1 /*
2 * Copyright (c) 2001, 2010, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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24
25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
27
28 #include "gc_implementation/g1/concurrentMark.hpp"
29 #include "gc_implementation/g1/g1RemSet.hpp"
30 #include "gc_implementation/g1/heapRegion.hpp"
31 #include "gc_implementation/parNew/parGCAllocBuffer.hpp"
32 #include "memory/barrierSet.hpp"
33 #include "memory/memRegion.hpp"
34 #include "memory/sharedHeap.hpp"
35
36 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
37 // It uses the "Garbage First" heap organization and algorithm, which
38 // may combine concurrent marking with parallel, incremental compaction of
39 // heap subsets that will yield large amounts of garbage.
40
41 class HeapRegion;
42 class HeapRegionSeq;
43 class PermanentGenerationSpec;
44 class GenerationSpec;
45 class OopsInHeapRegionClosure;
46 class G1ScanHeapEvacClosure;
47 class ObjectClosure;
48 class SpaceClosure;
49 class CompactibleSpaceClosure;
50 class Space;
51 class G1CollectorPolicy;
52 class GenRemSet;
53 class G1RemSet;
54 class HeapRegionRemSetIterator;
55 class ConcurrentMark;
56 class ConcurrentMarkThread;
57 class ConcurrentG1Refine;
58 class ConcurrentZFThread;
59
60 typedef OverflowTaskQueue<StarTask> RefToScanQueue;
61 typedef GenericTaskQueueSet<RefToScanQueue> RefToScanQueueSet;
62
63 typedef int RegionIdx_t; // needs to hold [ 0..max_regions() )
64 typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion )
65
66 enum G1GCThreadGroups {
67 G1CRGroup = 0,
68 G1ZFGroup = 1,
69 G1CMGroup = 2,
70 G1CLGroup = 3
71 };
72
73 enum GCAllocPurpose {
74 GCAllocForTenured,
75 GCAllocForSurvived,
76 GCAllocPurposeCount
77 };
78
79 class YoungList : public CHeapObj {
80 private:
81 G1CollectedHeap* _g1h;
82
83 HeapRegion* _head;
84
85 HeapRegion* _survivor_head;
86 HeapRegion* _survivor_tail;
87
88 HeapRegion* _curr;
89
90 size_t _length;
91 size_t _survivor_length;
92
93 size_t _last_sampled_rs_lengths;
94 size_t _sampled_rs_lengths;
95
96 void empty_list(HeapRegion* list);
97
98 public:
99 YoungList(G1CollectedHeap* g1h);
100
101 void push_region(HeapRegion* hr);
102 void add_survivor_region(HeapRegion* hr);
103
104 void empty_list();
105 bool is_empty() { return _length == 0; }
106 size_t length() { return _length; }
107 size_t survivor_length() { return _survivor_length; }
108
109 void rs_length_sampling_init();
110 bool rs_length_sampling_more();
111 void rs_length_sampling_next();
112
113 void reset_sampled_info() {
114 _last_sampled_rs_lengths = 0;
115 }
116 size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
117
118 // for development purposes
119 void reset_auxilary_lists();
120 void clear() { _head = NULL; _length = 0; }
121
122 void clear_survivors() {
123 _survivor_head = NULL;
124 _survivor_tail = NULL;
125 _survivor_length = 0;
126 }
127
128 HeapRegion* first_region() { return _head; }
129 HeapRegion* first_survivor_region() { return _survivor_head; }
130 HeapRegion* last_survivor_region() { return _survivor_tail; }
131
132 // debugging
133 bool check_list_well_formed();
134 bool check_list_empty(bool check_sample = true);
135 void print();
136 };
137
138 class RefineCardTableEntryClosure;
139 class G1CollectedHeap : public SharedHeap {
140 friend class VM_G1CollectForAllocation;
141 friend class VM_GenCollectForPermanentAllocation;
142 friend class VM_G1CollectFull;
143 friend class VM_G1IncCollectionPause;
144 friend class VMStructs;
145
146 // Closures used in implementation.
147 friend class G1ParCopyHelper;
148 friend class G1IsAliveClosure;
149 friend class G1EvacuateFollowersClosure;
150 friend class G1ParScanThreadState;
151 friend class G1ParScanClosureSuper;
152 friend class G1ParEvacuateFollowersClosure;
153 friend class G1ParTask;
154 friend class G1FreeGarbageRegionClosure;
155 friend class RefineCardTableEntryClosure;
156 friend class G1PrepareCompactClosure;
157 friend class RegionSorter;
158 friend class CountRCClosure;
159 friend class EvacPopObjClosure;
160 friend class G1ParCleanupCTTask;
161
162 // Other related classes.
163 friend class G1MarkSweep;
164
165 private:
166 // The one and only G1CollectedHeap, so static functions can find it.
167 static G1CollectedHeap* _g1h;
168
169 static size_t _humongous_object_threshold_in_words;
170
171 // Storage for the G1 heap (excludes the permanent generation).
172 VirtualSpace _g1_storage;
173 MemRegion _g1_reserved;
174
175 // The part of _g1_storage that is currently committed.
176 MemRegion _g1_committed;
177
178 // The maximum part of _g1_storage that has ever been committed.
179 MemRegion _g1_max_committed;
180
181 // The number of regions that are completely free.
182 size_t _free_regions;
183
184 // The number of regions we could create by expansion.
185 size_t _expansion_regions;
186
187 // Return the number of free regions in the heap (by direct counting.)
188 size_t count_free_regions();
189 // Return the number of free regions on the free and unclean lists.
190 size_t count_free_regions_list();
191
192 // The block offset table for the G1 heap.
193 G1BlockOffsetSharedArray* _bot_shared;
194
195 // Move all of the regions off the free lists, then rebuild those free
196 // lists, before and after full GC.
197 void tear_down_region_lists();
198 void rebuild_region_lists();
199 // This sets all non-empty regions to need zero-fill (which they will if
200 // they are empty after full collection.)
201 void set_used_regions_to_need_zero_fill();
202
203 // The sequence of all heap regions in the heap.
204 HeapRegionSeq* _hrs;
205
206 // The region from which normal-sized objects are currently being
207 // allocated. May be NULL.
208 HeapRegion* _cur_alloc_region;
209
210 // Postcondition: cur_alloc_region == NULL.
211 void abandon_cur_alloc_region();
212 void abandon_gc_alloc_regions();
213
214 // The to-space memory regions into which objects are being copied during
215 // a GC.
216 HeapRegion* _gc_alloc_regions[GCAllocPurposeCount];
217 size_t _gc_alloc_region_counts[GCAllocPurposeCount];
218 // These are the regions, one per GCAllocPurpose, that are half-full
219 // at the end of a collection and that we want to reuse during the
220 // next collection.
221 HeapRegion* _retained_gc_alloc_regions[GCAllocPurposeCount];
222 // This specifies whether we will keep the last half-full region at
223 // the end of a collection so that it can be reused during the next
224 // collection (this is specified per GCAllocPurpose)
225 bool _retain_gc_alloc_region[GCAllocPurposeCount];
226
227 // A list of the regions that have been set to be alloc regions in the
228 // current collection.
229 HeapRegion* _gc_alloc_region_list;
230
231 // Determines PLAB size for a particular allocation purpose.
232 static size_t desired_plab_sz(GCAllocPurpose purpose);
233
234 // When called by par thread, require par_alloc_during_gc_lock() to be held.
235 void push_gc_alloc_region(HeapRegion* hr);
236
237 // This should only be called single-threaded. Undeclares all GC alloc
238 // regions.
239 void forget_alloc_region_list();
240
241 // Should be used to set an alloc region, because there's other
242 // associated bookkeeping.
243 void set_gc_alloc_region(int purpose, HeapRegion* r);
244
245 // Check well-formedness of alloc region list.
246 bool check_gc_alloc_regions();
247
248 // Outside of GC pauses, the number of bytes used in all regions other
249 // than the current allocation region.
250 size_t _summary_bytes_used;
251
252 // This is used for a quick test on whether a reference points into
253 // the collection set or not. Basically, we have an array, with one
254 // byte per region, and that byte denotes whether the corresponding
255 // region is in the collection set or not. The entry corresponding
256 // the bottom of the heap, i.e., region 0, is pointed to by
257 // _in_cset_fast_test_base. The _in_cset_fast_test field has been
258 // biased so that it actually points to address 0 of the address
259 // space, to make the test as fast as possible (we can simply shift
260 // the address to address into it, instead of having to subtract the
261 // bottom of the heap from the address before shifting it; basically
262 // it works in the same way the card table works).
263 bool* _in_cset_fast_test;
264
265 // The allocated array used for the fast test on whether a reference
266 // points into the collection set or not. This field is also used to
267 // free the array.
268 bool* _in_cset_fast_test_base;
269
270 // The length of the _in_cset_fast_test_base array.
271 size_t _in_cset_fast_test_length;
272
273 volatile unsigned _gc_time_stamp;
274
275 size_t* _surviving_young_words;
276
277 void setup_surviving_young_words();
278 void update_surviving_young_words(size_t* surv_young_words);
279 void cleanup_surviving_young_words();
280
281 // It decides whether an explicit GC should start a concurrent cycle
282 // instead of doing a STW GC. Currently, a concurrent cycle is
283 // explicitly started if:
284 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
285 // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
286 bool should_do_concurrent_full_gc(GCCause::Cause cause);
287
288 // Keeps track of how many "full collections" (i.e., Full GCs or
289 // concurrent cycles) we have completed. The number of them we have
290 // started is maintained in _total_full_collections in CollectedHeap.
291 volatile unsigned int _full_collections_completed;
292
293 protected:
294
295 // Returns "true" iff none of the gc alloc regions have any allocations
296 // since the last call to "save_marks".
297 bool all_alloc_regions_no_allocs_since_save_marks();
298 // Perform finalization stuff on all allocation regions.
299 void retire_all_alloc_regions();
300
301 // The number of regions allocated to hold humongous objects.
302 int _num_humongous_regions;
303 YoungList* _young_list;
304
305 // The current policy object for the collector.
306 G1CollectorPolicy* _g1_policy;
307
308 // Parallel allocation lock to protect the current allocation region.
309 Mutex _par_alloc_during_gc_lock;
310 Mutex* par_alloc_during_gc_lock() { return &_par_alloc_during_gc_lock; }
311
312 // If possible/desirable, allocate a new HeapRegion for normal object
313 // allocation sufficient for an allocation of the given "word_size".
314 // If "do_expand" is true, will attempt to expand the heap if necessary
315 // to to satisfy the request. If "zero_filled" is true, requires a
316 // zero-filled region.
317 // (Returning NULL will trigger a GC.)
318 virtual HeapRegion* newAllocRegion_work(size_t word_size,
319 bool do_expand,
320 bool zero_filled);
321
322 virtual HeapRegion* newAllocRegion(size_t word_size,
323 bool zero_filled = true) {
324 return newAllocRegion_work(word_size, false, zero_filled);
325 }
326 virtual HeapRegion* newAllocRegionWithExpansion(int purpose,
327 size_t word_size,
328 bool zero_filled = true);
329
330 // Attempt to allocate an object of the given (very large) "word_size".
331 // Returns "NULL" on failure.
332 virtual HeapWord* humongousObjAllocate(size_t word_size);
333
334 // If possible, allocate a block of the given word_size, else return "NULL".
335 // Returning NULL will trigger GC or heap expansion.
336 // These two methods have rather awkward pre- and
337 // post-conditions. If they are called outside a safepoint, then
338 // they assume that the caller is holding the heap lock. Upon return
339 // they release the heap lock, if they are returning a non-NULL
340 // value. attempt_allocation_slow() also dirties the cards of a
341 // newly-allocated young region after it releases the heap
342 // lock. This change in interface was the neatest way to achieve
343 // this card dirtying without affecting mem_allocate(), which is a
344 // more frequently called method. We tried two or three different
345 // approaches, but they were even more hacky.
346 HeapWord* attempt_allocation(size_t word_size,
347 bool permit_collection_pause = true);
348
349 HeapWord* attempt_allocation_slow(size_t word_size,
350 bool permit_collection_pause = true);
351
352 // Allocate blocks during garbage collection. Will ensure an
353 // allocation region, either by picking one or expanding the
354 // heap, and then allocate a block of the given size. The block
355 // may not be a humongous - it must fit into a single heap region.
356 HeapWord* allocate_during_gc(GCAllocPurpose purpose, size_t word_size);
357 HeapWord* par_allocate_during_gc(GCAllocPurpose purpose, size_t word_size);
358
359 HeapWord* allocate_during_gc_slow(GCAllocPurpose purpose,
360 HeapRegion* alloc_region,
361 bool par,
362 size_t word_size);
363
364 // Ensure that no further allocations can happen in "r", bearing in mind
365 // that parallel threads might be attempting allocations.
366 void par_allocate_remaining_space(HeapRegion* r);
367
368 // Retires an allocation region when it is full or at the end of a
369 // GC pause.
370 void retire_alloc_region(HeapRegion* alloc_region, bool par);
371
372 // - if explicit_gc is true, the GC is for a System.gc() or a heap
373 // inspection request and should collect the entire heap
374 // - if clear_all_soft_refs is true, all soft references are cleared
375 // during the GC
376 // - if explicit_gc is false, word_size describes the allocation that
377 // the GC should attempt (at least) to satisfy
378 void do_collection(bool explicit_gc,
379 bool clear_all_soft_refs,
380 size_t word_size);
381
382 // Callback from VM_G1CollectFull operation.
383 // Perform a full collection.
384 void do_full_collection(bool clear_all_soft_refs);
385
386 // Resize the heap if necessary after a full collection. If this is
387 // after a collect-for allocation, "word_size" is the allocation size,
388 // and will be considered part of the used portion of the heap.
389 void resize_if_necessary_after_full_collection(size_t word_size);
390
391 // Callback from VM_G1CollectForAllocation operation.
392 // This function does everything necessary/possible to satisfy a
393 // failed allocation request (including collection, expansion, etc.)
394 HeapWord* satisfy_failed_allocation(size_t word_size);
395
396 // Attempting to expand the heap sufficiently
397 // to support an allocation of the given "word_size". If
398 // successful, perform the allocation and return the address of the
399 // allocated block, or else "NULL".
400 virtual HeapWord* expand_and_allocate(size_t word_size);
401
402 public:
403 // Expand the garbage-first heap by at least the given size (in bytes!).
404 // (Rounds up to a HeapRegion boundary.)
405 virtual void expand(size_t expand_bytes);
406
407 // Do anything common to GC's.
408 virtual void gc_prologue(bool full);
409 virtual void gc_epilogue(bool full);
410
411 // We register a region with the fast "in collection set" test. We
412 // simply set to true the array slot corresponding to this region.
413 void register_region_with_in_cset_fast_test(HeapRegion* r) {
414 assert(_in_cset_fast_test_base != NULL, "sanity");
415 assert(r->in_collection_set(), "invariant");
416 int index = r->hrs_index();
417 assert(0 <= index && (size_t) index < _in_cset_fast_test_length, "invariant");
418 assert(!_in_cset_fast_test_base[index], "invariant");
419 _in_cset_fast_test_base[index] = true;
420 }
421
422 // This is a fast test on whether a reference points into the
423 // collection set or not. It does not assume that the reference
424 // points into the heap; if it doesn't, it will return false.
425 bool in_cset_fast_test(oop obj) {
426 assert(_in_cset_fast_test != NULL, "sanity");
427 if (_g1_committed.contains((HeapWord*) obj)) {
428 // no need to subtract the bottom of the heap from obj,
429 // _in_cset_fast_test is biased
430 size_t index = ((size_t) obj) >> HeapRegion::LogOfHRGrainBytes;
431 bool ret = _in_cset_fast_test[index];
432 // let's make sure the result is consistent with what the slower
433 // test returns
434 assert( ret || !obj_in_cs(obj), "sanity");
435 assert(!ret || obj_in_cs(obj), "sanity");
436 return ret;
437 } else {
438 return false;
439 }
440 }
441
442 void clear_cset_fast_test() {
443 assert(_in_cset_fast_test_base != NULL, "sanity");
444 memset(_in_cset_fast_test_base, false,
445 _in_cset_fast_test_length * sizeof(bool));
446 }
447
448 // This is called at the end of either a concurrent cycle or a Full
449 // GC to update the number of full collections completed. Those two
450 // can happen in a nested fashion, i.e., we start a concurrent
451 // cycle, a Full GC happens half-way through it which ends first,
452 // and then the cycle notices that a Full GC happened and ends
453 // too. The outer parameter is a boolean to help us do a bit tighter
454 // consistency checking in the method. If outer is false, the caller
455 // is the inner caller in the nesting (i.e., the Full GC). If outer
456 // is true, the caller is the outer caller in this nesting (i.e.,
457 // the concurrent cycle). Further nesting is not currently
458 // supported. The end of the this call also notifies the
459 // FullGCCount_lock in case a Java thread is waiting for a full GC
460 // to happen (e.g., it called System.gc() with
461 // +ExplicitGCInvokesConcurrent).
462 void increment_full_collections_completed(bool outer);
463
464 unsigned int full_collections_completed() {
465 return _full_collections_completed;
466 }
467
468 protected:
469
470 // Shrink the garbage-first heap by at most the given size (in bytes!).
471 // (Rounds down to a HeapRegion boundary.)
472 virtual void shrink(size_t expand_bytes);
473 void shrink_helper(size_t expand_bytes);
474
475 #if TASKQUEUE_STATS
476 static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
477 void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
478 void reset_taskqueue_stats();
479 #endif // TASKQUEUE_STATS
480
481 // Do an incremental collection: identify a collection set, and evacuate
482 // its live objects elsewhere.
483 virtual void do_collection_pause();
484
485 // The guts of the incremental collection pause, executed by the vm
486 // thread.
487 virtual void do_collection_pause_at_safepoint(double target_pause_time_ms);
488
489 // Actually do the work of evacuating the collection set.
490 virtual void evacuate_collection_set();
491
492 // If this is an appropriate right time, do a collection pause.
493 // The "word_size" argument, if non-zero, indicates the size of an
494 // allocation request that is prompting this query.
495 void do_collection_pause_if_appropriate(size_t word_size);
496
497 // The g1 remembered set of the heap.
498 G1RemSet* _g1_rem_set;
499 // And it's mod ref barrier set, used to track updates for the above.
500 ModRefBarrierSet* _mr_bs;
501
502 // A set of cards that cover the objects for which the Rsets should be updated
503 // concurrently after the collection.
504 DirtyCardQueueSet _dirty_card_queue_set;
505
506 // The Heap Region Rem Set Iterator.
507 HeapRegionRemSetIterator** _rem_set_iterator;
508
509 // The closure used to refine a single card.
510 RefineCardTableEntryClosure* _refine_cte_cl;
511
512 // A function to check the consistency of dirty card logs.
513 void check_ct_logs_at_safepoint();
514
515 // A DirtyCardQueueSet that is used to hold cards that contain
516 // references into the current collection set. This is used to
517 // update the remembered sets of the regions in the collection
518 // set in the event of an evacuation failure.
519 DirtyCardQueueSet _into_cset_dirty_card_queue_set;
520
521 // After a collection pause, make the regions in the CS into free
522 // regions.
523 void free_collection_set(HeapRegion* cs_head);
524
525 // Abandon the current collection set without recording policy
526 // statistics or updating free lists.
527 void abandon_collection_set(HeapRegion* cs_head);
528
529 // Applies "scan_non_heap_roots" to roots outside the heap,
530 // "scan_rs" to roots inside the heap (having done "set_region" to
531 // indicate the region in which the root resides), and does "scan_perm"
532 // (setting the generation to the perm generation.) If "scan_rs" is
533 // NULL, then this step is skipped. The "worker_i"
534 // param is for use with parallel roots processing, and should be
535 // the "i" of the calling parallel worker thread's work(i) function.
536 // In the sequential case this param will be ignored.
537 void g1_process_strong_roots(bool collecting_perm_gen,
538 SharedHeap::ScanningOption so,
539 OopClosure* scan_non_heap_roots,
540 OopsInHeapRegionClosure* scan_rs,
541 OopsInGenClosure* scan_perm,
542 int worker_i);
543
544 // Apply "blk" to all the weak roots of the system. These include
545 // JNI weak roots, the code cache, system dictionary, symbol table,
546 // string table, and referents of reachable weak refs.
547 void g1_process_weak_roots(OopClosure* root_closure,
548 OopClosure* non_root_closure);
549
550 // Invoke "save_marks" on all heap regions.
551 void save_marks();
552
553 // Free a heap region.
554 void free_region(HeapRegion* hr);
555 // A component of "free_region", exposed for 'batching'.
556 // All the params after "hr" are out params: the used bytes of the freed
557 // region(s), the number of H regions cleared, the number of regions
558 // freed, and pointers to the head and tail of a list of freed contig
559 // regions, linked throught the "next_on_unclean_list" field.
560 void free_region_work(HeapRegion* hr,
561 size_t& pre_used,
562 size_t& cleared_h,
563 size_t& freed_regions,
564 UncleanRegionList* list,
565 bool par = false);
566
567
568 // The concurrent marker (and the thread it runs in.)
569 ConcurrentMark* _cm;
570 ConcurrentMarkThread* _cmThread;
571 bool _mark_in_progress;
572
573 // The concurrent refiner.
574 ConcurrentG1Refine* _cg1r;
575
576 // The concurrent zero-fill thread.
577 ConcurrentZFThread* _czft;
578
579 // The parallel task queues
580 RefToScanQueueSet *_task_queues;
581
582 // True iff a evacuation has failed in the current collection.
583 bool _evacuation_failed;
584
585 // Set the attribute indicating whether evacuation has failed in the
586 // current collection.
587 void set_evacuation_failed(bool b) { _evacuation_failed = b; }
588
589 // Failed evacuations cause some logical from-space objects to have
590 // forwarding pointers to themselves. Reset them.
591 void remove_self_forwarding_pointers();
592
593 // When one is non-null, so is the other. Together, they each pair is
594 // an object with a preserved mark, and its mark value.
595 GrowableArray<oop>* _objs_with_preserved_marks;
596 GrowableArray<markOop>* _preserved_marks_of_objs;
597
598 // Preserve the mark of "obj", if necessary, in preparation for its mark
599 // word being overwritten with a self-forwarding-pointer.
600 void preserve_mark_if_necessary(oop obj, markOop m);
601
602 // The stack of evac-failure objects left to be scanned.
603 GrowableArray<oop>* _evac_failure_scan_stack;
604 // The closure to apply to evac-failure objects.
605
606 OopsInHeapRegionClosure* _evac_failure_closure;
607 // Set the field above.
608 void
609 set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
610 _evac_failure_closure = evac_failure_closure;
611 }
612
613 // Push "obj" on the scan stack.
614 void push_on_evac_failure_scan_stack(oop obj);
615 // Process scan stack entries until the stack is empty.
616 void drain_evac_failure_scan_stack();
617 // True iff an invocation of "drain_scan_stack" is in progress; to
618 // prevent unnecessary recursion.
619 bool _drain_in_progress;
620
621 // Do any necessary initialization for evacuation-failure handling.
622 // "cl" is the closure that will be used to process evac-failure
623 // objects.
624 void init_for_evac_failure(OopsInHeapRegionClosure* cl);
625 // Do any necessary cleanup for evacuation-failure handling data
626 // structures.
627 void finalize_for_evac_failure();
628
629 // An attempt to evacuate "obj" has failed; take necessary steps.
630 void handle_evacuation_failure(oop obj);
631 oop handle_evacuation_failure_par(OopsInHeapRegionClosure* cl, oop obj);
632 void handle_evacuation_failure_common(oop obj, markOop m);
633
634
635 // Ensure that the relevant gc_alloc regions are set.
636 void get_gc_alloc_regions();
637 // We're done with GC alloc regions. We are going to tear down the
638 // gc alloc list and remove the gc alloc tag from all the regions on
639 // that list. However, we will also retain the last (i.e., the one
640 // that is half-full) GC alloc region, per GCAllocPurpose, for
641 // possible reuse during the next collection, provided
642 // _retain_gc_alloc_region[] indicates that it should be the
643 // case. Said regions are kept in the _retained_gc_alloc_regions[]
644 // array. If the parameter totally is set, we will not retain any
645 // regions, irrespective of what _retain_gc_alloc_region[]
646 // indicates.
647 void release_gc_alloc_regions(bool totally);
648 #ifndef PRODUCT
649 // Useful for debugging.
650 void print_gc_alloc_regions();
651 #endif // !PRODUCT
652
653 // ("Weak") Reference processing support
654 ReferenceProcessor* _ref_processor;
655
656 enum G1H_process_strong_roots_tasks {
657 G1H_PS_mark_stack_oops_do,
658 G1H_PS_refProcessor_oops_do,
659 // Leave this one last.
660 G1H_PS_NumElements
661 };
662
663 SubTasksDone* _process_strong_tasks;
664
665 // List of regions which require zero filling.
666 UncleanRegionList _unclean_region_list;
667 bool _unclean_regions_coming;
668
669 public:
670 void set_refine_cte_cl_concurrency(bool concurrent);
671
672 RefToScanQueue *task_queue(int i) const;
673
674 // A set of cards where updates happened during the GC
675 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
676
677 // A DirtyCardQueueSet that is used to hold cards that contain
678 // references into the current collection set. This is used to
679 // update the remembered sets of the regions in the collection
680 // set in the event of an evacuation failure.
681 DirtyCardQueueSet& into_cset_dirty_card_queue_set()
682 { return _into_cset_dirty_card_queue_set; }
683
684 // Create a G1CollectedHeap with the specified policy.
685 // Must call the initialize method afterwards.
686 // May not return if something goes wrong.
687 G1CollectedHeap(G1CollectorPolicy* policy);
688
689 // Initialize the G1CollectedHeap to have the initial and
690 // maximum sizes, permanent generation, and remembered and barrier sets
691 // specified by the policy object.
692 jint initialize();
693
694 void ref_processing_init();
695
696 void set_par_threads(int t) {
697 SharedHeap::set_par_threads(t);
698 _process_strong_tasks->set_par_threads(t);
699 }
700
701 virtual CollectedHeap::Name kind() const {
702 return CollectedHeap::G1CollectedHeap;
703 }
704
705 // The current policy object for the collector.
706 G1CollectorPolicy* g1_policy() const { return _g1_policy; }
707
708 // Adaptive size policy. No such thing for g1.
709 virtual AdaptiveSizePolicy* size_policy() { return NULL; }
710
711 // The rem set and barrier set.
712 G1RemSet* g1_rem_set() const { return _g1_rem_set; }
713 ModRefBarrierSet* mr_bs() const { return _mr_bs; }
714
715 // The rem set iterator.
716 HeapRegionRemSetIterator* rem_set_iterator(int i) {
717 return _rem_set_iterator[i];
718 }
719
720 HeapRegionRemSetIterator* rem_set_iterator() {
721 return _rem_set_iterator[0];
722 }
723
724 unsigned get_gc_time_stamp() {
725 return _gc_time_stamp;
726 }
727
728 void reset_gc_time_stamp() {
729 _gc_time_stamp = 0;
730 OrderAccess::fence();
731 }
732
733 void increment_gc_time_stamp() {
734 ++_gc_time_stamp;
735 OrderAccess::fence();
736 }
737
738 void iterate_dirty_card_closure(CardTableEntryClosure* cl,
739 DirtyCardQueue* into_cset_dcq,
740 bool concurrent, int worker_i);
741
742 // The shared block offset table array.
743 G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
744
745 // Reference Processing accessor
746 ReferenceProcessor* ref_processor() { return _ref_processor; }
747
748 // Reserved (g1 only; super method includes perm), capacity and the used
749 // portion in bytes.
750 size_t g1_reserved_obj_bytes() const { return _g1_reserved.byte_size(); }
751 virtual size_t capacity() const;
752 virtual size_t used() const;
753 // This should be called when we're not holding the heap lock. The
754 // result might be a bit inaccurate.
755 size_t used_unlocked() const;
756 size_t recalculate_used() const;
757 #ifndef PRODUCT
758 size_t recalculate_used_regions() const;
759 #endif // PRODUCT
760
761 // These virtual functions do the actual allocation.
762 virtual HeapWord* mem_allocate(size_t word_size,
763 bool is_noref,
764 bool is_tlab,
765 bool* gc_overhead_limit_was_exceeded);
766
767 // Some heaps may offer a contiguous region for shared non-blocking
768 // allocation, via inlined code (by exporting the address of the top and
769 // end fields defining the extent of the contiguous allocation region.)
770 // But G1CollectedHeap doesn't yet support this.
771
772 // Return an estimate of the maximum allocation that could be performed
773 // without triggering any collection or expansion activity. In a
774 // generational collector, for example, this is probably the largest
775 // allocation that could be supported (without expansion) in the youngest
776 // generation. It is "unsafe" because no locks are taken; the result
777 // should be treated as an approximation, not a guarantee, for use in
778 // heuristic resizing decisions.
779 virtual size_t unsafe_max_alloc();
780
781 virtual bool is_maximal_no_gc() const {
782 return _g1_storage.uncommitted_size() == 0;
783 }
784
785 // The total number of regions in the heap.
786 size_t n_regions();
787
788 // The number of regions that are completely free.
789 size_t max_regions();
790
791 // The number of regions that are completely free.
792 size_t free_regions();
793
794 // The number of regions that are not completely free.
795 size_t used_regions() { return n_regions() - free_regions(); }
796
797 // True iff the ZF thread should run.
798 bool should_zf();
799
800 // The number of regions available for "regular" expansion.
801 size_t expansion_regions() { return _expansion_regions; }
802
803 #ifndef PRODUCT
804 bool regions_accounted_for();
805 bool print_region_accounting_info();
806 void print_region_counts();
807 #endif
808
809 HeapRegion* alloc_region_from_unclean_list(bool zero_filled);
810 HeapRegion* alloc_region_from_unclean_list_locked(bool zero_filled);
811
812 void put_region_on_unclean_list(HeapRegion* r);
813 void put_region_on_unclean_list_locked(HeapRegion* r);
814
815 void prepend_region_list_on_unclean_list(UncleanRegionList* list);
816 void prepend_region_list_on_unclean_list_locked(UncleanRegionList* list);
817
818 void set_unclean_regions_coming(bool b);
819 void set_unclean_regions_coming_locked(bool b);
820 // Wait for cleanup to be complete.
821 void wait_for_cleanup_complete();
822 // Like above, but assumes that the calling thread owns the Heap_lock.
823 void wait_for_cleanup_complete_locked();
824
825 // Return the head of the unclean list.
826 HeapRegion* peek_unclean_region_list_locked();
827 // Remove and return the head of the unclean list.
828 HeapRegion* pop_unclean_region_list_locked();
829
830 // List of regions which are zero filled and ready for allocation.
831 HeapRegion* _free_region_list;
832 // Number of elements on the free list.
833 size_t _free_region_list_size;
834
835 // If the head of the unclean list is ZeroFilled, move it to the free
836 // list.
837 bool move_cleaned_region_to_free_list_locked();
838 bool move_cleaned_region_to_free_list();
839
840 void put_free_region_on_list_locked(HeapRegion* r);
841 void put_free_region_on_list(HeapRegion* r);
842
843 // Remove and return the head element of the free list.
844 HeapRegion* pop_free_region_list_locked();
845
846 // If "zero_filled" is true, we first try the free list, then we try the
847 // unclean list, zero-filling the result. If "zero_filled" is false, we
848 // first try the unclean list, then the zero-filled list.
849 HeapRegion* alloc_free_region_from_lists(bool zero_filled);
850
851 // Verify the integrity of the region lists.
852 void remove_allocated_regions_from_lists();
853 bool verify_region_lists();
854 bool verify_region_lists_locked();
855 size_t unclean_region_list_length();
856 size_t free_region_list_length();
857
858 // Perform a collection of the heap; intended for use in implementing
859 // "System.gc". This probably implies as full a collection as the
860 // "CollectedHeap" supports.
861 virtual void collect(GCCause::Cause cause);
862
863 // The same as above but assume that the caller holds the Heap_lock.
864 void collect_locked(GCCause::Cause cause);
865
866 // This interface assumes that it's being called by the
867 // vm thread. It collects the heap assuming that the
868 // heap lock is already held and that we are executing in
869 // the context of the vm thread.
870 virtual void collect_as_vm_thread(GCCause::Cause cause);
871
872 // True iff a evacuation has failed in the most-recent collection.
873 bool evacuation_failed() { return _evacuation_failed; }
874
875 // Free a region if it is totally full of garbage. Returns the number of
876 // bytes freed (0 ==> didn't free it).
877 size_t free_region_if_totally_empty(HeapRegion *hr);
878 void free_region_if_totally_empty_work(HeapRegion *hr,
879 size_t& pre_used,
880 size_t& cleared_h_regions,
881 size_t& freed_regions,
882 UncleanRegionList* list,
883 bool par = false);
884
885 // If we've done free region work that yields the given changes, update
886 // the relevant global variables.
887 void finish_free_region_work(size_t pre_used,
888 size_t cleared_h_regions,
889 size_t freed_regions,
890 UncleanRegionList* list);
891
892
893 // Returns "TRUE" iff "p" points into the allocated area of the heap.
894 virtual bool is_in(const void* p) const;
895
896 // Return "TRUE" iff the given object address is within the collection
897 // set.
898 inline bool obj_in_cs(oop obj);
899
900 // Return "TRUE" iff the given object address is in the reserved
901 // region of g1 (excluding the permanent generation).
902 bool is_in_g1_reserved(const void* p) const {
903 return _g1_reserved.contains(p);
904 }
905
906 // Returns a MemRegion that corresponds to the space that has been
907 // committed in the heap
908 MemRegion g1_committed() {
909 return _g1_committed;
910 }
911
912 NOT_PRODUCT(bool is_in_closed_subset(const void* p) const;)
913
914 // Dirty card table entries covering a list of young regions.
915 void dirtyCardsForYoungRegions(CardTableModRefBS* ct_bs, HeapRegion* list);
916
917 // This resets the card table to all zeros. It is used after
918 // a collection pause which used the card table to claim cards.
919 void cleanUpCardTable();
920
921 // Iteration functions.
922
923 // Iterate over all the ref-containing fields of all objects, calling
924 // "cl.do_oop" on each.
925 virtual void oop_iterate(OopClosure* cl) {
926 oop_iterate(cl, true);
927 }
928 void oop_iterate(OopClosure* cl, bool do_perm);
929
930 // Same as above, restricted to a memory region.
931 virtual void oop_iterate(MemRegion mr, OopClosure* cl) {
932 oop_iterate(mr, cl, true);
933 }
934 void oop_iterate(MemRegion mr, OopClosure* cl, bool do_perm);
935
936 // Iterate over all objects, calling "cl.do_object" on each.
937 virtual void object_iterate(ObjectClosure* cl) {
938 object_iterate(cl, true);
939 }
940 virtual void safe_object_iterate(ObjectClosure* cl) {
941 object_iterate(cl, true);
942 }
943 void object_iterate(ObjectClosure* cl, bool do_perm);
944
945 // Iterate over all objects allocated since the last collection, calling
946 // "cl.do_object" on each. The heap must have been initialized properly
947 // to support this function, or else this call will fail.
948 virtual void object_iterate_since_last_GC(ObjectClosure* cl);
949
950 // Iterate over all spaces in use in the heap, in ascending address order.
951 virtual void space_iterate(SpaceClosure* cl);
952
953 // Iterate over heap regions, in address order, terminating the
954 // iteration early if the "doHeapRegion" method returns "true".
955 void heap_region_iterate(HeapRegionClosure* blk);
956
957 // Iterate over heap regions starting with r (or the first region if "r"
958 // is NULL), in address order, terminating early if the "doHeapRegion"
959 // method returns "true".
960 void heap_region_iterate_from(HeapRegion* r, HeapRegionClosure* blk);
961
962 // As above but starting from the region at index idx.
963 void heap_region_iterate_from(int idx, HeapRegionClosure* blk);
964
965 HeapRegion* region_at(size_t idx);
966
967 // Divide the heap region sequence into "chunks" of some size (the number
968 // of regions divided by the number of parallel threads times some
969 // overpartition factor, currently 4). Assumes that this will be called
970 // in parallel by ParallelGCThreads worker threads with discinct worker
971 // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel
972 // calls will use the same "claim_value", and that that claim value is
973 // different from the claim_value of any heap region before the start of
974 // the iteration. Applies "blk->doHeapRegion" to each of the regions, by
975 // attempting to claim the first region in each chunk, and, if
976 // successful, applying the closure to each region in the chunk (and
977 // setting the claim value of the second and subsequent regions of the
978 // chunk.) For now requires that "doHeapRegion" always returns "false",
979 // i.e., that a closure never attempt to abort a traversal.
980 void heap_region_par_iterate_chunked(HeapRegionClosure* blk,
981 int worker,
982 jint claim_value);
983
984 // It resets all the region claim values to the default.
985 void reset_heap_region_claim_values();
986
987 #ifdef ASSERT
988 bool check_heap_region_claim_values(jint claim_value);
989 #endif // ASSERT
990
991 // Iterate over the regions (if any) in the current collection set.
992 void collection_set_iterate(HeapRegionClosure* blk);
993
994 // As above but starting from region r
995 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
996
997 // Returns the first (lowest address) compactible space in the heap.
998 virtual CompactibleSpace* first_compactible_space();
999
1000 // A CollectedHeap will contain some number of spaces. This finds the
1001 // space containing a given address, or else returns NULL.
1002 virtual Space* space_containing(const void* addr) const;
1003
1004 // A G1CollectedHeap will contain some number of heap regions. This
1005 // finds the region containing a given address, or else returns NULL.
1006 HeapRegion* heap_region_containing(const void* addr) const;
1007
1008 // Like the above, but requires "addr" to be in the heap (to avoid a
1009 // null-check), and unlike the above, may return an continuing humongous
1010 // region.
1011 HeapRegion* heap_region_containing_raw(const void* addr) const;
1012
1013 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1014 // each address in the (reserved) heap is a member of exactly
1015 // one block. The defining characteristic of a block is that it is
1016 // possible to find its size, and thus to progress forward to the next
1017 // block. (Blocks may be of different sizes.) Thus, blocks may
1018 // represent Java objects, or they might be free blocks in a
1019 // free-list-based heap (or subheap), as long as the two kinds are
1020 // distinguishable and the size of each is determinable.
1021
1022 // Returns the address of the start of the "block" that contains the
1023 // address "addr". We say "blocks" instead of "object" since some heaps
1024 // may not pack objects densely; a chunk may either be an object or a
1025 // non-object.
1026 virtual HeapWord* block_start(const void* addr) const;
1027
1028 // Requires "addr" to be the start of a chunk, and returns its size.
1029 // "addr + size" is required to be the start of a new chunk, or the end
1030 // of the active area of the heap.
1031 virtual size_t block_size(const HeapWord* addr) const;
1032
1033 // Requires "addr" to be the start of a block, and returns "TRUE" iff
1034 // the block is an object.
1035 virtual bool block_is_obj(const HeapWord* addr) const;
1036
1037 // Does this heap support heap inspection? (+PrintClassHistogram)
1038 virtual bool supports_heap_inspection() const { return true; }
1039
1040 // Section on thread-local allocation buffers (TLABs)
1041 // See CollectedHeap for semantics.
1042
1043 virtual bool supports_tlab_allocation() const;
1044 virtual size_t tlab_capacity(Thread* thr) const;
1045 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
1046 virtual HeapWord* allocate_new_tlab(size_t word_size);
1047
1048 // Can a compiler initialize a new object without store barriers?
1049 // This permission only extends from the creation of a new object
1050 // via a TLAB up to the first subsequent safepoint. If such permission
1051 // is granted for this heap type, the compiler promises to call
1052 // defer_store_barrier() below on any slow path allocation of
1053 // a new object for which such initializing store barriers will
1054 // have been elided. G1, like CMS, allows this, but should be
1055 // ready to provide a compensating write barrier as necessary
1056 // if that storage came out of a non-young region. The efficiency
1057 // of this implementation depends crucially on being able to
1058 // answer very efficiently in constant time whether a piece of
1059 // storage in the heap comes from a young region or not.
1060 // See ReduceInitialCardMarks.
1061 virtual bool can_elide_tlab_store_barriers() const {
1062 // 6920090: Temporarily disabled, because of lingering
1063 // instabilities related to RICM with G1. In the
1064 // interim, the option ReduceInitialCardMarksForG1
1065 // below is left solely as a debugging device at least
1066 // until 6920109 fixes the instabilities.
1067 return ReduceInitialCardMarksForG1;
1068 }
1069
1070 virtual bool card_mark_must_follow_store() const {
1071 return true;
1072 }
1073
1074 bool is_in_young(oop obj) {
1075 HeapRegion* hr = heap_region_containing(obj);
1076 return hr != NULL && hr->is_young();
1077 }
1078
1079 // We don't need barriers for initializing stores to objects
1080 // in the young gen: for the SATB pre-barrier, there is no
1081 // pre-value that needs to be remembered; for the remembered-set
1082 // update logging post-barrier, we don't maintain remembered set
1083 // information for young gen objects. Note that non-generational
1084 // G1 does not have any "young" objects, should not elide
1085 // the rs logging barrier and so should always answer false below.
1086 // However, non-generational G1 (-XX:-G1Gen) appears to have
1087 // bit-rotted so was not tested below.
1088 virtual bool can_elide_initializing_store_barrier(oop new_obj) {
1089 // Re 6920090, 6920109 above.
1090 assert(ReduceInitialCardMarksForG1, "Else cannot be here");
1091 assert(G1Gen || !is_in_young(new_obj),
1092 "Non-generational G1 should never return true below");
1093 return is_in_young(new_obj);
1094 }
1095
1096 // Can a compiler elide a store barrier when it writes
1097 // a permanent oop into the heap? Applies when the compiler
1098 // is storing x to the heap, where x->is_perm() is true.
1099 virtual bool can_elide_permanent_oop_store_barriers() const {
1100 // At least until perm gen collection is also G1-ified, at
1101 // which point this should return false.
1102 return true;
1103 }
1104
1105 virtual bool allocs_are_zero_filled();
1106
1107 // The boundary between a "large" and "small" array of primitives, in
1108 // words.
1109 virtual size_t large_typearray_limit();
1110
1111 // Returns "true" iff the given word_size is "very large".
1112 static bool isHumongous(size_t word_size) {
1113 // Note this has to be strictly greater-than as the TLABs
1114 // are capped at the humongous thresold and we want to
1115 // ensure that we don't try to allocate a TLAB as
1116 // humongous and that we don't allocate a humongous
1117 // object in a TLAB.
1118 return word_size > _humongous_object_threshold_in_words;
1119 }
1120
1121 // Update mod union table with the set of dirty cards.
1122 void updateModUnion();
1123
1124 // Set the mod union bits corresponding to the given memRegion. Note
1125 // that this is always a safe operation, since it doesn't clear any
1126 // bits.
1127 void markModUnionRange(MemRegion mr);
1128
1129 // Records the fact that a marking phase is no longer in progress.
1130 void set_marking_complete() {
1131 _mark_in_progress = false;
1132 }
1133 void set_marking_started() {
1134 _mark_in_progress = true;
1135 }
1136 bool mark_in_progress() {
1137 return _mark_in_progress;
1138 }
1139
1140 // Print the maximum heap capacity.
1141 virtual size_t max_capacity() const;
1142
1143 virtual jlong millis_since_last_gc();
1144
1145 // Perform any cleanup actions necessary before allowing a verification.
1146 virtual void prepare_for_verify();
1147
1148 // Perform verification.
1149
1150 // use_prev_marking == true -> use "prev" marking information,
1151 // use_prev_marking == false -> use "next" marking information
1152 // NOTE: Only the "prev" marking information is guaranteed to be
1153 // consistent most of the time, so most calls to this should use
1154 // use_prev_marking == true. Currently, there is only one case where
1155 // this is called with use_prev_marking == false, which is to verify
1156 // the "next" marking information at the end of remark.
1157 void verify(bool allow_dirty, bool silent, bool use_prev_marking);
1158
1159 // Override; it uses the "prev" marking information
1160 virtual void verify(bool allow_dirty, bool silent);
1161 // Default behavior by calling print(tty);
1162 virtual void print() const;
1163 // This calls print_on(st, PrintHeapAtGCExtended).
1164 virtual void print_on(outputStream* st) const;
1165 // If extended is true, it will print out information for all
1166 // regions in the heap by calling print_on_extended(st).
1167 virtual void print_on(outputStream* st, bool extended) const;
1168 virtual void print_on_extended(outputStream* st) const;
1169
1170 virtual void print_gc_threads_on(outputStream* st) const;
1171 virtual void gc_threads_do(ThreadClosure* tc) const;
1172
1173 // Override
1174 void print_tracing_info() const;
1175
1176 // If "addr" is a pointer into the (reserved?) heap, returns a positive
1177 // number indicating the "arena" within the heap in which "addr" falls.
1178 // Or else returns 0.
1179 virtual int addr_to_arena_id(void* addr) const;
1180
1181 // Convenience function to be used in situations where the heap type can be
1182 // asserted to be this type.
1183 static G1CollectedHeap* heap();
1184
1185 void empty_young_list();
1186 bool should_set_young_locked();
1187
1188 void set_region_short_lived_locked(HeapRegion* hr);
1189 // add appropriate methods for any other surv rate groups
1190
1191 YoungList* young_list() { return _young_list; }
1192
1193 // debugging
1194 bool check_young_list_well_formed() {
1195 return _young_list->check_list_well_formed();
1196 }
1197
1198 bool check_young_list_empty(bool check_heap,
1199 bool check_sample = true);
1200
1201 // *** Stuff related to concurrent marking. It's not clear to me that so
1202 // many of these need to be public.
1203
1204 // The functions below are helper functions that a subclass of
1205 // "CollectedHeap" can use in the implementation of its virtual
1206 // functions.
1207 // This performs a concurrent marking of the live objects in a
1208 // bitmap off to the side.
1209 void doConcurrentMark();
1210
1211 // This is called from the marksweep collector which then does
1212 // a concurrent mark and verifies that the results agree with
1213 // the stop the world marking.
1214 void checkConcurrentMark();
1215 void do_sync_mark();
1216
1217 bool isMarkedPrev(oop obj) const;
1218 bool isMarkedNext(oop obj) const;
1219
1220 // use_prev_marking == true -> use "prev" marking information,
1221 // use_prev_marking == false -> use "next" marking information
1222 bool is_obj_dead_cond(const oop obj,
1223 const HeapRegion* hr,
1224 const bool use_prev_marking) const {
1225 if (use_prev_marking) {
1226 return is_obj_dead(obj, hr);
1227 } else {
1228 return is_obj_ill(obj, hr);
1229 }
1230 }
1231
1232 // Determine if an object is dead, given the object and also
1233 // the region to which the object belongs. An object is dead
1234 // iff a) it was not allocated since the last mark and b) it
1235 // is not marked.
1236
1237 bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1238 return
1239 !hr->obj_allocated_since_prev_marking(obj) &&
1240 !isMarkedPrev(obj);
1241 }
1242
1243 // This is used when copying an object to survivor space.
1244 // If the object is marked live, then we mark the copy live.
1245 // If the object is allocated since the start of this mark
1246 // cycle, then we mark the copy live.
1247 // If the object has been around since the previous mark
1248 // phase, and hasn't been marked yet during this phase,
1249 // then we don't mark it, we just wait for the
1250 // current marking cycle to get to it.
1251
1252 // This function returns true when an object has been
1253 // around since the previous marking and hasn't yet
1254 // been marked during this marking.
1255
1256 bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1257 return
1258 !hr->obj_allocated_since_next_marking(obj) &&
1259 !isMarkedNext(obj);
1260 }
1261
1262 // Determine if an object is dead, given only the object itself.
1263 // This will find the region to which the object belongs and
1264 // then call the region version of the same function.
1265
1266 // Added if it is in permanent gen it isn't dead.
1267 // Added if it is NULL it isn't dead.
1268
1269 // use_prev_marking == true -> use "prev" marking information,
1270 // use_prev_marking == false -> use "next" marking information
1271 bool is_obj_dead_cond(const oop obj,
1272 const bool use_prev_marking) {
1273 if (use_prev_marking) {
1274 return is_obj_dead(obj);
1275 } else {
1276 return is_obj_ill(obj);
1277 }
1278 }
1279
1280 bool is_obj_dead(const oop obj) {
1281 const HeapRegion* hr = heap_region_containing(obj);
1282 if (hr == NULL) {
1283 if (Universe::heap()->is_in_permanent(obj))
1284 return false;
1285 else if (obj == NULL) return false;
1286 else return true;
1287 }
1288 else return is_obj_dead(obj, hr);
1289 }
1290
1291 bool is_obj_ill(const oop obj) {
1292 const HeapRegion* hr = heap_region_containing(obj);
1293 if (hr == NULL) {
1294 if (Universe::heap()->is_in_permanent(obj))
1295 return false;
1296 else if (obj == NULL) return false;
1297 else return true;
1298 }
1299 else return is_obj_ill(obj, hr);
1300 }
1301
1302 // The following is just to alert the verification code
1303 // that a full collection has occurred and that the
1304 // remembered sets are no longer up to date.
1305 bool _full_collection;
1306 void set_full_collection() { _full_collection = true;}
1307 void clear_full_collection() {_full_collection = false;}
1308 bool full_collection() {return _full_collection;}
1309
1310 ConcurrentMark* concurrent_mark() const { return _cm; }
1311 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1312
1313 // The dirty cards region list is used to record a subset of regions
1314 // whose cards need clearing. The list if populated during the
1315 // remembered set scanning and drained during the card table
1316 // cleanup. Although the methods are reentrant, population/draining
1317 // phases must not overlap. For synchronization purposes the last
1318 // element on the list points to itself.
1319 HeapRegion* _dirty_cards_region_list;
1320 void push_dirty_cards_region(HeapRegion* hr);
1321 HeapRegion* pop_dirty_cards_region();
1322
1323 public:
1324 void stop_conc_gc_threads();
1325
1326 // <NEW PREDICTION>
1327
1328 double predict_region_elapsed_time_ms(HeapRegion* hr, bool young);
1329 void check_if_region_is_too_expensive(double predicted_time_ms);
1330 size_t pending_card_num();
1331 size_t max_pending_card_num();
1332 size_t cards_scanned();
1333
1334 // </NEW PREDICTION>
1335
1336 protected:
1337 size_t _max_heap_capacity;
1338
1339 // debug_only(static void check_for_valid_allocation_state();)
1340
1341 public:
1342 // Temporary: call to mark things unimplemented for the G1 heap (e.g.,
1343 // MemoryService). In productization, we can make this assert false
1344 // to catch such places (as well as searching for calls to this...)
1345 static void g1_unimplemented();
1346
1347 };
1348
1349 #define use_local_bitmaps 1
1350 #define verify_local_bitmaps 0
1351 #define oop_buffer_length 256
1352
1353 #ifndef PRODUCT
1354 class GCLabBitMap;
1355 class GCLabBitMapClosure: public BitMapClosure {
1356 private:
1357 ConcurrentMark* _cm;
1358 GCLabBitMap* _bitmap;
1359
1360 public:
1361 GCLabBitMapClosure(ConcurrentMark* cm,
1362 GCLabBitMap* bitmap) {
1363 _cm = cm;
1364 _bitmap = bitmap;
1365 }
1366
1367 virtual bool do_bit(size_t offset);
1368 };
1369 #endif // !PRODUCT
1370
1371 class GCLabBitMap: public BitMap {
1372 private:
1373 ConcurrentMark* _cm;
1374
1375 int _shifter;
1376 size_t _bitmap_word_covers_words;
1377
1378 // beginning of the heap
1379 HeapWord* _heap_start;
1380
1381 // this is the actual start of the GCLab
1382 HeapWord* _real_start_word;
1383
1384 // this is the actual end of the GCLab
1385 HeapWord* _real_end_word;
1386
1387 // this is the first word, possibly located before the actual start
1388 // of the GCLab, that corresponds to the first bit of the bitmap
1389 HeapWord* _start_word;
1390
1391 // size of a GCLab in words
1392 size_t _gclab_word_size;
1393
1394 static int shifter() {
1395 return MinObjAlignment - 1;
1396 }
1397
1398 // how many heap words does a single bitmap word corresponds to?
1399 static size_t bitmap_word_covers_words() {
1400 return BitsPerWord << shifter();
1401 }
1402
1403 size_t gclab_word_size() const {
1404 return _gclab_word_size;
1405 }
1406
1407 // Calculates actual GCLab size in words
1408 size_t gclab_real_word_size() const {
1409 return bitmap_size_in_bits(pointer_delta(_real_end_word, _start_word))
1410 / BitsPerWord;
1411 }
1412
1413 static size_t bitmap_size_in_bits(size_t gclab_word_size) {
1414 size_t bits_in_bitmap = gclab_word_size >> shifter();
1415 // We are going to ensure that the beginning of a word in this
1416 // bitmap also corresponds to the beginning of a word in the
1417 // global marking bitmap. To handle the case where a GCLab
1418 // starts from the middle of the bitmap, we need to add enough
1419 // space (i.e. up to a bitmap word) to ensure that we have
1420 // enough bits in the bitmap.
1421 return bits_in_bitmap + BitsPerWord - 1;
1422 }
1423 public:
1424 GCLabBitMap(HeapWord* heap_start, size_t gclab_word_size)
1425 : BitMap(bitmap_size_in_bits(gclab_word_size)),
1426 _cm(G1CollectedHeap::heap()->concurrent_mark()),
1427 _shifter(shifter()),
1428 _bitmap_word_covers_words(bitmap_word_covers_words()),
1429 _heap_start(heap_start),
1430 _gclab_word_size(gclab_word_size),
1431 _real_start_word(NULL),
1432 _real_end_word(NULL),
1433 _start_word(NULL)
1434 {
1435 guarantee( size_in_words() >= bitmap_size_in_words(),
1436 "just making sure");
1437 }
1438
1439 inline unsigned heapWordToOffset(HeapWord* addr) {
1440 unsigned offset = (unsigned) pointer_delta(addr, _start_word) >> _shifter;
1441 assert(offset < size(), "offset should be within bounds");
1442 return offset;
1443 }
1444
1445 inline HeapWord* offsetToHeapWord(size_t offset) {
1446 HeapWord* addr = _start_word + (offset << _shifter);
1447 assert(_real_start_word <= addr && addr < _real_end_word, "invariant");
1448 return addr;
1449 }
1450
1451 bool fields_well_formed() {
1452 bool ret1 = (_real_start_word == NULL) &&
1453 (_real_end_word == NULL) &&
1454 (_start_word == NULL);
1455 if (ret1)
1456 return true;
1457
1458 bool ret2 = _real_start_word >= _start_word &&
1459 _start_word < _real_end_word &&
1460 (_real_start_word + _gclab_word_size) == _real_end_word &&
1461 (_start_word + _gclab_word_size + _bitmap_word_covers_words)
1462 > _real_end_word;
1463 return ret2;
1464 }
1465
1466 inline bool mark(HeapWord* addr) {
1467 guarantee(use_local_bitmaps, "invariant");
1468 assert(fields_well_formed(), "invariant");
1469
1470 if (addr >= _real_start_word && addr < _real_end_word) {
1471 assert(!isMarked(addr), "should not have already been marked");
1472
1473 // first mark it on the bitmap
1474 at_put(heapWordToOffset(addr), true);
1475
1476 return true;
1477 } else {
1478 return false;
1479 }
1480 }
1481
1482 inline bool isMarked(HeapWord* addr) {
1483 guarantee(use_local_bitmaps, "invariant");
1484 assert(fields_well_formed(), "invariant");
1485
1486 return at(heapWordToOffset(addr));
1487 }
1488
1489 void set_buffer(HeapWord* start) {
1490 guarantee(use_local_bitmaps, "invariant");
1491 clear();
1492
1493 assert(start != NULL, "invariant");
1494 _real_start_word = start;
1495 _real_end_word = start + _gclab_word_size;
1496
1497 size_t diff =
1498 pointer_delta(start, _heap_start) % _bitmap_word_covers_words;
1499 _start_word = start - diff;
1500
1501 assert(fields_well_formed(), "invariant");
1502 }
1503
1504 #ifndef PRODUCT
1505 void verify() {
1506 // verify that the marks have been propagated
1507 GCLabBitMapClosure cl(_cm, this);
1508 iterate(&cl);
1509 }
1510 #endif // PRODUCT
1511
1512 void retire() {
1513 guarantee(use_local_bitmaps, "invariant");
1514 assert(fields_well_formed(), "invariant");
1515
1516 if (_start_word != NULL) {
1517 CMBitMap* mark_bitmap = _cm->nextMarkBitMap();
1518
1519 // this means that the bitmap was set up for the GCLab
1520 assert(_real_start_word != NULL && _real_end_word != NULL, "invariant");
1521
1522 mark_bitmap->mostly_disjoint_range_union(this,
1523 0, // always start from the start of the bitmap
1524 _start_word,
1525 gclab_real_word_size());
1526 _cm->grayRegionIfNecessary(MemRegion(_real_start_word, _real_end_word));
1527
1528 #ifndef PRODUCT
1529 if (use_local_bitmaps && verify_local_bitmaps)
1530 verify();
1531 #endif // PRODUCT
1532 } else {
1533 assert(_real_start_word == NULL && _real_end_word == NULL, "invariant");
1534 }
1535 }
1536
1537 size_t bitmap_size_in_words() const {
1538 return (bitmap_size_in_bits(gclab_word_size()) + BitsPerWord - 1) / BitsPerWord;
1539 }
1540
1541 };
1542
1543 class G1ParGCAllocBuffer: public ParGCAllocBuffer {
1544 private:
1545 bool _retired;
1546 bool _during_marking;
1547 GCLabBitMap _bitmap;
1548
1549 public:
1550 G1ParGCAllocBuffer(size_t gclab_word_size) :
1551 ParGCAllocBuffer(gclab_word_size),
1552 _during_marking(G1CollectedHeap::heap()->mark_in_progress()),
1553 _bitmap(G1CollectedHeap::heap()->reserved_region().start(), gclab_word_size),
1554 _retired(false)
1555 { }
1556
1557 inline bool mark(HeapWord* addr) {
1558 guarantee(use_local_bitmaps, "invariant");
1559 assert(_during_marking, "invariant");
1560 return _bitmap.mark(addr);
1561 }
1562
1563 inline void set_buf(HeapWord* buf) {
1564 if (use_local_bitmaps && _during_marking)
1565 _bitmap.set_buffer(buf);
1566 ParGCAllocBuffer::set_buf(buf);
1567 _retired = false;
1568 }
1569
1570 inline void retire(bool end_of_gc, bool retain) {
1571 if (_retired)
1572 return;
1573 if (use_local_bitmaps && _during_marking) {
1574 _bitmap.retire();
1575 }
1576 ParGCAllocBuffer::retire(end_of_gc, retain);
1577 _retired = true;
1578 }
1579 };
1580
1581 class G1ParScanThreadState : public StackObj {
1582 protected:
1583 G1CollectedHeap* _g1h;
1584 RefToScanQueue* _refs;
1585 DirtyCardQueue _dcq;
1586 CardTableModRefBS* _ct_bs;
1587 G1RemSet* _g1_rem;
1588
1589 G1ParGCAllocBuffer _surviving_alloc_buffer;
1590 G1ParGCAllocBuffer _tenured_alloc_buffer;
1591 G1ParGCAllocBuffer* _alloc_buffers[GCAllocPurposeCount];
1592 ageTable _age_table;
1593
1594 size_t _alloc_buffer_waste;
1595 size_t _undo_waste;
1596
1597 OopsInHeapRegionClosure* _evac_failure_cl;
1598 G1ParScanHeapEvacClosure* _evac_cl;
1599 G1ParScanPartialArrayClosure* _partial_scan_cl;
1600
1601 int _hash_seed;
1602 int _queue_num;
1603
1604 size_t _term_attempts;
1605
1606 double _start;
1607 double _start_strong_roots;
1608 double _strong_roots_time;
1609 double _start_term;
1610 double _term_time;
1611
1612 // Map from young-age-index (0 == not young, 1 is youngest) to
1613 // surviving words. base is what we get back from the malloc call
1614 size_t* _surviving_young_words_base;
1615 // this points into the array, as we use the first few entries for padding
1616 size_t* _surviving_young_words;
1617
1618 #define PADDING_ELEM_NUM (DEFAULT_CACHE_LINE_SIZE / sizeof(size_t))
1619
1620 void add_to_alloc_buffer_waste(size_t waste) { _alloc_buffer_waste += waste; }
1621
1622 void add_to_undo_waste(size_t waste) { _undo_waste += waste; }
1623
1624 DirtyCardQueue& dirty_card_queue() { return _dcq; }
1625 CardTableModRefBS* ctbs() { return _ct_bs; }
1626
1627 template <class T> void immediate_rs_update(HeapRegion* from, T* p, int tid) {
1628 if (!from->is_survivor()) {
1629 _g1_rem->par_write_ref(from, p, tid);
1630 }
1631 }
1632
1633 template <class T> void deferred_rs_update(HeapRegion* from, T* p, int tid) {
1634 // If the new value of the field points to the same region or
1635 // is the to-space, we don't need to include it in the Rset updates.
1636 if (!from->is_in_reserved(oopDesc::load_decode_heap_oop(p)) && !from->is_survivor()) {
1637 size_t card_index = ctbs()->index_for(p);
1638 // If the card hasn't been added to the buffer, do it.
1639 if (ctbs()->mark_card_deferred(card_index)) {
1640 dirty_card_queue().enqueue((jbyte*)ctbs()->byte_for_index(card_index));
1641 }
1642 }
1643 }
1644
1645 public:
1646 G1ParScanThreadState(G1CollectedHeap* g1h, int queue_num);
1647
1648 ~G1ParScanThreadState() {
1649 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words_base);
1650 }
1651
1652 RefToScanQueue* refs() { return _refs; }
1653 ageTable* age_table() { return &_age_table; }
1654
1655 G1ParGCAllocBuffer* alloc_buffer(GCAllocPurpose purpose) {
1656 return _alloc_buffers[purpose];
1657 }
1658
1659 size_t alloc_buffer_waste() const { return _alloc_buffer_waste; }
1660 size_t undo_waste() const { return _undo_waste; }
1661
1662 template <class T> void push_on_queue(T* ref) {
1663 assert(ref != NULL, "invariant");
1664 assert(has_partial_array_mask(ref) ||
1665 _g1h->is_in_g1_reserved(oopDesc::load_decode_heap_oop(ref)), "invariant");
1666 #ifdef ASSERT
1667 if (has_partial_array_mask(ref)) {
1668 oop p = clear_partial_array_mask(ref);
1669 // Verify that we point into the CS
1670 assert(_g1h->obj_in_cs(p), "Should be in CS");
1671 }
1672 #endif
1673 refs()->push(ref);
1674 }
1675
1676 void pop_from_queue(StarTask& ref) {
1677 if (refs()->pop_local(ref)) {
1678 assert((oop*)ref != NULL, "pop_local() returned true");
1679 assert(UseCompressedOops || !ref.is_narrow(), "Error");
1680 assert(has_partial_array_mask((oop*)ref) ||
1681 _g1h->is_in_g1_reserved(ref.is_narrow() ? oopDesc::load_decode_heap_oop((narrowOop*)ref)
1682 : oopDesc::load_decode_heap_oop((oop*)ref)),
1683 "invariant");
1684 } else {
1685 StarTask null_task;
1686 ref = null_task;
1687 }
1688 }
1689
1690 void pop_from_overflow_queue(StarTask& ref) {
1691 StarTask new_ref;
1692 refs()->pop_overflow(new_ref);
1693 assert((oop*)new_ref != NULL, "pop() from a local non-empty stack");
1694 assert(UseCompressedOops || !new_ref.is_narrow(), "Error");
1695 assert(has_partial_array_mask((oop*)new_ref) ||
1696 _g1h->is_in_g1_reserved(new_ref.is_narrow() ? oopDesc::load_decode_heap_oop((narrowOop*)new_ref)
1697 : oopDesc::load_decode_heap_oop((oop*)new_ref)),
1698 "invariant");
1699 ref = new_ref;
1700 }
1701
1702 int refs_to_scan() { return refs()->size(); }
1703 int overflowed_refs_to_scan() { return refs()->overflow_stack()->length(); }
1704
1705 template <class T> void update_rs(HeapRegion* from, T* p, int tid) {
1706 if (G1DeferredRSUpdate) {
1707 deferred_rs_update(from, p, tid);
1708 } else {
1709 immediate_rs_update(from, p, tid);
1710 }
1711 }
1712
1713 HeapWord* allocate_slow(GCAllocPurpose purpose, size_t word_sz) {
1714
1715 HeapWord* obj = NULL;
1716 size_t gclab_word_size = _g1h->desired_plab_sz(purpose);
1717 if (word_sz * 100 < gclab_word_size * ParallelGCBufferWastePct) {
1718 G1ParGCAllocBuffer* alloc_buf = alloc_buffer(purpose);
1719 assert(gclab_word_size == alloc_buf->word_sz(),
1720 "dynamic resizing is not supported");
1721 add_to_alloc_buffer_waste(alloc_buf->words_remaining());
1722 alloc_buf->retire(false, false);
1723
1724 HeapWord* buf = _g1h->par_allocate_during_gc(purpose, gclab_word_size);
1725 if (buf == NULL) return NULL; // Let caller handle allocation failure.
1726 // Otherwise.
1727 alloc_buf->set_buf(buf);
1728
1729 obj = alloc_buf->allocate(word_sz);
1730 assert(obj != NULL, "buffer was definitely big enough...");
1731 } else {
1732 obj = _g1h->par_allocate_during_gc(purpose, word_sz);
1733 }
1734 return obj;
1735 }
1736
1737 HeapWord* allocate(GCAllocPurpose purpose, size_t word_sz) {
1738 HeapWord* obj = alloc_buffer(purpose)->allocate(word_sz);
1739 if (obj != NULL) return obj;
1740 return allocate_slow(purpose, word_sz);
1741 }
1742
1743 void undo_allocation(GCAllocPurpose purpose, HeapWord* obj, size_t word_sz) {
1744 if (alloc_buffer(purpose)->contains(obj)) {
1745 assert(alloc_buffer(purpose)->contains(obj + word_sz - 1),
1746 "should contain whole object");
1747 alloc_buffer(purpose)->undo_allocation(obj, word_sz);
1748 } else {
1749 CollectedHeap::fill_with_object(obj, word_sz);
1750 add_to_undo_waste(word_sz);
1751 }
1752 }
1753
1754 void set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_cl) {
1755 _evac_failure_cl = evac_failure_cl;
1756 }
1757 OopsInHeapRegionClosure* evac_failure_closure() {
1758 return _evac_failure_cl;
1759 }
1760
1761 void set_evac_closure(G1ParScanHeapEvacClosure* evac_cl) {
1762 _evac_cl = evac_cl;
1763 }
1764
1765 void set_partial_scan_closure(G1ParScanPartialArrayClosure* partial_scan_cl) {
1766 _partial_scan_cl = partial_scan_cl;
1767 }
1768
1769 int* hash_seed() { return &_hash_seed; }
1770 int queue_num() { return _queue_num; }
1771
1772 size_t term_attempts() const { return _term_attempts; }
1773 void note_term_attempt() { _term_attempts++; }
1774
1775 void start_strong_roots() {
1776 _start_strong_roots = os::elapsedTime();
1777 }
1778 void end_strong_roots() {
1779 _strong_roots_time += (os::elapsedTime() - _start_strong_roots);
1780 }
1781 double strong_roots_time() const { return _strong_roots_time; }
1782
1783 void start_term_time() {
1784 note_term_attempt();
1785 _start_term = os::elapsedTime();
1786 }
1787 void end_term_time() {
1788 _term_time += (os::elapsedTime() - _start_term);
1789 }
1790 double term_time() const { return _term_time; }
1791
1792 double elapsed_time() const {
1793 return os::elapsedTime() - _start;
1794 }
1795
1796 static void
1797 print_termination_stats_hdr(outputStream* const st = gclog_or_tty);
1798 void
1799 print_termination_stats(int i, outputStream* const st = gclog_or_tty) const;
1800
1801 size_t* surviving_young_words() {
1802 // We add on to hide entry 0 which accumulates surviving words for
1803 // age -1 regions (i.e. non-young ones)
1804 return _surviving_young_words;
1805 }
1806
1807 void retire_alloc_buffers() {
1808 for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
1809 size_t waste = _alloc_buffers[ap]->words_remaining();
1810 add_to_alloc_buffer_waste(waste);
1811 _alloc_buffers[ap]->retire(true, false);
1812 }
1813 }
1814
1815 private:
1816 template <class T> void deal_with_reference(T* ref_to_scan) {
1817 if (has_partial_array_mask(ref_to_scan)) {
1818 _partial_scan_cl->do_oop_nv(ref_to_scan);
1819 } else {
1820 // Note: we can use "raw" versions of "region_containing" because
1821 // "obj_to_scan" is definitely in the heap, and is not in a
1822 // humongous region.
1823 HeapRegion* r = _g1h->heap_region_containing_raw(ref_to_scan);
1824 _evac_cl->set_region(r);
1825 _evac_cl->do_oop_nv(ref_to_scan);
1826 }
1827 }
1828
1829 public:
1830 void trim_queue() {
1831 // I've replicated the loop twice, first to drain the overflow
1832 // queue, second to drain the task queue. This is better than
1833 // having a single loop, which checks both conditions and, inside
1834 // it, either pops the overflow queue or the task queue, as each
1835 // loop is tighter. Also, the decision to drain the overflow queue
1836 // first is not arbitrary, as the overflow queue is not visible
1837 // to the other workers, whereas the task queue is. So, we want to
1838 // drain the "invisible" entries first, while allowing the other
1839 // workers to potentially steal the "visible" entries.
1840
1841 while (refs_to_scan() > 0 || overflowed_refs_to_scan() > 0) {
1842 while (overflowed_refs_to_scan() > 0) {
1843 StarTask ref_to_scan;
1844 assert((oop*)ref_to_scan == NULL, "Constructed above");
1845 pop_from_overflow_queue(ref_to_scan);
1846 // We shouldn't have pushed it on the queue if it was not
1847 // pointing into the CSet.
1848 assert((oop*)ref_to_scan != NULL, "Follows from inner loop invariant");
1849 if (ref_to_scan.is_narrow()) {
1850 assert(UseCompressedOops, "Error");
1851 narrowOop* p = (narrowOop*)ref_to_scan;
1852 assert(!has_partial_array_mask(p) &&
1853 _g1h->is_in_g1_reserved(oopDesc::load_decode_heap_oop(p)), "sanity");
1854 deal_with_reference(p);
1855 } else {
1856 oop* p = (oop*)ref_to_scan;
1857 assert((has_partial_array_mask(p) && _g1h->is_in_g1_reserved(clear_partial_array_mask(p))) ||
1858 _g1h->is_in_g1_reserved(oopDesc::load_decode_heap_oop(p)), "sanity");
1859 deal_with_reference(p);
1860 }
1861 }
1862
1863 while (refs_to_scan() > 0) {
1864 StarTask ref_to_scan;
1865 assert((oop*)ref_to_scan == NULL, "Constructed above");
1866 pop_from_queue(ref_to_scan);
1867 if ((oop*)ref_to_scan != NULL) {
1868 if (ref_to_scan.is_narrow()) {
1869 assert(UseCompressedOops, "Error");
1870 narrowOop* p = (narrowOop*)ref_to_scan;
1871 assert(!has_partial_array_mask(p) &&
1872 _g1h->is_in_g1_reserved(oopDesc::load_decode_heap_oop(p)), "sanity");
1873 deal_with_reference(p);
1874 } else {
1875 oop* p = (oop*)ref_to_scan;
1876 assert((has_partial_array_mask(p) && _g1h->obj_in_cs(clear_partial_array_mask(p))) ||
1877 _g1h->is_in_g1_reserved(oopDesc::load_decode_heap_oop(p)), "sanity");
1878 deal_with_reference(p);
1879 }
1880 }
1881 }
1882 }
1883 }
1884 };
1885
1886 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP