1 /*
2 * Copyright (c) 2001, 2015, 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 *
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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,
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23 */
24
25 #ifndef SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP
26 #define SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP
27
28 #include "gc/g1/concurrentMark.hpp"
29 #include "gc/g1/evacuationInfo.hpp"
30 #include "gc/g1/g1AllocRegion.hpp"
31 #include "gc/g1/g1AllocationContext.hpp"
32 #include "gc/g1/g1Allocator.hpp"
33 #include "gc/g1/g1BiasedArray.hpp"
34 #include "gc/g1/g1CollectorState.hpp"
35 #include "gc/g1/g1HRPrinter.hpp"
36 #include "gc/g1/g1InCSetState.hpp"
37 #include "gc/g1/g1MonitoringSupport.hpp"
38 #include "gc/g1/g1SATBCardTableModRefBS.hpp"
39 #include "gc/g1/g1YCTypes.hpp"
40 #include "gc/g1/hSpaceCounters.hpp"
41 #include "gc/g1/heapRegionManager.hpp"
42 #include "gc/g1/heapRegionSet.hpp"
43 #include "gc/shared/barrierSet.hpp"
44 #include "gc/shared/collectedHeap.hpp"
45 #include "memory/memRegion.hpp"
46 #include "utilities/stack.hpp"
47
48 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
49 // It uses the "Garbage First" heap organization and algorithm, which
50 // may combine concurrent marking with parallel, incremental compaction of
51 // heap subsets that will yield large amounts of garbage.
52
53 // Forward declarations
54 class HeapRegion;
55 class HRRSCleanupTask;
56 class GenerationSpec;
57 class OopsInHeapRegionClosure;
58 class G1KlassScanClosure;
59 class G1ParScanThreadState;
60 class ObjectClosure;
61 class SpaceClosure;
62 class CompactibleSpaceClosure;
63 class Space;
64 class G1CollectorPolicy;
65 class GenRemSet;
66 class G1RemSet;
67 class HeapRegionRemSetIterator;
68 class ConcurrentMark;
69 class ConcurrentMarkThread;
70 class ConcurrentG1Refine;
71 class ConcurrentGCTimer;
72 class GenerationCounters;
73 class STWGCTimer;
74 class G1NewTracer;
75 class G1OldTracer;
76 class EvacuationFailedInfo;
77 class nmethod;
78 class Ticks;
79 class FlexibleWorkGang;
80
81 typedef OverflowTaskQueue<StarTask, mtGC> RefToScanQueue;
82 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
83
84 typedef int RegionIdx_t; // needs to hold [ 0..max_regions() )
85 typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion )
86
87 class YoungList : public CHeapObj<mtGC> {
88 private:
89 G1CollectedHeap* _g1h;
90
91 HeapRegion* _head;
92
93 HeapRegion* _survivor_head;
94 HeapRegion* _survivor_tail;
95
96 HeapRegion* _curr;
97
98 uint _length;
99 uint _survivor_length;
100
101 size_t _last_sampled_rs_lengths;
102 size_t _sampled_rs_lengths;
103
104 void empty_list(HeapRegion* list);
105
106 public:
107 YoungList(G1CollectedHeap* g1h);
108
109 void push_region(HeapRegion* hr);
110 void add_survivor_region(HeapRegion* hr);
111
112 void empty_list();
113 bool is_empty() { return _length == 0; }
114 uint length() { return _length; }
115 uint eden_length() { return length() - survivor_length(); }
116 uint survivor_length() { return _survivor_length; }
117
118 // Currently we do not keep track of the used byte sum for the
119 // young list and the survivors and it'd be quite a lot of work to
120 // do so. When we'll eventually replace the young list with
121 // instances of HeapRegionLinkedList we'll get that for free. So,
122 // we'll report the more accurate information then.
123 size_t eden_used_bytes() {
124 assert(length() >= survivor_length(), "invariant");
125 return (size_t) eden_length() * HeapRegion::GrainBytes;
126 }
127 size_t survivor_used_bytes() {
128 return (size_t) survivor_length() * HeapRegion::GrainBytes;
129 }
130
131 void rs_length_sampling_init();
132 bool rs_length_sampling_more();
133 void rs_length_sampling_next();
134
135 void reset_sampled_info() {
136 _last_sampled_rs_lengths = 0;
137 }
138 size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
139
140 // for development purposes
141 void reset_auxilary_lists();
142 void clear() { _head = NULL; _length = 0; }
143
144 void clear_survivors() {
145 _survivor_head = NULL;
146 _survivor_tail = NULL;
147 _survivor_length = 0;
148 }
149
150 HeapRegion* first_region() { return _head; }
151 HeapRegion* first_survivor_region() { return _survivor_head; }
152 HeapRegion* last_survivor_region() { return _survivor_tail; }
153
154 // debugging
155 bool check_list_well_formed();
156 bool check_list_empty(bool check_sample = true);
157 void print();
158 };
159
160 // The G1 STW is alive closure.
161 // An instance is embedded into the G1CH and used as the
162 // (optional) _is_alive_non_header closure in the STW
163 // reference processor. It is also extensively used during
164 // reference processing during STW evacuation pauses.
165 class G1STWIsAliveClosure: public BoolObjectClosure {
166 G1CollectedHeap* _g1;
167 public:
168 G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
169 bool do_object_b(oop p);
170 };
171
172 class RefineCardTableEntryClosure;
173
174 class G1RegionMappingChangedListener : public G1MappingChangedListener {
175 private:
176 void reset_from_card_cache(uint start_idx, size_t num_regions);
177 public:
178 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
179 };
180
181 class G1CollectedHeap : public CollectedHeap {
182 friend class VM_CollectForMetadataAllocation;
183 friend class VM_G1CollectForAllocation;
184 friend class VM_G1CollectFull;
185 friend class VM_G1IncCollectionPause;
186 friend class VMStructs;
187 friend class MutatorAllocRegion;
188 friend class SurvivorGCAllocRegion;
189 friend class OldGCAllocRegion;
190 friend class G1Allocator;
191 friend class G1ArchiveAllocator;
192
193 // Closures used in implementation.
194 friend class G1ParScanThreadState;
195 friend class G1ParTask;
196 friend class G1ParGCAllocator;
197 friend class G1PrepareCompactClosure;
198
199 // Other related classes.
200 friend class HeapRegionClaimer;
201
202 // Testing classes.
203 friend class G1CheckCSetFastTableClosure;
204
205 private:
206 FlexibleWorkGang* _workers;
207
208 static size_t _humongous_object_threshold_in_words;
209
210 // The secondary free list which contains regions that have been
211 // freed up during the cleanup process. This will be appended to
212 // the master free list when appropriate.
213 FreeRegionList _secondary_free_list;
214
215 // It keeps track of the old regions.
216 HeapRegionSet _old_set;
217
218 // It keeps track of the humongous regions.
219 HeapRegionSet _humongous_set;
220
221 void eagerly_reclaim_humongous_regions();
222
223 // The number of regions we could create by expansion.
224 uint _expansion_regions;
225
226 // The block offset table for the G1 heap.
227 G1BlockOffsetSharedArray* _bot_shared;
228
229 // Tears down the region sets / lists so that they are empty and the
230 // regions on the heap do not belong to a region set / list. The
231 // only exception is the humongous set which we leave unaltered. If
232 // free_list_only is true, it will only tear down the master free
233 // list. It is called before a Full GC (free_list_only == false) or
234 // before heap shrinking (free_list_only == true).
235 void tear_down_region_sets(bool free_list_only);
236
237 // Rebuilds the region sets / lists so that they are repopulated to
238 // reflect the contents of the heap. The only exception is the
239 // humongous set which was not torn down in the first place. If
240 // free_list_only is true, it will only rebuild the master free
241 // list. It is called after a Full GC (free_list_only == false) or
242 // after heap shrinking (free_list_only == true).
243 void rebuild_region_sets(bool free_list_only);
244
245 // Callback for region mapping changed events.
246 G1RegionMappingChangedListener _listener;
247
248 // The sequence of all heap regions in the heap.
249 HeapRegionManager _hrm;
250
251 // Class that handles the different kinds of allocations.
252 G1Allocator* _allocator;
253
254 // Class that handles archive allocation ranges.
255 G1ArchiveAllocator* _archive_allocator;
256
257 // Statistics for each allocation context
258 AllocationContextStats _allocation_context_stats;
259
260 // PLAB sizing policy for survivors.
261 PLABStats _survivor_plab_stats;
262
263 // PLAB sizing policy for tenured objects.
264 PLABStats _old_plab_stats;
265
266 // It specifies whether we should attempt to expand the heap after a
267 // region allocation failure. If heap expansion fails we set this to
268 // false so that we don't re-attempt the heap expansion (it's likely
269 // that subsequent expansion attempts will also fail if one fails).
270 // Currently, it is only consulted during GC and it's reset at the
271 // start of each GC.
272 bool _expand_heap_after_alloc_failure;
273
274 // It resets the mutator alloc region before new allocations can take place.
275 void init_mutator_alloc_region();
276
277 // It releases the mutator alloc region.
278 void release_mutator_alloc_region();
279
280 // It initializes the GC alloc regions at the start of a GC.
281 void init_gc_alloc_regions(EvacuationInfo& evacuation_info);
282
283 // It releases the GC alloc regions at the end of a GC.
284 void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info);
285
286 // It does any cleanup that needs to be done on the GC alloc regions
287 // before a Full GC.
288 void abandon_gc_alloc_regions();
289
290 // Helper for monitoring and management support.
291 G1MonitoringSupport* _g1mm;
292
293 // Records whether the region at the given index is (still) a
294 // candidate for eager reclaim. Only valid for humongous start
295 // regions; other regions have unspecified values. Humongous start
296 // regions are initialized at start of collection pause, with
297 // candidates removed from the set as they are found reachable from
298 // roots or the young generation.
299 class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> {
300 protected:
301 bool default_value() const { return false; }
302 public:
303 void clear() { G1BiasedMappedArray<bool>::clear(); }
304 void set_candidate(uint region, bool value) {
305 set_by_index(region, value);
306 }
307 bool is_candidate(uint region) {
308 return get_by_index(region);
309 }
310 };
311
312 HumongousReclaimCandidates _humongous_reclaim_candidates;
313 // Stores whether during humongous object registration we found candidate regions.
314 // If not, we can skip a few steps.
315 bool _has_humongous_reclaim_candidates;
316
317 volatile unsigned _gc_time_stamp;
318
319 size_t* _surviving_young_words;
320
321 G1HRPrinter _hr_printer;
322
323 void setup_surviving_young_words();
324 void update_surviving_young_words(size_t* surv_young_words);
325 void cleanup_surviving_young_words();
326
327 // It decides whether an explicit GC should start a concurrent cycle
328 // instead of doing a STW GC. Currently, a concurrent cycle is
329 // explicitly started if:
330 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
331 // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
332 // (c) cause == _dcmd_gc_run and +ExplicitGCInvokesConcurrent.
333 // (d) cause == _g1_humongous_allocation
334 bool should_do_concurrent_full_gc(GCCause::Cause cause);
335
336 // indicates whether we are in young or mixed GC mode
337 G1CollectorState _collector_state;
338
339 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
340 // concurrent cycles) we have started.
341 volatile uint _old_marking_cycles_started;
342
343 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
344 // concurrent cycles) we have completed.
345 volatile uint _old_marking_cycles_completed;
346
347 bool _heap_summary_sent;
348
349 // This is a non-product method that is helpful for testing. It is
350 // called at the end of a GC and artificially expands the heap by
351 // allocating a number of dead regions. This way we can induce very
352 // frequent marking cycles and stress the cleanup / concurrent
353 // cleanup code more (as all the regions that will be allocated by
354 // this method will be found dead by the marking cycle).
355 void allocate_dummy_regions() PRODUCT_RETURN;
356
357 // Clear RSets after a compaction. It also resets the GC time stamps.
358 void clear_rsets_post_compaction();
359
360 // If the HR printer is active, dump the state of the regions in the
361 // heap after a compaction.
362 void print_hrm_post_compaction();
363
364 // Create a memory mapper for auxiliary data structures of the given size and
365 // translation factor.
366 static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description,
367 size_t size,
368 size_t translation_factor);
369
370 double verify(bool guard, const char* msg);
371 void verify_before_gc();
372 void verify_after_gc();
373
374 void log_gc_header();
375 void log_gc_footer(double pause_time_sec);
376
377 void trace_heap(GCWhen::Type when, const GCTracer* tracer);
378
379 // These are macros so that, if the assert fires, we get the correct
380 // line number, file, etc.
381
382 #define heap_locking_asserts_err_msg(_extra_message_) \
383 err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \
384 (_extra_message_), \
385 BOOL_TO_STR(Heap_lock->owned_by_self()), \
386 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \
387 BOOL_TO_STR(Thread::current()->is_VM_thread()))
388
389 #define assert_heap_locked() \
390 do { \
391 assert(Heap_lock->owned_by_self(), \
392 heap_locking_asserts_err_msg("should be holding the Heap_lock")); \
393 } while (0)
394
395 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \
396 do { \
397 assert(Heap_lock->owned_by_self() || \
398 (SafepointSynchronize::is_at_safepoint() && \
399 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
400 heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
401 "should be at a safepoint")); \
402 } while (0)
403
404 #define assert_heap_locked_and_not_at_safepoint() \
405 do { \
406 assert(Heap_lock->owned_by_self() && \
407 !SafepointSynchronize::is_at_safepoint(), \
408 heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
409 "should not be at a safepoint")); \
410 } while (0)
411
412 #define assert_heap_not_locked() \
413 do { \
414 assert(!Heap_lock->owned_by_self(), \
415 heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
416 } while (0)
417
418 #define assert_heap_not_locked_and_not_at_safepoint() \
419 do { \
420 assert(!Heap_lock->owned_by_self() && \
421 !SafepointSynchronize::is_at_safepoint(), \
422 heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
423 "should not be at a safepoint")); \
424 } while (0)
425
426 #define assert_at_safepoint(_should_be_vm_thread_) \
427 do { \
428 assert(SafepointSynchronize::is_at_safepoint() && \
429 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
430 heap_locking_asserts_err_msg("should be at a safepoint")); \
431 } while (0)
432
433 #define assert_not_at_safepoint() \
434 do { \
435 assert(!SafepointSynchronize::is_at_safepoint(), \
436 heap_locking_asserts_err_msg("should not be at a safepoint")); \
437 } while (0)
438
439 protected:
440
441 // The young region list.
442 YoungList* _young_list;
443
444 // The current policy object for the collector.
445 G1CollectorPolicy* _g1_policy;
446
447 // This is the second level of trying to allocate a new region. If
448 // new_region() didn't find a region on the free_list, this call will
449 // check whether there's anything available on the
450 // secondary_free_list and/or wait for more regions to appear on
451 // that list, if _free_regions_coming is set.
452 HeapRegion* new_region_try_secondary_free_list(bool is_old);
453
454 // Try to allocate a single non-humongous HeapRegion sufficient for
455 // an allocation of the given word_size. If do_expand is true,
456 // attempt to expand the heap if necessary to satisfy the allocation
457 // request. If the region is to be used as an old region or for a
458 // humongous object, set is_old to true. If not, to false.
459 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
460
461 // Initialize a contiguous set of free regions of length num_regions
462 // and starting at index first so that they appear as a single
463 // humongous region.
464 HeapWord* humongous_obj_allocate_initialize_regions(uint first,
465 uint num_regions,
466 size_t word_size,
467 AllocationContext_t context);
468
469 // Attempt to allocate a humongous object of the given size. Return
470 // NULL if unsuccessful.
471 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context);
472
473 // The following two methods, allocate_new_tlab() and
474 // mem_allocate(), are the two main entry points from the runtime
475 // into the G1's allocation routines. They have the following
476 // assumptions:
477 //
478 // * They should both be called outside safepoints.
479 //
480 // * They should both be called without holding the Heap_lock.
481 //
482 // * All allocation requests for new TLABs should go to
483 // allocate_new_tlab().
484 //
485 // * All non-TLAB allocation requests should go to mem_allocate().
486 //
487 // * If either call cannot satisfy the allocation request using the
488 // current allocating region, they will try to get a new one. If
489 // this fails, they will attempt to do an evacuation pause and
490 // retry the allocation.
491 //
492 // * If all allocation attempts fail, even after trying to schedule
493 // an evacuation pause, allocate_new_tlab() will return NULL,
494 // whereas mem_allocate() will attempt a heap expansion and/or
495 // schedule a Full GC.
496 //
497 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
498 // should never be called with word_size being humongous. All
499 // humongous allocation requests should go to mem_allocate() which
500 // will satisfy them with a special path.
501
502 virtual HeapWord* allocate_new_tlab(size_t word_size);
503
504 virtual HeapWord* mem_allocate(size_t word_size,
505 bool* gc_overhead_limit_was_exceeded);
506
507 // The following three methods take a gc_count_before_ret
508 // parameter which is used to return the GC count if the method
509 // returns NULL. Given that we are required to read the GC count
510 // while holding the Heap_lock, and these paths will take the
511 // Heap_lock at some point, it's easier to get them to read the GC
512 // count while holding the Heap_lock before they return NULL instead
513 // of the caller (namely: mem_allocate()) having to also take the
514 // Heap_lock just to read the GC count.
515
516 // First-level mutator allocation attempt: try to allocate out of
517 // the mutator alloc region without taking the Heap_lock. This
518 // should only be used for non-humongous allocations.
519 inline HeapWord* attempt_allocation(size_t word_size,
520 uint* gc_count_before_ret,
521 uint* gclocker_retry_count_ret);
522
523 // Second-level mutator allocation attempt: take the Heap_lock and
524 // retry the allocation attempt, potentially scheduling a GC
525 // pause. This should only be used for non-humongous allocations.
526 HeapWord* attempt_allocation_slow(size_t word_size,
527 AllocationContext_t context,
528 uint* gc_count_before_ret,
529 uint* gclocker_retry_count_ret);
530
531 // Takes the Heap_lock and attempts a humongous allocation. It can
532 // potentially schedule a GC pause.
533 HeapWord* attempt_allocation_humongous(size_t word_size,
534 uint* gc_count_before_ret,
535 uint* gclocker_retry_count_ret);
536
537 // Allocation attempt that should be called during safepoints (e.g.,
538 // at the end of a successful GC). expect_null_mutator_alloc_region
539 // specifies whether the mutator alloc region is expected to be NULL
540 // or not.
541 HeapWord* attempt_allocation_at_safepoint(size_t word_size,
542 AllocationContext_t context,
543 bool expect_null_mutator_alloc_region);
544
545 // It dirties the cards that cover the block so that so that the post
546 // write barrier never queues anything when updating objects on this
547 // block. It is assumed (and in fact we assert) that the block
548 // belongs to a young region.
549 inline void dirty_young_block(HeapWord* start, size_t word_size);
550
551 // Allocate blocks during garbage collection. Will ensure an
552 // allocation region, either by picking one or expanding the
553 // heap, and then allocate a block of the given size. The block
554 // may not be a humongous - it must fit into a single heap region.
555 inline HeapWord* par_allocate_during_gc(InCSetState dest,
556 size_t word_size,
557 AllocationContext_t context);
558 // Ensure that no further allocations can happen in "r", bearing in mind
559 // that parallel threads might be attempting allocations.
560 void par_allocate_remaining_space(HeapRegion* r);
561
562 // Allocation attempt during GC for a survivor object / PLAB.
563 inline HeapWord* survivor_attempt_allocation(size_t word_size,
564 AllocationContext_t context);
565
566 // Allocation attempt during GC for an old object / PLAB.
567 inline HeapWord* old_attempt_allocation(size_t word_size,
568 AllocationContext_t context);
569
570 // These methods are the "callbacks" from the G1AllocRegion class.
571
572 // For mutator alloc regions.
573 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
574 void retire_mutator_alloc_region(HeapRegion* alloc_region,
575 size_t allocated_bytes);
576
577 // For GC alloc regions.
578 HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
579 InCSetState dest);
580 void retire_gc_alloc_region(HeapRegion* alloc_region,
581 size_t allocated_bytes, InCSetState dest);
582
583 // Allocate the highest free region in the reserved heap. This will commit
584 // regions as necessary.
585 HeapRegion* alloc_highest_free_region();
586
587 // - if explicit_gc is true, the GC is for a System.gc() or a heap
588 // inspection request and should collect the entire heap
589 // - if clear_all_soft_refs is true, all soft references should be
590 // cleared during the GC
591 // - if explicit_gc is false, word_size describes the allocation that
592 // the GC should attempt (at least) to satisfy
593 // - it returns false if it is unable to do the collection due to the
594 // GC locker being active, true otherwise
595 bool do_collection(bool explicit_gc,
596 bool clear_all_soft_refs,
597 size_t word_size);
598
599 // Callback from VM_G1CollectFull operation.
600 // Perform a full collection.
601 virtual void do_full_collection(bool clear_all_soft_refs);
602
603 // Resize the heap if necessary after a full collection. If this is
604 // after a collect-for allocation, "word_size" is the allocation size,
605 // and will be considered part of the used portion of the heap.
606 void resize_if_necessary_after_full_collection(size_t word_size);
607
608 // Callback from VM_G1CollectForAllocation operation.
609 // This function does everything necessary/possible to satisfy a
610 // failed allocation request (including collection, expansion, etc.)
611 HeapWord* satisfy_failed_allocation(size_t word_size,
612 AllocationContext_t context,
613 bool* succeeded);
614
615 // Attempting to expand the heap sufficiently
616 // to support an allocation of the given "word_size". If
617 // successful, perform the allocation and return the address of the
618 // allocated block, or else "NULL".
619 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context);
620
621 // Process any reference objects discovered during
622 // an incremental evacuation pause.
623 void process_discovered_references();
624
625 // Enqueue any remaining discovered references
626 // after processing.
627 void enqueue_discovered_references();
628
629 public:
630 FlexibleWorkGang* workers() const { return _workers; }
631
632 G1Allocator* allocator() {
633 return _allocator;
634 }
635
636 G1MonitoringSupport* g1mm() {
637 assert(_g1mm != NULL, "should have been initialized");
638 return _g1mm;
639 }
640
641 // Expand the garbage-first heap by at least the given size (in bytes!).
642 // Returns true if the heap was expanded by the requested amount;
643 // false otherwise.
644 // (Rounds up to a HeapRegion boundary.)
645 bool expand(size_t expand_bytes);
646
647 // Returns the PLAB statistics for a given destination.
648 inline PLABStats* alloc_buffer_stats(InCSetState dest);
649
650 // Determines PLAB size for a given destination.
651 inline size_t desired_plab_sz(InCSetState dest);
652
653 inline AllocationContextStats& allocation_context_stats();
654
655 // Do anything common to GC's.
656 void gc_prologue(bool full);
657 void gc_epilogue(bool full);
658
659 // Modify the reclaim candidate set and test for presence.
660 // These are only valid for starts_humongous regions.
661 inline void set_humongous_reclaim_candidate(uint region, bool value);
662 inline bool is_humongous_reclaim_candidate(uint region);
663
664 // Remove from the reclaim candidate set. Also remove from the
665 // collection set so that later encounters avoid the slow path.
666 inline void set_humongous_is_live(oop obj);
667
668 // Register the given region to be part of the collection set.
669 inline void register_humongous_region_with_cset(uint index);
670 // Register regions with humongous objects (actually on the start region) in
671 // the in_cset_fast_test table.
672 void register_humongous_regions_with_cset();
673 // We register a region with the fast "in collection set" test. We
674 // simply set to true the array slot corresponding to this region.
675 void register_young_region_with_cset(HeapRegion* r) {
676 _in_cset_fast_test.set_in_young(r->hrm_index());
677 }
678 void register_old_region_with_cset(HeapRegion* r) {
679 _in_cset_fast_test.set_in_old(r->hrm_index());
680 }
681 void clear_in_cset(const HeapRegion* hr) {
682 _in_cset_fast_test.clear(hr);
683 }
684
685 void clear_cset_fast_test() {
686 _in_cset_fast_test.clear();
687 }
688
689 // This is called at the start of either a concurrent cycle or a Full
690 // GC to update the number of old marking cycles started.
691 void increment_old_marking_cycles_started();
692
693 // This is called at the end of either a concurrent cycle or a Full
694 // GC to update the number of old marking cycles completed. Those two
695 // can happen in a nested fashion, i.e., we start a concurrent
696 // cycle, a Full GC happens half-way through it which ends first,
697 // and then the cycle notices that a Full GC happened and ends
698 // too. The concurrent parameter is a boolean to help us do a bit
699 // tighter consistency checking in the method. If concurrent is
700 // false, the caller is the inner caller in the nesting (i.e., the
701 // Full GC). If concurrent is true, the caller is the outer caller
702 // in this nesting (i.e., the concurrent cycle). Further nesting is
703 // not currently supported. The end of this call also notifies
704 // the FullGCCount_lock in case a Java thread is waiting for a full
705 // GC to happen (e.g., it called System.gc() with
706 // +ExplicitGCInvokesConcurrent).
707 void increment_old_marking_cycles_completed(bool concurrent);
708
709 uint old_marking_cycles_completed() {
710 return _old_marking_cycles_completed;
711 }
712
713 void register_concurrent_cycle_start(const Ticks& start_time);
714 void register_concurrent_cycle_end();
715 void trace_heap_after_concurrent_cycle();
716
717 G1HRPrinter* hr_printer() { return &_hr_printer; }
718
719 // Frees a non-humongous region by initializing its contents and
720 // adding it to the free list that's passed as a parameter (this is
721 // usually a local list which will be appended to the master free
722 // list later). The used bytes of freed regions are accumulated in
723 // pre_used. If par is true, the region's RSet will not be freed
724 // up. The assumption is that this will be done later.
725 // The locked parameter indicates if the caller has already taken
726 // care of proper synchronization. This may allow some optimizations.
727 void free_region(HeapRegion* hr,
728 FreeRegionList* free_list,
729 bool par,
730 bool locked = false);
731
732 // Frees a humongous region by collapsing it into individual regions
733 // and calling free_region() for each of them. The freed regions
734 // will be added to the free list that's passed as a parameter (this
735 // is usually a local list which will be appended to the master free
736 // list later). The used bytes of freed regions are accumulated in
737 // pre_used. If par is true, the region's RSet will not be freed
738 // up. The assumption is that this will be done later.
739 void free_humongous_region(HeapRegion* hr,
740 FreeRegionList* free_list,
741 bool par);
742
743 // Facility for allocating in 'archive' regions in high heap memory and
744 // recording the allocated ranges. These should all be called from the
745 // VM thread at safepoints, without the heap lock held. They can be used
746 // to create and archive a set of heap regions which can be mapped at the
747 // same fixed addresses in a subsequent JVM invocation.
748 void begin_archive_alloc_range();
749
750 // Check if the requested size would be too large for an archive allocation.
751 bool is_archive_alloc_too_large(size_t word_size);
752
753 // Allocate memory of the requested size from the archive region. This will
754 // return NULL if the size is too large or if no memory is available. It
755 // does not trigger a garbage collection.
756 HeapWord* archive_mem_allocate(size_t word_size);
757
758 // Optionally aligns the end address and returns the allocated ranges in
759 // an array of MemRegions in order of ascending addresses.
760 void end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
761 size_t end_alignment_in_bytes = 0);
762
763 // Facility for allocating a fixed range within the heap and marking
764 // the containing regions as 'archive'. For use at JVM init time, when the
765 // caller may mmap archived heap data at the specified range(s).
766 // Verify that the MemRegions specified in the argument array are within the
767 // reserved heap.
768 bool check_archive_addresses(MemRegion* range, size_t count);
769
770 // Commit the appropriate G1 regions containing the specified MemRegions
771 // and mark them as 'archive' regions. The regions in the array must be
772 // non-overlapping and in order of ascending address.
773 bool alloc_archive_regions(MemRegion* range, size_t count);
774
775 // Insert any required filler objects in the G1 regions around the specified
776 // ranges to make the regions parseable. This must be called after
777 // alloc_archive_regions, and after class loading has occurred.
778 void fill_archive_regions(MemRegion* range, size_t count);
779
780 protected:
781
782 // Shrink the garbage-first heap by at most the given size (in bytes!).
783 // (Rounds down to a HeapRegion boundary.)
784 virtual void shrink(size_t expand_bytes);
785 void shrink_helper(size_t expand_bytes);
786
787 #if TASKQUEUE_STATS
788 static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
789 void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
790 void reset_taskqueue_stats();
791 #endif // TASKQUEUE_STATS
792
793 // Schedule the VM operation that will do an evacuation pause to
794 // satisfy an allocation request of word_size. *succeeded will
795 // return whether the VM operation was successful (it did do an
796 // evacuation pause) or not (another thread beat us to it or the GC
797 // locker was active). Given that we should not be holding the
798 // Heap_lock when we enter this method, we will pass the
799 // gc_count_before (i.e., total_collections()) as a parameter since
800 // it has to be read while holding the Heap_lock. Currently, both
801 // methods that call do_collection_pause() release the Heap_lock
802 // before the call, so it's easy to read gc_count_before just before.
803 HeapWord* do_collection_pause(size_t word_size,
804 uint gc_count_before,
805 bool* succeeded,
806 GCCause::Cause gc_cause);
807
808 // The guts of the incremental collection pause, executed by the vm
809 // thread. It returns false if it is unable to do the collection due
810 // to the GC locker being active, true otherwise
811 bool do_collection_pause_at_safepoint(double target_pause_time_ms);
812
813 // Actually do the work of evacuating the collection set.
814 void evacuate_collection_set(EvacuationInfo& evacuation_info);
815
816 // The g1 remembered set of the heap.
817 G1RemSet* _g1_rem_set;
818
819 // A set of cards that cover the objects for which the Rsets should be updated
820 // concurrently after the collection.
821 DirtyCardQueueSet _dirty_card_queue_set;
822
823 // The closure used to refine a single card.
824 RefineCardTableEntryClosure* _refine_cte_cl;
825
826 // A DirtyCardQueueSet that is used to hold cards that contain
827 // references into the current collection set. This is used to
828 // update the remembered sets of the regions in the collection
829 // set in the event of an evacuation failure.
830 DirtyCardQueueSet _into_cset_dirty_card_queue_set;
831
832 // After a collection pause, make the regions in the CS into free
833 // regions.
834 void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info);
835
836 // Abandon the current collection set without recording policy
837 // statistics or updating free lists.
838 void abandon_collection_set(HeapRegion* cs_head);
839
840 // The concurrent marker (and the thread it runs in.)
841 ConcurrentMark* _cm;
842 ConcurrentMarkThread* _cmThread;
843
844 // The concurrent refiner.
845 ConcurrentG1Refine* _cg1r;
846
847 // The parallel task queues
848 RefToScanQueueSet *_task_queues;
849
850 // True iff a evacuation has failed in the current collection.
851 bool _evacuation_failed;
852
853 EvacuationFailedInfo* _evacuation_failed_info_array;
854
855 // Failed evacuations cause some logical from-space objects to have
856 // forwarding pointers to themselves. Reset them.
857 void remove_self_forwarding_pointers();
858
859 // Together, these store an object with a preserved mark, and its mark value.
860 Stack<oop, mtGC> _objs_with_preserved_marks;
861 Stack<markOop, mtGC> _preserved_marks_of_objs;
862
863 // Preserve the mark of "obj", if necessary, in preparation for its mark
864 // word being overwritten with a self-forwarding-pointer.
865 void preserve_mark_if_necessary(oop obj, markOop m);
866
867 // The stack of evac-failure objects left to be scanned.
868 GrowableArray<oop>* _evac_failure_scan_stack;
869 // The closure to apply to evac-failure objects.
870
871 OopsInHeapRegionClosure* _evac_failure_closure;
872 // Set the field above.
873 void
874 set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
875 _evac_failure_closure = evac_failure_closure;
876 }
877
878 // Push "obj" on the scan stack.
879 void push_on_evac_failure_scan_stack(oop obj);
880 // Process scan stack entries until the stack is empty.
881 void drain_evac_failure_scan_stack();
882 // True iff an invocation of "drain_scan_stack" is in progress; to
883 // prevent unnecessary recursion.
884 bool _drain_in_progress;
885
886 // Do any necessary initialization for evacuation-failure handling.
887 // "cl" is the closure that will be used to process evac-failure
888 // objects.
889 void init_for_evac_failure(OopsInHeapRegionClosure* cl);
890 // Do any necessary cleanup for evacuation-failure handling data
891 // structures.
892 void finalize_for_evac_failure();
893
894 // An attempt to evacuate "obj" has failed; take necessary steps.
895 oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj);
896 void handle_evacuation_failure_common(oop obj, markOop m);
897
898 #ifndef PRODUCT
899 // Support for forcing evacuation failures. Analogous to
900 // PromotionFailureALot for the other collectors.
901
902 // Records whether G1EvacuationFailureALot should be in effect
903 // for the current GC
904 bool _evacuation_failure_alot_for_current_gc;
905
906 // Used to record the GC number for interval checking when
907 // determining whether G1EvaucationFailureALot is in effect
908 // for the current GC.
909 size_t _evacuation_failure_alot_gc_number;
910
911 // Count of the number of evacuations between failures.
912 volatile size_t _evacuation_failure_alot_count;
913
914 // Set whether G1EvacuationFailureALot should be in effect
915 // for the current GC (based upon the type of GC and which
916 // command line flags are set);
917 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
918 bool during_initial_mark,
919 bool during_marking);
920
921 inline void set_evacuation_failure_alot_for_current_gc();
922
923 // Return true if it's time to cause an evacuation failure.
924 inline bool evacuation_should_fail();
925
926 // Reset the G1EvacuationFailureALot counters. Should be called at
927 // the end of an evacuation pause in which an evacuation failure occurred.
928 inline void reset_evacuation_should_fail();
929 #endif // !PRODUCT
930
931 // ("Weak") Reference processing support.
932 //
933 // G1 has 2 instances of the reference processor class. One
934 // (_ref_processor_cm) handles reference object discovery
935 // and subsequent processing during concurrent marking cycles.
936 //
937 // The other (_ref_processor_stw) handles reference object
938 // discovery and processing during full GCs and incremental
939 // evacuation pauses.
940 //
941 // During an incremental pause, reference discovery will be
942 // temporarily disabled for _ref_processor_cm and will be
943 // enabled for _ref_processor_stw. At the end of the evacuation
944 // pause references discovered by _ref_processor_stw will be
945 // processed and discovery will be disabled. The previous
946 // setting for reference object discovery for _ref_processor_cm
947 // will be re-instated.
948 //
949 // At the start of marking:
950 // * Discovery by the CM ref processor is verified to be inactive
951 // and it's discovered lists are empty.
952 // * Discovery by the CM ref processor is then enabled.
953 //
954 // At the end of marking:
955 // * Any references on the CM ref processor's discovered
956 // lists are processed (possibly MT).
957 //
958 // At the start of full GC we:
959 // * Disable discovery by the CM ref processor and
960 // empty CM ref processor's discovered lists
961 // (without processing any entries).
962 // * Verify that the STW ref processor is inactive and it's
963 // discovered lists are empty.
964 // * Temporarily set STW ref processor discovery as single threaded.
965 // * Temporarily clear the STW ref processor's _is_alive_non_header
966 // field.
967 // * Finally enable discovery by the STW ref processor.
968 //
969 // The STW ref processor is used to record any discovered
970 // references during the full GC.
971 //
972 // At the end of a full GC we:
973 // * Enqueue any reference objects discovered by the STW ref processor
974 // that have non-live referents. This has the side-effect of
975 // making the STW ref processor inactive by disabling discovery.
976 // * Verify that the CM ref processor is still inactive
977 // and no references have been placed on it's discovered
978 // lists (also checked as a precondition during initial marking).
979
980 // The (stw) reference processor...
981 ReferenceProcessor* _ref_processor_stw;
982
983 STWGCTimer* _gc_timer_stw;
984 ConcurrentGCTimer* _gc_timer_cm;
985
986 G1OldTracer* _gc_tracer_cm;
987 G1NewTracer* _gc_tracer_stw;
988
989 // During reference object discovery, the _is_alive_non_header
990 // closure (if non-null) is applied to the referent object to
991 // determine whether the referent is live. If so then the
992 // reference object does not need to be 'discovered' and can
993 // be treated as a regular oop. This has the benefit of reducing
994 // the number of 'discovered' reference objects that need to
995 // be processed.
996 //
997 // Instance of the is_alive closure for embedding into the
998 // STW reference processor as the _is_alive_non_header field.
999 // Supplying a value for the _is_alive_non_header field is
1000 // optional but doing so prevents unnecessary additions to
1001 // the discovered lists during reference discovery.
1002 G1STWIsAliveClosure _is_alive_closure_stw;
1003
1004 // The (concurrent marking) reference processor...
1005 ReferenceProcessor* _ref_processor_cm;
1006
1007 // Instance of the concurrent mark is_alive closure for embedding
1008 // into the Concurrent Marking reference processor as the
1009 // _is_alive_non_header field. Supplying a value for the
1010 // _is_alive_non_header field is optional but doing so prevents
1011 // unnecessary additions to the discovered lists during reference
1012 // discovery.
1013 G1CMIsAliveClosure _is_alive_closure_cm;
1014
1015 // Cache used by G1CollectedHeap::start_cset_region_for_worker().
1016 HeapRegion** _worker_cset_start_region;
1017
1018 // Time stamp to validate the regions recorded in the cache
1019 // used by G1CollectedHeap::start_cset_region_for_worker().
1020 // The heap region entry for a given worker is valid iff
1021 // the associated time stamp value matches the current value
1022 // of G1CollectedHeap::_gc_time_stamp.
1023 uint* _worker_cset_start_region_time_stamp;
1024
1025 volatile bool _free_regions_coming;
1026
1027 public:
1028
1029 void set_refine_cte_cl_concurrency(bool concurrent);
1030
1031 RefToScanQueue *task_queue(uint i) const;
1032
1033 uint num_task_queues() const;
1034
1035 // A set of cards where updates happened during the GC
1036 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
1037
1038 // A DirtyCardQueueSet that is used to hold cards that contain
1039 // references into the current collection set. This is used to
1040 // update the remembered sets of the regions in the collection
1041 // set in the event of an evacuation failure.
1042 DirtyCardQueueSet& into_cset_dirty_card_queue_set()
1043 { return _into_cset_dirty_card_queue_set; }
1044
1045 // Create a G1CollectedHeap with the specified policy.
1046 // Must call the initialize method afterwards.
1047 // May not return if something goes wrong.
1048 G1CollectedHeap(G1CollectorPolicy* policy);
1049
1050 // Initialize the G1CollectedHeap to have the initial and
1051 // maximum sizes and remembered and barrier sets
1052 // specified by the policy object.
1053 jint initialize();
1054
1055 virtual void stop();
1056
1057 // Return the (conservative) maximum heap alignment for any G1 heap
1058 static size_t conservative_max_heap_alignment();
1059
1060 // Does operations required after initialization has been done.
1061 void post_initialize();
1062
1063 // Initialize weak reference processing.
1064 void ref_processing_init();
1065
1066 virtual Name kind() const {
1067 return CollectedHeap::G1CollectedHeap;
1068 }
1069
1070 G1CollectorState* collector_state() { return &_collector_state; }
1071
1072 // The current policy object for the collector.
1073 G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1074
1075 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); }
1076
1077 // Adaptive size policy. No such thing for g1.
1078 virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1079
1080 // The rem set and barrier set.
1081 G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1082
1083 unsigned get_gc_time_stamp() {
1084 return _gc_time_stamp;
1085 }
1086
1087 inline void reset_gc_time_stamp();
1088
1089 void check_gc_time_stamps() PRODUCT_RETURN;
1090
1091 inline void increment_gc_time_stamp();
1092
1093 // Reset the given region's GC timestamp. If it's starts humongous,
1094 // also reset the GC timestamp of its corresponding
1095 // continues humongous regions too.
1096 void reset_gc_time_stamps(HeapRegion* hr);
1097
1098 void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1099 DirtyCardQueue* into_cset_dcq,
1100 bool concurrent, uint worker_i);
1101
1102 // The shared block offset table array.
1103 G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1104
1105 // Reference Processing accessors
1106
1107 // The STW reference processor....
1108 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1109
1110 // The Concurrent Marking reference processor...
1111 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1112
1113 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1114 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1115
1116 virtual size_t capacity() const;
1117 virtual size_t used() const;
1118 // This should be called when we're not holding the heap lock. The
1119 // result might be a bit inaccurate.
1120 size_t used_unlocked() const;
1121 size_t recalculate_used() const;
1122
1123 // These virtual functions do the actual allocation.
1124 // Some heaps may offer a contiguous region for shared non-blocking
1125 // allocation, via inlined code (by exporting the address of the top and
1126 // end fields defining the extent of the contiguous allocation region.)
1127 // But G1CollectedHeap doesn't yet support this.
1128
1129 virtual bool is_maximal_no_gc() const {
1130 return _hrm.available() == 0;
1131 }
1132
1133 // The current number of regions in the heap.
1134 uint num_regions() const { return _hrm.length(); }
1135
1136 // The max number of regions in the heap.
1137 uint max_regions() const { return _hrm.max_length(); }
1138
1139 // The number of regions that are completely free.
1140 uint num_free_regions() const { return _hrm.num_free_regions(); }
1141
1142 MemoryUsage get_auxiliary_data_memory_usage() const {
1143 return _hrm.get_auxiliary_data_memory_usage();
1144 }
1145
1146 // The number of regions that are not completely free.
1147 uint num_used_regions() const { return num_regions() - num_free_regions(); }
1148
1149 void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1150 void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1151 void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1152 void verify_dirty_young_regions() PRODUCT_RETURN;
1153
1154 #ifndef PRODUCT
1155 // Make sure that the given bitmap has no marked objects in the
1156 // range [from,limit). If it does, print an error message and return
1157 // false. Otherwise, just return true. bitmap_name should be "prev"
1158 // or "next".
1159 bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
1160 HeapWord* from, HeapWord* limit);
1161
1162 // Verify that the prev / next bitmap range [tams,end) for the given
1163 // region has no marks. Return true if all is well, false if errors
1164 // are detected.
1165 bool verify_bitmaps(const char* caller, HeapRegion* hr);
1166 #endif // PRODUCT
1167
1168 // If G1VerifyBitmaps is set, verify that the marking bitmaps for
1169 // the given region do not have any spurious marks. If errors are
1170 // detected, print appropriate error messages and crash.
1171 void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN;
1172
1173 // If G1VerifyBitmaps is set, verify that the marking bitmaps do not
1174 // have any spurious marks. If errors are detected, print
1175 // appropriate error messages and crash.
1176 void check_bitmaps(const char* caller) PRODUCT_RETURN;
1177
1178 // Do sanity check on the contents of the in-cset fast test table.
1179 bool check_cset_fast_test() PRODUCT_RETURN_( return true; );
1180
1181 // verify_region_sets() performs verification over the region
1182 // lists. It will be compiled in the product code to be used when
1183 // necessary (i.e., during heap verification).
1184 void verify_region_sets();
1185
1186 // verify_region_sets_optional() is planted in the code for
1187 // list verification in non-product builds (and it can be enabled in
1188 // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1).
1189 #if HEAP_REGION_SET_FORCE_VERIFY
1190 void verify_region_sets_optional() {
1191 verify_region_sets();
1192 }
1193 #else // HEAP_REGION_SET_FORCE_VERIFY
1194 void verify_region_sets_optional() { }
1195 #endif // HEAP_REGION_SET_FORCE_VERIFY
1196
1197 #ifdef ASSERT
1198 bool is_on_master_free_list(HeapRegion* hr) {
1199 return _hrm.is_free(hr);
1200 }
1201 #endif // ASSERT
1202
1203 // Wrapper for the region list operations that can be called from
1204 // methods outside this class.
1205
1206 void secondary_free_list_add(FreeRegionList* list) {
1207 _secondary_free_list.add_ordered(list);
1208 }
1209
1210 void append_secondary_free_list() {
1211 _hrm.insert_list_into_free_list(&_secondary_free_list);
1212 }
1213
1214 void append_secondary_free_list_if_not_empty_with_lock() {
1215 // If the secondary free list looks empty there's no reason to
1216 // take the lock and then try to append it.
1217 if (!_secondary_free_list.is_empty()) {
1218 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1219 append_secondary_free_list();
1220 }
1221 }
1222
1223 inline void old_set_remove(HeapRegion* hr);
1224
1225 size_t non_young_capacity_bytes() {
1226 return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1227 }
1228
1229 void set_free_regions_coming();
1230 void reset_free_regions_coming();
1231 bool free_regions_coming() { return _free_regions_coming; }
1232 void wait_while_free_regions_coming();
1233
1234 // Determine whether the given region is one that we are using as an
1235 // old GC alloc region.
1236 bool is_old_gc_alloc_region(HeapRegion* hr) {
1237 return _allocator->is_retained_old_region(hr);
1238 }
1239
1240 // Perform a collection of the heap; intended for use in implementing
1241 // "System.gc". This probably implies as full a collection as the
1242 // "CollectedHeap" supports.
1243 virtual void collect(GCCause::Cause cause);
1244
1245 // The same as above but assume that the caller holds the Heap_lock.
1246 void collect_locked(GCCause::Cause cause);
1247
1248 virtual bool copy_allocation_context_stats(const jint* contexts,
1249 jlong* totals,
1250 jbyte* accuracy,
1251 jint len);
1252
1253 // True iff an evacuation has failed in the most-recent collection.
1254 bool evacuation_failed() { return _evacuation_failed; }
1255
1256 void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed);
1257 void prepend_to_freelist(FreeRegionList* list);
1258 void decrement_summary_bytes(size_t bytes);
1259
1260 // Returns "TRUE" iff "p" points into the committed areas of the heap.
1261 virtual bool is_in(const void* p) const;
1262 #ifdef ASSERT
1263 // Returns whether p is in one of the available areas of the heap. Slow but
1264 // extensive version.
1265 bool is_in_exact(const void* p) const;
1266 #endif
1267
1268 // Return "TRUE" iff the given object address is within the collection
1269 // set. Slow implementation.
1270 inline bool obj_in_cs(oop obj);
1271
1272 inline bool is_in_cset(const HeapRegion *hr);
1273 inline bool is_in_cset(oop obj);
1274
1275 inline bool is_in_cset_or_humongous(const oop obj);
1276
1277 private:
1278 // This array is used for a quick test on whether a reference points into
1279 // the collection set or not. Each of the array's elements denotes whether the
1280 // corresponding region is in the collection set or not.
1281 G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test;
1282
1283 public:
1284
1285 inline InCSetState in_cset_state(const oop obj);
1286
1287 // Return "TRUE" iff the given object address is in the reserved
1288 // region of g1.
1289 bool is_in_g1_reserved(const void* p) const {
1290 return _hrm.reserved().contains(p);
1291 }
1292
1293 // Returns a MemRegion that corresponds to the space that has been
1294 // reserved for the heap
1295 MemRegion g1_reserved() const {
1296 return _hrm.reserved();
1297 }
1298
1299 virtual bool is_in_closed_subset(const void* p) const;
1300
1301 G1SATBCardTableLoggingModRefBS* g1_barrier_set() {
1302 return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set());
1303 }
1304
1305 // This resets the card table to all zeros. It is used after
1306 // a collection pause which used the card table to claim cards.
1307 void cleanUpCardTable();
1308
1309 // Iteration functions.
1310
1311 // Iterate over all objects, calling "cl.do_object" on each.
1312 virtual void object_iterate(ObjectClosure* cl);
1313
1314 virtual void safe_object_iterate(ObjectClosure* cl) {
1315 object_iterate(cl);
1316 }
1317
1318 // Iterate over heap regions, in address order, terminating the
1319 // iteration early if the "doHeapRegion" method returns "true".
1320 void heap_region_iterate(HeapRegionClosure* blk) const;
1321
1322 // Return the region with the given index. It assumes the index is valid.
1323 inline HeapRegion* region_at(uint index) const;
1324
1325 // Calculate the region index of the given address. Given address must be
1326 // within the heap.
1327 inline uint addr_to_region(HeapWord* addr) const;
1328
1329 inline HeapWord* bottom_addr_for_region(uint index) const;
1330
1331 // Iterate over the heap regions in parallel. Assumes that this will be called
1332 // in parallel by ParallelGCThreads worker threads with distinct worker ids
1333 // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion"
1334 // to each of the regions, by attempting to claim the region using the
1335 // HeapRegionClaimer and, if successful, applying the closure to the claimed
1336 // region. The concurrent argument should be set to true if iteration is
1337 // performed concurrently, during which no assumptions are made for consistent
1338 // attributes of the heap regions (as they might be modified while iterating).
1339 void heap_region_par_iterate(HeapRegionClosure* cl,
1340 uint worker_id,
1341 HeapRegionClaimer* hrclaimer,
1342 bool concurrent = false) const;
1343
1344 // Clear the cached cset start regions and (more importantly)
1345 // the time stamps. Called when we reset the GC time stamp.
1346 void clear_cset_start_regions();
1347
1348 // Given the id of a worker, obtain or calculate a suitable
1349 // starting region for iterating over the current collection set.
1350 HeapRegion* start_cset_region_for_worker(uint worker_i);
1351
1352 // Iterate over the regions (if any) in the current collection set.
1353 void collection_set_iterate(HeapRegionClosure* blk);
1354
1355 // As above but starting from region r
1356 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1357
1358 HeapRegion* next_compaction_region(const HeapRegion* from) const;
1359
1360 // Returns the HeapRegion that contains addr. addr must not be NULL.
1361 template <class T>
1362 inline HeapRegion* heap_region_containing_raw(const T addr) const;
1363
1364 // Returns the HeapRegion that contains addr. addr must not be NULL.
1365 // If addr is within a humongous continues region, it returns its humongous start region.
1366 template <class T>
1367 inline HeapRegion* heap_region_containing(const T addr) const;
1368
1369 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1370 // each address in the (reserved) heap is a member of exactly
1371 // one block. The defining characteristic of a block is that it is
1372 // possible to find its size, and thus to progress forward to the next
1373 // block. (Blocks may be of different sizes.) Thus, blocks may
1374 // represent Java objects, or they might be free blocks in a
1375 // free-list-based heap (or subheap), as long as the two kinds are
1376 // distinguishable and the size of each is determinable.
1377
1378 // Returns the address of the start of the "block" that contains the
1379 // address "addr". We say "blocks" instead of "object" since some heaps
1380 // may not pack objects densely; a chunk may either be an object or a
1381 // non-object.
1382 virtual HeapWord* block_start(const void* addr) const;
1383
1384 // Requires "addr" to be the start of a chunk, and returns its size.
1385 // "addr + size" is required to be the start of a new chunk, or the end
1386 // of the active area of the heap.
1387 virtual size_t block_size(const HeapWord* addr) const;
1388
1389 // Requires "addr" to be the start of a block, and returns "TRUE" iff
1390 // the block is an object.
1391 virtual bool block_is_obj(const HeapWord* addr) const;
1392
1393 // Section on thread-local allocation buffers (TLABs)
1394 // See CollectedHeap for semantics.
1395
1396 bool supports_tlab_allocation() const;
1397 size_t tlab_capacity(Thread* ignored) const;
1398 size_t tlab_used(Thread* ignored) const;
1399 size_t max_tlab_size() const;
1400 size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1401
1402 // Can a compiler initialize a new object without store barriers?
1403 // This permission only extends from the creation of a new object
1404 // via a TLAB up to the first subsequent safepoint. If such permission
1405 // is granted for this heap type, the compiler promises to call
1406 // defer_store_barrier() below on any slow path allocation of
1407 // a new object for which such initializing store barriers will
1408 // have been elided. G1, like CMS, allows this, but should be
1409 // ready to provide a compensating write barrier as necessary
1410 // if that storage came out of a non-young region. The efficiency
1411 // of this implementation depends crucially on being able to
1412 // answer very efficiently in constant time whether a piece of
1413 // storage in the heap comes from a young region or not.
1414 // See ReduceInitialCardMarks.
1415 virtual bool can_elide_tlab_store_barriers() const {
1416 return true;
1417 }
1418
1419 virtual bool card_mark_must_follow_store() const {
1420 return true;
1421 }
1422
1423 inline bool is_in_young(const oop obj);
1424
1425 virtual bool is_scavengable(const void* addr);
1426
1427 // We don't need barriers for initializing stores to objects
1428 // in the young gen: for the SATB pre-barrier, there is no
1429 // pre-value that needs to be remembered; for the remembered-set
1430 // update logging post-barrier, we don't maintain remembered set
1431 // information for young gen objects.
1432 virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1433
1434 // Returns "true" iff the given word_size is "very large".
1435 static bool is_humongous(size_t word_size) {
1436 // Note this has to be strictly greater-than as the TLABs
1437 // are capped at the humongous threshold and we want to
1438 // ensure that we don't try to allocate a TLAB as
1439 // humongous and that we don't allocate a humongous
1440 // object in a TLAB.
1441 return word_size > _humongous_object_threshold_in_words;
1442 }
1443
1444 // Returns the humongous threshold for a specific region size
1445 static size_t humongous_threshold_for(size_t region_size) {
1446 return (region_size / 2);
1447 }
1448
1449 // Update mod union table with the set of dirty cards.
1450 void updateModUnion();
1451
1452 // Set the mod union bits corresponding to the given memRegion. Note
1453 // that this is always a safe operation, since it doesn't clear any
1454 // bits.
1455 void markModUnionRange(MemRegion mr);
1456
1457 // Print the maximum heap capacity.
1458 virtual size_t max_capacity() const;
1459
1460 virtual jlong millis_since_last_gc();
1461
1462
1463 // Convenience function to be used in situations where the heap type can be
1464 // asserted to be this type.
1465 static G1CollectedHeap* heap();
1466
1467 void set_region_short_lived_locked(HeapRegion* hr);
1468 // add appropriate methods for any other surv rate groups
1469
1470 YoungList* young_list() const { return _young_list; }
1471
1472 // debugging
1473 bool check_young_list_well_formed() {
1474 return _young_list->check_list_well_formed();
1475 }
1476
1477 bool check_young_list_empty(bool check_heap,
1478 bool check_sample = true);
1479
1480 // *** Stuff related to concurrent marking. It's not clear to me that so
1481 // many of these need to be public.
1482
1483 // The functions below are helper functions that a subclass of
1484 // "CollectedHeap" can use in the implementation of its virtual
1485 // functions.
1486 // This performs a concurrent marking of the live objects in a
1487 // bitmap off to the side.
1488 void doConcurrentMark();
1489
1490 bool isMarkedPrev(oop obj) const;
1491 bool isMarkedNext(oop obj) const;
1492
1493 // Determine if an object is dead, given the object and also
1494 // the region to which the object belongs. An object is dead
1495 // iff a) it was not allocated since the last mark, b) it
1496 // is not marked, and c) it is not in an archive region.
1497 bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1498 return
1499 !hr->obj_allocated_since_prev_marking(obj) &&
1500 !isMarkedPrev(obj) &&
1501 !hr->is_archive();
1502 }
1503
1504 // This function returns true when an object has been
1505 // around since the previous marking and hasn't yet
1506 // been marked during this marking, and is not in an archive region.
1507 bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1508 return
1509 !hr->obj_allocated_since_next_marking(obj) &&
1510 !isMarkedNext(obj) &&
1511 !hr->is_archive();
1512 }
1513
1514 // Determine if an object is dead, given only the object itself.
1515 // This will find the region to which the object belongs and
1516 // then call the region version of the same function.
1517
1518 // Added if it is NULL it isn't dead.
1519
1520 inline bool is_obj_dead(const oop obj) const;
1521
1522 inline bool is_obj_ill(const oop obj) const;
1523
1524 bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1525 HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1526 bool is_marked(oop obj, VerifyOption vo);
1527 const char* top_at_mark_start_str(VerifyOption vo);
1528
1529 ConcurrentMark* concurrent_mark() const { return _cm; }
1530
1531 // Refinement
1532
1533 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1534
1535 // The dirty cards region list is used to record a subset of regions
1536 // whose cards need clearing. The list if populated during the
1537 // remembered set scanning and drained during the card table
1538 // cleanup. Although the methods are reentrant, population/draining
1539 // phases must not overlap. For synchronization purposes the last
1540 // element on the list points to itself.
1541 HeapRegion* _dirty_cards_region_list;
1542 void push_dirty_cards_region(HeapRegion* hr);
1543 HeapRegion* pop_dirty_cards_region();
1544
1545 // Optimized nmethod scanning support routines
1546
1547 // Register the given nmethod with the G1 heap.
1548 virtual void register_nmethod(nmethod* nm);
1549
1550 // Unregister the given nmethod from the G1 heap.
1551 virtual void unregister_nmethod(nmethod* nm);
1552
1553 // Free up superfluous code root memory.
1554 void purge_code_root_memory();
1555
1556 // Rebuild the strong code root lists for each region
1557 // after a full GC.
1558 void rebuild_strong_code_roots();
1559
1560 // Delete entries for dead interned string and clean up unreferenced symbols
1561 // in symbol table, possibly in parallel.
1562 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1563
1564 // Parallel phase of unloading/cleaning after G1 concurrent mark.
1565 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred);
1566
1567 // Redirty logged cards in the refinement queue.
1568 void redirty_logged_cards();
1569 // Verification
1570
1571 // Perform any cleanup actions necessary before allowing a verification.
1572 virtual void prepare_for_verify();
1573
1574 // Perform verification.
1575
1576 // vo == UsePrevMarking -> use "prev" marking information,
1577 // vo == UseNextMarking -> use "next" marking information
1578 // vo == UseMarkWord -> use the mark word in the object header
1579 //
1580 // NOTE: Only the "prev" marking information is guaranteed to be
1581 // consistent most of the time, so most calls to this should use
1582 // vo == UsePrevMarking.
1583 // Currently, there is only one case where this is called with
1584 // vo == UseNextMarking, which is to verify the "next" marking
1585 // information at the end of remark.
1586 // Currently there is only one place where this is called with
1587 // vo == UseMarkWord, which is to verify the marking during a
1588 // full GC.
1589 void verify(bool silent, VerifyOption vo);
1590
1591 // Override; it uses the "prev" marking information
1592 virtual void verify(bool silent);
1593
1594 // The methods below are here for convenience and dispatch the
1595 // appropriate method depending on value of the given VerifyOption
1596 // parameter. The values for that parameter, and their meanings,
1597 // are the same as those above.
1598
1599 bool is_obj_dead_cond(const oop obj,
1600 const HeapRegion* hr,
1601 const VerifyOption vo) const;
1602
1603 bool is_obj_dead_cond(const oop obj,
1604 const VerifyOption vo) const;
1605
1606 G1HeapSummary create_g1_heap_summary();
1607
1608 // Printing
1609
1610 virtual void print_on(outputStream* st) const;
1611 virtual void print_extended_on(outputStream* st) const;
1612 virtual void print_on_error(outputStream* st) const;
1613
1614 virtual void print_gc_threads_on(outputStream* st) const;
1615 virtual void gc_threads_do(ThreadClosure* tc) const;
1616
1617 // Override
1618 void print_tracing_info() const;
1619
1620 // The following two methods are helpful for debugging RSet issues.
1621 void print_cset_rsets() PRODUCT_RETURN;
1622 void print_all_rsets() PRODUCT_RETURN;
1623
1624 public:
1625 size_t pending_card_num();
1626 size_t cards_scanned();
1627
1628 protected:
1629 size_t _max_heap_capacity;
1630 };
1631
1632 #endif // SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP