Tue, 16 Sep 2014 14:27:40 +0200
8057768: Make heap region region type in G1 HeapRegion explicit
Reviewed-by: brutisso, tschatzl
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);
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;
350 // This is a non-product method that is helpful for testing. It is
351 // called at the end of a GC and artificially expands the heap by
352 // allocating a number of dead regions. This way we can induce very
353 // frequent marking cycles and stress the cleanup / concurrent
354 // cleanup code more (as all the regions that will be allocated by
355 // this method will be found dead by the marking cycle).
356 void allocate_dummy_regions() PRODUCT_RETURN;
358 // Clear RSets after a compaction. It also resets the GC time stamps.
359 void clear_rsets_post_compaction();
361 // If the HR printer is active, dump the state of the regions in the
362 // heap after a compaction.
363 void print_hrm_post_compaction();
365 double verify(bool guard, const char* msg);
366 void verify_before_gc();
367 void verify_after_gc();
369 void log_gc_header();
370 void log_gc_footer(double pause_time_sec);
372 // These are macros so that, if the assert fires, we get the correct
373 // line number, file, etc.
375 #define heap_locking_asserts_err_msg(_extra_message_) \
376 err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \
377 (_extra_message_), \
378 BOOL_TO_STR(Heap_lock->owned_by_self()), \
379 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \
380 BOOL_TO_STR(Thread::current()->is_VM_thread()))
382 #define assert_heap_locked() \
383 do { \
384 assert(Heap_lock->owned_by_self(), \
385 heap_locking_asserts_err_msg("should be holding the Heap_lock")); \
386 } while (0)
388 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \
389 do { \
390 assert(Heap_lock->owned_by_self() || \
391 (SafepointSynchronize::is_at_safepoint() && \
392 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
393 heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
394 "should be at a safepoint")); \
395 } while (0)
397 #define assert_heap_locked_and_not_at_safepoint() \
398 do { \
399 assert(Heap_lock->owned_by_self() && \
400 !SafepointSynchronize::is_at_safepoint(), \
401 heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
402 "should not be at a safepoint")); \
403 } while (0)
405 #define assert_heap_not_locked() \
406 do { \
407 assert(!Heap_lock->owned_by_self(), \
408 heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
409 } while (0)
411 #define assert_heap_not_locked_and_not_at_safepoint() \
412 do { \
413 assert(!Heap_lock->owned_by_self() && \
414 !SafepointSynchronize::is_at_safepoint(), \
415 heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
416 "should not be at a safepoint")); \
417 } while (0)
419 #define assert_at_safepoint(_should_be_vm_thread_) \
420 do { \
421 assert(SafepointSynchronize::is_at_safepoint() && \
422 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
423 heap_locking_asserts_err_msg("should be at a safepoint")); \
424 } while (0)
426 #define assert_not_at_safepoint() \
427 do { \
428 assert(!SafepointSynchronize::is_at_safepoint(), \
429 heap_locking_asserts_err_msg("should not be at a safepoint")); \
430 } while (0)
432 protected:
434 // The young region list.
435 YoungList* _young_list;
437 // The current policy object for the collector.
438 G1CollectorPolicy* _g1_policy;
440 // This is the second level of trying to allocate a new region. If
441 // new_region() didn't find a region on the free_list, this call will
442 // check whether there's anything available on the
443 // secondary_free_list and/or wait for more regions to appear on
444 // that list, if _free_regions_coming is set.
445 HeapRegion* new_region_try_secondary_free_list(bool is_old);
447 // Try to allocate a single non-humongous HeapRegion sufficient for
448 // an allocation of the given word_size. If do_expand is true,
449 // attempt to expand the heap if necessary to satisfy the allocation
450 // request. If the region is to be used as an old region or for a
451 // humongous object, set is_old to true. If not, to false.
452 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
454 // Initialize a contiguous set of free regions of length num_regions
455 // and starting at index first so that they appear as a single
456 // humongous region.
457 HeapWord* humongous_obj_allocate_initialize_regions(uint first,
458 uint num_regions,
459 size_t word_size,
460 AllocationContext_t context);
462 // Attempt to allocate a humongous object of the given size. Return
463 // NULL if unsuccessful.
464 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context);
466 // The following two methods, allocate_new_tlab() and
467 // mem_allocate(), are the two main entry points from the runtime
468 // into the G1's allocation routines. They have the following
469 // assumptions:
470 //
471 // * They should both be called outside safepoints.
472 //
473 // * They should both be called without holding the Heap_lock.
474 //
475 // * All allocation requests for new TLABs should go to
476 // allocate_new_tlab().
477 //
478 // * All non-TLAB allocation requests should go to mem_allocate().
479 //
480 // * If either call cannot satisfy the allocation request using the
481 // current allocating region, they will try to get a new one. If
482 // this fails, they will attempt to do an evacuation pause and
483 // retry the allocation.
484 //
485 // * If all allocation attempts fail, even after trying to schedule
486 // an evacuation pause, allocate_new_tlab() will return NULL,
487 // whereas mem_allocate() will attempt a heap expansion and/or
488 // schedule a Full GC.
489 //
490 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
491 // should never be called with word_size being humongous. All
492 // humongous allocation requests should go to mem_allocate() which
493 // will satisfy them with a special path.
495 virtual HeapWord* allocate_new_tlab(size_t word_size);
497 virtual HeapWord* mem_allocate(size_t word_size,
498 bool* gc_overhead_limit_was_exceeded);
500 // The following three methods take a gc_count_before_ret
501 // parameter which is used to return the GC count if the method
502 // returns NULL. Given that we are required to read the GC count
503 // while holding the Heap_lock, and these paths will take the
504 // Heap_lock at some point, it's easier to get them to read the GC
505 // count while holding the Heap_lock before they return NULL instead
506 // of the caller (namely: mem_allocate()) having to also take the
507 // Heap_lock just to read the GC count.
509 // First-level mutator allocation attempt: try to allocate out of
510 // the mutator alloc region without taking the Heap_lock. This
511 // should only be used for non-humongous allocations.
512 inline HeapWord* attempt_allocation(size_t word_size,
513 unsigned int* gc_count_before_ret,
514 int* gclocker_retry_count_ret);
516 // Second-level mutator allocation attempt: take the Heap_lock and
517 // retry the allocation attempt, potentially scheduling a GC
518 // pause. This should only be used for non-humongous allocations.
519 HeapWord* attempt_allocation_slow(size_t word_size,
520 AllocationContext_t context,
521 unsigned int* gc_count_before_ret,
522 int* gclocker_retry_count_ret);
524 // Takes the Heap_lock and attempts a humongous allocation. It can
525 // potentially schedule a GC pause.
526 HeapWord* attempt_allocation_humongous(size_t word_size,
527 unsigned int* gc_count_before_ret,
528 int* gclocker_retry_count_ret);
530 // Allocation attempt that should be called during safepoints (e.g.,
531 // at the end of a successful GC). expect_null_mutator_alloc_region
532 // specifies whether the mutator alloc region is expected to be NULL
533 // or not.
534 HeapWord* attempt_allocation_at_safepoint(size_t word_size,
535 AllocationContext_t context,
536 bool expect_null_mutator_alloc_region);
538 // It dirties the cards that cover the block so that so that the post
539 // write barrier never queues anything when updating objects on this
540 // block. It is assumed (and in fact we assert) that the block
541 // belongs to a young region.
542 inline void dirty_young_block(HeapWord* start, size_t word_size);
544 // Allocate blocks during garbage collection. Will ensure an
545 // allocation region, either by picking one or expanding the
546 // heap, and then allocate a block of the given size. The block
547 // may not be a humongous - it must fit into a single heap region.
548 HeapWord* par_allocate_during_gc(GCAllocPurpose purpose,
549 size_t word_size,
550 AllocationContext_t context);
552 HeapWord* allocate_during_gc_slow(GCAllocPurpose purpose,
553 HeapRegion* alloc_region,
554 bool par,
555 size_t word_size);
557 // Ensure that no further allocations can happen in "r", bearing in mind
558 // that parallel threads might be attempting allocations.
559 void par_allocate_remaining_space(HeapRegion* r);
561 // Allocation attempt during GC for a survivor object / PLAB.
562 inline HeapWord* survivor_attempt_allocation(size_t word_size,
563 AllocationContext_t context);
565 // Allocation attempt during GC for an old object / PLAB.
566 inline HeapWord* old_attempt_allocation(size_t word_size,
567 AllocationContext_t context);
569 // These methods are the "callbacks" from the G1AllocRegion class.
571 // For mutator alloc regions.
572 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
573 void retire_mutator_alloc_region(HeapRegion* alloc_region,
574 size_t allocated_bytes);
576 // For GC alloc regions.
577 HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
578 GCAllocPurpose ap);
579 void retire_gc_alloc_region(HeapRegion* alloc_region,
580 size_t allocated_bytes, GCAllocPurpose ap);
582 // - if explicit_gc is true, the GC is for a System.gc() or a heap
583 // inspection request and should collect the entire heap
584 // - if clear_all_soft_refs is true, all soft references should be
585 // cleared during the GC
586 // - if explicit_gc is false, word_size describes the allocation that
587 // the GC should attempt (at least) to satisfy
588 // - it returns false if it is unable to do the collection due to the
589 // GC locker being active, true otherwise
590 bool do_collection(bool explicit_gc,
591 bool clear_all_soft_refs,
592 size_t word_size);
594 // Callback from VM_G1CollectFull operation.
595 // Perform a full collection.
596 virtual void do_full_collection(bool clear_all_soft_refs);
598 // Resize the heap if necessary after a full collection. If this is
599 // after a collect-for allocation, "word_size" is the allocation size,
600 // and will be considered part of the used portion of the heap.
601 void resize_if_necessary_after_full_collection(size_t word_size);
603 // Callback from VM_G1CollectForAllocation operation.
604 // This function does everything necessary/possible to satisfy a
605 // failed allocation request (including collection, expansion, etc.)
606 HeapWord* satisfy_failed_allocation(size_t word_size,
607 AllocationContext_t context,
608 bool* succeeded);
610 // Attempting to expand the heap sufficiently
611 // to support an allocation of the given "word_size". If
612 // successful, perform the allocation and return the address of the
613 // allocated block, or else "NULL".
614 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context);
616 // Process any reference objects discovered during
617 // an incremental evacuation pause.
618 void process_discovered_references(uint no_of_gc_workers);
620 // Enqueue any remaining discovered references
621 // after processing.
622 void enqueue_discovered_references(uint no_of_gc_workers);
624 public:
626 G1Allocator* allocator() {
627 return _allocator;
628 }
630 G1MonitoringSupport* g1mm() {
631 assert(_g1mm != NULL, "should have been initialized");
632 return _g1mm;
633 }
635 // Expand the garbage-first heap by at least the given size (in bytes!).
636 // Returns true if the heap was expanded by the requested amount;
637 // false otherwise.
638 // (Rounds up to a HeapRegion boundary.)
639 bool expand(size_t expand_bytes);
641 // Returns the PLAB statistics given a purpose.
642 PLABStats* stats_for_purpose(GCAllocPurpose purpose) {
643 PLABStats* stats = NULL;
645 switch (purpose) {
646 case GCAllocForSurvived:
647 stats = &_survivor_plab_stats;
648 break;
649 case GCAllocForTenured:
650 stats = &_old_plab_stats;
651 break;
652 default:
653 assert(false, "unrecognized GCAllocPurpose");
654 }
656 return stats;
657 }
659 // Determines PLAB size for a particular allocation purpose.
660 size_t desired_plab_sz(GCAllocPurpose purpose);
662 inline AllocationContextStats& allocation_context_stats();
664 // Do anything common to GC's.
665 virtual void gc_prologue(bool full);
666 virtual void gc_epilogue(bool full);
668 inline void set_humongous_is_live(oop obj);
670 bool humongous_is_live(uint region) {
671 return _humongous_is_live.is_live(region);
672 }
674 // Returns whether the given region (which must be a humongous (start) region)
675 // is to be considered conservatively live regardless of any other conditions.
676 bool humongous_region_is_always_live(uint index);
677 // Register the given region to be part of the collection set.
678 inline void register_humongous_region_with_in_cset_fast_test(uint index);
679 // Register regions with humongous objects (actually on the start region) in
680 // the in_cset_fast_test table.
681 void register_humongous_regions_with_in_cset_fast_test();
682 // We register a region with the fast "in collection set" test. We
683 // simply set to true the array slot corresponding to this region.
684 void register_region_with_in_cset_fast_test(HeapRegion* r) {
685 _in_cset_fast_test.set_in_cset(r->hrm_index());
686 }
688 // This is a fast test on whether a reference points into the
689 // collection set or not. Assume that the reference
690 // points into the heap.
691 inline bool in_cset_fast_test(oop obj);
693 void clear_cset_fast_test() {
694 _in_cset_fast_test.clear();
695 }
697 // This is called at the start of either a concurrent cycle or a Full
698 // GC to update the number of old marking cycles started.
699 void increment_old_marking_cycles_started();
701 // This is called at the end of either a concurrent cycle or a Full
702 // GC to update the number of old marking cycles completed. Those two
703 // can happen in a nested fashion, i.e., we start a concurrent
704 // cycle, a Full GC happens half-way through it which ends first,
705 // and then the cycle notices that a Full GC happened and ends
706 // too. The concurrent parameter is a boolean to help us do a bit
707 // tighter consistency checking in the method. If concurrent is
708 // false, the caller is the inner caller in the nesting (i.e., the
709 // Full GC). If concurrent is true, the caller is the outer caller
710 // in this nesting (i.e., the concurrent cycle). Further nesting is
711 // not currently supported. The end of this call also notifies
712 // the FullGCCount_lock in case a Java thread is waiting for a full
713 // GC to happen (e.g., it called System.gc() with
714 // +ExplicitGCInvokesConcurrent).
715 void increment_old_marking_cycles_completed(bool concurrent);
717 unsigned int old_marking_cycles_completed() {
718 return _old_marking_cycles_completed;
719 }
721 void register_concurrent_cycle_start(const Ticks& start_time);
722 void register_concurrent_cycle_end();
723 void trace_heap_after_concurrent_cycle();
725 G1YCType yc_type();
727 G1HRPrinter* hr_printer() { return &_hr_printer; }
729 // Frees a non-humongous region by initializing its contents and
730 // adding it to the free list that's passed as a parameter (this is
731 // usually a local list which will be appended to the master free
732 // list later). The used bytes of freed regions are accumulated in
733 // pre_used. If par is true, the region's RSet will not be freed
734 // up. The assumption is that this will be done later.
735 // The locked parameter indicates if the caller has already taken
736 // care of proper synchronization. This may allow some optimizations.
737 void free_region(HeapRegion* hr,
738 FreeRegionList* free_list,
739 bool par,
740 bool locked = false);
742 // Frees a humongous region by collapsing it into individual regions
743 // and calling free_region() for each of them. The freed regions
744 // will be added to the free list that's passed as a parameter (this
745 // is usually a local list which will be appended to the master free
746 // list later). The used bytes of freed regions are accumulated in
747 // pre_used. If par is true, the region's RSet will not be freed
748 // up. The assumption is that this will be done later.
749 void free_humongous_region(HeapRegion* hr,
750 FreeRegionList* free_list,
751 bool par);
752 protected:
754 // Shrink the garbage-first heap by at most the given size (in bytes!).
755 // (Rounds down to a HeapRegion boundary.)
756 virtual void shrink(size_t expand_bytes);
757 void shrink_helper(size_t expand_bytes);
759 #if TASKQUEUE_STATS
760 static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
761 void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
762 void reset_taskqueue_stats();
763 #endif // TASKQUEUE_STATS
765 // Schedule the VM operation that will do an evacuation pause to
766 // satisfy an allocation request of word_size. *succeeded will
767 // return whether the VM operation was successful (it did do an
768 // evacuation pause) or not (another thread beat us to it or the GC
769 // locker was active). Given that we should not be holding the
770 // Heap_lock when we enter this method, we will pass the
771 // gc_count_before (i.e., total_collections()) as a parameter since
772 // it has to be read while holding the Heap_lock. Currently, both
773 // methods that call do_collection_pause() release the Heap_lock
774 // before the call, so it's easy to read gc_count_before just before.
775 HeapWord* do_collection_pause(size_t word_size,
776 unsigned int gc_count_before,
777 bool* succeeded,
778 GCCause::Cause gc_cause);
780 // The guts of the incremental collection pause, executed by the vm
781 // thread. It returns false if it is unable to do the collection due
782 // to the GC locker being active, true otherwise
783 bool do_collection_pause_at_safepoint(double target_pause_time_ms);
785 // Actually do the work of evacuating the collection set.
786 void evacuate_collection_set(EvacuationInfo& evacuation_info);
788 // The g1 remembered set of the heap.
789 G1RemSet* _g1_rem_set;
791 // A set of cards that cover the objects for which the Rsets should be updated
792 // concurrently after the collection.
793 DirtyCardQueueSet _dirty_card_queue_set;
795 // The closure used to refine a single card.
796 RefineCardTableEntryClosure* _refine_cte_cl;
798 // A function to check the consistency of dirty card logs.
799 void check_ct_logs_at_safepoint();
801 // A DirtyCardQueueSet that is used to hold cards that contain
802 // references into the current collection set. This is used to
803 // update the remembered sets of the regions in the collection
804 // set in the event of an evacuation failure.
805 DirtyCardQueueSet _into_cset_dirty_card_queue_set;
807 // After a collection pause, make the regions in the CS into free
808 // regions.
809 void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info);
811 // Abandon the current collection set without recording policy
812 // statistics or updating free lists.
813 void abandon_collection_set(HeapRegion* cs_head);
815 // Applies "scan_non_heap_roots" to roots outside the heap,
816 // "scan_rs" to roots inside the heap (having done "set_region" to
817 // indicate the region in which the root resides),
818 // and does "scan_metadata" If "scan_rs" is
819 // NULL, then this step is skipped. The "worker_i"
820 // param is for use with parallel roots processing, and should be
821 // the "i" of the calling parallel worker thread's work(i) function.
822 // In the sequential case this param will be ignored.
823 void g1_process_roots(OopClosure* scan_non_heap_roots,
824 OopClosure* scan_non_heap_weak_roots,
825 OopsInHeapRegionClosure* scan_rs,
826 CLDClosure* scan_strong_clds,
827 CLDClosure* scan_weak_clds,
828 CodeBlobClosure* scan_strong_code,
829 uint worker_i);
831 // The concurrent marker (and the thread it runs in.)
832 ConcurrentMark* _cm;
833 ConcurrentMarkThread* _cmThread;
834 bool _mark_in_progress;
836 // The concurrent refiner.
837 ConcurrentG1Refine* _cg1r;
839 // The parallel task queues
840 RefToScanQueueSet *_task_queues;
842 // True iff a evacuation has failed in the current collection.
843 bool _evacuation_failed;
845 EvacuationFailedInfo* _evacuation_failed_info_array;
847 // Failed evacuations cause some logical from-space objects to have
848 // forwarding pointers to themselves. Reset them.
849 void remove_self_forwarding_pointers();
851 // Together, these store an object with a preserved mark, and its mark value.
852 Stack<oop, mtGC> _objs_with_preserved_marks;
853 Stack<markOop, mtGC> _preserved_marks_of_objs;
855 // Preserve the mark of "obj", if necessary, in preparation for its mark
856 // word being overwritten with a self-forwarding-pointer.
857 void preserve_mark_if_necessary(oop obj, markOop m);
859 // The stack of evac-failure objects left to be scanned.
860 GrowableArray<oop>* _evac_failure_scan_stack;
861 // The closure to apply to evac-failure objects.
863 OopsInHeapRegionClosure* _evac_failure_closure;
864 // Set the field above.
865 void
866 set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
867 _evac_failure_closure = evac_failure_closure;
868 }
870 // Push "obj" on the scan stack.
871 void push_on_evac_failure_scan_stack(oop obj);
872 // Process scan stack entries until the stack is empty.
873 void drain_evac_failure_scan_stack();
874 // True iff an invocation of "drain_scan_stack" is in progress; to
875 // prevent unnecessary recursion.
876 bool _drain_in_progress;
878 // Do any necessary initialization for evacuation-failure handling.
879 // "cl" is the closure that will be used to process evac-failure
880 // objects.
881 void init_for_evac_failure(OopsInHeapRegionClosure* cl);
882 // Do any necessary cleanup for evacuation-failure handling data
883 // structures.
884 void finalize_for_evac_failure();
886 // An attempt to evacuate "obj" has failed; take necessary steps.
887 oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj);
888 void handle_evacuation_failure_common(oop obj, markOop m);
890 #ifndef PRODUCT
891 // Support for forcing evacuation failures. Analogous to
892 // PromotionFailureALot for the other collectors.
894 // Records whether G1EvacuationFailureALot should be in effect
895 // for the current GC
896 bool _evacuation_failure_alot_for_current_gc;
898 // Used to record the GC number for interval checking when
899 // determining whether G1EvaucationFailureALot is in effect
900 // for the current GC.
901 size_t _evacuation_failure_alot_gc_number;
903 // Count of the number of evacuations between failures.
904 volatile size_t _evacuation_failure_alot_count;
906 // Set whether G1EvacuationFailureALot should be in effect
907 // for the current GC (based upon the type of GC and which
908 // command line flags are set);
909 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
910 bool during_initial_mark,
911 bool during_marking);
913 inline void set_evacuation_failure_alot_for_current_gc();
915 // Return true if it's time to cause an evacuation failure.
916 inline bool evacuation_should_fail();
918 // Reset the G1EvacuationFailureALot counters. Should be called at
919 // the end of an evacuation pause in which an evacuation failure occurred.
920 inline void reset_evacuation_should_fail();
921 #endif // !PRODUCT
923 // ("Weak") Reference processing support.
924 //
925 // G1 has 2 instances of the reference processor class. One
926 // (_ref_processor_cm) handles reference object discovery
927 // and subsequent processing during concurrent marking cycles.
928 //
929 // The other (_ref_processor_stw) handles reference object
930 // discovery and processing during full GCs and incremental
931 // evacuation pauses.
932 //
933 // During an incremental pause, reference discovery will be
934 // temporarily disabled for _ref_processor_cm and will be
935 // enabled for _ref_processor_stw. At the end of the evacuation
936 // pause references discovered by _ref_processor_stw will be
937 // processed and discovery will be disabled. The previous
938 // setting for reference object discovery for _ref_processor_cm
939 // will be re-instated.
940 //
941 // At the start of marking:
942 // * Discovery by the CM ref processor is verified to be inactive
943 // and it's discovered lists are empty.
944 // * Discovery by the CM ref processor is then enabled.
945 //
946 // At the end of marking:
947 // * Any references on the CM ref processor's discovered
948 // lists are processed (possibly MT).
949 //
950 // At the start of full GC we:
951 // * Disable discovery by the CM ref processor and
952 // empty CM ref processor's discovered lists
953 // (without processing any entries).
954 // * Verify that the STW ref processor is inactive and it's
955 // discovered lists are empty.
956 // * Temporarily set STW ref processor discovery as single threaded.
957 // * Temporarily clear the STW ref processor's _is_alive_non_header
958 // field.
959 // * Finally enable discovery by the STW ref processor.
960 //
961 // The STW ref processor is used to record any discovered
962 // references during the full GC.
963 //
964 // At the end of a full GC we:
965 // * Enqueue any reference objects discovered by the STW ref processor
966 // that have non-live referents. This has the side-effect of
967 // making the STW ref processor inactive by disabling discovery.
968 // * Verify that the CM ref processor is still inactive
969 // and no references have been placed on it's discovered
970 // lists (also checked as a precondition during initial marking).
972 // The (stw) reference processor...
973 ReferenceProcessor* _ref_processor_stw;
975 STWGCTimer* _gc_timer_stw;
976 ConcurrentGCTimer* _gc_timer_cm;
978 G1OldTracer* _gc_tracer_cm;
979 G1NewTracer* _gc_tracer_stw;
981 // During reference object discovery, the _is_alive_non_header
982 // closure (if non-null) is applied to the referent object to
983 // determine whether the referent is live. If so then the
984 // reference object does not need to be 'discovered' and can
985 // be treated as a regular oop. This has the benefit of reducing
986 // the number of 'discovered' reference objects that need to
987 // be processed.
988 //
989 // Instance of the is_alive closure for embedding into the
990 // STW reference processor as the _is_alive_non_header field.
991 // Supplying a value for the _is_alive_non_header field is
992 // optional but doing so prevents unnecessary additions to
993 // the discovered lists during reference discovery.
994 G1STWIsAliveClosure _is_alive_closure_stw;
996 // The (concurrent marking) reference processor...
997 ReferenceProcessor* _ref_processor_cm;
999 // Instance of the concurrent mark is_alive closure for embedding
1000 // into the Concurrent Marking reference processor as the
1001 // _is_alive_non_header field. Supplying a value for the
1002 // _is_alive_non_header field is optional but doing so prevents
1003 // unnecessary additions to the discovered lists during reference
1004 // discovery.
1005 G1CMIsAliveClosure _is_alive_closure_cm;
1007 // Cache used by G1CollectedHeap::start_cset_region_for_worker().
1008 HeapRegion** _worker_cset_start_region;
1010 // Time stamp to validate the regions recorded in the cache
1011 // used by G1CollectedHeap::start_cset_region_for_worker().
1012 // The heap region entry for a given worker is valid iff
1013 // the associated time stamp value matches the current value
1014 // of G1CollectedHeap::_gc_time_stamp.
1015 unsigned int* _worker_cset_start_region_time_stamp;
1017 enum G1H_process_roots_tasks {
1018 G1H_PS_filter_satb_buffers,
1019 G1H_PS_refProcessor_oops_do,
1020 // Leave this one last.
1021 G1H_PS_NumElements
1022 };
1024 SubTasksDone* _process_strong_tasks;
1026 volatile bool _free_regions_coming;
1028 public:
1030 SubTasksDone* process_strong_tasks() { return _process_strong_tasks; }
1032 void set_refine_cte_cl_concurrency(bool concurrent);
1034 RefToScanQueue *task_queue(int i) const;
1036 // A set of cards where updates happened during the GC
1037 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
1039 // A DirtyCardQueueSet that is used to hold cards that contain
1040 // references into the current collection set. This is used to
1041 // update the remembered sets of the regions in the collection
1042 // set in the event of an evacuation failure.
1043 DirtyCardQueueSet& into_cset_dirty_card_queue_set()
1044 { return _into_cset_dirty_card_queue_set; }
1046 // Create a G1CollectedHeap with the specified policy.
1047 // Must call the initialize method afterwards.
1048 // May not return if something goes wrong.
1049 G1CollectedHeap(G1CollectorPolicy* policy);
1051 // Initialize the G1CollectedHeap to have the initial and
1052 // maximum sizes and remembered and barrier sets
1053 // specified by the policy object.
1054 jint initialize();
1056 virtual void stop();
1058 // Return the (conservative) maximum heap alignment for any G1 heap
1059 static size_t conservative_max_heap_alignment();
1061 // Initialize weak reference processing.
1062 virtual void ref_processing_init();
1064 void set_par_threads(uint t) {
1065 SharedHeap::set_par_threads(t);
1066 // Done in SharedHeap but oddly there are
1067 // two _process_strong_tasks's in a G1CollectedHeap
1068 // so do it here too.
1069 _process_strong_tasks->set_n_threads(t);
1070 }
1072 // Set _n_par_threads according to a policy TBD.
1073 void set_par_threads();
1075 void set_n_termination(int t) {
1076 _process_strong_tasks->set_n_threads(t);
1077 }
1079 virtual CollectedHeap::Name kind() const {
1080 return CollectedHeap::G1CollectedHeap;
1081 }
1083 // The current policy object for the collector.
1084 G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1086 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); }
1088 // Adaptive size policy. No such thing for g1.
1089 virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1091 // The rem set and barrier set.
1092 G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1094 unsigned get_gc_time_stamp() {
1095 return _gc_time_stamp;
1096 }
1098 inline void reset_gc_time_stamp();
1100 void check_gc_time_stamps() PRODUCT_RETURN;
1102 inline void increment_gc_time_stamp();
1104 // Reset the given region's GC timestamp. If it's starts humongous,
1105 // also reset the GC timestamp of its corresponding
1106 // continues humongous regions too.
1107 void reset_gc_time_stamps(HeapRegion* hr);
1109 void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1110 DirtyCardQueue* into_cset_dcq,
1111 bool concurrent, uint worker_i);
1113 // The shared block offset table array.
1114 G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1116 // Reference Processing accessors
1118 // The STW reference processor....
1119 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1121 // The Concurrent Marking reference processor...
1122 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1124 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1125 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1127 virtual size_t capacity() const;
1128 virtual size_t used() const;
1129 // This should be called when we're not holding the heap lock. The
1130 // result might be a bit inaccurate.
1131 size_t used_unlocked() const;
1132 size_t recalculate_used() const;
1134 // These virtual functions do the actual allocation.
1135 // Some heaps may offer a contiguous region for shared non-blocking
1136 // allocation, via inlined code (by exporting the address of the top and
1137 // end fields defining the extent of the contiguous allocation region.)
1138 // But G1CollectedHeap doesn't yet support this.
1140 virtual bool is_maximal_no_gc() const {
1141 return _hrm.available() == 0;
1142 }
1144 // The current number of regions in the heap.
1145 uint num_regions() const { return _hrm.length(); }
1147 // The max number of regions in the heap.
1148 uint max_regions() const { return _hrm.max_length(); }
1150 // The number of regions that are completely free.
1151 uint num_free_regions() const { return _hrm.num_free_regions(); }
1153 // The number of regions that are not completely free.
1154 uint num_used_regions() const { return num_regions() - num_free_regions(); }
1156 void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1157 void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1158 void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1159 void verify_dirty_young_regions() PRODUCT_RETURN;
1161 #ifndef PRODUCT
1162 // Make sure that the given bitmap has no marked objects in the
1163 // range [from,limit). If it does, print an error message and return
1164 // false. Otherwise, just return true. bitmap_name should be "prev"
1165 // or "next".
1166 bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
1167 HeapWord* from, HeapWord* limit);
1169 // Verify that the prev / next bitmap range [tams,end) for the given
1170 // region has no marks. Return true if all is well, false if errors
1171 // are detected.
1172 bool verify_bitmaps(const char* caller, HeapRegion* hr);
1173 #endif // PRODUCT
1175 // If G1VerifyBitmaps is set, verify that the marking bitmaps for
1176 // the given region do not have any spurious marks. If errors are
1177 // detected, print appropriate error messages and crash.
1178 void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN;
1180 // If G1VerifyBitmaps is set, verify that the marking bitmaps do not
1181 // have any spurious marks. If errors are detected, print
1182 // appropriate error messages and crash.
1183 void check_bitmaps(const char* caller) PRODUCT_RETURN;
1185 // verify_region_sets() performs verification over the region
1186 // lists. It will be compiled in the product code to be used when
1187 // necessary (i.e., during heap verification).
1188 void verify_region_sets();
1190 // verify_region_sets_optional() is planted in the code for
1191 // list verification in non-product builds (and it can be enabled in
1192 // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1).
1193 #if HEAP_REGION_SET_FORCE_VERIFY
1194 void verify_region_sets_optional() {
1195 verify_region_sets();
1196 }
1197 #else // HEAP_REGION_SET_FORCE_VERIFY
1198 void verify_region_sets_optional() { }
1199 #endif // HEAP_REGION_SET_FORCE_VERIFY
1201 #ifdef ASSERT
1202 bool is_on_master_free_list(HeapRegion* hr) {
1203 return _hrm.is_free(hr);
1204 }
1205 #endif // ASSERT
1207 // Wrapper for the region list operations that can be called from
1208 // methods outside this class.
1210 void secondary_free_list_add(FreeRegionList* list) {
1211 _secondary_free_list.add_ordered(list);
1212 }
1214 void append_secondary_free_list() {
1215 _hrm.insert_list_into_free_list(&_secondary_free_list);
1216 }
1218 void append_secondary_free_list_if_not_empty_with_lock() {
1219 // If the secondary free list looks empty there's no reason to
1220 // take the lock and then try to append it.
1221 if (!_secondary_free_list.is_empty()) {
1222 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1223 append_secondary_free_list();
1224 }
1225 }
1227 inline void old_set_remove(HeapRegion* hr);
1229 size_t non_young_capacity_bytes() {
1230 return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1231 }
1233 void set_free_regions_coming();
1234 void reset_free_regions_coming();
1235 bool free_regions_coming() { return _free_regions_coming; }
1236 void wait_while_free_regions_coming();
1238 // Determine whether the given region is one that we are using as an
1239 // old GC alloc region.
1240 bool is_old_gc_alloc_region(HeapRegion* hr) {
1241 return _allocator->is_retained_old_region(hr);
1242 }
1244 // Perform a collection of the heap; intended for use in implementing
1245 // "System.gc". This probably implies as full a collection as the
1246 // "CollectedHeap" supports.
1247 virtual void collect(GCCause::Cause cause);
1249 // The same as above but assume that the caller holds the Heap_lock.
1250 void collect_locked(GCCause::Cause cause);
1252 virtual void copy_allocation_context_stats(const jint* contexts,
1253 jlong* totals,
1254 jbyte* accuracy,
1255 jint len);
1257 // True iff an evacuation has failed in the most-recent collection.
1258 bool evacuation_failed() { return _evacuation_failed; }
1260 void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed);
1261 void prepend_to_freelist(FreeRegionList* list);
1262 void decrement_summary_bytes(size_t bytes);
1264 // Returns "TRUE" iff "p" points into the committed areas of the heap.
1265 virtual bool is_in(const void* p) const;
1266 #ifdef ASSERT
1267 // Returns whether p is in one of the available areas of the heap. Slow but
1268 // extensive version.
1269 bool is_in_exact(const void* p) const;
1270 #endif
1272 // Return "TRUE" iff the given object address is within the collection
1273 // set. Slow implementation.
1274 inline bool obj_in_cs(oop obj);
1276 inline bool is_in_cset(oop obj);
1278 inline bool is_in_cset_or_humongous(const oop obj);
1280 enum in_cset_state_t {
1281 InNeither, // neither in collection set nor humongous
1282 InCSet, // region is in collection set only
1283 IsHumongous // region is a humongous start region
1284 };
1285 private:
1286 // Instances of this class are used for quick tests on whether a reference points
1287 // into the collection set or is a humongous object (points into a humongous
1288 // object).
1289 // Each of the array's elements denotes whether the corresponding region is in
1290 // the collection set or a humongous region.
1291 // We use this to quickly reclaim humongous objects: by making a humongous region
1292 // succeed this test, we sort-of add it to the collection set. During the reference
1293 // iteration closures, when we see a humongous region, we simply mark it as
1294 // referenced, i.e. live.
1295 class G1FastCSetBiasedMappedArray : public G1BiasedMappedArray<char> {
1296 protected:
1297 char default_value() const { return G1CollectedHeap::InNeither; }
1298 public:
1299 void set_humongous(uintptr_t index) {
1300 assert(get_by_index(index) != InCSet, "Should not overwrite InCSet values");
1301 set_by_index(index, G1CollectedHeap::IsHumongous);
1302 }
1304 void clear_humongous(uintptr_t index) {
1305 set_by_index(index, G1CollectedHeap::InNeither);
1306 }
1308 void set_in_cset(uintptr_t index) {
1309 assert(get_by_index(index) != G1CollectedHeap::IsHumongous, "Should not overwrite IsHumongous value");
1310 set_by_index(index, G1CollectedHeap::InCSet);
1311 }
1313 bool is_in_cset_or_humongous(HeapWord* addr) const { return get_by_address(addr) != G1CollectedHeap::InNeither; }
1314 bool is_in_cset(HeapWord* addr) const { return get_by_address(addr) == G1CollectedHeap::InCSet; }
1315 G1CollectedHeap::in_cset_state_t at(HeapWord* addr) const { return (G1CollectedHeap::in_cset_state_t)get_by_address(addr); }
1316 void clear() { G1BiasedMappedArray<char>::clear(); }
1317 };
1319 // This array is used for a quick test on whether a reference points into
1320 // the collection set or not. Each of the array's elements denotes whether the
1321 // corresponding region is in the collection set or not.
1322 G1FastCSetBiasedMappedArray _in_cset_fast_test;
1324 public:
1326 inline in_cset_state_t in_cset_state(const oop obj);
1328 // Return "TRUE" iff the given object address is in the reserved
1329 // region of g1.
1330 bool is_in_g1_reserved(const void* p) const {
1331 return _hrm.reserved().contains(p);
1332 }
1334 // Returns a MemRegion that corresponds to the space that has been
1335 // reserved for the heap
1336 MemRegion g1_reserved() const {
1337 return _hrm.reserved();
1338 }
1340 virtual bool is_in_closed_subset(const void* p) const;
1342 G1SATBCardTableLoggingModRefBS* g1_barrier_set() {
1343 return (G1SATBCardTableLoggingModRefBS*) barrier_set();
1344 }
1346 // This resets the card table to all zeros. It is used after
1347 // a collection pause which used the card table to claim cards.
1348 void cleanUpCardTable();
1350 // Iteration functions.
1352 // Iterate over all the ref-containing fields of all objects, calling
1353 // "cl.do_oop" on each.
1354 virtual void oop_iterate(ExtendedOopClosure* cl);
1356 // Iterate over all objects, calling "cl.do_object" on each.
1357 virtual void object_iterate(ObjectClosure* cl);
1359 virtual void safe_object_iterate(ObjectClosure* cl) {
1360 object_iterate(cl);
1361 }
1363 // Iterate over all spaces in use in the heap, in ascending address order.
1364 virtual void space_iterate(SpaceClosure* cl);
1366 // Iterate over heap regions, in address order, terminating the
1367 // iteration early if the "doHeapRegion" method returns "true".
1368 void heap_region_iterate(HeapRegionClosure* blk) const;
1370 // Return the region with the given index. It assumes the index is valid.
1371 inline HeapRegion* region_at(uint index) const;
1373 // Calculate the region index of the given address. Given address must be
1374 // within the heap.
1375 inline uint addr_to_region(HeapWord* addr) const;
1377 inline HeapWord* bottom_addr_for_region(uint index) const;
1379 // Divide the heap region sequence into "chunks" of some size (the number
1380 // of regions divided by the number of parallel threads times some
1381 // overpartition factor, currently 4). Assumes that this will be called
1382 // in parallel by ParallelGCThreads worker threads with discinct worker
1383 // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel
1384 // calls will use the same "claim_value", and that that claim value is
1385 // different from the claim_value of any heap region before the start of
1386 // the iteration. Applies "blk->doHeapRegion" to each of the regions, by
1387 // attempting to claim the first region in each chunk, and, if
1388 // successful, applying the closure to each region in the chunk (and
1389 // setting the claim value of the second and subsequent regions of the
1390 // chunk.) For now requires that "doHeapRegion" always returns "false",
1391 // i.e., that a closure never attempt to abort a traversal.
1392 void heap_region_par_iterate_chunked(HeapRegionClosure* cl,
1393 uint worker_id,
1394 uint num_workers,
1395 jint claim_value) const;
1397 // It resets all the region claim values to the default.
1398 void reset_heap_region_claim_values();
1400 // Resets the claim values of regions in the current
1401 // collection set to the default.
1402 void reset_cset_heap_region_claim_values();
1404 #ifdef ASSERT
1405 bool check_heap_region_claim_values(jint claim_value);
1407 // Same as the routine above but only checks regions in the
1408 // current collection set.
1409 bool check_cset_heap_region_claim_values(jint claim_value);
1410 #endif // ASSERT
1412 // Clear the cached cset start regions and (more importantly)
1413 // the time stamps. Called when we reset the GC time stamp.
1414 void clear_cset_start_regions();
1416 // Given the id of a worker, obtain or calculate a suitable
1417 // starting region for iterating over the current collection set.
1418 HeapRegion* start_cset_region_for_worker(uint worker_i);
1420 // Iterate over the regions (if any) in the current collection set.
1421 void collection_set_iterate(HeapRegionClosure* blk);
1423 // As above but starting from region r
1424 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1426 HeapRegion* next_compaction_region(const HeapRegion* from) const;
1428 // A CollectedHeap will contain some number of spaces. This finds the
1429 // space containing a given address, or else returns NULL.
1430 virtual Space* space_containing(const void* addr) const;
1432 // Returns the HeapRegion that contains addr. addr must not be NULL.
1433 template <class T>
1434 inline HeapRegion* heap_region_containing_raw(const T addr) const;
1436 // Returns the HeapRegion that contains addr. addr must not be NULL.
1437 // If addr is within a humongous continues region, it returns its humongous start region.
1438 template <class T>
1439 inline HeapRegion* heap_region_containing(const T addr) const;
1441 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1442 // each address in the (reserved) heap is a member of exactly
1443 // one block. The defining characteristic of a block is that it is
1444 // possible to find its size, and thus to progress forward to the next
1445 // block. (Blocks may be of different sizes.) Thus, blocks may
1446 // represent Java objects, or they might be free blocks in a
1447 // free-list-based heap (or subheap), as long as the two kinds are
1448 // distinguishable and the size of each is determinable.
1450 // Returns the address of the start of the "block" that contains the
1451 // address "addr". We say "blocks" instead of "object" since some heaps
1452 // may not pack objects densely; a chunk may either be an object or a
1453 // non-object.
1454 virtual HeapWord* block_start(const void* addr) const;
1456 // Requires "addr" to be the start of a chunk, and returns its size.
1457 // "addr + size" is required to be the start of a new chunk, or the end
1458 // of the active area of the heap.
1459 virtual size_t block_size(const HeapWord* addr) const;
1461 // Requires "addr" to be the start of a block, and returns "TRUE" iff
1462 // the block is an object.
1463 virtual bool block_is_obj(const HeapWord* addr) const;
1465 // Does this heap support heap inspection? (+PrintClassHistogram)
1466 virtual bool supports_heap_inspection() const { return true; }
1468 // Section on thread-local allocation buffers (TLABs)
1469 // See CollectedHeap for semantics.
1471 bool supports_tlab_allocation() const;
1472 size_t tlab_capacity(Thread* ignored) const;
1473 size_t tlab_used(Thread* ignored) const;
1474 size_t max_tlab_size() const;
1475 size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1477 // Can a compiler initialize a new object without store barriers?
1478 // This permission only extends from the creation of a new object
1479 // via a TLAB up to the first subsequent safepoint. If such permission
1480 // is granted for this heap type, the compiler promises to call
1481 // defer_store_barrier() below on any slow path allocation of
1482 // a new object for which such initializing store barriers will
1483 // have been elided. G1, like CMS, allows this, but should be
1484 // ready to provide a compensating write barrier as necessary
1485 // if that storage came out of a non-young region. The efficiency
1486 // of this implementation depends crucially on being able to
1487 // answer very efficiently in constant time whether a piece of
1488 // storage in the heap comes from a young region or not.
1489 // See ReduceInitialCardMarks.
1490 virtual bool can_elide_tlab_store_barriers() const {
1491 return true;
1492 }
1494 virtual bool card_mark_must_follow_store() const {
1495 return true;
1496 }
1498 inline bool is_in_young(const oop obj);
1500 #ifdef ASSERT
1501 virtual bool is_in_partial_collection(const void* p);
1502 #endif
1504 virtual bool is_scavengable(const void* addr);
1506 // We don't need barriers for initializing stores to objects
1507 // in the young gen: for the SATB pre-barrier, there is no
1508 // pre-value that needs to be remembered; for the remembered-set
1509 // update logging post-barrier, we don't maintain remembered set
1510 // information for young gen objects.
1511 virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1513 // Returns "true" iff the given word_size is "very large".
1514 static bool isHumongous(size_t word_size) {
1515 // Note this has to be strictly greater-than as the TLABs
1516 // are capped at the humongous thresold and we want to
1517 // ensure that we don't try to allocate a TLAB as
1518 // humongous and that we don't allocate a humongous
1519 // object in a TLAB.
1520 return word_size > _humongous_object_threshold_in_words;
1521 }
1523 // Update mod union table with the set of dirty cards.
1524 void updateModUnion();
1526 // Set the mod union bits corresponding to the given memRegion. Note
1527 // that this is always a safe operation, since it doesn't clear any
1528 // bits.
1529 void markModUnionRange(MemRegion mr);
1531 // Records the fact that a marking phase is no longer in progress.
1532 void set_marking_complete() {
1533 _mark_in_progress = false;
1534 }
1535 void set_marking_started() {
1536 _mark_in_progress = true;
1537 }
1538 bool mark_in_progress() {
1539 return _mark_in_progress;
1540 }
1542 // Print the maximum heap capacity.
1543 virtual size_t max_capacity() const;
1545 virtual jlong millis_since_last_gc();
1548 // Convenience function to be used in situations where the heap type can be
1549 // asserted to be this type.
1550 static G1CollectedHeap* heap();
1552 void set_region_short_lived_locked(HeapRegion* hr);
1553 // add appropriate methods for any other surv rate groups
1555 YoungList* young_list() const { return _young_list; }
1557 // debugging
1558 bool check_young_list_well_formed() {
1559 return _young_list->check_list_well_formed();
1560 }
1562 bool check_young_list_empty(bool check_heap,
1563 bool check_sample = true);
1565 // *** Stuff related to concurrent marking. It's not clear to me that so
1566 // many of these need to be public.
1568 // The functions below are helper functions that a subclass of
1569 // "CollectedHeap" can use in the implementation of its virtual
1570 // functions.
1571 // This performs a concurrent marking of the live objects in a
1572 // bitmap off to the side.
1573 void doConcurrentMark();
1575 bool isMarkedPrev(oop obj) const;
1576 bool isMarkedNext(oop obj) const;
1578 // Determine if an object is dead, given the object and also
1579 // the region to which the object belongs. An object is dead
1580 // iff a) it was not allocated since the last mark and b) it
1581 // is not marked.
1582 bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1583 return
1584 !hr->obj_allocated_since_prev_marking(obj) &&
1585 !isMarkedPrev(obj);
1586 }
1588 // This function returns true when an object has been
1589 // around since the previous marking and hasn't yet
1590 // been marked during this marking.
1591 bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1592 return
1593 !hr->obj_allocated_since_next_marking(obj) &&
1594 !isMarkedNext(obj);
1595 }
1597 // Determine if an object is dead, given only the object itself.
1598 // This will find the region to which the object belongs and
1599 // then call the region version of the same function.
1601 // Added if it is NULL it isn't dead.
1603 inline bool is_obj_dead(const oop obj) const;
1605 inline bool is_obj_ill(const oop obj) const;
1607 bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1608 HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1609 bool is_marked(oop obj, VerifyOption vo);
1610 const char* top_at_mark_start_str(VerifyOption vo);
1612 ConcurrentMark* concurrent_mark() const { return _cm; }
1614 // Refinement
1616 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1618 // The dirty cards region list is used to record a subset of regions
1619 // whose cards need clearing. The list if populated during the
1620 // remembered set scanning and drained during the card table
1621 // cleanup. Although the methods are reentrant, population/draining
1622 // phases must not overlap. For synchronization purposes the last
1623 // element on the list points to itself.
1624 HeapRegion* _dirty_cards_region_list;
1625 void push_dirty_cards_region(HeapRegion* hr);
1626 HeapRegion* pop_dirty_cards_region();
1628 // Optimized nmethod scanning support routines
1630 // Register the given nmethod with the G1 heap
1631 virtual void register_nmethod(nmethod* nm);
1633 // Unregister the given nmethod from the G1 heap
1634 virtual void unregister_nmethod(nmethod* nm);
1636 // Migrate the nmethods in the code root lists of the regions
1637 // in the collection set to regions in to-space. In the event
1638 // of an evacuation failure, nmethods that reference objects
1639 // that were not successfullly evacuated are not migrated.
1640 void migrate_strong_code_roots();
1642 // Free up superfluous code root memory.
1643 void purge_code_root_memory();
1645 // Rebuild the stong code root lists for each region
1646 // after a full GC
1647 void rebuild_strong_code_roots();
1649 // Delete entries for dead interned string and clean up unreferenced symbols
1650 // in symbol table, possibly in parallel.
1651 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1653 // Parallel phase of unloading/cleaning after G1 concurrent mark.
1654 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred);
1656 // Redirty logged cards in the refinement queue.
1657 void redirty_logged_cards();
1658 // Verification
1660 // The following is just to alert the verification code
1661 // that a full collection has occurred and that the
1662 // remembered sets are no longer up to date.
1663 bool _full_collection;
1664 void set_full_collection() { _full_collection = true;}
1665 void clear_full_collection() {_full_collection = false;}
1666 bool full_collection() {return _full_collection;}
1668 // Perform any cleanup actions necessary before allowing a verification.
1669 virtual void prepare_for_verify();
1671 // Perform verification.
1673 // vo == UsePrevMarking -> use "prev" marking information,
1674 // vo == UseNextMarking -> use "next" marking information
1675 // vo == UseMarkWord -> use the mark word in the object header
1676 //
1677 // NOTE: Only the "prev" marking information is guaranteed to be
1678 // consistent most of the time, so most calls to this should use
1679 // vo == UsePrevMarking.
1680 // Currently, there is only one case where this is called with
1681 // vo == UseNextMarking, which is to verify the "next" marking
1682 // information at the end of remark.
1683 // Currently there is only one place where this is called with
1684 // vo == UseMarkWord, which is to verify the marking during a
1685 // full GC.
1686 void verify(bool silent, VerifyOption vo);
1688 // Override; it uses the "prev" marking information
1689 virtual void verify(bool silent);
1691 // The methods below are here for convenience and dispatch the
1692 // appropriate method depending on value of the given VerifyOption
1693 // parameter. The values for that parameter, and their meanings,
1694 // are the same as those above.
1696 bool is_obj_dead_cond(const oop obj,
1697 const HeapRegion* hr,
1698 const VerifyOption vo) const;
1700 bool is_obj_dead_cond(const oop obj,
1701 const VerifyOption vo) const;
1703 // Printing
1705 virtual void print_on(outputStream* st) const;
1706 virtual void print_extended_on(outputStream* st) const;
1707 virtual void print_on_error(outputStream* st) const;
1709 virtual void print_gc_threads_on(outputStream* st) const;
1710 virtual void gc_threads_do(ThreadClosure* tc) const;
1712 // Override
1713 void print_tracing_info() const;
1715 // The following two methods are helpful for debugging RSet issues.
1716 void print_cset_rsets() PRODUCT_RETURN;
1717 void print_all_rsets() PRODUCT_RETURN;
1719 public:
1720 size_t pending_card_num();
1721 size_t cards_scanned();
1723 protected:
1724 size_t _max_heap_capacity;
1725 };
1727 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP