1 /*
2 * Copyright (c) 2001, 2016, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/metadataOnStackMark.hpp"
27 #include "classfile/stringTable.hpp"
28 #include "classfile/symbolTable.hpp"
29 #include "code/codeCache.hpp"
30 #include "code/icBuffer.hpp"
31 #include "gc/g1/bufferingOopClosure.hpp"
32 #include "gc/g1/concurrentG1Refine.hpp"
33 #include "gc/g1/concurrentG1RefineThread.hpp"
34 #include "gc/g1/concurrentMarkThread.inline.hpp"
35 #include "gc/g1/g1Allocator.inline.hpp"
36 #include "gc/g1/g1CollectedHeap.inline.hpp"
37 #include "gc/g1/g1CollectionSet.hpp"
38 #include "gc/g1/g1CollectorPolicy.hpp"
39 #include "gc/g1/g1CollectorState.hpp"
40 #include "gc/g1/g1EvacStats.inline.hpp"
41 #include "gc/g1/g1GCPhaseTimes.hpp"
42 #include "gc/g1/g1HeapSizingPolicy.hpp"
43 #include "gc/g1/g1HeapTransition.hpp"
44 #include "gc/g1/g1HeapVerifier.hpp"
45 #include "gc/g1/g1HotCardCache.hpp"
46 #include "gc/g1/g1MarkSweep.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/g1StringDedup.hpp"
55 #include "gc/g1/g1YCTypes.hpp"
56 #include "gc/g1/heapRegion.inline.hpp"
57 #include "gc/g1/heapRegionRemSet.hpp"
58 #include "gc/g1/heapRegionSet.inline.hpp"
59 #include "gc/g1/suspendibleThreadSet.hpp"
60 #include "gc/g1/vm_operations_g1.hpp"
61 #include "gc/shared/gcHeapSummary.hpp"
62 #include "gc/shared/gcId.hpp"
63 #include "gc/shared/gcLocker.inline.hpp"
64 #include "gc/shared/gcTimer.hpp"
65 #include "gc/shared/gcTrace.hpp"
66 #include "gc/shared/gcTraceTime.inline.hpp"
67 #include "gc/shared/generationSpec.hpp"
68 #include "gc/shared/isGCActiveMark.hpp"
69 #include "gc/shared/preservedMarks.inline.hpp"
70 #include "gc/shared/referenceProcessor.inline.hpp"
71 #include "gc/shared/taskqueue.inline.hpp"
72 #include "logging/log.hpp"
73 #include "memory/allocation.hpp"
74 #include "memory/iterator.hpp"
75 #include "memory/resourceArea.hpp"
76 #include "oops/oop.inline.hpp"
77 #include "runtime/atomic.inline.hpp"
78 #include "runtime/init.hpp"
79 #include "runtime/orderAccess.inline.hpp"
80 #include "runtime/vmThread.hpp"
81 #include "utilities/globalDefinitions.hpp"
82 #include "utilities/stack.inline.hpp"
83
84 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
85
86 // INVARIANTS/NOTES
87 //
88 // All allocation activity covered by the G1CollectedHeap interface is
89 // serialized by acquiring the HeapLock. This happens in mem_allocate
90 // and allocate_new_tlab, which are the "entry" points to the
91 // allocation code from the rest of the JVM. (Note that this does not
92 // apply to TLAB allocation, which is not part of this interface: it
93 // is done by clients of this interface.)
94
95 // Local to this file.
96
97 class RefineCardTableEntryClosure: public CardTableEntryClosure {
98 bool _concurrent;
99 public:
100 RefineCardTableEntryClosure() : _concurrent(true) { }
101
102 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
103 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, NULL);
104 // This path is executed by the concurrent refine or mutator threads,
105 // concurrently, and so we do not care if card_ptr contains references
106 // that point into the collection set.
107 assert(!oops_into_cset, "should be");
108
109 if (_concurrent && SuspendibleThreadSet::should_yield()) {
110 // Caller will actually yield.
111 return false;
112 }
113 // Otherwise, we finished successfully; return true.
114 return true;
115 }
116
117 void set_concurrent(bool b) { _concurrent = b; }
118 };
119
120
121 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
122 private:
123 size_t _num_dirtied;
124 G1CollectedHeap* _g1h;
125 G1SATBCardTableLoggingModRefBS* _g1_bs;
126
127 HeapRegion* region_for_card(jbyte* card_ptr) const {
128 return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr));
129 }
130
131 bool will_become_free(HeapRegion* hr) const {
132 // A region will be freed by free_collection_set if the region is in the
133 // collection set and has not had an evacuation failure.
134 return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
135 }
136
137 public:
138 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(),
139 _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { }
140
141 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
142 HeapRegion* hr = region_for_card(card_ptr);
143
144 // Should only dirty cards in regions that won't be freed.
145 if (!will_become_free(hr)) {
146 *card_ptr = CardTableModRefBS::dirty_card_val();
147 _num_dirtied++;
148 }
149
150 return true;
151 }
152
153 size_t num_dirtied() const { return _num_dirtied; }
154 };
155
156
157 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
158 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
159 }
160
161 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
162 // The from card cache is not the memory that is actually committed. So we cannot
163 // take advantage of the zero_filled parameter.
164 reset_from_card_cache(start_idx, num_regions);
165 }
166
167 // Returns true if the reference points to an object that
168 // can move in an incremental collection.
169 bool G1CollectedHeap::is_scavengable(const void* p) {
170 HeapRegion* hr = heap_region_containing(p);
171 return !hr->is_pinned();
172 }
173
174 // Private methods.
175
176 HeapRegion*
177 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
178 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
179 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
180 if (!_secondary_free_list.is_empty()) {
181 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
182 "secondary_free_list has %u entries",
183 _secondary_free_list.length());
184 // It looks as if there are free regions available on the
185 // secondary_free_list. Let's move them to the free_list and try
186 // again to allocate from it.
187 append_secondary_free_list();
188
189 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
190 "empty we should have moved at least one entry to the free_list");
191 HeapRegion* res = _hrm.allocate_free_region(is_old);
192 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
193 "allocated " HR_FORMAT " from secondary_free_list",
194 HR_FORMAT_PARAMS(res));
195 return res;
196 }
197
198 // Wait here until we get notified either when (a) there are no
199 // more free regions coming or (b) some regions have been moved on
200 // the secondary_free_list.
201 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
202 }
203
204 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
205 "could not allocate from secondary_free_list");
206 return NULL;
207 }
208
209 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
210 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
211 "the only time we use this to allocate a humongous region is "
212 "when we are allocating a single humongous region");
213
214 HeapRegion* res;
215 if (G1StressConcRegionFreeing) {
216 if (!_secondary_free_list.is_empty()) {
217 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
218 "forced to look at the secondary_free_list");
219 res = new_region_try_secondary_free_list(is_old);
220 if (res != NULL) {
221 return res;
222 }
223 }
224 }
225
226 res = _hrm.allocate_free_region(is_old);
227
228 if (res == NULL) {
229 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
230 "res == NULL, trying the secondary_free_list");
231 res = new_region_try_secondary_free_list(is_old);
232 }
233 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
234 // Currently, only attempts to allocate GC alloc regions set
235 // do_expand to true. So, we should only reach here during a
236 // safepoint. If this assumption changes we might have to
237 // reconsider the use of _expand_heap_after_alloc_failure.
238 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
239
240 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
241 word_size * HeapWordSize);
242
243 if (expand(word_size * HeapWordSize)) {
244 // Given that expand() succeeded in expanding the heap, and we
245 // always expand the heap by an amount aligned to the heap
246 // region size, the free list should in theory not be empty.
247 // In either case allocate_free_region() will check for NULL.
248 res = _hrm.allocate_free_region(is_old);
249 } else {
250 _expand_heap_after_alloc_failure = false;
251 }
252 }
253 return res;
254 }
255
256 HeapWord*
257 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
258 uint num_regions,
259 size_t word_size,
260 AllocationContext_t context) {
261 assert(first != G1_NO_HRM_INDEX, "pre-condition");
262 assert(is_humongous(word_size), "word_size should be humongous");
263 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
264
265 // Index of last region in the series.
266 uint last = first + num_regions - 1;
267
268 // We need to initialize the region(s) we just discovered. This is
269 // a bit tricky given that it can happen concurrently with
270 // refinement threads refining cards on these regions and
271 // potentially wanting to refine the BOT as they are scanning
272 // those cards (this can happen shortly after a cleanup; see CR
273 // 6991377). So we have to set up the region(s) carefully and in
274 // a specific order.
275
276 // The word size sum of all the regions we will allocate.
277 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
278 assert(word_size <= word_size_sum, "sanity");
279
280 // This will be the "starts humongous" region.
281 HeapRegion* first_hr = region_at(first);
282 // The header of the new object will be placed at the bottom of
283 // the first region.
284 HeapWord* new_obj = first_hr->bottom();
285 // This will be the new top of the new object.
286 HeapWord* obj_top = new_obj + word_size;
287
288 // First, we need to zero the header of the space that we will be
289 // allocating. When we update top further down, some refinement
290 // threads might try to scan the region. By zeroing the header we
291 // ensure that any thread that will try to scan the region will
292 // come across the zero klass word and bail out.
293 //
294 // NOTE: It would not have been correct to have used
295 // CollectedHeap::fill_with_object() and make the space look like
296 // an int array. The thread that is doing the allocation will
297 // later update the object header to a potentially different array
298 // type and, for a very short period of time, the klass and length
299 // fields will be inconsistent. This could cause a refinement
300 // thread to calculate the object size incorrectly.
301 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
302
303 // How many words we use for filler objects.
304 size_t word_fill_size = word_size_sum - word_size;
305
306 // How many words memory we "waste" which cannot hold a filler object.
307 size_t words_not_fillable = 0;
308
309 if (word_fill_size >= min_fill_size()) {
310 fill_with_objects(obj_top, word_fill_size);
311 } else if (word_fill_size > 0) {
312 // We have space to fill, but we cannot fit an object there.
313 words_not_fillable = word_fill_size;
314 word_fill_size = 0;
315 }
316
317 // We will set up the first region as "starts humongous". This
318 // will also update the BOT covering all the regions to reflect
319 // that there is a single object that starts at the bottom of the
320 // first region.
321 first_hr->set_starts_humongous(obj_top, word_fill_size);
322 first_hr->set_allocation_context(context);
323 // Then, if there are any, we will set up the "continues
324 // humongous" regions.
325 HeapRegion* hr = NULL;
326 for (uint i = first + 1; i <= last; ++i) {
327 hr = region_at(i);
328 hr->set_continues_humongous(first_hr);
329 hr->set_allocation_context(context);
330 }
331
332 // Up to this point no concurrent thread would have been able to
333 // do any scanning on any region in this series. All the top
334 // fields still point to bottom, so the intersection between
335 // [bottom,top] and [card_start,card_end] will be empty. Before we
336 // update the top fields, we'll do a storestore to make sure that
337 // no thread sees the update to top before the zeroing of the
338 // object header and the BOT initialization.
339 OrderAccess::storestore();
340
341 // Now, we will update the top fields of the "continues humongous"
342 // regions except the last one.
343 for (uint i = first; i < last; ++i) {
344 hr = region_at(i);
345 hr->set_top(hr->end());
346 }
347
348 hr = region_at(last);
349 // If we cannot fit a filler object, we must set top to the end
350 // of the humongous object, otherwise we cannot iterate the heap
351 // and the BOT will not be complete.
352 hr->set_top(hr->end() - words_not_fillable);
353
354 assert(hr->bottom() < obj_top && obj_top <= hr->end(),
355 "obj_top should be in last region");
356
357 _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
358
359 assert(words_not_fillable == 0 ||
360 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
361 "Miscalculation in humongous allocation");
362
363 increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
364
365 for (uint i = first; i <= last; ++i) {
366 hr = region_at(i);
367 _humongous_set.add(hr);
368 _hr_printer.alloc(hr);
369 }
370
371 return new_obj;
372 }
373
374 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
375 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
376 return align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
377 }
378
379 // If could fit into free regions w/o expansion, try.
380 // Otherwise, if can expand, do so.
381 // Otherwise, if using ex regions might help, try with ex given back.
382 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
383 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
384
385 _verifier->verify_region_sets_optional();
386
387 uint first = G1_NO_HRM_INDEX;
388 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
389
390 if (obj_regions == 1) {
391 // Only one region to allocate, try to use a fast path by directly allocating
392 // from the free lists. Do not try to expand here, we will potentially do that
393 // later.
394 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
395 if (hr != NULL) {
396 first = hr->hrm_index();
397 }
398 } else {
399 // We can't allocate humongous regions spanning more than one region while
400 // cleanupComplete() is running, since some of the regions we find to be
401 // empty might not yet be added to the free list. It is not straightforward
402 // to know in which list they are on so that we can remove them. We only
403 // need to do this if we need to allocate more than one region to satisfy the
404 // current humongous allocation request. If we are only allocating one region
405 // we use the one-region region allocation code (see above), that already
406 // potentially waits for regions from the secondary free list.
407 wait_while_free_regions_coming();
408 append_secondary_free_list_if_not_empty_with_lock();
409
410 // Policy: Try only empty regions (i.e. already committed first). Maybe we
411 // are lucky enough to find some.
412 first = _hrm.find_contiguous_only_empty(obj_regions);
413 if (first != G1_NO_HRM_INDEX) {
414 _hrm.allocate_free_regions_starting_at(first, obj_regions);
415 }
416 }
417
418 if (first == G1_NO_HRM_INDEX) {
419 // Policy: We could not find enough regions for the humongous object in the
420 // free list. Look through the heap to find a mix of free and uncommitted regions.
421 // If so, try expansion.
422 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
423 if (first != G1_NO_HRM_INDEX) {
424 // We found something. Make sure these regions are committed, i.e. expand
425 // the heap. Alternatively we could do a defragmentation GC.
426 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
427 word_size * HeapWordSize);
428
429
430 _hrm.expand_at(first, obj_regions);
431 g1_policy()->record_new_heap_size(num_regions());
432
433 #ifdef ASSERT
434 for (uint i = first; i < first + obj_regions; ++i) {
435 HeapRegion* hr = region_at(i);
436 assert(hr->is_free(), "sanity");
437 assert(hr->is_empty(), "sanity");
438 assert(is_on_master_free_list(hr), "sanity");
439 }
440 #endif
441 _hrm.allocate_free_regions_starting_at(first, obj_regions);
442 } else {
443 // Policy: Potentially trigger a defragmentation GC.
444 }
445 }
446
447 HeapWord* result = NULL;
448 if (first != G1_NO_HRM_INDEX) {
449 result = humongous_obj_allocate_initialize_regions(first, obj_regions,
450 word_size, context);
451 assert(result != NULL, "it should always return a valid result");
452
453 // A successful humongous object allocation changes the used space
454 // information of the old generation so we need to recalculate the
455 // sizes and update the jstat counters here.
456 g1mm()->update_sizes();
457 }
458
459 _verifier->verify_region_sets_optional();
460
461 return result;
462 }
463
464 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
465 assert_heap_not_locked_and_not_at_safepoint();
466 assert(!is_humongous(word_size), "we do not allow humongous TLABs");
467
468 uint dummy_gc_count_before;
469 uint dummy_gclocker_retry_count = 0;
470 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
471 }
472
473 HeapWord*
474 G1CollectedHeap::mem_allocate(size_t word_size,
475 bool* gc_overhead_limit_was_exceeded) {
476 assert_heap_not_locked_and_not_at_safepoint();
477
478 // Loop until the allocation is satisfied, or unsatisfied after GC.
479 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
480 uint gc_count_before;
481
482 HeapWord* result = NULL;
483 if (!is_humongous(word_size)) {
484 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
485 } else {
486 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
487 }
488 if (result != NULL) {
489 return result;
490 }
491
492 // Create the garbage collection operation...
493 VM_G1CollectForAllocation op(gc_count_before, word_size);
494 op.set_allocation_context(AllocationContext::current());
495
496 // ...and get the VM thread to execute it.
497 VMThread::execute(&op);
498
499 if (op.prologue_succeeded() && op.pause_succeeded()) {
500 // If the operation was successful we'll return the result even
501 // if it is NULL. If the allocation attempt failed immediately
502 // after a Full GC, it's unlikely we'll be able to allocate now.
503 HeapWord* result = op.result();
504 if (result != NULL && !is_humongous(word_size)) {
505 // Allocations that take place on VM operations do not do any
506 // card dirtying and we have to do it here. We only have to do
507 // this for non-humongous allocations, though.
508 dirty_young_block(result, word_size);
509 }
510 return result;
511 } else {
512 if (gclocker_retry_count > GCLockerRetryAllocationCount) {
513 return NULL;
514 }
515 assert(op.result() == NULL,
516 "the result should be NULL if the VM op did not succeed");
517 }
518
519 // Give a warning if we seem to be looping forever.
520 if ((QueuedAllocationWarningCount > 0) &&
521 (try_count % QueuedAllocationWarningCount == 0)) {
522 log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count);
523 }
524 }
525
526 ShouldNotReachHere();
527 return NULL;
528 }
529
530 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
531 AllocationContext_t context,
532 uint* gc_count_before_ret,
533 uint* gclocker_retry_count_ret) {
534 // Make sure you read the note in attempt_allocation_humongous().
535
536 assert_heap_not_locked_and_not_at_safepoint();
537 assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
538 "be called for humongous allocation requests");
539
540 // We should only get here after the first-level allocation attempt
541 // (attempt_allocation()) failed to allocate.
542
543 // We will loop until a) we manage to successfully perform the
544 // allocation or b) we successfully schedule a collection which
545 // fails to perform the allocation. b) is the only case when we'll
546 // return NULL.
547 HeapWord* result = NULL;
548 for (int try_count = 1; /* we'll return */; try_count += 1) {
549 bool should_try_gc;
550 uint gc_count_before;
551
552 {
553 MutexLockerEx x(Heap_lock);
554 result = _allocator->attempt_allocation_locked(word_size, context);
555 if (result != NULL) {
556 return result;
557 }
558
559 if (GCLocker::is_active_and_needs_gc()) {
560 if (g1_policy()->can_expand_young_list()) {
561 // No need for an ergo verbose message here,
562 // can_expand_young_list() does this when it returns true.
563 result = _allocator->attempt_allocation_force(word_size, context);
564 if (result != NULL) {
565 return result;
566 }
567 }
568 should_try_gc = false;
569 } else {
570 // The GCLocker may not be active but the GCLocker initiated
571 // GC may not yet have been performed (GCLocker::needs_gc()
572 // returns true). In this case we do not try this GC and
573 // wait until the GCLocker initiated GC is performed, and
574 // then retry the allocation.
575 if (GCLocker::needs_gc()) {
576 should_try_gc = false;
577 } else {
578 // Read the GC count while still holding the Heap_lock.
579 gc_count_before = total_collections();
580 should_try_gc = true;
581 }
582 }
583 }
584
585 if (should_try_gc) {
586 bool succeeded;
587 result = do_collection_pause(word_size, gc_count_before, &succeeded,
588 GCCause::_g1_inc_collection_pause);
589 if (result != NULL) {
590 assert(succeeded, "only way to get back a non-NULL result");
591 return result;
592 }
593
594 if (succeeded) {
595 // If we get here we successfully scheduled a collection which
596 // failed to allocate. No point in trying to allocate
597 // further. We'll just return NULL.
598 MutexLockerEx x(Heap_lock);
599 *gc_count_before_ret = total_collections();
600 return NULL;
601 }
602 } else {
603 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
604 MutexLockerEx x(Heap_lock);
605 *gc_count_before_ret = total_collections();
606 return NULL;
607 }
608 // The GCLocker is either active or the GCLocker initiated
609 // GC has not yet been performed. Stall until it is and
610 // then retry the allocation.
611 GCLocker::stall_until_clear();
612 (*gclocker_retry_count_ret) += 1;
613 }
614
615 // We can reach here if we were unsuccessful in scheduling a
616 // collection (because another thread beat us to it) or if we were
617 // stalled due to the GC locker. In either can we should retry the
618 // allocation attempt in case another thread successfully
619 // performed a collection and reclaimed enough space. We do the
620 // first attempt (without holding the Heap_lock) here and the
621 // follow-on attempt will be at the start of the next loop
622 // iteration (after taking the Heap_lock).
623 result = _allocator->attempt_allocation(word_size, context);
624 if (result != NULL) {
625 return result;
626 }
627
628 // Give a warning if we seem to be looping forever.
629 if ((QueuedAllocationWarningCount > 0) &&
630 (try_count % QueuedAllocationWarningCount == 0)) {
631 log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() "
632 "retries %d times", try_count);
633 }
634 }
635
636 ShouldNotReachHere();
637 return NULL;
638 }
639
640 void G1CollectedHeap::begin_archive_alloc_range() {
641 assert_at_safepoint(true /* should_be_vm_thread */);
642 if (_archive_allocator == NULL) {
643 _archive_allocator = G1ArchiveAllocator::create_allocator(this);
644 }
645 }
646
647 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
648 // Allocations in archive regions cannot be of a size that would be considered
649 // humongous even for a minimum-sized region, because G1 region sizes/boundaries
650 // may be different at archive-restore time.
651 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
652 }
653
654 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
655 assert_at_safepoint(true /* should_be_vm_thread */);
656 assert(_archive_allocator != NULL, "_archive_allocator not initialized");
657 if (is_archive_alloc_too_large(word_size)) {
658 return NULL;
659 }
660 return _archive_allocator->archive_mem_allocate(word_size);
661 }
662
663 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
664 size_t end_alignment_in_bytes) {
665 assert_at_safepoint(true /* should_be_vm_thread */);
666 assert(_archive_allocator != NULL, "_archive_allocator not initialized");
667
668 // Call complete_archive to do the real work, filling in the MemRegion
669 // array with the archive regions.
670 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
671 delete _archive_allocator;
672 _archive_allocator = NULL;
673 }
674
675 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
676 assert(ranges != NULL, "MemRegion array NULL");
677 assert(count != 0, "No MemRegions provided");
678 MemRegion reserved = _hrm.reserved();
679 for (size_t i = 0; i < count; i++) {
680 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
681 return false;
682 }
683 }
684 return true;
685 }
686
687 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, size_t count) {
688 assert(!is_init_completed(), "Expect to be called at JVM init time");
689 assert(ranges != NULL, "MemRegion array NULL");
690 assert(count != 0, "No MemRegions provided");
691 MutexLockerEx x(Heap_lock);
692
693 MemRegion reserved = _hrm.reserved();
694 HeapWord* prev_last_addr = NULL;
695 HeapRegion* prev_last_region = NULL;
696
697 // Temporarily disable pretouching of heap pages. This interface is used
698 // when mmap'ing archived heap data in, so pre-touching is wasted.
699 FlagSetting fs(AlwaysPreTouch, false);
700
701 // Enable archive object checking in G1MarkSweep. We have to let it know
702 // about each archive range, so that objects in those ranges aren't marked.
703 G1MarkSweep::enable_archive_object_check();
704
705 // For each specified MemRegion range, allocate the corresponding G1
706 // regions and mark them as archive regions. We expect the ranges in
707 // ascending starting address order, without overlap.
708 for (size_t i = 0; i < count; i++) {
709 MemRegion curr_range = ranges[i];
710 HeapWord* start_address = curr_range.start();
711 size_t word_size = curr_range.word_size();
712 HeapWord* last_address = curr_range.last();
713 size_t commits = 0;
714
715 guarantee(reserved.contains(start_address) && reserved.contains(last_address),
716 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
717 p2i(start_address), p2i(last_address));
718 guarantee(start_address > prev_last_addr,
719 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
720 p2i(start_address), p2i(prev_last_addr));
721 prev_last_addr = last_address;
722
723 // Check for ranges that start in the same G1 region in which the previous
724 // range ended, and adjust the start address so we don't try to allocate
725 // the same region again. If the current range is entirely within that
726 // region, skip it, just adjusting the recorded top.
727 HeapRegion* start_region = _hrm.addr_to_region(start_address);
728 if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
729 start_address = start_region->end();
730 if (start_address > last_address) {
731 increase_used(word_size * HeapWordSize);
732 start_region->set_top(last_address + 1);
733 continue;
734 }
735 start_region->set_top(start_address);
736 curr_range = MemRegion(start_address, last_address + 1);
737 start_region = _hrm.addr_to_region(start_address);
738 }
739
740 // Perform the actual region allocation, exiting if it fails.
741 // Then note how much new space we have allocated.
742 if (!_hrm.allocate_containing_regions(curr_range, &commits)) {
743 return false;
744 }
745 increase_used(word_size * HeapWordSize);
746 if (commits != 0) {
747 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
748 HeapRegion::GrainWords * HeapWordSize * commits);
749
750 }
751
752 // Mark each G1 region touched by the range as archive, add it to the old set,
753 // and set the allocation context and top.
754 HeapRegion* curr_region = _hrm.addr_to_region(start_address);
755 HeapRegion* last_region = _hrm.addr_to_region(last_address);
756 prev_last_region = last_region;
757
758 while (curr_region != NULL) {
759 assert(curr_region->is_empty() && !curr_region->is_pinned(),
760 "Region already in use (index %u)", curr_region->hrm_index());
761 curr_region->set_allocation_context(AllocationContext::system());
762 curr_region->set_archive();
763 _hr_printer.alloc(curr_region);
764 _old_set.add(curr_region);
765 if (curr_region != last_region) {
766 curr_region->set_top(curr_region->end());
767 curr_region = _hrm.next_region_in_heap(curr_region);
768 } else {
769 curr_region->set_top(last_address + 1);
770 curr_region = NULL;
771 }
772 }
773
774 // Notify mark-sweep of the archive range.
775 G1MarkSweep::set_range_archive(curr_range, true);
776 }
777 return true;
778 }
779
780 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
781 assert(!is_init_completed(), "Expect to be called at JVM init time");
782 assert(ranges != NULL, "MemRegion array NULL");
783 assert(count != 0, "No MemRegions provided");
784 MemRegion reserved = _hrm.reserved();
785 HeapWord *prev_last_addr = NULL;
786 HeapRegion* prev_last_region = NULL;
787
788 // For each MemRegion, create filler objects, if needed, in the G1 regions
789 // that contain the address range. The address range actually within the
790 // MemRegion will not be modified. That is assumed to have been initialized
791 // elsewhere, probably via an mmap of archived heap data.
792 MutexLockerEx x(Heap_lock);
793 for (size_t i = 0; i < count; i++) {
794 HeapWord* start_address = ranges[i].start();
795 HeapWord* last_address = ranges[i].last();
796
797 assert(reserved.contains(start_address) && reserved.contains(last_address),
798 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
799 p2i(start_address), p2i(last_address));
800 assert(start_address > prev_last_addr,
801 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
802 p2i(start_address), p2i(prev_last_addr));
803
804 HeapRegion* start_region = _hrm.addr_to_region(start_address);
805 HeapRegion* last_region = _hrm.addr_to_region(last_address);
806 HeapWord* bottom_address = start_region->bottom();
807
808 // Check for a range beginning in the same region in which the
809 // previous one ended.
810 if (start_region == prev_last_region) {
811 bottom_address = prev_last_addr + 1;
812 }
813
814 // Verify that the regions were all marked as archive regions by
815 // alloc_archive_regions.
816 HeapRegion* curr_region = start_region;
817 while (curr_region != NULL) {
818 guarantee(curr_region->is_archive(),
819 "Expected archive region at index %u", curr_region->hrm_index());
820 if (curr_region != last_region) {
821 curr_region = _hrm.next_region_in_heap(curr_region);
822 } else {
823 curr_region = NULL;
824 }
825 }
826
827 prev_last_addr = last_address;
828 prev_last_region = last_region;
829
830 // Fill the memory below the allocated range with dummy object(s),
831 // if the region bottom does not match the range start, or if the previous
832 // range ended within the same G1 region, and there is a gap.
833 if (start_address != bottom_address) {
834 size_t fill_size = pointer_delta(start_address, bottom_address);
835 G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
836 increase_used(fill_size * HeapWordSize);
837 }
838 }
839 }
840
841 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size,
842 uint* gc_count_before_ret,
843 uint* gclocker_retry_count_ret) {
844 assert_heap_not_locked_and_not_at_safepoint();
845 assert(!is_humongous(word_size), "attempt_allocation() should not "
846 "be called for humongous allocation requests");
847
848 AllocationContext_t context = AllocationContext::current();
849 HeapWord* result = _allocator->attempt_allocation(word_size, context);
850
851 if (result == NULL) {
852 result = attempt_allocation_slow(word_size,
853 context,
854 gc_count_before_ret,
855 gclocker_retry_count_ret);
856 }
857 assert_heap_not_locked();
858 if (result != NULL) {
859 dirty_young_block(result, word_size);
860 }
861 return result;
862 }
863
864 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
865 assert(!is_init_completed(), "Expect to be called at JVM init time");
866 assert(ranges != NULL, "MemRegion array NULL");
867 assert(count != 0, "No MemRegions provided");
868 MemRegion reserved = _hrm.reserved();
869 HeapWord* prev_last_addr = NULL;
870 HeapRegion* prev_last_region = NULL;
871 size_t size_used = 0;
872 size_t uncommitted_regions = 0;
873
874 // For each Memregion, free the G1 regions that constitute it, and
875 // notify mark-sweep that the range is no longer to be considered 'archive.'
876 MutexLockerEx x(Heap_lock);
877 for (size_t i = 0; i < count; i++) {
878 HeapWord* start_address = ranges[i].start();
879 HeapWord* last_address = ranges[i].last();
880
881 assert(reserved.contains(start_address) && reserved.contains(last_address),
882 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
883 p2i(start_address), p2i(last_address));
884 assert(start_address > prev_last_addr,
885 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
886 p2i(start_address), p2i(prev_last_addr));
887 size_used += ranges[i].byte_size();
888 prev_last_addr = last_address;
889
890 HeapRegion* start_region = _hrm.addr_to_region(start_address);
891 HeapRegion* last_region = _hrm.addr_to_region(last_address);
892
893 // Check for ranges that start in the same G1 region in which the previous
894 // range ended, and adjust the start address so we don't try to free
895 // the same region again. If the current range is entirely within that
896 // region, skip it.
897 if (start_region == prev_last_region) {
898 start_address = start_region->end();
899 if (start_address > last_address) {
900 continue;
901 }
902 start_region = _hrm.addr_to_region(start_address);
903 }
904 prev_last_region = last_region;
905
906 // After verifying that each region was marked as an archive region by
907 // alloc_archive_regions, set it free and empty and uncommit it.
908 HeapRegion* curr_region = start_region;
909 while (curr_region != NULL) {
910 guarantee(curr_region->is_archive(),
911 "Expected archive region at index %u", curr_region->hrm_index());
912 uint curr_index = curr_region->hrm_index();
913 _old_set.remove(curr_region);
914 curr_region->set_free();
915 curr_region->set_top(curr_region->bottom());
916 if (curr_region != last_region) {
917 curr_region = _hrm.next_region_in_heap(curr_region);
918 } else {
919 curr_region = NULL;
920 }
921 _hrm.shrink_at(curr_index, 1);
922 uncommitted_regions++;
923 }
924
925 // Notify mark-sweep that this is no longer an archive range.
926 G1MarkSweep::set_range_archive(ranges[i], false);
927 }
928
929 if (uncommitted_regions != 0) {
930 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
931 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
932 }
933 decrease_used(size_used);
934 }
935
936 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
937 uint* gc_count_before_ret,
938 uint* gclocker_retry_count_ret) {
939 // The structure of this method has a lot of similarities to
940 // attempt_allocation_slow(). The reason these two were not merged
941 // into a single one is that such a method would require several "if
942 // allocation is not humongous do this, otherwise do that"
943 // conditional paths which would obscure its flow. In fact, an early
944 // version of this code did use a unified method which was harder to
945 // follow and, as a result, it had subtle bugs that were hard to
946 // track down. So keeping these two methods separate allows each to
947 // be more readable. It will be good to keep these two in sync as
948 // much as possible.
949
950 assert_heap_not_locked_and_not_at_safepoint();
951 assert(is_humongous(word_size), "attempt_allocation_humongous() "
952 "should only be called for humongous allocations");
953
954 // Humongous objects can exhaust the heap quickly, so we should check if we
955 // need to start a marking cycle at each humongous object allocation. We do
956 // the check before we do the actual allocation. The reason for doing it
957 // before the allocation is that we avoid having to keep track of the newly
958 // allocated memory while we do a GC.
959 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
960 word_size)) {
961 collect(GCCause::_g1_humongous_allocation);
962 }
963
964 // We will loop until a) we manage to successfully perform the
965 // allocation or b) we successfully schedule a collection which
966 // fails to perform the allocation. b) is the only case when we'll
967 // return NULL.
968 HeapWord* result = NULL;
969 for (int try_count = 1; /* we'll return */; try_count += 1) {
970 bool should_try_gc;
971 uint gc_count_before;
972
973 {
974 MutexLockerEx x(Heap_lock);
975
976 // Given that humongous objects are not allocated in young
977 // regions, we'll first try to do the allocation without doing a
978 // collection hoping that there's enough space in the heap.
979 result = humongous_obj_allocate(word_size, AllocationContext::current());
980 if (result != NULL) {
981 size_t size_in_regions = humongous_obj_size_in_regions(word_size);
982 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
983 return result;
984 }
985
986 if (GCLocker::is_active_and_needs_gc()) {
987 should_try_gc = false;
988 } else {
989 // The GCLocker may not be active but the GCLocker initiated
990 // GC may not yet have been performed (GCLocker::needs_gc()
991 // returns true). In this case we do not try this GC and
992 // wait until the GCLocker initiated GC is performed, and
993 // then retry the allocation.
994 if (GCLocker::needs_gc()) {
995 should_try_gc = false;
996 } else {
997 // Read the GC count while still holding the Heap_lock.
998 gc_count_before = total_collections();
999 should_try_gc = true;
1000 }
1001 }
1002 }
1003
1004 if (should_try_gc) {
1005 // If we failed to allocate the humongous object, we should try to
1006 // do a collection pause (if we're allowed) in case it reclaims
1007 // enough space for the allocation to succeed after the pause.
1008
1009 bool succeeded;
1010 result = do_collection_pause(word_size, gc_count_before, &succeeded,
1011 GCCause::_g1_humongous_allocation);
1012 if (result != NULL) {
1013 assert(succeeded, "only way to get back a non-NULL result");
1014 return result;
1015 }
1016
1017 if (succeeded) {
1018 // If we get here we successfully scheduled a collection which
1019 // failed to allocate. No point in trying to allocate
1020 // further. We'll just return NULL.
1021 MutexLockerEx x(Heap_lock);
1022 *gc_count_before_ret = total_collections();
1023 return NULL;
1024 }
1025 } else {
1026 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1027 MutexLockerEx x(Heap_lock);
1028 *gc_count_before_ret = total_collections();
1029 return NULL;
1030 }
1031 // The GCLocker is either active or the GCLocker initiated
1032 // GC has not yet been performed. Stall until it is and
1033 // then retry the allocation.
1034 GCLocker::stall_until_clear();
1035 (*gclocker_retry_count_ret) += 1;
1036 }
1037
1038 // We can reach here if we were unsuccessful in scheduling a
1039 // collection (because another thread beat us to it) or if we were
1040 // stalled due to the GC locker. In either can we should retry the
1041 // allocation attempt in case another thread successfully
1042 // performed a collection and reclaimed enough space. Give a
1043 // warning if we seem to be looping forever.
1044
1045 if ((QueuedAllocationWarningCount > 0) &&
1046 (try_count % QueuedAllocationWarningCount == 0)) {
1047 log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() "
1048 "retries %d times", try_count);
1049 }
1050 }
1051
1052 ShouldNotReachHere();
1053 return NULL;
1054 }
1055
1056 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1057 AllocationContext_t context,
1058 bool expect_null_mutator_alloc_region) {
1059 assert_at_safepoint(true /* should_be_vm_thread */);
1060 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region,
1061 "the current alloc region was unexpectedly found to be non-NULL");
1062
1063 if (!is_humongous(word_size)) {
1064 return _allocator->attempt_allocation_locked(word_size, context);
1065 } else {
1066 HeapWord* result = humongous_obj_allocate(word_size, context);
1067 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1068 collector_state()->set_initiate_conc_mark_if_possible(true);
1069 }
1070 return result;
1071 }
1072
1073 ShouldNotReachHere();
1074 }
1075
1076 class PostMCRemSetClearClosure: public HeapRegionClosure {
1077 G1CollectedHeap* _g1h;
1078 ModRefBarrierSet* _mr_bs;
1079 public:
1080 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1081 _g1h(g1h), _mr_bs(mr_bs) {}
1082
1083 bool doHeapRegion(HeapRegion* r) {
1084 HeapRegionRemSet* hrrs = r->rem_set();
1085
1086 _g1h->reset_gc_time_stamps(r);
1087
1088 if (r->is_continues_humongous()) {
1089 // We'll assert that the strong code root list and RSet is empty
1090 assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1091 assert(hrrs->occupied() == 0, "RSet should be empty");
1092 } else {
1093 hrrs->clear();
1094 }
1095 // You might think here that we could clear just the cards
1096 // corresponding to the used region. But no: if we leave a dirty card
1097 // in a region we might allocate into, then it would prevent that card
1098 // from being enqueued, and cause it to be missed.
1099 // Re: the performance cost: we shouldn't be doing full GC anyway!
1100 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1101
1102 return false;
1103 }
1104 };
1105
1106 void G1CollectedHeap::clear_rsets_post_compaction() {
1107 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1108 heap_region_iterate(&rs_clear);
1109 }
1110
1111 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1112 G1CollectedHeap* _g1h;
1113 UpdateRSOopClosure _cl;
1114 public:
1115 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, uint worker_i = 0) :
1116 _cl(g1->g1_rem_set(), worker_i),
1117 _g1h(g1)
1118 { }
1119
1120 bool doHeapRegion(HeapRegion* r) {
1121 if (!r->is_continues_humongous()) {
1122 _cl.set_from(r);
1123 r->oop_iterate(&_cl);
1124 }
1125 return false;
1126 }
1127 };
1128
1129 class ParRebuildRSTask: public AbstractGangTask {
1130 G1CollectedHeap* _g1;
1131 HeapRegionClaimer _hrclaimer;
1132
1133 public:
1134 ParRebuildRSTask(G1CollectedHeap* g1) :
1135 AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {}
1136
1137 void work(uint worker_id) {
1138 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1139 _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer);
1140 }
1141 };
1142
1143 class PostCompactionPrinterClosure: public HeapRegionClosure {
1144 private:
1145 G1HRPrinter* _hr_printer;
1146 public:
1147 bool doHeapRegion(HeapRegion* hr) {
1148 assert(!hr->is_young(), "not expecting to find young regions");
1149 _hr_printer->post_compaction(hr);
1150 return false;
1151 }
1152
1153 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1154 : _hr_printer(hr_printer) { }
1155 };
1156
1157 void G1CollectedHeap::print_hrm_post_compaction() {
1158 if (_hr_printer.is_active()) {
1159 PostCompactionPrinterClosure cl(hr_printer());
1160 heap_region_iterate(&cl);
1161 }
1162
1163 }
1164
1165 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1166 bool clear_all_soft_refs) {
1167 assert_at_safepoint(true /* should_be_vm_thread */);
1168
1169 if (GCLocker::check_active_before_gc()) {
1170 return false;
1171 }
1172
1173 STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1174 gc_timer->register_gc_start();
1175
1176 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1177 GCIdMark gc_id_mark;
1178 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1179
1180 SvcGCMarker sgcm(SvcGCMarker::FULL);
1181 ResourceMark rm;
1182
1183 print_heap_before_gc();
1184 print_heap_regions();
1185 trace_heap_before_gc(gc_tracer);
1186
1187 size_t metadata_prev_used = MetaspaceAux::used_bytes();
1188
1189 _verifier->verify_region_sets_optional();
1190
1191 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1192 collector_policy()->should_clear_all_soft_refs();
1193
1194 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1195
1196 {
1197 IsGCActiveMark x;
1198
1199 // Timing
1200 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1201 GCTraceCPUTime tcpu;
1202
1203 {
1204 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1205 TraceCollectorStats tcs(g1mm()->full_collection_counters());
1206 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1207
1208 G1HeapTransition heap_transition(this);
1209 g1_policy()->record_full_collection_start();
1210
1211 // Note: When we have a more flexible GC logging framework that
1212 // allows us to add optional attributes to a GC log record we
1213 // could consider timing and reporting how long we wait in the
1214 // following two methods.
1215 wait_while_free_regions_coming();
1216 // If we start the compaction before the CM threads finish
1217 // scanning the root regions we might trip them over as we'll
1218 // be moving objects / updating references. So let's wait until
1219 // they are done. By telling them to abort, they should complete
1220 // early.
1221 _cm->root_regions()->abort();
1222 _cm->root_regions()->wait_until_scan_finished();
1223 append_secondary_free_list_if_not_empty_with_lock();
1224
1225 gc_prologue(true);
1226 increment_total_collections(true /* full gc */);
1227 increment_old_marking_cycles_started();
1228
1229 assert(used() == recalculate_used(), "Should be equal");
1230
1231 _verifier->verify_before_gc();
1232
1233 _verifier->check_bitmaps("Full GC Start");
1234 pre_full_gc_dump(gc_timer);
1235
1236 #if defined(COMPILER2) || INCLUDE_JVMCI
1237 DerivedPointerTable::clear();
1238 #endif
1239
1240 // Disable discovery and empty the discovered lists
1241 // for the CM ref processor.
1242 ref_processor_cm()->disable_discovery();
1243 ref_processor_cm()->abandon_partial_discovery();
1244 ref_processor_cm()->verify_no_references_recorded();
1245
1246 // Abandon current iterations of concurrent marking and concurrent
1247 // refinement, if any are in progress.
1248 concurrent_mark()->abort();
1249
1250 // Make sure we'll choose a new allocation region afterwards.
1251 _allocator->release_mutator_alloc_region();
1252 _allocator->abandon_gc_alloc_regions();
1253 g1_rem_set()->cleanupHRRS();
1254
1255 // We may have added regions to the current incremental collection
1256 // set between the last GC or pause and now. We need to clear the
1257 // incremental collection set and then start rebuilding it afresh
1258 // after this full GC.
1259 abandon_collection_set(collection_set()->inc_head());
1260 collection_set()->clear_incremental();
1261 collection_set()->stop_incremental_building();
1262
1263 tear_down_region_sets(false /* free_list_only */);
1264 collector_state()->set_gcs_are_young(true);
1265
1266 // See the comments in g1CollectedHeap.hpp and
1267 // G1CollectedHeap::ref_processing_init() about
1268 // how reference processing currently works in G1.
1269
1270 // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1271 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1272
1273 // Temporarily clear the STW ref processor's _is_alive_non_header field.
1274 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1275
1276 ref_processor_stw()->enable_discovery();
1277 ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1278
1279 // Do collection work
1280 {
1281 HandleMark hm; // Discard invalid handles created during gc
1282 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1283 }
1284
1285 assert(num_free_regions() == 0, "we should not have added any free regions");
1286 rebuild_region_sets(false /* free_list_only */);
1287
1288 // Enqueue any discovered reference objects that have
1289 // not been removed from the discovered lists.
1290 ref_processor_stw()->enqueue_discovered_references();
1291
1292 #if defined(COMPILER2) || INCLUDE_JVMCI
1293 DerivedPointerTable::update_pointers();
1294 #endif
1295
1296 MemoryService::track_memory_usage();
1297
1298 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1299 ref_processor_stw()->verify_no_references_recorded();
1300
1301 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1302 ClassLoaderDataGraph::purge();
1303 MetaspaceAux::verify_metrics();
1304
1305 // Note: since we've just done a full GC, concurrent
1306 // marking is no longer active. Therefore we need not
1307 // re-enable reference discovery for the CM ref processor.
1308 // That will be done at the start of the next marking cycle.
1309 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1310 ref_processor_cm()->verify_no_references_recorded();
1311
1312 reset_gc_time_stamp();
1313 // Since everything potentially moved, we will clear all remembered
1314 // sets, and clear all cards. Later we will rebuild remembered
1315 // sets. We will also reset the GC time stamps of the regions.
1316 clear_rsets_post_compaction();
1317 check_gc_time_stamps();
1318
1319 resize_if_necessary_after_full_collection();
1320
1321 // We should do this after we potentially resize the heap so
1322 // that all the COMMIT / UNCOMMIT events are generated before
1323 // the compaction events.
1324 print_hrm_post_compaction();
1325
1326 if (_hot_card_cache->use_cache()) {
1327 _hot_card_cache->reset_card_counts();
1328 _hot_card_cache->reset_hot_cache();
1329 }
1330
1331 // Rebuild remembered sets of all regions.
1332 uint n_workers =
1333 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1334 workers()->active_workers(),
1335 Threads::number_of_non_daemon_threads());
1336 workers()->set_active_workers(n_workers);
1337
1338 ParRebuildRSTask rebuild_rs_task(this);
1339 workers()->run_task(&rebuild_rs_task);
1340
1341 // Rebuild the strong code root lists for each region
1342 rebuild_strong_code_roots();
1343
1344 if (true) { // FIXME
1345 MetaspaceGC::compute_new_size();
1346 }
1347
1348 #ifdef TRACESPINNING
1349 ParallelTaskTerminator::print_termination_counts();
1350 #endif
1351
1352 // Discard all rset updates
1353 JavaThread::dirty_card_queue_set().abandon_logs();
1354 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1355
1356 // At this point there should be no regions in the
1357 // entire heap tagged as young.
1358 assert(check_young_list_empty(), "young list should be empty at this point");
1359
1360 // Update the number of full collections that have been completed.
1361 increment_old_marking_cycles_completed(false /* concurrent */);
1362
1363 _hrm.verify_optional();
1364 _verifier->verify_region_sets_optional();
1365
1366 _verifier->verify_after_gc();
1367
1368 // Clear the previous marking bitmap, if needed for bitmap verification.
1369 // Note we cannot do this when we clear the next marking bitmap in
1370 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1371 // objects marked during a full GC against the previous bitmap.
1372 // But we need to clear it before calling check_bitmaps below since
1373 // the full GC has compacted objects and updated TAMS but not updated
1374 // the prev bitmap.
1375 if (G1VerifyBitmaps) {
1376 GCTraceTime(Debug, gc)("Clear Bitmap for Verification");
1377 _cm->clear_prev_bitmap(workers());
1378 }
1379 _verifier->check_bitmaps("Full GC End");
1380
1381 // Start a new incremental collection set for the next pause
1382 assert(collection_set()->head() == NULL, "must be");
1383 collection_set()->start_incremental_building();
1384
1385 clear_cset_fast_test();
1386
1387 _allocator->init_mutator_alloc_region();
1388
1389 g1_policy()->record_full_collection_end();
1390
1391 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1392 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1393 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1394 // before any GC notifications are raised.
1395 g1mm()->update_sizes();
1396
1397 gc_epilogue(true);
1398
1399 heap_transition.print();
1400
1401 print_heap_after_gc();
1402 print_heap_regions();
1403 trace_heap_after_gc(gc_tracer);
1404
1405 post_full_gc_dump(gc_timer);
1406 }
1407
1408 gc_timer->register_gc_end();
1409 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1410 }
1411
1412 return true;
1413 }
1414
1415 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1416 // Currently, there is no facility in the do_full_collection(bool) API to notify
1417 // the caller that the collection did not succeed (e.g., because it was locked
1418 // out by the GC locker). So, right now, we'll ignore the return value.
1419 bool dummy = do_full_collection(true, /* explicit_gc */
1420 clear_all_soft_refs);
1421 }
1422
1423 void G1CollectedHeap::resize_if_necessary_after_full_collection() {
1424 // Include bytes that will be pre-allocated to support collections, as "used".
1425 const size_t used_after_gc = used();
1426 const size_t capacity_after_gc = capacity();
1427 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1428
1429 // This is enforced in arguments.cpp.
1430 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1431 "otherwise the code below doesn't make sense");
1432
1433 // We don't have floating point command-line arguments
1434 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1435 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1436 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1437 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1438
1439 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1440 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1441
1442 // We have to be careful here as these two calculations can overflow
1443 // 32-bit size_t's.
1444 double used_after_gc_d = (double) used_after_gc;
1445 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1446 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1447
1448 // Let's make sure that they are both under the max heap size, which
1449 // by default will make them fit into a size_t.
1450 double desired_capacity_upper_bound = (double) max_heap_size;
1451 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1452 desired_capacity_upper_bound);
1453 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1454 desired_capacity_upper_bound);
1455
1456 // We can now safely turn them into size_t's.
1457 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1458 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1459
1460 // This assert only makes sense here, before we adjust them
1461 // with respect to the min and max heap size.
1462 assert(minimum_desired_capacity <= maximum_desired_capacity,
1463 "minimum_desired_capacity = " SIZE_FORMAT ", "
1464 "maximum_desired_capacity = " SIZE_FORMAT,
1465 minimum_desired_capacity, maximum_desired_capacity);
1466
1467 // Should not be greater than the heap max size. No need to adjust
1468 // it with respect to the heap min size as it's a lower bound (i.e.,
1469 // we'll try to make the capacity larger than it, not smaller).
1470 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1471 // Should not be less than the heap min size. No need to adjust it
1472 // with respect to the heap max size as it's an upper bound (i.e.,
1473 // we'll try to make the capacity smaller than it, not greater).
1474 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1475
1476 if (capacity_after_gc < minimum_desired_capacity) {
1477 // Don't expand unless it's significant
1478 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1479
1480 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). "
1481 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1482 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio);
1483
1484 expand(expand_bytes);
1485
1486 // No expansion, now see if we want to shrink
1487 } else if (capacity_after_gc > maximum_desired_capacity) {
1488 // Capacity too large, compute shrinking size
1489 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1490
1491 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). "
1492 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1493 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio);
1494
1495 shrink(shrink_bytes);
1496 }
1497 }
1498
1499 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1500 AllocationContext_t context,
1501 bool do_gc,
1502 bool clear_all_soft_refs,
1503 bool expect_null_mutator_alloc_region,
1504 bool* gc_succeeded) {
1505 *gc_succeeded = true;
1506 // Let's attempt the allocation first.
1507 HeapWord* result =
1508 attempt_allocation_at_safepoint(word_size,
1509 context,
1510 expect_null_mutator_alloc_region);
1511 if (result != NULL) {
1512 assert(*gc_succeeded, "sanity");
1513 return result;
1514 }
1515
1516 // In a G1 heap, we're supposed to keep allocation from failing by
1517 // incremental pauses. Therefore, at least for now, we'll favor
1518 // expansion over collection. (This might change in the future if we can
1519 // do something smarter than full collection to satisfy a failed alloc.)
1520 result = expand_and_allocate(word_size, context);
1521 if (result != NULL) {
1522 assert(*gc_succeeded, "sanity");
1523 return result;
1524 }
1525
1526 if (do_gc) {
1527 // Expansion didn't work, we'll try to do a Full GC.
1528 *gc_succeeded = do_full_collection(false, /* explicit_gc */
1529 clear_all_soft_refs);
1530 }
1531
1532 return NULL;
1533 }
1534
1535 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1536 AllocationContext_t context,
1537 bool* succeeded) {
1538 assert_at_safepoint(true /* should_be_vm_thread */);
1539
1540 // Attempts to allocate followed by Full GC.
1541 HeapWord* result =
1542 satisfy_failed_allocation_helper(word_size,
1543 context,
1544 true, /* do_gc */
1545 false, /* clear_all_soft_refs */
1546 false, /* expect_null_mutator_alloc_region */
1547 succeeded);
1548
1549 if (result != NULL || !*succeeded) {
1550 return result;
1551 }
1552
1553 // Attempts to allocate followed by Full GC that will collect all soft references.
1554 result = satisfy_failed_allocation_helper(word_size,
1555 context,
1556 true, /* do_gc */
1557 true, /* clear_all_soft_refs */
1558 true, /* expect_null_mutator_alloc_region */
1559 succeeded);
1560
1561 if (result != NULL || !*succeeded) {
1562 return result;
1563 }
1564
1565 // Attempts to allocate, no GC
1566 result = satisfy_failed_allocation_helper(word_size,
1567 context,
1568 false, /* do_gc */
1569 false, /* clear_all_soft_refs */
1570 true, /* expect_null_mutator_alloc_region */
1571 succeeded);
1572
1573 if (result != NULL) {
1574 assert(*succeeded, "sanity");
1575 return result;
1576 }
1577
1578 assert(!collector_policy()->should_clear_all_soft_refs(),
1579 "Flag should have been handled and cleared prior to this point");
1580
1581 // What else? We might try synchronous finalization later. If the total
1582 // space available is large enough for the allocation, then a more
1583 // complete compaction phase than we've tried so far might be
1584 // appropriate.
1585 assert(*succeeded, "sanity");
1586 return NULL;
1587 }
1588
1589 // Attempting to expand the heap sufficiently
1590 // to support an allocation of the given "word_size". If
1591 // successful, perform the allocation and return the address of the
1592 // allocated block, or else "NULL".
1593
1594 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1595 assert_at_safepoint(true /* should_be_vm_thread */);
1596
1597 _verifier->verify_region_sets_optional();
1598
1599 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1600 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1601 word_size * HeapWordSize);
1602
1603
1604 if (expand(expand_bytes)) {
1605 _hrm.verify_optional();
1606 _verifier->verify_region_sets_optional();
1607 return attempt_allocation_at_safepoint(word_size,
1608 context,
1609 false /* expect_null_mutator_alloc_region */);
1610 }
1611 return NULL;
1612 }
1613
1614 bool G1CollectedHeap::expand(size_t expand_bytes, double* expand_time_ms) {
1615 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1616 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1617 HeapRegion::GrainBytes);
1618
1619 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount:" SIZE_FORMAT "B expansion amount:" SIZE_FORMAT "B",
1620 expand_bytes, aligned_expand_bytes);
1621
1622 if (is_maximal_no_gc()) {
1623 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1624 return false;
1625 }
1626
1627 double expand_heap_start_time_sec = os::elapsedTime();
1628 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1629 assert(regions_to_expand > 0, "Must expand by at least one region");
1630
1631 uint expanded_by = _hrm.expand_by(regions_to_expand);
1632 if (expand_time_ms != NULL) {
1633 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1634 }
1635
1636 if (expanded_by > 0) {
1637 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1638 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1639 g1_policy()->record_new_heap_size(num_regions());
1640 } else {
1641 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1642
1643 // The expansion of the virtual storage space was unsuccessful.
1644 // Let's see if it was because we ran out of swap.
1645 if (G1ExitOnExpansionFailure &&
1646 _hrm.available() >= regions_to_expand) {
1647 // We had head room...
1648 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1649 }
1650 }
1651 return regions_to_expand > 0;
1652 }
1653
1654 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1655 size_t aligned_shrink_bytes =
1656 ReservedSpace::page_align_size_down(shrink_bytes);
1657 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1658 HeapRegion::GrainBytes);
1659 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1660
1661 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1662 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1663
1664
1665 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",
1666 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1667 if (num_regions_removed > 0) {
1668 g1_policy()->record_new_heap_size(num_regions());
1669 } else {
1670 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1671 }
1672 }
1673
1674 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1675 _verifier->verify_region_sets_optional();
1676
1677 // We should only reach here at the end of a Full GC which means we
1678 // should not not be holding to any GC alloc regions. The method
1679 // below will make sure of that and do any remaining clean up.
1680 _allocator->abandon_gc_alloc_regions();
1681
1682 // Instead of tearing down / rebuilding the free lists here, we
1683 // could instead use the remove_all_pending() method on free_list to
1684 // remove only the ones that we need to remove.
1685 tear_down_region_sets(true /* free_list_only */);
1686 shrink_helper(shrink_bytes);
1687 rebuild_region_sets(true /* free_list_only */);
1688
1689 _hrm.verify_optional();
1690 _verifier->verify_region_sets_optional();
1691 }
1692
1693 // Public methods.
1694
1695 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) :
1696 CollectedHeap(),
1697 _collector_policy(collector_policy),
1698 _g1_policy(create_g1_policy()),
1699 _collection_set(this, _g1_policy),
1700 _dirty_card_queue_set(false),
1701 _is_alive_closure_cm(this),
1702 _is_alive_closure_stw(this),
1703 _ref_processor_cm(NULL),
1704 _ref_processor_stw(NULL),
1705 _bot(NULL),
1706 _hot_card_cache(NULL),
1707 _g1_rem_set(NULL),
1708 _cg1r(NULL),
1709 _g1mm(NULL),
1710 _refine_cte_cl(NULL),
1711 _preserved_marks_set(true /* in_c_heap */),
1712 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1713 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1714 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1715 _humongous_reclaim_candidates(),
1716 _has_humongous_reclaim_candidates(false),
1717 _archive_allocator(NULL),
1718 _free_regions_coming(false),
1719 _gc_time_stamp(0),
1720 _summary_bytes_used(0),
1721 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1722 _old_evac_stats("Old", OldPLABSize, PLABWeight),
1723 _expand_heap_after_alloc_failure(true),
1724 _old_marking_cycles_started(0),
1725 _old_marking_cycles_completed(0),
1726 _in_cset_fast_test(),
1727 _worker_cset_start_region(NULL),
1728 _worker_cset_start_region_time_stamp(NULL),
1729 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1730 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()) {
1731
1732 _workers = new WorkGang("GC Thread", ParallelGCThreads,
1733 /* are_GC_task_threads */true,
1734 /* are_ConcurrentGC_threads */false);
1735 _workers->initialize_workers();
1736 _verifier = new G1HeapVerifier(this);
1737
1738 _allocator = G1Allocator::create_allocator(this);
1739
1740 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics());
1741
1742 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1743
1744 // Override the default _filler_array_max_size so that no humongous filler
1745 // objects are created.
1746 _filler_array_max_size = _humongous_object_threshold_in_words;
1747
1748 uint n_queues = ParallelGCThreads;
1749 _task_queues = new RefToScanQueueSet(n_queues);
1750
1751 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1752 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(uint, n_queues, mtGC);
1753 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1754
1755 for (uint i = 0; i < n_queues; i++) {
1756 RefToScanQueue* q = new RefToScanQueue();
1757 q->initialize();
1758 _task_queues->register_queue(i, q);
1759 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1760 }
1761 clear_cset_start_regions();
1762
1763 // Initialize the G1EvacuationFailureALot counters and flags.
1764 NOT_PRODUCT(reset_evacuation_should_fail();)
1765
1766 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1767 }
1768
1769 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1770 size_t size,
1771 size_t translation_factor) {
1772 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1773 // Allocate a new reserved space, preferring to use large pages.
1774 ReservedSpace rs(size, preferred_page_size);
1775 G1RegionToSpaceMapper* result =
1776 G1RegionToSpaceMapper::create_mapper(rs,
1777 size,
1778 rs.alignment(),
1779 HeapRegion::GrainBytes,
1780 translation_factor,
1781 mtGC);
1782
1783 os::trace_page_sizes_for_requested_size(description,
1784 size,
1785 preferred_page_size,
1786 rs.alignment(),
1787 rs.base(),
1788 rs.size());
1789
1790 return result;
1791 }
1792
1793 jint G1CollectedHeap::initialize() {
1794 CollectedHeap::pre_initialize();
1795 os::enable_vtime();
1796
1797 // Necessary to satisfy locking discipline assertions.
1798
1799 MutexLocker x(Heap_lock);
1800
1801 // While there are no constraints in the GC code that HeapWordSize
1802 // be any particular value, there are multiple other areas in the
1803 // system which believe this to be true (e.g. oop->object_size in some
1804 // cases incorrectly returns the size in wordSize units rather than
1805 // HeapWordSize).
1806 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1807
1808 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1809 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1810 size_t heap_alignment = collector_policy()->heap_alignment();
1811
1812 // Ensure that the sizes are properly aligned.
1813 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1814 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1815 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1816
1817 _refine_cte_cl = new RefineCardTableEntryClosure();
1818
1819 jint ecode = JNI_OK;
1820 _cg1r = ConcurrentG1Refine::create(_refine_cte_cl, &ecode);
1821 if (_cg1r == NULL) {
1822 return ecode;
1823 }
1824
1825 // Reserve the maximum.
1826
1827 // When compressed oops are enabled, the preferred heap base
1828 // is calculated by subtracting the requested size from the
1829 // 32Gb boundary and using the result as the base address for
1830 // heap reservation. If the requested size is not aligned to
1831 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1832 // into the ReservedHeapSpace constructor) then the actual
1833 // base of the reserved heap may end up differing from the
1834 // address that was requested (i.e. the preferred heap base).
1835 // If this happens then we could end up using a non-optimal
1836 // compressed oops mode.
1837
1838 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1839 heap_alignment);
1840
1841 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1842
1843 // Create the barrier set for the entire reserved region.
1844 G1SATBCardTableLoggingModRefBS* bs
1845 = new G1SATBCardTableLoggingModRefBS(reserved_region());
1846 bs->initialize();
1847 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity");
1848 set_barrier_set(bs);
1849
1850 // Create the hot card cache.
1851 _hot_card_cache = new G1HotCardCache(this);
1852
1853 // Also create a G1 rem set.
1854 _g1_rem_set = new G1RemSet(this, g1_barrier_set(), _hot_card_cache);
1855
1856 // Carve out the G1 part of the heap.
1857 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1858 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
1859 G1RegionToSpaceMapper* heap_storage =
1860 G1RegionToSpaceMapper::create_mapper(g1_rs,
1861 g1_rs.size(),
1862 page_size,
1863 HeapRegion::GrainBytes,
1864 1,
1865 mtJavaHeap);
1866 os::trace_page_sizes("Heap",
1867 collector_policy()->min_heap_byte_size(),
1868 max_byte_size,
1869 page_size,
1870 heap_rs.base(),
1871 heap_rs.size());
1872 heap_storage->set_mapping_changed_listener(&_listener);
1873
1874 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1875 G1RegionToSpaceMapper* bot_storage =
1876 create_aux_memory_mapper("Block Offset Table",
1877 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1878 G1BlockOffsetTable::heap_map_factor());
1879
1880 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
1881 G1RegionToSpaceMapper* cardtable_storage =
1882 create_aux_memory_mapper("Card Table",
1883 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize),
1884 G1SATBCardTableLoggingModRefBS::heap_map_factor());
1885
1886 G1RegionToSpaceMapper* card_counts_storage =
1887 create_aux_memory_mapper("Card Counts Table",
1888 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1889 G1CardCounts::heap_map_factor());
1890
1891 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1892 G1RegionToSpaceMapper* prev_bitmap_storage =
1893 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1894 G1RegionToSpaceMapper* next_bitmap_storage =
1895 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1896
1897 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1898 g1_barrier_set()->initialize(cardtable_storage);
1899 // Do later initialization work for concurrent refinement.
1900 _hot_card_cache->initialize(card_counts_storage);
1901
1902 // 6843694 - ensure that the maximum region index can fit
1903 // in the remembered set structures.
1904 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1905 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1906
1907 g1_rem_set()->initialize(max_capacity(), max_regions());
1908
1909 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1910 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1911 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1912 "too many cards per region");
1913
1914 FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1915
1916 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1917
1918 {
1919 HeapWord* start = _hrm.reserved().start();
1920 HeapWord* end = _hrm.reserved().end();
1921 size_t granularity = HeapRegion::GrainBytes;
1922
1923 _in_cset_fast_test.initialize(start, end, granularity);
1924 _humongous_reclaim_candidates.initialize(start, end, granularity);
1925 }
1926
1927 // Create the G1ConcurrentMark data structure and thread.
1928 // (Must do this late, so that "max_regions" is defined.)
1929 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1930 if (_cm == NULL || !_cm->completed_initialization()) {
1931 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
1932 return JNI_ENOMEM;
1933 }
1934 _cmThread = _cm->cmThread();
1935
1936 // Now expand into the initial heap size.
1937 if (!expand(init_byte_size)) {
1938 vm_shutdown_during_initialization("Failed to allocate initial heap.");
1939 return JNI_ENOMEM;
1940 }
1941
1942 // Perform any initialization actions delegated to the policy.
1943 g1_policy()->init(this, &_collection_set);
1944
1945 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1946 SATB_Q_FL_lock,
1947 G1SATBProcessCompletedThreshold,
1948 Shared_SATB_Q_lock);
1949
1950 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
1951 DirtyCardQ_CBL_mon,
1952 DirtyCardQ_FL_lock,
1953 (int)concurrent_g1_refine()->yellow_zone(),
1954 (int)concurrent_g1_refine()->red_zone(),
1955 Shared_DirtyCardQ_lock,
1956 NULL, // fl_owner
1957 true); // init_free_ids
1958
1959 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
1960 DirtyCardQ_CBL_mon,
1961 DirtyCardQ_FL_lock,
1962 -1, // never trigger processing
1963 -1, // no limit on length
1964 Shared_DirtyCardQ_lock,
1965 &JavaThread::dirty_card_queue_set());
1966
1967 // Here we allocate the dummy HeapRegion that is required by the
1968 // G1AllocRegion class.
1969 HeapRegion* dummy_region = _hrm.get_dummy_region();
1970
1971 // We'll re-use the same region whether the alloc region will
1972 // require BOT updates or not and, if it doesn't, then a non-young
1973 // region will complain that it cannot support allocations without
1974 // BOT updates. So we'll tag the dummy region as eden to avoid that.
1975 dummy_region->set_eden();
1976 // Make sure it's full.
1977 dummy_region->set_top(dummy_region->end());
1978 G1AllocRegion::setup(this, dummy_region);
1979
1980 _allocator->init_mutator_alloc_region();
1981
1982 // Do create of the monitoring and management support so that
1983 // values in the heap have been properly initialized.
1984 _g1mm = new G1MonitoringSupport(this);
1985
1986 G1StringDedup::initialize();
1987
1988 _preserved_marks_set.init(ParallelGCThreads);
1989
1990 return JNI_OK;
1991 }
1992
1993 void G1CollectedHeap::stop() {
1994 // Stop all concurrent threads. We do this to make sure these threads
1995 // do not continue to execute and access resources (e.g. logging)
1996 // that are destroyed during shutdown.
1997 _cg1r->stop();
1998 _cmThread->stop();
1999 if (G1StringDedup::is_enabled()) {
2000 G1StringDedup::stop();
2001 }
2002 }
2003
2004 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2005 return HeapRegion::max_region_size();
2006 }
2007
2008 void G1CollectedHeap::post_initialize() {
2009 ref_processing_init();
2010 }
2011
2012 void G1CollectedHeap::ref_processing_init() {
2013 // Reference processing in G1 currently works as follows:
2014 //
2015 // * There are two reference processor instances. One is
2016 // used to record and process discovered references
2017 // during concurrent marking; the other is used to
2018 // record and process references during STW pauses
2019 // (both full and incremental).
2020 // * Both ref processors need to 'span' the entire heap as
2021 // the regions in the collection set may be dotted around.
2022 //
2023 // * For the concurrent marking ref processor:
2024 // * Reference discovery is enabled at initial marking.
2025 // * Reference discovery is disabled and the discovered
2026 // references processed etc during remarking.
2027 // * Reference discovery is MT (see below).
2028 // * Reference discovery requires a barrier (see below).
2029 // * Reference processing may or may not be MT
2030 // (depending on the value of ParallelRefProcEnabled
2031 // and ParallelGCThreads).
2032 // * A full GC disables reference discovery by the CM
2033 // ref processor and abandons any entries on it's
2034 // discovered lists.
2035 //
2036 // * For the STW processor:
2037 // * Non MT discovery is enabled at the start of a full GC.
2038 // * Processing and enqueueing during a full GC is non-MT.
2039 // * During a full GC, references are processed after marking.
2040 //
2041 // * Discovery (may or may not be MT) is enabled at the start
2042 // of an incremental evacuation pause.
2043 // * References are processed near the end of a STW evacuation pause.
2044 // * For both types of GC:
2045 // * Discovery is atomic - i.e. not concurrent.
2046 // * Reference discovery will not need a barrier.
2047
2048 MemRegion mr = reserved_region();
2049
2050 // Concurrent Mark ref processor
2051 _ref_processor_cm =
2052 new ReferenceProcessor(mr, // span
2053 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2054 // mt processing
2055 ParallelGCThreads,
2056 // degree of mt processing
2057 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2058 // mt discovery
2059 MAX2(ParallelGCThreads, ConcGCThreads),
2060 // degree of mt discovery
2061 false,
2062 // Reference discovery is not atomic
2063 &_is_alive_closure_cm);
2064 // is alive closure
2065 // (for efficiency/performance)
2066
2067 // STW ref processor
2068 _ref_processor_stw =
2069 new ReferenceProcessor(mr, // span
2070 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2071 // mt processing
2072 ParallelGCThreads,
2073 // degree of mt processing
2074 (ParallelGCThreads > 1),
2075 // mt discovery
2076 ParallelGCThreads,
2077 // degree of mt discovery
2078 true,
2079 // Reference discovery is atomic
2080 &_is_alive_closure_stw);
2081 // is alive closure
2082 // (for efficiency/performance)
2083 }
2084
2085 CollectorPolicy* G1CollectedHeap::collector_policy() const {
2086 return _collector_policy;
2087 }
2088
2089 size_t G1CollectedHeap::capacity() const {
2090 return _hrm.length() * HeapRegion::GrainBytes;
2091 }
2092
2093 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2094 hr->reset_gc_time_stamp();
2095 }
2096
2097 #ifndef PRODUCT
2098
2099 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2100 private:
2101 unsigned _gc_time_stamp;
2102 bool _failures;
2103
2104 public:
2105 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2106 _gc_time_stamp(gc_time_stamp), _failures(false) { }
2107
2108 virtual bool doHeapRegion(HeapRegion* hr) {
2109 unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2110 if (_gc_time_stamp != region_gc_time_stamp) {
2111 log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr),
2112 region_gc_time_stamp, _gc_time_stamp);
2113 _failures = true;
2114 }
2115 return false;
2116 }
2117
2118 bool failures() { return _failures; }
2119 };
2120
2121 void G1CollectedHeap::check_gc_time_stamps() {
2122 CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2123 heap_region_iterate(&cl);
2124 guarantee(!cl.failures(), "all GC time stamps should have been reset");
2125 }
2126 #endif // PRODUCT
2127
2128 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) {
2129 _hot_card_cache->drain(cl, worker_i);
2130 }
2131
2132 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) {
2133 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2134 size_t n_completed_buffers = 0;
2135 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2136 n_completed_buffers++;
2137 }
2138 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
2139 dcqs.clear_n_completed_buffers();
2140 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2141 }
2142
2143 // Computes the sum of the storage used by the various regions.
2144 size_t G1CollectedHeap::used() const {
2145 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
2146 if (_archive_allocator != NULL) {
2147 result += _archive_allocator->used();
2148 }
2149 return result;
2150 }
2151
2152 size_t G1CollectedHeap::used_unlocked() const {
2153 return _summary_bytes_used;
2154 }
2155
2156 class SumUsedClosure: public HeapRegionClosure {
2157 size_t _used;
2158 public:
2159 SumUsedClosure() : _used(0) {}
2160 bool doHeapRegion(HeapRegion* r) {
2161 _used += r->used();
2162 return false;
2163 }
2164 size_t result() { return _used; }
2165 };
2166
2167 size_t G1CollectedHeap::recalculate_used() const {
2168 double recalculate_used_start = os::elapsedTime();
2169
2170 SumUsedClosure blk;
2171 heap_region_iterate(&blk);
2172
2173 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2174 return blk.result();
2175 }
2176
2177 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
2178 switch (cause) {
2179 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2180 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent;
2181 case GCCause::_update_allocation_context_stats_inc: return true;
2182 case GCCause::_wb_conc_mark: return true;
2183 default : return false;
2184 }
2185 }
2186
2187 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2188 switch (cause) {
2189 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2190 case GCCause::_g1_humongous_allocation: return true;
2191 default: return is_user_requested_concurrent_full_gc(cause);
2192 }
2193 }
2194
2195 #ifndef PRODUCT
2196 void G1CollectedHeap::allocate_dummy_regions() {
2197 // Let's fill up most of the region
2198 size_t word_size = HeapRegion::GrainWords - 1024;
2199 // And as a result the region we'll allocate will be humongous.
2200 guarantee(is_humongous(word_size), "sanity");
2201
2202 // _filler_array_max_size is set to humongous object threshold
2203 // but temporarily change it to use CollectedHeap::fill_with_object().
2204 SizeTFlagSetting fs(_filler_array_max_size, word_size);
2205
2206 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2207 // Let's use the existing mechanism for the allocation
2208 HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2209 AllocationContext::system());
2210 if (dummy_obj != NULL) {
2211 MemRegion mr(dummy_obj, word_size);
2212 CollectedHeap::fill_with_object(mr);
2213 } else {
2214 // If we can't allocate once, we probably cannot allocate
2215 // again. Let's get out of the loop.
2216 break;
2217 }
2218 }
2219 }
2220 #endif // !PRODUCT
2221
2222 void G1CollectedHeap::increment_old_marking_cycles_started() {
2223 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2224 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2225 "Wrong marking cycle count (started: %d, completed: %d)",
2226 _old_marking_cycles_started, _old_marking_cycles_completed);
2227
2228 _old_marking_cycles_started++;
2229 }
2230
2231 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2232 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2233
2234 // We assume that if concurrent == true, then the caller is a
2235 // concurrent thread that was joined the Suspendible Thread
2236 // Set. If there's ever a cheap way to check this, we should add an
2237 // assert here.
2238
2239 // Given that this method is called at the end of a Full GC or of a
2240 // concurrent cycle, and those can be nested (i.e., a Full GC can
2241 // interrupt a concurrent cycle), the number of full collections
2242 // completed should be either one (in the case where there was no
2243 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2244 // behind the number of full collections started.
2245
2246 // This is the case for the inner caller, i.e. a Full GC.
2247 assert(concurrent ||
2248 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2249 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2250 "for inner caller (Full GC): _old_marking_cycles_started = %u "
2251 "is inconsistent with _old_marking_cycles_completed = %u",
2252 _old_marking_cycles_started, _old_marking_cycles_completed);
2253
2254 // This is the case for the outer caller, i.e. the concurrent cycle.
2255 assert(!concurrent ||
2256 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2257 "for outer caller (concurrent cycle): "
2258 "_old_marking_cycles_started = %u "
2259 "is inconsistent with _old_marking_cycles_completed = %u",
2260 _old_marking_cycles_started, _old_marking_cycles_completed);
2261
2262 _old_marking_cycles_completed += 1;
2263
2264 // We need to clear the "in_progress" flag in the CM thread before
2265 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2266 // is set) so that if a waiter requests another System.gc() it doesn't
2267 // incorrectly see that a marking cycle is still in progress.
2268 if (concurrent) {
2269 _cmThread->set_idle();
2270 }
2271
2272 // This notify_all() will ensure that a thread that called
2273 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2274 // and it's waiting for a full GC to finish will be woken up. It is
2275 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2276 FullGCCount_lock->notify_all();
2277 }
2278
2279 void G1CollectedHeap::collect(GCCause::Cause cause) {
2280 assert_heap_not_locked();
2281
2282 uint gc_count_before;
2283 uint old_marking_count_before;
2284 uint full_gc_count_before;
2285 bool retry_gc;
2286
2287 do {
2288 retry_gc = false;
2289
2290 {
2291 MutexLocker ml(Heap_lock);
2292
2293 // Read the GC count while holding the Heap_lock
2294 gc_count_before = total_collections();
2295 full_gc_count_before = total_full_collections();
2296 old_marking_count_before = _old_marking_cycles_started;
2297 }
2298
2299 if (should_do_concurrent_full_gc(cause)) {
2300 // Schedule an initial-mark evacuation pause that will start a
2301 // concurrent cycle. We're setting word_size to 0 which means that
2302 // we are not requesting a post-GC allocation.
2303 VM_G1IncCollectionPause op(gc_count_before,
2304 0, /* word_size */
2305 true, /* should_initiate_conc_mark */
2306 g1_policy()->max_pause_time_ms(),
2307 cause);
2308 op.set_allocation_context(AllocationContext::current());
2309
2310 VMThread::execute(&op);
2311 if (!op.pause_succeeded()) {
2312 if (old_marking_count_before == _old_marking_cycles_started) {
2313 retry_gc = op.should_retry_gc();
2314 } else {
2315 // A Full GC happened while we were trying to schedule the
2316 // initial-mark GC. No point in starting a new cycle given
2317 // that the whole heap was collected anyway.
2318 }
2319
2320 if (retry_gc) {
2321 if (GCLocker::is_active_and_needs_gc()) {
2322 GCLocker::stall_until_clear();
2323 }
2324 }
2325 }
2326 } else {
2327 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2328 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2329
2330 // Schedule a standard evacuation pause. We're setting word_size
2331 // to 0 which means that we are not requesting a post-GC allocation.
2332 VM_G1IncCollectionPause op(gc_count_before,
2333 0, /* word_size */
2334 false, /* should_initiate_conc_mark */
2335 g1_policy()->max_pause_time_ms(),
2336 cause);
2337 VMThread::execute(&op);
2338 } else {
2339 // Schedule a Full GC.
2340 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2341 VMThread::execute(&op);
2342 }
2343 }
2344 } while (retry_gc);
2345 }
2346
2347 bool G1CollectedHeap::is_in(const void* p) const {
2348 if (_hrm.reserved().contains(p)) {
2349 // Given that we know that p is in the reserved space,
2350 // heap_region_containing() should successfully
2351 // return the containing region.
2352 HeapRegion* hr = heap_region_containing(p);
2353 return hr->is_in(p);
2354 } else {
2355 return false;
2356 }
2357 }
2358
2359 #ifdef ASSERT
2360 bool G1CollectedHeap::is_in_exact(const void* p) const {
2361 bool contains = reserved_region().contains(p);
2362 bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2363 if (contains && available) {
2364 return true;
2365 } else {
2366 return false;
2367 }
2368 }
2369 #endif
2370
2371 bool G1CollectedHeap::obj_in_cs(oop obj) {
2372 HeapRegion* r = _hrm.addr_to_region((HeapWord*) obj);
2373 return r != NULL && r->in_collection_set();
2374 }
2375
2376 // Iteration functions.
2377
2378 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion.
2379
2380 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2381 ExtendedOopClosure* _cl;
2382 public:
2383 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {}
2384 bool doHeapRegion(HeapRegion* r) {
2385 if (!r->is_continues_humongous()) {
2386 r->oop_iterate(_cl);
2387 }
2388 return false;
2389 }
2390 };
2391
2392 // Iterates an ObjectClosure over all objects within a HeapRegion.
2393
2394 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2395 ObjectClosure* _cl;
2396 public:
2397 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2398 bool doHeapRegion(HeapRegion* r) {
2399 if (!r->is_continues_humongous()) {
2400 r->object_iterate(_cl);
2401 }
2402 return false;
2403 }
2404 };
2405
2406 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2407 IterateObjectClosureRegionClosure blk(cl);
2408 heap_region_iterate(&blk);
2409 }
2410
2411 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2412 _hrm.iterate(cl);
2413 }
2414
2415 void
2416 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl,
2417 uint worker_id,
2418 HeapRegionClaimer *hrclaimer,
2419 bool concurrent) const {
2420 _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent);
2421 }
2422
2423 // Clear the cached CSet starting regions and (more importantly)
2424 // the time stamps. Called when we reset the GC time stamp.
2425 void G1CollectedHeap::clear_cset_start_regions() {
2426 assert(_worker_cset_start_region != NULL, "sanity");
2427 assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2428
2429 for (uint i = 0; i < ParallelGCThreads; i++) {
2430 _worker_cset_start_region[i] = NULL;
2431 _worker_cset_start_region_time_stamp[i] = 0;
2432 }
2433 }
2434
2435 // Given the id of a worker, obtain or calculate a suitable
2436 // starting region for iterating over the current collection set.
2437 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2438 assert(get_gc_time_stamp() > 0, "should have been updated by now");
2439
2440 HeapRegion* result = NULL;
2441 unsigned gc_time_stamp = get_gc_time_stamp();
2442
2443 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2444 // Cached starting region for current worker was set
2445 // during the current pause - so it's valid.
2446 // Note: the cached starting heap region may be NULL
2447 // (when the collection set is empty).
2448 result = _worker_cset_start_region[worker_i];
2449 assert(result == NULL || result->in_collection_set(), "sanity");
2450 return result;
2451 }
2452
2453 // The cached entry was not valid so let's calculate
2454 // a suitable starting heap region for this worker.
2455
2456 // We want the parallel threads to start their collection
2457 // set iteration at different collection set regions to
2458 // avoid contention.
2459 // If we have:
2460 // n collection set regions
2461 // p threads
2462 // Then thread t will start at region floor ((t * n) / p)
2463
2464 result = collection_set()->head();
2465 uint cs_size = collection_set()->region_length();
2466 uint active_workers = workers()->active_workers();
2467
2468 uint end_ind = (cs_size * worker_i) / active_workers;
2469 uint start_ind = 0;
2470
2471 if (worker_i > 0 &&
2472 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2473 // Previous workers starting region is valid
2474 // so let's iterate from there
2475 start_ind = (cs_size * (worker_i - 1)) / active_workers;
2476 OrderAccess::loadload();
2477 result = _worker_cset_start_region[worker_i - 1];
2478 }
2479
2480 for (uint i = start_ind; i < end_ind; i++) {
2481 result = result->next_in_collection_set();
2482 }
2483
2484 // Note: the calculated starting heap region may be NULL
2485 // (when the collection set is empty).
2486 assert(result == NULL || result->in_collection_set(), "sanity");
2487 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2488 "should be updated only once per pause");
2489 _worker_cset_start_region[worker_i] = result;
2490 OrderAccess::storestore();
2491 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2492 return result;
2493 }
2494
2495 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2496 HeapRegion* r = collection_set()->head();
2497 while (r != NULL) {
2498 HeapRegion* next = r->next_in_collection_set();
2499 if (cl->doHeapRegion(r)) {
2500 cl->incomplete();
2501 return;
2502 }
2503 r = next;
2504 }
2505 }
2506
2507 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2508 HeapRegionClosure *cl) {
2509 if (r == NULL) {
2510 // The CSet is empty so there's nothing to do.
2511 return;
2512 }
2513
2514 assert(r->in_collection_set(),
2515 "Start region must be a member of the collection set.");
2516 HeapRegion* cur = r;
2517 while (cur != NULL) {
2518 HeapRegion* next = cur->next_in_collection_set();
2519 if (cl->doHeapRegion(cur) && false) {
2520 cl->incomplete();
2521 return;
2522 }
2523 cur = next;
2524 }
2525 cur = collection_set()->head();
2526 while (cur != r) {
2527 HeapRegion* next = cur->next_in_collection_set();
2528 if (cl->doHeapRegion(cur) && false) {
2529 cl->incomplete();
2530 return;
2531 }
2532 cur = next;
2533 }
2534 }
2535
2536 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2537 HeapRegion* result = _hrm.next_region_in_heap(from);
2538 while (result != NULL && result->is_pinned()) {
2539 result = _hrm.next_region_in_heap(result);
2540 }
2541 return result;
2542 }
2543
2544 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2545 HeapRegion* hr = heap_region_containing(addr);
2546 return hr->block_start(addr);
2547 }
2548
2549 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2550 HeapRegion* hr = heap_region_containing(addr);
2551 return hr->block_size(addr);
2552 }
2553
2554 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2555 HeapRegion* hr = heap_region_containing(addr);
2556 return hr->block_is_obj(addr);
2557 }
2558
2559 bool G1CollectedHeap::supports_tlab_allocation() const {
2560 return true;
2561 }
2562
2563 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2564 return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2565 }
2566
2567 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2568 return _eden.length() * HeapRegion::GrainBytes;
2569 }
2570
2571 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2572 // must be equal to the humongous object limit.
2573 size_t G1CollectedHeap::max_tlab_size() const {
2574 return align_size_down(_humongous_object_threshold_in_words, MinObjAlignment);
2575 }
2576
2577 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2578 AllocationContext_t context = AllocationContext::current();
2579 return _allocator->unsafe_max_tlab_alloc(context);
2580 }
2581
2582 size_t G1CollectedHeap::max_capacity() const {
2583 return _hrm.reserved().byte_size();
2584 }
2585
2586 jlong G1CollectedHeap::millis_since_last_gc() {
2587 // assert(false, "NYI");
2588 return 0;
2589 }
2590
2591 void G1CollectedHeap::prepare_for_verify() {
2592 _verifier->prepare_for_verify();
2593 }
2594
2595 void G1CollectedHeap::verify(VerifyOption vo) {
2596 _verifier->verify(vo);
2597 }
2598
2599 class PrintRegionClosure: public HeapRegionClosure {
2600 outputStream* _st;
2601 public:
2602 PrintRegionClosure(outputStream* st) : _st(st) {}
2603 bool doHeapRegion(HeapRegion* r) {
2604 r->print_on(_st);
2605 return false;
2606 }
2607 };
2608
2609 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2610 const HeapRegion* hr,
2611 const VerifyOption vo) const {
2612 switch (vo) {
2613 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2614 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2615 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked() && !hr->is_archive();
2616 default: ShouldNotReachHere();
2617 }
2618 return false; // keep some compilers happy
2619 }
2620
2621 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2622 const VerifyOption vo) const {
2623 switch (vo) {
2624 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2625 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2626 case VerifyOption_G1UseMarkWord: {
2627 HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj);
2628 return !obj->is_gc_marked() && !hr->is_archive();
2629 }
2630 default: ShouldNotReachHere();
2631 }
2632 return false; // keep some compilers happy
2633 }
2634
2635 void G1CollectedHeap::print_heap_regions() const {
2636 Log(gc, heap, region) log;
2637 if (log.is_trace()) {
2638 ResourceMark rm;
2639 print_regions_on(log.trace_stream());
2640 }
2641 }
2642
2643 void G1CollectedHeap::print_on(outputStream* st) const {
2644 assert_locked_or_safepoint(Heap_lock);
2645
2646 st->print(" %-20s", "garbage-first heap");
2647 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2648 capacity()/K, used_unlocked()/K);
2649 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")",
2650 p2i(_hrm.reserved().start()),
2651 p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords),
2652 p2i(_hrm.reserved().end()));
2653 st->cr();
2654 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2655 uint young_regions = young_regions_count();
2656 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2657 (size_t) young_regions * HeapRegion::GrainBytes / K);
2658 uint survivor_regions = survivor_regions_count();
2659 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2660 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2661 st->cr();
2662 MetaspaceAux::print_on(st);
2663 }
2664
2665 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2666 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2667 "HS=humongous(starts), HC=humongous(continues), "
2668 "CS=collection set, F=free, A=archive, TS=gc time stamp, "
2669 "AC=allocation context, "
2670 "TAMS=top-at-mark-start (previous, next)");
2671 PrintRegionClosure blk(st);
2672 heap_region_iterate(&blk);
2673 }
2674
2675 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2676 print_on(st);
2677
2678 // Print the per-region information.
2679 print_regions_on(st);
2680 }
2681
2682 void G1CollectedHeap::print_on_error(outputStream* st) const {
2683 this->CollectedHeap::print_on_error(st);
2684
2685 if (_cm != NULL) {
2686 st->cr();
2687 _cm->print_on_error(st);
2688 }
2689 }
2690
2691 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2692 workers()->print_worker_threads_on(st);
2693 _cmThread->print_on(st);
2694 st->cr();
2695 _cm->print_worker_threads_on(st);
2696 _cg1r->print_worker_threads_on(st); // also prints the sample thread
2697 if (G1StringDedup::is_enabled()) {
2698 G1StringDedup::print_worker_threads_on(st);
2699 }
2700 }
2701
2702 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2703 workers()->threads_do(tc);
2704 tc->do_thread(_cmThread);
2705 _cm->threads_do(tc);
2706 _cg1r->threads_do(tc); // also iterates over the sample thread
2707 if (G1StringDedup::is_enabled()) {
2708 G1StringDedup::threads_do(tc);
2709 }
2710 }
2711
2712 void G1CollectedHeap::print_tracing_info() const {
2713 g1_rem_set()->print_summary_info();
2714 concurrent_mark()->print_summary_info();
2715 }
2716
2717 #ifndef PRODUCT
2718 // Helpful for debugging RSet issues.
2719
2720 class PrintRSetsClosure : public HeapRegionClosure {
2721 private:
2722 const char* _msg;
2723 size_t _occupied_sum;
2724
2725 public:
2726 bool doHeapRegion(HeapRegion* r) {
2727 HeapRegionRemSet* hrrs = r->rem_set();
2728 size_t occupied = hrrs->occupied();
2729 _occupied_sum += occupied;
2730
2731 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2732 if (occupied == 0) {
2733 tty->print_cr(" RSet is empty");
2734 } else {
2735 hrrs->print();
2736 }
2737 tty->print_cr("----------");
2738 return false;
2739 }
2740
2741 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2742 tty->cr();
2743 tty->print_cr("========================================");
2744 tty->print_cr("%s", msg);
2745 tty->cr();
2746 }
2747
2748 ~PrintRSetsClosure() {
2749 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2750 tty->print_cr("========================================");
2751 tty->cr();
2752 }
2753 };
2754
2755 void G1CollectedHeap::print_cset_rsets() {
2756 PrintRSetsClosure cl("Printing CSet RSets");
2757 collection_set_iterate(&cl);
2758 }
2759
2760 void G1CollectedHeap::print_all_rsets() {
2761 PrintRSetsClosure cl("Printing All RSets");;
2762 heap_region_iterate(&cl);
2763 }
2764 #endif // PRODUCT
2765
2766 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2767
2768 size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes;
2769 size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes;
2770 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2771
2772 size_t eden_capacity_bytes =
2773 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2774
2775 VirtualSpaceSummary heap_summary = create_heap_space_summary();
2776 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2777 eden_capacity_bytes, survivor_used_bytes, num_regions());
2778 }
2779
2780 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2781 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2782 stats->unused(), stats->used(), stats->region_end_waste(),
2783 stats->regions_filled(), stats->direct_allocated(),
2784 stats->failure_used(), stats->failure_waste());
2785 }
2786
2787 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2788 const G1HeapSummary& heap_summary = create_g1_heap_summary();
2789 gc_tracer->report_gc_heap_summary(when, heap_summary);
2790
2791 const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2792 gc_tracer->report_metaspace_summary(when, metaspace_summary);
2793 }
2794
2795 G1CollectedHeap* G1CollectedHeap::heap() {
2796 CollectedHeap* heap = Universe::heap();
2797 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2798 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap");
2799 return (G1CollectedHeap*)heap;
2800 }
2801
2802 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
2803 // always_do_update_barrier = false;
2804 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2805 // Fill TLAB's and such
2806 accumulate_statistics_all_tlabs();
2807 ensure_parsability(true);
2808
2809 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2810 }
2811
2812 void G1CollectedHeap::gc_epilogue(bool full) {
2813 // we are at the end of the GC. Total collections has already been increased.
2814 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2815
2816 // FIXME: what is this about?
2817 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2818 // is set.
2819 #if defined(COMPILER2) || INCLUDE_JVMCI
2820 assert(DerivedPointerTable::is_empty(), "derived pointer present");
2821 #endif
2822 // always_do_update_barrier = true;
2823
2824 resize_all_tlabs();
2825 allocation_context_stats().update(full);
2826
2827 // We have just completed a GC. Update the soft reference
2828 // policy with the new heap occupancy
2829 Universe::update_heap_info_at_gc();
2830 }
2831
2832 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2833 uint gc_count_before,
2834 bool* succeeded,
2835 GCCause::Cause gc_cause) {
2836 assert_heap_not_locked_and_not_at_safepoint();
2837 VM_G1IncCollectionPause op(gc_count_before,
2838 word_size,
2839 false, /* should_initiate_conc_mark */
2840 g1_policy()->max_pause_time_ms(),
2841 gc_cause);
2842
2843 op.set_allocation_context(AllocationContext::current());
2844 VMThread::execute(&op);
2845
2846 HeapWord* result = op.result();
2847 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
2848 assert(result == NULL || ret_succeeded,
2849 "the result should be NULL if the VM did not succeed");
2850 *succeeded = ret_succeeded;
2851
2852 assert_heap_not_locked();
2853 return result;
2854 }
2855
2856 void
2857 G1CollectedHeap::doConcurrentMark() {
2858 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
2859 if (!_cmThread->in_progress()) {
2860 _cmThread->set_started();
2861 CGC_lock->notify();
2862 }
2863 }
2864
2865 size_t G1CollectedHeap::pending_card_num() {
2866 size_t extra_cards = 0;
2867 JavaThread *curr = Threads::first();
2868 while (curr != NULL) {
2869 DirtyCardQueue& dcq = curr->dirty_card_queue();
2870 extra_cards += dcq.size();
2871 curr = curr->next();
2872 }
2873 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2874 size_t buffer_size = dcqs.buffer_size();
2875 size_t buffer_num = dcqs.completed_buffers_num();
2876
2877 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
2878 // in bytes - not the number of 'entries'. We need to convert
2879 // into a number of cards.
2880 return (buffer_size * buffer_num + extra_cards) / oopSize;
2881 }
2882
2883 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
2884 private:
2885 size_t _total_humongous;
2886 size_t _candidate_humongous;
2887
2888 DirtyCardQueue _dcq;
2889
2890 // We don't nominate objects with many remembered set entries, on
2891 // the assumption that such objects are likely still live.
2892 bool is_remset_small(HeapRegion* region) const {
2893 HeapRegionRemSet* const rset = region->rem_set();
2894 return G1EagerReclaimHumongousObjectsWithStaleRefs
2895 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)
2896 : rset->is_empty();
2897 }
2898
2899 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const {
2900 assert(region->is_starts_humongous(), "Must start a humongous object");
2901
2902 oop obj = oop(region->bottom());
2903
2904 // Dead objects cannot be eager reclaim candidates. Due to class
2905 // unloading it is unsafe to query their classes so we return early.
2906 if (heap->is_obj_dead(obj, region)) {
2907 return false;
2908 }
2909
2910 // Candidate selection must satisfy the following constraints
2911 // while concurrent marking is in progress:
2912 //
2913 // * In order to maintain SATB invariants, an object must not be
2914 // reclaimed if it was allocated before the start of marking and
2915 // has not had its references scanned. Such an object must have
2916 // its references (including type metadata) scanned to ensure no
2917 // live objects are missed by the marking process. Objects
2918 // allocated after the start of concurrent marking don't need to
2919 // be scanned.
2920 //
2921 // * An object must not be reclaimed if it is on the concurrent
2922 // mark stack. Objects allocated after the start of concurrent
2923 // marking are never pushed on the mark stack.
2924 //
2925 // Nominating only objects allocated after the start of concurrent
2926 // marking is sufficient to meet both constraints. This may miss
2927 // some objects that satisfy the constraints, but the marking data
2928 // structures don't support efficiently performing the needed
2929 // additional tests or scrubbing of the mark stack.
2930 //
2931 // However, we presently only nominate is_typeArray() objects.
2932 // A humongous object containing references induces remembered
2933 // set entries on other regions. In order to reclaim such an
2934 // object, those remembered sets would need to be cleaned up.
2935 //
2936 // We also treat is_typeArray() objects specially, allowing them
2937 // to be reclaimed even if allocated before the start of
2938 // concurrent mark. For this we rely on mark stack insertion to
2939 // exclude is_typeArray() objects, preventing reclaiming an object
2940 // that is in the mark stack. We also rely on the metadata for
2941 // such objects to be built-in and so ensured to be kept live.
2942 // Frequent allocation and drop of large binary blobs is an
2943 // important use case for eager reclaim, and this special handling
2944 // may reduce needed headroom.
2945
2946 return obj->is_typeArray() && is_remset_small(region);
2947 }
2948
2949 public:
2950 RegisterHumongousWithInCSetFastTestClosure()
2951 : _total_humongous(0),
2952 _candidate_humongous(0),
2953 _dcq(&JavaThread::dirty_card_queue_set()) {
2954 }
2955
2956 virtual bool doHeapRegion(HeapRegion* r) {
2957 if (!r->is_starts_humongous()) {
2958 return false;
2959 }
2960 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2961
2962 bool is_candidate = humongous_region_is_candidate(g1h, r);
2963 uint rindex = r->hrm_index();
2964 g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
2965 if (is_candidate) {
2966 _candidate_humongous++;
2967 g1h->register_humongous_region_with_cset(rindex);
2968 // Is_candidate already filters out humongous object with large remembered sets.
2969 // If we have a humongous object with a few remembered sets, we simply flush these
2970 // remembered set entries into the DCQS. That will result in automatic
2971 // re-evaluation of their remembered set entries during the following evacuation
2972 // phase.
2973 if (!r->rem_set()->is_empty()) {
2974 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
2975 "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
2976 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
2977 HeapRegionRemSetIterator hrrs(r->rem_set());
2978 size_t card_index;
2979 while (hrrs.has_next(card_index)) {
2980 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
2981 // The remembered set might contain references to already freed
2982 // regions. Filter out such entries to avoid failing card table
2983 // verification.
2984 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) {
2985 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
2986 *card_ptr = CardTableModRefBS::dirty_card_val();
2987 _dcq.enqueue(card_ptr);
2988 }
2989 }
2990 }
2991 assert(hrrs.n_yielded() == r->rem_set()->occupied(),
2992 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
2993 hrrs.n_yielded(), r->rem_set()->occupied());
2994 r->rem_set()->clear_locked();
2995 }
2996 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
2997 }
2998 _total_humongous++;
2999
3000 return false;
3001 }
3002
3003 size_t total_humongous() const { return _total_humongous; }
3004 size_t candidate_humongous() const { return _candidate_humongous; }
3005
3006 void flush_rem_set_entries() { _dcq.flush(); }
3007 };
3008
3009 void G1CollectedHeap::register_humongous_regions_with_cset() {
3010 if (!G1EagerReclaimHumongousObjects) {
3011 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
3012 return;
3013 }
3014 double time = os::elapsed_counter();
3015
3016 // Collect reclaim candidate information and register candidates with cset.
3017 RegisterHumongousWithInCSetFastTestClosure cl;
3018 heap_region_iterate(&cl);
3019
3020 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
3021 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
3022 cl.total_humongous(),
3023 cl.candidate_humongous());
3024 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
3025
3026 // Finally flush all remembered set entries to re-check into the global DCQS.
3027 cl.flush_rem_set_entries();
3028 }
3029
3030 class VerifyRegionRemSetClosure : public HeapRegionClosure {
3031 public:
3032 bool doHeapRegion(HeapRegion* hr) {
3033 if (!hr->is_archive() && !hr->is_continues_humongous()) {
3034 hr->verify_rem_set();
3035 }
3036 return false;
3037 }
3038 };
3039
3040 uint G1CollectedHeap::num_task_queues() const {
3041 return _task_queues->size();
3042 }
3043
3044 #if TASKQUEUE_STATS
3045 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3046 st->print_raw_cr("GC Task Stats");
3047 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3048 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3049 }
3050
3051 void G1CollectedHeap::print_taskqueue_stats() const {
3052 if (!log_is_enabled(Trace, gc, task, stats)) {
3053 return;
3054 }
3055 Log(gc, task, stats) log;
3056 ResourceMark rm;
3057 outputStream* st = log.trace_stream();
3058
3059 print_taskqueue_stats_hdr(st);
3060
3061 TaskQueueStats totals;
3062 const uint n = num_task_queues();
3063 for (uint i = 0; i < n; ++i) {
3064 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
3065 totals += task_queue(i)->stats;
3066 }
3067 st->print_raw("tot "); totals.print(st); st->cr();
3068
3069 DEBUG_ONLY(totals.verify());
3070 }
3071
3072 void G1CollectedHeap::reset_taskqueue_stats() {
3073 const uint n = num_task_queues();
3074 for (uint i = 0; i < n; ++i) {
3075 task_queue(i)->stats.reset();
3076 }
3077 }
3078 #endif // TASKQUEUE_STATS
3079
3080 void G1CollectedHeap::wait_for_root_region_scanning() {
3081 double scan_wait_start = os::elapsedTime();
3082 // We have to wait until the CM threads finish scanning the
3083 // root regions as it's the only way to ensure that all the
3084 // objects on them have been correctly scanned before we start
3085 // moving them during the GC.
3086 bool waited = _cm->root_regions()->wait_until_scan_finished();
3087 double wait_time_ms = 0.0;
3088 if (waited) {
3089 double scan_wait_end = os::elapsedTime();
3090 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3091 }
3092 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
3093 }
3094
3095 bool
3096 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3097 assert_at_safepoint(true /* should_be_vm_thread */);
3098 guarantee(!is_gc_active(), "collection is not reentrant");
3099
3100 if (GCLocker::check_active_before_gc()) {
3101 return false;
3102 }
3103
3104 _gc_timer_stw->register_gc_start();
3105
3106 GCIdMark gc_id_mark;
3107 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3108
3109 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3110 ResourceMark rm;
3111
3112 g1_policy()->note_gc_start();
3113
3114 wait_for_root_region_scanning();
3115
3116 print_heap_before_gc();
3117 print_heap_regions();
3118 trace_heap_before_gc(_gc_tracer_stw);
3119
3120 _verifier->verify_region_sets_optional();
3121 _verifier->verify_dirty_young_regions();
3122
3123 // We should not be doing initial mark unless the conc mark thread is running
3124 if (!_cmThread->should_terminate()) {
3125 // This call will decide whether this pause is an initial-mark
3126 // pause. If it is, during_initial_mark_pause() will return true
3127 // for the duration of this pause.
3128 g1_policy()->decide_on_conc_mark_initiation();
3129 }
3130
3131 // We do not allow initial-mark to be piggy-backed on a mixed GC.
3132 assert(!collector_state()->during_initial_mark_pause() ||
3133 collector_state()->gcs_are_young(), "sanity");
3134
3135 // We also do not allow mixed GCs during marking.
3136 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity");
3137
3138 // Record whether this pause is an initial mark. When the current
3139 // thread has completed its logging output and it's safe to signal
3140 // the CM thread, the flag's value in the policy has been reset.
3141 bool should_start_conc_mark = collector_state()->during_initial_mark_pause();
3142
3143 // Inner scope for scope based logging, timers, and stats collection
3144 {
3145 EvacuationInfo evacuation_info;
3146
3147 if (collector_state()->during_initial_mark_pause()) {
3148 // We are about to start a marking cycle, so we increment the
3149 // full collection counter.
3150 increment_old_marking_cycles_started();
3151 _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
3152 }
3153
3154 _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
3155
3156 GCTraceCPUTime tcpu;
3157
3158 FormatBuffer<> gc_string("Pause ");
3159 if (collector_state()->during_initial_mark_pause()) {
3160 gc_string.append("Initial Mark");
3161 } else if (collector_state()->gcs_are_young()) {
3162 gc_string.append("Young");
3163 } else {
3164 gc_string.append("Mixed");
3165 }
3166 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true);
3167
3168 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
3169 workers()->active_workers(),
3170 Threads::number_of_non_daemon_threads());
3171 workers()->set_active_workers(active_workers);
3172
3173 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3174 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3175
3176 // If the secondary_free_list is not empty, append it to the
3177 // free_list. No need to wait for the cleanup operation to finish;
3178 // the region allocation code will check the secondary_free_list
3179 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3180 // set, skip this step so that the region allocation code has to
3181 // get entries from the secondary_free_list.
3182 if (!G1StressConcRegionFreeing) {
3183 append_secondary_free_list_if_not_empty_with_lock();
3184 }
3185
3186 G1HeapTransition heap_transition(this);
3187 size_t heap_used_bytes_before_gc = used();
3188
3189 // Don't dynamically change the number of GC threads this early. A value of
3190 // 0 is used to indicate serial work. When parallel work is done,
3191 // it will be set.
3192
3193 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3194 IsGCActiveMark x;
3195
3196 gc_prologue(false);
3197 increment_total_collections(false /* full gc */);
3198 increment_gc_time_stamp();
3199
3200 if (VerifyRememberedSets) {
3201 log_info(gc, verify)("[Verifying RemSets before GC]");
3202 VerifyRegionRemSetClosure v_cl;
3203 heap_region_iterate(&v_cl);
3204 }
3205
3206 _verifier->verify_before_gc();
3207
3208 _verifier->check_bitmaps("GC Start");
3209
3210 #if defined(COMPILER2) || INCLUDE_JVMCI
3211 DerivedPointerTable::clear();
3212 #endif
3213
3214 // Please see comment in g1CollectedHeap.hpp and
3215 // G1CollectedHeap::ref_processing_init() to see how
3216 // reference processing currently works in G1.
3217
3218 // Enable discovery in the STW reference processor
3219 if (g1_policy()->should_process_references()) {
3220 ref_processor_stw()->enable_discovery();
3221 } else {
3222 ref_processor_stw()->disable_discovery();
3223 }
3224
3225 {
3226 // We want to temporarily turn off discovery by the
3227 // CM ref processor, if necessary, and turn it back on
3228 // on again later if we do. Using a scoped
3229 // NoRefDiscovery object will do this.
3230 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3231
3232 // Forget the current alloc region (we might even choose it to be part
3233 // of the collection set!).
3234 _allocator->release_mutator_alloc_region();
3235
3236 // This timing is only used by the ergonomics to handle our pause target.
3237 // It is unclear why this should not include the full pause. We will
3238 // investigate this in CR 7178365.
3239 //
3240 // Preserving the old comment here if that helps the investigation:
3241 //
3242 // The elapsed time induced by the start time below deliberately elides
3243 // the possible verification above.
3244 double sample_start_time_sec = os::elapsedTime();
3245
3246 g1_policy()->record_collection_pause_start(sample_start_time_sec);
3247
3248 if (collector_state()->during_initial_mark_pause()) {
3249 concurrent_mark()->checkpointRootsInitialPre();
3250 }
3251
3252 g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor);
3253
3254 evacuation_info.set_collectionset_regions(collection_set()->region_length());
3255
3256 // Make sure the remembered sets are up to date. This needs to be
3257 // done before register_humongous_regions_with_cset(), because the
3258 // remembered sets are used there to choose eager reclaim candidates.
3259 // If the remembered sets are not up to date we might miss some
3260 // entries that need to be handled.
3261 g1_rem_set()->cleanupHRRS();
3262
3263 register_humongous_regions_with_cset();
3264
3265 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table.");
3266
3267 _cm->note_start_of_gc();
3268 // We call this after finalize_cset() to
3269 // ensure that the CSet has been finalized.
3270 _cm->verify_no_cset_oops();
3271
3272 if (_hr_printer.is_active()) {
3273 HeapRegion* hr = collection_set()->head();
3274 while (hr != NULL) {
3275 _hr_printer.cset(hr);
3276 hr = hr->next_in_collection_set();
3277 }
3278 }
3279
3280 // Initialize the GC alloc regions.
3281 _allocator->init_gc_alloc_regions(evacuation_info);
3282
3283 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length());
3284 pre_evacuate_collection_set();
3285
3286 // Actually do the work...
3287 evacuate_collection_set(evacuation_info, &per_thread_states);
3288
3289 post_evacuate_collection_set(evacuation_info, &per_thread_states);
3290
3291 const size_t* surviving_young_words = per_thread_states.surviving_young_words();
3292 free_collection_set(collection_set()->head(), evacuation_info, surviving_young_words);
3293
3294 eagerly_reclaim_humongous_regions();
3295
3296 collection_set()->clear_head();
3297
3298 record_obj_copy_mem_stats();
3299 _survivor_evac_stats.adjust_desired_plab_sz();
3300 _old_evac_stats.adjust_desired_plab_sz();
3301
3302 // Start a new incremental collection set for the next pause.
3303 collection_set()->start_incremental_building();
3304
3305 clear_cset_fast_test();
3306
3307 guarantee(_eden.length() == 0, "eden should have been cleared");
3308 g1_policy()->transfer_survivors_to_cset(survivor());
3309
3310 if (evacuation_failed()) {
3311 set_used(recalculate_used());
3312 if (_archive_allocator != NULL) {
3313 _archive_allocator->clear_used();
3314 }
3315 for (uint i = 0; i < ParallelGCThreads; i++) {
3316 if (_evacuation_failed_info_array[i].has_failed()) {
3317 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3318 }
3319 }
3320 } else {
3321 // The "used" of the the collection set have already been subtracted
3322 // when they were freed. Add in the bytes evacuated.
3323 increase_used(g1_policy()->bytes_copied_during_gc());
3324 }
3325
3326 if (collector_state()->during_initial_mark_pause()) {
3327 // We have to do this before we notify the CM threads that
3328 // they can start working to make sure that all the
3329 // appropriate initialization is done on the CM object.
3330 concurrent_mark()->checkpointRootsInitialPost();
3331 collector_state()->set_mark_in_progress(true);
3332 // Note that we don't actually trigger the CM thread at
3333 // this point. We do that later when we're sure that
3334 // the current thread has completed its logging output.
3335 }
3336
3337 allocate_dummy_regions();
3338
3339 _allocator->init_mutator_alloc_region();
3340
3341 {
3342 size_t expand_bytes = _heap_sizing_policy->expansion_amount();
3343 if (expand_bytes > 0) {
3344 size_t bytes_before = capacity();
3345 // No need for an ergo logging here,
3346 // expansion_amount() does this when it returns a value > 0.
3347 double expand_ms;
3348 if (!expand(expand_bytes, &expand_ms)) {
3349 // We failed to expand the heap. Cannot do anything about it.
3350 }
3351 g1_policy()->phase_times()->record_expand_heap_time(expand_ms);
3352 }
3353 }
3354
3355 // We redo the verification but now wrt to the new CSet which
3356 // has just got initialized after the previous CSet was freed.
3357 _cm->verify_no_cset_oops();
3358 _cm->note_end_of_gc();
3359
3360 // This timing is only used by the ergonomics to handle our pause target.
3361 // It is unclear why this should not include the full pause. We will
3362 // investigate this in CR 7178365.
3363 double sample_end_time_sec = os::elapsedTime();
3364 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3365 size_t total_cards_scanned = per_thread_states.total_cards_scanned();
3366 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc);
3367
3368 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
3369 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc());
3370
3371 MemoryService::track_memory_usage();
3372
3373 // In prepare_for_verify() below we'll need to scan the deferred
3374 // update buffers to bring the RSets up-to-date if
3375 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
3376 // the update buffers we'll probably need to scan cards on the
3377 // regions we just allocated to (i.e., the GC alloc
3378 // regions). However, during the last GC we called
3379 // set_saved_mark() on all the GC alloc regions, so card
3380 // scanning might skip the [saved_mark_word()...top()] area of
3381 // those regions (i.e., the area we allocated objects into
3382 // during the last GC). But it shouldn't. Given that
3383 // saved_mark_word() is conditional on whether the GC time stamp
3384 // on the region is current or not, by incrementing the GC time
3385 // stamp here we invalidate all the GC time stamps on all the
3386 // regions and saved_mark_word() will simply return top() for
3387 // all the regions. This is a nicer way of ensuring this rather
3388 // than iterating over the regions and fixing them. In fact, the
3389 // GC time stamp increment here also ensures that
3390 // saved_mark_word() will return top() between pauses, i.e.,
3391 // during concurrent refinement. So we don't need the
3392 // is_gc_active() check to decided which top to use when
3393 // scanning cards (see CR 7039627).
3394 increment_gc_time_stamp();
3395
3396 if (VerifyRememberedSets) {
3397 log_info(gc, verify)("[Verifying RemSets after GC]");
3398 VerifyRegionRemSetClosure v_cl;
3399 heap_region_iterate(&v_cl);
3400 }
3401
3402 _verifier->verify_after_gc();
3403 _verifier->check_bitmaps("GC End");
3404
3405 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3406 ref_processor_stw()->verify_no_references_recorded();
3407
3408 // CM reference discovery will be re-enabled if necessary.
3409 }
3410
3411 #ifdef TRACESPINNING
3412 ParallelTaskTerminator::print_termination_counts();
3413 #endif
3414
3415 gc_epilogue(false);
3416 }
3417
3418 // Print the remainder of the GC log output.
3419 if (evacuation_failed()) {
3420 log_info(gc)("To-space exhausted");
3421 }
3422
3423 g1_policy()->print_phases();
3424 heap_transition.print();
3425
3426 // It is not yet to safe to tell the concurrent mark to
3427 // start as we have some optional output below. We don't want the
3428 // output from the concurrent mark thread interfering with this
3429 // logging output either.
3430
3431 _hrm.verify_optional();
3432 _verifier->verify_region_sets_optional();
3433
3434 TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3435 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3436
3437 print_heap_after_gc();
3438 print_heap_regions();
3439 trace_heap_after_gc(_gc_tracer_stw);
3440
3441 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3442 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3443 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3444 // before any GC notifications are raised.
3445 g1mm()->update_sizes();
3446
3447 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3448 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
3449 _gc_timer_stw->register_gc_end();
3450 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3451 }
3452 // It should now be safe to tell the concurrent mark thread to start
3453 // without its logging output interfering with the logging output
3454 // that came from the pause.
3455
3456 if (should_start_conc_mark) {
3457 // CAUTION: after the doConcurrentMark() call below,
3458 // the concurrent marking thread(s) could be running
3459 // concurrently with us. Make sure that anything after
3460 // this point does not assume that we are the only GC thread
3461 // running. Note: of course, the actual marking work will
3462 // not start until the safepoint itself is released in
3463 // SuspendibleThreadSet::desynchronize().
3464 doConcurrentMark();
3465 }
3466
3467 return true;
3468 }
3469
3470 void G1CollectedHeap::remove_self_forwarding_pointers() {
3471 G1ParRemoveSelfForwardPtrsTask rsfp_task;
3472 workers()->run_task(&rsfp_task);
3473 }
3474
3475 void G1CollectedHeap::restore_after_evac_failure() {
3476 double remove_self_forwards_start = os::elapsedTime();
3477
3478 remove_self_forwarding_pointers();
3479 _preserved_marks_set.restore(workers());
3480
3481 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3482 }
3483
3484 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) {
3485 if (!_evacuation_failed) {
3486 _evacuation_failed = true;
3487 }
3488
3489 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3490 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3491 }
3492
3493 bool G1ParEvacuateFollowersClosure::offer_termination() {
3494 G1ParScanThreadState* const pss = par_scan_state();
3495 start_term_time();
3496 const bool res = terminator()->offer_termination();
3497 end_term_time();
3498 return res;
3499 }
3500
3501 void G1ParEvacuateFollowersClosure::do_void() {
3502 G1ParScanThreadState* const pss = par_scan_state();
3503 pss->trim_queue();
3504 do {
3505 pss->steal_and_trim_queue(queues());
3506 } while (!offer_termination());
3507 }
3508
3509 class G1ParTask : public AbstractGangTask {
3510 protected:
3511 G1CollectedHeap* _g1h;
3512 G1ParScanThreadStateSet* _pss;
3513 RefToScanQueueSet* _queues;
3514 G1RootProcessor* _root_processor;
3515 ParallelTaskTerminator _terminator;
3516 uint _n_workers;
3517
3518 public:
3519 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers)
3520 : AbstractGangTask("G1 collection"),
3521 _g1h(g1h),
3522 _pss(per_thread_states),
3523 _queues(task_queues),
3524 _root_processor(root_processor),
3525 _terminator(n_workers, _queues),
3526 _n_workers(n_workers)
3527 {}
3528
3529 void work(uint worker_id) {
3530 if (worker_id >= _n_workers) return; // no work needed this round
3531
3532 double start_sec = os::elapsedTime();
3533 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec);
3534
3535 {
3536 ResourceMark rm;
3537 HandleMark hm;
3538
3539 ReferenceProcessor* rp = _g1h->ref_processor_stw();
3540
3541 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
3542 pss->set_ref_processor(rp);
3543
3544 double start_strong_roots_sec = os::elapsedTime();
3545
3546 _root_processor->evacuate_roots(pss->closures(), worker_id);
3547
3548 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, pss);
3549
3550 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid
3551 // treating the nmethods visited to act as roots for concurrent marking.
3552 // We only want to make sure that the oops in the nmethods are adjusted with regard to the
3553 // objects copied by the current evacuation.
3554 size_t cards_scanned = _g1h->g1_rem_set()->oops_into_collection_set_do(&push_heap_rs_cl,
3555 pss->closures()->weak_codeblobs(),
3556 worker_id);
3557
3558 _pss->add_cards_scanned(worker_id, cards_scanned);
3559
3560 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec;
3561
3562 double term_sec = 0.0;
3563 size_t evac_term_attempts = 0;
3564 {
3565 double start = os::elapsedTime();
3566 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator);
3567 evac.do_void();
3568
3569 evac_term_attempts = evac.term_attempts();
3570 term_sec = evac.term_time();
3571 double elapsed_sec = os::elapsedTime() - start;
3572 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
3573 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
3574 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts);
3575 }
3576
3577 assert(pss->queue_is_empty(), "should be empty");
3578
3579 if (log_is_enabled(Debug, gc, task, stats)) {
3580 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3581 size_t lab_waste;
3582 size_t lab_undo_waste;
3583 pss->waste(lab_waste, lab_undo_waste);
3584 _g1h->print_termination_stats(worker_id,
3585 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */
3586 strong_roots_sec * 1000.0, /* strong roots time */
3587 term_sec * 1000.0, /* evac term time */
3588 evac_term_attempts, /* evac term attempts */
3589 lab_waste, /* alloc buffer waste */
3590 lab_undo_waste /* undo waste */
3591 );
3592 }
3593
3594 // Close the inner scope so that the ResourceMark and HandleMark
3595 // destructors are executed here and are included as part of the
3596 // "GC Worker Time".
3597 }
3598 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
3599 }
3600 };
3601
3602 void G1CollectedHeap::print_termination_stats_hdr() {
3603 log_debug(gc, task, stats)("GC Termination Stats");
3604 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------");
3605 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo");
3606 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------");
3607 }
3608
3609 void G1CollectedHeap::print_termination_stats(uint worker_id,
3610 double elapsed_ms,
3611 double strong_roots_ms,
3612 double term_ms,
3613 size_t term_attempts,
3614 size_t alloc_buffer_waste,
3615 size_t undo_waste) const {
3616 log_debug(gc, task, stats)
3617 ("%3d %9.2f %9.2f %6.2f "
3618 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
3619 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
3620 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms,
3621 term_ms, term_ms * 100 / elapsed_ms, term_attempts,
3622 (alloc_buffer_waste + undo_waste) * HeapWordSize / K,
3623 alloc_buffer_waste * HeapWordSize / K,
3624 undo_waste * HeapWordSize / K);
3625 }
3626
3627 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
3628 private:
3629 BoolObjectClosure* _is_alive;
3630 int _initial_string_table_size;
3631 int _initial_symbol_table_size;
3632
3633 bool _process_strings;
3634 int _strings_processed;
3635 int _strings_removed;
3636
3637 bool _process_symbols;
3638 int _symbols_processed;
3639 int _symbols_removed;
3640
3641 public:
3642 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
3643 AbstractGangTask("String/Symbol Unlinking"),
3644 _is_alive(is_alive),
3645 _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
3646 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
3647
3648 _initial_string_table_size = StringTable::the_table()->table_size();
3649 _initial_symbol_table_size = SymbolTable::the_table()->table_size();
3650 if (process_strings) {
3651 StringTable::clear_parallel_claimed_index();
3652 }
3653 if (process_symbols) {
3654 SymbolTable::clear_parallel_claimed_index();
3655 }
3656 }
3657
3658 ~G1StringSymbolTableUnlinkTask() {
3659 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
3660 "claim value %d after unlink less than initial string table size %d",
3661 StringTable::parallel_claimed_index(), _initial_string_table_size);
3662 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
3663 "claim value %d after unlink less than initial symbol table size %d",
3664 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size);
3665
3666 log_info(gc, stringtable)(
3667 "Cleaned string and symbol table, "
3668 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, "
3669 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
3670 strings_processed(), strings_removed(),
3671 symbols_processed(), symbols_removed());
3672 }
3673
3674 void work(uint worker_id) {
3675 int strings_processed = 0;
3676 int strings_removed = 0;
3677 int symbols_processed = 0;
3678 int symbols_removed = 0;
3679 if (_process_strings) {
3680 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
3681 Atomic::add(strings_processed, &_strings_processed);
3682 Atomic::add(strings_removed, &_strings_removed);
3683 }
3684 if (_process_symbols) {
3685 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
3686 Atomic::add(symbols_processed, &_symbols_processed);
3687 Atomic::add(symbols_removed, &_symbols_removed);
3688 }
3689 }
3690
3691 size_t strings_processed() const { return (size_t)_strings_processed; }
3692 size_t strings_removed() const { return (size_t)_strings_removed; }
3693
3694 size_t symbols_processed() const { return (size_t)_symbols_processed; }
3695 size_t symbols_removed() const { return (size_t)_symbols_removed; }
3696 };
3697
3698 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
3699 private:
3700 static Monitor* _lock;
3701
3702 BoolObjectClosure* const _is_alive;
3703 const bool _unloading_occurred;
3704 const uint _num_workers;
3705
3706 // Variables used to claim nmethods.
3707 CompiledMethod* _first_nmethod;
3708 volatile CompiledMethod* _claimed_nmethod;
3709
3710 // The list of nmethods that need to be processed by the second pass.
3711 volatile CompiledMethod* _postponed_list;
3712 volatile uint _num_entered_barrier;
3713
3714 public:
3715 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
3716 _is_alive(is_alive),
3717 _unloading_occurred(unloading_occurred),
3718 _num_workers(num_workers),
3719 _first_nmethod(NULL),
3720 _claimed_nmethod(NULL),
3721 _postponed_list(NULL),
3722 _num_entered_barrier(0)
3723 {
3724 CompiledMethod::increase_unloading_clock();
3725 // Get first alive nmethod
3726 CompiledMethodIterator iter = CompiledMethodIterator();
3727 if(iter.next_alive()) {
3728 _first_nmethod = iter.method();
3729 }
3730 _claimed_nmethod = (volatile CompiledMethod*)_first_nmethod;
3731 }
3732
3733 ~G1CodeCacheUnloadingTask() {
3734 CodeCache::verify_clean_inline_caches();
3735
3736 CodeCache::set_needs_cache_clean(false);
3737 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
3738
3739 CodeCache::verify_icholder_relocations();
3740 }
3741
3742 private:
3743 void add_to_postponed_list(CompiledMethod* nm) {
3744 CompiledMethod* old;
3745 do {
3746 old = (CompiledMethod*)_postponed_list;
3747 nm->set_unloading_next(old);
3748 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
3749 }
3750
3751 void clean_nmethod(CompiledMethod* nm) {
3752 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
3753
3754 if (postponed) {
3755 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
3756 add_to_postponed_list(nm);
3757 }
3758
3759 // Mark that this thread has been cleaned/unloaded.
3760 // After this call, it will be safe to ask if this nmethod was unloaded or not.
3761 nm->set_unloading_clock(CompiledMethod::global_unloading_clock());
3762 }
3763
3764 void clean_nmethod_postponed(CompiledMethod* nm) {
3765 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
3766 }
3767
3768 static const int MaxClaimNmethods = 16;
3769
3770 void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) {
3771 CompiledMethod* first;
3772 CompiledMethodIterator last;
3773
3774 do {
3775 *num_claimed_nmethods = 0;
3776
3777 first = (CompiledMethod*)_claimed_nmethod;
3778 last = CompiledMethodIterator(first);
3779
3780 if (first != NULL) {
3781
3782 for (int i = 0; i < MaxClaimNmethods; i++) {
3783 if (!last.next_alive()) {
3784 break;
3785 }
3786 claimed_nmethods[i] = last.method();
3787 (*num_claimed_nmethods)++;
3788 }
3789 }
3790
3791 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first);
3792 }
3793
3794 CompiledMethod* claim_postponed_nmethod() {
3795 CompiledMethod* claim;
3796 CompiledMethod* next;
3797
3798 do {
3799 claim = (CompiledMethod*)_postponed_list;
3800 if (claim == NULL) {
3801 return NULL;
3802 }
3803
3804 next = claim->unloading_next();
3805
3806 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
3807
3808 return claim;
3809 }
3810
3811 public:
3812 // Mark that we're done with the first pass of nmethod cleaning.
3813 void barrier_mark(uint worker_id) {
3814 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3815 _num_entered_barrier++;
3816 if (_num_entered_barrier == _num_workers) {
3817 ml.notify_all();
3818 }
3819 }
3820
3821 // See if we have to wait for the other workers to
3822 // finish their first-pass nmethod cleaning work.
3823 void barrier_wait(uint worker_id) {
3824 if (_num_entered_barrier < _num_workers) {
3825 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3826 while (_num_entered_barrier < _num_workers) {
3827 ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
3828 }
3829 }
3830 }
3831
3832 // Cleaning and unloading of nmethods. Some work has to be postponed
3833 // to the second pass, when we know which nmethods survive.
3834 void work_first_pass(uint worker_id) {
3835 // The first nmethods is claimed by the first worker.
3836 if (worker_id == 0 && _first_nmethod != NULL) {
3837 clean_nmethod(_first_nmethod);
3838 _first_nmethod = NULL;
3839 }
3840
3841 int num_claimed_nmethods;
3842 CompiledMethod* claimed_nmethods[MaxClaimNmethods];
3843
3844 while (true) {
3845 claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
3846
3847 if (num_claimed_nmethods == 0) {
3848 break;
3849 }
3850
3851 for (int i = 0; i < num_claimed_nmethods; i++) {
3852 clean_nmethod(claimed_nmethods[i]);
3853 }
3854 }
3855 }
3856
3857 void work_second_pass(uint worker_id) {
3858 CompiledMethod* nm;
3859 // Take care of postponed nmethods.
3860 while ((nm = claim_postponed_nmethod()) != NULL) {
3861 clean_nmethod_postponed(nm);
3862 }
3863 }
3864 };
3865
3866 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
3867
3868 class G1KlassCleaningTask : public StackObj {
3869 BoolObjectClosure* _is_alive;
3870 volatile jint _clean_klass_tree_claimed;
3871 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
3872
3873 public:
3874 G1KlassCleaningTask(BoolObjectClosure* is_alive) :
3875 _is_alive(is_alive),
3876 _clean_klass_tree_claimed(0),
3877 _klass_iterator() {
3878 }
3879
3880 private:
3881 bool claim_clean_klass_tree_task() {
3882 if (_clean_klass_tree_claimed) {
3883 return false;
3884 }
3885
3886 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
3887 }
3888
3889 InstanceKlass* claim_next_klass() {
3890 Klass* klass;
3891 do {
3892 klass =_klass_iterator.next_klass();
3893 } while (klass != NULL && !klass->is_instance_klass());
3894
3895 // this can be null so don't call InstanceKlass::cast
3896 return static_cast<InstanceKlass*>(klass);
3897 }
3898
3899 public:
3900
3901 void clean_klass(InstanceKlass* ik) {
3902 ik->clean_weak_instanceklass_links(_is_alive);
3903 }
3904
3905 void work() {
3906 ResourceMark rm;
3907
3908 // One worker will clean the subklass/sibling klass tree.
3909 if (claim_clean_klass_tree_task()) {
3910 Klass::clean_subklass_tree(_is_alive);
3911 }
3912
3913 // All workers will help cleaning the classes,
3914 InstanceKlass* klass;
3915 while ((klass = claim_next_klass()) != NULL) {
3916 clean_klass(klass);
3917 }
3918 }
3919 };
3920
3921 // To minimize the remark pause times, the tasks below are done in parallel.
3922 class G1ParallelCleaningTask : public AbstractGangTask {
3923 private:
3924 G1StringSymbolTableUnlinkTask _string_symbol_task;
3925 G1CodeCacheUnloadingTask _code_cache_task;
3926 G1KlassCleaningTask _klass_cleaning_task;
3927
3928 public:
3929 // The constructor is run in the VMThread.
3930 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
3931 AbstractGangTask("Parallel Cleaning"),
3932 _string_symbol_task(is_alive, process_strings, process_symbols),
3933 _code_cache_task(num_workers, is_alive, unloading_occurred),
3934 _klass_cleaning_task(is_alive) {
3935 }
3936
3937 // The parallel work done by all worker threads.
3938 void work(uint worker_id) {
3939 // Do first pass of code cache cleaning.
3940 _code_cache_task.work_first_pass(worker_id);
3941
3942 // Let the threads mark that the first pass is done.
3943 _code_cache_task.barrier_mark(worker_id);
3944
3945 // Clean the Strings and Symbols.
3946 _string_symbol_task.work(worker_id);
3947
3948 // Wait for all workers to finish the first code cache cleaning pass.
3949 _code_cache_task.barrier_wait(worker_id);
3950
3951 // Do the second code cache cleaning work, which realize on
3952 // the liveness information gathered during the first pass.
3953 _code_cache_task.work_second_pass(worker_id);
3954
3955 // Clean all klasses that were not unloaded.
3956 _klass_cleaning_task.work();
3957 }
3958 };
3959
3960
3961 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
3962 bool process_strings,
3963 bool process_symbols,
3964 bool class_unloading_occurred) {
3965 uint n_workers = workers()->active_workers();
3966
3967 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
3968 n_workers, class_unloading_occurred);
3969 workers()->run_task(&g1_unlink_task);
3970 }
3971
3972 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
3973 bool process_strings, bool process_symbols) {
3974 { // Timing scope
3975 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
3976 workers()->run_task(&g1_unlink_task);
3977 }
3978 }
3979
3980 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3981 private:
3982 DirtyCardQueueSet* _queue;
3983 G1CollectedHeap* _g1h;
3984 public:
3985 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"),
3986 _queue(queue), _g1h(g1h) { }
3987
3988 virtual void work(uint worker_id) {
3989 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
3990 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
3991
3992 RedirtyLoggedCardTableEntryClosure cl(_g1h);
3993 _queue->par_apply_closure_to_all_completed_buffers(&cl);
3994
3995 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3996 }
3997 };
3998
3999 void G1CollectedHeap::redirty_logged_cards() {
4000 double redirty_logged_cards_start = os::elapsedTime();
4001
4002 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this);
4003 dirty_card_queue_set().reset_for_par_iteration();
4004 workers()->run_task(&redirty_task);
4005
4006 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
4007 dcq.merge_bufferlists(&dirty_card_queue_set());
4008 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
4009
4010 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
4011 }
4012
4013 // Weak Reference Processing support
4014
4015 // An always "is_alive" closure that is used to preserve referents.
4016 // If the object is non-null then it's alive. Used in the preservation
4017 // of referent objects that are pointed to by reference objects
4018 // discovered by the CM ref processor.
4019 class G1AlwaysAliveClosure: public BoolObjectClosure {
4020 G1CollectedHeap* _g1;
4021 public:
4022 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4023 bool do_object_b(oop p) {
4024 if (p != NULL) {
4025 return true;
4026 }
4027 return false;
4028 }
4029 };
4030
4031 bool G1STWIsAliveClosure::do_object_b(oop p) {
4032 // An object is reachable if it is outside the collection set,
4033 // or is inside and copied.
4034 return !_g1->is_in_cset(p) || p->is_forwarded();
4035 }
4036
4037 // Non Copying Keep Alive closure
4038 class G1KeepAliveClosure: public OopClosure {
4039 G1CollectedHeap* _g1;
4040 public:
4041 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4042 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
4043 void do_oop(oop* p) {
4044 oop obj = *p;
4045 assert(obj != NULL, "the caller should have filtered out NULL values");
4046
4047 const InCSetState cset_state = _g1->in_cset_state(obj);
4048 if (!cset_state.is_in_cset_or_humongous()) {
4049 return;
4050 }
4051 if (cset_state.is_in_cset()) {
4052 assert( obj->is_forwarded(), "invariant" );
4053 *p = obj->forwardee();
4054 } else {
4055 assert(!obj->is_forwarded(), "invariant" );
4056 assert(cset_state.is_humongous(),
4057 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value());
4058 _g1->set_humongous_is_live(obj);
4059 }
4060 }
4061 };
4062
4063 // Copying Keep Alive closure - can be called from both
4064 // serial and parallel code as long as different worker
4065 // threads utilize different G1ParScanThreadState instances
4066 // and different queues.
4067
4068 class G1CopyingKeepAliveClosure: public OopClosure {
4069 G1CollectedHeap* _g1h;
4070 OopClosure* _copy_non_heap_obj_cl;
4071 G1ParScanThreadState* _par_scan_state;
4072
4073 public:
4074 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
4075 OopClosure* non_heap_obj_cl,
4076 G1ParScanThreadState* pss):
4077 _g1h(g1h),
4078 _copy_non_heap_obj_cl(non_heap_obj_cl),
4079 _par_scan_state(pss)
4080 {}
4081
4082 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
4083 virtual void do_oop( oop* p) { do_oop_work(p); }
4084
4085 template <class T> void do_oop_work(T* p) {
4086 oop obj = oopDesc::load_decode_heap_oop(p);
4087
4088 if (_g1h->is_in_cset_or_humongous(obj)) {
4089 // If the referent object has been forwarded (either copied
4090 // to a new location or to itself in the event of an
4091 // evacuation failure) then we need to update the reference
4092 // field and, if both reference and referent are in the G1
4093 // heap, update the RSet for the referent.
4094 //
4095 // If the referent has not been forwarded then we have to keep
4096 // it alive by policy. Therefore we have copy the referent.
4097 //
4098 // If the reference field is in the G1 heap then we can push
4099 // on the PSS queue. When the queue is drained (after each
4100 // phase of reference processing) the object and it's followers
4101 // will be copied, the reference field set to point to the
4102 // new location, and the RSet updated. Otherwise we need to
4103 // use the the non-heap or metadata closures directly to copy
4104 // the referent object and update the pointer, while avoiding
4105 // updating the RSet.
4106
4107 if (_g1h->is_in_g1_reserved(p)) {
4108 _par_scan_state->push_on_queue(p);
4109 } else {
4110 assert(!Metaspace::contains((const void*)p),
4111 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p));
4112 _copy_non_heap_obj_cl->do_oop(p);
4113 }
4114 }
4115 }
4116 };
4117
4118 // Serial drain queue closure. Called as the 'complete_gc'
4119 // closure for each discovered list in some of the
4120 // reference processing phases.
4121
4122 class G1STWDrainQueueClosure: public VoidClosure {
4123 protected:
4124 G1CollectedHeap* _g1h;
4125 G1ParScanThreadState* _par_scan_state;
4126
4127 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4128
4129 public:
4130 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
4131 _g1h(g1h),
4132 _par_scan_state(pss)
4133 { }
4134
4135 void do_void() {
4136 G1ParScanThreadState* const pss = par_scan_state();
4137 pss->trim_queue();
4138 }
4139 };
4140
4141 // Parallel Reference Processing closures
4142
4143 // Implementation of AbstractRefProcTaskExecutor for parallel reference
4144 // processing during G1 evacuation pauses.
4145
4146 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
4147 private:
4148 G1CollectedHeap* _g1h;
4149 G1ParScanThreadStateSet* _pss;
4150 RefToScanQueueSet* _queues;
4151 WorkGang* _workers;
4152 uint _active_workers;
4153
4154 public:
4155 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
4156 G1ParScanThreadStateSet* per_thread_states,
4157 WorkGang* workers,
4158 RefToScanQueueSet *task_queues,
4159 uint n_workers) :
4160 _g1h(g1h),
4161 _pss(per_thread_states),
4162 _queues(task_queues),
4163 _workers(workers),
4164 _active_workers(n_workers)
4165 {
4166 g1h->ref_processor_stw()->set_active_mt_degree(n_workers);
4167 }
4168
4169 // Executes the given task using concurrent marking worker threads.
4170 virtual void execute(ProcessTask& task);
4171 virtual void execute(EnqueueTask& task);
4172 };
4173
4174 // Gang task for possibly parallel reference processing
4175
4176 class G1STWRefProcTaskProxy: public AbstractGangTask {
4177 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
4178 ProcessTask& _proc_task;
4179 G1CollectedHeap* _g1h;
4180 G1ParScanThreadStateSet* _pss;
4181 RefToScanQueueSet* _task_queues;
4182 ParallelTaskTerminator* _terminator;
4183
4184 public:
4185 G1STWRefProcTaskProxy(ProcessTask& proc_task,
4186 G1CollectedHeap* g1h,
4187 G1ParScanThreadStateSet* per_thread_states,
4188 RefToScanQueueSet *task_queues,
4189 ParallelTaskTerminator* terminator) :
4190 AbstractGangTask("Process reference objects in parallel"),
4191 _proc_task(proc_task),
4192 _g1h(g1h),
4193 _pss(per_thread_states),
4194 _task_queues(task_queues),
4195 _terminator(terminator)
4196 {}
4197
4198 virtual void work(uint worker_id) {
4199 // The reference processing task executed by a single worker.
4200 ResourceMark rm;
4201 HandleMark hm;
4202
4203 G1STWIsAliveClosure is_alive(_g1h);
4204
4205 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
4206 pss->set_ref_processor(NULL);
4207
4208 // Keep alive closure.
4209 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4210
4211 // Complete GC closure
4212 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator);
4213
4214 // Call the reference processing task's work routine.
4215 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
4216
4217 // Note we cannot assert that the refs array is empty here as not all
4218 // of the processing tasks (specifically phase2 - pp2_work) execute
4219 // the complete_gc closure (which ordinarily would drain the queue) so
4220 // the queue may not be empty.
4221 }
4222 };
4223
4224 // Driver routine for parallel reference processing.
4225 // Creates an instance of the ref processing gang
4226 // task and has the worker threads execute it.
4227 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
4228 assert(_workers != NULL, "Need parallel worker threads.");
4229
4230 ParallelTaskTerminator terminator(_active_workers, _queues);
4231 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
4232
4233 _workers->run_task(&proc_task_proxy);
4234 }
4235
4236 // Gang task for parallel reference enqueueing.
4237
4238 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
4239 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
4240 EnqueueTask& _enq_task;
4241
4242 public:
4243 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
4244 AbstractGangTask("Enqueue reference objects in parallel"),
4245 _enq_task(enq_task)
4246 { }
4247
4248 virtual void work(uint worker_id) {
4249 _enq_task.work(worker_id);
4250 }
4251 };
4252
4253 // Driver routine for parallel reference enqueueing.
4254 // Creates an instance of the ref enqueueing gang
4255 // task and has the worker threads execute it.
4256
4257 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
4258 assert(_workers != NULL, "Need parallel worker threads.");
4259
4260 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
4261
4262 _workers->run_task(&enq_task_proxy);
4263 }
4264
4265 // End of weak reference support closures
4266
4267 // Abstract task used to preserve (i.e. copy) any referent objects
4268 // that are in the collection set and are pointed to by reference
4269 // objects discovered by the CM ref processor.
4270
4271 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
4272 protected:
4273 G1CollectedHeap* _g1h;
4274 G1ParScanThreadStateSet* _pss;
4275 RefToScanQueueSet* _queues;
4276 ParallelTaskTerminator _terminator;
4277 uint _n_workers;
4278
4279 public:
4280 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) :
4281 AbstractGangTask("ParPreserveCMReferents"),
4282 _g1h(g1h),
4283 _pss(per_thread_states),
4284 _queues(task_queues),
4285 _terminator(workers, _queues),
4286 _n_workers(workers)
4287 {
4288 g1h->ref_processor_cm()->set_active_mt_degree(workers);
4289 }
4290
4291 void work(uint worker_id) {
4292 G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id);
4293
4294 ResourceMark rm;
4295 HandleMark hm;
4296
4297 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
4298 pss->set_ref_processor(NULL);
4299 assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4300
4301 // Is alive closure
4302 G1AlwaysAliveClosure always_alive(_g1h);
4303
4304 // Copying keep alive closure. Applied to referent objects that need
4305 // to be copied.
4306 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4307
4308 ReferenceProcessor* rp = _g1h->ref_processor_cm();
4309
4310 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
4311 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
4312
4313 // limit is set using max_num_q() - which was set using ParallelGCThreads.
4314 // So this must be true - but assert just in case someone decides to
4315 // change the worker ids.
4316 assert(worker_id < limit, "sanity");
4317 assert(!rp->discovery_is_atomic(), "check this code");
4318
4319 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
4320 for (uint idx = worker_id; idx < limit; idx += stride) {
4321 DiscoveredList& ref_list = rp->discovered_refs()[idx];
4322
4323 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
4324 while (iter.has_next()) {
4325 // Since discovery is not atomic for the CM ref processor, we
4326 // can see some null referent objects.
4327 iter.load_ptrs(DEBUG_ONLY(true));
4328 oop ref = iter.obj();
4329
4330 // This will filter nulls.
4331 if (iter.is_referent_alive()) {
4332 iter.make_referent_alive();
4333 }
4334 iter.move_to_next();
4335 }
4336 }
4337
4338 // Drain the queue - which may cause stealing
4339 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator);
4340 drain_queue.do_void();
4341 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
4342 assert(pss->queue_is_empty(), "should be");
4343 }
4344 };
4345
4346 void G1CollectedHeap::process_weak_jni_handles() {
4347 double ref_proc_start = os::elapsedTime();
4348
4349 G1STWIsAliveClosure is_alive(this);
4350 G1KeepAliveClosure keep_alive(this);
4351 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
4352
4353 double ref_proc_time = os::elapsedTime() - ref_proc_start;
4354 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4355 }
4356
4357 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) {
4358 // Any reference objects, in the collection set, that were 'discovered'
4359 // by the CM ref processor should have already been copied (either by
4360 // applying the external root copy closure to the discovered lists, or
4361 // by following an RSet entry).
4362 //
4363 // But some of the referents, that are in the collection set, that these
4364 // reference objects point to may not have been copied: the STW ref
4365 // processor would have seen that the reference object had already
4366 // been 'discovered' and would have skipped discovering the reference,
4367 // but would not have treated the reference object as a regular oop.
4368 // As a result the copy closure would not have been applied to the
4369 // referent object.
4370 //
4371 // We need to explicitly copy these referent objects - the references
4372 // will be processed at the end of remarking.
4373 //
4374 // We also need to do this copying before we process the reference
4375 // objects discovered by the STW ref processor in case one of these
4376 // referents points to another object which is also referenced by an
4377 // object discovered by the STW ref processor.
4378 double preserve_cm_referents_time = 0.0;
4379
4380 // To avoid spawning task when there is no work to do, check that
4381 // a concurrent cycle is active and that some references have been
4382 // discovered.
4383 if (concurrent_mark()->cmThread()->during_cycle() &&
4384 ref_processor_cm()->has_discovered_references()) {
4385 double preserve_cm_referents_start = os::elapsedTime();
4386 uint no_of_gc_workers = workers()->active_workers();
4387 G1ParPreserveCMReferentsTask keep_cm_referents(this,
4388 per_thread_states,
4389 no_of_gc_workers,
4390 _task_queues);
4391 workers()->run_task(&keep_cm_referents);
4392 preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start;
4393 }
4394
4395 g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0);
4396 }
4397
4398 // Weak Reference processing during an evacuation pause (part 1).
4399 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4400 double ref_proc_start = os::elapsedTime();
4401
4402 ReferenceProcessor* rp = _ref_processor_stw;
4403 assert(rp->discovery_enabled(), "should have been enabled");
4404
4405 // Closure to test whether a referent is alive.
4406 G1STWIsAliveClosure is_alive(this);
4407
4408 // Even when parallel reference processing is enabled, the processing
4409 // of JNI refs is serial and performed serially by the current thread
4410 // rather than by a worker. The following PSS will be used for processing
4411 // JNI refs.
4412
4413 // Use only a single queue for this PSS.
4414 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0);
4415 pss->set_ref_processor(NULL);
4416 assert(pss->queue_is_empty(), "pre-condition");
4417
4418 // Keep alive closure.
4419 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss);
4420
4421 // Serial Complete GC closure
4422 G1STWDrainQueueClosure drain_queue(this, pss);
4423
4424 // Setup the soft refs policy...
4425 rp->setup_policy(false);
4426
4427 ReferenceProcessorStats stats;
4428 if (!rp->processing_is_mt()) {
4429 // Serial reference processing...
4430 stats = rp->process_discovered_references(&is_alive,
4431 &keep_alive,
4432 &drain_queue,
4433 NULL,
4434 _gc_timer_stw);
4435 } else {
4436 uint no_of_gc_workers = workers()->active_workers();
4437
4438 // Parallel reference processing
4439 assert(no_of_gc_workers <= rp->max_num_q(),
4440 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4441 no_of_gc_workers, rp->max_num_q());
4442
4443 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers);
4444 stats = rp->process_discovered_references(&is_alive,
4445 &keep_alive,
4446 &drain_queue,
4447 &par_task_executor,
4448 _gc_timer_stw);
4449 }
4450
4451 _gc_tracer_stw->report_gc_reference_stats(stats);
4452
4453 // We have completed copying any necessary live referent objects.
4454 assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4455
4456 double ref_proc_time = os::elapsedTime() - ref_proc_start;
4457 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4458 }
4459
4460 // Weak Reference processing during an evacuation pause (part 2).
4461 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4462 double ref_enq_start = os::elapsedTime();
4463
4464 ReferenceProcessor* rp = _ref_processor_stw;
4465 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
4466
4467 // Now enqueue any remaining on the discovered lists on to
4468 // the pending list.
4469 if (!rp->processing_is_mt()) {
4470 // Serial reference processing...
4471 rp->enqueue_discovered_references();
4472 } else {
4473 // Parallel reference enqueueing
4474
4475 uint n_workers = workers()->active_workers();
4476
4477 assert(n_workers <= rp->max_num_q(),
4478 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4479 n_workers, rp->max_num_q());
4480
4481 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers);
4482 rp->enqueue_discovered_references(&par_task_executor);
4483 }
4484
4485 rp->verify_no_references_recorded();
4486 assert(!rp->discovery_enabled(), "should have been disabled");
4487
4488 // FIXME
4489 // CM's reference processing also cleans up the string and symbol tables.
4490 // Should we do that here also? We could, but it is a serial operation
4491 // and could significantly increase the pause time.
4492
4493 double ref_enq_time = os::elapsedTime() - ref_enq_start;
4494 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
4495 }
4496
4497 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
4498 double merge_pss_time_start = os::elapsedTime();
4499 per_thread_states->flush();
4500 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0);
4501 }
4502
4503 void G1CollectedHeap::pre_evacuate_collection_set() {
4504 _expand_heap_after_alloc_failure = true;
4505 _evacuation_failed = false;
4506
4507 // Disable the hot card cache.
4508 _hot_card_cache->reset_hot_cache_claimed_index();
4509 _hot_card_cache->set_use_cache(false);
4510
4511 g1_rem_set()->prepare_for_oops_into_collection_set_do();
4512 _preserved_marks_set.assert_empty();
4513 }
4514
4515 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4516 // Should G1EvacuationFailureALot be in effect for this GC?
4517 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
4518
4519 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
4520 double start_par_time_sec = os::elapsedTime();
4521 double end_par_time_sec;
4522
4523 {
4524 const uint n_workers = workers()->active_workers();
4525 G1RootProcessor root_processor(this, n_workers);
4526 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers);
4527 // InitialMark needs claim bits to keep track of the marked-through CLDs.
4528 if (collector_state()->during_initial_mark_pause()) {
4529 ClassLoaderDataGraph::clear_claimed_marks();
4530 }
4531
4532 print_termination_stats_hdr();
4533
4534 workers()->run_task(&g1_par_task);
4535 end_par_time_sec = os::elapsedTime();
4536
4537 // Closing the inner scope will execute the destructor
4538 // for the G1RootProcessor object. We record the current
4539 // elapsed time before closing the scope so that time
4540 // taken for the destructor is NOT included in the
4541 // reported parallel time.
4542 }
4543
4544 G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4545
4546 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
4547 phase_times->record_par_time(par_time_ms);
4548
4549 double code_root_fixup_time_ms =
4550 (os::elapsedTime() - end_par_time_sec) * 1000.0;
4551 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
4552 }
4553
4554 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4555 // Process any discovered reference objects - we have
4556 // to do this _before_ we retire the GC alloc regions
4557 // as we may have to copy some 'reachable' referent
4558 // objects (and their reachable sub-graphs) that were
4559 // not copied during the pause.
4560 if (g1_policy()->should_process_references()) {
4561 preserve_cm_referents(per_thread_states);
4562 process_discovered_references(per_thread_states);
4563 } else {
4564 ref_processor_stw()->verify_no_references_recorded();
4565 process_weak_jni_handles();
4566 }
4567
4568 if (G1StringDedup::is_enabled()) {
4569 double fixup_start = os::elapsedTime();
4570
4571 G1STWIsAliveClosure is_alive(this);
4572 G1KeepAliveClosure keep_alive(this);
4573 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times());
4574
4575 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
4576 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
4577 }
4578
4579 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4580
4581 if (evacuation_failed()) {
4582 restore_after_evac_failure();
4583
4584 // Reset the G1EvacuationFailureALot counters and flags
4585 // Note: the values are reset only when an actual
4586 // evacuation failure occurs.
4587 NOT_PRODUCT(reset_evacuation_should_fail();)
4588 }
4589
4590 _preserved_marks_set.assert_empty();
4591
4592 // Enqueue any remaining references remaining on the STW
4593 // reference processor's discovered lists. We need to do
4594 // this after the card table is cleaned (and verified) as
4595 // the act of enqueueing entries on to the pending list
4596 // will log these updates (and dirty their associated
4597 // cards). We need these updates logged to update any
4598 // RSets.
4599 if (g1_policy()->should_process_references()) {
4600 enqueue_discovered_references(per_thread_states);
4601 } else {
4602 g1_policy()->phase_times()->record_ref_enq_time(0);
4603 }
4604
4605 _allocator->release_gc_alloc_regions(evacuation_info);
4606
4607 merge_per_thread_state_info(per_thread_states);
4608
4609 // Reset and re-enable the hot card cache.
4610 // Note the counts for the cards in the regions in the
4611 // collection set are reset when the collection set is freed.
4612 _hot_card_cache->reset_hot_cache();
4613 _hot_card_cache->set_use_cache(true);
4614
4615 purge_code_root_memory();
4616
4617 redirty_logged_cards();
4618 #if defined(COMPILER2) || INCLUDE_JVMCI
4619 DerivedPointerTable::update_pointers();
4620 #endif
4621 }
4622
4623 void G1CollectedHeap::record_obj_copy_mem_stats() {
4624 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4625
4626 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4627 create_g1_evac_summary(&_old_evac_stats));
4628 }
4629
4630 void G1CollectedHeap::free_region(HeapRegion* hr,
4631 FreeRegionList* free_list,
4632 bool par,
4633 bool locked) {
4634 assert(!hr->is_free(), "the region should not be free");
4635 assert(!hr->is_empty(), "the region should not be empty");
4636 assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
4637 assert(free_list != NULL, "pre-condition");
4638
4639 if (G1VerifyBitmaps) {
4640 MemRegion mr(hr->bottom(), hr->end());
4641 concurrent_mark()->clearRangePrevBitmap(mr);
4642 }
4643
4644 // Clear the card counts for this region.
4645 // Note: we only need to do this if the region is not young
4646 // (since we don't refine cards in young regions).
4647 if (!hr->is_young()) {
4648 _hot_card_cache->reset_card_counts(hr);
4649 }
4650 hr->hr_clear(par, true /* clear_space */, locked /* locked */);
4651 free_list->add_ordered(hr);
4652 }
4653
4654 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4655 FreeRegionList* free_list,
4656 bool par) {
4657 assert(hr->is_humongous(), "this is only for humongous regions");
4658 assert(free_list != NULL, "pre-condition");
4659 hr->clear_humongous();
4660 free_region(hr, free_list, par);
4661 }
4662
4663 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4664 const uint humongous_regions_removed) {
4665 if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4666 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4667 _old_set.bulk_remove(old_regions_removed);
4668 _humongous_set.bulk_remove(humongous_regions_removed);
4669 }
4670
4671 }
4672
4673 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4674 assert(list != NULL, "list can't be null");
4675 if (!list->is_empty()) {
4676 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4677 _hrm.insert_list_into_free_list(list);
4678 }
4679 }
4680
4681 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4682 decrease_used(bytes);
4683 }
4684
4685 class G1ParScrubRemSetTask: public AbstractGangTask {
4686 protected:
4687 G1RemSet* _g1rs;
4688 HeapRegionClaimer _hrclaimer;
4689
4690 public:
4691 G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) :
4692 AbstractGangTask("G1 ScrubRS"),
4693 _g1rs(g1_rs),
4694 _hrclaimer(num_workers) {
4695 }
4696
4697 void work(uint worker_id) {
4698 _g1rs->scrub(worker_id, &_hrclaimer);
4699 }
4700 };
4701
4702 void G1CollectedHeap::scrub_rem_set() {
4703 uint num_workers = workers()->active_workers();
4704 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers);
4705 workers()->run_task(&g1_par_scrub_rs_task);
4706 }
4707
4708 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4709 size_t pre_used = 0;
4710 FreeRegionList local_free_list("Local List for CSet Freeing");
4711
4712 double young_time_ms = 0.0;
4713 double non_young_time_ms = 0.0;
4714
4715 _eden.clear();
4716
4717 G1Policy* policy = g1_policy();
4718
4719 double start_sec = os::elapsedTime();
4720 bool non_young = true;
4721
4722 HeapRegion* cur = cs_head;
4723 int age_bound = -1;
4724 size_t rs_lengths = 0;
4725
4726 while (cur != NULL) {
4727 assert(!is_on_master_free_list(cur), "sanity");
4728 if (non_young) {
4729 if (cur->is_young()) {
4730 double end_sec = os::elapsedTime();
4731 double elapsed_ms = (end_sec - start_sec) * 1000.0;
4732 non_young_time_ms += elapsed_ms;
4733
4734 start_sec = os::elapsedTime();
4735 non_young = false;
4736 }
4737 } else {
4738 if (!cur->is_young()) {
4739 double end_sec = os::elapsedTime();
4740 double elapsed_ms = (end_sec - start_sec) * 1000.0;
4741 young_time_ms += elapsed_ms;
4742
4743 start_sec = os::elapsedTime();
4744 non_young = true;
4745 }
4746 }
4747
4748 rs_lengths += cur->rem_set()->occupied_locked();
4749
4750 HeapRegion* next = cur->next_in_collection_set();
4751 assert(cur->in_collection_set(), "bad CS");
4752 cur->set_next_in_collection_set(NULL);
4753 clear_in_cset(cur);
4754
4755 if (cur->is_young()) {
4756 int index = cur->young_index_in_cset();
4757 assert(index != -1, "invariant");
4758 assert((uint) index < collection_set()->young_region_length(), "invariant");
4759 size_t words_survived = surviving_young_words[index];
4760 cur->record_surv_words_in_group(words_survived);
4761
4762 } else {
4763 int index = cur->young_index_in_cset();
4764 assert(index == -1, "invariant");
4765 }
4766
4767 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
4768 (!cur->is_young() && cur->young_index_in_cset() == -1),
4769 "invariant" );
4770
4771 if (!cur->evacuation_failed()) {
4772 MemRegion used_mr = cur->used_region();
4773
4774 // And the region is empty.
4775 assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
4776 pre_used += cur->used();
4777 free_region(cur, &local_free_list, false /* par */, true /* locked */);
4778 } else {
4779 cur->uninstall_surv_rate_group();
4780 if (cur->is_young()) {
4781 cur->set_young_index_in_cset(-1);
4782 }
4783 cur->set_evacuation_failed(false);
4784 // When moving a young gen region to old gen, we "allocate" that whole region
4785 // there. This is in addition to any already evacuated objects. Notify the
4786 // policy about that.
4787 // Old gen regions do not cause an additional allocation: both the objects
4788 // still in the region and the ones already moved are accounted for elsewhere.
4789 if (cur->is_young()) {
4790 policy->add_bytes_allocated_in_old_since_last_gc(HeapRegion::GrainBytes);
4791 }
4792 // The region is now considered to be old.
4793 cur->set_old();
4794 // Do some allocation statistics accounting. Regions that failed evacuation
4795 // are always made old, so there is no need to update anything in the young
4796 // gen statistics, but we need to update old gen statistics.
4797 size_t used_words = cur->marked_bytes() / HeapWordSize;
4798 _old_evac_stats.add_failure_used_and_waste(used_words, HeapRegion::GrainWords - used_words);
4799 _old_set.add(cur);
4800 evacuation_info.increment_collectionset_used_after(cur->used());
4801 }
4802 cur = next;
4803 }
4804
4805 evacuation_info.set_regions_freed(local_free_list.length());
4806 policy->record_max_rs_lengths(rs_lengths);
4807 policy->cset_regions_freed();
4808
4809 double end_sec = os::elapsedTime();
4810 double elapsed_ms = (end_sec - start_sec) * 1000.0;
4811
4812 if (non_young) {
4813 non_young_time_ms += elapsed_ms;
4814 } else {
4815 young_time_ms += elapsed_ms;
4816 }
4817
4818 prepend_to_freelist(&local_free_list);
4819 decrement_summary_bytes(pre_used);
4820 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
4821 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
4822 }
4823
4824 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4825 private:
4826 FreeRegionList* _free_region_list;
4827 HeapRegionSet* _proxy_set;
4828 uint _humongous_regions_removed;
4829 size_t _freed_bytes;
4830 public:
4831
4832 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4833 _free_region_list(free_region_list), _humongous_regions_removed(0), _freed_bytes(0) {
4834 }
4835
4836 virtual bool doHeapRegion(HeapRegion* r) {
4837 if (!r->is_starts_humongous()) {
4838 return false;
4839 }
4840
4841 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4842
4843 oop obj = (oop)r->bottom();
4844 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
4845
4846 // The following checks whether the humongous object is live are sufficient.
4847 // The main additional check (in addition to having a reference from the roots
4848 // or the young gen) is whether the humongous object has a remembered set entry.
4849 //
4850 // A humongous object cannot be live if there is no remembered set for it
4851 // because:
4852 // - there can be no references from within humongous starts regions referencing
4853 // the object because we never allocate other objects into them.
4854 // (I.e. there are no intra-region references that may be missed by the
4855 // remembered set)
4856 // - as soon there is a remembered set entry to the humongous starts region
4857 // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4858 // until the end of a concurrent mark.
4859 //
4860 // It is not required to check whether the object has been found dead by marking
4861 // or not, in fact it would prevent reclamation within a concurrent cycle, as
4862 // all objects allocated during that time are considered live.
4863 // SATB marking is even more conservative than the remembered set.
4864 // So if at this point in the collection there is no remembered set entry,
4865 // nobody has a reference to it.
4866 // At the start of collection we flush all refinement logs, and remembered sets
4867 // are completely up-to-date wrt to references to the humongous object.
4868 //
4869 // Other implementation considerations:
4870 // - never consider object arrays at this time because they would pose
4871 // considerable effort for cleaning up the the remembered sets. This is
4872 // required because stale remembered sets might reference locations that
4873 // are currently allocated into.
4874 uint region_idx = r->hrm_index();
4875 if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4876 !r->rem_set()->is_empty()) {
4877 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",
4878 region_idx,
4879 (size_t)obj->size() * HeapWordSize,
4880 p2i(r->bottom()),
4881 r->rem_set()->occupied(),
4882 r->rem_set()->strong_code_roots_list_length(),
4883 next_bitmap->isMarked(r->bottom()),
4884 g1h->is_humongous_reclaim_candidate(region_idx),
4885 obj->is_typeArray()
4886 );
4887 return false;
4888 }
4889
4890 guarantee(obj->is_typeArray(),
4891 "Only eagerly reclaiming type arrays is supported, but the object "
4892 PTR_FORMAT " is not.", p2i(r->bottom()));
4893
4894 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",
4895 region_idx,
4896 (size_t)obj->size() * HeapWordSize,
4897 p2i(r->bottom()),
4898 r->rem_set()->occupied(),
4899 r->rem_set()->strong_code_roots_list_length(),
4900 next_bitmap->isMarked(r->bottom()),
4901 g1h->is_humongous_reclaim_candidate(region_idx),
4902 obj->is_typeArray()
4903 );
4904
4905 // Need to clear mark bit of the humongous object if already set.
4906 if (next_bitmap->isMarked(r->bottom())) {
4907 next_bitmap->clear(r->bottom());
4908 }
4909 do {
4910 HeapRegion* next = g1h->next_region_in_humongous(r);
4911 _freed_bytes += r->used();
4912 r->set_containing_set(NULL);
4913 _humongous_regions_removed++;
4914 g1h->free_humongous_region(r, _free_region_list, false);
4915 r = next;
4916 } while (r != NULL);
4917
4918 return false;
4919 }
4920
4921 uint humongous_free_count() {
4922 return _humongous_regions_removed;
4923 }
4924
4925 size_t bytes_freed() const {
4926 return _freed_bytes;
4927 }
4928 };
4929
4930 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4931 assert_at_safepoint(true);
4932
4933 if (!G1EagerReclaimHumongousObjects ||
4934 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
4935 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
4936 return;
4937 }
4938
4939 double start_time = os::elapsedTime();
4940
4941 FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
4942
4943 G1FreeHumongousRegionClosure cl(&local_cleanup_list);
4944 heap_region_iterate(&cl);
4945
4946 remove_from_old_sets(0, cl.humongous_free_count());
4947
4948 G1HRPrinter* hrp = hr_printer();
4949 if (hrp->is_active()) {
4950 FreeRegionListIterator iter(&local_cleanup_list);
4951 while (iter.more_available()) {
4952 HeapRegion* hr = iter.get_next();
4953 hrp->cleanup(hr);
4954 }
4955 }
4956
4957 prepend_to_freelist(&local_cleanup_list);
4958 decrement_summary_bytes(cl.bytes_freed());
4959
4960 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
4961 cl.humongous_free_count());
4962 }
4963
4964 // This routine is similar to the above but does not record
4965 // any policy statistics or update free lists; we are abandoning
4966 // the current incremental collection set in preparation of a
4967 // full collection. After the full GC we will start to build up
4968 // the incremental collection set again.
4969 // This is only called when we're doing a full collection
4970 // and is immediately followed by the tearing down of the young list.
4971
4972 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
4973 HeapRegion* cur = cs_head;
4974
4975 while (cur != NULL) {
4976 HeapRegion* next = cur->next_in_collection_set();
4977 assert(cur->in_collection_set(), "bad CS");
4978 cur->set_next_in_collection_set(NULL);
4979 clear_in_cset(cur);
4980 cur->set_young_index_in_cset(-1);
4981 cur = next;
4982 }
4983 }
4984
4985 void G1CollectedHeap::set_free_regions_coming() {
4986 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming");
4987
4988 assert(!free_regions_coming(), "pre-condition");
4989 _free_regions_coming = true;
4990 }
4991
4992 void G1CollectedHeap::reset_free_regions_coming() {
4993 assert(free_regions_coming(), "pre-condition");
4994
4995 {
4996 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
4997 _free_regions_coming = false;
4998 SecondaryFreeList_lock->notify_all();
4999 }
5000
5001 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming");
5002 }
5003
5004 void G1CollectedHeap::wait_while_free_regions_coming() {
5005 // Most of the time we won't have to wait, so let's do a quick test
5006 // first before we take the lock.
5007 if (!free_regions_coming()) {
5008 return;
5009 }
5010
5011 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions");
5012
5013 {
5014 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5015 while (free_regions_coming()) {
5016 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
5017 }
5018 }
5019
5020 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions");
5021 }
5022
5023 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
5024 return _allocator->is_retained_old_region(hr);
5025 }
5026
5027 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
5028 _eden.add(hr);
5029 _g1_policy->set_region_eden(hr);
5030 }
5031
5032 #ifdef ASSERT
5033
5034 class NoYoungRegionsClosure: public HeapRegionClosure {
5035 private:
5036 bool _success;
5037 public:
5038 NoYoungRegionsClosure() : _success(true) { }
5039 bool doHeapRegion(HeapRegion* r) {
5040 if (r->is_young()) {
5041 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
5042 p2i(r->bottom()), p2i(r->end()));
5043 _success = false;
5044 }
5045 return false;
5046 }
5047 bool success() { return _success; }
5048 };
5049
5050 bool G1CollectedHeap::check_young_list_empty() {
5051 bool ret = (young_regions_count() == 0);
5052
5053 NoYoungRegionsClosure closure;
5054 heap_region_iterate(&closure);
5055 ret = ret && closure.success();
5056
5057 return ret;
5058 }
5059
5060 #endif // ASSERT
5061
5062 class TearDownRegionSetsClosure : public HeapRegionClosure {
5063 private:
5064 HeapRegionSet *_old_set;
5065
5066 public:
5067 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
5068
5069 bool doHeapRegion(HeapRegion* r) {
5070 if (r->is_old()) {
5071 _old_set->remove(r);
5072 } else if(r->is_young()) {
5073 r->uninstall_surv_rate_group();
5074 } else {
5075 // We ignore free regions, we'll empty the free list afterwards.
5076 // We ignore humongous regions, we're not tearing down the
5077 // humongous regions set.
5078 assert(r->is_free() || r->is_humongous(),
5079 "it cannot be another type");
5080 }
5081 return false;
5082 }
5083
5084 ~TearDownRegionSetsClosure() {
5085 assert(_old_set->is_empty(), "post-condition");
5086 }
5087 };
5088
5089 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
5090 assert_at_safepoint(true /* should_be_vm_thread */);
5091
5092 if (!free_list_only) {
5093 TearDownRegionSetsClosure cl(&_old_set);
5094 heap_region_iterate(&cl);
5095
5096 // Note that emptying the _young_list is postponed and instead done as
5097 // the first step when rebuilding the regions sets again. The reason for
5098 // this is that during a full GC string deduplication needs to know if
5099 // a collected region was young or old when the full GC was initiated.
5100 }
5101 _hrm.remove_all_free_regions();
5102 }
5103
5104 void G1CollectedHeap::increase_used(size_t bytes) {
5105 _summary_bytes_used += bytes;
5106 }
5107
5108 void G1CollectedHeap::decrease_used(size_t bytes) {
5109 assert(_summary_bytes_used >= bytes,
5110 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
5111 _summary_bytes_used, bytes);
5112 _summary_bytes_used -= bytes;
5113 }
5114
5115 void G1CollectedHeap::set_used(size_t bytes) {
5116 _summary_bytes_used = bytes;
5117 }
5118
5119 class RebuildRegionSetsClosure : public HeapRegionClosure {
5120 private:
5121 bool _free_list_only;
5122 HeapRegionSet* _old_set;
5123 HeapRegionManager* _hrm;
5124 size_t _total_used;
5125
5126 public:
5127 RebuildRegionSetsClosure(bool free_list_only,
5128 HeapRegionSet* old_set, HeapRegionManager* hrm) :
5129 _free_list_only(free_list_only),
5130 _old_set(old_set), _hrm(hrm), _total_used(0) {
5131 assert(_hrm->num_free_regions() == 0, "pre-condition");
5132 if (!free_list_only) {
5133 assert(_old_set->is_empty(), "pre-condition");
5134 }
5135 }
5136
5137 bool doHeapRegion(HeapRegion* r) {
5138 if (r->is_empty()) {
5139 // Add free regions to the free list
5140 r->set_free();
5141 r->set_allocation_context(AllocationContext::system());
5142 _hrm->insert_into_free_list(r);
5143 } else if (!_free_list_only) {
5144
5145 if (r->is_humongous()) {
5146 // We ignore humongous regions. We left the humongous set unchanged.
5147 } else {
5148 assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
5149 // We now consider all regions old, so register as such. Leave
5150 // archive regions set that way, however, while still adding
5151 // them to the old set.
5152 if (!r->is_archive()) {
5153 r->set_old();
5154 }
5155 _old_set->add(r);
5156 }
5157 _total_used += r->used();
5158 }
5159
5160 return false;
5161 }
5162
5163 size_t total_used() {
5164 return _total_used;
5165 }
5166 };
5167
5168 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
5169 assert_at_safepoint(true /* should_be_vm_thread */);
5170
5171 if (!free_list_only) {
5172 _eden.clear();
5173 _survivor.clear();
5174 }
5175
5176 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
5177 heap_region_iterate(&cl);
5178
5179 if (!free_list_only) {
5180 set_used(cl.total_used());
5181 if (_archive_allocator != NULL) {
5182 _archive_allocator->clear_used();
5183 }
5184 }
5185 assert(used_unlocked() == recalculate_used(),
5186 "inconsistent used_unlocked(), "
5187 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT,
5188 used_unlocked(), recalculate_used());
5189 }
5190
5191 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
5192 _refine_cte_cl->set_concurrent(concurrent);
5193 }
5194
5195 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
5196 HeapRegion* hr = heap_region_containing(p);
5197 return hr->is_in(p);
5198 }
5199
5200 // Methods for the mutator alloc region
5201
5202 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
5203 bool force) {
5204 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5205 assert(!force || g1_policy()->can_expand_young_list(),
5206 "if force is true we should be able to expand the young list");
5207 bool should_allocate = g1_policy()->should_allocate_mutator_region();
5208 if (force || should_allocate) {
5209 HeapRegion* new_alloc_region = new_region(word_size,
5210 false /* is_old */,
5211 false /* do_expand */);
5212 if (new_alloc_region != NULL) {
5213 set_region_short_lived_locked(new_alloc_region);
5214 _hr_printer.alloc(new_alloc_region, !should_allocate);
5215 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
5216 return new_alloc_region;
5217 }
5218 }
5219 return NULL;
5220 }
5221
5222 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
5223 size_t allocated_bytes) {
5224 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5225 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
5226
5227 collection_set()->add_eden_region(alloc_region);
5228 increase_used(allocated_bytes);
5229 _hr_printer.retire(alloc_region);
5230 // We update the eden sizes here, when the region is retired,
5231 // instead of when it's allocated, since this is the point that its
5232 // used space has been recored in _summary_bytes_used.
5233 g1mm()->update_eden_size();
5234 }
5235
5236 // Methods for the GC alloc regions
5237
5238 bool G1CollectedHeap::has_more_regions(InCSetState dest) {
5239 if (dest.is_old()) {
5240 return true;
5241 } else {
5242 return survivor_regions_count() < g1_policy()->max_survivor_regions();
5243 }
5244 }
5245
5246 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) {
5247 assert(FreeList_lock->owned_by_self(), "pre-condition");
5248
5249 if (!has_more_regions(dest)) {
5250 return NULL;
5251 }
5252
5253 const bool is_survivor = dest.is_young();
5254
5255 HeapRegion* new_alloc_region = new_region(word_size,
5256 !is_survivor,
5257 true /* do_expand */);
5258 if (new_alloc_region != NULL) {
5259 // We really only need to do this for old regions given that we
5260 // should never scan survivors. But it doesn't hurt to do it
5261 // for survivors too.
5262 new_alloc_region->record_timestamp();
5263 if (is_survivor) {
5264 new_alloc_region->set_survivor();
5265 _survivor.add(new_alloc_region);
5266 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
5267 } else {
5268 new_alloc_region->set_old();
5269 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
5270 }
5271 _hr_printer.alloc(new_alloc_region);
5272 bool during_im = collector_state()->during_initial_mark_pause();
5273 new_alloc_region->note_start_of_copying(during_im);
5274 return new_alloc_region;
5275 }
5276 return NULL;
5277 }
5278
5279 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
5280 size_t allocated_bytes,
5281 InCSetState dest) {
5282 bool during_im = collector_state()->during_initial_mark_pause();
5283 alloc_region->note_end_of_copying(during_im);
5284 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
5285 if (dest.is_old()) {
5286 _old_set.add(alloc_region);
5287 }
5288 _hr_printer.retire(alloc_region);
5289 }
5290
5291 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
5292 bool expanded = false;
5293 uint index = _hrm.find_highest_free(&expanded);
5294
5295 if (index != G1_NO_HRM_INDEX) {
5296 if (expanded) {
5297 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
5298 HeapRegion::GrainWords * HeapWordSize);
5299 }
5300 _hrm.allocate_free_regions_starting_at(index, 1);
5301 return region_at(index);
5302 }
5303 return NULL;
5304 }
5305
5306 // Optimized nmethod scanning
5307
5308 class RegisterNMethodOopClosure: public OopClosure {
5309 G1CollectedHeap* _g1h;
5310 nmethod* _nm;
5311
5312 template <class T> void do_oop_work(T* p) {
5313 T heap_oop = oopDesc::load_heap_oop(p);
5314 if (!oopDesc::is_null(heap_oop)) {
5315 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5316 HeapRegion* hr = _g1h->heap_region_containing(obj);
5317 assert(!hr->is_continues_humongous(),
5318 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5319 " starting at " HR_FORMAT,
5320 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5321
5322 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
5323 hr->add_strong_code_root_locked(_nm);
5324 }
5325 }
5326
5327 public:
5328 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5329 _g1h(g1h), _nm(nm) {}
5330
5331 void do_oop(oop* p) { do_oop_work(p); }
5332 void do_oop(narrowOop* p) { do_oop_work(p); }
5333 };
5334
5335 class UnregisterNMethodOopClosure: public OopClosure {
5336 G1CollectedHeap* _g1h;
5337 nmethod* _nm;
5338
5339 template <class T> void do_oop_work(T* p) {
5340 T heap_oop = oopDesc::load_heap_oop(p);
5341 if (!oopDesc::is_null(heap_oop)) {
5342 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5343 HeapRegion* hr = _g1h->heap_region_containing(obj);
5344 assert(!hr->is_continues_humongous(),
5345 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5346 " starting at " HR_FORMAT,
5347 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5348
5349 hr->remove_strong_code_root(_nm);
5350 }
5351 }
5352
5353 public:
5354 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5355 _g1h(g1h), _nm(nm) {}
5356
5357 void do_oop(oop* p) { do_oop_work(p); }
5358 void do_oop(narrowOop* p) { do_oop_work(p); }
5359 };
5360
5361 void G1CollectedHeap::register_nmethod(nmethod* nm) {
5362 CollectedHeap::register_nmethod(nm);
5363
5364 guarantee(nm != NULL, "sanity");
5365 RegisterNMethodOopClosure reg_cl(this, nm);
5366 nm->oops_do(®_cl);
5367 }
5368
5369 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
5370 CollectedHeap::unregister_nmethod(nm);
5371
5372 guarantee(nm != NULL, "sanity");
5373 UnregisterNMethodOopClosure reg_cl(this, nm);
5374 nm->oops_do(®_cl, true);
5375 }
5376
5377 void G1CollectedHeap::purge_code_root_memory() {
5378 double purge_start = os::elapsedTime();
5379 G1CodeRootSet::purge();
5380 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
5381 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
5382 }
5383
5384 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
5385 G1CollectedHeap* _g1h;
5386
5387 public:
5388 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
5389 _g1h(g1h) {}
5390
5391 void do_code_blob(CodeBlob* cb) {
5392 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
5393 if (nm == NULL) {
5394 return;
5395 }
5396
5397 if (ScavengeRootsInCode) {
5398 _g1h->register_nmethod(nm);
5399 }
5400 }
5401 };
5402
5403 void G1CollectedHeap::rebuild_strong_code_roots() {
5404 RebuildStrongCodeRootClosure blob_cl(this);
5405 CodeCache::blobs_do(&blob_cl);
5406 }