1 /*
2 * Copyright (c) 2001, 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/metadataOnStackMark.hpp"
27 #include "classfile/stringTable.hpp"
28 #include "classfile/symbolTable.hpp"
29 #include "code/codeCache.hpp"
30 #include "code/icBuffer.hpp"
31 #include "gc/g1/bufferingOopClosure.hpp"
32 #include "gc/g1/concurrentG1Refine.hpp"
33 #include "gc/g1/concurrentG1RefineThread.hpp"
34 #include "gc/g1/concurrentMarkThread.inline.hpp"
35 #include "gc/g1/g1Allocator.inline.hpp"
36 #include "gc/g1/g1CollectedHeap.inline.hpp"
37 #include "gc/g1/g1CollectionSet.hpp"
38 #include "gc/g1/g1CollectorPolicy.hpp"
39 #include "gc/g1/g1CollectorState.hpp"
40 #include "gc/g1/g1EvacStats.inline.hpp"
41 #include "gc/g1/g1FullCollector.hpp"
42 #include "gc/g1/g1FullGCScope.hpp"
43 #include "gc/g1/g1GCPhaseTimes.hpp"
44 #include "gc/g1/g1HeapSizingPolicy.hpp"
45 #include "gc/g1/g1HeapTransition.hpp"
46 #include "gc/g1/g1HeapVerifier.hpp"
47 #include "gc/g1/g1HotCardCache.hpp"
48 #include "gc/g1/g1OopClosures.inline.hpp"
49 #include "gc/g1/g1ParScanThreadState.inline.hpp"
50 #include "gc/g1/g1Policy.hpp"
51 #include "gc/g1/g1RegionToSpaceMapper.hpp"
52 #include "gc/g1/g1RemSet.inline.hpp"
53 #include "gc/g1/g1RootClosures.hpp"
54 #include "gc/g1/g1RootProcessor.hpp"
55 #include "gc/g1/g1StringDedup.hpp"
56 #include "gc/g1/g1YCTypes.hpp"
57 #include "gc/g1/heapRegion.inline.hpp"
58 #include "gc/g1/heapRegionRemSet.hpp"
59 #include "gc/g1/heapRegionSet.inline.hpp"
60 #include "gc/g1/suspendibleThreadSet.hpp"
61 #include "gc/g1/vm_operations_g1.hpp"
62 #include "gc/shared/gcHeapSummary.hpp"
63 #include "gc/shared/gcId.hpp"
64 #include "gc/shared/gcLocker.inline.hpp"
65 #include "gc/shared/gcTimer.hpp"
66 #include "gc/shared/gcTrace.hpp"
67 #include "gc/shared/gcTraceTime.inline.hpp"
68 #include "gc/shared/generationSpec.hpp"
69 #include "gc/shared/isGCActiveMark.hpp"
70 #include "gc/shared/preservedMarks.inline.hpp"
71 #include "gc/shared/referenceProcessor.inline.hpp"
72 #include "gc/shared/taskqueue.inline.hpp"
73 #include "logging/log.hpp"
74 #include "memory/allocation.hpp"
75 #include "memory/iterator.hpp"
76 #include "memory/resourceArea.hpp"
77 #include "oops/oop.inline.hpp"
78 #include "prims/resolvedMethodTable.hpp"
79 #include "runtime/atomic.hpp"
80 #include "runtime/init.hpp"
81 #include "runtime/orderAccess.inline.hpp"
82 #include "runtime/vmThread.hpp"
83 #include "utilities/align.hpp"
84 #include "utilities/globalDefinitions.hpp"
85 #include "utilities/stack.inline.hpp"
86
87 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
88
89 // INVARIANTS/NOTES
90 //
91 // All allocation activity covered by the G1CollectedHeap interface is
92 // serialized by acquiring the HeapLock. This happens in mem_allocate
93 // and allocate_new_tlab, which are the "entry" points to the
94 // allocation code from the rest of the JVM. (Note that this does not
95 // apply to TLAB allocation, which is not part of this interface: it
96 // is done by clients of this interface.)
97
98 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
99 private:
100 size_t _num_dirtied;
101 G1CollectedHeap* _g1h;
102 G1SATBCardTableLoggingModRefBS* _g1_bs;
103
104 HeapRegion* region_for_card(jbyte* card_ptr) const {
105 return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr));
106 }
107
108 bool will_become_free(HeapRegion* hr) const {
109 // A region will be freed by free_collection_set if the region is in the
110 // collection set and has not had an evacuation failure.
111 return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
112 }
113
114 public:
115 RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(),
116 _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { }
117
118 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
119 HeapRegion* hr = region_for_card(card_ptr);
120
121 // Should only dirty cards in regions that won't be freed.
122 if (!will_become_free(hr)) {
123 *card_ptr = CardTableModRefBS::dirty_card_val();
124 _num_dirtied++;
125 }
126
127 return true;
128 }
129
130 size_t num_dirtied() const { return _num_dirtied; }
131 };
132
133
134 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
135 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
136 }
137
138 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
139 // The from card cache is not the memory that is actually committed. So we cannot
140 // take advantage of the zero_filled parameter.
141 reset_from_card_cache(start_idx, num_regions);
142 }
143
144 // Returns true if the reference points to an object that
145 // can move in an incremental collection.
146 bool G1CollectedHeap::is_scavengable(const void* p) {
147 HeapRegion* hr = heap_region_containing(p);
148 return !hr->is_pinned();
149 }
150
151
152 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
153 MemRegion mr) {
154 return new HeapRegion(hrs_index, bot(), mr);
155 }
156
157 // Private methods.
158
159 HeapRegion*
160 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
161 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
162 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
163 if (!_secondary_free_list.is_empty()) {
164 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
165 "secondary_free_list has %u entries",
166 _secondary_free_list.length());
167 // It looks as if there are free regions available on the
168 // secondary_free_list. Let's move them to the free_list and try
169 // again to allocate from it.
170 append_secondary_free_list();
171
172 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
173 "empty we should have moved at least one entry to the free_list");
174 HeapRegion* res = _hrm.allocate_free_region(is_old);
175 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
176 "allocated " HR_FORMAT " from secondary_free_list",
177 HR_FORMAT_PARAMS(res));
178 return res;
179 }
180
181 // Wait here until we get notified either when (a) there are no
182 // more free regions coming or (b) some regions have been moved on
183 // the secondary_free_list.
184 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
185 }
186
187 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
188 "could not allocate from secondary_free_list");
189 return NULL;
190 }
191
192 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
193 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
194 "the only time we use this to allocate a humongous region is "
195 "when we are allocating a single humongous region");
196
197 HeapRegion* res;
198 if (G1StressConcRegionFreeing) {
199 if (!_secondary_free_list.is_empty()) {
200 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
201 "forced to look at the secondary_free_list");
202 res = new_region_try_secondary_free_list(is_old);
203 if (res != NULL) {
204 return res;
205 }
206 }
207 }
208
209 res = _hrm.allocate_free_region(is_old);
210
211 if (res == NULL) {
212 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
213 "res == NULL, trying the secondary_free_list");
214 res = new_region_try_secondary_free_list(is_old);
215 }
216 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
217 // Currently, only attempts to allocate GC alloc regions set
218 // do_expand to true. So, we should only reach here during a
219 // safepoint. If this assumption changes we might have to
220 // reconsider the use of _expand_heap_after_alloc_failure.
221 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
222
223 log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
224 word_size * HeapWordSize);
225
226 if (expand(word_size * HeapWordSize)) {
227 // Given that expand() succeeded in expanding the heap, and we
228 // always expand the heap by an amount aligned to the heap
229 // region size, the free list should in theory not be empty.
230 // In either case allocate_free_region() will check for NULL.
231 res = _hrm.allocate_free_region(is_old);
232 } else {
233 _expand_heap_after_alloc_failure = false;
234 }
235 }
236 return res;
237 }
238
239 HeapWord*
240 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
241 uint num_regions,
242 size_t word_size,
243 AllocationContext_t context) {
244 assert(first != G1_NO_HRM_INDEX, "pre-condition");
245 assert(is_humongous(word_size), "word_size should be humongous");
246 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
247
248 // Index of last region in the series.
249 uint last = first + num_regions - 1;
250
251 // We need to initialize the region(s) we just discovered. This is
252 // a bit tricky given that it can happen concurrently with
253 // refinement threads refining cards on these regions and
254 // potentially wanting to refine the BOT as they are scanning
255 // those cards (this can happen shortly after a cleanup; see CR
256 // 6991377). So we have to set up the region(s) carefully and in
257 // a specific order.
258
259 // The word size sum of all the regions we will allocate.
260 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
261 assert(word_size <= word_size_sum, "sanity");
262
263 // This will be the "starts humongous" region.
264 HeapRegion* first_hr = region_at(first);
265 // The header of the new object will be placed at the bottom of
266 // the first region.
267 HeapWord* new_obj = first_hr->bottom();
268 // This will be the new top of the new object.
269 HeapWord* obj_top = new_obj + word_size;
270
271 // First, we need to zero the header of the space that we will be
272 // allocating. When we update top further down, some refinement
273 // threads might try to scan the region. By zeroing the header we
274 // ensure that any thread that will try to scan the region will
275 // come across the zero klass word and bail out.
276 //
277 // NOTE: It would not have been correct to have used
278 // CollectedHeap::fill_with_object() and make the space look like
279 // an int array. The thread that is doing the allocation will
280 // later update the object header to a potentially different array
281 // type and, for a very short period of time, the klass and length
282 // fields will be inconsistent. This could cause a refinement
283 // thread to calculate the object size incorrectly.
284 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
285
286 // Next, pad out the unused tail of the last region with filler
287 // objects, for improved usage accounting.
288 // How many words we use for filler objects.
289 size_t word_fill_size = word_size_sum - word_size;
290
291 // How many words memory we "waste" which cannot hold a filler object.
292 size_t words_not_fillable = 0;
293
294 if (word_fill_size >= min_fill_size()) {
295 fill_with_objects(obj_top, word_fill_size);
296 } else if (word_fill_size > 0) {
297 // We have space to fill, but we cannot fit an object there.
298 words_not_fillable = word_fill_size;
299 word_fill_size = 0;
300 }
301
302 // We will set up the first region as "starts humongous". This
303 // will also update the BOT covering all the regions to reflect
304 // that there is a single object that starts at the bottom of the
305 // first region.
306 first_hr->set_starts_humongous(obj_top, word_fill_size);
307 first_hr->set_allocation_context(context);
308 // Then, if there are any, we will set up the "continues
309 // humongous" regions.
310 HeapRegion* hr = NULL;
311 for (uint i = first + 1; i <= last; ++i) {
312 hr = region_at(i);
313 hr->set_continues_humongous(first_hr);
314 hr->set_allocation_context(context);
315 }
316
317 // Up to this point no concurrent thread would have been able to
318 // do any scanning on any region in this series. All the top
319 // fields still point to bottom, so the intersection between
320 // [bottom,top] and [card_start,card_end] will be empty. Before we
321 // update the top fields, we'll do a storestore to make sure that
322 // no thread sees the update to top before the zeroing of the
323 // object header and the BOT initialization.
324 OrderAccess::storestore();
325
326 // Now, we will update the top fields of the "continues humongous"
327 // regions except the last one.
328 for (uint i = first; i < last; ++i) {
329 hr = region_at(i);
330 hr->set_top(hr->end());
331 }
332
333 hr = region_at(last);
334 // If we cannot fit a filler object, we must set top to the end
335 // of the humongous object, otherwise we cannot iterate the heap
336 // and the BOT will not be complete.
337 hr->set_top(hr->end() - words_not_fillable);
338
339 assert(hr->bottom() < obj_top && obj_top <= hr->end(),
340 "obj_top should be in last region");
341
342 _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
343
344 assert(words_not_fillable == 0 ||
345 first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
346 "Miscalculation in humongous allocation");
347
348 increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
349
350 for (uint i = first; i <= last; ++i) {
351 hr = region_at(i);
352 _humongous_set.add(hr);
353 _hr_printer.alloc(hr);
354 }
355
356 return new_obj;
357 }
358
359 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
360 assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
361 return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
362 }
363
364 // If could fit into free regions w/o expansion, try.
365 // Otherwise, if can expand, do so.
366 // Otherwise, if using ex regions might help, try with ex given back.
367 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
368 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
369
370 _verifier->verify_region_sets_optional();
371
372 uint first = G1_NO_HRM_INDEX;
373 uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
374
375 if (obj_regions == 1) {
376 // Only one region to allocate, try to use a fast path by directly allocating
377 // from the free lists. Do not try to expand here, we will potentially do that
378 // later.
379 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
380 if (hr != NULL) {
381 first = hr->hrm_index();
382 }
383 } else {
384 // We can't allocate humongous regions spanning more than one region while
385 // cleanupComplete() is running, since some of the regions we find to be
386 // empty might not yet be added to the free list. It is not straightforward
387 // to know in which list they are on so that we can remove them. We only
388 // need to do this if we need to allocate more than one region to satisfy the
389 // current humongous allocation request. If we are only allocating one region
390 // we use the one-region region allocation code (see above), that already
391 // potentially waits for regions from the secondary free list.
392 wait_while_free_regions_coming();
393 append_secondary_free_list_if_not_empty_with_lock();
394
395 // Policy: Try only empty regions (i.e. already committed first). Maybe we
396 // are lucky enough to find some.
397 first = _hrm.find_contiguous_only_empty(obj_regions);
398 if (first != G1_NO_HRM_INDEX) {
399 _hrm.allocate_free_regions_starting_at(first, obj_regions);
400 }
401 }
402
403 if (first == G1_NO_HRM_INDEX) {
404 // Policy: We could not find enough regions for the humongous object in the
405 // free list. Look through the heap to find a mix of free and uncommitted regions.
406 // If so, try expansion.
407 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
408 if (first != G1_NO_HRM_INDEX) {
409 // We found something. Make sure these regions are committed, i.e. expand
410 // the heap. Alternatively we could do a defragmentation GC.
411 log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
412 word_size * HeapWordSize);
413
414 _hrm.expand_at(first, obj_regions, workers());
415 g1_policy()->record_new_heap_size(num_regions());
416
417 #ifdef ASSERT
418 for (uint i = first; i < first + obj_regions; ++i) {
419 HeapRegion* hr = region_at(i);
420 assert(hr->is_free(), "sanity");
421 assert(hr->is_empty(), "sanity");
422 assert(is_on_master_free_list(hr), "sanity");
423 }
424 #endif
425 _hrm.allocate_free_regions_starting_at(first, obj_regions);
426 } else {
427 // Policy: Potentially trigger a defragmentation GC.
428 }
429 }
430
431 HeapWord* result = NULL;
432 if (first != G1_NO_HRM_INDEX) {
433 result = humongous_obj_allocate_initialize_regions(first, obj_regions,
434 word_size, context);
435 assert(result != NULL, "it should always return a valid result");
436
437 // A successful humongous object allocation changes the used space
438 // information of the old generation so we need to recalculate the
439 // sizes and update the jstat counters here.
440 g1mm()->update_sizes();
441 }
442
443 _verifier->verify_region_sets_optional();
444
445 return result;
446 }
447
448 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
449 assert_heap_not_locked_and_not_at_safepoint();
450 assert(!is_humongous(word_size), "we do not allow humongous TLABs");
451
452 uint dummy_gc_count_before;
453 uint dummy_gclocker_retry_count = 0;
454 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
455 }
456
457 HeapWord*
458 G1CollectedHeap::mem_allocate(size_t word_size,
459 bool* gc_overhead_limit_was_exceeded) {
460 assert_heap_not_locked_and_not_at_safepoint();
461
462 // Loop until the allocation is satisfied, or unsatisfied after GC.
463 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
464 uint gc_count_before;
465
466 HeapWord* result = NULL;
467 if (!is_humongous(word_size)) {
468 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
469 } else {
470 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
471 }
472 if (result != NULL) {
473 return result;
474 }
475
476 // Create the garbage collection operation...
477 VM_G1CollectForAllocation op(gc_count_before, word_size);
478 op.set_allocation_context(AllocationContext::current());
479
480 // ...and get the VM thread to execute it.
481 VMThread::execute(&op);
482
483 if (op.prologue_succeeded() && op.pause_succeeded()) {
484 // If the operation was successful we'll return the result even
485 // if it is NULL. If the allocation attempt failed immediately
486 // after a Full GC, it's unlikely we'll be able to allocate now.
487 HeapWord* result = op.result();
488 if (result != NULL && !is_humongous(word_size)) {
489 // Allocations that take place on VM operations do not do any
490 // card dirtying and we have to do it here. We only have to do
491 // this for non-humongous allocations, though.
492 dirty_young_block(result, word_size);
493 }
494 return result;
495 } else {
496 if (gclocker_retry_count > GCLockerRetryAllocationCount) {
497 return NULL;
498 }
499 assert(op.result() == NULL,
500 "the result should be NULL if the VM op did not succeed");
501 }
502
503 // Give a warning if we seem to be looping forever.
504 if ((QueuedAllocationWarningCount > 0) &&
505 (try_count % QueuedAllocationWarningCount == 0)) {
506 log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count);
507 }
508 }
509
510 ShouldNotReachHere();
511 return NULL;
512 }
513
514 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
515 AllocationContext_t context,
516 uint* gc_count_before_ret,
517 uint* gclocker_retry_count_ret) {
518 // Make sure you read the note in attempt_allocation_humongous().
519
520 assert_heap_not_locked_and_not_at_safepoint();
521 assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
522 "be called for humongous allocation requests");
523
524 // We should only get here after the first-level allocation attempt
525 // (attempt_allocation()) failed to allocate.
526
527 // We will loop until a) we manage to successfully perform the
528 // allocation or b) we successfully schedule a collection which
529 // fails to perform the allocation. b) is the only case when we'll
530 // return NULL.
531 HeapWord* result = NULL;
532 for (int try_count = 1; /* we'll return */; try_count += 1) {
533 bool should_try_gc;
534 uint gc_count_before;
535
536 {
537 MutexLockerEx x(Heap_lock);
538 result = _allocator->attempt_allocation_locked(word_size, context);
539 if (result != NULL) {
540 return result;
541 }
542
543 if (GCLocker::is_active_and_needs_gc()) {
544 if (g1_policy()->can_expand_young_list()) {
545 // No need for an ergo verbose message here,
546 // can_expand_young_list() does this when it returns true.
547 result = _allocator->attempt_allocation_force(word_size, context);
548 if (result != NULL) {
549 return result;
550 }
551 }
552 should_try_gc = false;
553 } else {
554 // The GCLocker may not be active but the GCLocker initiated
555 // GC may not yet have been performed (GCLocker::needs_gc()
556 // returns true). In this case we do not try this GC and
557 // wait until the GCLocker initiated GC is performed, and
558 // then retry the allocation.
559 if (GCLocker::needs_gc()) {
560 should_try_gc = false;
561 } else {
562 // Read the GC count while still holding the Heap_lock.
563 gc_count_before = total_collections();
564 should_try_gc = true;
565 }
566 }
567 }
568
569 if (should_try_gc) {
570 bool succeeded;
571 result = do_collection_pause(word_size, gc_count_before, &succeeded,
572 GCCause::_g1_inc_collection_pause);
573 if (result != NULL) {
574 assert(succeeded, "only way to get back a non-NULL result");
575 return result;
576 }
577
578 if (succeeded) {
579 // If we get here we successfully scheduled a collection which
580 // failed to allocate. No point in trying to allocate
581 // further. We'll just return NULL.
582 MutexLockerEx x(Heap_lock);
583 *gc_count_before_ret = total_collections();
584 return NULL;
585 }
586 } else {
587 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
588 MutexLockerEx x(Heap_lock);
589 *gc_count_before_ret = total_collections();
590 return NULL;
591 }
592 // The GCLocker is either active or the GCLocker initiated
593 // GC has not yet been performed. Stall until it is and
594 // then retry the allocation.
595 GCLocker::stall_until_clear();
596 (*gclocker_retry_count_ret) += 1;
597 }
598
599 // We can reach here if we were unsuccessful in scheduling a
600 // collection (because another thread beat us to it) or if we were
601 // stalled due to the GC locker. In either can we should retry the
602 // allocation attempt in case another thread successfully
603 // performed a collection and reclaimed enough space. We do the
604 // first attempt (without holding the Heap_lock) here and the
605 // follow-on attempt will be at the start of the next loop
606 // iteration (after taking the Heap_lock).
607 result = _allocator->attempt_allocation(word_size, context);
608 if (result != NULL) {
609 return result;
610 }
611
612 // Give a warning if we seem to be looping forever.
613 if ((QueuedAllocationWarningCount > 0) &&
614 (try_count % QueuedAllocationWarningCount == 0)) {
615 log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() "
616 "retries %d times", try_count);
617 }
618 }
619
620 ShouldNotReachHere();
621 return NULL;
622 }
623
624 void G1CollectedHeap::begin_archive_alloc_range() {
625 assert_at_safepoint(true /* should_be_vm_thread */);
626 if (_archive_allocator == NULL) {
627 _archive_allocator = G1ArchiveAllocator::create_allocator(this);
628 }
629 }
630
631 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
632 // Allocations in archive regions cannot be of a size that would be considered
633 // humongous even for a minimum-sized region, because G1 region sizes/boundaries
634 // may be different at archive-restore time.
635 return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
636 }
637
638 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
639 assert_at_safepoint(true /* should_be_vm_thread */);
640 assert(_archive_allocator != NULL, "_archive_allocator not initialized");
641 if (is_archive_alloc_too_large(word_size)) {
642 return NULL;
643 }
644 return _archive_allocator->archive_mem_allocate(word_size);
645 }
646
647 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
648 size_t end_alignment_in_bytes) {
649 assert_at_safepoint(true /* should_be_vm_thread */);
650 assert(_archive_allocator != NULL, "_archive_allocator not initialized");
651
652 // Call complete_archive to do the real work, filling in the MemRegion
653 // array with the archive regions.
654 _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
655 delete _archive_allocator;
656 _archive_allocator = NULL;
657 }
658
659 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
660 assert(ranges != NULL, "MemRegion array NULL");
661 assert(count != 0, "No MemRegions provided");
662 MemRegion reserved = _hrm.reserved();
663 for (size_t i = 0; i < count; i++) {
664 if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
665 return false;
666 }
667 }
668 return true;
669 }
670
671 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, size_t count) {
672 assert(!is_init_completed(), "Expect to be called at JVM init time");
673 assert(ranges != NULL, "MemRegion array NULL");
674 assert(count != 0, "No MemRegions provided");
675 MutexLockerEx x(Heap_lock);
676
677 MemRegion reserved = _hrm.reserved();
678 HeapWord* prev_last_addr = NULL;
679 HeapRegion* prev_last_region = NULL;
680
681 // Temporarily disable pretouching of heap pages. This interface is used
682 // when mmap'ing archived heap data in, so pre-touching is wasted.
683 FlagSetting fs(AlwaysPreTouch, false);
684
685 // Enable archive object checking used by G1MarkSweep. We have to let it know
686 // about each archive range, so that objects in those ranges aren't marked.
687 G1ArchiveAllocator::enable_archive_object_check();
688
689 // For each specified MemRegion range, allocate the corresponding G1
690 // regions and mark them as archive regions. We expect the ranges in
691 // ascending starting address order, without overlap.
692 for (size_t i = 0; i < count; i++) {
693 MemRegion curr_range = ranges[i];
694 HeapWord* start_address = curr_range.start();
695 size_t word_size = curr_range.word_size();
696 HeapWord* last_address = curr_range.last();
697 size_t commits = 0;
698
699 guarantee(reserved.contains(start_address) && reserved.contains(last_address),
700 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
701 p2i(start_address), p2i(last_address));
702 guarantee(start_address > prev_last_addr,
703 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
704 p2i(start_address), p2i(prev_last_addr));
705 prev_last_addr = last_address;
706
707 // Check for ranges that start in the same G1 region in which the previous
708 // range ended, and adjust the start address so we don't try to allocate
709 // the same region again. If the current range is entirely within that
710 // region, skip it, just adjusting the recorded top.
711 HeapRegion* start_region = _hrm.addr_to_region(start_address);
712 if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
713 start_address = start_region->end();
714 if (start_address > last_address) {
715 increase_used(word_size * HeapWordSize);
716 start_region->set_top(last_address + 1);
717 continue;
718 }
719 start_region->set_top(start_address);
720 curr_range = MemRegion(start_address, last_address + 1);
721 start_region = _hrm.addr_to_region(start_address);
722 }
723
724 // Perform the actual region allocation, exiting if it fails.
725 // Then note how much new space we have allocated.
726 if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) {
727 return false;
728 }
729 increase_used(word_size * HeapWordSize);
730 if (commits != 0) {
731 log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
732 HeapRegion::GrainWords * HeapWordSize * commits);
733
734 }
735
736 // Mark each G1 region touched by the range as archive, add it to the old set,
737 // and set the allocation context and top.
738 HeapRegion* curr_region = _hrm.addr_to_region(start_address);
739 HeapRegion* last_region = _hrm.addr_to_region(last_address);
740 prev_last_region = last_region;
741
742 while (curr_region != NULL) {
743 assert(curr_region->is_empty() && !curr_region->is_pinned(),
744 "Region already in use (index %u)", curr_region->hrm_index());
745 curr_region->set_allocation_context(AllocationContext::system());
746 curr_region->set_archive();
747 _hr_printer.alloc(curr_region);
748 _old_set.add(curr_region);
749 if (curr_region != last_region) {
750 curr_region->set_top(curr_region->end());
751 curr_region = _hrm.next_region_in_heap(curr_region);
752 } else {
753 curr_region->set_top(last_address + 1);
754 curr_region = NULL;
755 }
756 }
757
758 // Notify mark-sweep of the archive range.
759 G1ArchiveAllocator::set_range_archive(curr_range, true);
760 }
761 return true;
762 }
763
764 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
765 assert(!is_init_completed(), "Expect to be called at JVM init time");
766 assert(ranges != NULL, "MemRegion array NULL");
767 assert(count != 0, "No MemRegions provided");
768 MemRegion reserved = _hrm.reserved();
769 HeapWord *prev_last_addr = NULL;
770 HeapRegion* prev_last_region = NULL;
771
772 // For each MemRegion, create filler objects, if needed, in the G1 regions
773 // that contain the address range. The address range actually within the
774 // MemRegion will not be modified. That is assumed to have been initialized
775 // elsewhere, probably via an mmap of archived heap data.
776 MutexLockerEx x(Heap_lock);
777 for (size_t i = 0; i < count; i++) {
778 HeapWord* start_address = ranges[i].start();
779 HeapWord* last_address = ranges[i].last();
780
781 assert(reserved.contains(start_address) && reserved.contains(last_address),
782 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
783 p2i(start_address), p2i(last_address));
784 assert(start_address > prev_last_addr,
785 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
786 p2i(start_address), p2i(prev_last_addr));
787
788 HeapRegion* start_region = _hrm.addr_to_region(start_address);
789 HeapRegion* last_region = _hrm.addr_to_region(last_address);
790 HeapWord* bottom_address = start_region->bottom();
791
792 // Check for a range beginning in the same region in which the
793 // previous one ended.
794 if (start_region == prev_last_region) {
795 bottom_address = prev_last_addr + 1;
796 }
797
798 // Verify that the regions were all marked as archive regions by
799 // alloc_archive_regions.
800 HeapRegion* curr_region = start_region;
801 while (curr_region != NULL) {
802 guarantee(curr_region->is_archive(),
803 "Expected archive region at index %u", curr_region->hrm_index());
804 if (curr_region != last_region) {
805 curr_region = _hrm.next_region_in_heap(curr_region);
806 } else {
807 curr_region = NULL;
808 }
809 }
810
811 prev_last_addr = last_address;
812 prev_last_region = last_region;
813
814 // Fill the memory below the allocated range with dummy object(s),
815 // if the region bottom does not match the range start, or if the previous
816 // range ended within the same G1 region, and there is a gap.
817 if (start_address != bottom_address) {
818 size_t fill_size = pointer_delta(start_address, bottom_address);
819 G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
820 increase_used(fill_size * HeapWordSize);
821 }
822 }
823 }
824
825 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size,
826 uint* gc_count_before_ret,
827 uint* gclocker_retry_count_ret) {
828 assert_heap_not_locked_and_not_at_safepoint();
829 assert(!is_humongous(word_size), "attempt_allocation() should not "
830 "be called for humongous allocation requests");
831
832 AllocationContext_t context = AllocationContext::current();
833 HeapWord* result = _allocator->attempt_allocation(word_size, context);
834
835 if (result == NULL) {
836 result = attempt_allocation_slow(word_size,
837 context,
838 gc_count_before_ret,
839 gclocker_retry_count_ret);
840 }
841 assert_heap_not_locked();
842 if (result != NULL) {
843 dirty_young_block(result, word_size);
844 }
845 return result;
846 }
847
848 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
849 assert(!is_init_completed(), "Expect to be called at JVM init time");
850 assert(ranges != NULL, "MemRegion array NULL");
851 assert(count != 0, "No MemRegions provided");
852 MemRegion reserved = _hrm.reserved();
853 HeapWord* prev_last_addr = NULL;
854 HeapRegion* prev_last_region = NULL;
855 size_t size_used = 0;
856 size_t uncommitted_regions = 0;
857
858 // For each Memregion, free the G1 regions that constitute it, and
859 // notify mark-sweep that the range is no longer to be considered 'archive.'
860 MutexLockerEx x(Heap_lock);
861 for (size_t i = 0; i < count; i++) {
862 HeapWord* start_address = ranges[i].start();
863 HeapWord* last_address = ranges[i].last();
864
865 assert(reserved.contains(start_address) && reserved.contains(last_address),
866 "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
867 p2i(start_address), p2i(last_address));
868 assert(start_address > prev_last_addr,
869 "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
870 p2i(start_address), p2i(prev_last_addr));
871 size_used += ranges[i].byte_size();
872 prev_last_addr = last_address;
873
874 HeapRegion* start_region = _hrm.addr_to_region(start_address);
875 HeapRegion* last_region = _hrm.addr_to_region(last_address);
876
877 // Check for ranges that start in the same G1 region in which the previous
878 // range ended, and adjust the start address so we don't try to free
879 // the same region again. If the current range is entirely within that
880 // region, skip it.
881 if (start_region == prev_last_region) {
882 start_address = start_region->end();
883 if (start_address > last_address) {
884 continue;
885 }
886 start_region = _hrm.addr_to_region(start_address);
887 }
888 prev_last_region = last_region;
889
890 // After verifying that each region was marked as an archive region by
891 // alloc_archive_regions, set it free and empty and uncommit it.
892 HeapRegion* curr_region = start_region;
893 while (curr_region != NULL) {
894 guarantee(curr_region->is_archive(),
895 "Expected archive region at index %u", curr_region->hrm_index());
896 uint curr_index = curr_region->hrm_index();
897 _old_set.remove(curr_region);
898 curr_region->set_free();
899 curr_region->set_top(curr_region->bottom());
900 if (curr_region != last_region) {
901 curr_region = _hrm.next_region_in_heap(curr_region);
902 } else {
903 curr_region = NULL;
904 }
905 _hrm.shrink_at(curr_index, 1);
906 uncommitted_regions++;
907 }
908
909 // Notify mark-sweep that this is no longer an archive range.
910 G1ArchiveAllocator::set_range_archive(ranges[i], false);
911 }
912
913 if (uncommitted_regions != 0) {
914 log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
915 HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
916 }
917 decrease_used(size_used);
918 }
919
920 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
921 uint* gc_count_before_ret,
922 uint* gclocker_retry_count_ret) {
923 // The structure of this method has a lot of similarities to
924 // attempt_allocation_slow(). The reason these two were not merged
925 // into a single one is that such a method would require several "if
926 // allocation is not humongous do this, otherwise do that"
927 // conditional paths which would obscure its flow. In fact, an early
928 // version of this code did use a unified method which was harder to
929 // follow and, as a result, it had subtle bugs that were hard to
930 // track down. So keeping these two methods separate allows each to
931 // be more readable. It will be good to keep these two in sync as
932 // much as possible.
933
934 assert_heap_not_locked_and_not_at_safepoint();
935 assert(is_humongous(word_size), "attempt_allocation_humongous() "
936 "should only be called for humongous allocations");
937
938 // Humongous objects can exhaust the heap quickly, so we should check if we
939 // need to start a marking cycle at each humongous object allocation. We do
940 // the check before we do the actual allocation. The reason for doing it
941 // before the allocation is that we avoid having to keep track of the newly
942 // allocated memory while we do a GC.
943 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
944 word_size)) {
945 collect(GCCause::_g1_humongous_allocation);
946 }
947
948 // We will loop until a) we manage to successfully perform the
949 // allocation or b) we successfully schedule a collection which
950 // fails to perform the allocation. b) is the only case when we'll
951 // return NULL.
952 HeapWord* result = NULL;
953 for (int try_count = 1; /* we'll return */; try_count += 1) {
954 bool should_try_gc;
955 uint gc_count_before;
956
957 {
958 MutexLockerEx x(Heap_lock);
959
960 // Given that humongous objects are not allocated in young
961 // regions, we'll first try to do the allocation without doing a
962 // collection hoping that there's enough space in the heap.
963 result = humongous_obj_allocate(word_size, AllocationContext::current());
964 if (result != NULL) {
965 size_t size_in_regions = humongous_obj_size_in_regions(word_size);
966 g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
967 return result;
968 }
969
970 if (GCLocker::is_active_and_needs_gc()) {
971 should_try_gc = false;
972 } else {
973 // The GCLocker may not be active but the GCLocker initiated
974 // GC may not yet have been performed (GCLocker::needs_gc()
975 // returns true). In this case we do not try this GC and
976 // wait until the GCLocker initiated GC is performed, and
977 // then retry the allocation.
978 if (GCLocker::needs_gc()) {
979 should_try_gc = false;
980 } else {
981 // Read the GC count while still holding the Heap_lock.
982 gc_count_before = total_collections();
983 should_try_gc = true;
984 }
985 }
986 }
987
988 if (should_try_gc) {
989 // If we failed to allocate the humongous object, we should try to
990 // do a collection pause (if we're allowed) in case it reclaims
991 // enough space for the allocation to succeed after the pause.
992
993 bool succeeded;
994 result = do_collection_pause(word_size, gc_count_before, &succeeded,
995 GCCause::_g1_humongous_allocation);
996 if (result != NULL) {
997 assert(succeeded, "only way to get back a non-NULL result");
998 return result;
999 }
1000
1001 if (succeeded) {
1002 // If we get here we successfully scheduled a collection which
1003 // failed to allocate. No point in trying to allocate
1004 // further. We'll just return NULL.
1005 MutexLockerEx x(Heap_lock);
1006 *gc_count_before_ret = total_collections();
1007 return NULL;
1008 }
1009 } else {
1010 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1011 MutexLockerEx x(Heap_lock);
1012 *gc_count_before_ret = total_collections();
1013 return NULL;
1014 }
1015 // The GCLocker is either active or the GCLocker initiated
1016 // GC has not yet been performed. Stall until it is and
1017 // then retry the allocation.
1018 GCLocker::stall_until_clear();
1019 (*gclocker_retry_count_ret) += 1;
1020 }
1021
1022 // We can reach here if we were unsuccessful in scheduling a
1023 // collection (because another thread beat us to it) or if we were
1024 // stalled due to the GC locker. In either can we should retry the
1025 // allocation attempt in case another thread successfully
1026 // performed a collection and reclaimed enough space. Give a
1027 // warning if we seem to be looping forever.
1028
1029 if ((QueuedAllocationWarningCount > 0) &&
1030 (try_count % QueuedAllocationWarningCount == 0)) {
1031 log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() "
1032 "retries %d times", try_count);
1033 }
1034 }
1035
1036 ShouldNotReachHere();
1037 return NULL;
1038 }
1039
1040 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1041 AllocationContext_t context,
1042 bool expect_null_mutator_alloc_region) {
1043 assert_at_safepoint(true /* should_be_vm_thread */);
1044 assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region,
1045 "the current alloc region was unexpectedly found to be non-NULL");
1046
1047 if (!is_humongous(word_size)) {
1048 return _allocator->attempt_allocation_locked(word_size, context);
1049 } else {
1050 HeapWord* result = humongous_obj_allocate(word_size, context);
1051 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1052 collector_state()->set_initiate_conc_mark_if_possible(true);
1053 }
1054 return result;
1055 }
1056
1057 ShouldNotReachHere();
1058 }
1059
1060 class PostCompactionPrinterClosure: public HeapRegionClosure {
1061 private:
1062 G1HRPrinter* _hr_printer;
1063 public:
1064 bool doHeapRegion(HeapRegion* hr) {
1065 assert(!hr->is_young(), "not expecting to find young regions");
1066 _hr_printer->post_compaction(hr);
1067 return false;
1068 }
1069
1070 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1071 : _hr_printer(hr_printer) { }
1072 };
1073
1074 void G1CollectedHeap::print_hrm_post_compaction() {
1075 if (_hr_printer.is_active()) {
1076 PostCompactionPrinterClosure cl(hr_printer());
1077 heap_region_iterate(&cl);
1078 }
1079
1080 }
1081
1082 void G1CollectedHeap::abort_concurrent_cycle() {
1083 // Note: When we have a more flexible GC logging framework that
1084 // allows us to add optional attributes to a GC log record we
1085 // could consider timing and reporting how long we wait in the
1086 // following two methods.
1087 wait_while_free_regions_coming();
1088 // If we start the compaction before the CM threads finish
1089 // scanning the root regions we might trip them over as we'll
1090 // be moving objects / updating references. So let's wait until
1091 // they are done. By telling them to abort, they should complete
1092 // early.
1093 _cm->root_regions()->abort();
1094 _cm->root_regions()->wait_until_scan_finished();
1095 append_secondary_free_list_if_not_empty_with_lock();
1096
1097 // Disable discovery and empty the discovered lists
1098 // for the CM ref processor.
1099 ref_processor_cm()->disable_discovery();
1100 ref_processor_cm()->abandon_partial_discovery();
1101 ref_processor_cm()->verify_no_references_recorded();
1102
1103 // Abandon current iterations of concurrent marking and concurrent
1104 // refinement, if any are in progress.
1105 concurrent_mark()->abort();
1106 }
1107
1108 void G1CollectedHeap::prepare_heap_for_full_collection() {
1109 // Make sure we'll choose a new allocation region afterwards.
1110 _allocator->release_mutator_alloc_region();
1111 _allocator->abandon_gc_alloc_regions();
1112 g1_rem_set()->cleanupHRRS();
1113
1114 // We may have added regions to the current incremental collection
1115 // set between the last GC or pause and now. We need to clear the
1116 // incremental collection set and then start rebuilding it afresh
1117 // after this full GC.
1118 abandon_collection_set(collection_set());
1119
1120 tear_down_region_sets(false /* free_list_only */);
1121 collector_state()->set_gcs_are_young(true);
1122 }
1123
1124 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) {
1125 assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1126 assert(used() == recalculate_used(), "Should be equal");
1127 _verifier->verify_region_sets_optional();
1128 _verifier->verify_before_gc();
1129 _verifier->check_bitmaps("Full GC Start");
1130 }
1131
1132 void G1CollectedHeap::prepare_heap_for_mutators() {
1133 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1134 ClassLoaderDataGraph::purge();
1135 MetaspaceAux::verify_metrics();
1136
1137 // Prepare heap for normal collections.
1138 assert(num_free_regions() == 0, "we should not have added any free regions");
1139 rebuild_region_sets(false /* free_list_only */);
1140 abort_refinement();
1141 resize_if_necessary_after_full_collection();
1142
1143 // Rebuild the strong code root lists for each region
1144 rebuild_strong_code_roots();
1145
1146 // Start a new incremental collection set for the next pause
1147 start_new_collection_set();
1148
1149 _allocator->init_mutator_alloc_region();
1150
1151 // Post collection state updates.
1152 MetaspaceGC::compute_new_size();
1153 }
1154
1155 void G1CollectedHeap::abort_refinement() {
1156 if (_hot_card_cache->use_cache()) {
1157 _hot_card_cache->reset_card_counts();
1158 _hot_card_cache->reset_hot_cache();
1159 }
1160
1161 // Discard all remembered set updates.
1162 JavaThread::dirty_card_queue_set().abandon_logs();
1163 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1164 }
1165
1166 void G1CollectedHeap::verify_after_full_collection() {
1167 check_gc_time_stamps();
1168 _hrm.verify_optional();
1169 _verifier->verify_region_sets_optional();
1170 _verifier->verify_after_gc();
1171 // Clear the previous marking bitmap, if needed for bitmap verification.
1172 // Note we cannot do this when we clear the next marking bitmap in
1173 // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1174 // objects marked during a full GC against the previous bitmap.
1175 // But we need to clear it before calling check_bitmaps below since
1176 // the full GC has compacted objects and updated TAMS but not updated
1177 // the prev bitmap.
1178 if (G1VerifyBitmaps) {
1179 GCTraceTime(Debug, gc)("Clear Bitmap for Verification");
1180 _cm->clear_prev_bitmap(workers());
1181 }
1182 _verifier->check_bitmaps("Full GC End");
1183
1184 // At this point there should be no regions in the
1185 // entire heap tagged as young.
1186 assert(check_young_list_empty(), "young list should be empty at this point");
1187
1188 // Note: since we've just done a full GC, concurrent
1189 // marking is no longer active. Therefore we need not
1190 // re-enable reference discovery for the CM ref processor.
1191 // That will be done at the start of the next marking cycle.
1192 // We also know that the STW processor should no longer
1193 // discover any new references.
1194 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1195 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1196 ref_processor_stw()->verify_no_references_recorded();
1197 ref_processor_cm()->verify_no_references_recorded();
1198 }
1199
1200 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) {
1201 print_hrm_post_compaction();
1202 heap_transition->print();
1203 print_heap_after_gc();
1204 print_heap_regions();
1205 #ifdef TRACESPINNING
1206 ParallelTaskTerminator::print_termination_counts();
1207 #endif
1208 }
1209
1210 void G1CollectedHeap::do_full_collection_inner(G1FullGCScope* scope) {
1211 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1212 g1_policy()->record_full_collection_start();
1213
1214 print_heap_before_gc();
1215 print_heap_regions();
1216
1217 abort_concurrent_cycle();
1218 verify_before_full_collection(scope->is_explicit_gc());
1219
1220 gc_prologue(true);
1221 prepare_heap_for_full_collection();
1222
1223 {
1224 G1FullCollector collector(scope, ref_processor_stw(), concurrent_mark()->nextMarkBitMap(), workers()->active_workers());
1225 // Prepare collection by putting reference processor
1226 // in a correct state.
1227 collector.prepare_collection();
1228
1229 // Do the actual collection.
1230 collector.collect();
1231
1232 collector.complete_collection();
1233 }
1234
1235 prepare_heap_for_mutators();
1236
1237 g1_policy()->record_full_collection_end();
1238 gc_epilogue(true);
1239
1240 // Post collection verification.
1241 verify_after_full_collection();
1242
1243 // Post collection logging.
1244 // We should do this after we potentially resize the heap so
1245 // that all the COMMIT / UNCOMMIT events are generated before
1246 // the compaction events.
1247 print_heap_after_full_collection(scope->heap_transition());
1248 }
1249 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1250 bool clear_all_soft_refs) {
1251 assert_at_safepoint(true /* should_be_vm_thread */);
1252
1253 if (GCLocker::check_active_before_gc()) {
1254 // Full GC was not completed.
1255 return false;
1256 }
1257
1258 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1259 collector_policy()->should_clear_all_soft_refs();
1260
1261 G1FullGCScope scope(explicit_gc, do_clear_all_soft_refs);
1262 do_full_collection_inner(&scope);
1263
1264 // Full collection was successfully completed.
1265 return true;
1266 }
1267
1268 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1269 // Currently, there is no facility in the do_full_collection(bool) API to notify
1270 // the caller that the collection did not succeed (e.g., because it was locked
1271 // out by the GC locker). So, right now, we'll ignore the return value.
1272 bool dummy = do_full_collection(true, /* explicit_gc */
1273 clear_all_soft_refs);
1274 }
1275
1276 void G1CollectedHeap::resize_if_necessary_after_full_collection() {
1277 // Include bytes that will be pre-allocated to support collections, as "used".
1278 const size_t used_after_gc = used();
1279 const size_t capacity_after_gc = capacity();
1280 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1281
1282 // This is enforced in arguments.cpp.
1283 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1284 "otherwise the code below doesn't make sense");
1285
1286 // We don't have floating point command-line arguments
1287 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1288 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1289 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1290 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1291
1292 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1293 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1294
1295 // We have to be careful here as these two calculations can overflow
1296 // 32-bit size_t's.
1297 double used_after_gc_d = (double) used_after_gc;
1298 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1299 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1300
1301 // Let's make sure that they are both under the max heap size, which
1302 // by default will make them fit into a size_t.
1303 double desired_capacity_upper_bound = (double) max_heap_size;
1304 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1305 desired_capacity_upper_bound);
1306 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1307 desired_capacity_upper_bound);
1308
1309 // We can now safely turn them into size_t's.
1310 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1311 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1312
1313 // This assert only makes sense here, before we adjust them
1314 // with respect to the min and max heap size.
1315 assert(minimum_desired_capacity <= maximum_desired_capacity,
1316 "minimum_desired_capacity = " SIZE_FORMAT ", "
1317 "maximum_desired_capacity = " SIZE_FORMAT,
1318 minimum_desired_capacity, maximum_desired_capacity);
1319
1320 // Should not be greater than the heap max size. No need to adjust
1321 // it with respect to the heap min size as it's a lower bound (i.e.,
1322 // we'll try to make the capacity larger than it, not smaller).
1323 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1324 // Should not be less than the heap min size. No need to adjust it
1325 // with respect to the heap max size as it's an upper bound (i.e.,
1326 // we'll try to make the capacity smaller than it, not greater).
1327 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1328
1329 if (capacity_after_gc < minimum_desired_capacity) {
1330 // Don't expand unless it's significant
1331 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1332
1333 log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). "
1334 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1335 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio);
1336
1337 expand(expand_bytes, _workers);
1338
1339 // No expansion, now see if we want to shrink
1340 } else if (capacity_after_gc > maximum_desired_capacity) {
1341 // Capacity too large, compute shrinking size
1342 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1343
1344 log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). "
1345 "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1346 capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio);
1347
1348 shrink(shrink_bytes);
1349 }
1350 }
1351
1352 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1353 AllocationContext_t context,
1354 bool do_gc,
1355 bool clear_all_soft_refs,
1356 bool expect_null_mutator_alloc_region,
1357 bool* gc_succeeded) {
1358 *gc_succeeded = true;
1359 // Let's attempt the allocation first.
1360 HeapWord* result =
1361 attempt_allocation_at_safepoint(word_size,
1362 context,
1363 expect_null_mutator_alloc_region);
1364 if (result != NULL) {
1365 assert(*gc_succeeded, "sanity");
1366 return result;
1367 }
1368
1369 // In a G1 heap, we're supposed to keep allocation from failing by
1370 // incremental pauses. Therefore, at least for now, we'll favor
1371 // expansion over collection. (This might change in the future if we can
1372 // do something smarter than full collection to satisfy a failed alloc.)
1373 result = expand_and_allocate(word_size, context);
1374 if (result != NULL) {
1375 assert(*gc_succeeded, "sanity");
1376 return result;
1377 }
1378
1379 if (do_gc) {
1380 // Expansion didn't work, we'll try to do a Full GC.
1381 *gc_succeeded = do_full_collection(false, /* explicit_gc */
1382 clear_all_soft_refs);
1383 }
1384
1385 return NULL;
1386 }
1387
1388 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1389 AllocationContext_t context,
1390 bool* succeeded) {
1391 assert_at_safepoint(true /* should_be_vm_thread */);
1392
1393 // Attempts to allocate followed by Full GC.
1394 HeapWord* result =
1395 satisfy_failed_allocation_helper(word_size,
1396 context,
1397 true, /* do_gc */
1398 false, /* clear_all_soft_refs */
1399 false, /* expect_null_mutator_alloc_region */
1400 succeeded);
1401
1402 if (result != NULL || !*succeeded) {
1403 return result;
1404 }
1405
1406 // Attempts to allocate followed by Full GC that will collect all soft references.
1407 result = satisfy_failed_allocation_helper(word_size,
1408 context,
1409 true, /* do_gc */
1410 true, /* clear_all_soft_refs */
1411 true, /* expect_null_mutator_alloc_region */
1412 succeeded);
1413
1414 if (result != NULL || !*succeeded) {
1415 return result;
1416 }
1417
1418 // Attempts to allocate, no GC
1419 result = satisfy_failed_allocation_helper(word_size,
1420 context,
1421 false, /* do_gc */
1422 false, /* clear_all_soft_refs */
1423 true, /* expect_null_mutator_alloc_region */
1424 succeeded);
1425
1426 if (result != NULL) {
1427 assert(*succeeded, "sanity");
1428 return result;
1429 }
1430
1431 assert(!collector_policy()->should_clear_all_soft_refs(),
1432 "Flag should have been handled and cleared prior to this point");
1433
1434 // What else? We might try synchronous finalization later. If the total
1435 // space available is large enough for the allocation, then a more
1436 // complete compaction phase than we've tried so far might be
1437 // appropriate.
1438 assert(*succeeded, "sanity");
1439 return NULL;
1440 }
1441
1442 // Attempting to expand the heap sufficiently
1443 // to support an allocation of the given "word_size". If
1444 // successful, perform the allocation and return the address of the
1445 // allocated block, or else "NULL".
1446
1447 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1448 assert_at_safepoint(true /* should_be_vm_thread */);
1449
1450 _verifier->verify_region_sets_optional();
1451
1452 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1453 log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1454 word_size * HeapWordSize);
1455
1456
1457 if (expand(expand_bytes, _workers)) {
1458 _hrm.verify_optional();
1459 _verifier->verify_region_sets_optional();
1460 return attempt_allocation_at_safepoint(word_size,
1461 context,
1462 false /* expect_null_mutator_alloc_region */);
1463 }
1464 return NULL;
1465 }
1466
1467 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) {
1468 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1469 aligned_expand_bytes = align_up(aligned_expand_bytes,
1470 HeapRegion::GrainBytes);
1471
1472 log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B",
1473 expand_bytes, aligned_expand_bytes);
1474
1475 if (is_maximal_no_gc()) {
1476 log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1477 return false;
1478 }
1479
1480 double expand_heap_start_time_sec = os::elapsedTime();
1481 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1482 assert(regions_to_expand > 0, "Must expand by at least one region");
1483
1484 uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers);
1485 if (expand_time_ms != NULL) {
1486 *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1487 }
1488
1489 if (expanded_by > 0) {
1490 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1491 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1492 g1_policy()->record_new_heap_size(num_regions());
1493 } else {
1494 log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1495
1496 // The expansion of the virtual storage space was unsuccessful.
1497 // Let's see if it was because we ran out of swap.
1498 if (G1ExitOnExpansionFailure &&
1499 _hrm.available() >= regions_to_expand) {
1500 // We had head room...
1501 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1502 }
1503 }
1504 return regions_to_expand > 0;
1505 }
1506
1507 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1508 size_t aligned_shrink_bytes =
1509 ReservedSpace::page_align_size_down(shrink_bytes);
1510 aligned_shrink_bytes = align_down(aligned_shrink_bytes,
1511 HeapRegion::GrainBytes);
1512 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1513
1514 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1515 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1516
1517
1518 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",
1519 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1520 if (num_regions_removed > 0) {
1521 g1_policy()->record_new_heap_size(num_regions());
1522 } else {
1523 log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1524 }
1525 }
1526
1527 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1528 _verifier->verify_region_sets_optional();
1529
1530 // We should only reach here at the end of a Full GC which means we
1531 // should not not be holding to any GC alloc regions. The method
1532 // below will make sure of that and do any remaining clean up.
1533 _allocator->abandon_gc_alloc_regions();
1534
1535 // Instead of tearing down / rebuilding the free lists here, we
1536 // could instead use the remove_all_pending() method on free_list to
1537 // remove only the ones that we need to remove.
1538 tear_down_region_sets(true /* free_list_only */);
1539 shrink_helper(shrink_bytes);
1540 rebuild_region_sets(true /* free_list_only */);
1541
1542 _hrm.verify_optional();
1543 _verifier->verify_region_sets_optional();
1544 }
1545
1546 // Public methods.
1547
1548 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) :
1549 CollectedHeap(),
1550 _collector_policy(collector_policy),
1551 _g1_policy(create_g1_policy()),
1552 _collection_set(this, _g1_policy),
1553 _dirty_card_queue_set(false),
1554 _is_alive_closure_cm(this),
1555 _is_alive_closure_stw(this),
1556 _ref_processor_cm(NULL),
1557 _ref_processor_stw(NULL),
1558 _bot(NULL),
1559 _hot_card_cache(NULL),
1560 _g1_rem_set(NULL),
1561 _cg1r(NULL),
1562 _g1mm(NULL),
1563 _preserved_marks_set(true /* in_c_heap */),
1564 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1565 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1566 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1567 _humongous_reclaim_candidates(),
1568 _has_humongous_reclaim_candidates(false),
1569 _archive_allocator(NULL),
1570 _free_regions_coming(false),
1571 _gc_time_stamp(0),
1572 _summary_bytes_used(0),
1573 _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1574 _old_evac_stats("Old", OldPLABSize, PLABWeight),
1575 _expand_heap_after_alloc_failure(true),
1576 _old_marking_cycles_started(0),
1577 _old_marking_cycles_completed(0),
1578 _in_cset_fast_test(),
1579 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1580 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()) {
1581
1582 _workers = new WorkGang("GC Thread", ParallelGCThreads,
1583 /* are_GC_task_threads */true,
1584 /* are_ConcurrentGC_threads */false);
1585 _workers->initialize_workers();
1586 _verifier = new G1HeapVerifier(this);
1587
1588 _allocator = G1Allocator::create_allocator(this);
1589
1590 _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics());
1591
1592 _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1593
1594 // Override the default _filler_array_max_size so that no humongous filler
1595 // objects are created.
1596 _filler_array_max_size = _humongous_object_threshold_in_words;
1597
1598 uint n_queues = ParallelGCThreads;
1599 _task_queues = new RefToScanQueueSet(n_queues);
1600
1601 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1602
1603 for (uint i = 0; i < n_queues; i++) {
1604 RefToScanQueue* q = new RefToScanQueue();
1605 q->initialize();
1606 _task_queues->register_queue(i, q);
1607 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1608 }
1609
1610 // Initialize the G1EvacuationFailureALot counters and flags.
1611 NOT_PRODUCT(reset_evacuation_should_fail();)
1612
1613 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1614 }
1615
1616 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1617 size_t size,
1618 size_t translation_factor) {
1619 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1620 // Allocate a new reserved space, preferring to use large pages.
1621 ReservedSpace rs(size, preferred_page_size);
1622 G1RegionToSpaceMapper* result =
1623 G1RegionToSpaceMapper::create_mapper(rs,
1624 size,
1625 rs.alignment(),
1626 HeapRegion::GrainBytes,
1627 translation_factor,
1628 mtGC);
1629
1630 os::trace_page_sizes_for_requested_size(description,
1631 size,
1632 preferred_page_size,
1633 rs.alignment(),
1634 rs.base(),
1635 rs.size());
1636
1637 return result;
1638 }
1639
1640 jint G1CollectedHeap::initialize_concurrent_refinement() {
1641 jint ecode = JNI_OK;
1642 _cg1r = ConcurrentG1Refine::create(&ecode);
1643 return ecode;
1644 }
1645
1646 jint G1CollectedHeap::initialize() {
1647 CollectedHeap::pre_initialize();
1648 os::enable_vtime();
1649
1650 // Necessary to satisfy locking discipline assertions.
1651
1652 MutexLocker x(Heap_lock);
1653
1654 // While there are no constraints in the GC code that HeapWordSize
1655 // be any particular value, there are multiple other areas in the
1656 // system which believe this to be true (e.g. oop->object_size in some
1657 // cases incorrectly returns the size in wordSize units rather than
1658 // HeapWordSize).
1659 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1660
1661 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1662 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1663 size_t heap_alignment = collector_policy()->heap_alignment();
1664
1665 // Ensure that the sizes are properly aligned.
1666 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1667 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1668 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1669
1670 // Reserve the maximum.
1671
1672 // When compressed oops are enabled, the preferred heap base
1673 // is calculated by subtracting the requested size from the
1674 // 32Gb boundary and using the result as the base address for
1675 // heap reservation. If the requested size is not aligned to
1676 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1677 // into the ReservedHeapSpace constructor) then the actual
1678 // base of the reserved heap may end up differing from the
1679 // address that was requested (i.e. the preferred heap base).
1680 // If this happens then we could end up using a non-optimal
1681 // compressed oops mode.
1682
1683 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1684 heap_alignment);
1685
1686 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1687
1688 // Create the barrier set for the entire reserved region.
1689 G1SATBCardTableLoggingModRefBS* bs
1690 = new G1SATBCardTableLoggingModRefBS(reserved_region());
1691 bs->initialize();
1692 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity");
1693 set_barrier_set(bs);
1694
1695 // Create the hot card cache.
1696 _hot_card_cache = new G1HotCardCache(this);
1697
1698 // Carve out the G1 part of the heap.
1699 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1700 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
1701 G1RegionToSpaceMapper* heap_storage =
1702 G1RegionToSpaceMapper::create_mapper(g1_rs,
1703 g1_rs.size(),
1704 page_size,
1705 HeapRegion::GrainBytes,
1706 1,
1707 mtJavaHeap);
1708 os::trace_page_sizes("Heap",
1709 collector_policy()->min_heap_byte_size(),
1710 max_byte_size,
1711 page_size,
1712 heap_rs.base(),
1713 heap_rs.size());
1714 heap_storage->set_mapping_changed_listener(&_listener);
1715
1716 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1717 G1RegionToSpaceMapper* bot_storage =
1718 create_aux_memory_mapper("Block Offset Table",
1719 G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1720 G1BlockOffsetTable::heap_map_factor());
1721
1722 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
1723 G1RegionToSpaceMapper* cardtable_storage =
1724 create_aux_memory_mapper("Card Table",
1725 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize),
1726 G1SATBCardTableLoggingModRefBS::heap_map_factor());
1727
1728 G1RegionToSpaceMapper* card_counts_storage =
1729 create_aux_memory_mapper("Card Counts Table",
1730 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1731 G1CardCounts::heap_map_factor());
1732
1733 size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1734 G1RegionToSpaceMapper* prev_bitmap_storage =
1735 create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1736 G1RegionToSpaceMapper* next_bitmap_storage =
1737 create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1738
1739 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1740 g1_barrier_set()->initialize(cardtable_storage);
1741 // Do later initialization work for concurrent refinement.
1742 _hot_card_cache->initialize(card_counts_storage);
1743
1744 // 6843694 - ensure that the maximum region index can fit
1745 // in the remembered set structures.
1746 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1747 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1748
1749 // Also create a G1 rem set.
1750 _g1_rem_set = new G1RemSet(this, g1_barrier_set(), _hot_card_cache);
1751 _g1_rem_set->initialize(max_capacity(), max_regions());
1752
1753 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1754 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1755 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1756 "too many cards per region");
1757
1758 FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1759
1760 _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1761
1762 {
1763 HeapWord* start = _hrm.reserved().start();
1764 HeapWord* end = _hrm.reserved().end();
1765 size_t granularity = HeapRegion::GrainBytes;
1766
1767 _in_cset_fast_test.initialize(start, end, granularity);
1768 _humongous_reclaim_candidates.initialize(start, end, granularity);
1769 }
1770
1771 // Create the G1ConcurrentMark data structure and thread.
1772 // (Must do this late, so that "max_regions" is defined.)
1773 _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1774 if (_cm == NULL || !_cm->completed_initialization()) {
1775 vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
1776 return JNI_ENOMEM;
1777 }
1778 _cmThread = _cm->cmThread();
1779
1780 // Now expand into the initial heap size.
1781 if (!expand(init_byte_size, _workers)) {
1782 vm_shutdown_during_initialization("Failed to allocate initial heap.");
1783 return JNI_ENOMEM;
1784 }
1785
1786 // Perform any initialization actions delegated to the policy.
1787 g1_policy()->init(this, &_collection_set);
1788
1789 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1790 SATB_Q_FL_lock,
1791 G1SATBProcessCompletedThreshold,
1792 Shared_SATB_Q_lock);
1793
1794 jint ecode = initialize_concurrent_refinement();
1795 if (ecode != JNI_OK) {
1796 return ecode;
1797 }
1798
1799 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1800 DirtyCardQ_FL_lock,
1801 (int)concurrent_g1_refine()->yellow_zone(),
1802 (int)concurrent_g1_refine()->red_zone(),
1803 Shared_DirtyCardQ_lock,
1804 NULL, // fl_owner
1805 true); // init_free_ids
1806
1807 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1808 DirtyCardQ_FL_lock,
1809 -1, // never trigger processing
1810 -1, // no limit on length
1811 Shared_DirtyCardQ_lock,
1812 &JavaThread::dirty_card_queue_set());
1813
1814 // Here we allocate the dummy HeapRegion that is required by the
1815 // G1AllocRegion class.
1816 HeapRegion* dummy_region = _hrm.get_dummy_region();
1817
1818 // We'll re-use the same region whether the alloc region will
1819 // require BOT updates or not and, if it doesn't, then a non-young
1820 // region will complain that it cannot support allocations without
1821 // BOT updates. So we'll tag the dummy region as eden to avoid that.
1822 dummy_region->set_eden();
1823 // Make sure it's full.
1824 dummy_region->set_top(dummy_region->end());
1825 G1AllocRegion::setup(this, dummy_region);
1826
1827 _allocator->init_mutator_alloc_region();
1828
1829 // Do create of the monitoring and management support so that
1830 // values in the heap have been properly initialized.
1831 _g1mm = new G1MonitoringSupport(this);
1832
1833 G1StringDedup::initialize();
1834
1835 _preserved_marks_set.init(ParallelGCThreads);
1836
1837 _collection_set.initialize(max_regions());
1838
1839 return JNI_OK;
1840 }
1841
1842 void G1CollectedHeap::stop() {
1843 // Stop all concurrent threads. We do this to make sure these threads
1844 // do not continue to execute and access resources (e.g. logging)
1845 // that are destroyed during shutdown.
1846 _cg1r->stop();
1847 _cmThread->stop();
1848 if (G1StringDedup::is_enabled()) {
1849 G1StringDedup::stop();
1850 }
1851 }
1852
1853 size_t G1CollectedHeap::conservative_max_heap_alignment() {
1854 return HeapRegion::max_region_size();
1855 }
1856
1857 void G1CollectedHeap::post_initialize() {
1858 ref_processing_init();
1859 }
1860
1861 void G1CollectedHeap::ref_processing_init() {
1862 // Reference processing in G1 currently works as follows:
1863 //
1864 // * There are two reference processor instances. One is
1865 // used to record and process discovered references
1866 // during concurrent marking; the other is used to
1867 // record and process references during STW pauses
1868 // (both full and incremental).
1869 // * Both ref processors need to 'span' the entire heap as
1870 // the regions in the collection set may be dotted around.
1871 //
1872 // * For the concurrent marking ref processor:
1873 // * Reference discovery is enabled at initial marking.
1874 // * Reference discovery is disabled and the discovered
1875 // references processed etc during remarking.
1876 // * Reference discovery is MT (see below).
1877 // * Reference discovery requires a barrier (see below).
1878 // * Reference processing may or may not be MT
1879 // (depending on the value of ParallelRefProcEnabled
1880 // and ParallelGCThreads).
1881 // * A full GC disables reference discovery by the CM
1882 // ref processor and abandons any entries on it's
1883 // discovered lists.
1884 //
1885 // * For the STW processor:
1886 // * Non MT discovery is enabled at the start of a full GC.
1887 // * Processing and enqueueing during a full GC is non-MT.
1888 // * During a full GC, references are processed after marking.
1889 //
1890 // * Discovery (may or may not be MT) is enabled at the start
1891 // of an incremental evacuation pause.
1892 // * References are processed near the end of a STW evacuation pause.
1893 // * For both types of GC:
1894 // * Discovery is atomic - i.e. not concurrent.
1895 // * Reference discovery will not need a barrier.
1896
1897 MemRegion mr = reserved_region();
1898
1899 // Concurrent Mark ref processor
1900 _ref_processor_cm =
1901 new ReferenceProcessor(mr, // span
1902 ParallelRefProcEnabled && (ParallelGCThreads > 1),
1903 // mt processing
1904 ParallelGCThreads,
1905 // degree of mt processing
1906 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
1907 // mt discovery
1908 MAX2(ParallelGCThreads, ConcGCThreads),
1909 // degree of mt discovery
1910 false,
1911 // Reference discovery is not atomic
1912 &_is_alive_closure_cm);
1913 // is alive closure
1914 // (for efficiency/performance)
1915
1916 // STW ref processor
1917 _ref_processor_stw =
1918 new ReferenceProcessor(mr, // span
1919 ParallelRefProcEnabled && (ParallelGCThreads > 1),
1920 // mt processing
1921 ParallelGCThreads,
1922 // degree of mt processing
1923 (ParallelGCThreads > 1),
1924 // mt discovery
1925 ParallelGCThreads,
1926 // degree of mt discovery
1927 true,
1928 // Reference discovery is atomic
1929 &_is_alive_closure_stw);
1930 // is alive closure
1931 // (for efficiency/performance)
1932 }
1933
1934 CollectorPolicy* G1CollectedHeap::collector_policy() const {
1935 return _collector_policy;
1936 }
1937
1938 size_t G1CollectedHeap::capacity() const {
1939 return _hrm.length() * HeapRegion::GrainBytes;
1940 }
1941
1942 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
1943 hr->reset_gc_time_stamp();
1944 }
1945
1946 #ifndef PRODUCT
1947
1948 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
1949 private:
1950 unsigned _gc_time_stamp;
1951 bool _failures;
1952
1953 public:
1954 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
1955 _gc_time_stamp(gc_time_stamp), _failures(false) { }
1956
1957 virtual bool doHeapRegion(HeapRegion* hr) {
1958 unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
1959 if (_gc_time_stamp != region_gc_time_stamp) {
1960 log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr),
1961 region_gc_time_stamp, _gc_time_stamp);
1962 _failures = true;
1963 }
1964 return false;
1965 }
1966
1967 bool failures() { return _failures; }
1968 };
1969
1970 void G1CollectedHeap::check_gc_time_stamps() {
1971 CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
1972 heap_region_iterate(&cl);
1973 guarantee(!cl.failures(), "all GC time stamps should have been reset");
1974 }
1975 #endif // PRODUCT
1976
1977 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) {
1978 _hot_card_cache->drain(cl, worker_i);
1979 }
1980
1981 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) {
1982 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
1983 size_t n_completed_buffers = 0;
1984 while (dcqs.apply_closure_during_gc(cl, worker_i)) {
1985 n_completed_buffers++;
1986 }
1987 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
1988 dcqs.clear_n_completed_buffers();
1989 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
1990 }
1991
1992 // Computes the sum of the storage used by the various regions.
1993 size_t G1CollectedHeap::used() const {
1994 size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
1995 if (_archive_allocator != NULL) {
1996 result += _archive_allocator->used();
1997 }
1998 return result;
1999 }
2000
2001 size_t G1CollectedHeap::used_unlocked() const {
2002 return _summary_bytes_used;
2003 }
2004
2005 class SumUsedClosure: public HeapRegionClosure {
2006 size_t _used;
2007 public:
2008 SumUsedClosure() : _used(0) {}
2009 bool doHeapRegion(HeapRegion* r) {
2010 _used += r->used();
2011 return false;
2012 }
2013 size_t result() { return _used; }
2014 };
2015
2016 size_t G1CollectedHeap::recalculate_used() const {
2017 double recalculate_used_start = os::elapsedTime();
2018
2019 SumUsedClosure blk;
2020 heap_region_iterate(&blk);
2021
2022 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2023 return blk.result();
2024 }
2025
2026 bool G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
2027 switch (cause) {
2028 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2029 case GCCause::_dcmd_gc_run: return ExplicitGCInvokesConcurrent;
2030 case GCCause::_update_allocation_context_stats_inc: return true;
2031 case GCCause::_wb_conc_mark: return true;
2032 default : return false;
2033 }
2034 }
2035
2036 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2037 switch (cause) {
2038 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2039 case GCCause::_g1_humongous_allocation: return true;
2040 default: return is_user_requested_concurrent_full_gc(cause);
2041 }
2042 }
2043
2044 #ifndef PRODUCT
2045 void G1CollectedHeap::allocate_dummy_regions() {
2046 // Let's fill up most of the region
2047 size_t word_size = HeapRegion::GrainWords - 1024;
2048 // And as a result the region we'll allocate will be humongous.
2049 guarantee(is_humongous(word_size), "sanity");
2050
2051 // _filler_array_max_size is set to humongous object threshold
2052 // but temporarily change it to use CollectedHeap::fill_with_object().
2053 SizeTFlagSetting fs(_filler_array_max_size, word_size);
2054
2055 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2056 // Let's use the existing mechanism for the allocation
2057 HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2058 AllocationContext::system());
2059 if (dummy_obj != NULL) {
2060 MemRegion mr(dummy_obj, word_size);
2061 CollectedHeap::fill_with_object(mr);
2062 } else {
2063 // If we can't allocate once, we probably cannot allocate
2064 // again. Let's get out of the loop.
2065 break;
2066 }
2067 }
2068 }
2069 #endif // !PRODUCT
2070
2071 void G1CollectedHeap::increment_old_marking_cycles_started() {
2072 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2073 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2074 "Wrong marking cycle count (started: %d, completed: %d)",
2075 _old_marking_cycles_started, _old_marking_cycles_completed);
2076
2077 _old_marking_cycles_started++;
2078 }
2079
2080 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2081 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2082
2083 // We assume that if concurrent == true, then the caller is a
2084 // concurrent thread that was joined the Suspendible Thread
2085 // Set. If there's ever a cheap way to check this, we should add an
2086 // assert here.
2087
2088 // Given that this method is called at the end of a Full GC or of a
2089 // concurrent cycle, and those can be nested (i.e., a Full GC can
2090 // interrupt a concurrent cycle), the number of full collections
2091 // completed should be either one (in the case where there was no
2092 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2093 // behind the number of full collections started.
2094
2095 // This is the case for the inner caller, i.e. a Full GC.
2096 assert(concurrent ||
2097 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2098 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2099 "for inner caller (Full GC): _old_marking_cycles_started = %u "
2100 "is inconsistent with _old_marking_cycles_completed = %u",
2101 _old_marking_cycles_started, _old_marking_cycles_completed);
2102
2103 // This is the case for the outer caller, i.e. the concurrent cycle.
2104 assert(!concurrent ||
2105 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2106 "for outer caller (concurrent cycle): "
2107 "_old_marking_cycles_started = %u "
2108 "is inconsistent with _old_marking_cycles_completed = %u",
2109 _old_marking_cycles_started, _old_marking_cycles_completed);
2110
2111 _old_marking_cycles_completed += 1;
2112
2113 // We need to clear the "in_progress" flag in the CM thread before
2114 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2115 // is set) so that if a waiter requests another System.gc() it doesn't
2116 // incorrectly see that a marking cycle is still in progress.
2117 if (concurrent) {
2118 _cmThread->set_idle();
2119 }
2120
2121 // This notify_all() will ensure that a thread that called
2122 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2123 // and it's waiting for a full GC to finish will be woken up. It is
2124 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2125 FullGCCount_lock->notify_all();
2126 }
2127
2128 void G1CollectedHeap::collect(GCCause::Cause cause) {
2129 assert_heap_not_locked();
2130
2131 uint gc_count_before;
2132 uint old_marking_count_before;
2133 uint full_gc_count_before;
2134 bool retry_gc;
2135
2136 do {
2137 retry_gc = false;
2138
2139 {
2140 MutexLocker ml(Heap_lock);
2141
2142 // Read the GC count while holding the Heap_lock
2143 gc_count_before = total_collections();
2144 full_gc_count_before = total_full_collections();
2145 old_marking_count_before = _old_marking_cycles_started;
2146 }
2147
2148 if (should_do_concurrent_full_gc(cause)) {
2149 // Schedule an initial-mark evacuation pause that will start a
2150 // concurrent cycle. We're setting word_size to 0 which means that
2151 // we are not requesting a post-GC allocation.
2152 VM_G1IncCollectionPause op(gc_count_before,
2153 0, /* word_size */
2154 true, /* should_initiate_conc_mark */
2155 g1_policy()->max_pause_time_ms(),
2156 cause);
2157 op.set_allocation_context(AllocationContext::current());
2158
2159 VMThread::execute(&op);
2160 if (!op.pause_succeeded()) {
2161 if (old_marking_count_before == _old_marking_cycles_started) {
2162 retry_gc = op.should_retry_gc();
2163 } else {
2164 // A Full GC happened while we were trying to schedule the
2165 // initial-mark GC. No point in starting a new cycle given
2166 // that the whole heap was collected anyway.
2167 }
2168
2169 if (retry_gc) {
2170 if (GCLocker::is_active_and_needs_gc()) {
2171 GCLocker::stall_until_clear();
2172 }
2173 }
2174 }
2175 } else {
2176 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2177 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2178
2179 // Schedule a standard evacuation pause. We're setting word_size
2180 // to 0 which means that we are not requesting a post-GC allocation.
2181 VM_G1IncCollectionPause op(gc_count_before,
2182 0, /* word_size */
2183 false, /* should_initiate_conc_mark */
2184 g1_policy()->max_pause_time_ms(),
2185 cause);
2186 VMThread::execute(&op);
2187 } else {
2188 // Schedule a Full GC.
2189 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2190 VMThread::execute(&op);
2191 }
2192 }
2193 } while (retry_gc);
2194 }
2195
2196 bool G1CollectedHeap::is_in(const void* p) const {
2197 if (_hrm.reserved().contains(p)) {
2198 // Given that we know that p is in the reserved space,
2199 // heap_region_containing() should successfully
2200 // return the containing region.
2201 HeapRegion* hr = heap_region_containing(p);
2202 return hr->is_in(p);
2203 } else {
2204 return false;
2205 }
2206 }
2207
2208 #ifdef ASSERT
2209 bool G1CollectedHeap::is_in_exact(const void* p) const {
2210 bool contains = reserved_region().contains(p);
2211 bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2212 if (contains && available) {
2213 return true;
2214 } else {
2215 return false;
2216 }
2217 }
2218 #endif
2219
2220 // Iteration functions.
2221
2222 // Iterates an ObjectClosure over all objects within a HeapRegion.
2223
2224 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2225 ObjectClosure* _cl;
2226 public:
2227 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2228 bool doHeapRegion(HeapRegion* r) {
2229 if (!r->is_continues_humongous()) {
2230 r->object_iterate(_cl);
2231 }
2232 return false;
2233 }
2234 };
2235
2236 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2237 IterateObjectClosureRegionClosure blk(cl);
2238 heap_region_iterate(&blk);
2239 }
2240
2241 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2242 _hrm.iterate(cl);
2243 }
2244
2245 void G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl,
2246 uint worker_id,
2247 HeapRegionClaimerBase *hrclaimer) const {
2248 _hrm.par_iterate(cl, worker_id, hrclaimer);
2249 }
2250
2251 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2252 _collection_set.iterate(cl);
2253 }
2254
2255 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) {
2256 _collection_set.iterate_from(cl, worker_id, workers()->active_workers());
2257 }
2258
2259 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2260 HeapRegion* hr = heap_region_containing(addr);
2261 return hr->block_start(addr);
2262 }
2263
2264 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2265 HeapRegion* hr = heap_region_containing(addr);
2266 return hr->block_size(addr);
2267 }
2268
2269 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2270 HeapRegion* hr = heap_region_containing(addr);
2271 return hr->block_is_obj(addr);
2272 }
2273
2274 bool G1CollectedHeap::supports_tlab_allocation() const {
2275 return true;
2276 }
2277
2278 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2279 return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2280 }
2281
2282 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2283 return _eden.length() * HeapRegion::GrainBytes;
2284 }
2285
2286 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2287 // must be equal to the humongous object limit.
2288 size_t G1CollectedHeap::max_tlab_size() const {
2289 return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
2290 }
2291
2292 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2293 AllocationContext_t context = AllocationContext::current();
2294 return _allocator->unsafe_max_tlab_alloc(context);
2295 }
2296
2297 size_t G1CollectedHeap::max_capacity() const {
2298 return _hrm.reserved().byte_size();
2299 }
2300
2301 jlong G1CollectedHeap::millis_since_last_gc() {
2302 // See the notes in GenCollectedHeap::millis_since_last_gc()
2303 // for more information about the implementation.
2304 jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) -
2305 _g1_policy->collection_pause_end_millis();
2306 if (ret_val < 0) {
2307 log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
2308 ". returning zero instead.", ret_val);
2309 return 0;
2310 }
2311 return ret_val;
2312 }
2313
2314 void G1CollectedHeap::prepare_for_verify() {
2315 _verifier->prepare_for_verify();
2316 }
2317
2318 void G1CollectedHeap::verify(VerifyOption vo) {
2319 _verifier->verify(vo);
2320 }
2321
2322 bool G1CollectedHeap::supports_concurrent_phase_control() const {
2323 return true;
2324 }
2325
2326 const char* const* G1CollectedHeap::concurrent_phases() const {
2327 return _cmThread->concurrent_phases();
2328 }
2329
2330 bool G1CollectedHeap::request_concurrent_phase(const char* phase) {
2331 return _cmThread->request_concurrent_phase(phase);
2332 }
2333
2334 class PrintRegionClosure: public HeapRegionClosure {
2335 outputStream* _st;
2336 public:
2337 PrintRegionClosure(outputStream* st) : _st(st) {}
2338 bool doHeapRegion(HeapRegion* r) {
2339 r->print_on(_st);
2340 return false;
2341 }
2342 };
2343
2344 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2345 const HeapRegion* hr,
2346 const VerifyOption vo) const {
2347 switch (vo) {
2348 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2349 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2350 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked() && !hr->is_archive();
2351 default: ShouldNotReachHere();
2352 }
2353 return false; // keep some compilers happy
2354 }
2355
2356 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2357 const VerifyOption vo) const {
2358 switch (vo) {
2359 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2360 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2361 case VerifyOption_G1UseMarkWord: {
2362 HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj);
2363 return !obj->is_gc_marked() && !hr->is_archive();
2364 }
2365 default: ShouldNotReachHere();
2366 }
2367 return false; // keep some compilers happy
2368 }
2369
2370 void G1CollectedHeap::print_heap_regions() const {
2371 Log(gc, heap, region) log;
2372 if (log.is_trace()) {
2373 ResourceMark rm;
2374 print_regions_on(log.trace_stream());
2375 }
2376 }
2377
2378 void G1CollectedHeap::print_on(outputStream* st) const {
2379 st->print(" %-20s", "garbage-first heap");
2380 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2381 capacity()/K, used_unlocked()/K);
2382 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")",
2383 p2i(_hrm.reserved().start()),
2384 p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords),
2385 p2i(_hrm.reserved().end()));
2386 st->cr();
2387 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2388 uint young_regions = young_regions_count();
2389 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2390 (size_t) young_regions * HeapRegion::GrainBytes / K);
2391 uint survivor_regions = survivor_regions_count();
2392 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2393 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2394 st->cr();
2395 MetaspaceAux::print_on(st);
2396 }
2397
2398 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2399 st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2400 "HS=humongous(starts), HC=humongous(continues), "
2401 "CS=collection set, F=free, A=archive, TS=gc time stamp, "
2402 "AC=allocation context, "
2403 "TAMS=top-at-mark-start (previous, next)");
2404 PrintRegionClosure blk(st);
2405 heap_region_iterate(&blk);
2406 }
2407
2408 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2409 print_on(st);
2410
2411 // Print the per-region information.
2412 print_regions_on(st);
2413 }
2414
2415 void G1CollectedHeap::print_on_error(outputStream* st) const {
2416 this->CollectedHeap::print_on_error(st);
2417
2418 if (_cm != NULL) {
2419 st->cr();
2420 _cm->print_on_error(st);
2421 }
2422 }
2423
2424 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2425 workers()->print_worker_threads_on(st);
2426 _cmThread->print_on(st);
2427 st->cr();
2428 _cm->print_worker_threads_on(st);
2429 _cg1r->print_worker_threads_on(st); // also prints the sample thread
2430 if (G1StringDedup::is_enabled()) {
2431 G1StringDedup::print_worker_threads_on(st);
2432 }
2433 }
2434
2435 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2436 workers()->threads_do(tc);
2437 tc->do_thread(_cmThread);
2438 _cm->threads_do(tc);
2439 _cg1r->threads_do(tc); // also iterates over the sample thread
2440 if (G1StringDedup::is_enabled()) {
2441 G1StringDedup::threads_do(tc);
2442 }
2443 }
2444
2445 void G1CollectedHeap::print_tracing_info() const {
2446 g1_rem_set()->print_summary_info();
2447 concurrent_mark()->print_summary_info();
2448 }
2449
2450 #ifndef PRODUCT
2451 // Helpful for debugging RSet issues.
2452
2453 class PrintRSetsClosure : public HeapRegionClosure {
2454 private:
2455 const char* _msg;
2456 size_t _occupied_sum;
2457
2458 public:
2459 bool doHeapRegion(HeapRegion* r) {
2460 HeapRegionRemSet* hrrs = r->rem_set();
2461 size_t occupied = hrrs->occupied();
2462 _occupied_sum += occupied;
2463
2464 tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2465 if (occupied == 0) {
2466 tty->print_cr(" RSet is empty");
2467 } else {
2468 hrrs->print();
2469 }
2470 tty->print_cr("----------");
2471 return false;
2472 }
2473
2474 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2475 tty->cr();
2476 tty->print_cr("========================================");
2477 tty->print_cr("%s", msg);
2478 tty->cr();
2479 }
2480
2481 ~PrintRSetsClosure() {
2482 tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2483 tty->print_cr("========================================");
2484 tty->cr();
2485 }
2486 };
2487
2488 void G1CollectedHeap::print_cset_rsets() {
2489 PrintRSetsClosure cl("Printing CSet RSets");
2490 collection_set_iterate(&cl);
2491 }
2492
2493 void G1CollectedHeap::print_all_rsets() {
2494 PrintRSetsClosure cl("Printing All RSets");;
2495 heap_region_iterate(&cl);
2496 }
2497 #endif // PRODUCT
2498
2499 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2500
2501 size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes;
2502 size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes;
2503 size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2504
2505 size_t eden_capacity_bytes =
2506 (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2507
2508 VirtualSpaceSummary heap_summary = create_heap_space_summary();
2509 return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2510 eden_capacity_bytes, survivor_used_bytes, num_regions());
2511 }
2512
2513 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2514 return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2515 stats->unused(), stats->used(), stats->region_end_waste(),
2516 stats->regions_filled(), stats->direct_allocated(),
2517 stats->failure_used(), stats->failure_waste());
2518 }
2519
2520 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2521 const G1HeapSummary& heap_summary = create_g1_heap_summary();
2522 gc_tracer->report_gc_heap_summary(when, heap_summary);
2523
2524 const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2525 gc_tracer->report_metaspace_summary(when, metaspace_summary);
2526 }
2527
2528 G1CollectedHeap* G1CollectedHeap::heap() {
2529 CollectedHeap* heap = Universe::heap();
2530 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2531 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap");
2532 return (G1CollectedHeap*)heap;
2533 }
2534
2535 void G1CollectedHeap::gc_prologue(bool full) {
2536 // always_do_update_barrier = false;
2537 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2538
2539 // This summary needs to be printed before incrementing total collections.
2540 g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2541
2542 // Update common counters.
2543 increment_total_collections(full /* full gc */);
2544 if (full) {
2545 increment_old_marking_cycles_started();
2546 reset_gc_time_stamp();
2547 } else {
2548 increment_gc_time_stamp();
2549 }
2550
2551 // Fill TLAB's and such
2552 double start = os::elapsedTime();
2553 accumulate_statistics_all_tlabs();
2554 ensure_parsability(true);
2555 g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2556 }
2557
2558 void G1CollectedHeap::gc_epilogue(bool full) {
2559 // Update common counters.
2560 if (full) {
2561 // Update the number of full collections that have been completed.
2562 increment_old_marking_cycles_completed(false /* concurrent */);
2563 }
2564
2565 // We are at the end of the GC. Total collections has already been increased.
2566 g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2567
2568 // FIXME: what is this about?
2569 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2570 // is set.
2571 #if defined(COMPILER2) || INCLUDE_JVMCI
2572 assert(DerivedPointerTable::is_empty(), "derived pointer present");
2573 #endif
2574 // always_do_update_barrier = true;
2575
2576 double start = os::elapsedTime();
2577 resize_all_tlabs();
2578 g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2579
2580 allocation_context_stats().update(full);
2581
2582 MemoryService::track_memory_usage();
2583 // We have just completed a GC. Update the soft reference
2584 // policy with the new heap occupancy
2585 Universe::update_heap_info_at_gc();
2586 }
2587
2588 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2589 uint gc_count_before,
2590 bool* succeeded,
2591 GCCause::Cause gc_cause) {
2592 assert_heap_not_locked_and_not_at_safepoint();
2593 VM_G1IncCollectionPause op(gc_count_before,
2594 word_size,
2595 false, /* should_initiate_conc_mark */
2596 g1_policy()->max_pause_time_ms(),
2597 gc_cause);
2598
2599 op.set_allocation_context(AllocationContext::current());
2600 VMThread::execute(&op);
2601
2602 HeapWord* result = op.result();
2603 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
2604 assert(result == NULL || ret_succeeded,
2605 "the result should be NULL if the VM did not succeed");
2606 *succeeded = ret_succeeded;
2607
2608 assert_heap_not_locked();
2609 return result;
2610 }
2611
2612 void
2613 G1CollectedHeap::doConcurrentMark() {
2614 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
2615 if (!_cmThread->in_progress()) {
2616 _cmThread->set_started();
2617 CGC_lock->notify();
2618 }
2619 }
2620
2621 size_t G1CollectedHeap::pending_card_num() {
2622 size_t extra_cards = 0;
2623 JavaThread *curr = Threads::first();
2624 while (curr != NULL) {
2625 DirtyCardQueue& dcq = curr->dirty_card_queue();
2626 extra_cards += dcq.size();
2627 curr = curr->next();
2628 }
2629 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2630 size_t buffer_size = dcqs.buffer_size();
2631 size_t buffer_num = dcqs.completed_buffers_num();
2632
2633 return buffer_size * buffer_num + extra_cards;
2634 }
2635
2636 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
2637 private:
2638 size_t _total_humongous;
2639 size_t _candidate_humongous;
2640
2641 DirtyCardQueue _dcq;
2642
2643 // We don't nominate objects with many remembered set entries, on
2644 // the assumption that such objects are likely still live.
2645 bool is_remset_small(HeapRegion* region) const {
2646 HeapRegionRemSet* const rset = region->rem_set();
2647 return G1EagerReclaimHumongousObjectsWithStaleRefs
2648 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)
2649 : rset->is_empty();
2650 }
2651
2652 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const {
2653 assert(region->is_starts_humongous(), "Must start a humongous object");
2654
2655 oop obj = oop(region->bottom());
2656
2657 // Dead objects cannot be eager reclaim candidates. Due to class
2658 // unloading it is unsafe to query their classes so we return early.
2659 if (heap->is_obj_dead(obj, region)) {
2660 return false;
2661 }
2662
2663 // Candidate selection must satisfy the following constraints
2664 // while concurrent marking is in progress:
2665 //
2666 // * In order to maintain SATB invariants, an object must not be
2667 // reclaimed if it was allocated before the start of marking and
2668 // has not had its references scanned. Such an object must have
2669 // its references (including type metadata) scanned to ensure no
2670 // live objects are missed by the marking process. Objects
2671 // allocated after the start of concurrent marking don't need to
2672 // be scanned.
2673 //
2674 // * An object must not be reclaimed if it is on the concurrent
2675 // mark stack. Objects allocated after the start of concurrent
2676 // marking are never pushed on the mark stack.
2677 //
2678 // Nominating only objects allocated after the start of concurrent
2679 // marking is sufficient to meet both constraints. This may miss
2680 // some objects that satisfy the constraints, but the marking data
2681 // structures don't support efficiently performing the needed
2682 // additional tests or scrubbing of the mark stack.
2683 //
2684 // However, we presently only nominate is_typeArray() objects.
2685 // A humongous object containing references induces remembered
2686 // set entries on other regions. In order to reclaim such an
2687 // object, those remembered sets would need to be cleaned up.
2688 //
2689 // We also treat is_typeArray() objects specially, allowing them
2690 // to be reclaimed even if allocated before the start of
2691 // concurrent mark. For this we rely on mark stack insertion to
2692 // exclude is_typeArray() objects, preventing reclaiming an object
2693 // that is in the mark stack. We also rely on the metadata for
2694 // such objects to be built-in and so ensured to be kept live.
2695 // Frequent allocation and drop of large binary blobs is an
2696 // important use case for eager reclaim, and this special handling
2697 // may reduce needed headroom.
2698
2699 return obj->is_typeArray() && is_remset_small(region);
2700 }
2701
2702 public:
2703 RegisterHumongousWithInCSetFastTestClosure()
2704 : _total_humongous(0),
2705 _candidate_humongous(0),
2706 _dcq(&JavaThread::dirty_card_queue_set()) {
2707 }
2708
2709 virtual bool doHeapRegion(HeapRegion* r) {
2710 if (!r->is_starts_humongous()) {
2711 return false;
2712 }
2713 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2714
2715 bool is_candidate = humongous_region_is_candidate(g1h, r);
2716 uint rindex = r->hrm_index();
2717 g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
2718 if (is_candidate) {
2719 _candidate_humongous++;
2720 g1h->register_humongous_region_with_cset(rindex);
2721 // Is_candidate already filters out humongous object with large remembered sets.
2722 // If we have a humongous object with a few remembered sets, we simply flush these
2723 // remembered set entries into the DCQS. That will result in automatic
2724 // re-evaluation of their remembered set entries during the following evacuation
2725 // phase.
2726 if (!r->rem_set()->is_empty()) {
2727 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
2728 "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
2729 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
2730 HeapRegionRemSetIterator hrrs(r->rem_set());
2731 size_t card_index;
2732 while (hrrs.has_next(card_index)) {
2733 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
2734 // The remembered set might contain references to already freed
2735 // regions. Filter out such entries to avoid failing card table
2736 // verification.
2737 if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) {
2738 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
2739 *card_ptr = CardTableModRefBS::dirty_card_val();
2740 _dcq.enqueue(card_ptr);
2741 }
2742 }
2743 }
2744 assert(hrrs.n_yielded() == r->rem_set()->occupied(),
2745 "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
2746 hrrs.n_yielded(), r->rem_set()->occupied());
2747 r->rem_set()->clear_locked();
2748 }
2749 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
2750 }
2751 _total_humongous++;
2752
2753 return false;
2754 }
2755
2756 size_t total_humongous() const { return _total_humongous; }
2757 size_t candidate_humongous() const { return _candidate_humongous; }
2758
2759 void flush_rem_set_entries() { _dcq.flush(); }
2760 };
2761
2762 void G1CollectedHeap::register_humongous_regions_with_cset() {
2763 if (!G1EagerReclaimHumongousObjects) {
2764 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
2765 return;
2766 }
2767 double time = os::elapsed_counter();
2768
2769 // Collect reclaim candidate information and register candidates with cset.
2770 RegisterHumongousWithInCSetFastTestClosure cl;
2771 heap_region_iterate(&cl);
2772
2773 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
2774 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
2775 cl.total_humongous(),
2776 cl.candidate_humongous());
2777 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
2778
2779 // Finally flush all remembered set entries to re-check into the global DCQS.
2780 cl.flush_rem_set_entries();
2781 }
2782
2783 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2784 public:
2785 bool doHeapRegion(HeapRegion* hr) {
2786 if (!hr->is_archive() && !hr->is_continues_humongous()) {
2787 hr->verify_rem_set();
2788 }
2789 return false;
2790 }
2791 };
2792
2793 uint G1CollectedHeap::num_task_queues() const {
2794 return _task_queues->size();
2795 }
2796
2797 #if TASKQUEUE_STATS
2798 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2799 st->print_raw_cr("GC Task Stats");
2800 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2801 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2802 }
2803
2804 void G1CollectedHeap::print_taskqueue_stats() const {
2805 if (!log_is_enabled(Trace, gc, task, stats)) {
2806 return;
2807 }
2808 Log(gc, task, stats) log;
2809 ResourceMark rm;
2810 outputStream* st = log.trace_stream();
2811
2812 print_taskqueue_stats_hdr(st);
2813
2814 TaskQueueStats totals;
2815 const uint n = num_task_queues();
2816 for (uint i = 0; i < n; ++i) {
2817 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2818 totals += task_queue(i)->stats;
2819 }
2820 st->print_raw("tot "); totals.print(st); st->cr();
2821
2822 DEBUG_ONLY(totals.verify());
2823 }
2824
2825 void G1CollectedHeap::reset_taskqueue_stats() {
2826 const uint n = num_task_queues();
2827 for (uint i = 0; i < n; ++i) {
2828 task_queue(i)->stats.reset();
2829 }
2830 }
2831 #endif // TASKQUEUE_STATS
2832
2833 void G1CollectedHeap::wait_for_root_region_scanning() {
2834 double scan_wait_start = os::elapsedTime();
2835 // We have to wait until the CM threads finish scanning the
2836 // root regions as it's the only way to ensure that all the
2837 // objects on them have been correctly scanned before we start
2838 // moving them during the GC.
2839 bool waited = _cm->root_regions()->wait_until_scan_finished();
2840 double wait_time_ms = 0.0;
2841 if (waited) {
2842 double scan_wait_end = os::elapsedTime();
2843 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2844 }
2845 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2846 }
2847
2848 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2849 private:
2850 G1HRPrinter* _hr_printer;
2851 public:
2852 G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2853
2854 virtual bool doHeapRegion(HeapRegion* r) {
2855 _hr_printer->cset(r);
2856 return false;
2857 }
2858 };
2859
2860 void G1CollectedHeap::start_new_collection_set() {
2861 collection_set()->start_incremental_building();
2862
2863 clear_cset_fast_test();
2864
2865 guarantee(_eden.length() == 0, "eden should have been cleared");
2866 g1_policy()->transfer_survivors_to_cset(survivor());
2867 }
2868
2869 bool
2870 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
2871 assert_at_safepoint(true /* should_be_vm_thread */);
2872 guarantee(!is_gc_active(), "collection is not reentrant");
2873
2874 if (GCLocker::check_active_before_gc()) {
2875 return false;
2876 }
2877
2878 _gc_timer_stw->register_gc_start();
2879
2880 GCIdMark gc_id_mark;
2881 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
2882
2883 SvcGCMarker sgcm(SvcGCMarker::MINOR);
2884 ResourceMark rm;
2885
2886 g1_policy()->note_gc_start();
2887
2888 wait_for_root_region_scanning();
2889
2890 print_heap_before_gc();
2891 print_heap_regions();
2892 trace_heap_before_gc(_gc_tracer_stw);
2893
2894 _verifier->verify_region_sets_optional();
2895 _verifier->verify_dirty_young_regions();
2896
2897 // We should not be doing initial mark unless the conc mark thread is running
2898 if (!_cmThread->should_terminate()) {
2899 // This call will decide whether this pause is an initial-mark
2900 // pause. If it is, during_initial_mark_pause() will return true
2901 // for the duration of this pause.
2902 g1_policy()->decide_on_conc_mark_initiation();
2903 }
2904
2905 // We do not allow initial-mark to be piggy-backed on a mixed GC.
2906 assert(!collector_state()->during_initial_mark_pause() ||
2907 collector_state()->gcs_are_young(), "sanity");
2908
2909 // We also do not allow mixed GCs during marking.
2910 assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity");
2911
2912 // Record whether this pause is an initial mark. When the current
2913 // thread has completed its logging output and it's safe to signal
2914 // the CM thread, the flag's value in the policy has been reset.
2915 bool should_start_conc_mark = collector_state()->during_initial_mark_pause();
2916
2917 // Inner scope for scope based logging, timers, and stats collection
2918 {
2919 EvacuationInfo evacuation_info;
2920
2921 if (collector_state()->during_initial_mark_pause()) {
2922 // We are about to start a marking cycle, so we increment the
2923 // full collection counter.
2924 increment_old_marking_cycles_started();
2925 _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
2926 }
2927
2928 _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
2929
2930 GCTraceCPUTime tcpu;
2931
2932 FormatBuffer<> gc_string("Pause ");
2933 if (collector_state()->during_initial_mark_pause()) {
2934 gc_string.append("Initial Mark");
2935 } else if (collector_state()->gcs_are_young()) {
2936 gc_string.append("Young");
2937 } else {
2938 gc_string.append("Mixed");
2939 }
2940 GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true);
2941
2942 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
2943 workers()->active_workers(),
2944 Threads::number_of_non_daemon_threads());
2945 workers()->update_active_workers(active_workers);
2946 log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
2947
2948 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
2949 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
2950
2951 // If the secondary_free_list is not empty, append it to the
2952 // free_list. No need to wait for the cleanup operation to finish;
2953 // the region allocation code will check the secondary_free_list
2954 // and wait if necessary. If the G1StressConcRegionFreeing flag is
2955 // set, skip this step so that the region allocation code has to
2956 // get entries from the secondary_free_list.
2957 if (!G1StressConcRegionFreeing) {
2958 append_secondary_free_list_if_not_empty_with_lock();
2959 }
2960
2961 G1HeapTransition heap_transition(this);
2962 size_t heap_used_bytes_before_gc = used();
2963
2964 // Don't dynamically change the number of GC threads this early. A value of
2965 // 0 is used to indicate serial work. When parallel work is done,
2966 // it will be set.
2967
2968 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
2969 IsGCActiveMark x;
2970
2971 gc_prologue(false);
2972
2973 if (VerifyRememberedSets) {
2974 log_info(gc, verify)("[Verifying RemSets before GC]");
2975 VerifyRegionRemSetClosure v_cl;
2976 heap_region_iterate(&v_cl);
2977 }
2978
2979 _verifier->verify_before_gc();
2980
2981 _verifier->check_bitmaps("GC Start");
2982
2983 #if defined(COMPILER2) || INCLUDE_JVMCI
2984 DerivedPointerTable::clear();
2985 #endif
2986
2987 // Please see comment in g1CollectedHeap.hpp and
2988 // G1CollectedHeap::ref_processing_init() to see how
2989 // reference processing currently works in G1.
2990
2991 // Enable discovery in the STW reference processor
2992 if (g1_policy()->should_process_references()) {
2993 ref_processor_stw()->enable_discovery();
2994 } else {
2995 ref_processor_stw()->disable_discovery();
2996 }
2997
2998 {
2999 // We want to temporarily turn off discovery by the
3000 // CM ref processor, if necessary, and turn it back on
3001 // on again later if we do. Using a scoped
3002 // NoRefDiscovery object will do this.
3003 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3004
3005 // Forget the current alloc region (we might even choose it to be part
3006 // of the collection set!).
3007 _allocator->release_mutator_alloc_region();
3008
3009 // This timing is only used by the ergonomics to handle our pause target.
3010 // It is unclear why this should not include the full pause. We will
3011 // investigate this in CR 7178365.
3012 //
3013 // Preserving the old comment here if that helps the investigation:
3014 //
3015 // The elapsed time induced by the start time below deliberately elides
3016 // the possible verification above.
3017 double sample_start_time_sec = os::elapsedTime();
3018
3019 g1_policy()->record_collection_pause_start(sample_start_time_sec);
3020
3021 if (collector_state()->during_initial_mark_pause()) {
3022 concurrent_mark()->checkpointRootsInitialPre();
3023 }
3024
3025 g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor);
3026
3027 evacuation_info.set_collectionset_regions(collection_set()->region_length());
3028
3029 // Make sure the remembered sets are up to date. This needs to be
3030 // done before register_humongous_regions_with_cset(), because the
3031 // remembered sets are used there to choose eager reclaim candidates.
3032 // If the remembered sets are not up to date we might miss some
3033 // entries that need to be handled.
3034 g1_rem_set()->cleanupHRRS();
3035
3036 register_humongous_regions_with_cset();
3037
3038 assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table.");
3039
3040 // We call this after finalize_cset() to
3041 // ensure that the CSet has been finalized.
3042 _cm->verify_no_cset_oops();
3043
3044 if (_hr_printer.is_active()) {
3045 G1PrintCollectionSetClosure cl(&_hr_printer);
3046 _collection_set.iterate(&cl);
3047 }
3048
3049 // Initialize the GC alloc regions.
3050 _allocator->init_gc_alloc_regions(evacuation_info);
3051
3052 G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length());
3053 pre_evacuate_collection_set();
3054
3055 // Actually do the work...
3056 evacuate_collection_set(evacuation_info, &per_thread_states);
3057
3058 post_evacuate_collection_set(evacuation_info, &per_thread_states);
3059
3060 const size_t* surviving_young_words = per_thread_states.surviving_young_words();
3061 free_collection_set(&_collection_set, evacuation_info, surviving_young_words);
3062
3063 eagerly_reclaim_humongous_regions();
3064
3065 record_obj_copy_mem_stats();
3066 _survivor_evac_stats.adjust_desired_plab_sz();
3067 _old_evac_stats.adjust_desired_plab_sz();
3068
3069 double start = os::elapsedTime();
3070 start_new_collection_set();
3071 g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0);
3072
3073 if (evacuation_failed()) {
3074 set_used(recalculate_used());
3075 if (_archive_allocator != NULL) {
3076 _archive_allocator->clear_used();
3077 }
3078 for (uint i = 0; i < ParallelGCThreads; i++) {
3079 if (_evacuation_failed_info_array[i].has_failed()) {
3080 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3081 }
3082 }
3083 } else {
3084 // The "used" of the the collection set have already been subtracted
3085 // when they were freed. Add in the bytes evacuated.
3086 increase_used(g1_policy()->bytes_copied_during_gc());
3087 }
3088
3089 if (collector_state()->during_initial_mark_pause()) {
3090 // We have to do this before we notify the CM threads that
3091 // they can start working to make sure that all the
3092 // appropriate initialization is done on the CM object.
3093 concurrent_mark()->checkpointRootsInitialPost();
3094 collector_state()->set_mark_in_progress(true);
3095 // Note that we don't actually trigger the CM thread at
3096 // this point. We do that later when we're sure that
3097 // the current thread has completed its logging output.
3098 }
3099
3100 allocate_dummy_regions();
3101
3102 _allocator->init_mutator_alloc_region();
3103
3104 {
3105 size_t expand_bytes = _heap_sizing_policy->expansion_amount();
3106 if (expand_bytes > 0) {
3107 size_t bytes_before = capacity();
3108 // No need for an ergo logging here,
3109 // expansion_amount() does this when it returns a value > 0.
3110 double expand_ms;
3111 if (!expand(expand_bytes, _workers, &expand_ms)) {
3112 // We failed to expand the heap. Cannot do anything about it.
3113 }
3114 g1_policy()->phase_times()->record_expand_heap_time(expand_ms);
3115 }
3116 }
3117
3118 // We redo the verification but now wrt to the new CSet which
3119 // has just got initialized after the previous CSet was freed.
3120 _cm->verify_no_cset_oops();
3121
3122 // This timing is only used by the ergonomics to handle our pause target.
3123 // It is unclear why this should not include the full pause. We will
3124 // investigate this in CR 7178365.
3125 double sample_end_time_sec = os::elapsedTime();
3126 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3127 size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards);
3128 g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc);
3129
3130 evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
3131 evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc());
3132
3133 if (VerifyRememberedSets) {
3134 log_info(gc, verify)("[Verifying RemSets after GC]");
3135 VerifyRegionRemSetClosure v_cl;
3136 heap_region_iterate(&v_cl);
3137 }
3138
3139 _verifier->verify_after_gc();
3140 _verifier->check_bitmaps("GC End");
3141
3142 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3143 ref_processor_stw()->verify_no_references_recorded();
3144
3145 // CM reference discovery will be re-enabled if necessary.
3146 }
3147
3148 #ifdef TRACESPINNING
3149 ParallelTaskTerminator::print_termination_counts();
3150 #endif
3151
3152 gc_epilogue(false);
3153 }
3154
3155 // Print the remainder of the GC log output.
3156 if (evacuation_failed()) {
3157 log_info(gc)("To-space exhausted");
3158 }
3159
3160 g1_policy()->print_phases();
3161 heap_transition.print();
3162
3163 // It is not yet to safe to tell the concurrent mark to
3164 // start as we have some optional output below. We don't want the
3165 // output from the concurrent mark thread interfering with this
3166 // logging output either.
3167
3168 _hrm.verify_optional();
3169 _verifier->verify_region_sets_optional();
3170
3171 TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3172 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3173
3174 print_heap_after_gc();
3175 print_heap_regions();
3176 trace_heap_after_gc(_gc_tracer_stw);
3177
3178 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3179 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3180 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3181 // before any GC notifications are raised.
3182 g1mm()->update_sizes();
3183
3184 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3185 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
3186 _gc_timer_stw->register_gc_end();
3187 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3188 }
3189 // It should now be safe to tell the concurrent mark thread to start
3190 // without its logging output interfering with the logging output
3191 // that came from the pause.
3192
3193 if (should_start_conc_mark) {
3194 // CAUTION: after the doConcurrentMark() call below,
3195 // the concurrent marking thread(s) could be running
3196 // concurrently with us. Make sure that anything after
3197 // this point does not assume that we are the only GC thread
3198 // running. Note: of course, the actual marking work will
3199 // not start until the safepoint itself is released in
3200 // SuspendibleThreadSet::desynchronize().
3201 doConcurrentMark();
3202 }
3203
3204 return true;
3205 }
3206
3207 void G1CollectedHeap::remove_self_forwarding_pointers() {
3208 G1ParRemoveSelfForwardPtrsTask rsfp_task;
3209 workers()->run_task(&rsfp_task);
3210 }
3211
3212 void G1CollectedHeap::restore_after_evac_failure() {
3213 double remove_self_forwards_start = os::elapsedTime();
3214
3215 remove_self_forwarding_pointers();
3216 SharedRestorePreservedMarksTaskExecutor task_executor(workers());
3217 _preserved_marks_set.restore(&task_executor);
3218
3219 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3220 }
3221
3222 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) {
3223 if (!_evacuation_failed) {
3224 _evacuation_failed = true;
3225 }
3226
3227 _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3228 _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3229 }
3230
3231 bool G1ParEvacuateFollowersClosure::offer_termination() {
3232 G1ParScanThreadState* const pss = par_scan_state();
3233 start_term_time();
3234 const bool res = terminator()->offer_termination();
3235 end_term_time();
3236 return res;
3237 }
3238
3239 void G1ParEvacuateFollowersClosure::do_void() {
3240 G1ParScanThreadState* const pss = par_scan_state();
3241 pss->trim_queue();
3242 do {
3243 pss->steal_and_trim_queue(queues());
3244 } while (!offer_termination());
3245 }
3246
3247 class G1ParTask : public AbstractGangTask {
3248 protected:
3249 G1CollectedHeap* _g1h;
3250 G1ParScanThreadStateSet* _pss;
3251 RefToScanQueueSet* _queues;
3252 G1RootProcessor* _root_processor;
3253 ParallelTaskTerminator _terminator;
3254 uint _n_workers;
3255
3256 public:
3257 G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers)
3258 : AbstractGangTask("G1 collection"),
3259 _g1h(g1h),
3260 _pss(per_thread_states),
3261 _queues(task_queues),
3262 _root_processor(root_processor),
3263 _terminator(n_workers, _queues),
3264 _n_workers(n_workers)
3265 {}
3266
3267 void work(uint worker_id) {
3268 if (worker_id >= _n_workers) return; // no work needed this round
3269
3270 double start_sec = os::elapsedTime();
3271 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec);
3272
3273 {
3274 ResourceMark rm;
3275 HandleMark hm;
3276
3277 ReferenceProcessor* rp = _g1h->ref_processor_stw();
3278
3279 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
3280 pss->set_ref_processor(rp);
3281
3282 double start_strong_roots_sec = os::elapsedTime();
3283
3284 _root_processor->evacuate_roots(pss->closures(), worker_id);
3285
3286 // We pass a weak code blobs closure to the remembered set scanning because we want to avoid
3287 // treating the nmethods visited to act as roots for concurrent marking.
3288 // We only want to make sure that the oops in the nmethods are adjusted with regard to the
3289 // objects copied by the current evacuation.
3290 _g1h->g1_rem_set()->oops_into_collection_set_do(pss,
3291 pss->closures()->weak_codeblobs(),
3292 worker_id);
3293
3294 double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec;
3295
3296 double term_sec = 0.0;
3297 size_t evac_term_attempts = 0;
3298 {
3299 double start = os::elapsedTime();
3300 G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator);
3301 evac.do_void();
3302
3303 evac_term_attempts = evac.term_attempts();
3304 term_sec = evac.term_time();
3305 double elapsed_sec = os::elapsedTime() - start;
3306 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
3307 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
3308 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts);
3309 }
3310
3311 assert(pss->queue_is_empty(), "should be empty");
3312
3313 if (log_is_enabled(Debug, gc, task, stats)) {
3314 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3315 size_t lab_waste;
3316 size_t lab_undo_waste;
3317 pss->waste(lab_waste, lab_undo_waste);
3318 _g1h->print_termination_stats(worker_id,
3319 (os::elapsedTime() - start_sec) * 1000.0, /* elapsed time */
3320 strong_roots_sec * 1000.0, /* strong roots time */
3321 term_sec * 1000.0, /* evac term time */
3322 evac_term_attempts, /* evac term attempts */
3323 lab_waste, /* alloc buffer waste */
3324 lab_undo_waste /* undo waste */
3325 );
3326 }
3327
3328 // Close the inner scope so that the ResourceMark and HandleMark
3329 // destructors are executed here and are included as part of the
3330 // "GC Worker Time".
3331 }
3332 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
3333 }
3334 };
3335
3336 void G1CollectedHeap::print_termination_stats_hdr() {
3337 log_debug(gc, task, stats)("GC Termination Stats");
3338 log_debug(gc, task, stats)(" elapsed --strong roots-- -------termination------- ------waste (KiB)------");
3339 log_debug(gc, task, stats)("thr ms ms %% ms %% attempts total alloc undo");
3340 log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------");
3341 }
3342
3343 void G1CollectedHeap::print_termination_stats(uint worker_id,
3344 double elapsed_ms,
3345 double strong_roots_ms,
3346 double term_ms,
3347 size_t term_attempts,
3348 size_t alloc_buffer_waste,
3349 size_t undo_waste) const {
3350 log_debug(gc, task, stats)
3351 ("%3d %9.2f %9.2f %6.2f "
3352 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
3353 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
3354 worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms,
3355 term_ms, term_ms * 100 / elapsed_ms, term_attempts,
3356 (alloc_buffer_waste + undo_waste) * HeapWordSize / K,
3357 alloc_buffer_waste * HeapWordSize / K,
3358 undo_waste * HeapWordSize / K);
3359 }
3360
3361 class G1StringAndSymbolCleaningTask : public AbstractGangTask {
3362 private:
3363 BoolObjectClosure* _is_alive;
3364 G1StringDedupUnlinkOrOopsDoClosure _dedup_closure;
3365
3366 int _initial_string_table_size;
3367 int _initial_symbol_table_size;
3368
3369 bool _process_strings;
3370 int _strings_processed;
3371 int _strings_removed;
3372
3373 bool _process_symbols;
3374 int _symbols_processed;
3375 int _symbols_removed;
3376
3377 bool _process_string_dedup;
3378
3379 public:
3380 G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) :
3381 AbstractGangTask("String/Symbol Unlinking"),
3382 _is_alive(is_alive),
3383 _dedup_closure(is_alive, NULL, false),
3384 _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
3385 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0),
3386 _process_string_dedup(process_string_dedup) {
3387
3388 _initial_string_table_size = StringTable::the_table()->table_size();
3389 _initial_symbol_table_size = SymbolTable::the_table()->table_size();
3390 if (process_strings) {
3391 StringTable::clear_parallel_claimed_index();
3392 }
3393 if (process_symbols) {
3394 SymbolTable::clear_parallel_claimed_index();
3395 }
3396 }
3397
3398 ~G1StringAndSymbolCleaningTask() {
3399 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
3400 "claim value %d after unlink less than initial string table size %d",
3401 StringTable::parallel_claimed_index(), _initial_string_table_size);
3402 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
3403 "claim value %d after unlink less than initial symbol table size %d",
3404 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size);
3405
3406 log_info(gc, stringtable)(
3407 "Cleaned string and symbol table, "
3408 "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, "
3409 "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
3410 strings_processed(), strings_removed(),
3411 symbols_processed(), symbols_removed());
3412 }
3413
3414 void work(uint worker_id) {
3415 int strings_processed = 0;
3416 int strings_removed = 0;
3417 int symbols_processed = 0;
3418 int symbols_removed = 0;
3419 if (_process_strings) {
3420 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
3421 Atomic::add(strings_processed, &_strings_processed);
3422 Atomic::add(strings_removed, &_strings_removed);
3423 }
3424 if (_process_symbols) {
3425 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
3426 Atomic::add(symbols_processed, &_symbols_processed);
3427 Atomic::add(symbols_removed, &_symbols_removed);
3428 }
3429 if (_process_string_dedup) {
3430 G1StringDedup::parallel_unlink(&_dedup_closure, worker_id);
3431 }
3432 }
3433
3434 size_t strings_processed() const { return (size_t)_strings_processed; }
3435 size_t strings_removed() const { return (size_t)_strings_removed; }
3436
3437 size_t symbols_processed() const { return (size_t)_symbols_processed; }
3438 size_t symbols_removed() const { return (size_t)_symbols_removed; }
3439 };
3440
3441 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
3442 private:
3443 static Monitor* _lock;
3444
3445 BoolObjectClosure* const _is_alive;
3446 const bool _unloading_occurred;
3447 const uint _num_workers;
3448
3449 // Variables used to claim nmethods.
3450 CompiledMethod* _first_nmethod;
3451 volatile CompiledMethod* _claimed_nmethod;
3452
3453 // The list of nmethods that need to be processed by the second pass.
3454 volatile CompiledMethod* _postponed_list;
3455 volatile uint _num_entered_barrier;
3456
3457 public:
3458 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
3459 _is_alive(is_alive),
3460 _unloading_occurred(unloading_occurred),
3461 _num_workers(num_workers),
3462 _first_nmethod(NULL),
3463 _claimed_nmethod(NULL),
3464 _postponed_list(NULL),
3465 _num_entered_barrier(0)
3466 {
3467 CompiledMethod::increase_unloading_clock();
3468 // Get first alive nmethod
3469 CompiledMethodIterator iter = CompiledMethodIterator();
3470 if(iter.next_alive()) {
3471 _first_nmethod = iter.method();
3472 }
3473 _claimed_nmethod = (volatile CompiledMethod*)_first_nmethod;
3474 }
3475
3476 ~G1CodeCacheUnloadingTask() {
3477 CodeCache::verify_clean_inline_caches();
3478
3479 CodeCache::set_needs_cache_clean(false);
3480 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
3481
3482 CodeCache::verify_icholder_relocations();
3483 }
3484
3485 private:
3486 void add_to_postponed_list(CompiledMethod* nm) {
3487 CompiledMethod* old;
3488 do {
3489 old = (CompiledMethod*)_postponed_list;
3490 nm->set_unloading_next(old);
3491 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
3492 }
3493
3494 void clean_nmethod(CompiledMethod* nm) {
3495 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
3496
3497 if (postponed) {
3498 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
3499 add_to_postponed_list(nm);
3500 }
3501
3502 // Mark that this thread has been cleaned/unloaded.
3503 // After this call, it will be safe to ask if this nmethod was unloaded or not.
3504 nm->set_unloading_clock(CompiledMethod::global_unloading_clock());
3505 }
3506
3507 void clean_nmethod_postponed(CompiledMethod* nm) {
3508 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
3509 }
3510
3511 static const int MaxClaimNmethods = 16;
3512
3513 void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) {
3514 CompiledMethod* first;
3515 CompiledMethodIterator last;
3516
3517 do {
3518 *num_claimed_nmethods = 0;
3519
3520 first = (CompiledMethod*)_claimed_nmethod;
3521 last = CompiledMethodIterator(first);
3522
3523 if (first != NULL) {
3524
3525 for (int i = 0; i < MaxClaimNmethods; i++) {
3526 if (!last.next_alive()) {
3527 break;
3528 }
3529 claimed_nmethods[i] = last.method();
3530 (*num_claimed_nmethods)++;
3531 }
3532 }
3533
3534 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first);
3535 }
3536
3537 CompiledMethod* claim_postponed_nmethod() {
3538 CompiledMethod* claim;
3539 CompiledMethod* next;
3540
3541 do {
3542 claim = (CompiledMethod*)_postponed_list;
3543 if (claim == NULL) {
3544 return NULL;
3545 }
3546
3547 next = claim->unloading_next();
3548
3549 } while ((CompiledMethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
3550
3551 return claim;
3552 }
3553
3554 public:
3555 // Mark that we're done with the first pass of nmethod cleaning.
3556 void barrier_mark(uint worker_id) {
3557 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3558 _num_entered_barrier++;
3559 if (_num_entered_barrier == _num_workers) {
3560 ml.notify_all();
3561 }
3562 }
3563
3564 // See if we have to wait for the other workers to
3565 // finish their first-pass nmethod cleaning work.
3566 void barrier_wait(uint worker_id) {
3567 if (_num_entered_barrier < _num_workers) {
3568 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3569 while (_num_entered_barrier < _num_workers) {
3570 ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
3571 }
3572 }
3573 }
3574
3575 // Cleaning and unloading of nmethods. Some work has to be postponed
3576 // to the second pass, when we know which nmethods survive.
3577 void work_first_pass(uint worker_id) {
3578 // The first nmethods is claimed by the first worker.
3579 if (worker_id == 0 && _first_nmethod != NULL) {
3580 clean_nmethod(_first_nmethod);
3581 _first_nmethod = NULL;
3582 }
3583
3584 int num_claimed_nmethods;
3585 CompiledMethod* claimed_nmethods[MaxClaimNmethods];
3586
3587 while (true) {
3588 claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
3589
3590 if (num_claimed_nmethods == 0) {
3591 break;
3592 }
3593
3594 for (int i = 0; i < num_claimed_nmethods; i++) {
3595 clean_nmethod(claimed_nmethods[i]);
3596 }
3597 }
3598 }
3599
3600 void work_second_pass(uint worker_id) {
3601 CompiledMethod* nm;
3602 // Take care of postponed nmethods.
3603 while ((nm = claim_postponed_nmethod()) != NULL) {
3604 clean_nmethod_postponed(nm);
3605 }
3606 }
3607 };
3608
3609 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
3610
3611 class G1KlassCleaningTask : public StackObj {
3612 BoolObjectClosure* _is_alive;
3613 volatile jint _clean_klass_tree_claimed;
3614 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
3615
3616 public:
3617 G1KlassCleaningTask(BoolObjectClosure* is_alive) :
3618 _is_alive(is_alive),
3619 _clean_klass_tree_claimed(0),
3620 _klass_iterator() {
3621 }
3622
3623 private:
3624 bool claim_clean_klass_tree_task() {
3625 if (_clean_klass_tree_claimed) {
3626 return false;
3627 }
3628
3629 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
3630 }
3631
3632 InstanceKlass* claim_next_klass() {
3633 Klass* klass;
3634 do {
3635 klass =_klass_iterator.next_klass();
3636 } while (klass != NULL && !klass->is_instance_klass());
3637
3638 // this can be null so don't call InstanceKlass::cast
3639 return static_cast<InstanceKlass*>(klass);
3640 }
3641
3642 public:
3643
3644 void clean_klass(InstanceKlass* ik) {
3645 ik->clean_weak_instanceklass_links(_is_alive);
3646 }
3647
3648 void work() {
3649 ResourceMark rm;
3650
3651 // One worker will clean the subklass/sibling klass tree.
3652 if (claim_clean_klass_tree_task()) {
3653 Klass::clean_subklass_tree(_is_alive);
3654 }
3655
3656 // All workers will help cleaning the classes,
3657 InstanceKlass* klass;
3658 while ((klass = claim_next_klass()) != NULL) {
3659 clean_klass(klass);
3660 }
3661 }
3662 };
3663
3664 class G1ResolvedMethodCleaningTask : public StackObj {
3665 BoolObjectClosure* _is_alive;
3666 volatile jint _resolved_method_task_claimed;
3667 public:
3668 G1ResolvedMethodCleaningTask(BoolObjectClosure* is_alive) :
3669 _is_alive(is_alive), _resolved_method_task_claimed(0) {}
3670
3671 bool claim_resolved_method_task() {
3672 if (_resolved_method_task_claimed) {
3673 return false;
3674 }
3675 return Atomic::cmpxchg(1, (jint*)&_resolved_method_task_claimed, 0) == 0;
3676 }
3677
3678 // These aren't big, one thread can do it all.
3679 void work() {
3680 if (claim_resolved_method_task()) {
3681 ResolvedMethodTable::unlink(_is_alive);
3682 }
3683 }
3684 };
3685
3686
3687 // To minimize the remark pause times, the tasks below are done in parallel.
3688 class G1ParallelCleaningTask : public AbstractGangTask {
3689 private:
3690 G1StringAndSymbolCleaningTask _string_symbol_task;
3691 G1CodeCacheUnloadingTask _code_cache_task;
3692 G1KlassCleaningTask _klass_cleaning_task;
3693 G1ResolvedMethodCleaningTask _resolved_method_cleaning_task;
3694
3695 public:
3696 // The constructor is run in the VMThread.
3697 G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) :
3698 AbstractGangTask("Parallel Cleaning"),
3699 _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()),
3700 _code_cache_task(num_workers, is_alive, unloading_occurred),
3701 _klass_cleaning_task(is_alive),
3702 _resolved_method_cleaning_task(is_alive) {
3703 }
3704
3705 // The parallel work done by all worker threads.
3706 void work(uint worker_id) {
3707 // Do first pass of code cache cleaning.
3708 _code_cache_task.work_first_pass(worker_id);
3709
3710 // Let the threads mark that the first pass is done.
3711 _code_cache_task.barrier_mark(worker_id);
3712
3713 // Clean the Strings and Symbols.
3714 _string_symbol_task.work(worker_id);
3715
3716 // Clean unreferenced things in the ResolvedMethodTable
3717 _resolved_method_cleaning_task.work();
3718
3719 // Wait for all workers to finish the first code cache cleaning pass.
3720 _code_cache_task.barrier_wait(worker_id);
3721
3722 // Do the second code cache cleaning work, which realize on
3723 // the liveness information gathered during the first pass.
3724 _code_cache_task.work_second_pass(worker_id);
3725
3726 // Clean all klasses that were not unloaded.
3727 _klass_cleaning_task.work();
3728 }
3729 };
3730
3731
3732 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
3733 bool class_unloading_occurred) {
3734 uint n_workers = workers()->active_workers();
3735
3736 G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred);
3737 workers()->run_task(&g1_unlink_task);
3738 }
3739
3740 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive,
3741 bool process_strings,
3742 bool process_symbols,
3743 bool process_string_dedup) {
3744 if (!process_strings && !process_symbols && !process_string_dedup) {
3745 // Nothing to clean.
3746 return;
3747 }
3748
3749 G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup);
3750 workers()->run_task(&g1_unlink_task);
3751
3752 }
3753
3754 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3755 private:
3756 DirtyCardQueueSet* _queue;
3757 G1CollectedHeap* _g1h;
3758 public:
3759 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"),
3760 _queue(queue), _g1h(g1h) { }
3761
3762 virtual void work(uint worker_id) {
3763 G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
3764 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
3765
3766 RedirtyLoggedCardTableEntryClosure cl(_g1h);
3767 _queue->par_apply_closure_to_all_completed_buffers(&cl);
3768
3769 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3770 }
3771 };
3772
3773 void G1CollectedHeap::redirty_logged_cards() {
3774 double redirty_logged_cards_start = os::elapsedTime();
3775
3776 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this);
3777 dirty_card_queue_set().reset_for_par_iteration();
3778 workers()->run_task(&redirty_task);
3779
3780 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
3781 dcq.merge_bufferlists(&dirty_card_queue_set());
3782 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
3783
3784 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3785 }
3786
3787 // Weak Reference Processing support
3788
3789 // An always "is_alive" closure that is used to preserve referents.
3790 // If the object is non-null then it's alive. Used in the preservation
3791 // of referent objects that are pointed to by reference objects
3792 // discovered by the CM ref processor.
3793 class G1AlwaysAliveClosure: public BoolObjectClosure {
3794 G1CollectedHeap* _g1;
3795 public:
3796 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3797 bool do_object_b(oop p) {
3798 if (p != NULL) {
3799 return true;
3800 }
3801 return false;
3802 }
3803 };
3804
3805 bool G1STWIsAliveClosure::do_object_b(oop p) {
3806 // An object is reachable if it is outside the collection set,
3807 // or is inside and copied.
3808 return !_g1->is_in_cset(p) || p->is_forwarded();
3809 }
3810
3811 // Non Copying Keep Alive closure
3812 class G1KeepAliveClosure: public OopClosure {
3813 G1CollectedHeap* _g1;
3814 public:
3815 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3816 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3817 void do_oop(oop* p) {
3818 oop obj = *p;
3819 assert(obj != NULL, "the caller should have filtered out NULL values");
3820
3821 const InCSetState cset_state = _g1->in_cset_state(obj);
3822 if (!cset_state.is_in_cset_or_humongous()) {
3823 return;
3824 }
3825 if (cset_state.is_in_cset()) {
3826 assert( obj->is_forwarded(), "invariant" );
3827 *p = obj->forwardee();
3828 } else {
3829 assert(!obj->is_forwarded(), "invariant" );
3830 assert(cset_state.is_humongous(),
3831 "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value());
3832 _g1->set_humongous_is_live(obj);
3833 }
3834 }
3835 };
3836
3837 // Copying Keep Alive closure - can be called from both
3838 // serial and parallel code as long as different worker
3839 // threads utilize different G1ParScanThreadState instances
3840 // and different queues.
3841
3842 class G1CopyingKeepAliveClosure: public OopClosure {
3843 G1CollectedHeap* _g1h;
3844 OopClosure* _copy_non_heap_obj_cl;
3845 G1ParScanThreadState* _par_scan_state;
3846
3847 public:
3848 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3849 OopClosure* non_heap_obj_cl,
3850 G1ParScanThreadState* pss):
3851 _g1h(g1h),
3852 _copy_non_heap_obj_cl(non_heap_obj_cl),
3853 _par_scan_state(pss)
3854 {}
3855
3856 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3857 virtual void do_oop( oop* p) { do_oop_work(p); }
3858
3859 template <class T> void do_oop_work(T* p) {
3860 oop obj = oopDesc::load_decode_heap_oop(p);
3861
3862 if (_g1h->is_in_cset_or_humongous(obj)) {
3863 // If the referent object has been forwarded (either copied
3864 // to a new location or to itself in the event of an
3865 // evacuation failure) then we need to update the reference
3866 // field and, if both reference and referent are in the G1
3867 // heap, update the RSet for the referent.
3868 //
3869 // If the referent has not been forwarded then we have to keep
3870 // it alive by policy. Therefore we have copy the referent.
3871 //
3872 // If the reference field is in the G1 heap then we can push
3873 // on the PSS queue. When the queue is drained (after each
3874 // phase of reference processing) the object and it's followers
3875 // will be copied, the reference field set to point to the
3876 // new location, and the RSet updated. Otherwise we need to
3877 // use the the non-heap or metadata closures directly to copy
3878 // the referent object and update the pointer, while avoiding
3879 // updating the RSet.
3880
3881 if (_g1h->is_in_g1_reserved(p)) {
3882 _par_scan_state->push_on_queue(p);
3883 } else {
3884 assert(!Metaspace::contains((const void*)p),
3885 "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p));
3886 _copy_non_heap_obj_cl->do_oop(p);
3887 }
3888 }
3889 }
3890 };
3891
3892 // Serial drain queue closure. Called as the 'complete_gc'
3893 // closure for each discovered list in some of the
3894 // reference processing phases.
3895
3896 class G1STWDrainQueueClosure: public VoidClosure {
3897 protected:
3898 G1CollectedHeap* _g1h;
3899 G1ParScanThreadState* _par_scan_state;
3900
3901 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
3902
3903 public:
3904 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
3905 _g1h(g1h),
3906 _par_scan_state(pss)
3907 { }
3908
3909 void do_void() {
3910 G1ParScanThreadState* const pss = par_scan_state();
3911 pss->trim_queue();
3912 }
3913 };
3914
3915 // Parallel Reference Processing closures
3916
3917 // Implementation of AbstractRefProcTaskExecutor for parallel reference
3918 // processing during G1 evacuation pauses.
3919
3920 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
3921 private:
3922 G1CollectedHeap* _g1h;
3923 G1ParScanThreadStateSet* _pss;
3924 RefToScanQueueSet* _queues;
3925 WorkGang* _workers;
3926 uint _active_workers;
3927
3928 public:
3929 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
3930 G1ParScanThreadStateSet* per_thread_states,
3931 WorkGang* workers,
3932 RefToScanQueueSet *task_queues,
3933 uint n_workers) :
3934 _g1h(g1h),
3935 _pss(per_thread_states),
3936 _queues(task_queues),
3937 _workers(workers),
3938 _active_workers(n_workers)
3939 {
3940 g1h->ref_processor_stw()->set_active_mt_degree(n_workers);
3941 }
3942
3943 // Executes the given task using concurrent marking worker threads.
3944 virtual void execute(ProcessTask& task);
3945 virtual void execute(EnqueueTask& task);
3946 };
3947
3948 // Gang task for possibly parallel reference processing
3949
3950 class G1STWRefProcTaskProxy: public AbstractGangTask {
3951 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
3952 ProcessTask& _proc_task;
3953 G1CollectedHeap* _g1h;
3954 G1ParScanThreadStateSet* _pss;
3955 RefToScanQueueSet* _task_queues;
3956 ParallelTaskTerminator* _terminator;
3957
3958 public:
3959 G1STWRefProcTaskProxy(ProcessTask& proc_task,
3960 G1CollectedHeap* g1h,
3961 G1ParScanThreadStateSet* per_thread_states,
3962 RefToScanQueueSet *task_queues,
3963 ParallelTaskTerminator* terminator) :
3964 AbstractGangTask("Process reference objects in parallel"),
3965 _proc_task(proc_task),
3966 _g1h(g1h),
3967 _pss(per_thread_states),
3968 _task_queues(task_queues),
3969 _terminator(terminator)
3970 {}
3971
3972 virtual void work(uint worker_id) {
3973 // The reference processing task executed by a single worker.
3974 ResourceMark rm;
3975 HandleMark hm;
3976
3977 G1STWIsAliveClosure is_alive(_g1h);
3978
3979 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
3980 pss->set_ref_processor(NULL);
3981
3982 // Keep alive closure.
3983 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
3984
3985 // Complete GC closure
3986 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator);
3987
3988 // Call the reference processing task's work routine.
3989 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
3990
3991 // Note we cannot assert that the refs array is empty here as not all
3992 // of the processing tasks (specifically phase2 - pp2_work) execute
3993 // the complete_gc closure (which ordinarily would drain the queue) so
3994 // the queue may not be empty.
3995 }
3996 };
3997
3998 // Driver routine for parallel reference processing.
3999 // Creates an instance of the ref processing gang
4000 // task and has the worker threads execute it.
4001 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
4002 assert(_workers != NULL, "Need parallel worker threads.");
4003
4004 ParallelTaskTerminator terminator(_active_workers, _queues);
4005 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
4006
4007 _workers->run_task(&proc_task_proxy);
4008 }
4009
4010 // Gang task for parallel reference enqueueing.
4011
4012 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
4013 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
4014 EnqueueTask& _enq_task;
4015
4016 public:
4017 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
4018 AbstractGangTask("Enqueue reference objects in parallel"),
4019 _enq_task(enq_task)
4020 { }
4021
4022 virtual void work(uint worker_id) {
4023 _enq_task.work(worker_id);
4024 }
4025 };
4026
4027 // Driver routine for parallel reference enqueueing.
4028 // Creates an instance of the ref enqueueing gang
4029 // task and has the worker threads execute it.
4030
4031 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
4032 assert(_workers != NULL, "Need parallel worker threads.");
4033
4034 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
4035
4036 _workers->run_task(&enq_task_proxy);
4037 }
4038
4039 // End of weak reference support closures
4040
4041 // Abstract task used to preserve (i.e. copy) any referent objects
4042 // that are in the collection set and are pointed to by reference
4043 // objects discovered by the CM ref processor.
4044
4045 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
4046 protected:
4047 G1CollectedHeap* _g1h;
4048 G1ParScanThreadStateSet* _pss;
4049 RefToScanQueueSet* _queues;
4050 ParallelTaskTerminator _terminator;
4051 uint _n_workers;
4052
4053 public:
4054 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) :
4055 AbstractGangTask("ParPreserveCMReferents"),
4056 _g1h(g1h),
4057 _pss(per_thread_states),
4058 _queues(task_queues),
4059 _terminator(workers, _queues),
4060 _n_workers(workers)
4061 {
4062 g1h->ref_processor_cm()->set_active_mt_degree(workers);
4063 }
4064
4065 void work(uint worker_id) {
4066 G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id);
4067
4068 ResourceMark rm;
4069 HandleMark hm;
4070
4071 G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
4072 pss->set_ref_processor(NULL);
4073 assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4074
4075 // Is alive closure
4076 G1AlwaysAliveClosure always_alive(_g1h);
4077
4078 // Copying keep alive closure. Applied to referent objects that need
4079 // to be copied.
4080 G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4081
4082 ReferenceProcessor* rp = _g1h->ref_processor_cm();
4083
4084 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
4085 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
4086
4087 // limit is set using max_num_q() - which was set using ParallelGCThreads.
4088 // So this must be true - but assert just in case someone decides to
4089 // change the worker ids.
4090 assert(worker_id < limit, "sanity");
4091 assert(!rp->discovery_is_atomic(), "check this code");
4092
4093 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
4094 for (uint idx = worker_id; idx < limit; idx += stride) {
4095 DiscoveredList& ref_list = rp->discovered_refs()[idx];
4096
4097 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
4098 while (iter.has_next()) {
4099 // Since discovery is not atomic for the CM ref processor, we
4100 // can see some null referent objects.
4101 iter.load_ptrs(DEBUG_ONLY(true));
4102 oop ref = iter.obj();
4103
4104 // This will filter nulls.
4105 if (iter.is_referent_alive()) {
4106 iter.make_referent_alive();
4107 }
4108 iter.move_to_next();
4109 }
4110 }
4111
4112 // Drain the queue - which may cause stealing
4113 G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator);
4114 drain_queue.do_void();
4115 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
4116 assert(pss->queue_is_empty(), "should be");
4117 }
4118 };
4119
4120 void G1CollectedHeap::process_weak_jni_handles() {
4121 double ref_proc_start = os::elapsedTime();
4122
4123 G1STWIsAliveClosure is_alive(this);
4124 G1KeepAliveClosure keep_alive(this);
4125 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
4126
4127 double ref_proc_time = os::elapsedTime() - ref_proc_start;
4128 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4129 }
4130
4131 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) {
4132 // Any reference objects, in the collection set, that were 'discovered'
4133 // by the CM ref processor should have already been copied (either by
4134 // applying the external root copy closure to the discovered lists, or
4135 // by following an RSet entry).
4136 //
4137 // But some of the referents, that are in the collection set, that these
4138 // reference objects point to may not have been copied: the STW ref
4139 // processor would have seen that the reference object had already
4140 // been 'discovered' and would have skipped discovering the reference,
4141 // but would not have treated the reference object as a regular oop.
4142 // As a result the copy closure would not have been applied to the
4143 // referent object.
4144 //
4145 // We need to explicitly copy these referent objects - the references
4146 // will be processed at the end of remarking.
4147 //
4148 // We also need to do this copying before we process the reference
4149 // objects discovered by the STW ref processor in case one of these
4150 // referents points to another object which is also referenced by an
4151 // object discovered by the STW ref processor.
4152 double preserve_cm_referents_time = 0.0;
4153
4154 // To avoid spawning task when there is no work to do, check that
4155 // a concurrent cycle is active and that some references have been
4156 // discovered.
4157 if (concurrent_mark()->cmThread()->during_cycle() &&
4158 ref_processor_cm()->has_discovered_references()) {
4159 double preserve_cm_referents_start = os::elapsedTime();
4160 uint no_of_gc_workers = workers()->active_workers();
4161 G1ParPreserveCMReferentsTask keep_cm_referents(this,
4162 per_thread_states,
4163 no_of_gc_workers,
4164 _task_queues);
4165 workers()->run_task(&keep_cm_referents);
4166 preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start;
4167 }
4168
4169 g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0);
4170 }
4171
4172 // Weak Reference processing during an evacuation pause (part 1).
4173 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4174 double ref_proc_start = os::elapsedTime();
4175
4176 ReferenceProcessor* rp = _ref_processor_stw;
4177 assert(rp->discovery_enabled(), "should have been enabled");
4178
4179 // Closure to test whether a referent is alive.
4180 G1STWIsAliveClosure is_alive(this);
4181
4182 // Even when parallel reference processing is enabled, the processing
4183 // of JNI refs is serial and performed serially by the current thread
4184 // rather than by a worker. The following PSS will be used for processing
4185 // JNI refs.
4186
4187 // Use only a single queue for this PSS.
4188 G1ParScanThreadState* pss = per_thread_states->state_for_worker(0);
4189 pss->set_ref_processor(NULL);
4190 assert(pss->queue_is_empty(), "pre-condition");
4191
4192 // Keep alive closure.
4193 G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss);
4194
4195 // Serial Complete GC closure
4196 G1STWDrainQueueClosure drain_queue(this, pss);
4197
4198 // Setup the soft refs policy...
4199 rp->setup_policy(false);
4200
4201 ReferenceProcessorStats stats;
4202 if (!rp->processing_is_mt()) {
4203 // Serial reference processing...
4204 stats = rp->process_discovered_references(&is_alive,
4205 &keep_alive,
4206 &drain_queue,
4207 NULL,
4208 _gc_timer_stw);
4209 } else {
4210 uint no_of_gc_workers = workers()->active_workers();
4211
4212 // Parallel reference processing
4213 assert(no_of_gc_workers <= rp->max_num_q(),
4214 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4215 no_of_gc_workers, rp->max_num_q());
4216
4217 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers);
4218 stats = rp->process_discovered_references(&is_alive,
4219 &keep_alive,
4220 &drain_queue,
4221 &par_task_executor,
4222 _gc_timer_stw);
4223 }
4224
4225 _gc_tracer_stw->report_gc_reference_stats(stats);
4226
4227 // We have completed copying any necessary live referent objects.
4228 assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4229
4230 double ref_proc_time = os::elapsedTime() - ref_proc_start;
4231 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4232 }
4233
4234 // Weak Reference processing during an evacuation pause (part 2).
4235 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4236 double ref_enq_start = os::elapsedTime();
4237
4238 ReferenceProcessor* rp = _ref_processor_stw;
4239 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
4240
4241 // Now enqueue any remaining on the discovered lists on to
4242 // the pending list.
4243 if (!rp->processing_is_mt()) {
4244 // Serial reference processing...
4245 rp->enqueue_discovered_references();
4246 } else {
4247 // Parallel reference enqueueing
4248
4249 uint n_workers = workers()->active_workers();
4250
4251 assert(n_workers <= rp->max_num_q(),
4252 "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4253 n_workers, rp->max_num_q());
4254
4255 G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers);
4256 rp->enqueue_discovered_references(&par_task_executor);
4257 }
4258
4259 rp->verify_no_references_recorded();
4260 assert(!rp->discovery_enabled(), "should have been disabled");
4261
4262 // FIXME
4263 // CM's reference processing also cleans up the string and symbol tables.
4264 // Should we do that here also? We could, but it is a serial operation
4265 // and could significantly increase the pause time.
4266
4267 double ref_enq_time = os::elapsedTime() - ref_enq_start;
4268 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
4269 }
4270
4271 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
4272 double merge_pss_time_start = os::elapsedTime();
4273 per_thread_states->flush();
4274 g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0);
4275 }
4276
4277 void G1CollectedHeap::pre_evacuate_collection_set() {
4278 _expand_heap_after_alloc_failure = true;
4279 _evacuation_failed = false;
4280
4281 // Disable the hot card cache.
4282 _hot_card_cache->reset_hot_cache_claimed_index();
4283 _hot_card_cache->set_use_cache(false);
4284
4285 g1_rem_set()->prepare_for_oops_into_collection_set_do();
4286 _preserved_marks_set.assert_empty();
4287
4288 G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4289
4290 // InitialMark needs claim bits to keep track of the marked-through CLDs.
4291 if (collector_state()->during_initial_mark_pause()) {
4292 double start_clear_claimed_marks = os::elapsedTime();
4293
4294 ClassLoaderDataGraph::clear_claimed_marks();
4295
4296 double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
4297 phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
4298 }
4299 }
4300
4301 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4302 // Should G1EvacuationFailureALot be in effect for this GC?
4303 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
4304
4305 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
4306
4307 G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4308
4309 double start_par_time_sec = os::elapsedTime();
4310 double end_par_time_sec;
4311
4312 {
4313 const uint n_workers = workers()->active_workers();
4314 G1RootProcessor root_processor(this, n_workers);
4315 G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers);
4316
4317 print_termination_stats_hdr();
4318
4319 workers()->run_task(&g1_par_task);
4320 end_par_time_sec = os::elapsedTime();
4321
4322 // Closing the inner scope will execute the destructor
4323 // for the G1RootProcessor object. We record the current
4324 // elapsed time before closing the scope so that time
4325 // taken for the destructor is NOT included in the
4326 // reported parallel time.
4327 }
4328
4329 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
4330 phase_times->record_par_time(par_time_ms);
4331
4332 double code_root_fixup_time_ms =
4333 (os::elapsedTime() - end_par_time_sec) * 1000.0;
4334 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
4335 }
4336
4337 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4338 // Process any discovered reference objects - we have
4339 // to do this _before_ we retire the GC alloc regions
4340 // as we may have to copy some 'reachable' referent
4341 // objects (and their reachable sub-graphs) that were
4342 // not copied during the pause.
4343 if (g1_policy()->should_process_references()) {
4344 preserve_cm_referents(per_thread_states);
4345 process_discovered_references(per_thread_states);
4346 } else {
4347 ref_processor_stw()->verify_no_references_recorded();
4348 process_weak_jni_handles();
4349 }
4350
4351 if (G1StringDedup::is_enabled()) {
4352 double fixup_start = os::elapsedTime();
4353
4354 G1STWIsAliveClosure is_alive(this);
4355 G1KeepAliveClosure keep_alive(this);
4356 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times());
4357
4358 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
4359 g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
4360 }
4361
4362 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4363
4364 if (evacuation_failed()) {
4365 restore_after_evac_failure();
4366
4367 // Reset the G1EvacuationFailureALot counters and flags
4368 // Note: the values are reset only when an actual
4369 // evacuation failure occurs.
4370 NOT_PRODUCT(reset_evacuation_should_fail();)
4371 }
4372
4373 _preserved_marks_set.assert_empty();
4374
4375 // Enqueue any remaining references remaining on the STW
4376 // reference processor's discovered lists. We need to do
4377 // this after the card table is cleaned (and verified) as
4378 // the act of enqueueing entries on to the pending list
4379 // will log these updates (and dirty their associated
4380 // cards). We need these updates logged to update any
4381 // RSets.
4382 if (g1_policy()->should_process_references()) {
4383 enqueue_discovered_references(per_thread_states);
4384 } else {
4385 g1_policy()->phase_times()->record_ref_enq_time(0);
4386 }
4387
4388 _allocator->release_gc_alloc_regions(evacuation_info);
4389
4390 merge_per_thread_state_info(per_thread_states);
4391
4392 // Reset and re-enable the hot card cache.
4393 // Note the counts for the cards in the regions in the
4394 // collection set are reset when the collection set is freed.
4395 _hot_card_cache->reset_hot_cache();
4396 _hot_card_cache->set_use_cache(true);
4397
4398 purge_code_root_memory();
4399
4400 redirty_logged_cards();
4401 #if defined(COMPILER2) || INCLUDE_JVMCI
4402 double start = os::elapsedTime();
4403 DerivedPointerTable::update_pointers();
4404 g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0);
4405 #endif
4406 g1_policy()->print_age_table();
4407 }
4408
4409 void G1CollectedHeap::record_obj_copy_mem_stats() {
4410 g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4411
4412 _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4413 create_g1_evac_summary(&_old_evac_stats));
4414 }
4415
4416 void G1CollectedHeap::free_region(HeapRegion* hr,
4417 FreeRegionList* free_list,
4418 bool skip_remset,
4419 bool skip_hot_card_cache,
4420 bool locked) {
4421 assert(!hr->is_free(), "the region should not be free");
4422 assert(!hr->is_empty(), "the region should not be empty");
4423 assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
4424 assert(free_list != NULL, "pre-condition");
4425
4426 if (G1VerifyBitmaps) {
4427 MemRegion mr(hr->bottom(), hr->end());
4428 concurrent_mark()->clearRangePrevBitmap(mr);
4429 }
4430
4431 // Clear the card counts for this region.
4432 // Note: we only need to do this if the region is not young
4433 // (since we don't refine cards in young regions).
4434 if (!skip_hot_card_cache && !hr->is_young()) {
4435 _hot_card_cache->reset_card_counts(hr);
4436 }
4437 hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */);
4438 free_list->add_ordered(hr);
4439 }
4440
4441 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4442 FreeRegionList* free_list,
4443 bool skip_remset) {
4444 assert(hr->is_humongous(), "this is only for humongous regions");
4445 assert(free_list != NULL, "pre-condition");
4446 hr->clear_humongous();
4447 free_region(hr, free_list, skip_remset);
4448 }
4449
4450 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4451 const uint humongous_regions_removed) {
4452 if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4453 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4454 _old_set.bulk_remove(old_regions_removed);
4455 _humongous_set.bulk_remove(humongous_regions_removed);
4456 }
4457
4458 }
4459
4460 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4461 assert(list != NULL, "list can't be null");
4462 if (!list->is_empty()) {
4463 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4464 _hrm.insert_list_into_free_list(list);
4465 }
4466 }
4467
4468 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4469 decrease_used(bytes);
4470 }
4471
4472 class G1ParScrubRemSetTask: public AbstractGangTask {
4473 protected:
4474 G1RemSet* _g1rs;
4475 HeapRegionClaimer _hrclaimer;
4476
4477 public:
4478 G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) :
4479 AbstractGangTask("G1 ScrubRS"),
4480 _g1rs(g1_rs),
4481 _hrclaimer(num_workers) {
4482 }
4483
4484 void work(uint worker_id) {
4485 _g1rs->scrub(worker_id, &_hrclaimer);
4486 }
4487 };
4488
4489 void G1CollectedHeap::scrub_rem_set() {
4490 uint num_workers = workers()->active_workers();
4491 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers);
4492 workers()->run_task(&g1_par_scrub_rs_task);
4493 }
4494
4495 class G1FreeCollectionSetTask : public AbstractGangTask {
4496 private:
4497
4498 // Closure applied to all regions in the collection set to do work that needs to
4499 // be done serially in a single thread.
4500 class G1SerialFreeCollectionSetClosure : public HeapRegionClosure {
4501 private:
4502 EvacuationInfo* _evacuation_info;
4503 const size_t* _surviving_young_words;
4504
4505 // Bytes used in successfully evacuated regions before the evacuation.
4506 size_t _before_used_bytes;
4507 // Bytes used in unsucessfully evacuated regions before the evacuation
4508 size_t _after_used_bytes;
4509
4510 size_t _bytes_allocated_in_old_since_last_gc;
4511
4512 size_t _failure_used_words;
4513 size_t _failure_waste_words;
4514
4515 FreeRegionList _local_free_list;
4516 public:
4517 G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4518 HeapRegionClosure(),
4519 _evacuation_info(evacuation_info),
4520 _surviving_young_words(surviving_young_words),
4521 _before_used_bytes(0),
4522 _after_used_bytes(0),
4523 _bytes_allocated_in_old_since_last_gc(0),
4524 _failure_used_words(0),
4525 _failure_waste_words(0),
4526 _local_free_list("Local Region List for CSet Freeing") {
4527 }
4528
4529 virtual bool doHeapRegion(HeapRegion* r) {
4530 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4531
4532 assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index());
4533 g1h->clear_in_cset(r);
4534
4535 if (r->is_young()) {
4536 assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(),
4537 "Young index %d is wrong for region %u of type %s with %u young regions",
4538 r->young_index_in_cset(),
4539 r->hrm_index(),
4540 r->get_type_str(),
4541 g1h->collection_set()->young_region_length());
4542 size_t words_survived = _surviving_young_words[r->young_index_in_cset()];
4543 r->record_surv_words_in_group(words_survived);
4544 }
4545
4546 if (!r->evacuation_failed()) {
4547 assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
4548 _before_used_bytes += r->used();
4549 g1h->free_region(r,
4550 &_local_free_list,
4551 true, /* skip_remset */
4552 true, /* skip_hot_card_cache */
4553 true /* locked */);
4554 } else {
4555 r->uninstall_surv_rate_group();
4556 r->set_young_index_in_cset(-1);
4557 r->set_evacuation_failed(false);
4558 // When moving a young gen region to old gen, we "allocate" that whole region
4559 // there. This is in addition to any already evacuated objects. Notify the
4560 // policy about that.
4561 // Old gen regions do not cause an additional allocation: both the objects
4562 // still in the region and the ones already moved are accounted for elsewhere.
4563 if (r->is_young()) {
4564 _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
4565 }
4566 // The region is now considered to be old.
4567 r->set_old();
4568 // Do some allocation statistics accounting. Regions that failed evacuation
4569 // are always made old, so there is no need to update anything in the young
4570 // gen statistics, but we need to update old gen statistics.
4571 size_t used_words = r->marked_bytes() / HeapWordSize;
4572
4573 _failure_used_words += used_words;
4574 _failure_waste_words += HeapRegion::GrainWords - used_words;
4575
4576 g1h->old_set_add(r);
4577 _after_used_bytes += r->used();
4578 }
4579 return false;
4580 }
4581
4582 void complete_work() {
4583 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4584
4585 _evacuation_info->set_regions_freed(_local_free_list.length());
4586 _evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4587
4588 g1h->prepend_to_freelist(&_local_free_list);
4589 g1h->decrement_summary_bytes(_before_used_bytes);
4590
4591 G1Policy* policy = g1h->g1_policy();
4592 policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4593
4594 g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4595 }
4596 };
4597
4598 G1CollectionSet* _collection_set;
4599 G1SerialFreeCollectionSetClosure _cl;
4600 const size_t* _surviving_young_words;
4601
4602 size_t _rs_lengths;
4603
4604 volatile jint _serial_work_claim;
4605
4606 struct WorkItem {
4607 uint region_idx;
4608 bool is_young;
4609 bool evacuation_failed;
4610
4611 WorkItem(HeapRegion* r) {
4612 region_idx = r->hrm_index();
4613 is_young = r->is_young();
4614 evacuation_failed = r->evacuation_failed();
4615 }
4616 };
4617
4618 volatile size_t _parallel_work_claim;
4619 size_t _num_work_items;
4620 WorkItem* _work_items;
4621
4622 void do_serial_work() {
4623 // Need to grab the lock to be allowed to modify the old region list.
4624 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4625 _collection_set->iterate(&_cl);
4626 }
4627
4628 void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) {
4629 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4630
4631 HeapRegion* r = g1h->region_at(region_idx);
4632 assert(!g1h->is_on_master_free_list(r), "sanity");
4633
4634 Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths);
4635
4636 if (!is_young) {
4637 g1h->_hot_card_cache->reset_card_counts(r);
4638 }
4639
4640 if (!evacuation_failed) {
4641 r->rem_set()->clear_locked();
4642 }
4643 }
4644
4645 class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure {
4646 private:
4647 size_t _cur_idx;
4648 WorkItem* _work_items;
4649 public:
4650 G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { }
4651
4652 virtual bool doHeapRegion(HeapRegion* r) {
4653 _work_items[_cur_idx++] = WorkItem(r);
4654 return false;
4655 }
4656 };
4657
4658 void prepare_work() {
4659 G1PrepareFreeCollectionSetClosure cl(_work_items);
4660 _collection_set->iterate(&cl);
4661 }
4662
4663 void complete_work() {
4664 _cl.complete_work();
4665
4666 G1Policy* policy = G1CollectedHeap::heap()->g1_policy();
4667 policy->record_max_rs_lengths(_rs_lengths);
4668 policy->cset_regions_freed();
4669 }
4670 public:
4671 G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4672 AbstractGangTask("G1 Free Collection Set"),
4673 _cl(evacuation_info, surviving_young_words),
4674 _collection_set(collection_set),
4675 _surviving_young_words(surviving_young_words),
4676 _serial_work_claim(0),
4677 _rs_lengths(0),
4678 _parallel_work_claim(0),
4679 _num_work_items(collection_set->region_length()),
4680 _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) {
4681 prepare_work();
4682 }
4683
4684 ~G1FreeCollectionSetTask() {
4685 complete_work();
4686 FREE_C_HEAP_ARRAY(WorkItem, _work_items);
4687 }
4688
4689 // Chunk size for work distribution. The chosen value has been determined experimentally
4690 // to be a good tradeoff between overhead and achievable parallelism.
4691 static uint chunk_size() { return 32; }
4692
4693 virtual void work(uint worker_id) {
4694 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
4695
4696 // Claim serial work.
4697 if (_serial_work_claim == 0) {
4698 jint value = Atomic::add(1, &_serial_work_claim) - 1;
4699 if (value == 0) {
4700 double serial_time = os::elapsedTime();
4701 do_serial_work();
4702 timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0);
4703 }
4704 }
4705
4706 // Start parallel work.
4707 double young_time = 0.0;
4708 bool has_young_time = false;
4709 double non_young_time = 0.0;
4710 bool has_non_young_time = false;
4711
4712 while (true) {
4713 size_t end = Atomic::add(chunk_size(), &_parallel_work_claim);
4714 size_t cur = end - chunk_size();
4715
4716 if (cur >= _num_work_items) {
4717 break;
4718 }
4719
4720 double start_time = os::elapsedTime();
4721
4722 end = MIN2(end, _num_work_items);
4723
4724 for (; cur < end; cur++) {
4725 bool is_young = _work_items[cur].is_young;
4726
4727 do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed);
4728
4729 double end_time = os::elapsedTime();
4730 double time_taken = end_time - start_time;
4731 if (is_young) {
4732 young_time += time_taken;
4733 has_young_time = true;
4734 } else {
4735 non_young_time += time_taken;
4736 has_non_young_time = true;
4737 }
4738 start_time = end_time;
4739 }
4740 }
4741
4742 if (has_young_time) {
4743 timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time);
4744 }
4745 if (has_non_young_time) {
4746 timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, young_time);
4747 }
4748 }
4749 };
4750
4751 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4752 _eden.clear();
4753
4754 double free_cset_start_time = os::elapsedTime();
4755
4756 {
4757 uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U);
4758 uint const num_workers = MIN2(workers()->active_workers(), num_chunks);
4759
4760 G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words);
4761
4762 log_debug(gc, ergo)("Running %s using %u workers for collection set length %u",
4763 cl.name(),
4764 num_workers,
4765 _collection_set.region_length());
4766 workers()->run_task(&cl, num_workers);
4767 }
4768 g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0);
4769
4770 collection_set->clear();
4771 }
4772
4773 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4774 private:
4775 FreeRegionList* _free_region_list;
4776 HeapRegionSet* _proxy_set;
4777 uint _humongous_objects_reclaimed;
4778 uint _humongous_regions_reclaimed;
4779 size_t _freed_bytes;
4780 public:
4781
4782 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4783 _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) {
4784 }
4785
4786 virtual bool doHeapRegion(HeapRegion* r) {
4787 if (!r->is_starts_humongous()) {
4788 return false;
4789 }
4790
4791 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4792
4793 oop obj = (oop)r->bottom();
4794 G1CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
4795
4796 // The following checks whether the humongous object is live are sufficient.
4797 // The main additional check (in addition to having a reference from the roots
4798 // or the young gen) is whether the humongous object has a remembered set entry.
4799 //
4800 // A humongous object cannot be live if there is no remembered set for it
4801 // because:
4802 // - there can be no references from within humongous starts regions referencing
4803 // the object because we never allocate other objects into them.
4804 // (I.e. there are no intra-region references that may be missed by the
4805 // remembered set)
4806 // - as soon there is a remembered set entry to the humongous starts region
4807 // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4808 // until the end of a concurrent mark.
4809 //
4810 // It is not required to check whether the object has been found dead by marking
4811 // or not, in fact it would prevent reclamation within a concurrent cycle, as
4812 // all objects allocated during that time are considered live.
4813 // SATB marking is even more conservative than the remembered set.
4814 // So if at this point in the collection there is no remembered set entry,
4815 // nobody has a reference to it.
4816 // At the start of collection we flush all refinement logs, and remembered sets
4817 // are completely up-to-date wrt to references to the humongous object.
4818 //
4819 // Other implementation considerations:
4820 // - never consider object arrays at this time because they would pose
4821 // considerable effort for cleaning up the the remembered sets. This is
4822 // required because stale remembered sets might reference locations that
4823 // are currently allocated into.
4824 uint region_idx = r->hrm_index();
4825 if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4826 !r->rem_set()->is_empty()) {
4827 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",
4828 region_idx,
4829 (size_t)obj->size() * HeapWordSize,
4830 p2i(r->bottom()),
4831 r->rem_set()->occupied(),
4832 r->rem_set()->strong_code_roots_list_length(),
4833 next_bitmap->isMarked(r->bottom()),
4834 g1h->is_humongous_reclaim_candidate(region_idx),
4835 obj->is_typeArray()
4836 );
4837 return false;
4838 }
4839
4840 guarantee(obj->is_typeArray(),
4841 "Only eagerly reclaiming type arrays is supported, but the object "
4842 PTR_FORMAT " is not.", p2i(r->bottom()));
4843
4844 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",
4845 region_idx,
4846 (size_t)obj->size() * HeapWordSize,
4847 p2i(r->bottom()),
4848 r->rem_set()->occupied(),
4849 r->rem_set()->strong_code_roots_list_length(),
4850 next_bitmap->isMarked(r->bottom()),
4851 g1h->is_humongous_reclaim_candidate(region_idx),
4852 obj->is_typeArray()
4853 );
4854
4855 // Need to clear mark bit of the humongous object if already set.
4856 if (next_bitmap->isMarked(r->bottom())) {
4857 next_bitmap->clear(r->bottom());
4858 }
4859 _humongous_objects_reclaimed++;
4860 do {
4861 HeapRegion* next = g1h->next_region_in_humongous(r);
4862 _freed_bytes += r->used();
4863 r->set_containing_set(NULL);
4864 _humongous_regions_reclaimed++;
4865 g1h->free_humongous_region(r, _free_region_list, false /* skip_remset */ );
4866 r = next;
4867 } while (r != NULL);
4868
4869 return false;
4870 }
4871
4872 uint humongous_objects_reclaimed() {
4873 return _humongous_objects_reclaimed;
4874 }
4875
4876 uint humongous_regions_reclaimed() {
4877 return _humongous_regions_reclaimed;
4878 }
4879
4880 size_t bytes_freed() const {
4881 return _freed_bytes;
4882 }
4883 };
4884
4885 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4886 assert_at_safepoint(true);
4887
4888 if (!G1EagerReclaimHumongousObjects ||
4889 (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
4890 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
4891 return;
4892 }
4893
4894 double start_time = os::elapsedTime();
4895
4896 FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
4897
4898 G1FreeHumongousRegionClosure cl(&local_cleanup_list);
4899 heap_region_iterate(&cl);
4900
4901 remove_from_old_sets(0, cl.humongous_regions_reclaimed());
4902
4903 G1HRPrinter* hrp = hr_printer();
4904 if (hrp->is_active()) {
4905 FreeRegionListIterator iter(&local_cleanup_list);
4906 while (iter.more_available()) {
4907 HeapRegion* hr = iter.get_next();
4908 hrp->cleanup(hr);
4909 }
4910 }
4911
4912 prepend_to_freelist(&local_cleanup_list);
4913 decrement_summary_bytes(cl.bytes_freed());
4914
4915 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
4916 cl.humongous_objects_reclaimed());
4917 }
4918
4919 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
4920 public:
4921 virtual bool doHeapRegion(HeapRegion* r) {
4922 assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
4923 G1CollectedHeap::heap()->clear_in_cset(r);
4924 r->set_young_index_in_cset(-1);
4925 return false;
4926 }
4927 };
4928
4929 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
4930 G1AbandonCollectionSetClosure cl;
4931 collection_set->iterate(&cl);
4932
4933 collection_set->clear();
4934 collection_set->stop_incremental_building();
4935 }
4936
4937 void G1CollectedHeap::set_free_regions_coming() {
4938 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming");
4939
4940 assert(!free_regions_coming(), "pre-condition");
4941 _free_regions_coming = true;
4942 }
4943
4944 void G1CollectedHeap::reset_free_regions_coming() {
4945 assert(free_regions_coming(), "pre-condition");
4946
4947 {
4948 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
4949 _free_regions_coming = false;
4950 SecondaryFreeList_lock->notify_all();
4951 }
4952
4953 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming");
4954 }
4955
4956 void G1CollectedHeap::wait_while_free_regions_coming() {
4957 // Most of the time we won't have to wait, so let's do a quick test
4958 // first before we take the lock.
4959 if (!free_regions_coming()) {
4960 return;
4961 }
4962
4963 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions");
4964
4965 {
4966 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
4967 while (free_regions_coming()) {
4968 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
4969 }
4970 }
4971
4972 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions");
4973 }
4974
4975 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
4976 return _allocator->is_retained_old_region(hr);
4977 }
4978
4979 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
4980 _eden.add(hr);
4981 _g1_policy->set_region_eden(hr);
4982 }
4983
4984 #ifdef ASSERT
4985
4986 class NoYoungRegionsClosure: public HeapRegionClosure {
4987 private:
4988 bool _success;
4989 public:
4990 NoYoungRegionsClosure() : _success(true) { }
4991 bool doHeapRegion(HeapRegion* r) {
4992 if (r->is_young()) {
4993 log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
4994 p2i(r->bottom()), p2i(r->end()));
4995 _success = false;
4996 }
4997 return false;
4998 }
4999 bool success() { return _success; }
5000 };
5001
5002 bool G1CollectedHeap::check_young_list_empty() {
5003 bool ret = (young_regions_count() == 0);
5004
5005 NoYoungRegionsClosure closure;
5006 heap_region_iterate(&closure);
5007 ret = ret && closure.success();
5008
5009 return ret;
5010 }
5011
5012 #endif // ASSERT
5013
5014 class TearDownRegionSetsClosure : public HeapRegionClosure {
5015 private:
5016 HeapRegionSet *_old_set;
5017
5018 public:
5019 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
5020
5021 bool doHeapRegion(HeapRegion* r) {
5022 if (r->is_old()) {
5023 _old_set->remove(r);
5024 } else if(r->is_young()) {
5025 r->uninstall_surv_rate_group();
5026 } else {
5027 // We ignore free regions, we'll empty the free list afterwards.
5028 // We ignore humongous regions, we're not tearing down the
5029 // humongous regions set.
5030 assert(r->is_free() || r->is_humongous(),
5031 "it cannot be another type");
5032 }
5033 return false;
5034 }
5035
5036 ~TearDownRegionSetsClosure() {
5037 assert(_old_set->is_empty(), "post-condition");
5038 }
5039 };
5040
5041 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
5042 assert_at_safepoint(true /* should_be_vm_thread */);
5043
5044 if (!free_list_only) {
5045 TearDownRegionSetsClosure cl(&_old_set);
5046 heap_region_iterate(&cl);
5047
5048 // Note that emptying the _young_list is postponed and instead done as
5049 // the first step when rebuilding the regions sets again. The reason for
5050 // this is that during a full GC string deduplication needs to know if
5051 // a collected region was young or old when the full GC was initiated.
5052 }
5053 _hrm.remove_all_free_regions();
5054 }
5055
5056 void G1CollectedHeap::increase_used(size_t bytes) {
5057 _summary_bytes_used += bytes;
5058 }
5059
5060 void G1CollectedHeap::decrease_used(size_t bytes) {
5061 assert(_summary_bytes_used >= bytes,
5062 "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
5063 _summary_bytes_used, bytes);
5064 _summary_bytes_used -= bytes;
5065 }
5066
5067 void G1CollectedHeap::set_used(size_t bytes) {
5068 _summary_bytes_used = bytes;
5069 }
5070
5071 class RebuildRegionSetsClosure : public HeapRegionClosure {
5072 private:
5073 bool _free_list_only;
5074 HeapRegionSet* _old_set;
5075 HeapRegionManager* _hrm;
5076 size_t _total_used;
5077
5078 public:
5079 RebuildRegionSetsClosure(bool free_list_only,
5080 HeapRegionSet* old_set, HeapRegionManager* hrm) :
5081 _free_list_only(free_list_only),
5082 _old_set(old_set), _hrm(hrm), _total_used(0) {
5083 assert(_hrm->num_free_regions() == 0, "pre-condition");
5084 if (!free_list_only) {
5085 assert(_old_set->is_empty(), "pre-condition");
5086 }
5087 }
5088
5089 bool doHeapRegion(HeapRegion* r) {
5090 if (r->is_empty()) {
5091 // Add free regions to the free list
5092 r->set_free();
5093 r->set_allocation_context(AllocationContext::system());
5094 _hrm->insert_into_free_list(r);
5095 } else if (!_free_list_only) {
5096
5097 if (r->is_humongous()) {
5098 // We ignore humongous regions. We left the humongous set unchanged.
5099 } else {
5100 assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
5101 // We now consider all regions old, so register as such. Leave
5102 // archive regions set that way, however, while still adding
5103 // them to the old set.
5104 if (!r->is_archive()) {
5105 r->set_old();
5106 }
5107 _old_set->add(r);
5108 }
5109 _total_used += r->used();
5110 }
5111
5112 return false;
5113 }
5114
5115 size_t total_used() {
5116 return _total_used;
5117 }
5118 };
5119
5120 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
5121 assert_at_safepoint(true /* should_be_vm_thread */);
5122
5123 if (!free_list_only) {
5124 _eden.clear();
5125 _survivor.clear();
5126 }
5127
5128 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
5129 heap_region_iterate(&cl);
5130
5131 if (!free_list_only) {
5132 set_used(cl.total_used());
5133 if (_archive_allocator != NULL) {
5134 _archive_allocator->clear_used();
5135 }
5136 }
5137 assert(used_unlocked() == recalculate_used(),
5138 "inconsistent used_unlocked(), "
5139 "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT,
5140 used_unlocked(), recalculate_used());
5141 }
5142
5143 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
5144 HeapRegion* hr = heap_region_containing(p);
5145 return hr->is_in(p);
5146 }
5147
5148 // Methods for the mutator alloc region
5149
5150 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
5151 bool force) {
5152 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5153 bool should_allocate = g1_policy()->should_allocate_mutator_region();
5154 if (force || should_allocate) {
5155 HeapRegion* new_alloc_region = new_region(word_size,
5156 false /* is_old */,
5157 false /* do_expand */);
5158 if (new_alloc_region != NULL) {
5159 set_region_short_lived_locked(new_alloc_region);
5160 _hr_printer.alloc(new_alloc_region, !should_allocate);
5161 _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
5162 return new_alloc_region;
5163 }
5164 }
5165 return NULL;
5166 }
5167
5168 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
5169 size_t allocated_bytes) {
5170 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5171 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
5172
5173 collection_set()->add_eden_region(alloc_region);
5174 increase_used(allocated_bytes);
5175 _hr_printer.retire(alloc_region);
5176 // We update the eden sizes here, when the region is retired,
5177 // instead of when it's allocated, since this is the point that its
5178 // used space has been recored in _summary_bytes_used.
5179 g1mm()->update_eden_size();
5180 }
5181
5182 // Methods for the GC alloc regions
5183
5184 bool G1CollectedHeap::has_more_regions(InCSetState dest) {
5185 if (dest.is_old()) {
5186 return true;
5187 } else {
5188 return survivor_regions_count() < g1_policy()->max_survivor_regions();
5189 }
5190 }
5191
5192 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) {
5193 assert(FreeList_lock->owned_by_self(), "pre-condition");
5194
5195 if (!has_more_regions(dest)) {
5196 return NULL;
5197 }
5198
5199 const bool is_survivor = dest.is_young();
5200
5201 HeapRegion* new_alloc_region = new_region(word_size,
5202 !is_survivor,
5203 true /* do_expand */);
5204 if (new_alloc_region != NULL) {
5205 // We really only need to do this for old regions given that we
5206 // should never scan survivors. But it doesn't hurt to do it
5207 // for survivors too.
5208 new_alloc_region->record_timestamp();
5209 if (is_survivor) {
5210 new_alloc_region->set_survivor();
5211 _survivor.add(new_alloc_region);
5212 _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
5213 } else {
5214 new_alloc_region->set_old();
5215 _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
5216 }
5217 _hr_printer.alloc(new_alloc_region);
5218 bool during_im = collector_state()->during_initial_mark_pause();
5219 new_alloc_region->note_start_of_copying(during_im);
5220 return new_alloc_region;
5221 }
5222 return NULL;
5223 }
5224
5225 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
5226 size_t allocated_bytes,
5227 InCSetState dest) {
5228 bool during_im = collector_state()->during_initial_mark_pause();
5229 alloc_region->note_end_of_copying(during_im);
5230 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
5231 if (dest.is_old()) {
5232 _old_set.add(alloc_region);
5233 }
5234 _hr_printer.retire(alloc_region);
5235 }
5236
5237 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
5238 bool expanded = false;
5239 uint index = _hrm.find_highest_free(&expanded);
5240
5241 if (index != G1_NO_HRM_INDEX) {
5242 if (expanded) {
5243 log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
5244 HeapRegion::GrainWords * HeapWordSize);
5245 }
5246 _hrm.allocate_free_regions_starting_at(index, 1);
5247 return region_at(index);
5248 }
5249 return NULL;
5250 }
5251
5252 // Optimized nmethod scanning
5253
5254 class RegisterNMethodOopClosure: public OopClosure {
5255 G1CollectedHeap* _g1h;
5256 nmethod* _nm;
5257
5258 template <class T> void do_oop_work(T* p) {
5259 T heap_oop = oopDesc::load_heap_oop(p);
5260 if (!oopDesc::is_null(heap_oop)) {
5261 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5262 HeapRegion* hr = _g1h->heap_region_containing(obj);
5263 assert(!hr->is_continues_humongous(),
5264 "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5265 " starting at " HR_FORMAT,
5266 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5267
5268 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
5269 hr->add_strong_code_root_locked(_nm);
5270 }
5271 }
5272
5273 public:
5274 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5275 _g1h(g1h), _nm(nm) {}
5276
5277 void do_oop(oop* p) { do_oop_work(p); }
5278 void do_oop(narrowOop* p) { do_oop_work(p); }
5279 };
5280
5281 class UnregisterNMethodOopClosure: public OopClosure {
5282 G1CollectedHeap* _g1h;
5283 nmethod* _nm;
5284
5285 template <class T> void do_oop_work(T* p) {
5286 T heap_oop = oopDesc::load_heap_oop(p);
5287 if (!oopDesc::is_null(heap_oop)) {
5288 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5289 HeapRegion* hr = _g1h->heap_region_containing(obj);
5290 assert(!hr->is_continues_humongous(),
5291 "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5292 " starting at " HR_FORMAT,
5293 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5294
5295 hr->remove_strong_code_root(_nm);
5296 }
5297 }
5298
5299 public:
5300 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5301 _g1h(g1h), _nm(nm) {}
5302
5303 void do_oop(oop* p) { do_oop_work(p); }
5304 void do_oop(narrowOop* p) { do_oop_work(p); }
5305 };
5306
5307 void G1CollectedHeap::register_nmethod(nmethod* nm) {
5308 CollectedHeap::register_nmethod(nm);
5309
5310 guarantee(nm != NULL, "sanity");
5311 RegisterNMethodOopClosure reg_cl(this, nm);
5312 nm->oops_do(®_cl);
5313 }
5314
5315 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
5316 CollectedHeap::unregister_nmethod(nm);
5317
5318 guarantee(nm != NULL, "sanity");
5319 UnregisterNMethodOopClosure reg_cl(this, nm);
5320 nm->oops_do(®_cl, true);
5321 }
5322
5323 void G1CollectedHeap::purge_code_root_memory() {
5324 double purge_start = os::elapsedTime();
5325 G1CodeRootSet::purge();
5326 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
5327 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
5328 }
5329
5330 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
5331 G1CollectedHeap* _g1h;
5332
5333 public:
5334 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
5335 _g1h(g1h) {}
5336
5337 void do_code_blob(CodeBlob* cb) {
5338 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
5339 if (nm == NULL) {
5340 return;
5341 }
5342
5343 if (ScavengeRootsInCode) {
5344 _g1h->register_nmethod(nm);
5345 }
5346 }
5347 };
5348
5349 void G1CollectedHeap::rebuild_strong_code_roots() {
5350 RebuildStrongCodeRootClosure blob_cl(this);
5351 CodeCache::blobs_do(&blob_cl);
5352 }