1 /*
2 * Copyright (c) 2001, 2014, 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.
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).
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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/g1MonitoringSupport.hpp"
36 #include "gc_implementation/g1/g1SATBCardTableModRefBS.hpp"
37 #include "gc_implementation/g1/g1YCTypes.hpp"
38 #include "gc_implementation/g1/heapRegionManager.hpp"
39 #include "gc_implementation/g1/heapRegionSet.hpp"
40 #include "gc_implementation/shared/hSpaceCounters.hpp"
41 #include "gc_implementation/shared/parGCAllocBuffer.hpp"
42 #include "memory/barrierSet.hpp"
43 #include "memory/memRegion.hpp"
44 #include "memory/sharedHeap.hpp"
45 #include "utilities/stack.hpp"
46
47 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
48 // It uses the "Garbage First" heap organization and algorithm, which
49 // may combine concurrent marking with parallel, incremental compaction of
50 // heap subsets that will yield large amounts of garbage.
51
52 // Forward declarations
53 class HeapRegion;
54 class HRRSCleanupTask;
55 class GenerationSpec;
56 class OopsInHeapRegionClosure;
57 class G1KlassScanClosure;
58 class G1ScanHeapEvacClosure;
59 class ObjectClosure;
60 class SpaceClosure;
61 class CompactibleSpaceClosure;
62 class Space;
63 class G1CollectorPolicy;
64 class GenRemSet;
65 class G1RemSet;
66 class HeapRegionRemSetIterator;
67 class ConcurrentMark;
68 class ConcurrentMarkThread;
69 class ConcurrentG1Refine;
70 class ConcurrentGCTimer;
71 class GenerationCounters;
72 class STWGCTimer;
73 class G1NewTracer;
74 class G1OldTracer;
75 class EvacuationFailedInfo;
76 class nmethod;
77 class Ticks;
78
79 typedef OverflowTaskQueue<StarTask, mtGC> RefToScanQueue;
80 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
81
82 typedef int RegionIdx_t; // needs to hold [ 0..max_regions() )
83 typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion )
84
85 class YoungList : public CHeapObj<mtGC> {
86 private:
87 G1CollectedHeap* _g1h;
88
89 HeapRegion* _head;
90
91 HeapRegion* _survivor_head;
92 HeapRegion* _survivor_tail;
93
94 HeapRegion* _curr;
95
96 uint _length;
97 uint _survivor_length;
98
99 size_t _last_sampled_rs_lengths;
100 size_t _sampled_rs_lengths;
101
102 void empty_list(HeapRegion* list);
103
104 public:
105 YoungList(G1CollectedHeap* g1h);
106
107 void push_region(HeapRegion* hr);
108 void add_survivor_region(HeapRegion* hr);
109
110 void empty_list();
111 bool is_empty() { return _length == 0; }
112 uint length() { return _length; }
113 uint survivor_length() { return _survivor_length; }
114
115 // Currently we do not keep track of the used byte sum for the
116 // young list and the survivors and it'd be quite a lot of work to
117 // do so. When we'll eventually replace the young list with
118 // instances of HeapRegionLinkedList we'll get that for free. So,
119 // we'll report the more accurate information then.
120 size_t eden_used_bytes() {
121 assert(length() >= survivor_length(), "invariant");
122 return (size_t) (length() - survivor_length()) * HeapRegion::GrainBytes;
123 }
124 size_t survivor_used_bytes() {
125 return (size_t) survivor_length() * HeapRegion::GrainBytes;
126 }
127
128 void rs_length_sampling_init();
129 bool rs_length_sampling_more();
130 void rs_length_sampling_next();
131
132 void reset_sampled_info() {
133 _last_sampled_rs_lengths = 0;
134 }
135 size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
136
137 // for development purposes
138 void reset_auxilary_lists();
139 void clear() { _head = NULL; _length = 0; }
140
141 void clear_survivors() {
142 _survivor_head = NULL;
143 _survivor_tail = NULL;
144 _survivor_length = 0;
145 }
146
147 HeapRegion* first_region() { return _head; }
148 HeapRegion* first_survivor_region() { return _survivor_head; }
149 HeapRegion* last_survivor_region() { return _survivor_tail; }
150
151 // debugging
152 bool check_list_well_formed();
153 bool check_list_empty(bool check_sample = true);
154 void print();
155 };
156
157 // The G1 STW is alive closure.
158 // An instance is embedded into the G1CH and used as the
159 // (optional) _is_alive_non_header closure in the STW
160 // reference processor. It is also extensively used during
161 // reference processing during STW evacuation pauses.
162 class G1STWIsAliveClosure: public BoolObjectClosure {
163 G1CollectedHeap* _g1;
164 public:
165 G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
166 bool do_object_b(oop p);
167 };
168
169 class RefineCardTableEntryClosure;
170
171 class G1RegionMappingChangedListener : public G1MappingChangedListener {
172 private:
173 void reset_from_card_cache(uint start_idx, size_t num_regions);
174 public:
175 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
176 };
177
178 class G1CollectedHeap : public SharedHeap {
179 friend class VM_CollectForMetadataAllocation;
180 friend class VM_G1CollectForAllocation;
181 friend class VM_G1CollectFull;
182 friend class VM_G1IncCollectionPause;
183 friend class VMStructs;
184 friend class MutatorAllocRegion;
185 friend class SurvivorGCAllocRegion;
186 friend class OldGCAllocRegion;
187 friend class G1Allocator;
188 friend class G1DefaultAllocator;
189 friend class G1ResManAllocator;
190
191 // Closures used in implementation.
192 template <G1Barrier barrier, G1Mark do_mark_object>
193 friend class G1ParCopyClosure;
194 friend class G1IsAliveClosure;
195 friend class G1EvacuateFollowersClosure;
196 friend class G1ParScanThreadState;
197 friend class G1ParScanClosureSuper;
198 friend class G1ParEvacuateFollowersClosure;
199 friend class G1ParTask;
200 friend class G1ParGCAllocator;
201 friend class G1DefaultParGCAllocator;
202 friend class G1FreeGarbageRegionClosure;
203 friend class RefineCardTableEntryClosure;
204 friend class G1PrepareCompactClosure;
205 friend class RegionSorter;
206 friend class RegionResetter;
207 friend class CountRCClosure;
208 friend class EvacPopObjClosure;
209 friend class G1ParCleanupCTTask;
210
211 friend class G1FreeHumongousRegionClosure;
212 // Other related classes.
213 friend class G1MarkSweep;
214 friend class HeapRegionClaimer;
215
216 private:
217 // The one and only G1CollectedHeap, so static functions can find it.
218 static G1CollectedHeap* _g1h;
219
220 static size_t _humongous_object_threshold_in_words;
221
222 // The secondary free list which contains regions that have been
223 // freed up during the cleanup process. This will be appended to
224 // the master free list when appropriate.
225 FreeRegionList _secondary_free_list;
226
227 // It keeps track of the old regions.
228 HeapRegionSet _old_set;
229
230 // It keeps track of the humongous regions.
231 HeapRegionSet _humongous_set;
232
233 void clear_humongous_is_live_table();
234 void eagerly_reclaim_humongous_regions();
235
236 // The number of regions we could create by expansion.
237 uint _expansion_regions;
238
239 // The block offset table for the G1 heap.
240 G1BlockOffsetSharedArray* _bot_shared;
241
242 // Tears down the region sets / lists so that they are empty and the
243 // regions on the heap do not belong to a region set / list. The
244 // only exception is the humongous set which we leave unaltered. If
245 // free_list_only is true, it will only tear down the master free
246 // list. It is called before a Full GC (free_list_only == false) or
247 // before heap shrinking (free_list_only == true).
248 void tear_down_region_sets(bool free_list_only);
249
250 // Rebuilds the region sets / lists so that they are repopulated to
251 // reflect the contents of the heap. The only exception is the
252 // humongous set which was not torn down in the first place. If
253 // free_list_only is true, it will only rebuild the master free
254 // list. It is called after a Full GC (free_list_only == false) or
255 // after heap shrinking (free_list_only == true).
256 void rebuild_region_sets(bool free_list_only);
257
258 // Callback for region mapping changed events.
259 G1RegionMappingChangedListener _listener;
260
261 // The sequence of all heap regions in the heap.
262 HeapRegionManager _hrm;
263
264 // Class that handles the different kinds of allocations.
265 G1Allocator* _allocator;
266
267 // Statistics for each allocation context
268 AllocationContextStats _allocation_context_stats;
269
270 // PLAB sizing policy for survivors.
271 PLABStats _survivor_plab_stats;
272
273 // PLAB sizing policy for tenured objects.
274 PLABStats _old_plab_stats;
275
276 // It specifies whether we should attempt to expand the heap after a
277 // region allocation failure. If heap expansion fails we set this to
278 // false so that we don't re-attempt the heap expansion (it's likely
279 // that subsequent expansion attempts will also fail if one fails).
280 // Currently, it is only consulted during GC and it's reset at the
281 // start of each GC.
282 bool _expand_heap_after_alloc_failure;
283
284 // It resets the mutator alloc region before new allocations can take place.
285 void init_mutator_alloc_region();
286
287 // It releases the mutator alloc region.
288 void release_mutator_alloc_region();
289
290 // It initializes the GC alloc regions at the start of a GC.
291 void init_gc_alloc_regions(EvacuationInfo& evacuation_info);
292
293 // It releases the GC alloc regions at the end of a GC.
294 void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info);
295
296 // It does any cleanup that needs to be done on the GC alloc regions
297 // before a Full GC.
298 void abandon_gc_alloc_regions();
299
300 // Helper for monitoring and management support.
301 G1MonitoringSupport* _g1mm;
302
303 // Records whether the region at the given index is kept live by roots or
304 // references from the young generation.
305 class HumongousIsLiveBiasedMappedArray : public G1BiasedMappedArray<bool> {
306 protected:
307 bool default_value() const { return false; }
308 public:
309 void clear() { G1BiasedMappedArray<bool>::clear(); }
310 void set_live(uint region) {
311 set_by_index(region, true);
312 }
313 bool is_live(uint region) {
314 return get_by_index(region);
315 }
316 };
317
318 HumongousIsLiveBiasedMappedArray _humongous_is_live;
319 // Stores whether during humongous object registration we found candidate regions.
320 // If not, we can skip a few steps.
321 bool _has_humongous_reclaim_candidates;
322
323 volatile unsigned _gc_time_stamp;
324
325 size_t* _surviving_young_words;
326
327 G1HRPrinter _hr_printer;
328
329 void setup_surviving_young_words();
330 void update_surviving_young_words(size_t* surv_young_words);
331 void cleanup_surviving_young_words();
332
333 // It decides whether an explicit GC should start a concurrent cycle
334 // instead of doing a STW GC. Currently, a concurrent cycle is
335 // explicitly started if:
336 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
337 // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
338 // (c) cause == _g1_humongous_allocation
339 bool should_do_concurrent_full_gc(GCCause::Cause cause);
340
341 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
342 // concurrent cycles) we have started.
343 volatile unsigned int _old_marking_cycles_started;
344
345 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
346 // concurrent cycles) we have completed.
347 volatile unsigned int _old_marking_cycles_completed;
348
349 bool _concurrent_cycle_started;
350 bool _heap_summary_sent;
351
352 // This is a non-product method that is helpful for testing. It is
353 // called at the end of a GC and artificially expands the heap by
354 // allocating a number of dead regions. This way we can induce very
355 // frequent marking cycles and stress the cleanup / concurrent
356 // cleanup code more (as all the regions that will be allocated by
357 // this method will be found dead by the marking cycle).
358 void allocate_dummy_regions() PRODUCT_RETURN;
359
360 // Clear RSets after a compaction. It also resets the GC time stamps.
361 void clear_rsets_post_compaction();
362
363 // If the HR printer is active, dump the state of the regions in the
364 // heap after a compaction.
365 void print_hrm_post_compaction();
366
367 double verify(bool guard, const char* msg);
368 void verify_before_gc();
369 void verify_after_gc();
370
371 void log_gc_header();
372 void log_gc_footer(double pause_time_sec);
373
374 // These are macros so that, if the assert fires, we get the correct
375 // line number, file, etc.
376
377 #define heap_locking_asserts_err_msg(_extra_message_) \
378 err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \
379 (_extra_message_), \
380 BOOL_TO_STR(Heap_lock->owned_by_self()), \
381 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \
382 BOOL_TO_STR(Thread::current()->is_VM_thread()))
383
384 #define assert_heap_locked() \
385 do { \
386 assert(Heap_lock->owned_by_self(), \
387 heap_locking_asserts_err_msg("should be holding the Heap_lock")); \
388 } while (0)
389
390 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \
391 do { \
392 assert(Heap_lock->owned_by_self() || \
393 (SafepointSynchronize::is_at_safepoint() && \
394 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
395 heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
396 "should be at a safepoint")); \
397 } while (0)
398
399 #define assert_heap_locked_and_not_at_safepoint() \
400 do { \
401 assert(Heap_lock->owned_by_self() && \
402 !SafepointSynchronize::is_at_safepoint(), \
403 heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
404 "should not be at a safepoint")); \
405 } while (0)
406
407 #define assert_heap_not_locked() \
408 do { \
409 assert(!Heap_lock->owned_by_self(), \
410 heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
411 } while (0)
412
413 #define assert_heap_not_locked_and_not_at_safepoint() \
414 do { \
415 assert(!Heap_lock->owned_by_self() && \
416 !SafepointSynchronize::is_at_safepoint(), \
417 heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
418 "should not be at a safepoint")); \
419 } while (0)
420
421 #define assert_at_safepoint(_should_be_vm_thread_) \
422 do { \
423 assert(SafepointSynchronize::is_at_safepoint() && \
424 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
425 heap_locking_asserts_err_msg("should be at a safepoint")); \
426 } while (0)
427
428 #define assert_not_at_safepoint() \
429 do { \
430 assert(!SafepointSynchronize::is_at_safepoint(), \
431 heap_locking_asserts_err_msg("should not be at a safepoint")); \
432 } while (0)
433
434 protected:
435
436 // The young region list.
437 YoungList* _young_list;
438
439 // The current policy object for the collector.
440 G1CollectorPolicy* _g1_policy;
441
442 // This is the second level of trying to allocate a new region. If
443 // new_region() didn't find a region on the free_list, this call will
444 // check whether there's anything available on the
445 // secondary_free_list and/or wait for more regions to appear on
446 // that list, if _free_regions_coming is set.
447 HeapRegion* new_region_try_secondary_free_list(bool is_old);
448
449 // Try to allocate a single non-humongous HeapRegion sufficient for
450 // an allocation of the given word_size. If do_expand is true,
451 // attempt to expand the heap if necessary to satisfy the allocation
452 // request. If the region is to be used as an old region or for a
453 // humongous object, set is_old to true. If not, to false.
454 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
455
456 // Initialize a contiguous set of free regions of length num_regions
457 // and starting at index first so that they appear as a single
458 // humongous region.
459 HeapWord* humongous_obj_allocate_initialize_regions(uint first,
460 uint num_regions,
461 size_t word_size,
462 AllocationContext_t context);
463
464 // Attempt to allocate a humongous object of the given size. Return
465 // NULL if unsuccessful.
466 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context);
467
468 // The following two methods, allocate_new_tlab() and
469 // mem_allocate(), are the two main entry points from the runtime
470 // into the G1's allocation routines. They have the following
471 // assumptions:
472 //
473 // * They should both be called outside safepoints.
474 //
475 // * They should both be called without holding the Heap_lock.
476 //
477 // * All allocation requests for new TLABs should go to
478 // allocate_new_tlab().
479 //
480 // * All non-TLAB allocation requests should go to mem_allocate().
481 //
482 // * If either call cannot satisfy the allocation request using the
483 // current allocating region, they will try to get a new one. If
484 // this fails, they will attempt to do an evacuation pause and
485 // retry the allocation.
486 //
487 // * If all allocation attempts fail, even after trying to schedule
488 // an evacuation pause, allocate_new_tlab() will return NULL,
489 // whereas mem_allocate() will attempt a heap expansion and/or
490 // schedule a Full GC.
491 //
492 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
493 // should never be called with word_size being humongous. All
494 // humongous allocation requests should go to mem_allocate() which
495 // will satisfy them with a special path.
496
497 virtual HeapWord* allocate_new_tlab(size_t word_size);
498
499 virtual HeapWord* mem_allocate(size_t word_size,
500 bool* gc_overhead_limit_was_exceeded);
501
502 // The following three methods take a gc_count_before_ret
503 // parameter which is used to return the GC count if the method
504 // returns NULL. Given that we are required to read the GC count
505 // while holding the Heap_lock, and these paths will take the
506 // Heap_lock at some point, it's easier to get them to read the GC
507 // count while holding the Heap_lock before they return NULL instead
508 // of the caller (namely: mem_allocate()) having to also take the
509 // Heap_lock just to read the GC count.
510
511 // First-level mutator allocation attempt: try to allocate out of
512 // the mutator alloc region without taking the Heap_lock. This
513 // should only be used for non-humongous allocations.
514 inline HeapWord* attempt_allocation(size_t word_size,
515 unsigned int* gc_count_before_ret,
516 int* gclocker_retry_count_ret);
517
518 // Second-level mutator allocation attempt: take the Heap_lock and
519 // retry the allocation attempt, potentially scheduling a GC
520 // pause. This should only be used for non-humongous allocations.
521 HeapWord* attempt_allocation_slow(size_t word_size,
522 AllocationContext_t context,
523 unsigned int* gc_count_before_ret,
524 int* gclocker_retry_count_ret);
525
526 // Takes the Heap_lock and attempts a humongous allocation. It can
527 // potentially schedule a GC pause.
528 HeapWord* attempt_allocation_humongous(size_t word_size,
529 unsigned int* gc_count_before_ret,
530 int* gclocker_retry_count_ret);
531
532 // Allocation attempt that should be called during safepoints (e.g.,
533 // at the end of a successful GC). expect_null_mutator_alloc_region
534 // specifies whether the mutator alloc region is expected to be NULL
535 // or not.
536 HeapWord* attempt_allocation_at_safepoint(size_t word_size,
537 AllocationContext_t context,
538 bool expect_null_mutator_alloc_region);
539
540 // It dirties the cards that cover the block so that so that the post
541 // write barrier never queues anything when updating objects on this
542 // block. It is assumed (and in fact we assert) that the block
543 // belongs to a young region.
544 inline void dirty_young_block(HeapWord* start, size_t word_size);
545
546 // Allocate blocks during garbage collection. Will ensure an
547 // allocation region, either by picking one or expanding the
548 // heap, and then allocate a block of the given size. The block
549 // may not be a humongous - it must fit into a single heap region.
550 HeapWord* par_allocate_during_gc(GCAllocPurpose purpose,
551 size_t word_size,
552 AllocationContext_t context);
553
554 HeapWord* allocate_during_gc_slow(GCAllocPurpose purpose,
555 HeapRegion* alloc_region,
556 bool par,
557 size_t word_size);
558
559 // Ensure that no further allocations can happen in "r", bearing in mind
560 // that parallel threads might be attempting allocations.
561 void par_allocate_remaining_space(HeapRegion* r);
562
563 // Allocation attempt during GC for a survivor object / PLAB.
564 inline HeapWord* survivor_attempt_allocation(size_t word_size,
565 AllocationContext_t context);
566
567 // Allocation attempt during GC for an old object / PLAB.
568 inline HeapWord* old_attempt_allocation(size_t word_size,
569 AllocationContext_t context);
570
571 // These methods are the "callbacks" from the G1AllocRegion class.
572
573 // For mutator alloc regions.
574 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
575 void retire_mutator_alloc_region(HeapRegion* alloc_region,
576 size_t allocated_bytes);
577
578 // For GC alloc regions.
579 HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
580 GCAllocPurpose ap);
581 void retire_gc_alloc_region(HeapRegion* alloc_region,
582 size_t allocated_bytes, GCAllocPurpose ap);
583
584 // - if explicit_gc is true, the GC is for a System.gc() or a heap
585 // inspection request and should collect the entire heap
586 // - if clear_all_soft_refs is true, all soft references should be
587 // cleared during the GC
588 // - if explicit_gc is false, word_size describes the allocation that
589 // the GC should attempt (at least) to satisfy
590 // - it returns false if it is unable to do the collection due to the
591 // GC locker being active, true otherwise
592 bool do_collection(bool explicit_gc,
593 bool clear_all_soft_refs,
594 size_t word_size);
595
596 // Callback from VM_G1CollectFull operation.
597 // Perform a full collection.
598 virtual void do_full_collection(bool clear_all_soft_refs);
599
600 // Resize the heap if necessary after a full collection. If this is
601 // after a collect-for allocation, "word_size" is the allocation size,
602 // and will be considered part of the used portion of the heap.
603 void resize_if_necessary_after_full_collection(size_t word_size);
604
605 // Callback from VM_G1CollectForAllocation operation.
606 // This function does everything necessary/possible to satisfy a
607 // failed allocation request (including collection, expansion, etc.)
608 HeapWord* satisfy_failed_allocation(size_t word_size,
609 AllocationContext_t context,
610 bool* succeeded);
611
612 // Attempting to expand the heap sufficiently
613 // to support an allocation of the given "word_size". If
614 // successful, perform the allocation and return the address of the
615 // allocated block, or else "NULL".
616 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context);
617
618 // Process any reference objects discovered during
619 // an incremental evacuation pause.
620 void process_discovered_references(uint no_of_gc_workers);
621
622 // Enqueue any remaining discovered references
623 // after processing.
624 void enqueue_discovered_references(uint no_of_gc_workers);
625
626 public:
627
628 G1Allocator* allocator() {
629 return _allocator;
630 }
631
632 G1MonitoringSupport* g1mm() {
633 assert(_g1mm != NULL, "should have been initialized");
634 return _g1mm;
635 }
636
637 // Expand the garbage-first heap by at least the given size (in bytes!).
638 // Returns true if the heap was expanded by the requested amount;
639 // false otherwise.
640 // (Rounds up to a HeapRegion boundary.)
641 bool expand(size_t expand_bytes);
642
643 // Returns the PLAB statistics given a purpose.
644 PLABStats* stats_for_purpose(GCAllocPurpose purpose) {
645 PLABStats* stats = NULL;
646
647 switch (purpose) {
648 case GCAllocForSurvived:
649 stats = &_survivor_plab_stats;
650 break;
651 case GCAllocForTenured:
652 stats = &_old_plab_stats;
653 break;
654 default:
655 assert(false, "unrecognized GCAllocPurpose");
656 }
657
658 return stats;
659 }
660
661 // Determines PLAB size for a particular allocation purpose.
662 size_t desired_plab_sz(GCAllocPurpose purpose);
663
664 inline AllocationContextStats& allocation_context_stats();
665
666 // Do anything common to GC's.
667 virtual void gc_prologue(bool full);
668 virtual void gc_epilogue(bool full);
669
670 inline void set_humongous_is_live(oop obj);
671
672 bool humongous_is_live(uint region) {
673 return _humongous_is_live.is_live(region);
674 }
675
676 // Returns whether the given region (which must be a humongous (start) region)
677 // is to be considered conservatively live regardless of any other conditions.
678 bool humongous_region_is_always_live(uint index);
679 // Register the given region to be part of the collection set.
680 inline void register_humongous_region_with_in_cset_fast_test(uint index);
681 // Register regions with humongous objects (actually on the start region) in
682 // the in_cset_fast_test table.
683 void register_humongous_regions_with_in_cset_fast_test();
684 // We register a region with the fast "in collection set" test. We
685 // simply set to true the array slot corresponding to this region.
686 void register_region_with_in_cset_fast_test(HeapRegion* r) {
687 _in_cset_fast_test.set_in_cset(r->hrm_index());
688 }
689
690 // This is a fast test on whether a reference points into the
691 // collection set or not. Assume that the reference
692 // points into the heap.
693 inline bool in_cset_fast_test(oop obj);
694
695 void clear_cset_fast_test() {
696 _in_cset_fast_test.clear();
697 }
698
699 // This is called at the start of either a concurrent cycle or a Full
700 // GC to update the number of old marking cycles started.
701 void increment_old_marking_cycles_started();
702
703 // This is called at the end of either a concurrent cycle or a Full
704 // GC to update the number of old marking cycles completed. Those two
705 // can happen in a nested fashion, i.e., we start a concurrent
706 // cycle, a Full GC happens half-way through it which ends first,
707 // and then the cycle notices that a Full GC happened and ends
708 // too. The concurrent parameter is a boolean to help us do a bit
709 // tighter consistency checking in the method. If concurrent is
710 // false, the caller is the inner caller in the nesting (i.e., the
711 // Full GC). If concurrent is true, the caller is the outer caller
712 // in this nesting (i.e., the concurrent cycle). Further nesting is
713 // not currently supported. The end of this call also notifies
714 // the FullGCCount_lock in case a Java thread is waiting for a full
715 // GC to happen (e.g., it called System.gc() with
716 // +ExplicitGCInvokesConcurrent).
717 void increment_old_marking_cycles_completed(bool concurrent);
718
719 unsigned int old_marking_cycles_completed() {
720 return _old_marking_cycles_completed;
721 }
722
723 void register_concurrent_cycle_start(const Ticks& start_time);
724 void register_concurrent_cycle_end();
725 void trace_heap_after_concurrent_cycle();
726
727 G1YCType yc_type();
728
729 G1HRPrinter* hr_printer() { return &_hr_printer; }
730
731 // Frees a non-humongous region by initializing its contents and
732 // adding it to the free list that's passed as a parameter (this is
733 // usually a local list which will be appended to the master free
734 // list later). The used bytes of freed regions are accumulated in
735 // pre_used. If par is true, the region's RSet will not be freed
736 // up. The assumption is that this will be done later.
737 // The locked parameter indicates if the caller has already taken
738 // care of proper synchronization. This may allow some optimizations.
739 void free_region(HeapRegion* hr,
740 FreeRegionList* free_list,
741 bool par,
742 bool locked = false);
743
744 // Frees a humongous region by collapsing it into individual regions
745 // and calling free_region() for each of them. The freed regions
746 // will be added to the free list that's passed as a parameter (this
747 // is usually a local list which will be appended to the master free
748 // list later). The used bytes of freed regions are accumulated in
749 // pre_used. If par is true, the region's RSet will not be freed
750 // up. The assumption is that this will be done later.
751 void free_humongous_region(HeapRegion* hr,
752 FreeRegionList* free_list,
753 bool par);
754 protected:
755
756 // Shrink the garbage-first heap by at most the given size (in bytes!).
757 // (Rounds down to a HeapRegion boundary.)
758 virtual void shrink(size_t expand_bytes);
759 void shrink_helper(size_t expand_bytes);
760
761 #if TASKQUEUE_STATS
762 static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
763 void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
764 void reset_taskqueue_stats();
765 #endif // TASKQUEUE_STATS
766
767 // Schedule the VM operation that will do an evacuation pause to
768 // satisfy an allocation request of word_size. *succeeded will
769 // return whether the VM operation was successful (it did do an
770 // evacuation pause) or not (another thread beat us to it or the GC
771 // locker was active). Given that we should not be holding the
772 // Heap_lock when we enter this method, we will pass the
773 // gc_count_before (i.e., total_collections()) as a parameter since
774 // it has to be read while holding the Heap_lock. Currently, both
775 // methods that call do_collection_pause() release the Heap_lock
776 // before the call, so it's easy to read gc_count_before just before.
777 HeapWord* do_collection_pause(size_t word_size,
778 unsigned int gc_count_before,
779 bool* succeeded,
780 GCCause::Cause gc_cause);
781
782 // The guts of the incremental collection pause, executed by the vm
783 // thread. It returns false if it is unable to do the collection due
784 // to the GC locker being active, true otherwise
785 bool do_collection_pause_at_safepoint(double target_pause_time_ms);
786
787 // Actually do the work of evacuating the collection set.
788 void evacuate_collection_set(EvacuationInfo& evacuation_info);
789
790 // The g1 remembered set of the heap.
791 G1RemSet* _g1_rem_set;
792
793 // A set of cards that cover the objects for which the Rsets should be updated
794 // concurrently after the collection.
795 DirtyCardQueueSet _dirty_card_queue_set;
796
797 // The closure used to refine a single card.
798 RefineCardTableEntryClosure* _refine_cte_cl;
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 // Applies "scan_non_heap_roots" to roots outside the heap,
815 // "scan_rs" to roots inside the heap (having done "set_region" to
816 // indicate the region in which the root resides),
817 // and does "scan_metadata" If "scan_rs" is
818 // NULL, then this step is skipped. The "worker_i"
819 // param is for use with parallel roots processing, and should be
820 // the "i" of the calling parallel worker thread's work(i) function.
821 // In the sequential case this param will be ignored.
822 void g1_process_roots(OopClosure* scan_non_heap_roots,
823 OopClosure* scan_non_heap_weak_roots,
824 OopsInHeapRegionClosure* scan_rs,
825 CLDClosure* scan_strong_clds,
826 CLDClosure* scan_weak_clds,
827 CodeBlobClosure* scan_strong_code,
828 uint worker_i);
829
830 // The concurrent marker (and the thread it runs in.)
831 ConcurrentMark* _cm;
832 ConcurrentMarkThread* _cmThread;
833 bool _mark_in_progress;
834
835 // The concurrent refiner.
836 ConcurrentG1Refine* _cg1r;
837
838 // The parallel task queues
839 RefToScanQueueSet *_task_queues;
840
841 // True iff a evacuation has failed in the current collection.
842 bool _evacuation_failed;
843
844 EvacuationFailedInfo* _evacuation_failed_info_array;
845
846 // Failed evacuations cause some logical from-space objects to have
847 // forwarding pointers to themselves. Reset them.
848 void remove_self_forwarding_pointers();
849
850 // Together, these store an object with a preserved mark, and its mark value.
851 Stack<oop, mtGC> _objs_with_preserved_marks;
852 Stack<markOop, mtGC> _preserved_marks_of_objs;
853
854 // Preserve the mark of "obj", if necessary, in preparation for its mark
855 // word being overwritten with a self-forwarding-pointer.
856 void preserve_mark_if_necessary(oop obj, markOop m);
857
858 // The stack of evac-failure objects left to be scanned.
859 GrowableArray<oop>* _evac_failure_scan_stack;
860 // The closure to apply to evac-failure objects.
861
862 OopsInHeapRegionClosure* _evac_failure_closure;
863 // Set the field above.
864 void
865 set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
866 _evac_failure_closure = evac_failure_closure;
867 }
868
869 // Push "obj" on the scan stack.
870 void push_on_evac_failure_scan_stack(oop obj);
871 // Process scan stack entries until the stack is empty.
872 void drain_evac_failure_scan_stack();
873 // True iff an invocation of "drain_scan_stack" is in progress; to
874 // prevent unnecessary recursion.
875 bool _drain_in_progress;
876
877 // Do any necessary initialization for evacuation-failure handling.
878 // "cl" is the closure that will be used to process evac-failure
879 // objects.
880 void init_for_evac_failure(OopsInHeapRegionClosure* cl);
881 // Do any necessary cleanup for evacuation-failure handling data
882 // structures.
883 void finalize_for_evac_failure();
884
885 // An attempt to evacuate "obj" has failed; take necessary steps.
886 oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj);
887 void handle_evacuation_failure_common(oop obj, markOop m);
888
889 #ifndef PRODUCT
890 // Support for forcing evacuation failures. Analogous to
891 // PromotionFailureALot for the other collectors.
892
893 // Records whether G1EvacuationFailureALot should be in effect
894 // for the current GC
895 bool _evacuation_failure_alot_for_current_gc;
896
897 // Used to record the GC number for interval checking when
898 // determining whether G1EvaucationFailureALot is in effect
899 // for the current GC.
900 size_t _evacuation_failure_alot_gc_number;
901
902 // Count of the number of evacuations between failures.
903 volatile size_t _evacuation_failure_alot_count;
904
905 // Set whether G1EvacuationFailureALot should be in effect
906 // for the current GC (based upon the type of GC and which
907 // command line flags are set);
908 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
909 bool during_initial_mark,
910 bool during_marking);
911
912 inline void set_evacuation_failure_alot_for_current_gc();
913
914 // Return true if it's time to cause an evacuation failure.
915 inline bool evacuation_should_fail();
916
917 // Reset the G1EvacuationFailureALot counters. Should be called at
918 // the end of an evacuation pause in which an evacuation failure occurred.
919 inline void reset_evacuation_should_fail();
920 #endif // !PRODUCT
921
922 // ("Weak") Reference processing support.
923 //
924 // G1 has 2 instances of the reference processor class. One
925 // (_ref_processor_cm) handles reference object discovery
926 // and subsequent processing during concurrent marking cycles.
927 //
928 // The other (_ref_processor_stw) handles reference object
929 // discovery and processing during full GCs and incremental
930 // evacuation pauses.
931 //
932 // During an incremental pause, reference discovery will be
933 // temporarily disabled for _ref_processor_cm and will be
934 // enabled for _ref_processor_stw. At the end of the evacuation
935 // pause references discovered by _ref_processor_stw will be
936 // processed and discovery will be disabled. The previous
937 // setting for reference object discovery for _ref_processor_cm
938 // will be re-instated.
939 //
940 // At the start of marking:
941 // * Discovery by the CM ref processor is verified to be inactive
942 // and it's discovered lists are empty.
943 // * Discovery by the CM ref processor is then enabled.
944 //
945 // At the end of marking:
946 // * Any references on the CM ref processor's discovered
947 // lists are processed (possibly MT).
948 //
949 // At the start of full GC we:
950 // * Disable discovery by the CM ref processor and
951 // empty CM ref processor's discovered lists
952 // (without processing any entries).
953 // * Verify that the STW ref processor is inactive and it's
954 // discovered lists are empty.
955 // * Temporarily set STW ref processor discovery as single threaded.
956 // * Temporarily clear the STW ref processor's _is_alive_non_header
957 // field.
958 // * Finally enable discovery by the STW ref processor.
959 //
960 // The STW ref processor is used to record any discovered
961 // references during the full GC.
962 //
963 // At the end of a full GC we:
964 // * Enqueue any reference objects discovered by the STW ref processor
965 // that have non-live referents. This has the side-effect of
966 // making the STW ref processor inactive by disabling discovery.
967 // * Verify that the CM ref processor is still inactive
968 // and no references have been placed on it's discovered
969 // lists (also checked as a precondition during initial marking).
970
971 // The (stw) reference processor...
972 ReferenceProcessor* _ref_processor_stw;
973
974 STWGCTimer* _gc_timer_stw;
975 ConcurrentGCTimer* _gc_timer_cm;
976
977 G1OldTracer* _gc_tracer_cm;
978 G1NewTracer* _gc_tracer_stw;
979
980 // During reference object discovery, the _is_alive_non_header
981 // closure (if non-null) is applied to the referent object to
982 // determine whether the referent is live. If so then the
983 // reference object does not need to be 'discovered' and can
984 // be treated as a regular oop. This has the benefit of reducing
985 // the number of 'discovered' reference objects that need to
986 // be processed.
987 //
988 // Instance of the is_alive closure for embedding into the
989 // STW reference processor as the _is_alive_non_header field.
990 // Supplying a value for the _is_alive_non_header field is
991 // optional but doing so prevents unnecessary additions to
992 // the discovered lists during reference discovery.
993 G1STWIsAliveClosure _is_alive_closure_stw;
994
995 // The (concurrent marking) reference processor...
996 ReferenceProcessor* _ref_processor_cm;
997
998 // Instance of the concurrent mark is_alive closure for embedding
999 // into the Concurrent Marking reference processor as the
1000 // _is_alive_non_header field. Supplying a value for the
1001 // _is_alive_non_header field is optional but doing so prevents
1002 // unnecessary additions to the discovered lists during reference
1003 // discovery.
1004 G1CMIsAliveClosure _is_alive_closure_cm;
1005
1006 // Cache used by G1CollectedHeap::start_cset_region_for_worker().
1007 HeapRegion** _worker_cset_start_region;
1008
1009 // Time stamp to validate the regions recorded in the cache
1010 // used by G1CollectedHeap::start_cset_region_for_worker().
1011 // The heap region entry for a given worker is valid iff
1012 // the associated time stamp value matches the current value
1013 // of G1CollectedHeap::_gc_time_stamp.
1014 unsigned int* _worker_cset_start_region_time_stamp;
1015
1016 enum G1H_process_roots_tasks {
1017 G1H_PS_filter_satb_buffers,
1018 G1H_PS_refProcessor_oops_do,
1019 // Leave this one last.
1020 G1H_PS_NumElements
1021 };
1022
1023 SubTasksDone* _process_strong_tasks;
1024
1025 volatile bool _free_regions_coming;
1026
1027 public:
1028
1029 SubTasksDone* process_strong_tasks() { return _process_strong_tasks; }
1030
1031 void set_refine_cte_cl_concurrency(bool concurrent);
1032
1033 RefToScanQueue *task_queue(int i) 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 // Initialize weak reference processing.
1061 virtual void ref_processing_init();
1062
1063 void set_par_threads(uint t) {
1064 SharedHeap::set_par_threads(t);
1065 // Done in SharedHeap but oddly there are
1066 // two _process_strong_tasks's in a G1CollectedHeap
1067 // so do it here too.
1068 _process_strong_tasks->set_n_threads(t);
1069 }
1070
1071 // Set _n_par_threads according to a policy TBD.
1072 void set_par_threads();
1073
1074 void set_n_termination(int t) {
1075 _process_strong_tasks->set_n_threads(t);
1076 }
1077
1078 virtual CollectedHeap::Name kind() const {
1079 return CollectedHeap::G1CollectedHeap;
1080 }
1081
1082 // The current policy object for the collector.
1083 G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1084
1085 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); }
1086
1087 // Adaptive size policy. No such thing for g1.
1088 virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1089
1090 // The rem set and barrier set.
1091 G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1092
1093 unsigned get_gc_time_stamp() {
1094 return _gc_time_stamp;
1095 }
1096
1097 inline void reset_gc_time_stamp();
1098
1099 void check_gc_time_stamps() PRODUCT_RETURN;
1100
1101 inline void increment_gc_time_stamp();
1102
1103 // Reset the given region's GC timestamp. If it's starts humongous,
1104 // also reset the GC timestamp of its corresponding
1105 // continues humongous regions too.
1106 void reset_gc_time_stamps(HeapRegion* hr);
1107
1108 void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1109 DirtyCardQueue* into_cset_dcq,
1110 bool concurrent, uint worker_i);
1111
1112 // The shared block offset table array.
1113 G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1114
1115 // Reference Processing accessors
1116
1117 // The STW reference processor....
1118 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1119
1120 // The Concurrent Marking reference processor...
1121 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1122
1123 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1124 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1125
1126 virtual size_t capacity() const;
1127 virtual size_t used() const;
1128 // This should be called when we're not holding the heap lock. The
1129 // result might be a bit inaccurate.
1130 size_t used_unlocked() const;
1131 size_t recalculate_used() const;
1132
1133 // These virtual functions do the actual allocation.
1134 // Some heaps may offer a contiguous region for shared non-blocking
1135 // allocation, via inlined code (by exporting the address of the top and
1136 // end fields defining the extent of the contiguous allocation region.)
1137 // But G1CollectedHeap doesn't yet support this.
1138
1139 virtual bool is_maximal_no_gc() const {
1140 return _hrm.available() == 0;
1141 }
1142
1143 // The current number of regions in the heap.
1144 uint num_regions() const { return _hrm.length(); }
1145
1146 // The max number of regions in the heap.
1147 uint max_regions() const { return _hrm.max_length(); }
1148
1149 // The number of regions that are completely free.
1150 uint num_free_regions() const { return _hrm.num_free_regions(); }
1151
1152 // The number of regions that are not completely free.
1153 uint num_used_regions() const { return num_regions() - num_free_regions(); }
1154
1155 void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1156 void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1157 void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1158 void verify_dirty_young_regions() PRODUCT_RETURN;
1159
1160 #ifndef PRODUCT
1161 // Make sure that the given bitmap has no marked objects in the
1162 // range [from,limit). If it does, print an error message and return
1163 // false. Otherwise, just return true. bitmap_name should be "prev"
1164 // or "next".
1165 bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
1166 HeapWord* from, HeapWord* limit);
1167
1168 // Verify that the prev / next bitmap range [tams,end) for the given
1169 // region has no marks. Return true if all is well, false if errors
1170 // are detected.
1171 bool verify_bitmaps(const char* caller, HeapRegion* hr);
1172 #endif // PRODUCT
1173
1174 // If G1VerifyBitmaps is set, verify that the marking bitmaps for
1175 // the given region do not have any spurious marks. If errors are
1176 // detected, print appropriate error messages and crash.
1177 void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN;
1178
1179 // If G1VerifyBitmaps is set, verify that the marking bitmaps do not
1180 // have any spurious marks. If errors are detected, print
1181 // appropriate error messages and crash.
1182 void check_bitmaps(const char* caller) PRODUCT_RETURN;
1183
1184 // verify_region_sets() performs verification over the region
1185 // lists. It will be compiled in the product code to be used when
1186 // necessary (i.e., during heap verification).
1187 void verify_region_sets();
1188
1189 // verify_region_sets_optional() is planted in the code for
1190 // list verification in non-product builds (and it can be enabled in
1191 // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1).
1192 #if HEAP_REGION_SET_FORCE_VERIFY
1193 void verify_region_sets_optional() {
1194 verify_region_sets();
1195 }
1196 #else // HEAP_REGION_SET_FORCE_VERIFY
1197 void verify_region_sets_optional() { }
1198 #endif // HEAP_REGION_SET_FORCE_VERIFY
1199
1200 #ifdef ASSERT
1201 bool is_on_master_free_list(HeapRegion* hr) {
1202 return _hrm.is_free(hr);
1203 }
1204 #endif // ASSERT
1205
1206 // Wrapper for the region list operations that can be called from
1207 // methods outside this class.
1208
1209 void secondary_free_list_add(FreeRegionList* list) {
1210 _secondary_free_list.add_ordered(list);
1211 }
1212
1213 void append_secondary_free_list() {
1214 _hrm.insert_list_into_free_list(&_secondary_free_list);
1215 }
1216
1217 void append_secondary_free_list_if_not_empty_with_lock() {
1218 // If the secondary free list looks empty there's no reason to
1219 // take the lock and then try to append it.
1220 if (!_secondary_free_list.is_empty()) {
1221 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1222 append_secondary_free_list();
1223 }
1224 }
1225
1226 inline void old_set_remove(HeapRegion* hr);
1227
1228 size_t non_young_capacity_bytes() {
1229 return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1230 }
1231
1232 void set_free_regions_coming();
1233 void reset_free_regions_coming();
1234 bool free_regions_coming() { return _free_regions_coming; }
1235 void wait_while_free_regions_coming();
1236
1237 // Determine whether the given region is one that we are using as an
1238 // old GC alloc region.
1239 bool is_old_gc_alloc_region(HeapRegion* hr) {
1240 return _allocator->is_retained_old_region(hr);
1241 }
1242
1243 // Perform a collection of the heap; intended for use in implementing
1244 // "System.gc". This probably implies as full a collection as the
1245 // "CollectedHeap" supports.
1246 virtual void collect(GCCause::Cause cause);
1247
1248 // The same as above but assume that the caller holds the Heap_lock.
1249 void collect_locked(GCCause::Cause cause);
1250
1251 virtual void copy_allocation_context_stats(const jint* contexts,
1252 jlong* totals,
1253 jbyte* accuracy,
1254 jint len);
1255
1256 // True iff an evacuation has failed in the most-recent collection.
1257 bool evacuation_failed() { return _evacuation_failed; }
1258
1259 void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed);
1260 void prepend_to_freelist(FreeRegionList* list);
1261 void decrement_summary_bytes(size_t bytes);
1262
1263 // Returns "TRUE" iff "p" points into the committed areas of the heap.
1264 virtual bool is_in(const void* p) const;
1265 #ifdef ASSERT
1266 // Returns whether p is in one of the available areas of the heap. Slow but
1267 // extensive version.
1268 bool is_in_exact(const void* p) const;
1269 #endif
1270
1271 // Return "TRUE" iff the given object address is within the collection
1272 // set. Slow implementation.
1273 inline bool obj_in_cs(oop obj);
1274
1275 inline bool is_in_cset(oop obj);
1276
1277 inline bool is_in_cset_or_humongous(const oop obj);
1278
1279 enum in_cset_state_t {
1280 InNeither, // neither in collection set nor humongous
1281 InCSet, // region is in collection set only
1282 IsHumongous // region is a humongous start region
1283 };
1284 private:
1285 // Instances of this class are used for quick tests on whether a reference points
1286 // into the collection set or is a humongous object (points into a humongous
1287 // object).
1288 // Each of the array's elements denotes whether the corresponding region is in
1289 // the collection set or a humongous region.
1290 // We use this to quickly reclaim humongous objects: by making a humongous region
1291 // succeed this test, we sort-of add it to the collection set. During the reference
1292 // iteration closures, when we see a humongous region, we simply mark it as
1293 // referenced, i.e. live.
1294 class G1FastCSetBiasedMappedArray : public G1BiasedMappedArray<char> {
1295 protected:
1296 char default_value() const { return G1CollectedHeap::InNeither; }
1297 public:
1298 void set_humongous(uintptr_t index) {
1299 assert(get_by_index(index) != InCSet, "Should not overwrite InCSet values");
1300 set_by_index(index, G1CollectedHeap::IsHumongous);
1301 }
1302
1303 void clear_humongous(uintptr_t index) {
1304 set_by_index(index, G1CollectedHeap::InNeither);
1305 }
1306
1307 void set_in_cset(uintptr_t index) {
1308 assert(get_by_index(index) != G1CollectedHeap::IsHumongous, "Should not overwrite IsHumongous value");
1309 set_by_index(index, G1CollectedHeap::InCSet);
1310 }
1311
1312 bool is_in_cset_or_humongous(HeapWord* addr) const { return get_by_address(addr) != G1CollectedHeap::InNeither; }
1313 bool is_in_cset(HeapWord* addr) const { return get_by_address(addr) == G1CollectedHeap::InCSet; }
1314 G1CollectedHeap::in_cset_state_t at(HeapWord* addr) const { return (G1CollectedHeap::in_cset_state_t)get_by_address(addr); }
1315 void clear() { G1BiasedMappedArray<char>::clear(); }
1316 };
1317
1318 // This array is used for a quick test on whether a reference points into
1319 // the collection set or not. Each of the array's elements denotes whether the
1320 // corresponding region is in the collection set or not.
1321 G1FastCSetBiasedMappedArray _in_cset_fast_test;
1322
1323 public:
1324
1325 inline in_cset_state_t in_cset_state(const oop obj);
1326
1327 // Return "TRUE" iff the given object address is in the reserved
1328 // region of g1.
1329 bool is_in_g1_reserved(const void* p) const {
1330 return _hrm.reserved().contains(p);
1331 }
1332
1333 // Returns a MemRegion that corresponds to the space that has been
1334 // reserved for the heap
1335 MemRegion g1_reserved() const {
1336 return _hrm.reserved();
1337 }
1338
1339 virtual bool is_in_closed_subset(const void* p) const;
1340
1341 G1SATBCardTableLoggingModRefBS* g1_barrier_set() {
1342 return (G1SATBCardTableLoggingModRefBS*) barrier_set();
1343 }
1344
1345 // This resets the card table to all zeros. It is used after
1346 // a collection pause which used the card table to claim cards.
1347 void cleanUpCardTable();
1348
1349 // Iteration functions.
1350
1351 // Iterate over all the ref-containing fields of all objects, calling
1352 // "cl.do_oop" on each.
1353 virtual void oop_iterate(ExtendedOopClosure* cl);
1354
1355 // Iterate over all objects, calling "cl.do_object" on each.
1356 virtual void object_iterate(ObjectClosure* cl);
1357
1358 virtual void safe_object_iterate(ObjectClosure* cl) {
1359 object_iterate(cl);
1360 }
1361
1362 // Iterate over all spaces in use in the heap, in ascending address order.
1363 virtual void space_iterate(SpaceClosure* cl);
1364
1365 // Iterate over heap regions, in address order, terminating the
1366 // iteration early if the "doHeapRegion" method returns "true".
1367 void heap_region_iterate(HeapRegionClosure* blk) const;
1368
1369 // Return the region with the given index. It assumes the index is valid.
1370 inline HeapRegion* region_at(uint index) const;
1371
1372 // Calculate the region index of the given address. Given address must be
1373 // within the heap.
1374 inline uint addr_to_region(HeapWord* addr) const;
1375
1376 inline HeapWord* bottom_addr_for_region(uint index) const;
1377
1378 // Iterate over the heap regions in parallel. Assumes that this will be called
1379 // in parallel by ParallelGCThreads worker threads with distinct worker ids
1380 // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion"
1381 // to each of the regions, by attempting to claim the region using the
1382 // HeapRegionClaimer and, if successful, applying the closure to the claimed
1383 // region.
1384 void heap_region_par_iterate(HeapRegionClosure* cl,
1385 uint worker_id,
1386 HeapRegionClaimer* hrclaimer) const;
1387
1388 // Clear the cached cset start regions and (more importantly)
1389 // the time stamps. Called when we reset the GC time stamp.
1390 void clear_cset_start_regions();
1391
1392 // Given the id of a worker, obtain or calculate a suitable
1393 // starting region for iterating over the current collection set.
1394 HeapRegion* start_cset_region_for_worker(uint worker_i);
1395
1396 // Iterate over the regions (if any) in the current collection set.
1397 void collection_set_iterate(HeapRegionClosure* blk);
1398
1399 // As above but starting from region r
1400 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1401
1402 HeapRegion* next_compaction_region(const HeapRegion* from) const;
1403
1404 // A CollectedHeap will contain some number of spaces. This finds the
1405 // space containing a given address, or else returns NULL.
1406 virtual Space* space_containing(const void* addr) const;
1407
1408 // Returns the HeapRegion that contains addr. addr must not be NULL.
1409 template <class T>
1410 inline HeapRegion* heap_region_containing_raw(const T addr) const;
1411
1412 // Returns the HeapRegion that contains addr. addr must not be NULL.
1413 // If addr is within a humongous continues region, it returns its humongous start region.
1414 template <class T>
1415 inline HeapRegion* heap_region_containing(const T addr) const;
1416
1417 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1418 // each address in the (reserved) heap is a member of exactly
1419 // one block. The defining characteristic of a block is that it is
1420 // possible to find its size, and thus to progress forward to the next
1421 // block. (Blocks may be of different sizes.) Thus, blocks may
1422 // represent Java objects, or they might be free blocks in a
1423 // free-list-based heap (or subheap), as long as the two kinds are
1424 // distinguishable and the size of each is determinable.
1425
1426 // Returns the address of the start of the "block" that contains the
1427 // address "addr". We say "blocks" instead of "object" since some heaps
1428 // may not pack objects densely; a chunk may either be an object or a
1429 // non-object.
1430 virtual HeapWord* block_start(const void* addr) const;
1431
1432 // Requires "addr" to be the start of a chunk, and returns its size.
1433 // "addr + size" is required to be the start of a new chunk, or the end
1434 // of the active area of the heap.
1435 virtual size_t block_size(const HeapWord* addr) const;
1436
1437 // Requires "addr" to be the start of a block, and returns "TRUE" iff
1438 // the block is an object.
1439 virtual bool block_is_obj(const HeapWord* addr) const;
1440
1441 // Does this heap support heap inspection? (+PrintClassHistogram)
1442 virtual bool supports_heap_inspection() const { return true; }
1443
1444 // Section on thread-local allocation buffers (TLABs)
1445 // See CollectedHeap for semantics.
1446
1447 bool supports_tlab_allocation() const;
1448 size_t tlab_capacity(Thread* ignored) const;
1449 size_t tlab_used(Thread* ignored) const;
1450 size_t max_tlab_size() const;
1451 size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1452
1453 // Can a compiler initialize a new object without store barriers?
1454 // This permission only extends from the creation of a new object
1455 // via a TLAB up to the first subsequent safepoint. If such permission
1456 // is granted for this heap type, the compiler promises to call
1457 // defer_store_barrier() below on any slow path allocation of
1458 // a new object for which such initializing store barriers will
1459 // have been elided. G1, like CMS, allows this, but should be
1460 // ready to provide a compensating write barrier as necessary
1461 // if that storage came out of a non-young region. The efficiency
1462 // of this implementation depends crucially on being able to
1463 // answer very efficiently in constant time whether a piece of
1464 // storage in the heap comes from a young region or not.
1465 // See ReduceInitialCardMarks.
1466 virtual bool can_elide_tlab_store_barriers() const {
1467 return true;
1468 }
1469
1470 virtual bool card_mark_must_follow_store() const {
1471 return true;
1472 }
1473
1474 inline bool is_in_young(const oop obj);
1475
1476 #ifdef ASSERT
1477 virtual bool is_in_partial_collection(const void* p);
1478 #endif
1479
1480 virtual bool is_scavengable(const void* addr);
1481
1482 // We don't need barriers for initializing stores to objects
1483 // in the young gen: for the SATB pre-barrier, there is no
1484 // pre-value that needs to be remembered; for the remembered-set
1485 // update logging post-barrier, we don't maintain remembered set
1486 // information for young gen objects.
1487 virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1488
1489 // Returns "true" iff the given word_size is "very large".
1490 static bool is_humongous(size_t word_size) {
1491 // Note this has to be strictly greater-than as the TLABs
1492 // are capped at the humongous threshold and we want to
1493 // ensure that we don't try to allocate a TLAB as
1494 // humongous and that we don't allocate a humongous
1495 // object in a TLAB.
1496 return word_size > _humongous_object_threshold_in_words;
1497 }
1498
1499 // Update mod union table with the set of dirty cards.
1500 void updateModUnion();
1501
1502 // Set the mod union bits corresponding to the given memRegion. Note
1503 // that this is always a safe operation, since it doesn't clear any
1504 // bits.
1505 void markModUnionRange(MemRegion mr);
1506
1507 // Records the fact that a marking phase is no longer in progress.
1508 void set_marking_complete() {
1509 _mark_in_progress = false;
1510 }
1511 void set_marking_started() {
1512 _mark_in_progress = true;
1513 }
1514 bool mark_in_progress() {
1515 return _mark_in_progress;
1516 }
1517
1518 // Print the maximum heap capacity.
1519 virtual size_t max_capacity() const;
1520
1521 virtual jlong millis_since_last_gc();
1522
1523
1524 // Convenience function to be used in situations where the heap type can be
1525 // asserted to be this type.
1526 static G1CollectedHeap* heap();
1527
1528 void set_region_short_lived_locked(HeapRegion* hr);
1529 // add appropriate methods for any other surv rate groups
1530
1531 YoungList* young_list() const { return _young_list; }
1532
1533 // debugging
1534 bool check_young_list_well_formed() {
1535 return _young_list->check_list_well_formed();
1536 }
1537
1538 bool check_young_list_empty(bool check_heap,
1539 bool check_sample = true);
1540
1541 // *** Stuff related to concurrent marking. It's not clear to me that so
1542 // many of these need to be public.
1543
1544 // The functions below are helper functions that a subclass of
1545 // "CollectedHeap" can use in the implementation of its virtual
1546 // functions.
1547 // This performs a concurrent marking of the live objects in a
1548 // bitmap off to the side.
1549 void doConcurrentMark();
1550
1551 bool isMarkedPrev(oop obj) const;
1552 bool isMarkedNext(oop obj) const;
1553
1554 // Determine if an object is dead, given the object and also
1555 // the region to which the object belongs. An object is dead
1556 // iff a) it was not allocated since the last mark and b) it
1557 // is not marked.
1558 bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1559 return
1560 !hr->obj_allocated_since_prev_marking(obj) &&
1561 !isMarkedPrev(obj);
1562 }
1563
1564 // This function returns true when an object has been
1565 // around since the previous marking and hasn't yet
1566 // been marked during this marking.
1567 bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1568 return
1569 !hr->obj_allocated_since_next_marking(obj) &&
1570 !isMarkedNext(obj);
1571 }
1572
1573 // Determine if an object is dead, given only the object itself.
1574 // This will find the region to which the object belongs and
1575 // then call the region version of the same function.
1576
1577 // Added if it is NULL it isn't dead.
1578
1579 inline bool is_obj_dead(const oop obj) const;
1580
1581 inline bool is_obj_ill(const oop obj) const;
1582
1583 bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1584 HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1585 bool is_marked(oop obj, VerifyOption vo);
1586 const char* top_at_mark_start_str(VerifyOption vo);
1587
1588 ConcurrentMark* concurrent_mark() const { return _cm; }
1589
1590 // Refinement
1591
1592 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1593
1594 // The dirty cards region list is used to record a subset of regions
1595 // whose cards need clearing. The list if populated during the
1596 // remembered set scanning and drained during the card table
1597 // cleanup. Although the methods are reentrant, population/draining
1598 // phases must not overlap. For synchronization purposes the last
1599 // element on the list points to itself.
1600 HeapRegion* _dirty_cards_region_list;
1601 void push_dirty_cards_region(HeapRegion* hr);
1602 HeapRegion* pop_dirty_cards_region();
1603
1604 // Optimized nmethod scanning support routines
1605
1606 // Register the given nmethod with the G1 heap.
1607 virtual void register_nmethod(nmethod* nm);
1608
1609 // Unregister the given nmethod from the G1 heap.
1610 virtual void unregister_nmethod(nmethod* nm);
1611
1612 // Free up superfluous code root memory.
1613 void purge_code_root_memory();
1614
1615 // Rebuild the strong code root lists for each region
1616 // after a full GC.
1617 void rebuild_strong_code_roots();
1618
1619 // Delete entries for dead interned string and clean up unreferenced symbols
1620 // in symbol table, possibly in parallel.
1621 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1622
1623 // Parallel phase of unloading/cleaning after G1 concurrent mark.
1624 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred);
1625
1626 // Redirty logged cards in the refinement queue.
1627 void redirty_logged_cards();
1628 // Verification
1629
1630 // The following is just to alert the verification code
1631 // that a full collection has occurred and that the
1632 // remembered sets are no longer up to date.
1633 bool _full_collection;
1634 void set_full_collection() { _full_collection = true;}
1635 void clear_full_collection() {_full_collection = false;}
1636 bool full_collection() {return _full_collection;}
1637
1638 // Perform any cleanup actions necessary before allowing a verification.
1639 virtual void prepare_for_verify();
1640
1641 // Perform verification.
1642
1643 // vo == UsePrevMarking -> use "prev" marking information,
1644 // vo == UseNextMarking -> use "next" marking information
1645 // vo == UseMarkWord -> use the mark word in the object header
1646 //
1647 // NOTE: Only the "prev" marking information is guaranteed to be
1648 // consistent most of the time, so most calls to this should use
1649 // vo == UsePrevMarking.
1650 // Currently, there is only one case where this is called with
1651 // vo == UseNextMarking, which is to verify the "next" marking
1652 // information at the end of remark.
1653 // Currently there is only one place where this is called with
1654 // vo == UseMarkWord, which is to verify the marking during a
1655 // full GC.
1656 void verify(bool silent, VerifyOption vo);
1657
1658 // Override; it uses the "prev" marking information
1659 virtual void verify(bool silent);
1660
1661 // The methods below are here for convenience and dispatch the
1662 // appropriate method depending on value of the given VerifyOption
1663 // parameter. The values for that parameter, and their meanings,
1664 // are the same as those above.
1665
1666 bool is_obj_dead_cond(const oop obj,
1667 const HeapRegion* hr,
1668 const VerifyOption vo) const;
1669
1670 bool is_obj_dead_cond(const oop obj,
1671 const VerifyOption vo) const;
1672
1673 // Printing
1674
1675 virtual void print_on(outputStream* st) const;
1676 virtual void print_extended_on(outputStream* st) const;
1677 virtual void print_on_error(outputStream* st) const;
1678
1679 virtual void print_gc_threads_on(outputStream* st) const;
1680 virtual void gc_threads_do(ThreadClosure* tc) const;
1681
1682 // Override
1683 void print_tracing_info() const;
1684
1685 // The following two methods are helpful for debugging RSet issues.
1686 void print_cset_rsets() PRODUCT_RETURN;
1687 void print_all_rsets() PRODUCT_RETURN;
1688
1689 public:
1690 size_t pending_card_num();
1691 size_t cards_scanned();
1692
1693 protected:
1694 size_t _max_heap_capacity;
1695 };
1696
1697 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP