Mon, 25 Aug 2014 09:10:13 +0200
8055416: Several vm/gc/heap/summary "After GC" events emitted for the same GC ID
Reviewed-by: brutisso, ehelin
1 /*
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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/g1AllocationContext.hpp"
29 #include "gc_implementation/g1/g1Allocator.hpp"
30 #include "gc_implementation/g1/concurrentMark.hpp"
31 #include "gc_implementation/g1/evacuationInfo.hpp"
32 #include "gc_implementation/g1/g1AllocRegion.hpp"
33 #include "gc_implementation/g1/g1BiasedArray.hpp"
34 #include "gc_implementation/g1/g1HRPrinter.hpp"
35 #include "gc_implementation/g1/g1MonitoringSupport.hpp"
36 #include "gc_implementation/g1/g1SATBCardTableModRefBS.hpp"
37 #include "gc_implementation/g1/g1YCTypes.hpp"
38 #include "gc_implementation/g1/heapRegionManager.hpp"
39 #include "gc_implementation/g1/heapRegionSet.hpp"
40 #include "gc_implementation/shared/hSpaceCounters.hpp"
41 #include "gc_implementation/shared/parGCAllocBuffer.hpp"
42 #include "memory/barrierSet.hpp"
43 #include "memory/memRegion.hpp"
44 #include "memory/sharedHeap.hpp"
45 #include "utilities/stack.hpp"
47 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
48 // It uses the "Garbage First" heap organization and algorithm, which
49 // may combine concurrent marking with parallel, incremental compaction of
50 // heap subsets that will yield large amounts of garbage.
52 // Forward declarations
53 class HeapRegion;
54 class HRRSCleanupTask;
55 class GenerationSpec;
56 class OopsInHeapRegionClosure;
57 class G1KlassScanClosure;
58 class G1ScanHeapEvacClosure;
59 class ObjectClosure;
60 class SpaceClosure;
61 class CompactibleSpaceClosure;
62 class Space;
63 class G1CollectorPolicy;
64 class GenRemSet;
65 class G1RemSet;
66 class HeapRegionRemSetIterator;
67 class ConcurrentMark;
68 class ConcurrentMarkThread;
69 class ConcurrentG1Refine;
70 class ConcurrentGCTimer;
71 class GenerationCounters;
72 class STWGCTimer;
73 class G1NewTracer;
74 class G1OldTracer;
75 class EvacuationFailedInfo;
76 class nmethod;
77 class Ticks;
79 typedef OverflowTaskQueue<StarTask, mtGC> RefToScanQueue;
80 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
82 typedef int RegionIdx_t; // needs to hold [ 0..max_regions() )
83 typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion )
85 class YoungList : public CHeapObj<mtGC> {
86 private:
87 G1CollectedHeap* _g1h;
89 HeapRegion* _head;
91 HeapRegion* _survivor_head;
92 HeapRegion* _survivor_tail;
94 HeapRegion* _curr;
96 uint _length;
97 uint _survivor_length;
99 size_t _last_sampled_rs_lengths;
100 size_t _sampled_rs_lengths;
102 void empty_list(HeapRegion* list);
104 public:
105 YoungList(G1CollectedHeap* g1h);
107 void push_region(HeapRegion* hr);
108 void add_survivor_region(HeapRegion* hr);
110 void empty_list();
111 bool is_empty() { return _length == 0; }
112 uint length() { return _length; }
113 uint survivor_length() { return _survivor_length; }
115 // Currently we do not keep track of the used byte sum for the
116 // young list and the survivors and it'd be quite a lot of work to
117 // do so. When we'll eventually replace the young list with
118 // instances of HeapRegionLinkedList we'll get that for free. So,
119 // we'll report the more accurate information then.
120 size_t eden_used_bytes() {
121 assert(length() >= survivor_length(), "invariant");
122 return (size_t) (length() - survivor_length()) * HeapRegion::GrainBytes;
123 }
124 size_t survivor_used_bytes() {
125 return (size_t) survivor_length() * HeapRegion::GrainBytes;
126 }
128 void rs_length_sampling_init();
129 bool rs_length_sampling_more();
130 void rs_length_sampling_next();
132 void reset_sampled_info() {
133 _last_sampled_rs_lengths = 0;
134 }
135 size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
137 // for development purposes
138 void reset_auxilary_lists();
139 void clear() { _head = NULL; _length = 0; }
141 void clear_survivors() {
142 _survivor_head = NULL;
143 _survivor_tail = NULL;
144 _survivor_length = 0;
145 }
147 HeapRegion* first_region() { return _head; }
148 HeapRegion* first_survivor_region() { return _survivor_head; }
149 HeapRegion* last_survivor_region() { return _survivor_tail; }
151 // debugging
152 bool check_list_well_formed();
153 bool check_list_empty(bool check_sample = true);
154 void print();
155 };
157 // The G1 STW is alive closure.
158 // An instance is embedded into the G1CH and used as the
159 // (optional) _is_alive_non_header closure in the STW
160 // reference processor. It is also extensively used during
161 // reference processing during STW evacuation pauses.
162 class G1STWIsAliveClosure: public BoolObjectClosure {
163 G1CollectedHeap* _g1;
164 public:
165 G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
166 bool do_object_b(oop p);
167 };
169 class RefineCardTableEntryClosure;
171 class G1RegionMappingChangedListener : public G1MappingChangedListener {
172 private:
173 void reset_from_card_cache(uint start_idx, size_t num_regions);
174 public:
175 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
176 };
178 class G1CollectedHeap : public SharedHeap {
179 friend class VM_CollectForMetadataAllocation;
180 friend class VM_G1CollectForAllocation;
181 friend class VM_G1CollectFull;
182 friend class VM_G1IncCollectionPause;
183 friend class VMStructs;
184 friend class MutatorAllocRegion;
185 friend class SurvivorGCAllocRegion;
186 friend class OldGCAllocRegion;
187 friend class G1Allocator;
188 friend class G1DefaultAllocator;
189 friend class G1ResManAllocator;
191 // Closures used in implementation.
192 template <G1Barrier barrier, G1Mark do_mark_object>
193 friend class G1ParCopyClosure;
194 friend class G1IsAliveClosure;
195 friend class G1EvacuateFollowersClosure;
196 friend class G1ParScanThreadState;
197 friend class G1ParScanClosureSuper;
198 friend class G1ParEvacuateFollowersClosure;
199 friend class G1ParTask;
200 friend class G1ParGCAllocator;
201 friend class G1DefaultParGCAllocator;
202 friend class G1FreeGarbageRegionClosure;
203 friend class RefineCardTableEntryClosure;
204 friend class G1PrepareCompactClosure;
205 friend class RegionSorter;
206 friend class RegionResetter;
207 friend class CountRCClosure;
208 friend class EvacPopObjClosure;
209 friend class G1ParCleanupCTTask;
211 friend class G1FreeHumongousRegionClosure;
212 // Other related classes.
213 friend class G1MarkSweep;
215 private:
216 // The one and only G1CollectedHeap, so static functions can find it.
217 static G1CollectedHeap* _g1h;
219 static size_t _humongous_object_threshold_in_words;
221 // The secondary free list which contains regions that have been
222 // freed up during the cleanup process. This will be appended to
223 // the master free list when appropriate.
224 FreeRegionList _secondary_free_list;
226 // It keeps track of the old regions.
227 HeapRegionSet _old_set;
229 // It keeps track of the humongous regions.
230 HeapRegionSet _humongous_set;
232 void clear_humongous_is_live_table();
233 void eagerly_reclaim_humongous_regions();
235 // The number of regions we could create by expansion.
236 uint _expansion_regions;
238 // The block offset table for the G1 heap.
239 G1BlockOffsetSharedArray* _bot_shared;
241 // Tears down the region sets / lists so that they are empty and the
242 // regions on the heap do not belong to a region set / list. The
243 // only exception is the humongous set which we leave unaltered. If
244 // free_list_only is true, it will only tear down the master free
245 // list. It is called before a Full GC (free_list_only == false) or
246 // before heap shrinking (free_list_only == true).
247 void tear_down_region_sets(bool free_list_only);
249 // Rebuilds the region sets / lists so that they are repopulated to
250 // reflect the contents of the heap. The only exception is the
251 // humongous set which was not torn down in the first place. If
252 // free_list_only is true, it will only rebuild the master free
253 // list. It is called after a Full GC (free_list_only == false) or
254 // after heap shrinking (free_list_only == true).
255 void rebuild_region_sets(bool free_list_only);
257 // Callback for region mapping changed events.
258 G1RegionMappingChangedListener _listener;
260 // The sequence of all heap regions in the heap.
261 HeapRegionManager _hrm;
263 // Class that handles the different kinds of allocations.
264 G1Allocator* _allocator;
266 // Statistics for each allocation context
267 AllocationContextStats _allocation_context_stats;
269 // PLAB sizing policy for survivors.
270 PLABStats _survivor_plab_stats;
272 // PLAB sizing policy for tenured objects.
273 PLABStats _old_plab_stats;
275 // It specifies whether we should attempt to expand the heap after a
276 // region allocation failure. If heap expansion fails we set this to
277 // false so that we don't re-attempt the heap expansion (it's likely
278 // that subsequent expansion attempts will also fail if one fails).
279 // Currently, it is only consulted during GC and it's reset at the
280 // start of each GC.
281 bool _expand_heap_after_alloc_failure;
283 // It resets the mutator alloc region before new allocations can take place.
284 void init_mutator_alloc_region();
286 // It releases the mutator alloc region.
287 void release_mutator_alloc_region();
289 // It initializes the GC alloc regions at the start of a GC.
290 void init_gc_alloc_regions(EvacuationInfo& evacuation_info);
292 // It releases the GC alloc regions at the end of a GC.
293 void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info);
295 // It does any cleanup that needs to be done on the GC alloc regions
296 // before a Full GC.
297 void abandon_gc_alloc_regions();
299 // Helper for monitoring and management support.
300 G1MonitoringSupport* _g1mm;
302 // Records whether the region at the given index is kept live by roots or
303 // references from the young generation.
304 class HumongousIsLiveBiasedMappedArray : public G1BiasedMappedArray<bool> {
305 protected:
306 bool default_value() const { return false; }
307 public:
308 void clear() { G1BiasedMappedArray<bool>::clear(); }
309 void set_live(uint region) {
310 set_by_index(region, true);
311 }
312 bool is_live(uint region) {
313 return get_by_index(region);
314 }
315 };
317 HumongousIsLiveBiasedMappedArray _humongous_is_live;
318 // Stores whether during humongous object registration we found candidate regions.
319 // If not, we can skip a few steps.
320 bool _has_humongous_reclaim_candidates;
322 volatile unsigned _gc_time_stamp;
324 size_t* _surviving_young_words;
326 G1HRPrinter _hr_printer;
328 void setup_surviving_young_words();
329 void update_surviving_young_words(size_t* surv_young_words);
330 void cleanup_surviving_young_words();
332 // It decides whether an explicit GC should start a concurrent cycle
333 // instead of doing a STW GC. Currently, a concurrent cycle is
334 // explicitly started if:
335 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
336 // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
337 // (c) cause == _g1_humongous_allocation
338 bool should_do_concurrent_full_gc(GCCause::Cause cause);
340 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
341 // concurrent cycles) we have started.
342 volatile unsigned int _old_marking_cycles_started;
344 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
345 // concurrent cycles) we have completed.
346 volatile unsigned int _old_marking_cycles_completed;
348 bool _concurrent_cycle_started;
349 bool _heap_summary_sent;
351 // This is a non-product method that is helpful for testing. It is
352 // called at the end of a GC and artificially expands the heap by
353 // allocating a number of dead regions. This way we can induce very
354 // frequent marking cycles and stress the cleanup / concurrent
355 // cleanup code more (as all the regions that will be allocated by
356 // this method will be found dead by the marking cycle).
357 void allocate_dummy_regions() PRODUCT_RETURN;
359 // Clear RSets after a compaction. It also resets the GC time stamps.
360 void clear_rsets_post_compaction();
362 // If the HR printer is active, dump the state of the regions in the
363 // heap after a compaction.
364 void print_hrm_post_compaction();
366 double verify(bool guard, const char* msg);
367 void verify_before_gc();
368 void verify_after_gc();
370 void log_gc_header();
371 void log_gc_footer(double pause_time_sec);
373 // These are macros so that, if the assert fires, we get the correct
374 // line number, file, etc.
376 #define heap_locking_asserts_err_msg(_extra_message_) \
377 err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \
378 (_extra_message_), \
379 BOOL_TO_STR(Heap_lock->owned_by_self()), \
380 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \
381 BOOL_TO_STR(Thread::current()->is_VM_thread()))
383 #define assert_heap_locked() \
384 do { \
385 assert(Heap_lock->owned_by_self(), \
386 heap_locking_asserts_err_msg("should be holding the Heap_lock")); \
387 } while (0)
389 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \
390 do { \
391 assert(Heap_lock->owned_by_self() || \
392 (SafepointSynchronize::is_at_safepoint() && \
393 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
394 heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
395 "should be at a safepoint")); \
396 } while (0)
398 #define assert_heap_locked_and_not_at_safepoint() \
399 do { \
400 assert(Heap_lock->owned_by_self() && \
401 !SafepointSynchronize::is_at_safepoint(), \
402 heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
403 "should not be at a safepoint")); \
404 } while (0)
406 #define assert_heap_not_locked() \
407 do { \
408 assert(!Heap_lock->owned_by_self(), \
409 heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
410 } while (0)
412 #define assert_heap_not_locked_and_not_at_safepoint() \
413 do { \
414 assert(!Heap_lock->owned_by_self() && \
415 !SafepointSynchronize::is_at_safepoint(), \
416 heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
417 "should not be at a safepoint")); \
418 } while (0)
420 #define assert_at_safepoint(_should_be_vm_thread_) \
421 do { \
422 assert(SafepointSynchronize::is_at_safepoint() && \
423 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
424 heap_locking_asserts_err_msg("should be at a safepoint")); \
425 } while (0)
427 #define assert_not_at_safepoint() \
428 do { \
429 assert(!SafepointSynchronize::is_at_safepoint(), \
430 heap_locking_asserts_err_msg("should not be at a safepoint")); \
431 } while (0)
433 protected:
435 // The young region list.
436 YoungList* _young_list;
438 // The current policy object for the collector.
439 G1CollectorPolicy* _g1_policy;
441 // This is the second level of trying to allocate a new region. If
442 // new_region() didn't find a region on the free_list, this call will
443 // check whether there's anything available on the
444 // secondary_free_list and/or wait for more regions to appear on
445 // that list, if _free_regions_coming is set.
446 HeapRegion* new_region_try_secondary_free_list(bool is_old);
448 // Try to allocate a single non-humongous HeapRegion sufficient for
449 // an allocation of the given word_size. If do_expand is true,
450 // attempt to expand the heap if necessary to satisfy the allocation
451 // request. If the region is to be used as an old region or for a
452 // humongous object, set is_old to true. If not, to false.
453 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
455 // Initialize a contiguous set of free regions of length num_regions
456 // and starting at index first so that they appear as a single
457 // humongous region.
458 HeapWord* humongous_obj_allocate_initialize_regions(uint first,
459 uint num_regions,
460 size_t word_size,
461 AllocationContext_t context);
463 // Attempt to allocate a humongous object of the given size. Return
464 // NULL if unsuccessful.
465 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context);
467 // The following two methods, allocate_new_tlab() and
468 // mem_allocate(), are the two main entry points from the runtime
469 // into the G1's allocation routines. They have the following
470 // assumptions:
471 //
472 // * They should both be called outside safepoints.
473 //
474 // * They should both be called without holding the Heap_lock.
475 //
476 // * All allocation requests for new TLABs should go to
477 // allocate_new_tlab().
478 //
479 // * All non-TLAB allocation requests should go to mem_allocate().
480 //
481 // * If either call cannot satisfy the allocation request using the
482 // current allocating region, they will try to get a new one. If
483 // this fails, they will attempt to do an evacuation pause and
484 // retry the allocation.
485 //
486 // * If all allocation attempts fail, even after trying to schedule
487 // an evacuation pause, allocate_new_tlab() will return NULL,
488 // whereas mem_allocate() will attempt a heap expansion and/or
489 // schedule a Full GC.
490 //
491 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
492 // should never be called with word_size being humongous. All
493 // humongous allocation requests should go to mem_allocate() which
494 // will satisfy them with a special path.
496 virtual HeapWord* allocate_new_tlab(size_t word_size);
498 virtual HeapWord* mem_allocate(size_t word_size,
499 bool* gc_overhead_limit_was_exceeded);
501 // The following three methods take a gc_count_before_ret
502 // parameter which is used to return the GC count if the method
503 // returns NULL. Given that we are required to read the GC count
504 // while holding the Heap_lock, and these paths will take the
505 // Heap_lock at some point, it's easier to get them to read the GC
506 // count while holding the Heap_lock before they return NULL instead
507 // of the caller (namely: mem_allocate()) having to also take the
508 // Heap_lock just to read the GC count.
510 // First-level mutator allocation attempt: try to allocate out of
511 // the mutator alloc region without taking the Heap_lock. This
512 // should only be used for non-humongous allocations.
513 inline HeapWord* attempt_allocation(size_t word_size,
514 unsigned int* gc_count_before_ret,
515 int* gclocker_retry_count_ret);
517 // Second-level mutator allocation attempt: take the Heap_lock and
518 // retry the allocation attempt, potentially scheduling a GC
519 // pause. This should only be used for non-humongous allocations.
520 HeapWord* attempt_allocation_slow(size_t word_size,
521 AllocationContext_t context,
522 unsigned int* gc_count_before_ret,
523 int* gclocker_retry_count_ret);
525 // Takes the Heap_lock and attempts a humongous allocation. It can
526 // potentially schedule a GC pause.
527 HeapWord* attempt_allocation_humongous(size_t word_size,
528 unsigned int* gc_count_before_ret,
529 int* gclocker_retry_count_ret);
531 // Allocation attempt that should be called during safepoints (e.g.,
532 // at the end of a successful GC). expect_null_mutator_alloc_region
533 // specifies whether the mutator alloc region is expected to be NULL
534 // or not.
535 HeapWord* attempt_allocation_at_safepoint(size_t word_size,
536 AllocationContext_t context,
537 bool expect_null_mutator_alloc_region);
539 // It dirties the cards that cover the block so that so that the post
540 // write barrier never queues anything when updating objects on this
541 // block. It is assumed (and in fact we assert) that the block
542 // belongs to a young region.
543 inline void dirty_young_block(HeapWord* start, size_t word_size);
545 // Allocate blocks during garbage collection. Will ensure an
546 // allocation region, either by picking one or expanding the
547 // heap, and then allocate a block of the given size. The block
548 // may not be a humongous - it must fit into a single heap region.
549 HeapWord* par_allocate_during_gc(GCAllocPurpose purpose,
550 size_t word_size,
551 AllocationContext_t context);
553 HeapWord* allocate_during_gc_slow(GCAllocPurpose purpose,
554 HeapRegion* alloc_region,
555 bool par,
556 size_t word_size);
558 // Ensure that no further allocations can happen in "r", bearing in mind
559 // that parallel threads might be attempting allocations.
560 void par_allocate_remaining_space(HeapRegion* r);
562 // Allocation attempt during GC for a survivor object / PLAB.
563 inline HeapWord* survivor_attempt_allocation(size_t word_size,
564 AllocationContext_t context);
566 // Allocation attempt during GC for an old object / PLAB.
567 inline HeapWord* old_attempt_allocation(size_t word_size,
568 AllocationContext_t context);
570 // These methods are the "callbacks" from the G1AllocRegion class.
572 // For mutator alloc regions.
573 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
574 void retire_mutator_alloc_region(HeapRegion* alloc_region,
575 size_t allocated_bytes);
577 // For GC alloc regions.
578 HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
579 GCAllocPurpose ap);
580 void retire_gc_alloc_region(HeapRegion* alloc_region,
581 size_t allocated_bytes, GCAllocPurpose ap);
583 // - if explicit_gc is true, the GC is for a System.gc() or a heap
584 // inspection request and should collect the entire heap
585 // - if clear_all_soft_refs is true, all soft references should be
586 // cleared during the GC
587 // - if explicit_gc is false, word_size describes the allocation that
588 // the GC should attempt (at least) to satisfy
589 // - it returns false if it is unable to do the collection due to the
590 // GC locker being active, true otherwise
591 bool do_collection(bool explicit_gc,
592 bool clear_all_soft_refs,
593 size_t word_size);
595 // Callback from VM_G1CollectFull operation.
596 // Perform a full collection.
597 virtual void do_full_collection(bool clear_all_soft_refs);
599 // Resize the heap if necessary after a full collection. If this is
600 // after a collect-for allocation, "word_size" is the allocation size,
601 // and will be considered part of the used portion of the heap.
602 void resize_if_necessary_after_full_collection(size_t word_size);
604 // Callback from VM_G1CollectForAllocation operation.
605 // This function does everything necessary/possible to satisfy a
606 // failed allocation request (including collection, expansion, etc.)
607 HeapWord* satisfy_failed_allocation(size_t word_size,
608 AllocationContext_t context,
609 bool* succeeded);
611 // Attempting to expand the heap sufficiently
612 // to support an allocation of the given "word_size". If
613 // successful, perform the allocation and return the address of the
614 // allocated block, or else "NULL".
615 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context);
617 // Process any reference objects discovered during
618 // an incremental evacuation pause.
619 void process_discovered_references(uint no_of_gc_workers);
621 // Enqueue any remaining discovered references
622 // after processing.
623 void enqueue_discovered_references(uint no_of_gc_workers);
625 public:
627 G1Allocator* allocator() {
628 return _allocator;
629 }
631 G1MonitoringSupport* g1mm() {
632 assert(_g1mm != NULL, "should have been initialized");
633 return _g1mm;
634 }
636 // Expand the garbage-first heap by at least the given size (in bytes!).
637 // Returns true if the heap was expanded by the requested amount;
638 // false otherwise.
639 // (Rounds up to a HeapRegion boundary.)
640 bool expand(size_t expand_bytes);
642 // Returns the PLAB statistics given a purpose.
643 PLABStats* stats_for_purpose(GCAllocPurpose purpose) {
644 PLABStats* stats = NULL;
646 switch (purpose) {
647 case GCAllocForSurvived:
648 stats = &_survivor_plab_stats;
649 break;
650 case GCAllocForTenured:
651 stats = &_old_plab_stats;
652 break;
653 default:
654 assert(false, "unrecognized GCAllocPurpose");
655 }
657 return stats;
658 }
660 // Determines PLAB size for a particular allocation purpose.
661 size_t desired_plab_sz(GCAllocPurpose purpose);
663 inline AllocationContextStats& allocation_context_stats();
665 // Do anything common to GC's.
666 virtual void gc_prologue(bool full);
667 virtual void gc_epilogue(bool full);
669 inline void set_humongous_is_live(oop obj);
671 bool humongous_is_live(uint region) {
672 return _humongous_is_live.is_live(region);
673 }
675 // Returns whether the given region (which must be a humongous (start) region)
676 // is to be considered conservatively live regardless of any other conditions.
677 bool humongous_region_is_always_live(uint index);
678 // Register the given region to be part of the collection set.
679 inline void register_humongous_region_with_in_cset_fast_test(uint index);
680 // Register regions with humongous objects (actually on the start region) in
681 // the in_cset_fast_test table.
682 void register_humongous_regions_with_in_cset_fast_test();
683 // We register a region with the fast "in collection set" test. We
684 // simply set to true the array slot corresponding to this region.
685 void register_region_with_in_cset_fast_test(HeapRegion* r) {
686 _in_cset_fast_test.set_in_cset(r->hrm_index());
687 }
689 // This is a fast test on whether a reference points into the
690 // collection set or not. Assume that the reference
691 // points into the heap.
692 inline bool in_cset_fast_test(oop obj);
694 void clear_cset_fast_test() {
695 _in_cset_fast_test.clear();
696 }
698 // This is called at the start of either a concurrent cycle or a Full
699 // GC to update the number of old marking cycles started.
700 void increment_old_marking_cycles_started();
702 // This is called at the end of either a concurrent cycle or a Full
703 // GC to update the number of old marking cycles completed. Those two
704 // can happen in a nested fashion, i.e., we start a concurrent
705 // cycle, a Full GC happens half-way through it which ends first,
706 // and then the cycle notices that a Full GC happened and ends
707 // too. The concurrent parameter is a boolean to help us do a bit
708 // tighter consistency checking in the method. If concurrent is
709 // false, the caller is the inner caller in the nesting (i.e., the
710 // Full GC). If concurrent is true, the caller is the outer caller
711 // in this nesting (i.e., the concurrent cycle). Further nesting is
712 // not currently supported. The end of this call also notifies
713 // the FullGCCount_lock in case a Java thread is waiting for a full
714 // GC to happen (e.g., it called System.gc() with
715 // +ExplicitGCInvokesConcurrent).
716 void increment_old_marking_cycles_completed(bool concurrent);
718 unsigned int old_marking_cycles_completed() {
719 return _old_marking_cycles_completed;
720 }
722 void register_concurrent_cycle_start(const Ticks& start_time);
723 void register_concurrent_cycle_end();
724 void trace_heap_after_concurrent_cycle();
726 G1YCType yc_type();
728 G1HRPrinter* hr_printer() { return &_hr_printer; }
730 // Frees a non-humongous region by initializing its contents and
731 // adding it to the free list that's passed as a parameter (this is
732 // usually a local list which will be appended to the master free
733 // list later). The used bytes of freed regions are accumulated in
734 // pre_used. If par is true, the region's RSet will not be freed
735 // up. The assumption is that this will be done later.
736 // The locked parameter indicates if the caller has already taken
737 // care of proper synchronization. This may allow some optimizations.
738 void free_region(HeapRegion* hr,
739 FreeRegionList* free_list,
740 bool par,
741 bool locked = false);
743 // Frees a humongous region by collapsing it into individual regions
744 // and calling free_region() for each of them. The freed regions
745 // will be added to the free list that's passed as a parameter (this
746 // is usually a local list which will be appended to the master free
747 // list later). The used bytes of freed regions are accumulated in
748 // pre_used. If par is true, the region's RSet will not be freed
749 // up. The assumption is that this will be done later.
750 void free_humongous_region(HeapRegion* hr,
751 FreeRegionList* free_list,
752 bool par);
753 protected:
755 // Shrink the garbage-first heap by at most the given size (in bytes!).
756 // (Rounds down to a HeapRegion boundary.)
757 virtual void shrink(size_t expand_bytes);
758 void shrink_helper(size_t expand_bytes);
760 #if TASKQUEUE_STATS
761 static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
762 void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
763 void reset_taskqueue_stats();
764 #endif // TASKQUEUE_STATS
766 // Schedule the VM operation that will do an evacuation pause to
767 // satisfy an allocation request of word_size. *succeeded will
768 // return whether the VM operation was successful (it did do an
769 // evacuation pause) or not (another thread beat us to it or the GC
770 // locker was active). Given that we should not be holding the
771 // Heap_lock when we enter this method, we will pass the
772 // gc_count_before (i.e., total_collections()) as a parameter since
773 // it has to be read while holding the Heap_lock. Currently, both
774 // methods that call do_collection_pause() release the Heap_lock
775 // before the call, so it's easy to read gc_count_before just before.
776 HeapWord* do_collection_pause(size_t word_size,
777 unsigned int gc_count_before,
778 bool* succeeded,
779 GCCause::Cause gc_cause);
781 // The guts of the incremental collection pause, executed by the vm
782 // thread. It returns false if it is unable to do the collection due
783 // to the GC locker being active, true otherwise
784 bool do_collection_pause_at_safepoint(double target_pause_time_ms);
786 // Actually do the work of evacuating the collection set.
787 void evacuate_collection_set(EvacuationInfo& evacuation_info);
789 // The g1 remembered set of the heap.
790 G1RemSet* _g1_rem_set;
792 // A set of cards that cover the objects for which the Rsets should be updated
793 // concurrently after the collection.
794 DirtyCardQueueSet _dirty_card_queue_set;
796 // The closure used to refine a single card.
797 RefineCardTableEntryClosure* _refine_cte_cl;
799 // A function to check the consistency of dirty card logs.
800 void check_ct_logs_at_safepoint();
802 // A DirtyCardQueueSet that is used to hold cards that contain
803 // references into the current collection set. This is used to
804 // update the remembered sets of the regions in the collection
805 // set in the event of an evacuation failure.
806 DirtyCardQueueSet _into_cset_dirty_card_queue_set;
808 // After a collection pause, make the regions in the CS into free
809 // regions.
810 void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info);
812 // Abandon the current collection set without recording policy
813 // statistics or updating free lists.
814 void abandon_collection_set(HeapRegion* cs_head);
816 // Applies "scan_non_heap_roots" to roots outside the heap,
817 // "scan_rs" to roots inside the heap (having done "set_region" to
818 // indicate the region in which the root resides),
819 // and does "scan_metadata" If "scan_rs" is
820 // NULL, then this step is skipped. The "worker_i"
821 // param is for use with parallel roots processing, and should be
822 // the "i" of the calling parallel worker thread's work(i) function.
823 // In the sequential case this param will be ignored.
824 void g1_process_roots(OopClosure* scan_non_heap_roots,
825 OopClosure* scan_non_heap_weak_roots,
826 OopsInHeapRegionClosure* scan_rs,
827 CLDClosure* scan_strong_clds,
828 CLDClosure* scan_weak_clds,
829 CodeBlobClosure* scan_strong_code,
830 uint worker_i);
832 // The concurrent marker (and the thread it runs in.)
833 ConcurrentMark* _cm;
834 ConcurrentMarkThread* _cmThread;
835 bool _mark_in_progress;
837 // The concurrent refiner.
838 ConcurrentG1Refine* _cg1r;
840 // The parallel task queues
841 RefToScanQueueSet *_task_queues;
843 // True iff a evacuation has failed in the current collection.
844 bool _evacuation_failed;
846 EvacuationFailedInfo* _evacuation_failed_info_array;
848 // Failed evacuations cause some logical from-space objects to have
849 // forwarding pointers to themselves. Reset them.
850 void remove_self_forwarding_pointers();
852 // Together, these store an object with a preserved mark, and its mark value.
853 Stack<oop, mtGC> _objs_with_preserved_marks;
854 Stack<markOop, mtGC> _preserved_marks_of_objs;
856 // Preserve the mark of "obj", if necessary, in preparation for its mark
857 // word being overwritten with a self-forwarding-pointer.
858 void preserve_mark_if_necessary(oop obj, markOop m);
860 // The stack of evac-failure objects left to be scanned.
861 GrowableArray<oop>* _evac_failure_scan_stack;
862 // The closure to apply to evac-failure objects.
864 OopsInHeapRegionClosure* _evac_failure_closure;
865 // Set the field above.
866 void
867 set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
868 _evac_failure_closure = evac_failure_closure;
869 }
871 // Push "obj" on the scan stack.
872 void push_on_evac_failure_scan_stack(oop obj);
873 // Process scan stack entries until the stack is empty.
874 void drain_evac_failure_scan_stack();
875 // True iff an invocation of "drain_scan_stack" is in progress; to
876 // prevent unnecessary recursion.
877 bool _drain_in_progress;
879 // Do any necessary initialization for evacuation-failure handling.
880 // "cl" is the closure that will be used to process evac-failure
881 // objects.
882 void init_for_evac_failure(OopsInHeapRegionClosure* cl);
883 // Do any necessary cleanup for evacuation-failure handling data
884 // structures.
885 void finalize_for_evac_failure();
887 // An attempt to evacuate "obj" has failed; take necessary steps.
888 oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj);
889 void handle_evacuation_failure_common(oop obj, markOop m);
891 #ifndef PRODUCT
892 // Support for forcing evacuation failures. Analogous to
893 // PromotionFailureALot for the other collectors.
895 // Records whether G1EvacuationFailureALot should be in effect
896 // for the current GC
897 bool _evacuation_failure_alot_for_current_gc;
899 // Used to record the GC number for interval checking when
900 // determining whether G1EvaucationFailureALot is in effect
901 // for the current GC.
902 size_t _evacuation_failure_alot_gc_number;
904 // Count of the number of evacuations between failures.
905 volatile size_t _evacuation_failure_alot_count;
907 // Set whether G1EvacuationFailureALot should be in effect
908 // for the current GC (based upon the type of GC and which
909 // command line flags are set);
910 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
911 bool during_initial_mark,
912 bool during_marking);
914 inline void set_evacuation_failure_alot_for_current_gc();
916 // Return true if it's time to cause an evacuation failure.
917 inline bool evacuation_should_fail();
919 // Reset the G1EvacuationFailureALot counters. Should be called at
920 // the end of an evacuation pause in which an evacuation failure occurred.
921 inline void reset_evacuation_should_fail();
922 #endif // !PRODUCT
924 // ("Weak") Reference processing support.
925 //
926 // G1 has 2 instances of the reference processor class. One
927 // (_ref_processor_cm) handles reference object discovery
928 // and subsequent processing during concurrent marking cycles.
929 //
930 // The other (_ref_processor_stw) handles reference object
931 // discovery and processing during full GCs and incremental
932 // evacuation pauses.
933 //
934 // During an incremental pause, reference discovery will be
935 // temporarily disabled for _ref_processor_cm and will be
936 // enabled for _ref_processor_stw. At the end of the evacuation
937 // pause references discovered by _ref_processor_stw will be
938 // processed and discovery will be disabled. The previous
939 // setting for reference object discovery for _ref_processor_cm
940 // will be re-instated.
941 //
942 // At the start of marking:
943 // * Discovery by the CM ref processor is verified to be inactive
944 // and it's discovered lists are empty.
945 // * Discovery by the CM ref processor is then enabled.
946 //
947 // At the end of marking:
948 // * Any references on the CM ref processor's discovered
949 // lists are processed (possibly MT).
950 //
951 // At the start of full GC we:
952 // * Disable discovery by the CM ref processor and
953 // empty CM ref processor's discovered lists
954 // (without processing any entries).
955 // * Verify that the STW ref processor is inactive and it's
956 // discovered lists are empty.
957 // * Temporarily set STW ref processor discovery as single threaded.
958 // * Temporarily clear the STW ref processor's _is_alive_non_header
959 // field.
960 // * Finally enable discovery by the STW ref processor.
961 //
962 // The STW ref processor is used to record any discovered
963 // references during the full GC.
964 //
965 // At the end of a full GC we:
966 // * Enqueue any reference objects discovered by the STW ref processor
967 // that have non-live referents. This has the side-effect of
968 // making the STW ref processor inactive by disabling discovery.
969 // * Verify that the CM ref processor is still inactive
970 // and no references have been placed on it's discovered
971 // lists (also checked as a precondition during initial marking).
973 // The (stw) reference processor...
974 ReferenceProcessor* _ref_processor_stw;
976 STWGCTimer* _gc_timer_stw;
977 ConcurrentGCTimer* _gc_timer_cm;
979 G1OldTracer* _gc_tracer_cm;
980 G1NewTracer* _gc_tracer_stw;
982 // During reference object discovery, the _is_alive_non_header
983 // closure (if non-null) is applied to the referent object to
984 // determine whether the referent is live. If so then the
985 // reference object does not need to be 'discovered' and can
986 // be treated as a regular oop. This has the benefit of reducing
987 // the number of 'discovered' reference objects that need to
988 // be processed.
989 //
990 // Instance of the is_alive closure for embedding into the
991 // STW reference processor as the _is_alive_non_header field.
992 // Supplying a value for the _is_alive_non_header field is
993 // optional but doing so prevents unnecessary additions to
994 // the discovered lists during reference discovery.
995 G1STWIsAliveClosure _is_alive_closure_stw;
997 // The (concurrent marking) reference processor...
998 ReferenceProcessor* _ref_processor_cm;
1000 // Instance of the concurrent mark is_alive closure for embedding
1001 // into the Concurrent Marking reference processor as the
1002 // _is_alive_non_header field. Supplying a value for the
1003 // _is_alive_non_header field is optional but doing so prevents
1004 // unnecessary additions to the discovered lists during reference
1005 // discovery.
1006 G1CMIsAliveClosure _is_alive_closure_cm;
1008 // Cache used by G1CollectedHeap::start_cset_region_for_worker().
1009 HeapRegion** _worker_cset_start_region;
1011 // Time stamp to validate the regions recorded in the cache
1012 // used by G1CollectedHeap::start_cset_region_for_worker().
1013 // The heap region entry for a given worker is valid iff
1014 // the associated time stamp value matches the current value
1015 // of G1CollectedHeap::_gc_time_stamp.
1016 unsigned int* _worker_cset_start_region_time_stamp;
1018 enum G1H_process_roots_tasks {
1019 G1H_PS_filter_satb_buffers,
1020 G1H_PS_refProcessor_oops_do,
1021 // Leave this one last.
1022 G1H_PS_NumElements
1023 };
1025 SubTasksDone* _process_strong_tasks;
1027 volatile bool _free_regions_coming;
1029 public:
1031 SubTasksDone* process_strong_tasks() { return _process_strong_tasks; }
1033 void set_refine_cte_cl_concurrency(bool concurrent);
1035 RefToScanQueue *task_queue(int i) const;
1037 // A set of cards where updates happened during the GC
1038 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
1040 // A DirtyCardQueueSet that is used to hold cards that contain
1041 // references into the current collection set. This is used to
1042 // update the remembered sets of the regions in the collection
1043 // set in the event of an evacuation failure.
1044 DirtyCardQueueSet& into_cset_dirty_card_queue_set()
1045 { return _into_cset_dirty_card_queue_set; }
1047 // Create a G1CollectedHeap with the specified policy.
1048 // Must call the initialize method afterwards.
1049 // May not return if something goes wrong.
1050 G1CollectedHeap(G1CollectorPolicy* policy);
1052 // Initialize the G1CollectedHeap to have the initial and
1053 // maximum sizes and remembered and barrier sets
1054 // specified by the policy object.
1055 jint initialize();
1057 virtual void stop();
1059 // Return the (conservative) maximum heap alignment for any G1 heap
1060 static size_t conservative_max_heap_alignment();
1062 // Initialize weak reference processing.
1063 virtual void ref_processing_init();
1065 void set_par_threads(uint t) {
1066 SharedHeap::set_par_threads(t);
1067 // Done in SharedHeap but oddly there are
1068 // two _process_strong_tasks's in a G1CollectedHeap
1069 // so do it here too.
1070 _process_strong_tasks->set_n_threads(t);
1071 }
1073 // Set _n_par_threads according to a policy TBD.
1074 void set_par_threads();
1076 void set_n_termination(int t) {
1077 _process_strong_tasks->set_n_threads(t);
1078 }
1080 virtual CollectedHeap::Name kind() const {
1081 return CollectedHeap::G1CollectedHeap;
1082 }
1084 // The current policy object for the collector.
1085 G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1087 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); }
1089 // Adaptive size policy. No such thing for g1.
1090 virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1092 // The rem set and barrier set.
1093 G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1095 unsigned get_gc_time_stamp() {
1096 return _gc_time_stamp;
1097 }
1099 inline void reset_gc_time_stamp();
1101 void check_gc_time_stamps() PRODUCT_RETURN;
1103 inline void increment_gc_time_stamp();
1105 // Reset the given region's GC timestamp. If it's starts humongous,
1106 // also reset the GC timestamp of its corresponding
1107 // continues humongous regions too.
1108 void reset_gc_time_stamps(HeapRegion* hr);
1110 void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1111 DirtyCardQueue* into_cset_dcq,
1112 bool concurrent, uint worker_i);
1114 // The shared block offset table array.
1115 G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1117 // Reference Processing accessors
1119 // The STW reference processor....
1120 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1122 // The Concurrent Marking reference processor...
1123 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1125 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1126 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1128 virtual size_t capacity() const;
1129 virtual size_t used() const;
1130 // This should be called when we're not holding the heap lock. The
1131 // result might be a bit inaccurate.
1132 size_t used_unlocked() const;
1133 size_t recalculate_used() const;
1135 // These virtual functions do the actual allocation.
1136 // Some heaps may offer a contiguous region for shared non-blocking
1137 // allocation, via inlined code (by exporting the address of the top and
1138 // end fields defining the extent of the contiguous allocation region.)
1139 // But G1CollectedHeap doesn't yet support this.
1141 virtual bool is_maximal_no_gc() const {
1142 return _hrm.available() == 0;
1143 }
1145 // The current number of regions in the heap.
1146 uint num_regions() const { return _hrm.length(); }
1148 // The max number of regions in the heap.
1149 uint max_regions() const { return _hrm.max_length(); }
1151 // The number of regions that are completely free.
1152 uint num_free_regions() const { return _hrm.num_free_regions(); }
1154 // The number of regions that are not completely free.
1155 uint num_used_regions() const { return num_regions() - num_free_regions(); }
1157 void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1158 void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1159 void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1160 void verify_dirty_young_regions() PRODUCT_RETURN;
1162 #ifndef PRODUCT
1163 // Make sure that the given bitmap has no marked objects in the
1164 // range [from,limit). If it does, print an error message and return
1165 // false. Otherwise, just return true. bitmap_name should be "prev"
1166 // or "next".
1167 bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
1168 HeapWord* from, HeapWord* limit);
1170 // Verify that the prev / next bitmap range [tams,end) for the given
1171 // region has no marks. Return true if all is well, false if errors
1172 // are detected.
1173 bool verify_bitmaps(const char* caller, HeapRegion* hr);
1174 #endif // PRODUCT
1176 // If G1VerifyBitmaps is set, verify that the marking bitmaps for
1177 // the given region do not have any spurious marks. If errors are
1178 // detected, print appropriate error messages and crash.
1179 void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN;
1181 // If G1VerifyBitmaps is set, verify that the marking bitmaps do not
1182 // have any spurious marks. If errors are detected, print
1183 // appropriate error messages and crash.
1184 void check_bitmaps(const char* caller) PRODUCT_RETURN;
1186 // verify_region_sets() performs verification over the region
1187 // lists. It will be compiled in the product code to be used when
1188 // necessary (i.e., during heap verification).
1189 void verify_region_sets();
1191 // verify_region_sets_optional() is planted in the code for
1192 // list verification in non-product builds (and it can be enabled in
1193 // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1).
1194 #if HEAP_REGION_SET_FORCE_VERIFY
1195 void verify_region_sets_optional() {
1196 verify_region_sets();
1197 }
1198 #else // HEAP_REGION_SET_FORCE_VERIFY
1199 void verify_region_sets_optional() { }
1200 #endif // HEAP_REGION_SET_FORCE_VERIFY
1202 #ifdef ASSERT
1203 bool is_on_master_free_list(HeapRegion* hr) {
1204 return _hrm.is_free(hr);
1205 }
1206 #endif // ASSERT
1208 // Wrapper for the region list operations that can be called from
1209 // methods outside this class.
1211 void secondary_free_list_add(FreeRegionList* list) {
1212 _secondary_free_list.add_ordered(list);
1213 }
1215 void append_secondary_free_list() {
1216 _hrm.insert_list_into_free_list(&_secondary_free_list);
1217 }
1219 void append_secondary_free_list_if_not_empty_with_lock() {
1220 // If the secondary free list looks empty there's no reason to
1221 // take the lock and then try to append it.
1222 if (!_secondary_free_list.is_empty()) {
1223 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1224 append_secondary_free_list();
1225 }
1226 }
1228 inline void old_set_remove(HeapRegion* hr);
1230 size_t non_young_capacity_bytes() {
1231 return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1232 }
1234 void set_free_regions_coming();
1235 void reset_free_regions_coming();
1236 bool free_regions_coming() { return _free_regions_coming; }
1237 void wait_while_free_regions_coming();
1239 // Determine whether the given region is one that we are using as an
1240 // old GC alloc region.
1241 bool is_old_gc_alloc_region(HeapRegion* hr) {
1242 return _allocator->is_retained_old_region(hr);
1243 }
1245 // Perform a collection of the heap; intended for use in implementing
1246 // "System.gc". This probably implies as full a collection as the
1247 // "CollectedHeap" supports.
1248 virtual void collect(GCCause::Cause cause);
1250 // The same as above but assume that the caller holds the Heap_lock.
1251 void collect_locked(GCCause::Cause cause);
1253 virtual bool copy_allocation_context_stats(const jint* contexts,
1254 jlong* totals,
1255 jbyte* accuracy,
1256 jint len);
1258 // True iff an evacuation has failed in the most-recent collection.
1259 bool evacuation_failed() { return _evacuation_failed; }
1261 void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed);
1262 void prepend_to_freelist(FreeRegionList* list);
1263 void decrement_summary_bytes(size_t bytes);
1265 // Returns "TRUE" iff "p" points into the committed areas of the heap.
1266 virtual bool is_in(const void* p) const;
1267 #ifdef ASSERT
1268 // Returns whether p is in one of the available areas of the heap. Slow but
1269 // extensive version.
1270 bool is_in_exact(const void* p) const;
1271 #endif
1273 // Return "TRUE" iff the given object address is within the collection
1274 // set. Slow implementation.
1275 inline bool obj_in_cs(oop obj);
1277 inline bool is_in_cset(oop obj);
1279 inline bool is_in_cset_or_humongous(const oop obj);
1281 enum in_cset_state_t {
1282 InNeither, // neither in collection set nor humongous
1283 InCSet, // region is in collection set only
1284 IsHumongous // region is a humongous start region
1285 };
1286 private:
1287 // Instances of this class are used for quick tests on whether a reference points
1288 // into the collection set or is a humongous object (points into a humongous
1289 // object).
1290 // Each of the array's elements denotes whether the corresponding region is in
1291 // the collection set or a humongous region.
1292 // We use this to quickly reclaim humongous objects: by making a humongous region
1293 // succeed this test, we sort-of add it to the collection set. During the reference
1294 // iteration closures, when we see a humongous region, we simply mark it as
1295 // referenced, i.e. live.
1296 class G1FastCSetBiasedMappedArray : public G1BiasedMappedArray<char> {
1297 protected:
1298 char default_value() const { return G1CollectedHeap::InNeither; }
1299 public:
1300 void set_humongous(uintptr_t index) {
1301 assert(get_by_index(index) != InCSet, "Should not overwrite InCSet values");
1302 set_by_index(index, G1CollectedHeap::IsHumongous);
1303 }
1305 void clear_humongous(uintptr_t index) {
1306 set_by_index(index, G1CollectedHeap::InNeither);
1307 }
1309 void set_in_cset(uintptr_t index) {
1310 assert(get_by_index(index) != G1CollectedHeap::IsHumongous, "Should not overwrite IsHumongous value");
1311 set_by_index(index, G1CollectedHeap::InCSet);
1312 }
1314 bool is_in_cset_or_humongous(HeapWord* addr) const { return get_by_address(addr) != G1CollectedHeap::InNeither; }
1315 bool is_in_cset(HeapWord* addr) const { return get_by_address(addr) == G1CollectedHeap::InCSet; }
1316 G1CollectedHeap::in_cset_state_t at(HeapWord* addr) const { return (G1CollectedHeap::in_cset_state_t)get_by_address(addr); }
1317 void clear() { G1BiasedMappedArray<char>::clear(); }
1318 };
1320 // This array is used for a quick test on whether a reference points into
1321 // the collection set or not. Each of the array's elements denotes whether the
1322 // corresponding region is in the collection set or not.
1323 G1FastCSetBiasedMappedArray _in_cset_fast_test;
1325 public:
1327 inline in_cset_state_t in_cset_state(const oop obj);
1329 // Return "TRUE" iff the given object address is in the reserved
1330 // region of g1.
1331 bool is_in_g1_reserved(const void* p) const {
1332 return _hrm.reserved().contains(p);
1333 }
1335 // Returns a MemRegion that corresponds to the space that has been
1336 // reserved for the heap
1337 MemRegion g1_reserved() const {
1338 return _hrm.reserved();
1339 }
1341 virtual bool is_in_closed_subset(const void* p) const;
1343 G1SATBCardTableLoggingModRefBS* g1_barrier_set() {
1344 return (G1SATBCardTableLoggingModRefBS*) barrier_set();
1345 }
1347 // This resets the card table to all zeros. It is used after
1348 // a collection pause which used the card table to claim cards.
1349 void cleanUpCardTable();
1351 // Iteration functions.
1353 // Iterate over all the ref-containing fields of all objects, calling
1354 // "cl.do_oop" on each.
1355 virtual void oop_iterate(ExtendedOopClosure* cl);
1357 // Iterate over all objects, calling "cl.do_object" on each.
1358 virtual void object_iterate(ObjectClosure* cl);
1360 virtual void safe_object_iterate(ObjectClosure* cl) {
1361 object_iterate(cl);
1362 }
1364 // Iterate over all spaces in use in the heap, in ascending address order.
1365 virtual void space_iterate(SpaceClosure* cl);
1367 // Iterate over heap regions, in address order, terminating the
1368 // iteration early if the "doHeapRegion" method returns "true".
1369 void heap_region_iterate(HeapRegionClosure* blk) const;
1371 // Return the region with the given index. It assumes the index is valid.
1372 inline HeapRegion* region_at(uint index) const;
1374 // Calculate the region index of the given address. Given address must be
1375 // within the heap.
1376 inline uint addr_to_region(HeapWord* addr) const;
1378 inline HeapWord* bottom_addr_for_region(uint index) const;
1380 // Divide the heap region sequence into "chunks" of some size (the number
1381 // of regions divided by the number of parallel threads times some
1382 // overpartition factor, currently 4). Assumes that this will be called
1383 // in parallel by ParallelGCThreads worker threads with discinct worker
1384 // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel
1385 // calls will use the same "claim_value", and that that claim value is
1386 // different from the claim_value of any heap region before the start of
1387 // the iteration. Applies "blk->doHeapRegion" to each of the regions, by
1388 // attempting to claim the first region in each chunk, and, if
1389 // successful, applying the closure to each region in the chunk (and
1390 // setting the claim value of the second and subsequent regions of the
1391 // chunk.) For now requires that "doHeapRegion" always returns "false",
1392 // i.e., that a closure never attempt to abort a traversal.
1393 void heap_region_par_iterate_chunked(HeapRegionClosure* cl,
1394 uint worker_id,
1395 uint num_workers,
1396 jint claim_value) const;
1398 // It resets all the region claim values to the default.
1399 void reset_heap_region_claim_values();
1401 // Resets the claim values of regions in the current
1402 // collection set to the default.
1403 void reset_cset_heap_region_claim_values();
1405 #ifdef ASSERT
1406 bool check_heap_region_claim_values(jint claim_value);
1408 // Same as the routine above but only checks regions in the
1409 // current collection set.
1410 bool check_cset_heap_region_claim_values(jint claim_value);
1411 #endif // ASSERT
1413 // Clear the cached cset start regions and (more importantly)
1414 // the time stamps. Called when we reset the GC time stamp.
1415 void clear_cset_start_regions();
1417 // Given the id of a worker, obtain or calculate a suitable
1418 // starting region for iterating over the current collection set.
1419 HeapRegion* start_cset_region_for_worker(uint worker_i);
1421 // Iterate over the regions (if any) in the current collection set.
1422 void collection_set_iterate(HeapRegionClosure* blk);
1424 // As above but starting from region r
1425 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1427 HeapRegion* next_compaction_region(const HeapRegion* from) const;
1429 // A CollectedHeap will contain some number of spaces. This finds the
1430 // space containing a given address, or else returns NULL.
1431 virtual Space* space_containing(const void* addr) const;
1433 // Returns the HeapRegion that contains addr. addr must not be NULL.
1434 template <class T>
1435 inline HeapRegion* heap_region_containing_raw(const T addr) const;
1437 // Returns the HeapRegion that contains addr. addr must not be NULL.
1438 // If addr is within a humongous continues region, it returns its humongous start region.
1439 template <class T>
1440 inline HeapRegion* heap_region_containing(const T addr) const;
1442 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1443 // each address in the (reserved) heap is a member of exactly
1444 // one block. The defining characteristic of a block is that it is
1445 // possible to find its size, and thus to progress forward to the next
1446 // block. (Blocks may be of different sizes.) Thus, blocks may
1447 // represent Java objects, or they might be free blocks in a
1448 // free-list-based heap (or subheap), as long as the two kinds are
1449 // distinguishable and the size of each is determinable.
1451 // Returns the address of the start of the "block" that contains the
1452 // address "addr". We say "blocks" instead of "object" since some heaps
1453 // may not pack objects densely; a chunk may either be an object or a
1454 // non-object.
1455 virtual HeapWord* block_start(const void* addr) const;
1457 // Requires "addr" to be the start of a chunk, and returns its size.
1458 // "addr + size" is required to be the start of a new chunk, or the end
1459 // of the active area of the heap.
1460 virtual size_t block_size(const HeapWord* addr) const;
1462 // Requires "addr" to be the start of a block, and returns "TRUE" iff
1463 // the block is an object.
1464 virtual bool block_is_obj(const HeapWord* addr) const;
1466 // Does this heap support heap inspection? (+PrintClassHistogram)
1467 virtual bool supports_heap_inspection() const { return true; }
1469 // Section on thread-local allocation buffers (TLABs)
1470 // See CollectedHeap for semantics.
1472 bool supports_tlab_allocation() const;
1473 size_t tlab_capacity(Thread* ignored) const;
1474 size_t tlab_used(Thread* ignored) const;
1475 size_t max_tlab_size() const;
1476 size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1478 // Can a compiler initialize a new object without store barriers?
1479 // This permission only extends from the creation of a new object
1480 // via a TLAB up to the first subsequent safepoint. If such permission
1481 // is granted for this heap type, the compiler promises to call
1482 // defer_store_barrier() below on any slow path allocation of
1483 // a new object for which such initializing store barriers will
1484 // have been elided. G1, like CMS, allows this, but should be
1485 // ready to provide a compensating write barrier as necessary
1486 // if that storage came out of a non-young region. The efficiency
1487 // of this implementation depends crucially on being able to
1488 // answer very efficiently in constant time whether a piece of
1489 // storage in the heap comes from a young region or not.
1490 // See ReduceInitialCardMarks.
1491 virtual bool can_elide_tlab_store_barriers() const {
1492 return true;
1493 }
1495 virtual bool card_mark_must_follow_store() const {
1496 return true;
1497 }
1499 inline bool is_in_young(const oop obj);
1501 #ifdef ASSERT
1502 virtual bool is_in_partial_collection(const void* p);
1503 #endif
1505 virtual bool is_scavengable(const void* addr);
1507 // We don't need barriers for initializing stores to objects
1508 // in the young gen: for the SATB pre-barrier, there is no
1509 // pre-value that needs to be remembered; for the remembered-set
1510 // update logging post-barrier, we don't maintain remembered set
1511 // information for young gen objects.
1512 virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1514 // Returns "true" iff the given word_size is "very large".
1515 static bool isHumongous(size_t word_size) {
1516 // Note this has to be strictly greater-than as the TLABs
1517 // are capped at the humongous thresold and we want to
1518 // ensure that we don't try to allocate a TLAB as
1519 // humongous and that we don't allocate a humongous
1520 // object in a TLAB.
1521 return word_size > _humongous_object_threshold_in_words;
1522 }
1524 // Update mod union table with the set of dirty cards.
1525 void updateModUnion();
1527 // Set the mod union bits corresponding to the given memRegion. Note
1528 // that this is always a safe operation, since it doesn't clear any
1529 // bits.
1530 void markModUnionRange(MemRegion mr);
1532 // Records the fact that a marking phase is no longer in progress.
1533 void set_marking_complete() {
1534 _mark_in_progress = false;
1535 }
1536 void set_marking_started() {
1537 _mark_in_progress = true;
1538 }
1539 bool mark_in_progress() {
1540 return _mark_in_progress;
1541 }
1543 // Print the maximum heap capacity.
1544 virtual size_t max_capacity() const;
1546 virtual jlong millis_since_last_gc();
1549 // Convenience function to be used in situations where the heap type can be
1550 // asserted to be this type.
1551 static G1CollectedHeap* heap();
1553 void set_region_short_lived_locked(HeapRegion* hr);
1554 // add appropriate methods for any other surv rate groups
1556 YoungList* young_list() const { return _young_list; }
1558 // debugging
1559 bool check_young_list_well_formed() {
1560 return _young_list->check_list_well_formed();
1561 }
1563 bool check_young_list_empty(bool check_heap,
1564 bool check_sample = true);
1566 // *** Stuff related to concurrent marking. It's not clear to me that so
1567 // many of these need to be public.
1569 // The functions below are helper functions that a subclass of
1570 // "CollectedHeap" can use in the implementation of its virtual
1571 // functions.
1572 // This performs a concurrent marking of the live objects in a
1573 // bitmap off to the side.
1574 void doConcurrentMark();
1576 bool isMarkedPrev(oop obj) const;
1577 bool isMarkedNext(oop obj) const;
1579 // Determine if an object is dead, given the object and also
1580 // the region to which the object belongs. An object is dead
1581 // iff a) it was not allocated since the last mark and b) it
1582 // is not marked.
1583 bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1584 return
1585 !hr->obj_allocated_since_prev_marking(obj) &&
1586 !isMarkedPrev(obj);
1587 }
1589 // This function returns true when an object has been
1590 // around since the previous marking and hasn't yet
1591 // been marked during this marking.
1592 bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1593 return
1594 !hr->obj_allocated_since_next_marking(obj) &&
1595 !isMarkedNext(obj);
1596 }
1598 // Determine if an object is dead, given only the object itself.
1599 // This will find the region to which the object belongs and
1600 // then call the region version of the same function.
1602 // Added if it is NULL it isn't dead.
1604 inline bool is_obj_dead(const oop obj) const;
1606 inline bool is_obj_ill(const oop obj) const;
1608 bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1609 HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1610 bool is_marked(oop obj, VerifyOption vo);
1611 const char* top_at_mark_start_str(VerifyOption vo);
1613 ConcurrentMark* concurrent_mark() const { return _cm; }
1615 // Refinement
1617 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1619 // The dirty cards region list is used to record a subset of regions
1620 // whose cards need clearing. The list if populated during the
1621 // remembered set scanning and drained during the card table
1622 // cleanup. Although the methods are reentrant, population/draining
1623 // phases must not overlap. For synchronization purposes the last
1624 // element on the list points to itself.
1625 HeapRegion* _dirty_cards_region_list;
1626 void push_dirty_cards_region(HeapRegion* hr);
1627 HeapRegion* pop_dirty_cards_region();
1629 // Optimized nmethod scanning support routines
1631 // Register the given nmethod with the G1 heap
1632 virtual void register_nmethod(nmethod* nm);
1634 // Unregister the given nmethod from the G1 heap
1635 virtual void unregister_nmethod(nmethod* nm);
1637 // Free up superfluous code root memory.
1638 void purge_code_root_memory();
1640 // Rebuild the stong code root lists for each region
1641 // after a full GC
1642 void rebuild_strong_code_roots();
1644 // Delete entries for dead interned string and clean up unreferenced symbols
1645 // in symbol table, possibly in parallel.
1646 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1648 // Parallel phase of unloading/cleaning after G1 concurrent mark.
1649 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred);
1651 // Redirty logged cards in the refinement queue.
1652 void redirty_logged_cards();
1653 // Verification
1655 // The following is just to alert the verification code
1656 // that a full collection has occurred and that the
1657 // remembered sets are no longer up to date.
1658 bool _full_collection;
1659 void set_full_collection() { _full_collection = true;}
1660 void clear_full_collection() {_full_collection = false;}
1661 bool full_collection() {return _full_collection;}
1663 // Perform any cleanup actions necessary before allowing a verification.
1664 virtual void prepare_for_verify();
1666 // Perform verification.
1668 // vo == UsePrevMarking -> use "prev" marking information,
1669 // vo == UseNextMarking -> use "next" marking information
1670 // vo == UseMarkWord -> use the mark word in the object header
1671 //
1672 // NOTE: Only the "prev" marking information is guaranteed to be
1673 // consistent most of the time, so most calls to this should use
1674 // vo == UsePrevMarking.
1675 // Currently, there is only one case where this is called with
1676 // vo == UseNextMarking, which is to verify the "next" marking
1677 // information at the end of remark.
1678 // Currently there is only one place where this is called with
1679 // vo == UseMarkWord, which is to verify the marking during a
1680 // full GC.
1681 void verify(bool silent, VerifyOption vo);
1683 // Override; it uses the "prev" marking information
1684 virtual void verify(bool silent);
1686 // The methods below are here for convenience and dispatch the
1687 // appropriate method depending on value of the given VerifyOption
1688 // parameter. The values for that parameter, and their meanings,
1689 // are the same as those above.
1691 bool is_obj_dead_cond(const oop obj,
1692 const HeapRegion* hr,
1693 const VerifyOption vo) const;
1695 bool is_obj_dead_cond(const oop obj,
1696 const VerifyOption vo) const;
1698 // Printing
1700 virtual void print_on(outputStream* st) const;
1701 virtual void print_extended_on(outputStream* st) const;
1702 virtual void print_on_error(outputStream* st) const;
1704 virtual void print_gc_threads_on(outputStream* st) const;
1705 virtual void gc_threads_do(ThreadClosure* tc) const;
1707 // Override
1708 void print_tracing_info() const;
1710 // The following two methods are helpful for debugging RSet issues.
1711 void print_cset_rsets() PRODUCT_RETURN;
1712 void print_all_rsets() PRODUCT_RETURN;
1714 public:
1715 size_t pending_card_num();
1716 size_t cards_scanned();
1718 protected:
1719 size_t _max_heap_capacity;
1720 };
1722 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP