1 /*
2 * Copyright (c) 2001, 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/metadataOnStackMark.hpp"
27 #include "classfile/stringTable.hpp"
28 #include "classfile/symbolTable.hpp"
29 #include "code/codeCache.hpp"
30 #include "code/icBuffer.hpp"
31 #include "gc/g1/bufferingOopClosure.hpp"
32 #include "gc/g1/concurrentMarkThread.inline.hpp"
33 #include "gc/g1/g1Allocator.inline.hpp"
34 #include "gc/g1/g1CollectedHeap.inline.hpp"
35 #include "gc/g1/g1CollectionSet.hpp"
36 #include "gc/g1/g1CollectorPolicy.hpp"
37 #include "gc/g1/g1CollectorState.hpp"
38 #include "gc/g1/g1ConcurrentRefine.hpp"
39 #include "gc/g1/g1ConcurrentRefineThread.hpp"
40 #include "gc/g1/g1EvacStats.inline.hpp"
41 #include "gc/g1/g1FullCollector.hpp"
42 #include "gc/g1/g1GCPhaseTimes.hpp"
43 #include "gc/g1/g1HeapSizingPolicy.hpp"
44 #include "gc/g1/g1HeapTransition.hpp"
45 #include "gc/g1/g1HeapVerifier.hpp"
46 #include "gc/g1/g1HotCardCache.hpp"
47 #include "gc/g1/g1OopClosures.inline.hpp"
48 #include "gc/g1/g1ParScanThreadState.inline.hpp"
49 #include "gc/g1/g1Policy.hpp"
50 #include "gc/g1/g1RegionToSpaceMapper.hpp"
51 #include "gc/g1/g1RemSet.hpp"
52 #include "gc/g1/g1RootClosures.hpp"
53 #include "gc/g1/g1RootProcessor.hpp"
54 #include "gc/g1/g1StringDedup.hpp"
55 #include "gc/g1/g1YCTypes.hpp"
56 #include "gc/g1/g1YoungRemSetSamplingThread.hpp"
57 #include "gc/g1/heapRegion.inline.hpp"
58 #include "gc/g1/heapRegionRemSet.hpp"
59 #include "gc/g1/heapRegionSet.inline.hpp"
60 #include "gc/g1/vm_operations_g1.hpp"
61 #include "gc/shared/gcHeapSummary.hpp"
62 #include "gc/shared/gcId.hpp"
63 #include "gc/shared/gcLocker.inline.hpp"
64 #include "gc/shared/gcTimer.hpp"
65 #include "gc/shared/gcTrace.hpp"
66 #include "gc/shared/gcTraceTime.inline.hpp"
67 #include "gc/shared/generationSpec.hpp"
68 #include "gc/shared/isGCActiveMark.hpp"
69 #include "gc/shared/preservedMarks.inline.hpp"
70 #include "gc/shared/suspendibleThreadSet.hpp"
71 #include "gc/shared/referenceProcessor.inline.hpp"
72 #include "gc/shared/taskqueue.inline.hpp"
73 #include "gc/shared/weakProcessor.hpp"
74 #include "logging/log.hpp"
75 #include "memory/allocation.hpp"
76 #include "memory/iterator.hpp"
77 #include "memory/resourceArea.hpp"
78 #include "oops/oop.inline.hpp"
79 #include "prims/resolvedMethodTable.hpp"
80 #include "runtime/atomic.hpp"
81 #include "runtime/init.hpp"
82 #include "runtime/orderAccess.inline.hpp"
83 #include "runtime/threadSMR.hpp"
84 #include "runtime/vmThread.hpp"
85 #include "utilities/align.hpp"
86 #include "utilities/globalDefinitions.hpp"
87 #include "utilities/stack.inline.hpp"
88
89 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
90
91 // INVARIANTS/NOTES
92 //
93 // All allocation activity covered by the G1CollectedHeap interface is
94 // serialized by acquiring the HeapLock. This happens in mem_allocate
95 // and allocate_new_tlab, which are the "entry" points to the
96 // allocation code from the rest of the JVM. (Note that this does not
97 // apply to TLAB allocation, which is not part of this interface: it
98 // is done by clients of this interface.)
99
100 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
101 private:
102 size_t _num_dirtied;
103 G1CollectedHeap* _g1h;
104 G1SATBCardTableLoggingModRefBS* _g1_bs;
105
106 HeapRegion* region_for_card(jbyte* card_ptr) const {
107 return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr));
108 }
109
110 bool will_become_free(HeapRegion* hr) const {
111 // A region will be freed by free_collection_set if the region is in the
112 // collection set and has not had an evacuation failure.
113 return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
114 }
115
116 public:
117 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(),
118 _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { }
119
120 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
121 HeapRegion* hr = region_for_card(card_ptr);
122
123 // Should only dirty cards in regions that won't be freed.
124 if (!will_become_free(hr)) {
125 *card_ptr = CardTableModRefBS::dirty_card_val();
126 _num_dirtied++;
127 }
128
129 return true;
130 }
131
132 size_t num_dirtied() const { return _num_dirtied; }
133 };
134
135
136 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
137 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
138 }
139
140 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
141 // The from card cache is not the memory that is actually committed. So we cannot
142 // take advantage of the zero_filled parameter.
143 reset_from_card_cache(start_idx, num_regions);
144 }
145
146
147 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
148 MemRegion mr) {
149 return new HeapRegion(hrs_index, bot(), mr);
150 }
151
152 // Private methods.
153
154 HeapRegion*
155 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
156 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
157 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
158 if (!_secondary_free_list.is_empty()) {
159 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
160 "secondary_free_list has %u entries",
161 _secondary_free_list.length());
162 // It looks as if there are free regions available on the
163 // secondary_free_list. Let's move them to the free_list and try
164 // again to allocate from it.
165 append_secondary_free_list();
166
167 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
168 "empty we should have moved at least one entry to the free_list");
169 HeapRegion* res = _hrm.allocate_free_region(is_old);
170 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
171 "allocated " HR_FORMAT " from secondary_free_list",
172 HR_FORMAT_PARAMS(res));
173 return res;
174 }
175
176 // Wait here until we get notified either when (a) there are no
177 // more free regions coming or (b) some regions have been moved on
178 // the secondary_free_list.
179 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
180 }
181
182 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
183 "could not allocate from secondary_free_list");
184 return NULL;
185 }
186
187 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
188 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
189 "the only time we use this to allocate a humongous region is "
190 "when we are allocating a single humongous region");
191
192 HeapRegion* res;
193 if (G1StressConcRegionFreeing) {
194 if (!_secondary_free_list.is_empty()) {
195 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
196 "forced to look at the secondary_free_list");
197 res = new_region_try_secondary_free_list(is_old);
198 if (res != NULL) {
199 return res;
200 }
201 }
202 }
203
204 res = _hrm.allocate_free_region(is_old);
205
206 if (res == NULL) {
207 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
208 "res == NULL, trying the secondary_free_list");
209 res = new_region_try_secondary_free_list(is_old);
210 }
211 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
212 // Currently, only attempts to allocate GC alloc regions set
213 // do_expand to true. So, we should only reach here during a
214 // safepoint. If this assumption changes we might have to
215 // reconsider the use of _expand_heap_after_alloc_failure.
216 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
217
218 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
219 word_size * HeapWordSize);
220
221 if (expand(word_size * HeapWordSize)) {
222 // Given that expand() succeeded in expanding the heap, and we
223 // always expand the heap by an amount aligned to the heap
224 // region size, the free list should in theory not be empty.
225 // In either case allocate_free_region() will check for NULL.
226 res = _hrm.allocate_free_region(is_old);
227 } else {
228 _expand_heap_after_alloc_failure = false;
229 }
230 }
231 return res;
232 }
233
234 HeapWord*
235 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
236 uint num_regions,
237 size_t word_size,
238 AllocationContext_t context) {
239 assert(first != G1_NO_HRM_INDEX, "pre-condition");
240 assert(is_humongous(word_size), "word_size should be humongous");
241 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
242
243 // Index of last region in the series.
244 uint last = first + num_regions - 1;
245
246 // We need to initialize the region(s) we just discovered. This is
247 // a bit tricky given that it can happen concurrently with
248 // refinement threads refining cards on these regions and
249 // potentially wanting to refine the BOT as they are scanning
250 // those cards (this can happen shortly after a cleanup; see CR
251 // 6991377). So we have to set up the region(s) carefully and in
252 // a specific order.
253
254 // The word size sum of all the regions we will allocate.
255 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
256 assert(word_size <= word_size_sum, "sanity");
257
258 // This will be the "starts humongous" region.
259 HeapRegion* first_hr = region_at(first);
260 // The header of the new object will be placed at the bottom of
261 // the first region.
262 HeapWord* new_obj = first_hr->bottom();
263 // This will be the new top of the new object.
264 HeapWord* obj_top = new_obj + word_size;
265
266 // First, we need to zero the header of the space that we will be
267 // allocating. When we update top further down, some refinement
268 // threads might try to scan the region. By zeroing the header we
269 // ensure that any thread that will try to scan the region will
270 // come across the zero klass word and bail out.
271 //
272 // NOTE: It would not have been correct to have used
273 // CollectedHeap::fill_with_object() and make the space look like
274 // an int array. The thread that is doing the allocation will
275 // later update the object header to a potentially different array
276 // type and, for a very short period of time, the klass and length
277 // fields will be inconsistent. This could cause a refinement
278 // thread to calculate the object size incorrectly.
279 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
280
281 // Next, pad out the unused tail of the last region with filler
282 // objects, for improved usage accounting.
283 // How many words we use for filler objects.
284 size_t word_fill_size = word_size_sum - word_size;
285
286 // How many words memory we "waste" which cannot hold a filler object.
287 size_t words_not_fillable = 0;
288
289 if (word_fill_size >= min_fill_size()) {
290 fill_with_objects(obj_top, word_fill_size);
291 } else if (word_fill_size > 0) {
292 // We have space to fill, but we cannot fit an object there.
293 words_not_fillable = word_fill_size;
294 word_fill_size = 0;
295 }
296
297 // We will set up the first region as "starts humongous". This
298 // will also update the BOT covering all the regions to reflect
299 // that there is a single object that starts at the bottom of the
300 // first region.
301 first_hr->set_starts_humongous(obj_top, word_fill_size);
302 first_hr->set_allocation_context(context);
303 // Then, if there are any, we will set up the "continues
304 // humongous" regions.
305 HeapRegion* hr = NULL;
306 for (uint i = first + 1; i <= last; ++i) {
307 hr = region_at(i);
308 hr->set_continues_humongous(first_hr);
309 hr->set_allocation_context(context);
310 }
311
312 // Up to this point no concurrent thread would have been able to
313 // do any scanning on any region in this series. All the top
314 // fields still point to bottom, so the intersection between
315 // [bottom,top] and [card_start,card_end] will be empty. Before we
316 // update the top fields, we'll do a storestore to make sure that
317 // no thread sees the update to top before the zeroing of the
318 // object header and the BOT initialization.
319 OrderAccess::storestore();
320
321 // Now, we will update the top fields of the "continues humongous"
322 // regions except the last one.
323 for (uint i = first; i < last; ++i) {
324 hr = region_at(i);
325 hr->set_top(hr->end());
326 }
327
328 hr = region_at(last);
329 // If we cannot fit a filler object, we must set top to the end
330 // of the humongous object, otherwise we cannot iterate the heap
331 // and the BOT will not be complete.
332 hr->set_top(hr->end() - words_not_fillable);
333
334 assert(hr->bottom() < obj_top && obj_top <= hr->end(),
335 "obj_top should be in last region");
336
337 _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
338
339 assert(words_not_fillable == 0 ||
340 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
341 "Miscalculation in humongous allocation");
342
343 increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
344
345 for (uint i = first; i <= last; ++i) {
346 hr = region_at(i);
347 _humongous_set.add(hr);
348 _hr_printer.alloc(hr);
349 }
350
351 return new_obj;
352 }
353
354 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
355 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
356 return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
357 }
358
359 // If could fit into free regions w/o expansion, try.
360 // Otherwise, if can expand, do so.
361 // Otherwise, if using ex regions might help, try with ex given back.
362 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
363 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
364
365 _verifier->verify_region_sets_optional();
366
367 uint first = G1_NO_HRM_INDEX;
368 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
369
370 if (obj_regions == 1) {
371 // Only one region to allocate, try to use a fast path by directly allocating
372 // from the free lists. Do not try to expand here, we will potentially do that
373 // later.
374 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
375 if (hr != NULL) {
376 first = hr->hrm_index();
377 }
378 } else {
379 // We can't allocate humongous regions spanning more than one region while
380 // cleanupComplete() is running, since some of the regions we find to be
381 // empty might not yet be added to the free list. It is not straightforward
382 // to know in which list they are on so that we can remove them. We only
383 // need to do this if we need to allocate more than one region to satisfy the
384 // current humongous allocation request. If we are only allocating one region
385 // we use the one-region region allocation code (see above), that already
386 // potentially waits for regions from the secondary free list.
387 wait_while_free_regions_coming();
388 append_secondary_free_list_if_not_empty_with_lock();
389
390 // Policy: Try only empty regions (i.e. already committed first). Maybe we
391 // are lucky enough to find some.
392 first = _hrm.find_contiguous_only_empty(obj_regions);
393 if (first != G1_NO_HRM_INDEX) {
394 _hrm.allocate_free_regions_starting_at(first, obj_regions);
395 }
396 }
397
398 if (first == G1_NO_HRM_INDEX) {
399 // Policy: We could not find enough regions for the humongous object in the
400 // free list. Look through the heap to find a mix of free and uncommitted regions.
401 // If so, try expansion.
402 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
403 if (first != G1_NO_HRM_INDEX) {
404 // We found something. Make sure these regions are committed, i.e. expand
405 // the heap. Alternatively we could do a defragmentation GC.
406 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
407 word_size * HeapWordSize);
408
409 _hrm.expand_at(first, obj_regions, workers());
410 g1_policy()->record_new_heap_size(num_regions());
411
412 #ifdef ASSERT
413 for (uint i = first; i < first + obj_regions; ++i) {
414 HeapRegion* hr = region_at(i);
415 assert(hr->is_free(), "sanity");
416 assert(hr->is_empty(), "sanity");
417 assert(is_on_master_free_list(hr), "sanity");
418 }
419 #endif
420 _hrm.allocate_free_regions_starting_at(first, obj_regions);
421 } else {
422 // Policy: Potentially trigger a defragmentation GC.
423 }
424 }
425
426 HeapWord* result = NULL;
427 if (first != G1_NO_HRM_INDEX) {
428 result = humongous_obj_allocate_initialize_regions(first, obj_regions,
429 word_size, context);
430 assert(result != NULL, "it should always return a valid result");
431
432 // A successful humongous object allocation changes the used space
433 // information of the old generation so we need to recalculate the
434 // sizes and update the jstat counters here.
435 g1mm()->update_sizes();
436 }
437
438 _verifier->verify_region_sets_optional();
439
440 return result;
441 }
442
443 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
444 assert_heap_not_locked_and_not_at_safepoint();
445 assert(!is_humongous(word_size), "we do not allow humongous TLABs");
446
447 uint dummy_gc_count_before;
448 uint dummy_gclocker_retry_count = 0;
449 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
450 }
451
452 HeapWord*
453 G1CollectedHeap::mem_allocate(size_t word_size,
454 bool* gc_overhead_limit_was_exceeded) {
455 assert_heap_not_locked_and_not_at_safepoint();
456
457 // Loop until the allocation is satisfied, or unsatisfied after GC.
458 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
459 uint gc_count_before;
460
461 HeapWord* result = NULL;
462 if (!is_humongous(word_size)) {
463 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
464 } else {
465 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
466 }
467 if (result != NULL) {
468 return result;
469 }
470
471 // Create the garbage collection operation...
472 VM_G1CollectForAllocation op(gc_count_before, word_size);
473 op.set_allocation_context(AllocationContext::current());
474
475 // ...and get the VM thread to execute it.
476 VMThread::execute(&op);
477
478 if (op.prologue_succeeded() && op.pause_succeeded()) {
479 // If the operation was successful we'll return the result even
480 // if it is NULL. If the allocation attempt failed immediately
481 // after a Full GC, it's unlikely we'll be able to allocate now.
482 HeapWord* result = op.result();
483 if (result != NULL && !is_humongous(word_size)) {
484 // Allocations that take place on VM operations do not do any
485 // card dirtying and we have to do it here. We only have to do
486 // this for non-humongous allocations, though.
487 dirty_young_block(result, word_size);
488 }
489 return result;
490 } else {
491 if (gclocker_retry_count > GCLockerRetryAllocationCount) {
492 return NULL;
493 }
494 assert(op.result() == NULL,
495 "the result should be NULL if the VM op did not succeed");
496 }
497
498 // Give a warning if we seem to be looping forever.
499 if ((QueuedAllocationWarningCount > 0) &&
500 (try_count % QueuedAllocationWarningCount == 0)) {
501 log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count);
502 }
503 }
504
505 ShouldNotReachHere();
506 return NULL;
507 }
508
509 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
510 AllocationContext_t context,
511 uint* gc_count_before_ret,
512 uint* gclocker_retry_count_ret) {
513 // Make sure you read the note in attempt_allocation_humongous().
514
515 assert_heap_not_locked_and_not_at_safepoint();
516 assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
517 "be called for humongous allocation requests");
518
519 // We should only get here after the first-level allocation attempt
520 // (attempt_allocation()) failed to allocate.
521
522 // We will loop until a) we manage to successfully perform the
523 // allocation or b) we successfully schedule a collection which
524 // fails to perform the allocation. b) is the only case when we'll
525 // return NULL.
526 HeapWord* result = NULL;
527 for (int try_count = 1; /* we'll return */; try_count += 1) {
528 bool should_try_gc;
529 uint gc_count_before;
530
531 {
532 MutexLockerEx x(Heap_lock);
533 result = _allocator->attempt_allocation_locked(word_size, context);
534 if (result != NULL) {
535 return result;
536 }
537
538 if (GCLocker::is_active_and_needs_gc()) {
539 if (g1_policy()->can_expand_young_list()) {
540 // No need for an ergo verbose message here,
541 // can_expand_young_list() does this when it returns true.
542 result = _allocator->attempt_allocation_force(word_size, context);
543 if (result != NULL) {
544 return result;
545 }
546 }
547 should_try_gc = false;
548 } else {
549 // The GCLocker may not be active but the GCLocker initiated
550 // GC may not yet have been performed (GCLocker::needs_gc()
551 // returns true). In this case we do not try this GC and
552 // wait until the GCLocker initiated GC is performed, and
553 // then retry the allocation.
554 if (GCLocker::needs_gc()) {
555 should_try_gc = false;
556 } else {
557 // Read the GC count while still holding the Heap_lock.
558 gc_count_before = total_collections();
559 should_try_gc = true;
560 }
561 }
562 }
563
564 if (should_try_gc) {
565 bool succeeded;
566 result = do_collection_pause(word_size, gc_count_before, &succeeded,
567 GCCause::_g1_inc_collection_pause);
568 if (result != NULL) {
569 assert(succeeded, "only way to get back a non-NULL result");
570 return result;
571 }
572
573 if (succeeded) {
574 // If we get here we successfully scheduled a collection which
575 // failed to allocate. No point in trying to allocate
576 // further. We'll just return NULL.
577 MutexLockerEx x(Heap_lock);
578 *gc_count_before_ret = total_collections();
579 return NULL;
580 }
581 } else {
582 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
583 MutexLockerEx x(Heap_lock);
584 *gc_count_before_ret = total_collections();
585 return NULL;
586 }
587 // The GCLocker is either active or the GCLocker initiated
588 // GC has not yet been performed. Stall until it is and
589 // then retry the allocation.
590 GCLocker::stall_until_clear();
591 (*gclocker_retry_count_ret) += 1;
592 }
593
594 // We can reach here if we were unsuccessful in scheduling a
595 // collection (because another thread beat us to it) or if we were
596 // stalled due to the GC locker. In either can we should retry the
597 // allocation attempt in case another thread successfully
598 // performed a collection and reclaimed enough space. We do the
599 // first attempt (without holding the Heap_lock) here and the
600 // follow-on attempt will be at the start of the next loop
601 // iteration (after taking the Heap_lock).
602 result = _allocator->attempt_allocation(word_size, context);
603 if (result != NULL) {
604 return result;
605 }
606
607 // Give a warning if we seem to be looping forever.
608 if ((QueuedAllocationWarningCount > 0) &&
609 (try_count % QueuedAllocationWarningCount == 0)) {
610 log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() "
611 "retries %d times", try_count);
612 }
613 }
614
615 ShouldNotReachHere();
616 return NULL;
617 }
618
619 void G1CollectedHeap::begin_archive_alloc_range(bool open) {
620 assert_at_safepoint(true /* should_be_vm_thread */);
621 if (_archive_allocator == NULL) {
622 _archive_allocator = G1ArchiveAllocator::create_allocator(this, open);
623 }
624 }
625
626 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
627 // Allocations in archive regions cannot be of a size that would be considered
628 // humongous even for a minimum-sized region, because G1 region sizes/boundaries
629 // may be different at archive-restore time.
630 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
631 }
632
633 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
634 assert_at_safepoint(true /* should_be_vm_thread */);
635 assert(_archive_allocator != NULL, "_archive_allocator not initialized");
636 if (is_archive_alloc_too_large(word_size)) {
637 return NULL;
638 }
639 return _archive_allocator->archive_mem_allocate(word_size);
640 }
641
642 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
643 size_t end_alignment_in_bytes) {
644 assert_at_safepoint(true /* should_be_vm_thread */);
645 assert(_archive_allocator != NULL, "_archive_allocator not initialized");
646
647 // Call complete_archive to do the real work, filling in the MemRegion
648 // array with the archive regions.
649 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
650 delete _archive_allocator;
651 _archive_allocator = NULL;
652 }
653
654 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
655 assert(ranges != NULL, "MemRegion array NULL");
656 assert(count != 0, "No MemRegions provided");
657 MemRegion reserved = _hrm.reserved();
658 for (size_t i = 0; i < count; i++) {
659 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
660 return false;
661 }
662 }
663 return true;
664 }
665
666 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges,
667 size_t count,
668 bool open) {
669 assert(!is_init_completed(), "Expect to be called at JVM init time");
670 assert(ranges != NULL, "MemRegion array NULL");
671 assert(count != 0, "No MemRegions provided");
672 MutexLockerEx x(Heap_lock);
673
674 MemRegion reserved = _hrm.reserved();
675 HeapWord* prev_last_addr = NULL;
676 HeapRegion* prev_last_region = NULL;
677
678 // Temporarily disable pretouching of heap pages. This interface is used
679 // when mmap'ing archived heap data in, so pre-touching is wasted.
680 FlagSetting fs(AlwaysPreTouch, false);
681
682 // Enable archive object checking used by G1MarkSweep. We have to let it know
683 // about each archive range, so that objects in those ranges aren't marked.
684 G1ArchiveAllocator::enable_archive_object_check();
685
686 // For each specified MemRegion range, allocate the corresponding G1
687 // regions and mark them as archive regions. We expect the ranges
688 // in ascending starting address order, without overlap.
689 for (size_t i = 0; i < count; i++) {
690 MemRegion curr_range = ranges[i];
691 HeapWord* start_address = curr_range.start();
692 size_t word_size = curr_range.word_size();
693 HeapWord* last_address = curr_range.last();
694 size_t commits = 0;
695
696 guarantee(reserved.contains(start_address) && reserved.contains(last_address),
697 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
698 p2i(start_address), p2i(last_address));
699 guarantee(start_address > prev_last_addr,
700 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
701 p2i(start_address), p2i(prev_last_addr));
702 prev_last_addr = last_address;
703
704 // Check for ranges that start in the same G1 region in which the previous
705 // range ended, and adjust the start address so we don't try to allocate
706 // the same region again. If the current range is entirely within that
707 // region, skip it, just adjusting the recorded top.
708 HeapRegion* start_region = _hrm.addr_to_region(start_address);
709 if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
710 start_address = start_region->end();
711 if (start_address > last_address) {
712 increase_used(word_size * HeapWordSize);
713 start_region->set_top(last_address + 1);
714 continue;
715 }
716 start_region->set_top(start_address);
717 curr_range = MemRegion(start_address, last_address + 1);
718 start_region = _hrm.addr_to_region(start_address);
719 }
720
721 // Perform the actual region allocation, exiting if it fails.
722 // Then note how much new space we have allocated.
723 if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) {
724 return false;
725 }
726 increase_used(word_size * HeapWordSize);
727 if (commits != 0) {
728 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
729 HeapRegion::GrainWords * HeapWordSize * commits);
730
731 }
732
733 // Mark each G1 region touched by the range as archive, add it to
734 // the old set, and set the allocation context and top.
735 HeapRegion* curr_region = _hrm.addr_to_region(start_address);
736 HeapRegion* last_region = _hrm.addr_to_region(last_address);
737 prev_last_region = last_region;
738
739 while (curr_region != NULL) {
740 assert(curr_region->is_empty() && !curr_region->is_pinned(),
741 "Region already in use (index %u)", curr_region->hrm_index());
742 curr_region->set_allocation_context(AllocationContext::system());
743 if (open) {
744 curr_region->set_open_archive();
745 } else {
746 curr_region->set_closed_archive();
747 }
748 _hr_printer.alloc(curr_region);
749 _old_set.add(curr_region);
750 HeapWord* top;
751 HeapRegion* next_region;
752 if (curr_region != last_region) {
753 top = curr_region->end();
754 next_region = _hrm.next_region_in_heap(curr_region);
755 } else {
756 top = last_address + 1;
757 next_region = NULL;
758 }
759 curr_region->set_top(top);
760 curr_region->set_first_dead(top);
761 curr_region->set_end_of_live(top);
762 curr_region = next_region;
763 }
764
765 // Notify mark-sweep of the archive
766 G1ArchiveAllocator::set_range_archive(curr_range, open);
767 }
768 return true;
769 }
770
771 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
772 assert(!is_init_completed(), "Expect to be called at JVM init time");
773 assert(ranges != NULL, "MemRegion array NULL");
774 assert(count != 0, "No MemRegions provided");
775 MemRegion reserved = _hrm.reserved();
776 HeapWord *prev_last_addr = NULL;
777 HeapRegion* prev_last_region = NULL;
778
779 // For each MemRegion, create filler objects, if needed, in the G1 regions
780 // that contain the address range. The address range actually within the
781 // MemRegion will not be modified. That is assumed to have been initialized
782 // elsewhere, probably via an mmap of archived heap data.
783 MutexLockerEx x(Heap_lock);
784 for (size_t i = 0; i < count; i++) {
785 HeapWord* start_address = ranges[i].start();
786 HeapWord* last_address = ranges[i].last();
787
788 assert(reserved.contains(start_address) && reserved.contains(last_address),
789 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
790 p2i(start_address), p2i(last_address));
791 assert(start_address > prev_last_addr,
792 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
793 p2i(start_address), p2i(prev_last_addr));
794
795 HeapRegion* start_region = _hrm.addr_to_region(start_address);
796 HeapRegion* last_region = _hrm.addr_to_region(last_address);
797 HeapWord* bottom_address = start_region->bottom();
798
799 // Check for a range beginning in the same region in which the
800 // previous one ended.
801 if (start_region == prev_last_region) {
802 bottom_address = prev_last_addr + 1;
803 }
804
805 // Verify that the regions were all marked as archive regions by
806 // alloc_archive_regions.
807 HeapRegion* curr_region = start_region;
808 while (curr_region != NULL) {
809 guarantee(curr_region->is_archive(),
810 "Expected archive region at index %u", curr_region->hrm_index());
811 if (curr_region != last_region) {
812 curr_region = _hrm.next_region_in_heap(curr_region);
813 } else {
814 curr_region = NULL;
815 }
816 }
817
818 prev_last_addr = last_address;
819 prev_last_region = last_region;
820
821 // Fill the memory below the allocated range with dummy object(s),
822 // if the region bottom does not match the range start, or if the previous
823 // range ended within the same G1 region, and there is a gap.
824 if (start_address != bottom_address) {
825 size_t fill_size = pointer_delta(start_address, bottom_address);
826 G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
827 increase_used(fill_size * HeapWordSize);
828 }
829 }
830 }
831
832 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size,
833 uint* gc_count_before_ret,
834 uint* gclocker_retry_count_ret) {
835 assert_heap_not_locked_and_not_at_safepoint();
836 assert(!is_humongous(word_size), "attempt_allocation() should not "
837 "be called for humongous allocation requests");
838
839 AllocationContext_t context = AllocationContext::current();
840 HeapWord* result = _allocator->attempt_allocation(word_size, context);
841
842 if (result == NULL) {
843 result = attempt_allocation_slow(word_size,
844 context,
845 gc_count_before_ret,
846 gclocker_retry_count_ret);
847 }
848 assert_heap_not_locked();
849 if (result != NULL) {
850 dirty_young_block(result, word_size);
851 }
852 return result;
853 }
854
855 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
856 assert(!is_init_completed(), "Expect to be called at JVM init time");
857 assert(ranges != NULL, "MemRegion array NULL");
858 assert(count != 0, "No MemRegions provided");
859 MemRegion reserved = _hrm.reserved();
860 HeapWord* prev_last_addr = NULL;
861 HeapRegion* prev_last_region = NULL;
862 size_t size_used = 0;
863 size_t uncommitted_regions = 0;
864
865 // For each Memregion, free the G1 regions that constitute it, and
866 // notify mark-sweep that the range is no longer to be considered 'archive.'
867 MutexLockerEx x(Heap_lock);
868 for (size_t i = 0; i < count; i++) {
869 HeapWord* start_address = ranges[i].start();
870 HeapWord* last_address = ranges[i].last();
871
872 assert(reserved.contains(start_address) && reserved.contains(last_address),
873 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
874 p2i(start_address), p2i(last_address));
875 assert(start_address > prev_last_addr,
876 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
877 p2i(start_address), p2i(prev_last_addr));
878 size_used += ranges[i].byte_size();
879 prev_last_addr = last_address;
880
881 HeapRegion* start_region = _hrm.addr_to_region(start_address);
882 HeapRegion* last_region = _hrm.addr_to_region(last_address);
883
884 // Check for ranges that start in the same G1 region in which the previous
885 // range ended, and adjust the start address so we don't try to free
886 // the same region again. If the current range is entirely within that
887 // region, skip it.
888 if (start_region == prev_last_region) {
889 start_address = start_region->end();
890 if (start_address > last_address) {
891 continue;
892 }
893 start_region = _hrm.addr_to_region(start_address);
894 }
895 prev_last_region = last_region;
896
897 // After verifying that each region was marked as an archive region by
898 // alloc_archive_regions, set it free and empty and uncommit it.
899 HeapRegion* curr_region = start_region;
900 while (curr_region != NULL) {
901 guarantee(curr_region->is_archive(),
902 "Expected archive region at index %u", curr_region->hrm_index());
903 uint curr_index = curr_region->hrm_index();
904 _old_set.remove(curr_region);
905 curr_region->set_free();
906 curr_region->set_top(curr_region->bottom());
907 if (curr_region != last_region) {
908 curr_region = _hrm.next_region_in_heap(curr_region);
909 } else {
910 curr_region = NULL;
911 }
912 _hrm.shrink_at(curr_index, 1);
913 uncommitted_regions++;
914 }
915
916 // Notify mark-sweep that this is no longer an archive range.
917 G1ArchiveAllocator::set_range_archive(ranges[i], false);
918 }
919
920 if (uncommitted_regions != 0) {
921 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
922 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
923 }
924 decrease_used(size_used);
925 }
926
927 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
928 uint* gc_count_before_ret,
929 uint* gclocker_retry_count_ret) {
930 // The structure of this method has a lot of similarities to
931 // attempt_allocation_slow(). The reason these two were not merged
932 // into a single one is that such a method would require several "if
933 // allocation is not humongous do this, otherwise do that"
934 // conditional paths which would obscure its flow. In fact, an early
935 // version of this code did use a unified method which was harder to
936 // follow and, as a result, it had subtle bugs that were hard to
937 // track down. So keeping these two methods separate allows each to
938 // be more readable. It will be good to keep these two in sync as
939 // much as possible.
940
941 assert_heap_not_locked_and_not_at_safepoint();
942 assert(is_humongous(word_size), "attempt_allocation_humongous() "
943 "should only be called for humongous allocations");
944
945 // Humongous objects can exhaust the heap quickly, so we should check if we
946 // need to start a marking cycle at each humongous object allocation. We do
947 // the check before we do the actual allocation. The reason for doing it
948 // before the allocation is that we avoid having to keep track of the newly
949 // allocated memory while we do a GC.
950 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
951 word_size)) {
952 collect(GCCause::_g1_humongous_allocation);
953 }
954
955 // We will loop until a) we manage to successfully perform the
956 // allocation or b) we successfully schedule a collection which
957 // fails to perform the allocation. b) is the only case when we'll
958 // return NULL.
959 HeapWord* result = NULL;
960 for (int try_count = 1; /* we'll return */; try_count += 1) {
961 bool should_try_gc;
962 uint gc_count_before;
963
964 {
965 MutexLockerEx x(Heap_lock);
966
967 // Given that humongous objects are not allocated in young
968 // regions, we'll first try to do the allocation without doing a
969 // collection hoping that there's enough space in the heap.
970 result = humongous_obj_allocate(word_size, AllocationContext::current());
971 if (result != NULL) {
972 size_t size_in_regions = humongous_obj_size_in_regions(word_size);
973 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
974 return result;
975 }
976
977 if (GCLocker::is_active_and_needs_gc()) {
978 should_try_gc = false;
979 } else {
980 // The GCLocker may not be active but the GCLocker initiated
981 // GC may not yet have been performed (GCLocker::needs_gc()
982 // returns true). In this case we do not try this GC and
983 // wait until the GCLocker initiated GC is performed, and
984 // then retry the allocation.
985 if (GCLocker::needs_gc()) {
986 should_try_gc = false;
987 } else {
988 // Read the GC count while still holding the Heap_lock.
989 gc_count_before = total_collections();
990 should_try_gc = true;
991 }
992 }
993 }
994
995 if (should_try_gc) {
996 // If we failed to allocate the humongous object, we should try to
997 // do a collection pause (if we're allowed) in case it reclaims
998 // enough space for the allocation to succeed after the pause.
999
1000 bool succeeded;
1001 result = do_collection_pause(word_size, gc_count_before, &succeeded,
1002 GCCause::_g1_humongous_allocation);
1003 if (result != NULL) {
1004 assert(succeeded, "only way to get back a non-NULL result");
1005 return result;
1006 }
1007
1008 if (succeeded) {
1009 // If we get here we successfully scheduled a collection which
1010 // failed to allocate. No point in trying to allocate
1011 // further. We'll just return NULL.
1012 MutexLockerEx x(Heap_lock);
1013 *gc_count_before_ret = total_collections();
1014 return NULL;
1015 }
1016 } else {
1017 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1018 MutexLockerEx x(Heap_lock);
1019 *gc_count_before_ret = total_collections();
1020 return NULL;
1021 }
1022 // The GCLocker is either active or the GCLocker initiated
1023 // GC has not yet been performed. Stall until it is and
1024 // then retry the allocation.
1025 GCLocker::stall_until_clear();
1026 (*gclocker_retry_count_ret) += 1;
1027 }
1028
1029 // We can reach here if we were unsuccessful in scheduling a
1030 // collection (because another thread beat us to it) or if we were
1031 // stalled due to the GC locker. In either can we should retry the
1032 // allocation attempt in case another thread successfully
1033 // performed a collection and reclaimed enough space. Give a
1034 // warning if we seem to be looping forever.
1035
1036 if ((QueuedAllocationWarningCount > 0) &&
1037 (try_count % QueuedAllocationWarningCount == 0)) {
1038 log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() "
1039 "retries %d times", try_count);
1040 }
1041 }
1042
1043 ShouldNotReachHere();
1044 return NULL;
1045 }
1046
1047 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1048 AllocationContext_t context,
1049 bool expect_null_mutator_alloc_region) {
1050 assert_at_safepoint(true /* should_be_vm_thread */);
1051 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region,
1052 "the current alloc region was unexpectedly found to be non-NULL");
1053
1054 if (!is_humongous(word_size)) {
1055 return _allocator->attempt_allocation_locked(word_size, context);
1056 } else {
1057 HeapWord* result = humongous_obj_allocate(word_size, context);
1058 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1059 collector_state()->set_initiate_conc_mark_if_possible(true);
1060 }
1061 return result;
1062 }
1063
1064 ShouldNotReachHere();
1065 }
1066
1067 class PostCompactionPrinterClosure: public HeapRegionClosure {
1068 private:
1069 G1HRPrinter* _hr_printer;
1070 public:
1071 bool doHeapRegion(HeapRegion* hr) {
1072 assert(!hr->is_young(), "not expecting to find young regions");
1073 _hr_printer->post_compaction(hr);
1074 return false;
1075 }
1076
1077 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1078 : _hr_printer(hr_printer) { }
1079 };
1080
1081 void G1CollectedHeap::print_hrm_post_compaction() {
1082 if (_hr_printer.is_active()) {
1083 PostCompactionPrinterClosure cl(hr_printer());
1084 heap_region_iterate(&cl);
1085 }
1086 }
1087
1088 G1HeapVerifier::G1VerifyType G1CollectedHeap::young_verification_type() {
1089 if (collector_state()->yc_type() == Mixed) {
1090 return G1HeapVerifier::G1VerifyMixed;
1091 } else {
1092 return G1HeapVerifier::G1VerifyYoung;
1093 }
1094 }
1095
1096 void G1CollectedHeap::abort_concurrent_cycle() {
1097 // Note: When we have a more flexible GC logging framework that
1098 // allows us to add optional attributes to a GC log record we
1099 // could consider timing and reporting how long we wait in the
1100 // following two methods.
1101 wait_while_free_regions_coming();
1102 // If we start the compaction before the CM threads finish
1103 // scanning the root regions we might trip them over as we'll
1104 // be moving objects / updating references. So let's wait until
1105 // they are done. By telling them to abort, they should complete
1106 // early.
1107 _cm->root_regions()->abort();
1108 _cm->root_regions()->wait_until_scan_finished();
1109 append_secondary_free_list_if_not_empty_with_lock();
1110
1111 // Disable discovery and empty the discovered lists
1112 // for the CM ref processor.
1113 ref_processor_cm()->disable_discovery();
1114 ref_processor_cm()->abandon_partial_discovery();
1115 ref_processor_cm()->verify_no_references_recorded();
1116
1117 // Abandon current iterations of concurrent marking and concurrent
1118 // refinement, if any are in progress.
1119 concurrent_mark()->abort();
1120 }
1121
1122 void G1CollectedHeap::prepare_heap_for_full_collection() {
1123 // Make sure we'll choose a new allocation region afterwards.
1124 _allocator->release_mutator_alloc_region();
1125 _allocator->abandon_gc_alloc_regions();
1126 g1_rem_set()->cleanupHRRS();
1127
1128 // We may have added regions to the current incremental collection
1129 // set between the last GC or pause and now. We need to clear the
1130 // incremental collection set and then start rebuilding it afresh
1131 // after this full GC.
1132 abandon_collection_set(collection_set());
1133
1134 tear_down_region_sets(false /* free_list_only */);
1135 collector_state()->set_gcs_are_young(true);
1136 }
1137
1138 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) {
1139 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1140 assert(used() == recalculate_used(), "Should be equal");
1141 _verifier->verify_region_sets_optional();
1142 _verifier->verify_before_gc(G1HeapVerifier::G1VerifyFull);
1143 _verifier->check_bitmaps("Full GC Start");
1144 }
1145
1146 void G1CollectedHeap::prepare_heap_for_mutators() {
1147 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1148 ClassLoaderDataGraph::purge();
1149 MetaspaceAux::verify_metrics();
1150
1151 // Prepare heap for normal collections.
1152 assert(num_free_regions() == 0, "we should not have added any free regions");
1153 rebuild_region_sets(false /* free_list_only */);
1154 abort_refinement();
1155 resize_if_necessary_after_full_collection();
1156
1157 // Rebuild the strong code root lists for each region
1158 rebuild_strong_code_roots();
1159
1160 // Start a new incremental collection set for the next pause
1161 start_new_collection_set();
1162
1163 _allocator->init_mutator_alloc_region();
1164
1165 // Post collection state updates.
1166 MetaspaceGC::compute_new_size();
1167 }
1168
1169 void G1CollectedHeap::abort_refinement() {
1170 if (_hot_card_cache->use_cache()) {
1171 _hot_card_cache->reset_hot_cache();
1172 }
1173
1174 // Discard all remembered set updates.
1175 JavaThread::dirty_card_queue_set().abandon_logs();
1176 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1177 }
1178
1179 void G1CollectedHeap::verify_after_full_collection() {
1180 check_gc_time_stamps();
1181 _hrm.verify_optional();
1182 _verifier->verify_region_sets_optional();
1183 _verifier->verify_after_gc(G1HeapVerifier::G1VerifyFull);
1184 // Clear the previous marking bitmap, if needed for bitmap verification.
1185 // Note we cannot do this when we clear the next marking bitmap in
1186 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1187 // objects marked during a full GC against the previous bitmap.
1188 // But we need to clear it before calling check_bitmaps below since
1189 // the full GC has compacted objects and updated TAMS but not updated
1190 // the prev bitmap.
1191 if (G1VerifyBitmaps) {
1192 GCTraceTime(Debug, gc)("Clear Bitmap for Verification");
1193 _cm->clear_prev_bitmap(workers());
1194 }
1195 _verifier->check_bitmaps("Full GC End");
1196
1197 // At this point there should be no regions in the
1198 // entire heap tagged as young.
1199 assert(check_young_list_empty(), "young list should be empty at this point");
1200
1201 // Note: since we've just done a full GC, concurrent
1202 // marking is no longer active. Therefore we need not
1203 // re-enable reference discovery for the CM ref processor.
1204 // That will be done at the start of the next marking cycle.
1205 // We also know that the STW processor should no longer
1206 // discover any new references.
1207 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1208 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1209 ref_processor_stw()->verify_no_references_recorded();
1210 ref_processor_cm()->verify_no_references_recorded();
1211 }
1212
1213 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) {
1214 // Post collection logging.
1215 // We should do this after we potentially resize the heap so
1216 // that all the COMMIT / UNCOMMIT events are generated before
1217 // the compaction events.
1218 print_hrm_post_compaction();
1219 heap_transition->print();
1220 print_heap_after_gc();
1221 print_heap_regions();
1222 #ifdef TRACESPINNING
1223 ParallelTaskTerminator::print_termination_counts();
1224 #endif
1225 }
1226
1227 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1228 bool clear_all_soft_refs) {
1229 assert_at_safepoint(true /* should_be_vm_thread */);
1230
1231 if (GCLocker::check_active_before_gc()) {
1232 // Full GC was not completed.
1233 return false;
1234 }
1235
1236 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1237 collector_policy()->should_clear_all_soft_refs();
1238
1239 G1FullCollector collector(this, explicit_gc, do_clear_all_soft_refs);
1240 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1241
1242 collector.prepare_collection();
1243 collector.collect();
1244 collector.complete_collection();
1245
1246 // Full collection was successfully completed.
1247 return true;
1248 }
1249
1250 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1251 // Currently, there is no facility in the do_full_collection(bool) API to notify
1252 // the caller that the collection did not succeed (e.g., because it was locked
1253 // out by the GC locker). So, right now, we'll ignore the return value.
1254 bool dummy = do_full_collection(true, /* explicit_gc */
1255 clear_all_soft_refs);
1256 }
1257
1258 void G1CollectedHeap::resize_if_necessary_after_full_collection() {
1259 // Capacity, free and used after the GC counted as full regions to
1260 // include the waste in the following calculations.
1261 const size_t capacity_after_gc = capacity();
1262 const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes();
1263
1264 // This is enforced in arguments.cpp.
1265 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1266 "otherwise the code below doesn't make sense");
1267
1268 // We don't have floating point command-line arguments
1269 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1270 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1271 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1272 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1273
1274 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1275 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1276
1277 // We have to be careful here as these two calculations can overflow
1278 // 32-bit size_t's.
1279 double used_after_gc_d = (double) used_after_gc;
1280 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1281 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1282
1283 // Let's make sure that they are both under the max heap size, which
1284 // by default will make them fit into a size_t.
1285 double desired_capacity_upper_bound = (double) max_heap_size;
1286 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1287 desired_capacity_upper_bound);
1288 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1289 desired_capacity_upper_bound);
1290
1291 // We can now safely turn them into size_t's.
1292 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1293 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1294
1295 // This assert only makes sense here, before we adjust them
1296 // with respect to the min and max heap size.
1297 assert(minimum_desired_capacity <= maximum_desired_capacity,
1298 "minimum_desired_capacity = " SIZE_FORMAT ", "
1299 "maximum_desired_capacity = " SIZE_FORMAT,
1300 minimum_desired_capacity, maximum_desired_capacity);
1301
1302 // Should not be greater than the heap max size. No need to adjust
1303 // it with respect to the heap min size as it's a lower bound (i.e.,
1304 // we'll try to make the capacity larger than it, not smaller).
1305 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1306 // Should not be less than the heap min size. No need to adjust it
1307 // with respect to the heap max size as it's an upper bound (i.e.,
1308 // we'll try to make the capacity smaller than it, not greater).
1309 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1310
1311 if (capacity_after_gc < minimum_desired_capacity) {
1312 // Don't expand unless it's significant
1313 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1314
1315 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). "
1316 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1317 "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1318 capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio);
1319
1320 expand(expand_bytes, _workers);
1321
1322 // No expansion, now see if we want to shrink
1323 } else if (capacity_after_gc > maximum_desired_capacity) {
1324 // Capacity too large, compute shrinking size
1325 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1326
1327 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). "
1328 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1329 "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1330 capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio);
1331
1332 shrink(shrink_bytes);
1333 }
1334 }
1335
1336 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1337 AllocationContext_t context,
1338 bool do_gc,
1339 bool clear_all_soft_refs,
1340 bool expect_null_mutator_alloc_region,
1341 bool* gc_succeeded) {
1342 *gc_succeeded = true;
1343 // Let's attempt the allocation first.
1344 HeapWord* result =
1345 attempt_allocation_at_safepoint(word_size,
1346 context,
1347 expect_null_mutator_alloc_region);
1348 if (result != NULL) {
1349 assert(*gc_succeeded, "sanity");
1350 return result;
1351 }
1352
1353 // In a G1 heap, we're supposed to keep allocation from failing by
1354 // incremental pauses. Therefore, at least for now, we'll favor
1355 // expansion over collection. (This might change in the future if we can
1356 // do something smarter than full collection to satisfy a failed alloc.)
1357 result = expand_and_allocate(word_size, context);
1358 if (result != NULL) {
1359 assert(*gc_succeeded, "sanity");
1360 return result;
1361 }
1362
1363 if (do_gc) {
1364 // Expansion didn't work, we'll try to do a Full GC.
1365 *gc_succeeded = do_full_collection(false, /* explicit_gc */
1366 clear_all_soft_refs);
1367 }
1368
1369 return NULL;
1370 }
1371
1372 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1373 AllocationContext_t context,
1374 bool* succeeded) {
1375 assert_at_safepoint(true /* should_be_vm_thread */);
1376
1377 // Attempts to allocate followed by Full GC.
1378 HeapWord* result =
1379 satisfy_failed_allocation_helper(word_size,
1380 context,
1381 true, /* do_gc */
1382 false, /* clear_all_soft_refs */
1383 false, /* expect_null_mutator_alloc_region */
1384 succeeded);
1385
1386 if (result != NULL || !*succeeded) {
1387 return result;
1388 }
1389
1390 // Attempts to allocate followed by Full GC that will collect all soft references.
1391 result = satisfy_failed_allocation_helper(word_size,
1392 context,
1393 true, /* do_gc */
1394 true, /* clear_all_soft_refs */
1395 true, /* expect_null_mutator_alloc_region */
1396 succeeded);
1397
1398 if (result != NULL || !*succeeded) {
1399 return result;
1400 }
1401
1402 // Attempts to allocate, no GC
1403 result = satisfy_failed_allocation_helper(word_size,
1404 context,
1405 false, /* do_gc */
1406 false, /* clear_all_soft_refs */
1407 true, /* expect_null_mutator_alloc_region */
1408 succeeded);
1409
1410 if (result != NULL) {
1411 assert(*succeeded, "sanity");
1412 return result;
1413 }
1414
1415 assert(!collector_policy()->should_clear_all_soft_refs(),
1416 "Flag should have been handled and cleared prior to this point");
1417
1418 // What else? We might try synchronous finalization later. If the total
1419 // space available is large enough for the allocation, then a more
1420 // complete compaction phase than we've tried so far might be
1421 // appropriate.
1422 assert(*succeeded, "sanity");
1423 return NULL;
1424 }
1425
1426 // Attempting to expand the heap sufficiently
1427 // to support an allocation of the given "word_size". If
1428 // successful, perform the allocation and return the address of the
1429 // allocated block, or else "NULL".
1430
1431 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1432 assert_at_safepoint(true /* should_be_vm_thread */);
1433
1434 _verifier->verify_region_sets_optional();
1435
1436 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1437 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1438 word_size * HeapWordSize);
1439
1440
1441 if (expand(expand_bytes, _workers)) {
1442 _hrm.verify_optional();
1443 _verifier->verify_region_sets_optional();
1444 return attempt_allocation_at_safepoint(word_size,
1445 context,
1446 false /* expect_null_mutator_alloc_region */);
1447 }
1448 return NULL;
1449 }
1450
1451 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) {
1452 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1453 aligned_expand_bytes = align_up(aligned_expand_bytes,
1454 HeapRegion::GrainBytes);
1455
1456 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B",
1457 expand_bytes, aligned_expand_bytes);
1458
1459 if (is_maximal_no_gc()) {
1460 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1461 return false;
1462 }
1463
1464 double expand_heap_start_time_sec = os::elapsedTime();
1465 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1466 assert(regions_to_expand > 0, "Must expand by at least one region");
1467
1468 uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers);
1469 if (expand_time_ms != NULL) {
1470 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1471 }
1472
1473 if (expanded_by > 0) {
1474 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1475 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1476 g1_policy()->record_new_heap_size(num_regions());
1477 } else {
1478 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1479
1480 // The expansion of the virtual storage space was unsuccessful.
1481 // Let's see if it was because we ran out of swap.
1482 if (G1ExitOnExpansionFailure &&
1483 _hrm.available() >= regions_to_expand) {
1484 // We had head room...
1485 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1486 }
1487 }
1488 return regions_to_expand > 0;
1489 }
1490
1491 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1492 size_t aligned_shrink_bytes =
1493 ReservedSpace::page_align_size_down(shrink_bytes);
1494 aligned_shrink_bytes = align_down(aligned_shrink_bytes,
1495 HeapRegion::GrainBytes);
1496 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1497
1498 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1499 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1500
1501
1502 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",
1503 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1504 if (num_regions_removed > 0) {
1505 g1_policy()->record_new_heap_size(num_regions());
1506 } else {
1507 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1508 }
1509 }
1510
1511 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1512 _verifier->verify_region_sets_optional();
1513
1514 // We should only reach here at the end of a Full GC which means we
1515 // should not not be holding to any GC alloc regions. The method
1516 // below will make sure of that and do any remaining clean up.
1517 _allocator->abandon_gc_alloc_regions();
1518
1519 // Instead of tearing down / rebuilding the free lists here, we
1520 // could instead use the remove_all_pending() method on free_list to
1521 // remove only the ones that we need to remove.
1522 tear_down_region_sets(true /* free_list_only */);
1523 shrink_helper(shrink_bytes);
1524 rebuild_region_sets(true /* free_list_only */);
1525
1526 _hrm.verify_optional();
1527 _verifier->verify_region_sets_optional();
1528 }
1529
1530 // Public methods.
1531
1532 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) :
1533 CollectedHeap(),
1534 _young_gen_sampling_thread(NULL),
1535 _collector_policy(collector_policy),
1536 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1537 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1538 _g1_policy(create_g1_policy(_gc_timer_stw)),
1539 _collection_set(this, _g1_policy),
1540 _dirty_card_queue_set(false),
1541 _is_alive_closure_cm(this),
1542 _is_alive_closure_stw(this),
1543 _ref_processor_cm(NULL),
1544 _ref_processor_stw(NULL),
1545 _bot(NULL),
1546 _hot_card_cache(NULL),
1547 _g1_rem_set(NULL),
1548 _cr(NULL),
1549 _g1mm(NULL),
1550 _preserved_marks_set(true /* in_c_heap */),
1551 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1552 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1553 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1554 _humongous_reclaim_candidates(),
1555 _has_humongous_reclaim_candidates(false),
1556 _archive_allocator(NULL),
1557 _free_regions_coming(false),
1558 _gc_time_stamp(0),
1559 _summary_bytes_used(0),
1560 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1561 _old_evac_stats("Old", OldPLABSize, PLABWeight),
1562 _expand_heap_after_alloc_failure(true),
1563 _old_marking_cycles_started(0),
1564 _old_marking_cycles_completed(0),
1565 _in_cset_fast_test() {
1566
1567 _workers = new WorkGang("GC Thread", ParallelGCThreads,
1568 /* are_GC_task_threads */true,
1569 /* are_ConcurrentGC_threads */false);
1570 _workers->initialize_workers();
1571 _verifier = new G1HeapVerifier(this);
1572
1573 _allocator = G1Allocator::create_allocator(this);
1574
1575 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics());
1576
1577 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1578
1579 // Override the default _filler_array_max_size so that no humongous filler
1580 // objects are created.
1581 _filler_array_max_size = _humongous_object_threshold_in_words;
1582
1583 uint n_queues = ParallelGCThreads;
1584 _task_queues = new RefToScanQueueSet(n_queues);
1585
1586 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1587
1588 for (uint i = 0; i < n_queues; i++) {
1589 RefToScanQueue* q = new RefToScanQueue();
1590 q->initialize();
1591 _task_queues->register_queue(i, q);
1592 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1593 }
1594
1595 // Initialize the G1EvacuationFailureALot counters and flags.
1596 NOT_PRODUCT(reset_evacuation_should_fail();)
1597
1598 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1599 }
1600
1601 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1602 size_t size,
1603 size_t translation_factor) {
1604 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1605 // Allocate a new reserved space, preferring to use large pages.
1606 ReservedSpace rs(size, preferred_page_size);
1607 G1RegionToSpaceMapper* result =
1608 G1RegionToSpaceMapper::create_mapper(rs,
1609 size,
1610 rs.alignment(),
1611 HeapRegion::GrainBytes,
1612 translation_factor,
1613 mtGC);
1614
1615 os::trace_page_sizes_for_requested_size(description,
1616 size,
1617 preferred_page_size,
1618 rs.alignment(),
1619 rs.base(),
1620 rs.size());
1621
1622 return result;
1623 }
1624
1625 jint G1CollectedHeap::initialize_concurrent_refinement() {
1626 jint ecode = JNI_OK;
1627 _cr = G1ConcurrentRefine::create(&ecode);
1628 return ecode;
1629 }
1630
1631 jint G1CollectedHeap::initialize_young_gen_sampling_thread() {
1632 _young_gen_sampling_thread = new G1YoungRemSetSamplingThread();
1633 if (_young_gen_sampling_thread->osthread() == NULL) {
1634 vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread");
1635 return JNI_ENOMEM;
1636 }
1637 return JNI_OK;
1638 }
1639
1640 jint G1CollectedHeap::initialize() {
1641 CollectedHeap::pre_initialize();
1642 os::enable_vtime();
1643
1644 // Necessary to satisfy locking discipline assertions.
1645
1646 MutexLocker x(Heap_lock);
1647
1648 // While there are no constraints in the GC code that HeapWordSize
1649 // be any particular value, there are multiple other areas in the
1650 // system which believe this to be true (e.g. oop->object_size in some
1651 // cases incorrectly returns the size in wordSize units rather than
1652 // HeapWordSize).
1653 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1654
1655 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1656 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1657 size_t heap_alignment = collector_policy()->heap_alignment();
1658
1659 // Ensure that the sizes are properly aligned.
1660 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1661 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1662 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1663
1664 // Reserve the maximum.
1665
1666 // When compressed oops are enabled, the preferred heap base
1667 // is calculated by subtracting the requested size from the
1668 // 32Gb boundary and using the result as the base address for
1669 // heap reservation. If the requested size is not aligned to
1670 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1671 // into the ReservedHeapSpace constructor) then the actual
1672 // base of the reserved heap may end up differing from the
1673 // address that was requested (i.e. the preferred heap base).
1674 // If this happens then we could end up using a non-optimal
1675 // compressed oops mode.
1676
1677 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1678 heap_alignment);
1679
1680 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1681
1682 // Create the barrier set for the entire reserved region.
1683 G1SATBCardTableLoggingModRefBS* bs
1684 = new G1SATBCardTableLoggingModRefBS(reserved_region());
1685 bs->initialize();
1686 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity");
1687 set_barrier_set(bs);
1688
1689 // Create the hot card cache.
1690 _hot_card_cache = new G1HotCardCache(this);
1691
1692 // Carve out the G1 part of the heap.
1693 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1694 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
1695 G1RegionToSpaceMapper* heap_storage =
1696 G1RegionToSpaceMapper::create_mapper(g1_rs,
1697 g1_rs.size(),
1698 page_size,
1699 HeapRegion::GrainBytes,
1700 1,
1701 mtJavaHeap);
1702 os::trace_page_sizes("Heap",
1703 collector_policy()->min_heap_byte_size(),
1704 max_byte_size,
1705 page_size,
1706 heap_rs.base(),
1707 heap_rs.size());
1708 heap_storage->set_mapping_changed_listener(&_listener);
1709
1710 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1711 G1RegionToSpaceMapper* bot_storage =
1712 create_aux_memory_mapper("Block Offset Table",
1713 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1714 G1BlockOffsetTable::heap_map_factor());
1715
1716 G1RegionToSpaceMapper* cardtable_storage =
1717 create_aux_memory_mapper("Card Table",
1718 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize),
1719 G1SATBCardTableLoggingModRefBS::heap_map_factor());
1720
1721 G1RegionToSpaceMapper* card_counts_storage =
1722 create_aux_memory_mapper("Card Counts Table",
1723 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1724 G1CardCounts::heap_map_factor());
1725
1726 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1727 G1RegionToSpaceMapper* prev_bitmap_storage =
1728 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1729 G1RegionToSpaceMapper* next_bitmap_storage =
1730 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1731
1732 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1733 g1_barrier_set()->initialize(cardtable_storage);
1734 // Do later initialization work for concurrent refinement.
1735 _hot_card_cache->initialize(card_counts_storage);
1736
1737 // 6843694 - ensure that the maximum region index can fit
1738 // in the remembered set structures.
1739 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1740 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1741
1742 // Also create a G1 rem set.
1743 _g1_rem_set = new G1RemSet(this, g1_barrier_set(), _hot_card_cache);
1744 _g1_rem_set->initialize(max_capacity(), max_regions());
1745
1746 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1747 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1748 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1749 "too many cards per region");
1750
1751 FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1752
1753 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1754
1755 {
1756 HeapWord* start = _hrm.reserved().start();
1757 HeapWord* end = _hrm.reserved().end();
1758 size_t granularity = HeapRegion::GrainBytes;
1759
1760 _in_cset_fast_test.initialize(start, end, granularity);
1761 _humongous_reclaim_candidates.initialize(start, end, granularity);
1762 }
1763
1764 // Create the G1ConcurrentMark data structure and thread.
1765 // (Must do this late, so that "max_regions" is defined.)
1766 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1767 if (_cm == NULL || !_cm->completed_initialization()) {
1768 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
1769 return JNI_ENOMEM;
1770 }
1771 _cmThread = _cm->cm_thread();
1772
1773 // Now expand into the initial heap size.
1774 if (!expand(init_byte_size, _workers)) {
1775 vm_shutdown_during_initialization("Failed to allocate initial heap.");
1776 return JNI_ENOMEM;
1777 }
1778
1779 // Perform any initialization actions delegated to the policy.
1780 g1_policy()->init(this, &_collection_set);
1781
1782 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1783 SATB_Q_FL_lock,
1784 G1SATBProcessCompletedThreshold,
1785 Shared_SATB_Q_lock);
1786
1787 jint ecode = initialize_concurrent_refinement();
1788 if (ecode != JNI_OK) {
1789 return ecode;
1790 }
1791
1792 ecode = initialize_young_gen_sampling_thread();
1793 if (ecode != JNI_OK) {
1794 return ecode;
1795 }
1796
1797 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1798 DirtyCardQ_FL_lock,
1799 (int)concurrent_refine()->yellow_zone(),
1800 (int)concurrent_refine()->red_zone(),
1801 Shared_DirtyCardQ_lock,
1802 NULL, // fl_owner
1803 true); // init_free_ids
1804
1805 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1806 DirtyCardQ_FL_lock,
1807 -1, // never trigger processing
1808 -1, // no limit on length
1809 Shared_DirtyCardQ_lock,
1810 &JavaThread::dirty_card_queue_set());
1811
1812 // Here we allocate the dummy HeapRegion that is required by the
1813 // G1AllocRegion class.
1814 HeapRegion* dummy_region = _hrm.get_dummy_region();
1815
1816 // We'll re-use the same region whether the alloc region will
1817 // require BOT updates or not and, if it doesn't, then a non-young
1818 // region will complain that it cannot support allocations without
1819 // BOT updates. So we'll tag the dummy region as eden to avoid that.
1820 dummy_region->set_eden();
1821 // Make sure it's full.
1822 dummy_region->set_top(dummy_region->end());
1823 G1AllocRegion::setup(this, dummy_region);
1824
1825 _allocator->init_mutator_alloc_region();
1826
1827 // Do create of the monitoring and management support so that
1828 // values in the heap have been properly initialized.
1829 _g1mm = new G1MonitoringSupport(this);
1830
1831 G1StringDedup::initialize();
1832
1833 _preserved_marks_set.init(ParallelGCThreads);
1834
1835 _collection_set.initialize(max_regions());
1836
1837 return JNI_OK;
1838 }
1839
1840 void G1CollectedHeap::stop() {
1841 // Stop all concurrent threads. We do this to make sure these threads
1842 // do not continue to execute and access resources (e.g. logging)
1843 // that are destroyed during shutdown.
1844 _cr->stop();
1845 _young_gen_sampling_thread->stop();
1846 _cmThread->stop();
1847 if (G1StringDedup::is_enabled()) {
1848 G1StringDedup::stop();
1849 }
1850 }
1851
1852 void G1CollectedHeap::safepoint_synchronize_begin() {
1853 SuspendibleThreadSet::synchronize();
1854 }
1855
1856 void G1CollectedHeap::safepoint_synchronize_end() {
1857 SuspendibleThreadSet::desynchronize();
1858 }
1859
1860 size_t G1CollectedHeap::conservative_max_heap_alignment() {
1861 return HeapRegion::max_region_size();
1862 }
1863
1864 void G1CollectedHeap::post_initialize() {
1865 ref_processing_init();
1866 }
1867
1868 void G1CollectedHeap::ref_processing_init() {
1869 // Reference processing in G1 currently works as follows:
1870 //
1871 // * There are two reference processor instances. One is
1872 // used to record and process discovered references
1873 // during concurrent marking; the other is used to
1874 // record and process references during STW pauses
1875 // (both full and incremental).
1876 // * Both ref processors need to 'span' the entire heap as
1877 // the regions in the collection set may be dotted around.
1878 //
1879 // * For the concurrent marking ref processor:
1880 // * Reference discovery is enabled at initial marking.
1881 // * Reference discovery is disabled and the discovered
1882 // references processed etc during remarking.
1883 // * Reference discovery is MT (see below).
1884 // * Reference discovery requires a barrier (see below).
1885 // * Reference processing may or may not be MT
1886 // (depending on the value of ParallelRefProcEnabled
1887 // and ParallelGCThreads).
1888 // * A full GC disables reference discovery by the CM
1889 // ref processor and abandons any entries on it's
1890 // discovered lists.
1891 //
1892 // * For the STW processor:
1893 // * Non MT discovery is enabled at the start of a full GC.
1894 // * Processing and enqueueing during a full GC is non-MT.
1895 // * During a full GC, references are processed after marking.
1896 //
1897 // * Discovery (may or may not be MT) is enabled at the start
1898 // of an incremental evacuation pause.
1899 // * References are processed near the end of a STW evacuation pause.
1900 // * For both types of GC:
1901 // * Discovery is atomic - i.e. not concurrent.
1902 // * Reference discovery will not need a barrier.
1903
1904 MemRegion mr = reserved_region();
1905
1906 bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1);
1907
1908 // Concurrent Mark ref processor
1909 _ref_processor_cm =
1910 new ReferenceProcessor(mr, // span
1911 mt_processing,
1912 // mt processing
1913 ParallelGCThreads,
1914 // degree of mt processing
1915 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
1916 // mt discovery
1917 MAX2(ParallelGCThreads, ConcGCThreads),
1918 // degree of mt discovery
1919 false,
1920 // Reference discovery is not atomic
1921 &_is_alive_closure_cm);
1922 // is alive closure
1923 // (for efficiency/performance)
1924
1925 // STW ref processor
1926 _ref_processor_stw =
1927 new ReferenceProcessor(mr, // span
1928 mt_processing,
1929 // mt processing
1930 ParallelGCThreads,
1931 // degree of mt processing
1932 (ParallelGCThreads > 1),
1933 // mt discovery
1934 ParallelGCThreads,
1935 // degree of mt discovery
1936 true,
1937 // Reference discovery is atomic
1938 &_is_alive_closure_stw);
1939 // is alive closure
1940 // (for efficiency/performance)
1941 }
1942
1943 CollectorPolicy* G1CollectedHeap::collector_policy() const {
1944 return _collector_policy;
1945 }
1946
1947 size_t G1CollectedHeap::capacity() const {
1948 return _hrm.length() * HeapRegion::GrainBytes;
1949 }
1950
1951 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const {
1952 return _hrm.total_free_bytes();
1953 }
1954
1955 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
1956 hr->reset_gc_time_stamp();
1957 }
1958
1959 #ifndef PRODUCT
1960
1961 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
1962 private:
1963 unsigned _gc_time_stamp;
1964 bool _failures;
1965
1966 public:
1967 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
1968 _gc_time_stamp(gc_time_stamp), _failures(false) { }
1969
1970 virtual bool doHeapRegion(HeapRegion* hr) {
1971 unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
1972 if (_gc_time_stamp != region_gc_time_stamp) {
1973 log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr),
1974 region_gc_time_stamp, _gc_time_stamp);
1975 _failures = true;
1976 }
1977 return false;
1978 }
1979
1980 bool failures() { return _failures; }
1981 };
1982
1983 void G1CollectedHeap::check_gc_time_stamps() {
1984 CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
1985 heap_region_iterate(&cl);
1986 guarantee(!cl.failures(), "all GC time stamps should have been reset");
1987 }
1988 #endif // PRODUCT
1989
1990 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) {
1991 _hot_card_cache->drain(cl, worker_i);
1992 }
1993
1994 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) {
1995 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
1996 size_t n_completed_buffers = 0;
1997 while (dcqs.apply_closure_during_gc(cl, worker_i)) {
1998 n_completed_buffers++;
1999 }
2000 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
2001 dcqs.clear_n_completed_buffers();
2002 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2003 }
2004
2005 // Computes the sum of the storage used by the various regions.
2006 size_t G1CollectedHeap::used() const {
2007 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
2008 if (_archive_allocator != NULL) {
2009 result += _archive_allocator->used();
2010 }
2011 return result;
2012 }
2013
2014 size_t G1CollectedHeap::used_unlocked() const {
2015 return _summary_bytes_used;
2016 }
2017
2018 class SumUsedClosure: public HeapRegionClosure {
2019 size_t _used;
2020 public:
2021 SumUsedClosure() : _used(0) {}
2022 bool doHeapRegion(HeapRegion* r) {
2023 _used += r->used();
2024 return false;
2025 }
2026 size_t result() { return _used; }
2027 };
2028
2029 size_t G1CollectedHeap::recalculate_used() const {
2030 double recalculate_used_start = os::elapsedTime();
2031
2032 SumUsedClosure blk;
2033 heap_region_iterate(&blk);
2034
2035 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2036 return blk.result();
2037 }
2038
2039 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
2040 switch (cause) {
2041 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2042 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent;
2043 case GCCause::_update_allocation_context_stats_inc: return true;
2044 case GCCause::_wb_conc_mark: return true;
2045 default : return false;
2046 }
2047 }
2048
2049 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2050 switch (cause) {
2051 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2052 case GCCause::_g1_humongous_allocation: return true;
2053 default: return is_user_requested_concurrent_full_gc(cause);
2054 }
2055 }
2056
2057 #ifndef PRODUCT
2058 void G1CollectedHeap::allocate_dummy_regions() {
2059 // Let's fill up most of the region
2060 size_t word_size = HeapRegion::GrainWords - 1024;
2061 // And as a result the region we'll allocate will be humongous.
2062 guarantee(is_humongous(word_size), "sanity");
2063
2064 // _filler_array_max_size is set to humongous object threshold
2065 // but temporarily change it to use CollectedHeap::fill_with_object().
2066 SizeTFlagSetting fs(_filler_array_max_size, word_size);
2067
2068 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2069 // Let's use the existing mechanism for the allocation
2070 HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2071 AllocationContext::system());
2072 if (dummy_obj != NULL) {
2073 MemRegion mr(dummy_obj, word_size);
2074 CollectedHeap::fill_with_object(mr);
2075 } else {
2076 // If we can't allocate once, we probably cannot allocate
2077 // again. Let's get out of the loop.
2078 break;
2079 }
2080 }
2081 }
2082 #endif // !PRODUCT
2083
2084 void G1CollectedHeap::increment_old_marking_cycles_started() {
2085 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2086 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2087 "Wrong marking cycle count (started: %d, completed: %d)",
2088 _old_marking_cycles_started, _old_marking_cycles_completed);
2089
2090 _old_marking_cycles_started++;
2091 }
2092
2093 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2094 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2095
2096 // We assume that if concurrent == true, then the caller is a
2097 // concurrent thread that was joined the Suspendible Thread
2098 // Set. If there's ever a cheap way to check this, we should add an
2099 // assert here.
2100
2101 // Given that this method is called at the end of a Full GC or of a
2102 // concurrent cycle, and those can be nested (i.e., a Full GC can
2103 // interrupt a concurrent cycle), the number of full collections
2104 // completed should be either one (in the case where there was no
2105 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2106 // behind the number of full collections started.
2107
2108 // This is the case for the inner caller, i.e. a Full GC.
2109 assert(concurrent ||
2110 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2111 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2112 "for inner caller (Full GC): _old_marking_cycles_started = %u "
2113 "is inconsistent with _old_marking_cycles_completed = %u",
2114 _old_marking_cycles_started, _old_marking_cycles_completed);
2115
2116 // This is the case for the outer caller, i.e. the concurrent cycle.
2117 assert(!concurrent ||
2118 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2119 "for outer caller (concurrent cycle): "
2120 "_old_marking_cycles_started = %u "
2121 "is inconsistent with _old_marking_cycles_completed = %u",
2122 _old_marking_cycles_started, _old_marking_cycles_completed);
2123
2124 _old_marking_cycles_completed += 1;
2125
2126 // We need to clear the "in_progress" flag in the CM thread before
2127 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2128 // is set) so that if a waiter requests another System.gc() it doesn't
2129 // incorrectly see that a marking cycle is still in progress.
2130 if (concurrent) {
2131 _cmThread->set_idle();
2132 }
2133
2134 // This notify_all() will ensure that a thread that called
2135 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2136 // and it's waiting for a full GC to finish will be woken up. It is
2137 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2138 FullGCCount_lock->notify_all();
2139 }
2140
2141 void G1CollectedHeap::collect(GCCause::Cause cause) {
2142 assert_heap_not_locked();
2143
2144 uint gc_count_before;
2145 uint old_marking_count_before;
2146 uint full_gc_count_before;
2147 bool retry_gc;
2148
2149 do {
2150 retry_gc = false;
2151
2152 {
2153 MutexLocker ml(Heap_lock);
2154
2155 // Read the GC count while holding the Heap_lock
2156 gc_count_before = total_collections();
2157 full_gc_count_before = total_full_collections();
2158 old_marking_count_before = _old_marking_cycles_started;
2159 }
2160
2161 if (should_do_concurrent_full_gc(cause)) {
2162 // Schedule an initial-mark evacuation pause that will start a
2163 // concurrent cycle. We're setting word_size to 0 which means that
2164 // we are not requesting a post-GC allocation.
2165 VM_G1IncCollectionPause op(gc_count_before,
2166 0, /* word_size */
2167 true, /* should_initiate_conc_mark */
2168 g1_policy()->max_pause_time_ms(),
2169 cause);
2170 op.set_allocation_context(AllocationContext::current());
2171
2172 VMThread::execute(&op);
2173 if (!op.pause_succeeded()) {
2174 if (old_marking_count_before == _old_marking_cycles_started) {
2175 retry_gc = op.should_retry_gc();
2176 } else {
2177 // A Full GC happened while we were trying to schedule the
2178 // initial-mark GC. No point in starting a new cycle given
2179 // that the whole heap was collected anyway.
2180 }
2181
2182 if (retry_gc) {
2183 if (GCLocker::is_active_and_needs_gc()) {
2184 GCLocker::stall_until_clear();
2185 }
2186 }
2187 }
2188 } else {
2189 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2190 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2191
2192 // Schedule a standard evacuation pause. We're setting word_size
2193 // to 0 which means that we are not requesting a post-GC allocation.
2194 VM_G1IncCollectionPause op(gc_count_before,
2195 0, /* word_size */
2196 false, /* should_initiate_conc_mark */
2197 g1_policy()->max_pause_time_ms(),
2198 cause);
2199 VMThread::execute(&op);
2200 } else {
2201 // Schedule a Full GC.
2202 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2203 VMThread::execute(&op);
2204 }
2205 }
2206 } while (retry_gc);
2207 }
2208
2209 bool G1CollectedHeap::is_in(const void* p) const {
2210 if (_hrm.reserved().contains(p)) {
2211 // Given that we know that p is in the reserved space,
2212 // heap_region_containing() should successfully
2213 // return the containing region.
2214 HeapRegion* hr = heap_region_containing(p);
2215 return hr->is_in(p);
2216 } else {
2217 return false;
2218 }
2219 }
2220
2221 #ifdef ASSERT
2222 bool G1CollectedHeap::is_in_exact(const void* p) const {
2223 bool contains = reserved_region().contains(p);
2224 bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2225 if (contains && available) {
2226 return true;
2227 } else {
2228 return false;
2229 }
2230 }
2231 #endif
2232
2233 // Iteration functions.
2234
2235 // Iterates an ObjectClosure over all objects within a HeapRegion.
2236
2237 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2238 ObjectClosure* _cl;
2239 public:
2240 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2241 bool doHeapRegion(HeapRegion* r) {
2242 if (!r->is_continues_humongous()) {
2243 r->object_iterate(_cl);
2244 }
2245 return false;
2246 }
2247 };
2248
2249 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2250 IterateObjectClosureRegionClosure blk(cl);
2251 heap_region_iterate(&blk);
2252 }
2253
2254 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2255 _hrm.iterate(cl);
2256 }
2257
2258 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
2259 HeapRegionClaimer *hrclaimer,
2260 uint worker_id) const {
2261 _hrm.par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id));
2262 }
2263
2264 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl,
2265 HeapRegionClaimer *hrclaimer) const {
2266 _hrm.par_iterate(cl, hrclaimer, 0);
2267 }
2268
2269 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2270 _collection_set.iterate(cl);
2271 }
2272
2273 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) {
2274 _collection_set.iterate_from(cl, worker_id, workers()->active_workers());
2275 }
2276
2277 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2278 HeapRegion* hr = heap_region_containing(addr);
2279 return hr->block_start(addr);
2280 }
2281
2282 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2283 HeapRegion* hr = heap_region_containing(addr);
2284 return hr->block_size(addr);
2285 }
2286
2287 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2288 HeapRegion* hr = heap_region_containing(addr);
2289 return hr->block_is_obj(addr);
2290 }
2291
2292 bool G1CollectedHeap::supports_tlab_allocation() const {
2293 return true;
2294 }
2295
2296 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2297 return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2298 }
2299
2300 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2301 return _eden.length() * HeapRegion::GrainBytes;
2302 }
2303
2304 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2305 // must be equal to the humongous object limit.
2306 size_t G1CollectedHeap::max_tlab_size() const {
2307 return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
2308 }
2309
2310 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2311 AllocationContext_t context = AllocationContext::current();
2312 return _allocator->unsafe_max_tlab_alloc(context);
2313 }
2314
2315 size_t G1CollectedHeap::max_capacity() const {
2316 return _hrm.reserved().byte_size();
2317 }
2318
2319 jlong G1CollectedHeap::millis_since_last_gc() {
2320 // See the notes in GenCollectedHeap::millis_since_last_gc()
2321 // for more information about the implementation.
2322 jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) -
2323 _g1_policy->collection_pause_end_millis();
2324 if (ret_val < 0) {
2325 log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
2326 ". returning zero instead.", ret_val);
2327 return 0;
2328 }
2329 return ret_val;
2330 }
2331
2332 void G1CollectedHeap::prepare_for_verify() {
2333 _verifier->prepare_for_verify();
2334 }
2335
2336 void G1CollectedHeap::verify(VerifyOption vo) {
2337 _verifier->verify(vo);
2338 }
2339
2340 bool G1CollectedHeap::supports_concurrent_phase_control() const {
2341 return true;
2342 }
2343
2344 const char* const* G1CollectedHeap::concurrent_phases() const {
2345 return _cmThread->concurrent_phases();
2346 }
2347
2348 bool G1CollectedHeap::request_concurrent_phase(const char* phase) {
2349 return _cmThread->request_concurrent_phase(phase);
2350 }
2351
2352 class PrintRegionClosure: public HeapRegionClosure {
2353 outputStream* _st;
2354 public:
2355 PrintRegionClosure(outputStream* st) : _st(st) {}
2356 bool doHeapRegion(HeapRegion* r) {
2357 r->print_on(_st);
2358 return false;
2359 }
2360 };
2361
2362 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2363 const HeapRegion* hr,
2364 const VerifyOption vo) const {
2365 switch (vo) {
2366 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2367 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2368 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr);
2369 default: ShouldNotReachHere();
2370 }
2371 return false; // keep some compilers happy
2372 }
2373
2374 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2375 const VerifyOption vo) const {
2376 switch (vo) {
2377 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2378 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2379 case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj);
2380 default: ShouldNotReachHere();
2381 }
2382 return false; // keep some compilers happy
2383 }
2384
2385 void G1CollectedHeap::print_heap_regions() const {
2386 LogTarget(Trace, gc, heap, region) lt;
2387 if (lt.is_enabled()) {
2388 LogStream ls(lt);
2389 print_regions_on(&ls);
2390 }
2391 }
2392
2393 void G1CollectedHeap::print_on(outputStream* st) const {
2394 st->print(" %-20s", "garbage-first heap");
2395 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2396 capacity()/K, used_unlocked()/K);
2397 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")",
2398 p2i(_hrm.reserved().start()),
2399 p2i(_hrm.reserved().end()));
2400 st->cr();
2401 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2402 uint young_regions = young_regions_count();
2403 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2404 (size_t) young_regions * HeapRegion::GrainBytes / K);
2405 uint survivor_regions = survivor_regions_count();
2406 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2407 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2408 st->cr();
2409 MetaspaceAux::print_on(st);
2410 }
2411
2412 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2413 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2414 "HS=humongous(starts), HC=humongous(continues), "
2415 "CS=collection set, F=free, A=archive, TS=gc time stamp, "
2416 "AC=allocation context, "
2417 "TAMS=top-at-mark-start (previous, next)");
2418 PrintRegionClosure blk(st);
2419 heap_region_iterate(&blk);
2420 }
2421
2422 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2423 print_on(st);
2424
2425 // Print the per-region information.
2426 print_regions_on(st);
2427 }
2428
2429 void G1CollectedHeap::print_on_error(outputStream* st) const {
2430 this->CollectedHeap::print_on_error(st);
2431
2432 if (_cm != NULL) {
2433 st->cr();
2434 _cm->print_on_error(st);
2435 }
2436 }
2437
2438 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2439 workers()->print_worker_threads_on(st);
2440 _cmThread->print_on(st);
2441 st->cr();
2442 _cm->print_worker_threads_on(st);
2443 _cr->print_threads_on(st);
2444 _young_gen_sampling_thread->print_on(st);
2445 if (G1StringDedup::is_enabled()) {
2446 G1StringDedup::print_worker_threads_on(st);
2447 }
2448 }
2449
2450 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2451 workers()->threads_do(tc);
2452 tc->do_thread(_cmThread);
2453 _cm->threads_do(tc);
2454 _cr->threads_do(tc);
2455 tc->do_thread(_young_gen_sampling_thread);
2456 if (G1StringDedup::is_enabled()) {
2457 G1StringDedup::threads_do(tc);
2458 }
2459 }
2460
2461 void G1CollectedHeap::print_tracing_info() const {
2462 g1_rem_set()->print_summary_info();
2463 concurrent_mark()->print_summary_info();
2464 }
2465
2466 #ifndef PRODUCT
2467 // Helpful for debugging RSet issues.
2468
2469 class PrintRSetsClosure : public HeapRegionClosure {
2470 private:
2471 const char* _msg;
2472 size_t _occupied_sum;
2473
2474 public:
2475 bool doHeapRegion(HeapRegion* r) {
2476 HeapRegionRemSet* hrrs = r->rem_set();
2477 size_t occupied = hrrs->occupied();
2478 _occupied_sum += occupied;
2479
2480 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2481 if (occupied == 0) {
2482 tty->print_cr(" RSet is empty");
2483 } else {
2484 hrrs->print();
2485 }
2486 tty->print_cr("----------");
2487 return false;
2488 }
2489
2490 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2491 tty->cr();
2492 tty->print_cr("========================================");
2493 tty->print_cr("%s", msg);
2494 tty->cr();
2495 }
2496
2497 ~PrintRSetsClosure() {
2498 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2499 tty->print_cr("========================================");
2500 tty->cr();
2501 }
2502 };
2503
2504 void G1CollectedHeap::print_cset_rsets() {
2505 PrintRSetsClosure cl("Printing CSet RSets");
2506 collection_set_iterate(&cl);
2507 }
2508
2509 void G1CollectedHeap::print_all_rsets() {
2510 PrintRSetsClosure cl("Printing All RSets");;
2511 heap_region_iterate(&cl);
2512 }
2513 #endif // PRODUCT
2514
2515 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2516
2517 size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes;
2518 size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes;
2519 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2520
2521 size_t eden_capacity_bytes =
2522 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2523
2524 VirtualSpaceSummary heap_summary = create_heap_space_summary();
2525 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2526 eden_capacity_bytes, survivor_used_bytes, num_regions());
2527 }
2528
2529 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2530 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2531 stats->unused(), stats->used(), stats->region_end_waste(),
2532 stats->regions_filled(), stats->direct_allocated(),
2533 stats->failure_used(), stats->failure_waste());
2534 }
2535
2536 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2537 const G1HeapSummary& heap_summary = create_g1_heap_summary();
2538 gc_tracer->report_gc_heap_summary(when, heap_summary);
2539
2540 const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2541 gc_tracer->report_metaspace_summary(when, metaspace_summary);
2542 }
2543
2544 G1CollectedHeap* G1CollectedHeap::heap() {
2545 CollectedHeap* heap = Universe::heap();
2546 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2547 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap");
2548 return (G1CollectedHeap*)heap;
2549 }
2550
2551 void G1CollectedHeap::gc_prologue(bool full) {
2552 // always_do_update_barrier = false;
2553 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2554
2555 // This summary needs to be printed before incrementing total collections.
2556 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2557
2558 // Update common counters.
2559 increment_total_collections(full /* full gc */);
2560 if (full) {
2561 increment_old_marking_cycles_started();
2562 reset_gc_time_stamp();
2563 } else {
2564 increment_gc_time_stamp();
2565 }
2566
2567 // Fill TLAB's and such
2568 double start = os::elapsedTime();
2569 accumulate_statistics_all_tlabs();
2570 ensure_parsability(true);
2571 g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2572 }
2573
2574 void G1CollectedHeap::gc_epilogue(bool full) {
2575 // Update common counters.
2576 if (full) {
2577 // Update the number of full collections that have been completed.
2578 increment_old_marking_cycles_completed(false /* concurrent */);
2579 }
2580
2581 // We are at the end of the GC. Total collections has already been increased.
2582 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2583
2584 // FIXME: what is this about?
2585 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2586 // is set.
2587 #if COMPILER2_OR_JVMCI
2588 assert(DerivedPointerTable::is_empty(), "derived pointer present");
2589 #endif
2590 // always_do_update_barrier = true;
2591
2592 double start = os::elapsedTime();
2593 resize_all_tlabs();
2594 g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2595
2596 allocation_context_stats().update(full);
2597
2598 MemoryService::track_memory_usage();
2599 // We have just completed a GC. Update the soft reference
2600 // policy with the new heap occupancy
2601 Universe::update_heap_info_at_gc();
2602 }
2603
2604 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2605 uint gc_count_before,
2606 bool* succeeded,
2607 GCCause::Cause gc_cause) {
2608 assert_heap_not_locked_and_not_at_safepoint();
2609 VM_G1IncCollectionPause op(gc_count_before,
2610 word_size,
2611 false, /* should_initiate_conc_mark */
2612 g1_policy()->max_pause_time_ms(),
2613 gc_cause);
2614
2615 op.set_allocation_context(AllocationContext::current());
2616 VMThread::execute(&op);
2617
2618 HeapWord* result = op.result();
2619 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
2620 assert(result == NULL || ret_succeeded,
2621 "the result should be NULL if the VM did not succeed");
2622 *succeeded = ret_succeeded;
2623
2624 assert_heap_not_locked();
2625 return result;
2626 }
2627
2628 void
2629 G1CollectedHeap::doConcurrentMark() {
2630 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
2631 if (!_cmThread->in_progress()) {
2632 _cmThread->set_started();
2633 CGC_lock->notify();
2634 }
2635 }
2636
2637 size_t G1CollectedHeap::pending_card_num() {
2638 size_t extra_cards = 0;
2639 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *curr = jtiwh.next(); ) {
2640 DirtyCardQueue& dcq = curr->dirty_card_queue();
2641 extra_cards += dcq.size();
2642 }
2643 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2644 size_t buffer_size = dcqs.buffer_size();
2645 size_t buffer_num = dcqs.completed_buffers_num();
2646
2647 return buffer_size * buffer_num + extra_cards;
2648 }
2649
2650 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
2651 private:
2652 size_t _total_humongous;
2653 size_t _candidate_humongous;
2654
2655 DirtyCardQueue _dcq;
2656
2657 // We don't nominate objects with many remembered set entries, on
2658 // the assumption that such objects are likely still live.
2659 bool is_remset_small(HeapRegion* region) const {
2660 HeapRegionRemSet* const rset = region->rem_set();
2661 return G1EagerReclaimHumongousObjectsWithStaleRefs
2662 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)
2663 : rset->is_empty();
2664 }
2665
2666 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const {
2667 assert(region->is_starts_humongous(), "Must start a humongous object");
2668
2669 oop obj = oop(region->bottom());
2670
2671 // Dead objects cannot be eager reclaim candidates. Due to class
2672 // unloading it is unsafe to query their classes so we return early.
2673 if (heap->is_obj_dead(obj, region)) {
2674 return false;
2675 }
2676
2677 // Candidate selection must satisfy the following constraints
2678 // while concurrent marking is in progress:
2679 //
2680 // * In order to maintain SATB invariants, an object must not be
2681 // reclaimed if it was allocated before the start of marking and
2682 // has not had its references scanned. Such an object must have
2683 // its references (including type metadata) scanned to ensure no
2684 // live objects are missed by the marking process. Objects
2685 // allocated after the start of concurrent marking don't need to
2686 // be scanned.
2687 //
2688 // * An object must not be reclaimed if it is on the concurrent
2689 // mark stack. Objects allocated after the start of concurrent
2690 // marking are never pushed on the mark stack.
2691 //
2692 // Nominating only objects allocated after the start of concurrent
2693 // marking is sufficient to meet both constraints. This may miss
2694 // some objects that satisfy the constraints, but the marking data
2695 // structures don't support efficiently performing the needed
2696 // additional tests or scrubbing of the mark stack.
2697 //
2698 // However, we presently only nominate is_typeArray() objects.
2699 // A humongous object containing references induces remembered
2700 // set entries on other regions. In order to reclaim such an
2701 // object, those remembered sets would need to be cleaned up.
2702 //
2703 // We also treat is_typeArray() objects specially, allowing them
2704 // to be reclaimed even if allocated before the start of
2705 // concurrent mark. For this we rely on mark stack insertion to
2706 // exclude is_typeArray() objects, preventing reclaiming an object
2707 // that is in the mark stack. We also rely on the metadata for
2708 // such objects to be built-in and so ensured to be kept live.
2709 // Frequent allocation and drop of large binary blobs is an
2710 // important use case for eager reclaim, and this special handling
2711 // may reduce needed headroom.
2712
2713 return obj->is_typeArray() && is_remset_small(region);
2714 }
2715
2716 public:
2717 RegisterHumongousWithInCSetFastTestClosure()
2718 : _total_humongous(0),
2719 _candidate_humongous(0),
2720 _dcq(&JavaThread::dirty_card_queue_set()) {
2721 }
2722
2723 virtual bool doHeapRegion(HeapRegion* r) {
2724 if (!r->is_starts_humongous()) {
2725 return false;
2726 }
2727 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2728
2729 bool is_candidate = humongous_region_is_candidate(g1h, r);
2730 uint rindex = r->hrm_index();
2731 g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
2732 if (is_candidate) {
2733 _candidate_humongous++;
2734 g1h->register_humongous_region_with_cset(rindex);
2735 // Is_candidate already filters out humongous object with large remembered sets.
2736 // If we have a humongous object with a few remembered sets, we simply flush these
2737 // remembered set entries into the DCQS. That will result in automatic
2738 // re-evaluation of their remembered set entries during the following evacuation
2739 // phase.
2740 if (!r->rem_set()->is_empty()) {
2741 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
2742 "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
2743 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
2744 HeapRegionRemSetIterator hrrs(r->rem_set());
2745 size_t card_index;
2746 while (hrrs.has_next(card_index)) {
2747 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
2748 // The remembered set might contain references to already freed
2749 // regions. Filter out such entries to avoid failing card table
2750 // verification.
2751 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) {
2752 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
2753 *card_ptr = CardTableModRefBS::dirty_card_val();
2754 _dcq.enqueue(card_ptr);
2755 }
2756 }
2757 }
2758 assert(hrrs.n_yielded() == r->rem_set()->occupied(),
2759 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
2760 hrrs.n_yielded(), r->rem_set()->occupied());
2761 r->rem_set()->clear_locked();
2762 }
2763 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
2764 }
2765 _total_humongous++;
2766
2767 return false;
2768 }
2769
2770 size_t total_humongous() const { return _total_humongous; }
2771 size_t candidate_humongous() const { return _candidate_humongous; }
2772
2773 void flush_rem_set_entries() { _dcq.flush(); }
2774 };
2775
2776 void G1CollectedHeap::register_humongous_regions_with_cset() {
2777 if (!G1EagerReclaimHumongousObjects) {
2778 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
2779 return;
2780 }
2781 double time = os::elapsed_counter();
2782
2783 // Collect reclaim candidate information and register candidates with cset.
2784 RegisterHumongousWithInCSetFastTestClosure cl;
2785 heap_region_iterate(&cl);
2786
2787 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
2788 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
2789 cl.total_humongous(),
2790 cl.candidate_humongous());
2791 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
2792
2793 // Finally flush all remembered set entries to re-check into the global DCQS.
2794 cl.flush_rem_set_entries();
2795 }
2796
2797 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2798 public:
2799 bool doHeapRegion(HeapRegion* hr) {
2800 if (!hr->is_archive() && !hr->is_continues_humongous()) {
2801 hr->verify_rem_set();
2802 }
2803 return false;
2804 }
2805 };
2806
2807 uint G1CollectedHeap::num_task_queues() const {
2808 return _task_queues->size();
2809 }
2810
2811 #if TASKQUEUE_STATS
2812 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2813 st->print_raw_cr("GC Task Stats");
2814 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2815 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2816 }
2817
2818 void G1CollectedHeap::print_taskqueue_stats() const {
2819 if (!log_is_enabled(Trace, gc, task, stats)) {
2820 return;
2821 }
2822 Log(gc, task, stats) log;
2823 ResourceMark rm;
2824 LogStream ls(log.trace());
2825 outputStream* st = &ls;
2826
2827 print_taskqueue_stats_hdr(st);
2828
2829 TaskQueueStats totals;
2830 const uint n = num_task_queues();
2831 for (uint i = 0; i < n; ++i) {
2832 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2833 totals += task_queue(i)->stats;
2834 }
2835 st->print_raw("tot "); totals.print(st); st->cr();
2836
2837 DEBUG_ONLY(totals.verify());
2838 }
2839
2840 void G1CollectedHeap::reset_taskqueue_stats() {
2841 const uint n = num_task_queues();
2842 for (uint i = 0; i < n; ++i) {
2843 task_queue(i)->stats.reset();
2844 }
2845 }
2846 #endif // TASKQUEUE_STATS
2847
2848 void G1CollectedHeap::wait_for_root_region_scanning() {
2849 double scan_wait_start = os::elapsedTime();
2850 // We have to wait until the CM threads finish scanning the
2851 // root regions as it's the only way to ensure that all the
2852 // objects on them have been correctly scanned before we start
2853 // moving them during the GC.
2854 bool waited = _cm->root_regions()->wait_until_scan_finished();
2855 double wait_time_ms = 0.0;
2856 if (waited) {
2857 double scan_wait_end = os::elapsedTime();
2858 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2859 }
2860 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2861 }
2862
2863 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2864 private:
2865 G1HRPrinter* _hr_printer;
2866 public:
2867 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2868
2869 virtual bool doHeapRegion(HeapRegion* r) {
2870 _hr_printer->cset(r);
2871 return false;
2872 }
2873 };
2874
2875 void G1CollectedHeap::start_new_collection_set() {
2876 collection_set()->start_incremental_building();
2877
2878 clear_cset_fast_test();
2879
2880 guarantee(_eden.length() == 0, "eden should have been cleared");
2881 g1_policy()->transfer_survivors_to_cset(survivor());
2882 }
2883
2884 bool
2885 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
2886 assert_at_safepoint(true /* should_be_vm_thread */);
2887 guarantee(!is_gc_active(), "collection is not reentrant");
2888
2889 if (GCLocker::check_active_before_gc()) {
2890 return false;
2891 }
2892
2893 _gc_timer_stw->register_gc_start();
2894
2895 GCIdMark gc_id_mark;
2896 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
2897
2898 SvcGCMarker sgcm(SvcGCMarker::MINOR);
2899 ResourceMark rm;
2900
2901 g1_policy()->note_gc_start();
2902
2903 wait_for_root_region_scanning();
2904
2905 print_heap_before_gc();
2906 print_heap_regions();
2907 trace_heap_before_gc(_gc_tracer_stw);
2908
2909 _verifier->verify_region_sets_optional();
2910 _verifier->verify_dirty_young_regions();
2911
2912 // We should not be doing initial mark unless the conc mark thread is running
2913 if (!_cmThread->should_terminate()) {
2914 // This call will decide whether this pause is an initial-mark
2915 // pause. If it is, during_initial_mark_pause() will return true
2916 // for the duration of this pause.
2917 g1_policy()->decide_on_conc_mark_initiation();
2918 }
2919
2920 // We do not allow initial-mark to be piggy-backed on a mixed GC.
2921 assert(!collector_state()->during_initial_mark_pause() ||
2922 collector_state()->gcs_are_young(), "sanity");
2923
2924 // We also do not allow mixed GCs during marking.
2925 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity");
2926
2927 // Record whether this pause is an initial mark. When the current
2928 // thread has completed its logging output and it's safe to signal
2929 // the CM thread, the flag's value in the policy has been reset.
2930 bool should_start_conc_mark = collector_state()->during_initial_mark_pause();
2931
2932 // Inner scope for scope based logging, timers, and stats collection
2933 {
2934 EvacuationInfo evacuation_info;
2935
2936 if (collector_state()->during_initial_mark_pause()) {
2937 // We are about to start a marking cycle, so we increment the
2938 // full collection counter.
2939 increment_old_marking_cycles_started();
2940 _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
2941 }
2942
2943 _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
2944
2945 GCTraceCPUTime tcpu;
2946
2947 FormatBuffer<> gc_string("Pause ");
2948 if (collector_state()->during_initial_mark_pause()) {
2949 gc_string.append("Initial Mark");
2950 } else if (collector_state()->gcs_are_young()) {
2951 gc_string.append("Young");
2952 } else {
2953 gc_string.append("Mixed");
2954 }
2955 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true);
2956
2957 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
2958 workers()->active_workers(),
2959 Threads::number_of_non_daemon_threads());
2960 workers()->update_active_workers(active_workers);
2961 log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
2962
2963 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
2964 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
2965
2966 // If the secondary_free_list is not empty, append it to the
2967 // free_list. No need to wait for the cleanup operation to finish;
2968 // the region allocation code will check the secondary_free_list
2969 // and wait if necessary. If the G1StressConcRegionFreeing flag is
2970 // set, skip this step so that the region allocation code has to
2971 // get entries from the secondary_free_list.
2972 if (!G1StressConcRegionFreeing) {
2973 append_secondary_free_list_if_not_empty_with_lock();
2974 }
2975
2976 G1HeapTransition heap_transition(this);
2977 size_t heap_used_bytes_before_gc = used();
2978
2979 // Don't dynamically change the number of GC threads this early. A value of
2980 // 0 is used to indicate serial work. When parallel work is done,
2981 // it will be set.
2982
2983 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
2984 IsGCActiveMark x;
2985
2986 gc_prologue(false);
2987
2988 if (VerifyRememberedSets) {
2989 log_info(gc, verify)("[Verifying RemSets before GC]");
2990 VerifyRegionRemSetClosure v_cl;
2991 heap_region_iterate(&v_cl);
2992 }
2993
2994 _verifier->verify_before_gc(young_verification_type());
2995
2996 _verifier->check_bitmaps("GC Start");
2997
2998 #if COMPILER2_OR_JVMCI
2999 DerivedPointerTable::clear();
3000 #endif
3001
3002 // Please see comment in g1CollectedHeap.hpp and
3003 // G1CollectedHeap::ref_processing_init() to see how
3004 // reference processing currently works in G1.
3005
3006 // Enable discovery in the STW reference processor
3007 if (g1_policy()->should_process_references()) {
3008 ref_processor_stw()->enable_discovery();
3009 } else {
3010 ref_processor_stw()->disable_discovery();
3011 }
3012
3013 {
3014 // We want to temporarily turn off discovery by the
3015 // CM ref processor, if necessary, and turn it back on
3016 // on again later if we do. Using a scoped
3017 // NoRefDiscovery object will do this.
3018 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3019
3020 // Forget the current alloc region (we might even choose it to be part
3021 // of the collection set!).
3022 _allocator->release_mutator_alloc_region();
3023
3024 // This timing is only used by the ergonomics to handle our pause target.
3025 // It is unclear why this should not include the full pause. We will
3026 // investigate this in CR 7178365.
3027 //
3028 // Preserving the old comment here if that helps the investigation:
3029 //
3030 // The elapsed time induced by the start time below deliberately elides
3031 // the possible verification above.
3032 double sample_start_time_sec = os::elapsedTime();
3033
3034 g1_policy()->record_collection_pause_start(sample_start_time_sec);
3035
3036 if (collector_state()->during_initial_mark_pause()) {
3037 concurrent_mark()->checkpoint_roots_initial_pre();
3038 }
3039
3040 g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor);
3041
3042 evacuation_info.set_collectionset_regions(collection_set()->region_length());
3043
3044 // Make sure the remembered sets are up to date. This needs to be
3045 // done before register_humongous_regions_with_cset(), because the
3046 // remembered sets are used there to choose eager reclaim candidates.
3047 // If the remembered sets are not up to date we might miss some
3048 // entries that need to be handled.
3049 g1_rem_set()->cleanupHRRS();
3050
3051 register_humongous_regions_with_cset();
3052
3053 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table.");
3054
3055 // We call this after finalize_cset() to
3056 // ensure that the CSet has been finalized.
3057 _cm->verify_no_cset_oops();
3058
3059 if (_hr_printer.is_active()) {
3060 G1PrintCollectionSetClosure cl(&_hr_printer);
3061 _collection_set.iterate(&cl);
3062 }
3063
3064 // Initialize the GC alloc regions.
3065 _allocator->init_gc_alloc_regions(evacuation_info);
3066
3067 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length());
3068 pre_evacuate_collection_set();
3069
3070 // Actually do the work...
3071 evacuate_collection_set(evacuation_info, &per_thread_states);
3072
3073 post_evacuate_collection_set(evacuation_info, &per_thread_states);
3074
3075 const size_t* surviving_young_words = per_thread_states.surviving_young_words();
3076 free_collection_set(&_collection_set, evacuation_info, surviving_young_words);
3077
3078 eagerly_reclaim_humongous_regions();
3079
3080 record_obj_copy_mem_stats();
3081 _survivor_evac_stats.adjust_desired_plab_sz();
3082 _old_evac_stats.adjust_desired_plab_sz();
3083
3084 double start = os::elapsedTime();
3085 start_new_collection_set();
3086 g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0);
3087
3088 if (evacuation_failed()) {
3089 set_used(recalculate_used());
3090 if (_archive_allocator != NULL) {
3091 _archive_allocator->clear_used();
3092 }
3093 for (uint i = 0; i < ParallelGCThreads; i++) {
3094 if (_evacuation_failed_info_array[i].has_failed()) {
3095 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3096 }
3097 }
3098 } else {
3099 // The "used" of the the collection set have already been subtracted
3100 // when they were freed. Add in the bytes evacuated.
3101 increase_used(g1_policy()->bytes_copied_during_gc());
3102 }
3103
3104 if (collector_state()->during_initial_mark_pause()) {
3105 // We have to do this before we notify the CM threads that
3106 // they can start working to make sure that all the
3107 // appropriate initialization is done on the CM object.
3108 concurrent_mark()->checkpoint_roots_initial_post();
3109 collector_state()->set_mark_in_progress(true);
3110 // Note that we don't actually trigger the CM thread at
3111 // this point. We do that later when we're sure that
3112 // the current thread has completed its logging output.
3113 }
3114
3115 allocate_dummy_regions();
3116
3117 _allocator->init_mutator_alloc_region();
3118
3119 {
3120 size_t expand_bytes = _heap_sizing_policy->expansion_amount();
3121 if (expand_bytes > 0) {
3122 size_t bytes_before = capacity();
3123 // No need for an ergo logging here,
3124 // expansion_amount() does this when it returns a value > 0.
3125 double expand_ms;
3126 if (!expand(expand_bytes, _workers, &expand_ms)) {
3127 // We failed to expand the heap. Cannot do anything about it.
3128 }
3129 g1_policy()->phase_times()->record_expand_heap_time(expand_ms);
3130 }
3131 }
3132
3133 // We redo the verification but now wrt to the new CSet which
3134 // has just got initialized after the previous CSet was freed.
3135 _cm->verify_no_cset_oops();
3136
3137 // This timing is only used by the ergonomics to handle our pause target.
3138 // It is unclear why this should not include the full pause. We will
3139 // investigate this in CR 7178365.
3140 double sample_end_time_sec = os::elapsedTime();
3141 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3142 size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards);
3143 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc);
3144
3145 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
3146 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc());
3147
3148 if (VerifyRememberedSets) {
3149 log_info(gc, verify)("[Verifying RemSets after GC]");
3150 VerifyRegionRemSetClosure v_cl;
3151 heap_region_iterate(&v_cl);
3152 }
3153
3154 _verifier->verify_after_gc(young_verification_type());
3155 _verifier->check_bitmaps("GC End");
3156
3157 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3158 ref_processor_stw()->verify_no_references_recorded();
3159
3160 // CM reference discovery will be re-enabled if necessary.
3161 }
3162
3163 #ifdef TRACESPINNING
3164 ParallelTaskTerminator::print_termination_counts();
3165 #endif
3166
3167 gc_epilogue(false);
3168 }
3169
3170 // Print the remainder of the GC log output.
3171 if (evacuation_failed()) {
3172 log_info(gc)("To-space exhausted");
3173 }
3174
3175 g1_policy()->print_phases();
3176 heap_transition.print();
3177
3178 // It is not yet to safe to tell the concurrent mark to
3179 // start as we have some optional output below. We don't want the
3180 // output from the concurrent mark thread interfering with this
3181 // logging output either.
3182
3183 _hrm.verify_optional();
3184 _verifier->verify_region_sets_optional();
3185
3186 TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3187 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3188
3189 print_heap_after_gc();
3190 print_heap_regions();
3191 trace_heap_after_gc(_gc_tracer_stw);
3192
3193 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3194 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3195 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3196 // before any GC notifications are raised.
3197 g1mm()->update_sizes();
3198
3199 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3200 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
3201 _gc_timer_stw->register_gc_end();
3202 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3203 }
3204 // It should now be safe to tell the concurrent mark thread to start
3205 // without its logging output interfering with the logging output
3206 // that came from the pause.
3207
3208 if (should_start_conc_mark) {
3209 // CAUTION: after the doConcurrentMark() call below,
3210 // the concurrent marking thread(s) could be running
3211 // concurrently with us. Make sure that anything after
3212 // this point does not assume that we are the only GC thread
3213 // running. Note: of course, the actual marking work will
3214 // not start until the safepoint itself is released in
3215 // SuspendibleThreadSet::desynchronize().
3216 doConcurrentMark();
3217 }
3218
3219 return true;
3220 }
3221
3222 void G1CollectedHeap::remove_self_forwarding_pointers() {
3223 G1ParRemoveSelfForwardPtrsTask rsfp_task;
3224 workers()->run_task(&rsfp_task);
3225 }
3226
3227 void G1CollectedHeap::restore_after_evac_failure() {
3228 double remove_self_forwards_start = os::elapsedTime();
3229
3230 remove_self_forwarding_pointers();
3231 SharedRestorePreservedMarksTaskExecutor task_executor(workers());
3232 _preserved_marks_set.restore(&task_executor);
3233
3234 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3235 }
3236
3237 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) {
3238 if (!_evacuation_failed) {
3239 _evacuation_failed = true;
3240 }
3241
3242 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3243 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3244 }
3245
3246 bool G1ParEvacuateFollowersClosure::offer_termination() {
3247 G1ParScanThreadState* const pss = par_scan_state();
3248 start_term_time();
3249 const bool res = terminator()->offer_termination();
3250 end_term_time();
3251 return res;
3252 }
3253
3254 void G1ParEvacuateFollowersClosure::do_void() {
3255 G1ParScanThreadState* const pss = par_scan_state();
3256 pss->trim_queue();
3257 do {
3258 pss->steal_and_trim_queue(queues());
3259 } while (!offer_termination());
3260 }
3261
3262 class G1ParTask : public AbstractGangTask {
3263 protected:
3264 G1CollectedHeap* _g1h;
3265 G1ParScanThreadStateSet* _pss;
3266 RefToScanQueueSet* _queues;
3267 G1RootProcessor* _root_processor;
3268 ParallelTaskTerminator _terminator;
3269 uint _n_workers;
3270
3271 public:
3272 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers)
3273 : AbstractGangTask("G1 collection"),
3274 _g1h(g1h),
3275 _pss(per_thread_states),
3276 _queues(task_queues),
3277 _root_processor(root_processor),
3278 _terminator(n_workers, _queues),
3279 _n_workers(n_workers)
3280 {}
3281
3282 void work(uint worker_id) {
3283 if (worker_id >= _n_workers) return; // no work needed this round
3284
3285 double start_sec = os::elapsedTime();
3286 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec);
3287
3288 {
3289 ResourceMark rm;
3290 HandleMark hm;
3291
3292 ReferenceProcessor* rp = _g1h->ref_processor_stw();
3293
3294 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
3295 pss->set_ref_processor(rp);
3296
3297 double start_strong_roots_sec = os::elapsedTime();
3298
3299 _root_processor->evacuate_roots(pss->closures(), worker_id);
3300
3301 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid
3302 // treating the nmethods visited to act as roots for concurrent marking.
3303 // We only want to make sure that the oops in the nmethods are adjusted with regard to the
3304 // objects copied by the current evacuation.
3305 _g1h->g1_rem_set()->oops_into_collection_set_do(pss,
3306 pss->closures()->weak_codeblobs(),
3307 worker_id);
3308
3309 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec;
3310
3311 double term_sec = 0.0;
3312 size_t evac_term_attempts = 0;
3313 {
3314 double start = os::elapsedTime();
3315 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator);
3316 evac.do_void();
3317
3318 evac_term_attempts = evac.term_attempts();
3319 term_sec = evac.term_time();
3320 double elapsed_sec = os::elapsedTime() - start;
3321 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
3322 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
3323 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts);
3324 }
3325
3326 assert(pss->queue_is_empty(), "should be empty");
3327
3328 if (log_is_enabled(Debug, gc, task, stats)) {
3329 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3330 size_t lab_waste;
3331 size_t lab_undo_waste;
3332 pss->waste(lab_waste, lab_undo_waste);
3333 _g1h->print_termination_stats(worker_id,
3334 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */
3335 strong_roots_sec * 1000.0, /* strong roots time */
3336 term_sec * 1000.0, /* evac term time */
3337 evac_term_attempts, /* evac term attempts */
3338 lab_waste, /* alloc buffer waste */
3339 lab_undo_waste /* undo waste */
3340 );
3341 }
3342
3343 // Close the inner scope so that the ResourceMark and HandleMark
3344 // destructors are executed here and are included as part of the
3345 // "GC Worker Time".
3346 }
3347 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
3348 }
3349 };
3350
3351 void G1CollectedHeap::print_termination_stats_hdr() {
3352 log_debug(gc, task, stats)("GC Termination Stats");
3353 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------");
3354 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo");
3355 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------");
3356 }
3357
3358 void G1CollectedHeap::print_termination_stats(uint worker_id,
3359 double elapsed_ms,
3360 double strong_roots_ms,
3361 double term_ms,
3362 size_t term_attempts,
3363 size_t alloc_buffer_waste,
3364 size_t undo_waste) const {
3365 log_debug(gc, task, stats)
3366 ("%3d %9.2f %9.2f %6.2f "
3367 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
3368 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
3369 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms,
3370 term_ms, term_ms * 100 / elapsed_ms, term_attempts,
3371 (alloc_buffer_waste + undo_waste) * HeapWordSize / K,
3372 alloc_buffer_waste * HeapWordSize / K,
3373 undo_waste * HeapWordSize / K);
3374 }
3375
3376 class G1StringAndSymbolCleaningTask : public AbstractGangTask {
3377 private:
3378 BoolObjectClosure* _is_alive;
3379 G1StringDedupUnlinkOrOopsDoClosure _dedup_closure;
3380
3381 int _initial_string_table_size;
3382 int _initial_symbol_table_size;
3383
3384 bool _process_strings;
3385 int _strings_processed;
3386 int _strings_removed;
3387
3388 bool _process_symbols;
3389 int _symbols_processed;
3390 int _symbols_removed;
3391
3392 bool _process_string_dedup;
3393
3394 public:
3395 G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) :
3396 AbstractGangTask("String/Symbol Unlinking"),
3397 _is_alive(is_alive),
3398 _dedup_closure(is_alive, NULL, false),
3399 _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
3400 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0),
3401 _process_string_dedup(process_string_dedup) {
3402
3403 _initial_string_table_size = StringTable::the_table()->table_size();
3404 _initial_symbol_table_size = SymbolTable::the_table()->table_size();
3405 if (process_strings) {
3406 StringTable::clear_parallel_claimed_index();
3407 }
3408 if (process_symbols) {
3409 SymbolTable::clear_parallel_claimed_index();
3410 }
3411 }
3412
3413 ~G1StringAndSymbolCleaningTask() {
3414 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
3415 "claim value %d after unlink less than initial string table size %d",
3416 StringTable::parallel_claimed_index(), _initial_string_table_size);
3417 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
3418 "claim value %d after unlink less than initial symbol table size %d",
3419 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size);
3420
3421 log_info(gc, stringtable)(
3422 "Cleaned string and symbol table, "
3423 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, "
3424 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
3425 strings_processed(), strings_removed(),
3426 symbols_processed(), symbols_removed());
3427 }
3428
3429 void work(uint worker_id) {
3430 int strings_processed = 0;
3431 int strings_removed = 0;
3432 int symbols_processed = 0;
3433 int symbols_removed = 0;
3434 if (_process_strings) {
3435 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
3436 Atomic::add(strings_processed, &_strings_processed);
3437 Atomic::add(strings_removed, &_strings_removed);
3438 }
3439 if (_process_symbols) {
3440 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
3441 Atomic::add(symbols_processed, &_symbols_processed);
3442 Atomic::add(symbols_removed, &_symbols_removed);
3443 }
3444 if (_process_string_dedup) {
3445 G1StringDedup::parallel_unlink(&_dedup_closure, worker_id);
3446 }
3447 }
3448
3449 size_t strings_processed() const { return (size_t)_strings_processed; }
3450 size_t strings_removed() const { return (size_t)_strings_removed; }
3451
3452 size_t symbols_processed() const { return (size_t)_symbols_processed; }
3453 size_t symbols_removed() const { return (size_t)_symbols_removed; }
3454 };
3455
3456 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
3457 private:
3458 static Monitor* _lock;
3459
3460 BoolObjectClosure* const _is_alive;
3461 const bool _unloading_occurred;
3462 const uint _num_workers;
3463
3464 // Variables used to claim nmethods.
3465 CompiledMethod* _first_nmethod;
3466 CompiledMethod* volatile _claimed_nmethod;
3467
3468 // The list of nmethods that need to be processed by the second pass.
3469 CompiledMethod* volatile _postponed_list;
3470 volatile uint _num_entered_barrier;
3471
3472 public:
3473 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
3474 _is_alive(is_alive),
3475 _unloading_occurred(unloading_occurred),
3476 _num_workers(num_workers),
3477 _first_nmethod(NULL),
3478 _claimed_nmethod(NULL),
3479 _postponed_list(NULL),
3480 _num_entered_barrier(0)
3481 {
3482 CompiledMethod::increase_unloading_clock();
3483 // Get first alive nmethod
3484 CompiledMethodIterator iter = CompiledMethodIterator();
3485 if(iter.next_alive()) {
3486 _first_nmethod = iter.method();
3487 }
3488 _claimed_nmethod = _first_nmethod;
3489 }
3490
3491 ~G1CodeCacheUnloadingTask() {
3492 CodeCache::verify_clean_inline_caches();
3493
3494 CodeCache::set_needs_cache_clean(false);
3495 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
3496
3497 CodeCache::verify_icholder_relocations();
3498 }
3499
3500 private:
3501 void add_to_postponed_list(CompiledMethod* nm) {
3502 CompiledMethod* old;
3503 do {
3504 old = _postponed_list;
3505 nm->set_unloading_next(old);
3506 } while (Atomic::cmpxchg(nm, &_postponed_list, old) != old);
3507 }
3508
3509 void clean_nmethod(CompiledMethod* nm) {
3510 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
3511
3512 if (postponed) {
3513 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
3514 add_to_postponed_list(nm);
3515 }
3516
3517 // Mark that this thread has been cleaned/unloaded.
3518 // After this call, it will be safe to ask if this nmethod was unloaded or not.
3519 nm->set_unloading_clock(CompiledMethod::global_unloading_clock());
3520 }
3521
3522 void clean_nmethod_postponed(CompiledMethod* nm) {
3523 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
3524 }
3525
3526 static const int MaxClaimNmethods = 16;
3527
3528 void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) {
3529 CompiledMethod* first;
3530 CompiledMethodIterator last;
3531
3532 do {
3533 *num_claimed_nmethods = 0;
3534
3535 first = _claimed_nmethod;
3536 last = CompiledMethodIterator(first);
3537
3538 if (first != NULL) {
3539
3540 for (int i = 0; i < MaxClaimNmethods; i++) {
3541 if (!last.next_alive()) {
3542 break;
3543 }
3544 claimed_nmethods[i] = last.method();
3545 (*num_claimed_nmethods)++;
3546 }
3547 }
3548
3549 } while (Atomic::cmpxchg(last.method(), &_claimed_nmethod, first) != first);
3550 }
3551
3552 CompiledMethod* claim_postponed_nmethod() {
3553 CompiledMethod* claim;
3554 CompiledMethod* next;
3555
3556 do {
3557 claim = _postponed_list;
3558 if (claim == NULL) {
3559 return NULL;
3560 }
3561
3562 next = claim->unloading_next();
3563
3564 } while (Atomic::cmpxchg(next, &_postponed_list, claim) != claim);
3565
3566 return claim;
3567 }
3568
3569 public:
3570 // Mark that we're done with the first pass of nmethod cleaning.
3571 void barrier_mark(uint worker_id) {
3572 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3573 _num_entered_barrier++;
3574 if (_num_entered_barrier == _num_workers) {
3575 ml.notify_all();
3576 }
3577 }
3578
3579 // See if we have to wait for the other workers to
3580 // finish their first-pass nmethod cleaning work.
3581 void barrier_wait(uint worker_id) {
3582 if (_num_entered_barrier < _num_workers) {
3583 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3584 while (_num_entered_barrier < _num_workers) {
3585 ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
3586 }
3587 }
3588 }
3589
3590 // Cleaning and unloading of nmethods. Some work has to be postponed
3591 // to the second pass, when we know which nmethods survive.
3592 void work_first_pass(uint worker_id) {
3593 // The first nmethods is claimed by the first worker.
3594 if (worker_id == 0 && _first_nmethod != NULL) {
3595 clean_nmethod(_first_nmethod);
3596 _first_nmethod = NULL;
3597 }
3598
3599 int num_claimed_nmethods;
3600 CompiledMethod* claimed_nmethods[MaxClaimNmethods];
3601
3602 while (true) {
3603 claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
3604
3605 if (num_claimed_nmethods == 0) {
3606 break;
3607 }
3608
3609 for (int i = 0; i < num_claimed_nmethods; i++) {
3610 clean_nmethod(claimed_nmethods[i]);
3611 }
3612 }
3613 }
3614
3615 void work_second_pass(uint worker_id) {
3616 CompiledMethod* nm;
3617 // Take care of postponed nmethods.
3618 while ((nm = claim_postponed_nmethod()) != NULL) {
3619 clean_nmethod_postponed(nm);
3620 }
3621 }
3622 };
3623
3624 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
3625
3626 class G1KlassCleaningTask : public StackObj {
3627 BoolObjectClosure* _is_alive;
3628 volatile int _clean_klass_tree_claimed;
3629 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
3630
3631 public:
3632 G1KlassCleaningTask(BoolObjectClosure* is_alive) :
3633 _is_alive(is_alive),
3634 _clean_klass_tree_claimed(0),
3635 _klass_iterator() {
3636 }
3637
3638 private:
3639 bool claim_clean_klass_tree_task() {
3640 if (_clean_klass_tree_claimed) {
3641 return false;
3642 }
3643
3644 return Atomic::cmpxchg(1, &_clean_klass_tree_claimed, 0) == 0;
3645 }
3646
3647 InstanceKlass* claim_next_klass() {
3648 Klass* klass;
3649 do {
3650 klass =_klass_iterator.next_klass();
3651 } while (klass != NULL && !klass->is_instance_klass());
3652
3653 // this can be null so don't call InstanceKlass::cast
3654 return static_cast<InstanceKlass*>(klass);
3655 }
3656
3657 public:
3658
3659 void clean_klass(InstanceKlass* ik) {
3660 ik->clean_weak_instanceklass_links(_is_alive);
3661 }
3662
3663 void work() {
3664 ResourceMark rm;
3665
3666 // One worker will clean the subklass/sibling klass tree.
3667 if (claim_clean_klass_tree_task()) {
3668 Klass::clean_subklass_tree(_is_alive);
3669 }
3670
3671 // All workers will help cleaning the classes,
3672 InstanceKlass* klass;
3673 while ((klass = claim_next_klass()) != NULL) {
3674 clean_klass(klass);
3675 }
3676 }
3677 };
3678
3679 class G1ResolvedMethodCleaningTask : public StackObj {
3680 BoolObjectClosure* _is_alive;
3681 volatile int _resolved_method_task_claimed;
3682 public:
3683 G1ResolvedMethodCleaningTask(BoolObjectClosure* is_alive) :
3684 _is_alive(is_alive), _resolved_method_task_claimed(0) {}
3685
3686 bool claim_resolved_method_task() {
3687 if (_resolved_method_task_claimed) {
3688 return false;
3689 }
3690 return Atomic::cmpxchg(1, &_resolved_method_task_claimed, 0) == 0;
3691 }
3692
3693 // These aren't big, one thread can do it all.
3694 void work() {
3695 if (claim_resolved_method_task()) {
3696 ResolvedMethodTable::unlink(_is_alive);
3697 }
3698 }
3699 };
3700
3701
3702 // To minimize the remark pause times, the tasks below are done in parallel.
3703 class G1ParallelCleaningTask : public AbstractGangTask {
3704 private:
3705 G1StringAndSymbolCleaningTask _string_symbol_task;
3706 G1CodeCacheUnloadingTask _code_cache_task;
3707 G1KlassCleaningTask _klass_cleaning_task;
3708 G1ResolvedMethodCleaningTask _resolved_method_cleaning_task;
3709
3710 public:
3711 // The constructor is run in the VMThread.
3712 G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) :
3713 AbstractGangTask("Parallel Cleaning"),
3714 _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()),
3715 _code_cache_task(num_workers, is_alive, unloading_occurred),
3716 _klass_cleaning_task(is_alive),
3717 _resolved_method_cleaning_task(is_alive) {
3718 }
3719
3720 // The parallel work done by all worker threads.
3721 void work(uint worker_id) {
3722 // Do first pass of code cache cleaning.
3723 _code_cache_task.work_first_pass(worker_id);
3724
3725 // Let the threads mark that the first pass is done.
3726 _code_cache_task.barrier_mark(worker_id);
3727
3728 // Clean the Strings and Symbols.
3729 _string_symbol_task.work(worker_id);
3730
3731 // Clean unreferenced things in the ResolvedMethodTable
3732 _resolved_method_cleaning_task.work();
3733
3734 // Wait for all workers to finish the first code cache cleaning pass.
3735 _code_cache_task.barrier_wait(worker_id);
3736
3737 // Do the second code cache cleaning work, which realize on
3738 // the liveness information gathered during the first pass.
3739 _code_cache_task.work_second_pass(worker_id);
3740
3741 // Clean all klasses that were not unloaded.
3742 _klass_cleaning_task.work();
3743 }
3744 };
3745
3746
3747 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
3748 bool class_unloading_occurred) {
3749 uint n_workers = workers()->active_workers();
3750
3751 G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred);
3752 workers()->run_task(&g1_unlink_task);
3753 }
3754
3755 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive,
3756 bool process_strings,
3757 bool process_symbols,
3758 bool process_string_dedup) {
3759 if (!process_strings && !process_symbols && !process_string_dedup) {
3760 // Nothing to clean.
3761 return;
3762 }
3763
3764 G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup);
3765 workers()->run_task(&g1_unlink_task);
3766
3767 }
3768
3769 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3770 private:
3771 DirtyCardQueueSet* _queue;
3772 G1CollectedHeap* _g1h;
3773 public:
3774 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"),
3775 _queue(queue), _g1h(g1h) { }
3776
3777 virtual void work(uint worker_id) {
3778 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
3779 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
3780
3781 RedirtyLoggedCardTableEntryClosure cl(_g1h);
3782 _queue->par_apply_closure_to_all_completed_buffers(&cl);
3783
3784 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3785 }
3786 };
3787
3788 void G1CollectedHeap::redirty_logged_cards() {
3789 double redirty_logged_cards_start = os::elapsedTime();
3790
3791 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this);
3792 dirty_card_queue_set().reset_for_par_iteration();
3793 workers()->run_task(&redirty_task);
3794
3795 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
3796 dcq.merge_bufferlists(&dirty_card_queue_set());
3797 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
3798
3799 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3800 }
3801
3802 // Weak Reference Processing support
3803
3804 // An always "is_alive" closure that is used to preserve referents.
3805 // If the object is non-null then it's alive. Used in the preservation
3806 // of referent objects that are pointed to by reference objects
3807 // discovered by the CM ref processor.
3808 class G1AlwaysAliveClosure: public BoolObjectClosure {
3809 G1CollectedHeap* _g1;
3810 public:
3811 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3812 bool do_object_b(oop p) {
3813 if (p != NULL) {
3814 return true;
3815 }
3816 return false;
3817 }
3818 };
3819
3820 bool G1STWIsAliveClosure::do_object_b(oop p) {
3821 // An object is reachable if it is outside the collection set,
3822 // or is inside and copied.
3823 return !_g1->is_in_cset(p) || p->is_forwarded();
3824 }
3825
3826 // Non Copying Keep Alive closure
3827 class G1KeepAliveClosure: public OopClosure {
3828 G1CollectedHeap* _g1;
3829 public:
3830 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3831 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3832 void do_oop(oop* p) {
3833 oop obj = *p;
3834 assert(obj != NULL, "the caller should have filtered out NULL values");
3835
3836 const InCSetState cset_state = _g1->in_cset_state(obj);
3837 if (!cset_state.is_in_cset_or_humongous()) {
3838 return;
3839 }
3840 if (cset_state.is_in_cset()) {
3841 assert( obj->is_forwarded(), "invariant" );
3842 *p = obj->forwardee();
3843 } else {
3844 assert(!obj->is_forwarded(), "invariant" );
3845 assert(cset_state.is_humongous(),
3846 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value());
3847 _g1->set_humongous_is_live(obj);
3848 }
3849 }
3850 };
3851
3852 // Copying Keep Alive closure - can be called from both
3853 // serial and parallel code as long as different worker
3854 // threads utilize different G1ParScanThreadState instances
3855 // and different queues.
3856
3857 class G1CopyingKeepAliveClosure: public OopClosure {
3858 G1CollectedHeap* _g1h;
3859 OopClosure* _copy_non_heap_obj_cl;
3860 G1ParScanThreadState* _par_scan_state;
3861
3862 public:
3863 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3864 OopClosure* non_heap_obj_cl,
3865 G1ParScanThreadState* pss):
3866 _g1h(g1h),
3867 _copy_non_heap_obj_cl(non_heap_obj_cl),
3868 _par_scan_state(pss)
3869 {}
3870
3871 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3872 virtual void do_oop( oop* p) { do_oop_work(p); }
3873
3874 template <class T> void do_oop_work(T* p) {
3875 oop obj = oopDesc::load_decode_heap_oop(p);
3876
3877 if (_g1h->is_in_cset_or_humongous(obj)) {
3878 // If the referent object has been forwarded (either copied
3879 // to a new location or to itself in the event of an
3880 // evacuation failure) then we need to update the reference
3881 // field and, if both reference and referent are in the G1
3882 // heap, update the RSet for the referent.
3883 //
3884 // If the referent has not been forwarded then we have to keep
3885 // it alive by policy. Therefore we have copy the referent.
3886 //
3887 // If the reference field is in the G1 heap then we can push
3888 // on the PSS queue. When the queue is drained (after each
3889 // phase of reference processing) the object and it's followers
3890 // will be copied, the reference field set to point to the
3891 // new location, and the RSet updated. Otherwise we need to
3892 // use the the non-heap or metadata closures directly to copy
3893 // the referent object and update the pointer, while avoiding
3894 // updating the RSet.
3895
3896 if (_g1h->is_in_g1_reserved(p)) {
3897 _par_scan_state->push_on_queue(p);
3898 } else {
3899 assert(!Metaspace::contains((const void*)p),
3900 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p));
3901 _copy_non_heap_obj_cl->do_oop(p);
3902 }
3903 }
3904 }
3905 };
3906
3907 // Serial drain queue closure. Called as the 'complete_gc'
3908 // closure for each discovered list in some of the
3909 // reference processing phases.
3910
3911 class G1STWDrainQueueClosure: public VoidClosure {
3912 protected:
3913 G1CollectedHeap* _g1h;
3914 G1ParScanThreadState* _par_scan_state;
3915
3916 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
3917
3918 public:
3919 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
3920 _g1h(g1h),
3921 _par_scan_state(pss)
3922 { }
3923
3924 void do_void() {
3925 G1ParScanThreadState* const pss = par_scan_state();
3926 pss->trim_queue();
3927 }
3928 };
3929
3930 // Parallel Reference Processing closures
3931
3932 // Implementation of AbstractRefProcTaskExecutor for parallel reference
3933 // processing during G1 evacuation pauses.
3934
3935 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
3936 private:
3937 G1CollectedHeap* _g1h;
3938 G1ParScanThreadStateSet* _pss;
3939 RefToScanQueueSet* _queues;
3940 WorkGang* _workers;
3941 uint _active_workers;
3942
3943 public:
3944 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
3945 G1ParScanThreadStateSet* per_thread_states,
3946 WorkGang* workers,
3947 RefToScanQueueSet *task_queues,
3948 uint n_workers) :
3949 _g1h(g1h),
3950 _pss(per_thread_states),
3951 _queues(task_queues),
3952 _workers(workers),
3953 _active_workers(n_workers)
3954 {
3955 g1h->ref_processor_stw()->set_active_mt_degree(n_workers);
3956 }
3957
3958 // Executes the given task using concurrent marking worker threads.
3959 virtual void execute(ProcessTask& task);
3960 virtual void execute(EnqueueTask& task);
3961 };
3962
3963 // Gang task for possibly parallel reference processing
3964
3965 class G1STWRefProcTaskProxy: public AbstractGangTask {
3966 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
3967 ProcessTask& _proc_task;
3968 G1CollectedHeap* _g1h;
3969 G1ParScanThreadStateSet* _pss;
3970 RefToScanQueueSet* _task_queues;
3971 ParallelTaskTerminator* _terminator;
3972
3973 public:
3974 G1STWRefProcTaskProxy(ProcessTask& proc_task,
3975 G1CollectedHeap* g1h,
3976 G1ParScanThreadStateSet* per_thread_states,
3977 RefToScanQueueSet *task_queues,
3978 ParallelTaskTerminator* terminator) :
3979 AbstractGangTask("Process reference objects in parallel"),
3980 _proc_task(proc_task),
3981 _g1h(g1h),
3982 _pss(per_thread_states),
3983 _task_queues(task_queues),
3984 _terminator(terminator)
3985 {}
3986
3987 virtual void work(uint worker_id) {
3988 // The reference processing task executed by a single worker.
3989 ResourceMark rm;
3990 HandleMark hm;
3991
3992 G1STWIsAliveClosure is_alive(_g1h);
3993
3994 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
3995 pss->set_ref_processor(NULL);
3996
3997 // Keep alive closure.
3998 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
3999
4000 // Complete GC closure
4001 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator);
4002
4003 // Call the reference processing task's work routine.
4004 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
4005
4006 // Note we cannot assert that the refs array is empty here as not all
4007 // of the processing tasks (specifically phase2 - pp2_work) execute
4008 // the complete_gc closure (which ordinarily would drain the queue) so
4009 // the queue may not be empty.
4010 }
4011 };
4012
4013 // Driver routine for parallel reference processing.
4014 // Creates an instance of the ref processing gang
4015 // task and has the worker threads execute it.
4016 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
4017 assert(_workers != NULL, "Need parallel worker threads.");
4018
4019 ParallelTaskTerminator terminator(_active_workers, _queues);
4020 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
4021
4022 _workers->run_task(&proc_task_proxy);
4023 }
4024
4025 // Gang task for parallel reference enqueueing.
4026
4027 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
4028 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
4029 EnqueueTask& _enq_task;
4030
4031 public:
4032 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
4033 AbstractGangTask("Enqueue reference objects in parallel"),
4034 _enq_task(enq_task)
4035 { }
4036
4037 virtual void work(uint worker_id) {
4038 _enq_task.work(worker_id);
4039 }
4040 };
4041
4042 // Driver routine for parallel reference enqueueing.
4043 // Creates an instance of the ref enqueueing gang
4044 // task and has the worker threads execute it.
4045
4046 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
4047 assert(_workers != NULL, "Need parallel worker threads.");
4048
4049 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
4050
4051 _workers->run_task(&enq_task_proxy);
4052 }
4053
4054 // End of weak reference support closures
4055
4056 // Abstract task used to preserve (i.e. copy) any referent objects
4057 // that are in the collection set and are pointed to by reference
4058 // objects discovered by the CM ref processor.
4059
4060 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
4061 protected:
4062 G1CollectedHeap* _g1h;
4063 G1ParScanThreadStateSet* _pss;
4064 RefToScanQueueSet* _queues;
4065 ParallelTaskTerminator _terminator;
4066 uint _n_workers;
4067
4068 public:
4069 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) :
4070 AbstractGangTask("ParPreserveCMReferents"),
4071 _g1h(g1h),
4072 _pss(per_thread_states),
4073 _queues(task_queues),
4074 _terminator(workers, _queues),
4075 _n_workers(workers)
4076 {
4077 g1h->ref_processor_cm()->set_active_mt_degree(workers);
4078 }
4079
4080 void work(uint worker_id) {
4081 G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id);
4082
4083 ResourceMark rm;
4084 HandleMark hm;
4085
4086 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
4087 pss->set_ref_processor(NULL);
4088 assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4089
4090 // Is alive closure
4091 G1AlwaysAliveClosure always_alive(_g1h);
4092
4093 // Copying keep alive closure. Applied to referent objects that need
4094 // to be copied.
4095 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4096
4097 ReferenceProcessor* rp = _g1h->ref_processor_cm();
4098
4099 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
4100 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
4101
4102 // limit is set using max_num_q() - which was set using ParallelGCThreads.
4103 // So this must be true - but assert just in case someone decides to
4104 // change the worker ids.
4105 assert(worker_id < limit, "sanity");
4106 assert(!rp->discovery_is_atomic(), "check this code");
4107
4108 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
4109 for (uint idx = worker_id; idx < limit; idx += stride) {
4110 DiscoveredList& ref_list = rp->discovered_refs()[idx];
4111
4112 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
4113 while (iter.has_next()) {
4114 // Since discovery is not atomic for the CM ref processor, we
4115 // can see some null referent objects.
4116 iter.load_ptrs(DEBUG_ONLY(true));
4117 oop ref = iter.obj();
4118
4119 // This will filter nulls.
4120 if (iter.is_referent_alive()) {
4121 iter.make_referent_alive();
4122 }
4123 iter.move_to_next();
4124 }
4125 }
4126
4127 // Drain the queue - which may cause stealing
4128 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator);
4129 drain_queue.do_void();
4130 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
4131 assert(pss->queue_is_empty(), "should be");
4132 }
4133 };
4134
4135 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) {
4136 // Any reference objects, in the collection set, that were 'discovered'
4137 // by the CM ref processor should have already been copied (either by
4138 // applying the external root copy closure to the discovered lists, or
4139 // by following an RSet entry).
4140 //
4141 // But some of the referents, that are in the collection set, that these
4142 // reference objects point to may not have been copied: the STW ref
4143 // processor would have seen that the reference object had already
4144 // been 'discovered' and would have skipped discovering the reference,
4145 // but would not have treated the reference object as a regular oop.
4146 // As a result the copy closure would not have been applied to the
4147 // referent object.
4148 //
4149 // We need to explicitly copy these referent objects - the references
4150 // will be processed at the end of remarking.
4151 //
4152 // We also need to do this copying before we process the reference
4153 // objects discovered by the STW ref processor in case one of these
4154 // referents points to another object which is also referenced by an
4155 // object discovered by the STW ref processor.
4156 double preserve_cm_referents_time = 0.0;
4157
4158 // To avoid spawning task when there is no work to do, check that
4159 // a concurrent cycle is active and that some references have been
4160 // discovered.
4161 if (concurrent_mark()->cm_thread()->during_cycle() &&
4162 ref_processor_cm()->has_discovered_references()) {
4163 double preserve_cm_referents_start = os::elapsedTime();
4164 uint no_of_gc_workers = workers()->active_workers();
4165 G1ParPreserveCMReferentsTask keep_cm_referents(this,
4166 per_thread_states,
4167 no_of_gc_workers,
4168 _task_queues);
4169 workers()->run_task(&keep_cm_referents);
4170 preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start;
4171 }
4172
4173 g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0);
4174 }
4175
4176 // Weak Reference processing during an evacuation pause (part 1).
4177 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4178 double ref_proc_start = os::elapsedTime();
4179
4180 ReferenceProcessor* rp = _ref_processor_stw;
4181 assert(rp->discovery_enabled(), "should have been enabled");
4182
4183 // Closure to test whether a referent is alive.
4184 G1STWIsAliveClosure is_alive(this);
4185
4186 // Even when parallel reference processing is enabled, the processing
4187 // of JNI refs is serial and performed serially by the current thread
4188 // rather than by a worker. The following PSS will be used for processing
4189 // JNI refs.
4190
4191 // Use only a single queue for this PSS.
4192 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0);
4193 pss->set_ref_processor(NULL);
4194 assert(pss->queue_is_empty(), "pre-condition");
4195
4196 // Keep alive closure.
4197 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss);
4198
4199 // Serial Complete GC closure
4200 G1STWDrainQueueClosure drain_queue(this, pss);
4201
4202 // Setup the soft refs policy...
4203 rp->setup_policy(false);
4204
4205 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times();
4206
4207 ReferenceProcessorStats stats;
4208 if (!rp->processing_is_mt()) {
4209 // Serial reference processing...
4210 stats = rp->process_discovered_references(&is_alive,
4211 &keep_alive,
4212 &drain_queue,
4213 NULL,
4214 pt);
4215 } else {
4216 uint no_of_gc_workers = workers()->active_workers();
4217
4218 // Parallel reference processing
4219 assert(no_of_gc_workers <= rp->max_num_q(),
4220 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4221 no_of_gc_workers, rp->max_num_q());
4222
4223 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers);
4224 stats = rp->process_discovered_references(&is_alive,
4225 &keep_alive,
4226 &drain_queue,
4227 &par_task_executor,
4228 pt);
4229 }
4230
4231 _gc_tracer_stw->report_gc_reference_stats(stats);
4232
4233 // We have completed copying any necessary live referent objects.
4234 assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4235
4236 double ref_proc_time = os::elapsedTime() - ref_proc_start;
4237 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4238 }
4239
4240 // Weak Reference processing during an evacuation pause (part 2).
4241 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4242 double ref_enq_start = os::elapsedTime();
4243
4244 ReferenceProcessor* rp = _ref_processor_stw;
4245 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
4246
4247 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times();
4248
4249 // Now enqueue any remaining on the discovered lists on to
4250 // the pending list.
4251 if (!rp->processing_is_mt()) {
4252 // Serial reference processing...
4253 rp->enqueue_discovered_references(NULL, pt);
4254 } else {
4255 // Parallel reference enqueueing
4256
4257 uint n_workers = workers()->active_workers();
4258
4259 assert(n_workers <= rp->max_num_q(),
4260 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4261 n_workers, rp->max_num_q());
4262
4263 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers);
4264 rp->enqueue_discovered_references(&par_task_executor, pt);
4265 }
4266
4267 rp->verify_no_references_recorded();
4268 assert(!rp->discovery_enabled(), "should have been disabled");
4269
4270 // If during an initial mark pause we install a pending list head which is not otherwise reachable
4271 // ensure that it is marked in the bitmap for concurrent marking to discover.
4272 if (collector_state()->during_initial_mark_pause()) {
4273 oop pll_head = Universe::reference_pending_list();
4274 if (pll_head != NULL) {
4275 _cm->mark_in_next_bitmap(pll_head);
4276 }
4277 }
4278
4279 // FIXME
4280 // CM's reference processing also cleans up the string and symbol tables.
4281 // Should we do that here also? We could, but it is a serial operation
4282 // and could significantly increase the pause time.
4283
4284 double ref_enq_time = os::elapsedTime() - ref_enq_start;
4285 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
4286 }
4287
4288 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
4289 double merge_pss_time_start = os::elapsedTime();
4290 per_thread_states->flush();
4291 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0);
4292 }
4293
4294 void G1CollectedHeap::pre_evacuate_collection_set() {
4295 _expand_heap_after_alloc_failure = true;
4296 _evacuation_failed = false;
4297
4298 // Disable the hot card cache.
4299 _hot_card_cache->reset_hot_cache_claimed_index();
4300 _hot_card_cache->set_use_cache(false);
4301
4302 g1_rem_set()->prepare_for_oops_into_collection_set_do();
4303 _preserved_marks_set.assert_empty();
4304
4305 G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4306
4307 // InitialMark needs claim bits to keep track of the marked-through CLDs.
4308 if (collector_state()->during_initial_mark_pause()) {
4309 double start_clear_claimed_marks = os::elapsedTime();
4310
4311 ClassLoaderDataGraph::clear_claimed_marks();
4312
4313 double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
4314 phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
4315 }
4316 }
4317
4318 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4319 // Should G1EvacuationFailureALot be in effect for this GC?
4320 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
4321
4322 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
4323
4324 G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4325
4326 double start_par_time_sec = os::elapsedTime();
4327 double end_par_time_sec;
4328
4329 {
4330 const uint n_workers = workers()->active_workers();
4331 G1RootProcessor root_processor(this, n_workers);
4332 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers);
4333
4334 print_termination_stats_hdr();
4335
4336 workers()->run_task(&g1_par_task);
4337 end_par_time_sec = os::elapsedTime();
4338
4339 // Closing the inner scope will execute the destructor
4340 // for the G1RootProcessor object. We record the current
4341 // elapsed time before closing the scope so that time
4342 // taken for the destructor is NOT included in the
4343 // reported parallel time.
4344 }
4345
4346 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
4347 phase_times->record_par_time(par_time_ms);
4348
4349 double code_root_fixup_time_ms =
4350 (os::elapsedTime() - end_par_time_sec) * 1000.0;
4351 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
4352 }
4353
4354 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4355 // Process any discovered reference objects - we have
4356 // to do this _before_ we retire the GC alloc regions
4357 // as we may have to copy some 'reachable' referent
4358 // objects (and their reachable sub-graphs) that were
4359 // not copied during the pause.
4360 if (g1_policy()->should_process_references()) {
4361 preserve_cm_referents(per_thread_states);
4362 process_discovered_references(per_thread_states);
4363 } else {
4364 ref_processor_stw()->verify_no_references_recorded();
4365 }
4366
4367 G1STWIsAliveClosure is_alive(this);
4368 G1KeepAliveClosure keep_alive(this);
4369
4370 {
4371 double start = os::elapsedTime();
4372
4373 WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
4374
4375 double time_ms = (os::elapsedTime() - start) * 1000.0;
4376 g1_policy()->phase_times()->record_ref_proc_time(time_ms);
4377 }
4378
4379 if (G1StringDedup::is_enabled()) {
4380 double fixup_start = os::elapsedTime();
4381
4382 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times());
4383
4384 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
4385 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
4386 }
4387
4388 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4389
4390 if (evacuation_failed()) {
4391 restore_after_evac_failure();
4392
4393 // Reset the G1EvacuationFailureALot counters and flags
4394 // Note: the values are reset only when an actual
4395 // evacuation failure occurs.
4396 NOT_PRODUCT(reset_evacuation_should_fail();)
4397 }
4398
4399 _preserved_marks_set.assert_empty();
4400
4401 // Enqueue any remaining references remaining on the STW
4402 // reference processor's discovered lists. We need to do
4403 // this after the card table is cleaned (and verified) as
4404 // the act of enqueueing entries on to the pending list
4405 // will log these updates (and dirty their associated
4406 // cards). We need these updates logged to update any
4407 // RSets.
4408 if (g1_policy()->should_process_references()) {
4409 enqueue_discovered_references(per_thread_states);
4410 } else {
4411 g1_policy()->phase_times()->record_ref_enq_time(0);
4412 }
4413
4414 _allocator->release_gc_alloc_regions(evacuation_info);
4415
4416 merge_per_thread_state_info(per_thread_states);
4417
4418 // Reset and re-enable the hot card cache.
4419 // Note the counts for the cards in the regions in the
4420 // collection set are reset when the collection set is freed.
4421 _hot_card_cache->reset_hot_cache();
4422 _hot_card_cache->set_use_cache(true);
4423
4424 purge_code_root_memory();
4425
4426 redirty_logged_cards();
4427 #if COMPILER2_OR_JVMCI
4428 double start = os::elapsedTime();
4429 DerivedPointerTable::update_pointers();
4430 g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0);
4431 #endif
4432 g1_policy()->print_age_table();
4433 }
4434
4435 void G1CollectedHeap::record_obj_copy_mem_stats() {
4436 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4437
4438 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4439 create_g1_evac_summary(&_old_evac_stats));
4440 }
4441
4442 void G1CollectedHeap::free_region(HeapRegion* hr,
4443 FreeRegionList* free_list,
4444 bool skip_remset,
4445 bool skip_hot_card_cache,
4446 bool locked) {
4447 assert(!hr->is_free(), "the region should not be free");
4448 assert(!hr->is_empty(), "the region should not be empty");
4449 assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
4450 assert(free_list != NULL, "pre-condition");
4451
4452 if (G1VerifyBitmaps) {
4453 MemRegion mr(hr->bottom(), hr->end());
4454 concurrent_mark()->clear_range_in_prev_bitmap(mr);
4455 }
4456
4457 // Clear the card counts for this region.
4458 // Note: we only need to do this if the region is not young
4459 // (since we don't refine cards in young regions).
4460 if (!skip_hot_card_cache && !hr->is_young()) {
4461 _hot_card_cache->reset_card_counts(hr);
4462 }
4463 hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */);
4464 free_list->add_ordered(hr);
4465 }
4466
4467 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4468 FreeRegionList* free_list,
4469 bool skip_remset) {
4470 assert(hr->is_humongous(), "this is only for humongous regions");
4471 assert(free_list != NULL, "pre-condition");
4472 hr->clear_humongous();
4473 free_region(hr, free_list, skip_remset);
4474 }
4475
4476 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4477 const uint humongous_regions_removed) {
4478 if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4479 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4480 _old_set.bulk_remove(old_regions_removed);
4481 _humongous_set.bulk_remove(humongous_regions_removed);
4482 }
4483
4484 }
4485
4486 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4487 assert(list != NULL, "list can't be null");
4488 if (!list->is_empty()) {
4489 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4490 _hrm.insert_list_into_free_list(list);
4491 }
4492 }
4493
4494 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4495 decrease_used(bytes);
4496 }
4497
4498 class G1ParScrubRemSetTask: public AbstractGangTask {
4499 protected:
4500 G1RemSet* _g1rs;
4501 HeapRegionClaimer _hrclaimer;
4502
4503 public:
4504 G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) :
4505 AbstractGangTask("G1 ScrubRS"),
4506 _g1rs(g1_rs),
4507 _hrclaimer(num_workers) {
4508 }
4509
4510 void work(uint worker_id) {
4511 _g1rs->scrub(worker_id, &_hrclaimer);
4512 }
4513 };
4514
4515 void G1CollectedHeap::scrub_rem_set() {
4516 uint num_workers = workers()->active_workers();
4517 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers);
4518 workers()->run_task(&g1_par_scrub_rs_task);
4519 }
4520
4521 class G1FreeCollectionSetTask : public AbstractGangTask {
4522 private:
4523
4524 // Closure applied to all regions in the collection set to do work that needs to
4525 // be done serially in a single thread.
4526 class G1SerialFreeCollectionSetClosure : public HeapRegionClosure {
4527 private:
4528 EvacuationInfo* _evacuation_info;
4529 const size_t* _surviving_young_words;
4530
4531 // Bytes used in successfully evacuated regions before the evacuation.
4532 size_t _before_used_bytes;
4533 // Bytes used in unsucessfully evacuated regions before the evacuation
4534 size_t _after_used_bytes;
4535
4536 size_t _bytes_allocated_in_old_since_last_gc;
4537
4538 size_t _failure_used_words;
4539 size_t _failure_waste_words;
4540
4541 FreeRegionList _local_free_list;
4542 public:
4543 G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4544 HeapRegionClosure(),
4545 _evacuation_info(evacuation_info),
4546 _surviving_young_words(surviving_young_words),
4547 _before_used_bytes(0),
4548 _after_used_bytes(0),
4549 _bytes_allocated_in_old_since_last_gc(0),
4550 _failure_used_words(0),
4551 _failure_waste_words(0),
4552 _local_free_list("Local Region List for CSet Freeing") {
4553 }
4554
4555 virtual bool doHeapRegion(HeapRegion* r) {
4556 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4557
4558 assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index());
4559 g1h->clear_in_cset(r);
4560
4561 if (r->is_young()) {
4562 assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(),
4563 "Young index %d is wrong for region %u of type %s with %u young regions",
4564 r->young_index_in_cset(),
4565 r->hrm_index(),
4566 r->get_type_str(),
4567 g1h->collection_set()->young_region_length());
4568 size_t words_survived = _surviving_young_words[r->young_index_in_cset()];
4569 r->record_surv_words_in_group(words_survived);
4570 }
4571
4572 if (!r->evacuation_failed()) {
4573 assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
4574 _before_used_bytes += r->used();
4575 g1h->free_region(r,
4576 &_local_free_list,
4577 true, /* skip_remset */
4578 true, /* skip_hot_card_cache */
4579 true /* locked */);
4580 } else {
4581 r->uninstall_surv_rate_group();
4582 r->set_young_index_in_cset(-1);
4583 r->set_evacuation_failed(false);
4584 // When moving a young gen region to old gen, we "allocate" that whole region
4585 // there. This is in addition to any already evacuated objects. Notify the
4586 // policy about that.
4587 // Old gen regions do not cause an additional allocation: both the objects
4588 // still in the region and the ones already moved are accounted for elsewhere.
4589 if (r->is_young()) {
4590 _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
4591 }
4592 // The region is now considered to be old.
4593 r->set_old();
4594 // Do some allocation statistics accounting. Regions that failed evacuation
4595 // are always made old, so there is no need to update anything in the young
4596 // gen statistics, but we need to update old gen statistics.
4597 size_t used_words = r->marked_bytes() / HeapWordSize;
4598
4599 _failure_used_words += used_words;
4600 _failure_waste_words += HeapRegion::GrainWords - used_words;
4601
4602 g1h->old_set_add(r);
4603 _after_used_bytes += r->used();
4604 }
4605 return false;
4606 }
4607
4608 void complete_work() {
4609 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4610
4611 _evacuation_info->set_regions_freed(_local_free_list.length());
4612 _evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4613
4614 g1h->prepend_to_freelist(&_local_free_list);
4615 g1h->decrement_summary_bytes(_before_used_bytes);
4616
4617 G1Policy* policy = g1h->g1_policy();
4618 policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4619
4620 g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4621 }
4622 };
4623
4624 G1CollectionSet* _collection_set;
4625 G1SerialFreeCollectionSetClosure _cl;
4626 const size_t* _surviving_young_words;
4627
4628 size_t _rs_lengths;
4629
4630 volatile jint _serial_work_claim;
4631
4632 struct WorkItem {
4633 uint region_idx;
4634 bool is_young;
4635 bool evacuation_failed;
4636
4637 WorkItem(HeapRegion* r) {
4638 region_idx = r->hrm_index();
4639 is_young = r->is_young();
4640 evacuation_failed = r->evacuation_failed();
4641 }
4642 };
4643
4644 volatile size_t _parallel_work_claim;
4645 size_t _num_work_items;
4646 WorkItem* _work_items;
4647
4648 void do_serial_work() {
4649 // Need to grab the lock to be allowed to modify the old region list.
4650 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4651 _collection_set->iterate(&_cl);
4652 }
4653
4654 void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) {
4655 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4656
4657 HeapRegion* r = g1h->region_at(region_idx);
4658 assert(!g1h->is_on_master_free_list(r), "sanity");
4659
4660 Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths);
4661
4662 if (!is_young) {
4663 g1h->_hot_card_cache->reset_card_counts(r);
4664 }
4665
4666 if (!evacuation_failed) {
4667 r->rem_set()->clear_locked();
4668 }
4669 }
4670
4671 class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure {
4672 private:
4673 size_t _cur_idx;
4674 WorkItem* _work_items;
4675 public:
4676 G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { }
4677
4678 virtual bool doHeapRegion(HeapRegion* r) {
4679 _work_items[_cur_idx++] = WorkItem(r);
4680 return false;
4681 }
4682 };
4683
4684 void prepare_work() {
4685 G1PrepareFreeCollectionSetClosure cl(_work_items);
4686 _collection_set->iterate(&cl);
4687 }
4688
4689 void complete_work() {
4690 _cl.complete_work();
4691
4692 G1Policy* policy = G1CollectedHeap::heap()->g1_policy();
4693 policy->record_max_rs_lengths(_rs_lengths);
4694 policy->cset_regions_freed();
4695 }
4696 public:
4697 G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4698 AbstractGangTask("G1 Free Collection Set"),
4699 _cl(evacuation_info, surviving_young_words),
4700 _collection_set(collection_set),
4701 _surviving_young_words(surviving_young_words),
4702 _serial_work_claim(0),
4703 _rs_lengths(0),
4704 _parallel_work_claim(0),
4705 _num_work_items(collection_set->region_length()),
4706 _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) {
4707 prepare_work();
4708 }
4709
4710 ~G1FreeCollectionSetTask() {
4711 complete_work();
4712 FREE_C_HEAP_ARRAY(WorkItem, _work_items);
4713 }
4714
4715 // Chunk size for work distribution. The chosen value has been determined experimentally
4716 // to be a good tradeoff between overhead and achievable parallelism.
4717 static uint chunk_size() { return 32; }
4718
4719 virtual void work(uint worker_id) {
4720 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
4721
4722 // Claim serial work.
4723 if (_serial_work_claim == 0) {
4724 jint value = Atomic::add(1, &_serial_work_claim) - 1;
4725 if (value == 0) {
4726 double serial_time = os::elapsedTime();
4727 do_serial_work();
4728 timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0);
4729 }
4730 }
4731
4732 // Start parallel work.
4733 double young_time = 0.0;
4734 bool has_young_time = false;
4735 double non_young_time = 0.0;
4736 bool has_non_young_time = false;
4737
4738 while (true) {
4739 size_t end = Atomic::add(chunk_size(), &_parallel_work_claim);
4740 size_t cur = end - chunk_size();
4741
4742 if (cur >= _num_work_items) {
4743 break;
4744 }
4745
4746 double start_time = os::elapsedTime();
4747
4748 end = MIN2(end, _num_work_items);
4749
4750 for (; cur < end; cur++) {
4751 bool is_young = _work_items[cur].is_young;
4752
4753 do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed);
4754
4755 double end_time = os::elapsedTime();
4756 double time_taken = end_time - start_time;
4757 if (is_young) {
4758 young_time += time_taken;
4759 has_young_time = true;
4760 } else {
4761 non_young_time += time_taken;
4762 has_non_young_time = true;
4763 }
4764 start_time = end_time;
4765 }
4766 }
4767
4768 if (has_young_time) {
4769 timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time);
4770 }
4771 if (has_non_young_time) {
4772 timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, young_time);
4773 }
4774 }
4775 };
4776
4777 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4778 _eden.clear();
4779
4780 double free_cset_start_time = os::elapsedTime();
4781
4782 {
4783 uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U);
4784 uint const num_workers = MIN2(workers()->active_workers(), num_chunks);
4785
4786 G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words);
4787
4788 log_debug(gc, ergo)("Running %s using %u workers for collection set length %u",
4789 cl.name(),
4790 num_workers,
4791 _collection_set.region_length());
4792 workers()->run_task(&cl, num_workers);
4793 }
4794 g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0);
4795
4796 collection_set->clear();
4797 }
4798
4799 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4800 private:
4801 FreeRegionList* _free_region_list;
4802 HeapRegionSet* _proxy_set;
4803 uint _humongous_objects_reclaimed;
4804 uint _humongous_regions_reclaimed;
4805 size_t _freed_bytes;
4806 public:
4807
4808 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4809 _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) {
4810 }
4811
4812 virtual bool doHeapRegion(HeapRegion* r) {
4813 if (!r->is_starts_humongous()) {
4814 return false;
4815 }
4816
4817 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4818
4819 oop obj = (oop)r->bottom();
4820 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap();
4821
4822 // The following checks whether the humongous object is live are sufficient.
4823 // The main additional check (in addition to having a reference from the roots
4824 // or the young gen) is whether the humongous object has a remembered set entry.
4825 //
4826 // A humongous object cannot be live if there is no remembered set for it
4827 // because:
4828 // - there can be no references from within humongous starts regions referencing
4829 // the object because we never allocate other objects into them.
4830 // (I.e. there are no intra-region references that may be missed by the
4831 // remembered set)
4832 // - as soon there is a remembered set entry to the humongous starts region
4833 // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4834 // until the end of a concurrent mark.
4835 //
4836 // It is not required to check whether the object has been found dead by marking
4837 // or not, in fact it would prevent reclamation within a concurrent cycle, as
4838 // all objects allocated during that time are considered live.
4839 // SATB marking is even more conservative than the remembered set.
4840 // So if at this point in the collection there is no remembered set entry,
4841 // nobody has a reference to it.
4842 // At the start of collection we flush all refinement logs, and remembered sets
4843 // are completely up-to-date wrt to references to the humongous object.
4844 //
4845 // Other implementation considerations:
4846 // - never consider object arrays at this time because they would pose
4847 // considerable effort for cleaning up the the remembered sets. This is
4848 // required because stale remembered sets might reference locations that
4849 // are currently allocated into.
4850 uint region_idx = r->hrm_index();
4851 if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4852 !r->rem_set()->is_empty()) {
4853 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",
4854 region_idx,
4855 (size_t)obj->size() * HeapWordSize,
4856 p2i(r->bottom()),
4857 r->rem_set()->occupied(),
4858 r->rem_set()->strong_code_roots_list_length(),
4859 next_bitmap->is_marked(r->bottom()),
4860 g1h->is_humongous_reclaim_candidate(region_idx),
4861 obj->is_typeArray()
4862 );
4863 return false;
4864 }
4865
4866 guarantee(obj->is_typeArray(),
4867 "Only eagerly reclaiming type arrays is supported, but the object "
4868 PTR_FORMAT " is not.", p2i(r->bottom()));
4869
4870 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",
4871 region_idx,
4872 (size_t)obj->size() * HeapWordSize,
4873 p2i(r->bottom()),
4874 r->rem_set()->occupied(),
4875 r->rem_set()->strong_code_roots_list_length(),
4876 next_bitmap->is_marked(r->bottom()),
4877 g1h->is_humongous_reclaim_candidate(region_idx),
4878 obj->is_typeArray()
4879 );
4880
4881 // Need to clear mark bit of the humongous object if already set.
4882 if (next_bitmap->is_marked(r->bottom())) {
4883 next_bitmap->clear(r->bottom());
4884 }
4885 _humongous_objects_reclaimed++;
4886 do {
4887 HeapRegion* next = g1h->next_region_in_humongous(r);
4888 _freed_bytes += r->used();
4889 r->set_containing_set(NULL);
4890 _humongous_regions_reclaimed++;
4891 g1h->free_humongous_region(r, _free_region_list, false /* skip_remset */ );
4892 r = next;
4893 } while (r != NULL);
4894
4895 return false;
4896 }
4897
4898 uint humongous_objects_reclaimed() {
4899 return _humongous_objects_reclaimed;
4900 }
4901
4902 uint humongous_regions_reclaimed() {
4903 return _humongous_regions_reclaimed;
4904 }
4905
4906 size_t bytes_freed() const {
4907 return _freed_bytes;
4908 }
4909 };
4910
4911 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4912 assert_at_safepoint(true);
4913
4914 if (!G1EagerReclaimHumongousObjects ||
4915 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
4916 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
4917 return;
4918 }
4919
4920 double start_time = os::elapsedTime();
4921
4922 FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
4923
4924 G1FreeHumongousRegionClosure cl(&local_cleanup_list);
4925 heap_region_iterate(&cl);
4926
4927 remove_from_old_sets(0, cl.humongous_regions_reclaimed());
4928
4929 G1HRPrinter* hrp = hr_printer();
4930 if (hrp->is_active()) {
4931 FreeRegionListIterator iter(&local_cleanup_list);
4932 while (iter.more_available()) {
4933 HeapRegion* hr = iter.get_next();
4934 hrp->cleanup(hr);
4935 }
4936 }
4937
4938 prepend_to_freelist(&local_cleanup_list);
4939 decrement_summary_bytes(cl.bytes_freed());
4940
4941 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
4942 cl.humongous_objects_reclaimed());
4943 }
4944
4945 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
4946 public:
4947 virtual bool doHeapRegion(HeapRegion* r) {
4948 assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
4949 G1CollectedHeap::heap()->clear_in_cset(r);
4950 r->set_young_index_in_cset(-1);
4951 return false;
4952 }
4953 };
4954
4955 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
4956 G1AbandonCollectionSetClosure cl;
4957 collection_set->iterate(&cl);
4958
4959 collection_set->clear();
4960 collection_set->stop_incremental_building();
4961 }
4962
4963 void G1CollectedHeap::set_free_regions_coming() {
4964 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming");
4965
4966 assert(!free_regions_coming(), "pre-condition");
4967 _free_regions_coming = true;
4968 }
4969
4970 void G1CollectedHeap::reset_free_regions_coming() {
4971 assert(free_regions_coming(), "pre-condition");
4972
4973 {
4974 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
4975 _free_regions_coming = false;
4976 SecondaryFreeList_lock->notify_all();
4977 }
4978
4979 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming");
4980 }
4981
4982 void G1CollectedHeap::wait_while_free_regions_coming() {
4983 // Most of the time we won't have to wait, so let's do a quick test
4984 // first before we take the lock.
4985 if (!free_regions_coming()) {
4986 return;
4987 }
4988
4989 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions");
4990
4991 {
4992 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
4993 while (free_regions_coming()) {
4994 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
4995 }
4996 }
4997
4998 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions");
4999 }
5000
5001 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
5002 return _allocator->is_retained_old_region(hr);
5003 }
5004
5005 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
5006 _eden.add(hr);
5007 _g1_policy->set_region_eden(hr);
5008 }
5009
5010 #ifdef ASSERT
5011
5012 class NoYoungRegionsClosure: public HeapRegionClosure {
5013 private:
5014 bool _success;
5015 public:
5016 NoYoungRegionsClosure() : _success(true) { }
5017 bool doHeapRegion(HeapRegion* r) {
5018 if (r->is_young()) {
5019 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
5020 p2i(r->bottom()), p2i(r->end()));
5021 _success = false;
5022 }
5023 return false;
5024 }
5025 bool success() { return _success; }
5026 };
5027
5028 bool G1CollectedHeap::check_young_list_empty() {
5029 bool ret = (young_regions_count() == 0);
5030
5031 NoYoungRegionsClosure closure;
5032 heap_region_iterate(&closure);
5033 ret = ret && closure.success();
5034
5035 return ret;
5036 }
5037
5038 #endif // ASSERT
5039
5040 class TearDownRegionSetsClosure : public HeapRegionClosure {
5041 private:
5042 HeapRegionSet *_old_set;
5043
5044 public:
5045 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
5046
5047 bool doHeapRegion(HeapRegion* r) {
5048 if (r->is_old()) {
5049 _old_set->remove(r);
5050 } else if(r->is_young()) {
5051 r->uninstall_surv_rate_group();
5052 } else {
5053 // We ignore free regions, we'll empty the free list afterwards.
5054 // We ignore humongous regions, we're not tearing down the
5055 // humongous regions set.
5056 assert(r->is_free() || r->is_humongous(),
5057 "it cannot be another type");
5058 }
5059 return false;
5060 }
5061
5062 ~TearDownRegionSetsClosure() {
5063 assert(_old_set->is_empty(), "post-condition");
5064 }
5065 };
5066
5067 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
5068 assert_at_safepoint(true /* should_be_vm_thread */);
5069
5070 if (!free_list_only) {
5071 TearDownRegionSetsClosure cl(&_old_set);
5072 heap_region_iterate(&cl);
5073
5074 // Note that emptying the _young_list is postponed and instead done as
5075 // the first step when rebuilding the regions sets again. The reason for
5076 // this is that during a full GC string deduplication needs to know if
5077 // a collected region was young or old when the full GC was initiated.
5078 }
5079 _hrm.remove_all_free_regions();
5080 }
5081
5082 void G1CollectedHeap::increase_used(size_t bytes) {
5083 _summary_bytes_used += bytes;
5084 }
5085
5086 void G1CollectedHeap::decrease_used(size_t bytes) {
5087 assert(_summary_bytes_used >= bytes,
5088 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
5089 _summary_bytes_used, bytes);
5090 _summary_bytes_used -= bytes;
5091 }
5092
5093 void G1CollectedHeap::set_used(size_t bytes) {
5094 _summary_bytes_used = bytes;
5095 }
5096
5097 class RebuildRegionSetsClosure : public HeapRegionClosure {
5098 private:
5099 bool _free_list_only;
5100 HeapRegionSet* _old_set;
5101 HeapRegionManager* _hrm;
5102 size_t _total_used;
5103
5104 public:
5105 RebuildRegionSetsClosure(bool free_list_only,
5106 HeapRegionSet* old_set, HeapRegionManager* hrm) :
5107 _free_list_only(free_list_only),
5108 _old_set(old_set), _hrm(hrm), _total_used(0) {
5109 assert(_hrm->num_free_regions() == 0, "pre-condition");
5110 if (!free_list_only) {
5111 assert(_old_set->is_empty(), "pre-condition");
5112 }
5113 }
5114
5115 bool doHeapRegion(HeapRegion* r) {
5116 if (r->is_empty()) {
5117 // Add free regions to the free list
5118 r->set_free();
5119 r->set_allocation_context(AllocationContext::system());
5120 _hrm->insert_into_free_list(r);
5121 } else if (!_free_list_only) {
5122
5123 if (r->is_humongous()) {
5124 // We ignore humongous regions. We left the humongous set unchanged.
5125 } else {
5126 assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
5127 // We now move all (non-humongous, non-old) regions to old gen, and register them as such.
5128 r->move_to_old();
5129 _old_set->add(r);
5130 }
5131 _total_used += r->used();
5132 }
5133
5134 return false;
5135 }
5136
5137 size_t total_used() {
5138 return _total_used;
5139 }
5140 };
5141
5142 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
5143 assert_at_safepoint(true /* should_be_vm_thread */);
5144
5145 if (!free_list_only) {
5146 _eden.clear();
5147 _survivor.clear();
5148 }
5149
5150 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
5151 heap_region_iterate(&cl);
5152
5153 if (!free_list_only) {
5154 set_used(cl.total_used());
5155 if (_archive_allocator != NULL) {
5156 _archive_allocator->clear_used();
5157 }
5158 }
5159 assert(used_unlocked() == recalculate_used(),
5160 "inconsistent used_unlocked(), "
5161 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT,
5162 used_unlocked(), recalculate_used());
5163 }
5164
5165 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
5166 HeapRegion* hr = heap_region_containing(p);
5167 return hr->is_in(p);
5168 }
5169
5170 // Methods for the mutator alloc region
5171
5172 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
5173 bool force) {
5174 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5175 bool should_allocate = g1_policy()->should_allocate_mutator_region();
5176 if (force || should_allocate) {
5177 HeapRegion* new_alloc_region = new_region(word_size,
5178 false /* is_old */,
5179 false /* do_expand */);
5180 if (new_alloc_region != NULL) {
5181 set_region_short_lived_locked(new_alloc_region);
5182 _hr_printer.alloc(new_alloc_region, !should_allocate);
5183 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
5184 return new_alloc_region;
5185 }
5186 }
5187 return NULL;
5188 }
5189
5190 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
5191 size_t allocated_bytes) {
5192 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5193 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
5194
5195 collection_set()->add_eden_region(alloc_region);
5196 increase_used(allocated_bytes);
5197 _hr_printer.retire(alloc_region);
5198 // We update the eden sizes here, when the region is retired,
5199 // instead of when it's allocated, since this is the point that its
5200 // used space has been recored in _summary_bytes_used.
5201 g1mm()->update_eden_size();
5202 }
5203
5204 // Methods for the GC alloc regions
5205
5206 bool G1CollectedHeap::has_more_regions(InCSetState dest) {
5207 if (dest.is_old()) {
5208 return true;
5209 } else {
5210 return survivor_regions_count() < g1_policy()->max_survivor_regions();
5211 }
5212 }
5213
5214 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) {
5215 assert(FreeList_lock->owned_by_self(), "pre-condition");
5216
5217 if (!has_more_regions(dest)) {
5218 return NULL;
5219 }
5220
5221 const bool is_survivor = dest.is_young();
5222
5223 HeapRegion* new_alloc_region = new_region(word_size,
5224 !is_survivor,
5225 true /* do_expand */);
5226 if (new_alloc_region != NULL) {
5227 // We really only need to do this for old regions given that we
5228 // should never scan survivors. But it doesn't hurt to do it
5229 // for survivors too.
5230 new_alloc_region->record_timestamp();
5231 if (is_survivor) {
5232 new_alloc_region->set_survivor();
5233 _survivor.add(new_alloc_region);
5234 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
5235 } else {
5236 new_alloc_region->set_old();
5237 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
5238 }
5239 _hr_printer.alloc(new_alloc_region);
5240 bool during_im = collector_state()->during_initial_mark_pause();
5241 new_alloc_region->note_start_of_copying(during_im);
5242 return new_alloc_region;
5243 }
5244 return NULL;
5245 }
5246
5247 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
5248 size_t allocated_bytes,
5249 InCSetState dest) {
5250 bool during_im = collector_state()->during_initial_mark_pause();
5251 alloc_region->note_end_of_copying(during_im);
5252 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
5253 if (dest.is_old()) {
5254 _old_set.add(alloc_region);
5255 }
5256 _hr_printer.retire(alloc_region);
5257 }
5258
5259 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
5260 bool expanded = false;
5261 uint index = _hrm.find_highest_free(&expanded);
5262
5263 if (index != G1_NO_HRM_INDEX) {
5264 if (expanded) {
5265 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
5266 HeapRegion::GrainWords * HeapWordSize);
5267 }
5268 _hrm.allocate_free_regions_starting_at(index, 1);
5269 return region_at(index);
5270 }
5271 return NULL;
5272 }
5273
5274 // Optimized nmethod scanning
5275
5276 class RegisterNMethodOopClosure: public OopClosure {
5277 G1CollectedHeap* _g1h;
5278 nmethod* _nm;
5279
5280 template <class T> void do_oop_work(T* p) {
5281 T heap_oop = oopDesc::load_heap_oop(p);
5282 if (!oopDesc::is_null(heap_oop)) {
5283 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5284 HeapRegion* hr = _g1h->heap_region_containing(obj);
5285 assert(!hr->is_continues_humongous(),
5286 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5287 " starting at " HR_FORMAT,
5288 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5289
5290 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
5291 hr->add_strong_code_root_locked(_nm);
5292 }
5293 }
5294
5295 public:
5296 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5297 _g1h(g1h), _nm(nm) {}
5298
5299 void do_oop(oop* p) { do_oop_work(p); }
5300 void do_oop(narrowOop* p) { do_oop_work(p); }
5301 };
5302
5303 class UnregisterNMethodOopClosure: public OopClosure {
5304 G1CollectedHeap* _g1h;
5305 nmethod* _nm;
5306
5307 template <class T> void do_oop_work(T* p) {
5308 T heap_oop = oopDesc::load_heap_oop(p);
5309 if (!oopDesc::is_null(heap_oop)) {
5310 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5311 HeapRegion* hr = _g1h->heap_region_containing(obj);
5312 assert(!hr->is_continues_humongous(),
5313 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5314 " starting at " HR_FORMAT,
5315 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5316
5317 hr->remove_strong_code_root(_nm);
5318 }
5319 }
5320
5321 public:
5322 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5323 _g1h(g1h), _nm(nm) {}
5324
5325 void do_oop(oop* p) { do_oop_work(p); }
5326 void do_oop(narrowOop* p) { do_oop_work(p); }
5327 };
5328
5329 // Returns true if the reference points to an object that
5330 // can move in an incremental collection.
5331 bool G1CollectedHeap::is_scavengable(oop obj) {
5332 HeapRegion* hr = heap_region_containing(obj);
5333 return !hr->is_pinned();
5334 }
5335
5336 void G1CollectedHeap::register_nmethod(nmethod* nm) {
5337 guarantee(nm != NULL, "sanity");
5338 RegisterNMethodOopClosure reg_cl(this, nm);
5339 nm->oops_do(®_cl);
5340 }
5341
5342 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
5343 guarantee(nm != NULL, "sanity");
5344 UnregisterNMethodOopClosure reg_cl(this, nm);
5345 nm->oops_do(®_cl, true);
5346 }
5347
5348 void G1CollectedHeap::purge_code_root_memory() {
5349 double purge_start = os::elapsedTime();
5350 G1CodeRootSet::purge();
5351 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
5352 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
5353 }
5354
5355 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
5356 G1CollectedHeap* _g1h;
5357
5358 public:
5359 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
5360 _g1h(g1h) {}
5361
5362 void do_code_blob(CodeBlob* cb) {
5363 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
5364 if (nm == NULL) {
5365 return;
5366 }
5367
5368 if (ScavengeRootsInCode) {
5369 _g1h->register_nmethod(nm);
5370 }
5371 }
5372 };
5373
5374 void G1CollectedHeap::rebuild_strong_code_roots() {
5375 RebuildStrongCodeRootClosure blob_cl(this);
5376 CodeCache::blobs_do(&blob_cl);
5377 }