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/concurrentG1Refine.hpp"
33 #include "gc/g1/concurrentG1RefineThread.hpp"
34 #include "gc/g1/concurrentMarkThread.inline.hpp"
35 #include "gc/g1/g1Allocator.inline.hpp"
36 #include "gc/g1/g1CollectedHeap.inline.hpp"
37 #include "gc/g1/g1CollectionSet.hpp"
38 #include "gc/g1/g1CollectorPolicy.hpp"
39 #include "gc/g1/g1CollectorState.hpp"
40 #include "gc/g1/g1EvacStats.inline.hpp"
41 #include "gc/g1/g1FullCollector.hpp"
42 #include "gc/g1/g1FullGCScope.hpp"
43 #include "gc/g1/g1GCPhaseTimes.hpp"
44 #include "gc/g1/g1HeapSizingPolicy.hpp"
45 #include "gc/g1/g1HeapTransition.hpp"
46 #include "gc/g1/g1HeapVerifier.hpp"
47 #include "gc/g1/g1HotCardCache.hpp"
48 #include "gc/g1/g1OopClosures.inline.hpp"
49 #include "gc/g1/g1ParScanThreadState.inline.hpp"
50 #include "gc/g1/g1Policy.hpp"
51 #include "gc/g1/g1RegionToSpaceMapper.hpp"
52 #include "gc/g1/g1RemSet.inline.hpp"
53 #include "gc/g1/g1RootClosures.hpp"
54 #include "gc/g1/g1RootProcessor.hpp"
55 #include "gc/g1/g1StringDedup.hpp"
56 #include "gc/g1/g1YCTypes.hpp"
57 #include "gc/g1/heapRegion.inline.hpp"
58 #include "gc/g1/heapRegionRemSet.hpp"
59 #include "gc/g1/heapRegionSet.inline.hpp"
60 #include "gc/g1/suspendibleThreadSet.hpp"
61 #include "gc/g1/vm_operations_g1.hpp"
62 #include "gc/shared/gcHeapSummary.hpp"
63 #include "gc/shared/gcId.hpp"
64 #include "gc/shared/gcLocker.inline.hpp"
65 #include "gc/shared/gcTimer.hpp"
66 #include "gc/shared/gcTrace.hpp"
67 #include "gc/shared/gcTraceTime.inline.hpp"
68 #include "gc/shared/generationSpec.hpp"
69 #include "gc/shared/isGCActiveMark.hpp"
70 #include "gc/shared/preservedMarks.inline.hpp"
71 #include "gc/shared/referenceProcessor.inline.hpp"
72 #include "gc/shared/taskqueue.inline.hpp"
73 #include "logging/log.hpp"
74 #include "memory/allocation.hpp"
75 #include "memory/iterator.hpp"
76 #include "memory/resourceArea.hpp"
77 #include "oops/oop.inline.hpp"
78 #include "prims/resolvedMethodTable.hpp"
79 #include "runtime/atomic.hpp"
80 #include "runtime/init.hpp"
81 #include "runtime/orderAccess.inline.hpp"
82 #include "runtime/vmThread.hpp"
83 #include "utilities/align.hpp"
84 #include "utilities/globalDefinitions.hpp"
85 #include "utilities/stack.inline.hpp"
86
87 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
88
89 // INVARIANTS/NOTES
90 //
91 // All allocation activity covered by the G1CollectedHeap interface is
92 // serialized by acquiring the HeapLock. This happens in mem_allocate
93 // and allocate_new_tlab, which are the "entry" points to the
94 // allocation code from the rest of the JVM. (Note that this does not
95 // apply to TLAB allocation, which is not part of this interface: it
96 // is done by clients of this interface.)
97
98 // Local to this file.
99
100 class RefineCardTableEntryClosure: public CardTableEntryClosure {
101 bool _concurrent;
102 public:
103 RefineCardTableEntryClosure() : _concurrent(true) { }
104
105 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
106 G1CollectedHeap::heap()->g1_rem_set()->refine_card_concurrently(card_ptr, worker_i);
107
108 if (_concurrent && SuspendibleThreadSet::should_yield()) {
109 // Caller will actually yield.
110 return false;
111 }
112 // Otherwise, we finished successfully; return true.
113 return true;
114 }
115
116 void set_concurrent(bool b) { _concurrent = b; }
117 };
118
119
120 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
121 private:
122 size_t _num_dirtied;
123 G1CollectedHeap* _g1h;
124 G1SATBCardTableLoggingModRefBS* _g1_bs;
125
126 HeapRegion* region_for_card(jbyte* card_ptr) const {
127 return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr));
128 }
129
130 bool will_become_free(HeapRegion* hr) const {
131 // A region will be freed by free_collection_set if the region is in the
132 // collection set and has not had an evacuation failure.
133 return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
134 }
135
136 public:
137 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(),
138 _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { }
139
140 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
141 HeapRegion* hr = region_for_card(card_ptr);
142
143 // Should only dirty cards in regions that won't be freed.
144 if (!will_become_free(hr)) {
145 *card_ptr = CardTableModRefBS::dirty_card_val();
146 _num_dirtied++;
147 }
148
149 return true;
150 }
151
152 size_t num_dirtied() const { return _num_dirtied; }
153 };
154
155
156 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
157 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
158 }
159
160 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
161 // The from card cache is not the memory that is actually committed. So we cannot
162 // take advantage of the zero_filled parameter.
163 reset_from_card_cache(start_idx, num_regions);
164 }
165
166 // Returns true if the reference points to an object that
167 // can move in an incremental collection.
168 bool G1CollectedHeap::is_scavengable(const void* p) {
169 HeapRegion* hr = heap_region_containing(p);
170 return !hr->is_pinned();
171 }
172
173
174 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
175 MemRegion mr) {
176 return new HeapRegion(hrs_index, bot(), mr);
177 }
178
179 // Private methods.
180
181 HeapRegion*
182 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
183 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
184 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
185 if (!_secondary_free_list.is_empty()) {
186 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
187 "secondary_free_list has %u entries",
188 _secondary_free_list.length());
189 // It looks as if there are free regions available on the
190 // secondary_free_list. Let's move them to the free_list and try
191 // again to allocate from it.
192 append_secondary_free_list();
193
194 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
195 "empty we should have moved at least one entry to the free_list");
196 HeapRegion* res = _hrm.allocate_free_region(is_old);
197 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
198 "allocated " HR_FORMAT " from secondary_free_list",
199 HR_FORMAT_PARAMS(res));
200 return res;
201 }
202
203 // Wait here until we get notified either when (a) there are no
204 // more free regions coming or (b) some regions have been moved on
205 // the secondary_free_list.
206 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
207 }
208
209 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
210 "could not allocate from secondary_free_list");
211 return NULL;
212 }
213
214 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
215 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
216 "the only time we use this to allocate a humongous region is "
217 "when we are allocating a single humongous region");
218
219 HeapRegion* res;
220 if (G1StressConcRegionFreeing) {
221 if (!_secondary_free_list.is_empty()) {
222 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
223 "forced to look at the secondary_free_list");
224 res = new_region_try_secondary_free_list(is_old);
225 if (res != NULL) {
226 return res;
227 }
228 }
229 }
230
231 res = _hrm.allocate_free_region(is_old);
232
233 if (res == NULL) {
234 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
235 "res == NULL, trying the secondary_free_list");
236 res = new_region_try_secondary_free_list(is_old);
237 }
238 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
239 // Currently, only attempts to allocate GC alloc regions set
240 // do_expand to true. So, we should only reach here during a
241 // safepoint. If this assumption changes we might have to
242 // reconsider the use of _expand_heap_after_alloc_failure.
243 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
244
245 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
246 word_size * HeapWordSize);
247
248 if (expand(word_size * HeapWordSize)) {
249 // Given that expand() succeeded in expanding the heap, and we
250 // always expand the heap by an amount aligned to the heap
251 // region size, the free list should in theory not be empty.
252 // In either case allocate_free_region() will check for NULL.
253 res = _hrm.allocate_free_region(is_old);
254 } else {
255 _expand_heap_after_alloc_failure = false;
256 }
257 }
258 return res;
259 }
260
261 HeapWord*
262 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
263 uint num_regions,
264 size_t word_size,
265 AllocationContext_t context) {
266 assert(first != G1_NO_HRM_INDEX, "pre-condition");
267 assert(is_humongous(word_size), "word_size should be humongous");
268 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
269
270 // Index of last region in the series.
271 uint last = first + num_regions - 1;
272
273 // We need to initialize the region(s) we just discovered. This is
274 // a bit tricky given that it can happen concurrently with
275 // refinement threads refining cards on these regions and
276 // potentially wanting to refine the BOT as they are scanning
277 // those cards (this can happen shortly after a cleanup; see CR
278 // 6991377). So we have to set up the region(s) carefully and in
279 // a specific order.
280
281 // The word size sum of all the regions we will allocate.
282 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
283 assert(word_size <= word_size_sum, "sanity");
284
285 // This will be the "starts humongous" region.
286 HeapRegion* first_hr = region_at(first);
287 // The header of the new object will be placed at the bottom of
288 // the first region.
289 HeapWord* new_obj = first_hr->bottom();
290 // This will be the new top of the new object.
291 HeapWord* obj_top = new_obj + word_size;
292
293 // First, we need to zero the header of the space that we will be
294 // allocating. When we update top further down, some refinement
295 // threads might try to scan the region. By zeroing the header we
296 // ensure that any thread that will try to scan the region will
297 // come across the zero klass word and bail out.
298 //
299 // NOTE: It would not have been correct to have used
300 // CollectedHeap::fill_with_object() and make the space look like
301 // an int array. The thread that is doing the allocation will
302 // later update the object header to a potentially different array
303 // type and, for a very short period of time, the klass and length
304 // fields will be inconsistent. This could cause a refinement
305 // thread to calculate the object size incorrectly.
306 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
307
308 // Next, pad out the unused tail of the last region with filler
309 // objects, for improved usage accounting.
310 // How many words we use for filler objects.
311 size_t word_fill_size = word_size_sum - word_size;
312
313 // How many words memory we "waste" which cannot hold a filler object.
314 size_t words_not_fillable = 0;
315
316 if (word_fill_size >= min_fill_size()) {
317 fill_with_objects(obj_top, word_fill_size);
318 } else if (word_fill_size > 0) {
319 // We have space to fill, but we cannot fit an object there.
320 words_not_fillable = word_fill_size;
321 word_fill_size = 0;
322 }
323
324 // We will set up the first region as "starts humongous". This
325 // will also update the BOT covering all the regions to reflect
326 // that there is a single object that starts at the bottom of the
327 // first region.
328 first_hr->set_starts_humongous(obj_top, word_fill_size);
329 first_hr->set_allocation_context(context);
330 // Then, if there are any, we will set up the "continues
331 // humongous" regions.
332 HeapRegion* hr = NULL;
333 for (uint i = first + 1; i <= last; ++i) {
334 hr = region_at(i);
335 hr->set_continues_humongous(first_hr);
336 hr->set_allocation_context(context);
337 }
338
339 // Up to this point no concurrent thread would have been able to
340 // do any scanning on any region in this series. All the top
341 // fields still point to bottom, so the intersection between
342 // [bottom,top] and [card_start,card_end] will be empty. Before we
343 // update the top fields, we'll do a storestore to make sure that
344 // no thread sees the update to top before the zeroing of the
345 // object header and the BOT initialization.
346 OrderAccess::storestore();
347
348 // Now, we will update the top fields of the "continues humongous"
349 // regions except the last one.
350 for (uint i = first; i < last; ++i) {
351 hr = region_at(i);
352 hr->set_top(hr->end());
353 }
354
355 hr = region_at(last);
356 // If we cannot fit a filler object, we must set top to the end
357 // of the humongous object, otherwise we cannot iterate the heap
358 // and the BOT will not be complete.
359 hr->set_top(hr->end() - words_not_fillable);
360
361 assert(hr->bottom() < obj_top && obj_top <= hr->end(),
362 "obj_top should be in last region");
363
364 _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
365
366 assert(words_not_fillable == 0 ||
367 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
368 "Miscalculation in humongous allocation");
369
370 increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
371
372 for (uint i = first; i <= last; ++i) {
373 hr = region_at(i);
374 _humongous_set.add(hr);
375 _hr_printer.alloc(hr);
376 }
377
378 return new_obj;
379 }
380
381 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
382 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
383 return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
384 }
385
386 // If could fit into free regions w/o expansion, try.
387 // Otherwise, if can expand, do so.
388 // Otherwise, if using ex regions might help, try with ex given back.
389 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
390 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
391
392 _verifier->verify_region_sets_optional();
393
394 uint first = G1_NO_HRM_INDEX;
395 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
396
397 if (obj_regions == 1) {
398 // Only one region to allocate, try to use a fast path by directly allocating
399 // from the free lists. Do not try to expand here, we will potentially do that
400 // later.
401 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
402 if (hr != NULL) {
403 first = hr->hrm_index();
404 }
405 } else {
406 // We can't allocate humongous regions spanning more than one region while
407 // cleanupComplete() is running, since some of the regions we find to be
408 // empty might not yet be added to the free list. It is not straightforward
409 // to know in which list they are on so that we can remove them. We only
410 // need to do this if we need to allocate more than one region to satisfy the
411 // current humongous allocation request. If we are only allocating one region
412 // we use the one-region region allocation code (see above), that already
413 // potentially waits for regions from the secondary free list.
414 wait_while_free_regions_coming();
415 append_secondary_free_list_if_not_empty_with_lock();
416
417 // Policy: Try only empty regions (i.e. already committed first). Maybe we
418 // are lucky enough to find some.
419 first = _hrm.find_contiguous_only_empty(obj_regions);
420 if (first != G1_NO_HRM_INDEX) {
421 _hrm.allocate_free_regions_starting_at(first, obj_regions);
422 }
423 }
424
425 if (first == G1_NO_HRM_INDEX) {
426 // Policy: We could not find enough regions for the humongous object in the
427 // free list. Look through the heap to find a mix of free and uncommitted regions.
428 // If so, try expansion.
429 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
430 if (first != G1_NO_HRM_INDEX) {
431 // We found something. Make sure these regions are committed, i.e. expand
432 // the heap. Alternatively we could do a defragmentation GC.
433 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
434 word_size * HeapWordSize);
435
436 _hrm.expand_at(first, obj_regions, workers());
437 g1_policy()->record_new_heap_size(num_regions());
438
439 #ifdef ASSERT
440 for (uint i = first; i < first + obj_regions; ++i) {
441 HeapRegion* hr = region_at(i);
442 assert(hr->is_free(), "sanity");
443 assert(hr->is_empty(), "sanity");
444 assert(is_on_master_free_list(hr), "sanity");
445 }
446 #endif
447 _hrm.allocate_free_regions_starting_at(first, obj_regions);
448 } else {
449 // Policy: Potentially trigger a defragmentation GC.
450 }
451 }
452
453 HeapWord* result = NULL;
454 if (first != G1_NO_HRM_INDEX) {
455 result = humongous_obj_allocate_initialize_regions(first, obj_regions,
456 word_size, context);
457 assert(result != NULL, "it should always return a valid result");
458
459 // A successful humongous object allocation changes the used space
460 // information of the old generation so we need to recalculate the
461 // sizes and update the jstat counters here.
462 g1mm()->update_sizes();
463 }
464
465 _verifier->verify_region_sets_optional();
466
467 return result;
468 }
469
470 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
471 assert_heap_not_locked_and_not_at_safepoint();
472 assert(!is_humongous(word_size), "we do not allow humongous TLABs");
473
474 uint dummy_gc_count_before;
475 uint dummy_gclocker_retry_count = 0;
476 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
477 }
478
479 HeapWord*
480 G1CollectedHeap::mem_allocate(size_t word_size,
481 bool* gc_overhead_limit_was_exceeded) {
482 assert_heap_not_locked_and_not_at_safepoint();
483
484 // Loop until the allocation is satisfied, or unsatisfied after GC.
485 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
486 uint gc_count_before;
487
488 HeapWord* result = NULL;
489 if (!is_humongous(word_size)) {
490 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
491 } else {
492 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
493 }
494 if (result != NULL) {
495 return result;
496 }
497
498 // Create the garbage collection operation...
499 VM_G1CollectForAllocation op(gc_count_before, word_size);
500 op.set_allocation_context(AllocationContext::current());
501
502 // ...and get the VM thread to execute it.
503 VMThread::execute(&op);
504
505 if (op.prologue_succeeded() && op.pause_succeeded()) {
506 // If the operation was successful we'll return the result even
507 // if it is NULL. If the allocation attempt failed immediately
508 // after a Full GC, it's unlikely we'll be able to allocate now.
509 HeapWord* result = op.result();
510 if (result != NULL && !is_humongous(word_size)) {
511 // Allocations that take place on VM operations do not do any
512 // card dirtying and we have to do it here. We only have to do
513 // this for non-humongous allocations, though.
514 dirty_young_block(result, word_size);
515 }
516 return result;
517 } else {
518 if (gclocker_retry_count > GCLockerRetryAllocationCount) {
519 return NULL;
520 }
521 assert(op.result() == NULL,
522 "the result should be NULL if the VM op did not succeed");
523 }
524
525 // Give a warning if we seem to be looping forever.
526 if ((QueuedAllocationWarningCount > 0) &&
527 (try_count % QueuedAllocationWarningCount == 0)) {
528 log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count);
529 }
530 }
531
532 ShouldNotReachHere();
533 return NULL;
534 }
535
536 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
537 AllocationContext_t context,
538 uint* gc_count_before_ret,
539 uint* gclocker_retry_count_ret) {
540 // Make sure you read the note in attempt_allocation_humongous().
541
542 assert_heap_not_locked_and_not_at_safepoint();
543 assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
544 "be called for humongous allocation requests");
545
546 // We should only get here after the first-level allocation attempt
547 // (attempt_allocation()) failed to allocate.
548
549 // We will loop until a) we manage to successfully perform the
550 // allocation or b) we successfully schedule a collection which
551 // fails to perform the allocation. b) is the only case when we'll
552 // return NULL.
553 HeapWord* result = NULL;
554 for (int try_count = 1; /* we'll return */; try_count += 1) {
555 bool should_try_gc;
556 uint gc_count_before;
557
558 {
559 MutexLockerEx x(Heap_lock);
560 result = _allocator->attempt_allocation_locked(word_size, context);
561 if (result != NULL) {
562 return result;
563 }
564
565 if (GCLocker::is_active_and_needs_gc()) {
566 if (g1_policy()->can_expand_young_list()) {
567 // No need for an ergo verbose message here,
568 // can_expand_young_list() does this when it returns true.
569 result = _allocator->attempt_allocation_force(word_size, context);
570 if (result != NULL) {
571 return result;
572 }
573 }
574 should_try_gc = false;
575 } else {
576 // The GCLocker may not be active but the GCLocker initiated
577 // GC may not yet have been performed (GCLocker::needs_gc()
578 // returns true). In this case we do not try this GC and
579 // wait until the GCLocker initiated GC is performed, and
580 // then retry the allocation.
581 if (GCLocker::needs_gc()) {
582 should_try_gc = false;
583 } else {
584 // Read the GC count while still holding the Heap_lock.
585 gc_count_before = total_collections();
586 should_try_gc = true;
587 }
588 }
589 }
590
591 if (should_try_gc) {
592 bool succeeded;
593 result = do_collection_pause(word_size, gc_count_before, &succeeded,
594 GCCause::_g1_inc_collection_pause);
595 if (result != NULL) {
596 assert(succeeded, "only way to get back a non-NULL result");
597 return result;
598 }
599
600 if (succeeded) {
601 // If we get here we successfully scheduled a collection which
602 // failed to allocate. No point in trying to allocate
603 // further. We'll just return NULL.
604 MutexLockerEx x(Heap_lock);
605 *gc_count_before_ret = total_collections();
606 return NULL;
607 }
608 } else {
609 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
610 MutexLockerEx x(Heap_lock);
611 *gc_count_before_ret = total_collections();
612 return NULL;
613 }
614 // The GCLocker is either active or the GCLocker initiated
615 // GC has not yet been performed. Stall until it is and
616 // then retry the allocation.
617 GCLocker::stall_until_clear();
618 (*gclocker_retry_count_ret) += 1;
619 }
620
621 // We can reach here if we were unsuccessful in scheduling a
622 // collection (because another thread beat us to it) or if we were
623 // stalled due to the GC locker. In either can we should retry the
624 // allocation attempt in case another thread successfully
625 // performed a collection and reclaimed enough space. We do the
626 // first attempt (without holding the Heap_lock) here and the
627 // follow-on attempt will be at the start of the next loop
628 // iteration (after taking the Heap_lock).
629 result = _allocator->attempt_allocation(word_size, context);
630 if (result != NULL) {
631 return result;
632 }
633
634 // Give a warning if we seem to be looping forever.
635 if ((QueuedAllocationWarningCount > 0) &&
636 (try_count % QueuedAllocationWarningCount == 0)) {
637 log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() "
638 "retries %d times", try_count);
639 }
640 }
641
642 ShouldNotReachHere();
643 return NULL;
644 }
645
646 void G1CollectedHeap::begin_archive_alloc_range() {
647 assert_at_safepoint(true /* should_be_vm_thread */);
648 if (_archive_allocator == NULL) {
649 _archive_allocator = G1ArchiveAllocator::create_allocator(this);
650 }
651 }
652
653 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
654 // Allocations in archive regions cannot be of a size that would be considered
655 // humongous even for a minimum-sized region, because G1 region sizes/boundaries
656 // may be different at archive-restore time.
657 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
658 }
659
660 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
661 assert_at_safepoint(true /* should_be_vm_thread */);
662 assert(_archive_allocator != NULL, "_archive_allocator not initialized");
663 if (is_archive_alloc_too_large(word_size)) {
664 return NULL;
665 }
666 return _archive_allocator->archive_mem_allocate(word_size);
667 }
668
669 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
670 size_t end_alignment_in_bytes) {
671 assert_at_safepoint(true /* should_be_vm_thread */);
672 assert(_archive_allocator != NULL, "_archive_allocator not initialized");
673
674 // Call complete_archive to do the real work, filling in the MemRegion
675 // array with the archive regions.
676 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
677 delete _archive_allocator;
678 _archive_allocator = NULL;
679 }
680
681 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
682 assert(ranges != NULL, "MemRegion array NULL");
683 assert(count != 0, "No MemRegions provided");
684 MemRegion reserved = _hrm.reserved();
685 for (size_t i = 0; i < count; i++) {
686 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
687 return false;
688 }
689 }
690 return true;
691 }
692
693 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, size_t count) {
694 assert(!is_init_completed(), "Expect to be called at JVM init time");
695 assert(ranges != NULL, "MemRegion array NULL");
696 assert(count != 0, "No MemRegions provided");
697 MutexLockerEx x(Heap_lock);
698
699 MemRegion reserved = _hrm.reserved();
700 HeapWord* prev_last_addr = NULL;
701 HeapRegion* prev_last_region = NULL;
702
703 // Temporarily disable pretouching of heap pages. This interface is used
704 // when mmap'ing archived heap data in, so pre-touching is wasted.
705 FlagSetting fs(AlwaysPreTouch, false);
706
707 // Enable archive object checking used by G1MarkSweep. We have to let it know
708 // about each archive range, so that objects in those ranges aren't marked.
709 G1ArchiveAllocator::enable_archive_object_check();
710
711 // For each specified MemRegion range, allocate the corresponding G1
712 // regions and mark them as archive regions. We expect the ranges in
713 // ascending starting address order, without overlap.
714 for (size_t i = 0; i < count; i++) {
715 MemRegion curr_range = ranges[i];
716 HeapWord* start_address = curr_range.start();
717 size_t word_size = curr_range.word_size();
718 HeapWord* last_address = curr_range.last();
719 size_t commits = 0;
720
721 guarantee(reserved.contains(start_address) && reserved.contains(last_address),
722 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
723 p2i(start_address), p2i(last_address));
724 guarantee(start_address > prev_last_addr,
725 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
726 p2i(start_address), p2i(prev_last_addr));
727 prev_last_addr = last_address;
728
729 // Check for ranges that start in the same G1 region in which the previous
730 // range ended, and adjust the start address so we don't try to allocate
731 // the same region again. If the current range is entirely within that
732 // region, skip it, just adjusting the recorded top.
733 HeapRegion* start_region = _hrm.addr_to_region(start_address);
734 if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
735 start_address = start_region->end();
736 if (start_address > last_address) {
737 increase_used(word_size * HeapWordSize);
738 start_region->set_top(last_address + 1);
739 continue;
740 }
741 start_region->set_top(start_address);
742 curr_range = MemRegion(start_address, last_address + 1);
743 start_region = _hrm.addr_to_region(start_address);
744 }
745
746 // Perform the actual region allocation, exiting if it fails.
747 // Then note how much new space we have allocated.
748 if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) {
749 return false;
750 }
751 increase_used(word_size * HeapWordSize);
752 if (commits != 0) {
753 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
754 HeapRegion::GrainWords * HeapWordSize * commits);
755
756 }
757
758 // Mark each G1 region touched by the range as archive, add it to the old set,
759 // and set the allocation context and top.
760 HeapRegion* curr_region = _hrm.addr_to_region(start_address);
761 HeapRegion* last_region = _hrm.addr_to_region(last_address);
762 prev_last_region = last_region;
763
764 while (curr_region != NULL) {
765 assert(curr_region->is_empty() && !curr_region->is_pinned(),
766 "Region already in use (index %u)", curr_region->hrm_index());
767 curr_region->set_allocation_context(AllocationContext::system());
768 curr_region->set_archive();
769 _hr_printer.alloc(curr_region);
770 _old_set.add(curr_region);
771 if (curr_region != last_region) {
772 curr_region->set_top(curr_region->end());
773 curr_region = _hrm.next_region_in_heap(curr_region);
774 } else {
775 curr_region->set_top(last_address + 1);
776 curr_region = NULL;
777 }
778 }
779
780 // Notify mark-sweep of the archive range.
781 G1ArchiveAllocator::set_range_archive(curr_range, true);
782 }
783 return true;
784 }
785
786 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
787 assert(!is_init_completed(), "Expect to be called at JVM init time");
788 assert(ranges != NULL, "MemRegion array NULL");
789 assert(count != 0, "No MemRegions provided");
790 MemRegion reserved = _hrm.reserved();
791 HeapWord *prev_last_addr = NULL;
792 HeapRegion* prev_last_region = NULL;
793
794 // For each MemRegion, create filler objects, if needed, in the G1 regions
795 // that contain the address range. The address range actually within the
796 // MemRegion will not be modified. That is assumed to have been initialized
797 // elsewhere, probably via an mmap of archived heap data.
798 MutexLockerEx x(Heap_lock);
799 for (size_t i = 0; i < count; i++) {
800 HeapWord* start_address = ranges[i].start();
801 HeapWord* last_address = ranges[i].last();
802
803 assert(reserved.contains(start_address) && reserved.contains(last_address),
804 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
805 p2i(start_address), p2i(last_address));
806 assert(start_address > prev_last_addr,
807 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
808 p2i(start_address), p2i(prev_last_addr));
809
810 HeapRegion* start_region = _hrm.addr_to_region(start_address);
811 HeapRegion* last_region = _hrm.addr_to_region(last_address);
812 HeapWord* bottom_address = start_region->bottom();
813
814 // Check for a range beginning in the same region in which the
815 // previous one ended.
816 if (start_region == prev_last_region) {
817 bottom_address = prev_last_addr + 1;
818 }
819
820 // Verify that the regions were all marked as archive regions by
821 // alloc_archive_regions.
822 HeapRegion* curr_region = start_region;
823 while (curr_region != NULL) {
824 guarantee(curr_region->is_archive(),
825 "Expected archive region at index %u", curr_region->hrm_index());
826 if (curr_region != last_region) {
827 curr_region = _hrm.next_region_in_heap(curr_region);
828 } else {
829 curr_region = NULL;
830 }
831 }
832
833 prev_last_addr = last_address;
834 prev_last_region = last_region;
835
836 // Fill the memory below the allocated range with dummy object(s),
837 // if the region bottom does not match the range start, or if the previous
838 // range ended within the same G1 region, and there is a gap.
839 if (start_address != bottom_address) {
840 size_t fill_size = pointer_delta(start_address, bottom_address);
841 G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
842 increase_used(fill_size * HeapWordSize);
843 }
844 }
845 }
846
847 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size,
848 uint* gc_count_before_ret,
849 uint* gclocker_retry_count_ret) {
850 assert_heap_not_locked_and_not_at_safepoint();
851 assert(!is_humongous(word_size), "attempt_allocation() should not "
852 "be called for humongous allocation requests");
853
854 AllocationContext_t context = AllocationContext::current();
855 HeapWord* result = _allocator->attempt_allocation(word_size, context);
856
857 if (result == NULL) {
858 result = attempt_allocation_slow(word_size,
859 context,
860 gc_count_before_ret,
861 gclocker_retry_count_ret);
862 }
863 assert_heap_not_locked();
864 if (result != NULL) {
865 dirty_young_block(result, word_size);
866 }
867 return result;
868 }
869
870 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
871 assert(!is_init_completed(), "Expect to be called at JVM init time");
872 assert(ranges != NULL, "MemRegion array NULL");
873 assert(count != 0, "No MemRegions provided");
874 MemRegion reserved = _hrm.reserved();
875 HeapWord* prev_last_addr = NULL;
876 HeapRegion* prev_last_region = NULL;
877 size_t size_used = 0;
878 size_t uncommitted_regions = 0;
879
880 // For each Memregion, free the G1 regions that constitute it, and
881 // notify mark-sweep that the range is no longer to be considered 'archive.'
882 MutexLockerEx x(Heap_lock);
883 for (size_t i = 0; i < count; i++) {
884 HeapWord* start_address = ranges[i].start();
885 HeapWord* last_address = ranges[i].last();
886
887 assert(reserved.contains(start_address) && reserved.contains(last_address),
888 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
889 p2i(start_address), p2i(last_address));
890 assert(start_address > prev_last_addr,
891 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
892 p2i(start_address), p2i(prev_last_addr));
893 size_used += ranges[i].byte_size();
894 prev_last_addr = last_address;
895
896 HeapRegion* start_region = _hrm.addr_to_region(start_address);
897 HeapRegion* last_region = _hrm.addr_to_region(last_address);
898
899 // Check for ranges that start in the same G1 region in which the previous
900 // range ended, and adjust the start address so we don't try to free
901 // the same region again. If the current range is entirely within that
902 // region, skip it.
903 if (start_region == prev_last_region) {
904 start_address = start_region->end();
905 if (start_address > last_address) {
906 continue;
907 }
908 start_region = _hrm.addr_to_region(start_address);
909 }
910 prev_last_region = last_region;
911
912 // After verifying that each region was marked as an archive region by
913 // alloc_archive_regions, set it free and empty and uncommit it.
914 HeapRegion* curr_region = start_region;
915 while (curr_region != NULL) {
916 guarantee(curr_region->is_archive(),
917 "Expected archive region at index %u", curr_region->hrm_index());
918 uint curr_index = curr_region->hrm_index();
919 _old_set.remove(curr_region);
920 curr_region->set_free();
921 curr_region->set_top(curr_region->bottom());
922 if (curr_region != last_region) {
923 curr_region = _hrm.next_region_in_heap(curr_region);
924 } else {
925 curr_region = NULL;
926 }
927 _hrm.shrink_at(curr_index, 1);
928 uncommitted_regions++;
929 }
930
931 // Notify mark-sweep that this is no longer an archive range.
932 G1ArchiveAllocator::set_range_archive(ranges[i], false);
933 }
934
935 if (uncommitted_regions != 0) {
936 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
937 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
938 }
939 decrease_used(size_used);
940 }
941
942 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
943 uint* gc_count_before_ret,
944 uint* gclocker_retry_count_ret) {
945 // The structure of this method has a lot of similarities to
946 // attempt_allocation_slow(). The reason these two were not merged
947 // into a single one is that such a method would require several "if
948 // allocation is not humongous do this, otherwise do that"
949 // conditional paths which would obscure its flow. In fact, an early
950 // version of this code did use a unified method which was harder to
951 // follow and, as a result, it had subtle bugs that were hard to
952 // track down. So keeping these two methods separate allows each to
953 // be more readable. It will be good to keep these two in sync as
954 // much as possible.
955
956 assert_heap_not_locked_and_not_at_safepoint();
957 assert(is_humongous(word_size), "attempt_allocation_humongous() "
958 "should only be called for humongous allocations");
959
960 // Humongous objects can exhaust the heap quickly, so we should check if we
961 // need to start a marking cycle at each humongous object allocation. We do
962 // the check before we do the actual allocation. The reason for doing it
963 // before the allocation is that we avoid having to keep track of the newly
964 // allocated memory while we do a GC.
965 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
966 word_size)) {
967 collect(GCCause::_g1_humongous_allocation);
968 }
969
970 // We will loop until a) we manage to successfully perform the
971 // allocation or b) we successfully schedule a collection which
972 // fails to perform the allocation. b) is the only case when we'll
973 // return NULL.
974 HeapWord* result = NULL;
975 for (int try_count = 1; /* we'll return */; try_count += 1) {
976 bool should_try_gc;
977 uint gc_count_before;
978
979 {
980 MutexLockerEx x(Heap_lock);
981
982 // Given that humongous objects are not allocated in young
983 // regions, we'll first try to do the allocation without doing a
984 // collection hoping that there's enough space in the heap.
985 result = humongous_obj_allocate(word_size, AllocationContext::current());
986 if (result != NULL) {
987 size_t size_in_regions = humongous_obj_size_in_regions(word_size);
988 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
989 return result;
990 }
991
992 if (GCLocker::is_active_and_needs_gc()) {
993 should_try_gc = false;
994 } else {
995 // The GCLocker may not be active but the GCLocker initiated
996 // GC may not yet have been performed (GCLocker::needs_gc()
997 // returns true). In this case we do not try this GC and
998 // wait until the GCLocker initiated GC is performed, and
999 // then retry the allocation.
1000 if (GCLocker::needs_gc()) {
1001 should_try_gc = false;
1002 } else {
1003 // Read the GC count while still holding the Heap_lock.
1004 gc_count_before = total_collections();
1005 should_try_gc = true;
1006 }
1007 }
1008 }
1009
1010 if (should_try_gc) {
1011 // If we failed to allocate the humongous object, we should try to
1012 // do a collection pause (if we're allowed) in case it reclaims
1013 // enough space for the allocation to succeed after the pause.
1014
1015 bool succeeded;
1016 result = do_collection_pause(word_size, gc_count_before, &succeeded,
1017 GCCause::_g1_humongous_allocation);
1018 if (result != NULL) {
1019 assert(succeeded, "only way to get back a non-NULL result");
1020 return result;
1021 }
1022
1023 if (succeeded) {
1024 // If we get here we successfully scheduled a collection which
1025 // failed to allocate. No point in trying to allocate
1026 // further. We'll just return NULL.
1027 MutexLockerEx x(Heap_lock);
1028 *gc_count_before_ret = total_collections();
1029 return NULL;
1030 }
1031 } else {
1032 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1033 MutexLockerEx x(Heap_lock);
1034 *gc_count_before_ret = total_collections();
1035 return NULL;
1036 }
1037 // The GCLocker is either active or the GCLocker initiated
1038 // GC has not yet been performed. Stall until it is and
1039 // then retry the allocation.
1040 GCLocker::stall_until_clear();
1041 (*gclocker_retry_count_ret) += 1;
1042 }
1043
1044 // We can reach here if we were unsuccessful in scheduling a
1045 // collection (because another thread beat us to it) or if we were
1046 // stalled due to the GC locker. In either can we should retry the
1047 // allocation attempt in case another thread successfully
1048 // performed a collection and reclaimed enough space. Give a
1049 // warning if we seem to be looping forever.
1050
1051 if ((QueuedAllocationWarningCount > 0) &&
1052 (try_count % QueuedAllocationWarningCount == 0)) {
1053 log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() "
1054 "retries %d times", try_count);
1055 }
1056 }
1057
1058 ShouldNotReachHere();
1059 return NULL;
1060 }
1061
1062 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1063 AllocationContext_t context,
1064 bool expect_null_mutator_alloc_region) {
1065 assert_at_safepoint(true /* should_be_vm_thread */);
1066 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region,
1067 "the current alloc region was unexpectedly found to be non-NULL");
1068
1069 if (!is_humongous(word_size)) {
1070 return _allocator->attempt_allocation_locked(word_size, context);
1071 } else {
1072 HeapWord* result = humongous_obj_allocate(word_size, context);
1073 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1074 collector_state()->set_initiate_conc_mark_if_possible(true);
1075 }
1076 return result;
1077 }
1078
1079 ShouldNotReachHere();
1080 }
1081
1082 class PostCompactionPrinterClosure: public HeapRegionClosure {
1083 private:
1084 G1HRPrinter* _hr_printer;
1085 public:
1086 bool doHeapRegion(HeapRegion* hr) {
1087 assert(!hr->is_young(), "not expecting to find young regions");
1088 _hr_printer->post_compaction(hr);
1089 return false;
1090 }
1091
1092 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1093 : _hr_printer(hr_printer) { }
1094 };
1095
1096 void G1CollectedHeap::print_hrm_post_compaction() {
1097 if (_hr_printer.is_active()) {
1098 PostCompactionPrinterClosure cl(hr_printer());
1099 heap_region_iterate(&cl);
1100 }
1101
1102 }
1103
1104 void G1CollectedHeap::abort_concurrent_cycle() {
1105 // Note: When we have a more flexible GC logging framework that
1106 // allows us to add optional attributes to a GC log record we
1107 // could consider timing and reporting how long we wait in the
1108 // following two methods.
1109 wait_while_free_regions_coming();
1110 // If we start the compaction before the CM threads finish
1111 // scanning the root regions we might trip them over as we'll
1112 // be moving objects / updating references. So let's wait until
1113 // they are done. By telling them to abort, they should complete
1114 // early.
1115 _cm->root_regions()->abort();
1116 _cm->root_regions()->wait_until_scan_finished();
1117 append_secondary_free_list_if_not_empty_with_lock();
1118
1119 // Disable discovery and empty the discovered lists
1120 // for the CM ref processor.
1121 ref_processor_cm()->disable_discovery();
1122 ref_processor_cm()->abandon_partial_discovery();
1123 ref_processor_cm()->verify_no_references_recorded();
1124
1125 // Abandon current iterations of concurrent marking and concurrent
1126 // refinement, if any are in progress.
1127 concurrent_mark()->abort();
1128 }
1129
1130 void G1CollectedHeap::prepare_heap_for_full_collection() {
1131 // Make sure we'll choose a new allocation region afterwards.
1132 _allocator->release_mutator_alloc_region();
1133 _allocator->abandon_gc_alloc_regions();
1134 g1_rem_set()->cleanupHRRS();
1135
1136 // We may have added regions to the current incremental collection
1137 // set between the last GC or pause and now. We need to clear the
1138 // incremental collection set and then start rebuilding it afresh
1139 // after this full GC.
1140 abandon_collection_set(collection_set());
1141
1142 tear_down_region_sets(false /* free_list_only */);
1143 collector_state()->set_gcs_are_young(true);
1144 }
1145
1146 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) {
1147 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1148 assert(used() == recalculate_used(), "Should be equal");
1149 _verifier->verify_region_sets_optional();
1150 _verifier->verify_before_gc();
1151 _verifier->check_bitmaps("Full GC Start");
1152 }
1153
1154 void G1CollectedHeap::prepare_heap_for_mutators() {
1155 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1156 ClassLoaderDataGraph::purge();
1157 MetaspaceAux::verify_metrics();
1158
1159 // Prepare heap for normal collections.
1160 assert(num_free_regions() == 0, "we should not have added any free regions");
1161 rebuild_region_sets(false /* free_list_only */);
1162 abort_refinement();
1163 resize_if_necessary_after_full_collection();
1164
1165 // Rebuild the strong code root lists for each region
1166 rebuild_strong_code_roots();
1167
1168 // Start a new incremental collection set for the next pause
1169 start_new_collection_set();
1170
1171 _allocator->init_mutator_alloc_region();
1172
1173 // Post collection state updates.
1174 MetaspaceGC::compute_new_size();
1175 }
1176
1177 void G1CollectedHeap::abort_refinement() {
1178 if (_hot_card_cache->use_cache()) {
1179 _hot_card_cache->reset_card_counts();
1180 _hot_card_cache->reset_hot_cache();
1181 }
1182
1183 // Discard all remembered set updates.
1184 JavaThread::dirty_card_queue_set().abandon_logs();
1185 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1186 }
1187
1188 void G1CollectedHeap::verify_after_full_collection() {
1189 check_gc_time_stamps();
1190 _hrm.verify_optional();
1191 _verifier->verify_region_sets_optional();
1192 _verifier->verify_after_gc();
1193 // Clear the previous marking bitmap, if needed for bitmap verification.
1194 // Note we cannot do this when we clear the next marking bitmap in
1195 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1196 // objects marked during a full GC against the previous bitmap.
1197 // But we need to clear it before calling check_bitmaps below since
1198 // the full GC has compacted objects and updated TAMS but not updated
1199 // the prev bitmap.
1200 if (G1VerifyBitmaps) {
1201 GCTraceTime(Debug, gc)("Clear Bitmap for Verification");
1202 _cm->clear_prev_bitmap(workers());
1203 }
1204 _verifier->check_bitmaps("Full GC End");
1205
1206 // At this point there should be no regions in the
1207 // entire heap tagged as young.
1208 assert(check_young_list_empty(), "young list should be empty at this point");
1209
1210 // Note: since we've just done a full GC, concurrent
1211 // marking is no longer active. Therefore we need not
1212 // re-enable reference discovery for the CM ref processor.
1213 // That will be done at the start of the next marking cycle.
1214 // We also know that the STW processor should no longer
1215 // discover any new references.
1216 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1217 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1218 ref_processor_stw()->verify_no_references_recorded();
1219 ref_processor_cm()->verify_no_references_recorded();
1220 }
1221
1222 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) {
1223 print_hrm_post_compaction();
1224 heap_transition->print();
1225 print_heap_after_gc();
1226 print_heap_regions();
1227 #ifdef TRACESPINNING
1228 ParallelTaskTerminator::print_termination_counts();
1229 #endif
1230 }
1231
1232 void G1CollectedHeap::do_full_collection_inner(G1FullGCScope* scope) {
1233 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1234 g1_policy()->record_full_collection_start();
1235
1236 print_heap_before_gc();
1237 print_heap_regions();
1238
1239 abort_concurrent_cycle();
1240 verify_before_full_collection(scope->is_explicit_gc());
1241
1242 gc_prologue(true);
1243 prepare_heap_for_full_collection();
1244
1245 {
1246 G1FullCollector collector(scope, ref_processor_stw(), concurrent_mark()->nextMarkBitMap(), workers()->active_workers());
1247 // Prepare collection by putting reference processor
1248 // in a correct state.
1249 collector.prepare_collection();
1250
1251 // Do the actual collection.
1252 collector.collect();
1253
1254 collector.complete_collection();
1255 }
1256
1257 prepare_heap_for_mutators();
1258
1259 g1_policy()->record_full_collection_end();
1260 gc_epilogue(true);
1261
1262 // Post collection verification.
1263 verify_after_full_collection();
1264
1265 // Post collection logging.
1266 // We should do this after we potentially resize the heap so
1267 // that all the COMMIT / UNCOMMIT events are generated before
1268 // the compaction events.
1269 print_heap_after_full_collection(scope->heap_transition());
1270 }
1271 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1272 bool clear_all_soft_refs) {
1273 assert_at_safepoint(true /* should_be_vm_thread */);
1274
1275 if (GCLocker::check_active_before_gc()) {
1276 // Full GC was not completed.
1277 return false;
1278 }
1279
1280 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1281 collector_policy()->should_clear_all_soft_refs();
1282
1283 G1FullGCScope scope(explicit_gc, do_clear_all_soft_refs);
1284 do_full_collection_inner(&scope);
1285
1286 // Full collection was successfully completed.
1287 return true;
1288 }
1289
1290 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1291 // Currently, there is no facility in the do_full_collection(bool) API to notify
1292 // the caller that the collection did not succeed (e.g., because it was locked
1293 // out by the GC locker). So, right now, we'll ignore the return value.
1294 bool dummy = do_full_collection(true, /* explicit_gc */
1295 clear_all_soft_refs);
1296 }
1297
1298 void G1CollectedHeap::resize_if_necessary_after_full_collection() {
1299 // Include bytes that will be pre-allocated to support collections, as "used".
1300 const size_t used_after_gc = used();
1301 const size_t capacity_after_gc = capacity();
1302 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1303
1304 // This is enforced in arguments.cpp.
1305 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1306 "otherwise the code below doesn't make sense");
1307
1308 // We don't have floating point command-line arguments
1309 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1310 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1311 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1312 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1313
1314 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1315 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1316
1317 // We have to be careful here as these two calculations can overflow
1318 // 32-bit size_t's.
1319 double used_after_gc_d = (double) used_after_gc;
1320 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1321 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1322
1323 // Let's make sure that they are both under the max heap size, which
1324 // by default will make them fit into a size_t.
1325 double desired_capacity_upper_bound = (double) max_heap_size;
1326 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1327 desired_capacity_upper_bound);
1328 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1329 desired_capacity_upper_bound);
1330
1331 // We can now safely turn them into size_t's.
1332 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1333 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1334
1335 // This assert only makes sense here, before we adjust them
1336 // with respect to the min and max heap size.
1337 assert(minimum_desired_capacity <= maximum_desired_capacity,
1338 "minimum_desired_capacity = " SIZE_FORMAT ", "
1339 "maximum_desired_capacity = " SIZE_FORMAT,
1340 minimum_desired_capacity, maximum_desired_capacity);
1341
1342 // Should not be greater than the heap max size. No need to adjust
1343 // it with respect to the heap min size as it's a lower bound (i.e.,
1344 // we'll try to make the capacity larger than it, not smaller).
1345 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1346 // Should not be less than the heap min size. No need to adjust it
1347 // with respect to the heap max size as it's an upper bound (i.e.,
1348 // we'll try to make the capacity smaller than it, not greater).
1349 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1350
1351 if (capacity_after_gc < minimum_desired_capacity) {
1352 // Don't expand unless it's significant
1353 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1354
1355 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). "
1356 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1357 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio);
1358
1359 expand(expand_bytes, _workers);
1360
1361 // No expansion, now see if we want to shrink
1362 } else if (capacity_after_gc > maximum_desired_capacity) {
1363 // Capacity too large, compute shrinking size
1364 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1365
1366 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). "
1367 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1368 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio);
1369
1370 shrink(shrink_bytes);
1371 }
1372 }
1373
1374 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1375 AllocationContext_t context,
1376 bool do_gc,
1377 bool clear_all_soft_refs,
1378 bool expect_null_mutator_alloc_region,
1379 bool* gc_succeeded) {
1380 *gc_succeeded = true;
1381 // Let's attempt the allocation first.
1382 HeapWord* result =
1383 attempt_allocation_at_safepoint(word_size,
1384 context,
1385 expect_null_mutator_alloc_region);
1386 if (result != NULL) {
1387 assert(*gc_succeeded, "sanity");
1388 return result;
1389 }
1390
1391 // In a G1 heap, we're supposed to keep allocation from failing by
1392 // incremental pauses. Therefore, at least for now, we'll favor
1393 // expansion over collection. (This might change in the future if we can
1394 // do something smarter than full collection to satisfy a failed alloc.)
1395 result = expand_and_allocate(word_size, context);
1396 if (result != NULL) {
1397 assert(*gc_succeeded, "sanity");
1398 return result;
1399 }
1400
1401 if (do_gc) {
1402 // Expansion didn't work, we'll try to do a Full GC.
1403 *gc_succeeded = do_full_collection(false, /* explicit_gc */
1404 clear_all_soft_refs);
1405 }
1406
1407 return NULL;
1408 }
1409
1410 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1411 AllocationContext_t context,
1412 bool* succeeded) {
1413 assert_at_safepoint(true /* should_be_vm_thread */);
1414
1415 // Attempts to allocate followed by Full GC.
1416 HeapWord* result =
1417 satisfy_failed_allocation_helper(word_size,
1418 context,
1419 true, /* do_gc */
1420 false, /* clear_all_soft_refs */
1421 false, /* expect_null_mutator_alloc_region */
1422 succeeded);
1423
1424 if (result != NULL || !*succeeded) {
1425 return result;
1426 }
1427
1428 // Attempts to allocate followed by Full GC that will collect all soft references.
1429 result = satisfy_failed_allocation_helper(word_size,
1430 context,
1431 true, /* do_gc */
1432 true, /* clear_all_soft_refs */
1433 true, /* expect_null_mutator_alloc_region */
1434 succeeded);
1435
1436 if (result != NULL || !*succeeded) {
1437 return result;
1438 }
1439
1440 // Attempts to allocate, no GC
1441 result = satisfy_failed_allocation_helper(word_size,
1442 context,
1443 false, /* do_gc */
1444 false, /* clear_all_soft_refs */
1445 true, /* expect_null_mutator_alloc_region */
1446 succeeded);
1447
1448 if (result != NULL) {
1449 assert(*succeeded, "sanity");
1450 return result;
1451 }
1452
1453 assert(!collector_policy()->should_clear_all_soft_refs(),
1454 "Flag should have been handled and cleared prior to this point");
1455
1456 // What else? We might try synchronous finalization later. If the total
1457 // space available is large enough for the allocation, then a more
1458 // complete compaction phase than we've tried so far might be
1459 // appropriate.
1460 assert(*succeeded, "sanity");
1461 return NULL;
1462 }
1463
1464 // Attempting to expand the heap sufficiently
1465 // to support an allocation of the given "word_size". If
1466 // successful, perform the allocation and return the address of the
1467 // allocated block, or else "NULL".
1468
1469 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1470 assert_at_safepoint(true /* should_be_vm_thread */);
1471
1472 _verifier->verify_region_sets_optional();
1473
1474 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1475 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1476 word_size * HeapWordSize);
1477
1478
1479 if (expand(expand_bytes, _workers)) {
1480 _hrm.verify_optional();
1481 _verifier->verify_region_sets_optional();
1482 return attempt_allocation_at_safepoint(word_size,
1483 context,
1484 false /* expect_null_mutator_alloc_region */);
1485 }
1486 return NULL;
1487 }
1488
1489 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) {
1490 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1491 aligned_expand_bytes = align_up(aligned_expand_bytes,
1492 HeapRegion::GrainBytes);
1493
1494 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B",
1495 expand_bytes, aligned_expand_bytes);
1496
1497 if (is_maximal_no_gc()) {
1498 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1499 return false;
1500 }
1501
1502 double expand_heap_start_time_sec = os::elapsedTime();
1503 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1504 assert(regions_to_expand > 0, "Must expand by at least one region");
1505
1506 uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers);
1507 if (expand_time_ms != NULL) {
1508 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1509 }
1510
1511 if (expanded_by > 0) {
1512 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1513 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1514 g1_policy()->record_new_heap_size(num_regions());
1515 } else {
1516 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1517
1518 // The expansion of the virtual storage space was unsuccessful.
1519 // Let's see if it was because we ran out of swap.
1520 if (G1ExitOnExpansionFailure &&
1521 _hrm.available() >= regions_to_expand) {
1522 // We had head room...
1523 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1524 }
1525 }
1526 return regions_to_expand > 0;
1527 }
1528
1529 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1530 size_t aligned_shrink_bytes =
1531 ReservedSpace::page_align_size_down(shrink_bytes);
1532 aligned_shrink_bytes = align_down(aligned_shrink_bytes,
1533 HeapRegion::GrainBytes);
1534 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1535
1536 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1537 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1538
1539
1540 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",
1541 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1542 if (num_regions_removed > 0) {
1543 g1_policy()->record_new_heap_size(num_regions());
1544 } else {
1545 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1546 }
1547 }
1548
1549 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1550 _verifier->verify_region_sets_optional();
1551
1552 // We should only reach here at the end of a Full GC which means we
1553 // should not not be holding to any GC alloc regions. The method
1554 // below will make sure of that and do any remaining clean up.
1555 _allocator->abandon_gc_alloc_regions();
1556
1557 // Instead of tearing down / rebuilding the free lists here, we
1558 // could instead use the remove_all_pending() method on free_list to
1559 // remove only the ones that we need to remove.
1560 tear_down_region_sets(true /* free_list_only */);
1561 shrink_helper(shrink_bytes);
1562 rebuild_region_sets(true /* free_list_only */);
1563
1564 _hrm.verify_optional();
1565 _verifier->verify_region_sets_optional();
1566 }
1567
1568 // Public methods.
1569
1570 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) :
1571 CollectedHeap(),
1572 _collector_policy(collector_policy),
1573 _g1_policy(create_g1_policy()),
1574 _collection_set(this, _g1_policy),
1575 _dirty_card_queue_set(false),
1576 _is_alive_closure_cm(this),
1577 _is_alive_closure_stw(this),
1578 _ref_processor_cm(NULL),
1579 _ref_processor_stw(NULL),
1580 _bot(NULL),
1581 _hot_card_cache(NULL),
1582 _g1_rem_set(NULL),
1583 _cg1r(NULL),
1584 _g1mm(NULL),
1585 _refine_cte_cl(NULL),
1586 _preserved_marks_set(true /* in_c_heap */),
1587 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1588 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1589 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1590 _humongous_reclaim_candidates(),
1591 _has_humongous_reclaim_candidates(false),
1592 _archive_allocator(NULL),
1593 _free_regions_coming(false),
1594 _gc_time_stamp(0),
1595 _summary_bytes_used(0),
1596 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1597 _old_evac_stats("Old", OldPLABSize, PLABWeight),
1598 _expand_heap_after_alloc_failure(true),
1599 _old_marking_cycles_started(0),
1600 _old_marking_cycles_completed(0),
1601 _in_cset_fast_test(),
1602 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1603 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()) {
1604
1605 _workers = new WorkGang("GC Thread", ParallelGCThreads,
1606 /* are_GC_task_threads */true,
1607 /* are_ConcurrentGC_threads */false);
1608 _workers->initialize_workers();
1609 _verifier = new G1HeapVerifier(this);
1610
1611 _allocator = G1Allocator::create_allocator(this);
1612
1613 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics());
1614
1615 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1616
1617 // Override the default _filler_array_max_size so that no humongous filler
1618 // objects are created.
1619 _filler_array_max_size = _humongous_object_threshold_in_words;
1620
1621 uint n_queues = ParallelGCThreads;
1622 _task_queues = new RefToScanQueueSet(n_queues);
1623
1624 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1625
1626 for (uint i = 0; i < n_queues; i++) {
1627 RefToScanQueue* q = new RefToScanQueue();
1628 q->initialize();
1629 _task_queues->register_queue(i, q);
1630 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1631 }
1632
1633 // Initialize the G1EvacuationFailureALot counters and flags.
1634 NOT_PRODUCT(reset_evacuation_should_fail();)
1635
1636 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1637 }
1638
1639 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1640 size_t size,
1641 size_t translation_factor) {
1642 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1643 // Allocate a new reserved space, preferring to use large pages.
1644 ReservedSpace rs(size, preferred_page_size);
1645 G1RegionToSpaceMapper* result =
1646 G1RegionToSpaceMapper::create_mapper(rs,
1647 size,
1648 rs.alignment(),
1649 HeapRegion::GrainBytes,
1650 translation_factor,
1651 mtGC);
1652
1653 os::trace_page_sizes_for_requested_size(description,
1654 size,
1655 preferred_page_size,
1656 rs.alignment(),
1657 rs.base(),
1658 rs.size());
1659
1660 return result;
1661 }
1662
1663 jint G1CollectedHeap::initialize() {
1664 CollectedHeap::pre_initialize();
1665 os::enable_vtime();
1666
1667 // Necessary to satisfy locking discipline assertions.
1668
1669 MutexLocker x(Heap_lock);
1670
1671 // While there are no constraints in the GC code that HeapWordSize
1672 // be any particular value, there are multiple other areas in the
1673 // system which believe this to be true (e.g. oop->object_size in some
1674 // cases incorrectly returns the size in wordSize units rather than
1675 // HeapWordSize).
1676 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1677
1678 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1679 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1680 size_t heap_alignment = collector_policy()->heap_alignment();
1681
1682 // Ensure that the sizes are properly aligned.
1683 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1684 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1685 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1686
1687 // Reserve the maximum.
1688
1689 // When compressed oops are enabled, the preferred heap base
1690 // is calculated by subtracting the requested size from the
1691 // 32Gb boundary and using the result as the base address for
1692 // heap reservation. If the requested size is not aligned to
1693 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1694 // into the ReservedHeapSpace constructor) then the actual
1695 // base of the reserved heap may end up differing from the
1696 // address that was requested (i.e. the preferred heap base).
1697 // If this happens then we could end up using a non-optimal
1698 // compressed oops mode.
1699
1700 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1701 heap_alignment);
1702
1703 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1704
1705 // Create the barrier set for the entire reserved region.
1706 G1SATBCardTableLoggingModRefBS* bs
1707 = new G1SATBCardTableLoggingModRefBS(reserved_region());
1708 bs->initialize();
1709 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity");
1710 set_barrier_set(bs);
1711
1712 // Create the hot card cache.
1713 _hot_card_cache = new G1HotCardCache(this);
1714
1715 // Carve out the G1 part of the heap.
1716 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1717 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
1718 G1RegionToSpaceMapper* heap_storage =
1719 G1RegionToSpaceMapper::create_mapper(g1_rs,
1720 g1_rs.size(),
1721 page_size,
1722 HeapRegion::GrainBytes,
1723 1,
1724 mtJavaHeap);
1725 os::trace_page_sizes("Heap",
1726 collector_policy()->min_heap_byte_size(),
1727 max_byte_size,
1728 page_size,
1729 heap_rs.base(),
1730 heap_rs.size());
1731 heap_storage->set_mapping_changed_listener(&_listener);
1732
1733 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1734 G1RegionToSpaceMapper* bot_storage =
1735 create_aux_memory_mapper("Block Offset Table",
1736 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1737 G1BlockOffsetTable::heap_map_factor());
1738
1739 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
1740 G1RegionToSpaceMapper* cardtable_storage =
1741 create_aux_memory_mapper("Card Table",
1742 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize),
1743 G1SATBCardTableLoggingModRefBS::heap_map_factor());
1744
1745 G1RegionToSpaceMapper* card_counts_storage =
1746 create_aux_memory_mapper("Card Counts Table",
1747 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1748 G1CardCounts::heap_map_factor());
1749
1750 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1751 G1RegionToSpaceMapper* prev_bitmap_storage =
1752 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1753 G1RegionToSpaceMapper* next_bitmap_storage =
1754 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1755
1756 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1757 g1_barrier_set()->initialize(cardtable_storage);
1758 // Do later initialization work for concurrent refinement.
1759 _hot_card_cache->initialize(card_counts_storage);
1760
1761 // 6843694 - ensure that the maximum region index can fit
1762 // in the remembered set structures.
1763 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1764 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1765
1766 // Also create a G1 rem set.
1767 _g1_rem_set = new G1RemSet(this, g1_barrier_set(), _hot_card_cache);
1768 _g1_rem_set->initialize(max_capacity(), max_regions());
1769
1770 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1771 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1772 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1773 "too many cards per region");
1774
1775 FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1776
1777 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1778
1779 {
1780 HeapWord* start = _hrm.reserved().start();
1781 HeapWord* end = _hrm.reserved().end();
1782 size_t granularity = HeapRegion::GrainBytes;
1783
1784 _in_cset_fast_test.initialize(start, end, granularity);
1785 _humongous_reclaim_candidates.initialize(start, end, granularity);
1786 }
1787
1788 // Create the G1ConcurrentMark data structure and thread.
1789 // (Must do this late, so that "max_regions" is defined.)
1790 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1791 if (_cm == NULL || !_cm->completed_initialization()) {
1792 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
1793 return JNI_ENOMEM;
1794 }
1795 _cmThread = _cm->cmThread();
1796
1797 // Now expand into the initial heap size.
1798 if (!expand(init_byte_size, _workers)) {
1799 vm_shutdown_during_initialization("Failed to allocate initial heap.");
1800 return JNI_ENOMEM;
1801 }
1802
1803 // Perform any initialization actions delegated to the policy.
1804 g1_policy()->init(this, &_collection_set);
1805
1806 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1807 SATB_Q_FL_lock,
1808 G1SATBProcessCompletedThreshold,
1809 Shared_SATB_Q_lock);
1810
1811 _refine_cte_cl = new RefineCardTableEntryClosure();
1812
1813 jint ecode = JNI_OK;
1814 _cg1r = ConcurrentG1Refine::create(_refine_cte_cl, &ecode);
1815 if (_cg1r == NULL) {
1816 return ecode;
1817 }
1818
1819 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
1820 DirtyCardQ_CBL_mon,
1821 DirtyCardQ_FL_lock,
1822 (int)concurrent_g1_refine()->yellow_zone(),
1823 (int)concurrent_g1_refine()->red_zone(),
1824 Shared_DirtyCardQ_lock,
1825 NULL, // fl_owner
1826 true); // init_free_ids
1827
1828 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
1829 DirtyCardQ_CBL_mon,
1830 DirtyCardQ_FL_lock,
1831 -1, // never trigger processing
1832 -1, // no limit on length
1833 Shared_DirtyCardQ_lock,
1834 &JavaThread::dirty_card_queue_set());
1835
1836 // Here we allocate the dummy HeapRegion that is required by the
1837 // G1AllocRegion class.
1838 HeapRegion* dummy_region = _hrm.get_dummy_region();
1839
1840 // We'll re-use the same region whether the alloc region will
1841 // require BOT updates or not and, if it doesn't, then a non-young
1842 // region will complain that it cannot support allocations without
1843 // BOT updates. So we'll tag the dummy region as eden to avoid that.
1844 dummy_region->set_eden();
1845 // Make sure it's full.
1846 dummy_region->set_top(dummy_region->end());
1847 G1AllocRegion::setup(this, dummy_region);
1848
1849 _allocator->init_mutator_alloc_region();
1850
1851 // Do create of the monitoring and management support so that
1852 // values in the heap have been properly initialized.
1853 _g1mm = new G1MonitoringSupport(this);
1854
1855 G1StringDedup::initialize();
1856
1857 _preserved_marks_set.init(ParallelGCThreads);
1858
1859 _collection_set.initialize(max_regions());
1860
1861 _g1_rem_set->initialize_periodic_summary_info();
1862
1863 return JNI_OK;
1864 }
1865
1866 void G1CollectedHeap::stop() {
1867 // Stop all concurrent threads. We do this to make sure these threads
1868 // do not continue to execute and access resources (e.g. logging)
1869 // that are destroyed during shutdown.
1870 _cg1r->stop();
1871 _cmThread->stop();
1872 if (G1StringDedup::is_enabled()) {
1873 G1StringDedup::stop();
1874 }
1875 }
1876
1877 size_t G1CollectedHeap::conservative_max_heap_alignment() {
1878 return HeapRegion::max_region_size();
1879 }
1880
1881 void G1CollectedHeap::post_initialize() {
1882 ref_processing_init();
1883 }
1884
1885 void G1CollectedHeap::ref_processing_init() {
1886 // Reference processing in G1 currently works as follows:
1887 //
1888 // * There are two reference processor instances. One is
1889 // used to record and process discovered references
1890 // during concurrent marking; the other is used to
1891 // record and process references during STW pauses
1892 // (both full and incremental).
1893 // * Both ref processors need to 'span' the entire heap as
1894 // the regions in the collection set may be dotted around.
1895 //
1896 // * For the concurrent marking ref processor:
1897 // * Reference discovery is enabled at initial marking.
1898 // * Reference discovery is disabled and the discovered
1899 // references processed etc during remarking.
1900 // * Reference discovery is MT (see below).
1901 // * Reference discovery requires a barrier (see below).
1902 // * Reference processing may or may not be MT
1903 // (depending on the value of ParallelRefProcEnabled
1904 // and ParallelGCThreads).
1905 // * A full GC disables reference discovery by the CM
1906 // ref processor and abandons any entries on it's
1907 // discovered lists.
1908 //
1909 // * For the STW processor:
1910 // * Non MT discovery is enabled at the start of a full GC.
1911 // * Processing and enqueueing during a full GC is non-MT.
1912 // * During a full GC, references are processed after marking.
1913 //
1914 // * Discovery (may or may not be MT) is enabled at the start
1915 // of an incremental evacuation pause.
1916 // * References are processed near the end of a STW evacuation pause.
1917 // * For both types of GC:
1918 // * Discovery is atomic - i.e. not concurrent.
1919 // * Reference discovery will not need a barrier.
1920
1921 MemRegion mr = reserved_region();
1922
1923 // Concurrent Mark ref processor
1924 _ref_processor_cm =
1925 new ReferenceProcessor(mr, // span
1926 ParallelRefProcEnabled && (ParallelGCThreads > 1),
1927 // mt processing
1928 ParallelGCThreads,
1929 // degree of mt processing
1930 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
1931 // mt discovery
1932 MAX2(ParallelGCThreads, ConcGCThreads),
1933 // degree of mt discovery
1934 false,
1935 // Reference discovery is not atomic
1936 &_is_alive_closure_cm);
1937 // is alive closure
1938 // (for efficiency/performance)
1939
1940 // STW ref processor
1941 _ref_processor_stw =
1942 new ReferenceProcessor(mr, // span
1943 ParallelRefProcEnabled && (ParallelGCThreads > 1),
1944 // mt processing
1945 ParallelGCThreads,
1946 // degree of mt processing
1947 (ParallelGCThreads > 1),
1948 // mt discovery
1949 ParallelGCThreads,
1950 // degree of mt discovery
1951 true,
1952 // Reference discovery is atomic
1953 &_is_alive_closure_stw);
1954 // is alive closure
1955 // (for efficiency/performance)
1956 }
1957
1958 CollectorPolicy* G1CollectedHeap::collector_policy() const {
1959 return _collector_policy;
1960 }
1961
1962 size_t G1CollectedHeap::capacity() const {
1963 return _hrm.length() * HeapRegion::GrainBytes;
1964 }
1965
1966 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
1967 hr->reset_gc_time_stamp();
1968 }
1969
1970 #ifndef PRODUCT
1971
1972 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
1973 private:
1974 unsigned _gc_time_stamp;
1975 bool _failures;
1976
1977 public:
1978 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
1979 _gc_time_stamp(gc_time_stamp), _failures(false) { }
1980
1981 virtual bool doHeapRegion(HeapRegion* hr) {
1982 unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
1983 if (_gc_time_stamp != region_gc_time_stamp) {
1984 log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr),
1985 region_gc_time_stamp, _gc_time_stamp);
1986 _failures = true;
1987 }
1988 return false;
1989 }
1990
1991 bool failures() { return _failures; }
1992 };
1993
1994 void G1CollectedHeap::check_gc_time_stamps() {
1995 CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
1996 heap_region_iterate(&cl);
1997 guarantee(!cl.failures(), "all GC time stamps should have been reset");
1998 }
1999 #endif // PRODUCT
2000
2001 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) {
2002 _hot_card_cache->drain(cl, worker_i);
2003 }
2004
2005 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) {
2006 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2007 size_t n_completed_buffers = 0;
2008 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2009 n_completed_buffers++;
2010 }
2011 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
2012 dcqs.clear_n_completed_buffers();
2013 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2014 }
2015
2016 // Computes the sum of the storage used by the various regions.
2017 size_t G1CollectedHeap::used() const {
2018 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
2019 if (_archive_allocator != NULL) {
2020 result += _archive_allocator->used();
2021 }
2022 return result;
2023 }
2024
2025 size_t G1CollectedHeap::used_unlocked() const {
2026 return _summary_bytes_used;
2027 }
2028
2029 class SumUsedClosure: public HeapRegionClosure {
2030 size_t _used;
2031 public:
2032 SumUsedClosure() : _used(0) {}
2033 bool doHeapRegion(HeapRegion* r) {
2034 _used += r->used();
2035 return false;
2036 }
2037 size_t result() { return _used; }
2038 };
2039
2040 size_t G1CollectedHeap::recalculate_used() const {
2041 double recalculate_used_start = os::elapsedTime();
2042
2043 SumUsedClosure blk;
2044 heap_region_iterate(&blk);
2045
2046 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2047 return blk.result();
2048 }
2049
2050 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
2051 switch (cause) {
2052 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2053 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent;
2054 case GCCause::_update_allocation_context_stats_inc: return true;
2055 case GCCause::_wb_conc_mark: return true;
2056 default : return false;
2057 }
2058 }
2059
2060 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2061 switch (cause) {
2062 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2063 case GCCause::_g1_humongous_allocation: return true;
2064 default: return is_user_requested_concurrent_full_gc(cause);
2065 }
2066 }
2067
2068 #ifndef PRODUCT
2069 void G1CollectedHeap::allocate_dummy_regions() {
2070 // Let's fill up most of the region
2071 size_t word_size = HeapRegion::GrainWords - 1024;
2072 // And as a result the region we'll allocate will be humongous.
2073 guarantee(is_humongous(word_size), "sanity");
2074
2075 // _filler_array_max_size is set to humongous object threshold
2076 // but temporarily change it to use CollectedHeap::fill_with_object().
2077 SizeTFlagSetting fs(_filler_array_max_size, word_size);
2078
2079 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2080 // Let's use the existing mechanism for the allocation
2081 HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2082 AllocationContext::system());
2083 if (dummy_obj != NULL) {
2084 MemRegion mr(dummy_obj, word_size);
2085 CollectedHeap::fill_with_object(mr);
2086 } else {
2087 // If we can't allocate once, we probably cannot allocate
2088 // again. Let's get out of the loop.
2089 break;
2090 }
2091 }
2092 }
2093 #endif // !PRODUCT
2094
2095 void G1CollectedHeap::increment_old_marking_cycles_started() {
2096 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2097 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2098 "Wrong marking cycle count (started: %d, completed: %d)",
2099 _old_marking_cycles_started, _old_marking_cycles_completed);
2100
2101 _old_marking_cycles_started++;
2102 }
2103
2104 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2105 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2106
2107 // We assume that if concurrent == true, then the caller is a
2108 // concurrent thread that was joined the Suspendible Thread
2109 // Set. If there's ever a cheap way to check this, we should add an
2110 // assert here.
2111
2112 // Given that this method is called at the end of a Full GC or of a
2113 // concurrent cycle, and those can be nested (i.e., a Full GC can
2114 // interrupt a concurrent cycle), the number of full collections
2115 // completed should be either one (in the case where there was no
2116 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2117 // behind the number of full collections started.
2118
2119 // This is the case for the inner caller, i.e. a Full GC.
2120 assert(concurrent ||
2121 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2122 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2123 "for inner caller (Full GC): _old_marking_cycles_started = %u "
2124 "is inconsistent with _old_marking_cycles_completed = %u",
2125 _old_marking_cycles_started, _old_marking_cycles_completed);
2126
2127 // This is the case for the outer caller, i.e. the concurrent cycle.
2128 assert(!concurrent ||
2129 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2130 "for outer caller (concurrent cycle): "
2131 "_old_marking_cycles_started = %u "
2132 "is inconsistent with _old_marking_cycles_completed = %u",
2133 _old_marking_cycles_started, _old_marking_cycles_completed);
2134
2135 _old_marking_cycles_completed += 1;
2136
2137 // We need to clear the "in_progress" flag in the CM thread before
2138 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2139 // is set) so that if a waiter requests another System.gc() it doesn't
2140 // incorrectly see that a marking cycle is still in progress.
2141 if (concurrent) {
2142 _cmThread->set_idle();
2143 }
2144
2145 // This notify_all() will ensure that a thread that called
2146 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2147 // and it's waiting for a full GC to finish will be woken up. It is
2148 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2149 FullGCCount_lock->notify_all();
2150 }
2151
2152 void G1CollectedHeap::collect(GCCause::Cause cause) {
2153 assert_heap_not_locked();
2154
2155 uint gc_count_before;
2156 uint old_marking_count_before;
2157 uint full_gc_count_before;
2158 bool retry_gc;
2159
2160 do {
2161 retry_gc = false;
2162
2163 {
2164 MutexLocker ml(Heap_lock);
2165
2166 // Read the GC count while holding the Heap_lock
2167 gc_count_before = total_collections();
2168 full_gc_count_before = total_full_collections();
2169 old_marking_count_before = _old_marking_cycles_started;
2170 }
2171
2172 if (should_do_concurrent_full_gc(cause)) {
2173 // Schedule an initial-mark evacuation pause that will start a
2174 // concurrent cycle. We're setting word_size to 0 which means that
2175 // we are not requesting a post-GC allocation.
2176 VM_G1IncCollectionPause op(gc_count_before,
2177 0, /* word_size */
2178 true, /* should_initiate_conc_mark */
2179 g1_policy()->max_pause_time_ms(),
2180 cause);
2181 op.set_allocation_context(AllocationContext::current());
2182
2183 VMThread::execute(&op);
2184 if (!op.pause_succeeded()) {
2185 if (old_marking_count_before == _old_marking_cycles_started) {
2186 retry_gc = op.should_retry_gc();
2187 } else {
2188 // A Full GC happened while we were trying to schedule the
2189 // initial-mark GC. No point in starting a new cycle given
2190 // that the whole heap was collected anyway.
2191 }
2192
2193 if (retry_gc) {
2194 if (GCLocker::is_active_and_needs_gc()) {
2195 GCLocker::stall_until_clear();
2196 }
2197 }
2198 }
2199 } else {
2200 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2201 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2202
2203 // Schedule a standard evacuation pause. We're setting word_size
2204 // to 0 which means that we are not requesting a post-GC allocation.
2205 VM_G1IncCollectionPause op(gc_count_before,
2206 0, /* word_size */
2207 false, /* should_initiate_conc_mark */
2208 g1_policy()->max_pause_time_ms(),
2209 cause);
2210 VMThread::execute(&op);
2211 } else {
2212 // Schedule a Full GC.
2213 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2214 VMThread::execute(&op);
2215 }
2216 }
2217 } while (retry_gc);
2218 }
2219
2220 bool G1CollectedHeap::is_in(const void* p) const {
2221 if (_hrm.reserved().contains(p)) {
2222 // Given that we know that p is in the reserved space,
2223 // heap_region_containing() should successfully
2224 // return the containing region.
2225 HeapRegion* hr = heap_region_containing(p);
2226 return hr->is_in(p);
2227 } else {
2228 return false;
2229 }
2230 }
2231
2232 #ifdef ASSERT
2233 bool G1CollectedHeap::is_in_exact(const void* p) const {
2234 bool contains = reserved_region().contains(p);
2235 bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2236 if (contains && available) {
2237 return true;
2238 } else {
2239 return false;
2240 }
2241 }
2242 #endif
2243
2244 // Iteration functions.
2245
2246 // Iterates an ObjectClosure over all objects within a HeapRegion.
2247
2248 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2249 ObjectClosure* _cl;
2250 public:
2251 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2252 bool doHeapRegion(HeapRegion* r) {
2253 if (!r->is_continues_humongous()) {
2254 r->object_iterate(_cl);
2255 }
2256 return false;
2257 }
2258 };
2259
2260 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2261 IterateObjectClosureRegionClosure blk(cl);
2262 heap_region_iterate(&blk);
2263 }
2264
2265 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2266 _hrm.iterate(cl);
2267 }
2268
2269 void G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl,
2270 uint worker_id,
2271 HeapRegionClaimerBase *hrclaimer) const {
2272 _hrm.par_iterate(cl, worker_id, hrclaimer);
2273 }
2274
2275 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2276 _collection_set.iterate(cl);
2277 }
2278
2279 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) {
2280 _collection_set.iterate_from(cl, worker_id, workers()->active_workers());
2281 }
2282
2283 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2284 HeapRegion* hr = heap_region_containing(addr);
2285 return hr->block_start(addr);
2286 }
2287
2288 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2289 HeapRegion* hr = heap_region_containing(addr);
2290 return hr->block_size(addr);
2291 }
2292
2293 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2294 HeapRegion* hr = heap_region_containing(addr);
2295 return hr->block_is_obj(addr);
2296 }
2297
2298 bool G1CollectedHeap::supports_tlab_allocation() const {
2299 return true;
2300 }
2301
2302 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2303 return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2304 }
2305
2306 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2307 return _eden.length() * HeapRegion::GrainBytes;
2308 }
2309
2310 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2311 // must be equal to the humongous object limit.
2312 size_t G1CollectedHeap::max_tlab_size() const {
2313 return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
2314 }
2315
2316 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2317 AllocationContext_t context = AllocationContext::current();
2318 return _allocator->unsafe_max_tlab_alloc(context);
2319 }
2320
2321 size_t G1CollectedHeap::max_capacity() const {
2322 return _hrm.reserved().byte_size();
2323 }
2324
2325 jlong G1CollectedHeap::millis_since_last_gc() {
2326 // See the notes in GenCollectedHeap::millis_since_last_gc()
2327 // for more information about the implementation.
2328 jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) -
2329 _g1_policy->collection_pause_end_millis();
2330 if (ret_val < 0) {
2331 log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
2332 ". returning zero instead.", ret_val);
2333 return 0;
2334 }
2335 return ret_val;
2336 }
2337
2338 void G1CollectedHeap::prepare_for_verify() {
2339 _verifier->prepare_for_verify();
2340 }
2341
2342 void G1CollectedHeap::verify(VerifyOption vo) {
2343 _verifier->verify(vo);
2344 }
2345
2346 bool G1CollectedHeap::supports_concurrent_phase_control() const {
2347 return true;
2348 }
2349
2350 const char* const* G1CollectedHeap::concurrent_phases() const {
2351 return _cmThread->concurrent_phases();
2352 }
2353
2354 bool G1CollectedHeap::request_concurrent_phase(const char* phase) {
2355 return _cmThread->request_concurrent_phase(phase);
2356 }
2357
2358 class PrintRegionClosure: public HeapRegionClosure {
2359 outputStream* _st;
2360 public:
2361 PrintRegionClosure(outputStream* st) : _st(st) {}
2362 bool doHeapRegion(HeapRegion* r) {
2363 r->print_on(_st);
2364 return false;
2365 }
2366 };
2367
2368 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2369 const HeapRegion* hr,
2370 const VerifyOption vo) const {
2371 switch (vo) {
2372 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2373 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2374 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked() && !hr->is_archive();
2375 default: ShouldNotReachHere();
2376 }
2377 return false; // keep some compilers happy
2378 }
2379
2380 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2381 const VerifyOption vo) const {
2382 switch (vo) {
2383 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2384 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2385 case VerifyOption_G1UseMarkWord: {
2386 HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj);
2387 return !obj->is_gc_marked() && !hr->is_archive();
2388 }
2389 default: ShouldNotReachHere();
2390 }
2391 return false; // keep some compilers happy
2392 }
2393
2394 void G1CollectedHeap::print_heap_regions() const {
2395 Log(gc, heap, region) log;
2396 if (log.is_trace()) {
2397 ResourceMark rm;
2398 print_regions_on(log.trace_stream());
2399 }
2400 }
2401
2402 void G1CollectedHeap::print_on(outputStream* st) const {
2403 st->print(" %-20s", "garbage-first heap");
2404 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2405 capacity()/K, used_unlocked()/K);
2406 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")",
2407 p2i(_hrm.reserved().start()),
2408 p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords),
2409 p2i(_hrm.reserved().end()));
2410 st->cr();
2411 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2412 uint young_regions = young_regions_count();
2413 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2414 (size_t) young_regions * HeapRegion::GrainBytes / K);
2415 uint survivor_regions = survivor_regions_count();
2416 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2417 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2418 st->cr();
2419 MetaspaceAux::print_on(st);
2420 }
2421
2422 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2423 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2424 "HS=humongous(starts), HC=humongous(continues), "
2425 "CS=collection set, F=free, A=archive, TS=gc time stamp, "
2426 "AC=allocation context, "
2427 "TAMS=top-at-mark-start (previous, next)");
2428 PrintRegionClosure blk(st);
2429 heap_region_iterate(&blk);
2430 }
2431
2432 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2433 print_on(st);
2434
2435 // Print the per-region information.
2436 print_regions_on(st);
2437 }
2438
2439 void G1CollectedHeap::print_on_error(outputStream* st) const {
2440 this->CollectedHeap::print_on_error(st);
2441
2442 if (_cm != NULL) {
2443 st->cr();
2444 _cm->print_on_error(st);
2445 }
2446 }
2447
2448 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2449 workers()->print_worker_threads_on(st);
2450 _cmThread->print_on(st);
2451 st->cr();
2452 _cm->print_worker_threads_on(st);
2453 _cg1r->print_worker_threads_on(st); // also prints the sample thread
2454 if (G1StringDedup::is_enabled()) {
2455 G1StringDedup::print_worker_threads_on(st);
2456 }
2457 }
2458
2459 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2460 workers()->threads_do(tc);
2461 tc->do_thread(_cmThread);
2462 _cm->threads_do(tc);
2463 _cg1r->threads_do(tc); // also iterates over the sample thread
2464 if (G1StringDedup::is_enabled()) {
2465 G1StringDedup::threads_do(tc);
2466 }
2467 }
2468
2469 void G1CollectedHeap::print_tracing_info() const {
2470 g1_rem_set()->print_summary_info();
2471 concurrent_mark()->print_summary_info();
2472 }
2473
2474 #ifndef PRODUCT
2475 // Helpful for debugging RSet issues.
2476
2477 class PrintRSetsClosure : public HeapRegionClosure {
2478 private:
2479 const char* _msg;
2480 size_t _occupied_sum;
2481
2482 public:
2483 bool doHeapRegion(HeapRegion* r) {
2484 HeapRegionRemSet* hrrs = r->rem_set();
2485 size_t occupied = hrrs->occupied();
2486 _occupied_sum += occupied;
2487
2488 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2489 if (occupied == 0) {
2490 tty->print_cr(" RSet is empty");
2491 } else {
2492 hrrs->print();
2493 }
2494 tty->print_cr("----------");
2495 return false;
2496 }
2497
2498 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2499 tty->cr();
2500 tty->print_cr("========================================");
2501 tty->print_cr("%s", msg);
2502 tty->cr();
2503 }
2504
2505 ~PrintRSetsClosure() {
2506 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2507 tty->print_cr("========================================");
2508 tty->cr();
2509 }
2510 };
2511
2512 void G1CollectedHeap::print_cset_rsets() {
2513 PrintRSetsClosure cl("Printing CSet RSets");
2514 collection_set_iterate(&cl);
2515 }
2516
2517 void G1CollectedHeap::print_all_rsets() {
2518 PrintRSetsClosure cl("Printing All RSets");;
2519 heap_region_iterate(&cl);
2520 }
2521 #endif // PRODUCT
2522
2523 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2524
2525 size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes;
2526 size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes;
2527 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2528
2529 size_t eden_capacity_bytes =
2530 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2531
2532 VirtualSpaceSummary heap_summary = create_heap_space_summary();
2533 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2534 eden_capacity_bytes, survivor_used_bytes, num_regions());
2535 }
2536
2537 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2538 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2539 stats->unused(), stats->used(), stats->region_end_waste(),
2540 stats->regions_filled(), stats->direct_allocated(),
2541 stats->failure_used(), stats->failure_waste());
2542 }
2543
2544 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2545 const G1HeapSummary& heap_summary = create_g1_heap_summary();
2546 gc_tracer->report_gc_heap_summary(when, heap_summary);
2547
2548 const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2549 gc_tracer->report_metaspace_summary(when, metaspace_summary);
2550 }
2551
2552 G1CollectedHeap* G1CollectedHeap::heap() {
2553 CollectedHeap* heap = Universe::heap();
2554 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2555 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap");
2556 return (G1CollectedHeap*)heap;
2557 }
2558
2559 void G1CollectedHeap::gc_prologue(bool full) {
2560 // always_do_update_barrier = false;
2561 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2562
2563 // This summary needs to be printed before incrementing total collections.
2564 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2565
2566 // Update common counters.
2567 increment_total_collections(full /* full gc */);
2568 if (full) {
2569 increment_old_marking_cycles_started();
2570 reset_gc_time_stamp();
2571 } else {
2572 increment_gc_time_stamp();
2573 }
2574
2575 // Fill TLAB's and such
2576 double start = os::elapsedTime();
2577 accumulate_statistics_all_tlabs();
2578 ensure_parsability(true);
2579 g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2580 }
2581
2582 void G1CollectedHeap::gc_epilogue(bool full) {
2583 // Update common counters.
2584 if (full) {
2585 // Update the number of full collections that have been completed.
2586 increment_old_marking_cycles_completed(false /* concurrent */);
2587 }
2588
2589 // We are at the end of the GC. Total collections has already been increased.
2590 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2591
2592 // FIXME: what is this about?
2593 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2594 // is set.
2595 #if defined(COMPILER2) || INCLUDE_JVMCI
2596 assert(DerivedPointerTable::is_empty(), "derived pointer present");
2597 #endif
2598 // always_do_update_barrier = true;
2599
2600 double start = os::elapsedTime();
2601 resize_all_tlabs();
2602 g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2603
2604 allocation_context_stats().update(full);
2605
2606 MemoryService::track_memory_usage();
2607 // We have just completed a GC. Update the soft reference
2608 // policy with the new heap occupancy
2609 Universe::update_heap_info_at_gc();
2610 }
2611
2612 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2613 uint gc_count_before,
2614 bool* succeeded,
2615 GCCause::Cause gc_cause) {
2616 assert_heap_not_locked_and_not_at_safepoint();
2617 VM_G1IncCollectionPause op(gc_count_before,
2618 word_size,
2619 false, /* should_initiate_conc_mark */
2620 g1_policy()->max_pause_time_ms(),
2621 gc_cause);
2622
2623 op.set_allocation_context(AllocationContext::current());
2624 VMThread::execute(&op);
2625
2626 HeapWord* result = op.result();
2627 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
2628 assert(result == NULL || ret_succeeded,
2629 "the result should be NULL if the VM did not succeed");
2630 *succeeded = ret_succeeded;
2631
2632 assert_heap_not_locked();
2633 return result;
2634 }
2635
2636 void
2637 G1CollectedHeap::doConcurrentMark() {
2638 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
2639 if (!_cmThread->in_progress()) {
2640 _cmThread->set_started();
2641 CGC_lock->notify();
2642 }
2643 }
2644
2645 size_t G1CollectedHeap::pending_card_num() {
2646 size_t extra_cards = 0;
2647 JavaThread *curr = Threads::first();
2648 while (curr != NULL) {
2649 DirtyCardQueue& dcq = curr->dirty_card_queue();
2650 extra_cards += dcq.size();
2651 curr = curr->next();
2652 }
2653 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2654 size_t buffer_size = dcqs.buffer_size();
2655 size_t buffer_num = dcqs.completed_buffers_num();
2656
2657 return buffer_size * buffer_num + extra_cards;
2658 }
2659
2660 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
2661 private:
2662 size_t _total_humongous;
2663 size_t _candidate_humongous;
2664
2665 DirtyCardQueue _dcq;
2666
2667 // We don't nominate objects with many remembered set entries, on
2668 // the assumption that such objects are likely still live.
2669 bool is_remset_small(HeapRegion* region) const {
2670 HeapRegionRemSet* const rset = region->rem_set();
2671 return G1EagerReclaimHumongousObjectsWithStaleRefs
2672 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)
2673 : rset->is_empty();
2674 }
2675
2676 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const {
2677 assert(region->is_starts_humongous(), "Must start a humongous object");
2678
2679 oop obj = oop(region->bottom());
2680
2681 // Dead objects cannot be eager reclaim candidates. Due to class
2682 // unloading it is unsafe to query their classes so we return early.
2683 if (heap->is_obj_dead(obj, region)) {
2684 return false;
2685 }
2686
2687 // Candidate selection must satisfy the following constraints
2688 // while concurrent marking is in progress:
2689 //
2690 // * In order to maintain SATB invariants, an object must not be
2691 // reclaimed if it was allocated before the start of marking and
2692 // has not had its references scanned. Such an object must have
2693 // its references (including type metadata) scanned to ensure no
2694 // live objects are missed by the marking process. Objects
2695 // allocated after the start of concurrent marking don't need to
2696 // be scanned.
2697 //
2698 // * An object must not be reclaimed if it is on the concurrent
2699 // mark stack. Objects allocated after the start of concurrent
2700 // marking are never pushed on the mark stack.
2701 //
2702 // Nominating only objects allocated after the start of concurrent
2703 // marking is sufficient to meet both constraints. This may miss
2704 // some objects that satisfy the constraints, but the marking data
2705 // structures don't support efficiently performing the needed
2706 // additional tests or scrubbing of the mark stack.
2707 //
2708 // However, we presently only nominate is_typeArray() objects.
2709 // A humongous object containing references induces remembered
2710 // set entries on other regions. In order to reclaim such an
2711 // object, those remembered sets would need to be cleaned up.
2712 //
2713 // We also treat is_typeArray() objects specially, allowing them
2714 // to be reclaimed even if allocated before the start of
2715 // concurrent mark. For this we rely on mark stack insertion to
2716 // exclude is_typeArray() objects, preventing reclaiming an object
2717 // that is in the mark stack. We also rely on the metadata for
2718 // such objects to be built-in and so ensured to be kept live.
2719 // Frequent allocation and drop of large binary blobs is an
2720 // important use case for eager reclaim, and this special handling
2721 // may reduce needed headroom.
2722
2723 return obj->is_typeArray() && is_remset_small(region);
2724 }
2725
2726 public:
2727 RegisterHumongousWithInCSetFastTestClosure()
2728 : _total_humongous(0),
2729 _candidate_humongous(0),
2730 _dcq(&JavaThread::dirty_card_queue_set()) {
2731 }
2732
2733 virtual bool doHeapRegion(HeapRegion* r) {
2734 if (!r->is_starts_humongous()) {
2735 return false;
2736 }
2737 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2738
2739 bool is_candidate = humongous_region_is_candidate(g1h, r);
2740 uint rindex = r->hrm_index();
2741 g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
2742 if (is_candidate) {
2743 _candidate_humongous++;
2744 g1h->register_humongous_region_with_cset(rindex);
2745 // Is_candidate already filters out humongous object with large remembered sets.
2746 // If we have a humongous object with a few remembered sets, we simply flush these
2747 // remembered set entries into the DCQS. That will result in automatic
2748 // re-evaluation of their remembered set entries during the following evacuation
2749 // phase.
2750 if (!r->rem_set()->is_empty()) {
2751 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
2752 "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
2753 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
2754 HeapRegionRemSetIterator hrrs(r->rem_set());
2755 size_t card_index;
2756 while (hrrs.has_next(card_index)) {
2757 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
2758 // The remembered set might contain references to already freed
2759 // regions. Filter out such entries to avoid failing card table
2760 // verification.
2761 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) {
2762 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
2763 *card_ptr = CardTableModRefBS::dirty_card_val();
2764 _dcq.enqueue(card_ptr);
2765 }
2766 }
2767 }
2768 assert(hrrs.n_yielded() == r->rem_set()->occupied(),
2769 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
2770 hrrs.n_yielded(), r->rem_set()->occupied());
2771 r->rem_set()->clear_locked();
2772 }
2773 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
2774 }
2775 _total_humongous++;
2776
2777 return false;
2778 }
2779
2780 size_t total_humongous() const { return _total_humongous; }
2781 size_t candidate_humongous() const { return _candidate_humongous; }
2782
2783 void flush_rem_set_entries() { _dcq.flush(); }
2784 };
2785
2786 void G1CollectedHeap::register_humongous_regions_with_cset() {
2787 if (!G1EagerReclaimHumongousObjects) {
2788 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
2789 return;
2790 }
2791 double time = os::elapsed_counter();
2792
2793 // Collect reclaim candidate information and register candidates with cset.
2794 RegisterHumongousWithInCSetFastTestClosure cl;
2795 heap_region_iterate(&cl);
2796
2797 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
2798 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
2799 cl.total_humongous(),
2800 cl.candidate_humongous());
2801 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
2802
2803 // Finally flush all remembered set entries to re-check into the global DCQS.
2804 cl.flush_rem_set_entries();
2805 }
2806
2807 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2808 public:
2809 bool doHeapRegion(HeapRegion* hr) {
2810 if (!hr->is_archive() && !hr->is_continues_humongous()) {
2811 hr->verify_rem_set();
2812 }
2813 return false;
2814 }
2815 };
2816
2817 uint G1CollectedHeap::num_task_queues() const {
2818 return _task_queues->size();
2819 }
2820
2821 #if TASKQUEUE_STATS
2822 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2823 st->print_raw_cr("GC Task Stats");
2824 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2825 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2826 }
2827
2828 void G1CollectedHeap::print_taskqueue_stats() const {
2829 if (!log_is_enabled(Trace, gc, task, stats)) {
2830 return;
2831 }
2832 Log(gc, task, stats) log;
2833 ResourceMark rm;
2834 outputStream* st = log.trace_stream();
2835
2836 print_taskqueue_stats_hdr(st);
2837
2838 TaskQueueStats totals;
2839 const uint n = num_task_queues();
2840 for (uint i = 0; i < n; ++i) {
2841 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2842 totals += task_queue(i)->stats;
2843 }
2844 st->print_raw("tot "); totals.print(st); st->cr();
2845
2846 DEBUG_ONLY(totals.verify());
2847 }
2848
2849 void G1CollectedHeap::reset_taskqueue_stats() {
2850 const uint n = num_task_queues();
2851 for (uint i = 0; i < n; ++i) {
2852 task_queue(i)->stats.reset();
2853 }
2854 }
2855 #endif // TASKQUEUE_STATS
2856
2857 void G1CollectedHeap::wait_for_root_region_scanning() {
2858 double scan_wait_start = os::elapsedTime();
2859 // We have to wait until the CM threads finish scanning the
2860 // root regions as it's the only way to ensure that all the
2861 // objects on them have been correctly scanned before we start
2862 // moving them during the GC.
2863 bool waited = _cm->root_regions()->wait_until_scan_finished();
2864 double wait_time_ms = 0.0;
2865 if (waited) {
2866 double scan_wait_end = os::elapsedTime();
2867 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2868 }
2869 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2870 }
2871
2872 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2873 private:
2874 G1HRPrinter* _hr_printer;
2875 public:
2876 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2877
2878 virtual bool doHeapRegion(HeapRegion* r) {
2879 _hr_printer->cset(r);
2880 return false;
2881 }
2882 };
2883
2884 void G1CollectedHeap::start_new_collection_set() {
2885 collection_set()->start_incremental_building();
2886
2887 clear_cset_fast_test();
2888
2889 guarantee(_eden.length() == 0, "eden should have been cleared");
2890 g1_policy()->transfer_survivors_to_cset(survivor());
2891 }
2892
2893 bool
2894 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
2895 assert_at_safepoint(true /* should_be_vm_thread */);
2896 guarantee(!is_gc_active(), "collection is not reentrant");
2897
2898 if (GCLocker::check_active_before_gc()) {
2899 return false;
2900 }
2901
2902 _gc_timer_stw->register_gc_start();
2903
2904 GCIdMark gc_id_mark;
2905 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
2906
2907 SvcGCMarker sgcm(SvcGCMarker::MINOR);
2908 ResourceMark rm;
2909
2910 g1_policy()->note_gc_start();
2911
2912 wait_for_root_region_scanning();
2913
2914 print_heap_before_gc();
2915 print_heap_regions();
2916 trace_heap_before_gc(_gc_tracer_stw);
2917
2918 _verifier->verify_region_sets_optional();
2919 _verifier->verify_dirty_young_regions();
2920
2921 // We should not be doing initial mark unless the conc mark thread is running
2922 if (!_cmThread->should_terminate()) {
2923 // This call will decide whether this pause is an initial-mark
2924 // pause. If it is, during_initial_mark_pause() will return true
2925 // for the duration of this pause.
2926 g1_policy()->decide_on_conc_mark_initiation();
2927 }
2928
2929 // We do not allow initial-mark to be piggy-backed on a mixed GC.
2930 assert(!collector_state()->during_initial_mark_pause() ||
2931 collector_state()->gcs_are_young(), "sanity");
2932
2933 // We also do not allow mixed GCs during marking.
2934 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity");
2935
2936 // Record whether this pause is an initial mark. When the current
2937 // thread has completed its logging output and it's safe to signal
2938 // the CM thread, the flag's value in the policy has been reset.
2939 bool should_start_conc_mark = collector_state()->during_initial_mark_pause();
2940
2941 // Inner scope for scope based logging, timers, and stats collection
2942 {
2943 EvacuationInfo evacuation_info;
2944
2945 if (collector_state()->during_initial_mark_pause()) {
2946 // We are about to start a marking cycle, so we increment the
2947 // full collection counter.
2948 increment_old_marking_cycles_started();
2949 _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
2950 }
2951
2952 _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
2953
2954 GCTraceCPUTime tcpu;
2955
2956 FormatBuffer<> gc_string("Pause ");
2957 if (collector_state()->during_initial_mark_pause()) {
2958 gc_string.append("Initial Mark");
2959 } else if (collector_state()->gcs_are_young()) {
2960 gc_string.append("Young");
2961 } else {
2962 gc_string.append("Mixed");
2963 }
2964 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true);
2965
2966 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
2967 workers()->active_workers(),
2968 Threads::number_of_non_daemon_threads());
2969 workers()->update_active_workers(active_workers);
2970 log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
2971
2972 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
2973 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
2974
2975 // If the secondary_free_list is not empty, append it to the
2976 // free_list. No need to wait for the cleanup operation to finish;
2977 // the region allocation code will check the secondary_free_list
2978 // and wait if necessary. If the G1StressConcRegionFreeing flag is
2979 // set, skip this step so that the region allocation code has to
2980 // get entries from the secondary_free_list.
2981 if (!G1StressConcRegionFreeing) {
2982 append_secondary_free_list_if_not_empty_with_lock();
2983 }
2984
2985 G1HeapTransition heap_transition(this);
2986 size_t heap_used_bytes_before_gc = used();
2987
2988 // Don't dynamically change the number of GC threads this early. A value of
2989 // 0 is used to indicate serial work. When parallel work is done,
2990 // it will be set.
2991
2992 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
2993 IsGCActiveMark x;
2994
2995 gc_prologue(false);
2996
2997 if (VerifyRememberedSets) {
2998 log_info(gc, verify)("[Verifying RemSets before GC]");
2999 VerifyRegionRemSetClosure v_cl;
3000 heap_region_iterate(&v_cl);
3001 }
3002
3003 _verifier->verify_before_gc();
3004
3005 _verifier->check_bitmaps("GC Start");
3006
3007 #if defined(COMPILER2) || INCLUDE_JVMCI
3008 DerivedPointerTable::clear();
3009 #endif
3010
3011 // Please see comment in g1CollectedHeap.hpp and
3012 // G1CollectedHeap::ref_processing_init() to see how
3013 // reference processing currently works in G1.
3014
3015 // Enable discovery in the STW reference processor
3016 if (g1_policy()->should_process_references()) {
3017 ref_processor_stw()->enable_discovery();
3018 } else {
3019 ref_processor_stw()->disable_discovery();
3020 }
3021
3022 {
3023 // We want to temporarily turn off discovery by the
3024 // CM ref processor, if necessary, and turn it back on
3025 // on again later if we do. Using a scoped
3026 // NoRefDiscovery object will do this.
3027 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3028
3029 // Forget the current alloc region (we might even choose it to be part
3030 // of the collection set!).
3031 _allocator->release_mutator_alloc_region();
3032
3033 // This timing is only used by the ergonomics to handle our pause target.
3034 // It is unclear why this should not include the full pause. We will
3035 // investigate this in CR 7178365.
3036 //
3037 // Preserving the old comment here if that helps the investigation:
3038 //
3039 // The elapsed time induced by the start time below deliberately elides
3040 // the possible verification above.
3041 double sample_start_time_sec = os::elapsedTime();
3042
3043 g1_policy()->record_collection_pause_start(sample_start_time_sec);
3044
3045 if (collector_state()->during_initial_mark_pause()) {
3046 concurrent_mark()->checkpointRootsInitialPre();
3047 }
3048
3049 g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor);
3050
3051 evacuation_info.set_collectionset_regions(collection_set()->region_length());
3052
3053 // Make sure the remembered sets are up to date. This needs to be
3054 // done before register_humongous_regions_with_cset(), because the
3055 // remembered sets are used there to choose eager reclaim candidates.
3056 // If the remembered sets are not up to date we might miss some
3057 // entries that need to be handled.
3058 g1_rem_set()->cleanupHRRS();
3059
3060 register_humongous_regions_with_cset();
3061
3062 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table.");
3063
3064 // We call this after finalize_cset() to
3065 // ensure that the CSet has been finalized.
3066 _cm->verify_no_cset_oops();
3067
3068 if (_hr_printer.is_active()) {
3069 G1PrintCollectionSetClosure cl(&_hr_printer);
3070 _collection_set.iterate(&cl);
3071 }
3072
3073 // Initialize the GC alloc regions.
3074 _allocator->init_gc_alloc_regions(evacuation_info);
3075
3076 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length());
3077 pre_evacuate_collection_set();
3078
3079 // Actually do the work...
3080 evacuate_collection_set(evacuation_info, &per_thread_states);
3081
3082 post_evacuate_collection_set(evacuation_info, &per_thread_states);
3083
3084 const size_t* surviving_young_words = per_thread_states.surviving_young_words();
3085 free_collection_set(&_collection_set, evacuation_info, surviving_young_words);
3086
3087 eagerly_reclaim_humongous_regions();
3088
3089 record_obj_copy_mem_stats();
3090 _survivor_evac_stats.adjust_desired_plab_sz();
3091 _old_evac_stats.adjust_desired_plab_sz();
3092
3093 double start = os::elapsedTime();
3094 start_new_collection_set();
3095 g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0);
3096
3097 if (evacuation_failed()) {
3098 set_used(recalculate_used());
3099 if (_archive_allocator != NULL) {
3100 _archive_allocator->clear_used();
3101 }
3102 for (uint i = 0; i < ParallelGCThreads; i++) {
3103 if (_evacuation_failed_info_array[i].has_failed()) {
3104 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3105 }
3106 }
3107 } else {
3108 // The "used" of the the collection set have already been subtracted
3109 // when they were freed. Add in the bytes evacuated.
3110 increase_used(g1_policy()->bytes_copied_during_gc());
3111 }
3112
3113 if (collector_state()->during_initial_mark_pause()) {
3114 // We have to do this before we notify the CM threads that
3115 // they can start working to make sure that all the
3116 // appropriate initialization is done on the CM object.
3117 concurrent_mark()->checkpointRootsInitialPost();
3118 collector_state()->set_mark_in_progress(true);
3119 // Note that we don't actually trigger the CM thread at
3120 // this point. We do that later when we're sure that
3121 // the current thread has completed its logging output.
3122 }
3123
3124 allocate_dummy_regions();
3125
3126 _allocator->init_mutator_alloc_region();
3127
3128 {
3129 size_t expand_bytes = _heap_sizing_policy->expansion_amount();
3130 if (expand_bytes > 0) {
3131 size_t bytes_before = capacity();
3132 // No need for an ergo logging here,
3133 // expansion_amount() does this when it returns a value > 0.
3134 double expand_ms;
3135 if (!expand(expand_bytes, _workers, &expand_ms)) {
3136 // We failed to expand the heap. Cannot do anything about it.
3137 }
3138 g1_policy()->phase_times()->record_expand_heap_time(expand_ms);
3139 }
3140 }
3141
3142 // We redo the verification but now wrt to the new CSet which
3143 // has just got initialized after the previous CSet was freed.
3144 _cm->verify_no_cset_oops();
3145
3146 // This timing is only used by the ergonomics to handle our pause target.
3147 // It is unclear why this should not include the full pause. We will
3148 // investigate this in CR 7178365.
3149 double sample_end_time_sec = os::elapsedTime();
3150 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3151 size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScannedCards);
3152 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc);
3153
3154 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
3155 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc());
3156
3157 if (VerifyRememberedSets) {
3158 log_info(gc, verify)("[Verifying RemSets after GC]");
3159 VerifyRegionRemSetClosure v_cl;
3160 heap_region_iterate(&v_cl);
3161 }
3162
3163 _verifier->verify_after_gc();
3164 _verifier->check_bitmaps("GC End");
3165
3166 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3167 ref_processor_stw()->verify_no_references_recorded();
3168
3169 // CM reference discovery will be re-enabled if necessary.
3170 }
3171
3172 #ifdef TRACESPINNING
3173 ParallelTaskTerminator::print_termination_counts();
3174 #endif
3175
3176 gc_epilogue(false);
3177 }
3178
3179 // Print the remainder of the GC log output.
3180 if (evacuation_failed()) {
3181 log_info(gc)("To-space exhausted");
3182 }
3183
3184 g1_policy()->print_phases();
3185 heap_transition.print();
3186
3187 // It is not yet to safe to tell the concurrent mark to
3188 // start as we have some optional output below. We don't want the
3189 // output from the concurrent mark thread interfering with this
3190 // logging output either.
3191
3192 _hrm.verify_optional();
3193 _verifier->verify_region_sets_optional();
3194
3195 TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3196 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3197
3198 print_heap_after_gc();
3199 print_heap_regions();
3200 trace_heap_after_gc(_gc_tracer_stw);
3201
3202 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3203 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3204 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3205 // before any GC notifications are raised.
3206 g1mm()->update_sizes();
3207
3208 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3209 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
3210 _gc_timer_stw->register_gc_end();
3211 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3212 }
3213 // It should now be safe to tell the concurrent mark thread to start
3214 // without its logging output interfering with the logging output
3215 // that came from the pause.
3216
3217 if (should_start_conc_mark) {
3218 // CAUTION: after the doConcurrentMark() call below,
3219 // the concurrent marking thread(s) could be running
3220 // concurrently with us. Make sure that anything after
3221 // this point does not assume that we are the only GC thread
3222 // running. Note: of course, the actual marking work will
3223 // not start until the safepoint itself is released in
3224 // SuspendibleThreadSet::desynchronize().
3225 doConcurrentMark();
3226 }
3227
3228 return true;
3229 }
3230
3231 void G1CollectedHeap::remove_self_forwarding_pointers() {
3232 G1ParRemoveSelfForwardPtrsTask rsfp_task;
3233 workers()->run_task(&rsfp_task);
3234 }
3235
3236 void G1CollectedHeap::restore_after_evac_failure() {
3237 double remove_self_forwards_start = os::elapsedTime();
3238
3239 remove_self_forwarding_pointers();
3240 SharedRestorePreservedMarksTaskExecutor task_executor(workers());
3241 _preserved_marks_set.restore(&task_executor);
3242
3243 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3244 }
3245
3246 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) {
3247 if (!_evacuation_failed) {
3248 _evacuation_failed = true;
3249 }
3250
3251 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3252 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3253 }
3254
3255 bool G1ParEvacuateFollowersClosure::offer_termination() {
3256 G1ParScanThreadState* const pss = par_scan_state();
3257 start_term_time();
3258 const bool res = terminator()->offer_termination();
3259 end_term_time();
3260 return res;
3261 }
3262
3263 void G1ParEvacuateFollowersClosure::do_void() {
3264 G1ParScanThreadState* const pss = par_scan_state();
3265 pss->trim_queue();
3266 do {
3267 pss->steal_and_trim_queue(queues());
3268 } while (!offer_termination());
3269 }
3270
3271 class G1ParTask : public AbstractGangTask {
3272 protected:
3273 G1CollectedHeap* _g1h;
3274 G1ParScanThreadStateSet* _pss;
3275 RefToScanQueueSet* _queues;
3276 G1RootProcessor* _root_processor;
3277 ParallelTaskTerminator _terminator;
3278 uint _n_workers;
3279
3280 public:
3281 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers)
3282 : AbstractGangTask("G1 collection"),
3283 _g1h(g1h),
3284 _pss(per_thread_states),
3285 _queues(task_queues),
3286 _root_processor(root_processor),
3287 _terminator(n_workers, _queues),
3288 _n_workers(n_workers)
3289 {}
3290
3291 void work(uint worker_id) {
3292 if (worker_id >= _n_workers) return; // no work needed this round
3293
3294 double start_sec = os::elapsedTime();
3295 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec);
3296
3297 {
3298 ResourceMark rm;
3299 HandleMark hm;
3300
3301 ReferenceProcessor* rp = _g1h->ref_processor_stw();
3302
3303 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
3304 pss->set_ref_processor(rp);
3305
3306 double start_strong_roots_sec = os::elapsedTime();
3307
3308 _root_processor->evacuate_roots(pss->closures(), worker_id);
3309
3310 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid
3311 // treating the nmethods visited to act as roots for concurrent marking.
3312 // We only want to make sure that the oops in the nmethods are adjusted with regard to the
3313 // objects copied by the current evacuation.
3314 _g1h->g1_rem_set()->oops_into_collection_set_do(pss,
3315 pss->closures()->weak_codeblobs(),
3316 worker_id);
3317
3318 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec;
3319
3320 double term_sec = 0.0;
3321 size_t evac_term_attempts = 0;
3322 {
3323 double start = os::elapsedTime();
3324 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator);
3325 evac.do_void();
3326
3327 evac_term_attempts = evac.term_attempts();
3328 term_sec = evac.term_time();
3329 double elapsed_sec = os::elapsedTime() - start;
3330 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
3331 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
3332 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts);
3333 }
3334
3335 assert(pss->queue_is_empty(), "should be empty");
3336
3337 if (log_is_enabled(Debug, gc, task, stats)) {
3338 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3339 size_t lab_waste;
3340 size_t lab_undo_waste;
3341 pss->waste(lab_waste, lab_undo_waste);
3342 _g1h->print_termination_stats(worker_id,
3343 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */
3344 strong_roots_sec * 1000.0, /* strong roots time */
3345 term_sec * 1000.0, /* evac term time */
3346 evac_term_attempts, /* evac term attempts */
3347 lab_waste, /* alloc buffer waste */
3348 lab_undo_waste /* undo waste */
3349 );
3350 }
3351
3352 // Close the inner scope so that the ResourceMark and HandleMark
3353 // destructors are executed here and are included as part of the
3354 // "GC Worker Time".
3355 }
3356 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
3357 }
3358 };
3359
3360 void G1CollectedHeap::print_termination_stats_hdr() {
3361 log_debug(gc, task, stats)("GC Termination Stats");
3362 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------");
3363 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo");
3364 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------");
3365 }
3366
3367 void G1CollectedHeap::print_termination_stats(uint worker_id,
3368 double elapsed_ms,
3369 double strong_roots_ms,
3370 double term_ms,
3371 size_t term_attempts,
3372 size_t alloc_buffer_waste,
3373 size_t undo_waste) const {
3374 log_debug(gc, task, stats)
3375 ("%3d %9.2f %9.2f %6.2f "
3376 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
3377 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
3378 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms,
3379 term_ms, term_ms * 100 / elapsed_ms, term_attempts,
3380 (alloc_buffer_waste + undo_waste) * HeapWordSize / K,
3381 alloc_buffer_waste * HeapWordSize / K,
3382 undo_waste * HeapWordSize / K);
3383 }
3384
3385 class G1StringAndSymbolCleaningTask : public AbstractGangTask {
3386 private:
3387 BoolObjectClosure* _is_alive;
3388 G1StringDedupUnlinkOrOopsDoClosure _dedup_closure;
3389
3390 int _initial_string_table_size;
3391 int _initial_symbol_table_size;
3392
3393 bool _process_strings;
3394 int _strings_processed;
3395 int _strings_removed;
3396
3397 bool _process_symbols;
3398 int _symbols_processed;
3399 int _symbols_removed;
3400
3401 bool _process_string_dedup;
3402
3403 public:
3404 G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) :
3405 AbstractGangTask("String/Symbol Unlinking"),
3406 _is_alive(is_alive),
3407 _dedup_closure(is_alive, NULL, false),
3408 _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
3409 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0),
3410 _process_string_dedup(process_string_dedup) {
3411
3412 _initial_string_table_size = StringTable::the_table()->table_size();
3413 _initial_symbol_table_size = SymbolTable::the_table()->table_size();
3414 if (process_strings) {
3415 StringTable::clear_parallel_claimed_index();
3416 }
3417 if (process_symbols) {
3418 SymbolTable::clear_parallel_claimed_index();
3419 }
3420 }
3421
3422 ~G1StringAndSymbolCleaningTask() {
3423 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
3424 "claim value %d after unlink less than initial string table size %d",
3425 StringTable::parallel_claimed_index(), _initial_string_table_size);
3426 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
3427 "claim value %d after unlink less than initial symbol table size %d",
3428 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size);
3429
3430 log_info(gc, stringtable)(
3431 "Cleaned string and symbol table, "
3432 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, "
3433 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
3434 strings_processed(), strings_removed(),
3435 symbols_processed(), symbols_removed());
3436 }
3437
3438 void work(uint worker_id) {
3439 int strings_processed = 0;
3440 int strings_removed = 0;
3441 int symbols_processed = 0;
3442 int symbols_removed = 0;
3443 if (_process_strings) {
3444 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
3445 Atomic::add(strings_processed, &_strings_processed);
3446 Atomic::add(strings_removed, &_strings_removed);
3447 }
3448 if (_process_symbols) {
3449 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
3450 Atomic::add(symbols_processed, &_symbols_processed);
3451 Atomic::add(symbols_removed, &_symbols_removed);
3452 }
3453 if (_process_string_dedup) {
3454 G1StringDedup::parallel_unlink(&_dedup_closure, worker_id);
3455 }
3456 }
3457
3458 size_t strings_processed() const { return (size_t)_strings_processed; }
3459 size_t strings_removed() const { return (size_t)_strings_removed; }
3460
3461 size_t symbols_processed() const { return (size_t)_symbols_processed; }
3462 size_t symbols_removed() const { return (size_t)_symbols_removed; }
3463 };
3464
3465 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
3466 private:
3467 static Monitor* _lock;
3468
3469 BoolObjectClosure* const _is_alive;
3470 const bool _unloading_occurred;
3471 const uint _num_workers;
3472
3473 // Variables used to claim nmethods.
3474 CompiledMethod* _first_nmethod;
3475 volatile CompiledMethod* _claimed_nmethod;
3476
3477 // The list of nmethods that need to be processed by the second pass.
3478 volatile CompiledMethod* _postponed_list;
3479 volatile uint _num_entered_barrier;
3480
3481 public:
3482 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
3483 _is_alive(is_alive),
3484 _unloading_occurred(unloading_occurred),
3485 _num_workers(num_workers),
3486 _first_nmethod(NULL),
3487 _claimed_nmethod(NULL),
3488 _postponed_list(NULL),
3489 _num_entered_barrier(0)
3490 {
3491 CompiledMethod::increase_unloading_clock();
3492 // Get first alive nmethod
3493 CompiledMethodIterator iter = CompiledMethodIterator();
3494 if(iter.next_alive()) {
3495 _first_nmethod = iter.method();
3496 }
3497 _claimed_nmethod = (volatile CompiledMethod*)_first_nmethod;
3498 }
3499
3500 ~G1CodeCacheUnloadingTask() {
3501 CodeCache::verify_clean_inline_caches();
3502
3503 CodeCache::set_needs_cache_clean(false);
3504 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
3505
3506 CodeCache::verify_icholder_relocations();
3507 }
3508
3509 private:
3510 void add_to_postponed_list(CompiledMethod* nm) {
3511 CompiledMethod* old;
3512 do {
3513 old = (CompiledMethod*)_postponed_list;
3514 nm->set_unloading_next(old);
3515 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
3516 }
3517
3518 void clean_nmethod(CompiledMethod* nm) {
3519 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
3520
3521 if (postponed) {
3522 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
3523 add_to_postponed_list(nm);
3524 }
3525
3526 // Mark that this thread has been cleaned/unloaded.
3527 // After this call, it will be safe to ask if this nmethod was unloaded or not.
3528 nm->set_unloading_clock(CompiledMethod::global_unloading_clock());
3529 }
3530
3531 void clean_nmethod_postponed(CompiledMethod* nm) {
3532 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
3533 }
3534
3535 static const int MaxClaimNmethods = 16;
3536
3537 void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) {
3538 CompiledMethod* first;
3539 CompiledMethodIterator last;
3540
3541 do {
3542 *num_claimed_nmethods = 0;
3543
3544 first = (CompiledMethod*)_claimed_nmethod;
3545 last = CompiledMethodIterator(first);
3546
3547 if (first != NULL) {
3548
3549 for (int i = 0; i < MaxClaimNmethods; i++) {
3550 if (!last.next_alive()) {
3551 break;
3552 }
3553 claimed_nmethods[i] = last.method();
3554 (*num_claimed_nmethods)++;
3555 }
3556 }
3557
3558 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first);
3559 }
3560
3561 CompiledMethod* claim_postponed_nmethod() {
3562 CompiledMethod* claim;
3563 CompiledMethod* next;
3564
3565 do {
3566 claim = (CompiledMethod*)_postponed_list;
3567 if (claim == NULL) {
3568 return NULL;
3569 }
3570
3571 next = claim->unloading_next();
3572
3573 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
3574
3575 return claim;
3576 }
3577
3578 public:
3579 // Mark that we're done with the first pass of nmethod cleaning.
3580 void barrier_mark(uint worker_id) {
3581 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3582 _num_entered_barrier++;
3583 if (_num_entered_barrier == _num_workers) {
3584 ml.notify_all();
3585 }
3586 }
3587
3588 // See if we have to wait for the other workers to
3589 // finish their first-pass nmethod cleaning work.
3590 void barrier_wait(uint worker_id) {
3591 if (_num_entered_barrier < _num_workers) {
3592 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3593 while (_num_entered_barrier < _num_workers) {
3594 ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
3595 }
3596 }
3597 }
3598
3599 // Cleaning and unloading of nmethods. Some work has to be postponed
3600 // to the second pass, when we know which nmethods survive.
3601 void work_first_pass(uint worker_id) {
3602 // The first nmethods is claimed by the first worker.
3603 if (worker_id == 0 && _first_nmethod != NULL) {
3604 clean_nmethod(_first_nmethod);
3605 _first_nmethod = NULL;
3606 }
3607
3608 int num_claimed_nmethods;
3609 CompiledMethod* claimed_nmethods[MaxClaimNmethods];
3610
3611 while (true) {
3612 claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
3613
3614 if (num_claimed_nmethods == 0) {
3615 break;
3616 }
3617
3618 for (int i = 0; i < num_claimed_nmethods; i++) {
3619 clean_nmethod(claimed_nmethods[i]);
3620 }
3621 }
3622 }
3623
3624 void work_second_pass(uint worker_id) {
3625 CompiledMethod* nm;
3626 // Take care of postponed nmethods.
3627 while ((nm = claim_postponed_nmethod()) != NULL) {
3628 clean_nmethod_postponed(nm);
3629 }
3630 }
3631 };
3632
3633 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
3634
3635 class G1KlassCleaningTask : public StackObj {
3636 BoolObjectClosure* _is_alive;
3637 volatile jint _clean_klass_tree_claimed;
3638 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
3639
3640 public:
3641 G1KlassCleaningTask(BoolObjectClosure* is_alive) :
3642 _is_alive(is_alive),
3643 _clean_klass_tree_claimed(0),
3644 _klass_iterator() {
3645 }
3646
3647 private:
3648 bool claim_clean_klass_tree_task() {
3649 if (_clean_klass_tree_claimed) {
3650 return false;
3651 }
3652
3653 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
3654 }
3655
3656 InstanceKlass* claim_next_klass() {
3657 Klass* klass;
3658 do {
3659 klass =_klass_iterator.next_klass();
3660 } while (klass != NULL && !klass->is_instance_klass());
3661
3662 // this can be null so don't call InstanceKlass::cast
3663 return static_cast<InstanceKlass*>(klass);
3664 }
3665
3666 public:
3667
3668 void clean_klass(InstanceKlass* ik) {
3669 ik->clean_weak_instanceklass_links(_is_alive);
3670 }
3671
3672 void work() {
3673 ResourceMark rm;
3674
3675 // One worker will clean the subklass/sibling klass tree.
3676 if (claim_clean_klass_tree_task()) {
3677 Klass::clean_subklass_tree(_is_alive);
3678 }
3679
3680 // All workers will help cleaning the classes,
3681 InstanceKlass* klass;
3682 while ((klass = claim_next_klass()) != NULL) {
3683 clean_klass(klass);
3684 }
3685 }
3686 };
3687
3688 class G1ResolvedMethodCleaningTask : public StackObj {
3689 BoolObjectClosure* _is_alive;
3690 volatile jint _resolved_method_task_claimed;
3691 public:
3692 G1ResolvedMethodCleaningTask(BoolObjectClosure* is_alive) :
3693 _is_alive(is_alive), _resolved_method_task_claimed(0) {}
3694
3695 bool claim_resolved_method_task() {
3696 if (_resolved_method_task_claimed) {
3697 return false;
3698 }
3699 return Atomic::cmpxchg(1, (jint*)&_resolved_method_task_claimed, 0) == 0;
3700 }
3701
3702 // These aren't big, one thread can do it all.
3703 void work() {
3704 if (claim_resolved_method_task()) {
3705 ResolvedMethodTable::unlink(_is_alive);
3706 }
3707 }
3708 };
3709
3710
3711 // To minimize the remark pause times, the tasks below are done in parallel.
3712 class G1ParallelCleaningTask : public AbstractGangTask {
3713 private:
3714 G1StringAndSymbolCleaningTask _string_symbol_task;
3715 G1CodeCacheUnloadingTask _code_cache_task;
3716 G1KlassCleaningTask _klass_cleaning_task;
3717 G1ResolvedMethodCleaningTask _resolved_method_cleaning_task;
3718
3719 public:
3720 // The constructor is run in the VMThread.
3721 G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) :
3722 AbstractGangTask("Parallel Cleaning"),
3723 _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()),
3724 _code_cache_task(num_workers, is_alive, unloading_occurred),
3725 _klass_cleaning_task(is_alive),
3726 _resolved_method_cleaning_task(is_alive) {
3727 }
3728
3729 // The parallel work done by all worker threads.
3730 void work(uint worker_id) {
3731 // Do first pass of code cache cleaning.
3732 _code_cache_task.work_first_pass(worker_id);
3733
3734 // Let the threads mark that the first pass is done.
3735 _code_cache_task.barrier_mark(worker_id);
3736
3737 // Clean the Strings and Symbols.
3738 _string_symbol_task.work(worker_id);
3739
3740 // Clean unreferenced things in the ResolvedMethodTable
3741 _resolved_method_cleaning_task.work();
3742
3743 // Wait for all workers to finish the first code cache cleaning pass.
3744 _code_cache_task.barrier_wait(worker_id);
3745
3746 // Do the second code cache cleaning work, which realize on
3747 // the liveness information gathered during the first pass.
3748 _code_cache_task.work_second_pass(worker_id);
3749
3750 // Clean all klasses that were not unloaded.
3751 _klass_cleaning_task.work();
3752 }
3753 };
3754
3755
3756 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
3757 bool class_unloading_occurred) {
3758 uint n_workers = workers()->active_workers();
3759
3760 G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred);
3761 workers()->run_task(&g1_unlink_task);
3762 }
3763
3764 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive,
3765 bool process_strings,
3766 bool process_symbols,
3767 bool process_string_dedup) {
3768 if (!process_strings && !process_symbols && !process_string_dedup) {
3769 // Nothing to clean.
3770 return;
3771 }
3772
3773 G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup);
3774 workers()->run_task(&g1_unlink_task);
3775
3776 }
3777
3778 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3779 private:
3780 DirtyCardQueueSet* _queue;
3781 G1CollectedHeap* _g1h;
3782 public:
3783 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"),
3784 _queue(queue), _g1h(g1h) { }
3785
3786 virtual void work(uint worker_id) {
3787 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
3788 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
3789
3790 RedirtyLoggedCardTableEntryClosure cl(_g1h);
3791 _queue->par_apply_closure_to_all_completed_buffers(&cl);
3792
3793 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3794 }
3795 };
3796
3797 void G1CollectedHeap::redirty_logged_cards() {
3798 double redirty_logged_cards_start = os::elapsedTime();
3799
3800 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this);
3801 dirty_card_queue_set().reset_for_par_iteration();
3802 workers()->run_task(&redirty_task);
3803
3804 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
3805 dcq.merge_bufferlists(&dirty_card_queue_set());
3806 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
3807
3808 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3809 }
3810
3811 // Weak Reference Processing support
3812
3813 // An always "is_alive" closure that is used to preserve referents.
3814 // If the object is non-null then it's alive. Used in the preservation
3815 // of referent objects that are pointed to by reference objects
3816 // discovered by the CM ref processor.
3817 class G1AlwaysAliveClosure: public BoolObjectClosure {
3818 G1CollectedHeap* _g1;
3819 public:
3820 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3821 bool do_object_b(oop p) {
3822 if (p != NULL) {
3823 return true;
3824 }
3825 return false;
3826 }
3827 };
3828
3829 bool G1STWIsAliveClosure::do_object_b(oop p) {
3830 // An object is reachable if it is outside the collection set,
3831 // or is inside and copied.
3832 return !_g1->is_in_cset(p) || p->is_forwarded();
3833 }
3834
3835 // Non Copying Keep Alive closure
3836 class G1KeepAliveClosure: public OopClosure {
3837 G1CollectedHeap* _g1;
3838 public:
3839 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3840 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3841 void do_oop(oop* p) {
3842 oop obj = *p;
3843 assert(obj != NULL, "the caller should have filtered out NULL values");
3844
3845 const InCSetState cset_state = _g1->in_cset_state(obj);
3846 if (!cset_state.is_in_cset_or_humongous()) {
3847 return;
3848 }
3849 if (cset_state.is_in_cset()) {
3850 assert( obj->is_forwarded(), "invariant" );
3851 *p = obj->forwardee();
3852 } else {
3853 assert(!obj->is_forwarded(), "invariant" );
3854 assert(cset_state.is_humongous(),
3855 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value());
3856 _g1->set_humongous_is_live(obj);
3857 }
3858 }
3859 };
3860
3861 // Copying Keep Alive closure - can be called from both
3862 // serial and parallel code as long as different worker
3863 // threads utilize different G1ParScanThreadState instances
3864 // and different queues.
3865
3866 class G1CopyingKeepAliveClosure: public OopClosure {
3867 G1CollectedHeap* _g1h;
3868 OopClosure* _copy_non_heap_obj_cl;
3869 G1ParScanThreadState* _par_scan_state;
3870
3871 public:
3872 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3873 OopClosure* non_heap_obj_cl,
3874 G1ParScanThreadState* pss):
3875 _g1h(g1h),
3876 _copy_non_heap_obj_cl(non_heap_obj_cl),
3877 _par_scan_state(pss)
3878 {}
3879
3880 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3881 virtual void do_oop( oop* p) { do_oop_work(p); }
3882
3883 template <class T> void do_oop_work(T* p) {
3884 oop obj = oopDesc::load_decode_heap_oop(p);
3885
3886 if (_g1h->is_in_cset_or_humongous(obj)) {
3887 // If the referent object has been forwarded (either copied
3888 // to a new location or to itself in the event of an
3889 // evacuation failure) then we need to update the reference
3890 // field and, if both reference and referent are in the G1
3891 // heap, update the RSet for the referent.
3892 //
3893 // If the referent has not been forwarded then we have to keep
3894 // it alive by policy. Therefore we have copy the referent.
3895 //
3896 // If the reference field is in the G1 heap then we can push
3897 // on the PSS queue. When the queue is drained (after each
3898 // phase of reference processing) the object and it's followers
3899 // will be copied, the reference field set to point to the
3900 // new location, and the RSet updated. Otherwise we need to
3901 // use the the non-heap or metadata closures directly to copy
3902 // the referent object and update the pointer, while avoiding
3903 // updating the RSet.
3904
3905 if (_g1h->is_in_g1_reserved(p)) {
3906 _par_scan_state->push_on_queue(p);
3907 } else {
3908 assert(!Metaspace::contains((const void*)p),
3909 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p));
3910 _copy_non_heap_obj_cl->do_oop(p);
3911 }
3912 }
3913 }
3914 };
3915
3916 // Serial drain queue closure. Called as the 'complete_gc'
3917 // closure for each discovered list in some of the
3918 // reference processing phases.
3919
3920 class G1STWDrainQueueClosure: public VoidClosure {
3921 protected:
3922 G1CollectedHeap* _g1h;
3923 G1ParScanThreadState* _par_scan_state;
3924
3925 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
3926
3927 public:
3928 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
3929 _g1h(g1h),
3930 _par_scan_state(pss)
3931 { }
3932
3933 void do_void() {
3934 G1ParScanThreadState* const pss = par_scan_state();
3935 pss->trim_queue();
3936 }
3937 };
3938
3939 // Parallel Reference Processing closures
3940
3941 // Implementation of AbstractRefProcTaskExecutor for parallel reference
3942 // processing during G1 evacuation pauses.
3943
3944 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
3945 private:
3946 G1CollectedHeap* _g1h;
3947 G1ParScanThreadStateSet* _pss;
3948 RefToScanQueueSet* _queues;
3949 WorkGang* _workers;
3950 uint _active_workers;
3951
3952 public:
3953 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
3954 G1ParScanThreadStateSet* per_thread_states,
3955 WorkGang* workers,
3956 RefToScanQueueSet *task_queues,
3957 uint n_workers) :
3958 _g1h(g1h),
3959 _pss(per_thread_states),
3960 _queues(task_queues),
3961 _workers(workers),
3962 _active_workers(n_workers)
3963 {
3964 g1h->ref_processor_stw()->set_active_mt_degree(n_workers);
3965 }
3966
3967 // Executes the given task using concurrent marking worker threads.
3968 virtual void execute(ProcessTask& task);
3969 virtual void execute(EnqueueTask& task);
3970 };
3971
3972 // Gang task for possibly parallel reference processing
3973
3974 class G1STWRefProcTaskProxy: public AbstractGangTask {
3975 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
3976 ProcessTask& _proc_task;
3977 G1CollectedHeap* _g1h;
3978 G1ParScanThreadStateSet* _pss;
3979 RefToScanQueueSet* _task_queues;
3980 ParallelTaskTerminator* _terminator;
3981
3982 public:
3983 G1STWRefProcTaskProxy(ProcessTask& proc_task,
3984 G1CollectedHeap* g1h,
3985 G1ParScanThreadStateSet* per_thread_states,
3986 RefToScanQueueSet *task_queues,
3987 ParallelTaskTerminator* terminator) :
3988 AbstractGangTask("Process reference objects in parallel"),
3989 _proc_task(proc_task),
3990 _g1h(g1h),
3991 _pss(per_thread_states),
3992 _task_queues(task_queues),
3993 _terminator(terminator)
3994 {}
3995
3996 virtual void work(uint worker_id) {
3997 // The reference processing task executed by a single worker.
3998 ResourceMark rm;
3999 HandleMark hm;
4000
4001 G1STWIsAliveClosure is_alive(_g1h);
4002
4003 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
4004 pss->set_ref_processor(NULL);
4005
4006 // Keep alive closure.
4007 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4008
4009 // Complete GC closure
4010 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator);
4011
4012 // Call the reference processing task's work routine.
4013 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
4014
4015 // Note we cannot assert that the refs array is empty here as not all
4016 // of the processing tasks (specifically phase2 - pp2_work) execute
4017 // the complete_gc closure (which ordinarily would drain the queue) so
4018 // the queue may not be empty.
4019 }
4020 };
4021
4022 // Driver routine for parallel reference processing.
4023 // Creates an instance of the ref processing gang
4024 // task and has the worker threads execute it.
4025 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
4026 assert(_workers != NULL, "Need parallel worker threads.");
4027
4028 ParallelTaskTerminator terminator(_active_workers, _queues);
4029 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
4030
4031 _workers->run_task(&proc_task_proxy);
4032 }
4033
4034 // Gang task for parallel reference enqueueing.
4035
4036 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
4037 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
4038 EnqueueTask& _enq_task;
4039
4040 public:
4041 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
4042 AbstractGangTask("Enqueue reference objects in parallel"),
4043 _enq_task(enq_task)
4044 { }
4045
4046 virtual void work(uint worker_id) {
4047 _enq_task.work(worker_id);
4048 }
4049 };
4050
4051 // Driver routine for parallel reference enqueueing.
4052 // Creates an instance of the ref enqueueing gang
4053 // task and has the worker threads execute it.
4054
4055 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
4056 assert(_workers != NULL, "Need parallel worker threads.");
4057
4058 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
4059
4060 _workers->run_task(&enq_task_proxy);
4061 }
4062
4063 // End of weak reference support closures
4064
4065 // Abstract task used to preserve (i.e. copy) any referent objects
4066 // that are in the collection set and are pointed to by reference
4067 // objects discovered by the CM ref processor.
4068
4069 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
4070 protected:
4071 G1CollectedHeap* _g1h;
4072 G1ParScanThreadStateSet* _pss;
4073 RefToScanQueueSet* _queues;
4074 ParallelTaskTerminator _terminator;
4075 uint _n_workers;
4076
4077 public:
4078 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) :
4079 AbstractGangTask("ParPreserveCMReferents"),
4080 _g1h(g1h),
4081 _pss(per_thread_states),
4082 _queues(task_queues),
4083 _terminator(workers, _queues),
4084 _n_workers(workers)
4085 {
4086 g1h->ref_processor_cm()->set_active_mt_degree(workers);
4087 }
4088
4089 void work(uint worker_id) {
4090 G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id);
4091
4092 ResourceMark rm;
4093 HandleMark hm;
4094
4095 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
4096 pss->set_ref_processor(NULL);
4097 assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4098
4099 // Is alive closure
4100 G1AlwaysAliveClosure always_alive(_g1h);
4101
4102 // Copying keep alive closure. Applied to referent objects that need
4103 // to be copied.
4104 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4105
4106 ReferenceProcessor* rp = _g1h->ref_processor_cm();
4107
4108 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
4109 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
4110
4111 // limit is set using max_num_q() - which was set using ParallelGCThreads.
4112 // So this must be true - but assert just in case someone decides to
4113 // change the worker ids.
4114 assert(worker_id < limit, "sanity");
4115 assert(!rp->discovery_is_atomic(), "check this code");
4116
4117 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
4118 for (uint idx = worker_id; idx < limit; idx += stride) {
4119 DiscoveredList& ref_list = rp->discovered_refs()[idx];
4120
4121 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
4122 while (iter.has_next()) {
4123 // Since discovery is not atomic for the CM ref processor, we
4124 // can see some null referent objects.
4125 iter.load_ptrs(DEBUG_ONLY(true));
4126 oop ref = iter.obj();
4127
4128 // This will filter nulls.
4129 if (iter.is_referent_alive()) {
4130 iter.make_referent_alive();
4131 }
4132 iter.move_to_next();
4133 }
4134 }
4135
4136 // Drain the queue - which may cause stealing
4137 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator);
4138 drain_queue.do_void();
4139 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
4140 assert(pss->queue_is_empty(), "should be");
4141 }
4142 };
4143
4144 void G1CollectedHeap::process_weak_jni_handles() {
4145 double ref_proc_start = os::elapsedTime();
4146
4147 G1STWIsAliveClosure is_alive(this);
4148 G1KeepAliveClosure keep_alive(this);
4149 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
4150
4151 double ref_proc_time = os::elapsedTime() - ref_proc_start;
4152 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4153 }
4154
4155 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) {
4156 // Any reference objects, in the collection set, that were 'discovered'
4157 // by the CM ref processor should have already been copied (either by
4158 // applying the external root copy closure to the discovered lists, or
4159 // by following an RSet entry).
4160 //
4161 // But some of the referents, that are in the collection set, that these
4162 // reference objects point to may not have been copied: the STW ref
4163 // processor would have seen that the reference object had already
4164 // been 'discovered' and would have skipped discovering the reference,
4165 // but would not have treated the reference object as a regular oop.
4166 // As a result the copy closure would not have been applied to the
4167 // referent object.
4168 //
4169 // We need to explicitly copy these referent objects - the references
4170 // will be processed at the end of remarking.
4171 //
4172 // We also need to do this copying before we process the reference
4173 // objects discovered by the STW ref processor in case one of these
4174 // referents points to another object which is also referenced by an
4175 // object discovered by the STW ref processor.
4176 double preserve_cm_referents_time = 0.0;
4177
4178 // To avoid spawning task when there is no work to do, check that
4179 // a concurrent cycle is active and that some references have been
4180 // discovered.
4181 if (concurrent_mark()->cmThread()->during_cycle() &&
4182 ref_processor_cm()->has_discovered_references()) {
4183 double preserve_cm_referents_start = os::elapsedTime();
4184 uint no_of_gc_workers = workers()->active_workers();
4185 G1ParPreserveCMReferentsTask keep_cm_referents(this,
4186 per_thread_states,
4187 no_of_gc_workers,
4188 _task_queues);
4189 workers()->run_task(&keep_cm_referents);
4190 preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start;
4191 }
4192
4193 g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0);
4194 }
4195
4196 // Weak Reference processing during an evacuation pause (part 1).
4197 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4198 double ref_proc_start = os::elapsedTime();
4199
4200 ReferenceProcessor* rp = _ref_processor_stw;
4201 assert(rp->discovery_enabled(), "should have been enabled");
4202
4203 // Closure to test whether a referent is alive.
4204 G1STWIsAliveClosure is_alive(this);
4205
4206 // Even when parallel reference processing is enabled, the processing
4207 // of JNI refs is serial and performed serially by the current thread
4208 // rather than by a worker. The following PSS will be used for processing
4209 // JNI refs.
4210
4211 // Use only a single queue for this PSS.
4212 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0);
4213 pss->set_ref_processor(NULL);
4214 assert(pss->queue_is_empty(), "pre-condition");
4215
4216 // Keep alive closure.
4217 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss);
4218
4219 // Serial Complete GC closure
4220 G1STWDrainQueueClosure drain_queue(this, pss);
4221
4222 // Setup the soft refs policy...
4223 rp->setup_policy(false);
4224
4225 ReferenceProcessorStats stats;
4226 if (!rp->processing_is_mt()) {
4227 // Serial reference processing...
4228 stats = rp->process_discovered_references(&is_alive,
4229 &keep_alive,
4230 &drain_queue,
4231 NULL,
4232 _gc_timer_stw);
4233 } else {
4234 uint no_of_gc_workers = workers()->active_workers();
4235
4236 // Parallel reference processing
4237 assert(no_of_gc_workers <= rp->max_num_q(),
4238 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4239 no_of_gc_workers, rp->max_num_q());
4240
4241 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers);
4242 stats = rp->process_discovered_references(&is_alive,
4243 &keep_alive,
4244 &drain_queue,
4245 &par_task_executor,
4246 _gc_timer_stw);
4247 }
4248
4249 _gc_tracer_stw->report_gc_reference_stats(stats);
4250
4251 // We have completed copying any necessary live referent objects.
4252 assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4253
4254 double ref_proc_time = os::elapsedTime() - ref_proc_start;
4255 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4256 }
4257
4258 // Weak Reference processing during an evacuation pause (part 2).
4259 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4260 double ref_enq_start = os::elapsedTime();
4261
4262 ReferenceProcessor* rp = _ref_processor_stw;
4263 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
4264
4265 // Now enqueue any remaining on the discovered lists on to
4266 // the pending list.
4267 if (!rp->processing_is_mt()) {
4268 // Serial reference processing...
4269 rp->enqueue_discovered_references();
4270 } else {
4271 // Parallel reference enqueueing
4272
4273 uint n_workers = workers()->active_workers();
4274
4275 assert(n_workers <= rp->max_num_q(),
4276 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4277 n_workers, rp->max_num_q());
4278
4279 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers);
4280 rp->enqueue_discovered_references(&par_task_executor);
4281 }
4282
4283 rp->verify_no_references_recorded();
4284 assert(!rp->discovery_enabled(), "should have been disabled");
4285
4286 // FIXME
4287 // CM's reference processing also cleans up the string and symbol tables.
4288 // Should we do that here also? We could, but it is a serial operation
4289 // and could significantly increase the pause time.
4290
4291 double ref_enq_time = os::elapsedTime() - ref_enq_start;
4292 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
4293 }
4294
4295 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
4296 double merge_pss_time_start = os::elapsedTime();
4297 per_thread_states->flush();
4298 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0);
4299 }
4300
4301 void G1CollectedHeap::pre_evacuate_collection_set() {
4302 _expand_heap_after_alloc_failure = true;
4303 _evacuation_failed = false;
4304
4305 // Disable the hot card cache.
4306 _hot_card_cache->reset_hot_cache_claimed_index();
4307 _hot_card_cache->set_use_cache(false);
4308
4309 g1_rem_set()->prepare_for_oops_into_collection_set_do();
4310 _preserved_marks_set.assert_empty();
4311
4312 G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4313
4314 // InitialMark needs claim bits to keep track of the marked-through CLDs.
4315 if (collector_state()->during_initial_mark_pause()) {
4316 double start_clear_claimed_marks = os::elapsedTime();
4317
4318 ClassLoaderDataGraph::clear_claimed_marks();
4319
4320 double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
4321 phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
4322 }
4323 }
4324
4325 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4326 // Should G1EvacuationFailureALot be in effect for this GC?
4327 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
4328
4329 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
4330
4331 G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4332
4333 double start_par_time_sec = os::elapsedTime();
4334 double end_par_time_sec;
4335
4336 {
4337 const uint n_workers = workers()->active_workers();
4338 G1RootProcessor root_processor(this, n_workers);
4339 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers);
4340
4341 print_termination_stats_hdr();
4342
4343 workers()->run_task(&g1_par_task);
4344 end_par_time_sec = os::elapsedTime();
4345
4346 // Closing the inner scope will execute the destructor
4347 // for the G1RootProcessor object. We record the current
4348 // elapsed time before closing the scope so that time
4349 // taken for the destructor is NOT included in the
4350 // reported parallel time.
4351 }
4352
4353 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
4354 phase_times->record_par_time(par_time_ms);
4355
4356 double code_root_fixup_time_ms =
4357 (os::elapsedTime() - end_par_time_sec) * 1000.0;
4358 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
4359 }
4360
4361 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4362 // Process any discovered reference objects - we have
4363 // to do this _before_ we retire the GC alloc regions
4364 // as we may have to copy some 'reachable' referent
4365 // objects (and their reachable sub-graphs) that were
4366 // not copied during the pause.
4367 if (g1_policy()->should_process_references()) {
4368 preserve_cm_referents(per_thread_states);
4369 process_discovered_references(per_thread_states);
4370 } else {
4371 ref_processor_stw()->verify_no_references_recorded();
4372 process_weak_jni_handles();
4373 }
4374
4375 if (G1StringDedup::is_enabled()) {
4376 double fixup_start = os::elapsedTime();
4377
4378 G1STWIsAliveClosure is_alive(this);
4379 G1KeepAliveClosure keep_alive(this);
4380 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times());
4381
4382 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
4383 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
4384 }
4385
4386 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4387
4388 if (evacuation_failed()) {
4389 restore_after_evac_failure();
4390
4391 // Reset the G1EvacuationFailureALot counters and flags
4392 // Note: the values are reset only when an actual
4393 // evacuation failure occurs.
4394 NOT_PRODUCT(reset_evacuation_should_fail();)
4395 }
4396
4397 _preserved_marks_set.assert_empty();
4398
4399 // Enqueue any remaining references remaining on the STW
4400 // reference processor's discovered lists. We need to do
4401 // this after the card table is cleaned (and verified) as
4402 // the act of enqueueing entries on to the pending list
4403 // will log these updates (and dirty their associated
4404 // cards). We need these updates logged to update any
4405 // RSets.
4406 if (g1_policy()->should_process_references()) {
4407 enqueue_discovered_references(per_thread_states);
4408 } else {
4409 g1_policy()->phase_times()->record_ref_enq_time(0);
4410 }
4411
4412 _allocator->release_gc_alloc_regions(evacuation_info);
4413
4414 merge_per_thread_state_info(per_thread_states);
4415
4416 // Reset and re-enable the hot card cache.
4417 // Note the counts for the cards in the regions in the
4418 // collection set are reset when the collection set is freed.
4419 _hot_card_cache->reset_hot_cache();
4420 _hot_card_cache->set_use_cache(true);
4421
4422 purge_code_root_memory();
4423
4424 redirty_logged_cards();
4425 #if defined(COMPILER2) || INCLUDE_JVMCI
4426 double start = os::elapsedTime();
4427 DerivedPointerTable::update_pointers();
4428 g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0);
4429 #endif
4430 g1_policy()->print_age_table();
4431 }
4432
4433 void G1CollectedHeap::record_obj_copy_mem_stats() {
4434 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4435
4436 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4437 create_g1_evac_summary(&_old_evac_stats));
4438 }
4439
4440 void G1CollectedHeap::free_region(HeapRegion* hr,
4441 FreeRegionList* free_list,
4442 bool skip_remset,
4443 bool skip_hot_card_cache,
4444 bool locked) {
4445 assert(!hr->is_free(), "the region should not be free");
4446 assert(!hr->is_empty(), "the region should not be empty");
4447 assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
4448 assert(free_list != NULL, "pre-condition");
4449
4450 if (G1VerifyBitmaps) {
4451 MemRegion mr(hr->bottom(), hr->end());
4452 concurrent_mark()->clearRangePrevBitmap(mr);
4453 }
4454
4455 // Clear the card counts for this region.
4456 // Note: we only need to do this if the region is not young
4457 // (since we don't refine cards in young regions).
4458 if (!skip_hot_card_cache && !hr->is_young()) {
4459 _hot_card_cache->reset_card_counts(hr);
4460 }
4461 hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */);
4462 free_list->add_ordered(hr);
4463 }
4464
4465 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4466 FreeRegionList* free_list,
4467 bool skip_remset) {
4468 assert(hr->is_humongous(), "this is only for humongous regions");
4469 assert(free_list != NULL, "pre-condition");
4470 hr->clear_humongous();
4471 free_region(hr, free_list, skip_remset);
4472 }
4473
4474 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4475 const uint humongous_regions_removed) {
4476 if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4477 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4478 _old_set.bulk_remove(old_regions_removed);
4479 _humongous_set.bulk_remove(humongous_regions_removed);
4480 }
4481
4482 }
4483
4484 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4485 assert(list != NULL, "list can't be null");
4486 if (!list->is_empty()) {
4487 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4488 _hrm.insert_list_into_free_list(list);
4489 }
4490 }
4491
4492 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4493 decrease_used(bytes);
4494 }
4495
4496 class G1ParScrubRemSetTask: public AbstractGangTask {
4497 protected:
4498 G1RemSet* _g1rs;
4499 HeapRegionClaimer _hrclaimer;
4500
4501 public:
4502 G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) :
4503 AbstractGangTask("G1 ScrubRS"),
4504 _g1rs(g1_rs),
4505 _hrclaimer(num_workers) {
4506 }
4507
4508 void work(uint worker_id) {
4509 _g1rs->scrub(worker_id, &_hrclaimer);
4510 }
4511 };
4512
4513 void G1CollectedHeap::scrub_rem_set() {
4514 uint num_workers = workers()->active_workers();
4515 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers);
4516 workers()->run_task(&g1_par_scrub_rs_task);
4517 }
4518
4519 class G1FreeCollectionSetTask : public AbstractGangTask {
4520 private:
4521
4522 // Closure applied to all regions in the collection set to do work that needs to
4523 // be done serially in a single thread.
4524 class G1SerialFreeCollectionSetClosure : public HeapRegionClosure {
4525 private:
4526 EvacuationInfo* _evacuation_info;
4527 const size_t* _surviving_young_words;
4528
4529 // Bytes used in successfully evacuated regions before the evacuation.
4530 size_t _before_used_bytes;
4531 // Bytes used in unsucessfully evacuated regions before the evacuation
4532 size_t _after_used_bytes;
4533
4534 size_t _bytes_allocated_in_old_since_last_gc;
4535
4536 size_t _failure_used_words;
4537 size_t _failure_waste_words;
4538
4539 FreeRegionList _local_free_list;
4540 public:
4541 G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4542 HeapRegionClosure(),
4543 _evacuation_info(evacuation_info),
4544 _surviving_young_words(surviving_young_words),
4545 _before_used_bytes(0),
4546 _after_used_bytes(0),
4547 _bytes_allocated_in_old_since_last_gc(0),
4548 _failure_used_words(0),
4549 _failure_waste_words(0),
4550 _local_free_list("Local Region List for CSet Freeing") {
4551 }
4552
4553 virtual bool doHeapRegion(HeapRegion* r) {
4554 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4555
4556 assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index());
4557 g1h->clear_in_cset(r);
4558
4559 if (r->is_young()) {
4560 assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(),
4561 "Young index %d is wrong for region %u of type %s with %u young regions",
4562 r->young_index_in_cset(),
4563 r->hrm_index(),
4564 r->get_type_str(),
4565 g1h->collection_set()->young_region_length());
4566 size_t words_survived = _surviving_young_words[r->young_index_in_cset()];
4567 r->record_surv_words_in_group(words_survived);
4568 }
4569
4570 if (!r->evacuation_failed()) {
4571 assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
4572 _before_used_bytes += r->used();
4573 g1h->free_region(r,
4574 &_local_free_list,
4575 true, /* skip_remset */
4576 true, /* skip_hot_card_cache */
4577 true /* locked */);
4578 } else {
4579 r->uninstall_surv_rate_group();
4580 r->set_young_index_in_cset(-1);
4581 r->set_evacuation_failed(false);
4582 // When moving a young gen region to old gen, we "allocate" that whole region
4583 // there. This is in addition to any already evacuated objects. Notify the
4584 // policy about that.
4585 // Old gen regions do not cause an additional allocation: both the objects
4586 // still in the region and the ones already moved are accounted for elsewhere.
4587 if (r->is_young()) {
4588 _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
4589 }
4590 // The region is now considered to be old.
4591 r->set_old();
4592 // Do some allocation statistics accounting. Regions that failed evacuation
4593 // are always made old, so there is no need to update anything in the young
4594 // gen statistics, but we need to update old gen statistics.
4595 size_t used_words = r->marked_bytes() / HeapWordSize;
4596
4597 _failure_used_words += used_words;
4598 _failure_waste_words += HeapRegion::GrainWords - used_words;
4599
4600 g1h->old_set_add(r);
4601 _after_used_bytes += r->used();
4602 }
4603 return false;
4604 }
4605
4606 void complete_work() {
4607 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4608
4609 _evacuation_info->set_regions_freed(_local_free_list.length());
4610 _evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4611
4612 g1h->prepend_to_freelist(&_local_free_list);
4613 g1h->decrement_summary_bytes(_before_used_bytes);
4614
4615 G1Policy* policy = g1h->g1_policy();
4616 policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4617
4618 g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4619 }
4620 };
4621
4622 G1CollectionSet* _collection_set;
4623 G1SerialFreeCollectionSetClosure _cl;
4624 const size_t* _surviving_young_words;
4625
4626 size_t _rs_lengths;
4627
4628 volatile jint _serial_work_claim;
4629
4630 struct WorkItem {
4631 uint region_idx;
4632 bool is_young;
4633 bool evacuation_failed;
4634
4635 WorkItem(HeapRegion* r) {
4636 region_idx = r->hrm_index();
4637 is_young = r->is_young();
4638 evacuation_failed = r->evacuation_failed();
4639 }
4640 };
4641
4642 volatile size_t _parallel_work_claim;
4643 size_t _num_work_items;
4644 WorkItem* _work_items;
4645
4646 void do_serial_work() {
4647 // Need to grab the lock to be allowed to modify the old region list.
4648 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4649 _collection_set->iterate(&_cl);
4650 }
4651
4652 void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) {
4653 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4654
4655 HeapRegion* r = g1h->region_at(region_idx);
4656 assert(!g1h->is_on_master_free_list(r), "sanity");
4657
4658 Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths);
4659
4660 if (!is_young) {
4661 g1h->_hot_card_cache->reset_card_counts(r);
4662 }
4663
4664 if (!evacuation_failed) {
4665 r->rem_set()->clear_locked();
4666 }
4667 }
4668
4669 class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure {
4670 private:
4671 size_t _cur_idx;
4672 WorkItem* _work_items;
4673 public:
4674 G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { }
4675
4676 virtual bool doHeapRegion(HeapRegion* r) {
4677 _work_items[_cur_idx++] = WorkItem(r);
4678 return false;
4679 }
4680 };
4681
4682 void prepare_work() {
4683 G1PrepareFreeCollectionSetClosure cl(_work_items);
4684 _collection_set->iterate(&cl);
4685 }
4686
4687 void complete_work() {
4688 _cl.complete_work();
4689
4690 G1Policy* policy = G1CollectedHeap::heap()->g1_policy();
4691 policy->record_max_rs_lengths(_rs_lengths);
4692 policy->cset_regions_freed();
4693 }
4694 public:
4695 G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4696 AbstractGangTask("G1 Free Collection Set"),
4697 _cl(evacuation_info, surviving_young_words),
4698 _collection_set(collection_set),
4699 _surviving_young_words(surviving_young_words),
4700 _serial_work_claim(0),
4701 _rs_lengths(0),
4702 _parallel_work_claim(0),
4703 _num_work_items(collection_set->region_length()),
4704 _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) {
4705 prepare_work();
4706 }
4707
4708 ~G1FreeCollectionSetTask() {
4709 complete_work();
4710 FREE_C_HEAP_ARRAY(WorkItem, _work_items);
4711 }
4712
4713 // Chunk size for work distribution. The chosen value has been determined experimentally
4714 // to be a good tradeoff between overhead and achievable parallelism.
4715 static uint chunk_size() { return 32; }
4716
4717 virtual void work(uint worker_id) {
4718 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
4719
4720 // Claim serial work.
4721 if (_serial_work_claim == 0) {
4722 jint value = Atomic::add(1, &_serial_work_claim) - 1;
4723 if (value == 0) {
4724 double serial_time = os::elapsedTime();
4725 do_serial_work();
4726 timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0);
4727 }
4728 }
4729
4730 // Start parallel work.
4731 double young_time = 0.0;
4732 bool has_young_time = false;
4733 double non_young_time = 0.0;
4734 bool has_non_young_time = false;
4735
4736 while (true) {
4737 size_t end = Atomic::add(chunk_size(), &_parallel_work_claim);
4738 size_t cur = end - chunk_size();
4739
4740 if (cur >= _num_work_items) {
4741 break;
4742 }
4743
4744 double start_time = os::elapsedTime();
4745
4746 end = MIN2(end, _num_work_items);
4747
4748 for (; cur < end; cur++) {
4749 bool is_young = _work_items[cur].is_young;
4750
4751 do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed);
4752
4753 double end_time = os::elapsedTime();
4754 double time_taken = end_time - start_time;
4755 if (is_young) {
4756 young_time += time_taken;
4757 has_young_time = true;
4758 } else {
4759 non_young_time += time_taken;
4760 has_non_young_time = true;
4761 }
4762 start_time = end_time;
4763 }
4764 }
4765
4766 if (has_young_time) {
4767 timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time);
4768 }
4769 if (has_non_young_time) {
4770 timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, young_time);
4771 }
4772 }
4773 };
4774
4775 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4776 _eden.clear();
4777
4778 double free_cset_start_time = os::elapsedTime();
4779
4780 {
4781 uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U);
4782 uint const num_workers = MIN2(workers()->active_workers(), num_chunks);
4783
4784 G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words);
4785
4786 log_debug(gc, ergo)("Running %s using %u workers for collection set length %u",
4787 cl.name(),
4788 num_workers,
4789 _collection_set.region_length());
4790 workers()->run_task(&cl, num_workers);
4791 }
4792 g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0);
4793
4794 collection_set->clear();
4795 }
4796
4797 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4798 private:
4799 FreeRegionList* _free_region_list;
4800 HeapRegionSet* _proxy_set;
4801 uint _humongous_objects_reclaimed;
4802 uint _humongous_regions_reclaimed;
4803 size_t _freed_bytes;
4804 public:
4805
4806 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4807 _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) {
4808 }
4809
4810 virtual bool doHeapRegion(HeapRegion* r) {
4811 if (!r->is_starts_humongous()) {
4812 return false;
4813 }
4814
4815 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4816
4817 oop obj = (oop)r->bottom();
4818 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
4819
4820 // The following checks whether the humongous object is live are sufficient.
4821 // The main additional check (in addition to having a reference from the roots
4822 // or the young gen) is whether the humongous object has a remembered set entry.
4823 //
4824 // A humongous object cannot be live if there is no remembered set for it
4825 // because:
4826 // - there can be no references from within humongous starts regions referencing
4827 // the object because we never allocate other objects into them.
4828 // (I.e. there are no intra-region references that may be missed by the
4829 // remembered set)
4830 // - as soon there is a remembered set entry to the humongous starts region
4831 // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4832 // until the end of a concurrent mark.
4833 //
4834 // It is not required to check whether the object has been found dead by marking
4835 // or not, in fact it would prevent reclamation within a concurrent cycle, as
4836 // all objects allocated during that time are considered live.
4837 // SATB marking is even more conservative than the remembered set.
4838 // So if at this point in the collection there is no remembered set entry,
4839 // nobody has a reference to it.
4840 // At the start of collection we flush all refinement logs, and remembered sets
4841 // are completely up-to-date wrt to references to the humongous object.
4842 //
4843 // Other implementation considerations:
4844 // - never consider object arrays at this time because they would pose
4845 // considerable effort for cleaning up the the remembered sets. This is
4846 // required because stale remembered sets might reference locations that
4847 // are currently allocated into.
4848 uint region_idx = r->hrm_index();
4849 if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4850 !r->rem_set()->is_empty()) {
4851 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",
4852 region_idx,
4853 (size_t)obj->size() * HeapWordSize,
4854 p2i(r->bottom()),
4855 r->rem_set()->occupied(),
4856 r->rem_set()->strong_code_roots_list_length(),
4857 next_bitmap->isMarked(r->bottom()),
4858 g1h->is_humongous_reclaim_candidate(region_idx),
4859 obj->is_typeArray()
4860 );
4861 return false;
4862 }
4863
4864 guarantee(obj->is_typeArray(),
4865 "Only eagerly reclaiming type arrays is supported, but the object "
4866 PTR_FORMAT " is not.", p2i(r->bottom()));
4867
4868 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",
4869 region_idx,
4870 (size_t)obj->size() * HeapWordSize,
4871 p2i(r->bottom()),
4872 r->rem_set()->occupied(),
4873 r->rem_set()->strong_code_roots_list_length(),
4874 next_bitmap->isMarked(r->bottom()),
4875 g1h->is_humongous_reclaim_candidate(region_idx),
4876 obj->is_typeArray()
4877 );
4878
4879 // Need to clear mark bit of the humongous object if already set.
4880 if (next_bitmap->isMarked(r->bottom())) {
4881 next_bitmap->clear(r->bottom());
4882 }
4883 _humongous_objects_reclaimed++;
4884 do {
4885 HeapRegion* next = g1h->next_region_in_humongous(r);
4886 _freed_bytes += r->used();
4887 r->set_containing_set(NULL);
4888 _humongous_regions_reclaimed++;
4889 g1h->free_humongous_region(r, _free_region_list, false /* skip_remset */ );
4890 r = next;
4891 } while (r != NULL);
4892
4893 return false;
4894 }
4895
4896 uint humongous_objects_reclaimed() {
4897 return _humongous_objects_reclaimed;
4898 }
4899
4900 uint humongous_regions_reclaimed() {
4901 return _humongous_regions_reclaimed;
4902 }
4903
4904 size_t bytes_freed() const {
4905 return _freed_bytes;
4906 }
4907 };
4908
4909 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4910 assert_at_safepoint(true);
4911
4912 if (!G1EagerReclaimHumongousObjects ||
4913 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
4914 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
4915 return;
4916 }
4917
4918 double start_time = os::elapsedTime();
4919
4920 FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
4921
4922 G1FreeHumongousRegionClosure cl(&local_cleanup_list);
4923 heap_region_iterate(&cl);
4924
4925 remove_from_old_sets(0, cl.humongous_regions_reclaimed());
4926
4927 G1HRPrinter* hrp = hr_printer();
4928 if (hrp->is_active()) {
4929 FreeRegionListIterator iter(&local_cleanup_list);
4930 while (iter.more_available()) {
4931 HeapRegion* hr = iter.get_next();
4932 hrp->cleanup(hr);
4933 }
4934 }
4935
4936 prepend_to_freelist(&local_cleanup_list);
4937 decrement_summary_bytes(cl.bytes_freed());
4938
4939 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
4940 cl.humongous_objects_reclaimed());
4941 }
4942
4943 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
4944 public:
4945 virtual bool doHeapRegion(HeapRegion* r) {
4946 assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
4947 G1CollectedHeap::heap()->clear_in_cset(r);
4948 r->set_young_index_in_cset(-1);
4949 return false;
4950 }
4951 };
4952
4953 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
4954 G1AbandonCollectionSetClosure cl;
4955 collection_set->iterate(&cl);
4956
4957 collection_set->clear();
4958 collection_set->stop_incremental_building();
4959 }
4960
4961 void G1CollectedHeap::set_free_regions_coming() {
4962 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming");
4963
4964 assert(!free_regions_coming(), "pre-condition");
4965 _free_regions_coming = true;
4966 }
4967
4968 void G1CollectedHeap::reset_free_regions_coming() {
4969 assert(free_regions_coming(), "pre-condition");
4970
4971 {
4972 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
4973 _free_regions_coming = false;
4974 SecondaryFreeList_lock->notify_all();
4975 }
4976
4977 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming");
4978 }
4979
4980 void G1CollectedHeap::wait_while_free_regions_coming() {
4981 // Most of the time we won't have to wait, so let's do a quick test
4982 // first before we take the lock.
4983 if (!free_regions_coming()) {
4984 return;
4985 }
4986
4987 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions");
4988
4989 {
4990 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
4991 while (free_regions_coming()) {
4992 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
4993 }
4994 }
4995
4996 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions");
4997 }
4998
4999 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
5000 return _allocator->is_retained_old_region(hr);
5001 }
5002
5003 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
5004 _eden.add(hr);
5005 _g1_policy->set_region_eden(hr);
5006 }
5007
5008 #ifdef ASSERT
5009
5010 class NoYoungRegionsClosure: public HeapRegionClosure {
5011 private:
5012 bool _success;
5013 public:
5014 NoYoungRegionsClosure() : _success(true) { }
5015 bool doHeapRegion(HeapRegion* r) {
5016 if (r->is_young()) {
5017 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
5018 p2i(r->bottom()), p2i(r->end()));
5019 _success = false;
5020 }
5021 return false;
5022 }
5023 bool success() { return _success; }
5024 };
5025
5026 bool G1CollectedHeap::check_young_list_empty() {
5027 bool ret = (young_regions_count() == 0);
5028
5029 NoYoungRegionsClosure closure;
5030 heap_region_iterate(&closure);
5031 ret = ret && closure.success();
5032
5033 return ret;
5034 }
5035
5036 #endif // ASSERT
5037
5038 class TearDownRegionSetsClosure : public HeapRegionClosure {
5039 private:
5040 HeapRegionSet *_old_set;
5041
5042 public:
5043 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
5044
5045 bool doHeapRegion(HeapRegion* r) {
5046 if (r->is_old()) {
5047 _old_set->remove(r);
5048 } else if(r->is_young()) {
5049 r->uninstall_surv_rate_group();
5050 } else {
5051 // We ignore free regions, we'll empty the free list afterwards.
5052 // We ignore humongous regions, we're not tearing down the
5053 // humongous regions set.
5054 assert(r->is_free() || r->is_humongous(),
5055 "it cannot be another type");
5056 }
5057 return false;
5058 }
5059
5060 ~TearDownRegionSetsClosure() {
5061 assert(_old_set->is_empty(), "post-condition");
5062 }
5063 };
5064
5065 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
5066 assert_at_safepoint(true /* should_be_vm_thread */);
5067
5068 if (!free_list_only) {
5069 TearDownRegionSetsClosure cl(&_old_set);
5070 heap_region_iterate(&cl);
5071
5072 // Note that emptying the _young_list is postponed and instead done as
5073 // the first step when rebuilding the regions sets again. The reason for
5074 // this is that during a full GC string deduplication needs to know if
5075 // a collected region was young or old when the full GC was initiated.
5076 }
5077 _hrm.remove_all_free_regions();
5078 }
5079
5080 void G1CollectedHeap::increase_used(size_t bytes) {
5081 _summary_bytes_used += bytes;
5082 }
5083
5084 void G1CollectedHeap::decrease_used(size_t bytes) {
5085 assert(_summary_bytes_used >= bytes,
5086 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
5087 _summary_bytes_used, bytes);
5088 _summary_bytes_used -= bytes;
5089 }
5090
5091 void G1CollectedHeap::set_used(size_t bytes) {
5092 _summary_bytes_used = bytes;
5093 }
5094
5095 class RebuildRegionSetsClosure : public HeapRegionClosure {
5096 private:
5097 bool _free_list_only;
5098 HeapRegionSet* _old_set;
5099 HeapRegionManager* _hrm;
5100 size_t _total_used;
5101
5102 public:
5103 RebuildRegionSetsClosure(bool free_list_only,
5104 HeapRegionSet* old_set, HeapRegionManager* hrm) :
5105 _free_list_only(free_list_only),
5106 _old_set(old_set), _hrm(hrm), _total_used(0) {
5107 assert(_hrm->num_free_regions() == 0, "pre-condition");
5108 if (!free_list_only) {
5109 assert(_old_set->is_empty(), "pre-condition");
5110 }
5111 }
5112
5113 bool doHeapRegion(HeapRegion* r) {
5114 if (r->is_empty()) {
5115 // Add free regions to the free list
5116 r->set_free();
5117 r->set_allocation_context(AllocationContext::system());
5118 _hrm->insert_into_free_list(r);
5119 } else if (!_free_list_only) {
5120
5121 if (r->is_humongous()) {
5122 // We ignore humongous regions. We left the humongous set unchanged.
5123 } else {
5124 assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
5125 // We now consider all regions old, so register as such. Leave
5126 // archive regions set that way, however, while still adding
5127 // them to the old set.
5128 if (!r->is_archive()) {
5129 r->set_old();
5130 }
5131 _old_set->add(r);
5132 }
5133 _total_used += r->used();
5134 }
5135
5136 return false;
5137 }
5138
5139 size_t total_used() {
5140 return _total_used;
5141 }
5142 };
5143
5144 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
5145 assert_at_safepoint(true /* should_be_vm_thread */);
5146
5147 if (!free_list_only) {
5148 _eden.clear();
5149 _survivor.clear();
5150 }
5151
5152 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
5153 heap_region_iterate(&cl);
5154
5155 if (!free_list_only) {
5156 set_used(cl.total_used());
5157 if (_archive_allocator != NULL) {
5158 _archive_allocator->clear_used();
5159 }
5160 }
5161 assert(used_unlocked() == recalculate_used(),
5162 "inconsistent used_unlocked(), "
5163 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT,
5164 used_unlocked(), recalculate_used());
5165 }
5166
5167 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
5168 _refine_cte_cl->set_concurrent(concurrent);
5169 }
5170
5171 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
5172 HeapRegion* hr = heap_region_containing(p);
5173 return hr->is_in(p);
5174 }
5175
5176 // Methods for the mutator alloc region
5177
5178 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
5179 bool force) {
5180 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5181 bool should_allocate = g1_policy()->should_allocate_mutator_region();
5182 if (force || should_allocate) {
5183 HeapRegion* new_alloc_region = new_region(word_size,
5184 false /* is_old */,
5185 false /* do_expand */);
5186 if (new_alloc_region != NULL) {
5187 set_region_short_lived_locked(new_alloc_region);
5188 _hr_printer.alloc(new_alloc_region, !should_allocate);
5189 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
5190 return new_alloc_region;
5191 }
5192 }
5193 return NULL;
5194 }
5195
5196 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
5197 size_t allocated_bytes) {
5198 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5199 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
5200
5201 collection_set()->add_eden_region(alloc_region);
5202 increase_used(allocated_bytes);
5203 _hr_printer.retire(alloc_region);
5204 // We update the eden sizes here, when the region is retired,
5205 // instead of when it's allocated, since this is the point that its
5206 // used space has been recored in _summary_bytes_used.
5207 g1mm()->update_eden_size();
5208 }
5209
5210 // Methods for the GC alloc regions
5211
5212 bool G1CollectedHeap::has_more_regions(InCSetState dest) {
5213 if (dest.is_old()) {
5214 return true;
5215 } else {
5216 return survivor_regions_count() < g1_policy()->max_survivor_regions();
5217 }
5218 }
5219
5220 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) {
5221 assert(FreeList_lock->owned_by_self(), "pre-condition");
5222
5223 if (!has_more_regions(dest)) {
5224 return NULL;
5225 }
5226
5227 const bool is_survivor = dest.is_young();
5228
5229 HeapRegion* new_alloc_region = new_region(word_size,
5230 !is_survivor,
5231 true /* do_expand */);
5232 if (new_alloc_region != NULL) {
5233 // We really only need to do this for old regions given that we
5234 // should never scan survivors. But it doesn't hurt to do it
5235 // for survivors too.
5236 new_alloc_region->record_timestamp();
5237 if (is_survivor) {
5238 new_alloc_region->set_survivor();
5239 _survivor.add(new_alloc_region);
5240 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
5241 } else {
5242 new_alloc_region->set_old();
5243 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
5244 }
5245 _hr_printer.alloc(new_alloc_region);
5246 bool during_im = collector_state()->during_initial_mark_pause();
5247 new_alloc_region->note_start_of_copying(during_im);
5248 return new_alloc_region;
5249 }
5250 return NULL;
5251 }
5252
5253 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
5254 size_t allocated_bytes,
5255 InCSetState dest) {
5256 bool during_im = collector_state()->during_initial_mark_pause();
5257 alloc_region->note_end_of_copying(during_im);
5258 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
5259 if (dest.is_old()) {
5260 _old_set.add(alloc_region);
5261 }
5262 _hr_printer.retire(alloc_region);
5263 }
5264
5265 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
5266 bool expanded = false;
5267 uint index = _hrm.find_highest_free(&expanded);
5268
5269 if (index != G1_NO_HRM_INDEX) {
5270 if (expanded) {
5271 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
5272 HeapRegion::GrainWords * HeapWordSize);
5273 }
5274 _hrm.allocate_free_regions_starting_at(index, 1);
5275 return region_at(index);
5276 }
5277 return NULL;
5278 }
5279
5280 // Optimized nmethod scanning
5281
5282 class RegisterNMethodOopClosure: public OopClosure {
5283 G1CollectedHeap* _g1h;
5284 nmethod* _nm;
5285
5286 template <class T> void do_oop_work(T* p) {
5287 T heap_oop = oopDesc::load_heap_oop(p);
5288 if (!oopDesc::is_null(heap_oop)) {
5289 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5290 HeapRegion* hr = _g1h->heap_region_containing(obj);
5291 assert(!hr->is_continues_humongous(),
5292 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5293 " starting at " HR_FORMAT,
5294 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5295
5296 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
5297 hr->add_strong_code_root_locked(_nm);
5298 }
5299 }
5300
5301 public:
5302 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5303 _g1h(g1h), _nm(nm) {}
5304
5305 void do_oop(oop* p) { do_oop_work(p); }
5306 void do_oop(narrowOop* p) { do_oop_work(p); }
5307 };
5308
5309 class UnregisterNMethodOopClosure: public OopClosure {
5310 G1CollectedHeap* _g1h;
5311 nmethod* _nm;
5312
5313 template <class T> void do_oop_work(T* p) {
5314 T heap_oop = oopDesc::load_heap_oop(p);
5315 if (!oopDesc::is_null(heap_oop)) {
5316 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5317 HeapRegion* hr = _g1h->heap_region_containing(obj);
5318 assert(!hr->is_continues_humongous(),
5319 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5320 " starting at " HR_FORMAT,
5321 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5322
5323 hr->remove_strong_code_root(_nm);
5324 }
5325 }
5326
5327 public:
5328 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5329 _g1h(g1h), _nm(nm) {}
5330
5331 void do_oop(oop* p) { do_oop_work(p); }
5332 void do_oop(narrowOop* p) { do_oop_work(p); }
5333 };
5334
5335 void G1CollectedHeap::register_nmethod(nmethod* nm) {
5336 CollectedHeap::register_nmethod(nm);
5337
5338 guarantee(nm != NULL, "sanity");
5339 RegisterNMethodOopClosure reg_cl(this, nm);
5340 nm->oops_do(®_cl);
5341 }
5342
5343 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
5344 CollectedHeap::unregister_nmethod(nm);
5345
5346 guarantee(nm != NULL, "sanity");
5347 UnregisterNMethodOopClosure reg_cl(this, nm);
5348 nm->oops_do(®_cl, true);
5349 }
5350
5351 void G1CollectedHeap::purge_code_root_memory() {
5352 double purge_start = os::elapsedTime();
5353 G1CodeRootSet::purge();
5354 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
5355 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
5356 }
5357
5358 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
5359 G1CollectedHeap* _g1h;
5360
5361 public:
5362 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
5363 _g1h(g1h) {}
5364
5365 void do_code_blob(CodeBlob* cb) {
5366 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
5367 if (nm == NULL) {
5368 return;
5369 }
5370
5371 if (ScavengeRootsInCode) {
5372 _g1h->register_nmethod(nm);
5373 }
5374 }
5375 };
5376
5377 void G1CollectedHeap::rebuild_strong_code_roots() {
5378 RebuildStrongCodeRootClosure blob_cl(this);
5379 CodeCache::blobs_do(&blob_cl);
5380 }