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
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7 * published by the Free Software Foundation.
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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).
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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/g1AllocationContext.hpp"
29 #include "gc_implementation/g1/g1Allocator.hpp"
30 #include "gc_implementation/g1/concurrentMark.hpp"
31 #include "gc_implementation/g1/evacuationInfo.hpp"
32 #include "gc_implementation/g1/g1AllocRegion.hpp"
33 #include "gc_implementation/g1/g1BiasedArray.hpp"
34 #include "gc_implementation/g1/g1HRPrinter.hpp"
35 #include "gc_implementation/g1/g1InCSetState.hpp"
36 #include "gc_implementation/g1/g1MonitoringSupport.hpp"
37 #include "gc_implementation/g1/g1SATBCardTableModRefBS.hpp"
38 #include "gc_implementation/g1/g1YCTypes.hpp"
39 #include "gc_implementation/g1/heapRegionManager.hpp"
40 #include "gc_implementation/g1/heapRegionSet.hpp"
41 #include "gc_implementation/shared/gcHeapSummary.hpp"
42 #include "gc_implementation/shared/hSpaceCounters.hpp"
43 #include "gc_implementation/shared/parGCAllocBuffer.hpp"
44 #include "memory/barrierSet.hpp"
45 #include "memory/memRegion.hpp"
46 #include "memory/sharedHeap.hpp"
47 #include "utilities/macros.hpp"
48 #include "utilities/stack.hpp"
49
50 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
51 // It uses the "Garbage First" heap organization and algorithm, which
52 // may combine concurrent marking with parallel, incremental compaction of
53 // heap subsets that will yield large amounts of garbage.
54
55 // Forward declarations
56 class HeapRegion;
57 class HRRSCleanupTask;
58 class GenerationSpec;
59 class OopsInHeapRegionClosure;
60 class G1KlassScanClosure;
61 class G1ScanHeapEvacClosure;
62 class ObjectClosure;
63 class SpaceClosure;
64 class CompactibleSpaceClosure;
65 class Space;
66 class G1CollectorPolicy;
67 class GenRemSet;
68 class G1RemSet;
69 class HeapRegionRemSetIterator;
70 class ConcurrentMark;
71 class ConcurrentMarkThread;
72 class ConcurrentG1Refine;
73 class ConcurrentGCTimer;
74 class GenerationCounters;
75 class STWGCTimer;
76 class G1NewTracer;
77 class G1OldTracer;
78 class EvacuationFailedInfo;
79 class nmethod;
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 survivor_length() { return _survivor_length; }
116
117 // Currently we do not keep track of the used byte sum for the
118 // young list and the survivors and it'd be quite a lot of work to
119 // do so. When we'll eventually replace the young list with
120 // instances of HeapRegionLinkedList we'll get that for free. So,
121 // we'll report the more accurate information then.
122 size_t eden_used_bytes() {
123 assert(length() >= survivor_length(), "invariant");
124 return (size_t) (length() - survivor_length()) * HeapRegion::GrainBytes;
125 }
126 size_t survivor_used_bytes() {
127 return (size_t) survivor_length() * HeapRegion::GrainBytes;
128 }
129
130 void rs_length_sampling_init();
131 bool rs_length_sampling_more();
132 void rs_length_sampling_next();
133
134 void reset_sampled_info() {
135 _last_sampled_rs_lengths = 0;
136 }
137 size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
138
139 // for development purposes
140 void reset_auxilary_lists();
141 void clear() { _head = NULL; _length = 0; }
142
143 void clear_survivors() {
144 _survivor_head = NULL;
145 _survivor_tail = NULL;
146 _survivor_length = 0;
147 }
148
149 HeapRegion* first_region() { return _head; }
150 HeapRegion* first_survivor_region() { return _survivor_head; }
151 HeapRegion* last_survivor_region() { return _survivor_tail; }
152
153 // debugging
154 bool check_list_well_formed();
155 bool check_list_empty(bool check_sample = true);
156 void print();
157 };
158
159 // The G1 STW is alive closure.
160 // An instance is embedded into the G1CH and used as the
161 // (optional) _is_alive_non_header closure in the STW
162 // reference processor. It is also extensively used during
163 // reference processing during STW evacuation pauses.
164 class G1STWIsAliveClosure: public BoolObjectClosure {
165 G1CollectedHeap* _g1;
166 public:
167 G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
168 bool do_object_b(oop p);
169 };
170
171 class RefineCardTableEntryClosure;
172
173 class G1RegionMappingChangedListener : public G1MappingChangedListener {
174 private:
175 void reset_from_card_cache(uint start_idx, size_t num_regions);
176 public:
177 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
178 };
179
180 class G1CollectedHeap : public SharedHeap {
181 friend class VM_CollectForMetadataAllocation;
182 friend class VM_G1CollectForAllocation;
183 friend class VM_G1CollectFull;
184 friend class VM_G1IncCollectionPause;
185 friend class VMStructs;
186 friend class MutatorAllocRegion;
187 friend class SurvivorGCAllocRegion;
188 friend class OldGCAllocRegion;
189 friend class G1Allocator;
190 friend class G1DefaultAllocator;
191 friend class G1ResManAllocator;
192
193 // Closures used in implementation.
194 template <G1Barrier barrier, G1Mark do_mark_object>
195 friend class G1ParCopyClosure;
196 friend class G1IsAliveClosure;
197 friend class G1EvacuateFollowersClosure;
198 friend class G1ParScanThreadState;
199 friend class G1ParScanClosureSuper;
200 friend class G1ParEvacuateFollowersClosure;
201 friend class G1ParTask;
202 friend class G1ParGCAllocator;
203 friend class G1DefaultParGCAllocator;
204 friend class G1FreeGarbageRegionClosure;
205 friend class RefineCardTableEntryClosure;
206 friend class G1PrepareCompactClosure;
207 friend class RegionSorter;
208 friend class RegionResetter;
209 friend class CountRCClosure;
210 friend class EvacPopObjClosure;
211 friend class G1ParCleanupCTTask;
212
213 friend class G1FreeHumongousRegionClosure;
214 // Other related classes.
215 friend class G1MarkSweep;
216
217 // Testing classes.
218 friend class G1CheckCSetFastTableClosure;
219
220 private:
221 // The one and only G1CollectedHeap, so static functions can find it.
222 static G1CollectedHeap* _g1h;
223
224 static size_t _humongous_object_threshold_in_words;
225
226 // The secondary free list which contains regions that have been
227 // freed up during the cleanup process. This will be appended to
228 // the master free list when appropriate.
229 FreeRegionList _secondary_free_list;
230
231 // It keeps track of the old regions.
232 HeapRegionSet _old_set;
233
234 // It keeps track of the humongous regions.
235 HeapRegionSet _humongous_set;
236
237 void eagerly_reclaim_humongous_regions();
238
239 // The number of regions we could create by expansion.
240 uint _expansion_regions;
241
242 // The block offset table for the G1 heap.
243 G1BlockOffsetSharedArray* _bot_shared;
244
245 // Tears down the region sets / lists so that they are empty and the
246 // regions on the heap do not belong to a region set / list. The
247 // only exception is the humongous set which we leave unaltered. If
248 // free_list_only is true, it will only tear down the master free
249 // list. It is called before a Full GC (free_list_only == false) or
250 // before heap shrinking (free_list_only == true).
251 void tear_down_region_sets(bool free_list_only);
252
253 // Rebuilds the region sets / lists so that they are repopulated to
254 // reflect the contents of the heap. The only exception is the
255 // humongous set which was not torn down in the first place. If
256 // free_list_only is true, it will only rebuild the master free
257 // list. It is called after a Full GC (free_list_only == false) or
258 // after heap shrinking (free_list_only == true).
259 void rebuild_region_sets(bool free_list_only);
260
261 // Callback for region mapping changed events.
262 G1RegionMappingChangedListener _listener;
263
264 // The sequence of all heap regions in the heap.
265 HeapRegionManager _hrm;
266
267 // Class that handles the different kinds of allocations.
268 G1Allocator* _allocator;
269
270 // Statistics for each allocation context
271 AllocationContextStats _allocation_context_stats;
272
273 // PLAB sizing policy for survivors.
274 PLABStats _survivor_plab_stats;
275
276 // PLAB sizing policy for tenured objects.
277 PLABStats _old_plab_stats;
278
279 // It specifies whether we should attempt to expand the heap after a
280 // region allocation failure. If heap expansion fails we set this to
281 // false so that we don't re-attempt the heap expansion (it's likely
282 // that subsequent expansion attempts will also fail if one fails).
283 // Currently, it is only consulted during GC and it's reset at the
284 // start of each GC.
285 bool _expand_heap_after_alloc_failure;
286
287 // It resets the mutator alloc region before new allocations can take place.
288 void init_mutator_alloc_region();
289
290 // It releases the mutator alloc region.
291 void release_mutator_alloc_region();
292
293 // It initializes the GC alloc regions at the start of a GC.
294 void init_gc_alloc_regions(EvacuationInfo& evacuation_info);
295
296 // It releases the GC alloc regions at the end of a GC.
297 void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info);
298
299 // It does any cleanup that needs to be done on the GC alloc regions
300 // before a Full GC.
301 void abandon_gc_alloc_regions();
302
303 // Helper for monitoring and management support.
304 G1MonitoringSupport* _g1mm;
305
306 // Records whether the region at the given index is (still) a
307 // candidate for eager reclaim. Only valid for humongous start
308 // regions; other regions have unspecified values. Humongous start
309 // regions are initialized at start of collection pause, with
310 // candidates removed from the set as they are found reachable from
311 // roots or the young generation.
312 class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> {
313 protected:
314 bool default_value() const { return false; }
315 public:
316 void clear() { G1BiasedMappedArray<bool>::clear(); }
317 void set_candidate(uint region, bool value) {
318 set_by_index(region, value);
319 }
320 bool is_candidate(uint region) {
321 return get_by_index(region);
322 }
323 };
324
325 HumongousReclaimCandidates _humongous_reclaim_candidates;
326 // Stores whether during humongous object registration we found candidate regions.
327 // If not, we can skip a few steps.
328 bool _has_humongous_reclaim_candidates;
329
330 volatile unsigned _gc_time_stamp;
331
332 size_t* _surviving_young_words;
333
334 G1HRPrinter _hr_printer;
335
336 void setup_surviving_young_words();
337 void update_surviving_young_words(size_t* surv_young_words);
338 void cleanup_surviving_young_words();
339
340 // It decides whether an explicit GC should start a concurrent cycle
341 // instead of doing a STW GC. Currently, a concurrent cycle is
342 // explicitly started if:
343 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
344 // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
345 // (c) cause == _g1_humongous_allocation
346 bool should_do_concurrent_full_gc(GCCause::Cause cause);
347
348 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
349 // concurrent cycles) we have started.
350 volatile uint _old_marking_cycles_started;
351
352 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
353 // concurrent cycles) we have completed.
354 volatile uint _old_marking_cycles_completed;
355
356 bool _concurrent_cycle_started;
357 bool _heap_summary_sent;
358
359 // This is a non-product method that is helpful for testing. It is
360 // called at the end of a GC and artificially expands the heap by
361 // allocating a number of dead regions. This way we can induce very
362 // frequent marking cycles and stress the cleanup / concurrent
363 // cleanup code more (as all the regions that will be allocated by
364 // this method will be found dead by the marking cycle).
365 void allocate_dummy_regions() PRODUCT_RETURN;
366
367 // Clear RSets after a compaction. It also resets the GC time stamps.
368 void clear_rsets_post_compaction();
369
370 // If the HR printer is active, dump the state of the regions in the
371 // heap after a compaction.
372 void print_hrm_post_compaction();
373
374 // Create a memory mapper for auxiliary data structures of the given size and
375 // translation factor.
376 static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description,
377 size_t size,
378 size_t translation_factor);
379
380 void trace_heap(GCWhen::Type when, GCTracer* tracer);
381
382 double verify(bool guard, const char* msg);
383 void verify_before_gc();
384 void verify_after_gc();
385
386 void log_gc_header();
387 void log_gc_footer(double pause_time_sec);
388
389 // These are macros so that, if the assert fires, we get the correct
390 // line number, file, etc.
391
392 #define heap_locking_asserts_err_msg(_extra_message_) \
393 err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \
394 (_extra_message_), \
395 BOOL_TO_STR(Heap_lock->owned_by_self()), \
396 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \
397 BOOL_TO_STR(Thread::current()->is_VM_thread()))
398
399 #define assert_heap_locked() \
400 do { \
401 assert(Heap_lock->owned_by_self(), \
402 heap_locking_asserts_err_msg("should be holding the Heap_lock")); \
403 } while (0)
404
405 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \
406 do { \
407 assert(Heap_lock->owned_by_self() || \
408 (SafepointSynchronize::is_at_safepoint() && \
409 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
410 heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
411 "should be at a safepoint")); \
412 } while (0)
413
414 #define assert_heap_locked_and_not_at_safepoint() \
415 do { \
416 assert(Heap_lock->owned_by_self() && \
417 !SafepointSynchronize::is_at_safepoint(), \
418 heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
419 "should not be at a safepoint")); \
420 } while (0)
421
422 #define assert_heap_not_locked() \
423 do { \
424 assert(!Heap_lock->owned_by_self(), \
425 heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
426 } while (0)
427
428 #define assert_heap_not_locked_and_not_at_safepoint() \
429 do { \
430 assert(!Heap_lock->owned_by_self() && \
431 !SafepointSynchronize::is_at_safepoint(), \
432 heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
433 "should not be at a safepoint")); \
434 } while (0)
435
436 #define assert_at_safepoint(_should_be_vm_thread_) \
437 do { \
438 assert(SafepointSynchronize::is_at_safepoint() && \
439 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
440 heap_locking_asserts_err_msg("should be at a safepoint")); \
441 } while (0)
442
443 #define assert_not_at_safepoint() \
444 do { \
445 assert(!SafepointSynchronize::is_at_safepoint(), \
446 heap_locking_asserts_err_msg("should not be at a safepoint")); \
447 } while (0)
448
449 protected:
450
451 // The young region list.
452 YoungList* _young_list;
453
454 // The current policy object for the collector.
455 G1CollectorPolicy* _g1_policy;
456
457 // This is the second level of trying to allocate a new region. If
458 // new_region() didn't find a region on the free_list, this call will
459 // check whether there's anything available on the
460 // secondary_free_list and/or wait for more regions to appear on
461 // that list, if _free_regions_coming is set.
462 HeapRegion* new_region_try_secondary_free_list(bool is_old);
463
464 // Try to allocate a single non-humongous HeapRegion sufficient for
465 // an allocation of the given word_size. If do_expand is true,
466 // attempt to expand the heap if necessary to satisfy the allocation
467 // request. If the region is to be used as an old region or for a
468 // humongous object, set is_old to true. If not, to false.
469 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
470
471 // Initialize a contiguous set of free regions of length num_regions
472 // and starting at index first so that they appear as a single
473 // humongous region.
474 HeapWord* humongous_obj_allocate_initialize_regions(uint first,
475 uint num_regions,
476 size_t word_size,
477 AllocationContext_t context);
478
479 // Attempt to allocate a humongous object of the given size. Return
480 // NULL if unsuccessful.
481 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context);
482
483 // The following two methods, allocate_new_tlab() and
484 // mem_allocate(), are the two main entry points from the runtime
485 // into the G1's allocation routines. They have the following
486 // assumptions:
487 //
488 // * They should both be called outside safepoints.
489 //
490 // * They should both be called without holding the Heap_lock.
491 //
492 // * All allocation requests for new TLABs should go to
493 // allocate_new_tlab().
494 //
495 // * All non-TLAB allocation requests should go to mem_allocate().
496 //
497 // * If either call cannot satisfy the allocation request using the
498 // current allocating region, they will try to get a new one. If
499 // this fails, they will attempt to do an evacuation pause and
500 // retry the allocation.
501 //
502 // * If all allocation attempts fail, even after trying to schedule
503 // an evacuation pause, allocate_new_tlab() will return NULL,
504 // whereas mem_allocate() will attempt a heap expansion and/or
505 // schedule a Full GC.
506 //
507 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
508 // should never be called with word_size being humongous. All
509 // humongous allocation requests should go to mem_allocate() which
510 // will satisfy them with a special path.
511
512 virtual HeapWord* allocate_new_tlab(size_t word_size);
513
514 virtual HeapWord* mem_allocate(size_t word_size,
515 bool* gc_overhead_limit_was_exceeded);
516
517 // The following three methods take a gc_count_before_ret
518 // parameter which is used to return the GC count if the method
519 // returns NULL. Given that we are required to read the GC count
520 // while holding the Heap_lock, and these paths will take the
521 // Heap_lock at some point, it's easier to get them to read the GC
522 // count while holding the Heap_lock before they return NULL instead
523 // of the caller (namely: mem_allocate()) having to also take the
524 // Heap_lock just to read the GC count.
525
526 // First-level mutator allocation attempt: try to allocate out of
527 // the mutator alloc region without taking the Heap_lock. This
528 // should only be used for non-humongous allocations.
529 inline HeapWord* attempt_allocation(size_t word_size,
530 uint* gc_count_before_ret,
531 uint* gclocker_retry_count_ret);
532
533 // Second-level mutator allocation attempt: take the Heap_lock and
534 // retry the allocation attempt, potentially scheduling a GC
535 // pause. This should only be used for non-humongous allocations.
536 HeapWord* attempt_allocation_slow(size_t word_size,
537 AllocationContext_t context,
538 uint* gc_count_before_ret,
539 uint* gclocker_retry_count_ret);
540
541 // Takes the Heap_lock and attempts a humongous allocation. It can
542 // potentially schedule a GC pause.
543 HeapWord* attempt_allocation_humongous(size_t word_size,
544 uint* gc_count_before_ret,
545 uint* gclocker_retry_count_ret);
546
547 // Allocation attempt that should be called during safepoints (e.g.,
548 // at the end of a successful GC). expect_null_mutator_alloc_region
549 // specifies whether the mutator alloc region is expected to be NULL
550 // or not.
551 HeapWord* attempt_allocation_at_safepoint(size_t word_size,
552 AllocationContext_t context,
553 bool expect_null_mutator_alloc_region);
554
555 // It dirties the cards that cover the block so that so that the post
556 // write barrier never queues anything when updating objects on this
557 // block. It is assumed (and in fact we assert) that the block
558 // belongs to a young region.
559 inline void dirty_young_block(HeapWord* start, size_t word_size);
560
561 // Allocate blocks during garbage collection. Will ensure an
562 // allocation region, either by picking one or expanding the
563 // heap, and then allocate a block of the given size. The block
564 // may not be a humongous - it must fit into a single heap region.
565 inline HeapWord* par_allocate_during_gc(InCSetState dest,
566 size_t word_size,
567 AllocationContext_t context);
568 // Ensure that no further allocations can happen in "r", bearing in mind
569 // that parallel threads might be attempting allocations.
570 void par_allocate_remaining_space(HeapRegion* r);
571
572 // Allocation attempt during GC for a survivor object / PLAB.
573 inline HeapWord* survivor_attempt_allocation(size_t word_size,
574 AllocationContext_t context);
575
576 // Allocation attempt during GC for an old object / PLAB.
577 inline HeapWord* old_attempt_allocation(size_t word_size,
578 AllocationContext_t context);
579
580 // These methods are the "callbacks" from the G1AllocRegion class.
581
582 // For mutator alloc regions.
583 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
584 void retire_mutator_alloc_region(HeapRegion* alloc_region,
585 size_t allocated_bytes);
586
587 // For GC alloc regions.
588 HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
589 InCSetState dest);
590 void retire_gc_alloc_region(HeapRegion* alloc_region,
591 size_t allocated_bytes, InCSetState dest);
592
593 // - if explicit_gc is true, the GC is for a System.gc() or a heap
594 // inspection request and should collect the entire heap
595 // - if clear_all_soft_refs is true, all soft references should be
596 // cleared during the GC
597 // - if explicit_gc is false, word_size describes the allocation that
598 // the GC should attempt (at least) to satisfy
599 // - it returns false if it is unable to do the collection due to the
600 // GC locker being active, true otherwise
601 bool do_collection(bool explicit_gc,
602 bool clear_all_soft_refs,
603 size_t word_size);
604
605 // Callback from VM_G1CollectFull operation.
606 // Perform a full collection.
607 virtual void do_full_collection(bool clear_all_soft_refs);
608
609 // Resize the heap if necessary after a full collection. If this is
610 // after a collect-for allocation, "word_size" is the allocation size,
611 // and will be considered part of the used portion of the heap.
612 void resize_if_necessary_after_full_collection(size_t word_size);
613
614 // Callback from VM_G1CollectForAllocation operation.
615 // This function does everything necessary/possible to satisfy a
616 // failed allocation request (including collection, expansion, etc.)
617 HeapWord* satisfy_failed_allocation(size_t word_size,
618 AllocationContext_t context,
619 bool* succeeded);
620
621 // Attempting to expand the heap sufficiently
622 // to support an allocation of the given "word_size". If
623 // successful, perform the allocation and return the address of the
624 // allocated block, or else "NULL".
625 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context);
626
627 // Process any reference objects discovered during
628 // an incremental evacuation pause.
629 void process_discovered_references(uint no_of_gc_workers);
630
631 // Enqueue any remaining discovered references
632 // after processing.
633 void enqueue_discovered_references(uint no_of_gc_workers);
634
635 public:
636
637 G1Allocator* allocator() {
638 return _allocator;
639 }
640
641 G1MonitoringSupport* g1mm() {
642 assert(_g1mm != NULL, "should have been initialized");
643 return _g1mm;
644 }
645
646 // Expand the garbage-first heap by at least the given size (in bytes!).
647 // Returns true if the heap was expanded by the requested amount;
648 // false otherwise.
649 // (Rounds up to a HeapRegion boundary.)
650 bool expand(size_t expand_bytes);
651
652 // Returns the PLAB statistics for a given destination.
653 inline PLABStats* alloc_buffer_stats(InCSetState dest);
654
655 // Determines PLAB size for a given destination.
656 inline size_t desired_plab_sz(InCSetState dest);
657
658 inline AllocationContextStats& allocation_context_stats();
659
660 // Do anything common to GC's.
661 virtual void gc_prologue(bool full);
662 virtual void gc_epilogue(bool full);
663
664 // Modify the reclaim candidate set and test for presence.
665 // These are only valid for starts_humongous regions.
666 inline void set_humongous_reclaim_candidate(uint region, bool value);
667 inline bool is_humongous_reclaim_candidate(uint region);
668
669 // Remove from the reclaim candidate set. Also remove from the
670 // collection set so that later encounters avoid the slow path.
671 inline void set_humongous_is_live(oop obj);
672
673 // Register the given region to be part of the collection set.
674 inline void register_humongous_region_with_in_cset_fast_test(uint index);
675 // Register regions with humongous objects (actually on the start region) in
676 // the in_cset_fast_test table.
677 void register_humongous_regions_with_in_cset_fast_test();
678 // We register a region with the fast "in collection set" test. We
679 // simply set to true the array slot corresponding to this region.
680 void register_young_region_with_in_cset_fast_test(HeapRegion* r) {
681 _in_cset_fast_test.set_in_young(r->hrm_index());
682 }
683 void register_old_region_with_in_cset_fast_test(HeapRegion* r) {
684 _in_cset_fast_test.set_in_old(r->hrm_index());
685 }
686
687 // This is a fast test on whether a reference points into the
688 // collection set or not. Assume that the reference
689 // points into the heap.
690 inline bool in_cset_fast_test(oop obj);
691
692 void clear_cset_fast_test() {
693 _in_cset_fast_test.clear();
694 }
695
696 // This is called at the start of either a concurrent cycle or a Full
697 // GC to update the number of old marking cycles started.
698 void increment_old_marking_cycles_started();
699
700 // This is called at the end of either a concurrent cycle or a Full
701 // GC to update the number of old marking cycles completed. Those two
702 // can happen in a nested fashion, i.e., we start a concurrent
703 // cycle, a Full GC happens half-way through it which ends first,
704 // and then the cycle notices that a Full GC happened and ends
705 // too. The concurrent parameter is a boolean to help us do a bit
706 // tighter consistency checking in the method. If concurrent is
707 // false, the caller is the inner caller in the nesting (i.e., the
708 // Full GC). If concurrent is true, the caller is the outer caller
709 // in this nesting (i.e., the concurrent cycle). Further nesting is
710 // not currently supported. The end of this call also notifies
711 // the FullGCCount_lock in case a Java thread is waiting for a full
712 // GC to happen (e.g., it called System.gc() with
713 // +ExplicitGCInvokesConcurrent).
714 void increment_old_marking_cycles_completed(bool concurrent);
715
716 uint old_marking_cycles_completed() {
717 return _old_marking_cycles_completed;
718 }
719
720 void register_concurrent_cycle_start(const Ticks& start_time);
721 void register_concurrent_cycle_end();
722 void trace_heap_after_concurrent_cycle();
723
724 G1YCType yc_type();
725
726 G1HRPrinter* hr_printer() { return &_hr_printer; }
727
728 // Frees a non-humongous region by initializing its contents and
729 // adding it to the free list that's passed as a parameter (this is
730 // usually a local list which will be appended to the master free
731 // list later). The used bytes of freed regions are accumulated in
732 // pre_used. If par is true, the region's RSet will not be freed
733 // up. The assumption is that this will be done later.
734 // The locked parameter indicates if the caller has already taken
735 // care of proper synchronization. This may allow some optimizations.
736 void free_region(HeapRegion* hr,
737 FreeRegionList* free_list,
738 bool par,
739 bool locked = false);
740
741 // Frees a humongous region by collapsing it into individual regions
742 // and calling free_region() for each of them. The freed regions
743 // will be added to the free list that's passed as a parameter (this
744 // is usually a local list which will be appended to the master free
745 // list later). The used bytes of freed regions are accumulated in
746 // pre_used. If par is true, the region's RSet will not be freed
747 // up. The assumption is that this will be done later.
748 void free_humongous_region(HeapRegion* hr,
749 FreeRegionList* free_list,
750 bool par);
751 protected:
752
753 // Shrink the garbage-first heap by at most the given size (in bytes!).
754 // (Rounds down to a HeapRegion boundary.)
755 virtual void shrink(size_t expand_bytes);
756 void shrink_helper(size_t expand_bytes);
757
758 #if TASKQUEUE_STATS
759 static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
760 void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
761 void reset_taskqueue_stats();
762 #endif // TASKQUEUE_STATS
763
764 // Schedule the VM operation that will do an evacuation pause to
765 // satisfy an allocation request of word_size. *succeeded will
766 // return whether the VM operation was successful (it did do an
767 // evacuation pause) or not (another thread beat us to it or the GC
768 // locker was active). Given that we should not be holding the
769 // Heap_lock when we enter this method, we will pass the
770 // gc_count_before (i.e., total_collections()) as a parameter since
771 // it has to be read while holding the Heap_lock. Currently, both
772 // methods that call do_collection_pause() release the Heap_lock
773 // before the call, so it's easy to read gc_count_before just before.
774 HeapWord* do_collection_pause(size_t word_size,
775 uint gc_count_before,
776 bool* succeeded,
777 GCCause::Cause gc_cause);
778
779 // The guts of the incremental collection pause, executed by the vm
780 // thread. It returns false if it is unable to do the collection due
781 // to the GC locker being active, true otherwise
782 bool do_collection_pause_at_safepoint(double target_pause_time_ms);
783
784 // Actually do the work of evacuating the collection set.
785 void evacuate_collection_set(EvacuationInfo& evacuation_info);
786
787 // The g1 remembered set of the heap.
788 G1RemSet* _g1_rem_set;
789
790 // A set of cards that cover the objects for which the Rsets should be updated
791 // concurrently after the collection.
792 DirtyCardQueueSet _dirty_card_queue_set;
793
794 // The closure used to refine a single card.
795 RefineCardTableEntryClosure* _refine_cte_cl;
796
797 // A function to check the consistency of dirty card logs.
798 void check_ct_logs_at_safepoint();
799
800 // A DirtyCardQueueSet that is used to hold cards that contain
801 // references into the current collection set. This is used to
802 // update the remembered sets of the regions in the collection
803 // set in the event of an evacuation failure.
804 DirtyCardQueueSet _into_cset_dirty_card_queue_set;
805
806 // After a collection pause, make the regions in the CS into free
807 // regions.
808 void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info);
809
810 // Abandon the current collection set without recording policy
811 // statistics or updating free lists.
812 void abandon_collection_set(HeapRegion* cs_head);
813
814 // The concurrent marker (and the thread it runs in.)
815 ConcurrentMark* _cm;
816 ConcurrentMarkThread* _cmThread;
817 bool _mark_in_progress;
818
819 // The concurrent refiner.
820 ConcurrentG1Refine* _cg1r;
821
822 // The parallel task queues
823 RefToScanQueueSet *_task_queues;
824
825 // True iff a evacuation has failed in the current collection.
826 bool _evacuation_failed;
827
828 EvacuationFailedInfo* _evacuation_failed_info_array;
829
830 // Failed evacuations cause some logical from-space objects to have
831 // forwarding pointers to themselves. Reset them.
832 void remove_self_forwarding_pointers();
833
834 // Together, these store an object with a preserved mark, and its mark value.
835 Stack<oop, mtGC> _objs_with_preserved_marks;
836 Stack<markOop, mtGC> _preserved_marks_of_objs;
837
838 // Preserve the mark of "obj", if necessary, in preparation for its mark
839 // word being overwritten with a self-forwarding-pointer.
840 void preserve_mark_if_necessary(oop obj, markOop m);
841
842 // The stack of evac-failure objects left to be scanned.
843 GrowableArray<oop>* _evac_failure_scan_stack;
844 // The closure to apply to evac-failure objects.
845
846 OopsInHeapRegionClosure* _evac_failure_closure;
847 // Set the field above.
848 void
849 set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
850 _evac_failure_closure = evac_failure_closure;
851 }
852
853 // Push "obj" on the scan stack.
854 void push_on_evac_failure_scan_stack(oop obj);
855 // Process scan stack entries until the stack is empty.
856 void drain_evac_failure_scan_stack();
857 // True iff an invocation of "drain_scan_stack" is in progress; to
858 // prevent unnecessary recursion.
859 bool _drain_in_progress;
860
861 // Do any necessary initialization for evacuation-failure handling.
862 // "cl" is the closure that will be used to process evac-failure
863 // objects.
864 void init_for_evac_failure(OopsInHeapRegionClosure* cl);
865 // Do any necessary cleanup for evacuation-failure handling data
866 // structures.
867 void finalize_for_evac_failure();
868
869 // An attempt to evacuate "obj" has failed; take necessary steps.
870 oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj);
871 void handle_evacuation_failure_common(oop obj, markOop m);
872
873 #ifndef PRODUCT
874 // Support for forcing evacuation failures. Analogous to
875 // PromotionFailureALot for the other collectors.
876
877 // Records whether G1EvacuationFailureALot should be in effect
878 // for the current GC
879 bool _evacuation_failure_alot_for_current_gc;
880
881 // Used to record the GC number for interval checking when
882 // determining whether G1EvaucationFailureALot is in effect
883 // for the current GC.
884 size_t _evacuation_failure_alot_gc_number;
885
886 // Count of the number of evacuations between failures.
887 volatile size_t _evacuation_failure_alot_count;
888
889 // Set whether G1EvacuationFailureALot should be in effect
890 // for the current GC (based upon the type of GC and which
891 // command line flags are set);
892 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
893 bool during_initial_mark,
894 bool during_marking);
895
896 inline void set_evacuation_failure_alot_for_current_gc();
897
898 // Return true if it's time to cause an evacuation failure.
899 inline bool evacuation_should_fail();
900
901 // Reset the G1EvacuationFailureALot counters. Should be called at
902 // the end of an evacuation pause in which an evacuation failure occurred.
903 inline void reset_evacuation_should_fail();
904 #endif // !PRODUCT
905
906 // ("Weak") Reference processing support.
907 //
908 // G1 has 2 instances of the reference processor class. One
909 // (_ref_processor_cm) handles reference object discovery
910 // and subsequent processing during concurrent marking cycles.
911 //
912 // The other (_ref_processor_stw) handles reference object
913 // discovery and processing during full GCs and incremental
914 // evacuation pauses.
915 //
916 // During an incremental pause, reference discovery will be
917 // temporarily disabled for _ref_processor_cm and will be
918 // enabled for _ref_processor_stw. At the end of the evacuation
919 // pause references discovered by _ref_processor_stw will be
920 // processed and discovery will be disabled. The previous
921 // setting for reference object discovery for _ref_processor_cm
922 // will be re-instated.
923 //
924 // At the start of marking:
925 // * Discovery by the CM ref processor is verified to be inactive
926 // and it's discovered lists are empty.
927 // * Discovery by the CM ref processor is then enabled.
928 //
929 // At the end of marking:
930 // * Any references on the CM ref processor's discovered
931 // lists are processed (possibly MT).
932 //
933 // At the start of full GC we:
934 // * Disable discovery by the CM ref processor and
935 // empty CM ref processor's discovered lists
936 // (without processing any entries).
937 // * Verify that the STW ref processor is inactive and it's
938 // discovered lists are empty.
939 // * Temporarily set STW ref processor discovery as single threaded.
940 // * Temporarily clear the STW ref processor's _is_alive_non_header
941 // field.
942 // * Finally enable discovery by the STW ref processor.
943 //
944 // The STW ref processor is used to record any discovered
945 // references during the full GC.
946 //
947 // At the end of a full GC we:
948 // * Enqueue any reference objects discovered by the STW ref processor
949 // that have non-live referents. This has the side-effect of
950 // making the STW ref processor inactive by disabling discovery.
951 // * Verify that the CM ref processor is still inactive
952 // and no references have been placed on it's discovered
953 // lists (also checked as a precondition during initial marking).
954
955 // The (stw) reference processor...
956 ReferenceProcessor* _ref_processor_stw;
957
958 STWGCTimer* _gc_timer_stw;
959 ConcurrentGCTimer* _gc_timer_cm;
960
961 G1OldTracer* _gc_tracer_cm;
962 G1NewTracer* _gc_tracer_stw;
963
964 // During reference object discovery, the _is_alive_non_header
965 // closure (if non-null) is applied to the referent object to
966 // determine whether the referent is live. If so then the
967 // reference object does not need to be 'discovered' and can
968 // be treated as a regular oop. This has the benefit of reducing
969 // the number of 'discovered' reference objects that need to
970 // be processed.
971 //
972 // Instance of the is_alive closure for embedding into the
973 // STW reference processor as the _is_alive_non_header field.
974 // Supplying a value for the _is_alive_non_header field is
975 // optional but doing so prevents unnecessary additions to
976 // the discovered lists during reference discovery.
977 G1STWIsAliveClosure _is_alive_closure_stw;
978
979 // The (concurrent marking) reference processor...
980 ReferenceProcessor* _ref_processor_cm;
981
982 // Instance of the concurrent mark is_alive closure for embedding
983 // into the Concurrent Marking reference processor as the
984 // _is_alive_non_header field. Supplying a value for the
985 // _is_alive_non_header field is optional but doing so prevents
986 // unnecessary additions to the discovered lists during reference
987 // discovery.
988 G1CMIsAliveClosure _is_alive_closure_cm;
989
990 // Cache used by G1CollectedHeap::start_cset_region_for_worker().
991 HeapRegion** _worker_cset_start_region;
992
993 // Time stamp to validate the regions recorded in the cache
994 // used by G1CollectedHeap::start_cset_region_for_worker().
995 // The heap region entry for a given worker is valid iff
996 // the associated time stamp value matches the current value
997 // of G1CollectedHeap::_gc_time_stamp.
998 uint* _worker_cset_start_region_time_stamp;
999
1000 volatile bool _free_regions_coming;
1001
1002 public:
1003
1004 void set_refine_cte_cl_concurrency(bool concurrent);
1005
1006 RefToScanQueue *task_queue(int i) const;
1007
1008 // A set of cards where updates happened during the GC
1009 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
1010
1011 // A DirtyCardQueueSet that is used to hold cards that contain
1012 // references into the current collection set. This is used to
1013 // update the remembered sets of the regions in the collection
1014 // set in the event of an evacuation failure.
1015 DirtyCardQueueSet& into_cset_dirty_card_queue_set()
1016 { return _into_cset_dirty_card_queue_set; }
1017
1018 // Create a G1CollectedHeap with the specified policy.
1019 // Must call the initialize method afterwards.
1020 // May not return if something goes wrong.
1021 G1CollectedHeap(G1CollectorPolicy* policy);
1022
1023 // Initialize the G1CollectedHeap to have the initial and
1024 // maximum sizes and remembered and barrier sets
1025 // specified by the policy object.
1026 jint initialize();
1027
1028 virtual void stop();
1029
1030 // Return the (conservative) maximum heap alignment for any G1 heap
1031 static size_t conservative_max_heap_alignment();
1032
1033 // Initialize weak reference processing.
1034 virtual void ref_processing_init();
1035
1036 // Explicitly import set_par_threads into this scope
1037 using SharedHeap::set_par_threads;
1038 // Set _n_par_threads according to a policy TBD.
1039 void set_par_threads();
1040
1041 virtual CollectedHeap::Name kind() const {
1042 return CollectedHeap::G1CollectedHeap;
1043 }
1044
1045 // The current policy object for the collector.
1046 G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1047
1048 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); }
1049
1050 // Adaptive size policy. No such thing for g1.
1051 virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1052
1053 // The rem set and barrier set.
1054 G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1055
1056 unsigned get_gc_time_stamp() {
1057 return _gc_time_stamp;
1058 }
1059
1060 inline void reset_gc_time_stamp();
1061
1062 void check_gc_time_stamps() PRODUCT_RETURN;
1063
1064 inline void increment_gc_time_stamp();
1065
1066 // Reset the given region's GC timestamp. If it's starts humongous,
1067 // also reset the GC timestamp of its corresponding
1068 // continues humongous regions too.
1069 void reset_gc_time_stamps(HeapRegion* hr);
1070
1071 void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1072 DirtyCardQueue* into_cset_dcq,
1073 bool concurrent, uint worker_i);
1074
1075 // The shared block offset table array.
1076 G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1077
1078 // Reference Processing accessors
1079
1080 // The STW reference processor....
1081 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1082
1083 // The Concurrent Marking reference processor...
1084 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1085
1086 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1087 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1088
1089 virtual size_t capacity() const;
1090 virtual size_t used() const;
1091 // This should be called when we're not holding the heap lock. The
1092 // result might be a bit inaccurate.
1093 size_t used_unlocked() const;
1094 size_t recalculate_used() const;
1095
1096 // These virtual functions do the actual allocation.
1097 // Some heaps may offer a contiguous region for shared non-blocking
1098 // allocation, via inlined code (by exporting the address of the top and
1099 // end fields defining the extent of the contiguous allocation region.)
1100 // But G1CollectedHeap doesn't yet support this.
1101
1102 virtual bool is_maximal_no_gc() const {
1103 return _hrm.available() == 0;
1104 }
1105
1106 // The current number of regions in the heap.
1107 uint num_regions() const { return _hrm.length(); }
1108
1109 // The max number of regions in the heap.
1110 uint max_regions() const { return _hrm.max_length(); }
1111
1112 // The number of regions that are completely free.
1113 uint num_free_regions() const { return _hrm.num_free_regions(); }
1114
1115 MemoryUsage get_auxiliary_data_memory_usage() const {
1116 return _hrm.get_auxiliary_data_memory_usage();
1117 }
1118
1119 // The number of regions that are not completely free.
1120 uint num_used_regions() const { return num_regions() - num_free_regions(); }
1121
1122 void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1123 void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1124 void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1125 void verify_dirty_young_regions() PRODUCT_RETURN;
1126
1127 #ifndef PRODUCT
1128 // Make sure that the given bitmap has no marked objects in the
1129 // range [from,limit). If it does, print an error message and return
1130 // false. Otherwise, just return true. bitmap_name should be "prev"
1131 // or "next".
1132 bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
1133 HeapWord* from, HeapWord* limit);
1134
1135 // Verify that the prev / next bitmap range [tams,end) for the given
1136 // region has no marks. Return true if all is well, false if errors
1137 // are detected.
1138 bool verify_bitmaps(const char* caller, HeapRegion* hr);
1139 #endif // PRODUCT
1140
1141 // If G1VerifyBitmaps is set, verify that the marking bitmaps for
1142 // the given region do not have any spurious marks. If errors are
1143 // detected, print appropriate error messages and crash.
1144 void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN;
1145
1146 // If G1VerifyBitmaps is set, verify that the marking bitmaps do not
1147 // have any spurious marks. If errors are detected, print
1148 // appropriate error messages and crash.
1149 void check_bitmaps(const char* caller) PRODUCT_RETURN;
1150
1151 // Do sanity check on the contents of the in-cset fast test table.
1152 bool check_cset_fast_test() PRODUCT_RETURN_( return true; );
1153
1154 void verify_region_sets();
1155
1156 // verify_region_sets_optional() is planted in the code for
1157 // list verification in debug builds.
1158 void verify_region_sets_optional() { DEBUG_ONLY(verify_region_sets();) }
1159
1160 #ifdef ASSERT
1161 bool is_on_master_free_list(HeapRegion* hr) {
1162 return _hrm.is_free(hr);
1163 }
1164 #endif // ASSERT
1165
1166 // Wrapper for the region list operations that can be called from
1167 // methods outside this class.
1168
1169 void secondary_free_list_add(FreeRegionList* list) {
1170 _secondary_free_list.add_ordered(list);
1171 }
1172
1173 void append_secondary_free_list() {
1174 _hrm.insert_list_into_free_list(&_secondary_free_list);
1175 }
1176
1177 void append_secondary_free_list_if_not_empty_with_lock() {
1178 // If the secondary free list looks empty there's no reason to
1179 // take the lock and then try to append it.
1180 if (!_secondary_free_list.is_empty()) {
1181 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1182 append_secondary_free_list();
1183 }
1184 }
1185
1186 inline void old_set_remove(HeapRegion* hr);
1187
1188 size_t non_young_capacity_bytes() {
1189 return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1190 }
1191
1192 void set_free_regions_coming();
1193 void reset_free_regions_coming();
1194 bool free_regions_coming() { return _free_regions_coming; }
1195 void wait_while_free_regions_coming();
1196
1197 // Determine whether the given region is one that we are using as an
1198 // old GC alloc region.
1199 bool is_old_gc_alloc_region(HeapRegion* hr) {
1200 return _allocator->is_retained_old_region(hr);
1201 }
1202
1203 // Perform a collection of the heap; intended for use in implementing
1204 // "System.gc". This probably implies as full a collection as the
1205 // "CollectedHeap" supports.
1206 virtual void collect(GCCause::Cause cause);
1207
1208 // The same as above but assume that the caller holds the Heap_lock.
1209 void collect_locked(GCCause::Cause cause);
1210
1211 virtual bool copy_allocation_context_stats(const jint* contexts,
1212 jlong* totals,
1213 jbyte* accuracy,
1214 jint len);
1215
1216 // True iff an evacuation has failed in the most-recent collection.
1217 bool evacuation_failed() { return _evacuation_failed; }
1218
1219 void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed);
1220 void prepend_to_freelist(FreeRegionList* list);
1221 void decrement_summary_bytes(size_t bytes);
1222
1223 // Returns "TRUE" iff "p" points into the committed areas of the heap.
1224 virtual bool is_in(const void* p) const;
1225 #ifdef ASSERT
1226 // Returns whether p is in one of the available areas of the heap. Slow but
1227 // extensive version.
1228 bool is_in_exact(const void* p) const;
1229 #endif
1230
1231 // Return "TRUE" iff the given object address is within the collection
1232 // set. Slow implementation.
1233 inline bool obj_in_cs(oop obj);
1234
1235 inline bool is_in_cset(oop obj);
1236
1237 inline bool is_in_cset_or_humongous(const oop obj);
1238
1239 private:
1240 // This array is used for a quick test on whether a reference points into
1241 // the collection set or not. Each of the array's elements denotes whether the
1242 // corresponding region is in the collection set or not.
1243 G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test;
1244
1245 public:
1246
1247 inline InCSetState in_cset_state(const oop obj);
1248
1249 // Return "TRUE" iff the given object address is in the reserved
1250 // region of g1.
1251 bool is_in_g1_reserved(const void* p) const {
1252 return _hrm.reserved().contains(p);
1253 }
1254
1255 // Returns a MemRegion that corresponds to the space that has been
1256 // reserved for the heap
1257 MemRegion g1_reserved() const {
1258 return _hrm.reserved();
1259 }
1260
1261 virtual bool is_in_closed_subset(const void* p) const;
1262
1263 G1SATBCardTableLoggingModRefBS* g1_barrier_set() {
1264 return (G1SATBCardTableLoggingModRefBS*) barrier_set();
1265 }
1266
1267 // This resets the card table to all zeros. It is used after
1268 // a collection pause which used the card table to claim cards.
1269 void cleanUpCardTable();
1270
1271 // Iteration functions.
1272
1273 // Iterate over all the ref-containing fields of all objects, calling
1274 // "cl.do_oop" on each.
1275 virtual void oop_iterate(ExtendedOopClosure* cl);
1276
1277 // Iterate over all objects, calling "cl.do_object" on each.
1278 virtual void object_iterate(ObjectClosure* cl);
1279
1280 virtual void safe_object_iterate(ObjectClosure* cl) {
1281 object_iterate(cl);
1282 }
1283
1284 // Iterate over all spaces in use in the heap, in ascending address order.
1285 virtual void space_iterate(SpaceClosure* cl);
1286
1287 // Iterate over heap regions, in address order, terminating the
1288 // iteration early if the "doHeapRegion" method returns "true".
1289 void heap_region_iterate(HeapRegionClosure* blk) const;
1290
1291 // Return the region with the given index. It assumes the index is valid.
1292 inline HeapRegion* region_at(uint index) const;
1293
1294 // Calculate the region index of the given address. Given address must be
1295 // within the heap.
1296 inline uint addr_to_region(HeapWord* addr) const;
1297
1298 inline HeapWord* bottom_addr_for_region(uint index) const;
1299
1300 // Divide the heap region sequence into "chunks" of some size (the number
1301 // of regions divided by the number of parallel threads times some
1302 // overpartition factor, currently 4). Assumes that this will be called
1303 // in parallel by ParallelGCThreads worker threads with discinct worker
1304 // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel
1305 // calls will use the same "claim_value", and that that claim value is
1306 // different from the claim_value of any heap region before the start of
1307 // the iteration. Applies "blk->doHeapRegion" to each of the regions, by
1308 // attempting to claim the first region in each chunk, and, if
1309 // successful, applying the closure to each region in the chunk (and
1310 // setting the claim value of the second and subsequent regions of the
1311 // chunk.) For now requires that "doHeapRegion" always returns "false",
1312 // i.e., that a closure never attempt to abort a traversal.
1313 void heap_region_par_iterate_chunked(HeapRegionClosure* cl,
1314 uint worker_id,
1315 uint num_workers,
1316 jint claim_value) const;
1317
1318 // It resets all the region claim values to the default.
1319 void reset_heap_region_claim_values();
1320
1321 // Resets the claim values of regions in the current
1322 // collection set to the default.
1323 void reset_cset_heap_region_claim_values();
1324
1325 #ifdef ASSERT
1326 bool check_heap_region_claim_values(jint claim_value);
1327
1328 // Same as the routine above but only checks regions in the
1329 // current collection set.
1330 bool check_cset_heap_region_claim_values(jint claim_value);
1331 #endif // ASSERT
1332
1333 // Clear the cached cset start regions and (more importantly)
1334 // the time stamps. Called when we reset the GC time stamp.
1335 void clear_cset_start_regions();
1336
1337 // Given the id of a worker, obtain or calculate a suitable
1338 // starting region for iterating over the current collection set.
1339 HeapRegion* start_cset_region_for_worker(uint worker_i);
1340
1341 // Iterate over the regions (if any) in the current collection set.
1342 void collection_set_iterate(HeapRegionClosure* blk);
1343
1344 // As above but starting from region r
1345 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1346
1347 HeapRegion* next_compaction_region(const HeapRegion* from) const;
1348
1349 // A CollectedHeap will contain some number of spaces. This finds the
1350 // space containing a given address, or else returns NULL.
1351 virtual Space* space_containing(const void* addr) const;
1352
1353 // Returns the HeapRegion that contains addr. addr must not be NULL.
1354 template <class T>
1355 inline HeapRegion* heap_region_containing_raw(const T addr) const;
1356
1357 // Returns the HeapRegion that contains addr. addr must not be NULL.
1358 // If addr is within a humongous continues region, it returns its humongous start region.
1359 template <class T>
1360 inline HeapRegion* heap_region_containing(const T addr) const;
1361
1362 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1363 // each address in the (reserved) heap is a member of exactly
1364 // one block. The defining characteristic of a block is that it is
1365 // possible to find its size, and thus to progress forward to the next
1366 // block. (Blocks may be of different sizes.) Thus, blocks may
1367 // represent Java objects, or they might be free blocks in a
1368 // free-list-based heap (or subheap), as long as the two kinds are
1369 // distinguishable and the size of each is determinable.
1370
1371 // Returns the address of the start of the "block" that contains the
1372 // address "addr". We say "blocks" instead of "object" since some heaps
1373 // may not pack objects densely; a chunk may either be an object or a
1374 // non-object.
1375 virtual HeapWord* block_start(const void* addr) const;
1376
1377 // Requires "addr" to be the start of a chunk, and returns its size.
1378 // "addr + size" is required to be the start of a new chunk, or the end
1379 // of the active area of the heap.
1380 virtual size_t block_size(const HeapWord* addr) const;
1381
1382 // Requires "addr" to be the start of a block, and returns "TRUE" iff
1383 // the block is an object.
1384 virtual bool block_is_obj(const HeapWord* addr) const;
1385
1386 // Does this heap support heap inspection? (+PrintClassHistogram)
1387 virtual bool supports_heap_inspection() const { return true; }
1388
1389 // Section on thread-local allocation buffers (TLABs)
1390 // See CollectedHeap for semantics.
1391
1392 bool supports_tlab_allocation() const;
1393 size_t tlab_capacity(Thread* ignored) const;
1394 size_t tlab_used(Thread* ignored) const;
1395 size_t max_tlab_size() const;
1396 size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1397
1398 // Can a compiler initialize a new object without store barriers?
1399 // This permission only extends from the creation of a new object
1400 // via a TLAB up to the first subsequent safepoint. If such permission
1401 // is granted for this heap type, the compiler promises to call
1402 // defer_store_barrier() below on any slow path allocation of
1403 // a new object for which such initializing store barriers will
1404 // have been elided. G1, like CMS, allows this, but should be
1405 // ready to provide a compensating write barrier as necessary
1406 // if that storage came out of a non-young region. The efficiency
1407 // of this implementation depends crucially on being able to
1408 // answer very efficiently in constant time whether a piece of
1409 // storage in the heap comes from a young region or not.
1410 // See ReduceInitialCardMarks.
1411 virtual bool can_elide_tlab_store_barriers() const {
1412 return true;
1413 }
1414
1415 virtual bool card_mark_must_follow_store() const {
1416 return true;
1417 }
1418
1419 inline bool is_in_young(const oop obj);
1420
1421 #ifdef ASSERT
1422 virtual bool is_in_partial_collection(const void* p);
1423 #endif
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 isHumongous(size_t word_size) {
1436 // Note this has to be strictly greater-than as the TLABs
1437 // are capped at the humongous thresold 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 // Update mod union table with the set of dirty cards.
1445 void updateModUnion();
1446
1447 // Set the mod union bits corresponding to the given memRegion. Note
1448 // that this is always a safe operation, since it doesn't clear any
1449 // bits.
1450 void markModUnionRange(MemRegion mr);
1451
1452 // Records the fact that a marking phase is no longer in progress.
1453 void set_marking_complete() {
1454 _mark_in_progress = false;
1455 }
1456 void set_marking_started() {
1457 _mark_in_progress = true;
1458 }
1459 bool mark_in_progress() {
1460 return _mark_in_progress;
1461 }
1462
1463 // Print the maximum heap capacity.
1464 virtual size_t max_capacity() const;
1465
1466 virtual jlong millis_since_last_gc();
1467
1468
1469 // Convenience function to be used in situations where the heap type can be
1470 // asserted to be this type.
1471 static G1CollectedHeap* heap();
1472
1473 void set_region_short_lived_locked(HeapRegion* hr);
1474 // add appropriate methods for any other surv rate groups
1475
1476 YoungList* young_list() const { return _young_list; }
1477
1478 // debugging
1479 bool check_young_list_well_formed() {
1480 return _young_list->check_list_well_formed();
1481 }
1482
1483 bool check_young_list_empty(bool check_heap,
1484 bool check_sample = true);
1485
1486 // *** Stuff related to concurrent marking. It's not clear to me that so
1487 // many of these need to be public.
1488
1489 // The functions below are helper functions that a subclass of
1490 // "CollectedHeap" can use in the implementation of its virtual
1491 // functions.
1492 // This performs a concurrent marking of the live objects in a
1493 // bitmap off to the side.
1494 void doConcurrentMark();
1495
1496 bool isMarkedPrev(oop obj) const;
1497 bool isMarkedNext(oop obj) const;
1498
1499 // Determine if an object is dead, given the object and also
1500 // the region to which the object belongs. An object is dead
1501 // iff a) it was not allocated since the last mark and b) it
1502 // is not marked.
1503 bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1504 return
1505 !hr->obj_allocated_since_prev_marking(obj) &&
1506 !isMarkedPrev(obj);
1507 }
1508
1509 // This function returns true when an object has been
1510 // around since the previous marking and hasn't yet
1511 // been marked during this marking.
1512 bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1513 return
1514 !hr->obj_allocated_since_next_marking(obj) &&
1515 !isMarkedNext(obj);
1516 }
1517
1518 // Determine if an object is dead, given only the object itself.
1519 // This will find the region to which the object belongs and
1520 // then call the region version of the same function.
1521
1522 // Added if it is NULL it isn't dead.
1523
1524 inline bool is_obj_dead(const oop obj) const;
1525
1526 inline bool is_obj_ill(const oop obj) const;
1527
1528 bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1529 HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1530 bool is_marked(oop obj, VerifyOption vo);
1531 const char* top_at_mark_start_str(VerifyOption vo);
1532
1533 ConcurrentMark* concurrent_mark() const { return _cm; }
1534
1535 // Refinement
1536
1537 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1538
1539 // The dirty cards region list is used to record a subset of regions
1540 // whose cards need clearing. The list if populated during the
1541 // remembered set scanning and drained during the card table
1542 // cleanup. Although the methods are reentrant, population/draining
1543 // phases must not overlap. For synchronization purposes the last
1544 // element on the list points to itself.
1545 HeapRegion* _dirty_cards_region_list;
1546 void push_dirty_cards_region(HeapRegion* hr);
1547 HeapRegion* pop_dirty_cards_region();
1548
1549 // Optimized nmethod scanning support routines
1550
1551 // Register the given nmethod with the G1 heap
1552 virtual void register_nmethod(nmethod* nm);
1553
1554 // Unregister the given nmethod from the G1 heap
1555 virtual void unregister_nmethod(nmethod* nm);
1556
1557 // Free up superfluous code root memory.
1558 void purge_code_root_memory();
1559
1560 // Rebuild the stong code root lists for each region
1561 // after a full GC
1562 void rebuild_strong_code_roots();
1563
1564 // Delete entries for dead interned string and clean up unreferenced symbols
1565 // in symbol table, possibly in parallel.
1566 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1567
1568 // Parallel phase of unloading/cleaning after G1 concurrent mark.
1569 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred);
1570
1571 // Redirty logged cards in the refinement queue.
1572 void redirty_logged_cards();
1573 // Verification
1574
1575 // The following is just to alert the verification code
1576 // that a full collection has occurred and that the
1577 // remembered sets are no longer up to date.
1578 bool _full_collection;
1579 void set_full_collection() { _full_collection = true;}
1580 void clear_full_collection() {_full_collection = false;}
1581 bool full_collection() {return _full_collection;}
1582
1583 // Perform any cleanup actions necessary before allowing a verification.
1584 virtual void prepare_for_verify();
1585
1586 // Perform verification.
1587
1588 // vo == UsePrevMarking -> use "prev" marking information,
1589 // vo == UseNextMarking -> use "next" marking information
1590 // vo == UseMarkWord -> use the mark word in the object header
1591 //
1592 // NOTE: Only the "prev" marking information is guaranteed to be
1593 // consistent most of the time, so most calls to this should use
1594 // vo == UsePrevMarking.
1595 // Currently, there is only one case where this is called with
1596 // vo == UseNextMarking, which is to verify the "next" marking
1597 // information at the end of remark.
1598 // Currently there is only one place where this is called with
1599 // vo == UseMarkWord, which is to verify the marking during a
1600 // full GC.
1601 void verify(bool silent, VerifyOption vo);
1602
1603 // Override; it uses the "prev" marking information
1604 virtual void verify(bool silent);
1605
1606 // The methods below are here for convenience and dispatch the
1607 // appropriate method depending on value of the given VerifyOption
1608 // parameter. The values for that parameter, and their meanings,
1609 // are the same as those above.
1610
1611 bool is_obj_dead_cond(const oop obj,
1612 const HeapRegion* hr,
1613 const VerifyOption vo) const;
1614
1615 bool is_obj_dead_cond(const oop obj,
1616 const VerifyOption vo) const;
1617
1618 G1HeapSummary create_g1_heap_summary();
1619
1620 // Printing
1621
1622 virtual void print_on(outputStream* st) const;
1623 virtual void print_extended_on(outputStream* st) const;
1624 virtual void print_on_error(outputStream* st) const;
1625
1626 virtual void print_gc_threads_on(outputStream* st) const;
1627 virtual void gc_threads_do(ThreadClosure* tc) const;
1628
1629 // Override
1630 void print_tracing_info() const;
1631
1632 // The following two methods are helpful for debugging RSet issues.
1633 void print_cset_rsets() PRODUCT_RETURN;
1634 void print_all_rsets() PRODUCT_RETURN;
1635
1636 public:
1637 size_t pending_card_num();
1638 size_t cards_scanned();
1639
1640 protected:
1641 size_t _max_heap_capacity;
1642 };
1643
1644 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP