1 /*
2 * Copyright (c) 2001, 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/metadataOnStackMark.hpp"
27 #include "classfile/stringTable.hpp"
28 #include "classfile/symbolTable.hpp"
29 #include "code/codeCache.hpp"
30 #include "code/icBuffer.hpp"
31 #include "gc/g1/bufferingOopClosure.hpp"
32 #include "gc/g1/concurrentMarkThread.inline.hpp"
33 #include "gc/g1/g1Allocator.inline.hpp"
34 #include "gc/g1/g1CollectedHeap.inline.hpp"
35 #include "gc/g1/g1CollectionSet.hpp"
36 #include "gc/g1/g1CollectorPolicy.hpp"
37 #include "gc/g1/g1CollectorState.hpp"
38 #include "gc/g1/g1ConcurrentRefine.hpp"
39 #include "gc/g1/g1ConcurrentRefineThread.hpp"
40 #include "gc/g1/g1EvacStats.inline.hpp"
41 #include "gc/g1/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/g1YoungRemSetSamplingThread.hpp"
58 #include "gc/g1/heapRegion.inline.hpp"
59 #include "gc/g1/heapRegionRemSet.hpp"
60 #include "gc/g1/heapRegionSet.inline.hpp"
61 #include "gc/g1/vm_operations_g1.hpp"
62 #include "gc/shared/gcHeapSummary.hpp"
63 #include "gc/shared/gcId.hpp"
64 #include "gc/shared/gcLocker.inline.hpp"
65 #include "gc/shared/gcTimer.hpp"
66 #include "gc/shared/gcTrace.hpp"
67 #include "gc/shared/gcTraceTime.inline.hpp"
68 #include "gc/shared/generationSpec.hpp"
69 #include "gc/shared/isGCActiveMark.hpp"
70 #include "gc/shared/preservedMarks.inline.hpp"
71 #include "gc/shared/suspendibleThreadSet.hpp"
72 #include "gc/shared/referenceProcessor.inline.hpp"
73 #include "gc/shared/taskqueue.inline.hpp"
74 #include "gc/shared/weakProcessor.hpp"
75 #include "logging/log.hpp"
76 #include "memory/allocation.hpp"
77 #include "memory/iterator.hpp"
78 #include "memory/resourceArea.hpp"
79 #include "oops/oop.inline.hpp"
80 #include "prims/resolvedMethodTable.hpp"
81 #include "runtime/atomic.hpp"
82 #include "runtime/init.hpp"
83 #include "runtime/orderAccess.inline.hpp"
84 #include "runtime/vmThread.hpp"
85 #include "utilities/align.hpp"
86 #include "utilities/globalDefinitions.hpp"
87 #include "utilities/stack.inline.hpp"
88
89 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
90
91 // INVARIANTS/NOTES
92 //
93 // All allocation activity covered by the G1CollectedHeap interface is
94 // serialized by acquiring the HeapLock. This happens in mem_allocate
95 // and allocate_new_tlab, which are the "entry" points to the
96 // allocation code from the rest of the JVM. (Note that this does not
97 // apply to TLAB allocation, which is not part of this interface: it
98 // is done by clients of this interface.)
99
100 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
101 private:
102 size_t _num_dirtied;
103 G1CollectedHeap* _g1h;
104 G1SATBCardTableLoggingModRefBS* _g1_bs;
105
106 HeapRegion* region_for_card(jbyte* card_ptr) const {
107 return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr));
108 }
109
110 bool will_become_free(HeapRegion* hr) const {
111 // A region will be freed by free_collection_set if the region is in the
112 // collection set and has not had an evacuation failure.
113 return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
114 }
115
116 public:
117 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(),
118 _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { }
119
120 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
121 HeapRegion* hr = region_for_card(card_ptr);
122
123 // Should only dirty cards in regions that won't be freed.
124 if (!will_become_free(hr)) {
125 *card_ptr = CardTableModRefBS::dirty_card_val();
126 _num_dirtied++;
127 }
128
129 return true;
130 }
131
132 size_t num_dirtied() const { return _num_dirtied; }
133 };
134
135
136 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
137 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
138 }
139
140 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
141 // The from card cache is not the memory that is actually committed. So we cannot
142 // take advantage of the zero_filled parameter.
143 reset_from_card_cache(start_idx, num_regions);
144 }
145
146 // Private methods.
147
148 HeapRegion*
149 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
150 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
151 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
152 if (!_secondary_free_list.is_empty()) {
153 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
154 "secondary_free_list has %u entries",
155 _secondary_free_list.length());
156 // It looks as if there are free regions available on the
157 // secondary_free_list. Let's move them to the free_list and try
158 // again to allocate from it.
159 append_secondary_free_list();
160
161 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
162 "empty we should have moved at least one entry to the free_list");
163 HeapRegion* res = _hrm.allocate_free_region(is_old);
164 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
165 "allocated " HR_FORMAT " from secondary_free_list",
166 HR_FORMAT_PARAMS(res));
167 return res;
168 }
169
170 // Wait here until we get notified either when (a) there are no
171 // more free regions coming or (b) some regions have been moved on
172 // the secondary_free_list.
173 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
174 }
175
176 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
177 "could not allocate from secondary_free_list");
178 return NULL;
179 }
180
181 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
182 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
183 "the only time we use this to allocate a humongous region is "
184 "when we are allocating a single humongous region");
185
186 HeapRegion* res;
187 if (G1StressConcRegionFreeing) {
188 if (!_secondary_free_list.is_empty()) {
189 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
190 "forced to look at the secondary_free_list");
191 res = new_region_try_secondary_free_list(is_old);
192 if (res != NULL) {
193 return res;
194 }
195 }
196 }
197
198 res = _hrm.allocate_free_region(is_old);
199
200 if (res == NULL) {
201 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
202 "res == NULL, trying the secondary_free_list");
203 res = new_region_try_secondary_free_list(is_old);
204 }
205 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
206 // Currently, only attempts to allocate GC alloc regions set
207 // do_expand to true. So, we should only reach here during a
208 // safepoint. If this assumption changes we might have to
209 // reconsider the use of _expand_heap_after_alloc_failure.
210 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
211
212 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
213 word_size * HeapWordSize);
214
215 if (expand(word_size * HeapWordSize)) {
216 // Given that expand() succeeded in expanding the heap, and we
217 // always expand the heap by an amount aligned to the heap
218 // region size, the free list should in theory not be empty.
219 // In either case allocate_free_region() will check for NULL.
220 res = _hrm.allocate_free_region(is_old);
221 } else {
222 _expand_heap_after_alloc_failure = false;
223 }
224 }
225 return res;
226 }
227
228 HeapWord*
229 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
230 uint num_regions,
231 size_t word_size,
232 AllocationContext_t context) {
233 assert(first != G1_NO_HRM_INDEX, "pre-condition");
234 assert(is_humongous(word_size), "word_size should be humongous");
235 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
236
237 // Index of last region in the series.
238 uint last = first + num_regions - 1;
239
240 // We need to initialize the region(s) we just discovered. This is
241 // a bit tricky given that it can happen concurrently with
242 // refinement threads refining cards on these regions and
243 // potentially wanting to refine the BOT as they are scanning
244 // those cards (this can happen shortly after a cleanup; see CR
245 // 6991377). So we have to set up the region(s) carefully and in
246 // a specific order.
247
248 // The word size sum of all the regions we will allocate.
249 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
250 assert(word_size <= word_size_sum, "sanity");
251
252 // This will be the "starts humongous" region.
253 HeapRegion* first_hr = region_at(first);
254 // The header of the new object will be placed at the bottom of
255 // the first region.
256 HeapWord* new_obj = first_hr->bottom();
257 // This will be the new top of the new object.
258 HeapWord* obj_top = new_obj + word_size;
259
260 // First, we need to zero the header of the space that we will be
261 // allocating. When we update top further down, some refinement
262 // threads might try to scan the region. By zeroing the header we
263 // ensure that any thread that will try to scan the region will
264 // come across the zero klass word and bail out.
265 //
266 // NOTE: It would not have been correct to have used
267 // CollectedHeap::fill_with_object() and make the space look like
268 // an int array. The thread that is doing the allocation will
269 // later update the object header to a potentially different array
270 // type and, for a very short period of time, the klass and length
271 // fields will be inconsistent. This could cause a refinement
272 // thread to calculate the object size incorrectly.
273 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
274
275 // Next, pad out the unused tail of the last region with filler
276 // objects, for improved usage accounting.
277 // How many words we use for filler objects.
278 size_t word_fill_size = word_size_sum - word_size;
279
280 // How many words memory we "waste" which cannot hold a filler object.
281 size_t words_not_fillable = 0;
282
283 if (word_fill_size >= min_fill_size()) {
284 fill_with_objects(obj_top, word_fill_size);
285 } else if (word_fill_size > 0) {
286 // We have space to fill, but we cannot fit an object there.
287 words_not_fillable = word_fill_size;
288 word_fill_size = 0;
289 }
290
291 // We will set up the first region as "starts humongous". This
292 // will also update the BOT covering all the regions to reflect
293 // that there is a single object that starts at the bottom of the
294 // first region.
295 first_hr->set_starts_humongous(obj_top, word_fill_size);
296 first_hr->set_allocation_context(context);
297 // Then, if there are any, we will set up the "continues
298 // humongous" regions.
299 HeapRegion* hr = NULL;
300 for (uint i = first + 1; i <= last; ++i) {
301 hr = region_at(i);
302 hr->set_continues_humongous(first_hr);
303 hr->set_allocation_context(context);
304 }
305
306 // Up to this point no concurrent thread would have been able to
307 // do any scanning on any region in this series. All the top
308 // fields still point to bottom, so the intersection between
309 // [bottom,top] and [card_start,card_end] will be empty. Before we
310 // update the top fields, we'll do a storestore to make sure that
311 // no thread sees the update to top before the zeroing of the
312 // object header and the BOT initialization.
313 OrderAccess::storestore();
314
315 // Now, we will update the top fields of the "continues humongous"
316 // regions except the last one.
317 for (uint i = first; i < last; ++i) {
318 hr = region_at(i);
319 hr->set_top(hr->end());
320 }
321
322 hr = region_at(last);
323 // If we cannot fit a filler object, we must set top to the end
324 // of the humongous object, otherwise we cannot iterate the heap
325 // and the BOT will not be complete.
326 hr->set_top(hr->end() - words_not_fillable);
327
328 assert(hr->bottom() < obj_top && obj_top <= hr->end(),
329 "obj_top should be in last region");
330
331 _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
332
333 assert(words_not_fillable == 0 ||
334 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
335 "Miscalculation in humongous allocation");
336
337 increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
338
339 for (uint i = first; i <= last; ++i) {
340 hr = region_at(i);
341 _humongous_set.add(hr);
342 _hr_printer.alloc(hr);
343 }
344
345 return new_obj;
346 }
347
348 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
349 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
350 return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
351 }
352
353 // If could fit into free regions w/o expansion, try.
354 // Otherwise, if can expand, do so.
355 // Otherwise, if using ex regions might help, try with ex given back.
356 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
357 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
358
359 _verifier->verify_region_sets_optional();
360
361 uint first = G1_NO_HRM_INDEX;
362 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
363
364 if (obj_regions == 1) {
365 // Only one region to allocate, try to use a fast path by directly allocating
366 // from the free lists. Do not try to expand here, we will potentially do that
367 // later.
368 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
369 if (hr != NULL) {
370 first = hr->hrm_index();
371 }
372 } else {
373 // We can't allocate humongous regions spanning more than one region while
374 // cleanupComplete() is running, since some of the regions we find to be
375 // empty might not yet be added to the free list. It is not straightforward
376 // to know in which list they are on so that we can remove them. We only
377 // need to do this if we need to allocate more than one region to satisfy the
378 // current humongous allocation request. If we are only allocating one region
379 // we use the one-region region allocation code (see above), that already
380 // potentially waits for regions from the secondary free list.
381 wait_while_free_regions_coming();
382 append_secondary_free_list_if_not_empty_with_lock();
383
384 // Policy: Try only empty regions (i.e. already committed first). Maybe we
385 // are lucky enough to find some.
386 first = _hrm.find_contiguous_only_empty(obj_regions);
387 if (first != G1_NO_HRM_INDEX) {
388 _hrm.allocate_free_regions_starting_at(first, obj_regions);
389 }
390 }
391
392 if (first == G1_NO_HRM_INDEX) {
393 // Policy: We could not find enough regions for the humongous object in the
394 // free list. Look through the heap to find a mix of free and uncommitted regions.
395 // If so, try expansion.
396 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
397 if (first != G1_NO_HRM_INDEX) {
398 // We found something. Make sure these regions are committed, i.e. expand
399 // the heap. Alternatively we could do a defragmentation GC.
400 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
401 word_size * HeapWordSize);
402
403 _hrm.expand_at(first, obj_regions, workers());
404 g1_policy()->record_new_heap_size(num_regions());
405
406 #ifdef ASSERT
407 for (uint i = first; i < first + obj_regions; ++i) {
408 HeapRegion* hr = region_at(i);
409 assert(hr->is_free(), "sanity");
410 assert(hr->is_empty(), "sanity");
411 assert(is_on_master_free_list(hr), "sanity");
412 }
413 #endif
414 _hrm.allocate_free_regions_starting_at(first, obj_regions);
415 } else {
416 // Policy: Potentially trigger a defragmentation GC.
417 }
418 }
419
420 HeapWord* result = NULL;
421 if (first != G1_NO_HRM_INDEX) {
422 result = humongous_obj_allocate_initialize_regions(first, obj_regions,
423 word_size, context);
424 assert(result != NULL, "it should always return a valid result");
425
426 // A successful humongous object allocation changes the used space
427 // information of the old generation so we need to recalculate the
428 // sizes and update the jstat counters here.
429 g1mm()->update_sizes();
430 }
431
432 _verifier->verify_region_sets_optional();
433
434 return result;
435 }
436
437 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
438 assert_heap_not_locked_and_not_at_safepoint();
439 assert(!is_humongous(word_size), "we do not allow humongous TLABs");
440
441 uint dummy_gc_count_before;
442 uint dummy_gclocker_retry_count = 0;
443 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
444 }
445
446 HeapWord*
447 G1CollectedHeap::mem_allocate(size_t word_size,
448 bool* gc_overhead_limit_was_exceeded) {
449 assert_heap_not_locked_and_not_at_safepoint();
450
451 // Loop until the allocation is satisfied, or unsatisfied after GC.
452 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
453 uint gc_count_before;
454
455 HeapWord* result = NULL;
456 if (!is_humongous(word_size)) {
457 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
458 } else {
459 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
460 }
461 if (result != NULL) {
462 return result;
463 }
464
465 // Create the garbage collection operation...
466 VM_G1CollectForAllocation op(gc_count_before, word_size);
467 op.set_allocation_context(AllocationContext::current());
468
469 // ...and get the VM thread to execute it.
470 VMThread::execute(&op);
471
472 if (op.prologue_succeeded() && op.pause_succeeded()) {
473 // If the operation was successful we'll return the result even
474 // if it is NULL. If the allocation attempt failed immediately
475 // after a Full GC, it's unlikely we'll be able to allocate now.
476 HeapWord* result = op.result();
477 if (result != NULL && !is_humongous(word_size)) {
478 // Allocations that take place on VM operations do not do any
479 // card dirtying and we have to do it here. We only have to do
480 // this for non-humongous allocations, though.
481 dirty_young_block(result, word_size);
482 }
483 return result;
484 } else {
485 if (gclocker_retry_count > GCLockerRetryAllocationCount) {
486 return NULL;
487 }
488 assert(op.result() == NULL,
489 "the result should be NULL if the VM op did not succeed");
490 }
491
492 // Give a warning if we seem to be looping forever.
493 if ((QueuedAllocationWarningCount > 0) &&
494 (try_count % QueuedAllocationWarningCount == 0)) {
495 log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count);
496 }
497 }
498
499 ShouldNotReachHere();
500 return NULL;
501 }
502
503 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
504 AllocationContext_t context,
505 uint* gc_count_before_ret,
506 uint* gclocker_retry_count_ret) {
507 // Make sure you read the note in attempt_allocation_humongous().
508
509 assert_heap_not_locked_and_not_at_safepoint();
510 assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
511 "be called for humongous allocation requests");
512
513 // We should only get here after the first-level allocation attempt
514 // (attempt_allocation()) failed to allocate.
515
516 // We will loop until a) we manage to successfully perform the
517 // allocation or b) we successfully schedule a collection which
518 // fails to perform the allocation. b) is the only case when we'll
519 // return NULL.
520 HeapWord* result = NULL;
521 for (int try_count = 1; /* we'll return */; try_count += 1) {
522 bool should_try_gc;
523 uint gc_count_before;
524
525 {
526 MutexLockerEx x(Heap_lock);
527 result = _allocator->attempt_allocation_locked(word_size, context);
528 if (result != NULL) {
529 return result;
530 }
531
532 if (GCLocker::is_active_and_needs_gc()) {
533 if (g1_policy()->can_expand_young_list()) {
534 // No need for an ergo verbose message here,
535 // can_expand_young_list() does this when it returns true.
536 result = _allocator->attempt_allocation_force(word_size, context);
537 if (result != NULL) {
538 return result;
539 }
540 }
541 should_try_gc = false;
542 } else {
543 // The GCLocker may not be active but the GCLocker initiated
544 // GC may not yet have been performed (GCLocker::needs_gc()
545 // returns true). In this case we do not try this GC and
546 // wait until the GCLocker initiated GC is performed, and
547 // then retry the allocation.
548 if (GCLocker::needs_gc()) {
549 should_try_gc = false;
550 } else {
551 // Read the GC count while still holding the Heap_lock.
552 gc_count_before = total_collections();
553 should_try_gc = true;
554 }
555 }
556 }
557
558 if (should_try_gc) {
559 bool succeeded;
560 result = do_collection_pause(word_size, gc_count_before, &succeeded,
561 GCCause::_g1_inc_collection_pause);
562 if (result != NULL) {
563 assert(succeeded, "only way to get back a non-NULL result");
564 return result;
565 }
566
567 if (succeeded) {
568 // If we get here we successfully scheduled a collection which
569 // failed to allocate. No point in trying to allocate
570 // further. We'll just return NULL.
571 MutexLockerEx x(Heap_lock);
572 *gc_count_before_ret = total_collections();
573 return NULL;
574 }
575 } else {
576 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
577 MutexLockerEx x(Heap_lock);
578 *gc_count_before_ret = total_collections();
579 return NULL;
580 }
581 // The GCLocker is either active or the GCLocker initiated
582 // GC has not yet been performed. Stall until it is and
583 // then retry the allocation.
584 GCLocker::stall_until_clear();
585 (*gclocker_retry_count_ret) += 1;
586 }
587
588 // We can reach here if we were unsuccessful in scheduling a
589 // collection (because another thread beat us to it) or if we were
590 // stalled due to the GC locker. In either can we should retry the
591 // allocation attempt in case another thread successfully
592 // performed a collection and reclaimed enough space. We do the
593 // first attempt (without holding the Heap_lock) here and the
594 // follow-on attempt will be at the start of the next loop
595 // iteration (after taking the Heap_lock).
596 result = _allocator->attempt_allocation(word_size, context);
597 if (result != NULL) {
598 return result;
599 }
600
601 // Give a warning if we seem to be looping forever.
602 if ((QueuedAllocationWarningCount > 0) &&
603 (try_count % QueuedAllocationWarningCount == 0)) {
604 log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() "
605 "retries %d times", try_count);
606 }
607 }
608
609 ShouldNotReachHere();
610 return NULL;
611 }
612
613 void G1CollectedHeap::begin_archive_alloc_range(bool open) {
614 assert_at_safepoint(true /* should_be_vm_thread */);
615 if (_archive_allocator == NULL) {
616 _archive_allocator = G1ArchiveAllocator::create_allocator(this, open);
617 }
618 }
619
620 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
621 // Allocations in archive regions cannot be of a size that would be considered
622 // humongous even for a minimum-sized region, because G1 region sizes/boundaries
623 // may be different at archive-restore time.
624 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
625 }
626
627 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
628 assert_at_safepoint(true /* should_be_vm_thread */);
629 assert(_archive_allocator != NULL, "_archive_allocator not initialized");
630 if (is_archive_alloc_too_large(word_size)) {
631 return NULL;
632 }
633 return _archive_allocator->archive_mem_allocate(word_size);
634 }
635
636 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
637 size_t end_alignment_in_bytes) {
638 assert_at_safepoint(true /* should_be_vm_thread */);
639 assert(_archive_allocator != NULL, "_archive_allocator not initialized");
640
641 // Call complete_archive to do the real work, filling in the MemRegion
642 // array with the archive regions.
643 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
644 delete _archive_allocator;
645 _archive_allocator = NULL;
646 }
647
648 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
649 assert(ranges != NULL, "MemRegion array NULL");
650 assert(count != 0, "No MemRegions provided");
651 MemRegion reserved = _hrm.reserved();
652 for (size_t i = 0; i < count; i++) {
653 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
654 return false;
655 }
656 }
657 return true;
658 }
659
660 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges,
661 size_t count,
662 bool open) {
663 assert(!is_init_completed(), "Expect to be called at JVM init time");
664 assert(ranges != NULL, "MemRegion array NULL");
665 assert(count != 0, "No MemRegions provided");
666 MutexLockerEx x(Heap_lock);
667
668 MemRegion reserved = _hrm.reserved();
669 HeapWord* prev_last_addr = NULL;
670 HeapRegion* prev_last_region = NULL;
671
672 // Temporarily disable pretouching of heap pages. This interface is used
673 // when mmap'ing archived heap data in, so pre-touching is wasted.
674 FlagSetting fs(AlwaysPreTouch, false);
675
676 // Enable archive object checking used by G1MarkSweep. We have to let it know
677 // about each archive range, so that objects in those ranges aren't marked.
678 G1ArchiveAllocator::enable_archive_object_check();
679
680 // For each specified MemRegion range, allocate the corresponding G1
681 // regions and mark them as archive regions. We expect the ranges
682 // in ascending starting address order, without overlap.
683 for (size_t i = 0; i < count; i++) {
684 MemRegion curr_range = ranges[i];
685 HeapWord* start_address = curr_range.start();
686 size_t word_size = curr_range.word_size();
687 HeapWord* last_address = curr_range.last();
688 size_t commits = 0;
689
690 guarantee(reserved.contains(start_address) && reserved.contains(last_address),
691 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
692 p2i(start_address), p2i(last_address));
693 guarantee(start_address > prev_last_addr,
694 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
695 p2i(start_address), p2i(prev_last_addr));
696 prev_last_addr = last_address;
697
698 // Check for ranges that start in the same G1 region in which the previous
699 // range ended, and adjust the start address so we don't try to allocate
700 // the same region again. If the current range is entirely within that
701 // region, skip it, just adjusting the recorded top.
702 HeapRegion* start_region = _hrm.addr_to_region(start_address);
703 if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
704 start_address = start_region->end();
705 if (start_address > last_address) {
706 increase_used(word_size * HeapWordSize);
707 start_region->set_top(last_address + 1);
708 continue;
709 }
710 start_region->set_top(start_address);
711 curr_range = MemRegion(start_address, last_address + 1);
712 start_region = _hrm.addr_to_region(start_address);
713 }
714
715 // Perform the actual region allocation, exiting if it fails.
716 // Then note how much new space we have allocated.
717 if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) {
718 return false;
719 }
720 increase_used(word_size * HeapWordSize);
721 if (commits != 0) {
722 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
723 HeapRegion::GrainWords * HeapWordSize * commits);
724
725 }
726
727 // Mark each G1 region touched by the range as archive, add it to
728 // the old set, and set the allocation context and top.
729 HeapRegion* curr_region = _hrm.addr_to_region(start_address);
730 HeapRegion* last_region = _hrm.addr_to_region(last_address);
731 prev_last_region = last_region;
732
733 while (curr_region != NULL) {
734 assert(curr_region->is_empty() && !curr_region->is_pinned(),
735 "Region already in use (index %u)", curr_region->hrm_index());
736 curr_region->set_allocation_context(AllocationContext::system());
737 if (open) {
738 curr_region->set_open_archive();
739 } else {
740 curr_region->set_closed_archive();
741 }
742 _hr_printer.alloc(curr_region);
743 _old_set.add(curr_region);
744 HeapWord* top;
745 HeapRegion* next_region;
746 if (curr_region != last_region) {
747 top = curr_region->end();
748 next_region = _hrm.next_region_in_heap(curr_region);
749 } else {
750 top = last_address + 1;
751 next_region = NULL;
752 }
753 curr_region->set_top(top);
754 curr_region->set_first_dead(top);
755 curr_region->set_end_of_live(top);
756 curr_region = next_region;
757 }
758
759 // Notify mark-sweep of the archive
760 G1ArchiveAllocator::set_range_archive(curr_range, open);
761 }
762 return true;
763 }
764
765 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
766 assert(!is_init_completed(), "Expect to be called at JVM init time");
767 assert(ranges != NULL, "MemRegion array NULL");
768 assert(count != 0, "No MemRegions provided");
769 MemRegion reserved = _hrm.reserved();
770 HeapWord *prev_last_addr = NULL;
771 HeapRegion* prev_last_region = NULL;
772
773 // For each MemRegion, create filler objects, if needed, in the G1 regions
774 // that contain the address range. The address range actually within the
775 // MemRegion will not be modified. That is assumed to have been initialized
776 // elsewhere, probably via an mmap of archived heap data.
777 MutexLockerEx x(Heap_lock);
778 for (size_t i = 0; i < count; i++) {
779 HeapWord* start_address = ranges[i].start();
780 HeapWord* last_address = ranges[i].last();
781
782 assert(reserved.contains(start_address) && reserved.contains(last_address),
783 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
784 p2i(start_address), p2i(last_address));
785 assert(start_address > prev_last_addr,
786 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
787 p2i(start_address), p2i(prev_last_addr));
788
789 HeapRegion* start_region = _hrm.addr_to_region(start_address);
790 HeapRegion* last_region = _hrm.addr_to_region(last_address);
791 HeapWord* bottom_address = start_region->bottom();
792
793 // Check for a range beginning in the same region in which the
794 // previous one ended.
795 if (start_region == prev_last_region) {
796 bottom_address = prev_last_addr + 1;
797 }
798
799 // Verify that the regions were all marked as archive regions by
800 // alloc_archive_regions.
801 HeapRegion* curr_region = start_region;
802 while (curr_region != NULL) {
803 guarantee(curr_region->is_archive(),
804 "Expected archive region at index %u", curr_region->hrm_index());
805 if (curr_region != last_region) {
806 curr_region = _hrm.next_region_in_heap(curr_region);
807 } else {
808 curr_region = NULL;
809 }
810 }
811
812 prev_last_addr = last_address;
813 prev_last_region = last_region;
814
815 // Fill the memory below the allocated range with dummy object(s),
816 // if the region bottom does not match the range start, or if the previous
817 // range ended within the same G1 region, and there is a gap.
818 if (start_address != bottom_address) {
819 size_t fill_size = pointer_delta(start_address, bottom_address);
820 G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
821 increase_used(fill_size * HeapWordSize);
822 }
823 }
824 }
825
826 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size,
827 uint* gc_count_before_ret,
828 uint* gclocker_retry_count_ret) {
829 assert_heap_not_locked_and_not_at_safepoint();
830 assert(!is_humongous(word_size), "attempt_allocation() should not "
831 "be called for humongous allocation requests");
832
833 AllocationContext_t context = AllocationContext::current();
834 HeapWord* result = _allocator->attempt_allocation(word_size, context);
835
836 if (result == NULL) {
837 result = attempt_allocation_slow(word_size,
838 context,
839 gc_count_before_ret,
840 gclocker_retry_count_ret);
841 }
842 assert_heap_not_locked();
843 if (result != NULL) {
844 dirty_young_block(result, word_size);
845 }
846 return result;
847 }
848
849 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
850 assert(!is_init_completed(), "Expect to be called at JVM init time");
851 assert(ranges != NULL, "MemRegion array NULL");
852 assert(count != 0, "No MemRegions provided");
853 MemRegion reserved = _hrm.reserved();
854 HeapWord* prev_last_addr = NULL;
855 HeapRegion* prev_last_region = NULL;
856 size_t size_used = 0;
857 size_t uncommitted_regions = 0;
858
859 // For each Memregion, free the G1 regions that constitute it, and
860 // notify mark-sweep that the range is no longer to be considered 'archive.'
861 MutexLockerEx x(Heap_lock);
862 for (size_t i = 0; i < count; i++) {
863 HeapWord* start_address = ranges[i].start();
864 HeapWord* last_address = ranges[i].last();
865
866 assert(reserved.contains(start_address) && reserved.contains(last_address),
867 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
868 p2i(start_address), p2i(last_address));
869 assert(start_address > prev_last_addr,
870 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
871 p2i(start_address), p2i(prev_last_addr));
872 size_used += ranges[i].byte_size();
873 prev_last_addr = last_address;
874
875 HeapRegion* start_region = _hrm.addr_to_region(start_address);
876 HeapRegion* last_region = _hrm.addr_to_region(last_address);
877
878 // Check for ranges that start in the same G1 region in which the previous
879 // range ended, and adjust the start address so we don't try to free
880 // the same region again. If the current range is entirely within that
881 // region, skip it.
882 if (start_region == prev_last_region) {
883 start_address = start_region->end();
884 if (start_address > last_address) {
885 continue;
886 }
887 start_region = _hrm.addr_to_region(start_address);
888 }
889 prev_last_region = last_region;
890
891 // After verifying that each region was marked as an archive region by
892 // alloc_archive_regions, set it free and empty and uncommit it.
893 HeapRegion* curr_region = start_region;
894 while (curr_region != NULL) {
895 guarantee(curr_region->is_archive(),
896 "Expected archive region at index %u", curr_region->hrm_index());
897 uint curr_index = curr_region->hrm_index();
898 _old_set.remove(curr_region);
899 curr_region->set_free();
900 curr_region->set_top(curr_region->bottom());
901 if (curr_region != last_region) {
902 curr_region = _hrm.next_region_in_heap(curr_region);
903 } else {
904 curr_region = NULL;
905 }
906 _hrm.shrink_at(curr_index, 1);
907 uncommitted_regions++;
908 }
909
910 // Notify mark-sweep that this is no longer an archive range.
911 G1ArchiveAllocator::set_range_archive(ranges[i], false);
912 }
913
914 if (uncommitted_regions != 0) {
915 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
916 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
917 }
918 decrease_used(size_used);
919 }
920
921 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
922 uint* gc_count_before_ret,
923 uint* gclocker_retry_count_ret) {
924 // The structure of this method has a lot of similarities to
925 // attempt_allocation_slow(). The reason these two were not merged
926 // into a single one is that such a method would require several "if
927 // allocation is not humongous do this, otherwise do that"
928 // conditional paths which would obscure its flow. In fact, an early
929 // version of this code did use a unified method which was harder to
930 // follow and, as a result, it had subtle bugs that were hard to
931 // track down. So keeping these two methods separate allows each to
932 // be more readable. It will be good to keep these two in sync as
933 // much as possible.
934
935 assert_heap_not_locked_and_not_at_safepoint();
936 assert(is_humongous(word_size), "attempt_allocation_humongous() "
937 "should only be called for humongous allocations");
938
939 // Humongous objects can exhaust the heap quickly, so we should check if we
940 // need to start a marking cycle at each humongous object allocation. We do
941 // the check before we do the actual allocation. The reason for doing it
942 // before the allocation is that we avoid having to keep track of the newly
943 // allocated memory while we do a GC.
944 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
945 word_size)) {
946 collect(GCCause::_g1_humongous_allocation);
947 }
948
949 // We will loop until a) we manage to successfully perform the
950 // allocation or b) we successfully schedule a collection which
951 // fails to perform the allocation. b) is the only case when we'll
952 // return NULL.
953 HeapWord* result = NULL;
954 for (int try_count = 1; /* we'll return */; try_count += 1) {
955 bool should_try_gc;
956 uint gc_count_before;
957
958 {
959 MutexLockerEx x(Heap_lock);
960
961 // Given that humongous objects are not allocated in young
962 // regions, we'll first try to do the allocation without doing a
963 // collection hoping that there's enough space in the heap.
964 result = humongous_obj_allocate(word_size, AllocationContext::current());
965 if (result != NULL) {
966 size_t size_in_regions = humongous_obj_size_in_regions(word_size);
967 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
968 return result;
969 }
970
971 if (GCLocker::is_active_and_needs_gc()) {
972 should_try_gc = false;
973 } else {
974 // The GCLocker may not be active but the GCLocker initiated
975 // GC may not yet have been performed (GCLocker::needs_gc()
976 // returns true). In this case we do not try this GC and
977 // wait until the GCLocker initiated GC is performed, and
978 // then retry the allocation.
979 if (GCLocker::needs_gc()) {
980 should_try_gc = false;
981 } else {
982 // Read the GC count while still holding the Heap_lock.
983 gc_count_before = total_collections();
984 should_try_gc = true;
985 }
986 }
987 }
988
989 if (should_try_gc) {
990 // If we failed to allocate the humongous object, we should try to
991 // do a collection pause (if we're allowed) in case it reclaims
992 // enough space for the allocation to succeed after the pause.
993
994 bool succeeded;
995 result = do_collection_pause(word_size, gc_count_before, &succeeded,
996 GCCause::_g1_humongous_allocation);
997 if (result != NULL) {
998 assert(succeeded, "only way to get back a non-NULL result");
999 return result;
1000 }
1001
1002 if (succeeded) {
1003 // If we get here we successfully scheduled a collection which
1004 // failed to allocate. No point in trying to allocate
1005 // further. We'll just return NULL.
1006 MutexLockerEx x(Heap_lock);
1007 *gc_count_before_ret = total_collections();
1008 return NULL;
1009 }
1010 } else {
1011 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1012 MutexLockerEx x(Heap_lock);
1013 *gc_count_before_ret = total_collections();
1014 return NULL;
1015 }
1016 // The GCLocker is either active or the GCLocker initiated
1017 // GC has not yet been performed. Stall until it is and
1018 // then retry the allocation.
1019 GCLocker::stall_until_clear();
1020 (*gclocker_retry_count_ret) += 1;
1021 }
1022
1023 // We can reach here if we were unsuccessful in scheduling a
1024 // collection (because another thread beat us to it) or if we were
1025 // stalled due to the GC locker. In either can we should retry the
1026 // allocation attempt in case another thread successfully
1027 // performed a collection and reclaimed enough space. Give a
1028 // warning if we seem to be looping forever.
1029
1030 if ((QueuedAllocationWarningCount > 0) &&
1031 (try_count % QueuedAllocationWarningCount == 0)) {
1032 log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() "
1033 "retries %d times", try_count);
1034 }
1035 }
1036
1037 ShouldNotReachHere();
1038 return NULL;
1039 }
1040
1041 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1042 AllocationContext_t context,
1043 bool expect_null_mutator_alloc_region) {
1044 assert_at_safepoint(true /* should_be_vm_thread */);
1045 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region,
1046 "the current alloc region was unexpectedly found to be non-NULL");
1047
1048 if (!is_humongous(word_size)) {
1049 return _allocator->attempt_allocation_locked(word_size, context);
1050 } else {
1051 HeapWord* result = humongous_obj_allocate(word_size, context);
1052 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1053 collector_state()->set_initiate_conc_mark_if_possible(true);
1054 }
1055 return result;
1056 }
1057
1058 ShouldNotReachHere();
1059 }
1060
1061 class PostCompactionPrinterClosure: public HeapRegionClosure {
1062 private:
1063 G1HRPrinter* _hr_printer;
1064 public:
1065 bool doHeapRegion(HeapRegion* hr) {
1066 assert(!hr->is_young(), "not expecting to find young regions");
1067 _hr_printer->post_compaction(hr);
1068 return false;
1069 }
1070
1071 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1072 : _hr_printer(hr_printer) { }
1073 };
1074
1075 void G1CollectedHeap::print_hrm_post_compaction() {
1076 if (_hr_printer.is_active()) {
1077 PostCompactionPrinterClosure cl(hr_printer());
1078 heap_region_iterate(&cl);
1079 }
1080
1081 }
1082
1083 void G1CollectedHeap::abort_concurrent_cycle() {
1084 // Note: When we have a more flexible GC logging framework that
1085 // allows us to add optional attributes to a GC log record we
1086 // could consider timing and reporting how long we wait in the
1087 // following two methods.
1088 wait_while_free_regions_coming();
1089 // If we start the compaction before the CM threads finish
1090 // scanning the root regions we might trip them over as we'll
1091 // be moving objects / updating references. So let's wait until
1092 // they are done. By telling them to abort, they should complete
1093 // early.
1094 _cm->root_regions()->abort();
1095 _cm->root_regions()->wait_until_scan_finished();
1096 append_secondary_free_list_if_not_empty_with_lock();
1097
1098 // Disable discovery and empty the discovered lists
1099 // for the CM ref processor.
1100 ref_processor_cm()->disable_discovery();
1101 ref_processor_cm()->abandon_partial_discovery();
1102 ref_processor_cm()->verify_no_references_recorded();
1103
1104 // Abandon current iterations of concurrent marking and concurrent
1105 // refinement, if any are in progress.
1106 concurrent_mark()->abort();
1107 }
1108
1109 void G1CollectedHeap::prepare_heap_for_full_collection() {
1110 // Make sure we'll choose a new allocation region afterwards.
1111 _allocator->release_mutator_alloc_region();
1112 _allocator->abandon_gc_alloc_regions();
1113 g1_rem_set()->cleanupHRRS();
1114
1115 // We may have added regions to the current incremental collection
1116 // set between the last GC or pause and now. We need to clear the
1117 // incremental collection set and then start rebuilding it afresh
1118 // after this full GC.
1119 abandon_collection_set(collection_set());
1120
1121 tear_down_region_sets(false /* free_list_only */);
1122 collector_state()->set_gcs_are_young(true);
1123 }
1124
1125 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) {
1126 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1127 assert(used() == recalculate_used(), "Should be equal");
1128 _verifier->verify_region_sets_optional();
1129 _verifier->verify_before_gc();
1130 _verifier->check_bitmaps("Full GC Start");
1131 }
1132
1133 void G1CollectedHeap::prepare_heap_for_mutators() {
1134 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1135 ClassLoaderDataGraph::purge();
1136 MetaspaceAux::verify_metrics();
1137
1138 // Prepare heap for normal collections.
1139 assert(num_free_regions() == 0, "we should not have added any free regions");
1140 rebuild_region_sets(false /* free_list_only */);
1141 abort_refinement();
1142 resize_if_necessary_after_full_collection();
1143
1144 // Rebuild the strong code root lists for each region
1145 rebuild_strong_code_roots();
1146
1147 // Start a new incremental collection set for the next pause
1148 start_new_collection_set();
1149
1150 _allocator->init_mutator_alloc_region();
1151
1152 // Post collection state updates.
1153 MetaspaceGC::compute_new_size();
1154 }
1155
1156 void G1CollectedHeap::abort_refinement() {
1157 if (_hot_card_cache->use_cache()) {
1158 _hot_card_cache->reset_card_counts();
1159 _hot_card_cache->reset_hot_cache();
1160 }
1161
1162 // Discard all remembered set updates.
1163 JavaThread::dirty_card_queue_set().abandon_logs();
1164 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1165 }
1166
1167 void G1CollectedHeap::verify_after_full_collection() {
1168 check_gc_time_stamps();
1169 _hrm.verify_optional();
1170 _verifier->verify_region_sets_optional();
1171 _verifier->verify_after_gc();
1172 // Clear the previous marking bitmap, if needed for bitmap verification.
1173 // Note we cannot do this when we clear the next marking bitmap in
1174 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1175 // objects marked during a full GC against the previous bitmap.
1176 // But we need to clear it before calling check_bitmaps below since
1177 // the full GC has compacted objects and updated TAMS but not updated
1178 // the prev bitmap.
1179 if (G1VerifyBitmaps) {
1180 GCTraceTime(Debug, gc)("Clear Bitmap for Verification");
1181 _cm->clear_prev_bitmap(workers());
1182 }
1183 _verifier->check_bitmaps("Full GC End");
1184
1185 // At this point there should be no regions in the
1186 // entire heap tagged as young.
1187 assert(check_young_list_empty(), "young list should be empty at this point");
1188
1189 // Note: since we've just done a full GC, concurrent
1190 // marking is no longer active. Therefore we need not
1191 // re-enable reference discovery for the CM ref processor.
1192 // That will be done at the start of the next marking cycle.
1193 // We also know that the STW processor should no longer
1194 // discover any new references.
1195 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1196 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1197 ref_processor_stw()->verify_no_references_recorded();
1198 ref_processor_cm()->verify_no_references_recorded();
1199 }
1200
1201 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) {
1202 print_hrm_post_compaction();
1203 heap_transition->print();
1204 print_heap_after_gc();
1205 print_heap_regions();
1206 #ifdef TRACESPINNING
1207 ParallelTaskTerminator::print_termination_counts();
1208 #endif
1209 }
1210
1211 void G1CollectedHeap::do_full_collection_inner(G1FullGCScope* scope) {
1212 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1213 g1_policy()->record_full_collection_start();
1214
1215 print_heap_before_gc();
1216 print_heap_regions();
1217
1218 abort_concurrent_cycle();
1219 verify_before_full_collection(scope->is_explicit_gc());
1220
1221 gc_prologue(true);
1222 prepare_heap_for_full_collection();
1223
1224 G1SerialFullCollector serial(scope, ref_processor_stw());
1225 serial.prepare_collection();
1226 serial.collect();
1227 serial.complete_collection();
1228
1229 prepare_heap_for_mutators();
1230
1231 g1_policy()->record_full_collection_end();
1232 gc_epilogue(true);
1233
1234 // Post collection verification.
1235 verify_after_full_collection();
1236
1237 // Post collection logging.
1238 // We should do this after we potentially resize the heap so
1239 // that all the COMMIT / UNCOMMIT events are generated before
1240 // the compaction events.
1241 print_heap_after_full_collection(scope->heap_transition());
1242 }
1243
1244 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1245 bool clear_all_soft_refs) {
1246 assert_at_safepoint(true /* should_be_vm_thread */);
1247
1248 if (GCLocker::check_active_before_gc()) {
1249 // Full GC was not completed.
1250 return false;
1251 }
1252
1253 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1254 collector_policy()->should_clear_all_soft_refs();
1255
1256 G1FullGCScope scope(explicit_gc, do_clear_all_soft_refs);
1257 do_full_collection_inner(&scope);
1258
1259 // Full collection was successfully completed.
1260 return true;
1261 }
1262
1263 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1264 // Currently, there is no facility in the do_full_collection(bool) API to notify
1265 // the caller that the collection did not succeed (e.g., because it was locked
1266 // out by the GC locker). So, right now, we'll ignore the return value.
1267 bool dummy = do_full_collection(true, /* explicit_gc */
1268 clear_all_soft_refs);
1269 }
1270
1271 void G1CollectedHeap::resize_if_necessary_after_full_collection() {
1272 // Include bytes that will be pre-allocated to support collections, as "used".
1273 const size_t used_after_gc = used();
1274 const size_t capacity_after_gc = capacity();
1275 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1276
1277 // This is enforced in arguments.cpp.
1278 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1279 "otherwise the code below doesn't make sense");
1280
1281 // We don't have floating point command-line arguments
1282 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1283 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1284 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1285 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1286
1287 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1288 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1289
1290 // We have to be careful here as these two calculations can overflow
1291 // 32-bit size_t's.
1292 double used_after_gc_d = (double) used_after_gc;
1293 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1294 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1295
1296 // Let's make sure that they are both under the max heap size, which
1297 // by default will make them fit into a size_t.
1298 double desired_capacity_upper_bound = (double) max_heap_size;
1299 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1300 desired_capacity_upper_bound);
1301 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1302 desired_capacity_upper_bound);
1303
1304 // We can now safely turn them into size_t's.
1305 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1306 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1307
1308 // This assert only makes sense here, before we adjust them
1309 // with respect to the min and max heap size.
1310 assert(minimum_desired_capacity <= maximum_desired_capacity,
1311 "minimum_desired_capacity = " SIZE_FORMAT ", "
1312 "maximum_desired_capacity = " SIZE_FORMAT,
1313 minimum_desired_capacity, maximum_desired_capacity);
1314
1315 // Should not be greater than the heap max size. No need to adjust
1316 // it with respect to the heap min size as it's a lower bound (i.e.,
1317 // we'll try to make the capacity larger than it, not smaller).
1318 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1319 // Should not be less than the heap min size. No need to adjust it
1320 // with respect to the heap max size as it's an upper bound (i.e.,
1321 // we'll try to make the capacity smaller than it, not greater).
1322 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1323
1324 if (capacity_after_gc < minimum_desired_capacity) {
1325 // Don't expand unless it's significant
1326 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1327
1328 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). "
1329 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1330 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio);
1331
1332 expand(expand_bytes, _workers);
1333
1334 // No expansion, now see if we want to shrink
1335 } else if (capacity_after_gc > maximum_desired_capacity) {
1336 // Capacity too large, compute shrinking size
1337 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1338
1339 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). "
1340 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1341 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio);
1342
1343 shrink(shrink_bytes);
1344 }
1345 }
1346
1347 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1348 AllocationContext_t context,
1349 bool do_gc,
1350 bool clear_all_soft_refs,
1351 bool expect_null_mutator_alloc_region,
1352 bool* gc_succeeded) {
1353 *gc_succeeded = true;
1354 // Let's attempt the allocation first.
1355 HeapWord* result =
1356 attempt_allocation_at_safepoint(word_size,
1357 context,
1358 expect_null_mutator_alloc_region);
1359 if (result != NULL) {
1360 assert(*gc_succeeded, "sanity");
1361 return result;
1362 }
1363
1364 // In a G1 heap, we're supposed to keep allocation from failing by
1365 // incremental pauses. Therefore, at least for now, we'll favor
1366 // expansion over collection. (This might change in the future if we can
1367 // do something smarter than full collection to satisfy a failed alloc.)
1368 result = expand_and_allocate(word_size, context);
1369 if (result != NULL) {
1370 assert(*gc_succeeded, "sanity");
1371 return result;
1372 }
1373
1374 if (do_gc) {
1375 // Expansion didn't work, we'll try to do a Full GC.
1376 *gc_succeeded = do_full_collection(false, /* explicit_gc */
1377 clear_all_soft_refs);
1378 }
1379
1380 return NULL;
1381 }
1382
1383 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1384 AllocationContext_t context,
1385 bool* succeeded) {
1386 assert_at_safepoint(true /* should_be_vm_thread */);
1387
1388 // Attempts to allocate followed by Full GC.
1389 HeapWord* result =
1390 satisfy_failed_allocation_helper(word_size,
1391 context,
1392 true, /* do_gc */
1393 false, /* clear_all_soft_refs */
1394 false, /* expect_null_mutator_alloc_region */
1395 succeeded);
1396
1397 if (result != NULL || !*succeeded) {
1398 return result;
1399 }
1400
1401 // Attempts to allocate followed by Full GC that will collect all soft references.
1402 result = satisfy_failed_allocation_helper(word_size,
1403 context,
1404 true, /* do_gc */
1405 true, /* clear_all_soft_refs */
1406 true, /* expect_null_mutator_alloc_region */
1407 succeeded);
1408
1409 if (result != NULL || !*succeeded) {
1410 return result;
1411 }
1412
1413 // Attempts to allocate, no GC
1414 result = satisfy_failed_allocation_helper(word_size,
1415 context,
1416 false, /* do_gc */
1417 false, /* clear_all_soft_refs */
1418 true, /* expect_null_mutator_alloc_region */
1419 succeeded);
1420
1421 if (result != NULL) {
1422 assert(*succeeded, "sanity");
1423 return result;
1424 }
1425
1426 assert(!collector_policy()->should_clear_all_soft_refs(),
1427 "Flag should have been handled and cleared prior to this point");
1428
1429 // What else? We might try synchronous finalization later. If the total
1430 // space available is large enough for the allocation, then a more
1431 // complete compaction phase than we've tried so far might be
1432 // appropriate.
1433 assert(*succeeded, "sanity");
1434 return NULL;
1435 }
1436
1437 // Attempting to expand the heap sufficiently
1438 // to support an allocation of the given "word_size". If
1439 // successful, perform the allocation and return the address of the
1440 // allocated block, or else "NULL".
1441
1442 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1443 assert_at_safepoint(true /* should_be_vm_thread */);
1444
1445 _verifier->verify_region_sets_optional();
1446
1447 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1448 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1449 word_size * HeapWordSize);
1450
1451
1452 if (expand(expand_bytes, _workers)) {
1453 _hrm.verify_optional();
1454 _verifier->verify_region_sets_optional();
1455 return attempt_allocation_at_safepoint(word_size,
1456 context,
1457 false /* expect_null_mutator_alloc_region */);
1458 }
1459 return NULL;
1460 }
1461
1462 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) {
1463 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1464 aligned_expand_bytes = align_up(aligned_expand_bytes,
1465 HeapRegion::GrainBytes);
1466
1467 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B",
1468 expand_bytes, aligned_expand_bytes);
1469
1470 if (is_maximal_no_gc()) {
1471 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1472 return false;
1473 }
1474
1475 double expand_heap_start_time_sec = os::elapsedTime();
1476 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1477 assert(regions_to_expand > 0, "Must expand by at least one region");
1478
1479 uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers);
1480 if (expand_time_ms != NULL) {
1481 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1482 }
1483
1484 if (expanded_by > 0) {
1485 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1486 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1487 g1_policy()->record_new_heap_size(num_regions());
1488 } else {
1489 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1490
1491 // The expansion of the virtual storage space was unsuccessful.
1492 // Let's see if it was because we ran out of swap.
1493 if (G1ExitOnExpansionFailure &&
1494 _hrm.available() >= regions_to_expand) {
1495 // We had head room...
1496 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1497 }
1498 }
1499 return regions_to_expand > 0;
1500 }
1501
1502 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1503 size_t aligned_shrink_bytes =
1504 ReservedSpace::page_align_size_down(shrink_bytes);
1505 aligned_shrink_bytes = align_down(aligned_shrink_bytes,
1506 HeapRegion::GrainBytes);
1507 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1508
1509 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1510 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1511
1512
1513 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",
1514 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1515 if (num_regions_removed > 0) {
1516 g1_policy()->record_new_heap_size(num_regions());
1517 } else {
1518 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1519 }
1520 }
1521
1522 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1523 _verifier->verify_region_sets_optional();
1524
1525 // We should only reach here at the end of a Full GC which means we
1526 // should not not be holding to any GC alloc regions. The method
1527 // below will make sure of that and do any remaining clean up.
1528 _allocator->abandon_gc_alloc_regions();
1529
1530 // Instead of tearing down / rebuilding the free lists here, we
1531 // could instead use the remove_all_pending() method on free_list to
1532 // remove only the ones that we need to remove.
1533 tear_down_region_sets(true /* free_list_only */);
1534 shrink_helper(shrink_bytes);
1535 rebuild_region_sets(true /* free_list_only */);
1536
1537 _hrm.verify_optional();
1538 _verifier->verify_region_sets_optional();
1539 }
1540
1541 // Public methods.
1542
1543 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) :
1544 CollectedHeap(),
1545 _young_gen_sampling_thread(NULL),
1546 _collector_policy(collector_policy),
1547 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1548 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1549 _g1_policy(create_g1_policy(_gc_timer_stw)),
1550 _collection_set(this, _g1_policy),
1551 _dirty_card_queue_set(false),
1552 _is_alive_closure_cm(this),
1553 _is_alive_closure_stw(this),
1554 _ref_processor_cm(NULL),
1555 _ref_processor_stw(NULL),
1556 _bot(NULL),
1557 _hot_card_cache(NULL),
1558 _g1_rem_set(NULL),
1559 _cr(NULL),
1560 _g1mm(NULL),
1561 _preserved_marks_set(true /* in_c_heap */),
1562 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1563 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1564 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1565 _humongous_reclaim_candidates(),
1566 _has_humongous_reclaim_candidates(false),
1567 _archive_allocator(NULL),
1568 _free_regions_coming(false),
1569 _gc_time_stamp(0),
1570 _summary_bytes_used(0),
1571 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1572 _old_evac_stats("Old", OldPLABSize, PLABWeight),
1573 _expand_heap_after_alloc_failure(true),
1574 _old_marking_cycles_started(0),
1575 _old_marking_cycles_completed(0),
1576 _in_cset_fast_test() {
1577
1578 _workers = new WorkGang("GC Thread", ParallelGCThreads,
1579 /* are_GC_task_threads */true,
1580 /* are_ConcurrentGC_threads */false);
1581 _workers->initialize_workers();
1582 _verifier = new G1HeapVerifier(this);
1583
1584 _allocator = G1Allocator::create_allocator(this);
1585
1586 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics());
1587
1588 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1589
1590 // Override the default _filler_array_max_size so that no humongous filler
1591 // objects are created.
1592 _filler_array_max_size = _humongous_object_threshold_in_words;
1593
1594 uint n_queues = ParallelGCThreads;
1595 _task_queues = new RefToScanQueueSet(n_queues);
1596
1597 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1598
1599 for (uint i = 0; i < n_queues; i++) {
1600 RefToScanQueue* q = new RefToScanQueue();
1601 q->initialize();
1602 _task_queues->register_queue(i, q);
1603 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1604 }
1605
1606 // Initialize the G1EvacuationFailureALot counters and flags.
1607 NOT_PRODUCT(reset_evacuation_should_fail();)
1608
1609 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1610 }
1611
1612 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1613 size_t size,
1614 size_t translation_factor) {
1615 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1616 // Allocate a new reserved space, preferring to use large pages.
1617 ReservedSpace rs(size, preferred_page_size);
1618 G1RegionToSpaceMapper* result =
1619 G1RegionToSpaceMapper::create_mapper(rs,
1620 size,
1621 rs.alignment(),
1622 HeapRegion::GrainBytes,
1623 translation_factor,
1624 mtGC);
1625
1626 os::trace_page_sizes_for_requested_size(description,
1627 size,
1628 preferred_page_size,
1629 rs.alignment(),
1630 rs.base(),
1631 rs.size());
1632
1633 return result;
1634 }
1635
1636 jint G1CollectedHeap::initialize_concurrent_refinement() {
1637 jint ecode = JNI_OK;
1638 _cr = G1ConcurrentRefine::create(&ecode);
1639 return ecode;
1640 }
1641
1642 jint G1CollectedHeap::initialize_young_gen_sampling_thread() {
1643 _young_gen_sampling_thread = new G1YoungRemSetSamplingThread();
1644 if (_young_gen_sampling_thread->osthread() == NULL) {
1645 vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread");
1646 return JNI_ENOMEM;
1647 }
1648 return JNI_OK;
1649 }
1650
1651 jint G1CollectedHeap::initialize() {
1652 CollectedHeap::pre_initialize();
1653 os::enable_vtime();
1654
1655 // Necessary to satisfy locking discipline assertions.
1656
1657 MutexLocker x(Heap_lock);
1658
1659 // While there are no constraints in the GC code that HeapWordSize
1660 // be any particular value, there are multiple other areas in the
1661 // system which believe this to be true (e.g. oop->object_size in some
1662 // cases incorrectly returns the size in wordSize units rather than
1663 // HeapWordSize).
1664 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1665
1666 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1667 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1668 size_t heap_alignment = collector_policy()->heap_alignment();
1669
1670 // Ensure that the sizes are properly aligned.
1671 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1672 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1673 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1674
1675 // Reserve the maximum.
1676
1677 // When compressed oops are enabled, the preferred heap base
1678 // is calculated by subtracting the requested size from the
1679 // 32Gb boundary and using the result as the base address for
1680 // heap reservation. If the requested size is not aligned to
1681 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1682 // into the ReservedHeapSpace constructor) then the actual
1683 // base of the reserved heap may end up differing from the
1684 // address that was requested (i.e. the preferred heap base).
1685 // If this happens then we could end up using a non-optimal
1686 // compressed oops mode.
1687
1688 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1689 heap_alignment);
1690
1691 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1692
1693 // Create the barrier set for the entire reserved region.
1694 G1SATBCardTableLoggingModRefBS* bs
1695 = new G1SATBCardTableLoggingModRefBS(reserved_region());
1696 bs->initialize();
1697 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity");
1698 set_barrier_set(bs);
1699
1700 // Create the hot card cache.
1701 _hot_card_cache = new G1HotCardCache(this);
1702
1703 // Carve out the G1 part of the heap.
1704 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1705 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
1706 G1RegionToSpaceMapper* heap_storage =
1707 G1RegionToSpaceMapper::create_mapper(g1_rs,
1708 g1_rs.size(),
1709 page_size,
1710 HeapRegion::GrainBytes,
1711 1,
1712 mtJavaHeap);
1713 os::trace_page_sizes("Heap",
1714 collector_policy()->min_heap_byte_size(),
1715 max_byte_size,
1716 page_size,
1717 heap_rs.base(),
1718 heap_rs.size());
1719 heap_storage->set_mapping_changed_listener(&_listener);
1720
1721 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1722 G1RegionToSpaceMapper* bot_storage =
1723 create_aux_memory_mapper("Block Offset Table",
1724 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1725 G1BlockOffsetTable::heap_map_factor());
1726
1727 G1RegionToSpaceMapper* cardtable_storage =
1728 create_aux_memory_mapper("Card Table",
1729 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize),
1730 G1SATBCardTableLoggingModRefBS::heap_map_factor());
1731
1732 G1RegionToSpaceMapper* card_counts_storage =
1733 create_aux_memory_mapper("Card Counts Table",
1734 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1735 G1CardCounts::heap_map_factor());
1736
1737 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1738 G1RegionToSpaceMapper* prev_bitmap_storage =
1739 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1740 G1RegionToSpaceMapper* next_bitmap_storage =
1741 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1742
1743 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1744 g1_barrier_set()->initialize(cardtable_storage);
1745 // Do later initialization work for concurrent refinement.
1746 _hot_card_cache->initialize(card_counts_storage);
1747
1748 // 6843694 - ensure that the maximum region index can fit
1749 // in the remembered set structures.
1750 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1751 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1752
1753 // Also create a G1 rem set.
1754 _g1_rem_set = new G1RemSet(this, g1_barrier_set(), _hot_card_cache);
1755 _g1_rem_set->initialize(max_capacity(), max_regions());
1756
1757 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1758 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1759 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1760 "too many cards per region");
1761
1762 FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1763
1764 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1765
1766 {
1767 HeapWord* start = _hrm.reserved().start();
1768 HeapWord* end = _hrm.reserved().end();
1769 size_t granularity = HeapRegion::GrainBytes;
1770
1771 _in_cset_fast_test.initialize(start, end, granularity);
1772 _humongous_reclaim_candidates.initialize(start, end, granularity);
1773 }
1774
1775 // Create the G1ConcurrentMark data structure and thread.
1776 // (Must do this late, so that "max_regions" is defined.)
1777 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1778 if (_cm == NULL || !_cm->completed_initialization()) {
1779 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
1780 return JNI_ENOMEM;
1781 }
1782 _cmThread = _cm->cm_thread();
1783
1784 // Now expand into the initial heap size.
1785 if (!expand(init_byte_size, _workers)) {
1786 vm_shutdown_during_initialization("Failed to allocate initial heap.");
1787 return JNI_ENOMEM;
1788 }
1789
1790 // Perform any initialization actions delegated to the policy.
1791 g1_policy()->init(this, &_collection_set);
1792
1793 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1794 SATB_Q_FL_lock,
1795 G1SATBProcessCompletedThreshold,
1796 Shared_SATB_Q_lock);
1797
1798 jint ecode = initialize_concurrent_refinement();
1799 if (ecode != JNI_OK) {
1800 return ecode;
1801 }
1802
1803 ecode = initialize_young_gen_sampling_thread();
1804 if (ecode != JNI_OK) {
1805 return ecode;
1806 }
1807
1808 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1809 DirtyCardQ_FL_lock,
1810 (int)concurrent_refine()->yellow_zone(),
1811 (int)concurrent_refine()->red_zone(),
1812 Shared_DirtyCardQ_lock,
1813 NULL, // fl_owner
1814 true); // init_free_ids
1815
1816 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1817 DirtyCardQ_FL_lock,
1818 -1, // never trigger processing
1819 -1, // no limit on length
1820 Shared_DirtyCardQ_lock,
1821 &JavaThread::dirty_card_queue_set());
1822
1823 // Here we allocate the dummy HeapRegion that is required by the
1824 // G1AllocRegion class.
1825 HeapRegion* dummy_region = _hrm.get_dummy_region();
1826
1827 // We'll re-use the same region whether the alloc region will
1828 // require BOT updates or not and, if it doesn't, then a non-young
1829 // region will complain that it cannot support allocations without
1830 // BOT updates. So we'll tag the dummy region as eden to avoid that.
1831 dummy_region->set_eden();
1832 // Make sure it's full.
1833 dummy_region->set_top(dummy_region->end());
1834 G1AllocRegion::setup(this, dummy_region);
1835
1836 _allocator->init_mutator_alloc_region();
1837
1838 // Do create of the monitoring and management support so that
1839 // values in the heap have been properly initialized.
1840 _g1mm = new G1MonitoringSupport(this);
1841
1842 G1StringDedup::initialize();
1843
1844 _preserved_marks_set.init(ParallelGCThreads);
1845
1846 _collection_set.initialize(max_regions());
1847
1848 return JNI_OK;
1849 }
1850
1851 void G1CollectedHeap::stop() {
1852 // Stop all concurrent threads. We do this to make sure these threads
1853 // do not continue to execute and access resources (e.g. logging)
1854 // that are destroyed during shutdown.
1855 _cr->stop();
1856 _young_gen_sampling_thread->stop();
1857 _cmThread->stop();
1858 if (G1StringDedup::is_enabled()) {
1859 G1StringDedup::stop();
1860 }
1861 }
1862
1863 void G1CollectedHeap::safepoint_synchronize_begin() {
1864 SuspendibleThreadSet::synchronize();
1865 }
1866
1867 void G1CollectedHeap::safepoint_synchronize_end() {
1868 SuspendibleThreadSet::desynchronize();
1869 }
1870
1871 size_t G1CollectedHeap::conservative_max_heap_alignment() {
1872 return HeapRegion::max_region_size();
1873 }
1874
1875 void G1CollectedHeap::post_initialize() {
1876 ref_processing_init();
1877 }
1878
1879 void G1CollectedHeap::ref_processing_init() {
1880 // Reference processing in G1 currently works as follows:
1881 //
1882 // * There are two reference processor instances. One is
1883 // used to record and process discovered references
1884 // during concurrent marking; the other is used to
1885 // record and process references during STW pauses
1886 // (both full and incremental).
1887 // * Both ref processors need to 'span' the entire heap as
1888 // the regions in the collection set may be dotted around.
1889 //
1890 // * For the concurrent marking ref processor:
1891 // * Reference discovery is enabled at initial marking.
1892 // * Reference discovery is disabled and the discovered
1893 // references processed etc during remarking.
1894 // * Reference discovery is MT (see below).
1895 // * Reference discovery requires a barrier (see below).
1896 // * Reference processing may or may not be MT
1897 // (depending on the value of ParallelRefProcEnabled
1898 // and ParallelGCThreads).
1899 // * A full GC disables reference discovery by the CM
1900 // ref processor and abandons any entries on it's
1901 // discovered lists.
1902 //
1903 // * For the STW processor:
1904 // * Non MT discovery is enabled at the start of a full GC.
1905 // * Processing and enqueueing during a full GC is non-MT.
1906 // * During a full GC, references are processed after marking.
1907 //
1908 // * Discovery (may or may not be MT) is enabled at the start
1909 // of an incremental evacuation pause.
1910 // * References are processed near the end of a STW evacuation pause.
1911 // * For both types of GC:
1912 // * Discovery is atomic - i.e. not concurrent.
1913 // * Reference discovery will not need a barrier.
1914
1915 MemRegion mr = reserved_region();
1916
1917 bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1);
1918
1919 // Concurrent Mark ref processor
1920 _ref_processor_cm =
1921 new ReferenceProcessor(mr, // span
1922 mt_processing,
1923 // mt processing
1924 ParallelGCThreads,
1925 // degree of mt processing
1926 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
1927 // mt discovery
1928 MAX2(ParallelGCThreads, ConcGCThreads),
1929 // degree of mt discovery
1930 false,
1931 // Reference discovery is not atomic
1932 &_is_alive_closure_cm);
1933 // is alive closure
1934 // (for efficiency/performance)
1935
1936 // STW ref processor
1937 _ref_processor_stw =
1938 new ReferenceProcessor(mr, // span
1939 mt_processing,
1940 // mt processing
1941 ParallelGCThreads,
1942 // degree of mt processing
1943 (ParallelGCThreads > 1),
1944 // mt discovery
1945 ParallelGCThreads,
1946 // degree of mt discovery
1947 true,
1948 // Reference discovery is atomic
1949 &_is_alive_closure_stw);
1950 // is alive closure
1951 // (for efficiency/performance)
1952 }
1953
1954 CollectorPolicy* G1CollectedHeap::collector_policy() const {
1955 return _collector_policy;
1956 }
1957
1958 size_t G1CollectedHeap::capacity() const {
1959 return _hrm.length() * HeapRegion::GrainBytes;
1960 }
1961
1962 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
1963 hr->reset_gc_time_stamp();
1964 }
1965
1966 #ifndef PRODUCT
1967
1968 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
1969 private:
1970 unsigned _gc_time_stamp;
1971 bool _failures;
1972
1973 public:
1974 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
1975 _gc_time_stamp(gc_time_stamp), _failures(false) { }
1976
1977 virtual bool doHeapRegion(HeapRegion* hr) {
1978 unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
1979 if (_gc_time_stamp != region_gc_time_stamp) {
1980 log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr),
1981 region_gc_time_stamp, _gc_time_stamp);
1982 _failures = true;
1983 }
1984 return false;
1985 }
1986
1987 bool failures() { return _failures; }
1988 };
1989
1990 void G1CollectedHeap::check_gc_time_stamps() {
1991 CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
1992 heap_region_iterate(&cl);
1993 guarantee(!cl.failures(), "all GC time stamps should have been reset");
1994 }
1995 #endif // PRODUCT
1996
1997 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) {
1998 _hot_card_cache->drain(cl, worker_i);
1999 }
2000
2001 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) {
2002 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2003 size_t n_completed_buffers = 0;
2004 while (dcqs.apply_closure_during_gc(cl, worker_i)) {
2005 n_completed_buffers++;
2006 }
2007 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
2008 dcqs.clear_n_completed_buffers();
2009 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2010 }
2011
2012 // Computes the sum of the storage used by the various regions.
2013 size_t G1CollectedHeap::used() const {
2014 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
2015 if (_archive_allocator != NULL) {
2016 result += _archive_allocator->used();
2017 }
2018 return result;
2019 }
2020
2021 size_t G1CollectedHeap::used_unlocked() const {
2022 return _summary_bytes_used;
2023 }
2024
2025 class SumUsedClosure: public HeapRegionClosure {
2026 size_t _used;
2027 public:
2028 SumUsedClosure() : _used(0) {}
2029 bool doHeapRegion(HeapRegion* r) {
2030 _used += r->used();
2031 return false;
2032 }
2033 size_t result() { return _used; }
2034 };
2035
2036 size_t G1CollectedHeap::recalculate_used() const {
2037 double recalculate_used_start = os::elapsedTime();
2038
2039 SumUsedClosure blk;
2040 heap_region_iterate(&blk);
2041
2042 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2043 return blk.result();
2044 }
2045
2046 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
2047 switch (cause) {
2048 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2049 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent;
2050 case GCCause::_update_allocation_context_stats_inc: return true;
2051 case GCCause::_wb_conc_mark: return true;
2052 default : return false;
2053 }
2054 }
2055
2056 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2057 switch (cause) {
2058 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2059 case GCCause::_g1_humongous_allocation: return true;
2060 default: return is_user_requested_concurrent_full_gc(cause);
2061 }
2062 }
2063
2064 #ifndef PRODUCT
2065 void G1CollectedHeap::allocate_dummy_regions() {
2066 // Let's fill up most of the region
2067 size_t word_size = HeapRegion::GrainWords - 1024;
2068 // And as a result the region we'll allocate will be humongous.
2069 guarantee(is_humongous(word_size), "sanity");
2070
2071 // _filler_array_max_size is set to humongous object threshold
2072 // but temporarily change it to use CollectedHeap::fill_with_object().
2073 SizeTFlagSetting fs(_filler_array_max_size, word_size);
2074
2075 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2076 // Let's use the existing mechanism for the allocation
2077 HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2078 AllocationContext::system());
2079 if (dummy_obj != NULL) {
2080 MemRegion mr(dummy_obj, word_size);
2081 CollectedHeap::fill_with_object(mr);
2082 } else {
2083 // If we can't allocate once, we probably cannot allocate
2084 // again. Let's get out of the loop.
2085 break;
2086 }
2087 }
2088 }
2089 #endif // !PRODUCT
2090
2091 void G1CollectedHeap::increment_old_marking_cycles_started() {
2092 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2093 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2094 "Wrong marking cycle count (started: %d, completed: %d)",
2095 _old_marking_cycles_started, _old_marking_cycles_completed);
2096
2097 _old_marking_cycles_started++;
2098 }
2099
2100 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2101 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2102
2103 // We assume that if concurrent == true, then the caller is a
2104 // concurrent thread that was joined the Suspendible Thread
2105 // Set. If there's ever a cheap way to check this, we should add an
2106 // assert here.
2107
2108 // Given that this method is called at the end of a Full GC or of a
2109 // concurrent cycle, and those can be nested (i.e., a Full GC can
2110 // interrupt a concurrent cycle), the number of full collections
2111 // completed should be either one (in the case where there was no
2112 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2113 // behind the number of full collections started.
2114
2115 // This is the case for the inner caller, i.e. a Full GC.
2116 assert(concurrent ||
2117 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2118 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2119 "for inner caller (Full GC): _old_marking_cycles_started = %u "
2120 "is inconsistent with _old_marking_cycles_completed = %u",
2121 _old_marking_cycles_started, _old_marking_cycles_completed);
2122
2123 // This is the case for the outer caller, i.e. the concurrent cycle.
2124 assert(!concurrent ||
2125 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2126 "for outer caller (concurrent cycle): "
2127 "_old_marking_cycles_started = %u "
2128 "is inconsistent with _old_marking_cycles_completed = %u",
2129 _old_marking_cycles_started, _old_marking_cycles_completed);
2130
2131 _old_marking_cycles_completed += 1;
2132
2133 // We need to clear the "in_progress" flag in the CM thread before
2134 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2135 // is set) so that if a waiter requests another System.gc() it doesn't
2136 // incorrectly see that a marking cycle is still in progress.
2137 if (concurrent) {
2138 _cmThread->set_idle();
2139 }
2140
2141 // This notify_all() will ensure that a thread that called
2142 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2143 // and it's waiting for a full GC to finish will be woken up. It is
2144 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2145 FullGCCount_lock->notify_all();
2146 }
2147
2148 void G1CollectedHeap::collect(GCCause::Cause cause) {
2149 assert_heap_not_locked();
2150
2151 uint gc_count_before;
2152 uint old_marking_count_before;
2153 uint full_gc_count_before;
2154 bool retry_gc;
2155
2156 do {
2157 retry_gc = false;
2158
2159 {
2160 MutexLocker ml(Heap_lock);
2161
2162 // Read the GC count while holding the Heap_lock
2163 gc_count_before = total_collections();
2164 full_gc_count_before = total_full_collections();
2165 old_marking_count_before = _old_marking_cycles_started;
2166 }
2167
2168 if (should_do_concurrent_full_gc(cause)) {
2169 // Schedule an initial-mark evacuation pause that will start a
2170 // concurrent cycle. We're setting word_size to 0 which means that
2171 // we are not requesting a post-GC allocation.
2172 VM_G1IncCollectionPause op(gc_count_before,
2173 0, /* word_size */
2174 true, /* should_initiate_conc_mark */
2175 g1_policy()->max_pause_time_ms(),
2176 cause);
2177 op.set_allocation_context(AllocationContext::current());
2178
2179 VMThread::execute(&op);
2180 if (!op.pause_succeeded()) {
2181 if (old_marking_count_before == _old_marking_cycles_started) {
2182 retry_gc = op.should_retry_gc();
2183 } else {
2184 // A Full GC happened while we were trying to schedule the
2185 // initial-mark GC. No point in starting a new cycle given
2186 // that the whole heap was collected anyway.
2187 }
2188
2189 if (retry_gc) {
2190 if (GCLocker::is_active_and_needs_gc()) {
2191 GCLocker::stall_until_clear();
2192 }
2193 }
2194 }
2195 } else {
2196 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2197 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2198
2199 // Schedule a standard evacuation pause. We're setting word_size
2200 // to 0 which means that we are not requesting a post-GC allocation.
2201 VM_G1IncCollectionPause op(gc_count_before,
2202 0, /* word_size */
2203 false, /* should_initiate_conc_mark */
2204 g1_policy()->max_pause_time_ms(),
2205 cause);
2206 VMThread::execute(&op);
2207 } else {
2208 // Schedule a Full GC.
2209 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2210 VMThread::execute(&op);
2211 }
2212 }
2213 } while (retry_gc);
2214 }
2215
2216 bool G1CollectedHeap::is_in(const void* p) const {
2217 if (_hrm.reserved().contains(p)) {
2218 // Given that we know that p is in the reserved space,
2219 // heap_region_containing() should successfully
2220 // return the containing region.
2221 HeapRegion* hr = heap_region_containing(p);
2222 return hr->is_in(p);
2223 } else {
2224 return false;
2225 }
2226 }
2227
2228 #ifdef ASSERT
2229 bool G1CollectedHeap::is_in_exact(const void* p) const {
2230 bool contains = reserved_region().contains(p);
2231 bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2232 if (contains && available) {
2233 return true;
2234 } else {
2235 return false;
2236 }
2237 }
2238 #endif
2239
2240 // Iteration functions.
2241
2242 // Iterates an ObjectClosure over all objects within a HeapRegion.
2243
2244 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2245 ObjectClosure* _cl;
2246 public:
2247 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2248 bool doHeapRegion(HeapRegion* r) {
2249 if (!r->is_continues_humongous()) {
2250 r->object_iterate(_cl);
2251 }
2252 return false;
2253 }
2254 };
2255
2256 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2257 IterateObjectClosureRegionClosure blk(cl);
2258 heap_region_iterate(&blk);
2259 }
2260
2261 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2262 _hrm.iterate(cl);
2263 }
2264
2265 void G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl,
2266 uint worker_id,
2267 HeapRegionClaimer *hrclaimer) const {
2268 _hrm.par_iterate(cl, worker_id, hrclaimer);
2269 }
2270
2271 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2272 _collection_set.iterate(cl);
2273 }
2274
2275 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) {
2276 _collection_set.iterate_from(cl, worker_id, workers()->active_workers());
2277 }
2278
2279 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2280 HeapRegion* result = _hrm.next_region_in_heap(from);
2281 while (result != NULL && result->is_pinned()) {
2282 result = _hrm.next_region_in_heap(result);
2283 }
2284 return result;
2285 }
2286
2287 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2288 HeapRegion* hr = heap_region_containing(addr);
2289 return hr->block_start(addr);
2290 }
2291
2292 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2293 HeapRegion* hr = heap_region_containing(addr);
2294 return hr->block_size(addr);
2295 }
2296
2297 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2298 HeapRegion* hr = heap_region_containing(addr);
2299 return hr->block_is_obj(addr);
2300 }
2301
2302 bool G1CollectedHeap::supports_tlab_allocation() const {
2303 return true;
2304 }
2305
2306 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2307 return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2308 }
2309
2310 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2311 return _eden.length() * HeapRegion::GrainBytes;
2312 }
2313
2314 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2315 // must be equal to the humongous object limit.
2316 size_t G1CollectedHeap::max_tlab_size() const {
2317 return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
2318 }
2319
2320 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2321 AllocationContext_t context = AllocationContext::current();
2322 return _allocator->unsafe_max_tlab_alloc(context);
2323 }
2324
2325 size_t G1CollectedHeap::max_capacity() const {
2326 return _hrm.reserved().byte_size();
2327 }
2328
2329 jlong G1CollectedHeap::millis_since_last_gc() {
2330 // See the notes in GenCollectedHeap::millis_since_last_gc()
2331 // for more information about the implementation.
2332 jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) -
2333 _g1_policy->collection_pause_end_millis();
2334 if (ret_val < 0) {
2335 log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
2336 ". returning zero instead.", ret_val);
2337 return 0;
2338 }
2339 return ret_val;
2340 }
2341
2342 void G1CollectedHeap::prepare_for_verify() {
2343 _verifier->prepare_for_verify();
2344 }
2345
2346 void G1CollectedHeap::verify(VerifyOption vo) {
2347 _verifier->verify(vo);
2348 }
2349
2350 bool G1CollectedHeap::supports_concurrent_phase_control() const {
2351 return true;
2352 }
2353
2354 const char* const* G1CollectedHeap::concurrent_phases() const {
2355 return _cmThread->concurrent_phases();
2356 }
2357
2358 bool G1CollectedHeap::request_concurrent_phase(const char* phase) {
2359 return _cmThread->request_concurrent_phase(phase);
2360 }
2361
2362 class PrintRegionClosure: public HeapRegionClosure {
2363 outputStream* _st;
2364 public:
2365 PrintRegionClosure(outputStream* st) : _st(st) {}
2366 bool doHeapRegion(HeapRegion* r) {
2367 r->print_on(_st);
2368 return false;
2369 }
2370 };
2371
2372 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2373 const HeapRegion* hr,
2374 const VerifyOption vo) const {
2375 switch (vo) {
2376 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2377 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2378 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked() && !hr->is_archive();
2379 default: ShouldNotReachHere();
2380 }
2381 return false; // keep some compilers happy
2382 }
2383
2384 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2385 const VerifyOption vo) const {
2386 switch (vo) {
2387 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2388 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2389 case VerifyOption_G1UseMarkWord: {
2390 HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj);
2391 return !obj->is_gc_marked() && !hr->is_archive();
2392 }
2393 default: ShouldNotReachHere();
2394 }
2395 return false; // keep some compilers happy
2396 }
2397
2398 void G1CollectedHeap::print_heap_regions() const {
2399 LogTarget(Trace, gc, heap, region) lt;
2400 if (lt.is_enabled()) {
2401 LogStream ls(lt);
2402 print_regions_on(&ls);
2403 }
2404 }
2405
2406 void G1CollectedHeap::print_on(outputStream* st) const {
2407 st->print(" %-20s", "garbage-first heap");
2408 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2409 capacity()/K, used_unlocked()/K);
2410 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")",
2411 p2i(_hrm.reserved().start()),
2412 p2i(_hrm.reserved().end()));
2413 st->cr();
2414 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2415 uint young_regions = young_regions_count();
2416 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2417 (size_t) young_regions * HeapRegion::GrainBytes / K);
2418 uint survivor_regions = survivor_regions_count();
2419 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2420 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2421 st->cr();
2422 MetaspaceAux::print_on(st);
2423 }
2424
2425 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2426 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2427 "HS=humongous(starts), HC=humongous(continues), "
2428 "CS=collection set, F=free, A=archive, TS=gc time stamp, "
2429 "AC=allocation context, "
2430 "TAMS=top-at-mark-start (previous, next)");
2431 PrintRegionClosure blk(st);
2432 heap_region_iterate(&blk);
2433 }
2434
2435 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2436 print_on(st);
2437
2438 // Print the per-region information.
2439 print_regions_on(st);
2440 }
2441
2442 void G1CollectedHeap::print_on_error(outputStream* st) const {
2443 this->CollectedHeap::print_on_error(st);
2444
2445 if (_cm != NULL) {
2446 st->cr();
2447 _cm->print_on_error(st);
2448 }
2449 }
2450
2451 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2452 workers()->print_worker_threads_on(st);
2453 _cmThread->print_on(st);
2454 st->cr();
2455 _cm->print_worker_threads_on(st);
2456 _cr->print_threads_on(st);
2457 _young_gen_sampling_thread->print_on(st);
2458 if (G1StringDedup::is_enabled()) {
2459 G1StringDedup::print_worker_threads_on(st);
2460 }
2461 }
2462
2463 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2464 workers()->threads_do(tc);
2465 tc->do_thread(_cmThread);
2466 _cm->threads_do(tc);
2467 _cr->threads_do(tc);
2468 tc->do_thread(_young_gen_sampling_thread);
2469 if (G1StringDedup::is_enabled()) {
2470 G1StringDedup::threads_do(tc);
2471 }
2472 }
2473
2474 void G1CollectedHeap::print_tracing_info() const {
2475 g1_rem_set()->print_summary_info();
2476 concurrent_mark()->print_summary_info();
2477 }
2478
2479 #ifndef PRODUCT
2480 // Helpful for debugging RSet issues.
2481
2482 class PrintRSetsClosure : public HeapRegionClosure {
2483 private:
2484 const char* _msg;
2485 size_t _occupied_sum;
2486
2487 public:
2488 bool doHeapRegion(HeapRegion* r) {
2489 HeapRegionRemSet* hrrs = r->rem_set();
2490 size_t occupied = hrrs->occupied();
2491 _occupied_sum += occupied;
2492
2493 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2494 if (occupied == 0) {
2495 tty->print_cr(" RSet is empty");
2496 } else {
2497 hrrs->print();
2498 }
2499 tty->print_cr("----------");
2500 return false;
2501 }
2502
2503 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2504 tty->cr();
2505 tty->print_cr("========================================");
2506 tty->print_cr("%s", msg);
2507 tty->cr();
2508 }
2509
2510 ~PrintRSetsClosure() {
2511 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2512 tty->print_cr("========================================");
2513 tty->cr();
2514 }
2515 };
2516
2517 void G1CollectedHeap::print_cset_rsets() {
2518 PrintRSetsClosure cl("Printing CSet RSets");
2519 collection_set_iterate(&cl);
2520 }
2521
2522 void G1CollectedHeap::print_all_rsets() {
2523 PrintRSetsClosure cl("Printing All RSets");;
2524 heap_region_iterate(&cl);
2525 }
2526 #endif // PRODUCT
2527
2528 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2529
2530 size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes;
2531 size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes;
2532 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2533
2534 size_t eden_capacity_bytes =
2535 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2536
2537 VirtualSpaceSummary heap_summary = create_heap_space_summary();
2538 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2539 eden_capacity_bytes, survivor_used_bytes, num_regions());
2540 }
2541
2542 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2543 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2544 stats->unused(), stats->used(), stats->region_end_waste(),
2545 stats->regions_filled(), stats->direct_allocated(),
2546 stats->failure_used(), stats->failure_waste());
2547 }
2548
2549 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2550 const G1HeapSummary& heap_summary = create_g1_heap_summary();
2551 gc_tracer->report_gc_heap_summary(when, heap_summary);
2552
2553 const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2554 gc_tracer->report_metaspace_summary(when, metaspace_summary);
2555 }
2556
2557 G1CollectedHeap* G1CollectedHeap::heap() {
2558 CollectedHeap* heap = Universe::heap();
2559 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2560 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap");
2561 return (G1CollectedHeap*)heap;
2562 }
2563
2564 void G1CollectedHeap::gc_prologue(bool full) {
2565 // always_do_update_barrier = false;
2566 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2567
2568 // This summary needs to be printed before incrementing total collections.
2569 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2570
2571 // Update common counters.
2572 increment_total_collections(full /* full gc */);
2573 if (full) {
2574 increment_old_marking_cycles_started();
2575 reset_gc_time_stamp();
2576 } else {
2577 increment_gc_time_stamp();
2578 }
2579
2580 // Fill TLAB's and such
2581 double start = os::elapsedTime();
2582 accumulate_statistics_all_tlabs();
2583 ensure_parsability(true);
2584 g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2585 }
2586
2587 void G1CollectedHeap::gc_epilogue(bool full) {
2588 // Update common counters.
2589 if (full) {
2590 // Update the number of full collections that have been completed.
2591 increment_old_marking_cycles_completed(false /* concurrent */);
2592 }
2593
2594 // We are at the end of the GC. Total collections has already been increased.
2595 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2596
2597 // FIXME: what is this about?
2598 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2599 // is set.
2600 #if COMPILER2_OR_JVMCI
2601 assert(DerivedPointerTable::is_empty(), "derived pointer present");
2602 #endif
2603 // always_do_update_barrier = true;
2604
2605 double start = os::elapsedTime();
2606 resize_all_tlabs();
2607 g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2608
2609 allocation_context_stats().update(full);
2610
2611 MemoryService::track_memory_usage();
2612 // We have just completed a GC. Update the soft reference
2613 // policy with the new heap occupancy
2614 Universe::update_heap_info_at_gc();
2615 }
2616
2617 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2618 uint gc_count_before,
2619 bool* succeeded,
2620 GCCause::Cause gc_cause) {
2621 assert_heap_not_locked_and_not_at_safepoint();
2622 VM_G1IncCollectionPause op(gc_count_before,
2623 word_size,
2624 false, /* should_initiate_conc_mark */
2625 g1_policy()->max_pause_time_ms(),
2626 gc_cause);
2627
2628 op.set_allocation_context(AllocationContext::current());
2629 VMThread::execute(&op);
2630
2631 HeapWord* result = op.result();
2632 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
2633 assert(result == NULL || ret_succeeded,
2634 "the result should be NULL if the VM did not succeed");
2635 *succeeded = ret_succeeded;
2636
2637 assert_heap_not_locked();
2638 return result;
2639 }
2640
2641 void
2642 G1CollectedHeap::doConcurrentMark() {
2643 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
2644 if (!_cmThread->in_progress()) {
2645 _cmThread->set_started();
2646 CGC_lock->notify();
2647 }
2648 }
2649
2650 size_t G1CollectedHeap::pending_card_num() {
2651 size_t extra_cards = 0;
2652 JavaThread *curr = Threads::first();
2653 while (curr != NULL) {
2654 DirtyCardQueue& dcq = curr->dirty_card_queue();
2655 extra_cards += dcq.size();
2656 curr = curr->next();
2657 }
2658 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2659 size_t buffer_size = dcqs.buffer_size();
2660 size_t buffer_num = dcqs.completed_buffers_num();
2661
2662 return buffer_size * buffer_num + extra_cards;
2663 }
2664
2665 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
2666 private:
2667 size_t _total_humongous;
2668 size_t _candidate_humongous;
2669
2670 DirtyCardQueue _dcq;
2671
2672 // We don't nominate objects with many remembered set entries, on
2673 // the assumption that such objects are likely still live.
2674 bool is_remset_small(HeapRegion* region) const {
2675 HeapRegionRemSet* const rset = region->rem_set();
2676 return G1EagerReclaimHumongousObjectsWithStaleRefs
2677 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)
2678 : rset->is_empty();
2679 }
2680
2681 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const {
2682 assert(region->is_starts_humongous(), "Must start a humongous object");
2683
2684 oop obj = oop(region->bottom());
2685
2686 // Dead objects cannot be eager reclaim candidates. Due to class
2687 // unloading it is unsafe to query their classes so we return early.
2688 if (heap->is_obj_dead(obj, region)) {
2689 return false;
2690 }
2691
2692 // Candidate selection must satisfy the following constraints
2693 // while concurrent marking is in progress:
2694 //
2695 // * In order to maintain SATB invariants, an object must not be
2696 // reclaimed if it was allocated before the start of marking and
2697 // has not had its references scanned. Such an object must have
2698 // its references (including type metadata) scanned to ensure no
2699 // live objects are missed by the marking process. Objects
2700 // allocated after the start of concurrent marking don't need to
2701 // be scanned.
2702 //
2703 // * An object must not be reclaimed if it is on the concurrent
2704 // mark stack. Objects allocated after the start of concurrent
2705 // marking are never pushed on the mark stack.
2706 //
2707 // Nominating only objects allocated after the start of concurrent
2708 // marking is sufficient to meet both constraints. This may miss
2709 // some objects that satisfy the constraints, but the marking data
2710 // structures don't support efficiently performing the needed
2711 // additional tests or scrubbing of the mark stack.
2712 //
2713 // However, we presently only nominate is_typeArray() objects.
2714 // A humongous object containing references induces remembered
2715 // set entries on other regions. In order to reclaim such an
2716 // object, those remembered sets would need to be cleaned up.
2717 //
2718 // We also treat is_typeArray() objects specially, allowing them
2719 // to be reclaimed even if allocated before the start of
2720 // concurrent mark. For this we rely on mark stack insertion to
2721 // exclude is_typeArray() objects, preventing reclaiming an object
2722 // that is in the mark stack. We also rely on the metadata for
2723 // such objects to be built-in and so ensured to be kept live.
2724 // Frequent allocation and drop of large binary blobs is an
2725 // important use case for eager reclaim, and this special handling
2726 // may reduce needed headroom.
2727
2728 return obj->is_typeArray() && is_remset_small(region);
2729 }
2730
2731 public:
2732 RegisterHumongousWithInCSetFastTestClosure()
2733 : _total_humongous(0),
2734 _candidate_humongous(0),
2735 _dcq(&JavaThread::dirty_card_queue_set()) {
2736 }
2737
2738 virtual bool doHeapRegion(HeapRegion* r) {
2739 if (!r->is_starts_humongous()) {
2740 return false;
2741 }
2742 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2743
2744 bool is_candidate = humongous_region_is_candidate(g1h, r);
2745 uint rindex = r->hrm_index();
2746 g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
2747 if (is_candidate) {
2748 _candidate_humongous++;
2749 g1h->register_humongous_region_with_cset(rindex);
2750 // Is_candidate already filters out humongous object with large remembered sets.
2751 // If we have a humongous object with a few remembered sets, we simply flush these
2752 // remembered set entries into the DCQS. That will result in automatic
2753 // re-evaluation of their remembered set entries during the following evacuation
2754 // phase.
2755 if (!r->rem_set()->is_empty()) {
2756 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
2757 "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
2758 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
2759 HeapRegionRemSetIterator hrrs(r->rem_set());
2760 size_t card_index;
2761 while (hrrs.has_next(card_index)) {
2762 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
2763 // The remembered set might contain references to already freed
2764 // regions. Filter out such entries to avoid failing card table
2765 // verification.
2766 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) {
2767 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
2768 *card_ptr = CardTableModRefBS::dirty_card_val();
2769 _dcq.enqueue(card_ptr);
2770 }
2771 }
2772 }
2773 assert(hrrs.n_yielded() == r->rem_set()->occupied(),
2774 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
2775 hrrs.n_yielded(), r->rem_set()->occupied());
2776 r->rem_set()->clear_locked();
2777 }
2778 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
2779 }
2780 _total_humongous++;
2781
2782 return false;
2783 }
2784
2785 size_t total_humongous() const { return _total_humongous; }
2786 size_t candidate_humongous() const { return _candidate_humongous; }
2787
2788 void flush_rem_set_entries() { _dcq.flush(); }
2789 };
2790
2791 void G1CollectedHeap::register_humongous_regions_with_cset() {
2792 if (!G1EagerReclaimHumongousObjects) {
2793 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
2794 return;
2795 }
2796 double time = os::elapsed_counter();
2797
2798 // Collect reclaim candidate information and register candidates with cset.
2799 RegisterHumongousWithInCSetFastTestClosure cl;
2800 heap_region_iterate(&cl);
2801
2802 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
2803 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
2804 cl.total_humongous(),
2805 cl.candidate_humongous());
2806 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
2807
2808 // Finally flush all remembered set entries to re-check into the global DCQS.
2809 cl.flush_rem_set_entries();
2810 }
2811
2812 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2813 public:
2814 bool doHeapRegion(HeapRegion* hr) {
2815 if (!hr->is_archive() && !hr->is_continues_humongous()) {
2816 hr->verify_rem_set();
2817 }
2818 return false;
2819 }
2820 };
2821
2822 uint G1CollectedHeap::num_task_queues() const {
2823 return _task_queues->size();
2824 }
2825
2826 #if TASKQUEUE_STATS
2827 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2828 st->print_raw_cr("GC Task Stats");
2829 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2830 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2831 }
2832
2833 void G1CollectedHeap::print_taskqueue_stats() const {
2834 if (!log_is_enabled(Trace, gc, task, stats)) {
2835 return;
2836 }
2837 Log(gc, task, stats) log;
2838 ResourceMark rm;
2839 LogStream ls(log.trace());
2840 outputStream* st = &ls;
2841
2842 print_taskqueue_stats_hdr(st);
2843
2844 TaskQueueStats totals;
2845 const uint n = num_task_queues();
2846 for (uint i = 0; i < n; ++i) {
2847 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2848 totals += task_queue(i)->stats;
2849 }
2850 st->print_raw("tot "); totals.print(st); st->cr();
2851
2852 DEBUG_ONLY(totals.verify());
2853 }
2854
2855 void G1CollectedHeap::reset_taskqueue_stats() {
2856 const uint n = num_task_queues();
2857 for (uint i = 0; i < n; ++i) {
2858 task_queue(i)->stats.reset();
2859 }
2860 }
2861 #endif // TASKQUEUE_STATS
2862
2863 void G1CollectedHeap::wait_for_root_region_scanning() {
2864 double scan_wait_start = os::elapsedTime();
2865 // We have to wait until the CM threads finish scanning the
2866 // root regions as it's the only way to ensure that all the
2867 // objects on them have been correctly scanned before we start
2868 // moving them during the GC.
2869 bool waited = _cm->root_regions()->wait_until_scan_finished();
2870 double wait_time_ms = 0.0;
2871 if (waited) {
2872 double scan_wait_end = os::elapsedTime();
2873 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2874 }
2875 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2876 }
2877
2878 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2879 private:
2880 G1HRPrinter* _hr_printer;
2881 public:
2882 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2883
2884 virtual bool doHeapRegion(HeapRegion* r) {
2885 _hr_printer->cset(r);
2886 return false;
2887 }
2888 };
2889
2890 void G1CollectedHeap::start_new_collection_set() {
2891 collection_set()->start_incremental_building();
2892
2893 clear_cset_fast_test();
2894
2895 guarantee(_eden.length() == 0, "eden should have been cleared");
2896 g1_policy()->transfer_survivors_to_cset(survivor());
2897 }
2898
2899 bool
2900 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
2901 assert_at_safepoint(true /* should_be_vm_thread */);
2902 guarantee(!is_gc_active(), "collection is not reentrant");
2903
2904 if (GCLocker::check_active_before_gc()) {
2905 return false;
2906 }
2907
2908 _gc_timer_stw->register_gc_start();
2909
2910 GCIdMark gc_id_mark;
2911 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
2912
2913 SvcGCMarker sgcm(SvcGCMarker::MINOR);
2914 ResourceMark rm;
2915
2916 g1_policy()->note_gc_start();
2917
2918 wait_for_root_region_scanning();
2919
2920 print_heap_before_gc();
2921 print_heap_regions();
2922 trace_heap_before_gc(_gc_tracer_stw);
2923
2924 _verifier->verify_region_sets_optional();
2925 _verifier->verify_dirty_young_regions();
2926
2927 // We should not be doing initial mark unless the conc mark thread is running
2928 if (!_cmThread->should_terminate()) {
2929 // This call will decide whether this pause is an initial-mark
2930 // pause. If it is, during_initial_mark_pause() will return true
2931 // for the duration of this pause.
2932 g1_policy()->decide_on_conc_mark_initiation();
2933 }
2934
2935 // We do not allow initial-mark to be piggy-backed on a mixed GC.
2936 assert(!collector_state()->during_initial_mark_pause() ||
2937 collector_state()->gcs_are_young(), "sanity");
2938
2939 // We also do not allow mixed GCs during marking.
2940 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity");
2941
2942 // Record whether this pause is an initial mark. When the current
2943 // thread has completed its logging output and it's safe to signal
2944 // the CM thread, the flag's value in the policy has been reset.
2945 bool should_start_conc_mark = collector_state()->during_initial_mark_pause();
2946
2947 // Inner scope for scope based logging, timers, and stats collection
2948 {
2949 EvacuationInfo evacuation_info;
2950
2951 if (collector_state()->during_initial_mark_pause()) {
2952 // We are about to start a marking cycle, so we increment the
2953 // full collection counter.
2954 increment_old_marking_cycles_started();
2955 _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
2956 }
2957
2958 _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
2959
2960 GCTraceCPUTime tcpu;
2961
2962 FormatBuffer<> gc_string("Pause ");
2963 if (collector_state()->during_initial_mark_pause()) {
2964 gc_string.append("Initial Mark");
2965 } else if (collector_state()->gcs_are_young()) {
2966 gc_string.append("Young");
2967 } else {
2968 gc_string.append("Mixed");
2969 }
2970 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true);
2971
2972 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
2973 workers()->active_workers(),
2974 Threads::number_of_non_daemon_threads());
2975 workers()->update_active_workers(active_workers);
2976 log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
2977
2978 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
2979 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
2980
2981 // If the secondary_free_list is not empty, append it to the
2982 // free_list. No need to wait for the cleanup operation to finish;
2983 // the region allocation code will check the secondary_free_list
2984 // and wait if necessary. If the G1StressConcRegionFreeing flag is
2985 // set, skip this step so that the region allocation code has to
2986 // get entries from the secondary_free_list.
2987 if (!G1StressConcRegionFreeing) {
2988 append_secondary_free_list_if_not_empty_with_lock();
2989 }
2990
2991 G1HeapTransition heap_transition(this);
2992 size_t heap_used_bytes_before_gc = used();
2993
2994 // Don't dynamically change the number of GC threads this early. A value of
2995 // 0 is used to indicate serial work. When parallel work is done,
2996 // it will be set.
2997
2998 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
2999 IsGCActiveMark x;
3000
3001 gc_prologue(false);
3002
3003 if (VerifyRememberedSets) {
3004 log_info(gc, verify)("[Verifying RemSets before GC]");
3005 VerifyRegionRemSetClosure v_cl;
3006 heap_region_iterate(&v_cl);
3007 }
3008
3009 _verifier->verify_before_gc();
3010
3011 _verifier->check_bitmaps("GC Start");
3012
3013 #if COMPILER2_OR_JVMCI
3014 DerivedPointerTable::clear();
3015 #endif
3016
3017 // Please see comment in g1CollectedHeap.hpp and
3018 // G1CollectedHeap::ref_processing_init() to see how
3019 // reference processing currently works in G1.
3020
3021 // Enable discovery in the STW reference processor
3022 if (g1_policy()->should_process_references()) {
3023 ref_processor_stw()->enable_discovery();
3024 } else {
3025 ref_processor_stw()->disable_discovery();
3026 }
3027
3028 {
3029 // We want to temporarily turn off discovery by the
3030 // CM ref processor, if necessary, and turn it back on
3031 // on again later if we do. Using a scoped
3032 // NoRefDiscovery object will do this.
3033 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3034
3035 // Forget the current alloc region (we might even choose it to be part
3036 // of the collection set!).
3037 _allocator->release_mutator_alloc_region();
3038
3039 // This timing is only used by the ergonomics to handle our pause target.
3040 // It is unclear why this should not include the full pause. We will
3041 // investigate this in CR 7178365.
3042 //
3043 // Preserving the old comment here if that helps the investigation:
3044 //
3045 // The elapsed time induced by the start time below deliberately elides
3046 // the possible verification above.
3047 double sample_start_time_sec = os::elapsedTime();
3048
3049 g1_policy()->record_collection_pause_start(sample_start_time_sec);
3050
3051 if (collector_state()->during_initial_mark_pause()) {
3052 concurrent_mark()->checkpoint_roots_initial_pre();
3053 }
3054
3055 g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor);
3056
3057 evacuation_info.set_collectionset_regions(collection_set()->region_length());
3058
3059 // Make sure the remembered sets are up to date. This needs to be
3060 // done before register_humongous_regions_with_cset(), because the
3061 // remembered sets are used there to choose eager reclaim candidates.
3062 // If the remembered sets are not up to date we might miss some
3063 // entries that need to be handled.
3064 g1_rem_set()->cleanupHRRS();
3065
3066 register_humongous_regions_with_cset();
3067
3068 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table.");
3069
3070 // We call this after finalize_cset() to
3071 // ensure that the CSet has been finalized.
3072 _cm->verify_no_cset_oops();
3073
3074 if (_hr_printer.is_active()) {
3075 G1PrintCollectionSetClosure cl(&_hr_printer);
3076 _collection_set.iterate(&cl);
3077 }
3078
3079 // Initialize the GC alloc regions.
3080 _allocator->init_gc_alloc_regions(evacuation_info);
3081
3082 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length());
3083 pre_evacuate_collection_set();
3084
3085 // Actually do the work...
3086 evacuate_collection_set(evacuation_info, &per_thread_states);
3087
3088 post_evacuate_collection_set(evacuation_info, &per_thread_states);
3089
3090 const size_t* surviving_young_words = per_thread_states.surviving_young_words();
3091 free_collection_set(&_collection_set, evacuation_info, surviving_young_words);
3092
3093 eagerly_reclaim_humongous_regions();
3094
3095 record_obj_copy_mem_stats();
3096 _survivor_evac_stats.adjust_desired_plab_sz();
3097 _old_evac_stats.adjust_desired_plab_sz();
3098
3099 double start = os::elapsedTime();
3100 start_new_collection_set();
3101 g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0);
3102
3103 if (evacuation_failed()) {
3104 set_used(recalculate_used());
3105 if (_archive_allocator != NULL) {
3106 _archive_allocator->clear_used();
3107 }
3108 for (uint i = 0; i < ParallelGCThreads; i++) {
3109 if (_evacuation_failed_info_array[i].has_failed()) {
3110 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3111 }
3112 }
3113 } else {
3114 // The "used" of the the collection set have already been subtracted
3115 // when they were freed. Add in the bytes evacuated.
3116 increase_used(g1_policy()->bytes_copied_during_gc());
3117 }
3118
3119 if (collector_state()->during_initial_mark_pause()) {
3120 // We have to do this before we notify the CM threads that
3121 // they can start working to make sure that all the
3122 // appropriate initialization is done on the CM object.
3123 concurrent_mark()->checkpoint_roots_initial_post();
3124 collector_state()->set_mark_in_progress(true);
3125 // Note that we don't actually trigger the CM thread at
3126 // this point. We do that later when we're sure that
3127 // the current thread has completed its logging output.
3128 }
3129
3130 allocate_dummy_regions();
3131
3132 _allocator->init_mutator_alloc_region();
3133
3134 {
3135 size_t expand_bytes = _heap_sizing_policy->expansion_amount();
3136 if (expand_bytes > 0) {
3137 size_t bytes_before = capacity();
3138 // No need for an ergo logging here,
3139 // expansion_amount() does this when it returns a value > 0.
3140 double expand_ms;
3141 if (!expand(expand_bytes, _workers, &expand_ms)) {
3142 // We failed to expand the heap. Cannot do anything about it.
3143 }
3144 g1_policy()->phase_times()->record_expand_heap_time(expand_ms);
3145 }
3146 }
3147
3148 // We redo the verification but now wrt to the new CSet which
3149 // has just got initialized after the previous CSet was freed.
3150 _cm->verify_no_cset_oops();
3151
3152 // This timing is only used by the ergonomics to handle our pause target.
3153 // It is unclear why this should not include the full pause. We will
3154 // investigate this in CR 7178365.
3155 double sample_end_time_sec = os::elapsedTime();
3156 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3157 size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards);
3158 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc);
3159
3160 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
3161 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc());
3162
3163 if (VerifyRememberedSets) {
3164 log_info(gc, verify)("[Verifying RemSets after GC]");
3165 VerifyRegionRemSetClosure v_cl;
3166 heap_region_iterate(&v_cl);
3167 }
3168
3169 _verifier->verify_after_gc();
3170 _verifier->check_bitmaps("GC End");
3171
3172 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3173 ref_processor_stw()->verify_no_references_recorded();
3174
3175 // CM reference discovery will be re-enabled if necessary.
3176 }
3177
3178 #ifdef TRACESPINNING
3179 ParallelTaskTerminator::print_termination_counts();
3180 #endif
3181
3182 gc_epilogue(false);
3183 }
3184
3185 // Print the remainder of the GC log output.
3186 if (evacuation_failed()) {
3187 log_info(gc)("To-space exhausted");
3188 }
3189
3190 g1_policy()->print_phases();
3191 heap_transition.print();
3192
3193 // It is not yet to safe to tell the concurrent mark to
3194 // start as we have some optional output below. We don't want the
3195 // output from the concurrent mark thread interfering with this
3196 // logging output either.
3197
3198 _hrm.verify_optional();
3199 _verifier->verify_region_sets_optional();
3200
3201 TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3202 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3203
3204 print_heap_after_gc();
3205 print_heap_regions();
3206 trace_heap_after_gc(_gc_tracer_stw);
3207
3208 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3209 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3210 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3211 // before any GC notifications are raised.
3212 g1mm()->update_sizes();
3213
3214 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3215 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
3216 _gc_timer_stw->register_gc_end();
3217 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3218 }
3219 // It should now be safe to tell the concurrent mark thread to start
3220 // without its logging output interfering with the logging output
3221 // that came from the pause.
3222
3223 if (should_start_conc_mark) {
3224 // CAUTION: after the doConcurrentMark() call below,
3225 // the concurrent marking thread(s) could be running
3226 // concurrently with us. Make sure that anything after
3227 // this point does not assume that we are the only GC thread
3228 // running. Note: of course, the actual marking work will
3229 // not start until the safepoint itself is released in
3230 // SuspendibleThreadSet::desynchronize().
3231 doConcurrentMark();
3232 }
3233
3234 return true;
3235 }
3236
3237 void G1CollectedHeap::remove_self_forwarding_pointers() {
3238 G1ParRemoveSelfForwardPtrsTask rsfp_task;
3239 workers()->run_task(&rsfp_task);
3240 }
3241
3242 void G1CollectedHeap::restore_after_evac_failure() {
3243 double remove_self_forwards_start = os::elapsedTime();
3244
3245 remove_self_forwarding_pointers();
3246 SharedRestorePreservedMarksTaskExecutor task_executor(workers());
3247 _preserved_marks_set.restore(&task_executor);
3248
3249 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3250 }
3251
3252 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) {
3253 if (!_evacuation_failed) {
3254 _evacuation_failed = true;
3255 }
3256
3257 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3258 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3259 }
3260
3261 bool G1ParEvacuateFollowersClosure::offer_termination() {
3262 G1ParScanThreadState* const pss = par_scan_state();
3263 start_term_time();
3264 const bool res = terminator()->offer_termination();
3265 end_term_time();
3266 return res;
3267 }
3268
3269 void G1ParEvacuateFollowersClosure::do_void() {
3270 G1ParScanThreadState* const pss = par_scan_state();
3271 pss->trim_queue();
3272 do {
3273 pss->steal_and_trim_queue(queues());
3274 } while (!offer_termination());
3275 }
3276
3277 class G1ParTask : public AbstractGangTask {
3278 protected:
3279 G1CollectedHeap* _g1h;
3280 G1ParScanThreadStateSet* _pss;
3281 RefToScanQueueSet* _queues;
3282 G1RootProcessor* _root_processor;
3283 ParallelTaskTerminator _terminator;
3284 uint _n_workers;
3285
3286 public:
3287 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers)
3288 : AbstractGangTask("G1 collection"),
3289 _g1h(g1h),
3290 _pss(per_thread_states),
3291 _queues(task_queues),
3292 _root_processor(root_processor),
3293 _terminator(n_workers, _queues),
3294 _n_workers(n_workers)
3295 {}
3296
3297 void work(uint worker_id) {
3298 if (worker_id >= _n_workers) return; // no work needed this round
3299
3300 double start_sec = os::elapsedTime();
3301 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec);
3302
3303 {
3304 ResourceMark rm;
3305 HandleMark hm;
3306
3307 ReferenceProcessor* rp = _g1h->ref_processor_stw();
3308
3309 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
3310 pss->set_ref_processor(rp);
3311
3312 double start_strong_roots_sec = os::elapsedTime();
3313
3314 _root_processor->evacuate_roots(pss->closures(), worker_id);
3315
3316 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid
3317 // treating the nmethods visited to act as roots for concurrent marking.
3318 // We only want to make sure that the oops in the nmethods are adjusted with regard to the
3319 // objects copied by the current evacuation.
3320 _g1h->g1_rem_set()->oops_into_collection_set_do(pss,
3321 pss->closures()->weak_codeblobs(),
3322 worker_id);
3323
3324 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec;
3325
3326 double term_sec = 0.0;
3327 size_t evac_term_attempts = 0;
3328 {
3329 double start = os::elapsedTime();
3330 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator);
3331 evac.do_void();
3332
3333 evac_term_attempts = evac.term_attempts();
3334 term_sec = evac.term_time();
3335 double elapsed_sec = os::elapsedTime() - start;
3336 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
3337 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
3338 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts);
3339 }
3340
3341 assert(pss->queue_is_empty(), "should be empty");
3342
3343 if (log_is_enabled(Debug, gc, task, stats)) {
3344 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3345 size_t lab_waste;
3346 size_t lab_undo_waste;
3347 pss->waste(lab_waste, lab_undo_waste);
3348 _g1h->print_termination_stats(worker_id,
3349 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */
3350 strong_roots_sec * 1000.0, /* strong roots time */
3351 term_sec * 1000.0, /* evac term time */
3352 evac_term_attempts, /* evac term attempts */
3353 lab_waste, /* alloc buffer waste */
3354 lab_undo_waste /* undo waste */
3355 );
3356 }
3357
3358 // Close the inner scope so that the ResourceMark and HandleMark
3359 // destructors are executed here and are included as part of the
3360 // "GC Worker Time".
3361 }
3362 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
3363 }
3364 };
3365
3366 void G1CollectedHeap::print_termination_stats_hdr() {
3367 log_debug(gc, task, stats)("GC Termination Stats");
3368 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------");
3369 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo");
3370 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------");
3371 }
3372
3373 void G1CollectedHeap::print_termination_stats(uint worker_id,
3374 double elapsed_ms,
3375 double strong_roots_ms,
3376 double term_ms,
3377 size_t term_attempts,
3378 size_t alloc_buffer_waste,
3379 size_t undo_waste) const {
3380 log_debug(gc, task, stats)
3381 ("%3d %9.2f %9.2f %6.2f "
3382 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
3383 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
3384 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms,
3385 term_ms, term_ms * 100 / elapsed_ms, term_attempts,
3386 (alloc_buffer_waste + undo_waste) * HeapWordSize / K,
3387 alloc_buffer_waste * HeapWordSize / K,
3388 undo_waste * HeapWordSize / K);
3389 }
3390
3391 class G1StringAndSymbolCleaningTask : public AbstractGangTask {
3392 private:
3393 BoolObjectClosure* _is_alive;
3394 G1StringDedupUnlinkOrOopsDoClosure _dedup_closure;
3395
3396 int _initial_string_table_size;
3397 int _initial_symbol_table_size;
3398
3399 bool _process_strings;
3400 int _strings_processed;
3401 int _strings_removed;
3402
3403 bool _process_symbols;
3404 int _symbols_processed;
3405 int _symbols_removed;
3406
3407 bool _process_string_dedup;
3408
3409 public:
3410 G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) :
3411 AbstractGangTask("String/Symbol Unlinking"),
3412 _is_alive(is_alive),
3413 _dedup_closure(is_alive, NULL, false),
3414 _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
3415 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0),
3416 _process_string_dedup(process_string_dedup) {
3417
3418 _initial_string_table_size = StringTable::the_table()->table_size();
3419 _initial_symbol_table_size = SymbolTable::the_table()->table_size();
3420 if (process_strings) {
3421 StringTable::clear_parallel_claimed_index();
3422 }
3423 if (process_symbols) {
3424 SymbolTable::clear_parallel_claimed_index();
3425 }
3426 }
3427
3428 ~G1StringAndSymbolCleaningTask() {
3429 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
3430 "claim value %d after unlink less than initial string table size %d",
3431 StringTable::parallel_claimed_index(), _initial_string_table_size);
3432 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
3433 "claim value %d after unlink less than initial symbol table size %d",
3434 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size);
3435
3436 log_info(gc, stringtable)(
3437 "Cleaned string and symbol table, "
3438 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, "
3439 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
3440 strings_processed(), strings_removed(),
3441 symbols_processed(), symbols_removed());
3442 }
3443
3444 void work(uint worker_id) {
3445 int strings_processed = 0;
3446 int strings_removed = 0;
3447 int symbols_processed = 0;
3448 int symbols_removed = 0;
3449 if (_process_strings) {
3450 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
3451 Atomic::add(strings_processed, &_strings_processed);
3452 Atomic::add(strings_removed, &_strings_removed);
3453 }
3454 if (_process_symbols) {
3455 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
3456 Atomic::add(symbols_processed, &_symbols_processed);
3457 Atomic::add(symbols_removed, &_symbols_removed);
3458 }
3459 if (_process_string_dedup) {
3460 G1StringDedup::parallel_unlink(&_dedup_closure, worker_id);
3461 }
3462 }
3463
3464 size_t strings_processed() const { return (size_t)_strings_processed; }
3465 size_t strings_removed() const { return (size_t)_strings_removed; }
3466
3467 size_t symbols_processed() const { return (size_t)_symbols_processed; }
3468 size_t symbols_removed() const { return (size_t)_symbols_removed; }
3469 };
3470
3471 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
3472 private:
3473 static Monitor* _lock;
3474
3475 BoolObjectClosure* const _is_alive;
3476 const bool _unloading_occurred;
3477 const uint _num_workers;
3478
3479 // Variables used to claim nmethods.
3480 CompiledMethod* _first_nmethod;
3481 CompiledMethod* volatile _claimed_nmethod;
3482
3483 // The list of nmethods that need to be processed by the second pass.
3484 CompiledMethod* volatile _postponed_list;
3485 volatile uint _num_entered_barrier;
3486
3487 public:
3488 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
3489 _is_alive(is_alive),
3490 _unloading_occurred(unloading_occurred),
3491 _num_workers(num_workers),
3492 _first_nmethod(NULL),
3493 _claimed_nmethod(NULL),
3494 _postponed_list(NULL),
3495 _num_entered_barrier(0)
3496 {
3497 CompiledMethod::increase_unloading_clock();
3498 // Get first alive nmethod
3499 CompiledMethodIterator iter = CompiledMethodIterator();
3500 if(iter.next_alive()) {
3501 _first_nmethod = iter.method();
3502 }
3503 _claimed_nmethod = _first_nmethod;
3504 }
3505
3506 ~G1CodeCacheUnloadingTask() {
3507 CodeCache::verify_clean_inline_caches();
3508
3509 CodeCache::set_needs_cache_clean(false);
3510 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
3511
3512 CodeCache::verify_icholder_relocations();
3513 }
3514
3515 private:
3516 void add_to_postponed_list(CompiledMethod* nm) {
3517 CompiledMethod* old;
3518 do {
3519 old = _postponed_list;
3520 nm->set_unloading_next(old);
3521 } while (Atomic::cmpxchg(nm, &_postponed_list, old) != old);
3522 }
3523
3524 void clean_nmethod(CompiledMethod* nm) {
3525 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
3526
3527 if (postponed) {
3528 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
3529 add_to_postponed_list(nm);
3530 }
3531
3532 // Mark that this thread has been cleaned/unloaded.
3533 // After this call, it will be safe to ask if this nmethod was unloaded or not.
3534 nm->set_unloading_clock(CompiledMethod::global_unloading_clock());
3535 }
3536
3537 void clean_nmethod_postponed(CompiledMethod* nm) {
3538 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
3539 }
3540
3541 static const int MaxClaimNmethods = 16;
3542
3543 void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) {
3544 CompiledMethod* first;
3545 CompiledMethodIterator last;
3546
3547 do {
3548 *num_claimed_nmethods = 0;
3549
3550 first = _claimed_nmethod;
3551 last = CompiledMethodIterator(first);
3552
3553 if (first != NULL) {
3554
3555 for (int i = 0; i < MaxClaimNmethods; i++) {
3556 if (!last.next_alive()) {
3557 break;
3558 }
3559 claimed_nmethods[i] = last.method();
3560 (*num_claimed_nmethods)++;
3561 }
3562 }
3563
3564 } while (Atomic::cmpxchg(last.method(), &_claimed_nmethod, first) != first);
3565 }
3566
3567 CompiledMethod* claim_postponed_nmethod() {
3568 CompiledMethod* claim;
3569 CompiledMethod* next;
3570
3571 do {
3572 claim = _postponed_list;
3573 if (claim == NULL) {
3574 return NULL;
3575 }
3576
3577 next = claim->unloading_next();
3578
3579 } while (Atomic::cmpxchg(next, &_postponed_list, claim) != claim);
3580
3581 return claim;
3582 }
3583
3584 public:
3585 // Mark that we're done with the first pass of nmethod cleaning.
3586 void barrier_mark(uint worker_id) {
3587 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3588 _num_entered_barrier++;
3589 if (_num_entered_barrier == _num_workers) {
3590 ml.notify_all();
3591 }
3592 }
3593
3594 // See if we have to wait for the other workers to
3595 // finish their first-pass nmethod cleaning work.
3596 void barrier_wait(uint worker_id) {
3597 if (_num_entered_barrier < _num_workers) {
3598 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3599 while (_num_entered_barrier < _num_workers) {
3600 ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
3601 }
3602 }
3603 }
3604
3605 // Cleaning and unloading of nmethods. Some work has to be postponed
3606 // to the second pass, when we know which nmethods survive.
3607 void work_first_pass(uint worker_id) {
3608 // The first nmethods is claimed by the first worker.
3609 if (worker_id == 0 && _first_nmethod != NULL) {
3610 clean_nmethod(_first_nmethod);
3611 _first_nmethod = NULL;
3612 }
3613
3614 int num_claimed_nmethods;
3615 CompiledMethod* claimed_nmethods[MaxClaimNmethods];
3616
3617 while (true) {
3618 claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
3619
3620 if (num_claimed_nmethods == 0) {
3621 break;
3622 }
3623
3624 for (int i = 0; i < num_claimed_nmethods; i++) {
3625 clean_nmethod(claimed_nmethods[i]);
3626 }
3627 }
3628 }
3629
3630 void work_second_pass(uint worker_id) {
3631 CompiledMethod* nm;
3632 // Take care of postponed nmethods.
3633 while ((nm = claim_postponed_nmethod()) != NULL) {
3634 clean_nmethod_postponed(nm);
3635 }
3636 }
3637 };
3638
3639 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
3640
3641 class G1KlassCleaningTask : public StackObj {
3642 BoolObjectClosure* _is_alive;
3643 volatile int _clean_klass_tree_claimed;
3644 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
3645
3646 public:
3647 G1KlassCleaningTask(BoolObjectClosure* is_alive) :
3648 _is_alive(is_alive),
3649 _clean_klass_tree_claimed(0),
3650 _klass_iterator() {
3651 }
3652
3653 private:
3654 bool claim_clean_klass_tree_task() {
3655 if (_clean_klass_tree_claimed) {
3656 return false;
3657 }
3658
3659 return Atomic::cmpxchg(1, &_clean_klass_tree_claimed, 0) == 0;
3660 }
3661
3662 InstanceKlass* claim_next_klass() {
3663 Klass* klass;
3664 do {
3665 klass =_klass_iterator.next_klass();
3666 } while (klass != NULL && !klass->is_instance_klass());
3667
3668 // this can be null so don't call InstanceKlass::cast
3669 return static_cast<InstanceKlass*>(klass);
3670 }
3671
3672 public:
3673
3674 void clean_klass(InstanceKlass* ik) {
3675 ik->clean_weak_instanceklass_links(_is_alive);
3676 }
3677
3678 void work() {
3679 ResourceMark rm;
3680
3681 // One worker will clean the subklass/sibling klass tree.
3682 if (claim_clean_klass_tree_task()) {
3683 Klass::clean_subklass_tree(_is_alive);
3684 }
3685
3686 // All workers will help cleaning the classes,
3687 InstanceKlass* klass;
3688 while ((klass = claim_next_klass()) != NULL) {
3689 clean_klass(klass);
3690 }
3691 }
3692 };
3693
3694 class G1ResolvedMethodCleaningTask : public StackObj {
3695 BoolObjectClosure* _is_alive;
3696 volatile int _resolved_method_task_claimed;
3697 public:
3698 G1ResolvedMethodCleaningTask(BoolObjectClosure* is_alive) :
3699 _is_alive(is_alive), _resolved_method_task_claimed(0) {}
3700
3701 bool claim_resolved_method_task() {
3702 if (_resolved_method_task_claimed) {
3703 return false;
3704 }
3705 return Atomic::cmpxchg(1, &_resolved_method_task_claimed, 0) == 0;
3706 }
3707
3708 // These aren't big, one thread can do it all.
3709 void work() {
3710 if (claim_resolved_method_task()) {
3711 ResolvedMethodTable::unlink(_is_alive);
3712 }
3713 }
3714 };
3715
3716
3717 // To minimize the remark pause times, the tasks below are done in parallel.
3718 class G1ParallelCleaningTask : public AbstractGangTask {
3719 private:
3720 G1StringAndSymbolCleaningTask _string_symbol_task;
3721 G1CodeCacheUnloadingTask _code_cache_task;
3722 G1KlassCleaningTask _klass_cleaning_task;
3723 G1ResolvedMethodCleaningTask _resolved_method_cleaning_task;
3724
3725 public:
3726 // The constructor is run in the VMThread.
3727 G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) :
3728 AbstractGangTask("Parallel Cleaning"),
3729 _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()),
3730 _code_cache_task(num_workers, is_alive, unloading_occurred),
3731 _klass_cleaning_task(is_alive),
3732 _resolved_method_cleaning_task(is_alive) {
3733 }
3734
3735 // The parallel work done by all worker threads.
3736 void work(uint worker_id) {
3737 // Do first pass of code cache cleaning.
3738 _code_cache_task.work_first_pass(worker_id);
3739
3740 // Let the threads mark that the first pass is done.
3741 _code_cache_task.barrier_mark(worker_id);
3742
3743 // Clean the Strings and Symbols.
3744 _string_symbol_task.work(worker_id);
3745
3746 // Clean unreferenced things in the ResolvedMethodTable
3747 _resolved_method_cleaning_task.work();
3748
3749 // Wait for all workers to finish the first code cache cleaning pass.
3750 _code_cache_task.barrier_wait(worker_id);
3751
3752 // Do the second code cache cleaning work, which realize on
3753 // the liveness information gathered during the first pass.
3754 _code_cache_task.work_second_pass(worker_id);
3755
3756 // Clean all klasses that were not unloaded.
3757 _klass_cleaning_task.work();
3758 }
3759 };
3760
3761
3762 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
3763 bool class_unloading_occurred) {
3764 uint n_workers = workers()->active_workers();
3765
3766 G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred);
3767 workers()->run_task(&g1_unlink_task);
3768 }
3769
3770 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive,
3771 bool process_strings,
3772 bool process_symbols,
3773 bool process_string_dedup) {
3774 if (!process_strings && !process_symbols && !process_string_dedup) {
3775 // Nothing to clean.
3776 return;
3777 }
3778
3779 G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup);
3780 workers()->run_task(&g1_unlink_task);
3781
3782 }
3783
3784 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3785 private:
3786 DirtyCardQueueSet* _queue;
3787 G1CollectedHeap* _g1h;
3788 public:
3789 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"),
3790 _queue(queue), _g1h(g1h) { }
3791
3792 virtual void work(uint worker_id) {
3793 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
3794 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
3795
3796 RedirtyLoggedCardTableEntryClosure cl(_g1h);
3797 _queue->par_apply_closure_to_all_completed_buffers(&cl);
3798
3799 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3800 }
3801 };
3802
3803 void G1CollectedHeap::redirty_logged_cards() {
3804 double redirty_logged_cards_start = os::elapsedTime();
3805
3806 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this);
3807 dirty_card_queue_set().reset_for_par_iteration();
3808 workers()->run_task(&redirty_task);
3809
3810 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
3811 dcq.merge_bufferlists(&dirty_card_queue_set());
3812 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
3813
3814 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3815 }
3816
3817 // Weak Reference Processing support
3818
3819 // An always "is_alive" closure that is used to preserve referents.
3820 // If the object is non-null then it's alive. Used in the preservation
3821 // of referent objects that are pointed to by reference objects
3822 // discovered by the CM ref processor.
3823 class G1AlwaysAliveClosure: public BoolObjectClosure {
3824 G1CollectedHeap* _g1;
3825 public:
3826 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3827 bool do_object_b(oop p) {
3828 if (p != NULL) {
3829 return true;
3830 }
3831 return false;
3832 }
3833 };
3834
3835 bool G1STWIsAliveClosure::do_object_b(oop p) {
3836 // An object is reachable if it is outside the collection set,
3837 // or is inside and copied.
3838 return !_g1->is_in_cset(p) || p->is_forwarded();
3839 }
3840
3841 // Non Copying Keep Alive closure
3842 class G1KeepAliveClosure: public OopClosure {
3843 G1CollectedHeap* _g1;
3844 public:
3845 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3846 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3847 void do_oop(oop* p) {
3848 oop obj = *p;
3849 assert(obj != NULL, "the caller should have filtered out NULL values");
3850
3851 const InCSetState cset_state = _g1->in_cset_state(obj);
3852 if (!cset_state.is_in_cset_or_humongous()) {
3853 return;
3854 }
3855 if (cset_state.is_in_cset()) {
3856 assert( obj->is_forwarded(), "invariant" );
3857 *p = obj->forwardee();
3858 } else {
3859 assert(!obj->is_forwarded(), "invariant" );
3860 assert(cset_state.is_humongous(),
3861 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value());
3862 _g1->set_humongous_is_live(obj);
3863 }
3864 }
3865 };
3866
3867 // Copying Keep Alive closure - can be called from both
3868 // serial and parallel code as long as different worker
3869 // threads utilize different G1ParScanThreadState instances
3870 // and different queues.
3871
3872 class G1CopyingKeepAliveClosure: public OopClosure {
3873 G1CollectedHeap* _g1h;
3874 OopClosure* _copy_non_heap_obj_cl;
3875 G1ParScanThreadState* _par_scan_state;
3876
3877 public:
3878 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3879 OopClosure* non_heap_obj_cl,
3880 G1ParScanThreadState* pss):
3881 _g1h(g1h),
3882 _copy_non_heap_obj_cl(non_heap_obj_cl),
3883 _par_scan_state(pss)
3884 {}
3885
3886 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3887 virtual void do_oop( oop* p) { do_oop_work(p); }
3888
3889 template <class T> void do_oop_work(T* p) {
3890 oop obj = oopDesc::load_decode_heap_oop(p);
3891
3892 if (_g1h->is_in_cset_or_humongous(obj)) {
3893 // If the referent object has been forwarded (either copied
3894 // to a new location or to itself in the event of an
3895 // evacuation failure) then we need to update the reference
3896 // field and, if both reference and referent are in the G1
3897 // heap, update the RSet for the referent.
3898 //
3899 // If the referent has not been forwarded then we have to keep
3900 // it alive by policy. Therefore we have copy the referent.
3901 //
3902 // If the reference field is in the G1 heap then we can push
3903 // on the PSS queue. When the queue is drained (after each
3904 // phase of reference processing) the object and it's followers
3905 // will be copied, the reference field set to point to the
3906 // new location, and the RSet updated. Otherwise we need to
3907 // use the the non-heap or metadata closures directly to copy
3908 // the referent object and update the pointer, while avoiding
3909 // updating the RSet.
3910
3911 if (_g1h->is_in_g1_reserved(p)) {
3912 _par_scan_state->push_on_queue(p);
3913 } else {
3914 assert(!Metaspace::contains((const void*)p),
3915 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p));
3916 _copy_non_heap_obj_cl->do_oop(p);
3917 }
3918 }
3919 }
3920 };
3921
3922 // Serial drain queue closure. Called as the 'complete_gc'
3923 // closure for each discovered list in some of the
3924 // reference processing phases.
3925
3926 class G1STWDrainQueueClosure: public VoidClosure {
3927 protected:
3928 G1CollectedHeap* _g1h;
3929 G1ParScanThreadState* _par_scan_state;
3930
3931 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
3932
3933 public:
3934 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
3935 _g1h(g1h),
3936 _par_scan_state(pss)
3937 { }
3938
3939 void do_void() {
3940 G1ParScanThreadState* const pss = par_scan_state();
3941 pss->trim_queue();
3942 }
3943 };
3944
3945 // Parallel Reference Processing closures
3946
3947 // Implementation of AbstractRefProcTaskExecutor for parallel reference
3948 // processing during G1 evacuation pauses.
3949
3950 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
3951 private:
3952 G1CollectedHeap* _g1h;
3953 G1ParScanThreadStateSet* _pss;
3954 RefToScanQueueSet* _queues;
3955 WorkGang* _workers;
3956 uint _active_workers;
3957
3958 public:
3959 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
3960 G1ParScanThreadStateSet* per_thread_states,
3961 WorkGang* workers,
3962 RefToScanQueueSet *task_queues,
3963 uint n_workers) :
3964 _g1h(g1h),
3965 _pss(per_thread_states),
3966 _queues(task_queues),
3967 _workers(workers),
3968 _active_workers(n_workers)
3969 {
3970 g1h->ref_processor_stw()->set_active_mt_degree(n_workers);
3971 }
3972
3973 // Executes the given task using concurrent marking worker threads.
3974 virtual void execute(ProcessTask& task);
3975 virtual void execute(EnqueueTask& task);
3976 };
3977
3978 // Gang task for possibly parallel reference processing
3979
3980 class G1STWRefProcTaskProxy: public AbstractGangTask {
3981 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
3982 ProcessTask& _proc_task;
3983 G1CollectedHeap* _g1h;
3984 G1ParScanThreadStateSet* _pss;
3985 RefToScanQueueSet* _task_queues;
3986 ParallelTaskTerminator* _terminator;
3987
3988 public:
3989 G1STWRefProcTaskProxy(ProcessTask& proc_task,
3990 G1CollectedHeap* g1h,
3991 G1ParScanThreadStateSet* per_thread_states,
3992 RefToScanQueueSet *task_queues,
3993 ParallelTaskTerminator* terminator) :
3994 AbstractGangTask("Process reference objects in parallel"),
3995 _proc_task(proc_task),
3996 _g1h(g1h),
3997 _pss(per_thread_states),
3998 _task_queues(task_queues),
3999 _terminator(terminator)
4000 {}
4001
4002 virtual void work(uint worker_id) {
4003 // The reference processing task executed by a single worker.
4004 ResourceMark rm;
4005 HandleMark hm;
4006
4007 G1STWIsAliveClosure is_alive(_g1h);
4008
4009 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
4010 pss->set_ref_processor(NULL);
4011
4012 // Keep alive closure.
4013 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4014
4015 // Complete GC closure
4016 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator);
4017
4018 // Call the reference processing task's work routine.
4019 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
4020
4021 // Note we cannot assert that the refs array is empty here as not all
4022 // of the processing tasks (specifically phase2 - pp2_work) execute
4023 // the complete_gc closure (which ordinarily would drain the queue) so
4024 // the queue may not be empty.
4025 }
4026 };
4027
4028 // Driver routine for parallel reference processing.
4029 // Creates an instance of the ref processing gang
4030 // task and has the worker threads execute it.
4031 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
4032 assert(_workers != NULL, "Need parallel worker threads.");
4033
4034 ParallelTaskTerminator terminator(_active_workers, _queues);
4035 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
4036
4037 _workers->run_task(&proc_task_proxy);
4038 }
4039
4040 // Gang task for parallel reference enqueueing.
4041
4042 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
4043 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
4044 EnqueueTask& _enq_task;
4045
4046 public:
4047 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
4048 AbstractGangTask("Enqueue reference objects in parallel"),
4049 _enq_task(enq_task)
4050 { }
4051
4052 virtual void work(uint worker_id) {
4053 _enq_task.work(worker_id);
4054 }
4055 };
4056
4057 // Driver routine for parallel reference enqueueing.
4058 // Creates an instance of the ref enqueueing gang
4059 // task and has the worker threads execute it.
4060
4061 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
4062 assert(_workers != NULL, "Need parallel worker threads.");
4063
4064 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
4065
4066 _workers->run_task(&enq_task_proxy);
4067 }
4068
4069 // End of weak reference support closures
4070
4071 // Abstract task used to preserve (i.e. copy) any referent objects
4072 // that are in the collection set and are pointed to by reference
4073 // objects discovered by the CM ref processor.
4074
4075 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
4076 protected:
4077 G1CollectedHeap* _g1h;
4078 G1ParScanThreadStateSet* _pss;
4079 RefToScanQueueSet* _queues;
4080 ParallelTaskTerminator _terminator;
4081 uint _n_workers;
4082
4083 public:
4084 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) :
4085 AbstractGangTask("ParPreserveCMReferents"),
4086 _g1h(g1h),
4087 _pss(per_thread_states),
4088 _queues(task_queues),
4089 _terminator(workers, _queues),
4090 _n_workers(workers)
4091 {
4092 g1h->ref_processor_cm()->set_active_mt_degree(workers);
4093 }
4094
4095 void work(uint worker_id) {
4096 G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id);
4097
4098 ResourceMark rm;
4099 HandleMark hm;
4100
4101 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
4102 pss->set_ref_processor(NULL);
4103 assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4104
4105 // Is alive closure
4106 G1AlwaysAliveClosure always_alive(_g1h);
4107
4108 // Copying keep alive closure. Applied to referent objects that need
4109 // to be copied.
4110 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4111
4112 ReferenceProcessor* rp = _g1h->ref_processor_cm();
4113
4114 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
4115 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
4116
4117 // limit is set using max_num_q() - which was set using ParallelGCThreads.
4118 // So this must be true - but assert just in case someone decides to
4119 // change the worker ids.
4120 assert(worker_id < limit, "sanity");
4121 assert(!rp->discovery_is_atomic(), "check this code");
4122
4123 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
4124 for (uint idx = worker_id; idx < limit; idx += stride) {
4125 DiscoveredList& ref_list = rp->discovered_refs()[idx];
4126
4127 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
4128 while (iter.has_next()) {
4129 // Since discovery is not atomic for the CM ref processor, we
4130 // can see some null referent objects.
4131 iter.load_ptrs(DEBUG_ONLY(true));
4132 oop ref = iter.obj();
4133
4134 // This will filter nulls.
4135 if (iter.is_referent_alive()) {
4136 iter.make_referent_alive();
4137 }
4138 iter.move_to_next();
4139 }
4140 }
4141
4142 // Drain the queue - which may cause stealing
4143 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator);
4144 drain_queue.do_void();
4145 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
4146 assert(pss->queue_is_empty(), "should be");
4147 }
4148 };
4149
4150 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) {
4151 // Any reference objects, in the collection set, that were 'discovered'
4152 // by the CM ref processor should have already been copied (either by
4153 // applying the external root copy closure to the discovered lists, or
4154 // by following an RSet entry).
4155 //
4156 // But some of the referents, that are in the collection set, that these
4157 // reference objects point to may not have been copied: the STW ref
4158 // processor would have seen that the reference object had already
4159 // been 'discovered' and would have skipped discovering the reference,
4160 // but would not have treated the reference object as a regular oop.
4161 // As a result the copy closure would not have been applied to the
4162 // referent object.
4163 //
4164 // We need to explicitly copy these referent objects - the references
4165 // will be processed at the end of remarking.
4166 //
4167 // We also need to do this copying before we process the reference
4168 // objects discovered by the STW ref processor in case one of these
4169 // referents points to another object which is also referenced by an
4170 // object discovered by the STW ref processor.
4171 double preserve_cm_referents_time = 0.0;
4172
4173 // To avoid spawning task when there is no work to do, check that
4174 // a concurrent cycle is active and that some references have been
4175 // discovered.
4176 if (concurrent_mark()->cm_thread()->during_cycle() &&
4177 ref_processor_cm()->has_discovered_references()) {
4178 double preserve_cm_referents_start = os::elapsedTime();
4179 uint no_of_gc_workers = workers()->active_workers();
4180 G1ParPreserveCMReferentsTask keep_cm_referents(this,
4181 per_thread_states,
4182 no_of_gc_workers,
4183 _task_queues);
4184 workers()->run_task(&keep_cm_referents);
4185 preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start;
4186 }
4187
4188 g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0);
4189 }
4190
4191 // Weak Reference processing during an evacuation pause (part 1).
4192 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4193 double ref_proc_start = os::elapsedTime();
4194
4195 ReferenceProcessor* rp = _ref_processor_stw;
4196 assert(rp->discovery_enabled(), "should have been enabled");
4197
4198 // Closure to test whether a referent is alive.
4199 G1STWIsAliveClosure is_alive(this);
4200
4201 // Even when parallel reference processing is enabled, the processing
4202 // of JNI refs is serial and performed serially by the current thread
4203 // rather than by a worker. The following PSS will be used for processing
4204 // JNI refs.
4205
4206 // Use only a single queue for this PSS.
4207 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0);
4208 pss->set_ref_processor(NULL);
4209 assert(pss->queue_is_empty(), "pre-condition");
4210
4211 // Keep alive closure.
4212 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss);
4213
4214 // Serial Complete GC closure
4215 G1STWDrainQueueClosure drain_queue(this, pss);
4216
4217 // Setup the soft refs policy...
4218 rp->setup_policy(false);
4219
4220 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times();
4221
4222 ReferenceProcessorStats stats;
4223 if (!rp->processing_is_mt()) {
4224 // Serial reference processing...
4225 stats = rp->process_discovered_references(&is_alive,
4226 &keep_alive,
4227 &drain_queue,
4228 NULL,
4229 pt);
4230 } else {
4231 uint no_of_gc_workers = workers()->active_workers();
4232
4233 // Parallel reference processing
4234 assert(no_of_gc_workers <= rp->max_num_q(),
4235 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4236 no_of_gc_workers, rp->max_num_q());
4237
4238 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers);
4239 stats = rp->process_discovered_references(&is_alive,
4240 &keep_alive,
4241 &drain_queue,
4242 &par_task_executor,
4243 pt);
4244 }
4245
4246 _gc_tracer_stw->report_gc_reference_stats(stats);
4247
4248 // We have completed copying any necessary live referent objects.
4249 assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4250
4251 double ref_proc_time = os::elapsedTime() - ref_proc_start;
4252 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4253 }
4254
4255 // Weak Reference processing during an evacuation pause (part 2).
4256 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4257 double ref_enq_start = os::elapsedTime();
4258
4259 ReferenceProcessor* rp = _ref_processor_stw;
4260 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
4261
4262 ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times();
4263
4264 // Now enqueue any remaining on the discovered lists on to
4265 // the pending list.
4266 if (!rp->processing_is_mt()) {
4267 // Serial reference processing...
4268 rp->enqueue_discovered_references(NULL, pt);
4269 } else {
4270 // Parallel reference enqueueing
4271
4272 uint n_workers = workers()->active_workers();
4273
4274 assert(n_workers <= rp->max_num_q(),
4275 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4276 n_workers, rp->max_num_q());
4277
4278 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers);
4279 rp->enqueue_discovered_references(&par_task_executor, pt);
4280 }
4281
4282 rp->verify_no_references_recorded();
4283 assert(!rp->discovery_enabled(), "should have been disabled");
4284
4285 // If during an initial mark pause we install a pending list head which is not otherwise reachable
4286 // ensure that it is marked in the bitmap for concurrent marking to discover.
4287 if (collector_state()->during_initial_mark_pause()) {
4288 oop pll_head = Universe::reference_pending_list();
4289 if (pll_head != NULL) {
4290 _cm->mark_in_next_bitmap(pll_head);
4291 }
4292 }
4293
4294 // FIXME
4295 // CM's reference processing also cleans up the string and symbol tables.
4296 // Should we do that here also? We could, but it is a serial operation
4297 // and could significantly increase the pause time.
4298
4299 double ref_enq_time = os::elapsedTime() - ref_enq_start;
4300 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
4301 }
4302
4303 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
4304 double merge_pss_time_start = os::elapsedTime();
4305 per_thread_states->flush();
4306 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0);
4307 }
4308
4309 void G1CollectedHeap::pre_evacuate_collection_set() {
4310 _expand_heap_after_alloc_failure = true;
4311 _evacuation_failed = false;
4312
4313 // Disable the hot card cache.
4314 _hot_card_cache->reset_hot_cache_claimed_index();
4315 _hot_card_cache->set_use_cache(false);
4316
4317 g1_rem_set()->prepare_for_oops_into_collection_set_do();
4318 _preserved_marks_set.assert_empty();
4319
4320 G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4321
4322 // InitialMark needs claim bits to keep track of the marked-through CLDs.
4323 if (collector_state()->during_initial_mark_pause()) {
4324 double start_clear_claimed_marks = os::elapsedTime();
4325
4326 ClassLoaderDataGraph::clear_claimed_marks();
4327
4328 double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
4329 phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
4330 }
4331 }
4332
4333 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4334 // Should G1EvacuationFailureALot be in effect for this GC?
4335 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
4336
4337 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
4338
4339 G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4340
4341 double start_par_time_sec = os::elapsedTime();
4342 double end_par_time_sec;
4343
4344 {
4345 const uint n_workers = workers()->active_workers();
4346 G1RootProcessor root_processor(this, n_workers);
4347 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers);
4348
4349 print_termination_stats_hdr();
4350
4351 workers()->run_task(&g1_par_task);
4352 end_par_time_sec = os::elapsedTime();
4353
4354 // Closing the inner scope will execute the destructor
4355 // for the G1RootProcessor object. We record the current
4356 // elapsed time before closing the scope so that time
4357 // taken for the destructor is NOT included in the
4358 // reported parallel time.
4359 }
4360
4361 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
4362 phase_times->record_par_time(par_time_ms);
4363
4364 double code_root_fixup_time_ms =
4365 (os::elapsedTime() - end_par_time_sec) * 1000.0;
4366 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
4367 }
4368
4369 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4370 // Process any discovered reference objects - we have
4371 // to do this _before_ we retire the GC alloc regions
4372 // as we may have to copy some 'reachable' referent
4373 // objects (and their reachable sub-graphs) that were
4374 // not copied during the pause.
4375 if (g1_policy()->should_process_references()) {
4376 preserve_cm_referents(per_thread_states);
4377 process_discovered_references(per_thread_states);
4378 } else {
4379 ref_processor_stw()->verify_no_references_recorded();
4380 }
4381
4382 G1STWIsAliveClosure is_alive(this);
4383 G1KeepAliveClosure keep_alive(this);
4384
4385 {
4386 double start = os::elapsedTime();
4387
4388 WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
4389
4390 double time_ms = (os::elapsedTime() - start) * 1000.0;
4391 g1_policy()->phase_times()->record_ref_proc_time(time_ms);
4392 }
4393
4394 if (G1StringDedup::is_enabled()) {
4395 double fixup_start = os::elapsedTime();
4396
4397 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times());
4398
4399 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
4400 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
4401 }
4402
4403 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4404
4405 if (evacuation_failed()) {
4406 restore_after_evac_failure();
4407
4408 // Reset the G1EvacuationFailureALot counters and flags
4409 // Note: the values are reset only when an actual
4410 // evacuation failure occurs.
4411 NOT_PRODUCT(reset_evacuation_should_fail();)
4412 }
4413
4414 _preserved_marks_set.assert_empty();
4415
4416 // Enqueue any remaining references remaining on the STW
4417 // reference processor's discovered lists. We need to do
4418 // this after the card table is cleaned (and verified) as
4419 // the act of enqueueing entries on to the pending list
4420 // will log these updates (and dirty their associated
4421 // cards). We need these updates logged to update any
4422 // RSets.
4423 if (g1_policy()->should_process_references()) {
4424 enqueue_discovered_references(per_thread_states);
4425 } else {
4426 g1_policy()->phase_times()->record_ref_enq_time(0);
4427 }
4428
4429 _allocator->release_gc_alloc_regions(evacuation_info);
4430
4431 merge_per_thread_state_info(per_thread_states);
4432
4433 // Reset and re-enable the hot card cache.
4434 // Note the counts for the cards in the regions in the
4435 // collection set are reset when the collection set is freed.
4436 _hot_card_cache->reset_hot_cache();
4437 _hot_card_cache->set_use_cache(true);
4438
4439 purge_code_root_memory();
4440
4441 redirty_logged_cards();
4442 #if COMPILER2_OR_JVMCI
4443 double start = os::elapsedTime();
4444 DerivedPointerTable::update_pointers();
4445 g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0);
4446 #endif
4447 g1_policy()->print_age_table();
4448 }
4449
4450 void G1CollectedHeap::record_obj_copy_mem_stats() {
4451 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4452
4453 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4454 create_g1_evac_summary(&_old_evac_stats));
4455 }
4456
4457 void G1CollectedHeap::free_region(HeapRegion* hr,
4458 FreeRegionList* free_list,
4459 bool skip_remset,
4460 bool skip_hot_card_cache,
4461 bool locked) {
4462 assert(!hr->is_free(), "the region should not be free");
4463 assert(!hr->is_empty(), "the region should not be empty");
4464 assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
4465 assert(free_list != NULL, "pre-condition");
4466
4467 if (G1VerifyBitmaps) {
4468 MemRegion mr(hr->bottom(), hr->end());
4469 concurrent_mark()->clear_range_in_prev_bitmap(mr);
4470 }
4471
4472 // Clear the card counts for this region.
4473 // Note: we only need to do this if the region is not young
4474 // (since we don't refine cards in young regions).
4475 if (!skip_hot_card_cache && !hr->is_young()) {
4476 _hot_card_cache->reset_card_counts(hr);
4477 }
4478 hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */);
4479 free_list->add_ordered(hr);
4480 }
4481
4482 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4483 FreeRegionList* free_list,
4484 bool skip_remset) {
4485 assert(hr->is_humongous(), "this is only for humongous regions");
4486 assert(free_list != NULL, "pre-condition");
4487 hr->clear_humongous();
4488 free_region(hr, free_list, skip_remset);
4489 }
4490
4491 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4492 const uint humongous_regions_removed) {
4493 if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4494 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4495 _old_set.bulk_remove(old_regions_removed);
4496 _humongous_set.bulk_remove(humongous_regions_removed);
4497 }
4498
4499 }
4500
4501 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4502 assert(list != NULL, "list can't be null");
4503 if (!list->is_empty()) {
4504 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4505 _hrm.insert_list_into_free_list(list);
4506 }
4507 }
4508
4509 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4510 decrease_used(bytes);
4511 }
4512
4513 class G1ParScrubRemSetTask: public AbstractGangTask {
4514 protected:
4515 G1RemSet* _g1rs;
4516 HeapRegionClaimer _hrclaimer;
4517
4518 public:
4519 G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) :
4520 AbstractGangTask("G1 ScrubRS"),
4521 _g1rs(g1_rs),
4522 _hrclaimer(num_workers) {
4523 }
4524
4525 void work(uint worker_id) {
4526 _g1rs->scrub(worker_id, &_hrclaimer);
4527 }
4528 };
4529
4530 void G1CollectedHeap::scrub_rem_set() {
4531 uint num_workers = workers()->active_workers();
4532 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers);
4533 workers()->run_task(&g1_par_scrub_rs_task);
4534 }
4535
4536 class G1FreeCollectionSetTask : public AbstractGangTask {
4537 private:
4538
4539 // Closure applied to all regions in the collection set to do work that needs to
4540 // be done serially in a single thread.
4541 class G1SerialFreeCollectionSetClosure : public HeapRegionClosure {
4542 private:
4543 EvacuationInfo* _evacuation_info;
4544 const size_t* _surviving_young_words;
4545
4546 // Bytes used in successfully evacuated regions before the evacuation.
4547 size_t _before_used_bytes;
4548 // Bytes used in unsucessfully evacuated regions before the evacuation
4549 size_t _after_used_bytes;
4550
4551 size_t _bytes_allocated_in_old_since_last_gc;
4552
4553 size_t _failure_used_words;
4554 size_t _failure_waste_words;
4555
4556 FreeRegionList _local_free_list;
4557 public:
4558 G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4559 HeapRegionClosure(),
4560 _evacuation_info(evacuation_info),
4561 _surviving_young_words(surviving_young_words),
4562 _before_used_bytes(0),
4563 _after_used_bytes(0),
4564 _bytes_allocated_in_old_since_last_gc(0),
4565 _failure_used_words(0),
4566 _failure_waste_words(0),
4567 _local_free_list("Local Region List for CSet Freeing") {
4568 }
4569
4570 virtual bool doHeapRegion(HeapRegion* r) {
4571 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4572
4573 assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index());
4574 g1h->clear_in_cset(r);
4575
4576 if (r->is_young()) {
4577 assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(),
4578 "Young index %d is wrong for region %u of type %s with %u young regions",
4579 r->young_index_in_cset(),
4580 r->hrm_index(),
4581 r->get_type_str(),
4582 g1h->collection_set()->young_region_length());
4583 size_t words_survived = _surviving_young_words[r->young_index_in_cset()];
4584 r->record_surv_words_in_group(words_survived);
4585 }
4586
4587 if (!r->evacuation_failed()) {
4588 assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
4589 _before_used_bytes += r->used();
4590 g1h->free_region(r,
4591 &_local_free_list,
4592 true, /* skip_remset */
4593 true, /* skip_hot_card_cache */
4594 true /* locked */);
4595 } else {
4596 r->uninstall_surv_rate_group();
4597 r->set_young_index_in_cset(-1);
4598 r->set_evacuation_failed(false);
4599 // When moving a young gen region to old gen, we "allocate" that whole region
4600 // there. This is in addition to any already evacuated objects. Notify the
4601 // policy about that.
4602 // Old gen regions do not cause an additional allocation: both the objects
4603 // still in the region and the ones already moved are accounted for elsewhere.
4604 if (r->is_young()) {
4605 _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
4606 }
4607 // The region is now considered to be old.
4608 r->set_old();
4609 // Do some allocation statistics accounting. Regions that failed evacuation
4610 // are always made old, so there is no need to update anything in the young
4611 // gen statistics, but we need to update old gen statistics.
4612 size_t used_words = r->marked_bytes() / HeapWordSize;
4613
4614 _failure_used_words += used_words;
4615 _failure_waste_words += HeapRegion::GrainWords - used_words;
4616
4617 g1h->old_set_add(r);
4618 _after_used_bytes += r->used();
4619 }
4620 return false;
4621 }
4622
4623 void complete_work() {
4624 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4625
4626 _evacuation_info->set_regions_freed(_local_free_list.length());
4627 _evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4628
4629 g1h->prepend_to_freelist(&_local_free_list);
4630 g1h->decrement_summary_bytes(_before_used_bytes);
4631
4632 G1Policy* policy = g1h->g1_policy();
4633 policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4634
4635 g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4636 }
4637 };
4638
4639 G1CollectionSet* _collection_set;
4640 G1SerialFreeCollectionSetClosure _cl;
4641 const size_t* _surviving_young_words;
4642
4643 size_t _rs_lengths;
4644
4645 volatile jint _serial_work_claim;
4646
4647 struct WorkItem {
4648 uint region_idx;
4649 bool is_young;
4650 bool evacuation_failed;
4651
4652 WorkItem(HeapRegion* r) {
4653 region_idx = r->hrm_index();
4654 is_young = r->is_young();
4655 evacuation_failed = r->evacuation_failed();
4656 }
4657 };
4658
4659 volatile size_t _parallel_work_claim;
4660 size_t _num_work_items;
4661 WorkItem* _work_items;
4662
4663 void do_serial_work() {
4664 // Need to grab the lock to be allowed to modify the old region list.
4665 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4666 _collection_set->iterate(&_cl);
4667 }
4668
4669 void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) {
4670 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4671
4672 HeapRegion* r = g1h->region_at(region_idx);
4673 assert(!g1h->is_on_master_free_list(r), "sanity");
4674
4675 Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths);
4676
4677 if (!is_young) {
4678 g1h->_hot_card_cache->reset_card_counts(r);
4679 }
4680
4681 if (!evacuation_failed) {
4682 r->rem_set()->clear_locked();
4683 }
4684 }
4685
4686 class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure {
4687 private:
4688 size_t _cur_idx;
4689 WorkItem* _work_items;
4690 public:
4691 G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { }
4692
4693 virtual bool doHeapRegion(HeapRegion* r) {
4694 _work_items[_cur_idx++] = WorkItem(r);
4695 return false;
4696 }
4697 };
4698
4699 void prepare_work() {
4700 G1PrepareFreeCollectionSetClosure cl(_work_items);
4701 _collection_set->iterate(&cl);
4702 }
4703
4704 void complete_work() {
4705 _cl.complete_work();
4706
4707 G1Policy* policy = G1CollectedHeap::heap()->g1_policy();
4708 policy->record_max_rs_lengths(_rs_lengths);
4709 policy->cset_regions_freed();
4710 }
4711 public:
4712 G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4713 AbstractGangTask("G1 Free Collection Set"),
4714 _cl(evacuation_info, surviving_young_words),
4715 _collection_set(collection_set),
4716 _surviving_young_words(surviving_young_words),
4717 _serial_work_claim(0),
4718 _rs_lengths(0),
4719 _parallel_work_claim(0),
4720 _num_work_items(collection_set->region_length()),
4721 _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) {
4722 prepare_work();
4723 }
4724
4725 ~G1FreeCollectionSetTask() {
4726 complete_work();
4727 FREE_C_HEAP_ARRAY(WorkItem, _work_items);
4728 }
4729
4730 // Chunk size for work distribution. The chosen value has been determined experimentally
4731 // to be a good tradeoff between overhead and achievable parallelism.
4732 static uint chunk_size() { return 32; }
4733
4734 virtual void work(uint worker_id) {
4735 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
4736
4737 // Claim serial work.
4738 if (_serial_work_claim == 0) {
4739 jint value = Atomic::add(1, &_serial_work_claim) - 1;
4740 if (value == 0) {
4741 double serial_time = os::elapsedTime();
4742 do_serial_work();
4743 timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0);
4744 }
4745 }
4746
4747 // Start parallel work.
4748 double young_time = 0.0;
4749 bool has_young_time = false;
4750 double non_young_time = 0.0;
4751 bool has_non_young_time = false;
4752
4753 while (true) {
4754 size_t end = Atomic::add(chunk_size(), &_parallel_work_claim);
4755 size_t cur = end - chunk_size();
4756
4757 if (cur >= _num_work_items) {
4758 break;
4759 }
4760
4761 double start_time = os::elapsedTime();
4762
4763 end = MIN2(end, _num_work_items);
4764
4765 for (; cur < end; cur++) {
4766 bool is_young = _work_items[cur].is_young;
4767
4768 do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed);
4769
4770 double end_time = os::elapsedTime();
4771 double time_taken = end_time - start_time;
4772 if (is_young) {
4773 young_time += time_taken;
4774 has_young_time = true;
4775 } else {
4776 non_young_time += time_taken;
4777 has_non_young_time = true;
4778 }
4779 start_time = end_time;
4780 }
4781 }
4782
4783 if (has_young_time) {
4784 timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time);
4785 }
4786 if (has_non_young_time) {
4787 timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, young_time);
4788 }
4789 }
4790 };
4791
4792 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4793 _eden.clear();
4794
4795 double free_cset_start_time = os::elapsedTime();
4796
4797 {
4798 uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U);
4799 uint const num_workers = MIN2(workers()->active_workers(), num_chunks);
4800
4801 G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words);
4802
4803 log_debug(gc, ergo)("Running %s using %u workers for collection set length %u",
4804 cl.name(),
4805 num_workers,
4806 _collection_set.region_length());
4807 workers()->run_task(&cl, num_workers);
4808 }
4809 g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0);
4810
4811 collection_set->clear();
4812 }
4813
4814 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4815 private:
4816 FreeRegionList* _free_region_list;
4817 HeapRegionSet* _proxy_set;
4818 uint _humongous_objects_reclaimed;
4819 uint _humongous_regions_reclaimed;
4820 size_t _freed_bytes;
4821 public:
4822
4823 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4824 _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) {
4825 }
4826
4827 virtual bool doHeapRegion(HeapRegion* r) {
4828 if (!r->is_starts_humongous()) {
4829 return false;
4830 }
4831
4832 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4833
4834 oop obj = (oop)r->bottom();
4835 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap();
4836
4837 // The following checks whether the humongous object is live are sufficient.
4838 // The main additional check (in addition to having a reference from the roots
4839 // or the young gen) is whether the humongous object has a remembered set entry.
4840 //
4841 // A humongous object cannot be live if there is no remembered set for it
4842 // because:
4843 // - there can be no references from within humongous starts regions referencing
4844 // the object because we never allocate other objects into them.
4845 // (I.e. there are no intra-region references that may be missed by the
4846 // remembered set)
4847 // - as soon there is a remembered set entry to the humongous starts region
4848 // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4849 // until the end of a concurrent mark.
4850 //
4851 // It is not required to check whether the object has been found dead by marking
4852 // or not, in fact it would prevent reclamation within a concurrent cycle, as
4853 // all objects allocated during that time are considered live.
4854 // SATB marking is even more conservative than the remembered set.
4855 // So if at this point in the collection there is no remembered set entry,
4856 // nobody has a reference to it.
4857 // At the start of collection we flush all refinement logs, and remembered sets
4858 // are completely up-to-date wrt to references to the humongous object.
4859 //
4860 // Other implementation considerations:
4861 // - never consider object arrays at this time because they would pose
4862 // considerable effort for cleaning up the the remembered sets. This is
4863 // required because stale remembered sets might reference locations that
4864 // are currently allocated into.
4865 uint region_idx = r->hrm_index();
4866 if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4867 !r->rem_set()->is_empty()) {
4868 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",
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 return false;
4879 }
4880
4881 guarantee(obj->is_typeArray(),
4882 "Only eagerly reclaiming type arrays is supported, but the object "
4883 PTR_FORMAT " is not.", p2i(r->bottom()));
4884
4885 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",
4886 region_idx,
4887 (size_t)obj->size() * HeapWordSize,
4888 p2i(r->bottom()),
4889 r->rem_set()->occupied(),
4890 r->rem_set()->strong_code_roots_list_length(),
4891 next_bitmap->is_marked(r->bottom()),
4892 g1h->is_humongous_reclaim_candidate(region_idx),
4893 obj->is_typeArray()
4894 );
4895
4896 // Need to clear mark bit of the humongous object if already set.
4897 if (next_bitmap->is_marked(r->bottom())) {
4898 next_bitmap->clear(r->bottom());
4899 }
4900 _humongous_objects_reclaimed++;
4901 do {
4902 HeapRegion* next = g1h->next_region_in_humongous(r);
4903 _freed_bytes += r->used();
4904 r->set_containing_set(NULL);
4905 _humongous_regions_reclaimed++;
4906 g1h->free_humongous_region(r, _free_region_list, false /* skip_remset */ );
4907 r = next;
4908 } while (r != NULL);
4909
4910 return false;
4911 }
4912
4913 uint humongous_objects_reclaimed() {
4914 return _humongous_objects_reclaimed;
4915 }
4916
4917 uint humongous_regions_reclaimed() {
4918 return _humongous_regions_reclaimed;
4919 }
4920
4921 size_t bytes_freed() const {
4922 return _freed_bytes;
4923 }
4924 };
4925
4926 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4927 assert_at_safepoint(true);
4928
4929 if (!G1EagerReclaimHumongousObjects ||
4930 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
4931 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
4932 return;
4933 }
4934
4935 double start_time = os::elapsedTime();
4936
4937 FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
4938
4939 G1FreeHumongousRegionClosure cl(&local_cleanup_list);
4940 heap_region_iterate(&cl);
4941
4942 remove_from_old_sets(0, cl.humongous_regions_reclaimed());
4943
4944 G1HRPrinter* hrp = hr_printer();
4945 if (hrp->is_active()) {
4946 FreeRegionListIterator iter(&local_cleanup_list);
4947 while (iter.more_available()) {
4948 HeapRegion* hr = iter.get_next();
4949 hrp->cleanup(hr);
4950 }
4951 }
4952
4953 prepend_to_freelist(&local_cleanup_list);
4954 decrement_summary_bytes(cl.bytes_freed());
4955
4956 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
4957 cl.humongous_objects_reclaimed());
4958 }
4959
4960 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
4961 public:
4962 virtual bool doHeapRegion(HeapRegion* r) {
4963 assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
4964 G1CollectedHeap::heap()->clear_in_cset(r);
4965 r->set_young_index_in_cset(-1);
4966 return false;
4967 }
4968 };
4969
4970 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
4971 G1AbandonCollectionSetClosure cl;
4972 collection_set->iterate(&cl);
4973
4974 collection_set->clear();
4975 collection_set->stop_incremental_building();
4976 }
4977
4978 void G1CollectedHeap::set_free_regions_coming() {
4979 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming");
4980
4981 assert(!free_regions_coming(), "pre-condition");
4982 _free_regions_coming = true;
4983 }
4984
4985 void G1CollectedHeap::reset_free_regions_coming() {
4986 assert(free_regions_coming(), "pre-condition");
4987
4988 {
4989 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
4990 _free_regions_coming = false;
4991 SecondaryFreeList_lock->notify_all();
4992 }
4993
4994 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming");
4995 }
4996
4997 void G1CollectedHeap::wait_while_free_regions_coming() {
4998 // Most of the time we won't have to wait, so let's do a quick test
4999 // first before we take the lock.
5000 if (!free_regions_coming()) {
5001 return;
5002 }
5003
5004 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions");
5005
5006 {
5007 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5008 while (free_regions_coming()) {
5009 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
5010 }
5011 }
5012
5013 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions");
5014 }
5015
5016 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
5017 return _allocator->is_retained_old_region(hr);
5018 }
5019
5020 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
5021 _eden.add(hr);
5022 _g1_policy->set_region_eden(hr);
5023 }
5024
5025 #ifdef ASSERT
5026
5027 class NoYoungRegionsClosure: public HeapRegionClosure {
5028 private:
5029 bool _success;
5030 public:
5031 NoYoungRegionsClosure() : _success(true) { }
5032 bool doHeapRegion(HeapRegion* r) {
5033 if (r->is_young()) {
5034 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
5035 p2i(r->bottom()), p2i(r->end()));
5036 _success = false;
5037 }
5038 return false;
5039 }
5040 bool success() { return _success; }
5041 };
5042
5043 bool G1CollectedHeap::check_young_list_empty() {
5044 bool ret = (young_regions_count() == 0);
5045
5046 NoYoungRegionsClosure closure;
5047 heap_region_iterate(&closure);
5048 ret = ret && closure.success();
5049
5050 return ret;
5051 }
5052
5053 #endif // ASSERT
5054
5055 class TearDownRegionSetsClosure : public HeapRegionClosure {
5056 private:
5057 HeapRegionSet *_old_set;
5058
5059 public:
5060 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
5061
5062 bool doHeapRegion(HeapRegion* r) {
5063 if (r->is_old()) {
5064 _old_set->remove(r);
5065 } else if(r->is_young()) {
5066 r->uninstall_surv_rate_group();
5067 } else {
5068 // We ignore free regions, we'll empty the free list afterwards.
5069 // We ignore humongous regions, we're not tearing down the
5070 // humongous regions set.
5071 assert(r->is_free() || r->is_humongous(),
5072 "it cannot be another type");
5073 }
5074 return false;
5075 }
5076
5077 ~TearDownRegionSetsClosure() {
5078 assert(_old_set->is_empty(), "post-condition");
5079 }
5080 };
5081
5082 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
5083 assert_at_safepoint(true /* should_be_vm_thread */);
5084
5085 if (!free_list_only) {
5086 TearDownRegionSetsClosure cl(&_old_set);
5087 heap_region_iterate(&cl);
5088
5089 // Note that emptying the _young_list is postponed and instead done as
5090 // the first step when rebuilding the regions sets again. The reason for
5091 // this is that during a full GC string deduplication needs to know if
5092 // a collected region was young or old when the full GC was initiated.
5093 }
5094 _hrm.remove_all_free_regions();
5095 }
5096
5097 void G1CollectedHeap::increase_used(size_t bytes) {
5098 _summary_bytes_used += bytes;
5099 }
5100
5101 void G1CollectedHeap::decrease_used(size_t bytes) {
5102 assert(_summary_bytes_used >= bytes,
5103 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
5104 _summary_bytes_used, bytes);
5105 _summary_bytes_used -= bytes;
5106 }
5107
5108 void G1CollectedHeap::set_used(size_t bytes) {
5109 _summary_bytes_used = bytes;
5110 }
5111
5112 class RebuildRegionSetsClosure : public HeapRegionClosure {
5113 private:
5114 bool _free_list_only;
5115 HeapRegionSet* _old_set;
5116 HeapRegionManager* _hrm;
5117 size_t _total_used;
5118
5119 public:
5120 RebuildRegionSetsClosure(bool free_list_only,
5121 HeapRegionSet* old_set, HeapRegionManager* hrm) :
5122 _free_list_only(free_list_only),
5123 _old_set(old_set), _hrm(hrm), _total_used(0) {
5124 assert(_hrm->num_free_regions() == 0, "pre-condition");
5125 if (!free_list_only) {
5126 assert(_old_set->is_empty(), "pre-condition");
5127 }
5128 }
5129
5130 bool doHeapRegion(HeapRegion* r) {
5131 if (r->is_empty()) {
5132 // Add free regions to the free list
5133 r->set_free();
5134 r->set_allocation_context(AllocationContext::system());
5135 _hrm->insert_into_free_list(r);
5136 } else if (!_free_list_only) {
5137
5138 if (r->is_humongous()) {
5139 // We ignore humongous regions. We left the humongous set unchanged.
5140 } else {
5141 assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
5142 // We now move all (non-humongous, non-old) regions to old gen, and register them as such.
5143 r->move_to_old();
5144 _old_set->add(r);
5145 }
5146 _total_used += r->used();
5147 }
5148
5149 return false;
5150 }
5151
5152 size_t total_used() {
5153 return _total_used;
5154 }
5155 };
5156
5157 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
5158 assert_at_safepoint(true /* should_be_vm_thread */);
5159
5160 if (!free_list_only) {
5161 _eden.clear();
5162 _survivor.clear();
5163 }
5164
5165 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
5166 heap_region_iterate(&cl);
5167
5168 if (!free_list_only) {
5169 set_used(cl.total_used());
5170 if (_archive_allocator != NULL) {
5171 _archive_allocator->clear_used();
5172 }
5173 }
5174 assert(used_unlocked() == recalculate_used(),
5175 "inconsistent used_unlocked(), "
5176 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT,
5177 used_unlocked(), recalculate_used());
5178 }
5179
5180 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
5181 HeapRegion* hr = heap_region_containing(p);
5182 return hr->is_in(p);
5183 }
5184
5185 // Methods for the mutator alloc region
5186
5187 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
5188 bool force) {
5189 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5190 bool should_allocate = g1_policy()->should_allocate_mutator_region();
5191 if (force || should_allocate) {
5192 HeapRegion* new_alloc_region = new_region(word_size,
5193 false /* is_old */,
5194 false /* do_expand */);
5195 if (new_alloc_region != NULL) {
5196 set_region_short_lived_locked(new_alloc_region);
5197 _hr_printer.alloc(new_alloc_region, !should_allocate);
5198 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
5199 return new_alloc_region;
5200 }
5201 }
5202 return NULL;
5203 }
5204
5205 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
5206 size_t allocated_bytes) {
5207 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5208 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
5209
5210 collection_set()->add_eden_region(alloc_region);
5211 increase_used(allocated_bytes);
5212 _hr_printer.retire(alloc_region);
5213 // We update the eden sizes here, when the region is retired,
5214 // instead of when it's allocated, since this is the point that its
5215 // used space has been recored in _summary_bytes_used.
5216 g1mm()->update_eden_size();
5217 }
5218
5219 // Methods for the GC alloc regions
5220
5221 bool G1CollectedHeap::has_more_regions(InCSetState dest) {
5222 if (dest.is_old()) {
5223 return true;
5224 } else {
5225 return survivor_regions_count() < g1_policy()->max_survivor_regions();
5226 }
5227 }
5228
5229 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) {
5230 assert(FreeList_lock->owned_by_self(), "pre-condition");
5231
5232 if (!has_more_regions(dest)) {
5233 return NULL;
5234 }
5235
5236 const bool is_survivor = dest.is_young();
5237
5238 HeapRegion* new_alloc_region = new_region(word_size,
5239 !is_survivor,
5240 true /* do_expand */);
5241 if (new_alloc_region != NULL) {
5242 // We really only need to do this for old regions given that we
5243 // should never scan survivors. But it doesn't hurt to do it
5244 // for survivors too.
5245 new_alloc_region->record_timestamp();
5246 if (is_survivor) {
5247 new_alloc_region->set_survivor();
5248 _survivor.add(new_alloc_region);
5249 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
5250 } else {
5251 new_alloc_region->set_old();
5252 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
5253 }
5254 _hr_printer.alloc(new_alloc_region);
5255 bool during_im = collector_state()->during_initial_mark_pause();
5256 new_alloc_region->note_start_of_copying(during_im);
5257 return new_alloc_region;
5258 }
5259 return NULL;
5260 }
5261
5262 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
5263 size_t allocated_bytes,
5264 InCSetState dest) {
5265 bool during_im = collector_state()->during_initial_mark_pause();
5266 alloc_region->note_end_of_copying(during_im);
5267 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
5268 if (dest.is_old()) {
5269 _old_set.add(alloc_region);
5270 }
5271 _hr_printer.retire(alloc_region);
5272 }
5273
5274 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
5275 bool expanded = false;
5276 uint index = _hrm.find_highest_free(&expanded);
5277
5278 if (index != G1_NO_HRM_INDEX) {
5279 if (expanded) {
5280 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
5281 HeapRegion::GrainWords * HeapWordSize);
5282 }
5283 _hrm.allocate_free_regions_starting_at(index, 1);
5284 return region_at(index);
5285 }
5286 return NULL;
5287 }
5288
5289 // Optimized nmethod scanning
5290
5291 class RegisterNMethodOopClosure: public OopClosure {
5292 G1CollectedHeap* _g1h;
5293 nmethod* _nm;
5294
5295 template <class T> void do_oop_work(T* p) {
5296 T heap_oop = oopDesc::load_heap_oop(p);
5297 if (!oopDesc::is_null(heap_oop)) {
5298 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5299 HeapRegion* hr = _g1h->heap_region_containing(obj);
5300 assert(!hr->is_continues_humongous(),
5301 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5302 " starting at " HR_FORMAT,
5303 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5304
5305 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
5306 hr->add_strong_code_root_locked(_nm);
5307 }
5308 }
5309
5310 public:
5311 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5312 _g1h(g1h), _nm(nm) {}
5313
5314 void do_oop(oop* p) { do_oop_work(p); }
5315 void do_oop(narrowOop* p) { do_oop_work(p); }
5316 };
5317
5318 class UnregisterNMethodOopClosure: public OopClosure {
5319 G1CollectedHeap* _g1h;
5320 nmethod* _nm;
5321
5322 template <class T> void do_oop_work(T* p) {
5323 T heap_oop = oopDesc::load_heap_oop(p);
5324 if (!oopDesc::is_null(heap_oop)) {
5325 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5326 HeapRegion* hr = _g1h->heap_region_containing(obj);
5327 assert(!hr->is_continues_humongous(),
5328 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5329 " starting at " HR_FORMAT,
5330 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5331
5332 hr->remove_strong_code_root(_nm);
5333 }
5334 }
5335
5336 public:
5337 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5338 _g1h(g1h), _nm(nm) {}
5339
5340 void do_oop(oop* p) { do_oop_work(p); }
5341 void do_oop(narrowOop* p) { do_oop_work(p); }
5342 };
5343
5344 // Returns true if the reference points to an object that
5345 // can move in an incremental collection.
5346 bool G1CollectedHeap::is_scavengable(oop obj) {
5347 HeapRegion* hr = heap_region_containing(obj);
5348 return !hr->is_pinned();
5349 }
5350
5351 void G1CollectedHeap::register_nmethod(nmethod* nm) {
5352 guarantee(nm != NULL, "sanity");
5353 RegisterNMethodOopClosure reg_cl(this, nm);
5354 nm->oops_do(®_cl);
5355 }
5356
5357 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
5358 guarantee(nm != NULL, "sanity");
5359 UnregisterNMethodOopClosure reg_cl(this, nm);
5360 nm->oops_do(®_cl, true);
5361 }
5362
5363 void G1CollectedHeap::purge_code_root_memory() {
5364 double purge_start = os::elapsedTime();
5365 G1CodeRootSet::purge();
5366 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
5367 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
5368 }
5369
5370 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
5371 G1CollectedHeap* _g1h;
5372
5373 public:
5374 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
5375 _g1h(g1h) {}
5376
5377 void do_code_blob(CodeBlob* cb) {
5378 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
5379 if (nm == NULL) {
5380 return;
5381 }
5382
5383 if (ScavengeRootsInCode) {
5384 _g1h->register_nmethod(nm);
5385 }
5386 }
5387 };
5388
5389 void G1CollectedHeap::rebuild_strong_code_roots() {
5390 RebuildStrongCodeRootClosure blob_cl(this);
5391 CodeCache::blobs_do(&blob_cl);
5392 }