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/g1MemoryPool.hpp"
48 #include "gc/g1/g1OopClosures.inline.hpp"
49 #include "gc/g1/g1ParScanThreadState.inline.hpp"
50 #include "gc/g1/g1Policy.hpp"
51 #include "gc/g1/g1RegionToSpaceMapper.hpp"
52 #include "gc/g1/g1RemSet.hpp"
53 #include "gc/g1/g1RootClosures.hpp"
54 #include "gc/g1/g1RootProcessor.hpp"
55 #include "gc/g1/g1StringDedup.hpp"
56 #include "gc/g1/g1YCTypes.hpp"
57 #include "gc/g1/g1YoungRemSetSamplingThread.hpp"
58 #include "gc/g1/heapRegion.inline.hpp"
59 #include "gc/g1/heapRegionRemSet.hpp"
60 #include "gc/g1/heapRegionSet.inline.hpp"
61 #include "gc/g1/vm_operations_g1.hpp"
62 #include "gc/shared/gcHeapSummary.hpp"
63 #include "gc/shared/gcId.hpp"
64 #include "gc/shared/gcLocker.inline.hpp"
65 #include "gc/shared/gcTimer.hpp"
66 #include "gc/shared/gcTrace.hpp"
67 #include "gc/shared/gcTraceTime.inline.hpp"
68 #include "gc/shared/generationSpec.hpp"
69 #include "gc/shared/isGCActiveMark.hpp"
70 #include "gc/shared/preservedMarks.inline.hpp"
71 #include "gc/shared/suspendibleThreadSet.hpp"
72 #include "gc/shared/referenceProcessor.inline.hpp"
73 #include "gc/shared/taskqueue.inline.hpp"
74 #include "gc/shared/weakProcessor.hpp"
75 #include "logging/log.hpp"
76 #include "memory/allocation.hpp"
77 #include "memory/iterator.hpp"
78 #include "memory/resourceArea.hpp"
79 #include "oops/oop.inline.hpp"
80 #include "prims/resolvedMethodTable.hpp"
81 #include "runtime/atomic.hpp"
82 #include "runtime/init.hpp"
83 #include "runtime/orderAccess.inline.hpp"
84 #include "runtime/threadSMR.hpp"
85 #include "runtime/vmThread.hpp"
86 #include "utilities/align.hpp"
87 #include "utilities/globalDefinitions.hpp"
88 #include "utilities/stack.inline.hpp"
89
90 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
91
92 // INVARIANTS/NOTES
93 //
94 // All allocation activity covered by the G1CollectedHeap interface is
95 // serialized by acquiring the HeapLock. This happens in mem_allocate
96 // and allocate_new_tlab, which are the "entry" points to the
97 // allocation code from the rest of the JVM. (Note that this does not
98 // apply to TLAB allocation, which is not part of this interface: it
99 // is done by clients of this interface.)
100
101 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
102 private:
103 size_t _num_dirtied;
104 G1CollectedHeap* _g1h;
105 G1SATBCardTableLoggingModRefBS* _g1_bs;
106
107 HeapRegion* region_for_card(jbyte* card_ptr) const {
108 return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr));
109 }
110
111 bool will_become_free(HeapRegion* hr) const {
112 // A region will be freed by free_collection_set if the region is in the
113 // collection set and has not had an evacuation failure.
114 return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
115 }
116
117 public:
118 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(),
119 _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { }
120
121 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
122 HeapRegion* hr = region_for_card(card_ptr);
123
124 // Should only dirty cards in regions that won't be freed.
125 if (!will_become_free(hr)) {
126 *card_ptr = CardTableModRefBS::dirty_card_val();
127 _num_dirtied++;
128 }
129
130 return true;
131 }
132
133 size_t num_dirtied() const { return _num_dirtied; }
134 };
135
136
137 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
138 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
139 }
140
141 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
142 // The from card cache is not the memory that is actually committed. So we cannot
143 // take advantage of the zero_filled parameter.
144 reset_from_card_cache(start_idx, num_regions);
145 }
146
147
148 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
149 MemRegion mr) {
150 return new HeapRegion(hrs_index, bot(), mr);
151 }
152
153 // Private methods.
154
155 HeapRegion*
156 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
157 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
158 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
159 if (!_secondary_free_list.is_empty()) {
160 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
161 "secondary_free_list has %u entries",
162 _secondary_free_list.length());
163 // It looks as if there are free regions available on the
164 // secondary_free_list. Let's move them to the free_list and try
165 // again to allocate from it.
166 append_secondary_free_list();
167
168 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
169 "empty we should have moved at least one entry to the free_list");
170 HeapRegion* res = _hrm.allocate_free_region(is_old);
171 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
172 "allocated " HR_FORMAT " from secondary_free_list",
173 HR_FORMAT_PARAMS(res));
174 return res;
175 }
176
177 // Wait here until we get notified either when (a) there are no
178 // more free regions coming or (b) some regions have been moved on
179 // the secondary_free_list.
180 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
181 }
182
183 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
184 "could not allocate from secondary_free_list");
185 return NULL;
186 }
187
188 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
189 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
190 "the only time we use this to allocate a humongous region is "
191 "when we are allocating a single humongous region");
192
193 HeapRegion* res;
194 if (G1StressConcRegionFreeing) {
195 if (!_secondary_free_list.is_empty()) {
196 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
197 "forced to look at the secondary_free_list");
198 res = new_region_try_secondary_free_list(is_old);
199 if (res != NULL) {
200 return res;
201 }
202 }
203 }
204
205 res = _hrm.allocate_free_region(is_old);
206
207 if (res == NULL) {
208 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
209 "res == NULL, trying the secondary_free_list");
210 res = new_region_try_secondary_free_list(is_old);
211 }
212 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
213 // Currently, only attempts to allocate GC alloc regions set
214 // do_expand to true. So, we should only reach here during a
215 // safepoint. If this assumption changes we might have to
216 // reconsider the use of _expand_heap_after_alloc_failure.
217 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
218
219 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
220 word_size * HeapWordSize);
221
222 if (expand(word_size * HeapWordSize)) {
223 // Given that expand() succeeded in expanding the heap, and we
224 // always expand the heap by an amount aligned to the heap
225 // region size, the free list should in theory not be empty.
226 // In either case allocate_free_region() will check for NULL.
227 res = _hrm.allocate_free_region(is_old);
228 } else {
229 _expand_heap_after_alloc_failure = false;
230 }
231 }
232 return res;
233 }
234
235 HeapWord*
236 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
237 uint num_regions,
238 size_t word_size,
239 AllocationContext_t context) {
240 assert(first != G1_NO_HRM_INDEX, "pre-condition");
241 assert(is_humongous(word_size), "word_size should be humongous");
242 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
243
244 // Index of last region in the series.
245 uint last = first + num_regions - 1;
246
247 // We need to initialize the region(s) we just discovered. This is
248 // a bit tricky given that it can happen concurrently with
249 // refinement threads refining cards on these regions and
250 // potentially wanting to refine the BOT as they are scanning
251 // those cards (this can happen shortly after a cleanup; see CR
252 // 6991377). So we have to set up the region(s) carefully and in
253 // a specific order.
254
255 // The word size sum of all the regions we will allocate.
256 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
257 assert(word_size <= word_size_sum, "sanity");
258
259 // This will be the "starts humongous" region.
260 HeapRegion* first_hr = region_at(first);
261 // The header of the new object will be placed at the bottom of
262 // the first region.
263 HeapWord* new_obj = first_hr->bottom();
264 // This will be the new top of the new object.
265 HeapWord* obj_top = new_obj + word_size;
266
267 // First, we need to zero the header of the space that we will be
268 // allocating. When we update top further down, some refinement
269 // threads might try to scan the region. By zeroing the header we
270 // ensure that any thread that will try to scan the region will
271 // come across the zero klass word and bail out.
272 //
273 // NOTE: It would not have been correct to have used
274 // CollectedHeap::fill_with_object() and make the space look like
275 // an int array. The thread that is doing the allocation will
276 // later update the object header to a potentially different array
277 // type and, for a very short period of time, the klass and length
278 // fields will be inconsistent. This could cause a refinement
279 // thread to calculate the object size incorrectly.
280 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
281
282 // Next, pad out the unused tail of the last region with filler
283 // objects, for improved usage accounting.
284 // How many words we use for filler objects.
285 size_t word_fill_size = word_size_sum - word_size;
286
287 // How many words memory we "waste" which cannot hold a filler object.
288 size_t words_not_fillable = 0;
289
290 if (word_fill_size >= min_fill_size()) {
291 fill_with_objects(obj_top, word_fill_size);
292 } else if (word_fill_size > 0) {
293 // We have space to fill, but we cannot fit an object there.
294 words_not_fillable = word_fill_size;
295 word_fill_size = 0;
296 }
297
298 // We will set up the first region as "starts humongous". This
299 // will also update the BOT covering all the regions to reflect
300 // that there is a single object that starts at the bottom of the
301 // first region.
302 first_hr->set_starts_humongous(obj_top, word_fill_size);
303 first_hr->set_allocation_context(context);
304 // Then, if there are any, we will set up the "continues
305 // humongous" regions.
306 HeapRegion* hr = NULL;
307 for (uint i = first + 1; i <= last; ++i) {
308 hr = region_at(i);
309 hr->set_continues_humongous(first_hr);
310 hr->set_allocation_context(context);
311 }
312
313 // Up to this point no concurrent thread would have been able to
314 // do any scanning on any region in this series. All the top
315 // fields still point to bottom, so the intersection between
316 // [bottom,top] and [card_start,card_end] will be empty. Before we
317 // update the top fields, we'll do a storestore to make sure that
318 // no thread sees the update to top before the zeroing of the
319 // object header and the BOT initialization.
320 OrderAccess::storestore();
321
322 // Now, we will update the top fields of the "continues humongous"
323 // regions except the last one.
324 for (uint i = first; i < last; ++i) {
325 hr = region_at(i);
326 hr->set_top(hr->end());
327 }
328
329 hr = region_at(last);
330 // If we cannot fit a filler object, we must set top to the end
331 // of the humongous object, otherwise we cannot iterate the heap
332 // and the BOT will not be complete.
333 hr->set_top(hr->end() - words_not_fillable);
334
335 assert(hr->bottom() < obj_top && obj_top <= hr->end(),
336 "obj_top should be in last region");
337
338 _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
339
340 assert(words_not_fillable == 0 ||
341 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
342 "Miscalculation in humongous allocation");
343
344 increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
345
346 for (uint i = first; i <= last; ++i) {
347 hr = region_at(i);
348 _humongous_set.add(hr);
349 _hr_printer.alloc(hr);
350 }
351
352 return new_obj;
353 }
354
355 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
356 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
357 return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
358 }
359
360 // If could fit into free regions w/o expansion, try.
361 // Otherwise, if can expand, do so.
362 // Otherwise, if using ex regions might help, try with ex given back.
363 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
364 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
365
366 _verifier->verify_region_sets_optional();
367
368 uint first = G1_NO_HRM_INDEX;
369 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
370
371 if (obj_regions == 1) {
372 // Only one region to allocate, try to use a fast path by directly allocating
373 // from the free lists. Do not try to expand here, we will potentially do that
374 // later.
375 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
376 if (hr != NULL) {
377 first = hr->hrm_index();
378 }
379 } else {
380 // We can't allocate humongous regions spanning more than one region while
381 // cleanupComplete() is running, since some of the regions we find to be
382 // empty might not yet be added to the free list. It is not straightforward
383 // to know in which list they are on so that we can remove them. We only
384 // need to do this if we need to allocate more than one region to satisfy the
385 // current humongous allocation request. If we are only allocating one region
386 // we use the one-region region allocation code (see above), that already
387 // potentially waits for regions from the secondary free list.
388 wait_while_free_regions_coming();
389 append_secondary_free_list_if_not_empty_with_lock();
390
391 // Policy: Try only empty regions (i.e. already committed first). Maybe we
392 // are lucky enough to find some.
393 first = _hrm.find_contiguous_only_empty(obj_regions);
394 if (first != G1_NO_HRM_INDEX) {
395 _hrm.allocate_free_regions_starting_at(first, obj_regions);
396 }
397 }
398
399 if (first == G1_NO_HRM_INDEX) {
400 // Policy: We could not find enough regions for the humongous object in the
401 // free list. Look through the heap to find a mix of free and uncommitted regions.
402 // If so, try expansion.
403 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
404 if (first != G1_NO_HRM_INDEX) {
405 // We found something. Make sure these regions are committed, i.e. expand
406 // the heap. Alternatively we could do a defragmentation GC.
407 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
408 word_size * HeapWordSize);
409
410 _hrm.expand_at(first, obj_regions, workers());
411 g1_policy()->record_new_heap_size(num_regions());
412
413 #ifdef ASSERT
414 for (uint i = first; i < first + obj_regions; ++i) {
415 HeapRegion* hr = region_at(i);
416 assert(hr->is_free(), "sanity");
417 assert(hr->is_empty(), "sanity");
418 assert(is_on_master_free_list(hr), "sanity");
419 }
420 #endif
421 _hrm.allocate_free_regions_starting_at(first, obj_regions);
422 } else {
423 // Policy: Potentially trigger a defragmentation GC.
424 }
425 }
426
427 HeapWord* result = NULL;
428 if (first != G1_NO_HRM_INDEX) {
429 result = humongous_obj_allocate_initialize_regions(first, obj_regions,
430 word_size, context);
431 assert(result != NULL, "it should always return a valid result");
432
433 // A successful humongous object allocation changes the used space
434 // information of the old generation so we need to recalculate the
435 // sizes and update the jstat counters here.
436 g1mm()->update_sizes();
437 }
438
439 _verifier->verify_region_sets_optional();
440
441 return result;
442 }
443
444 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
445 assert_heap_not_locked_and_not_at_safepoint();
446 assert(!is_humongous(word_size), "we do not allow humongous TLABs");
447
448 uint dummy_gc_count_before;
449 uint dummy_gclocker_retry_count = 0;
450 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
451 }
452
453 HeapWord*
454 G1CollectedHeap::mem_allocate(size_t word_size,
455 bool* gc_overhead_limit_was_exceeded) {
456 assert_heap_not_locked_and_not_at_safepoint();
457
458 // Loop until the allocation is satisfied, or unsatisfied after GC.
459 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
460 uint gc_count_before;
461
462 HeapWord* result = NULL;
463 if (!is_humongous(word_size)) {
464 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
465 } else {
466 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
467 }
468 if (result != NULL) {
469 return result;
470 }
471
472 // Create the garbage collection operation...
473 VM_G1CollectForAllocation op(gc_count_before, word_size);
474 op.set_allocation_context(AllocationContext::current());
475
476 // ...and get the VM thread to execute it.
477 VMThread::execute(&op);
478
479 if (op.prologue_succeeded() && op.pause_succeeded()) {
480 // If the operation was successful we'll return the result even
481 // if it is NULL. If the allocation attempt failed immediately
482 // after a Full GC, it's unlikely we'll be able to allocate now.
483 HeapWord* result = op.result();
484 if (result != NULL && !is_humongous(word_size)) {
485 // Allocations that take place on VM operations do not do any
486 // card dirtying and we have to do it here. We only have to do
487 // this for non-humongous allocations, though.
488 dirty_young_block(result, word_size);
489 }
490 return result;
491 } else {
492 if (gclocker_retry_count > GCLockerRetryAllocationCount) {
493 return NULL;
494 }
495 assert(op.result() == NULL,
496 "the result should be NULL if the VM op did not succeed");
497 }
498
499 // Give a warning if we seem to be looping forever.
500 if ((QueuedAllocationWarningCount > 0) &&
501 (try_count % QueuedAllocationWarningCount == 0)) {
502 log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count);
503 }
504 }
505
506 ShouldNotReachHere();
507 return NULL;
508 }
509
510 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
511 AllocationContext_t context,
512 uint* gc_count_before_ret,
513 uint* gclocker_retry_count_ret) {
514 // Make sure you read the note in attempt_allocation_humongous().
515
516 assert_heap_not_locked_and_not_at_safepoint();
517 assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
518 "be called for humongous allocation requests");
519
520 // We should only get here after the first-level allocation attempt
521 // (attempt_allocation()) failed to allocate.
522
523 // We will loop until a) we manage to successfully perform the
524 // allocation or b) we successfully schedule a collection which
525 // fails to perform the allocation. b) is the only case when we'll
526 // return NULL.
527 HeapWord* result = NULL;
528 for (int try_count = 1; /* we'll return */; try_count += 1) {
529 bool should_try_gc;
530 uint gc_count_before;
531
532 {
533 MutexLockerEx x(Heap_lock);
534 result = _allocator->attempt_allocation_locked(word_size, context);
535 if (result != NULL) {
536 return result;
537 }
538
539 if (GCLocker::is_active_and_needs_gc()) {
540 if (g1_policy()->can_expand_young_list()) {
541 // No need for an ergo verbose message here,
542 // can_expand_young_list() does this when it returns true.
543 result = _allocator->attempt_allocation_force(word_size, context);
544 if (result != NULL) {
545 return result;
546 }
547 }
548 should_try_gc = false;
549 } else {
550 // The GCLocker may not be active but the GCLocker initiated
551 // GC may not yet have been performed (GCLocker::needs_gc()
552 // returns true). In this case we do not try this GC and
553 // wait until the GCLocker initiated GC is performed, and
554 // then retry the allocation.
555 if (GCLocker::needs_gc()) {
556 should_try_gc = false;
557 } else {
558 // Read the GC count while still holding the Heap_lock.
559 gc_count_before = total_collections();
560 should_try_gc = true;
561 }
562 }
563 }
564
565 if (should_try_gc) {
566 bool succeeded;
567 result = do_collection_pause(word_size, gc_count_before, &succeeded,
568 GCCause::_g1_inc_collection_pause);
569 if (result != NULL) {
570 assert(succeeded, "only way to get back a non-NULL result");
571 return result;
572 }
573
574 if (succeeded) {
575 // If we get here we successfully scheduled a collection which
576 // failed to allocate. No point in trying to allocate
577 // further. We'll just return NULL.
578 MutexLockerEx x(Heap_lock);
579 *gc_count_before_ret = total_collections();
580 return NULL;
581 }
582 } else {
583 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
584 MutexLockerEx x(Heap_lock);
585 *gc_count_before_ret = total_collections();
586 return NULL;
587 }
588 // The GCLocker is either active or the GCLocker initiated
589 // GC has not yet been performed. Stall until it is and
590 // then retry the allocation.
591 GCLocker::stall_until_clear();
592 (*gclocker_retry_count_ret) += 1;
593 }
594
595 // We can reach here if we were unsuccessful in scheduling a
596 // collection (because another thread beat us to it) or if we were
597 // stalled due to the GC locker. In either can we should retry the
598 // allocation attempt in case another thread successfully
599 // performed a collection and reclaimed enough space. We do the
600 // first attempt (without holding the Heap_lock) here and the
601 // follow-on attempt will be at the start of the next loop
602 // iteration (after taking the Heap_lock).
603 result = _allocator->attempt_allocation(word_size, context);
604 if (result != NULL) {
605 return result;
606 }
607
608 // Give a warning if we seem to be looping forever.
609 if ((QueuedAllocationWarningCount > 0) &&
610 (try_count % QueuedAllocationWarningCount == 0)) {
611 log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() "
612 "retries %d times", try_count);
613 }
614 }
615
616 ShouldNotReachHere();
617 return NULL;
618 }
619
620 void G1CollectedHeap::begin_archive_alloc_range(bool open) {
621 assert_at_safepoint(true /* should_be_vm_thread */);
622 if (_archive_allocator == NULL) {
623 _archive_allocator = G1ArchiveAllocator::create_allocator(this, open);
624 }
625 }
626
627 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
628 // Allocations in archive regions cannot be of a size that would be considered
629 // humongous even for a minimum-sized region, because G1 region sizes/boundaries
630 // may be different at archive-restore time.
631 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
632 }
633
634 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
635 assert_at_safepoint(true /* should_be_vm_thread */);
636 assert(_archive_allocator != NULL, "_archive_allocator not initialized");
637 if (is_archive_alloc_too_large(word_size)) {
638 return NULL;
639 }
640 return _archive_allocator->archive_mem_allocate(word_size);
641 }
642
643 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
644 size_t end_alignment_in_bytes) {
645 assert_at_safepoint(true /* should_be_vm_thread */);
646 assert(_archive_allocator != NULL, "_archive_allocator not initialized");
647
648 // Call complete_archive to do the real work, filling in the MemRegion
649 // array with the archive regions.
650 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
651 delete _archive_allocator;
652 _archive_allocator = NULL;
653 }
654
655 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
656 assert(ranges != NULL, "MemRegion array NULL");
657 assert(count != 0, "No MemRegions provided");
658 MemRegion reserved = _hrm.reserved();
659 for (size_t i = 0; i < count; i++) {
660 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
661 return false;
662 }
663 }
664 return true;
665 }
666
667 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges,
668 size_t count,
669 bool open) {
670 assert(!is_init_completed(), "Expect to be called at JVM init time");
671 assert(ranges != NULL, "MemRegion array NULL");
672 assert(count != 0, "No MemRegions provided");
673 MutexLockerEx x(Heap_lock);
674
675 MemRegion reserved = _hrm.reserved();
676 HeapWord* prev_last_addr = NULL;
677 HeapRegion* prev_last_region = NULL;
678
679 // Temporarily disable pretouching of heap pages. This interface is used
680 // when mmap'ing archived heap data in, so pre-touching is wasted.
681 FlagSetting fs(AlwaysPreTouch, false);
682
683 // Enable archive object checking used by G1MarkSweep. We have to let it know
684 // about each archive range, so that objects in those ranges aren't marked.
685 G1ArchiveAllocator::enable_archive_object_check();
686
687 // For each specified MemRegion range, allocate the corresponding G1
688 // regions and mark them as archive regions. We expect the ranges
689 // in ascending starting address order, without overlap.
690 for (size_t i = 0; i < count; i++) {
691 MemRegion curr_range = ranges[i];
692 HeapWord* start_address = curr_range.start();
693 size_t word_size = curr_range.word_size();
694 HeapWord* last_address = curr_range.last();
695 size_t commits = 0;
696
697 guarantee(reserved.contains(start_address) && reserved.contains(last_address),
698 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
699 p2i(start_address), p2i(last_address));
700 guarantee(start_address > prev_last_addr,
701 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
702 p2i(start_address), p2i(prev_last_addr));
703 prev_last_addr = last_address;
704
705 // Check for ranges that start in the same G1 region in which the previous
706 // range ended, and adjust the start address so we don't try to allocate
707 // the same region again. If the current range is entirely within that
708 // region, skip it, just adjusting the recorded top.
709 HeapRegion* start_region = _hrm.addr_to_region(start_address);
710 if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
711 start_address = start_region->end();
712 if (start_address > last_address) {
713 increase_used(word_size * HeapWordSize);
714 start_region->set_top(last_address + 1);
715 continue;
716 }
717 start_region->set_top(start_address);
718 curr_range = MemRegion(start_address, last_address + 1);
719 start_region = _hrm.addr_to_region(start_address);
720 }
721
722 // Perform the actual region allocation, exiting if it fails.
723 // Then note how much new space we have allocated.
724 if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) {
725 return false;
726 }
727 increase_used(word_size * HeapWordSize);
728 if (commits != 0) {
729 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
730 HeapRegion::GrainWords * HeapWordSize * commits);
731
732 }
733
734 // Mark each G1 region touched by the range as archive, add it to
735 // the old set, and set the allocation context and top.
736 HeapRegion* curr_region = _hrm.addr_to_region(start_address);
737 HeapRegion* last_region = _hrm.addr_to_region(last_address);
738 prev_last_region = last_region;
739
740 while (curr_region != NULL) {
741 assert(curr_region->is_empty() && !curr_region->is_pinned(),
742 "Region already in use (index %u)", curr_region->hrm_index());
743 curr_region->set_allocation_context(AllocationContext::system());
744 if (open) {
745 curr_region->set_open_archive();
746 } else {
747 curr_region->set_closed_archive();
748 }
749 _hr_printer.alloc(curr_region);
750 _old_set.add(curr_region);
751 HeapWord* top;
752 HeapRegion* next_region;
753 if (curr_region != last_region) {
754 top = curr_region->end();
755 next_region = _hrm.next_region_in_heap(curr_region);
756 } else {
757 top = last_address + 1;
758 next_region = NULL;
759 }
760 curr_region->set_top(top);
761 curr_region->set_first_dead(top);
762 curr_region->set_end_of_live(top);
763 curr_region = next_region;
764 }
765
766 // Notify mark-sweep of the archive
767 G1ArchiveAllocator::set_range_archive(curr_range, open);
768 }
769 return true;
770 }
771
772 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
773 assert(!is_init_completed(), "Expect to be called at JVM init time");
774 assert(ranges != NULL, "MemRegion array NULL");
775 assert(count != 0, "No MemRegions provided");
776 MemRegion reserved = _hrm.reserved();
777 HeapWord *prev_last_addr = NULL;
778 HeapRegion* prev_last_region = NULL;
779
780 // For each MemRegion, create filler objects, if needed, in the G1 regions
781 // that contain the address range. The address range actually within the
782 // MemRegion will not be modified. That is assumed to have been initialized
783 // elsewhere, probably via an mmap of archived heap data.
784 MutexLockerEx x(Heap_lock);
785 for (size_t i = 0; i < count; i++) {
786 HeapWord* start_address = ranges[i].start();
787 HeapWord* last_address = ranges[i].last();
788
789 assert(reserved.contains(start_address) && reserved.contains(last_address),
790 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
791 p2i(start_address), p2i(last_address));
792 assert(start_address > prev_last_addr,
793 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
794 p2i(start_address), p2i(prev_last_addr));
795
796 HeapRegion* start_region = _hrm.addr_to_region(start_address);
797 HeapRegion* last_region = _hrm.addr_to_region(last_address);
798 HeapWord* bottom_address = start_region->bottom();
799
800 // Check for a range beginning in the same region in which the
801 // previous one ended.
802 if (start_region == prev_last_region) {
803 bottom_address = prev_last_addr + 1;
804 }
805
806 // Verify that the regions were all marked as archive regions by
807 // alloc_archive_regions.
808 HeapRegion* curr_region = start_region;
809 while (curr_region != NULL) {
810 guarantee(curr_region->is_archive(),
811 "Expected archive region at index %u", curr_region->hrm_index());
812 if (curr_region != last_region) {
813 curr_region = _hrm.next_region_in_heap(curr_region);
814 } else {
815 curr_region = NULL;
816 }
817 }
818
819 prev_last_addr = last_address;
820 prev_last_region = last_region;
821
822 // Fill the memory below the allocated range with dummy object(s),
823 // if the region bottom does not match the range start, or if the previous
824 // range ended within the same G1 region, and there is a gap.
825 if (start_address != bottom_address) {
826 size_t fill_size = pointer_delta(start_address, bottom_address);
827 G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
828 increase_used(fill_size * HeapWordSize);
829 }
830 }
831 }
832
833 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size,
834 uint* gc_count_before_ret,
835 uint* gclocker_retry_count_ret) {
836 assert_heap_not_locked_and_not_at_safepoint();
837 assert(!is_humongous(word_size), "attempt_allocation() should not "
838 "be called for humongous allocation requests");
839
840 AllocationContext_t context = AllocationContext::current();
841 HeapWord* result = _allocator->attempt_allocation(word_size, context);
842
843 if (result == NULL) {
844 result = attempt_allocation_slow(word_size,
845 context,
846 gc_count_before_ret,
847 gclocker_retry_count_ret);
848 }
849 assert_heap_not_locked();
850 if (result != NULL) {
851 dirty_young_block(result, word_size);
852 }
853 return result;
854 }
855
856 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
857 assert(!is_init_completed(), "Expect to be called at JVM init time");
858 assert(ranges != NULL, "MemRegion array NULL");
859 assert(count != 0, "No MemRegions provided");
860 MemRegion reserved = _hrm.reserved();
861 HeapWord* prev_last_addr = NULL;
862 HeapRegion* prev_last_region = NULL;
863 size_t size_used = 0;
864 size_t uncommitted_regions = 0;
865
866 // For each Memregion, free the G1 regions that constitute it, and
867 // notify mark-sweep that the range is no longer to be considered 'archive.'
868 MutexLockerEx x(Heap_lock);
869 for (size_t i = 0; i < count; i++) {
870 HeapWord* start_address = ranges[i].start();
871 HeapWord* last_address = ranges[i].last();
872
873 assert(reserved.contains(start_address) && reserved.contains(last_address),
874 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
875 p2i(start_address), p2i(last_address));
876 assert(start_address > prev_last_addr,
877 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
878 p2i(start_address), p2i(prev_last_addr));
879 size_used += ranges[i].byte_size();
880 prev_last_addr = last_address;
881
882 HeapRegion* start_region = _hrm.addr_to_region(start_address);
883 HeapRegion* last_region = _hrm.addr_to_region(last_address);
884
885 // Check for ranges that start in the same G1 region in which the previous
886 // range ended, and adjust the start address so we don't try to free
887 // the same region again. If the current range is entirely within that
888 // region, skip it.
889 if (start_region == prev_last_region) {
890 start_address = start_region->end();
891 if (start_address > last_address) {
892 continue;
893 }
894 start_region = _hrm.addr_to_region(start_address);
895 }
896 prev_last_region = last_region;
897
898 // After verifying that each region was marked as an archive region by
899 // alloc_archive_regions, set it free and empty and uncommit it.
900 HeapRegion* curr_region = start_region;
901 while (curr_region != NULL) {
902 guarantee(curr_region->is_archive(),
903 "Expected archive region at index %u", curr_region->hrm_index());
904 uint curr_index = curr_region->hrm_index();
905 _old_set.remove(curr_region);
906 curr_region->set_free();
907 curr_region->set_top(curr_region->bottom());
908 if (curr_region != last_region) {
909 curr_region = _hrm.next_region_in_heap(curr_region);
910 } else {
911 curr_region = NULL;
912 }
913 _hrm.shrink_at(curr_index, 1);
914 uncommitted_regions++;
915 }
916
917 // Notify mark-sweep that this is no longer an archive range.
918 G1ArchiveAllocator::set_range_archive(ranges[i], false);
919 }
920
921 if (uncommitted_regions != 0) {
922 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
923 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
924 }
925 decrease_used(size_used);
926 }
927
928 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
929 uint* gc_count_before_ret,
930 uint* gclocker_retry_count_ret) {
931 // The structure of this method has a lot of similarities to
932 // attempt_allocation_slow(). The reason these two were not merged
933 // into a single one is that such a method would require several "if
934 // allocation is not humongous do this, otherwise do that"
935 // conditional paths which would obscure its flow. In fact, an early
936 // version of this code did use a unified method which was harder to
937 // follow and, as a result, it had subtle bugs that were hard to
938 // track down. So keeping these two methods separate allows each to
939 // be more readable. It will be good to keep these two in sync as
940 // much as possible.
941
942 assert_heap_not_locked_and_not_at_safepoint();
943 assert(is_humongous(word_size), "attempt_allocation_humongous() "
944 "should only be called for humongous allocations");
945
946 // Humongous objects can exhaust the heap quickly, so we should check if we
947 // need to start a marking cycle at each humongous object allocation. We do
948 // the check before we do the actual allocation. The reason for doing it
949 // before the allocation is that we avoid having to keep track of the newly
950 // allocated memory while we do a GC.
951 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
952 word_size)) {
953 collect(GCCause::_g1_humongous_allocation);
954 }
955
956 // We will loop until a) we manage to successfully perform the
957 // allocation or b) we successfully schedule a collection which
958 // fails to perform the allocation. b) is the only case when we'll
959 // return NULL.
960 HeapWord* result = NULL;
961 for (int try_count = 1; /* we'll return */; try_count += 1) {
962 bool should_try_gc;
963 uint gc_count_before;
964
965 {
966 MutexLockerEx x(Heap_lock);
967
968 // Given that humongous objects are not allocated in young
969 // regions, we'll first try to do the allocation without doing a
970 // collection hoping that there's enough space in the heap.
971 result = humongous_obj_allocate(word_size, AllocationContext::current());
972 if (result != NULL) {
973 size_t size_in_regions = humongous_obj_size_in_regions(word_size);
974 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
975 return result;
976 }
977
978 if (GCLocker::is_active_and_needs_gc()) {
979 should_try_gc = false;
980 } else {
981 // The GCLocker may not be active but the GCLocker initiated
982 // GC may not yet have been performed (GCLocker::needs_gc()
983 // returns true). In this case we do not try this GC and
984 // wait until the GCLocker initiated GC is performed, and
985 // then retry the allocation.
986 if (GCLocker::needs_gc()) {
987 should_try_gc = false;
988 } else {
989 // Read the GC count while still holding the Heap_lock.
990 gc_count_before = total_collections();
991 should_try_gc = true;
992 }
993 }
994 }
995
996 if (should_try_gc) {
997 // If we failed to allocate the humongous object, we should try to
998 // do a collection pause (if we're allowed) in case it reclaims
999 // enough space for the allocation to succeed after the pause.
1000
1001 bool succeeded;
1002 result = do_collection_pause(word_size, gc_count_before, &succeeded,
1003 GCCause::_g1_humongous_allocation);
1004 if (result != NULL) {
1005 assert(succeeded, "only way to get back a non-NULL result");
1006 return result;
1007 }
1008
1009 if (succeeded) {
1010 // If we get here we successfully scheduled a collection which
1011 // failed to allocate. No point in trying to allocate
1012 // further. We'll just return NULL.
1013 MutexLockerEx x(Heap_lock);
1014 *gc_count_before_ret = total_collections();
1015 return NULL;
1016 }
1017 } else {
1018 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1019 MutexLockerEx x(Heap_lock);
1020 *gc_count_before_ret = total_collections();
1021 return NULL;
1022 }
1023 // The GCLocker is either active or the GCLocker initiated
1024 // GC has not yet been performed. Stall until it is and
1025 // then retry the allocation.
1026 GCLocker::stall_until_clear();
1027 (*gclocker_retry_count_ret) += 1;
1028 }
1029
1030 // We can reach here if we were unsuccessful in scheduling a
1031 // collection (because another thread beat us to it) or if we were
1032 // stalled due to the GC locker. In either can we should retry the
1033 // allocation attempt in case another thread successfully
1034 // performed a collection and reclaimed enough space. Give a
1035 // warning if we seem to be looping forever.
1036
1037 if ((QueuedAllocationWarningCount > 0) &&
1038 (try_count % QueuedAllocationWarningCount == 0)) {
1039 log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() "
1040 "retries %d times", try_count);
1041 }
1042 }
1043
1044 ShouldNotReachHere();
1045 return NULL;
1046 }
1047
1048 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1049 AllocationContext_t context,
1050 bool expect_null_mutator_alloc_region) {
1051 assert_at_safepoint(true /* should_be_vm_thread */);
1052 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region,
1053 "the current alloc region was unexpectedly found to be non-NULL");
1054
1055 if (!is_humongous(word_size)) {
1056 return _allocator->attempt_allocation_locked(word_size, context);
1057 } else {
1058 HeapWord* result = humongous_obj_allocate(word_size, context);
1059 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1060 collector_state()->set_initiate_conc_mark_if_possible(true);
1061 }
1062 return result;
1063 }
1064
1065 ShouldNotReachHere();
1066 }
1067
1068 class PostCompactionPrinterClosure: public HeapRegionClosure {
1069 private:
1070 G1HRPrinter* _hr_printer;
1071 public:
1072 bool doHeapRegion(HeapRegion* hr) {
1073 assert(!hr->is_young(), "not expecting to find young regions");
1074 _hr_printer->post_compaction(hr);
1075 return false;
1076 }
1077
1078 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1079 : _hr_printer(hr_printer) { }
1080 };
1081
1082 void G1CollectedHeap::print_hrm_post_compaction() {
1083 if (_hr_printer.is_active()) {
1084 PostCompactionPrinterClosure cl(hr_printer());
1085 heap_region_iterate(&cl);
1086 }
1087
1088 }
1089
1090 void G1CollectedHeap::abort_concurrent_cycle() {
1091 // Note: When we have a more flexible GC logging framework that
1092 // allows us to add optional attributes to a GC log record we
1093 // could consider timing and reporting how long we wait in the
1094 // following two methods.
1095 wait_while_free_regions_coming();
1096 // If we start the compaction before the CM threads finish
1097 // scanning the root regions we might trip them over as we'll
1098 // be moving objects / updating references. So let's wait until
1099 // they are done. By telling them to abort, they should complete
1100 // early.
1101 _cm->root_regions()->abort();
1102 _cm->root_regions()->wait_until_scan_finished();
1103 append_secondary_free_list_if_not_empty_with_lock();
1104
1105 // Disable discovery and empty the discovered lists
1106 // for the CM ref processor.
1107 ref_processor_cm()->disable_discovery();
1108 ref_processor_cm()->abandon_partial_discovery();
1109 ref_processor_cm()->verify_no_references_recorded();
1110
1111 // Abandon current iterations of concurrent marking and concurrent
1112 // refinement, if any are in progress.
1113 concurrent_mark()->abort();
1114 }
1115
1116 void G1CollectedHeap::prepare_heap_for_full_collection() {
1117 // Make sure we'll choose a new allocation region afterwards.
1118 _allocator->release_mutator_alloc_region();
1119 _allocator->abandon_gc_alloc_regions();
1120 g1_rem_set()->cleanupHRRS();
1121
1122 // We may have added regions to the current incremental collection
1123 // set between the last GC or pause and now. We need to clear the
1124 // incremental collection set and then start rebuilding it afresh
1125 // after this full GC.
1126 abandon_collection_set(collection_set());
1127
1128 tear_down_region_sets(false /* free_list_only */);
1129 collector_state()->set_gcs_are_young(true);
1130 }
1131
1132 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) {
1133 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1134 assert(used() == recalculate_used(), "Should be equal");
1135 _verifier->verify_region_sets_optional();
1136 _verifier->verify_before_gc();
1137 _verifier->check_bitmaps("Full GC Start");
1138 }
1139
1140 void G1CollectedHeap::prepare_heap_for_mutators() {
1141 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1142 ClassLoaderDataGraph::purge();
1143 MetaspaceAux::verify_metrics();
1144
1145 // Prepare heap for normal collections.
1146 assert(num_free_regions() == 0, "we should not have added any free regions");
1147 rebuild_region_sets(false /* free_list_only */);
1148 abort_refinement();
1149 resize_if_necessary_after_full_collection();
1150
1151 // Rebuild the strong code root lists for each region
1152 rebuild_strong_code_roots();
1153
1154 // Start a new incremental collection set for the next pause
1155 start_new_collection_set();
1156
1157 _allocator->init_mutator_alloc_region();
1158
1159 // Post collection state updates.
1160 MetaspaceGC::compute_new_size();
1161 }
1162
1163 void G1CollectedHeap::abort_refinement() {
1164 if (_hot_card_cache->use_cache()) {
1165 _hot_card_cache->reset_hot_cache();
1166 }
1167
1168 // Discard all remembered set updates.
1169 JavaThread::dirty_card_queue_set().abandon_logs();
1170 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1171 }
1172
1173 void G1CollectedHeap::verify_after_full_collection() {
1174 check_gc_time_stamps();
1175 _hrm.verify_optional();
1176 _verifier->verify_region_sets_optional();
1177 _verifier->verify_after_gc();
1178 // Clear the previous marking bitmap, if needed for bitmap verification.
1179 // Note we cannot do this when we clear the next marking bitmap in
1180 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1181 // objects marked during a full GC against the previous bitmap.
1182 // But we need to clear it before calling check_bitmaps below since
1183 // the full GC has compacted objects and updated TAMS but not updated
1184 // the prev bitmap.
1185 if (G1VerifyBitmaps) {
1186 GCTraceTime(Debug, gc)("Clear Bitmap for Verification");
1187 _cm->clear_prev_bitmap(workers());
1188 }
1189 _verifier->check_bitmaps("Full GC End");
1190
1191 // At this point there should be no regions in the
1192 // entire heap tagged as young.
1193 assert(check_young_list_empty(), "young list should be empty at this point");
1194
1195 // Note: since we've just done a full GC, concurrent
1196 // marking is no longer active. Therefore we need not
1197 // re-enable reference discovery for the CM ref processor.
1198 // That will be done at the start of the next marking cycle.
1199 // We also know that the STW processor should no longer
1200 // discover any new references.
1201 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1202 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1203 ref_processor_stw()->verify_no_references_recorded();
1204 ref_processor_cm()->verify_no_references_recorded();
1205 }
1206
1207 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) {
1208 // Post collection logging.
1209 // We should do this after we potentially resize the heap so
1210 // that all the COMMIT / UNCOMMIT events are generated before
1211 // the compaction events.
1212 print_hrm_post_compaction();
1213 heap_transition->print();
1214 print_heap_after_gc();
1215 print_heap_regions();
1216 #ifdef TRACESPINNING
1217 ParallelTaskTerminator::print_termination_counts();
1218 #endif
1219 }
1220
1221 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1222 bool clear_all_soft_refs) {
1223 assert_at_safepoint(true /* should_be_vm_thread */);
1224
1225 if (GCLocker::check_active_before_gc()) {
1226 // Full GC was not completed.
1227 return false;
1228 }
1229
1230 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1231 collector_policy()->should_clear_all_soft_refs();
1232
1233 G1FullCollector collector(this, &_full_gc_memory_manager, explicit_gc, do_clear_all_soft_refs);
1234 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1235
1236 collector.prepare_collection();
1237 collector.collect();
1238 collector.complete_collection();
1239
1240 // Full collection was successfully completed.
1241 return true;
1242 }
1243
1244 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1245 // Currently, there is no facility in the do_full_collection(bool) API to notify
1246 // the caller that the collection did not succeed (e.g., because it was locked
1247 // out by the GC locker). So, right now, we'll ignore the return value.
1248 bool dummy = do_full_collection(true, /* explicit_gc */
1249 clear_all_soft_refs);
1250 }
1251
1252 void G1CollectedHeap::resize_if_necessary_after_full_collection() {
1253 // Capacity, free and used after the GC counted as full regions to
1254 // include the waste in the following calculations.
1255 const size_t capacity_after_gc = capacity();
1256 const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes();
1257
1258 // This is enforced in arguments.cpp.
1259 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1260 "otherwise the code below doesn't make sense");
1261
1262 // We don't have floating point command-line arguments
1263 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1264 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1265 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1266 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1267
1268 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1269 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1270
1271 // We have to be careful here as these two calculations can overflow
1272 // 32-bit size_t's.
1273 double used_after_gc_d = (double) used_after_gc;
1274 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1275 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1276
1277 // Let's make sure that they are both under the max heap size, which
1278 // by default will make them fit into a size_t.
1279 double desired_capacity_upper_bound = (double) max_heap_size;
1280 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1281 desired_capacity_upper_bound);
1282 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1283 desired_capacity_upper_bound);
1284
1285 // We can now safely turn them into size_t's.
1286 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1287 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1288
1289 // This assert only makes sense here, before we adjust them
1290 // with respect to the min and max heap size.
1291 assert(minimum_desired_capacity <= maximum_desired_capacity,
1292 "minimum_desired_capacity = " SIZE_FORMAT ", "
1293 "maximum_desired_capacity = " SIZE_FORMAT,
1294 minimum_desired_capacity, maximum_desired_capacity);
1295
1296 // Should not be greater than the heap max size. No need to adjust
1297 // it with respect to the heap min size as it's a lower bound (i.e.,
1298 // we'll try to make the capacity larger than it, not smaller).
1299 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1300 // Should not be less than the heap min size. No need to adjust it
1301 // with respect to the heap max size as it's an upper bound (i.e.,
1302 // we'll try to make the capacity smaller than it, not greater).
1303 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1304
1305 if (capacity_after_gc < minimum_desired_capacity) {
1306 // Don't expand unless it's significant
1307 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1308
1309 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). "
1310 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1311 "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1312 capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio);
1313
1314 expand(expand_bytes, _workers);
1315
1316 // No expansion, now see if we want to shrink
1317 } else if (capacity_after_gc > maximum_desired_capacity) {
1318 // Capacity too large, compute shrinking size
1319 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1320
1321 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). "
1322 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1323 "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1324 capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio);
1325
1326 shrink(shrink_bytes);
1327 }
1328 }
1329
1330 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1331 AllocationContext_t context,
1332 bool do_gc,
1333 bool clear_all_soft_refs,
1334 bool expect_null_mutator_alloc_region,
1335 bool* gc_succeeded) {
1336 *gc_succeeded = true;
1337 // Let's attempt the allocation first.
1338 HeapWord* result =
1339 attempt_allocation_at_safepoint(word_size,
1340 context,
1341 expect_null_mutator_alloc_region);
1342 if (result != NULL) {
1343 assert(*gc_succeeded, "sanity");
1344 return result;
1345 }
1346
1347 // In a G1 heap, we're supposed to keep allocation from failing by
1348 // incremental pauses. Therefore, at least for now, we'll favor
1349 // expansion over collection. (This might change in the future if we can
1350 // do something smarter than full collection to satisfy a failed alloc.)
1351 result = expand_and_allocate(word_size, context);
1352 if (result != NULL) {
1353 assert(*gc_succeeded, "sanity");
1354 return result;
1355 }
1356
1357 if (do_gc) {
1358 // Expansion didn't work, we'll try to do a Full GC.
1359 *gc_succeeded = do_full_collection(false, /* explicit_gc */
1360 clear_all_soft_refs);
1361 }
1362
1363 return NULL;
1364 }
1365
1366 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1367 AllocationContext_t context,
1368 bool* succeeded) {
1369 assert_at_safepoint(true /* should_be_vm_thread */);
1370
1371 // Attempts to allocate followed by Full GC.
1372 HeapWord* result =
1373 satisfy_failed_allocation_helper(word_size,
1374 context,
1375 true, /* do_gc */
1376 false, /* clear_all_soft_refs */
1377 false, /* expect_null_mutator_alloc_region */
1378 succeeded);
1379
1380 if (result != NULL || !*succeeded) {
1381 return result;
1382 }
1383
1384 // Attempts to allocate followed by Full GC that will collect all soft references.
1385 result = satisfy_failed_allocation_helper(word_size,
1386 context,
1387 true, /* do_gc */
1388 true, /* clear_all_soft_refs */
1389 true, /* expect_null_mutator_alloc_region */
1390 succeeded);
1391
1392 if (result != NULL || !*succeeded) {
1393 return result;
1394 }
1395
1396 // Attempts to allocate, no GC
1397 result = satisfy_failed_allocation_helper(word_size,
1398 context,
1399 false, /* do_gc */
1400 false, /* clear_all_soft_refs */
1401 true, /* expect_null_mutator_alloc_region */
1402 succeeded);
1403
1404 if (result != NULL) {
1405 assert(*succeeded, "sanity");
1406 return result;
1407 }
1408
1409 assert(!collector_policy()->should_clear_all_soft_refs(),
1410 "Flag should have been handled and cleared prior to this point");
1411
1412 // What else? We might try synchronous finalization later. If the total
1413 // space available is large enough for the allocation, then a more
1414 // complete compaction phase than we've tried so far might be
1415 // appropriate.
1416 assert(*succeeded, "sanity");
1417 return NULL;
1418 }
1419
1420 // Attempting to expand the heap sufficiently
1421 // to support an allocation of the given "word_size". If
1422 // successful, perform the allocation and return the address of the
1423 // allocated block, or else "NULL".
1424
1425 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1426 assert_at_safepoint(true /* should_be_vm_thread */);
1427
1428 _verifier->verify_region_sets_optional();
1429
1430 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1431 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1432 word_size * HeapWordSize);
1433
1434
1435 if (expand(expand_bytes, _workers)) {
1436 _hrm.verify_optional();
1437 _verifier->verify_region_sets_optional();
1438 return attempt_allocation_at_safepoint(word_size,
1439 context,
1440 false /* expect_null_mutator_alloc_region */);
1441 }
1442 return NULL;
1443 }
1444
1445 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) {
1446 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1447 aligned_expand_bytes = align_up(aligned_expand_bytes,
1448 HeapRegion::GrainBytes);
1449
1450 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B",
1451 expand_bytes, aligned_expand_bytes);
1452
1453 if (is_maximal_no_gc()) {
1454 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1455 return false;
1456 }
1457
1458 double expand_heap_start_time_sec = os::elapsedTime();
1459 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1460 assert(regions_to_expand > 0, "Must expand by at least one region");
1461
1462 uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers);
1463 if (expand_time_ms != NULL) {
1464 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1465 }
1466
1467 if (expanded_by > 0) {
1468 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1469 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1470 g1_policy()->record_new_heap_size(num_regions());
1471 } else {
1472 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1473
1474 // The expansion of the virtual storage space was unsuccessful.
1475 // Let's see if it was because we ran out of swap.
1476 if (G1ExitOnExpansionFailure &&
1477 _hrm.available() >= regions_to_expand) {
1478 // We had head room...
1479 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1480 }
1481 }
1482 return regions_to_expand > 0;
1483 }
1484
1485 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1486 size_t aligned_shrink_bytes =
1487 ReservedSpace::page_align_size_down(shrink_bytes);
1488 aligned_shrink_bytes = align_down(aligned_shrink_bytes,
1489 HeapRegion::GrainBytes);
1490 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1491
1492 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1493 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1494
1495
1496 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",
1497 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1498 if (num_regions_removed > 0) {
1499 g1_policy()->record_new_heap_size(num_regions());
1500 } else {
1501 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1502 }
1503 }
1504
1505 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1506 _verifier->verify_region_sets_optional();
1507
1508 // We should only reach here at the end of a Full GC which means we
1509 // should not not be holding to any GC alloc regions. The method
1510 // below will make sure of that and do any remaining clean up.
1511 _allocator->abandon_gc_alloc_regions();
1512
1513 // Instead of tearing down / rebuilding the free lists here, we
1514 // could instead use the remove_all_pending() method on free_list to
1515 // remove only the ones that we need to remove.
1516 tear_down_region_sets(true /* free_list_only */);
1517 shrink_helper(shrink_bytes);
1518 rebuild_region_sets(true /* free_list_only */);
1519
1520 _hrm.verify_optional();
1521 _verifier->verify_region_sets_optional();
1522 }
1523
1524 // Public methods.
1525
1526 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) :
1527 CollectedHeap(),
1528 _young_gen_sampling_thread(NULL),
1529 _collector_policy(collector_policy),
1530 _memory_manager("G1 Young Generation", "end of minor GC"),
1531 _full_gc_memory_manager("G1 Old Generation", "end of major GC"),
1532 _eden_pool(NULL),
1533 _survivor_pool(NULL),
1534 _old_pool(NULL),
1535 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1536 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1537 _g1_policy(create_g1_policy(_gc_timer_stw)),
1538 _collection_set(this, _g1_policy),
1539 _dirty_card_queue_set(false),
1540 _is_alive_closure_cm(this),
1541 _is_alive_closure_stw(this),
1542 _ref_processor_cm(NULL),
1543 _ref_processor_stw(NULL),
1544 _bot(NULL),
1545 _hot_card_cache(NULL),
1546 _g1_rem_set(NULL),
1547 _cr(NULL),
1548 _g1mm(NULL),
1549 _preserved_marks_set(true /* in_c_heap */),
1550 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1551 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1552 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1553 _humongous_reclaim_candidates(),
1554 _has_humongous_reclaim_candidates(false),
1555 _archive_allocator(NULL),
1556 _free_regions_coming(false),
1557 _gc_time_stamp(0),
1558 _summary_bytes_used(0),
1559 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1560 _old_evac_stats("Old", OldPLABSize, PLABWeight),
1561 _expand_heap_after_alloc_failure(true),
1562 _old_marking_cycles_started(0),
1563 _old_marking_cycles_completed(0),
1564 _in_cset_fast_test() {
1565
1566 _workers = new WorkGang("GC Thread", ParallelGCThreads,
1567 /* are_GC_task_threads */true,
1568 /* are_ConcurrentGC_threads */false);
1569 _workers->initialize_workers();
1570 _verifier = new G1HeapVerifier(this);
1571
1572 _allocator = G1Allocator::create_allocator(this);
1573
1574 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics());
1575
1576 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1577
1578 // Override the default _filler_array_max_size so that no humongous filler
1579 // objects are created.
1580 _filler_array_max_size = _humongous_object_threshold_in_words;
1581
1582 uint n_queues = ParallelGCThreads;
1583 _task_queues = new RefToScanQueueSet(n_queues);
1584
1585 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1586
1587 for (uint i = 0; i < n_queues; i++) {
1588 RefToScanQueue* q = new RefToScanQueue();
1589 q->initialize();
1590 _task_queues->register_queue(i, q);
1591 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1592 }
1593
1594 // Initialize the G1EvacuationFailureALot counters and flags.
1595 NOT_PRODUCT(reset_evacuation_should_fail();)
1596
1597 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1598 }
1599
1600 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1601 size_t size,
1602 size_t translation_factor) {
1603 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1604 // Allocate a new reserved space, preferring to use large pages.
1605 ReservedSpace rs(size, preferred_page_size);
1606 G1RegionToSpaceMapper* result =
1607 G1RegionToSpaceMapper::create_mapper(rs,
1608 size,
1609 rs.alignment(),
1610 HeapRegion::GrainBytes,
1611 translation_factor,
1612 mtGC);
1613
1614 os::trace_page_sizes_for_requested_size(description,
1615 size,
1616 preferred_page_size,
1617 rs.alignment(),
1618 rs.base(),
1619 rs.size());
1620
1621 return result;
1622 }
1623
1624 jint G1CollectedHeap::initialize_concurrent_refinement() {
1625 jint ecode = JNI_OK;
1626 _cr = G1ConcurrentRefine::create(&ecode);
1627 return ecode;
1628 }
1629
1630 jint G1CollectedHeap::initialize_young_gen_sampling_thread() {
1631 _young_gen_sampling_thread = new G1YoungRemSetSamplingThread();
1632 if (_young_gen_sampling_thread->osthread() == NULL) {
1633 vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread");
1634 return JNI_ENOMEM;
1635 }
1636 return JNI_OK;
1637 }
1638
1639 jint G1CollectedHeap::initialize() {
1640 CollectedHeap::pre_initialize();
1641 os::enable_vtime();
1642
1643 // Necessary to satisfy locking discipline assertions.
1644
1645 MutexLocker x(Heap_lock);
1646
1647 // While there are no constraints in the GC code that HeapWordSize
1648 // be any particular value, there are multiple other areas in the
1649 // system which believe this to be true (e.g. oop->object_size in some
1650 // cases incorrectly returns the size in wordSize units rather than
1651 // HeapWordSize).
1652 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1653
1654 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1655 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1656 size_t heap_alignment = collector_policy()->heap_alignment();
1657
1658 // Ensure that the sizes are properly aligned.
1659 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1660 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1661 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1662
1663 // Reserve the maximum.
1664
1665 // When compressed oops are enabled, the preferred heap base
1666 // is calculated by subtracting the requested size from the
1667 // 32Gb boundary and using the result as the base address for
1668 // heap reservation. If the requested size is not aligned to
1669 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1670 // into the ReservedHeapSpace constructor) then the actual
1671 // base of the reserved heap may end up differing from the
1672 // address that was requested (i.e. the preferred heap base).
1673 // If this happens then we could end up using a non-optimal
1674 // compressed oops mode.
1675
1676 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1677 heap_alignment);
1678
1679 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1680
1681 // Create the barrier set for the entire reserved region.
1682 G1SATBCardTableLoggingModRefBS* bs
1683 = new G1SATBCardTableLoggingModRefBS(reserved_region());
1684 bs->initialize();
1685 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity");
1686 set_barrier_set(bs);
1687
1688 // Create the hot card cache.
1689 _hot_card_cache = new G1HotCardCache(this);
1690
1691 // Carve out the G1 part of the heap.
1692 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1693 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
1694 G1RegionToSpaceMapper* heap_storage =
1695 G1RegionToSpaceMapper::create_mapper(g1_rs,
1696 g1_rs.size(),
1697 page_size,
1698 HeapRegion::GrainBytes,
1699 1,
1700 mtJavaHeap);
1701 os::trace_page_sizes("Heap",
1702 collector_policy()->min_heap_byte_size(),
1703 max_byte_size,
1704 page_size,
1705 heap_rs.base(),
1706 heap_rs.size());
1707 heap_storage->set_mapping_changed_listener(&_listener);
1708
1709 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1710 G1RegionToSpaceMapper* bot_storage =
1711 create_aux_memory_mapper("Block Offset Table",
1712 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1713 G1BlockOffsetTable::heap_map_factor());
1714
1715 G1RegionToSpaceMapper* cardtable_storage =
1716 create_aux_memory_mapper("Card Table",
1717 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize),
1718 G1SATBCardTableLoggingModRefBS::heap_map_factor());
1719
1720 G1RegionToSpaceMapper* card_counts_storage =
1721 create_aux_memory_mapper("Card Counts Table",
1722 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1723 G1CardCounts::heap_map_factor());
1724
1725 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1726 G1RegionToSpaceMapper* prev_bitmap_storage =
1727 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1728 G1RegionToSpaceMapper* next_bitmap_storage =
1729 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1730
1731 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1732 g1_barrier_set()->initialize(cardtable_storage);
1733 // Do later initialization work for concurrent refinement.
1734 _hot_card_cache->initialize(card_counts_storage);
1735
1736 // 6843694 - ensure that the maximum region index can fit
1737 // in the remembered set structures.
1738 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1739 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1740
1741 // Also create a G1 rem set.
1742 _g1_rem_set = new G1RemSet(this, g1_barrier_set(), _hot_card_cache);
1743 _g1_rem_set->initialize(max_capacity(), max_regions());
1744
1745 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1746 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1747 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1748 "too many cards per region");
1749
1750 FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1751
1752 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1753
1754 {
1755 HeapWord* start = _hrm.reserved().start();
1756 HeapWord* end = _hrm.reserved().end();
1757 size_t granularity = HeapRegion::GrainBytes;
1758
1759 _in_cset_fast_test.initialize(start, end, granularity);
1760 _humongous_reclaim_candidates.initialize(start, end, granularity);
1761 }
1762
1763 // Create the G1ConcurrentMark data structure and thread.
1764 // (Must do this late, so that "max_regions" is defined.)
1765 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1766 if (_cm == NULL || !_cm->completed_initialization()) {
1767 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
1768 return JNI_ENOMEM;
1769 }
1770 _cmThread = _cm->cm_thread();
1771
1772 // Now expand into the initial heap size.
1773 if (!expand(init_byte_size, _workers)) {
1774 vm_shutdown_during_initialization("Failed to allocate initial heap.");
1775 return JNI_ENOMEM;
1776 }
1777
1778 // Perform any initialization actions delegated to the policy.
1779 g1_policy()->init(this, &_collection_set);
1780
1781 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1782 SATB_Q_FL_lock,
1783 G1SATBProcessCompletedThreshold,
1784 Shared_SATB_Q_lock);
1785
1786 jint ecode = initialize_concurrent_refinement();
1787 if (ecode != JNI_OK) {
1788 return ecode;
1789 }
1790
1791 ecode = initialize_young_gen_sampling_thread();
1792 if (ecode != JNI_OK) {
1793 return ecode;
1794 }
1795
1796 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1797 DirtyCardQ_FL_lock,
1798 (int)concurrent_refine()->yellow_zone(),
1799 (int)concurrent_refine()->red_zone(),
1800 Shared_DirtyCardQ_lock,
1801 NULL, // fl_owner
1802 true); // init_free_ids
1803
1804 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1805 DirtyCardQ_FL_lock,
1806 -1, // never trigger processing
1807 -1, // no limit on length
1808 Shared_DirtyCardQ_lock,
1809 &JavaThread::dirty_card_queue_set());
1810
1811 // Here we allocate the dummy HeapRegion that is required by the
1812 // G1AllocRegion class.
1813 HeapRegion* dummy_region = _hrm.get_dummy_region();
1814
1815 // We'll re-use the same region whether the alloc region will
1816 // require BOT updates or not and, if it doesn't, then a non-young
1817 // region will complain that it cannot support allocations without
1818 // BOT updates. So we'll tag the dummy region as eden to avoid that.
1819 dummy_region->set_eden();
1820 // Make sure it's full.
1821 dummy_region->set_top(dummy_region->end());
1822 G1AllocRegion::setup(this, dummy_region);
1823
1824 _allocator->init_mutator_alloc_region();
1825
1826 // Do create of the monitoring and management support so that
1827 // values in the heap have been properly initialized.
1828 _g1mm = new G1MonitoringSupport(this);
1829
1830 _eden_pool = new G1EdenPool(this);
1831 _survivor_pool = new G1SurvivorPool(this);
1832 _old_pool = new G1OldGenPool(this);
1833
1834 _full_gc_memory_manager.add_pool(_eden_pool);
1835 _full_gc_memory_manager.add_pool(_survivor_pool);
1836 _full_gc_memory_manager.add_pool(_old_pool);
1837
1838 _memory_manager.add_pool(_eden_pool);
1839 _memory_manager.add_pool(_survivor_pool);
1840
1841 G1StringDedup::initialize();
1842
1843 _preserved_marks_set.init(ParallelGCThreads);
1844
1845 _collection_set.initialize(max_regions());
1846
1847 return JNI_OK;
1848 }
1849
1850 void G1CollectedHeap::stop() {
1851 // Stop all concurrent threads. We do this to make sure these threads
1852 // do not continue to execute and access resources (e.g. logging)
1853 // that are destroyed during shutdown.
1854 _cr->stop();
1855 _young_gen_sampling_thread->stop();
1856 _cmThread->stop();
1857 if (G1StringDedup::is_enabled()) {
1858 G1StringDedup::stop();
1859 }
1860 }
1861
1862 void G1CollectedHeap::safepoint_synchronize_begin() {
1863 SuspendibleThreadSet::synchronize();
1864 }
1865
1866 void G1CollectedHeap::safepoint_synchronize_end() {
1867 SuspendibleThreadSet::desynchronize();
1868 }
1869
1870 size_t G1CollectedHeap::conservative_max_heap_alignment() {
1871 return HeapRegion::max_region_size();
1872 }
1873
1874 void G1CollectedHeap::post_initialize() {
1875 ref_processing_init();
1876 }
1877
1878 void G1CollectedHeap::ref_processing_init() {
1879 // Reference processing in G1 currently works as follows:
1880 //
1881 // * There are two reference processor instances. One is
1882 // used to record and process discovered references
1883 // during concurrent marking; the other is used to
1884 // record and process references during STW pauses
1885 // (both full and incremental).
1886 // * Both ref processors need to 'span' the entire heap as
1887 // the regions in the collection set may be dotted around.
1888 //
1889 // * For the concurrent marking ref processor:
1890 // * Reference discovery is enabled at initial marking.
1891 // * Reference discovery is disabled and the discovered
1892 // references processed etc during remarking.
1893 // * Reference discovery is MT (see below).
1894 // * Reference discovery requires a barrier (see below).
1895 // * Reference processing may or may not be MT
1896 // (depending on the value of ParallelRefProcEnabled
1897 // and ParallelGCThreads).
1898 // * A full GC disables reference discovery by the CM
1899 // ref processor and abandons any entries on it's
1900 // discovered lists.
1901 //
1902 // * For the STW processor:
1903 // * Non MT discovery is enabled at the start of a full GC.
1904 // * Processing and enqueueing during a full GC is non-MT.
1905 // * During a full GC, references are processed after marking.
1906 //
1907 // * Discovery (may or may not be MT) is enabled at the start
1908 // of an incremental evacuation pause.
1909 // * References are processed near the end of a STW evacuation pause.
1910 // * For both types of GC:
1911 // * Discovery is atomic - i.e. not concurrent.
1912 // * Reference discovery will not need a barrier.
1913
1914 MemRegion mr = reserved_region();
1915
1916 bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1);
1917
1918 // Concurrent Mark ref processor
1919 _ref_processor_cm =
1920 new ReferenceProcessor(mr, // span
1921 mt_processing,
1922 // mt processing
1923 ParallelGCThreads,
1924 // degree of mt processing
1925 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
1926 // mt discovery
1927 MAX2(ParallelGCThreads, ConcGCThreads),
1928 // degree of mt discovery
1929 false,
1930 // Reference discovery is not atomic
1931 &_is_alive_closure_cm);
1932 // is alive closure
1933 // (for efficiency/performance)
1934
1935 // STW ref processor
1936 _ref_processor_stw =
1937 new ReferenceProcessor(mr, // span
1938 mt_processing,
1939 // mt processing
1940 ParallelGCThreads,
1941 // degree of mt processing
1942 (ParallelGCThreads > 1),
1943 // mt discovery
1944 ParallelGCThreads,
1945 // degree of mt discovery
1946 true,
1947 // Reference discovery is atomic
1948 &_is_alive_closure_stw);
1949 // is alive closure
1950 // (for efficiency/performance)
1951 }
1952
1953 CollectorPolicy* G1CollectedHeap::collector_policy() const {
1954 return _collector_policy;
1955 }
1956
1957 size_t G1CollectedHeap::capacity() const {
1958 return _hrm.length() * HeapRegion::GrainBytes;
1959 }
1960
1961 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const {
1962 return _hrm.total_free_bytes();
1963 }
1964
1965 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
1966 hr->reset_gc_time_stamp();
1967 }
1968
1969 #ifndef PRODUCT
1970
1971 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
1972 private:
1973 unsigned _gc_time_stamp;
1974 bool _failures;
1975
1976 public:
1977 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
1978 _gc_time_stamp(gc_time_stamp), _failures(false) { }
1979
1980 virtual bool doHeapRegion(HeapRegion* hr) {
1981 unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
1982 if (_gc_time_stamp != region_gc_time_stamp) {
1983 log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr),
1984 region_gc_time_stamp, _gc_time_stamp);
1985 _failures = true;
1986 }
1987 return false;
1988 }
1989
1990 bool failures() { return _failures; }
1991 };
1992
1993 void G1CollectedHeap::check_gc_time_stamps() {
1994 CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
1995 heap_region_iterate(&cl);
1996 guarantee(!cl.failures(), "all GC time stamps should have been reset");
1997 }
1998 #endif // PRODUCT
1999
2000 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) {
2001 _hot_card_cache->drain(cl, worker_i);
2002 }
2003
2004 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) {
2005 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2006 size_t n_completed_buffers = 0;
2007 while (dcqs.apply_closure_during_gc(cl, worker_i)) {
2008 n_completed_buffers++;
2009 }
2010 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
2011 dcqs.clear_n_completed_buffers();
2012 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2013 }
2014
2015 // Computes the sum of the storage used by the various regions.
2016 size_t G1CollectedHeap::used() const {
2017 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
2018 if (_archive_allocator != NULL) {
2019 result += _archive_allocator->used();
2020 }
2021 return result;
2022 }
2023
2024 size_t G1CollectedHeap::used_unlocked() const {
2025 return _summary_bytes_used;
2026 }
2027
2028 class SumUsedClosure: public HeapRegionClosure {
2029 size_t _used;
2030 public:
2031 SumUsedClosure() : _used(0) {}
2032 bool doHeapRegion(HeapRegion* r) {
2033 _used += r->used();
2034 return false;
2035 }
2036 size_t result() { return _used; }
2037 };
2038
2039 size_t G1CollectedHeap::recalculate_used() const {
2040 double recalculate_used_start = os::elapsedTime();
2041
2042 SumUsedClosure blk;
2043 heap_region_iterate(&blk);
2044
2045 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2046 return blk.result();
2047 }
2048
2049 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
2050 switch (cause) {
2051 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2052 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent;
2053 case GCCause::_update_allocation_context_stats_inc: return true;
2054 case GCCause::_wb_conc_mark: return true;
2055 default : return false;
2056 }
2057 }
2058
2059 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2060 switch (cause) {
2061 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2062 case GCCause::_g1_humongous_allocation: return true;
2063 default: return is_user_requested_concurrent_full_gc(cause);
2064 }
2065 }
2066
2067 #ifndef PRODUCT
2068 void G1CollectedHeap::allocate_dummy_regions() {
2069 // Let's fill up most of the region
2070 size_t word_size = HeapRegion::GrainWords - 1024;
2071 // And as a result the region we'll allocate will be humongous.
2072 guarantee(is_humongous(word_size), "sanity");
2073
2074 // _filler_array_max_size is set to humongous object threshold
2075 // but temporarily change it to use CollectedHeap::fill_with_object().
2076 SizeTFlagSetting fs(_filler_array_max_size, word_size);
2077
2078 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2079 // Let's use the existing mechanism for the allocation
2080 HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2081 AllocationContext::system());
2082 if (dummy_obj != NULL) {
2083 MemRegion mr(dummy_obj, word_size);
2084 CollectedHeap::fill_with_object(mr);
2085 } else {
2086 // If we can't allocate once, we probably cannot allocate
2087 // again. Let's get out of the loop.
2088 break;
2089 }
2090 }
2091 }
2092 #endif // !PRODUCT
2093
2094 void G1CollectedHeap::increment_old_marking_cycles_started() {
2095 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2096 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2097 "Wrong marking cycle count (started: %d, completed: %d)",
2098 _old_marking_cycles_started, _old_marking_cycles_completed);
2099
2100 _old_marking_cycles_started++;
2101 }
2102
2103 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2104 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2105
2106 // We assume that if concurrent == true, then the caller is a
2107 // concurrent thread that was joined the Suspendible Thread
2108 // Set. If there's ever a cheap way to check this, we should add an
2109 // assert here.
2110
2111 // Given that this method is called at the end of a Full GC or of a
2112 // concurrent cycle, and those can be nested (i.e., a Full GC can
2113 // interrupt a concurrent cycle), the number of full collections
2114 // completed should be either one (in the case where there was no
2115 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2116 // behind the number of full collections started.
2117
2118 // This is the case for the inner caller, i.e. a Full GC.
2119 assert(concurrent ||
2120 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2121 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2122 "for inner caller (Full GC): _old_marking_cycles_started = %u "
2123 "is inconsistent with _old_marking_cycles_completed = %u",
2124 _old_marking_cycles_started, _old_marking_cycles_completed);
2125
2126 // This is the case for the outer caller, i.e. the concurrent cycle.
2127 assert(!concurrent ||
2128 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2129 "for outer caller (concurrent cycle): "
2130 "_old_marking_cycles_started = %u "
2131 "is inconsistent with _old_marking_cycles_completed = %u",
2132 _old_marking_cycles_started, _old_marking_cycles_completed);
2133
2134 _old_marking_cycles_completed += 1;
2135
2136 // We need to clear the "in_progress" flag in the CM thread before
2137 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2138 // is set) so that if a waiter requests another System.gc() it doesn't
2139 // incorrectly see that a marking cycle is still in progress.
2140 if (concurrent) {
2141 _cmThread->set_idle();
2142 }
2143
2144 // This notify_all() will ensure that a thread that called
2145 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2146 // and it's waiting for a full GC to finish will be woken up. It is
2147 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2148 FullGCCount_lock->notify_all();
2149 }
2150
2151 void G1CollectedHeap::collect(GCCause::Cause cause) {
2152 assert_heap_not_locked();
2153
2154 uint gc_count_before;
2155 uint old_marking_count_before;
2156 uint full_gc_count_before;
2157 bool retry_gc;
2158
2159 do {
2160 retry_gc = false;
2161
2162 {
2163 MutexLocker ml(Heap_lock);
2164
2165 // Read the GC count while holding the Heap_lock
2166 gc_count_before = total_collections();
2167 full_gc_count_before = total_full_collections();
2168 old_marking_count_before = _old_marking_cycles_started;
2169 }
2170
2171 if (should_do_concurrent_full_gc(cause)) {
2172 // Schedule an initial-mark evacuation pause that will start a
2173 // concurrent cycle. We're setting word_size to 0 which means that
2174 // we are not requesting a post-GC allocation.
2175 VM_G1IncCollectionPause op(gc_count_before,
2176 0, /* word_size */
2177 true, /* should_initiate_conc_mark */
2178 g1_policy()->max_pause_time_ms(),
2179 cause);
2180 op.set_allocation_context(AllocationContext::current());
2181
2182 VMThread::execute(&op);
2183 if (!op.pause_succeeded()) {
2184 if (old_marking_count_before == _old_marking_cycles_started) {
2185 retry_gc = op.should_retry_gc();
2186 } else {
2187 // A Full GC happened while we were trying to schedule the
2188 // initial-mark GC. No point in starting a new cycle given
2189 // that the whole heap was collected anyway.
2190 }
2191
2192 if (retry_gc) {
2193 if (GCLocker::is_active_and_needs_gc()) {
2194 GCLocker::stall_until_clear();
2195 }
2196 }
2197 }
2198 } else {
2199 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2200 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2201
2202 // Schedule a standard evacuation pause. We're setting word_size
2203 // to 0 which means that we are not requesting a post-GC allocation.
2204 VM_G1IncCollectionPause op(gc_count_before,
2205 0, /* word_size */
2206 false, /* should_initiate_conc_mark */
2207 g1_policy()->max_pause_time_ms(),
2208 cause);
2209 VMThread::execute(&op);
2210 } else {
2211 // Schedule a Full GC.
2212 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2213 VMThread::execute(&op);
2214 }
2215 }
2216 } while (retry_gc);
2217 }
2218
2219 bool G1CollectedHeap::is_in(const void* p) const {
2220 if (_hrm.reserved().contains(p)) {
2221 // Given that we know that p is in the reserved space,
2222 // heap_region_containing() should successfully
2223 // return the containing region.
2224 HeapRegion* hr = heap_region_containing(p);
2225 return hr->is_in(p);
2226 } else {
2227 return false;
2228 }
2229 }
2230
2231 #ifdef ASSERT
2232 bool G1CollectedHeap::is_in_exact(const void* p) const {
2233 bool contains = reserved_region().contains(p);
2234 bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2235 if (contains && available) {
2236 return true;
2237 } else {
2238 return false;
2239 }
2240 }
2241 #endif
2242
2243 // Iteration functions.
2244
2245 // Iterates an ObjectClosure over all objects within a HeapRegion.
2246
2247 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2248 ObjectClosure* _cl;
2249 public:
2250 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2251 bool doHeapRegion(HeapRegion* r) {
2252 if (!r->is_continues_humongous()) {
2253 r->object_iterate(_cl);
2254 }
2255 return false;
2256 }
2257 };
2258
2259 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2260 IterateObjectClosureRegionClosure blk(cl);
2261 heap_region_iterate(&blk);
2262 }
2263
2264 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2265 _hrm.iterate(cl);
2266 }
2267
2268 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
2269 HeapRegionClaimer *hrclaimer,
2270 uint worker_id) const {
2271 _hrm.par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id));
2272 }
2273
2274 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl,
2275 HeapRegionClaimer *hrclaimer) const {
2276 _hrm.par_iterate(cl, hrclaimer, 0);
2277 }
2278
2279 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2280 _collection_set.iterate(cl);
2281 }
2282
2283 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) {
2284 _collection_set.iterate_from(cl, worker_id, workers()->active_workers());
2285 }
2286
2287 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2288 HeapRegion* hr = heap_region_containing(addr);
2289 return hr->block_start(addr);
2290 }
2291
2292 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2293 HeapRegion* hr = heap_region_containing(addr);
2294 return hr->block_size(addr);
2295 }
2296
2297 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2298 HeapRegion* hr = heap_region_containing(addr);
2299 return hr->block_is_obj(addr);
2300 }
2301
2302 bool G1CollectedHeap::supports_tlab_allocation() const {
2303 return true;
2304 }
2305
2306 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2307 return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2308 }
2309
2310 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2311 return _eden.length() * HeapRegion::GrainBytes;
2312 }
2313
2314 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2315 // must be equal to the humongous object limit.
2316 size_t G1CollectedHeap::max_tlab_size() const {
2317 return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
2318 }
2319
2320 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2321 AllocationContext_t context = AllocationContext::current();
2322 return _allocator->unsafe_max_tlab_alloc(context);
2323 }
2324
2325 size_t G1CollectedHeap::max_capacity() const {
2326 return _hrm.reserved().byte_size();
2327 }
2328
2329 jlong G1CollectedHeap::millis_since_last_gc() {
2330 // See the notes in GenCollectedHeap::millis_since_last_gc()
2331 // for more information about the implementation.
2332 jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) -
2333 _g1_policy->collection_pause_end_millis();
2334 if (ret_val < 0) {
2335 log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
2336 ". returning zero instead.", ret_val);
2337 return 0;
2338 }
2339 return ret_val;
2340 }
2341
2342 void G1CollectedHeap::prepare_for_verify() {
2343 _verifier->prepare_for_verify();
2344 }
2345
2346 void G1CollectedHeap::verify(VerifyOption vo) {
2347 _verifier->verify(vo);
2348 }
2349
2350 bool G1CollectedHeap::supports_concurrent_phase_control() const {
2351 return true;
2352 }
2353
2354 const char* const* G1CollectedHeap::concurrent_phases() const {
2355 return _cmThread->concurrent_phases();
2356 }
2357
2358 bool G1CollectedHeap::request_concurrent_phase(const char* phase) {
2359 return _cmThread->request_concurrent_phase(phase);
2360 }
2361
2362 class PrintRegionClosure: public HeapRegionClosure {
2363 outputStream* _st;
2364 public:
2365 PrintRegionClosure(outputStream* st) : _st(st) {}
2366 bool doHeapRegion(HeapRegion* r) {
2367 r->print_on(_st);
2368 return false;
2369 }
2370 };
2371
2372 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2373 const HeapRegion* hr,
2374 const VerifyOption vo) const {
2375 switch (vo) {
2376 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2377 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2378 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr);
2379 default: ShouldNotReachHere();
2380 }
2381 return false; // keep some compilers happy
2382 }
2383
2384 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2385 const VerifyOption vo) const {
2386 switch (vo) {
2387 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2388 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2389 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj);
2390 default: ShouldNotReachHere();
2391 }
2392 return false; // keep some compilers happy
2393 }
2394
2395 void G1CollectedHeap::print_heap_regions() const {
2396 LogTarget(Trace, gc, heap, region) lt;
2397 if (lt.is_enabled()) {
2398 LogStream ls(lt);
2399 print_regions_on(&ls);
2400 }
2401 }
2402
2403 void G1CollectedHeap::print_on(outputStream* st) const {
2404 st->print(" %-20s", "garbage-first heap");
2405 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2406 capacity()/K, used_unlocked()/K);
2407 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")",
2408 p2i(_hrm.reserved().start()),
2409 p2i(_hrm.reserved().end()));
2410 st->cr();
2411 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2412 uint young_regions = young_regions_count();
2413 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2414 (size_t) young_regions * HeapRegion::GrainBytes / K);
2415 uint survivor_regions = survivor_regions_count();
2416 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2417 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2418 st->cr();
2419 MetaspaceAux::print_on(st);
2420 }
2421
2422 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2423 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2424 "HS=humongous(starts), HC=humongous(continues), "
2425 "CS=collection set, F=free, A=archive, TS=gc time stamp, "
2426 "AC=allocation context, "
2427 "TAMS=top-at-mark-start (previous, next)");
2428 PrintRegionClosure blk(st);
2429 heap_region_iterate(&blk);
2430 }
2431
2432 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2433 print_on(st);
2434
2435 // Print the per-region information.
2436 print_regions_on(st);
2437 }
2438
2439 void G1CollectedHeap::print_on_error(outputStream* st) const {
2440 this->CollectedHeap::print_on_error(st);
2441
2442 if (_cm != NULL) {
2443 st->cr();
2444 _cm->print_on_error(st);
2445 }
2446 }
2447
2448 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2449 workers()->print_worker_threads_on(st);
2450 _cmThread->print_on(st);
2451 st->cr();
2452 _cm->print_worker_threads_on(st);
2453 _cr->print_threads_on(st);
2454 _young_gen_sampling_thread->print_on(st);
2455 if (G1StringDedup::is_enabled()) {
2456 G1StringDedup::print_worker_threads_on(st);
2457 }
2458 }
2459
2460 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2461 workers()->threads_do(tc);
2462 tc->do_thread(_cmThread);
2463 _cm->threads_do(tc);
2464 _cr->threads_do(tc);
2465 tc->do_thread(_young_gen_sampling_thread);
2466 if (G1StringDedup::is_enabled()) {
2467 G1StringDedup::threads_do(tc);
2468 }
2469 }
2470
2471 void G1CollectedHeap::print_tracing_info() const {
2472 g1_rem_set()->print_summary_info();
2473 concurrent_mark()->print_summary_info();
2474 }
2475
2476 #ifndef PRODUCT
2477 // Helpful for debugging RSet issues.
2478
2479 class PrintRSetsClosure : public HeapRegionClosure {
2480 private:
2481 const char* _msg;
2482 size_t _occupied_sum;
2483
2484 public:
2485 bool doHeapRegion(HeapRegion* r) {
2486 HeapRegionRemSet* hrrs = r->rem_set();
2487 size_t occupied = hrrs->occupied();
2488 _occupied_sum += occupied;
2489
2490 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2491 if (occupied == 0) {
2492 tty->print_cr(" RSet is empty");
2493 } else {
2494 hrrs->print();
2495 }
2496 tty->print_cr("----------");
2497 return false;
2498 }
2499
2500 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2501 tty->cr();
2502 tty->print_cr("========================================");
2503 tty->print_cr("%s", msg);
2504 tty->cr();
2505 }
2506
2507 ~PrintRSetsClosure() {
2508 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2509 tty->print_cr("========================================");
2510 tty->cr();
2511 }
2512 };
2513
2514 void G1CollectedHeap::print_cset_rsets() {
2515 PrintRSetsClosure cl("Printing CSet RSets");
2516 collection_set_iterate(&cl);
2517 }
2518
2519 void G1CollectedHeap::print_all_rsets() {
2520 PrintRSetsClosure cl("Printing All RSets");;
2521 heap_region_iterate(&cl);
2522 }
2523 #endif // PRODUCT
2524
2525 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2526
2527 size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes;
2528 size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes;
2529 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2530
2531 size_t eden_capacity_bytes =
2532 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2533
2534 VirtualSpaceSummary heap_summary = create_heap_space_summary();
2535 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2536 eden_capacity_bytes, survivor_used_bytes, num_regions());
2537 }
2538
2539 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2540 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2541 stats->unused(), stats->used(), stats->region_end_waste(),
2542 stats->regions_filled(), stats->direct_allocated(),
2543 stats->failure_used(), stats->failure_waste());
2544 }
2545
2546 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2547 const G1HeapSummary& heap_summary = create_g1_heap_summary();
2548 gc_tracer->report_gc_heap_summary(when, heap_summary);
2549
2550 const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2551 gc_tracer->report_metaspace_summary(when, metaspace_summary);
2552 }
2553
2554 G1CollectedHeap* G1CollectedHeap::heap() {
2555 CollectedHeap* heap = Universe::heap();
2556 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2557 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap");
2558 return (G1CollectedHeap*)heap;
2559 }
2560
2561 void G1CollectedHeap::gc_prologue(bool full) {
2562 // always_do_update_barrier = false;
2563 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2564
2565 // This summary needs to be printed before incrementing total collections.
2566 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2567
2568 // Update common counters.
2569 increment_total_collections(full /* full gc */);
2570 if (full) {
2571 increment_old_marking_cycles_started();
2572 reset_gc_time_stamp();
2573 } else {
2574 increment_gc_time_stamp();
2575 }
2576
2577 // Fill TLAB's and such
2578 double start = os::elapsedTime();
2579 accumulate_statistics_all_tlabs();
2580 ensure_parsability(true);
2581 g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2582 }
2583
2584 void G1CollectedHeap::gc_epilogue(bool full) {
2585 // Update common counters.
2586 if (full) {
2587 // Update the number of full collections that have been completed.
2588 increment_old_marking_cycles_completed(false /* concurrent */);
2589 }
2590
2591 // We are at the end of the GC. Total collections has already been increased.
2592 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2593
2594 // FIXME: what is this about?
2595 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2596 // is set.
2597 #if COMPILER2_OR_JVMCI
2598 assert(DerivedPointerTable::is_empty(), "derived pointer present");
2599 #endif
2600 // always_do_update_barrier = true;
2601
2602 double start = os::elapsedTime();
2603 resize_all_tlabs();
2604 g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2605
2606 allocation_context_stats().update(full);
2607
2608 MemoryService::track_memory_usage();
2609 // We have just completed a GC. Update the soft reference
2610 // policy with the new heap occupancy
2611 Universe::update_heap_info_at_gc();
2612 }
2613
2614 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2615 uint gc_count_before,
2616 bool* succeeded,
2617 GCCause::Cause gc_cause) {
2618 assert_heap_not_locked_and_not_at_safepoint();
2619 VM_G1IncCollectionPause op(gc_count_before,
2620 word_size,
2621 false, /* should_initiate_conc_mark */
2622 g1_policy()->max_pause_time_ms(),
2623 gc_cause);
2624
2625 op.set_allocation_context(AllocationContext::current());
2626 VMThread::execute(&op);
2627
2628 HeapWord* result = op.result();
2629 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
2630 assert(result == NULL || ret_succeeded,
2631 "the result should be NULL if the VM did not succeed");
2632 *succeeded = ret_succeeded;
2633
2634 assert_heap_not_locked();
2635 return result;
2636 }
2637
2638 void
2639 G1CollectedHeap::doConcurrentMark() {
2640 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
2641 if (!_cmThread->in_progress()) {
2642 _cmThread->set_started();
2643 CGC_lock->notify();
2644 }
2645 }
2646
2647 size_t G1CollectedHeap::pending_card_num() {
2648 size_t extra_cards = 0;
2649 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *curr = jtiwh.next(); ) {
2650 DirtyCardQueue& dcq = curr->dirty_card_queue();
2651 extra_cards += dcq.size();
2652 }
2653 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2654 size_t buffer_size = dcqs.buffer_size();
2655 size_t buffer_num = dcqs.completed_buffers_num();
2656
2657 return buffer_size * buffer_num + extra_cards;
2658 }
2659
2660 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
2661 private:
2662 size_t _total_humongous;
2663 size_t _candidate_humongous;
2664
2665 DirtyCardQueue _dcq;
2666
2667 // We don't nominate objects with many remembered set entries, on
2668 // the assumption that such objects are likely still live.
2669 bool is_remset_small(HeapRegion* region) const {
2670 HeapRegionRemSet* const rset = region->rem_set();
2671 return G1EagerReclaimHumongousObjectsWithStaleRefs
2672 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)
2673 : rset->is_empty();
2674 }
2675
2676 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const {
2677 assert(region->is_starts_humongous(), "Must start a humongous object");
2678
2679 oop obj = oop(region->bottom());
2680
2681 // Dead objects cannot be eager reclaim candidates. Due to class
2682 // unloading it is unsafe to query their classes so we return early.
2683 if (heap->is_obj_dead(obj, region)) {
2684 return false;
2685 }
2686
2687 // Candidate selection must satisfy the following constraints
2688 // while concurrent marking is in progress:
2689 //
2690 // * In order to maintain SATB invariants, an object must not be
2691 // reclaimed if it was allocated before the start of marking and
2692 // has not had its references scanned. Such an object must have
2693 // its references (including type metadata) scanned to ensure no
2694 // live objects are missed by the marking process. Objects
2695 // allocated after the start of concurrent marking don't need to
2696 // be scanned.
2697 //
2698 // * An object must not be reclaimed if it is on the concurrent
2699 // mark stack. Objects allocated after the start of concurrent
2700 // marking are never pushed on the mark stack.
2701 //
2702 // Nominating only objects allocated after the start of concurrent
2703 // marking is sufficient to meet both constraints. This may miss
2704 // some objects that satisfy the constraints, but the marking data
2705 // structures don't support efficiently performing the needed
2706 // additional tests or scrubbing of the mark stack.
2707 //
2708 // However, we presently only nominate is_typeArray() objects.
2709 // A humongous object containing references induces remembered
2710 // set entries on other regions. In order to reclaim such an
2711 // object, those remembered sets would need to be cleaned up.
2712 //
2713 // We also treat is_typeArray() objects specially, allowing them
2714 // to be reclaimed even if allocated before the start of
2715 // concurrent mark. For this we rely on mark stack insertion to
2716 // exclude is_typeArray() objects, preventing reclaiming an object
2717 // that is in the mark stack. We also rely on the metadata for
2718 // such objects to be built-in and so ensured to be kept live.
2719 // Frequent allocation and drop of large binary blobs is an
2720 // important use case for eager reclaim, and this special handling
2721 // may reduce needed headroom.
2722
2723 return obj->is_typeArray() && is_remset_small(region);
2724 }
2725
2726 public:
2727 RegisterHumongousWithInCSetFastTestClosure()
2728 : _total_humongous(0),
2729 _candidate_humongous(0),
2730 _dcq(&JavaThread::dirty_card_queue_set()) {
2731 }
2732
2733 virtual bool doHeapRegion(HeapRegion* r) {
2734 if (!r->is_starts_humongous()) {
2735 return false;
2736 }
2737 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2738
2739 bool is_candidate = humongous_region_is_candidate(g1h, r);
2740 uint rindex = r->hrm_index();
2741 g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
2742 if (is_candidate) {
2743 _candidate_humongous++;
2744 g1h->register_humongous_region_with_cset(rindex);
2745 // Is_candidate already filters out humongous object with large remembered sets.
2746 // If we have a humongous object with a few remembered sets, we simply flush these
2747 // remembered set entries into the DCQS. That will result in automatic
2748 // re-evaluation of their remembered set entries during the following evacuation
2749 // phase.
2750 if (!r->rem_set()->is_empty()) {
2751 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
2752 "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
2753 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
2754 HeapRegionRemSetIterator hrrs(r->rem_set());
2755 size_t card_index;
2756 while (hrrs.has_next(card_index)) {
2757 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
2758 // The remembered set might contain references to already freed
2759 // regions. Filter out such entries to avoid failing card table
2760 // verification.
2761 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) {
2762 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
2763 *card_ptr = CardTableModRefBS::dirty_card_val();
2764 _dcq.enqueue(card_ptr);
2765 }
2766 }
2767 }
2768 assert(hrrs.n_yielded() == r->rem_set()->occupied(),
2769 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
2770 hrrs.n_yielded(), r->rem_set()->occupied());
2771 r->rem_set()->clear_locked();
2772 }
2773 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
2774 }
2775 _total_humongous++;
2776
2777 return false;
2778 }
2779
2780 size_t total_humongous() const { return _total_humongous; }
2781 size_t candidate_humongous() const { return _candidate_humongous; }
2782
2783 void flush_rem_set_entries() { _dcq.flush(); }
2784 };
2785
2786 void G1CollectedHeap::register_humongous_regions_with_cset() {
2787 if (!G1EagerReclaimHumongousObjects) {
2788 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
2789 return;
2790 }
2791 double time = os::elapsed_counter();
2792
2793 // Collect reclaim candidate information and register candidates with cset.
2794 RegisterHumongousWithInCSetFastTestClosure cl;
2795 heap_region_iterate(&cl);
2796
2797 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
2798 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
2799 cl.total_humongous(),
2800 cl.candidate_humongous());
2801 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
2802
2803 // Finally flush all remembered set entries to re-check into the global DCQS.
2804 cl.flush_rem_set_entries();
2805 }
2806
2807 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2808 public:
2809 bool doHeapRegion(HeapRegion* hr) {
2810 if (!hr->is_archive() && !hr->is_continues_humongous()) {
2811 hr->verify_rem_set();
2812 }
2813 return false;
2814 }
2815 };
2816
2817 uint G1CollectedHeap::num_task_queues() const {
2818 return _task_queues->size();
2819 }
2820
2821 #if TASKQUEUE_STATS
2822 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2823 st->print_raw_cr("GC Task Stats");
2824 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2825 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2826 }
2827
2828 void G1CollectedHeap::print_taskqueue_stats() const {
2829 if (!log_is_enabled(Trace, gc, task, stats)) {
2830 return;
2831 }
2832 Log(gc, task, stats) log;
2833 ResourceMark rm;
2834 LogStream ls(log.trace());
2835 outputStream* st = &ls;
2836
2837 print_taskqueue_stats_hdr(st);
2838
2839 TaskQueueStats totals;
2840 const uint n = num_task_queues();
2841 for (uint i = 0; i < n; ++i) {
2842 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2843 totals += task_queue(i)->stats;
2844 }
2845 st->print_raw("tot "); totals.print(st); st->cr();
2846
2847 DEBUG_ONLY(totals.verify());
2848 }
2849
2850 void G1CollectedHeap::reset_taskqueue_stats() {
2851 const uint n = num_task_queues();
2852 for (uint i = 0; i < n; ++i) {
2853 task_queue(i)->stats.reset();
2854 }
2855 }
2856 #endif // TASKQUEUE_STATS
2857
2858 void G1CollectedHeap::wait_for_root_region_scanning() {
2859 double scan_wait_start = os::elapsedTime();
2860 // We have to wait until the CM threads finish scanning the
2861 // root regions as it's the only way to ensure that all the
2862 // objects on them have been correctly scanned before we start
2863 // moving them during the GC.
2864 bool waited = _cm->root_regions()->wait_until_scan_finished();
2865 double wait_time_ms = 0.0;
2866 if (waited) {
2867 double scan_wait_end = os::elapsedTime();
2868 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2869 }
2870 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2871 }
2872
2873 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2874 private:
2875 G1HRPrinter* _hr_printer;
2876 public:
2877 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2878
2879 virtual bool doHeapRegion(HeapRegion* r) {
2880 _hr_printer->cset(r);
2881 return false;
2882 }
2883 };
2884
2885 void G1CollectedHeap::start_new_collection_set() {
2886 collection_set()->start_incremental_building();
2887
2888 clear_cset_fast_test();
2889
2890 guarantee(_eden.length() == 0, "eden should have been cleared");
2891 g1_policy()->transfer_survivors_to_cset(survivor());
2892 }
2893
2894 bool
2895 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
2896 assert_at_safepoint(true /* should_be_vm_thread */);
2897 guarantee(!is_gc_active(), "collection is not reentrant");
2898
2899 if (GCLocker::check_active_before_gc()) {
2900 return false;
2901 }
2902
2903 _gc_timer_stw->register_gc_start();
2904
2905 GCIdMark gc_id_mark;
2906 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
2907
2908 SvcGCMarker sgcm(SvcGCMarker::MINOR);
2909 ResourceMark rm;
2910
2911 g1_policy()->note_gc_start();
2912
2913 wait_for_root_region_scanning();
2914
2915 print_heap_before_gc();
2916 print_heap_regions();
2917 trace_heap_before_gc(_gc_tracer_stw);
2918
2919 _verifier->verify_region_sets_optional();
2920 _verifier->verify_dirty_young_regions();
2921
2922 // We should not be doing initial mark unless the conc mark thread is running
2923 if (!_cmThread->should_terminate()) {
2924 // This call will decide whether this pause is an initial-mark
2925 // pause. If it is, during_initial_mark_pause() will return true
2926 // for the duration of this pause.
2927 g1_policy()->decide_on_conc_mark_initiation();
2928 }
2929
2930 // We do not allow initial-mark to be piggy-backed on a mixed GC.
2931 assert(!collector_state()->during_initial_mark_pause() ||
2932 collector_state()->gcs_are_young(), "sanity");
2933
2934 // We also do not allow mixed GCs during marking.
2935 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity");
2936
2937 // Record whether this pause is an initial mark. When the current
2938 // thread has completed its logging output and it's safe to signal
2939 // the CM thread, the flag's value in the policy has been reset.
2940 bool should_start_conc_mark = collector_state()->during_initial_mark_pause();
2941
2942 // Inner scope for scope based logging, timers, and stats collection
2943 {
2944 EvacuationInfo evacuation_info;
2945
2946 if (collector_state()->during_initial_mark_pause()) {
2947 // We are about to start a marking cycle, so we increment the
2948 // full collection counter.
2949 increment_old_marking_cycles_started();
2950 _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
2951 }
2952
2953 _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
2954
2955 GCTraceCPUTime tcpu;
2956
2957 FormatBuffer<> gc_string("Pause ");
2958 if (collector_state()->during_initial_mark_pause()) {
2959 gc_string.append("Initial Mark");
2960 } else if (collector_state()->gcs_are_young()) {
2961 gc_string.append("Young");
2962 } else {
2963 gc_string.append("Mixed");
2964 }
2965 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true);
2966
2967 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
2968 workers()->active_workers(),
2969 Threads::number_of_non_daemon_threads());
2970 workers()->update_active_workers(active_workers);
2971 log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
2972
2973 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
2974 TraceMemoryManagerStats tms(&_memory_manager, gc_cause());
2975
2976 // If the secondary_free_list is not empty, append it to the
2977 // free_list. No need to wait for the cleanup operation to finish;
2978 // the region allocation code will check the secondary_free_list
2979 // and wait if necessary. If the G1StressConcRegionFreeing flag is
2980 // set, skip this step so that the region allocation code has to
2981 // get entries from the secondary_free_list.
2982 if (!G1StressConcRegionFreeing) {
2983 append_secondary_free_list_if_not_empty_with_lock();
2984 }
2985
2986 G1HeapTransition heap_transition(this);
2987 size_t heap_used_bytes_before_gc = used();
2988
2989 // Don't dynamically change the number of GC threads this early. A value of
2990 // 0 is used to indicate serial work. When parallel work is done,
2991 // it will be set.
2992
2993 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
2994 IsGCActiveMark x;
2995
2996 gc_prologue(false);
2997
2998 if (VerifyRememberedSets) {
2999 log_info(gc, verify)("[Verifying RemSets before GC]");
3000 VerifyRegionRemSetClosure v_cl;
3001 heap_region_iterate(&v_cl);
3002 }
3003
3004 _verifier->verify_before_gc();
3005
3006 _verifier->check_bitmaps("GC Start");
3007
3008 #if COMPILER2_OR_JVMCI
3009 DerivedPointerTable::clear();
3010 #endif
3011
3012 // Please see comment in g1CollectedHeap.hpp and
3013 // G1CollectedHeap::ref_processing_init() to see how
3014 // reference processing currently works in G1.
3015
3016 // Enable discovery in the STW reference processor
3017 if (g1_policy()->should_process_references()) {
3018 ref_processor_stw()->enable_discovery();
3019 } else {
3020 ref_processor_stw()->disable_discovery();
3021 }
3022
3023 {
3024 // We want to temporarily turn off discovery by the
3025 // CM ref processor, if necessary, and turn it back on
3026 // on again later if we do. Using a scoped
3027 // NoRefDiscovery object will do this.
3028 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3029
3030 // Forget the current alloc region (we might even choose it to be part
3031 // of the collection set!).
3032 _allocator->release_mutator_alloc_region();
3033
3034 // This timing is only used by the ergonomics to handle our pause target.
3035 // It is unclear why this should not include the full pause. We will
3036 // investigate this in CR 7178365.
3037 //
3038 // Preserving the old comment here if that helps the investigation:
3039 //
3040 // The elapsed time induced by the start time below deliberately elides
3041 // the possible verification above.
3042 double sample_start_time_sec = os::elapsedTime();
3043
3044 g1_policy()->record_collection_pause_start(sample_start_time_sec);
3045
3046 if (collector_state()->during_initial_mark_pause()) {
3047 concurrent_mark()->checkpoint_roots_initial_pre();
3048 }
3049
3050 g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor);
3051
3052 evacuation_info.set_collectionset_regions(collection_set()->region_length());
3053
3054 // Make sure the remembered sets are up to date. This needs to be
3055 // done before register_humongous_regions_with_cset(), because the
3056 // remembered sets are used there to choose eager reclaim candidates.
3057 // If the remembered sets are not up to date we might miss some
3058 // entries that need to be handled.
3059 g1_rem_set()->cleanupHRRS();
3060
3061 register_humongous_regions_with_cset();
3062
3063 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table.");
3064
3065 // We call this after finalize_cset() to
3066 // ensure that the CSet has been finalized.
3067 _cm->verify_no_cset_oops();
3068
3069 if (_hr_printer.is_active()) {
3070 G1PrintCollectionSetClosure cl(&_hr_printer);
3071 _collection_set.iterate(&cl);
3072 }
3073
3074 // Initialize the GC alloc regions.
3075 _allocator->init_gc_alloc_regions(evacuation_info);
3076
3077 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length());
3078 pre_evacuate_collection_set();
3079
3080 // Actually do the work...
3081 evacuate_collection_set(evacuation_info, &per_thread_states);
3082
3083 post_evacuate_collection_set(evacuation_info, &per_thread_states);
3084
3085 const size_t* surviving_young_words = per_thread_states.surviving_young_words();
3086 free_collection_set(&_collection_set, evacuation_info, surviving_young_words);
3087
3088 eagerly_reclaim_humongous_regions();
3089
3090 record_obj_copy_mem_stats();
3091 _survivor_evac_stats.adjust_desired_plab_sz();
3092 _old_evac_stats.adjust_desired_plab_sz();
3093
3094 double start = os::elapsedTime();
3095 start_new_collection_set();
3096 g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0);
3097
3098 if (evacuation_failed()) {
3099 set_used(recalculate_used());
3100 if (_archive_allocator != NULL) {
3101 _archive_allocator->clear_used();
3102 }
3103 for (uint i = 0; i < ParallelGCThreads; i++) {
3104 if (_evacuation_failed_info_array[i].has_failed()) {
3105 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3106 }
3107 }
3108 } else {
3109 // The "used" of the the collection set have already been subtracted
3110 // when they were freed. Add in the bytes evacuated.
3111 increase_used(g1_policy()->bytes_copied_during_gc());
3112 }
3113
3114 if (collector_state()->during_initial_mark_pause()) {
3115 // We have to do this before we notify the CM threads that
3116 // they can start working to make sure that all the
3117 // appropriate initialization is done on the CM object.
3118 concurrent_mark()->checkpoint_roots_initial_post();
3119 collector_state()->set_mark_in_progress(true);
3120 // Note that we don't actually trigger the CM thread at
3121 // this point. We do that later when we're sure that
3122 // the current thread has completed its logging output.
3123 }
3124
3125 allocate_dummy_regions();
3126
3127 _allocator->init_mutator_alloc_region();
3128
3129 {
3130 size_t expand_bytes = _heap_sizing_policy->expansion_amount();
3131 if (expand_bytes > 0) {
3132 size_t bytes_before = capacity();
3133 // No need for an ergo logging here,
3134 // expansion_amount() does this when it returns a value > 0.
3135 double expand_ms;
3136 if (!expand(expand_bytes, _workers, &expand_ms)) {
3137 // We failed to expand the heap. Cannot do anything about it.
3138 }
3139 g1_policy()->phase_times()->record_expand_heap_time(expand_ms);
3140 }
3141 }
3142
3143 // We redo the verification but now wrt to the new CSet which
3144 // has just got initialized after the previous CSet was freed.
3145 _cm->verify_no_cset_oops();
3146
3147 // This timing is only used by the ergonomics to handle our pause target.
3148 // It is unclear why this should not include the full pause. We will
3149 // investigate this in CR 7178365.
3150 double sample_end_time_sec = os::elapsedTime();
3151 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3152 size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards);
3153 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc);
3154
3155 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
3156 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc());
3157
3158 if (VerifyRememberedSets) {
3159 log_info(gc, verify)("[Verifying RemSets after GC]");
3160 VerifyRegionRemSetClosure v_cl;
3161 heap_region_iterate(&v_cl);
3162 }
3163
3164 _verifier->verify_after_gc();
3165 _verifier->check_bitmaps("GC End");
3166
3167 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3168 ref_processor_stw()->verify_no_references_recorded();
3169
3170 // CM reference discovery will be re-enabled if necessary.
3171 }
3172
3173 #ifdef TRACESPINNING
3174 ParallelTaskTerminator::print_termination_counts();
3175 #endif
3176
3177 gc_epilogue(false);
3178 }
3179
3180 // Print the remainder of the GC log output.
3181 if (evacuation_failed()) {
3182 log_info(gc)("To-space exhausted");
3183 }
3184
3185 g1_policy()->print_phases();
3186 heap_transition.print();
3187
3188 // It is not yet to safe to tell the concurrent mark to
3189 // start as we have some optional output below. We don't want the
3190 // output from the concurrent mark thread interfering with this
3191 // logging output either.
3192
3193 _hrm.verify_optional();
3194 _verifier->verify_region_sets_optional();
3195
3196 TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3197 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3198
3199 print_heap_after_gc();
3200 print_heap_regions();
3201 trace_heap_after_gc(_gc_tracer_stw);
3202
3203 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3204 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3205 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3206 // before any GC notifications are raised.
3207 g1mm()->update_sizes();
3208
3209 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3210 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
3211 _gc_timer_stw->register_gc_end();
3212 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3213 }
3214 // It should now be safe to tell the concurrent mark thread to start
3215 // without its logging output interfering with the logging output
3216 // that came from the pause.
3217
3218 if (should_start_conc_mark) {
3219 // CAUTION: after the doConcurrentMark() call below,
3220 // the concurrent marking thread(s) could be running
3221 // concurrently with us. Make sure that anything after
3222 // this point does not assume that we are the only GC thread
3223 // running. Note: of course, the actual marking work will
3224 // not start until the safepoint itself is released in
3225 // SuspendibleThreadSet::desynchronize().
3226 doConcurrentMark();
3227 }
3228
3229 return true;
3230 }
3231
3232 void G1CollectedHeap::remove_self_forwarding_pointers() {
3233 G1ParRemoveSelfForwardPtrsTask rsfp_task;
3234 workers()->run_task(&rsfp_task);
3235 }
3236
3237 void G1CollectedHeap::restore_after_evac_failure() {
3238 double remove_self_forwards_start = os::elapsedTime();
3239
3240 remove_self_forwarding_pointers();
3241 SharedRestorePreservedMarksTaskExecutor task_executor(workers());
3242 _preserved_marks_set.restore(&task_executor);
3243
3244 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3245 }
3246
3247 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) {
3248 if (!_evacuation_failed) {
3249 _evacuation_failed = true;
3250 }
3251
3252 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3253 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3254 }
3255
3256 bool G1ParEvacuateFollowersClosure::offer_termination() {
3257 G1ParScanThreadState* const pss = par_scan_state();
3258 start_term_time();
3259 const bool res = terminator()->offer_termination();
3260 end_term_time();
3261 return res;
3262 }
3263
3264 void G1ParEvacuateFollowersClosure::do_void() {
3265 G1ParScanThreadState* const pss = par_scan_state();
3266 pss->trim_queue();
3267 do {
3268 pss->steal_and_trim_queue(queues());
3269 } while (!offer_termination());
3270 }
3271
3272 class G1ParTask : public AbstractGangTask {
3273 protected:
3274 G1CollectedHeap* _g1h;
3275 G1ParScanThreadStateSet* _pss;
3276 RefToScanQueueSet* _queues;
3277 G1RootProcessor* _root_processor;
3278 ParallelTaskTerminator _terminator;
3279 uint _n_workers;
3280
3281 public:
3282 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers)
3283 : AbstractGangTask("G1 collection"),
3284 _g1h(g1h),
3285 _pss(per_thread_states),
3286 _queues(task_queues),
3287 _root_processor(root_processor),
3288 _terminator(n_workers, _queues),
3289 _n_workers(n_workers)
3290 {}
3291
3292 void work(uint worker_id) {
3293 if (worker_id >= _n_workers) return; // no work needed this round
3294
3295 double start_sec = os::elapsedTime();
3296 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec);
3297
3298 {
3299 ResourceMark rm;
3300 HandleMark hm;
3301
3302 ReferenceProcessor* rp = _g1h->ref_processor_stw();
3303
3304 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
3305 pss->set_ref_processor(rp);
3306
3307 double start_strong_roots_sec = os::elapsedTime();
3308
3309 _root_processor->evacuate_roots(pss->closures(), worker_id);
3310
3311 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid
3312 // treating the nmethods visited to act as roots for concurrent marking.
3313 // We only want to make sure that the oops in the nmethods are adjusted with regard to the
3314 // objects copied by the current evacuation.
3315 _g1h->g1_rem_set()->oops_into_collection_set_do(pss,
3316 pss->closures()->weak_codeblobs(),
3317 worker_id);
3318
3319 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec;
3320
3321 double term_sec = 0.0;
3322 size_t evac_term_attempts = 0;
3323 {
3324 double start = os::elapsedTime();
3325 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator);
3326 evac.do_void();
3327
3328 evac_term_attempts = evac.term_attempts();
3329 term_sec = evac.term_time();
3330 double elapsed_sec = os::elapsedTime() - start;
3331 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
3332 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
3333 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts);
3334 }
3335
3336 assert(pss->queue_is_empty(), "should be empty");
3337
3338 if (log_is_enabled(Debug, gc, task, stats)) {
3339 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3340 size_t lab_waste;
3341 size_t lab_undo_waste;
3342 pss->waste(lab_waste, lab_undo_waste);
3343 _g1h->print_termination_stats(worker_id,
3344 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */
3345 strong_roots_sec * 1000.0, /* strong roots time */
3346 term_sec * 1000.0, /* evac term time */
3347 evac_term_attempts, /* evac term attempts */
3348 lab_waste, /* alloc buffer waste */
3349 lab_undo_waste /* undo waste */
3350 );
3351 }
3352
3353 // Close the inner scope so that the ResourceMark and HandleMark
3354 // destructors are executed here and are included as part of the
3355 // "GC Worker Time".
3356 }
3357 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
3358 }
3359 };
3360
3361 void G1CollectedHeap::print_termination_stats_hdr() {
3362 log_debug(gc, task, stats)("GC Termination Stats");
3363 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------");
3364 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo");
3365 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------");
3366 }
3367
3368 void G1CollectedHeap::print_termination_stats(uint worker_id,
3369 double elapsed_ms,
3370 double strong_roots_ms,
3371 double term_ms,
3372 size_t term_attempts,
3373 size_t alloc_buffer_waste,
3374 size_t undo_waste) const {
3375 log_debug(gc, task, stats)
3376 ("%3d %9.2f %9.2f %6.2f "
3377 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
3378 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
3379 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms,
3380 term_ms, term_ms * 100 / elapsed_ms, term_attempts,
3381 (alloc_buffer_waste + undo_waste) * HeapWordSize / K,
3382 alloc_buffer_waste * HeapWordSize / K,
3383 undo_waste * HeapWordSize / K);
3384 }
3385
3386 class G1StringAndSymbolCleaningTask : public AbstractGangTask {
3387 private:
3388 BoolObjectClosure* _is_alive;
3389 G1StringDedupUnlinkOrOopsDoClosure _dedup_closure;
3390
3391 int _initial_string_table_size;
3392 int _initial_symbol_table_size;
3393
3394 bool _process_strings;
3395 int _strings_processed;
3396 int _strings_removed;
3397
3398 bool _process_symbols;
3399 int _symbols_processed;
3400 int _symbols_removed;
3401
3402 bool _process_string_dedup;
3403
3404 public:
3405 G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) :
3406 AbstractGangTask("String/Symbol Unlinking"),
3407 _is_alive(is_alive),
3408 _dedup_closure(is_alive, NULL, false),
3409 _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
3410 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0),
3411 _process_string_dedup(process_string_dedup) {
3412
3413 _initial_string_table_size = StringTable::the_table()->table_size();
3414 _initial_symbol_table_size = SymbolTable::the_table()->table_size();
3415 if (process_strings) {
3416 StringTable::clear_parallel_claimed_index();
3417 }
3418 if (process_symbols) {
3419 SymbolTable::clear_parallel_claimed_index();
3420 }
3421 }
3422
3423 ~G1StringAndSymbolCleaningTask() {
3424 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
3425 "claim value %d after unlink less than initial string table size %d",
3426 StringTable::parallel_claimed_index(), _initial_string_table_size);
3427 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
3428 "claim value %d after unlink less than initial symbol table size %d",
3429 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size);
3430
3431 log_info(gc, stringtable)(
3432 "Cleaned string and symbol table, "
3433 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, "
3434 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
3435 strings_processed(), strings_removed(),
3436 symbols_processed(), symbols_removed());
3437 }
3438
3439 void work(uint worker_id) {
3440 int strings_processed = 0;
3441 int strings_removed = 0;
3442 int symbols_processed = 0;
3443 int symbols_removed = 0;
3444 if (_process_strings) {
3445 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
3446 Atomic::add(strings_processed, &_strings_processed);
3447 Atomic::add(strings_removed, &_strings_removed);
3448 }
3449 if (_process_symbols) {
3450 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
3451 Atomic::add(symbols_processed, &_symbols_processed);
3452 Atomic::add(symbols_removed, &_symbols_removed);
3453 }
3454 if (_process_string_dedup) {
3455 G1StringDedup::parallel_unlink(&_dedup_closure, worker_id);
3456 }
3457 }
3458
3459 size_t strings_processed() const { return (size_t)_strings_processed; }
3460 size_t strings_removed() const { return (size_t)_strings_removed; }
3461
3462 size_t symbols_processed() const { return (size_t)_symbols_processed; }
3463 size_t symbols_removed() const { return (size_t)_symbols_removed; }
3464 };
3465
3466 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
3467 private:
3468 static Monitor* _lock;
3469
3470 BoolObjectClosure* const _is_alive;
3471 const bool _unloading_occurred;
3472 const uint _num_workers;
3473
3474 // Variables used to claim nmethods.
3475 CompiledMethod* _first_nmethod;
3476 CompiledMethod* volatile _claimed_nmethod;
3477
3478 // The list of nmethods that need to be processed by the second pass.
3479 CompiledMethod* volatile _postponed_list;
3480 volatile uint _num_entered_barrier;
3481
3482 public:
3483 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
3484 _is_alive(is_alive),
3485 _unloading_occurred(unloading_occurred),
3486 _num_workers(num_workers),
3487 _first_nmethod(NULL),
3488 _claimed_nmethod(NULL),
3489 _postponed_list(NULL),
3490 _num_entered_barrier(0)
3491 {
3492 CompiledMethod::increase_unloading_clock();
3493 // Get first alive nmethod
3494 CompiledMethodIterator iter = CompiledMethodIterator();
3495 if(iter.next_alive()) {
3496 _first_nmethod = iter.method();
3497 }
3498 _claimed_nmethod = _first_nmethod;
3499 }
3500
3501 ~G1CodeCacheUnloadingTask() {
3502 CodeCache::verify_clean_inline_caches();
3503
3504 CodeCache::set_needs_cache_clean(false);
3505 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
3506
3507 CodeCache::verify_icholder_relocations();
3508 }
3509
3510 private:
3511 void add_to_postponed_list(CompiledMethod* nm) {
3512 CompiledMethod* old;
3513 do {
3514 old = _postponed_list;
3515 nm->set_unloading_next(old);
3516 } while (Atomic::cmpxchg(nm, &_postponed_list, old) != old);
3517 }
3518
3519 void clean_nmethod(CompiledMethod* nm) {
3520 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
3521
3522 if (postponed) {
3523 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
3524 add_to_postponed_list(nm);
3525 }
3526
3527 // Mark that this thread has been cleaned/unloaded.
3528 // After this call, it will be safe to ask if this nmethod was unloaded or not.
3529 nm->set_unloading_clock(CompiledMethod::global_unloading_clock());
3530 }
3531
3532 void clean_nmethod_postponed(CompiledMethod* nm) {
3533 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
3534 }
3535
3536 static const int MaxClaimNmethods = 16;
3537
3538 void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) {
3539 CompiledMethod* first;
3540 CompiledMethodIterator last;
3541
3542 do {
3543 *num_claimed_nmethods = 0;
3544
3545 first = _claimed_nmethod;
3546 last = CompiledMethodIterator(first);
3547
3548 if (first != NULL) {
3549
3550 for (int i = 0; i < MaxClaimNmethods; i++) {
3551 if (!last.next_alive()) {
3552 break;
3553 }
3554 claimed_nmethods[i] = last.method();
3555 (*num_claimed_nmethods)++;
3556 }
3557 }
3558
3559 } while (Atomic::cmpxchg(last.method(), &_claimed_nmethod, first) != first);
3560 }
3561
3562 CompiledMethod* claim_postponed_nmethod() {
3563 CompiledMethod* claim;
3564 CompiledMethod* next;
3565
3566 do {
3567 claim = _postponed_list;
3568 if (claim == NULL) {
3569 return NULL;
3570 }
3571
3572 next = claim->unloading_next();
3573
3574 } while (Atomic::cmpxchg(next, &_postponed_list, claim) != claim);
3575
3576 return claim;
3577 }
3578
3579 public:
3580 // Mark that we're done with the first pass of nmethod cleaning.
3581 void barrier_mark(uint worker_id) {
3582 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3583 _num_entered_barrier++;
3584 if (_num_entered_barrier == _num_workers) {
3585 ml.notify_all();
3586 }
3587 }
3588
3589 // See if we have to wait for the other workers to
3590 // finish their first-pass nmethod cleaning work.
3591 void barrier_wait(uint worker_id) {
3592 if (_num_entered_barrier < _num_workers) {
3593 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3594 while (_num_entered_barrier < _num_workers) {
3595 ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
3596 }
3597 }
3598 }
3599
3600 // Cleaning and unloading of nmethods. Some work has to be postponed
3601 // to the second pass, when we know which nmethods survive.
3602 void work_first_pass(uint worker_id) {
3603 // The first nmethods is claimed by the first worker.
3604 if (worker_id == 0 && _first_nmethod != NULL) {
3605 clean_nmethod(_first_nmethod);
3606 _first_nmethod = NULL;
3607 }
3608
3609 int num_claimed_nmethods;
3610 CompiledMethod* claimed_nmethods[MaxClaimNmethods];
3611
3612 while (true) {
3613 claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
3614
3615 if (num_claimed_nmethods == 0) {
3616 break;
3617 }
3618
3619 for (int i = 0; i < num_claimed_nmethods; i++) {
3620 clean_nmethod(claimed_nmethods[i]);
3621 }
3622 }
3623 }
3624
3625 void work_second_pass(uint worker_id) {
3626 CompiledMethod* nm;
3627 // Take care of postponed nmethods.
3628 while ((nm = claim_postponed_nmethod()) != NULL) {
3629 clean_nmethod_postponed(nm);
3630 }
3631 }
3632 };
3633
3634 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
3635
3636 class G1KlassCleaningTask : public StackObj {
3637 BoolObjectClosure* _is_alive;
3638 volatile int _clean_klass_tree_claimed;
3639 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
3640
3641 public:
3642 G1KlassCleaningTask(BoolObjectClosure* is_alive) :
3643 _is_alive(is_alive),
3644 _clean_klass_tree_claimed(0),
3645 _klass_iterator() {
3646 }
3647
3648 private:
3649 bool claim_clean_klass_tree_task() {
3650 if (_clean_klass_tree_claimed) {
3651 return false;
3652 }
3653
3654 return Atomic::cmpxchg(1, &_clean_klass_tree_claimed, 0) == 0;
3655 }
3656
3657 InstanceKlass* claim_next_klass() {
3658 Klass* klass;
3659 do {
3660 klass =_klass_iterator.next_klass();
3661 } while (klass != NULL && !klass->is_instance_klass());
3662
3663 // this can be null so don't call InstanceKlass::cast
3664 return static_cast<InstanceKlass*>(klass);
3665 }
3666
3667 public:
3668
3669 void clean_klass(InstanceKlass* ik) {
3670 ik->clean_weak_instanceklass_links(_is_alive);
3671 }
3672
3673 void work() {
3674 ResourceMark rm;
3675
3676 // One worker will clean the subklass/sibling klass tree.
3677 if (claim_clean_klass_tree_task()) {
3678 Klass::clean_subklass_tree(_is_alive);
3679 }
3680
3681 // All workers will help cleaning the classes,
3682 InstanceKlass* klass;
3683 while ((klass = claim_next_klass()) != NULL) {
3684 clean_klass(klass);
3685 }
3686 }
3687 };
3688
3689 class G1ResolvedMethodCleaningTask : public StackObj {
3690 BoolObjectClosure* _is_alive;
3691 volatile int _resolved_method_task_claimed;
3692 public:
3693 G1ResolvedMethodCleaningTask(BoolObjectClosure* is_alive) :
3694 _is_alive(is_alive), _resolved_method_task_claimed(0) {}
3695
3696 bool claim_resolved_method_task() {
3697 if (_resolved_method_task_claimed) {
3698 return false;
3699 }
3700 return Atomic::cmpxchg(1, &_resolved_method_task_claimed, 0) == 0;
3701 }
3702
3703 // These aren't big, one thread can do it all.
3704 void work() {
3705 if (claim_resolved_method_task()) {
3706 ResolvedMethodTable::unlink(_is_alive);
3707 }
3708 }
3709 };
3710
3711
3712 // To minimize the remark pause times, the tasks below are done in parallel.
3713 class G1ParallelCleaningTask : public AbstractGangTask {
3714 private:
3715 G1StringAndSymbolCleaningTask _string_symbol_task;
3716 G1CodeCacheUnloadingTask _code_cache_task;
3717 G1KlassCleaningTask _klass_cleaning_task;
3718 G1ResolvedMethodCleaningTask _resolved_method_cleaning_task;
3719
3720 public:
3721 // The constructor is run in the VMThread.
3722 G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) :
3723 AbstractGangTask("Parallel Cleaning"),
3724 _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()),
3725 _code_cache_task(num_workers, is_alive, unloading_occurred),
3726 _klass_cleaning_task(is_alive),
3727 _resolved_method_cleaning_task(is_alive) {
3728 }
3729
3730 // The parallel work done by all worker threads.
3731 void work(uint worker_id) {
3732 // Do first pass of code cache cleaning.
3733 _code_cache_task.work_first_pass(worker_id);
3734
3735 // Let the threads mark that the first pass is done.
3736 _code_cache_task.barrier_mark(worker_id);
3737
3738 // Clean the Strings and Symbols.
3739 _string_symbol_task.work(worker_id);
3740
3741 // Clean unreferenced things in the ResolvedMethodTable
3742 _resolved_method_cleaning_task.work();
3743
3744 // Wait for all workers to finish the first code cache cleaning pass.
3745 _code_cache_task.barrier_wait(worker_id);
3746
3747 // Do the second code cache cleaning work, which realize on
3748 // the liveness information gathered during the first pass.
3749 _code_cache_task.work_second_pass(worker_id);
3750
3751 // Clean all klasses that were not unloaded.
3752 _klass_cleaning_task.work();
3753 }
3754 };
3755
3756
3757 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
3758 bool class_unloading_occurred) {
3759 uint n_workers = workers()->active_workers();
3760
3761 G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred);
3762 workers()->run_task(&g1_unlink_task);
3763 }
3764
3765 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive,
3766 bool process_strings,
3767 bool process_symbols,
3768 bool process_string_dedup) {
3769 if (!process_strings && !process_symbols && !process_string_dedup) {
3770 // Nothing to clean.
3771 return;
3772 }
3773
3774 G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup);
3775 workers()->run_task(&g1_unlink_task);
3776
3777 }
3778
3779 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3780 private:
3781 DirtyCardQueueSet* _queue;
3782 G1CollectedHeap* _g1h;
3783 public:
3784 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"),
3785 _queue(queue), _g1h(g1h) { }
3786
3787 virtual void work(uint worker_id) {
3788 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
3789 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
3790
3791 RedirtyLoggedCardTableEntryClosure cl(_g1h);
3792 _queue->par_apply_closure_to_all_completed_buffers(&cl);
3793
3794 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3795 }
3796 };
3797
3798 void G1CollectedHeap::redirty_logged_cards() {
3799 double redirty_logged_cards_start = os::elapsedTime();
3800
3801 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this);
3802 dirty_card_queue_set().reset_for_par_iteration();
3803 workers()->run_task(&redirty_task);
3804
3805 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
3806 dcq.merge_bufferlists(&dirty_card_queue_set());
3807 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
3808
3809 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3810 }
3811
3812 // Weak Reference Processing support
3813
3814 // An always "is_alive" closure that is used to preserve referents.
3815 // If the object is non-null then it's alive. Used in the preservation
3816 // of referent objects that are pointed to by reference objects
3817 // discovered by the CM ref processor.
3818 class G1AlwaysAliveClosure: public BoolObjectClosure {
3819 G1CollectedHeap* _g1;
3820 public:
3821 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3822 bool do_object_b(oop p) {
3823 if (p != NULL) {
3824 return true;
3825 }
3826 return false;
3827 }
3828 };
3829
3830 bool G1STWIsAliveClosure::do_object_b(oop p) {
3831 // An object is reachable if it is outside the collection set,
3832 // or is inside and copied.
3833 return !_g1->is_in_cset(p) || p->is_forwarded();
3834 }
3835
3836 // Non Copying Keep Alive closure
3837 class G1KeepAliveClosure: public OopClosure {
3838 G1CollectedHeap* _g1;
3839 public:
3840 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3841 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3842 void do_oop(oop* p) {
3843 oop obj = *p;
3844 assert(obj != NULL, "the caller should have filtered out NULL values");
3845
3846 const InCSetState cset_state = _g1->in_cset_state(obj);
3847 if (!cset_state.is_in_cset_or_humongous()) {
3848 return;
3849 }
3850 if (cset_state.is_in_cset()) {
3851 assert( obj->is_forwarded(), "invariant" );
3852 *p = obj->forwardee();
3853 } else {
3854 assert(!obj->is_forwarded(), "invariant" );
3855 assert(cset_state.is_humongous(),
3856 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value());
3857 _g1->set_humongous_is_live(obj);
3858 }
3859 }
3860 };
3861
3862 // Copying Keep Alive closure - can be called from both
3863 // serial and parallel code as long as different worker
3864 // threads utilize different G1ParScanThreadState instances
3865 // and different queues.
3866
3867 class G1CopyingKeepAliveClosure: public OopClosure {
3868 G1CollectedHeap* _g1h;
3869 OopClosure* _copy_non_heap_obj_cl;
3870 G1ParScanThreadState* _par_scan_state;
3871
3872 public:
3873 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3874 OopClosure* non_heap_obj_cl,
3875 G1ParScanThreadState* pss):
3876 _g1h(g1h),
3877 _copy_non_heap_obj_cl(non_heap_obj_cl),
3878 _par_scan_state(pss)
3879 {}
3880
3881 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3882 virtual void do_oop( oop* p) { do_oop_work(p); }
3883
3884 template <class T> void do_oop_work(T* p) {
3885 oop obj = oopDesc::load_decode_heap_oop(p);
3886
3887 if (_g1h->is_in_cset_or_humongous(obj)) {
3888 // If the referent object has been forwarded (either copied
3889 // to a new location or to itself in the event of an
3890 // evacuation failure) then we need to update the reference
3891 // field and, if both reference and referent are in the G1
3892 // heap, update the RSet for the referent.
3893 //
3894 // If the referent has not been forwarded then we have to keep
3895 // it alive by policy. Therefore we have copy the referent.
3896 //
3897 // If the reference field is in the G1 heap then we can push
3898 // on the PSS queue. When the queue is drained (after each
3899 // phase of reference processing) the object and it's followers
3900 // will be copied, the reference field set to point to the
3901 // new location, and the RSet updated. Otherwise we need to
3902 // use the the non-heap or metadata closures directly to copy
3903 // the referent object and update the pointer, while avoiding
3904 // updating the RSet.
3905
3906 if (_g1h->is_in_g1_reserved(p)) {
3907 _par_scan_state->push_on_queue(p);
3908 } else {
3909 assert(!Metaspace::contains((const void*)p),
3910 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p));
3911 _copy_non_heap_obj_cl->do_oop(p);
3912 }
3913 }
3914 }
3915 };
3916
3917 // Serial drain queue closure. Called as the 'complete_gc'
3918 // closure for each discovered list in some of the
3919 // reference processing phases.
3920
3921 class G1STWDrainQueueClosure: public VoidClosure {
3922 protected:
3923 G1CollectedHeap* _g1h;
3924 G1ParScanThreadState* _par_scan_state;
3925
3926 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
3927
3928 public:
3929 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
3930 _g1h(g1h),
3931 _par_scan_state(pss)
3932 { }
3933
3934 void do_void() {
3935 G1ParScanThreadState* const pss = par_scan_state();
3936 pss->trim_queue();
3937 }
3938 };
3939
3940 // Parallel Reference Processing closures
3941
3942 // Implementation of AbstractRefProcTaskExecutor for parallel reference
3943 // processing during G1 evacuation pauses.
3944
3945 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
3946 private:
3947 G1CollectedHeap* _g1h;
3948 G1ParScanThreadStateSet* _pss;
3949 RefToScanQueueSet* _queues;
3950 WorkGang* _workers;
3951 uint _active_workers;
3952
3953 public:
3954 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
3955 G1ParScanThreadStateSet* per_thread_states,
3956 WorkGang* workers,
3957 RefToScanQueueSet *task_queues,
3958 uint n_workers) :
3959 _g1h(g1h),
3960 _pss(per_thread_states),
3961 _queues(task_queues),
3962 _workers(workers),
3963 _active_workers(n_workers)
3964 {
3965 g1h->ref_processor_stw()->set_active_mt_degree(n_workers);
3966 }
3967
3968 // Executes the given task using concurrent marking worker threads.
3969 virtual void execute(ProcessTask& task);
3970 virtual void execute(EnqueueTask& task);
3971 };
3972
3973 // Gang task for possibly parallel reference processing
3974
3975 class G1STWRefProcTaskProxy: public AbstractGangTask {
3976 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
3977 ProcessTask& _proc_task;
3978 G1CollectedHeap* _g1h;
3979 G1ParScanThreadStateSet* _pss;
3980 RefToScanQueueSet* _task_queues;
3981 ParallelTaskTerminator* _terminator;
3982
3983 public:
3984 G1STWRefProcTaskProxy(ProcessTask& proc_task,
3985 G1CollectedHeap* g1h,
3986 G1ParScanThreadStateSet* per_thread_states,
3987 RefToScanQueueSet *task_queues,
3988 ParallelTaskTerminator* terminator) :
3989 AbstractGangTask("Process reference objects in parallel"),
3990 _proc_task(proc_task),
3991 _g1h(g1h),
3992 _pss(per_thread_states),
3993 _task_queues(task_queues),
3994 _terminator(terminator)
3995 {}
3996
3997 virtual void work(uint worker_id) {
3998 // The reference processing task executed by a single worker.
3999 ResourceMark rm;
4000 HandleMark hm;
4001
4002 G1STWIsAliveClosure is_alive(_g1h);
4003
4004 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
4005 pss->set_ref_processor(NULL);
4006
4007 // Keep alive closure.
4008 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4009
4010 // Complete GC closure
4011 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator);
4012
4013 // Call the reference processing task's work routine.
4014 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
4015
4016 // Note we cannot assert that the refs array is empty here as not all
4017 // of the processing tasks (specifically phase2 - pp2_work) execute
4018 // the complete_gc closure (which ordinarily would drain the queue) so
4019 // the queue may not be empty.
4020 }
4021 };
4022
4023 // Driver routine for parallel reference processing.
4024 // Creates an instance of the ref processing gang
4025 // task and has the worker threads execute it.
4026 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
4027 assert(_workers != NULL, "Need parallel worker threads.");
4028
4029 ParallelTaskTerminator terminator(_active_workers, _queues);
4030 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
4031
4032 _workers->run_task(&proc_task_proxy);
4033 }
4034
4035 // Gang task for parallel reference enqueueing.
4036
4037 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
4038 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
4039 EnqueueTask& _enq_task;
4040
4041 public:
4042 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
4043 AbstractGangTask("Enqueue reference objects in parallel"),
4044 _enq_task(enq_task)
4045 { }
4046
4047 virtual void work(uint worker_id) {
4048 _enq_task.work(worker_id);
4049 }
4050 };
4051
4052 // Driver routine for parallel reference enqueueing.
4053 // Creates an instance of the ref enqueueing gang
4054 // task and has the worker threads execute it.
4055
4056 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
4057 assert(_workers != NULL, "Need parallel worker threads.");
4058
4059 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
4060
4061 _workers->run_task(&enq_task_proxy);
4062 }
4063
4064 // End of weak reference support closures
4065
4066 // Abstract task used to preserve (i.e. copy) any referent objects
4067 // that are in the collection set and are pointed to by reference
4068 // objects discovered by the CM ref processor.
4069
4070 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
4071 protected:
4072 G1CollectedHeap* _g1h;
4073 G1ParScanThreadStateSet* _pss;
4074 RefToScanQueueSet* _queues;
4075 ParallelTaskTerminator _terminator;
4076 uint _n_workers;
4077
4078 public:
4079 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) :
4080 AbstractGangTask("ParPreserveCMReferents"),
4081 _g1h(g1h),
4082 _pss(per_thread_states),
4083 _queues(task_queues),
4084 _terminator(workers, _queues),
4085 _n_workers(workers)
4086 {
4087 g1h->ref_processor_cm()->set_active_mt_degree(workers);
4088 }
4089
4090 void work(uint worker_id) {
4091 G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id);
4092
4093 ResourceMark rm;
4094 HandleMark hm;
4095
4096 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
4097 pss->set_ref_processor(NULL);
4098 assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4099
4100 // Is alive closure
4101 G1AlwaysAliveClosure always_alive(_g1h);
4102
4103 // Copying keep alive closure. Applied to referent objects that need
4104 // to be copied.
4105 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4106
4107 ReferenceProcessor* rp = _g1h->ref_processor_cm();
4108
4109 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
4110 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
4111
4112 // limit is set using max_num_q() - which was set using ParallelGCThreads.
4113 // So this must be true - but assert just in case someone decides to
4114 // change the worker ids.
4115 assert(worker_id < limit, "sanity");
4116 assert(!rp->discovery_is_atomic(), "check this code");
4117
4118 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
4119 for (uint idx = worker_id; idx < limit; idx += stride) {
4120 DiscoveredList& ref_list = rp->discovered_refs()[idx];
4121
4122 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
4123 while (iter.has_next()) {
4124 // Since discovery is not atomic for the CM ref processor, we
4125 // can see some null referent objects.
4126 iter.load_ptrs(DEBUG_ONLY(true));
4127 oop ref = iter.obj();
4128
4129 // This will filter nulls.
4130 if (iter.is_referent_alive()) {
4131 iter.make_referent_alive();
4132 }
4133 iter.move_to_next();
4134 }
4135 }
4136
4137 // Drain the queue - which may cause stealing
4138 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator);
4139 drain_queue.do_void();
4140 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
4141 assert(pss->queue_is_empty(), "should be");
4142 }
4143 };
4144
4145 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) {
4146 // Any reference objects, in the collection set, that were 'discovered'
4147 // by the CM ref processor should have already been copied (either by
4148 // applying the external root copy closure to the discovered lists, or
4149 // by following an RSet entry).
4150 //
4151 // But some of the referents, that are in the collection set, that these
4152 // reference objects point to may not have been copied: the STW ref
4153 // processor would have seen that the reference object had already
4154 // been 'discovered' and would have skipped discovering the reference,
4155 // but would not have treated the reference object as a regular oop.
4156 // As a result the copy closure would not have been applied to the
4157 // referent object.
4158 //
4159 // We need to explicitly copy these referent objects - the references
4160 // will be processed at the end of remarking.
4161 //
4162 // We also need to do this copying before we process the reference
4163 // objects discovered by the STW ref processor in case one of these
4164 // referents points to another object which is also referenced by an
4165 // object discovered by the STW ref processor.
4166 double preserve_cm_referents_time = 0.0;
4167
4168 // To avoid spawning task when there is no work to do, check that
4169 // a concurrent cycle is active and that some references have been
4170 // discovered.
4171 if (concurrent_mark()->cm_thread()->during_cycle() &&
4172 ref_processor_cm()->has_discovered_references()) {
4173 double preserve_cm_referents_start = os::elapsedTime();
4174 uint no_of_gc_workers = workers()->active_workers();
4175 G1ParPreserveCMReferentsTask keep_cm_referents(this,
4176 per_thread_states,
4177 no_of_gc_workers,
4178 _task_queues);
4179 workers()->run_task(&keep_cm_referents);
4180 preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start;
4181 }
4182
4183 g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0);
4184 }
4185
4186 // Weak Reference processing during an evacuation pause (part 1).
4187 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4188 double ref_proc_start = os::elapsedTime();
4189
4190 ReferenceProcessor* rp = _ref_processor_stw;
4191 assert(rp->discovery_enabled(), "should have been enabled");
4192
4193 // Closure to test whether a referent is alive.
4194 G1STWIsAliveClosure is_alive(this);
4195
4196 // Even when parallel reference processing is enabled, the processing
4197 // of JNI refs is serial and performed serially by the current thread
4198 // rather than by a worker. The following PSS will be used for processing
4199 // JNI refs.
4200
4201 // Use only a single queue for this PSS.
4202 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0);
4203 pss->set_ref_processor(NULL);
4204 assert(pss->queue_is_empty(), "pre-condition");
4205
4206 // Keep alive closure.
4207 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss);
4208
4209 // Serial Complete GC closure
4210 G1STWDrainQueueClosure drain_queue(this, pss);
4211
4212 // Setup the soft refs policy...
4213 rp->setup_policy(false);
4214
4215 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times();
4216
4217 ReferenceProcessorStats stats;
4218 if (!rp->processing_is_mt()) {
4219 // Serial reference processing...
4220 stats = rp->process_discovered_references(&is_alive,
4221 &keep_alive,
4222 &drain_queue,
4223 NULL,
4224 pt);
4225 } else {
4226 uint no_of_gc_workers = workers()->active_workers();
4227
4228 // Parallel reference processing
4229 assert(no_of_gc_workers <= rp->max_num_q(),
4230 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4231 no_of_gc_workers, rp->max_num_q());
4232
4233 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers);
4234 stats = rp->process_discovered_references(&is_alive,
4235 &keep_alive,
4236 &drain_queue,
4237 &par_task_executor,
4238 pt);
4239 }
4240
4241 _gc_tracer_stw->report_gc_reference_stats(stats);
4242
4243 // We have completed copying any necessary live referent objects.
4244 assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4245
4246 double ref_proc_time = os::elapsedTime() - ref_proc_start;
4247 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4248 }
4249
4250 // Weak Reference processing during an evacuation pause (part 2).
4251 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4252 double ref_enq_start = os::elapsedTime();
4253
4254 ReferenceProcessor* rp = _ref_processor_stw;
4255 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
4256
4257 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times();
4258
4259 // Now enqueue any remaining on the discovered lists on to
4260 // the pending list.
4261 if (!rp->processing_is_mt()) {
4262 // Serial reference processing...
4263 rp->enqueue_discovered_references(NULL, pt);
4264 } else {
4265 // Parallel reference enqueueing
4266
4267 uint n_workers = workers()->active_workers();
4268
4269 assert(n_workers <= rp->max_num_q(),
4270 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4271 n_workers, rp->max_num_q());
4272
4273 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers);
4274 rp->enqueue_discovered_references(&par_task_executor, pt);
4275 }
4276
4277 rp->verify_no_references_recorded();
4278 assert(!rp->discovery_enabled(), "should have been disabled");
4279
4280 // If during an initial mark pause we install a pending list head which is not otherwise reachable
4281 // ensure that it is marked in the bitmap for concurrent marking to discover.
4282 if (collector_state()->during_initial_mark_pause()) {
4283 oop pll_head = Universe::reference_pending_list();
4284 if (pll_head != NULL) {
4285 _cm->mark_in_next_bitmap(pll_head);
4286 }
4287 }
4288
4289 // FIXME
4290 // CM's reference processing also cleans up the string and symbol tables.
4291 // Should we do that here also? We could, but it is a serial operation
4292 // and could significantly increase the pause time.
4293
4294 double ref_enq_time = os::elapsedTime() - ref_enq_start;
4295 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
4296 }
4297
4298 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
4299 double merge_pss_time_start = os::elapsedTime();
4300 per_thread_states->flush();
4301 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0);
4302 }
4303
4304 void G1CollectedHeap::pre_evacuate_collection_set() {
4305 _expand_heap_after_alloc_failure = true;
4306 _evacuation_failed = false;
4307
4308 // Disable the hot card cache.
4309 _hot_card_cache->reset_hot_cache_claimed_index();
4310 _hot_card_cache->set_use_cache(false);
4311
4312 g1_rem_set()->prepare_for_oops_into_collection_set_do();
4313 _preserved_marks_set.assert_empty();
4314
4315 G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4316
4317 // InitialMark needs claim bits to keep track of the marked-through CLDs.
4318 if (collector_state()->during_initial_mark_pause()) {
4319 double start_clear_claimed_marks = os::elapsedTime();
4320
4321 ClassLoaderDataGraph::clear_claimed_marks();
4322
4323 double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
4324 phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
4325 }
4326 }
4327
4328 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4329 // Should G1EvacuationFailureALot be in effect for this GC?
4330 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
4331
4332 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
4333
4334 G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4335
4336 double start_par_time_sec = os::elapsedTime();
4337 double end_par_time_sec;
4338
4339 {
4340 const uint n_workers = workers()->active_workers();
4341 G1RootProcessor root_processor(this, n_workers);
4342 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers);
4343
4344 print_termination_stats_hdr();
4345
4346 workers()->run_task(&g1_par_task);
4347 end_par_time_sec = os::elapsedTime();
4348
4349 // Closing the inner scope will execute the destructor
4350 // for the G1RootProcessor object. We record the current
4351 // elapsed time before closing the scope so that time
4352 // taken for the destructor is NOT included in the
4353 // reported parallel time.
4354 }
4355
4356 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
4357 phase_times->record_par_time(par_time_ms);
4358
4359 double code_root_fixup_time_ms =
4360 (os::elapsedTime() - end_par_time_sec) * 1000.0;
4361 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
4362 }
4363
4364 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4365 // Process any discovered reference objects - we have
4366 // to do this _before_ we retire the GC alloc regions
4367 // as we may have to copy some 'reachable' referent
4368 // objects (and their reachable sub-graphs) that were
4369 // not copied during the pause.
4370 if (g1_policy()->should_process_references()) {
4371 preserve_cm_referents(per_thread_states);
4372 process_discovered_references(per_thread_states);
4373 } else {
4374 ref_processor_stw()->verify_no_references_recorded();
4375 }
4376
4377 G1STWIsAliveClosure is_alive(this);
4378 G1KeepAliveClosure keep_alive(this);
4379
4380 {
4381 double start = os::elapsedTime();
4382
4383 WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
4384
4385 double time_ms = (os::elapsedTime() - start) * 1000.0;
4386 g1_policy()->phase_times()->record_ref_proc_time(time_ms);
4387 }
4388
4389 if (G1StringDedup::is_enabled()) {
4390 double fixup_start = os::elapsedTime();
4391
4392 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times());
4393
4394 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
4395 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
4396 }
4397
4398 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4399
4400 if (evacuation_failed()) {
4401 restore_after_evac_failure();
4402
4403 // Reset the G1EvacuationFailureALot counters and flags
4404 // Note: the values are reset only when an actual
4405 // evacuation failure occurs.
4406 NOT_PRODUCT(reset_evacuation_should_fail();)
4407 }
4408
4409 _preserved_marks_set.assert_empty();
4410
4411 // Enqueue any remaining references remaining on the STW
4412 // reference processor's discovered lists. We need to do
4413 // this after the card table is cleaned (and verified) as
4414 // the act of enqueueing entries on to the pending list
4415 // will log these updates (and dirty their associated
4416 // cards). We need these updates logged to update any
4417 // RSets.
4418 if (g1_policy()->should_process_references()) {
4419 enqueue_discovered_references(per_thread_states);
4420 } else {
4421 g1_policy()->phase_times()->record_ref_enq_time(0);
4422 }
4423
4424 _allocator->release_gc_alloc_regions(evacuation_info);
4425
4426 merge_per_thread_state_info(per_thread_states);
4427
4428 // Reset and re-enable the hot card cache.
4429 // Note the counts for the cards in the regions in the
4430 // collection set are reset when the collection set is freed.
4431 _hot_card_cache->reset_hot_cache();
4432 _hot_card_cache->set_use_cache(true);
4433
4434 purge_code_root_memory();
4435
4436 redirty_logged_cards();
4437 #if COMPILER2_OR_JVMCI
4438 double start = os::elapsedTime();
4439 DerivedPointerTable::update_pointers();
4440 g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0);
4441 #endif
4442 g1_policy()->print_age_table();
4443 }
4444
4445 void G1CollectedHeap::record_obj_copy_mem_stats() {
4446 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4447
4448 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4449 create_g1_evac_summary(&_old_evac_stats));
4450 }
4451
4452 void G1CollectedHeap::free_region(HeapRegion* hr,
4453 FreeRegionList* free_list,
4454 bool skip_remset,
4455 bool skip_hot_card_cache,
4456 bool locked) {
4457 assert(!hr->is_free(), "the region should not be free");
4458 assert(!hr->is_empty(), "the region should not be empty");
4459 assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
4460 assert(free_list != NULL, "pre-condition");
4461
4462 if (G1VerifyBitmaps) {
4463 MemRegion mr(hr->bottom(), hr->end());
4464 concurrent_mark()->clear_range_in_prev_bitmap(mr);
4465 }
4466
4467 // Clear the card counts for this region.
4468 // Note: we only need to do this if the region is not young
4469 // (since we don't refine cards in young regions).
4470 if (!skip_hot_card_cache && !hr->is_young()) {
4471 _hot_card_cache->reset_card_counts(hr);
4472 }
4473 hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */);
4474 free_list->add_ordered(hr);
4475 }
4476
4477 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4478 FreeRegionList* free_list,
4479 bool skip_remset) {
4480 assert(hr->is_humongous(), "this is only for humongous regions");
4481 assert(free_list != NULL, "pre-condition");
4482 hr->clear_humongous();
4483 free_region(hr, free_list, skip_remset);
4484 }
4485
4486 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4487 const uint humongous_regions_removed) {
4488 if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4489 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4490 _old_set.bulk_remove(old_regions_removed);
4491 _humongous_set.bulk_remove(humongous_regions_removed);
4492 }
4493
4494 }
4495
4496 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4497 assert(list != NULL, "list can't be null");
4498 if (!list->is_empty()) {
4499 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4500 _hrm.insert_list_into_free_list(list);
4501 }
4502 }
4503
4504 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4505 decrease_used(bytes);
4506 }
4507
4508 class G1ParScrubRemSetTask: public AbstractGangTask {
4509 protected:
4510 G1RemSet* _g1rs;
4511 HeapRegionClaimer _hrclaimer;
4512
4513 public:
4514 G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) :
4515 AbstractGangTask("G1 ScrubRS"),
4516 _g1rs(g1_rs),
4517 _hrclaimer(num_workers) {
4518 }
4519
4520 void work(uint worker_id) {
4521 _g1rs->scrub(worker_id, &_hrclaimer);
4522 }
4523 };
4524
4525 void G1CollectedHeap::scrub_rem_set() {
4526 uint num_workers = workers()->active_workers();
4527 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers);
4528 workers()->run_task(&g1_par_scrub_rs_task);
4529 }
4530
4531 class G1FreeCollectionSetTask : public AbstractGangTask {
4532 private:
4533
4534 // Closure applied to all regions in the collection set to do work that needs to
4535 // be done serially in a single thread.
4536 class G1SerialFreeCollectionSetClosure : public HeapRegionClosure {
4537 private:
4538 EvacuationInfo* _evacuation_info;
4539 const size_t* _surviving_young_words;
4540
4541 // Bytes used in successfully evacuated regions before the evacuation.
4542 size_t _before_used_bytes;
4543 // Bytes used in unsucessfully evacuated regions before the evacuation
4544 size_t _after_used_bytes;
4545
4546 size_t _bytes_allocated_in_old_since_last_gc;
4547
4548 size_t _failure_used_words;
4549 size_t _failure_waste_words;
4550
4551 FreeRegionList _local_free_list;
4552 public:
4553 G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4554 HeapRegionClosure(),
4555 _evacuation_info(evacuation_info),
4556 _surviving_young_words(surviving_young_words),
4557 _before_used_bytes(0),
4558 _after_used_bytes(0),
4559 _bytes_allocated_in_old_since_last_gc(0),
4560 _failure_used_words(0),
4561 _failure_waste_words(0),
4562 _local_free_list("Local Region List for CSet Freeing") {
4563 }
4564
4565 virtual bool doHeapRegion(HeapRegion* r) {
4566 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4567
4568 assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index());
4569 g1h->clear_in_cset(r);
4570
4571 if (r->is_young()) {
4572 assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(),
4573 "Young index %d is wrong for region %u of type %s with %u young regions",
4574 r->young_index_in_cset(),
4575 r->hrm_index(),
4576 r->get_type_str(),
4577 g1h->collection_set()->young_region_length());
4578 size_t words_survived = _surviving_young_words[r->young_index_in_cset()];
4579 r->record_surv_words_in_group(words_survived);
4580 }
4581
4582 if (!r->evacuation_failed()) {
4583 assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
4584 _before_used_bytes += r->used();
4585 g1h->free_region(r,
4586 &_local_free_list,
4587 true, /* skip_remset */
4588 true, /* skip_hot_card_cache */
4589 true /* locked */);
4590 } else {
4591 r->uninstall_surv_rate_group();
4592 r->set_young_index_in_cset(-1);
4593 r->set_evacuation_failed(false);
4594 // When moving a young gen region to old gen, we "allocate" that whole region
4595 // there. This is in addition to any already evacuated objects. Notify the
4596 // policy about that.
4597 // Old gen regions do not cause an additional allocation: both the objects
4598 // still in the region and the ones already moved are accounted for elsewhere.
4599 if (r->is_young()) {
4600 _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
4601 }
4602 // The region is now considered to be old.
4603 r->set_old();
4604 // Do some allocation statistics accounting. Regions that failed evacuation
4605 // are always made old, so there is no need to update anything in the young
4606 // gen statistics, but we need to update old gen statistics.
4607 size_t used_words = r->marked_bytes() / HeapWordSize;
4608
4609 _failure_used_words += used_words;
4610 _failure_waste_words += HeapRegion::GrainWords - used_words;
4611
4612 g1h->old_set_add(r);
4613 _after_used_bytes += r->used();
4614 }
4615 return false;
4616 }
4617
4618 void complete_work() {
4619 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4620
4621 _evacuation_info->set_regions_freed(_local_free_list.length());
4622 _evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4623
4624 g1h->prepend_to_freelist(&_local_free_list);
4625 g1h->decrement_summary_bytes(_before_used_bytes);
4626
4627 G1Policy* policy = g1h->g1_policy();
4628 policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4629
4630 g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4631 }
4632 };
4633
4634 G1CollectionSet* _collection_set;
4635 G1SerialFreeCollectionSetClosure _cl;
4636 const size_t* _surviving_young_words;
4637
4638 size_t _rs_lengths;
4639
4640 volatile jint _serial_work_claim;
4641
4642 struct WorkItem {
4643 uint region_idx;
4644 bool is_young;
4645 bool evacuation_failed;
4646
4647 WorkItem(HeapRegion* r) {
4648 region_idx = r->hrm_index();
4649 is_young = r->is_young();
4650 evacuation_failed = r->evacuation_failed();
4651 }
4652 };
4653
4654 volatile size_t _parallel_work_claim;
4655 size_t _num_work_items;
4656 WorkItem* _work_items;
4657
4658 void do_serial_work() {
4659 // Need to grab the lock to be allowed to modify the old region list.
4660 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4661 _collection_set->iterate(&_cl);
4662 }
4663
4664 void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) {
4665 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4666
4667 HeapRegion* r = g1h->region_at(region_idx);
4668 assert(!g1h->is_on_master_free_list(r), "sanity");
4669
4670 Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths);
4671
4672 if (!is_young) {
4673 g1h->_hot_card_cache->reset_card_counts(r);
4674 }
4675
4676 if (!evacuation_failed) {
4677 r->rem_set()->clear_locked();
4678 }
4679 }
4680
4681 class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure {
4682 private:
4683 size_t _cur_idx;
4684 WorkItem* _work_items;
4685 public:
4686 G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { }
4687
4688 virtual bool doHeapRegion(HeapRegion* r) {
4689 _work_items[_cur_idx++] = WorkItem(r);
4690 return false;
4691 }
4692 };
4693
4694 void prepare_work() {
4695 G1PrepareFreeCollectionSetClosure cl(_work_items);
4696 _collection_set->iterate(&cl);
4697 }
4698
4699 void complete_work() {
4700 _cl.complete_work();
4701
4702 G1Policy* policy = G1CollectedHeap::heap()->g1_policy();
4703 policy->record_max_rs_lengths(_rs_lengths);
4704 policy->cset_regions_freed();
4705 }
4706 public:
4707 G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4708 AbstractGangTask("G1 Free Collection Set"),
4709 _cl(evacuation_info, surviving_young_words),
4710 _collection_set(collection_set),
4711 _surviving_young_words(surviving_young_words),
4712 _serial_work_claim(0),
4713 _rs_lengths(0),
4714 _parallel_work_claim(0),
4715 _num_work_items(collection_set->region_length()),
4716 _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) {
4717 prepare_work();
4718 }
4719
4720 ~G1FreeCollectionSetTask() {
4721 complete_work();
4722 FREE_C_HEAP_ARRAY(WorkItem, _work_items);
4723 }
4724
4725 // Chunk size for work distribution. The chosen value has been determined experimentally
4726 // to be a good tradeoff between overhead and achievable parallelism.
4727 static uint chunk_size() { return 32; }
4728
4729 virtual void work(uint worker_id) {
4730 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
4731
4732 // Claim serial work.
4733 if (_serial_work_claim == 0) {
4734 jint value = Atomic::add(1, &_serial_work_claim) - 1;
4735 if (value == 0) {
4736 double serial_time = os::elapsedTime();
4737 do_serial_work();
4738 timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0);
4739 }
4740 }
4741
4742 // Start parallel work.
4743 double young_time = 0.0;
4744 bool has_young_time = false;
4745 double non_young_time = 0.0;
4746 bool has_non_young_time = false;
4747
4748 while (true) {
4749 size_t end = Atomic::add(chunk_size(), &_parallel_work_claim);
4750 size_t cur = end - chunk_size();
4751
4752 if (cur >= _num_work_items) {
4753 break;
4754 }
4755
4756 double start_time = os::elapsedTime();
4757
4758 end = MIN2(end, _num_work_items);
4759
4760 for (; cur < end; cur++) {
4761 bool is_young = _work_items[cur].is_young;
4762
4763 do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed);
4764
4765 double end_time = os::elapsedTime();
4766 double time_taken = end_time - start_time;
4767 if (is_young) {
4768 young_time += time_taken;
4769 has_young_time = true;
4770 } else {
4771 non_young_time += time_taken;
4772 has_non_young_time = true;
4773 }
4774 start_time = end_time;
4775 }
4776 }
4777
4778 if (has_young_time) {
4779 timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time);
4780 }
4781 if (has_non_young_time) {
4782 timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, young_time);
4783 }
4784 }
4785 };
4786
4787 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4788 _eden.clear();
4789
4790 double free_cset_start_time = os::elapsedTime();
4791
4792 {
4793 uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U);
4794 uint const num_workers = MIN2(workers()->active_workers(), num_chunks);
4795
4796 G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words);
4797
4798 log_debug(gc, ergo)("Running %s using %u workers for collection set length %u",
4799 cl.name(),
4800 num_workers,
4801 _collection_set.region_length());
4802 workers()->run_task(&cl, num_workers);
4803 }
4804 g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0);
4805
4806 collection_set->clear();
4807 }
4808
4809 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4810 private:
4811 FreeRegionList* _free_region_list;
4812 HeapRegionSet* _proxy_set;
4813 uint _humongous_objects_reclaimed;
4814 uint _humongous_regions_reclaimed;
4815 size_t _freed_bytes;
4816 public:
4817
4818 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4819 _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) {
4820 }
4821
4822 virtual bool doHeapRegion(HeapRegion* r) {
4823 if (!r->is_starts_humongous()) {
4824 return false;
4825 }
4826
4827 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4828
4829 oop obj = (oop)r->bottom();
4830 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap();
4831
4832 // The following checks whether the humongous object is live are sufficient.
4833 // The main additional check (in addition to having a reference from the roots
4834 // or the young gen) is whether the humongous object has a remembered set entry.
4835 //
4836 // A humongous object cannot be live if there is no remembered set for it
4837 // because:
4838 // - there can be no references from within humongous starts regions referencing
4839 // the object because we never allocate other objects into them.
4840 // (I.e. there are no intra-region references that may be missed by the
4841 // remembered set)
4842 // - as soon there is a remembered set entry to the humongous starts region
4843 // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4844 // until the end of a concurrent mark.
4845 //
4846 // It is not required to check whether the object has been found dead by marking
4847 // or not, in fact it would prevent reclamation within a concurrent cycle, as
4848 // all objects allocated during that time are considered live.
4849 // SATB marking is even more conservative than the remembered set.
4850 // So if at this point in the collection there is no remembered set entry,
4851 // nobody has a reference to it.
4852 // At the start of collection we flush all refinement logs, and remembered sets
4853 // are completely up-to-date wrt to references to the humongous object.
4854 //
4855 // Other implementation considerations:
4856 // - never consider object arrays at this time because they would pose
4857 // considerable effort for cleaning up the the remembered sets. This is
4858 // required because stale remembered sets might reference locations that
4859 // are currently allocated into.
4860 uint region_idx = r->hrm_index();
4861 if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4862 !r->rem_set()->is_empty()) {
4863 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",
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 return false;
4874 }
4875
4876 guarantee(obj->is_typeArray(),
4877 "Only eagerly reclaiming type arrays is supported, but the object "
4878 PTR_FORMAT " is not.", p2i(r->bottom()));
4879
4880 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",
4881 region_idx,
4882 (size_t)obj->size() * HeapWordSize,
4883 p2i(r->bottom()),
4884 r->rem_set()->occupied(),
4885 r->rem_set()->strong_code_roots_list_length(),
4886 next_bitmap->is_marked(r->bottom()),
4887 g1h->is_humongous_reclaim_candidate(region_idx),
4888 obj->is_typeArray()
4889 );
4890
4891 // Need to clear mark bit of the humongous object if already set.
4892 if (next_bitmap->is_marked(r->bottom())) {
4893 next_bitmap->clear(r->bottom());
4894 }
4895 _humongous_objects_reclaimed++;
4896 do {
4897 HeapRegion* next = g1h->next_region_in_humongous(r);
4898 _freed_bytes += r->used();
4899 r->set_containing_set(NULL);
4900 _humongous_regions_reclaimed++;
4901 g1h->free_humongous_region(r, _free_region_list, false /* skip_remset */ );
4902 r = next;
4903 } while (r != NULL);
4904
4905 return false;
4906 }
4907
4908 uint humongous_objects_reclaimed() {
4909 return _humongous_objects_reclaimed;
4910 }
4911
4912 uint humongous_regions_reclaimed() {
4913 return _humongous_regions_reclaimed;
4914 }
4915
4916 size_t bytes_freed() const {
4917 return _freed_bytes;
4918 }
4919 };
4920
4921 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4922 assert_at_safepoint(true);
4923
4924 if (!G1EagerReclaimHumongousObjects ||
4925 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
4926 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
4927 return;
4928 }
4929
4930 double start_time = os::elapsedTime();
4931
4932 FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
4933
4934 G1FreeHumongousRegionClosure cl(&local_cleanup_list);
4935 heap_region_iterate(&cl);
4936
4937 remove_from_old_sets(0, cl.humongous_regions_reclaimed());
4938
4939 G1HRPrinter* hrp = hr_printer();
4940 if (hrp->is_active()) {
4941 FreeRegionListIterator iter(&local_cleanup_list);
4942 while (iter.more_available()) {
4943 HeapRegion* hr = iter.get_next();
4944 hrp->cleanup(hr);
4945 }
4946 }
4947
4948 prepend_to_freelist(&local_cleanup_list);
4949 decrement_summary_bytes(cl.bytes_freed());
4950
4951 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
4952 cl.humongous_objects_reclaimed());
4953 }
4954
4955 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
4956 public:
4957 virtual bool doHeapRegion(HeapRegion* r) {
4958 assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
4959 G1CollectedHeap::heap()->clear_in_cset(r);
4960 r->set_young_index_in_cset(-1);
4961 return false;
4962 }
4963 };
4964
4965 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
4966 G1AbandonCollectionSetClosure cl;
4967 collection_set->iterate(&cl);
4968
4969 collection_set->clear();
4970 collection_set->stop_incremental_building();
4971 }
4972
4973 void G1CollectedHeap::set_free_regions_coming() {
4974 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming");
4975
4976 assert(!free_regions_coming(), "pre-condition");
4977 _free_regions_coming = true;
4978 }
4979
4980 void G1CollectedHeap::reset_free_regions_coming() {
4981 assert(free_regions_coming(), "pre-condition");
4982
4983 {
4984 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
4985 _free_regions_coming = false;
4986 SecondaryFreeList_lock->notify_all();
4987 }
4988
4989 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming");
4990 }
4991
4992 void G1CollectedHeap::wait_while_free_regions_coming() {
4993 // Most of the time we won't have to wait, so let's do a quick test
4994 // first before we take the lock.
4995 if (!free_regions_coming()) {
4996 return;
4997 }
4998
4999 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions");
5000
5001 {
5002 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5003 while (free_regions_coming()) {
5004 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
5005 }
5006 }
5007
5008 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions");
5009 }
5010
5011 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
5012 return _allocator->is_retained_old_region(hr);
5013 }
5014
5015 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
5016 _eden.add(hr);
5017 _g1_policy->set_region_eden(hr);
5018 }
5019
5020 #ifdef ASSERT
5021
5022 class NoYoungRegionsClosure: public HeapRegionClosure {
5023 private:
5024 bool _success;
5025 public:
5026 NoYoungRegionsClosure() : _success(true) { }
5027 bool doHeapRegion(HeapRegion* r) {
5028 if (r->is_young()) {
5029 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
5030 p2i(r->bottom()), p2i(r->end()));
5031 _success = false;
5032 }
5033 return false;
5034 }
5035 bool success() { return _success; }
5036 };
5037
5038 bool G1CollectedHeap::check_young_list_empty() {
5039 bool ret = (young_regions_count() == 0);
5040
5041 NoYoungRegionsClosure closure;
5042 heap_region_iterate(&closure);
5043 ret = ret && closure.success();
5044
5045 return ret;
5046 }
5047
5048 #endif // ASSERT
5049
5050 class TearDownRegionSetsClosure : public HeapRegionClosure {
5051 private:
5052 HeapRegionSet *_old_set;
5053
5054 public:
5055 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
5056
5057 bool doHeapRegion(HeapRegion* r) {
5058 if (r->is_old()) {
5059 _old_set->remove(r);
5060 } else if(r->is_young()) {
5061 r->uninstall_surv_rate_group();
5062 } else {
5063 // We ignore free regions, we'll empty the free list afterwards.
5064 // We ignore humongous regions, we're not tearing down the
5065 // humongous regions set.
5066 assert(r->is_free() || r->is_humongous(),
5067 "it cannot be another type");
5068 }
5069 return false;
5070 }
5071
5072 ~TearDownRegionSetsClosure() {
5073 assert(_old_set->is_empty(), "post-condition");
5074 }
5075 };
5076
5077 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
5078 assert_at_safepoint(true /* should_be_vm_thread */);
5079
5080 if (!free_list_only) {
5081 TearDownRegionSetsClosure cl(&_old_set);
5082 heap_region_iterate(&cl);
5083
5084 // Note that emptying the _young_list is postponed and instead done as
5085 // the first step when rebuilding the regions sets again. The reason for
5086 // this is that during a full GC string deduplication needs to know if
5087 // a collected region was young or old when the full GC was initiated.
5088 }
5089 _hrm.remove_all_free_regions();
5090 }
5091
5092 void G1CollectedHeap::increase_used(size_t bytes) {
5093 _summary_bytes_used += bytes;
5094 }
5095
5096 void G1CollectedHeap::decrease_used(size_t bytes) {
5097 assert(_summary_bytes_used >= bytes,
5098 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
5099 _summary_bytes_used, bytes);
5100 _summary_bytes_used -= bytes;
5101 }
5102
5103 void G1CollectedHeap::set_used(size_t bytes) {
5104 _summary_bytes_used = bytes;
5105 }
5106
5107 class RebuildRegionSetsClosure : public HeapRegionClosure {
5108 private:
5109 bool _free_list_only;
5110 HeapRegionSet* _old_set;
5111 HeapRegionManager* _hrm;
5112 size_t _total_used;
5113
5114 public:
5115 RebuildRegionSetsClosure(bool free_list_only,
5116 HeapRegionSet* old_set, HeapRegionManager* hrm) :
5117 _free_list_only(free_list_only),
5118 _old_set(old_set), _hrm(hrm), _total_used(0) {
5119 assert(_hrm->num_free_regions() == 0, "pre-condition");
5120 if (!free_list_only) {
5121 assert(_old_set->is_empty(), "pre-condition");
5122 }
5123 }
5124
5125 bool doHeapRegion(HeapRegion* r) {
5126 if (r->is_empty()) {
5127 // Add free regions to the free list
5128 r->set_free();
5129 r->set_allocation_context(AllocationContext::system());
5130 _hrm->insert_into_free_list(r);
5131 } else if (!_free_list_only) {
5132
5133 if (r->is_humongous()) {
5134 // We ignore humongous regions. We left the humongous set unchanged.
5135 } else {
5136 assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
5137 // We now move all (non-humongous, non-old) regions to old gen, and register them as such.
5138 r->move_to_old();
5139 _old_set->add(r);
5140 }
5141 _total_used += r->used();
5142 }
5143
5144 return false;
5145 }
5146
5147 size_t total_used() {
5148 return _total_used;
5149 }
5150 };
5151
5152 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
5153 assert_at_safepoint(true /* should_be_vm_thread */);
5154
5155 if (!free_list_only) {
5156 _eden.clear();
5157 _survivor.clear();
5158 }
5159
5160 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
5161 heap_region_iterate(&cl);
5162
5163 if (!free_list_only) {
5164 set_used(cl.total_used());
5165 if (_archive_allocator != NULL) {
5166 _archive_allocator->clear_used();
5167 }
5168 }
5169 assert(used_unlocked() == recalculate_used(),
5170 "inconsistent used_unlocked(), "
5171 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT,
5172 used_unlocked(), recalculate_used());
5173 }
5174
5175 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
5176 HeapRegion* hr = heap_region_containing(p);
5177 return hr->is_in(p);
5178 }
5179
5180 // Methods for the mutator alloc region
5181
5182 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
5183 bool force) {
5184 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5185 bool should_allocate = g1_policy()->should_allocate_mutator_region();
5186 if (force || should_allocate) {
5187 HeapRegion* new_alloc_region = new_region(word_size,
5188 false /* is_old */,
5189 false /* do_expand */);
5190 if (new_alloc_region != NULL) {
5191 set_region_short_lived_locked(new_alloc_region);
5192 _hr_printer.alloc(new_alloc_region, !should_allocate);
5193 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
5194 return new_alloc_region;
5195 }
5196 }
5197 return NULL;
5198 }
5199
5200 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
5201 size_t allocated_bytes) {
5202 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5203 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
5204
5205 collection_set()->add_eden_region(alloc_region);
5206 increase_used(allocated_bytes);
5207 _hr_printer.retire(alloc_region);
5208 // We update the eden sizes here, when the region is retired,
5209 // instead of when it's allocated, since this is the point that its
5210 // used space has been recored in _summary_bytes_used.
5211 g1mm()->update_eden_size();
5212 }
5213
5214 // Methods for the GC alloc regions
5215
5216 bool G1CollectedHeap::has_more_regions(InCSetState dest) {
5217 if (dest.is_old()) {
5218 return true;
5219 } else {
5220 return survivor_regions_count() < g1_policy()->max_survivor_regions();
5221 }
5222 }
5223
5224 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) {
5225 assert(FreeList_lock->owned_by_self(), "pre-condition");
5226
5227 if (!has_more_regions(dest)) {
5228 return NULL;
5229 }
5230
5231 const bool is_survivor = dest.is_young();
5232
5233 HeapRegion* new_alloc_region = new_region(word_size,
5234 !is_survivor,
5235 true /* do_expand */);
5236 if (new_alloc_region != NULL) {
5237 // We really only need to do this for old regions given that we
5238 // should never scan survivors. But it doesn't hurt to do it
5239 // for survivors too.
5240 new_alloc_region->record_timestamp();
5241 if (is_survivor) {
5242 new_alloc_region->set_survivor();
5243 _survivor.add(new_alloc_region);
5244 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
5245 } else {
5246 new_alloc_region->set_old();
5247 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
5248 }
5249 _hr_printer.alloc(new_alloc_region);
5250 bool during_im = collector_state()->during_initial_mark_pause();
5251 new_alloc_region->note_start_of_copying(during_im);
5252 return new_alloc_region;
5253 }
5254 return NULL;
5255 }
5256
5257 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
5258 size_t allocated_bytes,
5259 InCSetState dest) {
5260 bool during_im = collector_state()->during_initial_mark_pause();
5261 alloc_region->note_end_of_copying(during_im);
5262 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
5263 if (dest.is_old()) {
5264 _old_set.add(alloc_region);
5265 }
5266 _hr_printer.retire(alloc_region);
5267 }
5268
5269 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
5270 bool expanded = false;
5271 uint index = _hrm.find_highest_free(&expanded);
5272
5273 if (index != G1_NO_HRM_INDEX) {
5274 if (expanded) {
5275 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
5276 HeapRegion::GrainWords * HeapWordSize);
5277 }
5278 _hrm.allocate_free_regions_starting_at(index, 1);
5279 return region_at(index);
5280 }
5281 return NULL;
5282 }
5283
5284 // Optimized nmethod scanning
5285
5286 class RegisterNMethodOopClosure: public OopClosure {
5287 G1CollectedHeap* _g1h;
5288 nmethod* _nm;
5289
5290 template <class T> void do_oop_work(T* p) {
5291 T heap_oop = oopDesc::load_heap_oop(p);
5292 if (!oopDesc::is_null(heap_oop)) {
5293 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5294 HeapRegion* hr = _g1h->heap_region_containing(obj);
5295 assert(!hr->is_continues_humongous(),
5296 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5297 " starting at " HR_FORMAT,
5298 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5299
5300 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
5301 hr->add_strong_code_root_locked(_nm);
5302 }
5303 }
5304
5305 public:
5306 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5307 _g1h(g1h), _nm(nm) {}
5308
5309 void do_oop(oop* p) { do_oop_work(p); }
5310 void do_oop(narrowOop* p) { do_oop_work(p); }
5311 };
5312
5313 class UnregisterNMethodOopClosure: public OopClosure {
5314 G1CollectedHeap* _g1h;
5315 nmethod* _nm;
5316
5317 template <class T> void do_oop_work(T* p) {
5318 T heap_oop = oopDesc::load_heap_oop(p);
5319 if (!oopDesc::is_null(heap_oop)) {
5320 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5321 HeapRegion* hr = _g1h->heap_region_containing(obj);
5322 assert(!hr->is_continues_humongous(),
5323 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5324 " starting at " HR_FORMAT,
5325 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5326
5327 hr->remove_strong_code_root(_nm);
5328 }
5329 }
5330
5331 public:
5332 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5333 _g1h(g1h), _nm(nm) {}
5334
5335 void do_oop(oop* p) { do_oop_work(p); }
5336 void do_oop(narrowOop* p) { do_oop_work(p); }
5337 };
5338
5339 // Returns true if the reference points to an object that
5340 // can move in an incremental collection.
5341 bool G1CollectedHeap::is_scavengable(oop obj) {
5342 HeapRegion* hr = heap_region_containing(obj);
5343 return !hr->is_pinned();
5344 }
5345
5346 void G1CollectedHeap::register_nmethod(nmethod* nm) {
5347 guarantee(nm != NULL, "sanity");
5348 RegisterNMethodOopClosure reg_cl(this, nm);
5349 nm->oops_do(®_cl);
5350 }
5351
5352 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
5353 guarantee(nm != NULL, "sanity");
5354 UnregisterNMethodOopClosure reg_cl(this, nm);
5355 nm->oops_do(®_cl, true);
5356 }
5357
5358 void G1CollectedHeap::purge_code_root_memory() {
5359 double purge_start = os::elapsedTime();
5360 G1CodeRootSet::purge();
5361 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
5362 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
5363 }
5364
5365 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
5366 G1CollectedHeap* _g1h;
5367
5368 public:
5369 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
5370 _g1h(g1h) {}
5371
5372 void do_code_blob(CodeBlob* cb) {
5373 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
5374 if (nm == NULL) {
5375 return;
5376 }
5377
5378 if (ScavengeRootsInCode) {
5379 _g1h->register_nmethod(nm);
5380 }
5381 }
5382 };
5383
5384 void G1CollectedHeap::rebuild_strong_code_roots() {
5385 RebuildStrongCodeRootClosure blob_cl(this);
5386 CodeCache::blobs_do(&blob_cl);
5387 }
5388
5389 GrowableArray<GCMemoryManager*> G1CollectedHeap::memory_managers() {
5390 GrowableArray<GCMemoryManager*> memory_managers(2);
5391 memory_managers.append(&_memory_manager);
5392 memory_managers.append(&_full_gc_memory_manager);
5393 return memory_managers;
5394 }
5395
5396 GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() {
5397 GrowableArray<MemoryPool*> memory_pools(3);
5398 memory_pools.append(_eden_pool);
5399 memory_pools.append(_survivor_pool);
5400 memory_pools.append(_old_pool);
5401 return memory_pools;
5402 }