }
1852
1853 size_t G1CollectedHeap::conservative_max_heap_alignment() {
1854 return HeapRegion::max_region_size();
1855 }
1856
1857 void G1CollectedHeap::post_initialize() {
1858 ref_processing_init();
1859 }
1860
1861 void G1CollectedHeap::ref_processing_init() {
1862 // Reference processing in G1 currently works as follows:
1863 //
1864 // * There are two reference processor instances. One is
1865 // used to record and process discovered references
1866 // during concurrent marking; the other is used to
1867 // record and process references during STW pauses
1868 // (both full and incremental).
1869 // * Both ref processors need to 'span' the entire heap as
1870 // the regions in the collection set may be dotted around.
1871 //
1872 // * For the concurrent marking ref processor:
1873 // * Reference discovery is enabled at initial marking.
1874 // * Reference discovery is disabled and the discovered
1875 // references processed etc during remarking.
1876 // * Reference discovery is MT (see below).
1877 // * Reference discovery requires a barrier (see below).
1878 // * Reference processing may or may not be MT
1879 // (depending on the value of ParallelRefProcEnabled
1880 // and ParallelGCThreads).
1881 // * A full GC disables reference discovery by the CM
1882 // ref processor and abandons any entries on it's
1883 // discovered lists.
1884 //
1885 // * For the STW processor:
1886 // * Non MT discovery is enabled at the start of a full GC.
1887 // * Processing and enqueueing during a full GC is non-MT.
1888 // * During a full GC, references are processed after marking.
1889 //
1890 // * Discovery (may or may not be MT) is enabled at the start
1891 // of an incremental evacuation pause.
1892 // * References are processed near the end of a STW evacuation pause.
1893 // * For both types of GC:
1894 // * Discovery is atomic - i.e. not concurrent.
1895 // * Reference discovery will not need a barrier.
1896
1897 MemRegion mr = reserved_region();
1898
1899 bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1);
1900
1901 // Concurrent Mark ref processor
1902 _ref_processor_cm =
1903 new ReferenceProcessor(mr, // span
1904 mt_processing,
1905 // mt processing
1906 ParallelGCThreads,
1907 // degree of mt processing
1908 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
1909 // mt discovery
1910 MAX2(ParallelGCThreads, ConcGCThreads),
1911 // degree of mt discovery
1912 false,
1913 // Reference discovery is not atomic
1914 &_is_alive_closure_cm);
1915 // is alive closure
1916 // (for efficiency/performance)
1917
1918 // STW ref processor
1919 _ref_processor_stw =
1920 new ReferenceProcessor(mr, // span
1921 mt_processing,
1922 // mt processing
1923 ParallelGCThreads,
1924 // degree of mt processing
1925 (ParallelGCThreads > 1),
1926 // mt discovery
1927 ParallelGCThreads,
1928 // degree of mt discovery
1929 true,
1930 // Reference discovery is atomic
1931 &_is_alive_closure_stw);
1932 // is alive closure
1933 // (for efficiency/performance)
1934 }
1935
1936 CollectorPolicy* G1CollectedHeap::collector_policy() const {
1937 return _collector_policy;
1938 }
1939
1940 size_t G1CollectedHeap::capacity() const {
1941 return _hrm.length() * HeapRegion::GrainBytes;
1942 }
1943
1944 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const {
1945 return _hrm.total_free_bytes();
1946 }
1947
1948 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
1949 hr->reset_gc_time_stamp();
1950 }
1951
1952 #ifndef PRODUCT
1953
1954 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
1955 private:
1956 unsigned _gc_time_stamp;
1957 bool _failures;
1958
1959 public:
1960 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
1961 _gc_time_stamp(gc_time_stamp), _failures(false) { }
1962
1963 virtual bool doHeapRegion(HeapRegion* hr) {
1964 unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
1965 if (_gc_time_stamp != region_gc_time_stamp) {
1966 log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr),
1967 region_gc_time_stamp, _gc_time_stamp);
1968 _failures = true;
1969 }
1970 return false;
1971 }
1972
1973 bool failures() { return _failures; }
1974 };
1975
1976 void G1CollectedHeap::check_gc_time_stamps() {
1977 CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
1978 heap_region_iterate(&cl);
1979 guarantee(!cl.failures(), "all GC time stamps should have been reset");
1980 }
1981 #endif // PRODUCT
1982
1983 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) {
1984 _hot_card_cache->drain(cl, worker_i);
1985 }
1986
1987 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) {
1988 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
1989 size_t n_completed_buffers = 0;
1990 while (dcqs.apply_closure_during_gc(cl, worker_i)) {
1991 n_completed_buffers++;
1992 }
1993 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
1994 dcqs.clear_n_completed_buffers();
1995 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
1996 }
1997
1998 // Computes the sum of the storage used by the various regions.
1999 size_t G1CollectedHeap::used() const {
2000 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
2001 if (_archive_allocator != NULL) {
2002 result += _archive_allocator->used();
2003 }
2004 return result;
2005 }
2006
2007 size_t G1CollectedHeap::used_unlocked() const {
2008 return _summary_bytes_used;
2009 }
2010
2011 class SumUsedClosure: public HeapRegionClosure {
2012 size_t _used;
2013 public:
2014 SumUsedClosure() : _used(0) {}
2015 bool doHeapRegion(HeapRegion* r) {
2016 _used += r->used();
2017 return false;
2018 }
2019 size_t result() { return _used; }
2020 };
2021
2022 size_t G1CollectedHeap::recalculate_used() const {
2023 double recalculate_used_start = os::elapsedTime();
2024
2025 SumUsedClosure blk;
2026 heap_region_iterate(&blk);
2027
2028 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2029 return blk.result();
2030 }
2031
2032 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
2033 switch (cause) {
2034 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2035 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent;
2036 case GCCause::_update_allocation_context_stats_inc: return true;
2037 case GCCause::_wb_conc_mark: return true;
2038 default : return false;
2039 }
2040 }
2041
2042 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2043 switch (cause) {
2044 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2045 case GCCause::_g1_humongous_allocation: return true;
2046 default: return is_user_requested_concurrent_full_gc(cause);
2047 }
2048 }
2049
2050 #ifndef PRODUCT
2051 void G1CollectedHeap::allocate_dummy_regions() {
2052 // Let's fill up most of the region
2053 size_t word_size = HeapRegion::GrainWords - 1024;
2054 // And as a result the region we'll allocate will be humongous.
2055 guarantee(is_humongous(word_size), "sanity");
2056
2057 // _filler_array_max_size is set to humongous object threshold
2058 // but temporarily change it to use CollectedHeap::fill_with_object().
2059 SizeTFlagSetting fs(_filler_array_max_size, word_size);
2060
2061 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2062 // Let's use the existing mechanism for the allocation
2063 HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2064 AllocationContext::system());
2065 if (dummy_obj != NULL) {
2066 MemRegion mr(dummy_obj, word_size);
2067 CollectedHeap::fill_with_object(mr);
2068 } else {
2069 // If we can't allocate once, we probably cannot allocate
2070 // again. Let's get out of the loop.
2071 break;
2072 }
2073 }
2074 }
2075 #endif // !PRODUCT
2076
2077 void G1CollectedHeap::increment_old_marking_cycles_started() {
2078 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2079 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2080 "Wrong marking cycle count (started: %d, completed: %d)",
2081 _old_marking_cycles_started, _old_marking_cycles_completed);
2082
2083 _old_marking_cycles_started++;
2084 }
2085
2086 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2087 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2088
2089 // We assume that if concurrent == true, then the caller is a
2090 // concurrent thread that was joined the Suspendible Thread
2091 // Set. If there's ever a cheap way to check this, we should add an
2092 // assert here.
2093
2094 // Given that this method is called at the end of a Full GC or of a
2095 // concurrent cycle, and those can be nested (i.e., a Full GC can
2096 // interrupt a concurrent cycle), the number of full collections
2097 // completed should be either one (in the case where there was no
2098 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2099 // behind the number of full collections started.
2100
2101 // This is the case for the inner caller, i.e. a Full GC.
2102 assert(concurrent ||
2103 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2104 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2105 "for inner caller (Full GC): _old_marking_cycles_started = %u "
2106 "is inconsistent with _old_marking_cycles_completed = %u",
2107 _old_marking_cycles_started, _old_marking_cycles_completed);
2108
2109 // This is the case for the outer caller, i.e. the concurrent cycle.
2110 assert(!concurrent ||
2111 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2112 "for outer caller (concurrent cycle): "
2113 "_old_marking_cycles_started = %u "
2114 "is inconsistent with _old_marking_cycles_completed = %u",
2115 _old_marking_cycles_started, _old_marking_cycles_completed);
2116
2117 _old_marking_cycles_completed += 1;
2118
2119 // We need to clear the "in_progress" flag in the CM thread before
2120 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2121 // is set) so that if a waiter requests another System.gc() it doesn't
2122 // incorrectly see that a marking cycle is still in progress.
2123 if (concurrent) {
2124 _cmThread->set_idle();
2125 }
2126
2127 // This notify_all() will ensure that a thread that called
2128 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2129 // and it's waiting for a full GC to finish will be woken up. It is
2130 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2131 FullGCCount_lock->notify_all();
2132 }
2133
2134 void G1CollectedHeap::collect(GCCause::Cause cause) {
2135 assert_heap_not_locked();
2136
2137 uint gc_count_before;
2138 uint old_marking_count_before;
2139 uint full_gc_count_before;
2140 bool retry_gc;
2141
2142 do {
2143 retry_gc = false;
2144
2145 {
2146 MutexLocker ml(Heap_lock);
2147
2148 // Read the GC count while holding the Heap_lock
2149 gc_count_before = total_collections();
2150 full_gc_count_before = total_full_collections();
2151 old_marking_count_before = _old_marking_cycles_started;
2152 }
2153
2154 if (should_do_concurrent_full_gc(cause)) {
2155 // Schedule an initial-mark evacuation pause that will start a
2156 // concurrent cycle. We're setting word_size to 0 which means that
2157 // we are not requesting a post-GC allocation.
2158 VM_G1IncCollectionPause op(gc_count_before,
2159 0, /* word_size */
2160 true, /* should_initiate_conc_mark */
2161 g1_policy()->max_pause_time_ms(),
2162 cause);
2163 op.set_allocation_context(AllocationContext::current());
2164
2165 VMThread::execute(&op);
2166 if (!op.pause_succeeded()) {
2167 if (old_marking_count_before == _old_marking_cycles_started) {
2168 retry_gc = op.should_retry_gc();
2169 } else {
2170 // A Full GC happened while we were trying to schedule the
2171 // initial-mark GC. No point in starting a new cycle given
2172 // that the whole heap was collected anyway.
2173 }
2174
2175 if (retry_gc) {
2176 if (GCLocker::is_active_and_needs_gc()) {
2177 GCLocker::stall_until_clear();
2178 }
2179 }
2180 }
2181 } else {
2182 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2183 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2184
2185 // Schedule a standard evacuation pause. We're setting word_size
2186 // to 0 which means that we are not requesting a post-GC allocation.
2187 VM_G1IncCollectionPause op(gc_count_before,
2188 0, /* word_size */
2189 false, /* should_initiate_conc_mark */
2190 g1_policy()->max_pause_time_ms(),
2191 cause);
2192 VMThread::execute(&op);
2193 } else {
2194 // Schedule a Full GC.
2195 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2196 VMThread::execute(&op);
2197 }
2198 }
2199 } while (retry_gc);
2200 }
2201
2202 bool G1CollectedHeap::is_in(const void* p) const {
2203 if (_hrm.reserved().contains(p)) {
2204 // Given that we know that p is in the reserved space,
2205 // heap_region_containing() should successfully
2206 // return the containing region.
2207 HeapRegion* hr = heap_region_containing(p);
2208 return hr->is_in(p);
2209 } else {
2210 return false;
2211 }
2212 }
2213
2214 #ifdef ASSERT
2215 bool G1CollectedHeap::is_in_exact(const void* p) const {
2216 bool contains = reserved_region().contains(p);
2217 bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2218 if (contains && available) {
2219 return true;
2220 } else {
2221 return false;
2222 }
2223 }
2224 #endif
2225
2226 // Iteration functions.
2227
2228 // Iterates an ObjectClosure over all objects within a HeapRegion.
2229
2230 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2231 ObjectClosure* _cl;
2232 public:
2233 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2234 bool doHeapRegion(HeapRegion* r) {
2235 if (!r->is_continues_humongous()) {
2236 r->object_iterate(_cl);
2237 }
2238 return false;
2239 }
2240 };
2241
2242 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2243 IterateObjectClosureRegionClosure blk(cl);
2244 heap_region_iterate(&blk);
2245 }
2246
2247 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2248 _hrm.iterate(cl);
2249 }
2250
2251 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
2252 HeapRegionClaimer *hrclaimer,
2253 uint worker_id) const {
2254 _hrm.par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id));
2255 }
2256
2257 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl,
2258 HeapRegionClaimer *hrclaimer) const {
2259 _hrm.par_iterate(cl, hrclaimer, 0);
2260 }
2261
2262 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2263 _collection_set.iterate(cl);
2264 }
2265
2266 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) {
2267 _collection_set.iterate_from(cl, worker_id, workers()->active_workers());
2268 }
2269
2270 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2271 HeapRegion* hr = heap_region_containing(addr);
2272 return hr->block_start(addr);
2273 }
2274
2275 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2276 HeapRegion* hr = heap_region_containing(addr);
2277 return hr->block_size(addr);
2278 }
2279
2280 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2281 HeapRegion* hr = heap_region_containing(addr);
2282 return hr->block_is_obj(addr);
2283 }
2284
2285 bool G1CollectedHeap::supports_tlab_allocation() const {
2286 return true;
2287 }
2288
2289 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2290 return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2291 }
2292
2293 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2294 return _eden.length() * HeapRegion::GrainBytes;
2295 }
2296
2297 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2298 // must be equal to the humongous object limit.
2299 size_t G1CollectedHeap::max_tlab_size() const {
2300 return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
2301 }
2302
2303 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2304 AllocationContext_t context = AllocationContext::current();
2305 return _allocator->unsafe_max_tlab_alloc(context);
2306 }
2307
2308 size_t G1CollectedHeap::max_capacity() const {
2309 return _hrm.reserved().byte_size();
2310 }
2311
2312 jlong G1CollectedHeap::millis_since_last_gc() {
2313 // See the notes in GenCollectedHeap::millis_since_last_gc()
2314 // for more information about the implementation.
2315 jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) -
2316 _g1_policy->collection_pause_end_millis();
2317 if (ret_val < 0) {
2318 log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
2319 ". returning zero instead.", ret_val);
2320 return 0;
2321 }
2322 return ret_val;
2323 }
2324
2325 void G1CollectedHeap::prepare_for_verify() {
2326 _verifier->prepare_for_verify();
2327 }
2328
2329 void G1CollectedHeap::verify(VerifyOption vo) {
2330 _verifier->verify(vo);
2331 }
2332
2333 bool G1CollectedHeap::supports_concurrent_phase_control() const {
2334 return true;
2335 }
2336
2337 const char* const* G1CollectedHeap::concurrent_phases() const {
2338 return _cmThread->concurrent_phases();
2339 }
2340
2341 bool G1CollectedHeap::request_concurrent_phase(const char* phase) {
2342 return _cmThread->request_concurrent_phase(phase);
2343 }
2344
2345 class PrintRegionClosure: public HeapRegionClosure {
2346 outputStream* _st;
2347 public:
2348 PrintRegionClosure(outputStream* st) : _st(st) {}
2349 bool doHeapRegion(HeapRegion* r) {
2350 r->print_on(_st);
2351 return false;
2352 }
2353 };
2354
2355 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2356 const HeapRegion* hr,
2357 const VerifyOption vo) const {
2358 switch (vo) {
2359 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2360 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2361 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr);
2362 default: ShouldNotReachHere();
2363 }
2364 return false; // keep some compilers happy
2365 }
2366
2367 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2368 const VerifyOption vo) const {
2369 switch (vo) {
2370 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2371 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2372 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj);
2373 default: ShouldNotReachHere();
2374 }
2375 return false; // keep some compilers happy
2376 }
2377
2378 void G1CollectedHeap::print_heap_regions() const {
2379 LogTarget(Trace, gc, heap, region) lt;
2380 if (lt.is_enabled()) {
2381 LogStream ls(lt);
2382 print_regions_on(&ls);
2383 }
2384 }
2385
2386 void G1CollectedHeap::print_on(outputStream* st) const {
2387 st->print(" %-20s", "garbage-first heap");
2388 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2389 capacity()/K, used_unlocked()/K);
2390 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")",
2391 p2i(_hrm.reserved().start()),
2392 p2i(_hrm.reserved().end()));
2393 st->cr();
2394 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2395 uint young_regions = young_regions_count();
2396 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2397 (size_t) young_regions * HeapRegion::GrainBytes / K);
2398 uint survivor_regions = survivor_regions_count();
2399 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2400 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2401 st->cr();
2402 MetaspaceAux::print_on(st);
2403 }
2404
2405 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2406 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2407 "HS=humongous(starts), HC=humongous(continues), "
2408 "CS=collection set, F=free, A=archive, TS=gc time stamp, "
2409 "AC=allocation context, "
2410 "TAMS=top-at-mark-start (previous, next)");
2411 PrintRegionClosure blk(st);
2412 heap_region_iterate(&blk);
2413 }
2414
2415 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2416 print_on(st);
2417
2418 // Print the per-region information.
2419 print_regions_on(st);
2420 }
2421
2422 void G1CollectedHeap::print_on_error(outputStream* st) const {
2423 this->CollectedHeap::print_on_error(st);
2424
2425 if (_cm != NULL) {
2426 st->cr();
2427 _cm->print_on_error(st);
2428 }
2429 }
2430
2431 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2432 workers()->print_worker_threads_on(st);
2433 _cmThread->print_on(st);
2434 st->cr();
2435 _cm->print_worker_threads_on(st);
2436 _cr->print_threads_on(st);
2437 _young_gen_sampling_thread->print_on(st);
2438 if (G1StringDedup::is_enabled()) {
2439 G1StringDedup::print_worker_threads_on(st);
2440 }
2441 }
2442
2443 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2444 workers()->threads_do(tc);
2445 tc->do_thread(_cmThread);
2446 _cm->threads_do(tc);
2447 _cr->threads_do(tc);
2448 tc->do_thread(_young_gen_sampling_thread);
2449 if (G1StringDedup::is_enabled()) {
2450 G1StringDedup::threads_do(tc);
2451 }
2452 }
2453
2454 void G1CollectedHeap::print_tracing_info() const {
2455 g1_rem_set()->print_summary_info();
2456 concurrent_mark()->print_summary_info();
2457 }
2458
2459 #ifndef PRODUCT
2460 // Helpful for debugging RSet issues.
2461
2462 class PrintRSetsClosure : public HeapRegionClosure {
2463 private:
2464 const char* _msg;
2465 size_t _occupied_sum;
2466
2467 public:
2468 bool doHeapRegion(HeapRegion* r) {
2469 HeapRegionRemSet* hrrs = r->rem_set();
2470 size_t occupied = hrrs->occupied();
2471 _occupied_sum += occupied;
2472
2473 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2474 if (occupied == 0) {
2475 tty->print_cr(" RSet is empty");
2476 } else {
2477 hrrs->print();
2478 }
2479 tty->print_cr("----------");
2480 return false;
2481 }
2482
2483 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2484 tty->cr();
2485 tty->print_cr("========================================");
2486 tty->print_cr("%s", msg);
2487 tty->cr();
2488 }
2489
2490 ~PrintRSetsClosure() {
2491 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2492 tty->print_cr("========================================");
2493 tty->cr();
2494 }
2495 };
2496
2497 void G1CollectedHeap::print_cset_rsets() {
2498 PrintRSetsClosure cl("Printing CSet RSets");
2499 collection_set_iterate(&cl);
2500 }
2501
2502 void G1CollectedHeap::print_all_rsets() {
2503 PrintRSetsClosure cl("Printing All RSets");;
2504 heap_region_iterate(&cl);
2505 }
2506 #endif // PRODUCT
2507
2508 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2509
2510 size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes;
2511 size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes;
2512 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2513
2514 size_t eden_capacity_bytes =
2515 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2516
2517 VirtualSpaceSummary heap_summary = create_heap_space_summary();
2518 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2519 eden_capacity_bytes, survivor_used_bytes, num_regions());
2520 }
2521
2522 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2523 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2524 stats->unused(), stats->used(), stats->region_end_waste(),
2525 stats->regions_filled(), stats->direct_allocated(),
2526 stats->failure_used(), stats->failure_waste());
2527 }
2528
2529 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2530 const G1HeapSummary& heap_summary = create_g1_heap_summary();
2531 gc_tracer->report_gc_heap_summary(when, heap_summary);
2532
2533 const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2534 gc_tracer->report_metaspace_summary(when, metaspace_summary);
2535 }
2536
2537 G1CollectedHeap* G1CollectedHeap::heap() {
2538 CollectedHeap* heap = Universe::heap();
2539 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2540 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap");
2541 return (G1CollectedHeap*)heap;
2542 }
2543
2544 void G1CollectedHeap::gc_prologue(bool full) {
2545 // always_do_update_barrier = false;
2546 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2547
2548 // This summary needs to be printed before incrementing total collections.
2549 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2550
2551 // Update common counters.
2552 increment_total_collections(full /* full gc */);
2553 if (full) {
2554 increment_old_marking_cycles_started();
2555 reset_gc_time_stamp();
2556 } else {
2557 increment_gc_time_stamp();
2558 }
2559
2560 // Fill TLAB's and such
2561 double start = os::elapsedTime();
2562 accumulate_statistics_all_tlabs();
2563 ensure_parsability(true);
2564 g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2565 }
2566
2567 void G1CollectedHeap::gc_epilogue(bool full) {
2568 // Update common counters.
2569 if (full) {
2570 // Update the number of full collections that have been completed.
2571 increment_old_marking_cycles_completed(false /* concurrent */);
2572 }
2573
2574 // We are at the end of the GC. Total collections has already been increased.
2575 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2576
2577 // FIXME: what is this about?
2578 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2579 // is set.
2580 #if COMPILER2_OR_JVMCI
2581 assert(DerivedPointerTable::is_empty(), "derived pointer present");
2582 #endif
2583 // always_do_update_barrier = true;
2584
2585 double start = os::elapsedTime();
2586 resize_all_tlabs();
2587 g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2588
2589 allocation_context_stats().update(full);
2590
2591 MemoryService::track_memory_usage();
2592 // We have just completed a GC. Update the soft reference
2593 // policy with the new heap occupancy
2594 Universe::update_heap_info_at_gc();
2595 }
2596
2597 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2598 uint gc_count_before,
2599 bool* succeeded,
2600 GCCause::Cause gc_cause) {
2601 assert_heap_not_locked_and_not_at_safepoint();
2602 VM_G1IncCollectionPause op(gc_count_before,
2603 word_size,
2604 false, /* should_initiate_conc_mark */
2605 g1_policy()->max_pause_time_ms(),
2606 gc_cause);
2607
2608 op.set_allocation_context(AllocationContext::current());
2609 VMThread::execute(&op);
2610
2611 HeapWord* result = op.result();
2612 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
2613 assert(result == NULL || ret_succeeded,
2614 "the result should be NULL if the VM did not succeed");
2615 *succeeded = ret_succeeded;
2616
2617 assert_heap_not_locked();
2618 return result;
2619 }
2620
2621 void
2622 G1CollectedHeap::doConcurrentMark() {
2623 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
2624 if (!_cmThread->in_progress()) {
2625 _cmThread->set_started();
2626 CGC_lock->notify();
2627 }
2628 }
2629
2630 size_t G1CollectedHeap::pending_card_num() {
2631 size_t extra_cards = 0;
2632 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *curr = jtiwh.next(); ) {
2633 DirtyCardQueue& dcq = curr->dirty_card_queue();
2634 extra_cards += dcq.size();
2635 }
2636 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2637 size_t buffer_size = dcqs.buffer_size();
2638 size_t buffer_num = dcqs.completed_buffers_num();
2639
2640 return buffer_size * buffer_num + extra_cards;
2641 }
2642
2643 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
2644 private:
2645 size_t _total_humongous;
2646 size_t _candidate_humongous;
2647
2648 DirtyCardQueue _dcq;
2649
2650 // We don't nominate objects with many remembered set entries, on
2651 // the assumption that such objects are likely still live.
2652 bool is_remset_small(HeapRegion* region) const {
2653 HeapRegionRemSet* const rset = region->rem_set();
2654 return G1EagerReclaimHumongousObjectsWithStaleRefs
2655 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)
2656 : rset->is_empty();
2657 }
2658
2659 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const {
2660 assert(region->is_starts_humongous(), "Must start a humongous object");
2661
2662 oop obj = oop(region->bottom());
2663
2664 // Dead objects cannot be eager reclaim candidates. Due to class
2665 // unloading it is unsafe to query their classes so we return early.
2666 if (heap->is_obj_dead(obj, region)) {
2667 return false;
2668 }
2669
2670 // Candidate selection must satisfy the following constraints
2671 // while concurrent marking is in progress:
2672 //
2673 // * In order to maintain SATB invariants, an object must not be
2674 // reclaimed if it was allocated before the start of marking and
2675 // has not had its references scanned. Such an object must have
2676 // its references (including type metadata) scanned to ensure no
2677 // live objects are missed by the marking process. Objects
2678 // allocated after the start of concurrent marking don't need to
2679 // be scanned.
2680 //
2681 // * An object must not be reclaimed if it is on the concurrent
2682 // mark stack. Objects allocated after the start of concurrent
2683 // marking are never pushed on the mark stack.
2684 //
2685 // Nominating only objects allocated after the start of concurrent
2686 // marking is sufficient to meet both constraints. This may miss
2687 // some objects that satisfy the constraints, but the marking data
2688 // structures don't support efficiently performing the needed
2689 // additional tests or scrubbing of the mark stack.
2690 //
2691 // However, we presently only nominate is_typeArray() objects.
2692 // A humongous object containing references induces remembered
2693 // set entries on other regions. In order to reclaim such an
2694 // object, those remembered sets would need to be cleaned up.
2695 //
2696 // We also treat is_typeArray() objects specially, allowing them
2697 // to be reclaimed even if allocated before the start of
2698 // concurrent mark. For this we rely on mark stack insertion to
2699 // exclude is_typeArray() objects, preventing reclaiming an object
2700 // that is in the mark stack. We also rely on the metadata for
2701 // such objects to be built-in and so ensured to be kept live.
2702 // Frequent allocation and drop of large binary blobs is an
2703 // important use case for eager reclaim, and this special handling
2704 // may reduce needed headroom.
2705
2706 return obj->is_typeArray() && is_remset_small(region);
2707 }
2708
2709 public:
2710 RegisterHumongousWithInCSetFastTestClosure()
2711 : _total_humongous(0),
2712 _candidate_humongous(0),
2713 _dcq(&JavaThread::dirty_card_queue_set()) {
2714 }
2715
2716 virtual bool doHeapRegion(HeapRegion* r) {
2717 if (!r->is_starts_humongous()) {
2718 return false;
2719 }
2720 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2721
2722 bool is_candidate = humongous_region_is_candidate(g1h, r);
2723 uint rindex = r->hrm_index();
2724 g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
2725 if (is_candidate) {
2726 _candidate_humongous++;
2727 g1h->register_humongous_region_with_cset(rindex);
2728 // Is_candidate already filters out humongous object with large remembered sets.
2729 // If we have a humongous object with a few remembered sets, we simply flush these
2730 // remembered set entries into the DCQS. That will result in automatic
2731 // re-evaluation of their remembered set entries during the following evacuation
2732 // phase.
2733 if (!r->rem_set()->is_empty()) {
2734 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
2735 "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
2736 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
2737 HeapRegionRemSetIterator hrrs(r->rem_set());
2738 size_t card_index;
2739 while (hrrs.has_next(card_index)) {
2740 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
2741 // The remembered set might contain references to already freed
2742 // regions. Filter out such entries to avoid failing card table
2743 // verification.
2744 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) {
2745 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
2746 *card_ptr = CardTableModRefBS::dirty_card_val();
2747 _dcq.enqueue(card_ptr);
2748 }
2749 }
2750 }
2751 assert(hrrs.n_yielded() == r->rem_set()->occupied(),
2752 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
2753 hrrs.n_yielded(), r->rem_set()->occupied());
2754 r->rem_set()->clear_locked();
2755 }
2756 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
2757 }
2758 _total_humongous++;
2759
2760 return false;
2761 }
2762
2763 size_t total_humongous() const { return _total_humongous; }
2764 size_t candidate_humongous() const { return _candidate_humongous; }
2765
2766 void flush_rem_set_entries() { _dcq.flush(); }
2767 };
2768
2769 void G1CollectedHeap::register_humongous_regions_with_cset() {
2770 if (!G1EagerReclaimHumongousObjects) {
2771 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
2772 return;
2773 }
2774 double time = os::elapsed_counter();
2775
2776 // Collect reclaim candidate information and register candidates with cset.
2777 RegisterHumongousWithInCSetFastTestClosure cl;
2778 heap_region_iterate(&cl);
2779
2780 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
2781 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
2782 cl.total_humongous(),
2783 cl.candidate_humongous());
2784 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
2785
2786 // Finally flush all remembered set entries to re-check into the global DCQS.
2787 cl.flush_rem_set_entries();
2788 }
2789
2790 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2791 public:
2792 bool doHeapRegion(HeapRegion* hr) {
2793 if (!hr->is_archive() && !hr->is_continues_humongous()) {
2794 hr->verify_rem_set();
2795 }
2796 return false;
2797 }
2798 };
2799
2800 uint G1CollectedHeap::num_task_queues() const {
2801 return _task_queues->size();
2802 }
2803
2804 #if TASKQUEUE_STATS
2805 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2806 st->print_raw_cr("GC Task Stats");
2807 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2808 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2809 }
2810
2811 void G1CollectedHeap::print_taskqueue_stats() const {
2812 if (!log_is_enabled(Trace, gc, task, stats)) {
2813 return;
2814 }
2815 Log(gc, task, stats) log;
2816 ResourceMark rm;
2817 LogStream ls(log.trace());
2818 outputStream* st = &ls;
2819
2820 print_taskqueue_stats_hdr(st);
2821
2822 TaskQueueStats totals;
2823 const uint n = num_task_queues();
2824 for (uint i = 0; i < n; ++i) {
2825 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2826 totals += task_queue(i)->stats;
2827 }
2828 st->print_raw("tot "); totals.print(st); st->cr();
2829
2830 DEBUG_ONLY(totals.verify());
2831 }
2832
2833 void G1CollectedHeap::reset_taskqueue_stats() {
2834 const uint n = num_task_queues();
2835 for (uint i = 0; i < n; ++i) {
2836 task_queue(i)->stats.reset();
2837 }
2838 }
2839 #endif // TASKQUEUE_STATS
2840
2841 void G1CollectedHeap::wait_for_root_region_scanning() {
2842 double scan_wait_start = os::elapsedTime();
2843 // We have to wait until the CM threads finish scanning the
2844 // root regions as it's the only way to ensure that all the
2845 // objects on them have been correctly scanned before we start
2846 // moving them during the GC.
2847 bool waited = _cm->root_regions()->wait_until_scan_finished();
2848 double wait_time_ms = 0.0;
2849 if (waited) {
2850 double scan_wait_end = os::elapsedTime();
2851 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2852 }
2853 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2854 }
2855
2856 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2857 private:
2858 G1HRPrinter* _hr_printer;
2859 public:
2860 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2861
2862 virtual bool doHeapRegion(HeapRegion* r) {
2863 _hr_printer->cset(r);
2864 return false;
2865 }
2866 };
2867
2868 void G1CollectedHeap::start_new_collection_set() {
2869 collection_set()->start_incremental_building();
2870
2871 clear_cset_fast_test();
2872
2873 guarantee(_eden.length() == 0, "eden should have been cleared");
2874 g1_policy()->transfer_survivors_to_cset(survivor());
2875 }
2876
2877 bool
2878 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
2879 assert_at_safepoint(true /* should_be_vm_thread */);
2880 guarantee(!is_gc_active(), "collection is not reentrant");
2881
2882 if (GCLocker::check_active_before_gc()) {
2883 return false;
2884 }
2885
2886 _gc_timer_stw->register_gc_start();
2887
2888 GCIdMark gc_id_mark;
2889 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
2890
2891 SvcGCMarker sgcm(SvcGCMarker::MINOR);
2892 ResourceMark rm;
2893
2894 g1_policy()->note_gc_start();
2895
2896 wait_for_root_region_scanning();
2897
2898 print_heap_before_gc();
2899 print_heap_regions();
2900 trace_heap_before_gc(_gc_tracer_stw);
2901
2902 _verifier->verify_region_sets_optional();
2903 _verifier->verify_dirty_young_regions();
2904
2905 // We should not be doing initial mark unless the conc mark thread is running
2906 if (!_cmThread->should_terminate()) {
2907 // This call will decide whether this pause is an initial-mark
2908 // pause. If it is, during_initial_mark_pause() will return true
2909 // for the duration of this pause.
2910 g1_policy()->decide_on_conc_mark_initiation();
2911 }
2912
2913 // We do not allow initial-mark to be piggy-backed on a mixed GC.
2914 assert(!collector_state()->during_initial_mark_pause() ||
2915 collector_state()->gcs_are_young(), "sanity");
2916
2917 // We also do not allow mixed GCs during marking.
2918 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity");
2919
2920 // Record whether this pause is an initial mark. When the current
2921 // thread has completed its logging output and it's safe to signal
2922 // the CM thread, the flag's value in the policy has been reset.
2923 bool should_start_conc_mark = collector_state()->during_initial_mark_pause();
2924
2925 // Inner scope for scope based logging, timers, and stats collection
2926 {
2927 EvacuationInfo evacuation_info;
2928
2929 if (collector_state()->during_initial_mark_pause()) {
2930 // We are about to start a marking cycle, so we increment the
2931 // full collection counter.
2932 increment_old_marking_cycles_started();
2933 _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
2934 }
2935
2936 _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
2937
2938 GCTraceCPUTime tcpu;
2939
2940 FormatBuffer<> gc_string("Pause ");
2941 if (collector_state()->during_initial_mark_pause()) {
2942 gc_string.append("Initial Mark");
2943 } else if (collector_state()->gcs_are_young()) {
2944 gc_string.append("Young");
2945 } else {
2946 gc_string.append("Mixed");
2947 }
2948 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true);
2949
2950 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
2951 workers()->active_workers(),
2952 Threads::number_of_non_daemon_threads());
2953 workers()->update_active_workers(active_workers);
2954 log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
2955
2956 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
2957 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
2958
2959 // If the secondary_free_list is not empty, append it to the
2960 // free_list. No need to wait for the cleanup operation to finish;
2961 // the region allocation code will check the secondary_free_list
2962 // and wait if necessary. If the G1StressConcRegionFreeing flag is
2963 // set, skip this step so that the region allocation code has to
2964 // get entries from the secondary_free_list.
2965 if (!G1StressConcRegionFreeing) {
2966 append_secondary_free_list_if_not_empty_with_lock();
2967 }
2968
2969 G1HeapTransition heap_transition(this);
2970 size_t heap_used_bytes_before_gc = used();
2971
2972 // Don't dynamically change the number of GC threads this early. A value of
2973 // 0 is used to indicate serial work. When parallel work is done,
2974 // it will be set.
2975
2976 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
2977 IsGCActiveMark x;
2978
2979 gc_prologue(false);
2980
2981 if (VerifyRememberedSets) {
2982 log_info(gc, verify)("[Verifying RemSets before GC]");
2983 VerifyRegionRemSetClosure v_cl;
2984 heap_region_iterate(&v_cl);
2985 }
2986
2987 _verifier->verify_before_gc();
2988
2989 _verifier->check_bitmaps("GC Start");
2990
2991 #if COMPILER2_OR_JVMCI
2992 DerivedPointerTable::clear();
2993 #endif
2994
2995 // Please see comment in g1CollectedHeap.hpp and
2996 // G1CollectedHeap::ref_processing_init() to see how
2997 // reference processing currently works in G1.
2998
2999 // Enable discovery in the STW reference processor
3000 if (g1_policy()->should_process_references()) {
3001 ref_processor_stw()->enable_discovery();
3002 } else {
3003 ref_processor_stw()->disable_discovery();
3004 }
3005
3006 {
3007 // We want to temporarily turn off discovery by the
3008 // CM ref processor, if necessary, and turn it back on
3009 // on again later if we do. Using a scoped
3010 // NoRefDiscovery object will do this.
3011 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3012
3013 // Forget the current alloc region (we might even choose it to be part
3014 // of the collection set!).
3015 _allocator->release_mutator_alloc_region();
3016
3017 // This timing is only used by the ergonomics to handle our pause target.
3018 // It is unclear why this should not include the full pause. We will
3019 // investigate this in CR 7178365.
3020 //
3021 // Preserving the old comment here if that helps the investigation:
3022 //
3023 // The elapsed time induced by the start time below deliberately elides
3024 // the possible verification above.
3025 double sample_start_time_sec = os::elapsedTime();
3026
3027 g1_policy()->record_collection_pause_start(sample_start_time_sec);
3028
3029 if (collector_state()->during_initial_mark_pause()) {
3030 concurrent_mark()->checkpoint_roots_initial_pre();
3031 }
3032
3033 g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor);
3034
3035 evacuation_info.set_collectionset_regions(collection_set()->region_length());
3036
3037 // Make sure the remembered sets are up to date. This needs to be
3038 // done before register_humongous_regions_with_cset(), because the
3039 // remembered sets are used there to choose eager reclaim candidates.
3040 // If the remembered sets are not up to date we might miss some
3041 // entries that need to be handled.
3042 g1_rem_set()->cleanupHRRS();
3043
3044 register_humongous_regions_with_cset();
3045
3046 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table.");
3047
3048 // We call this after finalize_cset() to
3049 // ensure that the CSet has been finalized.
3050 _cm->verify_no_cset_oops();
3051
3052 if (_hr_printer.is_active()) {
3053 G1PrintCollectionSetClosure cl(&_hr_printer);
3054 _collection_set.iterate(&cl);
3055 }
3056
3057 // Initialize the GC alloc regions.
3058 _allocator->init_gc_alloc_regions(evacuation_info);
3059
3060 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length());
3061 pre_evacuate_collection_set();
3062
3063 // Actually do the work...
3064 evacuate_collection_set(evacuation_info, &per_thread_states);
3065
3066 post_evacuate_collection_set(evacuation_info, &per_thread_states);
3067
3068 const size_t* surviving_young_words = per_thread_states.surviving_young_words();
3069 free_collection_set(&_collection_set, evacuation_info, surviving_young_words);
3070
3071 eagerly_reclaim_humongous_regions();
3072
3073 record_obj_copy_mem_stats();
3074 _survivor_evac_stats.adjust_desired_plab_sz();
3075 _old_evac_stats.adjust_desired_plab_sz();
3076
3077 double start = os::elapsedTime();
3078 start_new_collection_set();
3079 g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0);
3080
3081 if (evacuation_failed()) {
3082 set_used(recalculate_used());
3083 if (_archive_allocator != NULL) {
3084 _archive_allocator->clear_used();
3085 }
3086 for (uint i = 0; i < ParallelGCThreads; i++) {
3087 if (_evacuation_failed_info_array[i].has_failed()) {
3088 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3089 }
3090 }
3091 } else {
3092 // The "used" of the the collection set have already been subtracted
3093 // when they were freed. Add in the bytes evacuated.
3094 increase_used(g1_policy()->bytes_copied_during_gc());
3095 }
3096
3097 if (collector_state()->during_initial_mark_pause()) {
3098 // We have to do this before we notify the CM threads that
3099 // they can start working to make sure that all the
3100 // appropriate initialization is done on the CM object.
3101 concurrent_mark()->checkpoint_roots_initial_post();
3102 collector_state()->set_mark_in_progress(true);
3103 // Note that we don't actually trigger the CM thread at
3104 // this point. We do that later when we're sure that
3105 // the current thread has completed its logging output.
3106 }
3107
3108 allocate_dummy_regions();
3109
3110 _allocator->init_mutator_alloc_region();
3111
3112 {
3113 size_t expand_bytes = _heap_sizing_policy->expansion_amount();
3114 if (expand_bytes > 0) {
3115 size_t bytes_before = capacity();
3116 // No need for an ergo logging here,
3117 // expansion_amount() does this when it returns a value > 0.
3118 double expand_ms;
3119 if (!expand(expand_bytes, _workers, &expand_ms)) {
3120 // We failed to expand the heap. Cannot do anything about it.
3121 }
3122 g1_policy()->phase_times()->record_expand_heap_time(expand_ms);
3123 }
3124 }
3125
3126 // We redo the verification but now wrt to the new CSet which
3127 // has just got initialized after the previous CSet was freed.
3128 _cm->verify_no_cset_oops();
3129
3130 // This timing is only used by the ergonomics to handle our pause target.
3131 // It is unclear why this should not include the full pause. We will
3132 // investigate this in CR 7178365.
3133 double sample_end_time_sec = os::elapsedTime();
3134 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3135 size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards);
3136 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc);
3137
3138 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
3139 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc());
3140
3141 if (VerifyRememberedSets) {
3142 log_info(gc, verify)("[Verifying RemSets after GC]");
3143 VerifyRegionRemSetClosure v_cl;
3144 heap_region_iterate(&v_cl);
3145 }
3146
3147 _verifier->verify_after_gc();
3148 _verifier->check_bitmaps("GC End");
3149
3150 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3151 ref_processor_stw()->verify_no_references_recorded();
3152
3153 // CM reference discovery will be re-enabled if necessary.
3154 }
3155
3156 #ifdef TRACESPINNING
3157 ParallelTaskTerminator::print_termination_counts();
3158 #endif
3159
3160 gc_epilogue(false);
3161 }
3162
3163 // Print the remainder of the GC log output.
3164 if (evacuation_failed()) {
3165 log_info(gc)("To-space exhausted");
3166 }
3167
3168 g1_policy()->print_phases();
3169 heap_transition.print();
3170
3171 // It is not yet to safe to tell the concurrent mark to
3172 // start as we have some optional output below. We don't want the
3173 // output from the concurrent mark thread interfering with this
3174 // logging output either.
3175
3176 _hrm.verify_optional();
3177 _verifier->verify_region_sets_optional();
3178
3179 TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3180 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3181
3182 print_heap_after_gc();
3183 print_heap_regions();
3184 trace_heap_after_gc(_gc_tracer_stw);
3185
3186 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3187 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3188 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3189 // before any GC notifications are raised.
3190 g1mm()->update_sizes();
3191
3192 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3193 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
3194 _gc_timer_stw->register_gc_end();
3195 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3196 }
3197 // It should now be safe to tell the concurrent mark thread to start
3198 // without its logging output interfering with the logging output
3199 // that came from the pause.
3200
3201 if (should_start_conc_mark) {
3202 // CAUTION: after the doConcurrentMark() call below,
3203 // the concurrent marking thread(s) could be running
3204 // concurrently with us. Make sure that anything after
3205 // this point does not assume that we are the only GC thread
3206 // running. Note: of course, the actual marking work will
3207 // not start until the safepoint itself is released in
3208 // SuspendibleThreadSet::desynchronize().
3209 doConcurrentMark();
3210 }
3211
3212 return true;
3213 }
3214
3215 void G1CollectedHeap::remove_self_forwarding_pointers() {
3216 G1ParRemoveSelfForwardPtrsTask rsfp_task;
3217 workers()->run_task(&rsfp_task);
3218 }
3219
3220 void G1CollectedHeap::restore_after_evac_failure() {
3221 double remove_self_forwards_start = os::elapsedTime();
3222
3223 remove_self_forwarding_pointers();
3224 SharedRestorePreservedMarksTaskExecutor task_executor(workers());
3225 _preserved_marks_set.restore(&task_executor);
3226
3227 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3228 }
3229
3230 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) {
3231 if (!_evacuation_failed) {
3232 _evacuation_failed = true;
3233 }
3234
3235 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3236 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3237 }
3238
3239 bool G1ParEvacuateFollowersClosure::offer_termination() {
3240 G1ParScanThreadState* const pss = par_scan_state();
3241 start_term_time();
3242 const bool res = terminator()->offer_termination();
3243 end_term_time();
3244 return res;
3245 }
3246
3247 void G1ParEvacuateFollowersClosure::do_void() {
3248 G1ParScanThreadState* const pss = par_scan_state();
3249 pss->trim_queue();
3250 do {
3251 pss->steal_and_trim_queue(queues());
3252 } while (!offer_termination());
3253 }
3254
3255 class G1ParTask : public AbstractGangTask {
3256 protected:
3257 G1CollectedHeap* _g1h;
3258 G1ParScanThreadStateSet* _pss;
3259 RefToScanQueueSet* _queues;
3260 G1RootProcessor* _root_processor;
3261 ParallelTaskTerminator _terminator;
3262 uint _n_workers;
3263
3264 public:
3265 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers)
3266 : AbstractGangTask("G1 collection"),
3267 _g1h(g1h),
3268 _pss(per_thread_states),
3269 _queues(task_queues),
3270 _root_processor(root_processor),
3271 _terminator(n_workers, _queues),
3272 _n_workers(n_workers)
3273 {}
3274
3275 void work(uint worker_id) {
3276 if (worker_id >= _n_workers) return; // no work needed this round
3277
3278 double start_sec = os::elapsedTime();
3279 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec);
3280
3281 {
3282 ResourceMark rm;
3283 HandleMark hm;
3284
3285 ReferenceProcessor* rp = _g1h->ref_processor_stw();
3286
3287 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
3288 pss->set_ref_processor(rp);
3289
3290 double start_strong_roots_sec = os::elapsedTime();
3291
3292 _root_processor->evacuate_roots(pss->closures(), worker_id);
3293
3294 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid
3295 // treating the nmethods visited to act as roots for concurrent marking.
3296 // We only want to make sure that the oops in the nmethods are adjusted with regard to the
3297 // objects copied by the current evacuation.
3298 _g1h->g1_rem_set()->oops_into_collection_set_do(pss,
3299 pss->closures()->weak_codeblobs(),
3300 worker_id);
3301
3302 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec;
3303
3304 double term_sec = 0.0;
3305 size_t evac_term_attempts = 0;
3306 {
3307 double start = os::elapsedTime();
3308 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator);
3309 evac.do_void();
3310
3311 evac_term_attempts = evac.term_attempts();
3312 term_sec = evac.term_time();
3313 double elapsed_sec = os::elapsedTime() - start;
3314 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
3315 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
3316 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts);
3317 }
3318
3319 assert(pss->queue_is_empty(), "should be empty");
3320
3321 if (log_is_enabled(Debug, gc, task, stats)) {
3322 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3323 size_t lab_waste;
3324 size_t lab_undo_waste;
3325 pss->waste(lab_waste, lab_undo_waste);
3326 _g1h->print_termination_stats(worker_id,
3327 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */
3328 strong_roots_sec * 1000.0, /* strong roots time */
3329 term_sec * 1000.0, /* evac term time */
3330 evac_term_attempts, /* evac term attempts */
3331 lab_waste, /* alloc buffer waste */
3332 lab_undo_waste /* undo waste */
3333 );
3334 }
3335
3336 // Close the inner scope so that the ResourceMark and HandleMark
3337 // destructors are executed here and are included as part of the
3338 // "GC Worker Time".
3339 }
3340 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
3341 }
3342 };
3343
3344 void G1CollectedHeap::print_termination_stats_hdr() {
3345 log_debug(gc, task, stats)("GC Termination Stats");
3346 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------");
3347 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo");
3348 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------");
3349 }
3350
3351 void G1CollectedHeap::print_termination_stats(uint worker_id,
3352 double elapsed_ms,
3353 double strong_roots_ms,
3354 double term_ms,
3355 size_t term_attempts,
3356 size_t alloc_buffer_waste,
3357 size_t undo_waste) const {
3358 log_debug(gc, task, stats)
3359 ("%3d %9.2f %9.2f %6.2f "
3360 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
3361 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
3362 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms,
3363 term_ms, term_ms * 100 / elapsed_ms, term_attempts,
3364 (alloc_buffer_waste + undo_waste) * HeapWordSize / K,
3365 alloc_buffer_waste * HeapWordSize / K,
3366 undo_waste * HeapWordSize / K);
3367 }
3368
3369 class G1StringAndSymbolCleaningTask : public AbstractGangTask {
3370 private:
3371 BoolObjectClosure* _is_alive;
3372 G1StringDedupUnlinkOrOopsDoClosure _dedup_closure;
3373
3374 int _initial_string_table_size;
3375 int _initial_symbol_table_size;
3376
3377 bool _process_strings;
3378 int _strings_processed;
3379 int _strings_removed;
3380
3381 bool _process_symbols;
3382 int _symbols_processed;
3383 int _symbols_removed;
3384
3385 bool _process_string_dedup;
3386
3387 public:
3388 G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) :
3389 AbstractGangTask("String/Symbol Unlinking"),
3390 _is_alive(is_alive),
3391 _dedup_closure(is_alive, NULL, false),
3392 _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
3393 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0),
3394 _process_string_dedup(process_string_dedup) {
3395
3396 _initial_string_table_size = StringTable::the_table()->table_size();
3397 _initial_symbol_table_size = SymbolTable::the_table()->table_size();
3398 if (process_strings) {
3399 StringTable::clear_parallel_claimed_index();
3400 }
3401 if (process_symbols) {
3402 SymbolTable::clear_parallel_claimed_index();
3403 }
3404 }
3405
3406 ~G1StringAndSymbolCleaningTask() {
3407 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
3408 "claim value %d after unlink less than initial string table size %d",
3409 StringTable::parallel_claimed_index(), _initial_string_table_size);
3410 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
3411 "claim value %d after unlink less than initial symbol table size %d",
3412 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size);
3413
3414 log_info(gc, stringtable)(
3415 "Cleaned string and symbol table, "
3416 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, "
3417 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
3418 strings_processed(), strings_removed(),
3419 symbols_processed(), symbols_removed());
3420 }
3421
3422 void work(uint worker_id) {
3423 int strings_processed = 0;
3424 int strings_removed = 0;
3425 int symbols_processed = 0;
3426 int symbols_removed = 0;
3427 if (_process_strings) {
3428 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
3429 Atomic::add(strings_processed, &_strings_processed);
3430 Atomic::add(strings_removed, &_strings_removed);
3431 }
3432 if (_process_symbols) {
3433 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
3434 Atomic::add(symbols_processed, &_symbols_processed);
3435 Atomic::add(symbols_removed, &_symbols_removed);
3436 }
3437 if (_process_string_dedup) {
3438 G1StringDedup::parallel_unlink(&_dedup_closure, worker_id);
3439 }
3440 }
3441
3442 size_t strings_processed() const { return (size_t)_strings_processed; }
3443 size_t strings_removed() const { return (size_t)_strings_removed; }
3444
3445 size_t symbols_processed() const { return (size_t)_symbols_processed; }
3446 size_t symbols_removed() const { return (size_t)_symbols_removed; }
3447 };
3448
3449 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
3450 private:
3451 static Monitor* _lock;
3452
3453 BoolObjectClosure* const _is_alive;
3454 const bool _unloading_occurred;
3455 const uint _num_workers;
3456
3457 // Variables used to claim nmethods.
3458 CompiledMethod* _first_nmethod;
3459 CompiledMethod* volatile _claimed_nmethod;
3460
3461 // The list of nmethods that need to be processed by the second pass.
3462 CompiledMethod* volatile _postponed_list;
3463 volatile uint _num_entered_barrier;
3464
3465 public:
3466 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
3467 _is_alive(is_alive),
3468 _unloading_occurred(unloading_occurred),
3469 _num_workers(num_workers),
3470 _first_nmethod(NULL),
3471 _claimed_nmethod(NULL),
3472 _postponed_list(NULL),
3473 _num_entered_barrier(0)
3474 {
3475 CompiledMethod::increase_unloading_clock();
3476 // Get first alive nmethod
3477 CompiledMethodIterator iter = CompiledMethodIterator();
3478 if(iter.next_alive()) {
3479 _first_nmethod = iter.method();
3480 }
3481 _claimed_nmethod = _first_nmethod;
3482 }
3483
3484 ~G1CodeCacheUnloadingTask() {
3485 CodeCache::verify_clean_inline_caches();
3486
3487 CodeCache::set_needs_cache_clean(false);
3488 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
3489
3490 CodeCache::verify_icholder_relocations();
3491 }
3492
3493 private:
3494 void add_to_postponed_list(CompiledMethod* nm) {
3495 CompiledMethod* old;
3496 do {
3497 old = _postponed_list;
3498 nm->set_unloading_next(old);
3499 } while (Atomic::cmpxchg(nm, &_postponed_list, old) != old);
3500 }
3501
3502 void clean_nmethod(CompiledMethod* nm) {
3503 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
3504
3505 if (postponed) {
3506 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
3507 add_to_postponed_list(nm);
3508 }
3509
3510 // Mark that this thread has been cleaned/unloaded.
3511 // After this call, it will be safe to ask if this nmethod was unloaded or not.
3512 nm->set_unloading_clock(CompiledMethod::global_unloading_clock());
3513 }
3514
3515 void clean_nmethod_postponed(CompiledMethod* nm) {
3516 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
3517 }
3518
3519 static const int MaxClaimNmethods = 16;
3520
3521 void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) {
3522 CompiledMethod* first;
3523 CompiledMethodIterator last;
3524
3525 do {
3526 *num_claimed_nmethods = 0;
3527
3528 first = _claimed_nmethod;
3529 last = CompiledMethodIterator(first);
3530
3531 if (first != NULL) {
3532
3533 for (int i = 0; i < MaxClaimNmethods; i++) {
3534 if (!last.next_alive()) {
3535 break;
3536 }
3537 claimed_nmethods[i] = last.method();
3538 (*num_claimed_nmethods)++;
3539 }
3540 }
3541
3542 } while (Atomic::cmpxchg(last.method(), &_claimed_nmethod, first) != first);
3543 }
3544
3545 CompiledMethod* claim_postponed_nmethod() {
3546 CompiledMethod* claim;
3547 CompiledMethod* next;
3548
3549 do {
3550 claim = _postponed_list;
3551 if (claim == NULL) {
3552 return NULL;
3553 }
3554
3555 next = claim->unloading_next();
3556
3557 } while (Atomic::cmpxchg(next, &_postponed_list, claim) != claim);
3558
3559 return claim;
3560 }
3561
3562 public:
3563 // Mark that we're done with the first pass of nmethod cleaning.
3564 void barrier_mark(uint worker_id) {
3565 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3566 _num_entered_barrier++;
3567 if (_num_entered_barrier == _num_workers) {
3568 ml.notify_all();
3569 }
3570 }
3571
3572 // See if we have to wait for the other workers to
3573 // finish their first-pass nmethod cleaning work.
3574 void barrier_wait(uint worker_id) {
3575 if (_num_entered_barrier < _num_workers) {
3576 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3577 while (_num_entered_barrier < _num_workers) {
3578 ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
3579 }
3580 }
3581 }
3582
3583 // Cleaning and unloading of nmethods. Some work has to be postponed
3584 // to the second pass, when we know which nmethods survive.
3585 void work_first_pass(uint worker_id) {
3586 // The first nmethods is claimed by the first worker.
3587 if (worker_id == 0 && _first_nmethod != NULL) {
3588 clean_nmethod(_first_nmethod);
3589 _first_nmethod = NULL;
3590 }
3591
3592 int num_claimed_nmethods;
3593 CompiledMethod* claimed_nmethods[MaxClaimNmethods];
3594
3595 while (true) {
3596 claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
3597
3598 if (num_claimed_nmethods == 0) {
3599 break;
3600 }
3601
3602 for (int i = 0; i < num_claimed_nmethods; i++) {
3603 clean_nmethod(claimed_nmethods[i]);
3604 }
3605 }
3606 }
3607
3608 void work_second_pass(uint worker_id) {
3609 CompiledMethod* nm;
3610 // Take care of postponed nmethods.
3611 while ((nm = claim_postponed_nmethod()) != NULL) {
3612 clean_nmethod_postponed(nm);
3613 }
3614 }
3615 };
3616
3617 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
3618
3619 class G1KlassCleaningTask : public StackObj {
3620 BoolObjectClosure* _is_alive;
3621 volatile int _clean_klass_tree_claimed;
3622 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
3623
3624 public:
3625 G1KlassCleaningTask(BoolObjectClosure* is_alive) :
3626 _is_alive(is_alive),
3627 _clean_klass_tree_claimed(0),
3628 _klass_iterator() {
3629 }
3630
3631 private:
3632 bool claim_clean_klass_tree_task() {
3633 if (_clean_klass_tree_claimed) {
3634 return false;
3635 }
3636
3637 return Atomic::cmpxchg(1, &_clean_klass_tree_claimed, 0) == 0;
3638 }
3639
3640 InstanceKlass* claim_next_klass() {
3641 Klass* klass;
3642 do {
3643 klass =_klass_iterator.next_klass();
3644 } while (klass != NULL && !klass->is_instance_klass());
3645
3646 // this can be null so don't call InstanceKlass::cast
3647 return static_cast<InstanceKlass*>(klass);
3648 }
3649
3650 public:
3651
3652 void clean_klass(InstanceKlass* ik) {
3653 ik->clean_weak_instanceklass_links(_is_alive);
3654 }
3655
3656 void work() {
3657 ResourceMark rm;
3658
3659 // One worker will clean the subklass/sibling klass tree.
3660 if (claim_clean_klass_tree_task()) {
3661 Klass::clean_subklass_tree(_is_alive);
3662 }
3663
3664 // All workers will help cleaning the classes,
3665 InstanceKlass* klass;
3666 while ((klass = claim_next_klass()) != NULL) {
3667 clean_klass(klass);
3668 }
3669 }
3670 };
3671
3672 class G1ResolvedMethodCleaningTask : public StackObj {
3673 BoolObjectClosure* _is_alive;
3674 volatile int _resolved_method_task_claimed;
3675 public:
3676 G1ResolvedMethodCleaningTask(BoolObjectClosure* is_alive) :
3677 _is_alive(is_alive), _resolved_method_task_claimed(0) {}
3678
3679 bool claim_resolved_method_task() {
3680 if (_resolved_method_task_claimed) {
3681 return false;
3682 }
3683 return Atomic::cmpxchg(1, &_resolved_method_task_claimed, 0) == 0;
3684 }
3685
3686 // These aren't big, one thread can do it all.
3687 void work() {
3688 if (claim_resolved_method_task()) {
3689 ResolvedMethodTable::unlink(_is_alive);
3690 }
3691 }
3692 };
3693
3694
3695 // To minimize the remark pause times, the tasks below are done in parallel.
3696 class G1ParallelCleaningTask : public AbstractGangTask {
3697 private:
3698 G1StringAndSymbolCleaningTask _string_symbol_task;
3699 G1CodeCacheUnloadingTask _code_cache_task;
3700 G1KlassCleaningTask _klass_cleaning_task;
3701 G1ResolvedMethodCleaningTask _resolved_method_cleaning_task;
3702
3703 public:
3704 // The constructor is run in the VMThread.
3705 G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) :
3706 AbstractGangTask("Parallel Cleaning"),
3707 _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()),
3708 _code_cache_task(num_workers, is_alive, unloading_occurred),
3709 _klass_cleaning_task(is_alive),
3710 _resolved_method_cleaning_task(is_alive) {
3711 }
3712
3713 // The parallel work done by all worker threads.
3714 void work(uint worker_id) {
3715 // Do first pass of code cache cleaning.
3716 _code_cache_task.work_first_pass(worker_id);
3717
3718 // Let the threads mark that the first pass is done.
3719 _code_cache_task.barrier_mark(worker_id);
3720
3721 // Clean the Strings and Symbols.
3722 _string_symbol_task.work(worker_id);
3723
3724 // Clean unreferenced things in the ResolvedMethodTable
3725 _resolved_method_cleaning_task.work();
3726
3727 // Wait for all workers to finish the first code cache cleaning pass.
3728 _code_cache_task.barrier_wait(worker_id);
3729
3730 // Do the second code cache cleaning work, which realize on
3731 // the liveness information gathered during the first pass.
3732 _code_cache_task.work_second_pass(worker_id);
3733
3734 // Clean all klasses that were not unloaded.
3735 _klass_cleaning_task.work();
3736 }
3737 };
3738
3739
3740 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
3741 bool class_unloading_occurred) {
3742 uint n_workers = workers()->active_workers();
3743
3744 G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred);
3745 workers()->run_task(&g1_unlink_task);
3746 }
3747
3748 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive,
3749 bool process_strings,
3750 bool process_symbols,
3751 bool process_string_dedup) {
3752 if (!process_strings && !process_symbols && !process_string_dedup) {
3753 // Nothing to clean.
3754 return;
3755 }
3756
3757 G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup);
3758 workers()->run_task(&g1_unlink_task);
3759
3760 }
3761
3762 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3763 private:
3764 DirtyCardQueueSet* _queue;
3765 G1CollectedHeap* _g1h;
3766 public:
3767 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"),
3768 _queue(queue), _g1h(g1h) { }
3769
3770 virtual void work(uint worker_id) {
3771 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
3772 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
3773
3774 RedirtyLoggedCardTableEntryClosure cl(_g1h);
3775 _queue->par_apply_closure_to_all_completed_buffers(&cl);
3776
3777 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3778 }
3779 };
3780
3781 void G1CollectedHeap::redirty_logged_cards() {
3782 double redirty_logged_cards_start = os::elapsedTime();
3783
3784 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this);
3785 dirty_card_queue_set().reset_for_par_iteration();
3786 workers()->run_task(&redirty_task);
3787
3788 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
3789 dcq.merge_bufferlists(&dirty_card_queue_set());
3790 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
3791
3792 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3793 }
3794
3795 // Weak Reference Processing support
3796
3797 // An always "is_alive" closure that is used to preserve referents.
3798 // If the object is non-null then it's alive. Used in the preservation
3799 // of referent objects that are pointed to by reference objects
3800 // discovered by the CM ref processor.
3801 class G1AlwaysAliveClosure: public BoolObjectClosure {
3802 G1CollectedHeap* _g1;
3803 public:
3804 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3805 bool do_object_b(oop p) {
3806 if (p != NULL) {
3807 return true;
3808 }
3809 return false;
3810 }
3811 };
3812
3813 bool G1STWIsAliveClosure::do_object_b(oop p) {
3814 // An object is reachable if it is outside the collection set,
3815 // or is inside and copied.
3816 return !_g1->is_in_cset(p) || p->is_forwarded();
3817 }
3818
3819 // Non Copying Keep Alive closure
3820 class G1KeepAliveClosure: public OopClosure {
3821 G1CollectedHeap* _g1;
3822 public:
3823 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3824 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3825 void do_oop(oop* p) {
3826 oop obj = *p;
3827 assert(obj != NULL, "the caller should have filtered out NULL values");
3828
3829 const InCSetState cset_state = _g1->in_cset_state(obj);
3830 if (!cset_state.is_in_cset_or_humongous()) {
3831 return;
3832 }
3833 if (cset_state.is_in_cset()) {
3834 assert( obj->is_forwarded(), "invariant" );
3835 *p = obj->forwardee();
3836 } else {
3837 assert(!obj->is_forwarded(), "invariant" );
3838 assert(cset_state.is_humongous(),
3839 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value());
3840 _g1->set_humongous_is_live(obj);
3841 }
3842 }
3843 };
3844
3845 // Copying Keep Alive closure - can be called from both
3846 // serial and parallel code as long as different worker
3847 // threads utilize different G1ParScanThreadState instances
3848 // and different queues.
3849
3850 class G1CopyingKeepAliveClosure: public OopClosure {
3851 G1CollectedHeap* _g1h;
3852 OopClosure* _copy_non_heap_obj_cl;
3853 G1ParScanThreadState* _par_scan_state;
3854
3855 public:
3856 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3857 OopClosure* non_heap_obj_cl,
3858 G1ParScanThreadState* pss):
3859 _g1h(g1h),
3860 _copy_non_heap_obj_cl(non_heap_obj_cl),
3861 _par_scan_state(pss)
3862 {}
3863
3864 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3865 virtual void do_oop( oop* p) { do_oop_work(p); }
3866
3867 template <class T> void do_oop_work(T* p) {
3868 oop obj = oopDesc::load_decode_heap_oop(p);
3869
3870 if (_g1h->is_in_cset_or_humongous(obj)) {
3871 // If the referent object has been forwarded (either copied
3872 // to a new location or to itself in the event of an
3873 // evacuation failure) then we need to update the reference
3874 // field and, if both reference and referent are in the G1
3875 // heap, update the RSet for the referent.
3876 //
3877 // If the referent has not been forwarded then we have to keep
3878 // it alive by policy. Therefore we have copy the referent.
3879 //
3880 // If the reference field is in the G1 heap then we can push
3881 // on the PSS queue. When the queue is drained (after each
3882 // phase of reference processing) the object and it's followers
3883 // will be copied, the reference field set to point to the
3884 // new location, and the RSet updated. Otherwise we need to
3885 // use the the non-heap or metadata closures directly to copy
3886 // the referent object and update the pointer, while avoiding
3887 // updating the RSet.
3888
3889 if (_g1h->is_in_g1_reserved(p)) {
3890 _par_scan_state->push_on_queue(p);
3891 } else {
3892 assert(!Metaspace::contains((const void*)p),
3893 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p));
3894 _copy_non_heap_obj_cl->do_oop(p);
3895 }
3896 }
3897 }
3898 };
3899
3900 // Serial drain queue closure. Called as the 'complete_gc'
3901 // closure for each discovered list in some of the
3902 // reference processing phases.
3903
3904 class G1STWDrainQueueClosure: public VoidClosure {
3905 protected:
3906 G1CollectedHeap* _g1h;
3907 G1ParScanThreadState* _par_scan_state;
3908
3909 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
3910
3911 public:
3912 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
3913 _g1h(g1h),
3914 _par_scan_state(pss)
3915 { }
3916
3917 void do_void() {
3918 G1ParScanThreadState* const pss = par_scan_state();
3919 pss->trim_queue();
3920 }
3921 };
3922
3923 // Parallel Reference Processing closures
3924
3925 // Implementation of AbstractRefProcTaskExecutor for parallel reference
3926 // processing during G1 evacuation pauses.
3927
3928 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
3929 private:
3930 G1CollectedHeap* _g1h;
3931 G1ParScanThreadStateSet* _pss;
3932 RefToScanQueueSet* _queues;
3933 WorkGang* _workers;
3934 uint _active_workers;
3935
3936 public:
3937 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
3938 G1ParScanThreadStateSet* per_thread_states,
3939 WorkGang* workers,
3940 RefToScanQueueSet *task_queues,
3941 uint n_workers) :
3942 _g1h(g1h),
3943 _pss(per_thread_states),
3944 _queues(task_queues),
3945 _workers(workers),
3946 _active_workers(n_workers)
3947 {
3948 g1h->ref_processor_stw()->set_active_mt_degree(n_workers);
3949 }
3950
3951 // Executes the given task using concurrent marking worker threads.
3952 virtual void execute(ProcessTask& task);
3953 virtual void execute(EnqueueTask& task);
3954 };
3955
3956 // Gang task for possibly parallel reference processing
3957
3958 class G1STWRefProcTaskProxy: public AbstractGangTask {
3959 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
3960 ProcessTask& _proc_task;
3961 G1CollectedHeap* _g1h;
3962 G1ParScanThreadStateSet* _pss;
3963 RefToScanQueueSet* _task_queues;
3964 ParallelTaskTerminator* _terminator;
3965
3966 public:
3967 G1STWRefProcTaskProxy(ProcessTask& proc_task,
3968 G1CollectedHeap* g1h,
3969 G1ParScanThreadStateSet* per_thread_states,
3970 RefToScanQueueSet *task_queues,
3971 ParallelTaskTerminator* terminator) :
3972 AbstractGangTask("Process reference objects in parallel"),
3973 _proc_task(proc_task),
3974 _g1h(g1h),
3975 _pss(per_thread_states),
3976 _task_queues(task_queues),
3977 _terminator(terminator)
3978 {}
3979
3980 virtual void work(uint worker_id) {
3981 // The reference processing task executed by a single worker.
3982 ResourceMark rm;
3983 HandleMark hm;
3984
3985 G1STWIsAliveClosure is_alive(_g1h);
3986
3987 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
3988 pss->set_ref_processor(NULL);
3989
3990 // Keep alive closure.
3991 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
3992
3993 // Complete GC closure
3994 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator);
3995
3996 // Call the reference processing task's work routine.
3997 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
3998
3999 // Note we cannot assert that the refs array is empty here as not all
4000 // of the processing tasks (specifically phase2 - pp2_work) execute
4001 // the complete_gc closure (which ordinarily would drain the queue) so
4002 // the queue may not be empty.
4003 }
4004 };
4005
4006 // Driver routine for parallel reference processing.
4007 // Creates an instance of the ref processing gang
4008 // task and has the worker threads execute it.
4009 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
4010 assert(_workers != NULL, "Need parallel worker threads.");
4011
4012 ParallelTaskTerminator terminator(_active_workers, _queues);
4013 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
4014
4015 _workers->run_task(&proc_task_proxy);
4016 }
4017
4018 // Gang task for parallel reference enqueueing.
4019
4020 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
4021 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
4022 EnqueueTask& _enq_task;
4023
4024 public:
4025 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
4026 AbstractGangTask("Enqueue reference objects in parallel"),
4027 _enq_task(enq_task)
4028 { }
4029
4030 virtual void work(uint worker_id) {
4031 _enq_task.work(worker_id);
4032 }
4033 };
4034
4035 // Driver routine for parallel reference enqueueing.
4036 // Creates an instance of the ref enqueueing gang
4037 // task and has the worker threads execute it.
4038
4039 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
4040 assert(_workers != NULL, "Need parallel worker threads.");
4041
4042 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
4043
4044 _workers->run_task(&enq_task_proxy);
4045 }
4046
4047 // End of weak reference support closures
4048
4049 // Abstract task used to preserve (i.e. copy) any referent objects
4050 // that are in the collection set and are pointed to by reference
4051 // objects discovered by the CM ref processor.
4052
4053 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
4054 protected:
4055 G1CollectedHeap* _g1h;
4056 G1ParScanThreadStateSet* _pss;
4057 RefToScanQueueSet* _queues;
4058 ParallelTaskTerminator _terminator;
4059 uint _n_workers;
4060
4061 public:
4062 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) :
4063 AbstractGangTask("ParPreserveCMReferents"),
4064 _g1h(g1h),
4065 _pss(per_thread_states),
4066 _queues(task_queues),
4067 _terminator(workers, _queues),
4068 _n_workers(workers)
4069 {
4070 g1h->ref_processor_cm()->set_active_mt_degree(workers);
4071 }
4072
4073 void work(uint worker_id) {
4074 G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id);
4075
4076 ResourceMark rm;
4077 HandleMark hm;
4078
4079 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
4080 pss->set_ref_processor(NULL);
4081 assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4082
4083 // Is alive closure
4084 G1AlwaysAliveClosure always_alive(_g1h);
4085
4086 // Copying keep alive closure. Applied to referent objects that need
4087 // to be copied.
4088 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4089
4090 ReferenceProcessor* rp = _g1h->ref_processor_cm();
4091
4092 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
4093 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
4094
4095 // limit is set using max_num_q() - which was set using ParallelGCThreads.
4096 // So this must be true - but assert just in case someone decides to
4097 // change the worker ids.
4098 assert(worker_id < limit, "sanity");
4099 assert(!rp->discovery_is_atomic(), "check this code");
4100
4101 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
4102 for (uint idx = worker_id; idx < limit; idx += stride) {
4103 DiscoveredList& ref_list = rp->discovered_refs()[idx];
4104
4105 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
4106 while (iter.has_next()) {
4107 // Since discovery is not atomic for the CM ref processor, we
4108 // can see some null referent objects.
4109 iter.load_ptrs(DEBUG_ONLY(true));
4110 oop ref = iter.obj();
4111
4112 // This will filter nulls.
4113 if (iter.is_referent_alive()) {
4114 iter.make_referent_alive();
4115 }
4116 iter.move_to_next();
4117 }
4118 }
4119
4120 // Drain the queue - which may cause stealing
4121 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator);
4122 drain_queue.do_void();
4123 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
4124 assert(pss->queue_is_empty(), "should be");
4125 }
4126 };
4127
4128 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) {
4129 // Any reference objects, in the collection set, that were 'discovered'
4130 // by the CM ref processor should have already been copied (either by
4131 // applying the external root copy closure to the discovered lists, or
4132 // by following an RSet entry).
4133 //
4134 // But some of the referents, that are in the collection set, that these
4135 // reference objects point to may not have been copied: the STW ref
4136 // processor would have seen that the reference object had already
4137 // been 'discovered' and would have skipped discovering the reference,
4138 // but would not have treated the reference object as a regular oop.
4139 // As a result the copy closure would not have been applied to the
4140 // referent object.
4141 //
4142 // We need to explicitly copy these referent objects - the references
4143 // will be processed at the end of remarking.
4144 //
4145 // We also need to do this copying before we process the reference
4146 // objects discovered by the STW ref processor in case one of these
4147 // referents points to another object which is also referenced by an
4148 // object discovered by the STW ref processor.
4149 double preserve_cm_referents_time = 0.0;
4150
4151 // To avoid spawning task when there is no work to do, check that
4152 // a concurrent cycle is active and that some references have been
4153 // discovered.
4154 if (concurrent_mark()->cm_thread()->during_cycle() &&
4155 ref_processor_cm()->has_discovered_references()) {
4156 double preserve_cm_referents_start = os::elapsedTime();
4157 uint no_of_gc_workers = workers()->active_workers();
4158 G1ParPreserveCMReferentsTask keep_cm_referents(this,
4159 per_thread_states,
4160 no_of_gc_workers,
4161 _task_queues);
4162 workers()->run_task(&keep_cm_referents);
4163 preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start;
4164 }
4165
4166 g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0);
4167 }
4168
4169 // Weak Reference processing during an evacuation pause (part 1).
4170 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4171 double ref_proc_start = os::elapsedTime();
4172
4173 ReferenceProcessor* rp = _ref_processor_stw;
4174 assert(rp->discovery_enabled(), "should have been enabled");
4175
4176 // Closure to test whether a referent is alive.
4177 G1STWIsAliveClosure is_alive(this);
4178
4179 // Even when parallel reference processing is enabled, the processing
4180 // of JNI refs is serial and performed serially by the current thread
4181 // rather than by a worker. The following PSS will be used for processing
4182 // JNI refs.
4183
4184 // Use only a single queue for this PSS.
4185 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0);
4186 pss->set_ref_processor(NULL);
4187 assert(pss->queue_is_empty(), "pre-condition");
4188
4189 // Keep alive closure.
4190 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss);
4191
4192 // Serial Complete GC closure
4193 G1STWDrainQueueClosure drain_queue(this, pss);
4194
4195 // Setup the soft refs policy...
4196 rp->setup_policy(false);
4197
4198 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times();
4199
4200 ReferenceProcessorStats stats;
4201 if (!rp->processing_is_mt()) {
4202 // Serial reference processing...
4203 stats = rp->process_discovered_references(&is_alive,
4204 &keep_alive,
4205 &drain_queue,
4206 NULL,
4207 pt);
4208 } else {
4209 uint no_of_gc_workers = workers()->active_workers();
4210
4211 // Parallel reference processing
4212 assert(no_of_gc_workers <= rp->max_num_q(),
4213 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4214 no_of_gc_workers, rp->max_num_q());
4215
4216 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers);
4217 stats = rp->process_discovered_references(&is_alive,
4218 &keep_alive,
4219 &drain_queue,
4220 &par_task_executor,
4221 pt);
4222 }
4223
4224 _gc_tracer_stw->report_gc_reference_stats(stats);
4225
4226 // We have completed copying any necessary live referent objects.
4227 assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4228
4229 double ref_proc_time = os::elapsedTime() - ref_proc_start;
4230 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4231 }
4232
4233 // Weak Reference processing during an evacuation pause (part 2).
4234 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4235 double ref_enq_start = os::elapsedTime();
4236
4237 ReferenceProcessor* rp = _ref_processor_stw;
4238 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
4239
4240 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times();
4241
4242 // Now enqueue any remaining on the discovered lists on to
4243 // the pending list.
4244 if (!rp->processing_is_mt()) {
4245 // Serial reference processing...
4246 rp->enqueue_discovered_references(NULL, pt);
4247 } else {
4248 // Parallel reference enqueueing
4249
4250 uint n_workers = workers()->active_workers();
4251
4252 assert(n_workers <= rp->max_num_q(),
4253 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4254 n_workers, rp->max_num_q());
4255
4256 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers);
4257 rp->enqueue_discovered_references(&par_task_executor, pt);
4258 }
4259
4260 rp->verify_no_references_recorded();
4261 assert(!rp->discovery_enabled(), "should have been disabled");
4262
4263 // If during an initial mark pause we install a pending list head which is not otherwise reachable
4264 // ensure that it is marked in the bitmap for concurrent marking to discover.
4265 if (collector_state()->during_initial_mark_pause()) {
4266 oop pll_head = Universe::reference_pending_list();
4267 if (pll_head != NULL) {
4268 _cm->mark_in_next_bitmap(pll_head);
4269 }
4270 }
4271
4272 // FIXME
4273 // CM's reference processing also cleans up the string and symbol tables.
4274 // Should we do that here also? We could, but it is a serial operation
4275 // and could significantly increase the pause time.
4276
4277 double ref_enq_time = os::elapsedTime() - ref_enq_start;
4278 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
4279 }
4280
4281 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
4282 double merge_pss_time_start = os::elapsedTime();
4283 per_thread_states->flush();
4284 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0);
4285 }
4286
4287 void G1CollectedHeap::pre_evacuate_collection_set() {
4288 _expand_heap_after_alloc_failure = true;
4289 _evacuation_failed = false;
4290
4291 // Disable the hot card cache.
4292 _hot_card_cache->reset_hot_cache_claimed_index();
4293 _hot_card_cache->set_use_cache(false);
4294
4295 g1_rem_set()->prepare_for_oops_into_collection_set_do();
4296 _preserved_marks_set.assert_empty();
4297
4298 G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4299
4300 // InitialMark needs claim bits to keep track of the marked-through CLDs.
4301 if (collector_state()->during_initial_mark_pause()) {
4302 double start_clear_claimed_marks = os::elapsedTime();
4303
4304 ClassLoaderDataGraph::clear_claimed_marks();
4305
4306 double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
4307 phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
4308 }
4309 }
4310
4311 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4312 // Should G1EvacuationFailureALot be in effect for this GC?
4313 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
4314
4315 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
4316
4317 G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4318
4319 double start_par_time_sec = os::elapsedTime();
4320 double end_par_time_sec;
4321
4322 {
4323 const uint n_workers = workers()->active_workers();
4324 G1RootProcessor root_processor(this, n_workers);
4325 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers);
4326
4327 print_termination_stats_hdr();
4328
4329 workers()->run_task(&g1_par_task);
4330 end_par_time_sec = os::elapsedTime();
4331
4332 // Closing the inner scope will execute the destructor
4333 // for the G1RootProcessor object. We record the current
4334 // elapsed time before closing the scope so that time
4335 // taken for the destructor is NOT included in the
4336 // reported parallel time.
4337 }
4338
4339 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
4340 phase_times->record_par_time(par_time_ms);
4341
4342 double code_root_fixup_time_ms =
4343 (os::elapsedTime() - end_par_time_sec) * 1000.0;
4344 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
4345 }
4346
4347 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4348 // Process any discovered reference objects - we have
4349 // to do this _before_ we retire the GC alloc regions
4350 // as we may have to copy some 'reachable' referent
4351 // objects (and their reachable sub-graphs) that were
4352 // not copied during the pause.
4353 if (g1_policy()->should_process_references()) {
4354 preserve_cm_referents(per_thread_states);
4355 process_discovered_references(per_thread_states);
4356 } else {
4357 ref_processor_stw()->verify_no_references_recorded();
4358 }
4359
4360 G1STWIsAliveClosure is_alive(this);
4361 G1KeepAliveClosure keep_alive(this);
4362
4363 {
4364 double start = os::elapsedTime();
4365
4366 WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
4367
4368 double time_ms = (os::elapsedTime() - start) * 1000.0;
4369 g1_policy()->phase_times()->record_ref_proc_time(time_ms);
4370 }
4371
4372 if (G1StringDedup::is_enabled()) {
4373 double fixup_start = os::elapsedTime();
4374
4375 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times());
4376
4377 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
4378 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
4379 }
4380
4381 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4382
4383 if (evacuation_failed()) {
4384 restore_after_evac_failure();
4385
4386 // Reset the G1EvacuationFailureALot counters and flags
4387 // Note: the values are reset only when an actual
4388 // evacuation failure occurs.
4389 NOT_PRODUCT(reset_evacuation_should_fail();)
4390 }
4391
4392 _preserved_marks_set.assert_empty();
4393
4394 // Enqueue any remaining references remaining on the STW
4395 // reference processor's discovered lists. We need to do
4396 // this after the card table is cleaned (and verified) as
4397 // the act of enqueueing entries on to the pending list
4398 // will log these updates (and dirty their associated
4399 // cards). We need these updates logged to update any
4400 // RSets.
4401 if (g1_policy()->should_process_references()) {
4402 enqueue_discovered_references(per_thread_states);
4403 } else {
4404 g1_policy()->phase_times()->record_ref_enq_time(0);
4405 }
4406
4407 _allocator->release_gc_alloc_regions(evacuation_info);
4408
4409 merge_per_thread_state_info(per_thread_states);
4410
4411 // Reset and re-enable the hot card cache.
4412 // Note the counts for the cards in the regions in the
4413 // collection set are reset when the collection set is freed.
4414 _hot_card_cache->reset_hot_cache();
4415 _hot_card_cache->set_use_cache(true);
4416
4417 purge_code_root_memory();
4418
4419 redirty_logged_cards();
4420 #if COMPILER2_OR_JVMCI
4421 double start = os::elapsedTime();
4422 DerivedPointerTable::update_pointers();
4423 g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0);
4424 #endif
4425 g1_policy()->print_age_table();
4426 }
4427
4428 void G1CollectedHeap::record_obj_copy_mem_stats() {
4429 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4430
4431 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4432 create_g1_evac_summary(&_old_evac_stats));
4433 }
4434
4435 void G1CollectedHeap::free_region(HeapRegion* hr,
4436 FreeRegionList* free_list,
4437 bool skip_remset,
4438 bool skip_hot_card_cache,
4439 bool locked) {
4440 assert(!hr->is_free(), "the region should not be free");
4441 assert(!hr->is_empty(), "the region should not be empty");
4442 assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
4443 assert(free_list != NULL, "pre-condition");
4444
4445 if (G1VerifyBitmaps) {
4446 MemRegion mr(hr->bottom(), hr->end());
4447 concurrent_mark()->clear_range_in_prev_bitmap(mr);
4448 }
4449
4450 // Clear the card counts for this region.
4451 // Note: we only need to do this if the region is not young
4452 // (since we don't refine cards in young regions).
4453 if (!skip_hot_card_cache && !hr->is_young()) {
4454 _hot_card_cache->reset_card_counts(hr);
4455 }
4456 hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */);
4457 free_list->add_ordered(hr);
4458 }
4459
4460 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4461 FreeRegionList* free_list,
4462 bool skip_remset) {
4463 assert(hr->is_humongous(), "this is only for humongous regions");
4464 assert(free_list != NULL, "pre-condition");
4465 hr->clear_humongous();
4466 free_region(hr, free_list, skip_remset);
4467 }
4468
4469 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4470 const uint humongous_regions_removed) {
4471 if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4472 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4473 _old_set.bulk_remove(old_regions_removed);
4474 _humongous_set.bulk_remove(humongous_regions_removed);
4475 }
4476
4477 }
4478
4479 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4480 assert(list != NULL, "list can't be null");
4481 if (!list->is_empty()) {
4482 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4483 _hrm.insert_list_into_free_list(list);
4484 }
4485 }
4486
4487 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4488 decrease_used(bytes);
4489 }
4490
4491 class G1ParScrubRemSetTask: public AbstractGangTask {
4492 protected:
4493 G1RemSet* _g1rs;
4494 HeapRegionClaimer _hrclaimer;
4495
4496 public:
4497 G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) :
4498 AbstractGangTask("G1 ScrubRS"),
4499 _g1rs(g1_rs),
4500 _hrclaimer(num_workers) {
4501 }
4502
4503 void work(uint worker_id) {
4504 _g1rs->scrub(worker_id, &_hrclaimer);
4505 }
4506 };
4507
4508 void G1CollectedHeap::scrub_rem_set() {
4509 uint num_workers = workers()->active_workers();
4510 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers);
4511 workers()->run_task(&g1_par_scrub_rs_task);
4512 }
4513
4514 class G1FreeCollectionSetTask : public AbstractGangTask {
4515 private:
4516
4517 // Closure applied to all regions in the collection set to do work that needs to
4518 // be done serially in a single thread.
4519 class G1SerialFreeCollectionSetClosure : public HeapRegionClosure {
4520 private:
4521 EvacuationInfo* _evacuation_info;
4522 const size_t* _surviving_young_words;
4523
4524 // Bytes used in successfully evacuated regions before the evacuation.
4525 size_t _before_used_bytes;
4526 // Bytes used in unsucessfully evacuated regions before the evacuation
4527 size_t _after_used_bytes;
4528
4529 size_t _bytes_allocated_in_old_since_last_gc;
4530
4531 size_t _failure_used_words;
4532 size_t _failure_waste_words;
4533
4534 FreeRegionList _local_free_list;
4535 public:
4536 G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4537 HeapRegionClosure(),
4538 _evacuation_info(evacuation_info),
4539 _surviving_young_words(surviving_young_words),
4540 _before_used_bytes(0),
4541 _after_used_bytes(0),
4542 _bytes_allocated_in_old_since_last_gc(0),
4543 _failure_used_words(0),
4544 _failure_waste_words(0),
4545 _local_free_list("Local Region List for CSet Freeing") {
4546 }
4547
4548 virtual bool doHeapRegion(HeapRegion* r) {
4549 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4550
4551 assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index());
4552 g1h->clear_in_cset(r);
4553
4554 if (r->is_young()) {
4555 assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(),
4556 "Young index %d is wrong for region %u of type %s with %u young regions",
4557 r->young_index_in_cset(),
4558 r->hrm_index(),
4559 r->get_type_str(),
4560 g1h->collection_set()->young_region_length());
4561 size_t words_survived = _surviving_young_words[r->young_index_in_cset()];
4562 r->record_surv_words_in_group(words_survived);
4563 }
4564
4565 if (!r->evacuation_failed()) {
4566 assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
4567 _before_used_bytes += r->used();
4568 g1h->free_region(r,
4569 &_local_free_list,
4570 true, /* skip_remset */
4571 true, /* skip_hot_card_cache */
4572 true /* locked */);
4573 } else {
4574 r->uninstall_surv_rate_group();
4575 r->set_young_index_in_cset(-1);
4576 r->set_evacuation_failed(false);
4577 // When moving a young gen region to old gen, we "allocate" that whole region
4578 // there. This is in addition to any already evacuated objects. Notify the
4579 // policy about that.
4580 // Old gen regions do not cause an additional allocation: both the objects
4581 // still in the region and the ones already moved are accounted for elsewhere.
4582 if (r->is_young()) {
4583 _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
4584 }
4585 // The region is now considered to be old.
4586 r->set_old();
4587 // Do some allocation statistics accounting. Regions that failed evacuation
4588 // are always made old, so there is no need to update anything in the young
4589 // gen statistics, but we need to update old gen statistics.
4590 size_t used_words = r->marked_bytes() / HeapWordSize;
4591
4592 _failure_used_words += used_words;
4593 _failure_waste_words += HeapRegion::GrainWords - used_words;
4594
4595 g1h->old_set_add(r);
4596 _after_used_bytes += r->used();
4597 }
4598 return false;
4599 }
4600
4601 void complete_work() {
4602 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4603
4604 _evacuation_info->set_regions_freed(_local_free_list.length());
4605 _evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4606
4607 g1h->prepend_to_freelist(&_local_free_list);
4608 g1h->decrement_summary_bytes(_before_used_bytes);
4609
4610 G1Policy* policy = g1h->g1_policy();
4611 policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4612
4613 g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4614 }
4615 };
4616
4617 G1CollectionSet* _collection_set;
4618 G1SerialFreeCollectionSetClosure _cl;
4619 const size_t* _surviving_young_words;
4620
4621 size_t _rs_lengths;
4622
4623 volatile jint _serial_work_claim;
4624
4625 struct WorkItem {
4626 uint region_idx;
4627 bool is_young;
4628 bool evacuation_failed;
4629
4630 WorkItem(HeapRegion* r) {
4631 region_idx = r->hrm_index();
4632 is_young = r->is_young();
4633 evacuation_failed = r->evacuation_failed();
4634 }
4635 };
4636
4637 volatile size_t _parallel_work_claim;
4638 size_t _num_work_items;
4639 WorkItem* _work_items;
4640
4641 void do_serial_work() {
4642 // Need to grab the lock to be allowed to modify the old region list.
4643 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4644 _collection_set->iterate(&_cl);
4645 }
4646
4647 void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) {
4648 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4649
4650 HeapRegion* r = g1h->region_at(region_idx);
4651 assert(!g1h->is_on_master_free_list(r), "sanity");
4652
4653 Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths);
4654
4655 if (!is_young) {
4656 g1h->_hot_card_cache->reset_card_counts(r);
4657 }
4658
4659 if (!evacuation_failed) {
4660 r->rem_set()->clear_locked();
4661 }
4662 }
4663
4664 class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure {
4665 private:
4666 size_t _cur_idx;
4667 WorkItem* _work_items;
4668 public:
4669 G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { }
4670
4671 virtual bool doHeapRegion(HeapRegion* r) {
4672 _work_items[_cur_idx++] = WorkItem(r);
4673 return false;
4674 }
4675 };
4676
4677 void prepare_work() {
4678 G1PrepareFreeCollectionSetClosure cl(_work_items);
4679 _collection_set->iterate(&cl);
4680 }
4681
4682 void complete_work() {
4683 _cl.complete_work();
4684
4685 G1Policy* policy = G1CollectedHeap::heap()->g1_policy();
4686 policy->record_max_rs_lengths(_rs_lengths);
4687 policy->cset_regions_freed();
4688 }
4689 public:
4690 G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4691 AbstractGangTask("G1 Free Collection Set"),
4692 _cl(evacuation_info, surviving_young_words),
4693 _collection_set(collection_set),
4694 _surviving_young_words(surviving_young_words),
4695 _serial_work_claim(0),
4696 _rs_lengths(0),
4697 _parallel_work_claim(0),
4698 _num_work_items(collection_set->region_length()),
4699 _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) {
4700 prepare_work();
4701 }
4702
4703 ~G1FreeCollectionSetTask() {
4704 complete_work();
4705 FREE_C_HEAP_ARRAY(WorkItem, _work_items);
4706 }
4707
4708 // Chunk size for work distribution. The chosen value has been determined experimentally
4709 // to be a good tradeoff between overhead and achievable parallelism.
4710 static uint chunk_size() { return 32; }
4711
4712 virtual void work(uint worker_id) {
4713 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
4714
4715 // Claim serial work.
4716 if (_serial_work_claim == 0) {
4717 jint value = Atomic::add(1, &_serial_work_claim) - 1;
4718 if (value == 0) {
4719 double serial_time = os::elapsedTime();
4720 do_serial_work();
4721 timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0);
4722 }
4723 }
4724
4725 // Start parallel work.
4726 double young_time = 0.0;
4727 bool has_young_time = false;
4728 double non_young_time = 0.0;
4729 bool has_non_young_time = false;
4730
4731 while (true) {
4732 size_t end = Atomic::add(chunk_size(), &_parallel_work_claim);
4733 size_t cur = end - chunk_size();
4734
4735 if (cur >= _num_work_items) {
4736 break;
4737 }
4738
4739 double start_time = os::elapsedTime();
4740
4741 end = MIN2(end, _num_work_items);
4742
4743 for (; cur < end; cur++) {
4744 bool is_young = _work_items[cur].is_young;
4745
4746 do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed);
4747
4748 double end_time = os::elapsedTime();
4749 double time_taken = end_time - start_time;
4750 if (is_young) {
4751 young_time += time_taken;
4752 has_young_time = true;
4753 } else {
4754 non_young_time += time_taken;
4755 has_non_young_time = true;
4756 }
4757 start_time = end_time;
4758 }
4759 }
4760
4761 if (has_young_time) {
4762 timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time);
4763 }
4764 if (has_non_young_time) {
4765 timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, young_time);
4766 }
4767 }
4768 };
4769
4770 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4771 _eden.clear();
4772
4773 double free_cset_start_time = os::elapsedTime();
4774
4775 {
4776 uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U);
4777 uint const num_workers = MIN2(workers()->active_workers(), num_chunks);
4778
4779 G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words);
4780
4781 log_debug(gc, ergo)("Running %s using %u workers for collection set length %u",
4782 cl.name(),
4783 num_workers,
4784 _collection_set.region_length());
4785 workers()->run_task(&cl, num_workers);
4786 }
4787 g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0);
4788
4789 collection_set->clear();
4790 }
4791
4792 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4793 private:
4794 FreeRegionList* _free_region_list;
4795 HeapRegionSet* _proxy_set;
4796 uint _humongous_objects_reclaimed;
4797 uint _humongous_regions_reclaimed;
4798 size_t _freed_bytes;
4799 public:
4800
4801 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4802 _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) {
4803 }
4804
4805 virtual bool doHeapRegion(HeapRegion* r) {
4806 if (!r->is_starts_humongous()) {
4807 return false;
4808 }
4809
4810 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4811
4812 oop obj = (oop)r->bottom();
4813 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap();
4814
4815 // The following checks whether the humongous object is live are sufficient.
4816 // The main additional check (in addition to having a reference from the roots
4817 // or the young gen) is whether the humongous object has a remembered set entry.
4818 //
4819 // A humongous object cannot be live if there is no remembered set for it
4820 // because:
4821 // - there can be no references from within humongous starts regions referencing
4822 // the object because we never allocate other objects into them.
4823 // (I.e. there are no intra-region references that may be missed by the
4824 // remembered set)
4825 // - as soon there is a remembered set entry to the humongous starts region
4826 // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4827 // until the end of a concurrent mark.
4828 //
4829 // It is not required to check whether the object has been found dead by marking
4830 // or not, in fact it would prevent reclamation within a concurrent cycle, as
4831 // all objects allocated during that time are considered live.
4832 // SATB marking is even more conservative than the remembered set.
4833 // So if at this point in the collection there is no remembered set entry,
4834 // nobody has a reference to it.
4835 // At the start of collection we flush all refinement logs, and remembered sets
4836 // are completely up-to-date wrt to references to the humongous object.
4837 //
4838 // Other implementation considerations:
4839 // - never consider object arrays at this time because they would pose
4840 // considerable effort for cleaning up the the remembered sets. This is
4841 // required because stale remembered sets might reference locations that
4842 // are currently allocated into.
4843 uint region_idx = r->hrm_index();
4844 if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4845 !r->rem_set()->is_empty()) {
4846 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",
4847 region_idx,
4848 (size_t)obj->size() * HeapWordSize,
4849 p2i(r->bottom()),
4850 r->rem_set()->occupied(),
4851 r->rem_set()->strong_code_roots_list_length(),
4852 next_bitmap->is_marked(r->bottom()),
4853 g1h->is_humongous_reclaim_candidate(region_idx),
4854 obj->is_typeArray()
4855 );
4856 return false;
4857 }
4858
4859 guarantee(obj->is_typeArray(),
4860 "Only eagerly reclaiming type arrays is supported, but the object "
4861 PTR_FORMAT " is not.", p2i(r->bottom()));
4862
4863 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",
4864 region_idx,
4865 (size_t)obj->size() * HeapWordSize,
4866 p2i(r->bottom()),
4867 r->rem_set()->occupied(),
4868 r->rem_set()->strong_code_roots_list_length(),
4869 next_bitmap->is_marked(r->bottom()),
4870 g1h->is_humongous_reclaim_candidate(region_idx),
4871 obj->is_typeArray()
4872 );
4873
4874 // Need to clear mark bit of the humongous object if already set.
4875 if (next_bitmap->is_marked(r->bottom())) {
4876 next_bitmap->clear(r->bottom());
4877 }
4878 _humongous_objects_reclaimed++;
4879 do {
4880 HeapRegion* next = g1h->next_region_in_humongous(r);
4881 _freed_bytes += r->used();
4882 r->set_containing_set(NULL);
4883 _humongous_regions_reclaimed++;
4884 g1h->free_humongous_region(r, _free_region_list, false /* skip_remset */ );
4885 r = next;
4886 } while (r != NULL);
4887
4888 return false;
4889 }
4890
4891 uint humongous_objects_reclaimed() {
4892 return _humongous_objects_reclaimed;
4893 }
4894
4895 uint humongous_regions_reclaimed() {
4896 return _humongous_regions_reclaimed;
4897 }
4898
4899 size_t bytes_freed() const {
4900 return _freed_bytes;
4901 }
4902 };
4903
4904 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4905 assert_at_safepoint(true);
4906
4907 if (!G1EagerReclaimHumongousObjects ||
4908 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
4909 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
4910 return;
4911 }
4912
4913 double start_time = os::elapsedTime();
4914
4915 FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
4916
4917 G1FreeHumongousRegionClosure cl(&local_cleanup_list);
4918 heap_region_iterate(&cl);
4919
4920 remove_from_old_sets(0, cl.humongous_regions_reclaimed());
4921
4922 G1HRPrinter* hrp = hr_printer();
4923 if (hrp->is_active()) {
4924 FreeRegionListIterator iter(&local_cleanup_list);
4925 while (iter.more_available()) {
4926 HeapRegion* hr = iter.get_next();
4927 hrp->cleanup(hr);
4928 }
4929 }
4930
4931 prepend_to_freelist(&local_cleanup_list);
4932 decrement_summary_bytes(cl.bytes_freed());
4933
4934 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
4935 cl.humongous_objects_reclaimed());
4936 }
4937
4938 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
4939 public:
4940 virtual bool doHeapRegion(HeapRegion* r) {
4941 assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
4942 G1CollectedHeap::heap()->clear_in_cset(r);
4943 r->set_young_index_in_cset(-1);
4944 return false;
4945 }
4946 };
4947
4948 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
4949 G1AbandonCollectionSetClosure cl;
4950 collection_set->iterate(&cl);
4951
4952 collection_set->clear();
4953 collection_set->stop_incremental_building();
4954 }
4955
4956 void G1CollectedHeap::set_free_regions_coming() {
4957 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming");
4958
4959 assert(!free_regions_coming(), "pre-condition");
4960 _free_regions_coming = true;
4961 }
4962
4963 void G1CollectedHeap::reset_free_regions_coming() {
4964 assert(free_regions_coming(), "pre-condition");
4965
4966 {
4967 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
4968 _free_regions_coming = false;
4969 SecondaryFreeList_lock->notify_all();
4970 }
4971
4972 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming");
4973 }
4974
4975 void G1CollectedHeap::wait_while_free_regions_coming() {
4976 // Most of the time we won't have to wait, so let's do a quick test
4977 // first before we take the lock.
4978 if (!free_regions_coming()) {
4979 return;
4980 }
4981
4982 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions");
4983
4984 {
4985 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
4986 while (free_regions_coming()) {
4987 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
4988 }
4989 }
4990
4991 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions");
4992 }
4993
4994 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
4995 return _allocator->is_retained_old_region(hr);
4996 }
4997
4998 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
4999 _eden.add(hr);
5000 _g1_policy->set_region_eden(hr);
5001 }
5002
5003 #ifdef ASSERT
5004
5005 class NoYoungRegionsClosure: public HeapRegionClosure {
5006 private:
5007 bool _success;
5008 public:
5009 NoYoungRegionsClosure() : _success(true) { }
5010 bool doHeapRegion(HeapRegion* r) {
5011 if (r->is_young()) {
5012 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
5013 p2i(r->bottom()), p2i(r->end()));
5014 _success = false;
5015 }
5016 return false;
5017 }
5018 bool success() { return _success; }
5019 };
5020
5021 bool G1CollectedHeap::check_young_list_empty() {
5022 bool ret = (young_regions_count() == 0);
5023
5024 NoYoungRegionsClosure closure;
5025 heap_region_iterate(&closure);
5026 ret = ret && closure.success();
5027
5028 return ret;
5029 }
5030
5031 #endif // ASSERT
5032
5033 class TearDownRegionSetsClosure : public HeapRegionClosure {
5034 private:
5035 HeapRegionSet *_old_set;
5036
5037 public:
5038 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
5039
5040 bool doHeapRegion(HeapRegion* r) {
5041 if (r->is_old()) {
5042 _old_set->remove(r);
5043 } else if(r->is_young()) {
5044 r->uninstall_surv_rate_group();
5045 } else {
5046 // We ignore free regions, we'll empty the free list afterwards.
5047 // We ignore humongous regions, we're not tearing down the
5048 // humongous regions set.
5049 assert(r->is_free() || r->is_humongous(),
5050 "it cannot be another type");
5051 }
5052 return false;
5053 }
5054
5055 ~TearDownRegionSetsClosure() {
5056 assert(_old_set->is_empty(), "post-condition");
5057 }
5058 };
5059
5060 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
5061 assert_at_safepoint(true /* should_be_vm_thread */);
5062
5063 if (!free_list_only) {
5064 TearDownRegionSetsClosure cl(&_old_set);
5065 heap_region_iterate(&cl);
5066
5067 // Note that emptying the _young_list is postponed and instead done as
5068 // the first step when rebuilding the regions sets again. The reason for
5069 // this is that during a full GC string deduplication needs to know if
5070 // a collected region was young or old when the full GC was initiated.
5071 }
5072 _hrm.remove_all_free_regions();
5073 }
5074
5075 void G1CollectedHeap::increase_used(size_t bytes) {
5076 _summary_bytes_used += bytes;
5077 }
5078
5079 void G1CollectedHeap::decrease_used(size_t bytes) {
5080 assert(_summary_bytes_used >= bytes,
5081 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
5082 _summary_bytes_used, bytes);
5083 _summary_bytes_used -= bytes;
5084 }
5085
5086 void G1CollectedHeap::set_used(size_t bytes) {
5087 _summary_bytes_used = bytes;
5088 }
5089
5090 class RebuildRegionSetsClosure : public HeapRegionClosure {
5091 private:
5092 bool _free_list_only;
5093 HeapRegionSet* _old_set;
5094 HeapRegionManager* _hrm;
5095 size_t _total_used;
5096
5097 public:
5098 RebuildRegionSetsClosure(bool free_list_only,
5099 HeapRegionSet* old_set, HeapRegionManager* hrm) :
5100 _free_list_only(free_list_only),
5101 _old_set(old_set), _hrm(hrm), _total_used(0) {
5102 assert(_hrm->num_free_regions() == 0, "pre-condition");
5103 if (!free_list_only) {
5104 assert(_old_set->is_empty(), "pre-condition");
5105 }
5106 }
5107
5108 bool doHeapRegion(HeapRegion* r) {
5109 if (r->is_empty()) {
5110 // Add free regions to the free list
5111 r->set_free();
5112 r->set_allocation_context(AllocationContext::system());
5113 _hrm->insert_into_free_list(r);
5114 } else if (!_free_list_only) {
5115
5116 if (r->is_humongous()) {
5117 // We ignore humongous regions. We left the humongous set unchanged.
5118 } else {
5119 assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
5120 // We now move all (non-humongous, non-old) regions to old gen, and register them as such.
5121 r->move_to_old();
5122 _old_set->add(r);
5123 }
5124 _total_used += r->used();
5125 }
5126
5127 return false;
5128 }
5129
5130 size_t total_used() {
5131 return _total_used;
5132 }
5133 };
5134
5135 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
5136 assert_at_safepoint(true /* should_be_vm_thread */);
5137
5138 if (!free_list_only) {
5139 _eden.clear();
5140 _survivor.clear();
5141 }
5142
5143 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
5144 heap_region_iterate(&cl);
5145
5146 if (!free_list_only) {
5147 set_used(cl.total_used());
5148 if (_archive_allocator != NULL) {
5149 _archive_allocator->clear_used();
5150 }
5151 }
5152 assert(used_unlocked() == recalculate_used(),
5153 "inconsistent used_unlocked(), "
5154 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT,
5155 used_unlocked(), recalculate_used());
5156 }
5157
5158 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
5159 HeapRegion* hr = heap_region_containing(p);
5160 return hr->is_in(p);
5161 }
5162
5163 // Methods for the mutator alloc region
5164
5165 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
5166 bool force) {
5167 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5168 bool should_allocate = g1_policy()->should_allocate_mutator_region();
5169 if (force || should_allocate) {
5170 HeapRegion* new_alloc_region = new_region(word_size,
5171 false /* is_old */,
5172 false /* do_expand */);
5173 if (new_alloc_region != NULL) {
5174 set_region_short_lived_locked(new_alloc_region);
5175 _hr_printer.alloc(new_alloc_region, !should_allocate);
5176 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
5177 return new_alloc_region;
5178 }
5179 }
5180 return NULL;
5181 }
5182
5183 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
5184 size_t allocated_bytes) {
5185 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5186 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
5187
5188 collection_set()->add_eden_region(alloc_region);
5189 increase_used(allocated_bytes);
5190 _hr_printer.retire(alloc_region);
5191 // We update the eden sizes here, when the region is retired,
5192 // instead of when it's allocated, since this is the point that its
5193 // used space has been recored in _summary_bytes_used.
5194 g1mm()->update_eden_size();
5195 }
5196
5197 // Methods for the GC alloc regions
5198
5199 bool G1CollectedHeap::has_more_regions(InCSetState dest) {
5200 if (dest.is_old()) {
5201 return true;
5202 } else {
5203 return survivor_regions_count() < g1_policy()->max_survivor_regions();
5204 }
5205 }
5206
5207 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) {
5208 assert(FreeList_lock->owned_by_self(), "pre-condition");
5209
5210 if (!has_more_regions(dest)) {
5211 return NULL;
5212 }
5213
5214 const bool is_survivor = dest.is_young();
5215
5216 HeapRegion* new_alloc_region = new_region(word_size,
5217 !is_survivor,
5218 true /* do_expand */);
5219 if (new_alloc_region != NULL) {
5220 // We really only need to do this for old regions given that we
5221 // should never scan survivors. But it doesn't hurt to do it
5222 // for survivors too.
5223 new_alloc_region->record_timestamp();
5224 if (is_survivor) {
5225 new_alloc_region->set_survivor();
5226 _survivor.add(new_alloc_region);
5227 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
5228 } else {
5229 new_alloc_region->set_old();
5230 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
5231 }
5232 _hr_printer.alloc(new_alloc_region);
5233 bool during_im = collector_state()->during_initial_mark_pause();
5234 new_alloc_region->note_start_of_copying(during_im);
5235 return new_alloc_region;
5236 }
5237 return NULL;
5238 }
5239
5240 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
5241 size_t allocated_bytes,
5242 InCSetState dest) {
5243 bool during_im = collector_state()->during_initial_mark_pause();
5244 alloc_region->note_end_of_copying(during_im);
5245 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
5246 if (dest.is_old()) {
5247 _old_set.add(alloc_region);
5248 }
5249 _hr_printer.retire(alloc_region);
5250 }
5251
5252 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
5253 bool expanded = false;
5254 uint index = _hrm.find_highest_free(&expanded);
5255
5256 if (index != G1_NO_HRM_INDEX) {
5257 if (expanded) {
5258 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
5259 HeapRegion::GrainWords * HeapWordSize);
5260 }
5261 _hrm.allocate_free_regions_starting_at(index, 1);
5262 return region_at(index);
5263 }
5264 return NULL;
5265 }
5266
5267 // Optimized nmethod scanning
5268
5269 class RegisterNMethodOopClosure: public OopClosure {
5270 G1CollectedHeap* _g1h;
5271 nmethod* _nm;
5272
5273 template <class T> void do_oop_work(T* p) {
5274 T heap_oop = oopDesc::load_heap_oop(p);
5275 if (!oopDesc::is_null(heap_oop)) {
5276 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5277 HeapRegion* hr = _g1h->heap_region_containing(obj);
5278 assert(!hr->is_continues_humongous(),
5279 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5280 " starting at " HR_FORMAT,
5281 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5282
5283 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
5284 hr->add_strong_code_root_locked(_nm);
5285 }
5286 }
5287
5288 public:
5289 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5290 _g1h(g1h), _nm(nm) {}
5291
5292 void do_oop(oop* p) { do_oop_work(p); }
5293 void do_oop(narrowOop* p) { do_oop_work(p); }
5294 };
5295
5296 class UnregisterNMethodOopClosure: public OopClosure {
5297 G1CollectedHeap* _g1h;
5298 nmethod* _nm;
5299
5300 template <class T> void do_oop_work(T* p) {
5301 T heap_oop = oopDesc::load_heap_oop(p);
5302 if (!oopDesc::is_null(heap_oop)) {
5303 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5304 HeapRegion* hr = _g1h->heap_region_containing(obj);
5305 assert(!hr->is_continues_humongous(),
5306 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5307 " starting at " HR_FORMAT,
5308 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5309
5310 hr->remove_strong_code_root(_nm);
5311 }
5312 }
5313
5314 public:
5315 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5316 _g1h(g1h), _nm(nm) {}
5317
5318 void do_oop(oop* p) { do_oop_work(p); }
5319 void do_oop(narrowOop* p) { do_oop_work(p); }
5320 };
5321
5322 // Returns true if the reference points to an object that
5323 // can move in an incremental collection.
5324 bool G1CollectedHeap::is_scavengable(oop obj) {
5325 HeapRegion* hr = heap_region_containing(obj);
5326 return !hr->is_pinned();
5327 }
5328
5329 void G1CollectedHeap::register_nmethod(nmethod* nm) {
5330 guarantee(nm != NULL, "sanity");
5331 RegisterNMethodOopClosure reg_cl(this, nm);
5332 nm->oops_do(®_cl);
5333 }
5334
5335 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
5336 guarantee(nm != NULL, "sanity");
5337 UnregisterNMethodOopClosure reg_cl(this, nm);
5338 nm->oops_do(®_cl, true);
5339 }
5340
5341 void G1CollectedHeap::purge_code_root_memory() {
5342 double purge_start = os::elapsedTime();
5343 G1CodeRootSet::purge();
5344 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
5345 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
5346 }
5347
5348 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
5349 G1CollectedHeap* _g1h;
5350
5351 public:
5352 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
5353 _g1h(g1h) {}
5354
5355 void do_code_blob(CodeBlob* cb) {
5356 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
5357 if (nm == NULL) {
5358 return;
5359 }
5360
5361 if (ScavengeRootsInCode) {
5362 _g1h->register_nmethod(nm);
5363 }
5364 }
5365 };
5366
5367 void G1CollectedHeap::rebuild_strong_code_roots() {
5368 RebuildStrongCodeRootClosure blob_cl(this);
5369 CodeCache::blobs_do(&blob_cl);
5370 }