1 /*
2 * Copyright (c) 2001, 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/metadataOnStackMark.hpp"
27 #include "classfile/stringTable.hpp"
28 #include "classfile/symbolTable.hpp"
29 #include "code/codeCache.hpp"
30 #include "code/icBuffer.hpp"
31 #include "gc/g1/bufferingOopClosure.hpp"
32 #include "gc/g1/concurrentMarkThread.inline.hpp"
33 #include "gc/g1/g1Allocator.inline.hpp"
34 #include "gc/g1/g1CollectedHeap.inline.hpp"
35 #include "gc/g1/g1CollectionSet.hpp"
36 #include "gc/g1/g1CollectorPolicy.hpp"
37 #include "gc/g1/g1CollectorState.hpp"
38 #include "gc/g1/g1ConcurrentRefine.hpp"
39 #include "gc/g1/g1ConcurrentRefineThread.hpp"
40 #include "gc/g1/g1EvacStats.inline.hpp"
41 #include "gc/g1/g1FullCollector.hpp"
42 #include "gc/g1/g1GCPhaseTimes.hpp"
43 #include "gc/g1/g1HeapSizingPolicy.hpp"
44 #include "gc/g1/g1HeapTransition.hpp"
45 #include "gc/g1/g1HeapVerifier.hpp"
46 #include "gc/g1/g1HotCardCache.hpp"
47 #include "gc/g1/g1OopClosures.inline.hpp"
48 #include "gc/g1/g1ParScanThreadState.inline.hpp"
49 #include "gc/g1/g1Policy.hpp"
50 #include "gc/g1/g1RegionToSpaceMapper.hpp"
51 #include "gc/g1/g1RemSet.hpp"
52 #include "gc/g1/g1RootClosures.hpp"
53 #include "gc/g1/g1RootProcessor.hpp"
54 #include "gc/g1/g1StringDedup.hpp"
55 #include "gc/g1/g1YCTypes.hpp"
56 #include "gc/g1/g1YoungRemSetSamplingThread.hpp"
57 #include "gc/g1/heapRegion.inline.hpp"
58 #include "gc/g1/heapRegionRemSet.hpp"
59 #include "gc/g1/heapRegionSet.inline.hpp"
60 #include "gc/g1/vm_operations_g1.hpp"
61 #include "gc/shared/gcHeapSummary.hpp"
62 #include "gc/shared/gcId.hpp"
63 #include "gc/shared/gcLocker.inline.hpp"
64 #include "gc/shared/gcTimer.hpp"
65 #include "gc/shared/gcTrace.hpp"
66 #include "gc/shared/gcTraceTime.inline.hpp"
67 #include "gc/shared/generationSpec.hpp"
68 #include "gc/shared/isGCActiveMark.hpp"
69 #include "gc/shared/preservedMarks.inline.hpp"
70 #include "gc/shared/suspendibleThreadSet.hpp"
71 #include "gc/shared/referenceProcessor.inline.hpp"
72 #include "gc/shared/taskqueue.inline.hpp"
73 #include "gc/shared/weakProcessor.hpp"
74 #include "logging/log.hpp"
75 #include "memory/allocation.hpp"
76 #include "memory/iterator.hpp"
77 #include "memory/resourceArea.hpp"
78 #include "oops/oop.inline.hpp"
79 #include "prims/resolvedMethodTable.hpp"
80 #include "runtime/atomic.hpp"
81 #include "runtime/init.hpp"
82 #include "runtime/orderAccess.inline.hpp"
83 #include "runtime/vmThread.hpp"
84 #include "utilities/align.hpp"
85 #include "utilities/globalDefinitions.hpp"
86 #include "utilities/stack.inline.hpp"
87
88 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
89
90 // INVARIANTS/NOTES
91 //
92 // All allocation activity covered by the G1CollectedHeap interface is
93 // serialized by acquiring the HeapLock. This happens in mem_allocate
94 // and allocate_new_tlab, which are the "entry" points to the
95 // allocation code from the rest of the JVM. (Note that this does not
96 // apply to TLAB allocation, which is not part of this interface: it
97 // is done by clients of this interface.)
98
99 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
100 private:
101 size_t _num_dirtied;
102 G1CollectedHeap* _g1h;
103 G1SATBCardTableLoggingModRefBS* _g1_bs;
104
105 HeapRegion* region_for_card(jbyte* card_ptr) const {
106 return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr));
107 }
108
109 bool will_become_free(HeapRegion* hr) const {
110 // A region will be freed by free_collection_set if the region is in the
111 // collection set and has not had an evacuation failure.
112 return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
113 }
114
115 public:
116 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(),
117 _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { }
118
119 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
120 HeapRegion* hr = region_for_card(card_ptr);
121
122 // Should only dirty cards in regions that won't be freed.
123 if (!will_become_free(hr)) {
124 *card_ptr = CardTableModRefBS::dirty_card_val();
125 _num_dirtied++;
126 }
127
128 return true;
129 }
130
131 size_t num_dirtied() const { return _num_dirtied; }
132 };
133
134
135 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
136 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
137 }
138
139 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
140 // The from card cache is not the memory that is actually committed. So we cannot
141 // take advantage of the zero_filled parameter.
142 reset_from_card_cache(start_idx, num_regions);
143 }
144
145
146 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
147 MemRegion mr) {
148 return new HeapRegion(hrs_index, bot(), mr);
149 }
150
151 // Private methods.
152
153 HeapRegion*
154 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
155 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
156 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
157 if (!_secondary_free_list.is_empty()) {
158 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
159 "secondary_free_list has %u entries",
160 _secondary_free_list.length());
161 // It looks as if there are free regions available on the
162 // secondary_free_list. Let's move them to the free_list and try
163 // again to allocate from it.
164 append_secondary_free_list();
165
166 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
167 "empty we should have moved at least one entry to the free_list");
168 HeapRegion* res = _hrm.allocate_free_region(is_old);
169 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
170 "allocated " HR_FORMAT " from secondary_free_list",
171 HR_FORMAT_PARAMS(res));
172 return res;
173 }
174
175 // Wait here until we get notified either when (a) there are no
176 // more free regions coming or (b) some regions have been moved on
177 // the secondary_free_list.
178 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
179 }
180
181 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
182 "could not allocate from secondary_free_list");
183 return NULL;
184 }
185
186 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
187 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
188 "the only time we use this to allocate a humongous region is "
189 "when we are allocating a single humongous region");
190
191 HeapRegion* res;
192 if (G1StressConcRegionFreeing) {
193 if (!_secondary_free_list.is_empty()) {
194 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
195 "forced to look at the secondary_free_list");
196 res = new_region_try_secondary_free_list(is_old);
197 if (res != NULL) {
198 return res;
199 }
200 }
201 }
202
203 res = _hrm.allocate_free_region(is_old);
204
205 if (res == NULL) {
206 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
207 "res == NULL, trying the secondary_free_list");
208 res = new_region_try_secondary_free_list(is_old);
209 }
210 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
211 // Currently, only attempts to allocate GC alloc regions set
212 // do_expand to true. So, we should only reach here during a
213 // safepoint. If this assumption changes we might have to
214 // reconsider the use of _expand_heap_after_alloc_failure.
215 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
216
217 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
218 word_size * HeapWordSize);
219
220 if (expand(word_size * HeapWordSize)) {
221 // Given that expand() succeeded in expanding the heap, and we
222 // always expand the heap by an amount aligned to the heap
223 // region size, the free list should in theory not be empty.
224 // In either case allocate_free_region() will check for NULL.
225 res = _hrm.allocate_free_region(is_old);
226 } else {
227 _expand_heap_after_alloc_failure = false;
228 }
229 }
230 return res;
231 }
232
233 HeapWord*
234 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
235 uint num_regions,
236 size_t word_size,
237 AllocationContext_t context) {
238 assert(first != G1_NO_HRM_INDEX, "pre-condition");
239 assert(is_humongous(word_size), "word_size should be humongous");
240 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
241
242 // Index of last region in the series.
243 uint last = first + num_regions - 1;
244
245 // We need to initialize the region(s) we just discovered. This is
246 // a bit tricky given that it can happen concurrently with
247 // refinement threads refining cards on these regions and
248 // potentially wanting to refine the BOT as they are scanning
249 // those cards (this can happen shortly after a cleanup; see CR
250 // 6991377). So we have to set up the region(s) carefully and in
251 // a specific order.
252
253 // The word size sum of all the regions we will allocate.
254 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
255 assert(word_size <= word_size_sum, "sanity");
256
257 // This will be the "starts humongous" region.
258 HeapRegion* first_hr = region_at(first);
259 // The header of the new object will be placed at the bottom of
260 // the first region.
261 HeapWord* new_obj = first_hr->bottom();
262 // This will be the new top of the new object.
263 HeapWord* obj_top = new_obj + word_size;
264
265 // First, we need to zero the header of the space that we will be
266 // allocating. When we update top further down, some refinement
267 // threads might try to scan the region. By zeroing the header we
268 // ensure that any thread that will try to scan the region will
269 // come across the zero klass word and bail out.
270 //
271 // NOTE: It would not have been correct to have used
272 // CollectedHeap::fill_with_object() and make the space look like
273 // an int array. The thread that is doing the allocation will
274 // later update the object header to a potentially different array
275 // type and, for a very short period of time, the klass and length
276 // fields will be inconsistent. This could cause a refinement
277 // thread to calculate the object size incorrectly.
278 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
279
280 // Next, pad out the unused tail of the last region with filler
281 // objects, for improved usage accounting.
282 // How many words we use for filler objects.
283 size_t word_fill_size = word_size_sum - word_size;
284
285 // How many words memory we "waste" which cannot hold a filler object.
286 size_t words_not_fillable = 0;
287
288 if (word_fill_size >= min_fill_size()) {
289 fill_with_objects(obj_top, word_fill_size);
290 } else if (word_fill_size > 0) {
291 // We have space to fill, but we cannot fit an object there.
292 words_not_fillable = word_fill_size;
293 word_fill_size = 0;
294 }
295
296 // We will set up the first region as "starts humongous". This
297 // will also update the BOT covering all the regions to reflect
298 // that there is a single object that starts at the bottom of the
299 // first region.
300 first_hr->set_starts_humongous(obj_top, word_fill_size);
301 first_hr->set_allocation_context(context);
302 // Then, if there are any, we will set up the "continues
303 // humongous" regions.
304 HeapRegion* hr = NULL;
305 for (uint i = first + 1; i <= last; ++i) {
306 hr = region_at(i);
307 hr->set_continues_humongous(first_hr);
308 hr->set_allocation_context(context);
309 }
310
311 // Up to this point no concurrent thread would have been able to
312 // do any scanning on any region in this series. All the top
313 // fields still point to bottom, so the intersection between
314 // [bottom,top] and [card_start,card_end] will be empty. Before we
315 // update the top fields, we'll do a storestore to make sure that
316 // no thread sees the update to top before the zeroing of the
317 // object header and the BOT initialization.
318 OrderAccess::storestore();
319
320 // Now, we will update the top fields of the "continues humongous"
321 // regions except the last one.
322 for (uint i = first; i < last; ++i) {
323 hr = region_at(i);
324 hr->set_top(hr->end());
325 }
326
327 hr = region_at(last);
328 // If we cannot fit a filler object, we must set top to the end
329 // of the humongous object, otherwise we cannot iterate the heap
330 // and the BOT will not be complete.
331 hr->set_top(hr->end() - words_not_fillable);
332
333 assert(hr->bottom() < obj_top && obj_top <= hr->end(),
334 "obj_top should be in last region");
335
336 _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
337
338 assert(words_not_fillable == 0 ||
339 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
340 "Miscalculation in humongous allocation");
341
342 increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
343
344 for (uint i = first; i <= last; ++i) {
345 hr = region_at(i);
346 _humongous_set.add(hr);
347 _hr_printer.alloc(hr);
348 }
349
350 return new_obj;
351 }
352
353 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
354 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
355 return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
356 }
357
358 // If could fit into free regions w/o expansion, try.
359 // Otherwise, if can expand, do so.
360 // Otherwise, if using ex regions might help, try with ex given back.
361 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
362 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
363
364 _verifier->verify_region_sets_optional();
365
366 uint first = G1_NO_HRM_INDEX;
367 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
368
369 if (obj_regions == 1) {
370 // Only one region to allocate, try to use a fast path by directly allocating
371 // from the free lists. Do not try to expand here, we will potentially do that
372 // later.
373 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
374 if (hr != NULL) {
375 first = hr->hrm_index();
376 }
377 } else {
378 // We can't allocate humongous regions spanning more than one region while
379 // cleanupComplete() is running, since some of the regions we find to be
380 // empty might not yet be added to the free list. It is not straightforward
381 // to know in which list they are on so that we can remove them. We only
382 // need to do this if we need to allocate more than one region to satisfy the
383 // current humongous allocation request. If we are only allocating one region
384 // we use the one-region region allocation code (see above), that already
385 // potentially waits for regions from the secondary free list.
386 wait_while_free_regions_coming();
387 append_secondary_free_list_if_not_empty_with_lock();
388
389 // Policy: Try only empty regions (i.e. already committed first). Maybe we
390 // are lucky enough to find some.
391 first = _hrm.find_contiguous_only_empty(obj_regions);
392 if (first != G1_NO_HRM_INDEX) {
393 _hrm.allocate_free_regions_starting_at(first, obj_regions);
394 }
395 }
396
397 if (first == G1_NO_HRM_INDEX) {
398 // Policy: We could not find enough regions for the humongous object in the
399 // free list. Look through the heap to find a mix of free and uncommitted regions.
400 // If so, try expansion.
401 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
402 if (first != G1_NO_HRM_INDEX) {
403 // We found something. Make sure these regions are committed, i.e. expand
404 // the heap. Alternatively we could do a defragmentation GC.
405 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
406 word_size * HeapWordSize);
407
408 _hrm.expand_at(first, obj_regions, workers());
409 g1_policy()->record_new_heap_size(num_regions());
410
411 #ifdef ASSERT
412 for (uint i = first; i < first + obj_regions; ++i) {
413 HeapRegion* hr = region_at(i);
414 assert(hr->is_free(), "sanity");
415 assert(hr->is_empty(), "sanity");
416 assert(is_on_master_free_list(hr), "sanity");
417 }
418 #endif
419 _hrm.allocate_free_regions_starting_at(first, obj_regions);
420 } else {
421 // Policy: Potentially trigger a defragmentation GC.
422 }
423 }
424
425 HeapWord* result = NULL;
426 if (first != G1_NO_HRM_INDEX) {
427 result = humongous_obj_allocate_initialize_regions(first, obj_regions,
428 word_size, context);
429 assert(result != NULL, "it should always return a valid result");
430
431 // A successful humongous object allocation changes the used space
432 // information of the old generation so we need to recalculate the
433 // sizes and update the jstat counters here.
434 g1mm()->update_sizes();
435 }
436
437 _verifier->verify_region_sets_optional();
438
439 return result;
440 }
441
442 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
443 assert_heap_not_locked_and_not_at_safepoint();
444 assert(!is_humongous(word_size), "we do not allow humongous TLABs");
445
446 uint dummy_gc_count_before;
447 uint dummy_gclocker_retry_count = 0;
448 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
449 }
450
451 HeapWord*
452 G1CollectedHeap::mem_allocate(size_t word_size,
453 bool* gc_overhead_limit_was_exceeded) {
454 assert_heap_not_locked_and_not_at_safepoint();
455
456 // Loop until the allocation is satisfied, or unsatisfied after GC.
457 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
458 uint gc_count_before;
459
460 HeapWord* result = NULL;
461 if (!is_humongous(word_size)) {
462 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
463 } else {
464 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
465 }
466 if (result != NULL) {
467 return result;
468 }
469
470 // Create the garbage collection operation...
471 VM_G1CollectForAllocation op(gc_count_before, word_size);
472 op.set_allocation_context(AllocationContext::current());
473
474 // ...and get the VM thread to execute it.
475 VMThread::execute(&op);
476
477 if (op.prologue_succeeded() && op.pause_succeeded()) {
478 // If the operation was successful we'll return the result even
479 // if it is NULL. If the allocation attempt failed immediately
480 // after a Full GC, it's unlikely we'll be able to allocate now.
481 HeapWord* result = op.result();
482 if (result != NULL && !is_humongous(word_size)) {
483 // Allocations that take place on VM operations do not do any
484 // card dirtying and we have to do it here. We only have to do
485 // this for non-humongous allocations, though.
486 dirty_young_block(result, word_size);
487 }
488 return result;
489 } else {
490 if (gclocker_retry_count > GCLockerRetryAllocationCount) {
491 return NULL;
492 }
493 assert(op.result() == NULL,
494 "the result should be NULL if the VM op did not succeed");
495 }
496
497 // Give a warning if we seem to be looping forever.
498 if ((QueuedAllocationWarningCount > 0) &&
499 (try_count % QueuedAllocationWarningCount == 0)) {
500 log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count);
501 }
502 }
503
504 ShouldNotReachHere();
505 return NULL;
506 }
507
508 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
509 AllocationContext_t context,
510 uint* gc_count_before_ret,
511 uint* gclocker_retry_count_ret) {
512 // Make sure you read the note in attempt_allocation_humongous().
513
514 assert_heap_not_locked_and_not_at_safepoint();
515 assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
516 "be called for humongous allocation requests");
517
518 // We should only get here after the first-level allocation attempt
519 // (attempt_allocation()) failed to allocate.
520
521 // We will loop until a) we manage to successfully perform the
522 // allocation or b) we successfully schedule a collection which
523 // fails to perform the allocation. b) is the only case when we'll
524 // return NULL.
525 HeapWord* result = NULL;
526 for (int try_count = 1; /* we'll return */; try_count += 1) {
527 bool should_try_gc;
528 uint gc_count_before;
529
530 {
531 MutexLockerEx x(Heap_lock);
532 result = _allocator->attempt_allocation_locked(word_size, context);
533 if (result != NULL) {
534 return result;
535 }
536
537 if (GCLocker::is_active_and_needs_gc()) {
538 if (g1_policy()->can_expand_young_list()) {
539 // No need for an ergo verbose message here,
540 // can_expand_young_list() does this when it returns true.
541 result = _allocator->attempt_allocation_force(word_size, context);
542 if (result != NULL) {
543 return result;
544 }
545 }
546 should_try_gc = false;
547 } else {
548 // The GCLocker may not be active but the GCLocker initiated
549 // GC may not yet have been performed (GCLocker::needs_gc()
550 // returns true). In this case we do not try this GC and
551 // wait until the GCLocker initiated GC is performed, and
552 // then retry the allocation.
553 if (GCLocker::needs_gc()) {
554 should_try_gc = false;
555 } else {
556 // Read the GC count while still holding the Heap_lock.
557 gc_count_before = total_collections();
558 should_try_gc = true;
559 }
560 }
561 }
562
563 if (should_try_gc) {
564 bool succeeded;
565 result = do_collection_pause(word_size, gc_count_before, &succeeded,
566 GCCause::_g1_inc_collection_pause);
567 if (result != NULL) {
568 assert(succeeded, "only way to get back a non-NULL result");
569 return result;
570 }
571
572 if (succeeded) {
573 // If we get here we successfully scheduled a collection which
574 // failed to allocate. No point in trying to allocate
575 // further. We'll just return NULL.
576 MutexLockerEx x(Heap_lock);
577 *gc_count_before_ret = total_collections();
578 return NULL;
579 }
580 } else {
581 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
582 MutexLockerEx x(Heap_lock);
583 *gc_count_before_ret = total_collections();
584 return NULL;
585 }
586 // The GCLocker is either active or the GCLocker initiated
587 // GC has not yet been performed. Stall until it is and
588 // then retry the allocation.
589 GCLocker::stall_until_clear();
590 (*gclocker_retry_count_ret) += 1;
591 }
592
593 // We can reach here if we were unsuccessful in scheduling a
594 // collection (because another thread beat us to it) or if we were
595 // stalled due to the GC locker. In either can we should retry the
596 // allocation attempt in case another thread successfully
597 // performed a collection and reclaimed enough space. We do the
598 // first attempt (without holding the Heap_lock) here and the
599 // follow-on attempt will be at the start of the next loop
600 // iteration (after taking the Heap_lock).
601 result = _allocator->attempt_allocation(word_size, context);
602 if (result != NULL) {
603 return result;
604 }
605
606 // Give a warning if we seem to be looping forever.
607 if ((QueuedAllocationWarningCount > 0) &&
608 (try_count % QueuedAllocationWarningCount == 0)) {
609 log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() "
610 "retries %d times", try_count);
611 }
612 }
613
614 ShouldNotReachHere();
615 return NULL;
616 }
617
618 void G1CollectedHeap::begin_archive_alloc_range(bool open) {
619 assert_at_safepoint(true /* should_be_vm_thread */);
620 if (_archive_allocator == NULL) {
621 _archive_allocator = G1ArchiveAllocator::create_allocator(this, open);
622 }
623 }
624
625 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
626 // Allocations in archive regions cannot be of a size that would be considered
627 // humongous even for a minimum-sized region, because G1 region sizes/boundaries
628 // may be different at archive-restore time.
629 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
630 }
631
632 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
633 assert_at_safepoint(true /* should_be_vm_thread */);
634 assert(_archive_allocator != NULL, "_archive_allocator not initialized");
635 if (is_archive_alloc_too_large(word_size)) {
636 return NULL;
637 }
638 return _archive_allocator->archive_mem_allocate(word_size);
639 }
640
641 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
642 size_t end_alignment_in_bytes) {
643 assert_at_safepoint(true /* should_be_vm_thread */);
644 assert(_archive_allocator != NULL, "_archive_allocator not initialized");
645
646 // Call complete_archive to do the real work, filling in the MemRegion
647 // array with the archive regions.
648 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
649 delete _archive_allocator;
650 _archive_allocator = NULL;
651 }
652
653 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
654 assert(ranges != NULL, "MemRegion array NULL");
655 assert(count != 0, "No MemRegions provided");
656 MemRegion reserved = _hrm.reserved();
657 for (size_t i = 0; i < count; i++) {
658 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
659 return false;
660 }
661 }
662 return true;
663 }
664
665 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges,
666 size_t count,
667 bool open) {
668 assert(!is_init_completed(), "Expect to be called at JVM init time");
669 assert(ranges != NULL, "MemRegion array NULL");
670 assert(count != 0, "No MemRegions provided");
671 MutexLockerEx x(Heap_lock);
672
673 MemRegion reserved = _hrm.reserved();
674 HeapWord* prev_last_addr = NULL;
675 HeapRegion* prev_last_region = NULL;
676
677 // Temporarily disable pretouching of heap pages. This interface is used
678 // when mmap'ing archived heap data in, so pre-touching is wasted.
679 FlagSetting fs(AlwaysPreTouch, false);
680
681 // Enable archive object checking used by G1MarkSweep. We have to let it know
682 // about each archive range, so that objects in those ranges aren't marked.
683 G1ArchiveAllocator::enable_archive_object_check();
684
685 // For each specified MemRegion range, allocate the corresponding G1
686 // regions and mark them as archive regions. We expect the ranges
687 // in ascending starting address order, without overlap.
688 for (size_t i = 0; i < count; i++) {
689 MemRegion curr_range = ranges[i];
690 HeapWord* start_address = curr_range.start();
691 size_t word_size = curr_range.word_size();
692 HeapWord* last_address = curr_range.last();
693 size_t commits = 0;
694
695 guarantee(reserved.contains(start_address) && reserved.contains(last_address),
696 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
697 p2i(start_address), p2i(last_address));
698 guarantee(start_address > prev_last_addr,
699 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
700 p2i(start_address), p2i(prev_last_addr));
701 prev_last_addr = last_address;
702
703 // Check for ranges that start in the same G1 region in which the previous
704 // range ended, and adjust the start address so we don't try to allocate
705 // the same region again. If the current range is entirely within that
706 // region, skip it, just adjusting the recorded top.
707 HeapRegion* start_region = _hrm.addr_to_region(start_address);
708 if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
709 start_address = start_region->end();
710 if (start_address > last_address) {
711 increase_used(word_size * HeapWordSize);
712 start_region->set_top(last_address + 1);
713 continue;
714 }
715 start_region->set_top(start_address);
716 curr_range = MemRegion(start_address, last_address + 1);
717 start_region = _hrm.addr_to_region(start_address);
718 }
719
720 // Perform the actual region allocation, exiting if it fails.
721 // Then note how much new space we have allocated.
722 if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) {
723 return false;
724 }
725 increase_used(word_size * HeapWordSize);
726 if (commits != 0) {
727 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
728 HeapRegion::GrainWords * HeapWordSize * commits);
729
730 }
731
732 // Mark each G1 region touched by the range as archive, add it to
733 // the old set, and set the allocation context and top.
734 HeapRegion* curr_region = _hrm.addr_to_region(start_address);
735 HeapRegion* last_region = _hrm.addr_to_region(last_address);
736 prev_last_region = last_region;
737
738 while (curr_region != NULL) {
739 assert(curr_region->is_empty() && !curr_region->is_pinned(),
740 "Region already in use (index %u)", curr_region->hrm_index());
741 curr_region->set_allocation_context(AllocationContext::system());
742 if (open) {
743 curr_region->set_open_archive();
744 } else {
745 curr_region->set_closed_archive();
746 }
747 _hr_printer.alloc(curr_region);
748 _old_set.add(curr_region);
749 HeapWord* top;
750 HeapRegion* next_region;
751 if (curr_region != last_region) {
752 top = curr_region->end();
753 next_region = _hrm.next_region_in_heap(curr_region);
754 } else {
755 top = last_address + 1;
756 next_region = NULL;
757 }
758 curr_region->set_top(top);
759 curr_region->set_first_dead(top);
760 curr_region->set_end_of_live(top);
761 curr_region = next_region;
762 }
763
764 // Notify mark-sweep of the archive
765 G1ArchiveAllocator::set_range_archive(curr_range, open);
766 }
767 return true;
768 }
769
770 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
771 assert(!is_init_completed(), "Expect to be called at JVM init time");
772 assert(ranges != NULL, "MemRegion array NULL");
773 assert(count != 0, "No MemRegions provided");
774 MemRegion reserved = _hrm.reserved();
775 HeapWord *prev_last_addr = NULL;
776 HeapRegion* prev_last_region = NULL;
777
778 // For each MemRegion, create filler objects, if needed, in the G1 regions
779 // that contain the address range. The address range actually within the
780 // MemRegion will not be modified. That is assumed to have been initialized
781 // elsewhere, probably via an mmap of archived heap data.
782 MutexLockerEx x(Heap_lock);
783 for (size_t i = 0; i < count; i++) {
784 HeapWord* start_address = ranges[i].start();
785 HeapWord* last_address = ranges[i].last();
786
787 assert(reserved.contains(start_address) && reserved.contains(last_address),
788 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
789 p2i(start_address), p2i(last_address));
790 assert(start_address > prev_last_addr,
791 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
792 p2i(start_address), p2i(prev_last_addr));
793
794 HeapRegion* start_region = _hrm.addr_to_region(start_address);
795 HeapRegion* last_region = _hrm.addr_to_region(last_address);
796 HeapWord* bottom_address = start_region->bottom();
797
798 // Check for a range beginning in the same region in which the
799 // previous one ended.
800 if (start_region == prev_last_region) {
801 bottom_address = prev_last_addr + 1;
802 }
803
804 // Verify that the regions were all marked as archive regions by
805 // alloc_archive_regions.
806 HeapRegion* curr_region = start_region;
807 while (curr_region != NULL) {
808 guarantee(curr_region->is_archive(),
809 "Expected archive region at index %u", curr_region->hrm_index());
810 if (curr_region != last_region) {
811 curr_region = _hrm.next_region_in_heap(curr_region);
812 } else {
813 curr_region = NULL;
814 }
815 }
816
817 prev_last_addr = last_address;
818 prev_last_region = last_region;
819
820 // Fill the memory below the allocated range with dummy object(s),
821 // if the region bottom does not match the range start, or if the previous
822 // range ended within the same G1 region, and there is a gap.
823 if (start_address != bottom_address) {
824 size_t fill_size = pointer_delta(start_address, bottom_address);
825 G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
826 increase_used(fill_size * HeapWordSize);
827 }
828 }
829 }
830
831 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size,
832 uint* gc_count_before_ret,
833 uint* gclocker_retry_count_ret) {
834 assert_heap_not_locked_and_not_at_safepoint();
835 assert(!is_humongous(word_size), "attempt_allocation() should not "
836 "be called for humongous allocation requests");
837
838 AllocationContext_t context = AllocationContext::current();
839 HeapWord* result = _allocator->attempt_allocation(word_size, context);
840
841 if (result == NULL) {
842 result = attempt_allocation_slow(word_size,
843 context,
844 gc_count_before_ret,
845 gclocker_retry_count_ret);
846 }
847 assert_heap_not_locked();
848 if (result != NULL) {
849 dirty_young_block(result, word_size);
850 }
851 return result;
852 }
853
854 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
855 assert(!is_init_completed(), "Expect to be called at JVM init time");
856 assert(ranges != NULL, "MemRegion array NULL");
857 assert(count != 0, "No MemRegions provided");
858 MemRegion reserved = _hrm.reserved();
859 HeapWord* prev_last_addr = NULL;
860 HeapRegion* prev_last_region = NULL;
861 size_t size_used = 0;
862 size_t uncommitted_regions = 0;
863
864 // For each Memregion, free the G1 regions that constitute it, and
865 // notify mark-sweep that the range is no longer to be considered 'archive.'
866 MutexLockerEx x(Heap_lock);
867 for (size_t i = 0; i < count; i++) {
868 HeapWord* start_address = ranges[i].start();
869 HeapWord* last_address = ranges[i].last();
870
871 assert(reserved.contains(start_address) && reserved.contains(last_address),
872 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
873 p2i(start_address), p2i(last_address));
874 assert(start_address > prev_last_addr,
875 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
876 p2i(start_address), p2i(prev_last_addr));
877 size_used += ranges[i].byte_size();
878 prev_last_addr = last_address;
879
880 HeapRegion* start_region = _hrm.addr_to_region(start_address);
881 HeapRegion* last_region = _hrm.addr_to_region(last_address);
882
883 // Check for ranges that start in the same G1 region in which the previous
884 // range ended, and adjust the start address so we don't try to free
885 // the same region again. If the current range is entirely within that
886 // region, skip it.
887 if (start_region == prev_last_region) {
888 start_address = start_region->end();
889 if (start_address > last_address) {
890 continue;
891 }
892 start_region = _hrm.addr_to_region(start_address);
893 }
894 prev_last_region = last_region;
895
896 // After verifying that each region was marked as an archive region by
897 // alloc_archive_regions, set it free and empty and uncommit it.
898 HeapRegion* curr_region = start_region;
899 while (curr_region != NULL) {
900 guarantee(curr_region->is_archive(),
901 "Expected archive region at index %u", curr_region->hrm_index());
902 uint curr_index = curr_region->hrm_index();
903 _old_set.remove(curr_region);
904 curr_region->set_free();
905 curr_region->set_top(curr_region->bottom());
906 if (curr_region != last_region) {
907 curr_region = _hrm.next_region_in_heap(curr_region);
908 } else {
909 curr_region = NULL;
910 }
911 _hrm.shrink_at(curr_index, 1);
912 uncommitted_regions++;
913 }
914
915 // Notify mark-sweep that this is no longer an archive range.
916 G1ArchiveAllocator::set_range_archive(ranges[i], false);
917 }
918
919 if (uncommitted_regions != 0) {
920 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
921 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
922 }
923 decrease_used(size_used);
924 }
925
926 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
927 uint* gc_count_before_ret,
928 uint* gclocker_retry_count_ret) {
929 // The structure of this method has a lot of similarities to
930 // attempt_allocation_slow(). The reason these two were not merged
931 // into a single one is that such a method would require several "if
932 // allocation is not humongous do this, otherwise do that"
933 // conditional paths which would obscure its flow. In fact, an early
934 // version of this code did use a unified method which was harder to
935 // follow and, as a result, it had subtle bugs that were hard to
936 // track down. So keeping these two methods separate allows each to
937 // be more readable. It will be good to keep these two in sync as
938 // much as possible.
939
940 assert_heap_not_locked_and_not_at_safepoint();
941 assert(is_humongous(word_size), "attempt_allocation_humongous() "
942 "should only be called for humongous allocations");
943
944 // Humongous objects can exhaust the heap quickly, so we should check if we
945 // need to start a marking cycle at each humongous object allocation. We do
946 // the check before we do the actual allocation. The reason for doing it
947 // before the allocation is that we avoid having to keep track of the newly
948 // allocated memory while we do a GC.
949 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
950 word_size)) {
951 collect(GCCause::_g1_humongous_allocation);
952 }
953
954 // We will loop until a) we manage to successfully perform the
955 // allocation or b) we successfully schedule a collection which
956 // fails to perform the allocation. b) is the only case when we'll
957 // return NULL.
958 HeapWord* result = NULL;
959 for (int try_count = 1; /* we'll return */; try_count += 1) {
960 bool should_try_gc;
961 uint gc_count_before;
962
963 {
964 MutexLockerEx x(Heap_lock);
965
966 // Given that humongous objects are not allocated in young
967 // regions, we'll first try to do the allocation without doing a
968 // collection hoping that there's enough space in the heap.
969 result = humongous_obj_allocate(word_size, AllocationContext::current());
970 if (result != NULL) {
971 size_t size_in_regions = humongous_obj_size_in_regions(word_size);
972 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
973 return result;
974 }
975
976 if (GCLocker::is_active_and_needs_gc()) {
977 should_try_gc = false;
978 } else {
979 // The GCLocker may not be active but the GCLocker initiated
980 // GC may not yet have been performed (GCLocker::needs_gc()
981 // returns true). In this case we do not try this GC and
982 // wait until the GCLocker initiated GC is performed, and
983 // then retry the allocation.
984 if (GCLocker::needs_gc()) {
985 should_try_gc = false;
986 } else {
987 // Read the GC count while still holding the Heap_lock.
988 gc_count_before = total_collections();
989 should_try_gc = true;
990 }
991 }
992 }
993
994 if (should_try_gc) {
995 // If we failed to allocate the humongous object, we should try to
996 // do a collection pause (if we're allowed) in case it reclaims
997 // enough space for the allocation to succeed after the pause.
998
999 bool succeeded;
1000 result = do_collection_pause(word_size, gc_count_before, &succeeded,
1001 GCCause::_g1_humongous_allocation);
1002 if (result != NULL) {
1003 assert(succeeded, "only way to get back a non-NULL result");
1004 return result;
1005 }
1006
1007 if (succeeded) {
1008 // If we get here we successfully scheduled a collection which
1009 // failed to allocate. No point in trying to allocate
1010 // further. We'll just return NULL.
1011 MutexLockerEx x(Heap_lock);
1012 *gc_count_before_ret = total_collections();
1013 return NULL;
1014 }
1015 } else {
1016 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1017 MutexLockerEx x(Heap_lock);
1018 *gc_count_before_ret = total_collections();
1019 return NULL;
1020 }
1021 // The GCLocker is either active or the GCLocker initiated
1022 // GC has not yet been performed. Stall until it is and
1023 // then retry the allocation.
1024 GCLocker::stall_until_clear();
1025 (*gclocker_retry_count_ret) += 1;
1026 }
1027
1028 // We can reach here if we were unsuccessful in scheduling a
1029 // collection (because another thread beat us to it) or if we were
1030 // stalled due to the GC locker. In either can we should retry the
1031 // allocation attempt in case another thread successfully
1032 // performed a collection and reclaimed enough space. Give a
1033 // warning if we seem to be looping forever.
1034
1035 if ((QueuedAllocationWarningCount > 0) &&
1036 (try_count % QueuedAllocationWarningCount == 0)) {
1037 log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() "
1038 "retries %d times", try_count);
1039 }
1040 }
1041
1042 ShouldNotReachHere();
1043 return NULL;
1044 }
1045
1046 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1047 AllocationContext_t context,
1048 bool expect_null_mutator_alloc_region) {
1049 assert_at_safepoint(true /* should_be_vm_thread */);
1050 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region,
1051 "the current alloc region was unexpectedly found to be non-NULL");
1052
1053 if (!is_humongous(word_size)) {
1054 return _allocator->attempt_allocation_locked(word_size, context);
1055 } else {
1056 HeapWord* result = humongous_obj_allocate(word_size, context);
1057 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1058 collector_state()->set_initiate_conc_mark_if_possible(true);
1059 }
1060 return result;
1061 }
1062
1063 ShouldNotReachHere();
1064 }
1065
1066 class PostCompactionPrinterClosure: public HeapRegionClosure {
1067 private:
1068 G1HRPrinter* _hr_printer;
1069 public:
1070 bool doHeapRegion(HeapRegion* hr) {
1071 assert(!hr->is_young(), "not expecting to find young regions");
1072 _hr_printer->post_compaction(hr);
1073 return false;
1074 }
1075
1076 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1077 : _hr_printer(hr_printer) { }
1078 };
1079
1080 void G1CollectedHeap::print_hrm_post_compaction() {
1081 if (_hr_printer.is_active()) {
1082 PostCompactionPrinterClosure cl(hr_printer());
1083 heap_region_iterate(&cl);
1084 }
1085
1086 }
1087
1088 void G1CollectedHeap::abort_concurrent_cycle() {
1089 // Note: When we have a more flexible GC logging framework that
1090 // allows us to add optional attributes to a GC log record we
1091 // could consider timing and reporting how long we wait in the
1092 // following two methods.
1093 wait_while_free_regions_coming();
1094 // If we start the compaction before the CM threads finish
1095 // scanning the root regions we might trip them over as we'll
1096 // be moving objects / updating references. So let's wait until
1097 // they are done. By telling them to abort, they should complete
1098 // early.
1099 _cm->root_regions()->abort();
1100 _cm->root_regions()->wait_until_scan_finished();
1101 append_secondary_free_list_if_not_empty_with_lock();
1102
1103 // Disable discovery and empty the discovered lists
1104 // for the CM ref processor.
1105 ref_processor_cm()->disable_discovery();
1106 ref_processor_cm()->abandon_partial_discovery();
1107 ref_processor_cm()->verify_no_references_recorded();
1108
1109 // Abandon current iterations of concurrent marking and concurrent
1110 // refinement, if any are in progress.
1111 concurrent_mark()->abort();
1112 }
1113
1114 void G1CollectedHeap::prepare_heap_for_full_collection() {
1115 // Make sure we'll choose a new allocation region afterwards.
1116 _allocator->release_mutator_alloc_region();
1117 _allocator->abandon_gc_alloc_regions();
1118 g1_rem_set()->cleanupHRRS();
1119
1120 // We may have added regions to the current incremental collection
1121 // set between the last GC or pause and now. We need to clear the
1122 // incremental collection set and then start rebuilding it afresh
1123 // after this full GC.
1124 abandon_collection_set(collection_set());
1125
1126 tear_down_region_sets(false /* free_list_only */);
1127 collector_state()->set_gcs_are_young(true);
1128 }
1129
1130 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) {
1131 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1132 assert(used() == recalculate_used(), "Should be equal");
1133 _verifier->verify_region_sets_optional();
1134 _verifier->verify_before_gc();
1135 _verifier->check_bitmaps("Full GC Start");
1136 }
1137
1138 void G1CollectedHeap::prepare_heap_for_mutators() {
1139 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1140 ClassLoaderDataGraph::purge();
1141 MetaspaceAux::verify_metrics();
1142
1143 // Prepare heap for normal collections.
1144 assert(num_free_regions() == 0, "we should not have added any free regions");
1145 rebuild_region_sets(false /* free_list_only */);
1146 abort_refinement();
1147 resize_if_necessary_after_full_collection();
1148
1149 // Rebuild the strong code root lists for each region
1150 rebuild_strong_code_roots();
1151
1152 // Start a new incremental collection set for the next pause
1153 start_new_collection_set();
1154
1155 _allocator->init_mutator_alloc_region();
1156
1157 // Post collection state updates.
1158 MetaspaceGC::compute_new_size();
1159 }
1160
1161 void G1CollectedHeap::abort_refinement() {
1162 if (_hot_card_cache->use_cache()) {
1163 _hot_card_cache->reset_hot_cache();
1164 }
1165
1166 // Discard all remembered set updates.
1167 JavaThread::dirty_card_queue_set().abandon_logs();
1168 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1169 }
1170
1171 void G1CollectedHeap::verify_after_full_collection() {
1172 check_gc_time_stamps();
1173 _hrm.verify_optional();
1174 _verifier->verify_region_sets_optional();
1175 _verifier->verify_after_gc();
1176 // Clear the previous marking bitmap, if needed for bitmap verification.
1177 // Note we cannot do this when we clear the next marking bitmap in
1178 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1179 // objects marked during a full GC against the previous bitmap.
1180 // But we need to clear it before calling check_bitmaps below since
1181 // the full GC has compacted objects and updated TAMS but not updated
1182 // the prev bitmap.
1183 if (G1VerifyBitmaps) {
1184 GCTraceTime(Debug, gc)("Clear Bitmap for Verification");
1185 _cm->clear_prev_bitmap(workers());
1186 }
1187 _verifier->check_bitmaps("Full GC End");
1188
1189 // At this point there should be no regions in the
1190 // entire heap tagged as young.
1191 assert(check_young_list_empty(), "young list should be empty at this point");
1192
1193 // Note: since we've just done a full GC, concurrent
1194 // marking is no longer active. Therefore we need not
1195 // re-enable reference discovery for the CM ref processor.
1196 // That will be done at the start of the next marking cycle.
1197 // We also know that the STW processor should no longer
1198 // discover any new references.
1199 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1200 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1201 ref_processor_stw()->verify_no_references_recorded();
1202 ref_processor_cm()->verify_no_references_recorded();
1203 }
1204
1205 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) {
1206 // Post collection logging.
1207 // We should do this after we potentially resize the heap so
1208 // that all the COMMIT / UNCOMMIT events are generated before
1209 // the compaction events.
1210 print_hrm_post_compaction();
1211 heap_transition->print();
1212 print_heap_after_gc();
1213 print_heap_regions();
1214 #ifdef TRACESPINNING
1215 ParallelTaskTerminator::print_termination_counts();
1216 #endif
1217 }
1218
1219 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1220 bool clear_all_soft_refs) {
1221 assert_at_safepoint(true /* should_be_vm_thread */);
1222
1223 if (GCLocker::check_active_before_gc()) {
1224 // Full GC was not completed.
1225 return false;
1226 }
1227
1228 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1229 collector_policy()->should_clear_all_soft_refs();
1230
1231 G1FullCollector collector(this, explicit_gc, do_clear_all_soft_refs);
1232 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1233
1234 collector.prepare_collection();
1235 collector.collect();
1236 collector.complete_collection();
1237
1238 // Full collection was successfully completed.
1239 return true;
1240 }
1241
1242 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1243 // Currently, there is no facility in the do_full_collection(bool) API to notify
1244 // the caller that the collection did not succeed (e.g., because it was locked
1245 // out by the GC locker). So, right now, we'll ignore the return value.
1246 bool dummy = do_full_collection(true, /* explicit_gc */
1247 clear_all_soft_refs);
1248 }
1249
1250 void G1CollectedHeap::resize_if_necessary_after_full_collection() {
1251 // Capacity, free and used after the GC counted as full regions to
1252 // include the waste in the following calculations.
1253 const size_t capacity_after_gc = capacity();
1254 const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes();
1255
1256 // This is enforced in arguments.cpp.
1257 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1258 "otherwise the code below doesn't make sense");
1259
1260 // We don't have floating point command-line arguments
1261 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1262 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1263 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1264 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1265
1266 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1267 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1268
1269 // We have to be careful here as these two calculations can overflow
1270 // 32-bit size_t's.
1271 double used_after_gc_d = (double) used_after_gc;
1272 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1273 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1274
1275 // Let's make sure that they are both under the max heap size, which
1276 // by default will make them fit into a size_t.
1277 double desired_capacity_upper_bound = (double) max_heap_size;
1278 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1279 desired_capacity_upper_bound);
1280 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1281 desired_capacity_upper_bound);
1282
1283 // We can now safely turn them into size_t's.
1284 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1285 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1286
1287 // This assert only makes sense here, before we adjust them
1288 // with respect to the min and max heap size.
1289 assert(minimum_desired_capacity <= maximum_desired_capacity,
1290 "minimum_desired_capacity = " SIZE_FORMAT ", "
1291 "maximum_desired_capacity = " SIZE_FORMAT,
1292 minimum_desired_capacity, maximum_desired_capacity);
1293
1294 // Should not be greater than the heap max size. No need to adjust
1295 // it with respect to the heap min size as it's a lower bound (i.e.,
1296 // we'll try to make the capacity larger than it, not smaller).
1297 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1298 // Should not be less than the heap min size. No need to adjust it
1299 // with respect to the heap max size as it's an upper bound (i.e.,
1300 // we'll try to make the capacity smaller than it, not greater).
1301 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1302
1303 if (capacity_after_gc < minimum_desired_capacity) {
1304 // Don't expand unless it's significant
1305 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1306
1307 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). "
1308 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1309 "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1310 capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio);
1311
1312 expand(expand_bytes, _workers);
1313
1314 // No expansion, now see if we want to shrink
1315 } else if (capacity_after_gc > maximum_desired_capacity) {
1316 // Capacity too large, compute shrinking size
1317 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1318
1319 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). "
1320 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1321 "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1322 capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio);
1323
1324 shrink(shrink_bytes);
1325 }
1326 }
1327
1328 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1329 AllocationContext_t context,
1330 bool do_gc,
1331 bool clear_all_soft_refs,
1332 bool expect_null_mutator_alloc_region,
1333 bool* gc_succeeded) {
1334 *gc_succeeded = true;
1335 // Let's attempt the allocation first.
1336 HeapWord* result =
1337 attempt_allocation_at_safepoint(word_size,
1338 context,
1339 expect_null_mutator_alloc_region);
1340 if (result != NULL) {
1341 assert(*gc_succeeded, "sanity");
1342 return result;
1343 }
1344
1345 // In a G1 heap, we're supposed to keep allocation from failing by
1346 // incremental pauses. Therefore, at least for now, we'll favor
1347 // expansion over collection. (This might change in the future if we can
1348 // do something smarter than full collection to satisfy a failed alloc.)
1349 result = expand_and_allocate(word_size, context);
1350 if (result != NULL) {
1351 assert(*gc_succeeded, "sanity");
1352 return result;
1353 }
1354
1355 if (do_gc) {
1356 // Expansion didn't work, we'll try to do a Full GC.
1357 *gc_succeeded = do_full_collection(false, /* explicit_gc */
1358 clear_all_soft_refs);
1359 }
1360
1361 return NULL;
1362 }
1363
1364 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1365 AllocationContext_t context,
1366 bool* succeeded) {
1367 assert_at_safepoint(true /* should_be_vm_thread */);
1368
1369 // Attempts to allocate followed by Full GC.
1370 HeapWord* result =
1371 satisfy_failed_allocation_helper(word_size,
1372 context,
1373 true, /* do_gc */
1374 false, /* clear_all_soft_refs */
1375 false, /* expect_null_mutator_alloc_region */
1376 succeeded);
1377
1378 if (result != NULL || !*succeeded) {
1379 return result;
1380 }
1381
1382 // Attempts to allocate followed by Full GC that will collect all soft references.
1383 result = satisfy_failed_allocation_helper(word_size,
1384 context,
1385 true, /* do_gc */
1386 true, /* clear_all_soft_refs */
1387 true, /* expect_null_mutator_alloc_region */
1388 succeeded);
1389
1390 if (result != NULL || !*succeeded) {
1391 return result;
1392 }
1393
1394 // Attempts to allocate, no GC
1395 result = satisfy_failed_allocation_helper(word_size,
1396 context,
1397 false, /* do_gc */
1398 false, /* clear_all_soft_refs */
1399 true, /* expect_null_mutator_alloc_region */
1400 succeeded);
1401
1402 if (result != NULL) {
1403 assert(*succeeded, "sanity");
1404 return result;
1405 }
1406
1407 assert(!collector_policy()->should_clear_all_soft_refs(),
1408 "Flag should have been handled and cleared prior to this point");
1409
1410 // What else? We might try synchronous finalization later. If the total
1411 // space available is large enough for the allocation, then a more
1412 // complete compaction phase than we've tried so far might be
1413 // appropriate.
1414 assert(*succeeded, "sanity");
1415 return NULL;
1416 }
1417
1418 // Attempting to expand the heap sufficiently
1419 // to support an allocation of the given "word_size". If
1420 // successful, perform the allocation and return the address of the
1421 // allocated block, or else "NULL".
1422
1423 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1424 assert_at_safepoint(true /* should_be_vm_thread */);
1425
1426 _verifier->verify_region_sets_optional();
1427
1428 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1429 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1430 word_size * HeapWordSize);
1431
1432
1433 if (expand(expand_bytes, _workers)) {
1434 _hrm.verify_optional();
1435 _verifier->verify_region_sets_optional();
1436 return attempt_allocation_at_safepoint(word_size,
1437 context,
1438 false /* expect_null_mutator_alloc_region */);
1439 }
1440 return NULL;
1441 }
1442
1443 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) {
1444 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1445 aligned_expand_bytes = align_up(aligned_expand_bytes,
1446 HeapRegion::GrainBytes);
1447
1448 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B",
1449 expand_bytes, aligned_expand_bytes);
1450
1451 if (is_maximal_no_gc()) {
1452 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1453 return false;
1454 }
1455
1456 double expand_heap_start_time_sec = os::elapsedTime();
1457 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1458 assert(regions_to_expand > 0, "Must expand by at least one region");
1459
1460 uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers);
1461 if (expand_time_ms != NULL) {
1462 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1463 }
1464
1465 if (expanded_by > 0) {
1466 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1467 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1468 g1_policy()->record_new_heap_size(num_regions());
1469 } else {
1470 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1471
1472 // The expansion of the virtual storage space was unsuccessful.
1473 // Let's see if it was because we ran out of swap.
1474 if (G1ExitOnExpansionFailure &&
1475 _hrm.available() >= regions_to_expand) {
1476 // We had head room...
1477 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1478 }
1479 }
1480 return regions_to_expand > 0;
1481 }
1482
1483 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1484 size_t aligned_shrink_bytes =
1485 ReservedSpace::page_align_size_down(shrink_bytes);
1486 aligned_shrink_bytes = align_down(aligned_shrink_bytes,
1487 HeapRegion::GrainBytes);
1488 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1489
1490 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1491 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1492
1493
1494 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",
1495 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1496 if (num_regions_removed > 0) {
1497 g1_policy()->record_new_heap_size(num_regions());
1498 } else {
1499 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1500 }
1501 }
1502
1503 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1504 _verifier->verify_region_sets_optional();
1505
1506 // We should only reach here at the end of a Full GC which means we
1507 // should not not be holding to any GC alloc regions. The method
1508 // below will make sure of that and do any remaining clean up.
1509 _allocator->abandon_gc_alloc_regions();
1510
1511 // Instead of tearing down / rebuilding the free lists here, we
1512 // could instead use the remove_all_pending() method on free_list to
1513 // remove only the ones that we need to remove.
1514 tear_down_region_sets(true /* free_list_only */);
1515 shrink_helper(shrink_bytes);
1516 rebuild_region_sets(true /* free_list_only */);
1517
1518 _hrm.verify_optional();
1519 _verifier->verify_region_sets_optional();
1520 }
1521
1522 // Public methods.
1523
1524 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) :
1525 CollectedHeap(),
1526 _young_gen_sampling_thread(NULL),
1527 _collector_policy(collector_policy),
1528 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1529 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1530 _g1_policy(create_g1_policy(_gc_timer_stw)),
1531 _collection_set(this, _g1_policy),
1532 _dirty_card_queue_set(false),
1533 _is_alive_closure_cm(this),
1534 _is_alive_closure_stw(this),
1535 _ref_processor_cm(NULL),
1536 _ref_processor_stw(NULL),
1537 _bot(NULL),
1538 _hot_card_cache(NULL),
1539 _g1_rem_set(NULL),
1540 _cr(NULL),
1541 _g1mm(NULL),
1542 _preserved_marks_set(true /* in_c_heap */),
1543 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1544 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1545 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1546 _humongous_reclaim_candidates(),
1547 _has_humongous_reclaim_candidates(false),
1548 _archive_allocator(NULL),
1549 _free_regions_coming(false),
1550 _gc_time_stamp(0),
1551 _summary_bytes_used(0),
1552 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1553 _old_evac_stats("Old", OldPLABSize, PLABWeight),
1554 _expand_heap_after_alloc_failure(true),
1555 _old_marking_cycles_started(0),
1556 _old_marking_cycles_completed(0),
1557 _in_cset_fast_test() {
1558
1559 _workers = new WorkGang("GC Thread", ParallelGCThreads,
1560 /* are_GC_task_threads */true,
1561 /* are_ConcurrentGC_threads */false);
1562 _workers->initialize_workers();
1563 _verifier = new G1HeapVerifier(this);
1564
1565 _allocator = G1Allocator::create_allocator(this);
1566
1567 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics());
1568
1569 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1570
1571 // Override the default _filler_array_max_size so that no humongous filler
1572 // objects are created.
1573 _filler_array_max_size = _humongous_object_threshold_in_words;
1574
1575 uint n_queues = ParallelGCThreads;
1576 _task_queues = new RefToScanQueueSet(n_queues);
1577
1578 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1579
1580 for (uint i = 0; i < n_queues; i++) {
1581 RefToScanQueue* q = new RefToScanQueue();
1582 q->initialize();
1583 _task_queues->register_queue(i, q);
1584 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1585 }
1586
1587 // Initialize the G1EvacuationFailureALot counters and flags.
1588 NOT_PRODUCT(reset_evacuation_should_fail();)
1589
1590 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1591 }
1592
1593 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1594 size_t size,
1595 size_t translation_factor) {
1596 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1597 // Allocate a new reserved space, preferring to use large pages.
1598 ReservedSpace rs(size, preferred_page_size);
1599 G1RegionToSpaceMapper* result =
1600 G1RegionToSpaceMapper::create_mapper(rs,
1601 size,
1602 rs.alignment(),
1603 HeapRegion::GrainBytes,
1604 translation_factor,
1605 mtGC);
1606
1607 os::trace_page_sizes_for_requested_size(description,
1608 size,
1609 preferred_page_size,
1610 rs.alignment(),
1611 rs.base(),
1612 rs.size());
1613
1614 return result;
1615 }
1616
1617 jint G1CollectedHeap::initialize_concurrent_refinement() {
1618 jint ecode = JNI_OK;
1619 _cr = G1ConcurrentRefine::create(&ecode);
1620 return ecode;
1621 }
1622
1623 jint G1CollectedHeap::initialize_young_gen_sampling_thread() {
1624 _young_gen_sampling_thread = new G1YoungRemSetSamplingThread();
1625 if (_young_gen_sampling_thread->osthread() == NULL) {
1626 vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread");
1627 return JNI_ENOMEM;
1628 }
1629 return JNI_OK;
1630 }
1631
1632 jint G1CollectedHeap::initialize() {
1633 CollectedHeap::pre_initialize();
1634 os::enable_vtime();
1635
1636 // Necessary to satisfy locking discipline assertions.
1637
1638 MutexLocker x(Heap_lock);
1639
1640 // While there are no constraints in the GC code that HeapWordSize
1641 // be any particular value, there are multiple other areas in the
1642 // system which believe this to be true (e.g. oop->object_size in some
1643 // cases incorrectly returns the size in wordSize units rather than
1644 // HeapWordSize).
1645 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1646
1647 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1648 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1649 size_t heap_alignment = collector_policy()->heap_alignment();
1650
1651 // Ensure that the sizes are properly aligned.
1652 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1653 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1654 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1655
1656 // Reserve the maximum.
1657
1658 // When compressed oops are enabled, the preferred heap base
1659 // is calculated by subtracting the requested size from the
1660 // 32Gb boundary and using the result as the base address for
1661 // heap reservation. If the requested size is not aligned to
1662 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1663 // into the ReservedHeapSpace constructor) then the actual
1664 // base of the reserved heap may end up differing from the
1665 // address that was requested (i.e. the preferred heap base).
1666 // If this happens then we could end up using a non-optimal
1667 // compressed oops mode.
1668
1669 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1670 heap_alignment);
1671
1672 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1673
1674 // Create the barrier set for the entire reserved region.
1675 G1SATBCardTableLoggingModRefBS* bs
1676 = new G1SATBCardTableLoggingModRefBS(reserved_region());
1677 bs->initialize();
1678 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity");
1679 set_barrier_set(bs);
1680
1681 // Create the hot card cache.
1682 _hot_card_cache = new G1HotCardCache(this);
1683
1684 // Carve out the G1 part of the heap.
1685 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1686 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
1687 G1RegionToSpaceMapper* heap_storage =
1688 G1RegionToSpaceMapper::create_mapper(g1_rs,
1689 g1_rs.size(),
1690 page_size,
1691 HeapRegion::GrainBytes,
1692 1,
1693 mtJavaHeap);
1694 os::trace_page_sizes("Heap",
1695 collector_policy()->min_heap_byte_size(),
1696 max_byte_size,
1697 page_size,
1698 heap_rs.base(),
1699 heap_rs.size());
1700 heap_storage->set_mapping_changed_listener(&_listener);
1701
1702 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1703 G1RegionToSpaceMapper* bot_storage =
1704 create_aux_memory_mapper("Block Offset Table",
1705 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1706 G1BlockOffsetTable::heap_map_factor());
1707
1708 G1RegionToSpaceMapper* cardtable_storage =
1709 create_aux_memory_mapper("Card Table",
1710 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize),
1711 G1SATBCardTableLoggingModRefBS::heap_map_factor());
1712
1713 G1RegionToSpaceMapper* card_counts_storage =
1714 create_aux_memory_mapper("Card Counts Table",
1715 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1716 G1CardCounts::heap_map_factor());
1717
1718 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1719 G1RegionToSpaceMapper* prev_bitmap_storage =
1720 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1721 G1RegionToSpaceMapper* next_bitmap_storage =
1722 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1723
1724 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1725 g1_barrier_set()->initialize(cardtable_storage);
1726 // Do later initialization work for concurrent refinement.
1727 _hot_card_cache->initialize(card_counts_storage);
1728
1729 // 6843694 - ensure that the maximum region index can fit
1730 // in the remembered set structures.
1731 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1732 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1733
1734 // Also create a G1 rem set.
1735 _g1_rem_set = new G1RemSet(this, g1_barrier_set(), _hot_card_cache);
1736 _g1_rem_set->initialize(max_capacity(), max_regions());
1737
1738 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1739 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1740 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1741 "too many cards per region");
1742
1743 FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1744
1745 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1746
1747 {
1748 HeapWord* start = _hrm.reserved().start();
1749 HeapWord* end = _hrm.reserved().end();
1750 size_t granularity = HeapRegion::GrainBytes;
1751
1752 _in_cset_fast_test.initialize(start, end, granularity);
1753 _humongous_reclaim_candidates.initialize(start, end, granularity);
1754 }
1755
1756 // Create the G1ConcurrentMark data structure and thread.
1757 // (Must do this late, so that "max_regions" is defined.)
1758 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1759 if (_cm == NULL || !_cm->completed_initialization()) {
1760 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
1761 return JNI_ENOMEM;
1762 }
1763 _cmThread = _cm->cm_thread();
1764
1765 // Now expand into the initial heap size.
1766 if (!expand(init_byte_size, _workers)) {
1767 vm_shutdown_during_initialization("Failed to allocate initial heap.");
1768 return JNI_ENOMEM;
1769 }
1770
1771 // Perform any initialization actions delegated to the policy.
1772 g1_policy()->init(this, &_collection_set);
1773
1774 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1775 SATB_Q_FL_lock,
1776 G1SATBProcessCompletedThreshold,
1777 Shared_SATB_Q_lock);
1778
1779 jint ecode = initialize_concurrent_refinement();
1780 if (ecode != JNI_OK) {
1781 return ecode;
1782 }
1783
1784 ecode = initialize_young_gen_sampling_thread();
1785 if (ecode != JNI_OK) {
1786 return ecode;
1787 }
1788
1789 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1790 DirtyCardQ_FL_lock,
1791 (int)concurrent_refine()->yellow_zone(),
1792 (int)concurrent_refine()->red_zone(),
1793 Shared_DirtyCardQ_lock,
1794 NULL, // fl_owner
1795 true); // init_free_ids
1796
1797 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1798 DirtyCardQ_FL_lock,
1799 -1, // never trigger processing
1800 -1, // no limit on length
1801 Shared_DirtyCardQ_lock,
1802 &JavaThread::dirty_card_queue_set());
1803
1804 // Here we allocate the dummy HeapRegion that is required by the
1805 // G1AllocRegion class.
1806 HeapRegion* dummy_region = _hrm.get_dummy_region();
1807
1808 // We'll re-use the same region whether the alloc region will
1809 // require BOT updates or not and, if it doesn't, then a non-young
1810 // region will complain that it cannot support allocations without
1811 // BOT updates. So we'll tag the dummy region as eden to avoid that.
1812 dummy_region->set_eden();
1813 // Make sure it's full.
1814 dummy_region->set_top(dummy_region->end());
1815 G1AllocRegion::setup(this, dummy_region);
1816
1817 _allocator->init_mutator_alloc_region();
1818
1819 // Do create of the monitoring and management support so that
1820 // values in the heap have been properly initialized.
1821 _g1mm = new G1MonitoringSupport(this);
1822
1823 G1StringDedup::initialize();
1824
1825 _preserved_marks_set.init(ParallelGCThreads);
1826
1827 _collection_set.initialize(max_regions());
1828
1829 return JNI_OK;
1830 }
1831
1832 void G1CollectedHeap::stop() {
1833 // Stop all concurrent threads. We do this to make sure these threads
1834 // do not continue to execute and access resources (e.g. logging)
1835 // that are destroyed during shutdown.
1836 _cr->stop();
1837 _young_gen_sampling_thread->stop();
1838 _cmThread->stop();
1839 if (G1StringDedup::is_enabled()) {
1840 G1StringDedup::stop();
1841 }
1842 }
1843
1844 void G1CollectedHeap::safepoint_synchronize_begin() {
1845 SuspendibleThreadSet::synchronize();
1846 }
1847
1848 void G1CollectedHeap::safepoint_synchronize_end() {
1849 SuspendibleThreadSet::desynchronize();
1850 }
1851
1852 size_t G1CollectedHeap::conservative_max_heap_alignment() {
1853 return HeapRegion::max_region_size();
1854 }
1855
1856 void G1CollectedHeap::post_initialize() {
1857 ref_processing_init();
1858 }
1859
1860 void G1CollectedHeap::ref_processing_init() {
1861 // Reference processing in G1 currently works as follows:
1862 //
1863 // * There are two reference processor instances. One is
1864 // used to record and process discovered references
1865 // during concurrent marking; the other is used to
1866 // record and process references during STW pauses
1867 // (both full and incremental).
1868 // * Both ref processors need to 'span' the entire heap as
1869 // the regions in the collection set may be dotted around.
1870 //
1871 // * For the concurrent marking ref processor:
1872 // * Reference discovery is enabled at initial marking.
1873 // * Reference discovery is disabled and the discovered
1874 // references processed etc during remarking.
1875 // * Reference discovery is MT (see below).
1876 // * Reference discovery requires a barrier (see below).
1877 // * Reference processing may or may not be MT
1878 // (depending on the value of ParallelRefProcEnabled
1879 // and ParallelGCThreads).
1880 // * A full GC disables reference discovery by the CM
1881 // ref processor and abandons any entries on it's
1882 // discovered lists.
1883 //
1884 // * For the STW processor:
1885 // * Non MT discovery is enabled at the start of a full GC.
1886 // * Processing and enqueueing during a full GC is non-MT.
1887 // * During a full GC, references are processed after marking.
1888 //
1889 // * Discovery (may or may not be MT) is enabled at the start
1890 // of an incremental evacuation pause.
1891 // * References are processed near the end of a STW evacuation pause.
1892 // * For both types of GC:
1893 // * Discovery is atomic - i.e. not concurrent.
1894 // * Reference discovery will not need a barrier.
1895
1896 MemRegion mr = reserved_region();
1897
1898 bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1);
1899
1900 // Concurrent Mark ref processor
1901 _ref_processor_cm =
1902 new ReferenceProcessor(mr, // span
1903 mt_processing,
1904 // mt processing
1905 ParallelGCThreads,
1906 // degree of mt processing
1907 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
1908 // mt discovery
1909 MAX2(ParallelGCThreads, ConcGCThreads),
1910 // degree of mt discovery
1911 false,
1912 // Reference discovery is not atomic
1913 &_is_alive_closure_cm);
1914 // is alive closure
1915 // (for efficiency/performance)
1916
1917 // STW ref processor
1918 _ref_processor_stw =
1919 new ReferenceProcessor(mr, // span
1920 mt_processing,
1921 // mt processing
1922 ParallelGCThreads,
1923 // degree of mt processing
1924 (ParallelGCThreads > 1),
1925 // mt discovery
1926 ParallelGCThreads,
1927 // degree of mt discovery
1928 true,
1929 // Reference discovery is atomic
1930 &_is_alive_closure_stw);
1931 // is alive closure
1932 // (for efficiency/performance)
1933 }
1934
1935 CollectorPolicy* G1CollectedHeap::collector_policy() const {
1936 return _collector_policy;
1937 }
1938
1939 size_t G1CollectedHeap::capacity() const {
1940 return _hrm.length() * HeapRegion::GrainBytes;
1941 }
1942
1943 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const {
1944 return _hrm.total_free_bytes();
1945 }
1946
1947 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
1948 hr->reset_gc_time_stamp();
1949 }
1950
1951 #ifndef PRODUCT
1952
1953 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
1954 private:
1955 unsigned _gc_time_stamp;
1956 bool _failures;
1957
1958 public:
1959 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
1960 _gc_time_stamp(gc_time_stamp), _failures(false) { }
1961
1962 virtual bool doHeapRegion(HeapRegion* hr) {
1963 unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
1964 if (_gc_time_stamp != region_gc_time_stamp) {
1965 log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr),
1966 region_gc_time_stamp, _gc_time_stamp);
1967 _failures = true;
1968 }
1969 return false;
1970 }
1971
1972 bool failures() { return _failures; }
1973 };
1974
1975 void G1CollectedHeap::check_gc_time_stamps() {
1976 CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
1977 heap_region_iterate(&cl);
1978 guarantee(!cl.failures(), "all GC time stamps should have been reset");
1979 }
1980 #endif // PRODUCT
1981
1982 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) {
1983 _hot_card_cache->drain(cl, worker_i);
1984 }
1985
1986 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) {
1987 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
1988 size_t n_completed_buffers = 0;
1989 while (dcqs.apply_closure_during_gc(cl, worker_i)) {
1990 n_completed_buffers++;
1991 }
1992 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
1993 dcqs.clear_n_completed_buffers();
1994 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
1995 }
1996
1997 // Computes the sum of the storage used by the various regions.
1998 size_t G1CollectedHeap::used() const {
1999 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
2000 if (_archive_allocator != NULL) {
2001 result += _archive_allocator->used();
2002 }
2003 return result;
2004 }
2005
2006 size_t G1CollectedHeap::used_unlocked() const {
2007 return _summary_bytes_used;
2008 }
2009
2010 class SumUsedClosure: public HeapRegionClosure {
2011 size_t _used;
2012 public:
2013 SumUsedClosure() : _used(0) {}
2014 bool doHeapRegion(HeapRegion* r) {
2015 _used += r->used();
2016 return false;
2017 }
2018 size_t result() { return _used; }
2019 };
2020
2021 size_t G1CollectedHeap::recalculate_used() const {
2022 double recalculate_used_start = os::elapsedTime();
2023
2024 SumUsedClosure blk;
2025 heap_region_iterate(&blk);
2026
2027 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2028 return blk.result();
2029 }
2030
2031 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
2032 switch (cause) {
2033 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2034 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent;
2035 case GCCause::_update_allocation_context_stats_inc: return true;
2036 case GCCause::_wb_conc_mark: return true;
2037 default : return false;
2038 }
2039 }
2040
2041 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2042 switch (cause) {
2043 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2044 case GCCause::_g1_humongous_allocation: return true;
2045 default: return is_user_requested_concurrent_full_gc(cause);
2046 }
2047 }
2048
2049 #ifndef PRODUCT
2050 void G1CollectedHeap::allocate_dummy_regions() {
2051 // Let's fill up most of the region
2052 size_t word_size = HeapRegion::GrainWords - 1024;
2053 // And as a result the region we'll allocate will be humongous.
2054 guarantee(is_humongous(word_size), "sanity");
2055
2056 // _filler_array_max_size is set to humongous object threshold
2057 // but temporarily change it to use CollectedHeap::fill_with_object().
2058 SizeTFlagSetting fs(_filler_array_max_size, word_size);
2059
2060 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2061 // Let's use the existing mechanism for the allocation
2062 HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2063 AllocationContext::system());
2064 if (dummy_obj != NULL) {
2065 MemRegion mr(dummy_obj, word_size);
2066 CollectedHeap::fill_with_object(mr);
2067 } else {
2068 // If we can't allocate once, we probably cannot allocate
2069 // again. Let's get out of the loop.
2070 break;
2071 }
2072 }
2073 }
2074 #endif // !PRODUCT
2075
2076 void G1CollectedHeap::increment_old_marking_cycles_started() {
2077 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2078 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2079 "Wrong marking cycle count (started: %d, completed: %d)",
2080 _old_marking_cycles_started, _old_marking_cycles_completed);
2081
2082 _old_marking_cycles_started++;
2083 }
2084
2085 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2086 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2087
2088 // We assume that if concurrent == true, then the caller is a
2089 // concurrent thread that was joined the Suspendible Thread
2090 // Set. If there's ever a cheap way to check this, we should add an
2091 // assert here.
2092
2093 // Given that this method is called at the end of a Full GC or of a
2094 // concurrent cycle, and those can be nested (i.e., a Full GC can
2095 // interrupt a concurrent cycle), the number of full collections
2096 // completed should be either one (in the case where there was no
2097 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2098 // behind the number of full collections started.
2099
2100 // This is the case for the inner caller, i.e. a Full GC.
2101 assert(concurrent ||
2102 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2103 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2104 "for inner caller (Full GC): _old_marking_cycles_started = %u "
2105 "is inconsistent with _old_marking_cycles_completed = %u",
2106 _old_marking_cycles_started, _old_marking_cycles_completed);
2107
2108 // This is the case for the outer caller, i.e. the concurrent cycle.
2109 assert(!concurrent ||
2110 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2111 "for outer caller (concurrent cycle): "
2112 "_old_marking_cycles_started = %u "
2113 "is inconsistent with _old_marking_cycles_completed = %u",
2114 _old_marking_cycles_started, _old_marking_cycles_completed);
2115
2116 _old_marking_cycles_completed += 1;
2117
2118 // We need to clear the "in_progress" flag in the CM thread before
2119 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2120 // is set) so that if a waiter requests another System.gc() it doesn't
2121 // incorrectly see that a marking cycle is still in progress.
2122 if (concurrent) {
2123 _cmThread->set_idle();
2124 }
2125
2126 // This notify_all() will ensure that a thread that called
2127 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2128 // and it's waiting for a full GC to finish will be woken up. It is
2129 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2130 FullGCCount_lock->notify_all();
2131 }
2132
2133 void G1CollectedHeap::collect(GCCause::Cause cause) {
2134 assert_heap_not_locked();
2135
2136 uint gc_count_before;
2137 uint old_marking_count_before;
2138 uint full_gc_count_before;
2139 bool retry_gc;
2140
2141 do {
2142 retry_gc = false;
2143
2144 {
2145 MutexLocker ml(Heap_lock);
2146
2147 // Read the GC count while holding the Heap_lock
2148 gc_count_before = total_collections();
2149 full_gc_count_before = total_full_collections();
2150 old_marking_count_before = _old_marking_cycles_started;
2151 }
2152
2153 if (should_do_concurrent_full_gc(cause)) {
2154 // Schedule an initial-mark evacuation pause that will start a
2155 // concurrent cycle. We're setting word_size to 0 which means that
2156 // we are not requesting a post-GC allocation.
2157 VM_G1IncCollectionPause op(gc_count_before,
2158 0, /* word_size */
2159 true, /* should_initiate_conc_mark */
2160 g1_policy()->max_pause_time_ms(),
2161 cause);
2162 op.set_allocation_context(AllocationContext::current());
2163
2164 VMThread::execute(&op);
2165 if (!op.pause_succeeded()) {
2166 if (old_marking_count_before == _old_marking_cycles_started) {
2167 retry_gc = op.should_retry_gc();
2168 } else {
2169 // A Full GC happened while we were trying to schedule the
2170 // initial-mark GC. No point in starting a new cycle given
2171 // that the whole heap was collected anyway.
2172 }
2173
2174 if (retry_gc) {
2175 if (GCLocker::is_active_and_needs_gc()) {
2176 GCLocker::stall_until_clear();
2177 }
2178 }
2179 }
2180 } else {
2181 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2182 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2183
2184 // Schedule a standard evacuation pause. We're setting word_size
2185 // to 0 which means that we are not requesting a post-GC allocation.
2186 VM_G1IncCollectionPause op(gc_count_before,
2187 0, /* word_size */
2188 false, /* should_initiate_conc_mark */
2189 g1_policy()->max_pause_time_ms(),
2190 cause);
2191 VMThread::execute(&op);
2192 } else {
2193 // Schedule a Full GC.
2194 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2195 VMThread::execute(&op);
2196 }
2197 }
2198 } while (retry_gc);
2199 }
2200
2201 bool G1CollectedHeap::is_in(const void* p) const {
2202 if (_hrm.reserved().contains(p)) {
2203 // Given that we know that p is in the reserved space,
2204 // heap_region_containing() should successfully
2205 // return the containing region.
2206 HeapRegion* hr = heap_region_containing(p);
2207 return hr->is_in(p);
2208 } else {
2209 return false;
2210 }
2211 }
2212
2213 #ifdef ASSERT
2214 bool G1CollectedHeap::is_in_exact(const void* p) const {
2215 bool contains = reserved_region().contains(p);
2216 bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2217 if (contains && available) {
2218 return true;
2219 } else {
2220 return false;
2221 }
2222 }
2223 #endif
2224
2225 // Iteration functions.
2226
2227 // Iterates an ObjectClosure over all objects within a HeapRegion.
2228
2229 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2230 ObjectClosure* _cl;
2231 public:
2232 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2233 bool doHeapRegion(HeapRegion* r) {
2234 if (!r->is_continues_humongous()) {
2235 r->object_iterate(_cl);
2236 }
2237 return false;
2238 }
2239 };
2240
2241 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2242 IterateObjectClosureRegionClosure blk(cl);
2243 heap_region_iterate(&blk);
2244 }
2245
2246 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2247 _hrm.iterate(cl);
2248 }
2249
2250 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
2251 HeapRegionClaimer *hrclaimer,
2252 uint worker_id) const {
2253 _hrm.par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id));
2254 }
2255
2256 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl,
2257 HeapRegionClaimer *hrclaimer) const {
2258 _hrm.par_iterate(cl, hrclaimer, 0);
2259 }
2260
2261 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2262 _collection_set.iterate(cl);
2263 }
2264
2265 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) {
2266 _collection_set.iterate_from(cl, worker_id, workers()->active_workers());
2267 }
2268
2269 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2270 HeapRegion* hr = heap_region_containing(addr);
2271 return hr->block_start(addr);
2272 }
2273
2274 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2275 HeapRegion* hr = heap_region_containing(addr);
2276 return hr->block_size(addr);
2277 }
2278
2279 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2280 HeapRegion* hr = heap_region_containing(addr);
2281 return hr->block_is_obj(addr);
2282 }
2283
2284 bool G1CollectedHeap::supports_tlab_allocation() const {
2285 return true;
2286 }
2287
2288 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2289 return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2290 }
2291
2292 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2293 return _eden.length() * HeapRegion::GrainBytes;
2294 }
2295
2296 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2297 // must be equal to the humongous object limit.
2298 size_t G1CollectedHeap::max_tlab_size() const {
2299 return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
2300 }
2301
2302 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2303 AllocationContext_t context = AllocationContext::current();
2304 return _allocator->unsafe_max_tlab_alloc(context);
2305 }
2306
2307 size_t G1CollectedHeap::max_capacity() const {
2308 return _hrm.reserved().byte_size();
2309 }
2310
2311 jlong G1CollectedHeap::millis_since_last_gc() {
2312 // See the notes in GenCollectedHeap::millis_since_last_gc()
2313 // for more information about the implementation.
2314 jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) -
2315 _g1_policy->collection_pause_end_millis();
2316 if (ret_val < 0) {
2317 log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
2318 ". returning zero instead.", ret_val);
2319 return 0;
2320 }
2321 return ret_val;
2322 }
2323
2324 void G1CollectedHeap::prepare_for_verify() {
2325 _verifier->prepare_for_verify();
2326 }
2327
2328 void G1CollectedHeap::verify(VerifyOption vo) {
2329 _verifier->verify(vo);
2330 }
2331
2332 bool G1CollectedHeap::supports_concurrent_phase_control() const {
2333 return true;
2334 }
2335
2336 const char* const* G1CollectedHeap::concurrent_phases() const {
2337 return _cmThread->concurrent_phases();
2338 }
2339
2340 bool G1CollectedHeap::request_concurrent_phase(const char* phase) {
2341 return _cmThread->request_concurrent_phase(phase);
2342 }
2343
2344 class PrintRegionClosure: public HeapRegionClosure {
2345 outputStream* _st;
2346 public:
2347 PrintRegionClosure(outputStream* st) : _st(st) {}
2348 bool doHeapRegion(HeapRegion* r) {
2349 r->print_on(_st);
2350 return false;
2351 }
2352 };
2353
2354 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2355 const HeapRegion* hr,
2356 const VerifyOption vo) const {
2357 switch (vo) {
2358 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2359 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2360 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr);
2361 default: ShouldNotReachHere();
2362 }
2363 return false; // keep some compilers happy
2364 }
2365
2366 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2367 const VerifyOption vo) const {
2368 switch (vo) {
2369 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2370 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2371 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj);
2372 default: ShouldNotReachHere();
2373 }
2374 return false; // keep some compilers happy
2375 }
2376
2377 void G1CollectedHeap::print_heap_regions() const {
2378 LogTarget(Trace, gc, heap, region) lt;
2379 if (lt.is_enabled()) {
2380 LogStream ls(lt);
2381 print_regions_on(&ls);
2382 }
2383 }
2384
2385 void G1CollectedHeap::print_on(outputStream* st) const {
2386 st->print(" %-20s", "garbage-first heap");
2387 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2388 capacity()/K, used_unlocked()/K);
2389 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")",
2390 p2i(_hrm.reserved().start()),
2391 p2i(_hrm.reserved().end()));
2392 st->cr();
2393 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2394 uint young_regions = young_regions_count();
2395 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2396 (size_t) young_regions * HeapRegion::GrainBytes / K);
2397 uint survivor_regions = survivor_regions_count();
2398 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2399 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2400 st->cr();
2401 MetaspaceAux::print_on(st);
2402 }
2403
2404 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2405 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2406 "HS=humongous(starts), HC=humongous(continues), "
2407 "CS=collection set, F=free, A=archive, TS=gc time stamp, "
2408 "AC=allocation context, "
2409 "TAMS=top-at-mark-start (previous, next)");
2410 PrintRegionClosure blk(st);
2411 heap_region_iterate(&blk);
2412 }
2413
2414 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2415 print_on(st);
2416
2417 // Print the per-region information.
2418 print_regions_on(st);
2419 }
2420
2421 void G1CollectedHeap::print_on_error(outputStream* st) const {
2422 this->CollectedHeap::print_on_error(st);
2423
2424 if (_cm != NULL) {
2425 st->cr();
2426 _cm->print_on_error(st);
2427 }
2428 }
2429
2430 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2431 workers()->print_worker_threads_on(st);
2432 _cmThread->print_on(st);
2433 st->cr();
2434 _cm->print_worker_threads_on(st);
2435 _cr->print_threads_on(st);
2436 _young_gen_sampling_thread->print_on(st);
2437 if (G1StringDedup::is_enabled()) {
2438 G1StringDedup::print_worker_threads_on(st);
2439 }
2440 }
2441
2442 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2443 workers()->threads_do(tc);
2444 tc->do_thread(_cmThread);
2445 _cm->threads_do(tc);
2446 _cr->threads_do(tc);
2447 tc->do_thread(_young_gen_sampling_thread);
2448 if (G1StringDedup::is_enabled()) {
2449 G1StringDedup::threads_do(tc);
2450 }
2451 }
2452
2453 void G1CollectedHeap::print_tracing_info() const {
2454 g1_rem_set()->print_summary_info();
2455 concurrent_mark()->print_summary_info();
2456 }
2457
2458 #ifndef PRODUCT
2459 // Helpful for debugging RSet issues.
2460
2461 class PrintRSetsClosure : public HeapRegionClosure {
2462 private:
2463 const char* _msg;
2464 size_t _occupied_sum;
2465
2466 public:
2467 bool doHeapRegion(HeapRegion* r) {
2468 HeapRegionRemSet* hrrs = r->rem_set();
2469 size_t occupied = hrrs->occupied();
2470 _occupied_sum += occupied;
2471
2472 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2473 if (occupied == 0) {
2474 tty->print_cr(" RSet is empty");
2475 } else {
2476 hrrs->print();
2477 }
2478 tty->print_cr("----------");
2479 return false;
2480 }
2481
2482 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2483 tty->cr();
2484 tty->print_cr("========================================");
2485 tty->print_cr("%s", msg);
2486 tty->cr();
2487 }
2488
2489 ~PrintRSetsClosure() {
2490 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2491 tty->print_cr("========================================");
2492 tty->cr();
2493 }
2494 };
2495
2496 void G1CollectedHeap::print_cset_rsets() {
2497 PrintRSetsClosure cl("Printing CSet RSets");
2498 collection_set_iterate(&cl);
2499 }
2500
2501 void G1CollectedHeap::print_all_rsets() {
2502 PrintRSetsClosure cl("Printing All RSets");;
2503 heap_region_iterate(&cl);
2504 }
2505 #endif // PRODUCT
2506
2507 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2508
2509 size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes;
2510 size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes;
2511 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2512
2513 size_t eden_capacity_bytes =
2514 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2515
2516 VirtualSpaceSummary heap_summary = create_heap_space_summary();
2517 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2518 eden_capacity_bytes, survivor_used_bytes, num_regions());
2519 }
2520
2521 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2522 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2523 stats->unused(), stats->used(), stats->region_end_waste(),
2524 stats->regions_filled(), stats->direct_allocated(),
2525 stats->failure_used(), stats->failure_waste());
2526 }
2527
2528 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2529 const G1HeapSummary& heap_summary = create_g1_heap_summary();
2530 gc_tracer->report_gc_heap_summary(when, heap_summary);
2531
2532 const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2533 gc_tracer->report_metaspace_summary(when, metaspace_summary);
2534 }
2535
2536 G1CollectedHeap* G1CollectedHeap::heap() {
2537 CollectedHeap* heap = Universe::heap();
2538 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2539 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap");
2540 return (G1CollectedHeap*)heap;
2541 }
2542
2543 void G1CollectedHeap::gc_prologue(bool full) {
2544 // always_do_update_barrier = false;
2545 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2546
2547 // This summary needs to be printed before incrementing total collections.
2548 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2549
2550 // Update common counters.
2551 increment_total_collections(full /* full gc */);
2552 if (full) {
2553 increment_old_marking_cycles_started();
2554 reset_gc_time_stamp();
2555 } else {
2556 increment_gc_time_stamp();
2557 }
2558
2559 // Fill TLAB's and such
2560 double start = os::elapsedTime();
2561 accumulate_statistics_all_tlabs();
2562 ensure_parsability(true);
2563 g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2564 }
2565
2566 void G1CollectedHeap::gc_epilogue(bool full) {
2567 // Update common counters.
2568 if (full) {
2569 // Update the number of full collections that have been completed.
2570 increment_old_marking_cycles_completed(false /* concurrent */);
2571 }
2572
2573 // We are at the end of the GC. Total collections has already been increased.
2574 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2575
2576 // FIXME: what is this about?
2577 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2578 // is set.
2579 #if COMPILER2_OR_JVMCI
2580 assert(DerivedPointerTable::is_empty(), "derived pointer present");
2581 #endif
2582 // always_do_update_barrier = true;
2583
2584 double start = os::elapsedTime();
2585 resize_all_tlabs();
2586 g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2587
2588 allocation_context_stats().update(full);
2589
2590 MemoryService::track_memory_usage();
2591 // We have just completed a GC. Update the soft reference
2592 // policy with the new heap occupancy
2593 Universe::update_heap_info_at_gc();
2594 }
2595
2596 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2597 uint gc_count_before,
2598 bool* succeeded,
2599 GCCause::Cause gc_cause) {
2600 assert_heap_not_locked_and_not_at_safepoint();
2601 VM_G1IncCollectionPause op(gc_count_before,
2602 word_size,
2603 false, /* should_initiate_conc_mark */
2604 g1_policy()->max_pause_time_ms(),
2605 gc_cause);
2606
2607 op.set_allocation_context(AllocationContext::current());
2608 VMThread::execute(&op);
2609
2610 HeapWord* result = op.result();
2611 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
2612 assert(result == NULL || ret_succeeded,
2613 "the result should be NULL if the VM did not succeed");
2614 *succeeded = ret_succeeded;
2615
2616 assert_heap_not_locked();
2617 return result;
2618 }
2619
2620 void
2621 G1CollectedHeap::doConcurrentMark() {
2622 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
2623 if (!_cmThread->in_progress()) {
2624 _cmThread->set_started();
2625 CGC_lock->notify();
2626 }
2627 }
2628
2629 size_t G1CollectedHeap::pending_card_num() {
2630 size_t extra_cards = 0;
2631 JavaThread *curr = Threads::first();
2632 while (curr != NULL) {
2633 DirtyCardQueue& dcq = curr->dirty_card_queue();
2634 extra_cards += dcq.size();
2635 curr = curr->next();
2636 }
2637 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2638 size_t buffer_size = dcqs.buffer_size();
2639 size_t buffer_num = dcqs.completed_buffers_num();
2640
2641 return buffer_size * buffer_num + extra_cards;
2642 }
2643
2644 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
2645 private:
2646 size_t _total_humongous;
2647 size_t _candidate_humongous;
2648
2649 DirtyCardQueue _dcq;
2650
2651 // We don't nominate objects with many remembered set entries, on
2652 // the assumption that such objects are likely still live.
2653 bool is_remset_small(HeapRegion* region) const {
2654 HeapRegionRemSet* const rset = region->rem_set();
2655 return G1EagerReclaimHumongousObjectsWithStaleRefs
2656 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)
2657 : rset->is_empty();
2658 }
2659
2660 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const {
2661 assert(region->is_starts_humongous(), "Must start a humongous object");
2662
2663 oop obj = oop(region->bottom());
2664
2665 // Dead objects cannot be eager reclaim candidates. Due to class
2666 // unloading it is unsafe to query their classes so we return early.
2667 if (heap->is_obj_dead(obj, region)) {
2668 return false;
2669 }
2670
2671 // Candidate selection must satisfy the following constraints
2672 // while concurrent marking is in progress:
2673 //
2674 // * In order to maintain SATB invariants, an object must not be
2675 // reclaimed if it was allocated before the start of marking and
2676 // has not had its references scanned. Such an object must have
2677 // its references (including type metadata) scanned to ensure no
2678 // live objects are missed by the marking process. Objects
2679 // allocated after the start of concurrent marking don't need to
2680 // be scanned.
2681 //
2682 // * An object must not be reclaimed if it is on the concurrent
2683 // mark stack. Objects allocated after the start of concurrent
2684 // marking are never pushed on the mark stack.
2685 //
2686 // Nominating only objects allocated after the start of concurrent
2687 // marking is sufficient to meet both constraints. This may miss
2688 // some objects that satisfy the constraints, but the marking data
2689 // structures don't support efficiently performing the needed
2690 // additional tests or scrubbing of the mark stack.
2691 //
2692 // However, we presently only nominate is_typeArray() objects.
2693 // A humongous object containing references induces remembered
2694 // set entries on other regions. In order to reclaim such an
2695 // object, those remembered sets would need to be cleaned up.
2696 //
2697 // We also treat is_typeArray() objects specially, allowing them
2698 // to be reclaimed even if allocated before the start of
2699 // concurrent mark. For this we rely on mark stack insertion to
2700 // exclude is_typeArray() objects, preventing reclaiming an object
2701 // that is in the mark stack. We also rely on the metadata for
2702 // such objects to be built-in and so ensured to be kept live.
2703 // Frequent allocation and drop of large binary blobs is an
2704 // important use case for eager reclaim, and this special handling
2705 // may reduce needed headroom.
2706
2707 return obj->is_typeArray() && is_remset_small(region);
2708 }
2709
2710 public:
2711 RegisterHumongousWithInCSetFastTestClosure()
2712 : _total_humongous(0),
2713 _candidate_humongous(0),
2714 _dcq(&JavaThread::dirty_card_queue_set()) {
2715 }
2716
2717 virtual bool doHeapRegion(HeapRegion* r) {
2718 if (!r->is_starts_humongous()) {
2719 return false;
2720 }
2721 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2722
2723 bool is_candidate = humongous_region_is_candidate(g1h, r);
2724 uint rindex = r->hrm_index();
2725 g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
2726 if (is_candidate) {
2727 _candidate_humongous++;
2728 g1h->register_humongous_region_with_cset(rindex);
2729 // Is_candidate already filters out humongous object with large remembered sets.
2730 // If we have a humongous object with a few remembered sets, we simply flush these
2731 // remembered set entries into the DCQS. That will result in automatic
2732 // re-evaluation of their remembered set entries during the following evacuation
2733 // phase.
2734 if (!r->rem_set()->is_empty()) {
2735 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
2736 "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
2737 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
2738 HeapRegionRemSetIterator hrrs(r->rem_set());
2739 size_t card_index;
2740 while (hrrs.has_next(card_index)) {
2741 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
2742 // The remembered set might contain references to already freed
2743 // regions. Filter out such entries to avoid failing card table
2744 // verification.
2745 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) {
2746 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
2747 *card_ptr = CardTableModRefBS::dirty_card_val();
2748 _dcq.enqueue(card_ptr);
2749 }
2750 }
2751 }
2752 assert(hrrs.n_yielded() == r->rem_set()->occupied(),
2753 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
2754 hrrs.n_yielded(), r->rem_set()->occupied());
2755 r->rem_set()->clear_locked();
2756 }
2757 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
2758 }
2759 _total_humongous++;
2760
2761 return false;
2762 }
2763
2764 size_t total_humongous() const { return _total_humongous; }
2765 size_t candidate_humongous() const { return _candidate_humongous; }
2766
2767 void flush_rem_set_entries() { _dcq.flush(); }
2768 };
2769
2770 void G1CollectedHeap::register_humongous_regions_with_cset() {
2771 if (!G1EagerReclaimHumongousObjects) {
2772 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
2773 return;
2774 }
2775 double time = os::elapsed_counter();
2776
2777 // Collect reclaim candidate information and register candidates with cset.
2778 RegisterHumongousWithInCSetFastTestClosure cl;
2779 heap_region_iterate(&cl);
2780
2781 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
2782 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
2783 cl.total_humongous(),
2784 cl.candidate_humongous());
2785 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
2786
2787 // Finally flush all remembered set entries to re-check into the global DCQS.
2788 cl.flush_rem_set_entries();
2789 }
2790
2791 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2792 public:
2793 bool doHeapRegion(HeapRegion* hr) {
2794 if (!hr->is_archive() && !hr->is_continues_humongous()) {
2795 hr->verify_rem_set();
2796 }
2797 return false;
2798 }
2799 };
2800
2801 uint G1CollectedHeap::num_task_queues() const {
2802 return _task_queues->size();
2803 }
2804
2805 #if TASKQUEUE_STATS
2806 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2807 st->print_raw_cr("GC Task Stats");
2808 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2809 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2810 }
2811
2812 void G1CollectedHeap::print_taskqueue_stats() const {
2813 if (!log_is_enabled(Trace, gc, task, stats)) {
2814 return;
2815 }
2816 Log(gc, task, stats) log;
2817 ResourceMark rm;
2818 LogStream ls(log.trace());
2819 outputStream* st = &ls;
2820
2821 print_taskqueue_stats_hdr(st);
2822
2823 TaskQueueStats totals;
2824 const uint n = num_task_queues();
2825 for (uint i = 0; i < n; ++i) {
2826 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2827 totals += task_queue(i)->stats;
2828 }
2829 st->print_raw("tot "); totals.print(st); st->cr();
2830
2831 DEBUG_ONLY(totals.verify());
2832 }
2833
2834 void G1CollectedHeap::reset_taskqueue_stats() {
2835 const uint n = num_task_queues();
2836 for (uint i = 0; i < n; ++i) {
2837 task_queue(i)->stats.reset();
2838 }
2839 }
2840 #endif // TASKQUEUE_STATS
2841
2842 void G1CollectedHeap::wait_for_root_region_scanning() {
2843 double scan_wait_start = os::elapsedTime();
2844 // We have to wait until the CM threads finish scanning the
2845 // root regions as it's the only way to ensure that all the
2846 // objects on them have been correctly scanned before we start
2847 // moving them during the GC.
2848 bool waited = _cm->root_regions()->wait_until_scan_finished();
2849 double wait_time_ms = 0.0;
2850 if (waited) {
2851 double scan_wait_end = os::elapsedTime();
2852 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2853 }
2854 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2855 }
2856
2857 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2858 private:
2859 G1HRPrinter* _hr_printer;
2860 public:
2861 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2862
2863 virtual bool doHeapRegion(HeapRegion* r) {
2864 _hr_printer->cset(r);
2865 return false;
2866 }
2867 };
2868
2869 void G1CollectedHeap::start_new_collection_set() {
2870 collection_set()->start_incremental_building();
2871
2872 clear_cset_fast_test();
2873
2874 guarantee(_eden.length() == 0, "eden should have been cleared");
2875 g1_policy()->transfer_survivors_to_cset(survivor());
2876 }
2877
2878 bool
2879 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
2880 assert_at_safepoint(true /* should_be_vm_thread */);
2881 guarantee(!is_gc_active(), "collection is not reentrant");
2882
2883 if (GCLocker::check_active_before_gc()) {
2884 return false;
2885 }
2886
2887 _gc_timer_stw->register_gc_start();
2888
2889 GCIdMark gc_id_mark;
2890 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
2891
2892 SvcGCMarker sgcm(SvcGCMarker::MINOR);
2893 ResourceMark rm;
2894
2895 g1_policy()->note_gc_start();
2896
2897 wait_for_root_region_scanning();
2898
2899 print_heap_before_gc();
2900 print_heap_regions();
2901 trace_heap_before_gc(_gc_tracer_stw);
2902
2903 _verifier->verify_region_sets_optional();
2904 _verifier->verify_dirty_young_regions();
2905
2906 // We should not be doing initial mark unless the conc mark thread is running
2907 if (!_cmThread->should_terminate()) {
2908 // This call will decide whether this pause is an initial-mark
2909 // pause. If it is, during_initial_mark_pause() will return true
2910 // for the duration of this pause.
2911 g1_policy()->decide_on_conc_mark_initiation();
2912 }
2913
2914 // We do not allow initial-mark to be piggy-backed on a mixed GC.
2915 assert(!collector_state()->during_initial_mark_pause() ||
2916 collector_state()->gcs_are_young(), "sanity");
2917
2918 // We also do not allow mixed GCs during marking.
2919 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity");
2920
2921 // Record whether this pause is an initial mark. When the current
2922 // thread has completed its logging output and it's safe to signal
2923 // the CM thread, the flag's value in the policy has been reset.
2924 bool should_start_conc_mark = collector_state()->during_initial_mark_pause();
2925
2926 // Inner scope for scope based logging, timers, and stats collection
2927 {
2928 EvacuationInfo evacuation_info;
2929
2930 if (collector_state()->during_initial_mark_pause()) {
2931 // We are about to start a marking cycle, so we increment the
2932 // full collection counter.
2933 increment_old_marking_cycles_started();
2934 _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
2935 }
2936
2937 _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
2938
2939 GCTraceCPUTime tcpu;
2940
2941 FormatBuffer<> gc_string("Pause ");
2942 if (collector_state()->during_initial_mark_pause()) {
2943 gc_string.append("Initial Mark");
2944 } else if (collector_state()->gcs_are_young()) {
2945 gc_string.append("Young");
2946 } else {
2947 gc_string.append("Mixed");
2948 }
2949 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true);
2950
2951 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
2952 workers()->active_workers(),
2953 Threads::number_of_non_daemon_threads());
2954 workers()->update_active_workers(active_workers);
2955 log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
2956
2957 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
2958 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
2959
2960 // If the secondary_free_list is not empty, append it to the
2961 // free_list. No need to wait for the cleanup operation to finish;
2962 // the region allocation code will check the secondary_free_list
2963 // and wait if necessary. If the G1StressConcRegionFreeing flag is
2964 // set, skip this step so that the region allocation code has to
2965 // get entries from the secondary_free_list.
2966 if (!G1StressConcRegionFreeing) {
2967 append_secondary_free_list_if_not_empty_with_lock();
2968 }
2969
2970 G1HeapTransition heap_transition(this);
2971 size_t heap_used_bytes_before_gc = used();
2972
2973 // Don't dynamically change the number of GC threads this early. A value of
2974 // 0 is used to indicate serial work. When parallel work is done,
2975 // it will be set.
2976
2977 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
2978 IsGCActiveMark x;
2979
2980 gc_prologue(false);
2981
2982 if (VerifyRememberedSets) {
2983 log_info(gc, verify)("[Verifying RemSets before GC]");
2984 VerifyRegionRemSetClosure v_cl;
2985 heap_region_iterate(&v_cl);
2986 }
2987
2988 _verifier->verify_before_gc();
2989
2990 _verifier->check_bitmaps("GC Start");
2991
2992 #if COMPILER2_OR_JVMCI
2993 DerivedPointerTable::clear();
2994 #endif
2995
2996 // Please see comment in g1CollectedHeap.hpp and
2997 // G1CollectedHeap::ref_processing_init() to see how
2998 // reference processing currently works in G1.
2999
3000 // Enable discovery in the STW reference processor
3001 if (g1_policy()->should_process_references()) {
3002 ref_processor_stw()->enable_discovery();
3003 } else {
3004 ref_processor_stw()->disable_discovery();
3005 }
3006
3007 {
3008 // We want to temporarily turn off discovery by the
3009 // CM ref processor, if necessary, and turn it back on
3010 // on again later if we do. Using a scoped
3011 // NoRefDiscovery object will do this.
3012 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3013
3014 // Forget the current alloc region (we might even choose it to be part
3015 // of the collection set!).
3016 _allocator->release_mutator_alloc_region();
3017
3018 // This timing is only used by the ergonomics to handle our pause target.
3019 // It is unclear why this should not include the full pause. We will
3020 // investigate this in CR 7178365.
3021 //
3022 // Preserving the old comment here if that helps the investigation:
3023 //
3024 // The elapsed time induced by the start time below deliberately elides
3025 // the possible verification above.
3026 double sample_start_time_sec = os::elapsedTime();
3027
3028 g1_policy()->record_collection_pause_start(sample_start_time_sec);
3029
3030 if (collector_state()->during_initial_mark_pause()) {
3031 concurrent_mark()->checkpoint_roots_initial_pre();
3032 }
3033
3034 g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor);
3035
3036 evacuation_info.set_collectionset_regions(collection_set()->region_length());
3037
3038 // Make sure the remembered sets are up to date. This needs to be
3039 // done before register_humongous_regions_with_cset(), because the
3040 // remembered sets are used there to choose eager reclaim candidates.
3041 // If the remembered sets are not up to date we might miss some
3042 // entries that need to be handled.
3043 g1_rem_set()->cleanupHRRS();
3044
3045 register_humongous_regions_with_cset();
3046
3047 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table.");
3048
3049 // We call this after finalize_cset() to
3050 // ensure that the CSet has been finalized.
3051 _cm->verify_no_cset_oops();
3052
3053 if (_hr_printer.is_active()) {
3054 G1PrintCollectionSetClosure cl(&_hr_printer);
3055 _collection_set.iterate(&cl);
3056 }
3057
3058 // Initialize the GC alloc regions.
3059 _allocator->init_gc_alloc_regions(evacuation_info);
3060
3061 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length());
3062 pre_evacuate_collection_set();
3063
3064 // Actually do the work...
3065 evacuate_collection_set(evacuation_info, &per_thread_states);
3066
3067 post_evacuate_collection_set(evacuation_info, &per_thread_states);
3068
3069 const size_t* surviving_young_words = per_thread_states.surviving_young_words();
3070 free_collection_set(&_collection_set, evacuation_info, surviving_young_words);
3071
3072 eagerly_reclaim_humongous_regions();
3073
3074 record_obj_copy_mem_stats();
3075 _survivor_evac_stats.adjust_desired_plab_sz();
3076 _old_evac_stats.adjust_desired_plab_sz();
3077
3078 double start = os::elapsedTime();
3079 start_new_collection_set();
3080 g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0);
3081
3082 if (evacuation_failed()) {
3083 set_used(recalculate_used());
3084 if (_archive_allocator != NULL) {
3085 _archive_allocator->clear_used();
3086 }
3087 for (uint i = 0; i < ParallelGCThreads; i++) {
3088 if (_evacuation_failed_info_array[i].has_failed()) {
3089 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3090 }
3091 }
3092 } else {
3093 // The "used" of the the collection set have already been subtracted
3094 // when they were freed. Add in the bytes evacuated.
3095 increase_used(g1_policy()->bytes_copied_during_gc());
3096 }
3097
3098 if (collector_state()->during_initial_mark_pause()) {
3099 // We have to do this before we notify the CM threads that
3100 // they can start working to make sure that all the
3101 // appropriate initialization is done on the CM object.
3102 concurrent_mark()->checkpoint_roots_initial_post();
3103 collector_state()->set_mark_in_progress(true);
3104 // Note that we don't actually trigger the CM thread at
3105 // this point. We do that later when we're sure that
3106 // the current thread has completed its logging output.
3107 }
3108
3109 allocate_dummy_regions();
3110
3111 _allocator->init_mutator_alloc_region();
3112
3113 {
3114 size_t expand_bytes = _heap_sizing_policy->expansion_amount();
3115 if (expand_bytes > 0) {
3116 size_t bytes_before = capacity();
3117 // No need for an ergo logging here,
3118 // expansion_amount() does this when it returns a value > 0.
3119 double expand_ms;
3120 if (!expand(expand_bytes, _workers, &expand_ms)) {
3121 // We failed to expand the heap. Cannot do anything about it.
3122 }
3123 g1_policy()->phase_times()->record_expand_heap_time(expand_ms);
3124 }
3125 }
3126
3127 // We redo the verification but now wrt to the new CSet which
3128 // has just got initialized after the previous CSet was freed.
3129 _cm->verify_no_cset_oops();
3130
3131 // This timing is only used by the ergonomics to handle our pause target.
3132 // It is unclear why this should not include the full pause. We will
3133 // investigate this in CR 7178365.
3134 double sample_end_time_sec = os::elapsedTime();
3135 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3136 size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards);
3137 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc);
3138
3139 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
3140 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc());
3141
3142 if (VerifyRememberedSets) {
3143 log_info(gc, verify)("[Verifying RemSets after GC]");
3144 VerifyRegionRemSetClosure v_cl;
3145 heap_region_iterate(&v_cl);
3146 }
3147
3148 _verifier->verify_after_gc();
3149 _verifier->check_bitmaps("GC End");
3150
3151 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3152 ref_processor_stw()->verify_no_references_recorded();
3153
3154 // CM reference discovery will be re-enabled if necessary.
3155 }
3156
3157 #ifdef TRACESPINNING
3158 ParallelTaskTerminator::print_termination_counts();
3159 #endif
3160
3161 gc_epilogue(false);
3162 }
3163
3164 // Print the remainder of the GC log output.
3165 if (evacuation_failed()) {
3166 log_info(gc)("To-space exhausted");
3167 }
3168
3169 g1_policy()->print_phases();
3170 heap_transition.print();
3171
3172 // It is not yet to safe to tell the concurrent mark to
3173 // start as we have some optional output below. We don't want the
3174 // output from the concurrent mark thread interfering with this
3175 // logging output either.
3176
3177 _hrm.verify_optional();
3178 _verifier->verify_region_sets_optional();
3179
3180 TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3181 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3182
3183 print_heap_after_gc();
3184 print_heap_regions();
3185 trace_heap_after_gc(_gc_tracer_stw);
3186
3187 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3188 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3189 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3190 // before any GC notifications are raised.
3191 g1mm()->update_sizes();
3192
3193 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3194 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
3195 _gc_timer_stw->register_gc_end();
3196 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3197 }
3198 // It should now be safe to tell the concurrent mark thread to start
3199 // without its logging output interfering with the logging output
3200 // that came from the pause.
3201
3202 if (should_start_conc_mark) {
3203 // CAUTION: after the doConcurrentMark() call below,
3204 // the concurrent marking thread(s) could be running
3205 // concurrently with us. Make sure that anything after
3206 // this point does not assume that we are the only GC thread
3207 // running. Note: of course, the actual marking work will
3208 // not start until the safepoint itself is released in
3209 // SuspendibleThreadSet::desynchronize().
3210 doConcurrentMark();
3211 }
3212
3213 return true;
3214 }
3215
3216 void G1CollectedHeap::remove_self_forwarding_pointers() {
3217 G1ParRemoveSelfForwardPtrsTask rsfp_task;
3218 workers()->run_task(&rsfp_task);
3219 }
3220
3221 void G1CollectedHeap::restore_after_evac_failure() {
3222 double remove_self_forwards_start = os::elapsedTime();
3223
3224 remove_self_forwarding_pointers();
3225 SharedRestorePreservedMarksTaskExecutor task_executor(workers());
3226 _preserved_marks_set.restore(&task_executor);
3227
3228 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3229 }
3230
3231 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) {
3232 if (!_evacuation_failed) {
3233 _evacuation_failed = true;
3234 }
3235
3236 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3237 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3238 }
3239
3240 bool G1ParEvacuateFollowersClosure::offer_termination() {
3241 G1ParScanThreadState* const pss = par_scan_state();
3242 start_term_time();
3243 const bool res = terminator()->offer_termination();
3244 end_term_time();
3245 return res;
3246 }
3247
3248 void G1ParEvacuateFollowersClosure::do_void() {
3249 G1ParScanThreadState* const pss = par_scan_state();
3250 pss->trim_queue();
3251 do {
3252 pss->steal_and_trim_queue(queues());
3253 } while (!offer_termination());
3254 }
3255
3256 class G1ParTask : public AbstractGangTask {
3257 protected:
3258 G1CollectedHeap* _g1h;
3259 G1ParScanThreadStateSet* _pss;
3260 RefToScanQueueSet* _queues;
3261 G1RootProcessor* _root_processor;
3262 ParallelTaskTerminator _terminator;
3263 uint _n_workers;
3264
3265 public:
3266 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers)
3267 : AbstractGangTask("G1 collection"),
3268 _g1h(g1h),
3269 _pss(per_thread_states),
3270 _queues(task_queues),
3271 _root_processor(root_processor),
3272 _terminator(n_workers, _queues),
3273 _n_workers(n_workers)
3274 {}
3275
3276 void work(uint worker_id) {
3277 if (worker_id >= _n_workers) return; // no work needed this round
3278
3279 double start_sec = os::elapsedTime();
3280 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec);
3281
3282 {
3283 ResourceMark rm;
3284 HandleMark hm;
3285
3286 ReferenceProcessor* rp = _g1h->ref_processor_stw();
3287
3288 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
3289 pss->set_ref_processor(rp);
3290
3291 double start_strong_roots_sec = os::elapsedTime();
3292
3293 _root_processor->evacuate_roots(pss->closures(), worker_id);
3294
3295 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid
3296 // treating the nmethods visited to act as roots for concurrent marking.
3297 // We only want to make sure that the oops in the nmethods are adjusted with regard to the
3298 // objects copied by the current evacuation.
3299 _g1h->g1_rem_set()->oops_into_collection_set_do(pss,
3300 pss->closures()->weak_codeblobs(),
3301 worker_id);
3302
3303 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec;
3304
3305 double term_sec = 0.0;
3306 size_t evac_term_attempts = 0;
3307 {
3308 double start = os::elapsedTime();
3309 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator);
3310 evac.do_void();
3311
3312 evac_term_attempts = evac.term_attempts();
3313 term_sec = evac.term_time();
3314 double elapsed_sec = os::elapsedTime() - start;
3315 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
3316 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
3317 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts);
3318 }
3319
3320 assert(pss->queue_is_empty(), "should be empty");
3321
3322 if (log_is_enabled(Debug, gc, task, stats)) {
3323 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3324 size_t lab_waste;
3325 size_t lab_undo_waste;
3326 pss->waste(lab_waste, lab_undo_waste);
3327 _g1h->print_termination_stats(worker_id,
3328 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */
3329 strong_roots_sec * 1000.0, /* strong roots time */
3330 term_sec * 1000.0, /* evac term time */
3331 evac_term_attempts, /* evac term attempts */
3332 lab_waste, /* alloc buffer waste */
3333 lab_undo_waste /* undo waste */
3334 );
3335 }
3336
3337 // Close the inner scope so that the ResourceMark and HandleMark
3338 // destructors are executed here and are included as part of the
3339 // "GC Worker Time".
3340 }
3341 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
3342 }
3343 };
3344
3345 void G1CollectedHeap::print_termination_stats_hdr() {
3346 log_debug(gc, task, stats)("GC Termination Stats");
3347 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------");
3348 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo");
3349 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------");
3350 }
3351
3352 void G1CollectedHeap::print_termination_stats(uint worker_id,
3353 double elapsed_ms,
3354 double strong_roots_ms,
3355 double term_ms,
3356 size_t term_attempts,
3357 size_t alloc_buffer_waste,
3358 size_t undo_waste) const {
3359 log_debug(gc, task, stats)
3360 ("%3d %9.2f %9.2f %6.2f "
3361 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
3362 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
3363 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms,
3364 term_ms, term_ms * 100 / elapsed_ms, term_attempts,
3365 (alloc_buffer_waste + undo_waste) * HeapWordSize / K,
3366 alloc_buffer_waste * HeapWordSize / K,
3367 undo_waste * HeapWordSize / K);
3368 }
3369
3370 class G1StringAndSymbolCleaningTask : public AbstractGangTask {
3371 private:
3372 BoolObjectClosure* _is_alive;
3373 G1StringDedupUnlinkOrOopsDoClosure _dedup_closure;
3374
3375 int _initial_string_table_size;
3376 int _initial_symbol_table_size;
3377
3378 bool _process_strings;
3379 int _strings_processed;
3380 int _strings_removed;
3381
3382 bool _process_symbols;
3383 int _symbols_processed;
3384 int _symbols_removed;
3385
3386 bool _process_string_dedup;
3387
3388 public:
3389 G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) :
3390 AbstractGangTask("String/Symbol Unlinking"),
3391 _is_alive(is_alive),
3392 _dedup_closure(is_alive, NULL, false),
3393 _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
3394 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0),
3395 _process_string_dedup(process_string_dedup) {
3396
3397 _initial_string_table_size = StringTable::the_table()->table_size();
3398 _initial_symbol_table_size = SymbolTable::the_table()->table_size();
3399 if (process_strings) {
3400 StringTable::clear_parallel_claimed_index();
3401 }
3402 if (process_symbols) {
3403 SymbolTable::clear_parallel_claimed_index();
3404 }
3405 }
3406
3407 ~G1StringAndSymbolCleaningTask() {
3408 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
3409 "claim value %d after unlink less than initial string table size %d",
3410 StringTable::parallel_claimed_index(), _initial_string_table_size);
3411 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
3412 "claim value %d after unlink less than initial symbol table size %d",
3413 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size);
3414
3415 log_info(gc, stringtable)(
3416 "Cleaned string and symbol table, "
3417 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, "
3418 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
3419 strings_processed(), strings_removed(),
3420 symbols_processed(), symbols_removed());
3421 }
3422
3423 void work(uint worker_id) {
3424 int strings_processed = 0;
3425 int strings_removed = 0;
3426 int symbols_processed = 0;
3427 int symbols_removed = 0;
3428 if (_process_strings) {
3429 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
3430 Atomic::add(strings_processed, &_strings_processed);
3431 Atomic::add(strings_removed, &_strings_removed);
3432 }
3433 if (_process_symbols) {
3434 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
3435 Atomic::add(symbols_processed, &_symbols_processed);
3436 Atomic::add(symbols_removed, &_symbols_removed);
3437 }
3438 if (_process_string_dedup) {
3439 G1StringDedup::parallel_unlink(&_dedup_closure, worker_id);
3440 }
3441 }
3442
3443 size_t strings_processed() const { return (size_t)_strings_processed; }
3444 size_t strings_removed() const { return (size_t)_strings_removed; }
3445
3446 size_t symbols_processed() const { return (size_t)_symbols_processed; }
3447 size_t symbols_removed() const { return (size_t)_symbols_removed; }
3448 };
3449
3450 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
3451 private:
3452 static Monitor* _lock;
3453
3454 BoolObjectClosure* const _is_alive;
3455 const bool _unloading_occurred;
3456 const uint _num_workers;
3457
3458 // Variables used to claim nmethods.
3459 CompiledMethod* _first_nmethod;
3460 CompiledMethod* volatile _claimed_nmethod;
3461
3462 // The list of nmethods that need to be processed by the second pass.
3463 CompiledMethod* volatile _postponed_list;
3464 volatile uint _num_entered_barrier;
3465
3466 public:
3467 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
3468 _is_alive(is_alive),
3469 _unloading_occurred(unloading_occurred),
3470 _num_workers(num_workers),
3471 _first_nmethod(NULL),
3472 _claimed_nmethod(NULL),
3473 _postponed_list(NULL),
3474 _num_entered_barrier(0)
3475 {
3476 CompiledMethod::increase_unloading_clock();
3477 // Get first alive nmethod
3478 CompiledMethodIterator iter = CompiledMethodIterator();
3479 if(iter.next_alive()) {
3480 _first_nmethod = iter.method();
3481 }
3482 _claimed_nmethod = _first_nmethod;
3483 }
3484
3485 ~G1CodeCacheUnloadingTask() {
3486 CodeCache::verify_clean_inline_caches();
3487
3488 CodeCache::set_needs_cache_clean(false);
3489 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
3490
3491 CodeCache::verify_icholder_relocations();
3492 }
3493
3494 private:
3495 void add_to_postponed_list(CompiledMethod* nm) {
3496 CompiledMethod* old;
3497 do {
3498 old = _postponed_list;
3499 nm->set_unloading_next(old);
3500 } while (Atomic::cmpxchg(nm, &_postponed_list, old) != old);
3501 }
3502
3503 void clean_nmethod(CompiledMethod* nm) {
3504 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
3505
3506 if (postponed) {
3507 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
3508 add_to_postponed_list(nm);
3509 }
3510
3511 // Mark that this thread has been cleaned/unloaded.
3512 // After this call, it will be safe to ask if this nmethod was unloaded or not.
3513 nm->set_unloading_clock(CompiledMethod::global_unloading_clock());
3514 }
3515
3516 void clean_nmethod_postponed(CompiledMethod* nm) {
3517 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
3518 }
3519
3520 static const int MaxClaimNmethods = 16;
3521
3522 void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) {
3523 CompiledMethod* first;
3524 CompiledMethodIterator last;
3525
3526 do {
3527 *num_claimed_nmethods = 0;
3528
3529 first = _claimed_nmethod;
3530 last = CompiledMethodIterator(first);
3531
3532 if (first != NULL) {
3533
3534 for (int i = 0; i < MaxClaimNmethods; i++) {
3535 if (!last.next_alive()) {
3536 break;
3537 }
3538 claimed_nmethods[i] = last.method();
3539 (*num_claimed_nmethods)++;
3540 }
3541 }
3542
3543 } while (Atomic::cmpxchg(last.method(), &_claimed_nmethod, first) != first);
3544 }
3545
3546 CompiledMethod* claim_postponed_nmethod() {
3547 CompiledMethod* claim;
3548 CompiledMethod* next;
3549
3550 do {
3551 claim = _postponed_list;
3552 if (claim == NULL) {
3553 return NULL;
3554 }
3555
3556 next = claim->unloading_next();
3557
3558 } while (Atomic::cmpxchg(next, &_postponed_list, claim) != claim);
3559
3560 return claim;
3561 }
3562
3563 public:
3564 // Mark that we're done with the first pass of nmethod cleaning.
3565 void barrier_mark(uint worker_id) {
3566 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3567 _num_entered_barrier++;
3568 if (_num_entered_barrier == _num_workers) {
3569 ml.notify_all();
3570 }
3571 }
3572
3573 // See if we have to wait for the other workers to
3574 // finish their first-pass nmethod cleaning work.
3575 void barrier_wait(uint worker_id) {
3576 if (_num_entered_barrier < _num_workers) {
3577 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3578 while (_num_entered_barrier < _num_workers) {
3579 ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
3580 }
3581 }
3582 }
3583
3584 // Cleaning and unloading of nmethods. Some work has to be postponed
3585 // to the second pass, when we know which nmethods survive.
3586 void work_first_pass(uint worker_id) {
3587 // The first nmethods is claimed by the first worker.
3588 if (worker_id == 0 && _first_nmethod != NULL) {
3589 clean_nmethod(_first_nmethod);
3590 _first_nmethod = NULL;
3591 }
3592
3593 int num_claimed_nmethods;
3594 CompiledMethod* claimed_nmethods[MaxClaimNmethods];
3595
3596 while (true) {
3597 claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
3598
3599 if (num_claimed_nmethods == 0) {
3600 break;
3601 }
3602
3603 for (int i = 0; i < num_claimed_nmethods; i++) {
3604 clean_nmethod(claimed_nmethods[i]);
3605 }
3606 }
3607 }
3608
3609 void work_second_pass(uint worker_id) {
3610 CompiledMethod* nm;
3611 // Take care of postponed nmethods.
3612 while ((nm = claim_postponed_nmethod()) != NULL) {
3613 clean_nmethod_postponed(nm);
3614 }
3615 }
3616 };
3617
3618 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
3619
3620 class G1KlassCleaningTask : public StackObj {
3621 BoolObjectClosure* _is_alive;
3622 volatile int _clean_klass_tree_claimed;
3623 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
3624
3625 public:
3626 G1KlassCleaningTask(BoolObjectClosure* is_alive) :
3627 _is_alive(is_alive),
3628 _clean_klass_tree_claimed(0),
3629 _klass_iterator() {
3630 }
3631
3632 private:
3633 bool claim_clean_klass_tree_task() {
3634 if (_clean_klass_tree_claimed) {
3635 return false;
3636 }
3637
3638 return Atomic::cmpxchg(1, &_clean_klass_tree_claimed, 0) == 0;
3639 }
3640
3641 InstanceKlass* claim_next_klass() {
3642 Klass* klass;
3643 do {
3644 klass =_klass_iterator.next_klass();
3645 } while (klass != NULL && !klass->is_instance_klass());
3646
3647 // this can be null so don't call InstanceKlass::cast
3648 return static_cast<InstanceKlass*>(klass);
3649 }
3650
3651 public:
3652
3653 void clean_klass(InstanceKlass* ik) {
3654 ik->clean_weak_instanceklass_links(_is_alive);
3655 }
3656
3657 void work() {
3658 ResourceMark rm;
3659
3660 // One worker will clean the subklass/sibling klass tree.
3661 if (claim_clean_klass_tree_task()) {
3662 Klass::clean_subklass_tree(_is_alive);
3663 }
3664
3665 // All workers will help cleaning the classes,
3666 InstanceKlass* klass;
3667 while ((klass = claim_next_klass()) != NULL) {
3668 clean_klass(klass);
3669 }
3670 }
3671 };
3672
3673 class G1ResolvedMethodCleaningTask : public StackObj {
3674 BoolObjectClosure* _is_alive;
3675 volatile int _resolved_method_task_claimed;
3676 public:
3677 G1ResolvedMethodCleaningTask(BoolObjectClosure* is_alive) :
3678 _is_alive(is_alive), _resolved_method_task_claimed(0) {}
3679
3680 bool claim_resolved_method_task() {
3681 if (_resolved_method_task_claimed) {
3682 return false;
3683 }
3684 return Atomic::cmpxchg(1, &_resolved_method_task_claimed, 0) == 0;
3685 }
3686
3687 // These aren't big, one thread can do it all.
3688 void work() {
3689 if (claim_resolved_method_task()) {
3690 ResolvedMethodTable::unlink(_is_alive);
3691 }
3692 }
3693 };
3694
3695
3696 // To minimize the remark pause times, the tasks below are done in parallel.
3697 class G1ParallelCleaningTask : public AbstractGangTask {
3698 private:
3699 G1StringAndSymbolCleaningTask _string_symbol_task;
3700 G1CodeCacheUnloadingTask _code_cache_task;
3701 G1KlassCleaningTask _klass_cleaning_task;
3702 G1ResolvedMethodCleaningTask _resolved_method_cleaning_task;
3703
3704 public:
3705 // The constructor is run in the VMThread.
3706 G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) :
3707 AbstractGangTask("Parallel Cleaning"),
3708 _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()),
3709 _code_cache_task(num_workers, is_alive, unloading_occurred),
3710 _klass_cleaning_task(is_alive),
3711 _resolved_method_cleaning_task(is_alive) {
3712 }
3713
3714 // The parallel work done by all worker threads.
3715 void work(uint worker_id) {
3716 // Do first pass of code cache cleaning.
3717 _code_cache_task.work_first_pass(worker_id);
3718
3719 // Let the threads mark that the first pass is done.
3720 _code_cache_task.barrier_mark(worker_id);
3721
3722 // Clean the Strings and Symbols.
3723 _string_symbol_task.work(worker_id);
3724
3725 // Clean unreferenced things in the ResolvedMethodTable
3726 _resolved_method_cleaning_task.work();
3727
3728 // Wait for all workers to finish the first code cache cleaning pass.
3729 _code_cache_task.barrier_wait(worker_id);
3730
3731 // Do the second code cache cleaning work, which realize on
3732 // the liveness information gathered during the first pass.
3733 _code_cache_task.work_second_pass(worker_id);
3734
3735 // Clean all klasses that were not unloaded.
3736 _klass_cleaning_task.work();
3737 }
3738 };
3739
3740
3741 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
3742 bool class_unloading_occurred) {
3743 uint n_workers = workers()->active_workers();
3744
3745 G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred);
3746 workers()->run_task(&g1_unlink_task);
3747 }
3748
3749 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive,
3750 bool process_strings,
3751 bool process_symbols,
3752 bool process_string_dedup) {
3753 if (!process_strings && !process_symbols && !process_string_dedup) {
3754 // Nothing to clean.
3755 return;
3756 }
3757
3758 G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup);
3759 workers()->run_task(&g1_unlink_task);
3760
3761 }
3762
3763 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3764 private:
3765 DirtyCardQueueSet* _queue;
3766 G1CollectedHeap* _g1h;
3767 public:
3768 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"),
3769 _queue(queue), _g1h(g1h) { }
3770
3771 virtual void work(uint worker_id) {
3772 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
3773 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
3774
3775 RedirtyLoggedCardTableEntryClosure cl(_g1h);
3776 _queue->par_apply_closure_to_all_completed_buffers(&cl);
3777
3778 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3779 }
3780 };
3781
3782 void G1CollectedHeap::redirty_logged_cards() {
3783 double redirty_logged_cards_start = os::elapsedTime();
3784
3785 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this);
3786 dirty_card_queue_set().reset_for_par_iteration();
3787 workers()->run_task(&redirty_task);
3788
3789 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
3790 dcq.merge_bufferlists(&dirty_card_queue_set());
3791 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
3792
3793 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3794 }
3795
3796 // Weak Reference Processing support
3797
3798 // An always "is_alive" closure that is used to preserve referents.
3799 // If the object is non-null then it's alive. Used in the preservation
3800 // of referent objects that are pointed to by reference objects
3801 // discovered by the CM ref processor.
3802 class G1AlwaysAliveClosure: public BoolObjectClosure {
3803 G1CollectedHeap* _g1;
3804 public:
3805 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3806 bool do_object_b(oop p) {
3807 if (p != NULL) {
3808 return true;
3809 }
3810 return false;
3811 }
3812 };
3813
3814 bool G1STWIsAliveClosure::do_object_b(oop p) {
3815 // An object is reachable if it is outside the collection set,
3816 // or is inside and copied.
3817 return !_g1->is_in_cset(p) || p->is_forwarded();
3818 }
3819
3820 // Non Copying Keep Alive closure
3821 class G1KeepAliveClosure: public OopClosure {
3822 G1CollectedHeap* _g1;
3823 public:
3824 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3825 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3826 void do_oop(oop* p) {
3827 oop obj = *p;
3828 assert(obj != NULL, "the caller should have filtered out NULL values");
3829
3830 const InCSetState cset_state = _g1->in_cset_state(obj);
3831 if (!cset_state.is_in_cset_or_humongous()) {
3832 return;
3833 }
3834 if (cset_state.is_in_cset()) {
3835 assert( obj->is_forwarded(), "invariant" );
3836 *p = obj->forwardee();
3837 } else {
3838 assert(!obj->is_forwarded(), "invariant" );
3839 assert(cset_state.is_humongous(),
3840 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value());
3841 _g1->set_humongous_is_live(obj);
3842 }
3843 }
3844 };
3845
3846 // Copying Keep Alive closure - can be called from both
3847 // serial and parallel code as long as different worker
3848 // threads utilize different G1ParScanThreadState instances
3849 // and different queues.
3850
3851 class G1CopyingKeepAliveClosure: public OopClosure {
3852 G1CollectedHeap* _g1h;
3853 OopClosure* _copy_non_heap_obj_cl;
3854 G1ParScanThreadState* _par_scan_state;
3855
3856 public:
3857 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3858 OopClosure* non_heap_obj_cl,
3859 G1ParScanThreadState* pss):
3860 _g1h(g1h),
3861 _copy_non_heap_obj_cl(non_heap_obj_cl),
3862 _par_scan_state(pss)
3863 {}
3864
3865 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3866 virtual void do_oop( oop* p) { do_oop_work(p); }
3867
3868 template <class T> void do_oop_work(T* p) {
3869 oop obj = oopDesc::load_decode_heap_oop(p);
3870
3871 if (_g1h->is_in_cset_or_humongous(obj)) {
3872 // If the referent object has been forwarded (either copied
3873 // to a new location or to itself in the event of an
3874 // evacuation failure) then we need to update the reference
3875 // field and, if both reference and referent are in the G1
3876 // heap, update the RSet for the referent.
3877 //
3878 // If the referent has not been forwarded then we have to keep
3879 // it alive by policy. Therefore we have copy the referent.
3880 //
3881 // If the reference field is in the G1 heap then we can push
3882 // on the PSS queue. When the queue is drained (after each
3883 // phase of reference processing) the object and it's followers
3884 // will be copied, the reference field set to point to the
3885 // new location, and the RSet updated. Otherwise we need to
3886 // use the the non-heap or metadata closures directly to copy
3887 // the referent object and update the pointer, while avoiding
3888 // updating the RSet.
3889
3890 if (_g1h->is_in_g1_reserved(p)) {
3891 _par_scan_state->push_on_queue(p);
3892 } else {
3893 assert(!Metaspace::contains((const void*)p),
3894 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p));
3895 _copy_non_heap_obj_cl->do_oop(p);
3896 }
3897 }
3898 }
3899 };
3900
3901 // Serial drain queue closure. Called as the 'complete_gc'
3902 // closure for each discovered list in some of the
3903 // reference processing phases.
3904
3905 class G1STWDrainQueueClosure: public VoidClosure {
3906 protected:
3907 G1CollectedHeap* _g1h;
3908 G1ParScanThreadState* _par_scan_state;
3909
3910 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
3911
3912 public:
3913 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
3914 _g1h(g1h),
3915 _par_scan_state(pss)
3916 { }
3917
3918 void do_void() {
3919 G1ParScanThreadState* const pss = par_scan_state();
3920 pss->trim_queue();
3921 }
3922 };
3923
3924 // Parallel Reference Processing closures
3925
3926 // Implementation of AbstractRefProcTaskExecutor for parallel reference
3927 // processing during G1 evacuation pauses.
3928
3929 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
3930 private:
3931 G1CollectedHeap* _g1h;
3932 G1ParScanThreadStateSet* _pss;
3933 RefToScanQueueSet* _queues;
3934 WorkGang* _workers;
3935 uint _active_workers;
3936
3937 public:
3938 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
3939 G1ParScanThreadStateSet* per_thread_states,
3940 WorkGang* workers,
3941 RefToScanQueueSet *task_queues,
3942 uint n_workers) :
3943 _g1h(g1h),
3944 _pss(per_thread_states),
3945 _queues(task_queues),
3946 _workers(workers),
3947 _active_workers(n_workers)
3948 {
3949 g1h->ref_processor_stw()->set_active_mt_degree(n_workers);
3950 }
3951
3952 // Executes the given task using concurrent marking worker threads.
3953 virtual void execute(ProcessTask& task);
3954 virtual void execute(EnqueueTask& task);
3955 };
3956
3957 // Gang task for possibly parallel reference processing
3958
3959 class G1STWRefProcTaskProxy: public AbstractGangTask {
3960 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
3961 ProcessTask& _proc_task;
3962 G1CollectedHeap* _g1h;
3963 G1ParScanThreadStateSet* _pss;
3964 RefToScanQueueSet* _task_queues;
3965 ParallelTaskTerminator* _terminator;
3966
3967 public:
3968 G1STWRefProcTaskProxy(ProcessTask& proc_task,
3969 G1CollectedHeap* g1h,
3970 G1ParScanThreadStateSet* per_thread_states,
3971 RefToScanQueueSet *task_queues,
3972 ParallelTaskTerminator* terminator) :
3973 AbstractGangTask("Process reference objects in parallel"),
3974 _proc_task(proc_task),
3975 _g1h(g1h),
3976 _pss(per_thread_states),
3977 _task_queues(task_queues),
3978 _terminator(terminator)
3979 {}
3980
3981 virtual void work(uint worker_id) {
3982 // The reference processing task executed by a single worker.
3983 ResourceMark rm;
3984 HandleMark hm;
3985
3986 G1STWIsAliveClosure is_alive(_g1h);
3987
3988 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
3989 pss->set_ref_processor(NULL);
3990
3991 // Keep alive closure.
3992 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
3993
3994 // Complete GC closure
3995 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator);
3996
3997 // Call the reference processing task's work routine.
3998 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
3999
4000 // Note we cannot assert that the refs array is empty here as not all
4001 // of the processing tasks (specifically phase2 - pp2_work) execute
4002 // the complete_gc closure (which ordinarily would drain the queue) so
4003 // the queue may not be empty.
4004 }
4005 };
4006
4007 // Driver routine for parallel reference processing.
4008 // Creates an instance of the ref processing gang
4009 // task and has the worker threads execute it.
4010 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
4011 assert(_workers != NULL, "Need parallel worker threads.");
4012
4013 ParallelTaskTerminator terminator(_active_workers, _queues);
4014 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
4015
4016 _workers->run_task(&proc_task_proxy);
4017 }
4018
4019 // Gang task for parallel reference enqueueing.
4020
4021 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
4022 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
4023 EnqueueTask& _enq_task;
4024
4025 public:
4026 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
4027 AbstractGangTask("Enqueue reference objects in parallel"),
4028 _enq_task(enq_task)
4029 { }
4030
4031 virtual void work(uint worker_id) {
4032 _enq_task.work(worker_id);
4033 }
4034 };
4035
4036 // Driver routine for parallel reference enqueueing.
4037 // Creates an instance of the ref enqueueing gang
4038 // task and has the worker threads execute it.
4039
4040 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
4041 assert(_workers != NULL, "Need parallel worker threads.");
4042
4043 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
4044
4045 _workers->run_task(&enq_task_proxy);
4046 }
4047
4048 // End of weak reference support closures
4049
4050 // Abstract task used to preserve (i.e. copy) any referent objects
4051 // that are in the collection set and are pointed to by reference
4052 // objects discovered by the CM ref processor.
4053
4054 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
4055 protected:
4056 G1CollectedHeap* _g1h;
4057 G1ParScanThreadStateSet* _pss;
4058 RefToScanQueueSet* _queues;
4059 ParallelTaskTerminator _terminator;
4060 uint _n_workers;
4061
4062 public:
4063 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) :
4064 AbstractGangTask("ParPreserveCMReferents"),
4065 _g1h(g1h),
4066 _pss(per_thread_states),
4067 _queues(task_queues),
4068 _terminator(workers, _queues),
4069 _n_workers(workers)
4070 {
4071 g1h->ref_processor_cm()->set_active_mt_degree(workers);
4072 }
4073
4074 void work(uint worker_id) {
4075 G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id);
4076
4077 ResourceMark rm;
4078 HandleMark hm;
4079
4080 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
4081 pss->set_ref_processor(NULL);
4082 assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4083
4084 // Is alive closure
4085 G1AlwaysAliveClosure always_alive(_g1h);
4086
4087 // Copying keep alive closure. Applied to referent objects that need
4088 // to be copied.
4089 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4090
4091 ReferenceProcessor* rp = _g1h->ref_processor_cm();
4092
4093 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
4094 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
4095
4096 // limit is set using max_num_q() - which was set using ParallelGCThreads.
4097 // So this must be true - but assert just in case someone decides to
4098 // change the worker ids.
4099 assert(worker_id < limit, "sanity");
4100 assert(!rp->discovery_is_atomic(), "check this code");
4101
4102 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
4103 for (uint idx = worker_id; idx < limit; idx += stride) {
4104 DiscoveredList& ref_list = rp->discovered_refs()[idx];
4105
4106 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
4107 while (iter.has_next()) {
4108 // Since discovery is not atomic for the CM ref processor, we
4109 // can see some null referent objects.
4110 iter.load_ptrs(DEBUG_ONLY(true));
4111 oop ref = iter.obj();
4112
4113 // This will filter nulls.
4114 if (iter.is_referent_alive()) {
4115 iter.make_referent_alive();
4116 }
4117 iter.move_to_next();
4118 }
4119 }
4120
4121 // Drain the queue - which may cause stealing
4122 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator);
4123 drain_queue.do_void();
4124 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
4125 assert(pss->queue_is_empty(), "should be");
4126 }
4127 };
4128
4129 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) {
4130 // Any reference objects, in the collection set, that were 'discovered'
4131 // by the CM ref processor should have already been copied (either by
4132 // applying the external root copy closure to the discovered lists, or
4133 // by following an RSet entry).
4134 //
4135 // But some of the referents, that are in the collection set, that these
4136 // reference objects point to may not have been copied: the STW ref
4137 // processor would have seen that the reference object had already
4138 // been 'discovered' and would have skipped discovering the reference,
4139 // but would not have treated the reference object as a regular oop.
4140 // As a result the copy closure would not have been applied to the
4141 // referent object.
4142 //
4143 // We need to explicitly copy these referent objects - the references
4144 // will be processed at the end of remarking.
4145 //
4146 // We also need to do this copying before we process the reference
4147 // objects discovered by the STW ref processor in case one of these
4148 // referents points to another object which is also referenced by an
4149 // object discovered by the STW ref processor.
4150 double preserve_cm_referents_time = 0.0;
4151
4152 // To avoid spawning task when there is no work to do, check that
4153 // a concurrent cycle is active and that some references have been
4154 // discovered.
4155 if (concurrent_mark()->cm_thread()->during_cycle() &&
4156 ref_processor_cm()->has_discovered_references()) {
4157 double preserve_cm_referents_start = os::elapsedTime();
4158 uint no_of_gc_workers = workers()->active_workers();
4159 G1ParPreserveCMReferentsTask keep_cm_referents(this,
4160 per_thread_states,
4161 no_of_gc_workers,
4162 _task_queues);
4163 workers()->run_task(&keep_cm_referents);
4164 preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start;
4165 }
4166
4167 g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0);
4168 }
4169
4170 // Weak Reference processing during an evacuation pause (part 1).
4171 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4172 double ref_proc_start = os::elapsedTime();
4173
4174 ReferenceProcessor* rp = _ref_processor_stw;
4175 assert(rp->discovery_enabled(), "should have been enabled");
4176
4177 // Closure to test whether a referent is alive.
4178 G1STWIsAliveClosure is_alive(this);
4179
4180 // Even when parallel reference processing is enabled, the processing
4181 // of JNI refs is serial and performed serially by the current thread
4182 // rather than by a worker. The following PSS will be used for processing
4183 // JNI refs.
4184
4185 // Use only a single queue for this PSS.
4186 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0);
4187 pss->set_ref_processor(NULL);
4188 assert(pss->queue_is_empty(), "pre-condition");
4189
4190 // Keep alive closure.
4191 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss);
4192
4193 // Serial Complete GC closure
4194 G1STWDrainQueueClosure drain_queue(this, pss);
4195
4196 // Setup the soft refs policy...
4197 rp->setup_policy(false);
4198
4199 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times();
4200
4201 ReferenceProcessorStats stats;
4202 if (!rp->processing_is_mt()) {
4203 // Serial reference processing...
4204 stats = rp->process_discovered_references(&is_alive,
4205 &keep_alive,
4206 &drain_queue,
4207 NULL,
4208 pt);
4209 } else {
4210 uint no_of_gc_workers = workers()->active_workers();
4211
4212 // Parallel reference processing
4213 assert(no_of_gc_workers <= rp->max_num_q(),
4214 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4215 no_of_gc_workers, rp->max_num_q());
4216
4217 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers);
4218 stats = rp->process_discovered_references(&is_alive,
4219 &keep_alive,
4220 &drain_queue,
4221 &par_task_executor,
4222 pt);
4223 }
4224
4225 _gc_tracer_stw->report_gc_reference_stats(stats);
4226
4227 // We have completed copying any necessary live referent objects.
4228 assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4229
4230 double ref_proc_time = os::elapsedTime() - ref_proc_start;
4231 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4232 }
4233
4234 // Weak Reference processing during an evacuation pause (part 2).
4235 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4236 double ref_enq_start = os::elapsedTime();
4237
4238 ReferenceProcessor* rp = _ref_processor_stw;
4239 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
4240
4241 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times();
4242
4243 // Now enqueue any remaining on the discovered lists on to
4244 // the pending list.
4245 if (!rp->processing_is_mt()) {
4246 // Serial reference processing...
4247 rp->enqueue_discovered_references(NULL, pt);
4248 } else {
4249 // Parallel reference enqueueing
4250
4251 uint n_workers = workers()->active_workers();
4252
4253 assert(n_workers <= rp->max_num_q(),
4254 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4255 n_workers, rp->max_num_q());
4256
4257 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers);
4258 rp->enqueue_discovered_references(&par_task_executor, pt);
4259 }
4260
4261 rp->verify_no_references_recorded();
4262 assert(!rp->discovery_enabled(), "should have been disabled");
4263
4264 // If during an initial mark pause we install a pending list head which is not otherwise reachable
4265 // ensure that it is marked in the bitmap for concurrent marking to discover.
4266 if (collector_state()->during_initial_mark_pause()) {
4267 oop pll_head = Universe::reference_pending_list();
4268 if (pll_head != NULL) {
4269 _cm->mark_in_next_bitmap(pll_head);
4270 }
4271 }
4272
4273 // FIXME
4274 // CM's reference processing also cleans up the string and symbol tables.
4275 // Should we do that here also? We could, but it is a serial operation
4276 // and could significantly increase the pause time.
4277
4278 double ref_enq_time = os::elapsedTime() - ref_enq_start;
4279 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
4280 }
4281
4282 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
4283 double merge_pss_time_start = os::elapsedTime();
4284 per_thread_states->flush();
4285 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0);
4286 }
4287
4288 void G1CollectedHeap::pre_evacuate_collection_set() {
4289 _expand_heap_after_alloc_failure = true;
4290 _evacuation_failed = false;
4291
4292 // Disable the hot card cache.
4293 _hot_card_cache->reset_hot_cache_claimed_index();
4294 _hot_card_cache->set_use_cache(false);
4295
4296 g1_rem_set()->prepare_for_oops_into_collection_set_do();
4297 _preserved_marks_set.assert_empty();
4298
4299 G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4300
4301 // InitialMark needs claim bits to keep track of the marked-through CLDs.
4302 if (collector_state()->during_initial_mark_pause()) {
4303 double start_clear_claimed_marks = os::elapsedTime();
4304
4305 ClassLoaderDataGraph::clear_claimed_marks();
4306
4307 double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
4308 phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
4309 }
4310 }
4311
4312 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4313 // Should G1EvacuationFailureALot be in effect for this GC?
4314 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
4315
4316 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
4317
4318 G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4319
4320 double start_par_time_sec = os::elapsedTime();
4321 double end_par_time_sec;
4322
4323 {
4324 const uint n_workers = workers()->active_workers();
4325 G1RootProcessor root_processor(this, n_workers);
4326 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers);
4327
4328 print_termination_stats_hdr();
4329
4330 workers()->run_task(&g1_par_task);
4331 end_par_time_sec = os::elapsedTime();
4332
4333 // Closing the inner scope will execute the destructor
4334 // for the G1RootProcessor object. We record the current
4335 // elapsed time before closing the scope so that time
4336 // taken for the destructor is NOT included in the
4337 // reported parallel time.
4338 }
4339
4340 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
4341 phase_times->record_par_time(par_time_ms);
4342
4343 double code_root_fixup_time_ms =
4344 (os::elapsedTime() - end_par_time_sec) * 1000.0;
4345 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
4346 }
4347
4348 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4349 // Process any discovered reference objects - we have
4350 // to do this _before_ we retire the GC alloc regions
4351 // as we may have to copy some 'reachable' referent
4352 // objects (and their reachable sub-graphs) that were
4353 // not copied during the pause.
4354 if (g1_policy()->should_process_references()) {
4355 preserve_cm_referents(per_thread_states);
4356 process_discovered_references(per_thread_states);
4357 } else {
4358 ref_processor_stw()->verify_no_references_recorded();
4359 }
4360
4361 G1STWIsAliveClosure is_alive(this);
4362 G1KeepAliveClosure keep_alive(this);
4363
4364 {
4365 double start = os::elapsedTime();
4366
4367 WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
4368
4369 double time_ms = (os::elapsedTime() - start) * 1000.0;
4370 g1_policy()->phase_times()->record_ref_proc_time(time_ms);
4371 }
4372
4373 if (G1StringDedup::is_enabled()) {
4374 double fixup_start = os::elapsedTime();
4375
4376 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times());
4377
4378 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
4379 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
4380 }
4381
4382 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4383
4384 if (evacuation_failed()) {
4385 restore_after_evac_failure();
4386
4387 // Reset the G1EvacuationFailureALot counters and flags
4388 // Note: the values are reset only when an actual
4389 // evacuation failure occurs.
4390 NOT_PRODUCT(reset_evacuation_should_fail();)
4391 }
4392
4393 _preserved_marks_set.assert_empty();
4394
4395 // Enqueue any remaining references remaining on the STW
4396 // reference processor's discovered lists. We need to do
4397 // this after the card table is cleaned (and verified) as
4398 // the act of enqueueing entries on to the pending list
4399 // will log these updates (and dirty their associated
4400 // cards). We need these updates logged to update any
4401 // RSets.
4402 if (g1_policy()->should_process_references()) {
4403 enqueue_discovered_references(per_thread_states);
4404 } else {
4405 g1_policy()->phase_times()->record_ref_enq_time(0);
4406 }
4407
4408 _allocator->release_gc_alloc_regions(evacuation_info);
4409
4410 merge_per_thread_state_info(per_thread_states);
4411
4412 // Reset and re-enable the hot card cache.
4413 // Note the counts for the cards in the regions in the
4414 // collection set are reset when the collection set is freed.
4415 _hot_card_cache->reset_hot_cache();
4416 _hot_card_cache->set_use_cache(true);
4417
4418 purge_code_root_memory();
4419
4420 redirty_logged_cards();
4421 #if COMPILER2_OR_JVMCI
4422 double start = os::elapsedTime();
4423 DerivedPointerTable::update_pointers();
4424 g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0);
4425 #endif
4426 g1_policy()->print_age_table();
4427 }
4428
4429 void G1CollectedHeap::record_obj_copy_mem_stats() {
4430 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4431
4432 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4433 create_g1_evac_summary(&_old_evac_stats));
4434 }
4435
4436 void G1CollectedHeap::free_region(HeapRegion* hr,
4437 FreeRegionList* free_list,
4438 bool skip_remset,
4439 bool skip_hot_card_cache,
4440 bool locked) {
4441 assert(!hr->is_free(), "the region should not be free");
4442 assert(!hr->is_empty(), "the region should not be empty");
4443 assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
4444 assert(free_list != NULL, "pre-condition");
4445
4446 if (G1VerifyBitmaps) {
4447 MemRegion mr(hr->bottom(), hr->end());
4448 concurrent_mark()->clear_range_in_prev_bitmap(mr);
4449 }
4450
4451 // Clear the card counts for this region.
4452 // Note: we only need to do this if the region is not young
4453 // (since we don't refine cards in young regions).
4454 if (!skip_hot_card_cache && !hr->is_young()) {
4455 _hot_card_cache->reset_card_counts(hr);
4456 }
4457 hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */);
4458 free_list->add_ordered(hr);
4459 }
4460
4461 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4462 FreeRegionList* free_list,
4463 bool skip_remset) {
4464 assert(hr->is_humongous(), "this is only for humongous regions");
4465 assert(free_list != NULL, "pre-condition");
4466 hr->clear_humongous();
4467 free_region(hr, free_list, skip_remset);
4468 }
4469
4470 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4471 const uint humongous_regions_removed) {
4472 if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4473 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4474 _old_set.bulk_remove(old_regions_removed);
4475 _humongous_set.bulk_remove(humongous_regions_removed);
4476 }
4477
4478 }
4479
4480 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4481 assert(list != NULL, "list can't be null");
4482 if (!list->is_empty()) {
4483 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4484 _hrm.insert_list_into_free_list(list);
4485 }
4486 }
4487
4488 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4489 decrease_used(bytes);
4490 }
4491
4492 class G1ParScrubRemSetTask: public AbstractGangTask {
4493 protected:
4494 G1RemSet* _g1rs;
4495 HeapRegionClaimer _hrclaimer;
4496
4497 public:
4498 G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) :
4499 AbstractGangTask("G1 ScrubRS"),
4500 _g1rs(g1_rs),
4501 _hrclaimer(num_workers) {
4502 }
4503
4504 void work(uint worker_id) {
4505 _g1rs->scrub(worker_id, &_hrclaimer);
4506 }
4507 };
4508
4509 void G1CollectedHeap::scrub_rem_set() {
4510 uint num_workers = workers()->active_workers();
4511 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers);
4512 workers()->run_task(&g1_par_scrub_rs_task);
4513 }
4514
4515 class G1FreeCollectionSetTask : public AbstractGangTask {
4516 private:
4517
4518 // Closure applied to all regions in the collection set to do work that needs to
4519 // be done serially in a single thread.
4520 class G1SerialFreeCollectionSetClosure : public HeapRegionClosure {
4521 private:
4522 EvacuationInfo* _evacuation_info;
4523 const size_t* _surviving_young_words;
4524
4525 // Bytes used in successfully evacuated regions before the evacuation.
4526 size_t _before_used_bytes;
4527 // Bytes used in unsucessfully evacuated regions before the evacuation
4528 size_t _after_used_bytes;
4529
4530 size_t _bytes_allocated_in_old_since_last_gc;
4531
4532 size_t _failure_used_words;
4533 size_t _failure_waste_words;
4534
4535 FreeRegionList _local_free_list;
4536 public:
4537 G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4538 HeapRegionClosure(),
4539 _evacuation_info(evacuation_info),
4540 _surviving_young_words(surviving_young_words),
4541 _before_used_bytes(0),
4542 _after_used_bytes(0),
4543 _bytes_allocated_in_old_since_last_gc(0),
4544 _failure_used_words(0),
4545 _failure_waste_words(0),
4546 _local_free_list("Local Region List for CSet Freeing") {
4547 }
4548
4549 virtual bool doHeapRegion(HeapRegion* r) {
4550 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4551
4552 assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index());
4553 g1h->clear_in_cset(r);
4554
4555 if (r->is_young()) {
4556 assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(),
4557 "Young index %d is wrong for region %u of type %s with %u young regions",
4558 r->young_index_in_cset(),
4559 r->hrm_index(),
4560 r->get_type_str(),
4561 g1h->collection_set()->young_region_length());
4562 size_t words_survived = _surviving_young_words[r->young_index_in_cset()];
4563 r->record_surv_words_in_group(words_survived);
4564 }
4565
4566 if (!r->evacuation_failed()) {
4567 assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
4568 _before_used_bytes += r->used();
4569 g1h->free_region(r,
4570 &_local_free_list,
4571 true, /* skip_remset */
4572 true, /* skip_hot_card_cache */
4573 true /* locked */);
4574 } else {
4575 r->uninstall_surv_rate_group();
4576 r->set_young_index_in_cset(-1);
4577 r->set_evacuation_failed(false);
4578 // When moving a young gen region to old gen, we "allocate" that whole region
4579 // there. This is in addition to any already evacuated objects. Notify the
4580 // policy about that.
4581 // Old gen regions do not cause an additional allocation: both the objects
4582 // still in the region and the ones already moved are accounted for elsewhere.
4583 if (r->is_young()) {
4584 _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
4585 }
4586 // The region is now considered to be old.
4587 r->set_old();
4588 // Do some allocation statistics accounting. Regions that failed evacuation
4589 // are always made old, so there is no need to update anything in the young
4590 // gen statistics, but we need to update old gen statistics.
4591 size_t used_words = r->marked_bytes() / HeapWordSize;
4592
4593 _failure_used_words += used_words;
4594 _failure_waste_words += HeapRegion::GrainWords - used_words;
4595
4596 g1h->old_set_add(r);
4597 _after_used_bytes += r->used();
4598 }
4599 return false;
4600 }
4601
4602 void complete_work() {
4603 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4604
4605 _evacuation_info->set_regions_freed(_local_free_list.length());
4606 _evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4607
4608 g1h->prepend_to_freelist(&_local_free_list);
4609 g1h->decrement_summary_bytes(_before_used_bytes);
4610
4611 G1Policy* policy = g1h->g1_policy();
4612 policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4613
4614 g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4615 }
4616 };
4617
4618 G1CollectionSet* _collection_set;
4619 G1SerialFreeCollectionSetClosure _cl;
4620 const size_t* _surviving_young_words;
4621
4622 size_t _rs_lengths;
4623
4624 volatile jint _serial_work_claim;
4625
4626 struct WorkItem {
4627 uint region_idx;
4628 bool is_young;
4629 bool evacuation_failed;
4630
4631 WorkItem(HeapRegion* r) {
4632 region_idx = r->hrm_index();
4633 is_young = r->is_young();
4634 evacuation_failed = r->evacuation_failed();
4635 }
4636 };
4637
4638 volatile size_t _parallel_work_claim;
4639 size_t _num_work_items;
4640 WorkItem* _work_items;
4641
4642 void do_serial_work() {
4643 // Need to grab the lock to be allowed to modify the old region list.
4644 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4645 _collection_set->iterate(&_cl);
4646 }
4647
4648 void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) {
4649 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4650
4651 HeapRegion* r = g1h->region_at(region_idx);
4652 assert(!g1h->is_on_master_free_list(r), "sanity");
4653
4654 Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths);
4655
4656 if (!is_young) {
4657 g1h->_hot_card_cache->reset_card_counts(r);
4658 }
4659
4660 if (!evacuation_failed) {
4661 r->rem_set()->clear_locked();
4662 }
4663 }
4664
4665 class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure {
4666 private:
4667 size_t _cur_idx;
4668 WorkItem* _work_items;
4669 public:
4670 G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { }
4671
4672 virtual bool doHeapRegion(HeapRegion* r) {
4673 _work_items[_cur_idx++] = WorkItem(r);
4674 return false;
4675 }
4676 };
4677
4678 void prepare_work() {
4679 G1PrepareFreeCollectionSetClosure cl(_work_items);
4680 _collection_set->iterate(&cl);
4681 }
4682
4683 void complete_work() {
4684 _cl.complete_work();
4685
4686 G1Policy* policy = G1CollectedHeap::heap()->g1_policy();
4687 policy->record_max_rs_lengths(_rs_lengths);
4688 policy->cset_regions_freed();
4689 }
4690 public:
4691 G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4692 AbstractGangTask("G1 Free Collection Set"),
4693 _cl(evacuation_info, surviving_young_words),
4694 _collection_set(collection_set),
4695 _surviving_young_words(surviving_young_words),
4696 _serial_work_claim(0),
4697 _rs_lengths(0),
4698 _parallel_work_claim(0),
4699 _num_work_items(collection_set->region_length()),
4700 _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) {
4701 prepare_work();
4702 }
4703
4704 ~G1FreeCollectionSetTask() {
4705 complete_work();
4706 FREE_C_HEAP_ARRAY(WorkItem, _work_items);
4707 }
4708
4709 // Chunk size for work distribution. The chosen value has been determined experimentally
4710 // to be a good tradeoff between overhead and achievable parallelism.
4711 static uint chunk_size() { return 32; }
4712
4713 virtual void work(uint worker_id) {
4714 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
4715
4716 // Claim serial work.
4717 if (_serial_work_claim == 0) {
4718 jint value = Atomic::add(1, &_serial_work_claim) - 1;
4719 if (value == 0) {
4720 double serial_time = os::elapsedTime();
4721 do_serial_work();
4722 timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0);
4723 }
4724 }
4725
4726 // Start parallel work.
4727 double young_time = 0.0;
4728 bool has_young_time = false;
4729 double non_young_time = 0.0;
4730 bool has_non_young_time = false;
4731
4732 while (true) {
4733 size_t end = Atomic::add(chunk_size(), &_parallel_work_claim);
4734 size_t cur = end - chunk_size();
4735
4736 if (cur >= _num_work_items) {
4737 break;
4738 }
4739
4740 double start_time = os::elapsedTime();
4741
4742 end = MIN2(end, _num_work_items);
4743
4744 for (; cur < end; cur++) {
4745 bool is_young = _work_items[cur].is_young;
4746
4747 do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed);
4748
4749 double end_time = os::elapsedTime();
4750 double time_taken = end_time - start_time;
4751 if (is_young) {
4752 young_time += time_taken;
4753 has_young_time = true;
4754 } else {
4755 non_young_time += time_taken;
4756 has_non_young_time = true;
4757 }
4758 start_time = end_time;
4759 }
4760 }
4761
4762 if (has_young_time) {
4763 timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time);
4764 }
4765 if (has_non_young_time) {
4766 timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, young_time);
4767 }
4768 }
4769 };
4770
4771 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4772 _eden.clear();
4773
4774 double free_cset_start_time = os::elapsedTime();
4775
4776 {
4777 uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U);
4778 uint const num_workers = MIN2(workers()->active_workers(), num_chunks);
4779
4780 G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words);
4781
4782 log_debug(gc, ergo)("Running %s using %u workers for collection set length %u",
4783 cl.name(),
4784 num_workers,
4785 _collection_set.region_length());
4786 workers()->run_task(&cl, num_workers);
4787 }
4788 g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0);
4789
4790 collection_set->clear();
4791 }
4792
4793 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4794 private:
4795 FreeRegionList* _free_region_list;
4796 HeapRegionSet* _proxy_set;
4797 uint _humongous_objects_reclaimed;
4798 uint _humongous_regions_reclaimed;
4799 size_t _freed_bytes;
4800 public:
4801
4802 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4803 _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) {
4804 }
4805
4806 virtual bool doHeapRegion(HeapRegion* r) {
4807 if (!r->is_starts_humongous()) {
4808 return false;
4809 }
4810
4811 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4812
4813 oop obj = (oop)r->bottom();
4814 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap();
4815
4816 // The following checks whether the humongous object is live are sufficient.
4817 // The main additional check (in addition to having a reference from the roots
4818 // or the young gen) is whether the humongous object has a remembered set entry.
4819 //
4820 // A humongous object cannot be live if there is no remembered set for it
4821 // because:
4822 // - there can be no references from within humongous starts regions referencing
4823 // the object because we never allocate other objects into them.
4824 // (I.e. there are no intra-region references that may be missed by the
4825 // remembered set)
4826 // - as soon there is a remembered set entry to the humongous starts region
4827 // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4828 // until the end of a concurrent mark.
4829 //
4830 // It is not required to check whether the object has been found dead by marking
4831 // or not, in fact it would prevent reclamation within a concurrent cycle, as
4832 // all objects allocated during that time are considered live.
4833 // SATB marking is even more conservative than the remembered set.
4834 // So if at this point in the collection there is no remembered set entry,
4835 // nobody has a reference to it.
4836 // At the start of collection we flush all refinement logs, and remembered sets
4837 // are completely up-to-date wrt to references to the humongous object.
4838 //
4839 // Other implementation considerations:
4840 // - never consider object arrays at this time because they would pose
4841 // considerable effort for cleaning up the the remembered sets. This is
4842 // required because stale remembered sets might reference locations that
4843 // are currently allocated into.
4844 uint region_idx = r->hrm_index();
4845 if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4846 !r->rem_set()->is_empty()) {
4847 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",
4848 region_idx,
4849 (size_t)obj->size() * HeapWordSize,
4850 p2i(r->bottom()),
4851 r->rem_set()->occupied(),
4852 r->rem_set()->strong_code_roots_list_length(),
4853 next_bitmap->is_marked(r->bottom()),
4854 g1h->is_humongous_reclaim_candidate(region_idx),
4855 obj->is_typeArray()
4856 );
4857 return false;
4858 }
4859
4860 guarantee(obj->is_typeArray(),
4861 "Only eagerly reclaiming type arrays is supported, but the object "
4862 PTR_FORMAT " is not.", p2i(r->bottom()));
4863
4864 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",
4865 region_idx,
4866 (size_t)obj->size() * HeapWordSize,
4867 p2i(r->bottom()),
4868 r->rem_set()->occupied(),
4869 r->rem_set()->strong_code_roots_list_length(),
4870 next_bitmap->is_marked(r->bottom()),
4871 g1h->is_humongous_reclaim_candidate(region_idx),
4872 obj->is_typeArray()
4873 );
4874
4875 // Need to clear mark bit of the humongous object if already set.
4876 if (next_bitmap->is_marked(r->bottom())) {
4877 next_bitmap->clear(r->bottom());
4878 }
4879 _humongous_objects_reclaimed++;
4880 do {
4881 HeapRegion* next = g1h->next_region_in_humongous(r);
4882 _freed_bytes += r->used();
4883 r->set_containing_set(NULL);
4884 _humongous_regions_reclaimed++;
4885 g1h->free_humongous_region(r, _free_region_list, false /* skip_remset */ );
4886 r = next;
4887 } while (r != NULL);
4888
4889 return false;
4890 }
4891
4892 uint humongous_objects_reclaimed() {
4893 return _humongous_objects_reclaimed;
4894 }
4895
4896 uint humongous_regions_reclaimed() {
4897 return _humongous_regions_reclaimed;
4898 }
4899
4900 size_t bytes_freed() const {
4901 return _freed_bytes;
4902 }
4903 };
4904
4905 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4906 assert_at_safepoint(true);
4907
4908 if (!G1EagerReclaimHumongousObjects ||
4909 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
4910 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
4911 return;
4912 }
4913
4914 double start_time = os::elapsedTime();
4915
4916 FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
4917
4918 G1FreeHumongousRegionClosure cl(&local_cleanup_list);
4919 heap_region_iterate(&cl);
4920
4921 remove_from_old_sets(0, cl.humongous_regions_reclaimed());
4922
4923 G1HRPrinter* hrp = hr_printer();
4924 if (hrp->is_active()) {
4925 FreeRegionListIterator iter(&local_cleanup_list);
4926 while (iter.more_available()) {
4927 HeapRegion* hr = iter.get_next();
4928 hrp->cleanup(hr);
4929 }
4930 }
4931
4932 prepend_to_freelist(&local_cleanup_list);
4933 decrement_summary_bytes(cl.bytes_freed());
4934
4935 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
4936 cl.humongous_objects_reclaimed());
4937 }
4938
4939 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
4940 public:
4941 virtual bool doHeapRegion(HeapRegion* r) {
4942 assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
4943 G1CollectedHeap::heap()->clear_in_cset(r);
4944 r->set_young_index_in_cset(-1);
4945 return false;
4946 }
4947 };
4948
4949 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
4950 G1AbandonCollectionSetClosure cl;
4951 collection_set->iterate(&cl);
4952
4953 collection_set->clear();
4954 collection_set->stop_incremental_building();
4955 }
4956
4957 void G1CollectedHeap::set_free_regions_coming() {
4958 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming");
4959
4960 assert(!free_regions_coming(), "pre-condition");
4961 _free_regions_coming = true;
4962 }
4963
4964 void G1CollectedHeap::reset_free_regions_coming() {
4965 assert(free_regions_coming(), "pre-condition");
4966
4967 {
4968 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
4969 _free_regions_coming = false;
4970 SecondaryFreeList_lock->notify_all();
4971 }
4972
4973 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming");
4974 }
4975
4976 void G1CollectedHeap::wait_while_free_regions_coming() {
4977 // Most of the time we won't have to wait, so let's do a quick test
4978 // first before we take the lock.
4979 if (!free_regions_coming()) {
4980 return;
4981 }
4982
4983 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions");
4984
4985 {
4986 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
4987 while (free_regions_coming()) {
4988 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
4989 }
4990 }
4991
4992 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions");
4993 }
4994
4995 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
4996 return _allocator->is_retained_old_region(hr);
4997 }
4998
4999 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
5000 _eden.add(hr);
5001 _g1_policy->set_region_eden(hr);
5002 }
5003
5004 #ifdef ASSERT
5005
5006 class NoYoungRegionsClosure: public HeapRegionClosure {
5007 private:
5008 bool _success;
5009 public:
5010 NoYoungRegionsClosure() : _success(true) { }
5011 bool doHeapRegion(HeapRegion* r) {
5012 if (r->is_young()) {
5013 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
5014 p2i(r->bottom()), p2i(r->end()));
5015 _success = false;
5016 }
5017 return false;
5018 }
5019 bool success() { return _success; }
5020 };
5021
5022 bool G1CollectedHeap::check_young_list_empty() {
5023 bool ret = (young_regions_count() == 0);
5024
5025 NoYoungRegionsClosure closure;
5026 heap_region_iterate(&closure);
5027 ret = ret && closure.success();
5028
5029 return ret;
5030 }
5031
5032 #endif // ASSERT
5033
5034 class TearDownRegionSetsClosure : public HeapRegionClosure {
5035 private:
5036 HeapRegionSet *_old_set;
5037
5038 public:
5039 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
5040
5041 bool doHeapRegion(HeapRegion* r) {
5042 if (r->is_old()) {
5043 _old_set->remove(r);
5044 } else if(r->is_young()) {
5045 r->uninstall_surv_rate_group();
5046 } else {
5047 // We ignore free regions, we'll empty the free list afterwards.
5048 // We ignore humongous regions, we're not tearing down the
5049 // humongous regions set.
5050 assert(r->is_free() || r->is_humongous(),
5051 "it cannot be another type");
5052 }
5053 return false;
5054 }
5055
5056 ~TearDownRegionSetsClosure() {
5057 assert(_old_set->is_empty(), "post-condition");
5058 }
5059 };
5060
5061 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
5062 assert_at_safepoint(true /* should_be_vm_thread */);
5063
5064 if (!free_list_only) {
5065 TearDownRegionSetsClosure cl(&_old_set);
5066 heap_region_iterate(&cl);
5067
5068 // Note that emptying the _young_list is postponed and instead done as
5069 // the first step when rebuilding the regions sets again. The reason for
5070 // this is that during a full GC string deduplication needs to know if
5071 // a collected region was young or old when the full GC was initiated.
5072 }
5073 _hrm.remove_all_free_regions();
5074 }
5075
5076 void G1CollectedHeap::increase_used(size_t bytes) {
5077 _summary_bytes_used += bytes;
5078 }
5079
5080 void G1CollectedHeap::decrease_used(size_t bytes) {
5081 assert(_summary_bytes_used >= bytes,
5082 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
5083 _summary_bytes_used, bytes);
5084 _summary_bytes_used -= bytes;
5085 }
5086
5087 void G1CollectedHeap::set_used(size_t bytes) {
5088 _summary_bytes_used = bytes;
5089 }
5090
5091 class RebuildRegionSetsClosure : public HeapRegionClosure {
5092 private:
5093 bool _free_list_only;
5094 HeapRegionSet* _old_set;
5095 HeapRegionManager* _hrm;
5096 size_t _total_used;
5097
5098 public:
5099 RebuildRegionSetsClosure(bool free_list_only,
5100 HeapRegionSet* old_set, HeapRegionManager* hrm) :
5101 _free_list_only(free_list_only),
5102 _old_set(old_set), _hrm(hrm), _total_used(0) {
5103 assert(_hrm->num_free_regions() == 0, "pre-condition");
5104 if (!free_list_only) {
5105 assert(_old_set->is_empty(), "pre-condition");
5106 }
5107 }
5108
5109 bool doHeapRegion(HeapRegion* r) {
5110 if (r->is_empty()) {
5111 // Add free regions to the free list
5112 r->set_free();
5113 r->set_allocation_context(AllocationContext::system());
5114 _hrm->insert_into_free_list(r);
5115 } else if (!_free_list_only) {
5116
5117 if (r->is_humongous()) {
5118 // We ignore humongous regions. We left the humongous set unchanged.
5119 } else {
5120 assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
5121 // We now move all (non-humongous, non-old) regions to old gen, and register them as such.
5122 r->move_to_old();
5123 _old_set->add(r);
5124 }
5125 _total_used += r->used();
5126 }
5127
5128 return false;
5129 }
5130
5131 size_t total_used() {
5132 return _total_used;
5133 }
5134 };
5135
5136 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
5137 assert_at_safepoint(true /* should_be_vm_thread */);
5138
5139 if (!free_list_only) {
5140 _eden.clear();
5141 _survivor.clear();
5142 }
5143
5144 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
5145 heap_region_iterate(&cl);
5146
5147 if (!free_list_only) {
5148 set_used(cl.total_used());
5149 if (_archive_allocator != NULL) {
5150 _archive_allocator->clear_used();
5151 }
5152 }
5153 assert(used_unlocked() == recalculate_used(),
5154 "inconsistent used_unlocked(), "
5155 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT,
5156 used_unlocked(), recalculate_used());
5157 }
5158
5159 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
5160 HeapRegion* hr = heap_region_containing(p);
5161 return hr->is_in(p);
5162 }
5163
5164 // Methods for the mutator alloc region
5165
5166 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
5167 bool force) {
5168 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5169 bool should_allocate = g1_policy()->should_allocate_mutator_region();
5170 if (force || should_allocate) {
5171 HeapRegion* new_alloc_region = new_region(word_size,
5172 false /* is_old */,
5173 false /* do_expand */);
5174 if (new_alloc_region != NULL) {
5175 set_region_short_lived_locked(new_alloc_region);
5176 _hr_printer.alloc(new_alloc_region, !should_allocate);
5177 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
5178 return new_alloc_region;
5179 }
5180 }
5181 return NULL;
5182 }
5183
5184 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
5185 size_t allocated_bytes) {
5186 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5187 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
5188
5189 collection_set()->add_eden_region(alloc_region);
5190 increase_used(allocated_bytes);
5191 _hr_printer.retire(alloc_region);
5192 // We update the eden sizes here, when the region is retired,
5193 // instead of when it's allocated, since this is the point that its
5194 // used space has been recored in _summary_bytes_used.
5195 g1mm()->update_eden_size();
5196 }
5197
5198 // Methods for the GC alloc regions
5199
5200 bool G1CollectedHeap::has_more_regions(InCSetState dest) {
5201 if (dest.is_old()) {
5202 return true;
5203 } else {
5204 return survivor_regions_count() < g1_policy()->max_survivor_regions();
5205 }
5206 }
5207
5208 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) {
5209 assert(FreeList_lock->owned_by_self(), "pre-condition");
5210
5211 if (!has_more_regions(dest)) {
5212 return NULL;
5213 }
5214
5215 const bool is_survivor = dest.is_young();
5216
5217 HeapRegion* new_alloc_region = new_region(word_size,
5218 !is_survivor,
5219 true /* do_expand */);
5220 if (new_alloc_region != NULL) {
5221 // We really only need to do this for old regions given that we
5222 // should never scan survivors. But it doesn't hurt to do it
5223 // for survivors too.
5224 new_alloc_region->record_timestamp();
5225 if (is_survivor) {
5226 new_alloc_region->set_survivor();
5227 _survivor.add(new_alloc_region);
5228 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
5229 } else {
5230 new_alloc_region->set_old();
5231 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
5232 }
5233 _hr_printer.alloc(new_alloc_region);
5234 bool during_im = collector_state()->during_initial_mark_pause();
5235 new_alloc_region->note_start_of_copying(during_im);
5236 return new_alloc_region;
5237 }
5238 return NULL;
5239 }
5240
5241 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
5242 size_t allocated_bytes,
5243 InCSetState dest) {
5244 bool during_im = collector_state()->during_initial_mark_pause();
5245 alloc_region->note_end_of_copying(during_im);
5246 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
5247 if (dest.is_old()) {
5248 _old_set.add(alloc_region);
5249 }
5250 _hr_printer.retire(alloc_region);
5251 }
5252
5253 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
5254 bool expanded = false;
5255 uint index = _hrm.find_highest_free(&expanded);
5256
5257 if (index != G1_NO_HRM_INDEX) {
5258 if (expanded) {
5259 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
5260 HeapRegion::GrainWords * HeapWordSize);
5261 }
5262 _hrm.allocate_free_regions_starting_at(index, 1);
5263 return region_at(index);
5264 }
5265 return NULL;
5266 }
5267
5268 // Optimized nmethod scanning
5269
5270 class RegisterNMethodOopClosure: public OopClosure {
5271 G1CollectedHeap* _g1h;
5272 nmethod* _nm;
5273
5274 template <class T> void do_oop_work(T* p) {
5275 T heap_oop = oopDesc::load_heap_oop(p);
5276 if (!oopDesc::is_null(heap_oop)) {
5277 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5278 HeapRegion* hr = _g1h->heap_region_containing(obj);
5279 assert(!hr->is_continues_humongous(),
5280 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5281 " starting at " HR_FORMAT,
5282 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5283
5284 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
5285 hr->add_strong_code_root_locked(_nm);
5286 }
5287 }
5288
5289 public:
5290 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5291 _g1h(g1h), _nm(nm) {}
5292
5293 void do_oop(oop* p) { do_oop_work(p); }
5294 void do_oop(narrowOop* p) { do_oop_work(p); }
5295 };
5296
5297 class UnregisterNMethodOopClosure: public OopClosure {
5298 G1CollectedHeap* _g1h;
5299 nmethod* _nm;
5300
5301 template <class T> void do_oop_work(T* p) {
5302 T heap_oop = oopDesc::load_heap_oop(p);
5303 if (!oopDesc::is_null(heap_oop)) {
5304 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5305 HeapRegion* hr = _g1h->heap_region_containing(obj);
5306 assert(!hr->is_continues_humongous(),
5307 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5308 " starting at " HR_FORMAT,
5309 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5310
5311 hr->remove_strong_code_root(_nm);
5312 }
5313 }
5314
5315 public:
5316 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5317 _g1h(g1h), _nm(nm) {}
5318
5319 void do_oop(oop* p) { do_oop_work(p); }
5320 void do_oop(narrowOop* p) { do_oop_work(p); }
5321 };
5322
5323 // Returns true if the reference points to an object that
5324 // can move in an incremental collection.
5325 bool G1CollectedHeap::is_scavengable(oop obj) {
5326 HeapRegion* hr = heap_region_containing(obj);
5327 return !hr->is_pinned();
5328 }
5329
5330 void G1CollectedHeap::register_nmethod(nmethod* nm) {
5331 guarantee(nm != NULL, "sanity");
5332 RegisterNMethodOopClosure reg_cl(this, nm);
5333 nm->oops_do(®_cl);
5334 }
5335
5336 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
5337 guarantee(nm != NULL, "sanity");
5338 UnregisterNMethodOopClosure reg_cl(this, nm);
5339 nm->oops_do(®_cl, true);
5340 }
5341
5342 void G1CollectedHeap::purge_code_root_memory() {
5343 double purge_start = os::elapsedTime();
5344 G1CodeRootSet::purge();
5345 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
5346 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
5347 }
5348
5349 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
5350 G1CollectedHeap* _g1h;
5351
5352 public:
5353 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
5354 _g1h(g1h) {}
5355
5356 void do_code_blob(CodeBlob* cb) {
5357 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
5358 if (nm == NULL) {
5359 return;
5360 }
5361
5362 if (ScavengeRootsInCode) {
5363 _g1h->register_nmethod(nm);
5364 }
5365 }
5366 };
5367
5368 void G1CollectedHeap::rebuild_strong_code_roots() {
5369 RebuildStrongCodeRootClosure blob_cl(this);
5370 CodeCache::blobs_do(&blob_cl);
5371 }