1 /*
2 * Copyright (c) 2001, 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/metadataOnStackMark.hpp"
27 #include "classfile/stringTable.hpp"
28 #include "classfile/symbolTable.hpp"
29 #include "code/codeCache.hpp"
30 #include "code/icBuffer.hpp"
31 #include "gc/g1/bufferingOopClosure.hpp"
32 #include "gc/g1/concurrentG1Refine.hpp"
33 #include "gc/g1/concurrentG1RefineThread.hpp"
34 #include "gc/g1/concurrentMarkThread.inline.hpp"
35 #include "gc/g1/g1Allocator.inline.hpp"
36 #include "gc/g1/g1CollectedHeap.inline.hpp"
37 #include "gc/g1/g1CollectionSet.hpp"
38 #include "gc/g1/g1CollectorPolicy.hpp"
39 #include "gc/g1/g1CollectorState.hpp"
40 #include "gc/g1/g1EvacStats.inline.hpp"
41 #include "gc/g1/g1FullGCScope.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.inline.hpp"
52 #include "gc/g1/g1RootClosures.hpp"
53 #include "gc/g1/g1RootProcessor.hpp"
54 #include "gc/g1/g1SerialFullCollector.hpp"
55 #include "gc/g1/g1StringDedup.hpp"
56 #include "gc/g1/g1YCTypes.hpp"
57 #include "gc/g1/heapRegion.inline.hpp"
58 #include "gc/g1/heapRegionRemSet.hpp"
59 #include "gc/g1/heapRegionSet.inline.hpp"
60 #include "gc/g1/suspendibleThreadSet.hpp"
61 #include "gc/g1/vm_operations_g1.hpp"
62 #include "gc/shared/gcHeapSummary.hpp"
63 #include "gc/shared/gcId.hpp"
64 #include "gc/shared/gcLocker.inline.hpp"
65 #include "gc/shared/gcTimer.hpp"
66 #include "gc/shared/gcTrace.hpp"
67 #include "gc/shared/gcTraceTime.inline.hpp"
68 #include "gc/shared/generationSpec.hpp"
69 #include "gc/shared/isGCActiveMark.hpp"
70 #include "gc/shared/preservedMarks.inline.hpp"
71 #include "gc/shared/referenceProcessor.inline.hpp"
72 #include "gc/shared/taskqueue.inline.hpp"
73 #include "logging/log.hpp"
74 #include "memory/allocation.hpp"
75 #include "memory/iterator.hpp"
76 #include "memory/resourceArea.hpp"
77 #include "oops/oop.inline.hpp"
78 #include "prims/resolvedMethodTable.hpp"
79 #include "runtime/atomic.hpp"
80 #include "runtime/init.hpp"
81 #include "runtime/orderAccess.inline.hpp"
82 #include "runtime/vmThread.hpp"
83 #include "utilities/align.hpp"
84 #include "utilities/globalDefinitions.hpp"
85 #include "utilities/stack.inline.hpp"
86
87 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
88
89 // INVARIANTS/NOTES
90 //
91 // All allocation activity covered by the G1CollectedHeap interface is
92 // serialized by acquiring the HeapLock. This happens in mem_allocate
93 // and allocate_new_tlab, which are the "entry" points to the
94 // allocation code from the rest of the JVM. (Note that this does not
95 // apply to TLAB allocation, which is not part of this interface: it
96 // is done by clients of this interface.)
97
98 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
99 private:
100 size_t _num_dirtied;
101 G1CollectedHeap* _g1h;
102 G1SATBCardTableLoggingModRefBS* _g1_bs;
103
104 HeapRegion* region_for_card(jbyte* card_ptr) const {
105 return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr));
106 }
107
108 bool will_become_free(HeapRegion* hr) const {
109 // A region will be freed by free_collection_set if the region is in the
110 // collection set and has not had an evacuation failure.
111 return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
112 }
113
114 public:
115 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(),
116 _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { }
117
118 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
119 HeapRegion* hr = region_for_card(card_ptr);
120
121 // Should only dirty cards in regions that won't be freed.
122 if (!will_become_free(hr)) {
123 *card_ptr = CardTableModRefBS::dirty_card_val();
124 _num_dirtied++;
125 }
126
127 return true;
128 }
129
130 size_t num_dirtied() const { return _num_dirtied; }
131 };
132
133
134 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
135 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
136 }
137
138 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
139 // The from card cache is not the memory that is actually committed. So we cannot
140 // take advantage of the zero_filled parameter.
141 reset_from_card_cache(start_idx, num_regions);
142 }
143
144 // Private methods.
145
146 HeapRegion*
147 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
148 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
149 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
150 if (!_secondary_free_list.is_empty()) {
151 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
152 "secondary_free_list has %u entries",
153 _secondary_free_list.length());
154 // It looks as if there are free regions available on the
155 // secondary_free_list. Let's move them to the free_list and try
156 // again to allocate from it.
157 append_secondary_free_list();
158
159 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
160 "empty we should have moved at least one entry to the free_list");
161 HeapRegion* res = _hrm.allocate_free_region(is_old);
162 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
163 "allocated " HR_FORMAT " from secondary_free_list",
164 HR_FORMAT_PARAMS(res));
165 return res;
166 }
167
168 // Wait here until we get notified either when (a) there are no
169 // more free regions coming or (b) some regions have been moved on
170 // the secondary_free_list.
171 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
172 }
173
174 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
175 "could not allocate from secondary_free_list");
176 return NULL;
177 }
178
179 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
180 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
181 "the only time we use this to allocate a humongous region is "
182 "when we are allocating a single humongous region");
183
184 HeapRegion* res;
185 if (G1StressConcRegionFreeing) {
186 if (!_secondary_free_list.is_empty()) {
187 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
188 "forced to look at the secondary_free_list");
189 res = new_region_try_secondary_free_list(is_old);
190 if (res != NULL) {
191 return res;
192 }
193 }
194 }
195
196 res = _hrm.allocate_free_region(is_old);
197
198 if (res == NULL) {
199 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
200 "res == NULL, trying the secondary_free_list");
201 res = new_region_try_secondary_free_list(is_old);
202 }
203 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
204 // Currently, only attempts to allocate GC alloc regions set
205 // do_expand to true. So, we should only reach here during a
206 // safepoint. If this assumption changes we might have to
207 // reconsider the use of _expand_heap_after_alloc_failure.
208 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
209
210 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
211 word_size * HeapWordSize);
212
213 if (expand(word_size * HeapWordSize)) {
214 // Given that expand() succeeded in expanding the heap, and we
215 // always expand the heap by an amount aligned to the heap
216 // region size, the free list should in theory not be empty.
217 // In either case allocate_free_region() will check for NULL.
218 res = _hrm.allocate_free_region(is_old);
219 } else {
220 _expand_heap_after_alloc_failure = false;
221 }
222 }
223 return res;
224 }
225
226 HeapWord*
227 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
228 uint num_regions,
229 size_t word_size,
230 AllocationContext_t context) {
231 assert(first != G1_NO_HRM_INDEX, "pre-condition");
232 assert(is_humongous(word_size), "word_size should be humongous");
233 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
234
235 // Index of last region in the series.
236 uint last = first + num_regions - 1;
237
238 // We need to initialize the region(s) we just discovered. This is
239 // a bit tricky given that it can happen concurrently with
240 // refinement threads refining cards on these regions and
241 // potentially wanting to refine the BOT as they are scanning
242 // those cards (this can happen shortly after a cleanup; see CR
243 // 6991377). So we have to set up the region(s) carefully and in
244 // a specific order.
245
246 // The word size sum of all the regions we will allocate.
247 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
248 assert(word_size <= word_size_sum, "sanity");
249
250 // This will be the "starts humongous" region.
251 HeapRegion* first_hr = region_at(first);
252 // The header of the new object will be placed at the bottom of
253 // the first region.
254 HeapWord* new_obj = first_hr->bottom();
255 // This will be the new top of the new object.
256 HeapWord* obj_top = new_obj + word_size;
257
258 // First, we need to zero the header of the space that we will be
259 // allocating. When we update top further down, some refinement
260 // threads might try to scan the region. By zeroing the header we
261 // ensure that any thread that will try to scan the region will
262 // come across the zero klass word and bail out.
263 //
264 // NOTE: It would not have been correct to have used
265 // CollectedHeap::fill_with_object() and make the space look like
266 // an int array. The thread that is doing the allocation will
267 // later update the object header to a potentially different array
268 // type and, for a very short period of time, the klass and length
269 // fields will be inconsistent. This could cause a refinement
270 // thread to calculate the object size incorrectly.
271 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
272
273 // Next, pad out the unused tail of the last region with filler
274 // objects, for improved usage accounting.
275 // How many words we use for filler objects.
276 size_t word_fill_size = word_size_sum - word_size;
277
278 // How many words memory we "waste" which cannot hold a filler object.
279 size_t words_not_fillable = 0;
280
281 if (word_fill_size >= min_fill_size()) {
282 fill_with_objects(obj_top, word_fill_size);
283 } else if (word_fill_size > 0) {
284 // We have space to fill, but we cannot fit an object there.
285 words_not_fillable = word_fill_size;
286 word_fill_size = 0;
287 }
288
289 // We will set up the first region as "starts humongous". This
290 // will also update the BOT covering all the regions to reflect
291 // that there is a single object that starts at the bottom of the
292 // first region.
293 first_hr->set_starts_humongous(obj_top, word_fill_size);
294 first_hr->set_allocation_context(context);
295 // Then, if there are any, we will set up the "continues
296 // humongous" regions.
297 HeapRegion* hr = NULL;
298 for (uint i = first + 1; i <= last; ++i) {
299 hr = region_at(i);
300 hr->set_continues_humongous(first_hr);
301 hr->set_allocation_context(context);
302 }
303
304 // Up to this point no concurrent thread would have been able to
305 // do any scanning on any region in this series. All the top
306 // fields still point to bottom, so the intersection between
307 // [bottom,top] and [card_start,card_end] will be empty. Before we
308 // update the top fields, we'll do a storestore to make sure that
309 // no thread sees the update to top before the zeroing of the
310 // object header and the BOT initialization.
311 OrderAccess::storestore();
312
313 // Now, we will update the top fields of the "continues humongous"
314 // regions except the last one.
315 for (uint i = first; i < last; ++i) {
316 hr = region_at(i);
317 hr->set_top(hr->end());
318 }
319
320 hr = region_at(last);
321 // If we cannot fit a filler object, we must set top to the end
322 // of the humongous object, otherwise we cannot iterate the heap
323 // and the BOT will not be complete.
324 hr->set_top(hr->end() - words_not_fillable);
325
326 assert(hr->bottom() < obj_top && obj_top <= hr->end(),
327 "obj_top should be in last region");
328
329 _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
330
331 assert(words_not_fillable == 0 ||
332 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
333 "Miscalculation in humongous allocation");
334
335 increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
336
337 for (uint i = first; i <= last; ++i) {
338 hr = region_at(i);
339 _humongous_set.add(hr);
340 _hr_printer.alloc(hr);
341 }
342
343 return new_obj;
344 }
345
346 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
347 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
348 return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
349 }
350
351 // If could fit into free regions w/o expansion, try.
352 // Otherwise, if can expand, do so.
353 // Otherwise, if using ex regions might help, try with ex given back.
354 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
355 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
356
357 _verifier->verify_region_sets_optional();
358
359 uint first = G1_NO_HRM_INDEX;
360 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
361
362 if (obj_regions == 1) {
363 // Only one region to allocate, try to use a fast path by directly allocating
364 // from the free lists. Do not try to expand here, we will potentially do that
365 // later.
366 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
367 if (hr != NULL) {
368 first = hr->hrm_index();
369 }
370 } else {
371 // We can't allocate humongous regions spanning more than one region while
372 // cleanupComplete() is running, since some of the regions we find to be
373 // empty might not yet be added to the free list. It is not straightforward
374 // to know in which list they are on so that we can remove them. We only
375 // need to do this if we need to allocate more than one region to satisfy the
376 // current humongous allocation request. If we are only allocating one region
377 // we use the one-region region allocation code (see above), that already
378 // potentially waits for regions from the secondary free list.
379 wait_while_free_regions_coming();
380 append_secondary_free_list_if_not_empty_with_lock();
381
382 // Policy: Try only empty regions (i.e. already committed first). Maybe we
383 // are lucky enough to find some.
384 first = _hrm.find_contiguous_only_empty(obj_regions);
385 if (first != G1_NO_HRM_INDEX) {
386 _hrm.allocate_free_regions_starting_at(first, obj_regions);
387 }
388 }
389
390 if (first == G1_NO_HRM_INDEX) {
391 // Policy: We could not find enough regions for the humongous object in the
392 // free list. Look through the heap to find a mix of free and uncommitted regions.
393 // If so, try expansion.
394 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
395 if (first != G1_NO_HRM_INDEX) {
396 // We found something. Make sure these regions are committed, i.e. expand
397 // the heap. Alternatively we could do a defragmentation GC.
398 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
399 word_size * HeapWordSize);
400
401 _hrm.expand_at(first, obj_regions, workers());
402 g1_policy()->record_new_heap_size(num_regions());
403
404 #ifdef ASSERT
405 for (uint i = first; i < first + obj_regions; ++i) {
406 HeapRegion* hr = region_at(i);
407 assert(hr->is_free(), "sanity");
408 assert(hr->is_empty(), "sanity");
409 assert(is_on_master_free_list(hr), "sanity");
410 }
411 #endif
412 _hrm.allocate_free_regions_starting_at(first, obj_regions);
413 } else {
414 // Policy: Potentially trigger a defragmentation GC.
415 }
416 }
417
418 HeapWord* result = NULL;
419 if (first != G1_NO_HRM_INDEX) {
420 result = humongous_obj_allocate_initialize_regions(first, obj_regions,
421 word_size, context);
422 assert(result != NULL, "it should always return a valid result");
423
424 // A successful humongous object allocation changes the used space
425 // information of the old generation so we need to recalculate the
426 // sizes and update the jstat counters here.
427 g1mm()->update_sizes();
428 }
429
430 _verifier->verify_region_sets_optional();
431
432 return result;
433 }
434
435 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
436 assert_heap_not_locked_and_not_at_safepoint();
437 assert(!is_humongous(word_size), "we do not allow humongous TLABs");
438
439 uint dummy_gc_count_before;
440 uint dummy_gclocker_retry_count = 0;
441 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
442 }
443
444 HeapWord*
445 G1CollectedHeap::mem_allocate(size_t word_size,
446 bool* gc_overhead_limit_was_exceeded) {
447 assert_heap_not_locked_and_not_at_safepoint();
448
449 // Loop until the allocation is satisfied, or unsatisfied after GC.
450 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
451 uint gc_count_before;
452
453 HeapWord* result = NULL;
454 if (!is_humongous(word_size)) {
455 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
456 } else {
457 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
458 }
459 if (result != NULL) {
460 return result;
461 }
462
463 // Create the garbage collection operation...
464 VM_G1CollectForAllocation op(gc_count_before, word_size);
465 op.set_allocation_context(AllocationContext::current());
466
467 // ...and get the VM thread to execute it.
468 VMThread::execute(&op);
469
470 if (op.prologue_succeeded() && op.pause_succeeded()) {
471 // If the operation was successful we'll return the result even
472 // if it is NULL. If the allocation attempt failed immediately
473 // after a Full GC, it's unlikely we'll be able to allocate now.
474 HeapWord* result = op.result();
475 if (result != NULL && !is_humongous(word_size)) {
476 // Allocations that take place on VM operations do not do any
477 // card dirtying and we have to do it here. We only have to do
478 // this for non-humongous allocations, though.
479 dirty_young_block(result, word_size);
480 }
481 return result;
482 } else {
483 if (gclocker_retry_count > GCLockerRetryAllocationCount) {
484 return NULL;
485 }
486 assert(op.result() == NULL,
487 "the result should be NULL if the VM op did not succeed");
488 }
489
490 // Give a warning if we seem to be looping forever.
491 if ((QueuedAllocationWarningCount > 0) &&
492 (try_count % QueuedAllocationWarningCount == 0)) {
493 log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count);
494 }
495 }
496
497 ShouldNotReachHere();
498 return NULL;
499 }
500
501 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
502 AllocationContext_t context,
503 uint* gc_count_before_ret,
504 uint* gclocker_retry_count_ret) {
505 // Make sure you read the note in attempt_allocation_humongous().
506
507 assert_heap_not_locked_and_not_at_safepoint();
508 assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
509 "be called for humongous allocation requests");
510
511 // We should only get here after the first-level allocation attempt
512 // (attempt_allocation()) failed to allocate.
513
514 // We will loop until a) we manage to successfully perform the
515 // allocation or b) we successfully schedule a collection which
516 // fails to perform the allocation. b) is the only case when we'll
517 // return NULL.
518 HeapWord* result = NULL;
519 for (int try_count = 1; /* we'll return */; try_count += 1) {
520 bool should_try_gc;
521 uint gc_count_before;
522
523 {
524 MutexLockerEx x(Heap_lock);
525 result = _allocator->attempt_allocation_locked(word_size, context);
526 if (result != NULL) {
527 return result;
528 }
529
530 if (GCLocker::is_active_and_needs_gc()) {
531 if (g1_policy()->can_expand_young_list()) {
532 // No need for an ergo verbose message here,
533 // can_expand_young_list() does this when it returns true.
534 result = _allocator->attempt_allocation_force(word_size, context);
535 if (result != NULL) {
536 return result;
537 }
538 }
539 should_try_gc = false;
540 } else {
541 // The GCLocker may not be active but the GCLocker initiated
542 // GC may not yet have been performed (GCLocker::needs_gc()
543 // returns true). In this case we do not try this GC and
544 // wait until the GCLocker initiated GC is performed, and
545 // then retry the allocation.
546 if (GCLocker::needs_gc()) {
547 should_try_gc = false;
548 } else {
549 // Read the GC count while still holding the Heap_lock.
550 gc_count_before = total_collections();
551 should_try_gc = true;
552 }
553 }
554 }
555
556 if (should_try_gc) {
557 bool succeeded;
558 result = do_collection_pause(word_size, gc_count_before, &succeeded,
559 GCCause::_g1_inc_collection_pause);
560 if (result != NULL) {
561 assert(succeeded, "only way to get back a non-NULL result");
562 return result;
563 }
564
565 if (succeeded) {
566 // If we get here we successfully scheduled a collection which
567 // failed to allocate. No point in trying to allocate
568 // further. We'll just return NULL.
569 MutexLockerEx x(Heap_lock);
570 *gc_count_before_ret = total_collections();
571 return NULL;
572 }
573 } else {
574 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
575 MutexLockerEx x(Heap_lock);
576 *gc_count_before_ret = total_collections();
577 return NULL;
578 }
579 // The GCLocker is either active or the GCLocker initiated
580 // GC has not yet been performed. Stall until it is and
581 // then retry the allocation.
582 GCLocker::stall_until_clear();
583 (*gclocker_retry_count_ret) += 1;
584 }
585
586 // We can reach here if we were unsuccessful in scheduling a
587 // collection (because another thread beat us to it) or if we were
588 // stalled due to the GC locker. In either can we should retry the
589 // allocation attempt in case another thread successfully
590 // performed a collection and reclaimed enough space. We do the
591 // first attempt (without holding the Heap_lock) here and the
592 // follow-on attempt will be at the start of the next loop
593 // iteration (after taking the Heap_lock).
594 result = _allocator->attempt_allocation(word_size, context);
595 if (result != NULL) {
596 return result;
597 }
598
599 // Give a warning if we seem to be looping forever.
600 if ((QueuedAllocationWarningCount > 0) &&
601 (try_count % QueuedAllocationWarningCount == 0)) {
602 log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() "
603 "retries %d times", try_count);
604 }
605 }
606
607 ShouldNotReachHere();
608 return NULL;
609 }
610
611 void G1CollectedHeap::begin_archive_alloc_range(bool open) {
612 assert_at_safepoint(true /* should_be_vm_thread */);
613 if (_archive_allocator == NULL) {
614 _archive_allocator = G1ArchiveAllocator::create_allocator(this, open);
615 }
616 }
617
618 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
619 // Allocations in archive regions cannot be of a size that would be considered
620 // humongous even for a minimum-sized region, because G1 region sizes/boundaries
621 // may be different at archive-restore time.
622 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
623 }
624
625 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
626 assert_at_safepoint(true /* should_be_vm_thread */);
627 assert(_archive_allocator != NULL, "_archive_allocator not initialized");
628 if (is_archive_alloc_too_large(word_size)) {
629 return NULL;
630 }
631 return _archive_allocator->archive_mem_allocate(word_size);
632 }
633
634 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
635 size_t end_alignment_in_bytes) {
636 assert_at_safepoint(true /* should_be_vm_thread */);
637 assert(_archive_allocator != NULL, "_archive_allocator not initialized");
638
639 // Call complete_archive to do the real work, filling in the MemRegion
640 // array with the archive regions.
641 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
642 delete _archive_allocator;
643 _archive_allocator = NULL;
644 }
645
646 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
647 assert(ranges != NULL, "MemRegion array NULL");
648 assert(count != 0, "No MemRegions provided");
649 MemRegion reserved = _hrm.reserved();
650 for (size_t i = 0; i < count; i++) {
651 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
652 return false;
653 }
654 }
655 return true;
656 }
657
658 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges,
659 size_t count,
660 bool open) {
661 assert(!is_init_completed(), "Expect to be called at JVM init time");
662 assert(ranges != NULL, "MemRegion array NULL");
663 assert(count != 0, "No MemRegions provided");
664 MutexLockerEx x(Heap_lock);
665
666 MemRegion reserved = _hrm.reserved();
667 HeapWord* prev_last_addr = NULL;
668 HeapRegion* prev_last_region = NULL;
669
670 // Temporarily disable pretouching of heap pages. This interface is used
671 // when mmap'ing archived heap data in, so pre-touching is wasted.
672 FlagSetting fs(AlwaysPreTouch, false);
673
674 // Enable archive object checking used by G1MarkSweep. We have to let it know
675 // about each archive range, so that objects in those ranges aren't marked.
676 G1ArchiveAllocator::enable_archive_object_check();
677
678 // For each specified MemRegion range, allocate the corresponding G1
679 // regions and mark them as archive regions. We expect the ranges
680 // in ascending starting address order, without overlap.
681 for (size_t i = 0; i < count; i++) {
682 MemRegion curr_range = ranges[i];
683 HeapWord* start_address = curr_range.start();
684 size_t word_size = curr_range.word_size();
685 HeapWord* last_address = curr_range.last();
686 size_t commits = 0;
687
688 guarantee(reserved.contains(start_address) && reserved.contains(last_address),
689 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
690 p2i(start_address), p2i(last_address));
691 guarantee(start_address > prev_last_addr,
692 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
693 p2i(start_address), p2i(prev_last_addr));
694 prev_last_addr = last_address;
695
696 // Check for ranges that start in the same G1 region in which the previous
697 // range ended, and adjust the start address so we don't try to allocate
698 // the same region again. If the current range is entirely within that
699 // region, skip it, just adjusting the recorded top.
700 HeapRegion* start_region = _hrm.addr_to_region(start_address);
701 if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
702 start_address = start_region->end();
703 if (start_address > last_address) {
704 increase_used(word_size * HeapWordSize);
705 start_region->set_top(last_address + 1);
706 continue;
707 }
708 start_region->set_top(start_address);
709 curr_range = MemRegion(start_address, last_address + 1);
710 start_region = _hrm.addr_to_region(start_address);
711 }
712
713 // Perform the actual region allocation, exiting if it fails.
714 // Then note how much new space we have allocated.
715 if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) {
716 return false;
717 }
718 increase_used(word_size * HeapWordSize);
719 if (commits != 0) {
720 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
721 HeapRegion::GrainWords * HeapWordSize * commits);
722
723 }
724
725 // Mark each G1 region touched by the range as archive, add it to
726 // the old set, and set the allocation context and top.
727 HeapRegion* curr_region = _hrm.addr_to_region(start_address);
728 HeapRegion* last_region = _hrm.addr_to_region(last_address);
729 prev_last_region = last_region;
730
731 while (curr_region != NULL) {
732 assert(curr_region->is_empty() && !curr_region->is_pinned(),
733 "Region already in use (index %u)", curr_region->hrm_index());
734 curr_region->set_allocation_context(AllocationContext::system());
735 if (open) {
736 curr_region->set_open_archive();
737 } else {
738 curr_region->set_closed_archive();
739 }
740 _hr_printer.alloc(curr_region);
741 _old_set.add(curr_region);
742 HeapWord* top;
743 HeapRegion* next_region;
744 if (curr_region != last_region) {
745 top = curr_region->end();
746 next_region = _hrm.next_region_in_heap(curr_region);
747 } else {
748 top = last_address + 1;
749 next_region = NULL;
750 }
751 curr_region->set_top(top);
752 curr_region->set_first_dead(top);
753 curr_region->set_end_of_live(top);
754 curr_region = next_region;
755 }
756
757 // Notify mark-sweep of the archive
758 G1ArchiveAllocator::set_range_archive(curr_range, open);
759 }
760 return true;
761 }
762
763 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
764 assert(!is_init_completed(), "Expect to be called at JVM init time");
765 assert(ranges != NULL, "MemRegion array NULL");
766 assert(count != 0, "No MemRegions provided");
767 MemRegion reserved = _hrm.reserved();
768 HeapWord *prev_last_addr = NULL;
769 HeapRegion* prev_last_region = NULL;
770
771 // For each MemRegion, create filler objects, if needed, in the G1 regions
772 // that contain the address range. The address range actually within the
773 // MemRegion will not be modified. That is assumed to have been initialized
774 // elsewhere, probably via an mmap of archived heap data.
775 MutexLockerEx x(Heap_lock);
776 for (size_t i = 0; i < count; i++) {
777 HeapWord* start_address = ranges[i].start();
778 HeapWord* last_address = ranges[i].last();
779
780 assert(reserved.contains(start_address) && reserved.contains(last_address),
781 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
782 p2i(start_address), p2i(last_address));
783 assert(start_address > prev_last_addr,
784 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
785 p2i(start_address), p2i(prev_last_addr));
786
787 HeapRegion* start_region = _hrm.addr_to_region(start_address);
788 HeapRegion* last_region = _hrm.addr_to_region(last_address);
789 HeapWord* bottom_address = start_region->bottom();
790
791 // Check for a range beginning in the same region in which the
792 // previous one ended.
793 if (start_region == prev_last_region) {
794 bottom_address = prev_last_addr + 1;
795 }
796
797 // Verify that the regions were all marked as archive regions by
798 // alloc_archive_regions.
799 HeapRegion* curr_region = start_region;
800 while (curr_region != NULL) {
801 guarantee(curr_region->is_archive(),
802 "Expected archive region at index %u", curr_region->hrm_index());
803 if (curr_region != last_region) {
804 curr_region = _hrm.next_region_in_heap(curr_region);
805 } else {
806 curr_region = NULL;
807 }
808 }
809
810 prev_last_addr = last_address;
811 prev_last_region = last_region;
812
813 // Fill the memory below the allocated range with dummy object(s),
814 // if the region bottom does not match the range start, or if the previous
815 // range ended within the same G1 region, and there is a gap.
816 if (start_address != bottom_address) {
817 size_t fill_size = pointer_delta(start_address, bottom_address);
818 G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
819 increase_used(fill_size * HeapWordSize);
820 }
821 }
822 }
823
824 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size,
825 uint* gc_count_before_ret,
826 uint* gclocker_retry_count_ret) {
827 assert_heap_not_locked_and_not_at_safepoint();
828 assert(!is_humongous(word_size), "attempt_allocation() should not "
829 "be called for humongous allocation requests");
830
831 AllocationContext_t context = AllocationContext::current();
832 HeapWord* result = _allocator->attempt_allocation(word_size, context);
833
834 if (result == NULL) {
835 result = attempt_allocation_slow(word_size,
836 context,
837 gc_count_before_ret,
838 gclocker_retry_count_ret);
839 }
840 assert_heap_not_locked();
841 if (result != NULL) {
842 dirty_young_block(result, word_size);
843 }
844 return result;
845 }
846
847 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
848 assert(!is_init_completed(), "Expect to be called at JVM init time");
849 assert(ranges != NULL, "MemRegion array NULL");
850 assert(count != 0, "No MemRegions provided");
851 MemRegion reserved = _hrm.reserved();
852 HeapWord* prev_last_addr = NULL;
853 HeapRegion* prev_last_region = NULL;
854 size_t size_used = 0;
855 size_t uncommitted_regions = 0;
856
857 // For each Memregion, free the G1 regions that constitute it, and
858 // notify mark-sweep that the range is no longer to be considered 'archive.'
859 MutexLockerEx x(Heap_lock);
860 for (size_t i = 0; i < count; i++) {
861 HeapWord* start_address = ranges[i].start();
862 HeapWord* last_address = ranges[i].last();
863
864 assert(reserved.contains(start_address) && reserved.contains(last_address),
865 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
866 p2i(start_address), p2i(last_address));
867 assert(start_address > prev_last_addr,
868 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
869 p2i(start_address), p2i(prev_last_addr));
870 size_used += ranges[i].byte_size();
871 prev_last_addr = last_address;
872
873 HeapRegion* start_region = _hrm.addr_to_region(start_address);
874 HeapRegion* last_region = _hrm.addr_to_region(last_address);
875
876 // Check for ranges that start in the same G1 region in which the previous
877 // range ended, and adjust the start address so we don't try to free
878 // the same region again. If the current range is entirely within that
879 // region, skip it.
880 if (start_region == prev_last_region) {
881 start_address = start_region->end();
882 if (start_address > last_address) {
883 continue;
884 }
885 start_region = _hrm.addr_to_region(start_address);
886 }
887 prev_last_region = last_region;
888
889 // After verifying that each region was marked as an archive region by
890 // alloc_archive_regions, set it free and empty and uncommit it.
891 HeapRegion* curr_region = start_region;
892 while (curr_region != NULL) {
893 guarantee(curr_region->is_archive(),
894 "Expected archive region at index %u", curr_region->hrm_index());
895 uint curr_index = curr_region->hrm_index();
896 _old_set.remove(curr_region);
897 curr_region->set_free();
898 curr_region->set_top(curr_region->bottom());
899 if (curr_region != last_region) {
900 curr_region = _hrm.next_region_in_heap(curr_region);
901 } else {
902 curr_region = NULL;
903 }
904 _hrm.shrink_at(curr_index, 1);
905 uncommitted_regions++;
906 }
907
908 // Notify mark-sweep that this is no longer an archive range.
909 G1ArchiveAllocator::set_range_archive(ranges[i], false);
910 }
911
912 if (uncommitted_regions != 0) {
913 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
914 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
915 }
916 decrease_used(size_used);
917 }
918
919 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
920 uint* gc_count_before_ret,
921 uint* gclocker_retry_count_ret) {
922 // The structure of this method has a lot of similarities to
923 // attempt_allocation_slow(). The reason these two were not merged
924 // into a single one is that such a method would require several "if
925 // allocation is not humongous do this, otherwise do that"
926 // conditional paths which would obscure its flow. In fact, an early
927 // version of this code did use a unified method which was harder to
928 // follow and, as a result, it had subtle bugs that were hard to
929 // track down. So keeping these two methods separate allows each to
930 // be more readable. It will be good to keep these two in sync as
931 // much as possible.
932
933 assert_heap_not_locked_and_not_at_safepoint();
934 assert(is_humongous(word_size), "attempt_allocation_humongous() "
935 "should only be called for humongous allocations");
936
937 // Humongous objects can exhaust the heap quickly, so we should check if we
938 // need to start a marking cycle at each humongous object allocation. We do
939 // the check before we do the actual allocation. The reason for doing it
940 // before the allocation is that we avoid having to keep track of the newly
941 // allocated memory while we do a GC.
942 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
943 word_size)) {
944 collect(GCCause::_g1_humongous_allocation);
945 }
946
947 // We will loop until a) we manage to successfully perform the
948 // allocation or b) we successfully schedule a collection which
949 // fails to perform the allocation. b) is the only case when we'll
950 // return NULL.
951 HeapWord* result = NULL;
952 for (int try_count = 1; /* we'll return */; try_count += 1) {
953 bool should_try_gc;
954 uint gc_count_before;
955
956 {
957 MutexLockerEx x(Heap_lock);
958
959 // Given that humongous objects are not allocated in young
960 // regions, we'll first try to do the allocation without doing a
961 // collection hoping that there's enough space in the heap.
962 result = humongous_obj_allocate(word_size, AllocationContext::current());
963 if (result != NULL) {
964 size_t size_in_regions = humongous_obj_size_in_regions(word_size);
965 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
966 return result;
967 }
968
969 if (GCLocker::is_active_and_needs_gc()) {
970 should_try_gc = false;
971 } else {
972 // The GCLocker may not be active but the GCLocker initiated
973 // GC may not yet have been performed (GCLocker::needs_gc()
974 // returns true). In this case we do not try this GC and
975 // wait until the GCLocker initiated GC is performed, and
976 // then retry the allocation.
977 if (GCLocker::needs_gc()) {
978 should_try_gc = false;
979 } else {
980 // Read the GC count while still holding the Heap_lock.
981 gc_count_before = total_collections();
982 should_try_gc = true;
983 }
984 }
985 }
986
987 if (should_try_gc) {
988 // If we failed to allocate the humongous object, we should try to
989 // do a collection pause (if we're allowed) in case it reclaims
990 // enough space for the allocation to succeed after the pause.
991
992 bool succeeded;
993 result = do_collection_pause(word_size, gc_count_before, &succeeded,
994 GCCause::_g1_humongous_allocation);
995 if (result != NULL) {
996 assert(succeeded, "only way to get back a non-NULL result");
997 return result;
998 }
999
1000 if (succeeded) {
1001 // If we get here we successfully scheduled a collection which
1002 // failed to allocate. No point in trying to allocate
1003 // further. We'll just return NULL.
1004 MutexLockerEx x(Heap_lock);
1005 *gc_count_before_ret = total_collections();
1006 return NULL;
1007 }
1008 } else {
1009 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1010 MutexLockerEx x(Heap_lock);
1011 *gc_count_before_ret = total_collections();
1012 return NULL;
1013 }
1014 // The GCLocker is either active or the GCLocker initiated
1015 // GC has not yet been performed. Stall until it is and
1016 // then retry the allocation.
1017 GCLocker::stall_until_clear();
1018 (*gclocker_retry_count_ret) += 1;
1019 }
1020
1021 // We can reach here if we were unsuccessful in scheduling a
1022 // collection (because another thread beat us to it) or if we were
1023 // stalled due to the GC locker. In either can we should retry the
1024 // allocation attempt in case another thread successfully
1025 // performed a collection and reclaimed enough space. Give a
1026 // warning if we seem to be looping forever.
1027
1028 if ((QueuedAllocationWarningCount > 0) &&
1029 (try_count % QueuedAllocationWarningCount == 0)) {
1030 log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() "
1031 "retries %d times", try_count);
1032 }
1033 }
1034
1035 ShouldNotReachHere();
1036 return NULL;
1037 }
1038
1039 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1040 AllocationContext_t context,
1041 bool expect_null_mutator_alloc_region) {
1042 assert_at_safepoint(true /* should_be_vm_thread */);
1043 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region,
1044 "the current alloc region was unexpectedly found to be non-NULL");
1045
1046 if (!is_humongous(word_size)) {
1047 return _allocator->attempt_allocation_locked(word_size, context);
1048 } else {
1049 HeapWord* result = humongous_obj_allocate(word_size, context);
1050 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1051 collector_state()->set_initiate_conc_mark_if_possible(true);
1052 }
1053 return result;
1054 }
1055
1056 ShouldNotReachHere();
1057 }
1058
1059 class PostCompactionPrinterClosure: public HeapRegionClosure {
1060 private:
1061 G1HRPrinter* _hr_printer;
1062 public:
1063 bool doHeapRegion(HeapRegion* hr) {
1064 assert(!hr->is_young(), "not expecting to find young regions");
1065 _hr_printer->post_compaction(hr);
1066 return false;
1067 }
1068
1069 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1070 : _hr_printer(hr_printer) { }
1071 };
1072
1073 void G1CollectedHeap::print_hrm_post_compaction() {
1074 if (_hr_printer.is_active()) {
1075 PostCompactionPrinterClosure cl(hr_printer());
1076 heap_region_iterate(&cl);
1077 }
1078
1079 }
1080
1081 void G1CollectedHeap::abort_concurrent_cycle() {
1082 // Note: When we have a more flexible GC logging framework that
1083 // allows us to add optional attributes to a GC log record we
1084 // could consider timing and reporting how long we wait in the
1085 // following two methods.
1086 wait_while_free_regions_coming();
1087 // If we start the compaction before the CM threads finish
1088 // scanning the root regions we might trip them over as we'll
1089 // be moving objects / updating references. So let's wait until
1090 // they are done. By telling them to abort, they should complete
1091 // early.
1092 _cm->root_regions()->abort();
1093 _cm->root_regions()->wait_until_scan_finished();
1094 append_secondary_free_list_if_not_empty_with_lock();
1095
1096 // Disable discovery and empty the discovered lists
1097 // for the CM ref processor.
1098 ref_processor_cm()->disable_discovery();
1099 ref_processor_cm()->abandon_partial_discovery();
1100 ref_processor_cm()->verify_no_references_recorded();
1101
1102 // Abandon current iterations of concurrent marking and concurrent
1103 // refinement, if any are in progress.
1104 concurrent_mark()->abort();
1105 }
1106
1107 void G1CollectedHeap::prepare_heap_for_full_collection() {
1108 // Make sure we'll choose a new allocation region afterwards.
1109 _allocator->release_mutator_alloc_region();
1110 _allocator->abandon_gc_alloc_regions();
1111 g1_rem_set()->cleanupHRRS();
1112
1113 // We may have added regions to the current incremental collection
1114 // set between the last GC or pause and now. We need to clear the
1115 // incremental collection set and then start rebuilding it afresh
1116 // after this full GC.
1117 abandon_collection_set(collection_set());
1118
1119 tear_down_region_sets(false /* free_list_only */);
1120 collector_state()->set_gcs_are_young(true);
1121 }
1122
1123 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) {
1124 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1125 assert(used() == recalculate_used(), "Should be equal");
1126 _verifier->verify_region_sets_optional();
1127 _verifier->verify_before_gc();
1128 _verifier->check_bitmaps("Full GC Start");
1129 }
1130
1131 void G1CollectedHeap::prepare_heap_for_mutators() {
1132 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1133 ClassLoaderDataGraph::purge();
1134 MetaspaceAux::verify_metrics();
1135
1136 // Prepare heap for normal collections.
1137 assert(num_free_regions() == 0, "we should not have added any free regions");
1138 rebuild_region_sets(false /* free_list_only */);
1139 abort_refinement();
1140 resize_if_necessary_after_full_collection();
1141
1142 // Rebuild the strong code root lists for each region
1143 rebuild_strong_code_roots();
1144
1145 // Start a new incremental collection set for the next pause
1146 start_new_collection_set();
1147
1148 _allocator->init_mutator_alloc_region();
1149
1150 // Post collection state updates.
1151 MetaspaceGC::compute_new_size();
1152 }
1153
1154 void G1CollectedHeap::abort_refinement() {
1155 if (_hot_card_cache->use_cache()) {
1156 _hot_card_cache->reset_card_counts();
1157 _hot_card_cache->reset_hot_cache();
1158 }
1159
1160 // Discard all remembered set updates.
1161 JavaThread::dirty_card_queue_set().abandon_logs();
1162 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1163 }
1164
1165 void G1CollectedHeap::verify_after_full_collection() {
1166 check_gc_time_stamps();
1167 _hrm.verify_optional();
1168 _verifier->verify_region_sets_optional();
1169 _verifier->verify_after_gc();
1170 // Clear the previous marking bitmap, if needed for bitmap verification.
1171 // Note we cannot do this when we clear the next marking bitmap in
1172 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1173 // objects marked during a full GC against the previous bitmap.
1174 // But we need to clear it before calling check_bitmaps below since
1175 // the full GC has compacted objects and updated TAMS but not updated
1176 // the prev bitmap.
1177 if (G1VerifyBitmaps) {
1178 GCTraceTime(Debug, gc)("Clear Bitmap for Verification");
1179 _cm->clear_prev_bitmap(workers());
1180 }
1181 _verifier->check_bitmaps("Full GC End");
1182
1183 // At this point there should be no regions in the
1184 // entire heap tagged as young.
1185 assert(check_young_list_empty(), "young list should be empty at this point");
1186
1187 // Note: since we've just done a full GC, concurrent
1188 // marking is no longer active. Therefore we need not
1189 // re-enable reference discovery for the CM ref processor.
1190 // That will be done at the start of the next marking cycle.
1191 // We also know that the STW processor should no longer
1192 // discover any new references.
1193 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1194 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1195 ref_processor_stw()->verify_no_references_recorded();
1196 ref_processor_cm()->verify_no_references_recorded();
1197 }
1198
1199 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) {
1200 print_hrm_post_compaction();
1201 heap_transition->print();
1202 print_heap_after_gc();
1203 print_heap_regions();
1204 #ifdef TRACESPINNING
1205 ParallelTaskTerminator::print_termination_counts();
1206 #endif
1207 }
1208
1209 void G1CollectedHeap::do_full_collection_inner(G1FullGCScope* scope) {
1210 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1211 g1_policy()->record_full_collection_start();
1212
1213 print_heap_before_gc();
1214 print_heap_regions();
1215
1216 abort_concurrent_cycle();
1217 verify_before_full_collection(scope->is_explicit_gc());
1218
1219 gc_prologue(true);
1220 prepare_heap_for_full_collection();
1221
1222 G1SerialFullCollector serial(scope, ref_processor_stw());
1223 serial.prepare_collection();
1224 serial.collect();
1225 serial.complete_collection();
1226
1227 prepare_heap_for_mutators();
1228
1229 g1_policy()->record_full_collection_end();
1230 gc_epilogue(true);
1231
1232 // Post collection verification.
1233 verify_after_full_collection();
1234
1235 // Post collection logging.
1236 // We should do this after we potentially resize the heap so
1237 // that all the COMMIT / UNCOMMIT events are generated before
1238 // the compaction events.
1239 print_heap_after_full_collection(scope->heap_transition());
1240 }
1241
1242 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1243 bool clear_all_soft_refs) {
1244 assert_at_safepoint(true /* should_be_vm_thread */);
1245
1246 if (GCLocker::check_active_before_gc()) {
1247 // Full GC was not completed.
1248 return false;
1249 }
1250
1251 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1252 collector_policy()->should_clear_all_soft_refs();
1253
1254 G1FullGCScope scope(explicit_gc, do_clear_all_soft_refs);
1255 do_full_collection_inner(&scope);
1256
1257 // Full collection was successfully completed.
1258 return true;
1259 }
1260
1261 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1262 // Currently, there is no facility in the do_full_collection(bool) API to notify
1263 // the caller that the collection did not succeed (e.g., because it was locked
1264 // out by the GC locker). So, right now, we'll ignore the return value.
1265 bool dummy = do_full_collection(true, /* explicit_gc */
1266 clear_all_soft_refs);
1267 }
1268
1269 void G1CollectedHeap::resize_if_necessary_after_full_collection() {
1270 // Include bytes that will be pre-allocated to support collections, as "used".
1271 const size_t used_after_gc = used();
1272 const size_t capacity_after_gc = capacity();
1273 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1274
1275 // This is enforced in arguments.cpp.
1276 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1277 "otherwise the code below doesn't make sense");
1278
1279 // We don't have floating point command-line arguments
1280 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1281 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1282 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1283 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1284
1285 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1286 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1287
1288 // We have to be careful here as these two calculations can overflow
1289 // 32-bit size_t's.
1290 double used_after_gc_d = (double) used_after_gc;
1291 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1292 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1293
1294 // Let's make sure that they are both under the max heap size, which
1295 // by default will make them fit into a size_t.
1296 double desired_capacity_upper_bound = (double) max_heap_size;
1297 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1298 desired_capacity_upper_bound);
1299 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1300 desired_capacity_upper_bound);
1301
1302 // We can now safely turn them into size_t's.
1303 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1304 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1305
1306 // This assert only makes sense here, before we adjust them
1307 // with respect to the min and max heap size.
1308 assert(minimum_desired_capacity <= maximum_desired_capacity,
1309 "minimum_desired_capacity = " SIZE_FORMAT ", "
1310 "maximum_desired_capacity = " SIZE_FORMAT,
1311 minimum_desired_capacity, maximum_desired_capacity);
1312
1313 // Should not be greater than the heap max size. No need to adjust
1314 // it with respect to the heap min size as it's a lower bound (i.e.,
1315 // we'll try to make the capacity larger than it, not smaller).
1316 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1317 // Should not be less than the heap min size. No need to adjust it
1318 // with respect to the heap max size as it's an upper bound (i.e.,
1319 // we'll try to make the capacity smaller than it, not greater).
1320 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1321
1322 if (capacity_after_gc < minimum_desired_capacity) {
1323 // Don't expand unless it's significant
1324 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1325
1326 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). "
1327 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1328 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio);
1329
1330 expand(expand_bytes, _workers);
1331
1332 // No expansion, now see if we want to shrink
1333 } else if (capacity_after_gc > maximum_desired_capacity) {
1334 // Capacity too large, compute shrinking size
1335 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1336
1337 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). "
1338 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1339 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio);
1340
1341 shrink(shrink_bytes);
1342 }
1343 }
1344
1345 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1346 AllocationContext_t context,
1347 bool do_gc,
1348 bool clear_all_soft_refs,
1349 bool expect_null_mutator_alloc_region,
1350 bool* gc_succeeded) {
1351 *gc_succeeded = true;
1352 // Let's attempt the allocation first.
1353 HeapWord* result =
1354 attempt_allocation_at_safepoint(word_size,
1355 context,
1356 expect_null_mutator_alloc_region);
1357 if (result != NULL) {
1358 assert(*gc_succeeded, "sanity");
1359 return result;
1360 }
1361
1362 // In a G1 heap, we're supposed to keep allocation from failing by
1363 // incremental pauses. Therefore, at least for now, we'll favor
1364 // expansion over collection. (This might change in the future if we can
1365 // do something smarter than full collection to satisfy a failed alloc.)
1366 result = expand_and_allocate(word_size, context);
1367 if (result != NULL) {
1368 assert(*gc_succeeded, "sanity");
1369 return result;
1370 }
1371
1372 if (do_gc) {
1373 // Expansion didn't work, we'll try to do a Full GC.
1374 *gc_succeeded = do_full_collection(false, /* explicit_gc */
1375 clear_all_soft_refs);
1376 }
1377
1378 return NULL;
1379 }
1380
1381 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1382 AllocationContext_t context,
1383 bool* succeeded) {
1384 assert_at_safepoint(true /* should_be_vm_thread */);
1385
1386 // Attempts to allocate followed by Full GC.
1387 HeapWord* result =
1388 satisfy_failed_allocation_helper(word_size,
1389 context,
1390 true, /* do_gc */
1391 false, /* clear_all_soft_refs */
1392 false, /* expect_null_mutator_alloc_region */
1393 succeeded);
1394
1395 if (result != NULL || !*succeeded) {
1396 return result;
1397 }
1398
1399 // Attempts to allocate followed by Full GC that will collect all soft references.
1400 result = satisfy_failed_allocation_helper(word_size,
1401 context,
1402 true, /* do_gc */
1403 true, /* clear_all_soft_refs */
1404 true, /* expect_null_mutator_alloc_region */
1405 succeeded);
1406
1407 if (result != NULL || !*succeeded) {
1408 return result;
1409 }
1410
1411 // Attempts to allocate, no GC
1412 result = satisfy_failed_allocation_helper(word_size,
1413 context,
1414 false, /* do_gc */
1415 false, /* clear_all_soft_refs */
1416 true, /* expect_null_mutator_alloc_region */
1417 succeeded);
1418
1419 if (result != NULL) {
1420 assert(*succeeded, "sanity");
1421 return result;
1422 }
1423
1424 assert(!collector_policy()->should_clear_all_soft_refs(),
1425 "Flag should have been handled and cleared prior to this point");
1426
1427 // What else? We might try synchronous finalization later. If the total
1428 // space available is large enough for the allocation, then a more
1429 // complete compaction phase than we've tried so far might be
1430 // appropriate.
1431 assert(*succeeded, "sanity");
1432 return NULL;
1433 }
1434
1435 // Attempting to expand the heap sufficiently
1436 // to support an allocation of the given "word_size". If
1437 // successful, perform the allocation and return the address of the
1438 // allocated block, or else "NULL".
1439
1440 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1441 assert_at_safepoint(true /* should_be_vm_thread */);
1442
1443 _verifier->verify_region_sets_optional();
1444
1445 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1446 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1447 word_size * HeapWordSize);
1448
1449
1450 if (expand(expand_bytes, _workers)) {
1451 _hrm.verify_optional();
1452 _verifier->verify_region_sets_optional();
1453 return attempt_allocation_at_safepoint(word_size,
1454 context,
1455 false /* expect_null_mutator_alloc_region */);
1456 }
1457 return NULL;
1458 }
1459
1460 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) {
1461 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1462 aligned_expand_bytes = align_up(aligned_expand_bytes,
1463 HeapRegion::GrainBytes);
1464
1465 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B",
1466 expand_bytes, aligned_expand_bytes);
1467
1468 if (is_maximal_no_gc()) {
1469 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1470 return false;
1471 }
1472
1473 double expand_heap_start_time_sec = os::elapsedTime();
1474 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1475 assert(regions_to_expand > 0, "Must expand by at least one region");
1476
1477 uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers);
1478 if (expand_time_ms != NULL) {
1479 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1480 }
1481
1482 if (expanded_by > 0) {
1483 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1484 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1485 g1_policy()->record_new_heap_size(num_regions());
1486 } else {
1487 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1488
1489 // The expansion of the virtual storage space was unsuccessful.
1490 // Let's see if it was because we ran out of swap.
1491 if (G1ExitOnExpansionFailure &&
1492 _hrm.available() >= regions_to_expand) {
1493 // We had head room...
1494 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1495 }
1496 }
1497 return regions_to_expand > 0;
1498 }
1499
1500 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1501 size_t aligned_shrink_bytes =
1502 ReservedSpace::page_align_size_down(shrink_bytes);
1503 aligned_shrink_bytes = align_down(aligned_shrink_bytes,
1504 HeapRegion::GrainBytes);
1505 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1506
1507 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1508 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1509
1510
1511 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",
1512 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1513 if (num_regions_removed > 0) {
1514 g1_policy()->record_new_heap_size(num_regions());
1515 } else {
1516 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1517 }
1518 }
1519
1520 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1521 _verifier->verify_region_sets_optional();
1522
1523 // We should only reach here at the end of a Full GC which means we
1524 // should not not be holding to any GC alloc regions. The method
1525 // below will make sure of that and do any remaining clean up.
1526 _allocator->abandon_gc_alloc_regions();
1527
1528 // Instead of tearing down / rebuilding the free lists here, we
1529 // could instead use the remove_all_pending() method on free_list to
1530 // remove only the ones that we need to remove.
1531 tear_down_region_sets(true /* free_list_only */);
1532 shrink_helper(shrink_bytes);
1533 rebuild_region_sets(true /* free_list_only */);
1534
1535 _hrm.verify_optional();
1536 _verifier->verify_region_sets_optional();
1537 }
1538
1539 // Public methods.
1540
1541 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) :
1542 CollectedHeap(),
1543 _collector_policy(collector_policy),
1544 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1545 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1546 _g1_policy(create_g1_policy(_gc_timer_stw)),
1547 _collection_set(this, _g1_policy),
1548 _dirty_card_queue_set(false),
1549 _is_alive_closure_cm(this),
1550 _is_alive_closure_stw(this),
1551 _ref_processor_cm(NULL),
1552 _ref_processor_stw(NULL),
1553 _bot(NULL),
1554 _hot_card_cache(NULL),
1555 _g1_rem_set(NULL),
1556 _cg1r(NULL),
1557 _g1mm(NULL),
1558 _preserved_marks_set(true /* in_c_heap */),
1559 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1560 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1561 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1562 _humongous_reclaim_candidates(),
1563 _has_humongous_reclaim_candidates(false),
1564 _archive_allocator(NULL),
1565 _free_regions_coming(false),
1566 _gc_time_stamp(0),
1567 _summary_bytes_used(0),
1568 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1569 _old_evac_stats("Old", OldPLABSize, PLABWeight),
1570 _expand_heap_after_alloc_failure(true),
1571 _old_marking_cycles_started(0),
1572 _old_marking_cycles_completed(0),
1573 _in_cset_fast_test() {
1574
1575 _workers = new WorkGang("GC Thread", ParallelGCThreads,
1576 /* are_GC_task_threads */true,
1577 /* are_ConcurrentGC_threads */false);
1578 _workers->initialize_workers();
1579 _verifier = new G1HeapVerifier(this);
1580
1581 _allocator = G1Allocator::create_allocator(this);
1582
1583 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics());
1584
1585 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1586
1587 // Override the default _filler_array_max_size so that no humongous filler
1588 // objects are created.
1589 _filler_array_max_size = _humongous_object_threshold_in_words;
1590
1591 uint n_queues = ParallelGCThreads;
1592 _task_queues = new RefToScanQueueSet(n_queues);
1593
1594 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1595
1596 for (uint i = 0; i < n_queues; i++) {
1597 RefToScanQueue* q = new RefToScanQueue();
1598 q->initialize();
1599 _task_queues->register_queue(i, q);
1600 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1601 }
1602
1603 // Initialize the G1EvacuationFailureALot counters and flags.
1604 NOT_PRODUCT(reset_evacuation_should_fail();)
1605
1606 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1607 }
1608
1609 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1610 size_t size,
1611 size_t translation_factor) {
1612 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1613 // Allocate a new reserved space, preferring to use large pages.
1614 ReservedSpace rs(size, preferred_page_size);
1615 G1RegionToSpaceMapper* result =
1616 G1RegionToSpaceMapper::create_mapper(rs,
1617 size,
1618 rs.alignment(),
1619 HeapRegion::GrainBytes,
1620 translation_factor,
1621 mtGC);
1622
1623 os::trace_page_sizes_for_requested_size(description,
1624 size,
1625 preferred_page_size,
1626 rs.alignment(),
1627 rs.base(),
1628 rs.size());
1629
1630 return result;
1631 }
1632
1633 jint G1CollectedHeap::initialize_concurrent_refinement() {
1634 jint ecode = JNI_OK;
1635 _cg1r = ConcurrentG1Refine::create(&ecode);
1636 return ecode;
1637 }
1638
1639 jint G1CollectedHeap::initialize() {
1640 CollectedHeap::pre_initialize();
1641 os::enable_vtime();
1642
1643 // Necessary to satisfy locking discipline assertions.
1644
1645 MutexLocker x(Heap_lock);
1646
1647 // While there are no constraints in the GC code that HeapWordSize
1648 // be any particular value, there are multiple other areas in the
1649 // system which believe this to be true (e.g. oop->object_size in some
1650 // cases incorrectly returns the size in wordSize units rather than
1651 // HeapWordSize).
1652 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1653
1654 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1655 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1656 size_t heap_alignment = collector_policy()->heap_alignment();
1657
1658 // Ensure that the sizes are properly aligned.
1659 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1660 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1661 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1662
1663 // Reserve the maximum.
1664
1665 // When compressed oops are enabled, the preferred heap base
1666 // is calculated by subtracting the requested size from the
1667 // 32Gb boundary and using the result as the base address for
1668 // heap reservation. If the requested size is not aligned to
1669 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1670 // into the ReservedHeapSpace constructor) then the actual
1671 // base of the reserved heap may end up differing from the
1672 // address that was requested (i.e. the preferred heap base).
1673 // If this happens then we could end up using a non-optimal
1674 // compressed oops mode.
1675
1676 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1677 heap_alignment);
1678
1679 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1680
1681 // Create the barrier set for the entire reserved region.
1682 G1SATBCardTableLoggingModRefBS* bs
1683 = new G1SATBCardTableLoggingModRefBS(reserved_region());
1684 bs->initialize();
1685 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity");
1686 set_barrier_set(bs);
1687
1688 // Create the hot card cache.
1689 _hot_card_cache = new G1HotCardCache(this);
1690
1691 // Carve out the G1 part of the heap.
1692 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1693 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
1694 G1RegionToSpaceMapper* heap_storage =
1695 G1RegionToSpaceMapper::create_mapper(g1_rs,
1696 g1_rs.size(),
1697 page_size,
1698 HeapRegion::GrainBytes,
1699 1,
1700 mtJavaHeap);
1701 os::trace_page_sizes("Heap",
1702 collector_policy()->min_heap_byte_size(),
1703 max_byte_size,
1704 page_size,
1705 heap_rs.base(),
1706 heap_rs.size());
1707 heap_storage->set_mapping_changed_listener(&_listener);
1708
1709 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1710 G1RegionToSpaceMapper* bot_storage =
1711 create_aux_memory_mapper("Block Offset Table",
1712 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1713 G1BlockOffsetTable::heap_map_factor());
1714
1715 G1RegionToSpaceMapper* cardtable_storage =
1716 create_aux_memory_mapper("Card Table",
1717 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize),
1718 G1SATBCardTableLoggingModRefBS::heap_map_factor());
1719
1720 G1RegionToSpaceMapper* card_counts_storage =
1721 create_aux_memory_mapper("Card Counts Table",
1722 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1723 G1CardCounts::heap_map_factor());
1724
1725 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1726 G1RegionToSpaceMapper* prev_bitmap_storage =
1727 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1728 G1RegionToSpaceMapper* next_bitmap_storage =
1729 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1730
1731 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1732 g1_barrier_set()->initialize(cardtable_storage);
1733 // Do later initialization work for concurrent refinement.
1734 _hot_card_cache->initialize(card_counts_storage);
1735
1736 // 6843694 - ensure that the maximum region index can fit
1737 // in the remembered set structures.
1738 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1739 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1740
1741 // Also create a G1 rem set.
1742 _g1_rem_set = new G1RemSet(this, g1_barrier_set(), _hot_card_cache);
1743 _g1_rem_set->initialize(max_capacity(), max_regions());
1744
1745 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1746 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1747 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1748 "too many cards per region");
1749
1750 FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1751
1752 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1753
1754 {
1755 HeapWord* start = _hrm.reserved().start();
1756 HeapWord* end = _hrm.reserved().end();
1757 size_t granularity = HeapRegion::GrainBytes;
1758
1759 _in_cset_fast_test.initialize(start, end, granularity);
1760 _humongous_reclaim_candidates.initialize(start, end, granularity);
1761 }
1762
1763 // Create the G1ConcurrentMark data structure and thread.
1764 // (Must do this late, so that "max_regions" is defined.)
1765 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1766 if (_cm == NULL || !_cm->completed_initialization()) {
1767 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
1768 return JNI_ENOMEM;
1769 }
1770 _cmThread = _cm->cmThread();
1771
1772 // Now expand into the initial heap size.
1773 if (!expand(init_byte_size, _workers)) {
1774 vm_shutdown_during_initialization("Failed to allocate initial heap.");
1775 return JNI_ENOMEM;
1776 }
1777
1778 // Perform any initialization actions delegated to the policy.
1779 g1_policy()->init(this, &_collection_set);
1780
1781 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1782 SATB_Q_FL_lock,
1783 G1SATBProcessCompletedThreshold,
1784 Shared_SATB_Q_lock);
1785
1786 jint ecode = initialize_concurrent_refinement();
1787 if (ecode != JNI_OK) {
1788 return ecode;
1789 }
1790
1791 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1792 DirtyCardQ_FL_lock,
1793 (int)concurrent_g1_refine()->yellow_zone(),
1794 (int)concurrent_g1_refine()->red_zone(),
1795 Shared_DirtyCardQ_lock,
1796 NULL, // fl_owner
1797 true); // init_free_ids
1798
1799 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1800 DirtyCardQ_FL_lock,
1801 -1, // never trigger processing
1802 -1, // no limit on length
1803 Shared_DirtyCardQ_lock,
1804 &JavaThread::dirty_card_queue_set());
1805
1806 // Here we allocate the dummy HeapRegion that is required by the
1807 // G1AllocRegion class.
1808 HeapRegion* dummy_region = _hrm.get_dummy_region();
1809
1810 // We'll re-use the same region whether the alloc region will
1811 // require BOT updates or not and, if it doesn't, then a non-young
1812 // region will complain that it cannot support allocations without
1813 // BOT updates. So we'll tag the dummy region as eden to avoid that.
1814 dummy_region->set_eden();
1815 // Make sure it's full.
1816 dummy_region->set_top(dummy_region->end());
1817 G1AllocRegion::setup(this, dummy_region);
1818
1819 _allocator->init_mutator_alloc_region();
1820
1821 // Do create of the monitoring and management support so that
1822 // values in the heap have been properly initialized.
1823 _g1mm = new G1MonitoringSupport(this);
1824
1825 G1StringDedup::initialize();
1826
1827 _preserved_marks_set.init(ParallelGCThreads);
1828
1829 _collection_set.initialize(max_regions());
1830
1831 return JNI_OK;
1832 }
1833
1834 void G1CollectedHeap::stop() {
1835 // Stop all concurrent threads. We do this to make sure these threads
1836 // do not continue to execute and access resources (e.g. logging)
1837 // that are destroyed during shutdown.
1838 _cg1r->stop();
1839 _cmThread->stop();
1840 if (G1StringDedup::is_enabled()) {
1841 G1StringDedup::stop();
1842 }
1843 }
1844
1845 void G1CollectedHeap::safepoint_synchronize_begin() {
1846 SuspendibleThreadSet::synchronize();
1847 }
1848
1849 void G1CollectedHeap::safepoint_synchronize_end() {
1850 SuspendibleThreadSet::desynchronize();
1851 }
1852
1853 size_t G1CollectedHeap::conservative_max_heap_alignment() {
1854 return HeapRegion::max_region_size();
1855 }
1856
1857 void G1CollectedHeap::post_initialize() {
1858 ref_processing_init();
1859 }
1860
1861 void G1CollectedHeap::ref_processing_init() {
1862 // Reference processing in G1 currently works as follows:
1863 //
1864 // * There are two reference processor instances. One is
1865 // used to record and process discovered references
1866 // during concurrent marking; the other is used to
1867 // record and process references during STW pauses
1868 // (both full and incremental).
1869 // * Both ref processors need to 'span' the entire heap as
1870 // the regions in the collection set may be dotted around.
1871 //
1872 // * For the concurrent marking ref processor:
1873 // * Reference discovery is enabled at initial marking.
1874 // * Reference discovery is disabled and the discovered
1875 // references processed etc during remarking.
1876 // * Reference discovery is MT (see below).
1877 // * Reference discovery requires a barrier (see below).
1878 // * Reference processing may or may not be MT
1879 // (depending on the value of ParallelRefProcEnabled
1880 // and ParallelGCThreads).
1881 // * A full GC disables reference discovery by the CM
1882 // ref processor and abandons any entries on it's
1883 // discovered lists.
1884 //
1885 // * For the STW processor:
1886 // * Non MT discovery is enabled at the start of a full GC.
1887 // * Processing and enqueueing during a full GC is non-MT.
1888 // * During a full GC, references are processed after marking.
1889 //
1890 // * Discovery (may or may not be MT) is enabled at the start
1891 // of an incremental evacuation pause.
1892 // * References are processed near the end of a STW evacuation pause.
1893 // * For both types of GC:
1894 // * Discovery is atomic - i.e. not concurrent.
1895 // * Reference discovery will not need a barrier.
1896
1897 MemRegion mr = reserved_region();
1898
1899 bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1);
1900
1901 // Concurrent Mark ref processor
1902 _ref_processor_cm =
1903 new ReferenceProcessor(mr, // span
1904 mt_processing,
1905 // mt processing
1906 ParallelGCThreads,
1907 // degree of mt processing
1908 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
1909 // mt discovery
1910 MAX2(ParallelGCThreads, ConcGCThreads),
1911 // degree of mt discovery
1912 false,
1913 // Reference discovery is not atomic
1914 &_is_alive_closure_cm);
1915 // is alive closure
1916 // (for efficiency/performance)
1917
1918 // STW ref processor
1919 _ref_processor_stw =
1920 new ReferenceProcessor(mr, // span
1921 mt_processing,
1922 // mt processing
1923 ParallelGCThreads,
1924 // degree of mt processing
1925 (ParallelGCThreads > 1),
1926 // mt discovery
1927 ParallelGCThreads,
1928 // degree of mt discovery
1929 true,
1930 // Reference discovery is atomic
1931 &_is_alive_closure_stw);
1932 // is alive closure
1933 // (for efficiency/performance)
1934 }
1935
1936 CollectorPolicy* G1CollectedHeap::collector_policy() const {
1937 return _collector_policy;
1938 }
1939
1940 size_t G1CollectedHeap::capacity() const {
1941 return _hrm.length() * HeapRegion::GrainBytes;
1942 }
1943
1944 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
1945 hr->reset_gc_time_stamp();
1946 }
1947
1948 #ifndef PRODUCT
1949
1950 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
1951 private:
1952 unsigned _gc_time_stamp;
1953 bool _failures;
1954
1955 public:
1956 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
1957 _gc_time_stamp(gc_time_stamp), _failures(false) { }
1958
1959 virtual bool doHeapRegion(HeapRegion* hr) {
1960 unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
1961 if (_gc_time_stamp != region_gc_time_stamp) {
1962 log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr),
1963 region_gc_time_stamp, _gc_time_stamp);
1964 _failures = true;
1965 }
1966 return false;
1967 }
1968
1969 bool failures() { return _failures; }
1970 };
1971
1972 void G1CollectedHeap::check_gc_time_stamps() {
1973 CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
1974 heap_region_iterate(&cl);
1975 guarantee(!cl.failures(), "all GC time stamps should have been reset");
1976 }
1977 #endif // PRODUCT
1978
1979 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) {
1980 _hot_card_cache->drain(cl, worker_i);
1981 }
1982
1983 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) {
1984 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
1985 size_t n_completed_buffers = 0;
1986 while (dcqs.apply_closure_during_gc(cl, worker_i)) {
1987 n_completed_buffers++;
1988 }
1989 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
1990 dcqs.clear_n_completed_buffers();
1991 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
1992 }
1993
1994 // Computes the sum of the storage used by the various regions.
1995 size_t G1CollectedHeap::used() const {
1996 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
1997 if (_archive_allocator != NULL) {
1998 result += _archive_allocator->used();
1999 }
2000 return result;
2001 }
2002
2003 size_t G1CollectedHeap::used_unlocked() const {
2004 return _summary_bytes_used;
2005 }
2006
2007 class SumUsedClosure: public HeapRegionClosure {
2008 size_t _used;
2009 public:
2010 SumUsedClosure() : _used(0) {}
2011 bool doHeapRegion(HeapRegion* r) {
2012 _used += r->used();
2013 return false;
2014 }
2015 size_t result() { return _used; }
2016 };
2017
2018 size_t G1CollectedHeap::recalculate_used() const {
2019 double recalculate_used_start = os::elapsedTime();
2020
2021 SumUsedClosure blk;
2022 heap_region_iterate(&blk);
2023
2024 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2025 return blk.result();
2026 }
2027
2028 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
2029 switch (cause) {
2030 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2031 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent;
2032 case GCCause::_update_allocation_context_stats_inc: return true;
2033 case GCCause::_wb_conc_mark: return true;
2034 default : return false;
2035 }
2036 }
2037
2038 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2039 switch (cause) {
2040 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2041 case GCCause::_g1_humongous_allocation: return true;
2042 default: return is_user_requested_concurrent_full_gc(cause);
2043 }
2044 }
2045
2046 #ifndef PRODUCT
2047 void G1CollectedHeap::allocate_dummy_regions() {
2048 // Let's fill up most of the region
2049 size_t word_size = HeapRegion::GrainWords - 1024;
2050 // And as a result the region we'll allocate will be humongous.
2051 guarantee(is_humongous(word_size), "sanity");
2052
2053 // _filler_array_max_size is set to humongous object threshold
2054 // but temporarily change it to use CollectedHeap::fill_with_object().
2055 SizeTFlagSetting fs(_filler_array_max_size, word_size);
2056
2057 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2058 // Let's use the existing mechanism for the allocation
2059 HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2060 AllocationContext::system());
2061 if (dummy_obj != NULL) {
2062 MemRegion mr(dummy_obj, word_size);
2063 CollectedHeap::fill_with_object(mr);
2064 } else {
2065 // If we can't allocate once, we probably cannot allocate
2066 // again. Let's get out of the loop.
2067 break;
2068 }
2069 }
2070 }
2071 #endif // !PRODUCT
2072
2073 void G1CollectedHeap::increment_old_marking_cycles_started() {
2074 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2075 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2076 "Wrong marking cycle count (started: %d, completed: %d)",
2077 _old_marking_cycles_started, _old_marking_cycles_completed);
2078
2079 _old_marking_cycles_started++;
2080 }
2081
2082 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2083 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2084
2085 // We assume that if concurrent == true, then the caller is a
2086 // concurrent thread that was joined the Suspendible Thread
2087 // Set. If there's ever a cheap way to check this, we should add an
2088 // assert here.
2089
2090 // Given that this method is called at the end of a Full GC or of a
2091 // concurrent cycle, and those can be nested (i.e., a Full GC can
2092 // interrupt a concurrent cycle), the number of full collections
2093 // completed should be either one (in the case where there was no
2094 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2095 // behind the number of full collections started.
2096
2097 // This is the case for the inner caller, i.e. a Full GC.
2098 assert(concurrent ||
2099 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2100 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2101 "for inner caller (Full GC): _old_marking_cycles_started = %u "
2102 "is inconsistent with _old_marking_cycles_completed = %u",
2103 _old_marking_cycles_started, _old_marking_cycles_completed);
2104
2105 // This is the case for the outer caller, i.e. the concurrent cycle.
2106 assert(!concurrent ||
2107 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2108 "for outer caller (concurrent cycle): "
2109 "_old_marking_cycles_started = %u "
2110 "is inconsistent with _old_marking_cycles_completed = %u",
2111 _old_marking_cycles_started, _old_marking_cycles_completed);
2112
2113 _old_marking_cycles_completed += 1;
2114
2115 // We need to clear the "in_progress" flag in the CM thread before
2116 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2117 // is set) so that if a waiter requests another System.gc() it doesn't
2118 // incorrectly see that a marking cycle is still in progress.
2119 if (concurrent) {
2120 _cmThread->set_idle();
2121 }
2122
2123 // This notify_all() will ensure that a thread that called
2124 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2125 // and it's waiting for a full GC to finish will be woken up. It is
2126 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2127 FullGCCount_lock->notify_all();
2128 }
2129
2130 void G1CollectedHeap::collect(GCCause::Cause cause) {
2131 assert_heap_not_locked();
2132
2133 uint gc_count_before;
2134 uint old_marking_count_before;
2135 uint full_gc_count_before;
2136 bool retry_gc;
2137
2138 do {
2139 retry_gc = false;
2140
2141 {
2142 MutexLocker ml(Heap_lock);
2143
2144 // Read the GC count while holding the Heap_lock
2145 gc_count_before = total_collections();
2146 full_gc_count_before = total_full_collections();
2147 old_marking_count_before = _old_marking_cycles_started;
2148 }
2149
2150 if (should_do_concurrent_full_gc(cause)) {
2151 // Schedule an initial-mark evacuation pause that will start a
2152 // concurrent cycle. We're setting word_size to 0 which means that
2153 // we are not requesting a post-GC allocation.
2154 VM_G1IncCollectionPause op(gc_count_before,
2155 0, /* word_size */
2156 true, /* should_initiate_conc_mark */
2157 g1_policy()->max_pause_time_ms(),
2158 cause);
2159 op.set_allocation_context(AllocationContext::current());
2160
2161 VMThread::execute(&op);
2162 if (!op.pause_succeeded()) {
2163 if (old_marking_count_before == _old_marking_cycles_started) {
2164 retry_gc = op.should_retry_gc();
2165 } else {
2166 // A Full GC happened while we were trying to schedule the
2167 // initial-mark GC. No point in starting a new cycle given
2168 // that the whole heap was collected anyway.
2169 }
2170
2171 if (retry_gc) {
2172 if (GCLocker::is_active_and_needs_gc()) {
2173 GCLocker::stall_until_clear();
2174 }
2175 }
2176 }
2177 } else {
2178 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2179 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2180
2181 // Schedule a standard evacuation pause. We're setting word_size
2182 // to 0 which means that we are not requesting a post-GC allocation.
2183 VM_G1IncCollectionPause op(gc_count_before,
2184 0, /* word_size */
2185 false, /* should_initiate_conc_mark */
2186 g1_policy()->max_pause_time_ms(),
2187 cause);
2188 VMThread::execute(&op);
2189 } else {
2190 // Schedule a Full GC.
2191 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2192 VMThread::execute(&op);
2193 }
2194 }
2195 } while (retry_gc);
2196 }
2197
2198 bool G1CollectedHeap::is_in(const void* p) const {
2199 if (_hrm.reserved().contains(p)) {
2200 // Given that we know that p is in the reserved space,
2201 // heap_region_containing() should successfully
2202 // return the containing region.
2203 HeapRegion* hr = heap_region_containing(p);
2204 return hr->is_in(p);
2205 } else {
2206 return false;
2207 }
2208 }
2209
2210 #ifdef ASSERT
2211 bool G1CollectedHeap::is_in_exact(const void* p) const {
2212 bool contains = reserved_region().contains(p);
2213 bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2214 if (contains && available) {
2215 return true;
2216 } else {
2217 return false;
2218 }
2219 }
2220 #endif
2221
2222 // Iteration functions.
2223
2224 // Iterates an ObjectClosure over all objects within a HeapRegion.
2225
2226 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2227 ObjectClosure* _cl;
2228 public:
2229 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2230 bool doHeapRegion(HeapRegion* r) {
2231 if (!r->is_continues_humongous()) {
2232 r->object_iterate(_cl);
2233 }
2234 return false;
2235 }
2236 };
2237
2238 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2239 IterateObjectClosureRegionClosure blk(cl);
2240 heap_region_iterate(&blk);
2241 }
2242
2243 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2244 _hrm.iterate(cl);
2245 }
2246
2247 void G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl,
2248 uint worker_id,
2249 HeapRegionClaimer *hrclaimer) const {
2250 _hrm.par_iterate(cl, worker_id, hrclaimer);
2251 }
2252
2253 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2254 _collection_set.iterate(cl);
2255 }
2256
2257 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) {
2258 _collection_set.iterate_from(cl, worker_id, workers()->active_workers());
2259 }
2260
2261 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2262 HeapRegion* result = _hrm.next_region_in_heap(from);
2263 while (result != NULL && result->is_pinned()) {
2264 result = _hrm.next_region_in_heap(result);
2265 }
2266 return result;
2267 }
2268
2269 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2270 HeapRegion* hr = heap_region_containing(addr);
2271 return hr->block_start(addr);
2272 }
2273
2274 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2275 HeapRegion* hr = heap_region_containing(addr);
2276 return hr->block_size(addr);
2277 }
2278
2279 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2280 HeapRegion* hr = heap_region_containing(addr);
2281 return hr->block_is_obj(addr);
2282 }
2283
2284 bool G1CollectedHeap::supports_tlab_allocation() const {
2285 return true;
2286 }
2287
2288 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2289 return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2290 }
2291
2292 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2293 return _eden.length() * HeapRegion::GrainBytes;
2294 }
2295
2296 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2297 // must be equal to the humongous object limit.
2298 size_t G1CollectedHeap::max_tlab_size() const {
2299 return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
2300 }
2301
2302 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2303 AllocationContext_t context = AllocationContext::current();
2304 return _allocator->unsafe_max_tlab_alloc(context);
2305 }
2306
2307 size_t G1CollectedHeap::max_capacity() const {
2308 return _hrm.reserved().byte_size();
2309 }
2310
2311 jlong G1CollectedHeap::millis_since_last_gc() {
2312 // See the notes in GenCollectedHeap::millis_since_last_gc()
2313 // for more information about the implementation.
2314 jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) -
2315 _g1_policy->collection_pause_end_millis();
2316 if (ret_val < 0) {
2317 log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
2318 ". returning zero instead.", ret_val);
2319 return 0;
2320 }
2321 return ret_val;
2322 }
2323
2324 void G1CollectedHeap::prepare_for_verify() {
2325 _verifier->prepare_for_verify();
2326 }
2327
2328 void G1CollectedHeap::verify(VerifyOption vo) {
2329 _verifier->verify(vo);
2330 }
2331
2332 bool G1CollectedHeap::supports_concurrent_phase_control() const {
2333 return true;
2334 }
2335
2336 const char* const* G1CollectedHeap::concurrent_phases() const {
2337 return _cmThread->concurrent_phases();
2338 }
2339
2340 bool G1CollectedHeap::request_concurrent_phase(const char* phase) {
2341 return _cmThread->request_concurrent_phase(phase);
2342 }
2343
2344 class PrintRegionClosure: public HeapRegionClosure {
2345 outputStream* _st;
2346 public:
2347 PrintRegionClosure(outputStream* st) : _st(st) {}
2348 bool doHeapRegion(HeapRegion* r) {
2349 r->print_on(_st);
2350 return false;
2351 }
2352 };
2353
2354 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2355 const HeapRegion* hr,
2356 const VerifyOption vo) const {
2357 switch (vo) {
2358 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2359 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2360 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked() && !hr->is_archive();
2361 default: ShouldNotReachHere();
2362 }
2363 return false; // keep some compilers happy
2364 }
2365
2366 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2367 const VerifyOption vo) const {
2368 switch (vo) {
2369 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2370 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2371 case VerifyOption_G1UseMarkWord: {
2372 HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj);
2373 return !obj->is_gc_marked() && !hr->is_archive();
2374 }
2375 default: ShouldNotReachHere();
2376 }
2377 return false; // keep some compilers happy
2378 }
2379
2380 void G1CollectedHeap::print_heap_regions() const {
2381 LogTarget(Trace, gc, heap, region) lt;
2382 if (lt.is_enabled()) {
2383 LogStream ls(lt);
2384 print_regions_on(&ls);
2385 }
2386 }
2387
2388 void G1CollectedHeap::print_on(outputStream* st) const {
2389 st->print(" %-20s", "garbage-first heap");
2390 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2391 capacity()/K, used_unlocked()/K);
2392 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")",
2393 p2i(_hrm.reserved().start()),
2394 p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords),
2395 p2i(_hrm.reserved().end()));
2396 st->cr();
2397 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2398 uint young_regions = young_regions_count();
2399 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2400 (size_t) young_regions * HeapRegion::GrainBytes / K);
2401 uint survivor_regions = survivor_regions_count();
2402 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2403 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2404 st->cr();
2405 MetaspaceAux::print_on(st);
2406 }
2407
2408 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2409 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2410 "HS=humongous(starts), HC=humongous(continues), "
2411 "CS=collection set, F=free, A=archive, TS=gc time stamp, "
2412 "AC=allocation context, "
2413 "TAMS=top-at-mark-start (previous, next)");
2414 PrintRegionClosure blk(st);
2415 heap_region_iterate(&blk);
2416 }
2417
2418 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2419 print_on(st);
2420
2421 // Print the per-region information.
2422 print_regions_on(st);
2423 }
2424
2425 void G1CollectedHeap::print_on_error(outputStream* st) const {
2426 this->CollectedHeap::print_on_error(st);
2427
2428 if (_cm != NULL) {
2429 st->cr();
2430 _cm->print_on_error(st);
2431 }
2432 }
2433
2434 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2435 workers()->print_worker_threads_on(st);
2436 _cmThread->print_on(st);
2437 st->cr();
2438 _cm->print_worker_threads_on(st);
2439 _cg1r->print_worker_threads_on(st); // also prints the sample thread
2440 if (G1StringDedup::is_enabled()) {
2441 G1StringDedup::print_worker_threads_on(st);
2442 }
2443 }
2444
2445 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2446 workers()->threads_do(tc);
2447 tc->do_thread(_cmThread);
2448 _cm->threads_do(tc);
2449 _cg1r->threads_do(tc); // also iterates over the sample thread
2450 if (G1StringDedup::is_enabled()) {
2451 G1StringDedup::threads_do(tc);
2452 }
2453 }
2454
2455 void G1CollectedHeap::print_tracing_info() const {
2456 g1_rem_set()->print_summary_info();
2457 concurrent_mark()->print_summary_info();
2458 }
2459
2460 #ifndef PRODUCT
2461 // Helpful for debugging RSet issues.
2462
2463 class PrintRSetsClosure : public HeapRegionClosure {
2464 private:
2465 const char* _msg;
2466 size_t _occupied_sum;
2467
2468 public:
2469 bool doHeapRegion(HeapRegion* r) {
2470 HeapRegionRemSet* hrrs = r->rem_set();
2471 size_t occupied = hrrs->occupied();
2472 _occupied_sum += occupied;
2473
2474 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2475 if (occupied == 0) {
2476 tty->print_cr(" RSet is empty");
2477 } else {
2478 hrrs->print();
2479 }
2480 tty->print_cr("----------");
2481 return false;
2482 }
2483
2484 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2485 tty->cr();
2486 tty->print_cr("========================================");
2487 tty->print_cr("%s", msg);
2488 tty->cr();
2489 }
2490
2491 ~PrintRSetsClosure() {
2492 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2493 tty->print_cr("========================================");
2494 tty->cr();
2495 }
2496 };
2497
2498 void G1CollectedHeap::print_cset_rsets() {
2499 PrintRSetsClosure cl("Printing CSet RSets");
2500 collection_set_iterate(&cl);
2501 }
2502
2503 void G1CollectedHeap::print_all_rsets() {
2504 PrintRSetsClosure cl("Printing All RSets");;
2505 heap_region_iterate(&cl);
2506 }
2507 #endif // PRODUCT
2508
2509 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2510
2511 size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes;
2512 size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes;
2513 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2514
2515 size_t eden_capacity_bytes =
2516 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2517
2518 VirtualSpaceSummary heap_summary = create_heap_space_summary();
2519 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2520 eden_capacity_bytes, survivor_used_bytes, num_regions());
2521 }
2522
2523 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2524 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2525 stats->unused(), stats->used(), stats->region_end_waste(),
2526 stats->regions_filled(), stats->direct_allocated(),
2527 stats->failure_used(), stats->failure_waste());
2528 }
2529
2530 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2531 const G1HeapSummary& heap_summary = create_g1_heap_summary();
2532 gc_tracer->report_gc_heap_summary(when, heap_summary);
2533
2534 const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2535 gc_tracer->report_metaspace_summary(when, metaspace_summary);
2536 }
2537
2538 G1CollectedHeap* G1CollectedHeap::heap() {
2539 CollectedHeap* heap = Universe::heap();
2540 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2541 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap");
2542 return (G1CollectedHeap*)heap;
2543 }
2544
2545 void G1CollectedHeap::gc_prologue(bool full) {
2546 // always_do_update_barrier = false;
2547 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2548
2549 // This summary needs to be printed before incrementing total collections.
2550 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2551
2552 // Update common counters.
2553 increment_total_collections(full /* full gc */);
2554 if (full) {
2555 increment_old_marking_cycles_started();
2556 reset_gc_time_stamp();
2557 } else {
2558 increment_gc_time_stamp();
2559 }
2560
2561 // Fill TLAB's and such
2562 double start = os::elapsedTime();
2563 accumulate_statistics_all_tlabs();
2564 ensure_parsability(true);
2565 g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2566 }
2567
2568 void G1CollectedHeap::gc_epilogue(bool full) {
2569 // Update common counters.
2570 if (full) {
2571 // Update the number of full collections that have been completed.
2572 increment_old_marking_cycles_completed(false /* concurrent */);
2573 }
2574
2575 // We are at the end of the GC. Total collections has already been increased.
2576 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2577
2578 // FIXME: what is this about?
2579 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2580 // is set.
2581 #if defined(COMPILER2) || INCLUDE_JVMCI
2582 assert(DerivedPointerTable::is_empty(), "derived pointer present");
2583 #endif
2584 // always_do_update_barrier = true;
2585
2586 double start = os::elapsedTime();
2587 resize_all_tlabs();
2588 g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2589
2590 allocation_context_stats().update(full);
2591
2592 MemoryService::track_memory_usage();
2593 // We have just completed a GC. Update the soft reference
2594 // policy with the new heap occupancy
2595 Universe::update_heap_info_at_gc();
2596 }
2597
2598 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2599 uint gc_count_before,
2600 bool* succeeded,
2601 GCCause::Cause gc_cause) {
2602 assert_heap_not_locked_and_not_at_safepoint();
2603 VM_G1IncCollectionPause op(gc_count_before,
2604 word_size,
2605 false, /* should_initiate_conc_mark */
2606 g1_policy()->max_pause_time_ms(),
2607 gc_cause);
2608
2609 op.set_allocation_context(AllocationContext::current());
2610 VMThread::execute(&op);
2611
2612 HeapWord* result = op.result();
2613 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
2614 assert(result == NULL || ret_succeeded,
2615 "the result should be NULL if the VM did not succeed");
2616 *succeeded = ret_succeeded;
2617
2618 assert_heap_not_locked();
2619 return result;
2620 }
2621
2622 void
2623 G1CollectedHeap::doConcurrentMark() {
2624 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
2625 if (!_cmThread->in_progress()) {
2626 _cmThread->set_started();
2627 CGC_lock->notify();
2628 }
2629 }
2630
2631 size_t G1CollectedHeap::pending_card_num() {
2632 size_t extra_cards = 0;
2633 JavaThread *curr = Threads::first();
2634 while (curr != NULL) {
2635 DirtyCardQueue& dcq = curr->dirty_card_queue();
2636 extra_cards += dcq.size();
2637 curr = curr->next();
2638 }
2639 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2640 size_t buffer_size = dcqs.buffer_size();
2641 size_t buffer_num = dcqs.completed_buffers_num();
2642
2643 return buffer_size * buffer_num + extra_cards;
2644 }
2645
2646 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
2647 private:
2648 size_t _total_humongous;
2649 size_t _candidate_humongous;
2650
2651 DirtyCardQueue _dcq;
2652
2653 // We don't nominate objects with many remembered set entries, on
2654 // the assumption that such objects are likely still live.
2655 bool is_remset_small(HeapRegion* region) const {
2656 HeapRegionRemSet* const rset = region->rem_set();
2657 return G1EagerReclaimHumongousObjectsWithStaleRefs
2658 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)
2659 : rset->is_empty();
2660 }
2661
2662 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const {
2663 assert(region->is_starts_humongous(), "Must start a humongous object");
2664
2665 oop obj = oop(region->bottom());
2666
2667 // Dead objects cannot be eager reclaim candidates. Due to class
2668 // unloading it is unsafe to query their classes so we return early.
2669 if (heap->is_obj_dead(obj, region)) {
2670 return false;
2671 }
2672
2673 // Candidate selection must satisfy the following constraints
2674 // while concurrent marking is in progress:
2675 //
2676 // * In order to maintain SATB invariants, an object must not be
2677 // reclaimed if it was allocated before the start of marking and
2678 // has not had its references scanned. Such an object must have
2679 // its references (including type metadata) scanned to ensure no
2680 // live objects are missed by the marking process. Objects
2681 // allocated after the start of concurrent marking don't need to
2682 // be scanned.
2683 //
2684 // * An object must not be reclaimed if it is on the concurrent
2685 // mark stack. Objects allocated after the start of concurrent
2686 // marking are never pushed on the mark stack.
2687 //
2688 // Nominating only objects allocated after the start of concurrent
2689 // marking is sufficient to meet both constraints. This may miss
2690 // some objects that satisfy the constraints, but the marking data
2691 // structures don't support efficiently performing the needed
2692 // additional tests or scrubbing of the mark stack.
2693 //
2694 // However, we presently only nominate is_typeArray() objects.
2695 // A humongous object containing references induces remembered
2696 // set entries on other regions. In order to reclaim such an
2697 // object, those remembered sets would need to be cleaned up.
2698 //
2699 // We also treat is_typeArray() objects specially, allowing them
2700 // to be reclaimed even if allocated before the start of
2701 // concurrent mark. For this we rely on mark stack insertion to
2702 // exclude is_typeArray() objects, preventing reclaiming an object
2703 // that is in the mark stack. We also rely on the metadata for
2704 // such objects to be built-in and so ensured to be kept live.
2705 // Frequent allocation and drop of large binary blobs is an
2706 // important use case for eager reclaim, and this special handling
2707 // may reduce needed headroom.
2708
2709 return obj->is_typeArray() && is_remset_small(region);
2710 }
2711
2712 public:
2713 RegisterHumongousWithInCSetFastTestClosure()
2714 : _total_humongous(0),
2715 _candidate_humongous(0),
2716 _dcq(&JavaThread::dirty_card_queue_set()) {
2717 }
2718
2719 virtual bool doHeapRegion(HeapRegion* r) {
2720 if (!r->is_starts_humongous()) {
2721 return false;
2722 }
2723 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2724
2725 bool is_candidate = humongous_region_is_candidate(g1h, r);
2726 uint rindex = r->hrm_index();
2727 g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
2728 if (is_candidate) {
2729 _candidate_humongous++;
2730 g1h->register_humongous_region_with_cset(rindex);
2731 // Is_candidate already filters out humongous object with large remembered sets.
2732 // If we have a humongous object with a few remembered sets, we simply flush these
2733 // remembered set entries into the DCQS. That will result in automatic
2734 // re-evaluation of their remembered set entries during the following evacuation
2735 // phase.
2736 if (!r->rem_set()->is_empty()) {
2737 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
2738 "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
2739 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
2740 HeapRegionRemSetIterator hrrs(r->rem_set());
2741 size_t card_index;
2742 while (hrrs.has_next(card_index)) {
2743 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
2744 // The remembered set might contain references to already freed
2745 // regions. Filter out such entries to avoid failing card table
2746 // verification.
2747 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) {
2748 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
2749 *card_ptr = CardTableModRefBS::dirty_card_val();
2750 _dcq.enqueue(card_ptr);
2751 }
2752 }
2753 }
2754 assert(hrrs.n_yielded() == r->rem_set()->occupied(),
2755 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
2756 hrrs.n_yielded(), r->rem_set()->occupied());
2757 r->rem_set()->clear_locked();
2758 }
2759 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
2760 }
2761 _total_humongous++;
2762
2763 return false;
2764 }
2765
2766 size_t total_humongous() const { return _total_humongous; }
2767 size_t candidate_humongous() const { return _candidate_humongous; }
2768
2769 void flush_rem_set_entries() { _dcq.flush(); }
2770 };
2771
2772 void G1CollectedHeap::register_humongous_regions_with_cset() {
2773 if (!G1EagerReclaimHumongousObjects) {
2774 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
2775 return;
2776 }
2777 double time = os::elapsed_counter();
2778
2779 // Collect reclaim candidate information and register candidates with cset.
2780 RegisterHumongousWithInCSetFastTestClosure cl;
2781 heap_region_iterate(&cl);
2782
2783 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
2784 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
2785 cl.total_humongous(),
2786 cl.candidate_humongous());
2787 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
2788
2789 // Finally flush all remembered set entries to re-check into the global DCQS.
2790 cl.flush_rem_set_entries();
2791 }
2792
2793 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2794 public:
2795 bool doHeapRegion(HeapRegion* hr) {
2796 if (!hr->is_archive() && !hr->is_continues_humongous()) {
2797 hr->verify_rem_set();
2798 }
2799 return false;
2800 }
2801 };
2802
2803 uint G1CollectedHeap::num_task_queues() const {
2804 return _task_queues->size();
2805 }
2806
2807 #if TASKQUEUE_STATS
2808 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2809 st->print_raw_cr("GC Task Stats");
2810 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2811 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2812 }
2813
2814 void G1CollectedHeap::print_taskqueue_stats() const {
2815 if (!log_is_enabled(Trace, gc, task, stats)) {
2816 return;
2817 }
2818 Log(gc, task, stats) log;
2819 ResourceMark rm;
2820 LogStream ls(log.trace());
2821 outputStream* st = &ls;
2822
2823 print_taskqueue_stats_hdr(st);
2824
2825 TaskQueueStats totals;
2826 const uint n = num_task_queues();
2827 for (uint i = 0; i < n; ++i) {
2828 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2829 totals += task_queue(i)->stats;
2830 }
2831 st->print_raw("tot "); totals.print(st); st->cr();
2832
2833 DEBUG_ONLY(totals.verify());
2834 }
2835
2836 void G1CollectedHeap::reset_taskqueue_stats() {
2837 const uint n = num_task_queues();
2838 for (uint i = 0; i < n; ++i) {
2839 task_queue(i)->stats.reset();
2840 }
2841 }
2842 #endif // TASKQUEUE_STATS
2843
2844 void G1CollectedHeap::wait_for_root_region_scanning() {
2845 double scan_wait_start = os::elapsedTime();
2846 // We have to wait until the CM threads finish scanning the
2847 // root regions as it's the only way to ensure that all the
2848 // objects on them have been correctly scanned before we start
2849 // moving them during the GC.
2850 bool waited = _cm->root_regions()->wait_until_scan_finished();
2851 double wait_time_ms = 0.0;
2852 if (waited) {
2853 double scan_wait_end = os::elapsedTime();
2854 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2855 }
2856 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2857 }
2858
2859 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2860 private:
2861 G1HRPrinter* _hr_printer;
2862 public:
2863 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2864
2865 virtual bool doHeapRegion(HeapRegion* r) {
2866 _hr_printer->cset(r);
2867 return false;
2868 }
2869 };
2870
2871 void G1CollectedHeap::start_new_collection_set() {
2872 collection_set()->start_incremental_building();
2873
2874 clear_cset_fast_test();
2875
2876 guarantee(_eden.length() == 0, "eden should have been cleared");
2877 g1_policy()->transfer_survivors_to_cset(survivor());
2878 }
2879
2880 bool
2881 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
2882 assert_at_safepoint(true /* should_be_vm_thread */);
2883 guarantee(!is_gc_active(), "collection is not reentrant");
2884
2885 if (GCLocker::check_active_before_gc()) {
2886 return false;
2887 }
2888
2889 _gc_timer_stw->register_gc_start();
2890
2891 GCIdMark gc_id_mark;
2892 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
2893
2894 SvcGCMarker sgcm(SvcGCMarker::MINOR);
2895 ResourceMark rm;
2896
2897 g1_policy()->note_gc_start();
2898
2899 wait_for_root_region_scanning();
2900
2901 print_heap_before_gc();
2902 print_heap_regions();
2903 trace_heap_before_gc(_gc_tracer_stw);
2904
2905 _verifier->verify_region_sets_optional();
2906 _verifier->verify_dirty_young_regions();
2907
2908 // We should not be doing initial mark unless the conc mark thread is running
2909 if (!_cmThread->should_terminate()) {
2910 // This call will decide whether this pause is an initial-mark
2911 // pause. If it is, during_initial_mark_pause() will return true
2912 // for the duration of this pause.
2913 g1_policy()->decide_on_conc_mark_initiation();
2914 }
2915
2916 // We do not allow initial-mark to be piggy-backed on a mixed GC.
2917 assert(!collector_state()->during_initial_mark_pause() ||
2918 collector_state()->gcs_are_young(), "sanity");
2919
2920 // We also do not allow mixed GCs during marking.
2921 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity");
2922
2923 // Record whether this pause is an initial mark. When the current
2924 // thread has completed its logging output and it's safe to signal
2925 // the CM thread, the flag's value in the policy has been reset.
2926 bool should_start_conc_mark = collector_state()->during_initial_mark_pause();
2927
2928 // Inner scope for scope based logging, timers, and stats collection
2929 {
2930 EvacuationInfo evacuation_info;
2931
2932 if (collector_state()->during_initial_mark_pause()) {
2933 // We are about to start a marking cycle, so we increment the
2934 // full collection counter.
2935 increment_old_marking_cycles_started();
2936 _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
2937 }
2938
2939 _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
2940
2941 GCTraceCPUTime tcpu;
2942
2943 FormatBuffer<> gc_string("Pause ");
2944 if (collector_state()->during_initial_mark_pause()) {
2945 gc_string.append("Initial Mark");
2946 } else if (collector_state()->gcs_are_young()) {
2947 gc_string.append("Young");
2948 } else {
2949 gc_string.append("Mixed");
2950 }
2951 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true);
2952
2953 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
2954 workers()->active_workers(),
2955 Threads::number_of_non_daemon_threads());
2956 workers()->update_active_workers(active_workers);
2957 log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
2958
2959 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
2960 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
2961
2962 // If the secondary_free_list is not empty, append it to the
2963 // free_list. No need to wait for the cleanup operation to finish;
2964 // the region allocation code will check the secondary_free_list
2965 // and wait if necessary. If the G1StressConcRegionFreeing flag is
2966 // set, skip this step so that the region allocation code has to
2967 // get entries from the secondary_free_list.
2968 if (!G1StressConcRegionFreeing) {
2969 append_secondary_free_list_if_not_empty_with_lock();
2970 }
2971
2972 G1HeapTransition heap_transition(this);
2973 size_t heap_used_bytes_before_gc = used();
2974
2975 // Don't dynamically change the number of GC threads this early. A value of
2976 // 0 is used to indicate serial work. When parallel work is done,
2977 // it will be set.
2978
2979 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
2980 IsGCActiveMark x;
2981
2982 gc_prologue(false);
2983
2984 if (VerifyRememberedSets) {
2985 log_info(gc, verify)("[Verifying RemSets before GC]");
2986 VerifyRegionRemSetClosure v_cl;
2987 heap_region_iterate(&v_cl);
2988 }
2989
2990 _verifier->verify_before_gc();
2991
2992 _verifier->check_bitmaps("GC Start");
2993
2994 #if defined(COMPILER2) || INCLUDE_JVMCI
2995 DerivedPointerTable::clear();
2996 #endif
2997
2998 // Please see comment in g1CollectedHeap.hpp and
2999 // G1CollectedHeap::ref_processing_init() to see how
3000 // reference processing currently works in G1.
3001
3002 // Enable discovery in the STW reference processor
3003 if (g1_policy()->should_process_references()) {
3004 ref_processor_stw()->enable_discovery();
3005 } else {
3006 ref_processor_stw()->disable_discovery();
3007 }
3008
3009 {
3010 // We want to temporarily turn off discovery by the
3011 // CM ref processor, if necessary, and turn it back on
3012 // on again later if we do. Using a scoped
3013 // NoRefDiscovery object will do this.
3014 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3015
3016 // Forget the current alloc region (we might even choose it to be part
3017 // of the collection set!).
3018 _allocator->release_mutator_alloc_region();
3019
3020 // This timing is only used by the ergonomics to handle our pause target.
3021 // It is unclear why this should not include the full pause. We will
3022 // investigate this in CR 7178365.
3023 //
3024 // Preserving the old comment here if that helps the investigation:
3025 //
3026 // The elapsed time induced by the start time below deliberately elides
3027 // the possible verification above.
3028 double sample_start_time_sec = os::elapsedTime();
3029
3030 g1_policy()->record_collection_pause_start(sample_start_time_sec);
3031
3032 if (collector_state()->during_initial_mark_pause()) {
3033 concurrent_mark()->checkpointRootsInitialPre();
3034 }
3035
3036 g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor);
3037
3038 evacuation_info.set_collectionset_regions(collection_set()->region_length());
3039
3040 // Make sure the remembered sets are up to date. This needs to be
3041 // done before register_humongous_regions_with_cset(), because the
3042 // remembered sets are used there to choose eager reclaim candidates.
3043 // If the remembered sets are not up to date we might miss some
3044 // entries that need to be handled.
3045 g1_rem_set()->cleanupHRRS();
3046
3047 register_humongous_regions_with_cset();
3048
3049 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table.");
3050
3051 // We call this after finalize_cset() to
3052 // ensure that the CSet has been finalized.
3053 _cm->verify_no_cset_oops();
3054
3055 if (_hr_printer.is_active()) {
3056 G1PrintCollectionSetClosure cl(&_hr_printer);
3057 _collection_set.iterate(&cl);
3058 }
3059
3060 // Initialize the GC alloc regions.
3061 _allocator->init_gc_alloc_regions(evacuation_info);
3062
3063 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length());
3064 pre_evacuate_collection_set();
3065
3066 // Actually do the work...
3067 evacuate_collection_set(evacuation_info, &per_thread_states);
3068
3069 post_evacuate_collection_set(evacuation_info, &per_thread_states);
3070
3071 const size_t* surviving_young_words = per_thread_states.surviving_young_words();
3072 free_collection_set(&_collection_set, evacuation_info, surviving_young_words);
3073
3074 eagerly_reclaim_humongous_regions();
3075
3076 record_obj_copy_mem_stats();
3077 _survivor_evac_stats.adjust_desired_plab_sz();
3078 _old_evac_stats.adjust_desired_plab_sz();
3079
3080 double start = os::elapsedTime();
3081 start_new_collection_set();
3082 g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0);
3083
3084 if (evacuation_failed()) {
3085 set_used(recalculate_used());
3086 if (_archive_allocator != NULL) {
3087 _archive_allocator->clear_used();
3088 }
3089 for (uint i = 0; i < ParallelGCThreads; i++) {
3090 if (_evacuation_failed_info_array[i].has_failed()) {
3091 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3092 }
3093 }
3094 } else {
3095 // The "used" of the the collection set have already been subtracted
3096 // when they were freed. Add in the bytes evacuated.
3097 increase_used(g1_policy()->bytes_copied_during_gc());
3098 }
3099
3100 if (collector_state()->during_initial_mark_pause()) {
3101 // We have to do this before we notify the CM threads that
3102 // they can start working to make sure that all the
3103 // appropriate initialization is done on the CM object.
3104 concurrent_mark()->checkpointRootsInitialPost();
3105 collector_state()->set_mark_in_progress(true);
3106 // Note that we don't actually trigger the CM thread at
3107 // this point. We do that later when we're sure that
3108 // the current thread has completed its logging output.
3109 }
3110
3111 allocate_dummy_regions();
3112
3113 _allocator->init_mutator_alloc_region();
3114
3115 {
3116 size_t expand_bytes = _heap_sizing_policy->expansion_amount();
3117 if (expand_bytes > 0) {
3118 size_t bytes_before = capacity();
3119 // No need for an ergo logging here,
3120 // expansion_amount() does this when it returns a value > 0.
3121 double expand_ms;
3122 if (!expand(expand_bytes, _workers, &expand_ms)) {
3123 // We failed to expand the heap. Cannot do anything about it.
3124 }
3125 g1_policy()->phase_times()->record_expand_heap_time(expand_ms);
3126 }
3127 }
3128
3129 // We redo the verification but now wrt to the new CSet which
3130 // has just got initialized after the previous CSet was freed.
3131 _cm->verify_no_cset_oops();
3132
3133 // This timing is only used by the ergonomics to handle our pause target.
3134 // It is unclear why this should not include the full pause. We will
3135 // investigate this in CR 7178365.
3136 double sample_end_time_sec = os::elapsedTime();
3137 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3138 size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards);
3139 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc);
3140
3141 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
3142 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc());
3143
3144 if (VerifyRememberedSets) {
3145 log_info(gc, verify)("[Verifying RemSets after GC]");
3146 VerifyRegionRemSetClosure v_cl;
3147 heap_region_iterate(&v_cl);
3148 }
3149
3150 _verifier->verify_after_gc();
3151 _verifier->check_bitmaps("GC End");
3152
3153 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3154 ref_processor_stw()->verify_no_references_recorded();
3155
3156 // CM reference discovery will be re-enabled if necessary.
3157 }
3158
3159 #ifdef TRACESPINNING
3160 ParallelTaskTerminator::print_termination_counts();
3161 #endif
3162
3163 gc_epilogue(false);
3164 }
3165
3166 // Print the remainder of the GC log output.
3167 if (evacuation_failed()) {
3168 log_info(gc)("To-space exhausted");
3169 }
3170
3171 g1_policy()->print_phases();
3172 heap_transition.print();
3173
3174 // It is not yet to safe to tell the concurrent mark to
3175 // start as we have some optional output below. We don't want the
3176 // output from the concurrent mark thread interfering with this
3177 // logging output either.
3178
3179 _hrm.verify_optional();
3180 _verifier->verify_region_sets_optional();
3181
3182 TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3183 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3184
3185 print_heap_after_gc();
3186 print_heap_regions();
3187 trace_heap_after_gc(_gc_tracer_stw);
3188
3189 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3190 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3191 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3192 // before any GC notifications are raised.
3193 g1mm()->update_sizes();
3194
3195 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3196 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
3197 _gc_timer_stw->register_gc_end();
3198 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3199 }
3200 // It should now be safe to tell the concurrent mark thread to start
3201 // without its logging output interfering with the logging output
3202 // that came from the pause.
3203
3204 if (should_start_conc_mark) {
3205 // CAUTION: after the doConcurrentMark() call below,
3206 // the concurrent marking thread(s) could be running
3207 // concurrently with us. Make sure that anything after
3208 // this point does not assume that we are the only GC thread
3209 // running. Note: of course, the actual marking work will
3210 // not start until the safepoint itself is released in
3211 // SuspendibleThreadSet::desynchronize().
3212 doConcurrentMark();
3213 }
3214
3215 return true;
3216 }
3217
3218 void G1CollectedHeap::remove_self_forwarding_pointers() {
3219 G1ParRemoveSelfForwardPtrsTask rsfp_task;
3220 workers()->run_task(&rsfp_task);
3221 }
3222
3223 void G1CollectedHeap::restore_after_evac_failure() {
3224 double remove_self_forwards_start = os::elapsedTime();
3225
3226 remove_self_forwarding_pointers();
3227 SharedRestorePreservedMarksTaskExecutor task_executor(workers());
3228 _preserved_marks_set.restore(&task_executor);
3229
3230 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3231 }
3232
3233 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) {
3234 if (!_evacuation_failed) {
3235 _evacuation_failed = true;
3236 }
3237
3238 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3239 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3240 }
3241
3242 bool G1ParEvacuateFollowersClosure::offer_termination() {
3243 G1ParScanThreadState* const pss = par_scan_state();
3244 start_term_time();
3245 const bool res = terminator()->offer_termination();
3246 end_term_time();
3247 return res;
3248 }
3249
3250 void G1ParEvacuateFollowersClosure::do_void() {
3251 G1ParScanThreadState* const pss = par_scan_state();
3252 pss->trim_queue();
3253 do {
3254 pss->steal_and_trim_queue(queues());
3255 } while (!offer_termination());
3256 }
3257
3258 class G1ParTask : public AbstractGangTask {
3259 protected:
3260 G1CollectedHeap* _g1h;
3261 G1ParScanThreadStateSet* _pss;
3262 RefToScanQueueSet* _queues;
3263 G1RootProcessor* _root_processor;
3264 ParallelTaskTerminator _terminator;
3265 uint _n_workers;
3266
3267 public:
3268 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers)
3269 : AbstractGangTask("G1 collection"),
3270 _g1h(g1h),
3271 _pss(per_thread_states),
3272 _queues(task_queues),
3273 _root_processor(root_processor),
3274 _terminator(n_workers, _queues),
3275 _n_workers(n_workers)
3276 {}
3277
3278 void work(uint worker_id) {
3279 if (worker_id >= _n_workers) return; // no work needed this round
3280
3281 double start_sec = os::elapsedTime();
3282 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec);
3283
3284 {
3285 ResourceMark rm;
3286 HandleMark hm;
3287
3288 ReferenceProcessor* rp = _g1h->ref_processor_stw();
3289
3290 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
3291 pss->set_ref_processor(rp);
3292
3293 double start_strong_roots_sec = os::elapsedTime();
3294
3295 _root_processor->evacuate_roots(pss->closures(), worker_id);
3296
3297 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid
3298 // treating the nmethods visited to act as roots for concurrent marking.
3299 // We only want to make sure that the oops in the nmethods are adjusted with regard to the
3300 // objects copied by the current evacuation.
3301 _g1h->g1_rem_set()->oops_into_collection_set_do(pss,
3302 pss->closures()->weak_codeblobs(),
3303 worker_id);
3304
3305 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec;
3306
3307 double term_sec = 0.0;
3308 size_t evac_term_attempts = 0;
3309 {
3310 double start = os::elapsedTime();
3311 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator);
3312 evac.do_void();
3313
3314 evac_term_attempts = evac.term_attempts();
3315 term_sec = evac.term_time();
3316 double elapsed_sec = os::elapsedTime() - start;
3317 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
3318 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
3319 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts);
3320 }
3321
3322 assert(pss->queue_is_empty(), "should be empty");
3323
3324 if (log_is_enabled(Debug, gc, task, stats)) {
3325 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3326 size_t lab_waste;
3327 size_t lab_undo_waste;
3328 pss->waste(lab_waste, lab_undo_waste);
3329 _g1h->print_termination_stats(worker_id,
3330 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */
3331 strong_roots_sec * 1000.0, /* strong roots time */
3332 term_sec * 1000.0, /* evac term time */
3333 evac_term_attempts, /* evac term attempts */
3334 lab_waste, /* alloc buffer waste */
3335 lab_undo_waste /* undo waste */
3336 );
3337 }
3338
3339 // Close the inner scope so that the ResourceMark and HandleMark
3340 // destructors are executed here and are included as part of the
3341 // "GC Worker Time".
3342 }
3343 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
3344 }
3345 };
3346
3347 void G1CollectedHeap::print_termination_stats_hdr() {
3348 log_debug(gc, task, stats)("GC Termination Stats");
3349 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------");
3350 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo");
3351 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------");
3352 }
3353
3354 void G1CollectedHeap::print_termination_stats(uint worker_id,
3355 double elapsed_ms,
3356 double strong_roots_ms,
3357 double term_ms,
3358 size_t term_attempts,
3359 size_t alloc_buffer_waste,
3360 size_t undo_waste) const {
3361 log_debug(gc, task, stats)
3362 ("%3d %9.2f %9.2f %6.2f "
3363 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
3364 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
3365 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms,
3366 term_ms, term_ms * 100 / elapsed_ms, term_attempts,
3367 (alloc_buffer_waste + undo_waste) * HeapWordSize / K,
3368 alloc_buffer_waste * HeapWordSize / K,
3369 undo_waste * HeapWordSize / K);
3370 }
3371
3372 class G1StringAndSymbolCleaningTask : public AbstractGangTask {
3373 private:
3374 BoolObjectClosure* _is_alive;
3375 G1StringDedupUnlinkOrOopsDoClosure _dedup_closure;
3376
3377 int _initial_string_table_size;
3378 int _initial_symbol_table_size;
3379
3380 bool _process_strings;
3381 int _strings_processed;
3382 int _strings_removed;
3383
3384 bool _process_symbols;
3385 int _symbols_processed;
3386 int _symbols_removed;
3387
3388 bool _process_string_dedup;
3389
3390 public:
3391 G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) :
3392 AbstractGangTask("String/Symbol Unlinking"),
3393 _is_alive(is_alive),
3394 _dedup_closure(is_alive, NULL, false),
3395 _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
3396 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0),
3397 _process_string_dedup(process_string_dedup) {
3398
3399 _initial_string_table_size = StringTable::the_table()->table_size();
3400 _initial_symbol_table_size = SymbolTable::the_table()->table_size();
3401 if (process_strings) {
3402 StringTable::clear_parallel_claimed_index();
3403 }
3404 if (process_symbols) {
3405 SymbolTable::clear_parallel_claimed_index();
3406 }
3407 }
3408
3409 ~G1StringAndSymbolCleaningTask() {
3410 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
3411 "claim value %d after unlink less than initial string table size %d",
3412 StringTable::parallel_claimed_index(), _initial_string_table_size);
3413 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
3414 "claim value %d after unlink less than initial symbol table size %d",
3415 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size);
3416
3417 log_info(gc, stringtable)(
3418 "Cleaned string and symbol table, "
3419 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, "
3420 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
3421 strings_processed(), strings_removed(),
3422 symbols_processed(), symbols_removed());
3423 }
3424
3425 void work(uint worker_id) {
3426 int strings_processed = 0;
3427 int strings_removed = 0;
3428 int symbols_processed = 0;
3429 int symbols_removed = 0;
3430 if (_process_strings) {
3431 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
3432 Atomic::add(strings_processed, &_strings_processed);
3433 Atomic::add(strings_removed, &_strings_removed);
3434 }
3435 if (_process_symbols) {
3436 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
3437 Atomic::add(symbols_processed, &_symbols_processed);
3438 Atomic::add(symbols_removed, &_symbols_removed);
3439 }
3440 if (_process_string_dedup) {
3441 G1StringDedup::parallel_unlink(&_dedup_closure, worker_id);
3442 }
3443 }
3444
3445 size_t strings_processed() const { return (size_t)_strings_processed; }
3446 size_t strings_removed() const { return (size_t)_strings_removed; }
3447
3448 size_t symbols_processed() const { return (size_t)_symbols_processed; }
3449 size_t symbols_removed() const { return (size_t)_symbols_removed; }
3450 };
3451
3452 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
3453 private:
3454 static Monitor* _lock;
3455
3456 BoolObjectClosure* const _is_alive;
3457 const bool _unloading_occurred;
3458 const uint _num_workers;
3459
3460 // Variables used to claim nmethods.
3461 CompiledMethod* _first_nmethod;
3462 CompiledMethod* volatile _claimed_nmethod;
3463
3464 // The list of nmethods that need to be processed by the second pass.
3465 CompiledMethod* volatile _postponed_list;
3466 volatile uint _num_entered_barrier;
3467
3468 public:
3469 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
3470 _is_alive(is_alive),
3471 _unloading_occurred(unloading_occurred),
3472 _num_workers(num_workers),
3473 _first_nmethod(NULL),
3474 _claimed_nmethod(NULL),
3475 _postponed_list(NULL),
3476 _num_entered_barrier(0)
3477 {
3478 CompiledMethod::increase_unloading_clock();
3479 // Get first alive nmethod
3480 CompiledMethodIterator iter = CompiledMethodIterator();
3481 if(iter.next_alive()) {
3482 _first_nmethod = iter.method();
3483 }
3484 _claimed_nmethod = _first_nmethod;
3485 }
3486
3487 ~G1CodeCacheUnloadingTask() {
3488 CodeCache::verify_clean_inline_caches();
3489
3490 CodeCache::set_needs_cache_clean(false);
3491 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
3492
3493 CodeCache::verify_icholder_relocations();
3494 }
3495
3496 private:
3497 void add_to_postponed_list(CompiledMethod* nm) {
3498 CompiledMethod* old;
3499 do {
3500 old = _postponed_list;
3501 nm->set_unloading_next(old);
3502 } while (Atomic::cmpxchg(nm, &_postponed_list, old) != old);
3503 }
3504
3505 void clean_nmethod(CompiledMethod* nm) {
3506 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
3507
3508 if (postponed) {
3509 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
3510 add_to_postponed_list(nm);
3511 }
3512
3513 // Mark that this thread has been cleaned/unloaded.
3514 // After this call, it will be safe to ask if this nmethod was unloaded or not.
3515 nm->set_unloading_clock(CompiledMethod::global_unloading_clock());
3516 }
3517
3518 void clean_nmethod_postponed(CompiledMethod* nm) {
3519 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
3520 }
3521
3522 static const int MaxClaimNmethods = 16;
3523
3524 void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) {
3525 CompiledMethod* first;
3526 CompiledMethodIterator last;
3527
3528 do {
3529 *num_claimed_nmethods = 0;
3530
3531 first = _claimed_nmethod;
3532 last = CompiledMethodIterator(first);
3533
3534 if (first != NULL) {
3535
3536 for (int i = 0; i < MaxClaimNmethods; i++) {
3537 if (!last.next_alive()) {
3538 break;
3539 }
3540 claimed_nmethods[i] = last.method();
3541 (*num_claimed_nmethods)++;
3542 }
3543 }
3544
3545 } while (Atomic::cmpxchg(last.method(), &_claimed_nmethod, first) != first);
3546 }
3547
3548 CompiledMethod* claim_postponed_nmethod() {
3549 CompiledMethod* claim;
3550 CompiledMethod* next;
3551
3552 do {
3553 claim = _postponed_list;
3554 if (claim == NULL) {
3555 return NULL;
3556 }
3557
3558 next = claim->unloading_next();
3559
3560 } while (Atomic::cmpxchg(next, &_postponed_list, claim) != claim);
3561
3562 return claim;
3563 }
3564
3565 public:
3566 // Mark that we're done with the first pass of nmethod cleaning.
3567 void barrier_mark(uint worker_id) {
3568 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3569 _num_entered_barrier++;
3570 if (_num_entered_barrier == _num_workers) {
3571 ml.notify_all();
3572 }
3573 }
3574
3575 // See if we have to wait for the other workers to
3576 // finish their first-pass nmethod cleaning work.
3577 void barrier_wait(uint worker_id) {
3578 if (_num_entered_barrier < _num_workers) {
3579 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3580 while (_num_entered_barrier < _num_workers) {
3581 ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
3582 }
3583 }
3584 }
3585
3586 // Cleaning and unloading of nmethods. Some work has to be postponed
3587 // to the second pass, when we know which nmethods survive.
3588 void work_first_pass(uint worker_id) {
3589 // The first nmethods is claimed by the first worker.
3590 if (worker_id == 0 && _first_nmethod != NULL) {
3591 clean_nmethod(_first_nmethod);
3592 _first_nmethod = NULL;
3593 }
3594
3595 int num_claimed_nmethods;
3596 CompiledMethod* claimed_nmethods[MaxClaimNmethods];
3597
3598 while (true) {
3599 claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
3600
3601 if (num_claimed_nmethods == 0) {
3602 break;
3603 }
3604
3605 for (int i = 0; i < num_claimed_nmethods; i++) {
3606 clean_nmethod(claimed_nmethods[i]);
3607 }
3608 }
3609 }
3610
3611 void work_second_pass(uint worker_id) {
3612 CompiledMethod* nm;
3613 // Take care of postponed nmethods.
3614 while ((nm = claim_postponed_nmethod()) != NULL) {
3615 clean_nmethod_postponed(nm);
3616 }
3617 }
3618 };
3619
3620 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
3621
3622 class G1KlassCleaningTask : public StackObj {
3623 BoolObjectClosure* _is_alive;
3624 volatile jint _clean_klass_tree_claimed;
3625 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
3626
3627 public:
3628 G1KlassCleaningTask(BoolObjectClosure* is_alive) :
3629 _is_alive(is_alive),
3630 _clean_klass_tree_claimed(0),
3631 _klass_iterator() {
3632 }
3633
3634 private:
3635 bool claim_clean_klass_tree_task() {
3636 if (_clean_klass_tree_claimed) {
3637 return false;
3638 }
3639
3640 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
3641 }
3642
3643 InstanceKlass* claim_next_klass() {
3644 Klass* klass;
3645 do {
3646 klass =_klass_iterator.next_klass();
3647 } while (klass != NULL && !klass->is_instance_klass());
3648
3649 // this can be null so don't call InstanceKlass::cast
3650 return static_cast<InstanceKlass*>(klass);
3651 }
3652
3653 public:
3654
3655 void clean_klass(InstanceKlass* ik) {
3656 ik->clean_weak_instanceklass_links(_is_alive);
3657 }
3658
3659 void work() {
3660 ResourceMark rm;
3661
3662 // One worker will clean the subklass/sibling klass tree.
3663 if (claim_clean_klass_tree_task()) {
3664 Klass::clean_subklass_tree(_is_alive);
3665 }
3666
3667 // All workers will help cleaning the classes,
3668 InstanceKlass* klass;
3669 while ((klass = claim_next_klass()) != NULL) {
3670 clean_klass(klass);
3671 }
3672 }
3673 };
3674
3675 class G1ResolvedMethodCleaningTask : public StackObj {
3676 BoolObjectClosure* _is_alive;
3677 volatile jint _resolved_method_task_claimed;
3678 public:
3679 G1ResolvedMethodCleaningTask(BoolObjectClosure* is_alive) :
3680 _is_alive(is_alive), _resolved_method_task_claimed(0) {}
3681
3682 bool claim_resolved_method_task() {
3683 if (_resolved_method_task_claimed) {
3684 return false;
3685 }
3686 return Atomic::cmpxchg(1, (jint*)&_resolved_method_task_claimed, 0) == 0;
3687 }
3688
3689 // These aren't big, one thread can do it all.
3690 void work() {
3691 if (claim_resolved_method_task()) {
3692 ResolvedMethodTable::unlink(_is_alive);
3693 }
3694 }
3695 };
3696
3697
3698 // To minimize the remark pause times, the tasks below are done in parallel.
3699 class G1ParallelCleaningTask : public AbstractGangTask {
3700 private:
3701 G1StringAndSymbolCleaningTask _string_symbol_task;
3702 G1CodeCacheUnloadingTask _code_cache_task;
3703 G1KlassCleaningTask _klass_cleaning_task;
3704 G1ResolvedMethodCleaningTask _resolved_method_cleaning_task;
3705
3706 public:
3707 // The constructor is run in the VMThread.
3708 G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) :
3709 AbstractGangTask("Parallel Cleaning"),
3710 _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()),
3711 _code_cache_task(num_workers, is_alive, unloading_occurred),
3712 _klass_cleaning_task(is_alive),
3713 _resolved_method_cleaning_task(is_alive) {
3714 }
3715
3716 // The parallel work done by all worker threads.
3717 void work(uint worker_id) {
3718 // Do first pass of code cache cleaning.
3719 _code_cache_task.work_first_pass(worker_id);
3720
3721 // Let the threads mark that the first pass is done.
3722 _code_cache_task.barrier_mark(worker_id);
3723
3724 // Clean the Strings and Symbols.
3725 _string_symbol_task.work(worker_id);
3726
3727 // Clean unreferenced things in the ResolvedMethodTable
3728 _resolved_method_cleaning_task.work();
3729
3730 // Wait for all workers to finish the first code cache cleaning pass.
3731 _code_cache_task.barrier_wait(worker_id);
3732
3733 // Do the second code cache cleaning work, which realize on
3734 // the liveness information gathered during the first pass.
3735 _code_cache_task.work_second_pass(worker_id);
3736
3737 // Clean all klasses that were not unloaded.
3738 _klass_cleaning_task.work();
3739 }
3740 };
3741
3742
3743 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
3744 bool class_unloading_occurred) {
3745 uint n_workers = workers()->active_workers();
3746
3747 G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred);
3748 workers()->run_task(&g1_unlink_task);
3749 }
3750
3751 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive,
3752 bool process_strings,
3753 bool process_symbols,
3754 bool process_string_dedup) {
3755 if (!process_strings && !process_symbols && !process_string_dedup) {
3756 // Nothing to clean.
3757 return;
3758 }
3759
3760 G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup);
3761 workers()->run_task(&g1_unlink_task);
3762
3763 }
3764
3765 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3766 private:
3767 DirtyCardQueueSet* _queue;
3768 G1CollectedHeap* _g1h;
3769 public:
3770 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"),
3771 _queue(queue), _g1h(g1h) { }
3772
3773 virtual void work(uint worker_id) {
3774 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
3775 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
3776
3777 RedirtyLoggedCardTableEntryClosure cl(_g1h);
3778 _queue->par_apply_closure_to_all_completed_buffers(&cl);
3779
3780 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3781 }
3782 };
3783
3784 void G1CollectedHeap::redirty_logged_cards() {
3785 double redirty_logged_cards_start = os::elapsedTime();
3786
3787 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this);
3788 dirty_card_queue_set().reset_for_par_iteration();
3789 workers()->run_task(&redirty_task);
3790
3791 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
3792 dcq.merge_bufferlists(&dirty_card_queue_set());
3793 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
3794
3795 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3796 }
3797
3798 // Weak Reference Processing support
3799
3800 // An always "is_alive" closure that is used to preserve referents.
3801 // If the object is non-null then it's alive. Used in the preservation
3802 // of referent objects that are pointed to by reference objects
3803 // discovered by the CM ref processor.
3804 class G1AlwaysAliveClosure: public BoolObjectClosure {
3805 G1CollectedHeap* _g1;
3806 public:
3807 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3808 bool do_object_b(oop p) {
3809 if (p != NULL) {
3810 return true;
3811 }
3812 return false;
3813 }
3814 };
3815
3816 bool G1STWIsAliveClosure::do_object_b(oop p) {
3817 // An object is reachable if it is outside the collection set,
3818 // or is inside and copied.
3819 return !_g1->is_in_cset(p) || p->is_forwarded();
3820 }
3821
3822 // Non Copying Keep Alive closure
3823 class G1KeepAliveClosure: public OopClosure {
3824 G1CollectedHeap* _g1;
3825 public:
3826 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3827 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3828 void do_oop(oop* p) {
3829 oop obj = *p;
3830 assert(obj != NULL, "the caller should have filtered out NULL values");
3831
3832 const InCSetState cset_state = _g1->in_cset_state(obj);
3833 if (!cset_state.is_in_cset_or_humongous()) {
3834 return;
3835 }
3836 if (cset_state.is_in_cset()) {
3837 assert( obj->is_forwarded(), "invariant" );
3838 *p = obj->forwardee();
3839 } else {
3840 assert(!obj->is_forwarded(), "invariant" );
3841 assert(cset_state.is_humongous(),
3842 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value());
3843 _g1->set_humongous_is_live(obj);
3844 }
3845 }
3846 };
3847
3848 // Copying Keep Alive closure - can be called from both
3849 // serial and parallel code as long as different worker
3850 // threads utilize different G1ParScanThreadState instances
3851 // and different queues.
3852
3853 class G1CopyingKeepAliveClosure: public OopClosure {
3854 G1CollectedHeap* _g1h;
3855 OopClosure* _copy_non_heap_obj_cl;
3856 G1ParScanThreadState* _par_scan_state;
3857
3858 public:
3859 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3860 OopClosure* non_heap_obj_cl,
3861 G1ParScanThreadState* pss):
3862 _g1h(g1h),
3863 _copy_non_heap_obj_cl(non_heap_obj_cl),
3864 _par_scan_state(pss)
3865 {}
3866
3867 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3868 virtual void do_oop( oop* p) { do_oop_work(p); }
3869
3870 template <class T> void do_oop_work(T* p) {
3871 oop obj = oopDesc::load_decode_heap_oop(p);
3872
3873 if (_g1h->is_in_cset_or_humongous(obj)) {
3874 // If the referent object has been forwarded (either copied
3875 // to a new location or to itself in the event of an
3876 // evacuation failure) then we need to update the reference
3877 // field and, if both reference and referent are in the G1
3878 // heap, update the RSet for the referent.
3879 //
3880 // If the referent has not been forwarded then we have to keep
3881 // it alive by policy. Therefore we have copy the referent.
3882 //
3883 // If the reference field is in the G1 heap then we can push
3884 // on the PSS queue. When the queue is drained (after each
3885 // phase of reference processing) the object and it's followers
3886 // will be copied, the reference field set to point to the
3887 // new location, and the RSet updated. Otherwise we need to
3888 // use the the non-heap or metadata closures directly to copy
3889 // the referent object and update the pointer, while avoiding
3890 // updating the RSet.
3891
3892 if (_g1h->is_in_g1_reserved(p)) {
3893 _par_scan_state->push_on_queue(p);
3894 } else {
3895 assert(!Metaspace::contains((const void*)p),
3896 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p));
3897 _copy_non_heap_obj_cl->do_oop(p);
3898 }
3899 }
3900 }
3901 };
3902
3903 // Serial drain queue closure. Called as the 'complete_gc'
3904 // closure for each discovered list in some of the
3905 // reference processing phases.
3906
3907 class G1STWDrainQueueClosure: public VoidClosure {
3908 protected:
3909 G1CollectedHeap* _g1h;
3910 G1ParScanThreadState* _par_scan_state;
3911
3912 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
3913
3914 public:
3915 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
3916 _g1h(g1h),
3917 _par_scan_state(pss)
3918 { }
3919
3920 void do_void() {
3921 G1ParScanThreadState* const pss = par_scan_state();
3922 pss->trim_queue();
3923 }
3924 };
3925
3926 // Parallel Reference Processing closures
3927
3928 // Implementation of AbstractRefProcTaskExecutor for parallel reference
3929 // processing during G1 evacuation pauses.
3930
3931 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
3932 private:
3933 G1CollectedHeap* _g1h;
3934 G1ParScanThreadStateSet* _pss;
3935 RefToScanQueueSet* _queues;
3936 WorkGang* _workers;
3937 uint _active_workers;
3938
3939 public:
3940 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
3941 G1ParScanThreadStateSet* per_thread_states,
3942 WorkGang* workers,
3943 RefToScanQueueSet *task_queues,
3944 uint n_workers) :
3945 _g1h(g1h),
3946 _pss(per_thread_states),
3947 _queues(task_queues),
3948 _workers(workers),
3949 _active_workers(n_workers)
3950 {
3951 g1h->ref_processor_stw()->set_active_mt_degree(n_workers);
3952 }
3953
3954 // Executes the given task using concurrent marking worker threads.
3955 virtual void execute(ProcessTask& task);
3956 virtual void execute(EnqueueTask& task);
3957 };
3958
3959 // Gang task for possibly parallel reference processing
3960
3961 class G1STWRefProcTaskProxy: public AbstractGangTask {
3962 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
3963 ProcessTask& _proc_task;
3964 G1CollectedHeap* _g1h;
3965 G1ParScanThreadStateSet* _pss;
3966 RefToScanQueueSet* _task_queues;
3967 ParallelTaskTerminator* _terminator;
3968
3969 public:
3970 G1STWRefProcTaskProxy(ProcessTask& proc_task,
3971 G1CollectedHeap* g1h,
3972 G1ParScanThreadStateSet* per_thread_states,
3973 RefToScanQueueSet *task_queues,
3974 ParallelTaskTerminator* terminator) :
3975 AbstractGangTask("Process reference objects in parallel"),
3976 _proc_task(proc_task),
3977 _g1h(g1h),
3978 _pss(per_thread_states),
3979 _task_queues(task_queues),
3980 _terminator(terminator)
3981 {}
3982
3983 virtual void work(uint worker_id) {
3984 // The reference processing task executed by a single worker.
3985 ResourceMark rm;
3986 HandleMark hm;
3987
3988 G1STWIsAliveClosure is_alive(_g1h);
3989
3990 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
3991 pss->set_ref_processor(NULL);
3992
3993 // Keep alive closure.
3994 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
3995
3996 // Complete GC closure
3997 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator);
3998
3999 // Call the reference processing task's work routine.
4000 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
4001
4002 // Note we cannot assert that the refs array is empty here as not all
4003 // of the processing tasks (specifically phase2 - pp2_work) execute
4004 // the complete_gc closure (which ordinarily would drain the queue) so
4005 // the queue may not be empty.
4006 }
4007 };
4008
4009 // Driver routine for parallel reference processing.
4010 // Creates an instance of the ref processing gang
4011 // task and has the worker threads execute it.
4012 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
4013 assert(_workers != NULL, "Need parallel worker threads.");
4014
4015 ParallelTaskTerminator terminator(_active_workers, _queues);
4016 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
4017
4018 _workers->run_task(&proc_task_proxy);
4019 }
4020
4021 // Gang task for parallel reference enqueueing.
4022
4023 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
4024 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
4025 EnqueueTask& _enq_task;
4026
4027 public:
4028 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
4029 AbstractGangTask("Enqueue reference objects in parallel"),
4030 _enq_task(enq_task)
4031 { }
4032
4033 virtual void work(uint worker_id) {
4034 _enq_task.work(worker_id);
4035 }
4036 };
4037
4038 // Driver routine for parallel reference enqueueing.
4039 // Creates an instance of the ref enqueueing gang
4040 // task and has the worker threads execute it.
4041
4042 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
4043 assert(_workers != NULL, "Need parallel worker threads.");
4044
4045 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
4046
4047 _workers->run_task(&enq_task_proxy);
4048 }
4049
4050 // End of weak reference support closures
4051
4052 // Abstract task used to preserve (i.e. copy) any referent objects
4053 // that are in the collection set and are pointed to by reference
4054 // objects discovered by the CM ref processor.
4055
4056 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
4057 protected:
4058 G1CollectedHeap* _g1h;
4059 G1ParScanThreadStateSet* _pss;
4060 RefToScanQueueSet* _queues;
4061 ParallelTaskTerminator _terminator;
4062 uint _n_workers;
4063
4064 public:
4065 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) :
4066 AbstractGangTask("ParPreserveCMReferents"),
4067 _g1h(g1h),
4068 _pss(per_thread_states),
4069 _queues(task_queues),
4070 _terminator(workers, _queues),
4071 _n_workers(workers)
4072 {
4073 g1h->ref_processor_cm()->set_active_mt_degree(workers);
4074 }
4075
4076 void work(uint worker_id) {
4077 G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id);
4078
4079 ResourceMark rm;
4080 HandleMark hm;
4081
4082 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
4083 pss->set_ref_processor(NULL);
4084 assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4085
4086 // Is alive closure
4087 G1AlwaysAliveClosure always_alive(_g1h);
4088
4089 // Copying keep alive closure. Applied to referent objects that need
4090 // to be copied.
4091 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4092
4093 ReferenceProcessor* rp = _g1h->ref_processor_cm();
4094
4095 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
4096 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
4097
4098 // limit is set using max_num_q() - which was set using ParallelGCThreads.
4099 // So this must be true - but assert just in case someone decides to
4100 // change the worker ids.
4101 assert(worker_id < limit, "sanity");
4102 assert(!rp->discovery_is_atomic(), "check this code");
4103
4104 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
4105 for (uint idx = worker_id; idx < limit; idx += stride) {
4106 DiscoveredList& ref_list = rp->discovered_refs()[idx];
4107
4108 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
4109 while (iter.has_next()) {
4110 // Since discovery is not atomic for the CM ref processor, we
4111 // can see some null referent objects.
4112 iter.load_ptrs(DEBUG_ONLY(true));
4113 oop ref = iter.obj();
4114
4115 // This will filter nulls.
4116 if (iter.is_referent_alive()) {
4117 iter.make_referent_alive();
4118 }
4119 iter.move_to_next();
4120 }
4121 }
4122
4123 // Drain the queue - which may cause stealing
4124 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator);
4125 drain_queue.do_void();
4126 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
4127 assert(pss->queue_is_empty(), "should be");
4128 }
4129 };
4130
4131 void G1CollectedHeap::process_weak_jni_handles() {
4132 double ref_proc_start = os::elapsedTime();
4133
4134 G1STWIsAliveClosure is_alive(this);
4135 G1KeepAliveClosure keep_alive(this);
4136 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
4137
4138 double ref_proc_time = os::elapsedTime() - ref_proc_start;
4139 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4140 }
4141
4142 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) {
4143 // Any reference objects, in the collection set, that were 'discovered'
4144 // by the CM ref processor should have already been copied (either by
4145 // applying the external root copy closure to the discovered lists, or
4146 // by following an RSet entry).
4147 //
4148 // But some of the referents, that are in the collection set, that these
4149 // reference objects point to may not have been copied: the STW ref
4150 // processor would have seen that the reference object had already
4151 // been 'discovered' and would have skipped discovering the reference,
4152 // but would not have treated the reference object as a regular oop.
4153 // As a result the copy closure would not have been applied to the
4154 // referent object.
4155 //
4156 // We need to explicitly copy these referent objects - the references
4157 // will be processed at the end of remarking.
4158 //
4159 // We also need to do this copying before we process the reference
4160 // objects discovered by the STW ref processor in case one of these
4161 // referents points to another object which is also referenced by an
4162 // object discovered by the STW ref processor.
4163 double preserve_cm_referents_time = 0.0;
4164
4165 // To avoid spawning task when there is no work to do, check that
4166 // a concurrent cycle is active and that some references have been
4167 // discovered.
4168 if (concurrent_mark()->cmThread()->during_cycle() &&
4169 ref_processor_cm()->has_discovered_references()) {
4170 double preserve_cm_referents_start = os::elapsedTime();
4171 uint no_of_gc_workers = workers()->active_workers();
4172 G1ParPreserveCMReferentsTask keep_cm_referents(this,
4173 per_thread_states,
4174 no_of_gc_workers,
4175 _task_queues);
4176 workers()->run_task(&keep_cm_referents);
4177 preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start;
4178 }
4179
4180 g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0);
4181 }
4182
4183 // Weak Reference processing during an evacuation pause (part 1).
4184 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4185 double ref_proc_start = os::elapsedTime();
4186
4187 ReferenceProcessor* rp = _ref_processor_stw;
4188 assert(rp->discovery_enabled(), "should have been enabled");
4189
4190 // Closure to test whether a referent is alive.
4191 G1STWIsAliveClosure is_alive(this);
4192
4193 // Even when parallel reference processing is enabled, the processing
4194 // of JNI refs is serial and performed serially by the current thread
4195 // rather than by a worker. The following PSS will be used for processing
4196 // JNI refs.
4197
4198 // Use only a single queue for this PSS.
4199 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0);
4200 pss->set_ref_processor(NULL);
4201 assert(pss->queue_is_empty(), "pre-condition");
4202
4203 // Keep alive closure.
4204 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss);
4205
4206 // Serial Complete GC closure
4207 G1STWDrainQueueClosure drain_queue(this, pss);
4208
4209 // Setup the soft refs policy...
4210 rp->setup_policy(false);
4211
4212 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times();
4213
4214 ReferenceProcessorStats stats;
4215 if (!rp->processing_is_mt()) {
4216 // Serial reference processing...
4217 stats = rp->process_discovered_references(&is_alive,
4218 &keep_alive,
4219 &drain_queue,
4220 NULL,
4221 pt);
4222 } else {
4223 uint no_of_gc_workers = workers()->active_workers();
4224
4225 // Parallel reference processing
4226 assert(no_of_gc_workers <= rp->max_num_q(),
4227 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4228 no_of_gc_workers, rp->max_num_q());
4229
4230 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers);
4231 stats = rp->process_discovered_references(&is_alive,
4232 &keep_alive,
4233 &drain_queue,
4234 &par_task_executor,
4235 pt);
4236 }
4237
4238 _gc_tracer_stw->report_gc_reference_stats(stats);
4239
4240 // We have completed copying any necessary live referent objects.
4241 assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4242
4243 double ref_proc_time = os::elapsedTime() - ref_proc_start;
4244 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4245 }
4246
4247 // Weak Reference processing during an evacuation pause (part 2).
4248 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4249 double ref_enq_start = os::elapsedTime();
4250
4251 ReferenceProcessor* rp = _ref_processor_stw;
4252 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
4253
4254 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times();
4255
4256 // Now enqueue any remaining on the discovered lists on to
4257 // the pending list.
4258 if (!rp->processing_is_mt()) {
4259 // Serial reference processing...
4260 rp->enqueue_discovered_references(NULL, pt);
4261 } else {
4262 // Parallel reference enqueueing
4263
4264 uint n_workers = workers()->active_workers();
4265
4266 assert(n_workers <= rp->max_num_q(),
4267 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4268 n_workers, rp->max_num_q());
4269
4270 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers);
4271 rp->enqueue_discovered_references(&par_task_executor, pt);
4272 }
4273
4274 rp->verify_no_references_recorded();
4275 assert(!rp->discovery_enabled(), "should have been disabled");
4276
4277 // If during an initial mark pause we install a pending list head which is not otherwise reachable
4278 // ensure that it is marked in the bitmap for concurrent marking to discover.
4279 if (collector_state()->during_initial_mark_pause()) {
4280 oop pll_head = Universe::reference_pending_list();
4281 if (pll_head != NULL) {
4282 _cm->mark_in_next_bitmap(pll_head);
4283 }
4284 }
4285
4286 // FIXME
4287 // CM's reference processing also cleans up the string and symbol tables.
4288 // Should we do that here also? We could, but it is a serial operation
4289 // and could significantly increase the pause time.
4290
4291 double ref_enq_time = os::elapsedTime() - ref_enq_start;
4292 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
4293 }
4294
4295 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
4296 double merge_pss_time_start = os::elapsedTime();
4297 per_thread_states->flush();
4298 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0);
4299 }
4300
4301 void G1CollectedHeap::pre_evacuate_collection_set() {
4302 _expand_heap_after_alloc_failure = true;
4303 _evacuation_failed = false;
4304
4305 // Disable the hot card cache.
4306 _hot_card_cache->reset_hot_cache_claimed_index();
4307 _hot_card_cache->set_use_cache(false);
4308
4309 g1_rem_set()->prepare_for_oops_into_collection_set_do();
4310 _preserved_marks_set.assert_empty();
4311
4312 G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4313
4314 // InitialMark needs claim bits to keep track of the marked-through CLDs.
4315 if (collector_state()->during_initial_mark_pause()) {
4316 double start_clear_claimed_marks = os::elapsedTime();
4317
4318 ClassLoaderDataGraph::clear_claimed_marks();
4319
4320 double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
4321 phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
4322 }
4323 }
4324
4325 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4326 // Should G1EvacuationFailureALot be in effect for this GC?
4327 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
4328
4329 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
4330
4331 G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4332
4333 double start_par_time_sec = os::elapsedTime();
4334 double end_par_time_sec;
4335
4336 {
4337 const uint n_workers = workers()->active_workers();
4338 G1RootProcessor root_processor(this, n_workers);
4339 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers);
4340
4341 print_termination_stats_hdr();
4342
4343 workers()->run_task(&g1_par_task);
4344 end_par_time_sec = os::elapsedTime();
4345
4346 // Closing the inner scope will execute the destructor
4347 // for the G1RootProcessor object. We record the current
4348 // elapsed time before closing the scope so that time
4349 // taken for the destructor is NOT included in the
4350 // reported parallel time.
4351 }
4352
4353 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
4354 phase_times->record_par_time(par_time_ms);
4355
4356 double code_root_fixup_time_ms =
4357 (os::elapsedTime() - end_par_time_sec) * 1000.0;
4358 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
4359 }
4360
4361 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4362 // Process any discovered reference objects - we have
4363 // to do this _before_ we retire the GC alloc regions
4364 // as we may have to copy some 'reachable' referent
4365 // objects (and their reachable sub-graphs) that were
4366 // not copied during the pause.
4367 if (g1_policy()->should_process_references()) {
4368 preserve_cm_referents(per_thread_states);
4369 process_discovered_references(per_thread_states);
4370 } else {
4371 ref_processor_stw()->verify_no_references_recorded();
4372 process_weak_jni_handles();
4373 }
4374
4375 if (G1StringDedup::is_enabled()) {
4376 double fixup_start = os::elapsedTime();
4377
4378 G1STWIsAliveClosure is_alive(this);
4379 G1KeepAliveClosure keep_alive(this);
4380 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times());
4381
4382 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
4383 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
4384 }
4385
4386 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4387
4388 if (evacuation_failed()) {
4389 restore_after_evac_failure();
4390
4391 // Reset the G1EvacuationFailureALot counters and flags
4392 // Note: the values are reset only when an actual
4393 // evacuation failure occurs.
4394 NOT_PRODUCT(reset_evacuation_should_fail();)
4395 }
4396
4397 _preserved_marks_set.assert_empty();
4398
4399 // Enqueue any remaining references remaining on the STW
4400 // reference processor's discovered lists. We need to do
4401 // this after the card table is cleaned (and verified) as
4402 // the act of enqueueing entries on to the pending list
4403 // will log these updates (and dirty their associated
4404 // cards). We need these updates logged to update any
4405 // RSets.
4406 if (g1_policy()->should_process_references()) {
4407 enqueue_discovered_references(per_thread_states);
4408 } else {
4409 g1_policy()->phase_times()->record_ref_enq_time(0);
4410 }
4411
4412 _allocator->release_gc_alloc_regions(evacuation_info);
4413
4414 merge_per_thread_state_info(per_thread_states);
4415
4416 // Reset and re-enable the hot card cache.
4417 // Note the counts for the cards in the regions in the
4418 // collection set are reset when the collection set is freed.
4419 _hot_card_cache->reset_hot_cache();
4420 _hot_card_cache->set_use_cache(true);
4421
4422 purge_code_root_memory();
4423
4424 redirty_logged_cards();
4425 #if defined(COMPILER2) || INCLUDE_JVMCI
4426 double start = os::elapsedTime();
4427 DerivedPointerTable::update_pointers();
4428 g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0);
4429 #endif
4430 g1_policy()->print_age_table();
4431 }
4432
4433 void G1CollectedHeap::record_obj_copy_mem_stats() {
4434 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4435
4436 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4437 create_g1_evac_summary(&_old_evac_stats));
4438 }
4439
4440 void G1CollectedHeap::free_region(HeapRegion* hr,
4441 FreeRegionList* free_list,
4442 bool skip_remset,
4443 bool skip_hot_card_cache,
4444 bool locked) {
4445 assert(!hr->is_free(), "the region should not be free");
4446 assert(!hr->is_empty(), "the region should not be empty");
4447 assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
4448 assert(free_list != NULL, "pre-condition");
4449
4450 if (G1VerifyBitmaps) {
4451 MemRegion mr(hr->bottom(), hr->end());
4452 concurrent_mark()->clearRangePrevBitmap(mr);
4453 }
4454
4455 // Clear the card counts for this region.
4456 // Note: we only need to do this if the region is not young
4457 // (since we don't refine cards in young regions).
4458 if (!skip_hot_card_cache && !hr->is_young()) {
4459 _hot_card_cache->reset_card_counts(hr);
4460 }
4461 hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */);
4462 free_list->add_ordered(hr);
4463 }
4464
4465 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4466 FreeRegionList* free_list,
4467 bool skip_remset) {
4468 assert(hr->is_humongous(), "this is only for humongous regions");
4469 assert(free_list != NULL, "pre-condition");
4470 hr->clear_humongous();
4471 free_region(hr, free_list, skip_remset);
4472 }
4473
4474 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4475 const uint humongous_regions_removed) {
4476 if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4477 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4478 _old_set.bulk_remove(old_regions_removed);
4479 _humongous_set.bulk_remove(humongous_regions_removed);
4480 }
4481
4482 }
4483
4484 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4485 assert(list != NULL, "list can't be null");
4486 if (!list->is_empty()) {
4487 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4488 _hrm.insert_list_into_free_list(list);
4489 }
4490 }
4491
4492 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4493 decrease_used(bytes);
4494 }
4495
4496 class G1ParScrubRemSetTask: public AbstractGangTask {
4497 protected:
4498 G1RemSet* _g1rs;
4499 HeapRegionClaimer _hrclaimer;
4500
4501 public:
4502 G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) :
4503 AbstractGangTask("G1 ScrubRS"),
4504 _g1rs(g1_rs),
4505 _hrclaimer(num_workers) {
4506 }
4507
4508 void work(uint worker_id) {
4509 _g1rs->scrub(worker_id, &_hrclaimer);
4510 }
4511 };
4512
4513 void G1CollectedHeap::scrub_rem_set() {
4514 uint num_workers = workers()->active_workers();
4515 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers);
4516 workers()->run_task(&g1_par_scrub_rs_task);
4517 }
4518
4519 class G1FreeCollectionSetTask : public AbstractGangTask {
4520 private:
4521
4522 // Closure applied to all regions in the collection set to do work that needs to
4523 // be done serially in a single thread.
4524 class G1SerialFreeCollectionSetClosure : public HeapRegionClosure {
4525 private:
4526 EvacuationInfo* _evacuation_info;
4527 const size_t* _surviving_young_words;
4528
4529 // Bytes used in successfully evacuated regions before the evacuation.
4530 size_t _before_used_bytes;
4531 // Bytes used in unsucessfully evacuated regions before the evacuation
4532 size_t _after_used_bytes;
4533
4534 size_t _bytes_allocated_in_old_since_last_gc;
4535
4536 size_t _failure_used_words;
4537 size_t _failure_waste_words;
4538
4539 FreeRegionList _local_free_list;
4540 public:
4541 G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4542 HeapRegionClosure(),
4543 _evacuation_info(evacuation_info),
4544 _surviving_young_words(surviving_young_words),
4545 _before_used_bytes(0),
4546 _after_used_bytes(0),
4547 _bytes_allocated_in_old_since_last_gc(0),
4548 _failure_used_words(0),
4549 _failure_waste_words(0),
4550 _local_free_list("Local Region List for CSet Freeing") {
4551 }
4552
4553 virtual bool doHeapRegion(HeapRegion* r) {
4554 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4555
4556 assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index());
4557 g1h->clear_in_cset(r);
4558
4559 if (r->is_young()) {
4560 assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(),
4561 "Young index %d is wrong for region %u of type %s with %u young regions",
4562 r->young_index_in_cset(),
4563 r->hrm_index(),
4564 r->get_type_str(),
4565 g1h->collection_set()->young_region_length());
4566 size_t words_survived = _surviving_young_words[r->young_index_in_cset()];
4567 r->record_surv_words_in_group(words_survived);
4568 }
4569
4570 if (!r->evacuation_failed()) {
4571 assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
4572 _before_used_bytes += r->used();
4573 g1h->free_region(r,
4574 &_local_free_list,
4575 true, /* skip_remset */
4576 true, /* skip_hot_card_cache */
4577 true /* locked */);
4578 } else {
4579 r->uninstall_surv_rate_group();
4580 r->set_young_index_in_cset(-1);
4581 r->set_evacuation_failed(false);
4582 // When moving a young gen region to old gen, we "allocate" that whole region
4583 // there. This is in addition to any already evacuated objects. Notify the
4584 // policy about that.
4585 // Old gen regions do not cause an additional allocation: both the objects
4586 // still in the region and the ones already moved are accounted for elsewhere.
4587 if (r->is_young()) {
4588 _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
4589 }
4590 // The region is now considered to be old.
4591 r->set_old();
4592 // Do some allocation statistics accounting. Regions that failed evacuation
4593 // are always made old, so there is no need to update anything in the young
4594 // gen statistics, but we need to update old gen statistics.
4595 size_t used_words = r->marked_bytes() / HeapWordSize;
4596
4597 _failure_used_words += used_words;
4598 _failure_waste_words += HeapRegion::GrainWords - used_words;
4599
4600 g1h->old_set_add(r);
4601 _after_used_bytes += r->used();
4602 }
4603 return false;
4604 }
4605
4606 void complete_work() {
4607 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4608
4609 _evacuation_info->set_regions_freed(_local_free_list.length());
4610 _evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4611
4612 g1h->prepend_to_freelist(&_local_free_list);
4613 g1h->decrement_summary_bytes(_before_used_bytes);
4614
4615 G1Policy* policy = g1h->g1_policy();
4616 policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4617
4618 g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4619 }
4620 };
4621
4622 G1CollectionSet* _collection_set;
4623 G1SerialFreeCollectionSetClosure _cl;
4624 const size_t* _surviving_young_words;
4625
4626 size_t _rs_lengths;
4627
4628 volatile jint _serial_work_claim;
4629
4630 struct WorkItem {
4631 uint region_idx;
4632 bool is_young;
4633 bool evacuation_failed;
4634
4635 WorkItem(HeapRegion* r) {
4636 region_idx = r->hrm_index();
4637 is_young = r->is_young();
4638 evacuation_failed = r->evacuation_failed();
4639 }
4640 };
4641
4642 volatile size_t _parallel_work_claim;
4643 size_t _num_work_items;
4644 WorkItem* _work_items;
4645
4646 void do_serial_work() {
4647 // Need to grab the lock to be allowed to modify the old region list.
4648 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4649 _collection_set->iterate(&_cl);
4650 }
4651
4652 void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) {
4653 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4654
4655 HeapRegion* r = g1h->region_at(region_idx);
4656 assert(!g1h->is_on_master_free_list(r), "sanity");
4657
4658 Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths);
4659
4660 if (!is_young) {
4661 g1h->_hot_card_cache->reset_card_counts(r);
4662 }
4663
4664 if (!evacuation_failed) {
4665 r->rem_set()->clear_locked();
4666 }
4667 }
4668
4669 class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure {
4670 private:
4671 size_t _cur_idx;
4672 WorkItem* _work_items;
4673 public:
4674 G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { }
4675
4676 virtual bool doHeapRegion(HeapRegion* r) {
4677 _work_items[_cur_idx++] = WorkItem(r);
4678 return false;
4679 }
4680 };
4681
4682 void prepare_work() {
4683 G1PrepareFreeCollectionSetClosure cl(_work_items);
4684 _collection_set->iterate(&cl);
4685 }
4686
4687 void complete_work() {
4688 _cl.complete_work();
4689
4690 G1Policy* policy = G1CollectedHeap::heap()->g1_policy();
4691 policy->record_max_rs_lengths(_rs_lengths);
4692 policy->cset_regions_freed();
4693 }
4694 public:
4695 G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4696 AbstractGangTask("G1 Free Collection Set"),
4697 _cl(evacuation_info, surviving_young_words),
4698 _collection_set(collection_set),
4699 _surviving_young_words(surviving_young_words),
4700 _serial_work_claim(0),
4701 _rs_lengths(0),
4702 _parallel_work_claim(0),
4703 _num_work_items(collection_set->region_length()),
4704 _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) {
4705 prepare_work();
4706 }
4707
4708 ~G1FreeCollectionSetTask() {
4709 complete_work();
4710 FREE_C_HEAP_ARRAY(WorkItem, _work_items);
4711 }
4712
4713 // Chunk size for work distribution. The chosen value has been determined experimentally
4714 // to be a good tradeoff between overhead and achievable parallelism.
4715 static uint chunk_size() { return 32; }
4716
4717 virtual void work(uint worker_id) {
4718 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
4719
4720 // Claim serial work.
4721 if (_serial_work_claim == 0) {
4722 jint value = Atomic::add(1, &_serial_work_claim) - 1;
4723 if (value == 0) {
4724 double serial_time = os::elapsedTime();
4725 do_serial_work();
4726 timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0);
4727 }
4728 }
4729
4730 // Start parallel work.
4731 double young_time = 0.0;
4732 bool has_young_time = false;
4733 double non_young_time = 0.0;
4734 bool has_non_young_time = false;
4735
4736 while (true) {
4737 size_t end = Atomic::add(chunk_size(), &_parallel_work_claim);
4738 size_t cur = end - chunk_size();
4739
4740 if (cur >= _num_work_items) {
4741 break;
4742 }
4743
4744 double start_time = os::elapsedTime();
4745
4746 end = MIN2(end, _num_work_items);
4747
4748 for (; cur < end; cur++) {
4749 bool is_young = _work_items[cur].is_young;
4750
4751 do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed);
4752
4753 double end_time = os::elapsedTime();
4754 double time_taken = end_time - start_time;
4755 if (is_young) {
4756 young_time += time_taken;
4757 has_young_time = true;
4758 } else {
4759 non_young_time += time_taken;
4760 has_non_young_time = true;
4761 }
4762 start_time = end_time;
4763 }
4764 }
4765
4766 if (has_young_time) {
4767 timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time);
4768 }
4769 if (has_non_young_time) {
4770 timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, young_time);
4771 }
4772 }
4773 };
4774
4775 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4776 _eden.clear();
4777
4778 double free_cset_start_time = os::elapsedTime();
4779
4780 {
4781 uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U);
4782 uint const num_workers = MIN2(workers()->active_workers(), num_chunks);
4783
4784 G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words);
4785
4786 log_debug(gc, ergo)("Running %s using %u workers for collection set length %u",
4787 cl.name(),
4788 num_workers,
4789 _collection_set.region_length());
4790 workers()->run_task(&cl, num_workers);
4791 }
4792 g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0);
4793
4794 collection_set->clear();
4795 }
4796
4797 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4798 private:
4799 FreeRegionList* _free_region_list;
4800 HeapRegionSet* _proxy_set;
4801 uint _humongous_objects_reclaimed;
4802 uint _humongous_regions_reclaimed;
4803 size_t _freed_bytes;
4804 public:
4805
4806 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4807 _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) {
4808 }
4809
4810 virtual bool doHeapRegion(HeapRegion* r) {
4811 if (!r->is_starts_humongous()) {
4812 return false;
4813 }
4814
4815 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4816
4817 oop obj = (oop)r->bottom();
4818 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
4819
4820 // The following checks whether the humongous object is live are sufficient.
4821 // The main additional check (in addition to having a reference from the roots
4822 // or the young gen) is whether the humongous object has a remembered set entry.
4823 //
4824 // A humongous object cannot be live if there is no remembered set for it
4825 // because:
4826 // - there can be no references from within humongous starts regions referencing
4827 // the object because we never allocate other objects into them.
4828 // (I.e. there are no intra-region references that may be missed by the
4829 // remembered set)
4830 // - as soon there is a remembered set entry to the humongous starts region
4831 // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4832 // until the end of a concurrent mark.
4833 //
4834 // It is not required to check whether the object has been found dead by marking
4835 // or not, in fact it would prevent reclamation within a concurrent cycle, as
4836 // all objects allocated during that time are considered live.
4837 // SATB marking is even more conservative than the remembered set.
4838 // So if at this point in the collection there is no remembered set entry,
4839 // nobody has a reference to it.
4840 // At the start of collection we flush all refinement logs, and remembered sets
4841 // are completely up-to-date wrt to references to the humongous object.
4842 //
4843 // Other implementation considerations:
4844 // - never consider object arrays at this time because they would pose
4845 // considerable effort for cleaning up the the remembered sets. This is
4846 // required because stale remembered sets might reference locations that
4847 // are currently allocated into.
4848 uint region_idx = r->hrm_index();
4849 if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4850 !r->rem_set()->is_empty()) {
4851 log_debug(gc, humongous)("Live humongous region %u object size " SIZE_FORMAT " start " PTR_FORMAT " with remset " SIZE_FORMAT " code roots " SIZE_FORMAT " is marked %d reclaim candidate %d type array %d",
4852 region_idx,
4853 (size_t)obj->size() * HeapWordSize,
4854 p2i(r->bottom()),
4855 r->rem_set()->occupied(),
4856 r->rem_set()->strong_code_roots_list_length(),
4857 next_bitmap->is_marked(r->bottom()),
4858 g1h->is_humongous_reclaim_candidate(region_idx),
4859 obj->is_typeArray()
4860 );
4861 return false;
4862 }
4863
4864 guarantee(obj->is_typeArray(),
4865 "Only eagerly reclaiming type arrays is supported, but the object "
4866 PTR_FORMAT " is not.", p2i(r->bottom()));
4867
4868 log_debug(gc, humongous)("Dead humongous region %u object size " SIZE_FORMAT " start " PTR_FORMAT " with remset " SIZE_FORMAT " code roots " SIZE_FORMAT " is marked %d reclaim candidate %d type array %d",
4869 region_idx,
4870 (size_t)obj->size() * HeapWordSize,
4871 p2i(r->bottom()),
4872 r->rem_set()->occupied(),
4873 r->rem_set()->strong_code_roots_list_length(),
4874 next_bitmap->is_marked(r->bottom()),
4875 g1h->is_humongous_reclaim_candidate(region_idx),
4876 obj->is_typeArray()
4877 );
4878
4879 // Need to clear mark bit of the humongous object if already set.
4880 if (next_bitmap->is_marked(r->bottom())) {
4881 next_bitmap->clear(r->bottom());
4882 }
4883 _humongous_objects_reclaimed++;
4884 do {
4885 HeapRegion* next = g1h->next_region_in_humongous(r);
4886 _freed_bytes += r->used();
4887 r->set_containing_set(NULL);
4888 _humongous_regions_reclaimed++;
4889 g1h->free_humongous_region(r, _free_region_list, false /* skip_remset */ );
4890 r = next;
4891 } while (r != NULL);
4892
4893 return false;
4894 }
4895
4896 uint humongous_objects_reclaimed() {
4897 return _humongous_objects_reclaimed;
4898 }
4899
4900 uint humongous_regions_reclaimed() {
4901 return _humongous_regions_reclaimed;
4902 }
4903
4904 size_t bytes_freed() const {
4905 return _freed_bytes;
4906 }
4907 };
4908
4909 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4910 assert_at_safepoint(true);
4911
4912 if (!G1EagerReclaimHumongousObjects ||
4913 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
4914 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
4915 return;
4916 }
4917
4918 double start_time = os::elapsedTime();
4919
4920 FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
4921
4922 G1FreeHumongousRegionClosure cl(&local_cleanup_list);
4923 heap_region_iterate(&cl);
4924
4925 remove_from_old_sets(0, cl.humongous_regions_reclaimed());
4926
4927 G1HRPrinter* hrp = hr_printer();
4928 if (hrp->is_active()) {
4929 FreeRegionListIterator iter(&local_cleanup_list);
4930 while (iter.more_available()) {
4931 HeapRegion* hr = iter.get_next();
4932 hrp->cleanup(hr);
4933 }
4934 }
4935
4936 prepend_to_freelist(&local_cleanup_list);
4937 decrement_summary_bytes(cl.bytes_freed());
4938
4939 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
4940 cl.humongous_objects_reclaimed());
4941 }
4942
4943 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
4944 public:
4945 virtual bool doHeapRegion(HeapRegion* r) {
4946 assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
4947 G1CollectedHeap::heap()->clear_in_cset(r);
4948 r->set_young_index_in_cset(-1);
4949 return false;
4950 }
4951 };
4952
4953 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
4954 G1AbandonCollectionSetClosure cl;
4955 collection_set->iterate(&cl);
4956
4957 collection_set->clear();
4958 collection_set->stop_incremental_building();
4959 }
4960
4961 void G1CollectedHeap::set_free_regions_coming() {
4962 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming");
4963
4964 assert(!free_regions_coming(), "pre-condition");
4965 _free_regions_coming = true;
4966 }
4967
4968 void G1CollectedHeap::reset_free_regions_coming() {
4969 assert(free_regions_coming(), "pre-condition");
4970
4971 {
4972 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
4973 _free_regions_coming = false;
4974 SecondaryFreeList_lock->notify_all();
4975 }
4976
4977 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming");
4978 }
4979
4980 void G1CollectedHeap::wait_while_free_regions_coming() {
4981 // Most of the time we won't have to wait, so let's do a quick test
4982 // first before we take the lock.
4983 if (!free_regions_coming()) {
4984 return;
4985 }
4986
4987 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions");
4988
4989 {
4990 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
4991 while (free_regions_coming()) {
4992 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
4993 }
4994 }
4995
4996 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions");
4997 }
4998
4999 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
5000 return _allocator->is_retained_old_region(hr);
5001 }
5002
5003 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
5004 _eden.add(hr);
5005 _g1_policy->set_region_eden(hr);
5006 }
5007
5008 #ifdef ASSERT
5009
5010 class NoYoungRegionsClosure: public HeapRegionClosure {
5011 private:
5012 bool _success;
5013 public:
5014 NoYoungRegionsClosure() : _success(true) { }
5015 bool doHeapRegion(HeapRegion* r) {
5016 if (r->is_young()) {
5017 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
5018 p2i(r->bottom()), p2i(r->end()));
5019 _success = false;
5020 }
5021 return false;
5022 }
5023 bool success() { return _success; }
5024 };
5025
5026 bool G1CollectedHeap::check_young_list_empty() {
5027 bool ret = (young_regions_count() == 0);
5028
5029 NoYoungRegionsClosure closure;
5030 heap_region_iterate(&closure);
5031 ret = ret && closure.success();
5032
5033 return ret;
5034 }
5035
5036 #endif // ASSERT
5037
5038 class TearDownRegionSetsClosure : public HeapRegionClosure {
5039 private:
5040 HeapRegionSet *_old_set;
5041
5042 public:
5043 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
5044
5045 bool doHeapRegion(HeapRegion* r) {
5046 if (r->is_old()) {
5047 _old_set->remove(r);
5048 } else if(r->is_young()) {
5049 r->uninstall_surv_rate_group();
5050 } else {
5051 // We ignore free regions, we'll empty the free list afterwards.
5052 // We ignore humongous regions, we're not tearing down the
5053 // humongous regions set.
5054 assert(r->is_free() || r->is_humongous(),
5055 "it cannot be another type");
5056 }
5057 return false;
5058 }
5059
5060 ~TearDownRegionSetsClosure() {
5061 assert(_old_set->is_empty(), "post-condition");
5062 }
5063 };
5064
5065 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
5066 assert_at_safepoint(true /* should_be_vm_thread */);
5067
5068 if (!free_list_only) {
5069 TearDownRegionSetsClosure cl(&_old_set);
5070 heap_region_iterate(&cl);
5071
5072 // Note that emptying the _young_list is postponed and instead done as
5073 // the first step when rebuilding the regions sets again. The reason for
5074 // this is that during a full GC string deduplication needs to know if
5075 // a collected region was young or old when the full GC was initiated.
5076 }
5077 _hrm.remove_all_free_regions();
5078 }
5079
5080 void G1CollectedHeap::increase_used(size_t bytes) {
5081 _summary_bytes_used += bytes;
5082 }
5083
5084 void G1CollectedHeap::decrease_used(size_t bytes) {
5085 assert(_summary_bytes_used >= bytes,
5086 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
5087 _summary_bytes_used, bytes);
5088 _summary_bytes_used -= bytes;
5089 }
5090
5091 void G1CollectedHeap::set_used(size_t bytes) {
5092 _summary_bytes_used = bytes;
5093 }
5094
5095 class RebuildRegionSetsClosure : public HeapRegionClosure {
5096 private:
5097 bool _free_list_only;
5098 HeapRegionSet* _old_set;
5099 HeapRegionManager* _hrm;
5100 size_t _total_used;
5101
5102 public:
5103 RebuildRegionSetsClosure(bool free_list_only,
5104 HeapRegionSet* old_set, HeapRegionManager* hrm) :
5105 _free_list_only(free_list_only),
5106 _old_set(old_set), _hrm(hrm), _total_used(0) {
5107 assert(_hrm->num_free_regions() == 0, "pre-condition");
5108 if (!free_list_only) {
5109 assert(_old_set->is_empty(), "pre-condition");
5110 }
5111 }
5112
5113 bool doHeapRegion(HeapRegion* r) {
5114 if (r->is_empty()) {
5115 // Add free regions to the free list
5116 r->set_free();
5117 r->set_allocation_context(AllocationContext::system());
5118 _hrm->insert_into_free_list(r);
5119 } else if (!_free_list_only) {
5120
5121 if (r->is_humongous()) {
5122 // We ignore humongous regions. We left the humongous set unchanged.
5123 } else {
5124 assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
5125 // We now move all (non-humongous, non-old) regions to old gen, and register them as such.
5126 r->move_to_old();
5127 _old_set->add(r);
5128 }
5129 _total_used += r->used();
5130 }
5131
5132 return false;
5133 }
5134
5135 size_t total_used() {
5136 return _total_used;
5137 }
5138 };
5139
5140 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
5141 assert_at_safepoint(true /* should_be_vm_thread */);
5142
5143 if (!free_list_only) {
5144 _eden.clear();
5145 _survivor.clear();
5146 }
5147
5148 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
5149 heap_region_iterate(&cl);
5150
5151 if (!free_list_only) {
5152 set_used(cl.total_used());
5153 if (_archive_allocator != NULL) {
5154 _archive_allocator->clear_used();
5155 }
5156 }
5157 assert(used_unlocked() == recalculate_used(),
5158 "inconsistent used_unlocked(), "
5159 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT,
5160 used_unlocked(), recalculate_used());
5161 }
5162
5163 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
5164 HeapRegion* hr = heap_region_containing(p);
5165 return hr->is_in(p);
5166 }
5167
5168 // Methods for the mutator alloc region
5169
5170 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
5171 bool force) {
5172 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5173 bool should_allocate = g1_policy()->should_allocate_mutator_region();
5174 if (force || should_allocate) {
5175 HeapRegion* new_alloc_region = new_region(word_size,
5176 false /* is_old */,
5177 false /* do_expand */);
5178 if (new_alloc_region != NULL) {
5179 set_region_short_lived_locked(new_alloc_region);
5180 _hr_printer.alloc(new_alloc_region, !should_allocate);
5181 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
5182 return new_alloc_region;
5183 }
5184 }
5185 return NULL;
5186 }
5187
5188 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
5189 size_t allocated_bytes) {
5190 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5191 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
5192
5193 collection_set()->add_eden_region(alloc_region);
5194 increase_used(allocated_bytes);
5195 _hr_printer.retire(alloc_region);
5196 // We update the eden sizes here, when the region is retired,
5197 // instead of when it's allocated, since this is the point that its
5198 // used space has been recored in _summary_bytes_used.
5199 g1mm()->update_eden_size();
5200 }
5201
5202 // Methods for the GC alloc regions
5203
5204 bool G1CollectedHeap::has_more_regions(InCSetState dest) {
5205 if (dest.is_old()) {
5206 return true;
5207 } else {
5208 return survivor_regions_count() < g1_policy()->max_survivor_regions();
5209 }
5210 }
5211
5212 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) {
5213 assert(FreeList_lock->owned_by_self(), "pre-condition");
5214
5215 if (!has_more_regions(dest)) {
5216 return NULL;
5217 }
5218
5219 const bool is_survivor = dest.is_young();
5220
5221 HeapRegion* new_alloc_region = new_region(word_size,
5222 !is_survivor,
5223 true /* do_expand */);
5224 if (new_alloc_region != NULL) {
5225 // We really only need to do this for old regions given that we
5226 // should never scan survivors. But it doesn't hurt to do it
5227 // for survivors too.
5228 new_alloc_region->record_timestamp();
5229 if (is_survivor) {
5230 new_alloc_region->set_survivor();
5231 _survivor.add(new_alloc_region);
5232 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
5233 } else {
5234 new_alloc_region->set_old();
5235 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
5236 }
5237 _hr_printer.alloc(new_alloc_region);
5238 bool during_im = collector_state()->during_initial_mark_pause();
5239 new_alloc_region->note_start_of_copying(during_im);
5240 return new_alloc_region;
5241 }
5242 return NULL;
5243 }
5244
5245 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
5246 size_t allocated_bytes,
5247 InCSetState dest) {
5248 bool during_im = collector_state()->during_initial_mark_pause();
5249 alloc_region->note_end_of_copying(during_im);
5250 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
5251 if (dest.is_old()) {
5252 _old_set.add(alloc_region);
5253 }
5254 _hr_printer.retire(alloc_region);
5255 }
5256
5257 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
5258 bool expanded = false;
5259 uint index = _hrm.find_highest_free(&expanded);
5260
5261 if (index != G1_NO_HRM_INDEX) {
5262 if (expanded) {
5263 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
5264 HeapRegion::GrainWords * HeapWordSize);
5265 }
5266 _hrm.allocate_free_regions_starting_at(index, 1);
5267 return region_at(index);
5268 }
5269 return NULL;
5270 }
5271
5272 // Optimized nmethod scanning
5273
5274 class RegisterNMethodOopClosure: public OopClosure {
5275 G1CollectedHeap* _g1h;
5276 nmethod* _nm;
5277
5278 template <class T> void do_oop_work(T* p) {
5279 T heap_oop = oopDesc::load_heap_oop(p);
5280 if (!oopDesc::is_null(heap_oop)) {
5281 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5282 HeapRegion* hr = _g1h->heap_region_containing(obj);
5283 assert(!hr->is_continues_humongous(),
5284 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5285 " starting at " HR_FORMAT,
5286 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5287
5288 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
5289 hr->add_strong_code_root_locked(_nm);
5290 }
5291 }
5292
5293 public:
5294 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5295 _g1h(g1h), _nm(nm) {}
5296
5297 void do_oop(oop* p) { do_oop_work(p); }
5298 void do_oop(narrowOop* p) { do_oop_work(p); }
5299 };
5300
5301 class UnregisterNMethodOopClosure: public OopClosure {
5302 G1CollectedHeap* _g1h;
5303 nmethod* _nm;
5304
5305 template <class T> void do_oop_work(T* p) {
5306 T heap_oop = oopDesc::load_heap_oop(p);
5307 if (!oopDesc::is_null(heap_oop)) {
5308 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5309 HeapRegion* hr = _g1h->heap_region_containing(obj);
5310 assert(!hr->is_continues_humongous(),
5311 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5312 " starting at " HR_FORMAT,
5313 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5314
5315 hr->remove_strong_code_root(_nm);
5316 }
5317 }
5318
5319 public:
5320 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5321 _g1h(g1h), _nm(nm) {}
5322
5323 void do_oop(oop* p) { do_oop_work(p); }
5324 void do_oop(narrowOop* p) { do_oop_work(p); }
5325 };
5326
5327 // Returns true if the reference points to an object that
5328 // can move in an incremental collection.
5329 bool G1CollectedHeap::is_scavengable(oop obj) {
5330 HeapRegion* hr = heap_region_containing(obj);
5331 return !hr->is_pinned();
5332 }
5333
5334 void G1CollectedHeap::register_nmethod(nmethod* nm) {
5335 guarantee(nm != NULL, "sanity");
5336 RegisterNMethodOopClosure reg_cl(this, nm);
5337 nm->oops_do(®_cl);
5338 }
5339
5340 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
5341 guarantee(nm != NULL, "sanity");
5342 UnregisterNMethodOopClosure reg_cl(this, nm);
5343 nm->oops_do(®_cl, true);
5344 }
5345
5346 void G1CollectedHeap::purge_code_root_memory() {
5347 double purge_start = os::elapsedTime();
5348 G1CodeRootSet::purge();
5349 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
5350 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
5351 }
5352
5353 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
5354 G1CollectedHeap* _g1h;
5355
5356 public:
5357 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
5358 _g1h(g1h) {}
5359
5360 void do_code_blob(CodeBlob* cb) {
5361 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
5362 if (nm == NULL) {
5363 return;
5364 }
5365
5366 if (ScavengeRootsInCode) {
5367 _g1h->register_nmethod(nm);
5368 }
5369 }
5370 };
5371
5372 void G1CollectedHeap::rebuild_strong_code_roots() {
5373 RebuildStrongCodeRootClosure blob_cl(this);
5374 CodeCache::blobs_do(&blob_cl);
5375 }