Tue, 26 Aug 2014 10:28:43 +0200
8029524: Remove unsused method CollectedHeap::unsafe_max_alloc()
Reviewed-by: pliden, jmasa
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 */) { }
187 // This specialization of release() makes sure that the last card that has been
188 // allocated into has been completely filled by a dummy object.
189 // This avoids races when remembered set scanning wants to update the BOT of the
190 // last card in the retained old gc alloc region, and allocation threads
191 // allocating into that card at the same time.
192 virtual HeapRegion* release();
193 };
195 // The G1 STW is alive closure.
196 // An instance is embedded into the G1CH and used as the
197 // (optional) _is_alive_non_header closure in the STW
198 // reference processor. It is also extensively used during
199 // reference processing during STW evacuation pauses.
200 class G1STWIsAliveClosure: public BoolObjectClosure {
201 G1CollectedHeap* _g1;
202 public:
203 G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
204 bool do_object_b(oop p);
205 };
207 class RefineCardTableEntryClosure;
209 class G1RegionMappingChangedListener : public G1MappingChangedListener {
210 private:
211 void reset_from_card_cache(uint start_idx, size_t num_regions);
212 public:
213 virtual void on_commit(uint start_idx, size_t num_regions);
214 };
216 class G1CollectedHeap : public SharedHeap {
217 friend class VM_CollectForMetadataAllocation;
218 friend class VM_G1CollectForAllocation;
219 friend class VM_G1CollectFull;
220 friend class VM_G1IncCollectionPause;
221 friend class VMStructs;
222 friend class MutatorAllocRegion;
223 friend class SurvivorGCAllocRegion;
224 friend class OldGCAllocRegion;
226 // Closures used in implementation.
227 template <G1Barrier barrier, G1Mark do_mark_object>
228 friend class G1ParCopyClosure;
229 friend class G1IsAliveClosure;
230 friend class G1EvacuateFollowersClosure;
231 friend class G1ParScanThreadState;
232 friend class G1ParScanClosureSuper;
233 friend class G1ParEvacuateFollowersClosure;
234 friend class G1ParTask;
235 friend class G1FreeGarbageRegionClosure;
236 friend class RefineCardTableEntryClosure;
237 friend class G1PrepareCompactClosure;
238 friend class RegionSorter;
239 friend class RegionResetter;
240 friend class CountRCClosure;
241 friend class EvacPopObjClosure;
242 friend class G1ParCleanupCTTask;
244 friend class G1FreeHumongousRegionClosure;
245 // Other related classes.
246 friend class G1MarkSweep;
248 private:
249 // The one and only G1CollectedHeap, so static functions can find it.
250 static G1CollectedHeap* _g1h;
252 static size_t _humongous_object_threshold_in_words;
254 // The secondary free list which contains regions that have been
255 // freed up during the cleanup process. This will be appended to
256 // the master free list when appropriate.
257 FreeRegionList _secondary_free_list;
259 // It keeps track of the old regions.
260 HeapRegionSet _old_set;
262 // It keeps track of the humongous regions.
263 HeapRegionSet _humongous_set;
265 void clear_humongous_is_live_table();
266 void eagerly_reclaim_humongous_regions();
268 // The number of regions we could create by expansion.
269 uint _expansion_regions;
271 // The block offset table for the G1 heap.
272 G1BlockOffsetSharedArray* _bot_shared;
274 // Tears down the region sets / lists so that they are empty and the
275 // regions on the heap do not belong to a region set / list. The
276 // only exception is the humongous set which we leave unaltered. If
277 // free_list_only is true, it will only tear down the master free
278 // list. It is called before a Full GC (free_list_only == false) or
279 // before heap shrinking (free_list_only == true).
280 void tear_down_region_sets(bool free_list_only);
282 // Rebuilds the region sets / lists so that they are repopulated to
283 // reflect the contents of the heap. The only exception is the
284 // humongous set which was not torn down in the first place. If
285 // free_list_only is true, it will only rebuild the master free
286 // list. It is called after a Full GC (free_list_only == false) or
287 // after heap shrinking (free_list_only == true).
288 void rebuild_region_sets(bool free_list_only);
290 // Callback for region mapping changed events.
291 G1RegionMappingChangedListener _listener;
293 // The sequence of all heap regions in the heap.
294 HeapRegionSeq _hrs;
296 // Alloc region used to satisfy mutator allocation requests.
297 MutatorAllocRegion _mutator_alloc_region;
299 // Alloc region used to satisfy allocation requests by the GC for
300 // survivor objects.
301 SurvivorGCAllocRegion _survivor_gc_alloc_region;
303 // PLAB sizing policy for survivors.
304 PLABStats _survivor_plab_stats;
306 // Alloc region used to satisfy allocation requests by the GC for
307 // old objects.
308 OldGCAllocRegion _old_gc_alloc_region;
310 // PLAB sizing policy for tenured objects.
311 PLABStats _old_plab_stats;
313 PLABStats* stats_for_purpose(GCAllocPurpose purpose) {
314 PLABStats* stats = NULL;
316 switch (purpose) {
317 case GCAllocForSurvived:
318 stats = &_survivor_plab_stats;
319 break;
320 case GCAllocForTenured:
321 stats = &_old_plab_stats;
322 break;
323 default:
324 assert(false, "unrecognized GCAllocPurpose");
325 }
327 return stats;
328 }
330 // The last old region we allocated to during the last GC.
331 // Typically, it is not full so we should re-use it during the next GC.
332 HeapRegion* _retained_old_gc_alloc_region;
334 // It specifies whether we should attempt to expand the heap after a
335 // region allocation failure. If heap expansion fails we set this to
336 // false so that we don't re-attempt the heap expansion (it's likely
337 // that subsequent expansion attempts will also fail if one fails).
338 // Currently, it is only consulted during GC and it's reset at the
339 // start of each GC.
340 bool _expand_heap_after_alloc_failure;
342 // It resets the mutator alloc region before new allocations can take place.
343 void init_mutator_alloc_region();
345 // It releases the mutator alloc region.
346 void release_mutator_alloc_region();
348 // It initializes the GC alloc regions at the start of a GC.
349 void init_gc_alloc_regions(EvacuationInfo& evacuation_info);
351 // Setup the retained old gc alloc region as the currrent old gc alloc region.
352 void use_retained_old_gc_alloc_region(EvacuationInfo& evacuation_info);
354 // It releases the GC alloc regions at the end of a GC.
355 void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info);
357 // It does any cleanup that needs to be done on the GC alloc regions
358 // before a Full GC.
359 void abandon_gc_alloc_regions();
361 // Helper for monitoring and management support.
362 G1MonitoringSupport* _g1mm;
364 // Determines PLAB size for a particular allocation purpose.
365 size_t desired_plab_sz(GCAllocPurpose purpose);
367 // Outside of GC pauses, the number of bytes used in all regions other
368 // than the current allocation region.
369 size_t _summary_bytes_used;
371 // Records whether the region at the given index is kept live by roots or
372 // references from the young generation.
373 class HumongousIsLiveBiasedMappedArray : public G1BiasedMappedArray<bool> {
374 protected:
375 bool default_value() const { return false; }
376 public:
377 void clear() { G1BiasedMappedArray<bool>::clear(); }
378 void set_live(uint region) {
379 set_by_index(region, true);
380 }
381 bool is_live(uint region) {
382 return get_by_index(region);
383 }
384 };
386 HumongousIsLiveBiasedMappedArray _humongous_is_live;
387 // Stores whether during humongous object registration we found candidate regions.
388 // If not, we can skip a few steps.
389 bool _has_humongous_reclaim_candidates;
391 volatile unsigned _gc_time_stamp;
393 size_t* _surviving_young_words;
395 G1HRPrinter _hr_printer;
397 void setup_surviving_young_words();
398 void update_surviving_young_words(size_t* surv_young_words);
399 void cleanup_surviving_young_words();
401 // It decides whether an explicit GC should start a concurrent cycle
402 // instead of doing a STW GC. Currently, a concurrent cycle is
403 // explicitly started if:
404 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
405 // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
406 // (c) cause == _g1_humongous_allocation
407 bool should_do_concurrent_full_gc(GCCause::Cause cause);
409 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
410 // concurrent cycles) we have started.
411 volatile unsigned int _old_marking_cycles_started;
413 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
414 // concurrent cycles) we have completed.
415 volatile unsigned int _old_marking_cycles_completed;
417 bool _concurrent_cycle_started;
419 // This is a non-product method that is helpful for testing. It is
420 // called at the end of a GC and artificially expands the heap by
421 // allocating a number of dead regions. This way we can induce very
422 // frequent marking cycles and stress the cleanup / concurrent
423 // cleanup code more (as all the regions that will be allocated by
424 // this method will be found dead by the marking cycle).
425 void allocate_dummy_regions() PRODUCT_RETURN;
427 // Clear RSets after a compaction. It also resets the GC time stamps.
428 void clear_rsets_post_compaction();
430 // If the HR printer is active, dump the state of the regions in the
431 // heap after a compaction.
432 void print_hrs_post_compaction();
434 double verify(bool guard, const char* msg);
435 void verify_before_gc();
436 void verify_after_gc();
438 void log_gc_header();
439 void log_gc_footer(double pause_time_sec);
441 // These are macros so that, if the assert fires, we get the correct
442 // line number, file, etc.
444 #define heap_locking_asserts_err_msg(_extra_message_) \
445 err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \
446 (_extra_message_), \
447 BOOL_TO_STR(Heap_lock->owned_by_self()), \
448 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \
449 BOOL_TO_STR(Thread::current()->is_VM_thread()))
451 #define assert_heap_locked() \
452 do { \
453 assert(Heap_lock->owned_by_self(), \
454 heap_locking_asserts_err_msg("should be holding the Heap_lock")); \
455 } while (0)
457 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \
458 do { \
459 assert(Heap_lock->owned_by_self() || \
460 (SafepointSynchronize::is_at_safepoint() && \
461 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
462 heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
463 "should be at a safepoint")); \
464 } while (0)
466 #define assert_heap_locked_and_not_at_safepoint() \
467 do { \
468 assert(Heap_lock->owned_by_self() && \
469 !SafepointSynchronize::is_at_safepoint(), \
470 heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
471 "should not be at a safepoint")); \
472 } while (0)
474 #define assert_heap_not_locked() \
475 do { \
476 assert(!Heap_lock->owned_by_self(), \
477 heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
478 } while (0)
480 #define assert_heap_not_locked_and_not_at_safepoint() \
481 do { \
482 assert(!Heap_lock->owned_by_self() && \
483 !SafepointSynchronize::is_at_safepoint(), \
484 heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
485 "should not be at a safepoint")); \
486 } while (0)
488 #define assert_at_safepoint(_should_be_vm_thread_) \
489 do { \
490 assert(SafepointSynchronize::is_at_safepoint() && \
491 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
492 heap_locking_asserts_err_msg("should be at a safepoint")); \
493 } while (0)
495 #define assert_not_at_safepoint() \
496 do { \
497 assert(!SafepointSynchronize::is_at_safepoint(), \
498 heap_locking_asserts_err_msg("should not be at a safepoint")); \
499 } while (0)
501 protected:
503 // The young region list.
504 YoungList* _young_list;
506 // The current policy object for the collector.
507 G1CollectorPolicy* _g1_policy;
509 // This is the second level of trying to allocate a new region. If
510 // new_region() didn't find a region on the free_list, this call will
511 // check whether there's anything available on the
512 // secondary_free_list and/or wait for more regions to appear on
513 // that list, if _free_regions_coming is set.
514 HeapRegion* new_region_try_secondary_free_list(bool is_old);
516 // Try to allocate a single non-humongous HeapRegion sufficient for
517 // an allocation of the given word_size. If do_expand is true,
518 // attempt to expand the heap if necessary to satisfy the allocation
519 // request. If the region is to be used as an old region or for a
520 // humongous object, set is_old to true. If not, to false.
521 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
523 // Initialize a contiguous set of free regions of length num_regions
524 // and starting at index first so that they appear as a single
525 // humongous region.
526 HeapWord* humongous_obj_allocate_initialize_regions(uint first,
527 uint num_regions,
528 size_t word_size);
530 // Attempt to allocate a humongous object of the given size. Return
531 // NULL if unsuccessful.
532 HeapWord* humongous_obj_allocate(size_t word_size);
534 // The following two methods, allocate_new_tlab() and
535 // mem_allocate(), are the two main entry points from the runtime
536 // into the G1's allocation routines. They have the following
537 // assumptions:
538 //
539 // * They should both be called outside safepoints.
540 //
541 // * They should both be called without holding the Heap_lock.
542 //
543 // * All allocation requests for new TLABs should go to
544 // allocate_new_tlab().
545 //
546 // * All non-TLAB allocation requests should go to mem_allocate().
547 //
548 // * If either call cannot satisfy the allocation request using the
549 // current allocating region, they will try to get a new one. If
550 // this fails, they will attempt to do an evacuation pause and
551 // retry the allocation.
552 //
553 // * If all allocation attempts fail, even after trying to schedule
554 // an evacuation pause, allocate_new_tlab() will return NULL,
555 // whereas mem_allocate() will attempt a heap expansion and/or
556 // schedule a Full GC.
557 //
558 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
559 // should never be called with word_size being humongous. All
560 // humongous allocation requests should go to mem_allocate() which
561 // will satisfy them with a special path.
563 virtual HeapWord* allocate_new_tlab(size_t word_size);
565 virtual HeapWord* mem_allocate(size_t word_size,
566 bool* gc_overhead_limit_was_exceeded);
568 // The following three methods take a gc_count_before_ret
569 // parameter which is used to return the GC count if the method
570 // returns NULL. Given that we are required to read the GC count
571 // while holding the Heap_lock, and these paths will take the
572 // Heap_lock at some point, it's easier to get them to read the GC
573 // count while holding the Heap_lock before they return NULL instead
574 // of the caller (namely: mem_allocate()) having to also take the
575 // Heap_lock just to read the GC count.
577 // First-level mutator allocation attempt: try to allocate out of
578 // the mutator alloc region without taking the Heap_lock. This
579 // should only be used for non-humongous allocations.
580 inline HeapWord* attempt_allocation(size_t word_size,
581 unsigned int* gc_count_before_ret,
582 int* gclocker_retry_count_ret);
584 // Second-level mutator allocation attempt: take the Heap_lock and
585 // retry the allocation attempt, potentially scheduling a GC
586 // pause. This should only be used for non-humongous allocations.
587 HeapWord* attempt_allocation_slow(size_t word_size,
588 unsigned int* gc_count_before_ret,
589 int* gclocker_retry_count_ret);
591 // Takes the Heap_lock and attempts a humongous allocation. It can
592 // potentially schedule a GC pause.
593 HeapWord* attempt_allocation_humongous(size_t word_size,
594 unsigned int* gc_count_before_ret,
595 int* gclocker_retry_count_ret);
597 // Allocation attempt that should be called during safepoints (e.g.,
598 // at the end of a successful GC). expect_null_mutator_alloc_region
599 // specifies whether the mutator alloc region is expected to be NULL
600 // or not.
601 HeapWord* attempt_allocation_at_safepoint(size_t word_size,
602 bool expect_null_mutator_alloc_region);
604 // It dirties the cards that cover the block so that so that the post
605 // write barrier never queues anything when updating objects on this
606 // block. It is assumed (and in fact we assert) that the block
607 // belongs to a young region.
608 inline void dirty_young_block(HeapWord* start, size_t word_size);
610 // Allocate blocks during garbage collection. Will ensure an
611 // allocation region, either by picking one or expanding the
612 // heap, and then allocate a block of the given size. The block
613 // may not be a humongous - it must fit into a single heap region.
614 HeapWord* par_allocate_during_gc(GCAllocPurpose purpose, size_t word_size);
616 HeapWord* allocate_during_gc_slow(GCAllocPurpose purpose,
617 HeapRegion* alloc_region,
618 bool par,
619 size_t word_size);
621 // Ensure that no further allocations can happen in "r", bearing in mind
622 // that parallel threads might be attempting allocations.
623 void par_allocate_remaining_space(HeapRegion* r);
625 // Allocation attempt during GC for a survivor object / PLAB.
626 inline HeapWord* survivor_attempt_allocation(size_t word_size);
628 // Allocation attempt during GC for an old object / PLAB.
629 inline HeapWord* old_attempt_allocation(size_t word_size);
631 // These methods are the "callbacks" from the G1AllocRegion class.
633 // For mutator alloc regions.
634 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
635 void retire_mutator_alloc_region(HeapRegion* alloc_region,
636 size_t allocated_bytes);
638 // For GC alloc regions.
639 HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
640 GCAllocPurpose ap);
641 void retire_gc_alloc_region(HeapRegion* alloc_region,
642 size_t allocated_bytes, GCAllocPurpose ap);
644 // - if explicit_gc is true, the GC is for a System.gc() or a heap
645 // inspection request and should collect the entire heap
646 // - if clear_all_soft_refs is true, all soft references should be
647 // cleared during the GC
648 // - if explicit_gc is false, word_size describes the allocation that
649 // the GC should attempt (at least) to satisfy
650 // - it returns false if it is unable to do the collection due to the
651 // GC locker being active, true otherwise
652 bool do_collection(bool explicit_gc,
653 bool clear_all_soft_refs,
654 size_t word_size);
656 // Callback from VM_G1CollectFull operation.
657 // Perform a full collection.
658 virtual void do_full_collection(bool clear_all_soft_refs);
660 // Resize the heap if necessary after a full collection. If this is
661 // after a collect-for allocation, "word_size" is the allocation size,
662 // and will be considered part of the used portion of the heap.
663 void resize_if_necessary_after_full_collection(size_t word_size);
665 // Callback from VM_G1CollectForAllocation operation.
666 // This function does everything necessary/possible to satisfy a
667 // failed allocation request (including collection, expansion, etc.)
668 HeapWord* satisfy_failed_allocation(size_t word_size, bool* succeeded);
670 // Attempting to expand the heap sufficiently
671 // to support an allocation of the given "word_size". If
672 // successful, perform the allocation and return the address of the
673 // allocated block, or else "NULL".
674 HeapWord* expand_and_allocate(size_t word_size);
676 // Process any reference objects discovered during
677 // an incremental evacuation pause.
678 void process_discovered_references(uint no_of_gc_workers);
680 // Enqueue any remaining discovered references
681 // after processing.
682 void enqueue_discovered_references(uint no_of_gc_workers);
684 public:
686 G1MonitoringSupport* g1mm() {
687 assert(_g1mm != NULL, "should have been initialized");
688 return _g1mm;
689 }
691 // Expand the garbage-first heap by at least the given size (in bytes!).
692 // Returns true if the heap was expanded by the requested amount;
693 // false otherwise.
694 // (Rounds up to a HeapRegion boundary.)
695 bool expand(size_t expand_bytes);
697 // Do anything common to GC's.
698 virtual void gc_prologue(bool full);
699 virtual void gc_epilogue(bool full);
701 inline void set_humongous_is_live(oop obj);
703 bool humongous_is_live(uint region) {
704 return _humongous_is_live.is_live(region);
705 }
707 // Returns whether the given region (which must be a humongous (start) region)
708 // is to be considered conservatively live regardless of any other conditions.
709 bool humongous_region_is_always_live(uint index);
710 // Register the given region to be part of the collection set.
711 inline void register_humongous_region_with_in_cset_fast_test(uint index);
712 // Register regions with humongous objects (actually on the start region) in
713 // the in_cset_fast_test table.
714 void register_humongous_regions_with_in_cset_fast_test();
715 // We register a region with the fast "in collection set" test. We
716 // simply set to true the array slot corresponding to this region.
717 void register_region_with_in_cset_fast_test(HeapRegion* r) {
718 _in_cset_fast_test.set_in_cset(r->hrs_index());
719 }
721 // This is a fast test on whether a reference points into the
722 // collection set or not. Assume that the reference
723 // points into the heap.
724 inline bool in_cset_fast_test(oop obj);
726 void clear_cset_fast_test() {
727 _in_cset_fast_test.clear();
728 }
730 // This is called at the start of either a concurrent cycle or a Full
731 // GC to update the number of old marking cycles started.
732 void increment_old_marking_cycles_started();
734 // This is called at the end of either a concurrent cycle or a Full
735 // GC to update the number of old marking cycles completed. Those two
736 // can happen in a nested fashion, i.e., we start a concurrent
737 // cycle, a Full GC happens half-way through it which ends first,
738 // and then the cycle notices that a Full GC happened and ends
739 // too. The concurrent parameter is a boolean to help us do a bit
740 // tighter consistency checking in the method. If concurrent is
741 // false, the caller is the inner caller in the nesting (i.e., the
742 // Full GC). If concurrent is true, the caller is the outer caller
743 // in this nesting (i.e., the concurrent cycle). Further nesting is
744 // not currently supported. The end of this call also notifies
745 // the FullGCCount_lock in case a Java thread is waiting for a full
746 // GC to happen (e.g., it called System.gc() with
747 // +ExplicitGCInvokesConcurrent).
748 void increment_old_marking_cycles_completed(bool concurrent);
750 unsigned int old_marking_cycles_completed() {
751 return _old_marking_cycles_completed;
752 }
754 void register_concurrent_cycle_start(const Ticks& start_time);
755 void register_concurrent_cycle_end();
756 void trace_heap_after_concurrent_cycle();
758 G1YCType yc_type();
760 G1HRPrinter* hr_printer() { return &_hr_printer; }
762 // Frees a non-humongous region by initializing its contents and
763 // adding it to the free list that's passed as a parameter (this is
764 // usually a local list which will be appended to the master free
765 // list later). The used bytes of freed regions are accumulated in
766 // pre_used. If par is true, the region's RSet will not be freed
767 // up. The assumption is that this will be done later.
768 // The locked parameter indicates if the caller has already taken
769 // care of proper synchronization. This may allow some optimizations.
770 void free_region(HeapRegion* hr,
771 FreeRegionList* free_list,
772 bool par,
773 bool locked = false);
775 // Frees a humongous region by collapsing it into individual regions
776 // and calling free_region() for each of them. The freed regions
777 // will be added to the free list that's passed as a parameter (this
778 // is usually a local list which will be appended to the master free
779 // list later). The used bytes of freed regions are accumulated in
780 // pre_used. If par is true, the region's RSet will not be freed
781 // up. The assumption is that this will be done later.
782 void free_humongous_region(HeapRegion* hr,
783 FreeRegionList* free_list,
784 bool par);
785 protected:
787 // Shrink the garbage-first heap by at most the given size (in bytes!).
788 // (Rounds down to a HeapRegion boundary.)
789 virtual void shrink(size_t expand_bytes);
790 void shrink_helper(size_t expand_bytes);
792 #if TASKQUEUE_STATS
793 static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
794 void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
795 void reset_taskqueue_stats();
796 #endif // TASKQUEUE_STATS
798 // Schedule the VM operation that will do an evacuation pause to
799 // satisfy an allocation request of word_size. *succeeded will
800 // return whether the VM operation was successful (it did do an
801 // evacuation pause) or not (another thread beat us to it or the GC
802 // locker was active). Given that we should not be holding the
803 // Heap_lock when we enter this method, we will pass the
804 // gc_count_before (i.e., total_collections()) as a parameter since
805 // it has to be read while holding the Heap_lock. Currently, both
806 // methods that call do_collection_pause() release the Heap_lock
807 // before the call, so it's easy to read gc_count_before just before.
808 HeapWord* do_collection_pause(size_t word_size,
809 unsigned int gc_count_before,
810 bool* succeeded,
811 GCCause::Cause gc_cause);
813 // The guts of the incremental collection pause, executed by the vm
814 // thread. It returns false if it is unable to do the collection due
815 // to the GC locker being active, true otherwise
816 bool do_collection_pause_at_safepoint(double target_pause_time_ms);
818 // Actually do the work of evacuating the collection set.
819 void evacuate_collection_set(EvacuationInfo& evacuation_info);
821 // The g1 remembered set of the heap.
822 G1RemSet* _g1_rem_set;
824 // A set of cards that cover the objects for which the Rsets should be updated
825 // concurrently after the collection.
826 DirtyCardQueueSet _dirty_card_queue_set;
828 // The closure used to refine a single card.
829 RefineCardTableEntryClosure* _refine_cte_cl;
831 // A function to check the consistency of dirty card logs.
832 void check_ct_logs_at_safepoint();
834 // A DirtyCardQueueSet that is used to hold cards that contain
835 // references into the current collection set. This is used to
836 // update the remembered sets of the regions in the collection
837 // set in the event of an evacuation failure.
838 DirtyCardQueueSet _into_cset_dirty_card_queue_set;
840 // After a collection pause, make the regions in the CS into free
841 // regions.
842 void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info);
844 // Abandon the current collection set without recording policy
845 // statistics or updating free lists.
846 void abandon_collection_set(HeapRegion* cs_head);
848 // Applies "scan_non_heap_roots" to roots outside the heap,
849 // "scan_rs" to roots inside the heap (having done "set_region" to
850 // indicate the region in which the root resides),
851 // and does "scan_metadata" If "scan_rs" is
852 // NULL, then this step is skipped. The "worker_i"
853 // param is for use with parallel roots processing, and should be
854 // the "i" of the calling parallel worker thread's work(i) function.
855 // In the sequential case this param will be ignored.
856 void g1_process_roots(OopClosure* scan_non_heap_roots,
857 OopClosure* scan_non_heap_weak_roots,
858 OopsInHeapRegionClosure* scan_rs,
859 CLDClosure* scan_strong_clds,
860 CLDClosure* scan_weak_clds,
861 CodeBlobClosure* scan_strong_code,
862 uint worker_i);
864 // The concurrent marker (and the thread it runs in.)
865 ConcurrentMark* _cm;
866 ConcurrentMarkThread* _cmThread;
867 bool _mark_in_progress;
869 // The concurrent refiner.
870 ConcurrentG1Refine* _cg1r;
872 // The parallel task queues
873 RefToScanQueueSet *_task_queues;
875 // True iff a evacuation has failed in the current collection.
876 bool _evacuation_failed;
878 EvacuationFailedInfo* _evacuation_failed_info_array;
880 // Failed evacuations cause some logical from-space objects to have
881 // forwarding pointers to themselves. Reset them.
882 void remove_self_forwarding_pointers();
884 // Together, these store an object with a preserved mark, and its mark value.
885 Stack<oop, mtGC> _objs_with_preserved_marks;
886 Stack<markOop, mtGC> _preserved_marks_of_objs;
888 // Preserve the mark of "obj", if necessary, in preparation for its mark
889 // word being overwritten with a self-forwarding-pointer.
890 void preserve_mark_if_necessary(oop obj, markOop m);
892 // The stack of evac-failure objects left to be scanned.
893 GrowableArray<oop>* _evac_failure_scan_stack;
894 // The closure to apply to evac-failure objects.
896 OopsInHeapRegionClosure* _evac_failure_closure;
897 // Set the field above.
898 void
899 set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
900 _evac_failure_closure = evac_failure_closure;
901 }
903 // Push "obj" on the scan stack.
904 void push_on_evac_failure_scan_stack(oop obj);
905 // Process scan stack entries until the stack is empty.
906 void drain_evac_failure_scan_stack();
907 // True iff an invocation of "drain_scan_stack" is in progress; to
908 // prevent unnecessary recursion.
909 bool _drain_in_progress;
911 // Do any necessary initialization for evacuation-failure handling.
912 // "cl" is the closure that will be used to process evac-failure
913 // objects.
914 void init_for_evac_failure(OopsInHeapRegionClosure* cl);
915 // Do any necessary cleanup for evacuation-failure handling data
916 // structures.
917 void finalize_for_evac_failure();
919 // An attempt to evacuate "obj" has failed; take necessary steps.
920 oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj);
921 void handle_evacuation_failure_common(oop obj, markOop m);
923 #ifndef PRODUCT
924 // Support for forcing evacuation failures. Analogous to
925 // PromotionFailureALot for the other collectors.
927 // Records whether G1EvacuationFailureALot should be in effect
928 // for the current GC
929 bool _evacuation_failure_alot_for_current_gc;
931 // Used to record the GC number for interval checking when
932 // determining whether G1EvaucationFailureALot is in effect
933 // for the current GC.
934 size_t _evacuation_failure_alot_gc_number;
936 // Count of the number of evacuations between failures.
937 volatile size_t _evacuation_failure_alot_count;
939 // Set whether G1EvacuationFailureALot should be in effect
940 // for the current GC (based upon the type of GC and which
941 // command line flags are set);
942 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
943 bool during_initial_mark,
944 bool during_marking);
946 inline void set_evacuation_failure_alot_for_current_gc();
948 // Return true if it's time to cause an evacuation failure.
949 inline bool evacuation_should_fail();
951 // Reset the G1EvacuationFailureALot counters. Should be called at
952 // the end of an evacuation pause in which an evacuation failure occurred.
953 inline void reset_evacuation_should_fail();
954 #endif // !PRODUCT
956 // ("Weak") Reference processing support.
957 //
958 // G1 has 2 instances of the reference processor class. One
959 // (_ref_processor_cm) handles reference object discovery
960 // and subsequent processing during concurrent marking cycles.
961 //
962 // The other (_ref_processor_stw) handles reference object
963 // discovery and processing during full GCs and incremental
964 // evacuation pauses.
965 //
966 // During an incremental pause, reference discovery will be
967 // temporarily disabled for _ref_processor_cm and will be
968 // enabled for _ref_processor_stw. At the end of the evacuation
969 // pause references discovered by _ref_processor_stw will be
970 // processed and discovery will be disabled. The previous
971 // setting for reference object discovery for _ref_processor_cm
972 // will be re-instated.
973 //
974 // At the start of marking:
975 // * Discovery by the CM ref processor is verified to be inactive
976 // and it's discovered lists are empty.
977 // * Discovery by the CM ref processor is then enabled.
978 //
979 // At the end of marking:
980 // * Any references on the CM ref processor's discovered
981 // lists are processed (possibly MT).
982 //
983 // At the start of full GC we:
984 // * Disable discovery by the CM ref processor and
985 // empty CM ref processor's discovered lists
986 // (without processing any entries).
987 // * Verify that the STW ref processor is inactive and it's
988 // discovered lists are empty.
989 // * Temporarily set STW ref processor discovery as single threaded.
990 // * Temporarily clear the STW ref processor's _is_alive_non_header
991 // field.
992 // * Finally enable discovery by the STW ref processor.
993 //
994 // The STW ref processor is used to record any discovered
995 // references during the full GC.
996 //
997 // At the end of a full GC we:
998 // * Enqueue any reference objects discovered by the STW ref processor
999 // that have non-live referents. This has the side-effect of
1000 // making the STW ref processor inactive by disabling discovery.
1001 // * Verify that the CM ref processor is still inactive
1002 // and no references have been placed on it's discovered
1003 // lists (also checked as a precondition during initial marking).
1005 // The (stw) reference processor...
1006 ReferenceProcessor* _ref_processor_stw;
1008 STWGCTimer* _gc_timer_stw;
1009 ConcurrentGCTimer* _gc_timer_cm;
1011 G1OldTracer* _gc_tracer_cm;
1012 G1NewTracer* _gc_tracer_stw;
1014 // During reference object discovery, the _is_alive_non_header
1015 // closure (if non-null) is applied to the referent object to
1016 // determine whether the referent is live. If so then the
1017 // reference object does not need to be 'discovered' and can
1018 // be treated as a regular oop. This has the benefit of reducing
1019 // the number of 'discovered' reference objects that need to
1020 // be processed.
1021 //
1022 // Instance of the is_alive closure for embedding into the
1023 // STW reference processor as the _is_alive_non_header field.
1024 // Supplying a value for the _is_alive_non_header field is
1025 // optional but doing so prevents unnecessary additions to
1026 // the discovered lists during reference discovery.
1027 G1STWIsAliveClosure _is_alive_closure_stw;
1029 // The (concurrent marking) reference processor...
1030 ReferenceProcessor* _ref_processor_cm;
1032 // Instance of the concurrent mark is_alive closure for embedding
1033 // into the Concurrent Marking reference processor as the
1034 // _is_alive_non_header field. Supplying a value for the
1035 // _is_alive_non_header field is optional but doing so prevents
1036 // unnecessary additions to the discovered lists during reference
1037 // discovery.
1038 G1CMIsAliveClosure _is_alive_closure_cm;
1040 // Cache used by G1CollectedHeap::start_cset_region_for_worker().
1041 HeapRegion** _worker_cset_start_region;
1043 // Time stamp to validate the regions recorded in the cache
1044 // used by G1CollectedHeap::start_cset_region_for_worker().
1045 // The heap region entry for a given worker is valid iff
1046 // the associated time stamp value matches the current value
1047 // of G1CollectedHeap::_gc_time_stamp.
1048 unsigned int* _worker_cset_start_region_time_stamp;
1050 enum G1H_process_roots_tasks {
1051 G1H_PS_filter_satb_buffers,
1052 G1H_PS_refProcessor_oops_do,
1053 // Leave this one last.
1054 G1H_PS_NumElements
1055 };
1057 SubTasksDone* _process_strong_tasks;
1059 volatile bool _free_regions_coming;
1061 public:
1063 SubTasksDone* process_strong_tasks() { return _process_strong_tasks; }
1065 void set_refine_cte_cl_concurrency(bool concurrent);
1067 RefToScanQueue *task_queue(int i) const;
1069 // A set of cards where updates happened during the GC
1070 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
1072 // A DirtyCardQueueSet that is used to hold cards that contain
1073 // references into the current collection set. This is used to
1074 // update the remembered sets of the regions in the collection
1075 // set in the event of an evacuation failure.
1076 DirtyCardQueueSet& into_cset_dirty_card_queue_set()
1077 { return _into_cset_dirty_card_queue_set; }
1079 // Create a G1CollectedHeap with the specified policy.
1080 // Must call the initialize method afterwards.
1081 // May not return if something goes wrong.
1082 G1CollectedHeap(G1CollectorPolicy* policy);
1084 // Initialize the G1CollectedHeap to have the initial and
1085 // maximum sizes and remembered and barrier sets
1086 // specified by the policy object.
1087 jint initialize();
1089 virtual void stop();
1091 // Return the (conservative) maximum heap alignment for any G1 heap
1092 static size_t conservative_max_heap_alignment();
1094 // Initialize weak reference processing.
1095 virtual void ref_processing_init();
1097 void set_par_threads(uint t) {
1098 SharedHeap::set_par_threads(t);
1099 // Done in SharedHeap but oddly there are
1100 // two _process_strong_tasks's in a G1CollectedHeap
1101 // so do it here too.
1102 _process_strong_tasks->set_n_threads(t);
1103 }
1105 // Set _n_par_threads according to a policy TBD.
1106 void set_par_threads();
1108 void set_n_termination(int t) {
1109 _process_strong_tasks->set_n_threads(t);
1110 }
1112 virtual CollectedHeap::Name kind() const {
1113 return CollectedHeap::G1CollectedHeap;
1114 }
1116 // The current policy object for the collector.
1117 G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1119 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); }
1121 // Adaptive size policy. No such thing for g1.
1122 virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1124 // The rem set and barrier set.
1125 G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1127 unsigned get_gc_time_stamp() {
1128 return _gc_time_stamp;
1129 }
1131 inline void reset_gc_time_stamp();
1133 void check_gc_time_stamps() PRODUCT_RETURN;
1135 inline void increment_gc_time_stamp();
1137 // Reset the given region's GC timestamp. If it's starts humongous,
1138 // also reset the GC timestamp of its corresponding
1139 // continues humongous regions too.
1140 void reset_gc_time_stamps(HeapRegion* hr);
1142 void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1143 DirtyCardQueue* into_cset_dcq,
1144 bool concurrent, uint worker_i);
1146 // The shared block offset table array.
1147 G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1149 // Reference Processing accessors
1151 // The STW reference processor....
1152 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1154 // The Concurrent Marking reference processor...
1155 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1157 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1158 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1160 virtual size_t capacity() const;
1161 virtual size_t used() const;
1162 // This should be called when we're not holding the heap lock. The
1163 // result might be a bit inaccurate.
1164 size_t used_unlocked() const;
1165 size_t recalculate_used() const;
1167 // These virtual functions do the actual allocation.
1168 // Some heaps may offer a contiguous region for shared non-blocking
1169 // allocation, via inlined code (by exporting the address of the top and
1170 // end fields defining the extent of the contiguous allocation region.)
1171 // But G1CollectedHeap doesn't yet support this.
1173 virtual bool is_maximal_no_gc() const {
1174 return _hrs.available() == 0;
1175 }
1177 // The current number of regions in the heap.
1178 uint num_regions() const { return _hrs.length(); }
1180 // The max number of regions in the heap.
1181 uint max_regions() const { return _hrs.max_length(); }
1183 // The number of regions that are completely free.
1184 uint num_free_regions() const { return _hrs.num_free_regions(); }
1186 // The number of regions that are not completely free.
1187 uint num_used_regions() const { return num_regions() - num_free_regions(); }
1189 void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1190 void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1191 void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1192 void verify_dirty_young_regions() PRODUCT_RETURN;
1194 #ifndef PRODUCT
1195 // Make sure that the given bitmap has no marked objects in the
1196 // range [from,limit). If it does, print an error message and return
1197 // false. Otherwise, just return true. bitmap_name should be "prev"
1198 // or "next".
1199 bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
1200 HeapWord* from, HeapWord* limit);
1202 // Verify that the prev / next bitmap range [tams,end) for the given
1203 // region has no marks. Return true if all is well, false if errors
1204 // are detected.
1205 bool verify_bitmaps(const char* caller, HeapRegion* hr);
1206 #endif // PRODUCT
1208 // If G1VerifyBitmaps is set, verify that the marking bitmaps for
1209 // the given region do not have any spurious marks. If errors are
1210 // detected, print appropriate error messages and crash.
1211 void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN;
1213 // If G1VerifyBitmaps is set, verify that the marking bitmaps do not
1214 // have any spurious marks. If errors are detected, print
1215 // appropriate error messages and crash.
1216 void check_bitmaps(const char* caller) PRODUCT_RETURN;
1218 // verify_region_sets() performs verification over the region
1219 // lists. It will be compiled in the product code to be used when
1220 // necessary (i.e., during heap verification).
1221 void verify_region_sets();
1223 // verify_region_sets_optional() is planted in the code for
1224 // list verification in non-product builds (and it can be enabled in
1225 // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1).
1226 #if HEAP_REGION_SET_FORCE_VERIFY
1227 void verify_region_sets_optional() {
1228 verify_region_sets();
1229 }
1230 #else // HEAP_REGION_SET_FORCE_VERIFY
1231 void verify_region_sets_optional() { }
1232 #endif // HEAP_REGION_SET_FORCE_VERIFY
1234 #ifdef ASSERT
1235 bool is_on_master_free_list(HeapRegion* hr) {
1236 return _hrs.is_free(hr);
1237 }
1238 #endif // ASSERT
1240 // Wrapper for the region list operations that can be called from
1241 // methods outside this class.
1243 void secondary_free_list_add(FreeRegionList* list) {
1244 _secondary_free_list.add_ordered(list);
1245 }
1247 void append_secondary_free_list() {
1248 _hrs.insert_list_into_free_list(&_secondary_free_list);
1249 }
1251 void append_secondary_free_list_if_not_empty_with_lock() {
1252 // If the secondary free list looks empty there's no reason to
1253 // take the lock and then try to append it.
1254 if (!_secondary_free_list.is_empty()) {
1255 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1256 append_secondary_free_list();
1257 }
1258 }
1260 inline void old_set_remove(HeapRegion* hr);
1262 size_t non_young_capacity_bytes() {
1263 return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1264 }
1266 void set_free_regions_coming();
1267 void reset_free_regions_coming();
1268 bool free_regions_coming() { return _free_regions_coming; }
1269 void wait_while_free_regions_coming();
1271 // Determine whether the given region is one that we are using as an
1272 // old GC alloc region.
1273 bool is_old_gc_alloc_region(HeapRegion* hr) {
1274 return hr == _retained_old_gc_alloc_region;
1275 }
1277 // Perform a collection of the heap; intended for use in implementing
1278 // "System.gc". This probably implies as full a collection as the
1279 // "CollectedHeap" supports.
1280 virtual void collect(GCCause::Cause cause);
1282 // The same as above but assume that the caller holds the Heap_lock.
1283 void collect_locked(GCCause::Cause cause);
1285 // True iff an evacuation has failed in the most-recent collection.
1286 bool evacuation_failed() { return _evacuation_failed; }
1288 void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed);
1289 void prepend_to_freelist(FreeRegionList* list);
1290 void decrement_summary_bytes(size_t bytes);
1292 // Returns "TRUE" iff "p" points into the committed areas of the heap.
1293 virtual bool is_in(const void* p) const;
1294 #ifdef ASSERT
1295 // Returns whether p is in one of the available areas of the heap. Slow but
1296 // extensive version.
1297 bool is_in_exact(const void* p) const;
1298 #endif
1300 // Return "TRUE" iff the given object address is within the collection
1301 // set. Slow implementation.
1302 inline bool obj_in_cs(oop obj);
1304 inline bool is_in_cset(oop obj);
1306 inline bool is_in_cset_or_humongous(const oop obj);
1308 enum in_cset_state_t {
1309 InNeither, // neither in collection set nor humongous
1310 InCSet, // region is in collection set only
1311 IsHumongous // region is a humongous start region
1312 };
1313 private:
1314 // Instances of this class are used for quick tests on whether a reference points
1315 // into the collection set or is a humongous object (points into a humongous
1316 // object).
1317 // Each of the array's elements denotes whether the corresponding region is in
1318 // the collection set or a humongous region.
1319 // We use this to quickly reclaim humongous objects: by making a humongous region
1320 // succeed this test, we sort-of add it to the collection set. During the reference
1321 // iteration closures, when we see a humongous region, we simply mark it as
1322 // referenced, i.e. live.
1323 class G1FastCSetBiasedMappedArray : public G1BiasedMappedArray<char> {
1324 protected:
1325 char default_value() const { return G1CollectedHeap::InNeither; }
1326 public:
1327 void set_humongous(uintptr_t index) {
1328 assert(get_by_index(index) != InCSet, "Should not overwrite InCSet values");
1329 set_by_index(index, G1CollectedHeap::IsHumongous);
1330 }
1332 void clear_humongous(uintptr_t index) {
1333 set_by_index(index, G1CollectedHeap::InNeither);
1334 }
1336 void set_in_cset(uintptr_t index) {
1337 assert(get_by_index(index) != G1CollectedHeap::IsHumongous, "Should not overwrite IsHumongous value");
1338 set_by_index(index, G1CollectedHeap::InCSet);
1339 }
1341 bool is_in_cset_or_humongous(HeapWord* addr) const { return get_by_address(addr) != G1CollectedHeap::InNeither; }
1342 bool is_in_cset(HeapWord* addr) const { return get_by_address(addr) == G1CollectedHeap::InCSet; }
1343 G1CollectedHeap::in_cset_state_t at(HeapWord* addr) const { return (G1CollectedHeap::in_cset_state_t)get_by_address(addr); }
1344 void clear() { G1BiasedMappedArray<char>::clear(); }
1345 };
1347 // This array is used for a quick test on whether a reference points into
1348 // the collection set or not. Each of the array's elements denotes whether the
1349 // corresponding region is in the collection set or not.
1350 G1FastCSetBiasedMappedArray _in_cset_fast_test;
1352 public:
1354 inline in_cset_state_t in_cset_state(const oop obj);
1356 // Return "TRUE" iff the given object address is in the reserved
1357 // region of g1.
1358 bool is_in_g1_reserved(const void* p) const {
1359 return _hrs.reserved().contains(p);
1360 }
1362 // Returns a MemRegion that corresponds to the space that has been
1363 // reserved for the heap
1364 MemRegion g1_reserved() const {
1365 return _hrs.reserved();
1366 }
1368 virtual bool is_in_closed_subset(const void* p) const;
1370 G1SATBCardTableLoggingModRefBS* g1_barrier_set() {
1371 return (G1SATBCardTableLoggingModRefBS*) barrier_set();
1372 }
1374 // This resets the card table to all zeros. It is used after
1375 // a collection pause which used the card table to claim cards.
1376 void cleanUpCardTable();
1378 // Iteration functions.
1380 // Iterate over all the ref-containing fields of all objects, calling
1381 // "cl.do_oop" on each.
1382 virtual void oop_iterate(ExtendedOopClosure* cl);
1384 // Iterate over all objects, calling "cl.do_object" on each.
1385 virtual void object_iterate(ObjectClosure* cl);
1387 virtual void safe_object_iterate(ObjectClosure* cl) {
1388 object_iterate(cl);
1389 }
1391 // Iterate over all spaces in use in the heap, in ascending address order.
1392 virtual void space_iterate(SpaceClosure* cl);
1394 // Iterate over heap regions, in address order, terminating the
1395 // iteration early if the "doHeapRegion" method returns "true".
1396 void heap_region_iterate(HeapRegionClosure* blk) const;
1398 // Return the region with the given index. It assumes the index is valid.
1399 inline HeapRegion* region_at(uint index) const;
1401 // Calculate the region index of the given address. Given address must be
1402 // within the heap.
1403 inline uint addr_to_region(HeapWord* addr) const;
1405 inline HeapWord* bottom_addr_for_region(uint index) const;
1407 // Divide the heap region sequence into "chunks" of some size (the number
1408 // of regions divided by the number of parallel threads times some
1409 // overpartition factor, currently 4). Assumes that this will be called
1410 // in parallel by ParallelGCThreads worker threads with discinct worker
1411 // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel
1412 // calls will use the same "claim_value", and that that claim value is
1413 // different from the claim_value of any heap region before the start of
1414 // the iteration. Applies "blk->doHeapRegion" to each of the regions, by
1415 // attempting to claim the first region in each chunk, and, if
1416 // successful, applying the closure to each region in the chunk (and
1417 // setting the claim value of the second and subsequent regions of the
1418 // chunk.) For now requires that "doHeapRegion" always returns "false",
1419 // i.e., that a closure never attempt to abort a traversal.
1420 void heap_region_par_iterate_chunked(HeapRegionClosure* cl,
1421 uint worker_id,
1422 uint num_workers,
1423 jint claim_value) const;
1425 // It resets all the region claim values to the default.
1426 void reset_heap_region_claim_values();
1428 // Resets the claim values of regions in the current
1429 // collection set to the default.
1430 void reset_cset_heap_region_claim_values();
1432 #ifdef ASSERT
1433 bool check_heap_region_claim_values(jint claim_value);
1435 // Same as the routine above but only checks regions in the
1436 // current collection set.
1437 bool check_cset_heap_region_claim_values(jint claim_value);
1438 #endif // ASSERT
1440 // Clear the cached cset start regions and (more importantly)
1441 // the time stamps. Called when we reset the GC time stamp.
1442 void clear_cset_start_regions();
1444 // Given the id of a worker, obtain or calculate a suitable
1445 // starting region for iterating over the current collection set.
1446 HeapRegion* start_cset_region_for_worker(uint worker_i);
1448 // Iterate over the regions (if any) in the current collection set.
1449 void collection_set_iterate(HeapRegionClosure* blk);
1451 // As above but starting from region r
1452 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1454 HeapRegion* next_compaction_region(const HeapRegion* from) const;
1456 // A CollectedHeap will contain some number of spaces. This finds the
1457 // space containing a given address, or else returns NULL.
1458 virtual Space* space_containing(const void* addr) const;
1460 // Returns the HeapRegion that contains addr. addr must not be NULL.
1461 template <class T>
1462 inline HeapRegion* heap_region_containing_raw(const T addr) const;
1464 // Returns the HeapRegion that contains addr. addr must not be NULL.
1465 // If addr is within a humongous continues region, it returns its humongous start region.
1466 template <class T>
1467 inline HeapRegion* heap_region_containing(const T addr) const;
1469 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1470 // each address in the (reserved) heap is a member of exactly
1471 // one block. The defining characteristic of a block is that it is
1472 // possible to find its size, and thus to progress forward to the next
1473 // block. (Blocks may be of different sizes.) Thus, blocks may
1474 // represent Java objects, or they might be free blocks in a
1475 // free-list-based heap (or subheap), as long as the two kinds are
1476 // distinguishable and the size of each is determinable.
1478 // Returns the address of the start of the "block" that contains the
1479 // address "addr". We say "blocks" instead of "object" since some heaps
1480 // may not pack objects densely; a chunk may either be an object or a
1481 // non-object.
1482 virtual HeapWord* block_start(const void* addr) const;
1484 // Requires "addr" to be the start of a chunk, and returns its size.
1485 // "addr + size" is required to be the start of a new chunk, or the end
1486 // of the active area of the heap.
1487 virtual size_t block_size(const HeapWord* addr) const;
1489 // Requires "addr" to be the start of a block, and returns "TRUE" iff
1490 // the block is an object.
1491 virtual bool block_is_obj(const HeapWord* addr) const;
1493 // Does this heap support heap inspection? (+PrintClassHistogram)
1494 virtual bool supports_heap_inspection() const { return true; }
1496 // Section on thread-local allocation buffers (TLABs)
1497 // See CollectedHeap for semantics.
1499 bool supports_tlab_allocation() const;
1500 size_t tlab_capacity(Thread* ignored) const;
1501 size_t tlab_used(Thread* ignored) const;
1502 size_t max_tlab_size() const;
1503 size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1505 // Can a compiler initialize a new object without store barriers?
1506 // This permission only extends from the creation of a new object
1507 // via a TLAB up to the first subsequent safepoint. If such permission
1508 // is granted for this heap type, the compiler promises to call
1509 // defer_store_barrier() below on any slow path allocation of
1510 // a new object for which such initializing store barriers will
1511 // have been elided. G1, like CMS, allows this, but should be
1512 // ready to provide a compensating write barrier as necessary
1513 // if that storage came out of a non-young region. The efficiency
1514 // of this implementation depends crucially on being able to
1515 // answer very efficiently in constant time whether a piece of
1516 // storage in the heap comes from a young region or not.
1517 // See ReduceInitialCardMarks.
1518 virtual bool can_elide_tlab_store_barriers() const {
1519 return true;
1520 }
1522 virtual bool card_mark_must_follow_store() const {
1523 return true;
1524 }
1526 inline bool is_in_young(const oop obj);
1528 #ifdef ASSERT
1529 virtual bool is_in_partial_collection(const void* p);
1530 #endif
1532 virtual bool is_scavengable(const void* addr);
1534 // We don't need barriers for initializing stores to objects
1535 // in the young gen: for the SATB pre-barrier, there is no
1536 // pre-value that needs to be remembered; for the remembered-set
1537 // update logging post-barrier, we don't maintain remembered set
1538 // information for young gen objects.
1539 virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1541 // Returns "true" iff the given word_size is "very large".
1542 static bool isHumongous(size_t word_size) {
1543 // Note this has to be strictly greater-than as the TLABs
1544 // are capped at the humongous thresold and we want to
1545 // ensure that we don't try to allocate a TLAB as
1546 // humongous and that we don't allocate a humongous
1547 // object in a TLAB.
1548 return word_size > _humongous_object_threshold_in_words;
1549 }
1551 // Update mod union table with the set of dirty cards.
1552 void updateModUnion();
1554 // Set the mod union bits corresponding to the given memRegion. Note
1555 // that this is always a safe operation, since it doesn't clear any
1556 // bits.
1557 void markModUnionRange(MemRegion mr);
1559 // Records the fact that a marking phase is no longer in progress.
1560 void set_marking_complete() {
1561 _mark_in_progress = false;
1562 }
1563 void set_marking_started() {
1564 _mark_in_progress = true;
1565 }
1566 bool mark_in_progress() {
1567 return _mark_in_progress;
1568 }
1570 // Print the maximum heap capacity.
1571 virtual size_t max_capacity() const;
1573 virtual jlong millis_since_last_gc();
1576 // Convenience function to be used in situations where the heap type can be
1577 // asserted to be this type.
1578 static G1CollectedHeap* heap();
1580 void set_region_short_lived_locked(HeapRegion* hr);
1581 // add appropriate methods for any other surv rate groups
1583 YoungList* young_list() const { return _young_list; }
1585 // debugging
1586 bool check_young_list_well_formed() {
1587 return _young_list->check_list_well_formed();
1588 }
1590 bool check_young_list_empty(bool check_heap,
1591 bool check_sample = true);
1593 // *** Stuff related to concurrent marking. It's not clear to me that so
1594 // many of these need to be public.
1596 // The functions below are helper functions that a subclass of
1597 // "CollectedHeap" can use in the implementation of its virtual
1598 // functions.
1599 // This performs a concurrent marking of the live objects in a
1600 // bitmap off to the side.
1601 void doConcurrentMark();
1603 bool isMarkedPrev(oop obj) const;
1604 bool isMarkedNext(oop obj) const;
1606 // Determine if an object is dead, given the object and also
1607 // the region to which the object belongs. An object is dead
1608 // iff a) it was not allocated since the last mark and b) it
1609 // is not marked.
1610 bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1611 return
1612 !hr->obj_allocated_since_prev_marking(obj) &&
1613 !isMarkedPrev(obj);
1614 }
1616 // This function returns true when an object has been
1617 // around since the previous marking and hasn't yet
1618 // been marked during this marking.
1619 bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1620 return
1621 !hr->obj_allocated_since_next_marking(obj) &&
1622 !isMarkedNext(obj);
1623 }
1625 // Determine if an object is dead, given only the object itself.
1626 // This will find the region to which the object belongs and
1627 // then call the region version of the same function.
1629 // Added if it is NULL it isn't dead.
1631 inline bool is_obj_dead(const oop obj) const;
1633 inline bool is_obj_ill(const oop obj) const;
1635 bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1636 HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1637 bool is_marked(oop obj, VerifyOption vo);
1638 const char* top_at_mark_start_str(VerifyOption vo);
1640 ConcurrentMark* concurrent_mark() const { return _cm; }
1642 // Refinement
1644 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1646 // The dirty cards region list is used to record a subset of regions
1647 // whose cards need clearing. The list if populated during the
1648 // remembered set scanning and drained during the card table
1649 // cleanup. Although the methods are reentrant, population/draining
1650 // phases must not overlap. For synchronization purposes the last
1651 // element on the list points to itself.
1652 HeapRegion* _dirty_cards_region_list;
1653 void push_dirty_cards_region(HeapRegion* hr);
1654 HeapRegion* pop_dirty_cards_region();
1656 // Optimized nmethod scanning support routines
1658 // Register the given nmethod with the G1 heap
1659 virtual void register_nmethod(nmethod* nm);
1661 // Unregister the given nmethod from the G1 heap
1662 virtual void unregister_nmethod(nmethod* nm);
1664 // Migrate the nmethods in the code root lists of the regions
1665 // in the collection set to regions in to-space. In the event
1666 // of an evacuation failure, nmethods that reference objects
1667 // that were not successfullly evacuated are not migrated.
1668 void migrate_strong_code_roots();
1670 // Free up superfluous code root memory.
1671 void purge_code_root_memory();
1673 // Rebuild the stong code root lists for each region
1674 // after a full GC
1675 void rebuild_strong_code_roots();
1677 // Delete entries for dead interned string and clean up unreferenced symbols
1678 // in symbol table, possibly in parallel.
1679 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1681 // Parallel phase of unloading/cleaning after G1 concurrent mark.
1682 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred);
1684 // Redirty logged cards in the refinement queue.
1685 void redirty_logged_cards();
1686 // Verification
1688 // The following is just to alert the verification code
1689 // that a full collection has occurred and that the
1690 // remembered sets are no longer up to date.
1691 bool _full_collection;
1692 void set_full_collection() { _full_collection = true;}
1693 void clear_full_collection() {_full_collection = false;}
1694 bool full_collection() {return _full_collection;}
1696 // Perform any cleanup actions necessary before allowing a verification.
1697 virtual void prepare_for_verify();
1699 // Perform verification.
1701 // vo == UsePrevMarking -> use "prev" marking information,
1702 // vo == UseNextMarking -> use "next" marking information
1703 // vo == UseMarkWord -> use the mark word in the object header
1704 //
1705 // NOTE: Only the "prev" marking information is guaranteed to be
1706 // consistent most of the time, so most calls to this should use
1707 // vo == UsePrevMarking.
1708 // Currently, there is only one case where this is called with
1709 // vo == UseNextMarking, which is to verify the "next" marking
1710 // information at the end of remark.
1711 // Currently there is only one place where this is called with
1712 // vo == UseMarkWord, which is to verify the marking during a
1713 // full GC.
1714 void verify(bool silent, VerifyOption vo);
1716 // Override; it uses the "prev" marking information
1717 virtual void verify(bool silent);
1719 // The methods below are here for convenience and dispatch the
1720 // appropriate method depending on value of the given VerifyOption
1721 // parameter. The values for that parameter, and their meanings,
1722 // are the same as those above.
1724 bool is_obj_dead_cond(const oop obj,
1725 const HeapRegion* hr,
1726 const VerifyOption vo) const;
1728 bool is_obj_dead_cond(const oop obj,
1729 const VerifyOption vo) const;
1731 // Printing
1733 virtual void print_on(outputStream* st) const;
1734 virtual void print_extended_on(outputStream* st) const;
1735 virtual void print_on_error(outputStream* st) const;
1737 virtual void print_gc_threads_on(outputStream* st) const;
1738 virtual void gc_threads_do(ThreadClosure* tc) const;
1740 // Override
1741 void print_tracing_info() const;
1743 // The following two methods are helpful for debugging RSet issues.
1744 void print_cset_rsets() PRODUCT_RETURN;
1745 void print_all_rsets() PRODUCT_RETURN;
1747 public:
1748 size_t pending_card_num();
1749 size_t cards_scanned();
1751 protected:
1752 size_t _max_heap_capacity;
1753 };
1755 class G1ParGCAllocBuffer: public ParGCAllocBuffer {
1756 private:
1757 bool _retired;
1759 public:
1760 G1ParGCAllocBuffer(size_t gclab_word_size);
1761 virtual ~G1ParGCAllocBuffer() {
1762 guarantee(_retired, "Allocation buffer has not been retired");
1763 }
1765 virtual void set_buf(HeapWord* buf) {
1766 ParGCAllocBuffer::set_buf(buf);
1767 _retired = false;
1768 }
1770 virtual void retire(bool end_of_gc, bool retain) {
1771 if (_retired) {
1772 return;
1773 }
1774 ParGCAllocBuffer::retire(end_of_gc, retain);
1775 _retired = true;
1776 }
1777 };
1779 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP