Wed, 23 Jul 2014 09:03:32 +0200
8027959: Early reclamation of large objects in G1
Summary: Try to reclaim humongous objects at every young collection after doing a conservative estimate of its liveness.
Reviewed-by: brutisso, mgerdin
1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
28 #include "gc_implementation/g1/concurrentMark.hpp"
29 #include "gc_implementation/g1/evacuationInfo.hpp"
30 #include "gc_implementation/g1/g1AllocRegion.hpp"
31 #include "gc_implementation/g1/g1BiasedArray.hpp"
32 #include "gc_implementation/g1/g1HRPrinter.hpp"
33 #include "gc_implementation/g1/g1MonitoringSupport.hpp"
34 #include "gc_implementation/g1/g1SATBCardTableModRefBS.hpp"
35 #include "gc_implementation/g1/g1YCTypes.hpp"
36 #include "gc_implementation/g1/heapRegionSeq.hpp"
37 #include "gc_implementation/g1/heapRegionSet.hpp"
38 #include "gc_implementation/shared/hSpaceCounters.hpp"
39 #include "gc_implementation/shared/parGCAllocBuffer.hpp"
40 #include "memory/barrierSet.hpp"
41 #include "memory/memRegion.hpp"
42 #include "memory/sharedHeap.hpp"
43 #include "utilities/stack.hpp"
45 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
46 // It uses the "Garbage First" heap organization and algorithm, which
47 // may combine concurrent marking with parallel, incremental compaction of
48 // heap subsets that will yield large amounts of garbage.
50 // Forward declarations
51 class HeapRegion;
52 class HRRSCleanupTask;
53 class GenerationSpec;
54 class OopsInHeapRegionClosure;
55 class G1KlassScanClosure;
56 class G1ScanHeapEvacClosure;
57 class ObjectClosure;
58 class SpaceClosure;
59 class CompactibleSpaceClosure;
60 class Space;
61 class G1CollectorPolicy;
62 class GenRemSet;
63 class G1RemSet;
64 class HeapRegionRemSetIterator;
65 class ConcurrentMark;
66 class ConcurrentMarkThread;
67 class ConcurrentG1Refine;
68 class ConcurrentGCTimer;
69 class GenerationCounters;
70 class STWGCTimer;
71 class G1NewTracer;
72 class G1OldTracer;
73 class EvacuationFailedInfo;
74 class nmethod;
75 class Ticks;
77 typedef OverflowTaskQueue<StarTask, mtGC> RefToScanQueue;
78 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
80 typedef int RegionIdx_t; // needs to hold [ 0..max_regions() )
81 typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion )
83 enum GCAllocPurpose {
84 GCAllocForTenured,
85 GCAllocForSurvived,
86 GCAllocPurposeCount
87 };
89 class YoungList : public CHeapObj<mtGC> {
90 private:
91 G1CollectedHeap* _g1h;
93 HeapRegion* _head;
95 HeapRegion* _survivor_head;
96 HeapRegion* _survivor_tail;
98 HeapRegion* _curr;
100 uint _length;
101 uint _survivor_length;
103 size_t _last_sampled_rs_lengths;
104 size_t _sampled_rs_lengths;
106 void empty_list(HeapRegion* list);
108 public:
109 YoungList(G1CollectedHeap* g1h);
111 void push_region(HeapRegion* hr);
112 void add_survivor_region(HeapRegion* hr);
114 void empty_list();
115 bool is_empty() { return _length == 0; }
116 uint length() { return _length; }
117 uint survivor_length() { return _survivor_length; }
119 // Currently we do not keep track of the used byte sum for the
120 // young list and the survivors and it'd be quite a lot of work to
121 // do so. When we'll eventually replace the young list with
122 // instances of HeapRegionLinkedList we'll get that for free. So,
123 // we'll report the more accurate information then.
124 size_t eden_used_bytes() {
125 assert(length() >= survivor_length(), "invariant");
126 return (size_t) (length() - survivor_length()) * HeapRegion::GrainBytes;
127 }
128 size_t survivor_used_bytes() {
129 return (size_t) survivor_length() * HeapRegion::GrainBytes;
130 }
132 void rs_length_sampling_init();
133 bool rs_length_sampling_more();
134 void rs_length_sampling_next();
136 void reset_sampled_info() {
137 _last_sampled_rs_lengths = 0;
138 }
139 size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
141 // for development purposes
142 void reset_auxilary_lists();
143 void clear() { _head = NULL; _length = 0; }
145 void clear_survivors() {
146 _survivor_head = NULL;
147 _survivor_tail = NULL;
148 _survivor_length = 0;
149 }
151 HeapRegion* first_region() { return _head; }
152 HeapRegion* first_survivor_region() { return _survivor_head; }
153 HeapRegion* last_survivor_region() { return _survivor_tail; }
155 // debugging
156 bool check_list_well_formed();
157 bool check_list_empty(bool check_sample = true);
158 void print();
159 };
161 class MutatorAllocRegion : public G1AllocRegion {
162 protected:
163 virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
164 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
165 public:
166 MutatorAllocRegion()
167 : G1AllocRegion("Mutator Alloc Region", false /* bot_updates */) { }
168 };
170 class SurvivorGCAllocRegion : public G1AllocRegion {
171 protected:
172 virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
173 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
174 public:
175 SurvivorGCAllocRegion()
176 : G1AllocRegion("Survivor GC Alloc Region", false /* bot_updates */) { }
177 };
179 class OldGCAllocRegion : public G1AllocRegion {
180 protected:
181 virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
182 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
183 public:
184 OldGCAllocRegion()
185 : G1AllocRegion("Old GC Alloc Region", true /* bot_updates */) { }
186 };
188 // The G1 STW is alive closure.
189 // An instance is embedded into the G1CH and used as the
190 // (optional) _is_alive_non_header closure in the STW
191 // reference processor. It is also extensively used during
192 // reference processing during STW evacuation pauses.
193 class G1STWIsAliveClosure: public BoolObjectClosure {
194 G1CollectedHeap* _g1;
195 public:
196 G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
197 bool do_object_b(oop p);
198 };
200 class RefineCardTableEntryClosure;
202 class G1CollectedHeap : public SharedHeap {
203 friend class VM_CollectForMetadataAllocation;
204 friend class VM_G1CollectForAllocation;
205 friend class VM_G1CollectFull;
206 friend class VM_G1IncCollectionPause;
207 friend class VMStructs;
208 friend class MutatorAllocRegion;
209 friend class SurvivorGCAllocRegion;
210 friend class OldGCAllocRegion;
212 // Closures used in implementation.
213 template <G1Barrier barrier, G1Mark do_mark_object>
214 friend class G1ParCopyClosure;
215 friend class G1IsAliveClosure;
216 friend class G1EvacuateFollowersClosure;
217 friend class G1ParScanThreadState;
218 friend class G1ParScanClosureSuper;
219 friend class G1ParEvacuateFollowersClosure;
220 friend class G1ParTask;
221 friend class G1FreeGarbageRegionClosure;
222 friend class RefineCardTableEntryClosure;
223 friend class G1PrepareCompactClosure;
224 friend class RegionSorter;
225 friend class RegionResetter;
226 friend class CountRCClosure;
227 friend class EvacPopObjClosure;
228 friend class G1ParCleanupCTTask;
230 friend class G1FreeHumongousRegionClosure;
231 // Other related classes.
232 friend class G1MarkSweep;
234 private:
235 // The one and only G1CollectedHeap, so static functions can find it.
236 static G1CollectedHeap* _g1h;
238 static size_t _humongous_object_threshold_in_words;
240 // Storage for the G1 heap.
241 VirtualSpace _g1_storage;
242 MemRegion _g1_reserved;
244 // The part of _g1_storage that is currently committed.
245 MemRegion _g1_committed;
247 // The master free list. It will satisfy all new region allocations.
248 FreeRegionList _free_list;
250 // The secondary free list which contains regions that have been
251 // freed up during the cleanup process. This will be appended to the
252 // master free list when appropriate.
253 FreeRegionList _secondary_free_list;
255 // It keeps track of the old regions.
256 HeapRegionSet _old_set;
258 // It keeps track of the humongous regions.
259 HeapRegionSet _humongous_set;
261 void clear_humongous_is_live_table();
262 void eagerly_reclaim_humongous_regions();
264 // The number of regions we could create by expansion.
265 uint _expansion_regions;
267 // The block offset table for the G1 heap.
268 G1BlockOffsetSharedArray* _bot_shared;
270 // Tears down the region sets / lists so that they are empty and the
271 // regions on the heap do not belong to a region set / list. The
272 // only exception is the humongous set which we leave unaltered. If
273 // free_list_only is true, it will only tear down the master free
274 // list. It is called before a Full GC (free_list_only == false) or
275 // before heap shrinking (free_list_only == true).
276 void tear_down_region_sets(bool free_list_only);
278 // Rebuilds the region sets / lists so that they are repopulated to
279 // reflect the contents of the heap. The only exception is the
280 // humongous set which was not torn down in the first place. If
281 // free_list_only is true, it will only rebuild the master free
282 // list. It is called after a Full GC (free_list_only == false) or
283 // after heap shrinking (free_list_only == true).
284 void rebuild_region_sets(bool free_list_only);
286 // The sequence of all heap regions in the heap.
287 HeapRegionSeq _hrs;
289 // Alloc region used to satisfy mutator allocation requests.
290 MutatorAllocRegion _mutator_alloc_region;
292 // Alloc region used to satisfy allocation requests by the GC for
293 // survivor objects.
294 SurvivorGCAllocRegion _survivor_gc_alloc_region;
296 // PLAB sizing policy for survivors.
297 PLABStats _survivor_plab_stats;
299 // Alloc region used to satisfy allocation requests by the GC for
300 // old objects.
301 OldGCAllocRegion _old_gc_alloc_region;
303 // PLAB sizing policy for tenured objects.
304 PLABStats _old_plab_stats;
306 PLABStats* stats_for_purpose(GCAllocPurpose purpose) {
307 PLABStats* stats = NULL;
309 switch (purpose) {
310 case GCAllocForSurvived:
311 stats = &_survivor_plab_stats;
312 break;
313 case GCAllocForTenured:
314 stats = &_old_plab_stats;
315 break;
316 default:
317 assert(false, "unrecognized GCAllocPurpose");
318 }
320 return stats;
321 }
323 // The last old region we allocated to during the last GC.
324 // Typically, it is not full so we should re-use it during the next GC.
325 HeapRegion* _retained_old_gc_alloc_region;
327 // It specifies whether we should attempt to expand the heap after a
328 // region allocation failure. If heap expansion fails we set this to
329 // false so that we don't re-attempt the heap expansion (it's likely
330 // that subsequent expansion attempts will also fail if one fails).
331 // Currently, it is only consulted during GC and it's reset at the
332 // start of each GC.
333 bool _expand_heap_after_alloc_failure;
335 // It resets the mutator alloc region before new allocations can take place.
336 void init_mutator_alloc_region();
338 // It releases the mutator alloc region.
339 void release_mutator_alloc_region();
341 // It initializes the GC alloc regions at the start of a GC.
342 void init_gc_alloc_regions(EvacuationInfo& evacuation_info);
344 // Setup the retained old gc alloc region as the currrent old gc alloc region.
345 void use_retained_old_gc_alloc_region(EvacuationInfo& evacuation_info);
347 // It releases the GC alloc regions at the end of a GC.
348 void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info);
350 // It does any cleanup that needs to be done on the GC alloc regions
351 // before a Full GC.
352 void abandon_gc_alloc_regions();
354 // Helper for monitoring and management support.
355 G1MonitoringSupport* _g1mm;
357 // Determines PLAB size for a particular allocation purpose.
358 size_t desired_plab_sz(GCAllocPurpose purpose);
360 // Outside of GC pauses, the number of bytes used in all regions other
361 // than the current allocation region.
362 size_t _summary_bytes_used;
364 // Records whether the region at the given index is kept live by roots or
365 // references from the young generation.
366 class HumongousIsLiveBiasedMappedArray : public G1BiasedMappedArray<bool> {
367 protected:
368 bool default_value() const { return false; }
369 public:
370 void clear() { G1BiasedMappedArray<bool>::clear(); }
371 void set_live(uint region) {
372 set_by_index(region, true);
373 }
374 bool is_live(uint region) {
375 return get_by_index(region);
376 }
377 };
379 HumongousIsLiveBiasedMappedArray _humongous_is_live;
380 // Stores whether during humongous object registration we found candidate regions.
381 // If not, we can skip a few steps.
382 bool _has_humongous_reclaim_candidates;
384 volatile unsigned _gc_time_stamp;
386 size_t* _surviving_young_words;
388 G1HRPrinter _hr_printer;
390 void setup_surviving_young_words();
391 void update_surviving_young_words(size_t* surv_young_words);
392 void cleanup_surviving_young_words();
394 // It decides whether an explicit GC should start a concurrent cycle
395 // instead of doing a STW GC. Currently, a concurrent cycle is
396 // explicitly started if:
397 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
398 // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
399 // (c) cause == _g1_humongous_allocation
400 bool should_do_concurrent_full_gc(GCCause::Cause cause);
402 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
403 // concurrent cycles) we have started.
404 volatile unsigned int _old_marking_cycles_started;
406 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
407 // concurrent cycles) we have completed.
408 volatile unsigned int _old_marking_cycles_completed;
410 bool _concurrent_cycle_started;
412 // This is a non-product method that is helpful for testing. It is
413 // called at the end of a GC and artificially expands the heap by
414 // allocating a number of dead regions. This way we can induce very
415 // frequent marking cycles and stress the cleanup / concurrent
416 // cleanup code more (as all the regions that will be allocated by
417 // this method will be found dead by the marking cycle).
418 void allocate_dummy_regions() PRODUCT_RETURN;
420 // Clear RSets after a compaction. It also resets the GC time stamps.
421 void clear_rsets_post_compaction();
423 // If the HR printer is active, dump the state of the regions in the
424 // heap after a compaction.
425 void print_hrs_post_compaction();
427 double verify(bool guard, const char* msg);
428 void verify_before_gc();
429 void verify_after_gc();
431 void log_gc_header();
432 void log_gc_footer(double pause_time_sec);
434 // These are macros so that, if the assert fires, we get the correct
435 // line number, file, etc.
437 #define heap_locking_asserts_err_msg(_extra_message_) \
438 err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \
439 (_extra_message_), \
440 BOOL_TO_STR(Heap_lock->owned_by_self()), \
441 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \
442 BOOL_TO_STR(Thread::current()->is_VM_thread()))
444 #define assert_heap_locked() \
445 do { \
446 assert(Heap_lock->owned_by_self(), \
447 heap_locking_asserts_err_msg("should be holding the Heap_lock")); \
448 } while (0)
450 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \
451 do { \
452 assert(Heap_lock->owned_by_self() || \
453 (SafepointSynchronize::is_at_safepoint() && \
454 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
455 heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
456 "should be at a safepoint")); \
457 } while (0)
459 #define assert_heap_locked_and_not_at_safepoint() \
460 do { \
461 assert(Heap_lock->owned_by_self() && \
462 !SafepointSynchronize::is_at_safepoint(), \
463 heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
464 "should not be at a safepoint")); \
465 } while (0)
467 #define assert_heap_not_locked() \
468 do { \
469 assert(!Heap_lock->owned_by_self(), \
470 heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
471 } while (0)
473 #define assert_heap_not_locked_and_not_at_safepoint() \
474 do { \
475 assert(!Heap_lock->owned_by_self() && \
476 !SafepointSynchronize::is_at_safepoint(), \
477 heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
478 "should not be at a safepoint")); \
479 } while (0)
481 #define assert_at_safepoint(_should_be_vm_thread_) \
482 do { \
483 assert(SafepointSynchronize::is_at_safepoint() && \
484 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
485 heap_locking_asserts_err_msg("should be at a safepoint")); \
486 } while (0)
488 #define assert_not_at_safepoint() \
489 do { \
490 assert(!SafepointSynchronize::is_at_safepoint(), \
491 heap_locking_asserts_err_msg("should not be at a safepoint")); \
492 } while (0)
494 protected:
496 // The young region list.
497 YoungList* _young_list;
499 // The current policy object for the collector.
500 G1CollectorPolicy* _g1_policy;
502 // This is the second level of trying to allocate a new region. If
503 // new_region() didn't find a region on the free_list, this call will
504 // check whether there's anything available on the
505 // secondary_free_list and/or wait for more regions to appear on
506 // that list, if _free_regions_coming is set.
507 HeapRegion* new_region_try_secondary_free_list(bool is_old);
509 // Try to allocate a single non-humongous HeapRegion sufficient for
510 // an allocation of the given word_size. If do_expand is true,
511 // attempt to expand the heap if necessary to satisfy the allocation
512 // request. If the region is to be used as an old region or for a
513 // humongous object, set is_old to true. If not, to false.
514 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
516 // Attempt to satisfy a humongous allocation request of the given
517 // size by finding a contiguous set of free regions of num_regions
518 // length and remove them from the master free list. Return the
519 // index of the first region or G1_NULL_HRS_INDEX if the search
520 // was unsuccessful.
521 uint humongous_obj_allocate_find_first(uint num_regions,
522 size_t word_size);
524 // Initialize a contiguous set of free regions of length num_regions
525 // and starting at index first so that they appear as a single
526 // humongous region.
527 HeapWord* humongous_obj_allocate_initialize_regions(uint first,
528 uint num_regions,
529 size_t word_size);
531 // Attempt to allocate a humongous object of the given size. Return
532 // NULL if unsuccessful.
533 HeapWord* humongous_obj_allocate(size_t word_size);
535 // The following two methods, allocate_new_tlab() and
536 // mem_allocate(), are the two main entry points from the runtime
537 // into the G1's allocation routines. They have the following
538 // assumptions:
539 //
540 // * They should both be called outside safepoints.
541 //
542 // * They should both be called without holding the Heap_lock.
543 //
544 // * All allocation requests for new TLABs should go to
545 // allocate_new_tlab().
546 //
547 // * All non-TLAB allocation requests should go to mem_allocate().
548 //
549 // * If either call cannot satisfy the allocation request using the
550 // current allocating region, they will try to get a new one. If
551 // this fails, they will attempt to do an evacuation pause and
552 // retry the allocation.
553 //
554 // * If all allocation attempts fail, even after trying to schedule
555 // an evacuation pause, allocate_new_tlab() will return NULL,
556 // whereas mem_allocate() will attempt a heap expansion and/or
557 // schedule a Full GC.
558 //
559 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
560 // should never be called with word_size being humongous. All
561 // humongous allocation requests should go to mem_allocate() which
562 // will satisfy them with a special path.
564 virtual HeapWord* allocate_new_tlab(size_t word_size);
566 virtual HeapWord* mem_allocate(size_t word_size,
567 bool* gc_overhead_limit_was_exceeded);
569 // The following three methods take a gc_count_before_ret
570 // parameter which is used to return the GC count if the method
571 // returns NULL. Given that we are required to read the GC count
572 // while holding the Heap_lock, and these paths will take the
573 // Heap_lock at some point, it's easier to get them to read the GC
574 // count while holding the Heap_lock before they return NULL instead
575 // of the caller (namely: mem_allocate()) having to also take the
576 // Heap_lock just to read the GC count.
578 // First-level mutator allocation attempt: try to allocate out of
579 // the mutator alloc region without taking the Heap_lock. This
580 // should only be used for non-humongous allocations.
581 inline HeapWord* attempt_allocation(size_t word_size,
582 unsigned int* gc_count_before_ret,
583 int* gclocker_retry_count_ret);
585 // Second-level mutator allocation attempt: take the Heap_lock and
586 // retry the allocation attempt, potentially scheduling a GC
587 // pause. This should only be used for non-humongous allocations.
588 HeapWord* attempt_allocation_slow(size_t word_size,
589 unsigned int* gc_count_before_ret,
590 int* gclocker_retry_count_ret);
592 // Takes the Heap_lock and attempts a humongous allocation. It can
593 // potentially schedule a GC pause.
594 HeapWord* attempt_allocation_humongous(size_t word_size,
595 unsigned int* gc_count_before_ret,
596 int* gclocker_retry_count_ret);
598 // Allocation attempt that should be called during safepoints (e.g.,
599 // at the end of a successful GC). expect_null_mutator_alloc_region
600 // specifies whether the mutator alloc region is expected to be NULL
601 // or not.
602 HeapWord* attempt_allocation_at_safepoint(size_t word_size,
603 bool expect_null_mutator_alloc_region);
605 // It dirties the cards that cover the block so that so that the post
606 // write barrier never queues anything when updating objects on this
607 // block. It is assumed (and in fact we assert) that the block
608 // belongs to a young region.
609 inline void dirty_young_block(HeapWord* start, size_t word_size);
611 // Allocate blocks during garbage collection. Will ensure an
612 // allocation region, either by picking one or expanding the
613 // heap, and then allocate a block of the given size. The block
614 // may not be a humongous - it must fit into a single heap region.
615 HeapWord* par_allocate_during_gc(GCAllocPurpose purpose, size_t word_size);
617 HeapWord* allocate_during_gc_slow(GCAllocPurpose purpose,
618 HeapRegion* alloc_region,
619 bool par,
620 size_t word_size);
622 // Ensure that no further allocations can happen in "r", bearing in mind
623 // that parallel threads might be attempting allocations.
624 void par_allocate_remaining_space(HeapRegion* r);
626 // Allocation attempt during GC for a survivor object / PLAB.
627 inline HeapWord* survivor_attempt_allocation(size_t word_size);
629 // Allocation attempt during GC for an old object / PLAB.
630 inline HeapWord* old_attempt_allocation(size_t word_size);
632 // These methods are the "callbacks" from the G1AllocRegion class.
634 // For mutator alloc regions.
635 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
636 void retire_mutator_alloc_region(HeapRegion* alloc_region,
637 size_t allocated_bytes);
639 // For GC alloc regions.
640 HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
641 GCAllocPurpose ap);
642 void retire_gc_alloc_region(HeapRegion* alloc_region,
643 size_t allocated_bytes, GCAllocPurpose ap);
645 // - if explicit_gc is true, the GC is for a System.gc() or a heap
646 // inspection request and should collect the entire heap
647 // - if clear_all_soft_refs is true, all soft references should be
648 // cleared during the GC
649 // - if explicit_gc is false, word_size describes the allocation that
650 // the GC should attempt (at least) to satisfy
651 // - it returns false if it is unable to do the collection due to the
652 // GC locker being active, true otherwise
653 bool do_collection(bool explicit_gc,
654 bool clear_all_soft_refs,
655 size_t word_size);
657 // Callback from VM_G1CollectFull operation.
658 // Perform a full collection.
659 virtual void do_full_collection(bool clear_all_soft_refs);
661 // Resize the heap if necessary after a full collection. If this is
662 // after a collect-for allocation, "word_size" is the allocation size,
663 // and will be considered part of the used portion of the heap.
664 void resize_if_necessary_after_full_collection(size_t word_size);
666 // Callback from VM_G1CollectForAllocation operation.
667 // This function does everything necessary/possible to satisfy a
668 // failed allocation request (including collection, expansion, etc.)
669 HeapWord* satisfy_failed_allocation(size_t word_size, bool* succeeded);
671 // Attempting to expand the heap sufficiently
672 // to support an allocation of the given "word_size". If
673 // successful, perform the allocation and return the address of the
674 // allocated block, or else "NULL".
675 HeapWord* expand_and_allocate(size_t word_size);
677 // Process any reference objects discovered during
678 // an incremental evacuation pause.
679 void process_discovered_references(uint no_of_gc_workers);
681 // Enqueue any remaining discovered references
682 // after processing.
683 void enqueue_discovered_references(uint no_of_gc_workers);
685 public:
687 G1MonitoringSupport* g1mm() {
688 assert(_g1mm != NULL, "should have been initialized");
689 return _g1mm;
690 }
692 // Expand the garbage-first heap by at least the given size (in bytes!).
693 // Returns true if the heap was expanded by the requested amount;
694 // false otherwise.
695 // (Rounds up to a HeapRegion boundary.)
696 bool expand(size_t expand_bytes);
698 // Do anything common to GC's.
699 virtual void gc_prologue(bool full);
700 virtual void gc_epilogue(bool full);
702 inline void set_humongous_is_live(oop obj);
704 bool humongous_is_live(uint region) {
705 return _humongous_is_live.is_live(region);
706 }
708 // Returns whether the given region (which must be a humongous (start) region)
709 // is to be considered conservatively live regardless of any other conditions.
710 bool humongous_region_is_always_live(uint index);
711 // Register the given region to be part of the collection set.
712 inline void register_humongous_region_with_in_cset_fast_test(uint index);
713 // Register regions with humongous objects (actually on the start region) in
714 // the in_cset_fast_test table.
715 void register_humongous_regions_with_in_cset_fast_test();
716 // We register a region with the fast "in collection set" test. We
717 // simply set to true the array slot corresponding to this region.
718 void register_region_with_in_cset_fast_test(HeapRegion* r) {
719 _in_cset_fast_test.set_in_cset(r->hrs_index());
720 }
722 // This is a fast test on whether a reference points into the
723 // collection set or not. Assume that the reference
724 // points into the heap.
725 inline bool in_cset_fast_test(oop obj);
727 void clear_cset_fast_test() {
728 _in_cset_fast_test.clear();
729 }
731 // This is called at the start of either a concurrent cycle or a Full
732 // GC to update the number of old marking cycles started.
733 void increment_old_marking_cycles_started();
735 // This is called at the end of either a concurrent cycle or a Full
736 // GC to update the number of old marking cycles completed. Those two
737 // can happen in a nested fashion, i.e., we start a concurrent
738 // cycle, a Full GC happens half-way through it which ends first,
739 // and then the cycle notices that a Full GC happened and ends
740 // too. The concurrent parameter is a boolean to help us do a bit
741 // tighter consistency checking in the method. If concurrent is
742 // false, the caller is the inner caller in the nesting (i.e., the
743 // Full GC). If concurrent is true, the caller is the outer caller
744 // in this nesting (i.e., the concurrent cycle). Further nesting is
745 // not currently supported. The end of this call also notifies
746 // the FullGCCount_lock in case a Java thread is waiting for a full
747 // GC to happen (e.g., it called System.gc() with
748 // +ExplicitGCInvokesConcurrent).
749 void increment_old_marking_cycles_completed(bool concurrent);
751 unsigned int old_marking_cycles_completed() {
752 return _old_marking_cycles_completed;
753 }
755 void register_concurrent_cycle_start(const Ticks& start_time);
756 void register_concurrent_cycle_end();
757 void trace_heap_after_concurrent_cycle();
759 G1YCType yc_type();
761 G1HRPrinter* hr_printer() { return &_hr_printer; }
763 // Frees a non-humongous region by initializing its contents and
764 // adding it to the free list that's passed as a parameter (this is
765 // usually a local list which will be appended to the master free
766 // list later). The used bytes of freed regions are accumulated in
767 // pre_used. If par is true, the region's RSet will not be freed
768 // up. The assumption is that this will be done later.
769 // The locked parameter indicates if the caller has already taken
770 // care of proper synchronization. This may allow some optimizations.
771 void free_region(HeapRegion* hr,
772 FreeRegionList* free_list,
773 bool par,
774 bool locked = false);
776 // Frees a humongous region by collapsing it into individual regions
777 // and calling free_region() for each of them. The freed regions
778 // will be added to the free list that's passed as a parameter (this
779 // is usually a local list which will be appended to the master free
780 // list later). The used bytes of freed regions are accumulated in
781 // pre_used. If par is true, the region's RSet will not be freed
782 // up. The assumption is that this will be done later.
783 void free_humongous_region(HeapRegion* hr,
784 FreeRegionList* free_list,
785 bool par);
786 protected:
788 // Shrink the garbage-first heap by at most the given size (in bytes!).
789 // (Rounds down to a HeapRegion boundary.)
790 virtual void shrink(size_t expand_bytes);
791 void shrink_helper(size_t expand_bytes);
793 #if TASKQUEUE_STATS
794 static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
795 void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
796 void reset_taskqueue_stats();
797 #endif // TASKQUEUE_STATS
799 // Schedule the VM operation that will do an evacuation pause to
800 // satisfy an allocation request of word_size. *succeeded will
801 // return whether the VM operation was successful (it did do an
802 // evacuation pause) or not (another thread beat us to it or the GC
803 // locker was active). Given that we should not be holding the
804 // Heap_lock when we enter this method, we will pass the
805 // gc_count_before (i.e., total_collections()) as a parameter since
806 // it has to be read while holding the Heap_lock. Currently, both
807 // methods that call do_collection_pause() release the Heap_lock
808 // before the call, so it's easy to read gc_count_before just before.
809 HeapWord* do_collection_pause(size_t word_size,
810 unsigned int gc_count_before,
811 bool* succeeded,
812 GCCause::Cause gc_cause);
814 // The guts of the incremental collection pause, executed by the vm
815 // thread. It returns false if it is unable to do the collection due
816 // to the GC locker being active, true otherwise
817 bool do_collection_pause_at_safepoint(double target_pause_time_ms);
819 // Actually do the work of evacuating the collection set.
820 void evacuate_collection_set(EvacuationInfo& evacuation_info);
822 // The g1 remembered set of the heap.
823 G1RemSet* _g1_rem_set;
825 // A set of cards that cover the objects for which the Rsets should be updated
826 // concurrently after the collection.
827 DirtyCardQueueSet _dirty_card_queue_set;
829 // The closure used to refine a single card.
830 RefineCardTableEntryClosure* _refine_cte_cl;
832 // A function to check the consistency of dirty card logs.
833 void check_ct_logs_at_safepoint();
835 // A DirtyCardQueueSet that is used to hold cards that contain
836 // references into the current collection set. This is used to
837 // update the remembered sets of the regions in the collection
838 // set in the event of an evacuation failure.
839 DirtyCardQueueSet _into_cset_dirty_card_queue_set;
841 // After a collection pause, make the regions in the CS into free
842 // regions.
843 void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info);
845 // Abandon the current collection set without recording policy
846 // statistics or updating free lists.
847 void abandon_collection_set(HeapRegion* cs_head);
849 // Applies "scan_non_heap_roots" to roots outside the heap,
850 // "scan_rs" to roots inside the heap (having done "set_region" to
851 // indicate the region in which the root resides),
852 // and does "scan_metadata" If "scan_rs" is
853 // NULL, then this step is skipped. The "worker_i"
854 // param is for use with parallel roots processing, and should be
855 // the "i" of the calling parallel worker thread's work(i) function.
856 // In the sequential case this param will be ignored.
857 void g1_process_roots(OopClosure* scan_non_heap_roots,
858 OopClosure* scan_non_heap_weak_roots,
859 OopsInHeapRegionClosure* scan_rs,
860 CLDClosure* scan_strong_clds,
861 CLDClosure* scan_weak_clds,
862 CodeBlobClosure* scan_strong_code,
863 uint worker_i);
865 // Notifies all the necessary spaces that the committed space has
866 // been updated (either expanded or shrunk). It should be called
867 // after _g1_storage is updated.
868 void update_committed_space(HeapWord* old_end, HeapWord* new_end);
870 // The concurrent marker (and the thread it runs in.)
871 ConcurrentMark* _cm;
872 ConcurrentMarkThread* _cmThread;
873 bool _mark_in_progress;
875 // The concurrent refiner.
876 ConcurrentG1Refine* _cg1r;
878 // The parallel task queues
879 RefToScanQueueSet *_task_queues;
881 // True iff a evacuation has failed in the current collection.
882 bool _evacuation_failed;
884 EvacuationFailedInfo* _evacuation_failed_info_array;
886 // Failed evacuations cause some logical from-space objects to have
887 // forwarding pointers to themselves. Reset them.
888 void remove_self_forwarding_pointers();
890 // Together, these store an object with a preserved mark, and its mark value.
891 Stack<oop, mtGC> _objs_with_preserved_marks;
892 Stack<markOop, mtGC> _preserved_marks_of_objs;
894 // Preserve the mark of "obj", if necessary, in preparation for its mark
895 // word being overwritten with a self-forwarding-pointer.
896 void preserve_mark_if_necessary(oop obj, markOop m);
898 // The stack of evac-failure objects left to be scanned.
899 GrowableArray<oop>* _evac_failure_scan_stack;
900 // The closure to apply to evac-failure objects.
902 OopsInHeapRegionClosure* _evac_failure_closure;
903 // Set the field above.
904 void
905 set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
906 _evac_failure_closure = evac_failure_closure;
907 }
909 // Push "obj" on the scan stack.
910 void push_on_evac_failure_scan_stack(oop obj);
911 // Process scan stack entries until the stack is empty.
912 void drain_evac_failure_scan_stack();
913 // True iff an invocation of "drain_scan_stack" is in progress; to
914 // prevent unnecessary recursion.
915 bool _drain_in_progress;
917 // Do any necessary initialization for evacuation-failure handling.
918 // "cl" is the closure that will be used to process evac-failure
919 // objects.
920 void init_for_evac_failure(OopsInHeapRegionClosure* cl);
921 // Do any necessary cleanup for evacuation-failure handling data
922 // structures.
923 void finalize_for_evac_failure();
925 // An attempt to evacuate "obj" has failed; take necessary steps.
926 oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj);
927 void handle_evacuation_failure_common(oop obj, markOop m);
929 #ifndef PRODUCT
930 // Support for forcing evacuation failures. Analogous to
931 // PromotionFailureALot for the other collectors.
933 // Records whether G1EvacuationFailureALot should be in effect
934 // for the current GC
935 bool _evacuation_failure_alot_for_current_gc;
937 // Used to record the GC number for interval checking when
938 // determining whether G1EvaucationFailureALot is in effect
939 // for the current GC.
940 size_t _evacuation_failure_alot_gc_number;
942 // Count of the number of evacuations between failures.
943 volatile size_t _evacuation_failure_alot_count;
945 // Set whether G1EvacuationFailureALot should be in effect
946 // for the current GC (based upon the type of GC and which
947 // command line flags are set);
948 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
949 bool during_initial_mark,
950 bool during_marking);
952 inline void set_evacuation_failure_alot_for_current_gc();
954 // Return true if it's time to cause an evacuation failure.
955 inline bool evacuation_should_fail();
957 // Reset the G1EvacuationFailureALot counters. Should be called at
958 // the end of an evacuation pause in which an evacuation failure occurred.
959 inline void reset_evacuation_should_fail();
960 #endif // !PRODUCT
962 // ("Weak") Reference processing support.
963 //
964 // G1 has 2 instances of the reference processor class. One
965 // (_ref_processor_cm) handles reference object discovery
966 // and subsequent processing during concurrent marking cycles.
967 //
968 // The other (_ref_processor_stw) handles reference object
969 // discovery and processing during full GCs and incremental
970 // evacuation pauses.
971 //
972 // During an incremental pause, reference discovery will be
973 // temporarily disabled for _ref_processor_cm and will be
974 // enabled for _ref_processor_stw. At the end of the evacuation
975 // pause references discovered by _ref_processor_stw will be
976 // processed and discovery will be disabled. The previous
977 // setting for reference object discovery for _ref_processor_cm
978 // will be re-instated.
979 //
980 // At the start of marking:
981 // * Discovery by the CM ref processor is verified to be inactive
982 // and it's discovered lists are empty.
983 // * Discovery by the CM ref processor is then enabled.
984 //
985 // At the end of marking:
986 // * Any references on the CM ref processor's discovered
987 // lists are processed (possibly MT).
988 //
989 // At the start of full GC we:
990 // * Disable discovery by the CM ref processor and
991 // empty CM ref processor's discovered lists
992 // (without processing any entries).
993 // * Verify that the STW ref processor is inactive and it's
994 // discovered lists are empty.
995 // * Temporarily set STW ref processor discovery as single threaded.
996 // * Temporarily clear the STW ref processor's _is_alive_non_header
997 // field.
998 // * Finally enable discovery by the STW ref processor.
999 //
1000 // The STW ref processor is used to record any discovered
1001 // references during the full GC.
1002 //
1003 // At the end of a full GC we:
1004 // * Enqueue any reference objects discovered by the STW ref processor
1005 // that have non-live referents. This has the side-effect of
1006 // making the STW ref processor inactive by disabling discovery.
1007 // * Verify that the CM ref processor is still inactive
1008 // and no references have been placed on it's discovered
1009 // lists (also checked as a precondition during initial marking).
1011 // The (stw) reference processor...
1012 ReferenceProcessor* _ref_processor_stw;
1014 STWGCTimer* _gc_timer_stw;
1015 ConcurrentGCTimer* _gc_timer_cm;
1017 G1OldTracer* _gc_tracer_cm;
1018 G1NewTracer* _gc_tracer_stw;
1020 // During reference object discovery, the _is_alive_non_header
1021 // closure (if non-null) is applied to the referent object to
1022 // determine whether the referent is live. If so then the
1023 // reference object does not need to be 'discovered' and can
1024 // be treated as a regular oop. This has the benefit of reducing
1025 // the number of 'discovered' reference objects that need to
1026 // be processed.
1027 //
1028 // Instance of the is_alive closure for embedding into the
1029 // STW reference processor as the _is_alive_non_header field.
1030 // Supplying a value for the _is_alive_non_header field is
1031 // optional but doing so prevents unnecessary additions to
1032 // the discovered lists during reference discovery.
1033 G1STWIsAliveClosure _is_alive_closure_stw;
1035 // The (concurrent marking) reference processor...
1036 ReferenceProcessor* _ref_processor_cm;
1038 // Instance of the concurrent mark is_alive closure for embedding
1039 // into the Concurrent Marking reference processor as the
1040 // _is_alive_non_header field. Supplying a value for the
1041 // _is_alive_non_header field is optional but doing so prevents
1042 // unnecessary additions to the discovered lists during reference
1043 // discovery.
1044 G1CMIsAliveClosure _is_alive_closure_cm;
1046 // Cache used by G1CollectedHeap::start_cset_region_for_worker().
1047 HeapRegion** _worker_cset_start_region;
1049 // Time stamp to validate the regions recorded in the cache
1050 // used by G1CollectedHeap::start_cset_region_for_worker().
1051 // The heap region entry for a given worker is valid iff
1052 // the associated time stamp value matches the current value
1053 // of G1CollectedHeap::_gc_time_stamp.
1054 unsigned int* _worker_cset_start_region_time_stamp;
1056 enum G1H_process_roots_tasks {
1057 G1H_PS_filter_satb_buffers,
1058 G1H_PS_refProcessor_oops_do,
1059 // Leave this one last.
1060 G1H_PS_NumElements
1061 };
1063 SubTasksDone* _process_strong_tasks;
1065 volatile bool _free_regions_coming;
1067 public:
1069 SubTasksDone* process_strong_tasks() { return _process_strong_tasks; }
1071 void set_refine_cte_cl_concurrency(bool concurrent);
1073 RefToScanQueue *task_queue(int i) const;
1075 // A set of cards where updates happened during the GC
1076 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
1078 // A DirtyCardQueueSet that is used to hold cards that contain
1079 // references into the current collection set. This is used to
1080 // update the remembered sets of the regions in the collection
1081 // set in the event of an evacuation failure.
1082 DirtyCardQueueSet& into_cset_dirty_card_queue_set()
1083 { return _into_cset_dirty_card_queue_set; }
1085 // Create a G1CollectedHeap with the specified policy.
1086 // Must call the initialize method afterwards.
1087 // May not return if something goes wrong.
1088 G1CollectedHeap(G1CollectorPolicy* policy);
1090 // Initialize the G1CollectedHeap to have the initial and
1091 // maximum sizes and remembered and barrier sets
1092 // specified by the policy object.
1093 jint initialize();
1095 virtual void stop();
1097 // Return the (conservative) maximum heap alignment for any G1 heap
1098 static size_t conservative_max_heap_alignment();
1100 // Initialize weak reference processing.
1101 virtual void ref_processing_init();
1103 void set_par_threads(uint t) {
1104 SharedHeap::set_par_threads(t);
1105 // Done in SharedHeap but oddly there are
1106 // two _process_strong_tasks's in a G1CollectedHeap
1107 // so do it here too.
1108 _process_strong_tasks->set_n_threads(t);
1109 }
1111 // Set _n_par_threads according to a policy TBD.
1112 void set_par_threads();
1114 void set_n_termination(int t) {
1115 _process_strong_tasks->set_n_threads(t);
1116 }
1118 virtual CollectedHeap::Name kind() const {
1119 return CollectedHeap::G1CollectedHeap;
1120 }
1122 // The current policy object for the collector.
1123 G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1125 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); }
1127 // Adaptive size policy. No such thing for g1.
1128 virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1130 // The rem set and barrier set.
1131 G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1133 unsigned get_gc_time_stamp() {
1134 return _gc_time_stamp;
1135 }
1137 inline void reset_gc_time_stamp();
1139 void check_gc_time_stamps() PRODUCT_RETURN;
1141 inline void increment_gc_time_stamp();
1143 // Reset the given region's GC timestamp. If it's starts humongous,
1144 // also reset the GC timestamp of its corresponding
1145 // continues humongous regions too.
1146 void reset_gc_time_stamps(HeapRegion* hr);
1148 void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1149 DirtyCardQueue* into_cset_dcq,
1150 bool concurrent, uint worker_i);
1152 // The shared block offset table array.
1153 G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1155 // Reference Processing accessors
1157 // The STW reference processor....
1158 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1160 // The Concurrent Marking reference processor...
1161 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1163 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1164 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1166 virtual size_t capacity() const;
1167 virtual size_t used() const;
1168 // This should be called when we're not holding the heap lock. The
1169 // result might be a bit inaccurate.
1170 size_t used_unlocked() const;
1171 size_t recalculate_used() const;
1173 // These virtual functions do the actual allocation.
1174 // Some heaps may offer a contiguous region for shared non-blocking
1175 // allocation, via inlined code (by exporting the address of the top and
1176 // end fields defining the extent of the contiguous allocation region.)
1177 // But G1CollectedHeap doesn't yet support this.
1179 // Return an estimate of the maximum allocation that could be performed
1180 // without triggering any collection or expansion activity. In a
1181 // generational collector, for example, this is probably the largest
1182 // allocation that could be supported (without expansion) in the youngest
1183 // generation. It is "unsafe" because no locks are taken; the result
1184 // should be treated as an approximation, not a guarantee, for use in
1185 // heuristic resizing decisions.
1186 virtual size_t unsafe_max_alloc();
1188 virtual bool is_maximal_no_gc() const {
1189 return _g1_storage.uncommitted_size() == 0;
1190 }
1192 // The total number of regions in the heap.
1193 uint n_regions() const { return _hrs.length(); }
1195 // The max number of regions in the heap.
1196 uint max_regions() const { return _hrs.max_length(); }
1198 // The number of regions that are completely free.
1199 uint free_regions() const { return _free_list.length(); }
1201 // The number of regions that are not completely free.
1202 uint used_regions() const { return n_regions() - free_regions(); }
1204 // The number of regions available for "regular" expansion.
1205 uint expansion_regions() const { return _expansion_regions; }
1207 // Factory method for HeapRegion instances. It will return NULL if
1208 // the allocation fails.
1209 HeapRegion* new_heap_region(uint hrs_index, HeapWord* bottom);
1211 void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1212 void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1213 void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1214 void verify_dirty_young_regions() PRODUCT_RETURN;
1216 #ifndef PRODUCT
1217 // Make sure that the given bitmap has no marked objects in the
1218 // range [from,limit). If it does, print an error message and return
1219 // false. Otherwise, just return true. bitmap_name should be "prev"
1220 // or "next".
1221 bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
1222 HeapWord* from, HeapWord* limit);
1224 // Verify that the prev / next bitmap range [tams,end) for the given
1225 // region has no marks. Return true if all is well, false if errors
1226 // are detected.
1227 bool verify_bitmaps(const char* caller, HeapRegion* hr);
1228 #endif // PRODUCT
1230 // If G1VerifyBitmaps is set, verify that the marking bitmaps for
1231 // the given region do not have any spurious marks. If errors are
1232 // detected, print appropriate error messages and crash.
1233 void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN;
1235 // If G1VerifyBitmaps is set, verify that the marking bitmaps do not
1236 // have any spurious marks. If errors are detected, print
1237 // appropriate error messages and crash.
1238 void check_bitmaps(const char* caller) PRODUCT_RETURN;
1240 // verify_region_sets() performs verification over the region
1241 // lists. It will be compiled in the product code to be used when
1242 // necessary (i.e., during heap verification).
1243 void verify_region_sets();
1245 // verify_region_sets_optional() is planted in the code for
1246 // list verification in non-product builds (and it can be enabled in
1247 // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1).
1248 #if HEAP_REGION_SET_FORCE_VERIFY
1249 void verify_region_sets_optional() {
1250 verify_region_sets();
1251 }
1252 #else // HEAP_REGION_SET_FORCE_VERIFY
1253 void verify_region_sets_optional() { }
1254 #endif // HEAP_REGION_SET_FORCE_VERIFY
1256 #ifdef ASSERT
1257 bool is_on_master_free_list(HeapRegion* hr) {
1258 return hr->containing_set() == &_free_list;
1259 }
1260 #endif // ASSERT
1262 // Wrapper for the region list operations that can be called from
1263 // methods outside this class.
1265 void secondary_free_list_add(FreeRegionList* list) {
1266 _secondary_free_list.add_ordered(list);
1267 }
1269 void append_secondary_free_list() {
1270 _free_list.add_ordered(&_secondary_free_list);
1271 }
1273 void append_secondary_free_list_if_not_empty_with_lock() {
1274 // If the secondary free list looks empty there's no reason to
1275 // take the lock and then try to append it.
1276 if (!_secondary_free_list.is_empty()) {
1277 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1278 append_secondary_free_list();
1279 }
1280 }
1282 inline void old_set_remove(HeapRegion* hr);
1284 size_t non_young_capacity_bytes() {
1285 return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1286 }
1288 void set_free_regions_coming();
1289 void reset_free_regions_coming();
1290 bool free_regions_coming() { return _free_regions_coming; }
1291 void wait_while_free_regions_coming();
1293 // Determine whether the given region is one that we are using as an
1294 // old GC alloc region.
1295 bool is_old_gc_alloc_region(HeapRegion* hr) {
1296 return hr == _retained_old_gc_alloc_region;
1297 }
1299 // Perform a collection of the heap; intended for use in implementing
1300 // "System.gc". This probably implies as full a collection as the
1301 // "CollectedHeap" supports.
1302 virtual void collect(GCCause::Cause cause);
1304 // The same as above but assume that the caller holds the Heap_lock.
1305 void collect_locked(GCCause::Cause cause);
1307 // True iff an evacuation has failed in the most-recent collection.
1308 bool evacuation_failed() { return _evacuation_failed; }
1310 void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed);
1311 void prepend_to_freelist(FreeRegionList* list);
1312 void decrement_summary_bytes(size_t bytes);
1314 // Returns "TRUE" iff "p" points into the committed areas of the heap.
1315 virtual bool is_in(const void* p) const;
1317 // Return "TRUE" iff the given object address is within the collection
1318 // set. Slow implementation.
1319 inline bool obj_in_cs(oop obj);
1321 inline bool is_in_cset(oop obj);
1323 inline bool is_in_cset_or_humongous(const oop obj);
1325 enum in_cset_state_t {
1326 InNeither, // neither in collection set nor humongous
1327 InCSet, // region is in collection set only
1328 IsHumongous // region is a humongous start region
1329 };
1330 private:
1331 // Instances of this class are used for quick tests on whether a reference points
1332 // into the collection set or is a humongous object (points into a humongous
1333 // object).
1334 // Each of the array's elements denotes whether the corresponding region is in
1335 // the collection set or a humongous region.
1336 // We use this to quickly reclaim humongous objects: by making a humongous region
1337 // succeed this test, we sort-of add it to the collection set. During the reference
1338 // iteration closures, when we see a humongous region, we simply mark it as
1339 // referenced, i.e. live.
1340 class G1FastCSetBiasedMappedArray : public G1BiasedMappedArray<char> {
1341 protected:
1342 char default_value() const { return G1CollectedHeap::InNeither; }
1343 public:
1344 void set_humongous(uintptr_t index) {
1345 assert(get_by_index(index) != InCSet, "Should not overwrite InCSet values");
1346 set_by_index(index, G1CollectedHeap::IsHumongous);
1347 }
1349 void clear_humongous(uintptr_t index) {
1350 set_by_index(index, G1CollectedHeap::InNeither);
1351 }
1353 void set_in_cset(uintptr_t index) {
1354 assert(get_by_index(index) != G1CollectedHeap::IsHumongous, "Should not overwrite IsHumongous value");
1355 set_by_index(index, G1CollectedHeap::InCSet);
1356 }
1358 bool is_in_cset_or_humongous(HeapWord* addr) const { return get_by_address(addr) != G1CollectedHeap::InNeither; }
1359 bool is_in_cset(HeapWord* addr) const { return get_by_address(addr) == G1CollectedHeap::InCSet; }
1360 G1CollectedHeap::in_cset_state_t at(HeapWord* addr) const { return (G1CollectedHeap::in_cset_state_t)get_by_address(addr); }
1361 void clear() { G1BiasedMappedArray<char>::clear(); }
1362 };
1364 // This array is used for a quick test on whether a reference points into
1365 // the collection set or not. Each of the array's elements denotes whether the
1366 // corresponding region is in the collection set or not.
1367 G1FastCSetBiasedMappedArray _in_cset_fast_test;
1369 public:
1371 inline in_cset_state_t in_cset_state(const oop obj);
1373 // Return "TRUE" iff the given object address is in the reserved
1374 // region of g1.
1375 bool is_in_g1_reserved(const void* p) const {
1376 return _g1_reserved.contains(p);
1377 }
1379 // Returns a MemRegion that corresponds to the space that has been
1380 // reserved for the heap
1381 MemRegion g1_reserved() {
1382 return _g1_reserved;
1383 }
1385 // Returns a MemRegion that corresponds to the space that has been
1386 // committed in the heap
1387 MemRegion g1_committed() {
1388 return _g1_committed;
1389 }
1391 virtual bool is_in_closed_subset(const void* p) const;
1393 G1SATBCardTableModRefBS* g1_barrier_set() {
1394 return (G1SATBCardTableModRefBS*) barrier_set();
1395 }
1397 // This resets the card table to all zeros. It is used after
1398 // a collection pause which used the card table to claim cards.
1399 void cleanUpCardTable();
1401 // Iteration functions.
1403 // Iterate over all the ref-containing fields of all objects, calling
1404 // "cl.do_oop" on each.
1405 virtual void oop_iterate(ExtendedOopClosure* cl);
1407 // Same as above, restricted to a memory region.
1408 void oop_iterate(MemRegion mr, ExtendedOopClosure* cl);
1410 // Iterate over all objects, calling "cl.do_object" on each.
1411 virtual void object_iterate(ObjectClosure* cl);
1413 virtual void safe_object_iterate(ObjectClosure* cl) {
1414 object_iterate(cl);
1415 }
1417 // Iterate over all spaces in use in the heap, in ascending address order.
1418 virtual void space_iterate(SpaceClosure* cl);
1420 // Iterate over heap regions, in address order, terminating the
1421 // iteration early if the "doHeapRegion" method returns "true".
1422 void heap_region_iterate(HeapRegionClosure* blk) const;
1424 // Return the region with the given index. It assumes the index is valid.
1425 inline HeapRegion* region_at(uint index) const;
1427 // Calculate the region index of the given address. Given address must be
1428 // within the heap.
1429 inline uint addr_to_region(HeapWord* addr) const;
1431 // Divide the heap region sequence into "chunks" of some size (the number
1432 // of regions divided by the number of parallel threads times some
1433 // overpartition factor, currently 4). Assumes that this will be called
1434 // in parallel by ParallelGCThreads worker threads with discinct worker
1435 // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel
1436 // calls will use the same "claim_value", and that that claim value is
1437 // different from the claim_value of any heap region before the start of
1438 // the iteration. Applies "blk->doHeapRegion" to each of the regions, by
1439 // attempting to claim the first region in each chunk, and, if
1440 // successful, applying the closure to each region in the chunk (and
1441 // setting the claim value of the second and subsequent regions of the
1442 // chunk.) For now requires that "doHeapRegion" always returns "false",
1443 // i.e., that a closure never attempt to abort a traversal.
1444 void heap_region_par_iterate_chunked(HeapRegionClosure* blk,
1445 uint worker,
1446 uint no_of_par_workers,
1447 jint claim_value);
1449 // It resets all the region claim values to the default.
1450 void reset_heap_region_claim_values();
1452 // Resets the claim values of regions in the current
1453 // collection set to the default.
1454 void reset_cset_heap_region_claim_values();
1456 #ifdef ASSERT
1457 bool check_heap_region_claim_values(jint claim_value);
1459 // Same as the routine above but only checks regions in the
1460 // current collection set.
1461 bool check_cset_heap_region_claim_values(jint claim_value);
1462 #endif // ASSERT
1464 // Clear the cached cset start regions and (more importantly)
1465 // the time stamps. Called when we reset the GC time stamp.
1466 void clear_cset_start_regions();
1468 // Given the id of a worker, obtain or calculate a suitable
1469 // starting region for iterating over the current collection set.
1470 HeapRegion* start_cset_region_for_worker(uint worker_i);
1472 // This is a convenience method that is used by the
1473 // HeapRegionIterator classes to calculate the starting region for
1474 // each worker so that they do not all start from the same region.
1475 HeapRegion* start_region_for_worker(uint worker_i, uint no_of_par_workers);
1477 // Iterate over the regions (if any) in the current collection set.
1478 void collection_set_iterate(HeapRegionClosure* blk);
1480 // As above but starting from region r
1481 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1483 HeapRegion* next_compaction_region(const HeapRegion* from) const;
1485 // A CollectedHeap will contain some number of spaces. This finds the
1486 // space containing a given address, or else returns NULL.
1487 virtual Space* space_containing(const void* addr) const;
1489 // A G1CollectedHeap will contain some number of heap regions. This
1490 // finds the region containing a given address, or else returns NULL.
1491 template <class T>
1492 inline HeapRegion* heap_region_containing(const T addr) const;
1494 // Like the above, but requires "addr" to be in the heap (to avoid a
1495 // null-check), and unlike the above, may return an continuing humongous
1496 // region.
1497 template <class T>
1498 inline HeapRegion* heap_region_containing_raw(const T addr) const;
1500 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1501 // each address in the (reserved) heap is a member of exactly
1502 // one block. The defining characteristic of a block is that it is
1503 // possible to find its size, and thus to progress forward to the next
1504 // block. (Blocks may be of different sizes.) Thus, blocks may
1505 // represent Java objects, or they might be free blocks in a
1506 // free-list-based heap (or subheap), as long as the two kinds are
1507 // distinguishable and the size of each is determinable.
1509 // Returns the address of the start of the "block" that contains the
1510 // address "addr". We say "blocks" instead of "object" since some heaps
1511 // may not pack objects densely; a chunk may either be an object or a
1512 // non-object.
1513 virtual HeapWord* block_start(const void* addr) const;
1515 // Requires "addr" to be the start of a chunk, and returns its size.
1516 // "addr + size" is required to be the start of a new chunk, or the end
1517 // of the active area of the heap.
1518 virtual size_t block_size(const HeapWord* addr) const;
1520 // Requires "addr" to be the start of a block, and returns "TRUE" iff
1521 // the block is an object.
1522 virtual bool block_is_obj(const HeapWord* addr) const;
1524 // Does this heap support heap inspection? (+PrintClassHistogram)
1525 virtual bool supports_heap_inspection() const { return true; }
1527 // Section on thread-local allocation buffers (TLABs)
1528 // See CollectedHeap for semantics.
1530 bool supports_tlab_allocation() const;
1531 size_t tlab_capacity(Thread* ignored) const;
1532 size_t tlab_used(Thread* ignored) const;
1533 size_t max_tlab_size() const;
1534 size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1536 // Can a compiler initialize a new object without store barriers?
1537 // This permission only extends from the creation of a new object
1538 // via a TLAB up to the first subsequent safepoint. If such permission
1539 // is granted for this heap type, the compiler promises to call
1540 // defer_store_barrier() below on any slow path allocation of
1541 // a new object for which such initializing store barriers will
1542 // have been elided. G1, like CMS, allows this, but should be
1543 // ready to provide a compensating write barrier as necessary
1544 // if that storage came out of a non-young region. The efficiency
1545 // of this implementation depends crucially on being able to
1546 // answer very efficiently in constant time whether a piece of
1547 // storage in the heap comes from a young region or not.
1548 // See ReduceInitialCardMarks.
1549 virtual bool can_elide_tlab_store_barriers() const {
1550 return true;
1551 }
1553 virtual bool card_mark_must_follow_store() const {
1554 return true;
1555 }
1557 inline bool is_in_young(const oop obj);
1559 #ifdef ASSERT
1560 virtual bool is_in_partial_collection(const void* p);
1561 #endif
1563 virtual bool is_scavengable(const void* addr);
1565 // We don't need barriers for initializing stores to objects
1566 // in the young gen: for the SATB pre-barrier, there is no
1567 // pre-value that needs to be remembered; for the remembered-set
1568 // update logging post-barrier, we don't maintain remembered set
1569 // information for young gen objects.
1570 virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1572 // Returns "true" iff the given word_size is "very large".
1573 static bool isHumongous(size_t word_size) {
1574 // Note this has to be strictly greater-than as the TLABs
1575 // are capped at the humongous thresold and we want to
1576 // ensure that we don't try to allocate a TLAB as
1577 // humongous and that we don't allocate a humongous
1578 // object in a TLAB.
1579 return word_size > _humongous_object_threshold_in_words;
1580 }
1582 // Update mod union table with the set of dirty cards.
1583 void updateModUnion();
1585 // Set the mod union bits corresponding to the given memRegion. Note
1586 // that this is always a safe operation, since it doesn't clear any
1587 // bits.
1588 void markModUnionRange(MemRegion mr);
1590 // Records the fact that a marking phase is no longer in progress.
1591 void set_marking_complete() {
1592 _mark_in_progress = false;
1593 }
1594 void set_marking_started() {
1595 _mark_in_progress = true;
1596 }
1597 bool mark_in_progress() {
1598 return _mark_in_progress;
1599 }
1601 // Print the maximum heap capacity.
1602 virtual size_t max_capacity() const;
1604 virtual jlong millis_since_last_gc();
1607 // Convenience function to be used in situations where the heap type can be
1608 // asserted to be this type.
1609 static G1CollectedHeap* heap();
1611 void set_region_short_lived_locked(HeapRegion* hr);
1612 // add appropriate methods for any other surv rate groups
1614 YoungList* young_list() const { return _young_list; }
1616 // debugging
1617 bool check_young_list_well_formed() {
1618 return _young_list->check_list_well_formed();
1619 }
1621 bool check_young_list_empty(bool check_heap,
1622 bool check_sample = true);
1624 // *** Stuff related to concurrent marking. It's not clear to me that so
1625 // many of these need to be public.
1627 // The functions below are helper functions that a subclass of
1628 // "CollectedHeap" can use in the implementation of its virtual
1629 // functions.
1630 // This performs a concurrent marking of the live objects in a
1631 // bitmap off to the side.
1632 void doConcurrentMark();
1634 bool isMarkedPrev(oop obj) const;
1635 bool isMarkedNext(oop obj) const;
1637 // Determine if an object is dead, given the object and also
1638 // the region to which the object belongs. An object is dead
1639 // iff a) it was not allocated since the last mark and b) it
1640 // is not marked.
1642 bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1643 return
1644 !hr->obj_allocated_since_prev_marking(obj) &&
1645 !isMarkedPrev(obj);
1646 }
1648 // This function returns true when an object has been
1649 // around since the previous marking and hasn't yet
1650 // been marked during this marking.
1652 bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1653 return
1654 !hr->obj_allocated_since_next_marking(obj) &&
1655 !isMarkedNext(obj);
1656 }
1658 // Determine if an object is dead, given only the object itself.
1659 // This will find the region to which the object belongs and
1660 // then call the region version of the same function.
1662 // Added if it is NULL it isn't dead.
1664 inline bool is_obj_dead(const oop obj) const;
1666 inline bool is_obj_ill(const oop obj) const;
1668 bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1669 HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1670 bool is_marked(oop obj, VerifyOption vo);
1671 const char* top_at_mark_start_str(VerifyOption vo);
1673 ConcurrentMark* concurrent_mark() const { return _cm; }
1675 // Refinement
1677 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1679 // The dirty cards region list is used to record a subset of regions
1680 // whose cards need clearing. The list if populated during the
1681 // remembered set scanning and drained during the card table
1682 // cleanup. Although the methods are reentrant, population/draining
1683 // phases must not overlap. For synchronization purposes the last
1684 // element on the list points to itself.
1685 HeapRegion* _dirty_cards_region_list;
1686 void push_dirty_cards_region(HeapRegion* hr);
1687 HeapRegion* pop_dirty_cards_region();
1689 // Optimized nmethod scanning support routines
1691 // Register the given nmethod with the G1 heap
1692 virtual void register_nmethod(nmethod* nm);
1694 // Unregister the given nmethod from the G1 heap
1695 virtual void unregister_nmethod(nmethod* nm);
1697 // Migrate the nmethods in the code root lists of the regions
1698 // in the collection set to regions in to-space. In the event
1699 // of an evacuation failure, nmethods that reference objects
1700 // that were not successfullly evacuated are not migrated.
1701 void migrate_strong_code_roots();
1703 // Free up superfluous code root memory.
1704 void purge_code_root_memory();
1706 // Rebuild the stong code root lists for each region
1707 // after a full GC
1708 void rebuild_strong_code_roots();
1710 // Delete entries for dead interned string and clean up unreferenced symbols
1711 // in symbol table, possibly in parallel.
1712 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1714 // Parallel phase of unloading/cleaning after G1 concurrent mark.
1715 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred);
1717 // Redirty logged cards in the refinement queue.
1718 void redirty_logged_cards();
1719 // Verification
1721 // The following is just to alert the verification code
1722 // that a full collection has occurred and that the
1723 // remembered sets are no longer up to date.
1724 bool _full_collection;
1725 void set_full_collection() { _full_collection = true;}
1726 void clear_full_collection() {_full_collection = false;}
1727 bool full_collection() {return _full_collection;}
1729 // Perform any cleanup actions necessary before allowing a verification.
1730 virtual void prepare_for_verify();
1732 // Perform verification.
1734 // vo == UsePrevMarking -> use "prev" marking information,
1735 // vo == UseNextMarking -> use "next" marking information
1736 // vo == UseMarkWord -> use the mark word in the object header
1737 //
1738 // NOTE: Only the "prev" marking information is guaranteed to be
1739 // consistent most of the time, so most calls to this should use
1740 // vo == UsePrevMarking.
1741 // Currently, there is only one case where this is called with
1742 // vo == UseNextMarking, which is to verify the "next" marking
1743 // information at the end of remark.
1744 // Currently there is only one place where this is called with
1745 // vo == UseMarkWord, which is to verify the marking during a
1746 // full GC.
1747 void verify(bool silent, VerifyOption vo);
1749 // Override; it uses the "prev" marking information
1750 virtual void verify(bool silent);
1752 // The methods below are here for convenience and dispatch the
1753 // appropriate method depending on value of the given VerifyOption
1754 // parameter. The values for that parameter, and their meanings,
1755 // are the same as those above.
1757 bool is_obj_dead_cond(const oop obj,
1758 const HeapRegion* hr,
1759 const VerifyOption vo) const;
1761 bool is_obj_dead_cond(const oop obj,
1762 const VerifyOption vo) const;
1764 // Printing
1766 virtual void print_on(outputStream* st) const;
1767 virtual void print_extended_on(outputStream* st) const;
1768 virtual void print_on_error(outputStream* st) const;
1770 virtual void print_gc_threads_on(outputStream* st) const;
1771 virtual void gc_threads_do(ThreadClosure* tc) const;
1773 // Override
1774 void print_tracing_info() const;
1776 // The following two methods are helpful for debugging RSet issues.
1777 void print_cset_rsets() PRODUCT_RETURN;
1778 void print_all_rsets() PRODUCT_RETURN;
1780 public:
1781 size_t pending_card_num();
1782 size_t cards_scanned();
1784 protected:
1785 size_t _max_heap_capacity;
1786 };
1788 class G1ParGCAllocBuffer: public ParGCAllocBuffer {
1789 private:
1790 bool _retired;
1792 public:
1793 G1ParGCAllocBuffer(size_t gclab_word_size);
1794 virtual ~G1ParGCAllocBuffer() {
1795 guarantee(_retired, "Allocation buffer has not been retired");
1796 }
1798 virtual void set_buf(HeapWord* buf) {
1799 ParGCAllocBuffer::set_buf(buf);
1800 _retired = false;
1801 }
1803 virtual void retire(bool end_of_gc, bool retain) {
1804 if (_retired) {
1805 return;
1806 }
1807 ParGCAllocBuffer::retire(end_of_gc, retain);
1808 _retired = true;
1809 }
1810 };
1812 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP