1 /*
2 * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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24
25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
27
28 #include "gc_implementation/g1/g1AllocationContext.hpp"
29 #include "gc_implementation/g1/g1Allocator.hpp"
30 #include "gc_implementation/g1/concurrentMark.hpp"
31 #include "gc_implementation/g1/evacuationInfo.hpp"
32 #include "gc_implementation/g1/g1AllocRegion.hpp"
33 #include "gc_implementation/g1/g1BiasedArray.hpp"
34 #include "gc_implementation/g1/g1HRPrinter.hpp"
35 #include "gc_implementation/g1/g1InCSetState.hpp"
36 #include "gc_implementation/g1/g1MonitoringSupport.hpp"
37 #include "gc_implementation/g1/g1SATBCardTableModRefBS.hpp"
38 #include "gc_implementation/g1/g1YCTypes.hpp"
39 #include "gc_implementation/g1/heapRegionManager.hpp"
40 #include "gc_implementation/g1/heapRegionSet.hpp"
41 #include "gc_implementation/shared/hSpaceCounters.hpp"
42 #include "gc_implementation/shared/parGCAllocBuffer.hpp"
43 #include "memory/barrierSet.hpp"
44 #include "memory/memRegion.hpp"
45 #include "memory/sharedHeap.hpp"
46 #include "utilities/stack.hpp"
47
48 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
49 // It uses the "Garbage First" heap organization and algorithm, which
50 // may combine concurrent marking with parallel, incremental compaction of
51 // heap subsets that will yield large amounts of garbage.
52
53 // Forward declarations
54 class HeapRegion;
55 class HRRSCleanupTask;
56 class GenerationSpec;
57 class OopsInHeapRegionClosure;
58 class G1KlassScanClosure;
59 class G1ParScanThreadState;
60 class ObjectClosure;
61 class SpaceClosure;
62 class CompactibleSpaceClosure;
63 class Space;
64 class G1CollectorPolicy;
65 class GenRemSet;
66 class G1RemSet;
67 class HeapRegionRemSetIterator;
68 class ConcurrentMark;
69 class ConcurrentMarkThread;
70 class ConcurrentG1Refine;
71 class ConcurrentGCTimer;
72 class GenerationCounters;
73 class STWGCTimer;
74 class G1NewTracer;
75 class G1OldTracer;
76 class EvacuationFailedInfo;
77 class nmethod;
78 class Ticks;
79
80 typedef OverflowTaskQueue<StarTask, mtGC> RefToScanQueue;
81 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
82
83 typedef int RegionIdx_t; // needs to hold [ 0..max_regions() )
84 typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion )
85
86 class YoungList : public CHeapObj<mtGC> {
87 private:
88 G1CollectedHeap* _g1h;
89
90 HeapRegion* _head;
91
92 HeapRegion* _survivor_head;
93 HeapRegion* _survivor_tail;
94
95 HeapRegion* _curr;
96
97 uint _length;
98 uint _survivor_length;
99
100 size_t _last_sampled_rs_lengths;
101 size_t _sampled_rs_lengths;
102
103 void empty_list(HeapRegion* list);
104
105 public:
106 YoungList(G1CollectedHeap* g1h);
107
108 void push_region(HeapRegion* hr);
109 void add_survivor_region(HeapRegion* hr);
110
111 void empty_list();
112 bool is_empty() { return _length == 0; }
113 uint length() { return _length; }
114 uint eden_length() { return length() - survivor_length(); }
115 uint survivor_length() { return _survivor_length; }
116
117 // Currently we do not keep track of the used byte sum for the
118 // young list and the survivors and it'd be quite a lot of work to
119 // do so. When we'll eventually replace the young list with
120 // instances of HeapRegionLinkedList we'll get that for free. So,
121 // we'll report the more accurate information then.
122 size_t eden_used_bytes() {
123 assert(length() >= survivor_length(), "invariant");
124 return (size_t) eden_length() * HeapRegion::GrainBytes;
125 }
126 size_t survivor_used_bytes() {
127 return (size_t) survivor_length() * HeapRegion::GrainBytes;
128 }
129
130 void rs_length_sampling_init();
131 bool rs_length_sampling_more();
132 void rs_length_sampling_next();
133
134 void reset_sampled_info() {
135 _last_sampled_rs_lengths = 0;
136 }
137 size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
138
139 // for development purposes
140 void reset_auxilary_lists();
141 void clear() { _head = NULL; _length = 0; }
142
143 void clear_survivors() {
144 _survivor_head = NULL;
145 _survivor_tail = NULL;
146 _survivor_length = 0;
147 }
148
149 HeapRegion* first_region() { return _head; }
150 HeapRegion* first_survivor_region() { return _survivor_head; }
151 HeapRegion* last_survivor_region() { return _survivor_tail; }
152
153 // debugging
154 bool check_list_well_formed();
155 bool check_list_empty(bool check_sample = true);
156 void print();
157 };
158
159 // The G1 STW is alive closure.
160 // An instance is embedded into the G1CH and used as the
161 // (optional) _is_alive_non_header closure in the STW
162 // reference processor. It is also extensively used during
163 // reference processing during STW evacuation pauses.
164 class G1STWIsAliveClosure: public BoolObjectClosure {
165 G1CollectedHeap* _g1;
166 public:
167 G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
168 bool do_object_b(oop p);
169 };
170
171 class RefineCardTableEntryClosure;
172
173 class G1RegionMappingChangedListener : public G1MappingChangedListener {
174 private:
175 void reset_from_card_cache(uint start_idx, size_t num_regions);
176 public:
177 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
178 };
179
180 class G1CollectedHeap : public SharedHeap {
181 friend class VM_CollectForMetadataAllocation;
182 friend class VM_G1CollectForAllocation;
183 friend class VM_G1CollectFull;
184 friend class VM_G1IncCollectionPause;
185 friend class VMStructs;
186 friend class MutatorAllocRegion;
187 friend class SurvivorGCAllocRegion;
188 friend class OldGCAllocRegion;
189 friend class G1Allocator;
190
191 // Closures used in implementation.
192 friend class G1ParScanThreadState;
193 friend class G1ParTask;
194 friend class G1ParGCAllocator;
195 friend class G1PrepareCompactClosure;
196
197 // Other related classes.
198 friend class HeapRegionClaimer;
199
200 // Testing classes.
201 friend class G1CheckCSetFastTableClosure;
202
203 private:
204 // The one and only G1CollectedHeap, so static functions can find it.
205 static G1CollectedHeap* _g1h;
206
207 static size_t _humongous_object_threshold_in_words;
208
209 // The secondary free list which contains regions that have been
210 // freed up during the cleanup process. This will be appended to
211 // the master free list when appropriate.
212 FreeRegionList _secondary_free_list;
213
214 // It keeps track of the old regions.
215 HeapRegionSet _old_set;
216
217 // It keeps track of the humongous regions.
218 HeapRegionSet _humongous_set;
219
220 void clear_humongous_is_live_table();
221 void eagerly_reclaim_humongous_regions();
222
223 // The number of regions we could create by expansion.
224 uint _expansion_regions;
225
226 // The block offset table for the G1 heap.
227 G1BlockOffsetSharedArray* _bot_shared;
228
229 // Tears down the region sets / lists so that they are empty and the
230 // regions on the heap do not belong to a region set / list. The
231 // only exception is the humongous set which we leave unaltered. If
232 // free_list_only is true, it will only tear down the master free
233 // list. It is called before a Full GC (free_list_only == false) or
234 // before heap shrinking (free_list_only == true).
235 void tear_down_region_sets(bool free_list_only);
236
237 // Rebuilds the region sets / lists so that they are repopulated to
238 // reflect the contents of the heap. The only exception is the
239 // humongous set which was not torn down in the first place. If
240 // free_list_only is true, it will only rebuild the master free
241 // list. It is called after a Full GC (free_list_only == false) or
242 // after heap shrinking (free_list_only == true).
243 void rebuild_region_sets(bool free_list_only);
244
245 // Callback for region mapping changed events.
246 G1RegionMappingChangedListener _listener;
247
248 // The sequence of all heap regions in the heap.
249 HeapRegionManager _hrm;
250
251 // Class that handles the different kinds of allocations.
252 G1Allocator* _allocator;
253
254 // Statistics for each allocation context
255 AllocationContextStats _allocation_context_stats;
256
257 // PLAB sizing policy for survivors.
258 PLABStats _survivor_plab_stats;
259
260 // PLAB sizing policy for tenured objects.
261 PLABStats _old_plab_stats;
262
263 // It specifies whether we should attempt to expand the heap after a
264 // region allocation failure. If heap expansion fails we set this to
265 // false so that we don't re-attempt the heap expansion (it's likely
266 // that subsequent expansion attempts will also fail if one fails).
267 // Currently, it is only consulted during GC and it's reset at the
268 // start of each GC.
269 bool _expand_heap_after_alloc_failure;
270
271 // It resets the mutator alloc region before new allocations can take place.
272 void init_mutator_alloc_region();
273
274 // It releases the mutator alloc region.
275 void release_mutator_alloc_region();
276
277 // It initializes the GC alloc regions at the start of a GC.
278 void init_gc_alloc_regions(EvacuationInfo& evacuation_info);
279
280 // It releases the GC alloc regions at the end of a GC.
281 void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info);
282
283 // It does any cleanup that needs to be done on the GC alloc regions
284 // before a Full GC.
285 void abandon_gc_alloc_regions();
286
287 // Helper for monitoring and management support.
288 G1MonitoringSupport* _g1mm;
289
290 // Records whether the region at the given index is kept live by roots or
291 // references from the young generation.
292 class HumongousIsLiveBiasedMappedArray : public G1BiasedMappedArray<bool> {
293 protected:
294 bool default_value() const { return false; }
295 public:
296 void clear() { G1BiasedMappedArray<bool>::clear(); }
297 void set_live(uint region) {
298 set_by_index(region, true);
299 }
300 bool is_live(uint region) {
301 return get_by_index(region);
302 }
303 };
304
305 HumongousIsLiveBiasedMappedArray _humongous_is_live;
306 // Stores whether during humongous object registration we found candidate regions.
307 // If not, we can skip a few steps.
308 bool _has_humongous_reclaim_candidates;
309
310 volatile unsigned _gc_time_stamp;
311
312 size_t* _surviving_young_words;
313
314 G1HRPrinter _hr_printer;
315
316 void setup_surviving_young_words();
317 void update_surviving_young_words(size_t* surv_young_words);
318 void cleanup_surviving_young_words();
319
320 // It decides whether an explicit GC should start a concurrent cycle
321 // instead of doing a STW GC. Currently, a concurrent cycle is
322 // explicitly started if:
323 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
324 // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
325 // (c) cause == _g1_humongous_allocation
326 bool should_do_concurrent_full_gc(GCCause::Cause cause);
327
328 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
329 // concurrent cycles) we have started.
330 volatile uint _old_marking_cycles_started;
331
332 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
333 // concurrent cycles) we have completed.
334 volatile uint _old_marking_cycles_completed;
335
336 bool _concurrent_cycle_started;
337 bool _heap_summary_sent;
338
339 // This is a non-product method that is helpful for testing. It is
340 // called at the end of a GC and artificially expands the heap by
341 // allocating a number of dead regions. This way we can induce very
342 // frequent marking cycles and stress the cleanup / concurrent
343 // cleanup code more (as all the regions that will be allocated by
344 // this method will be found dead by the marking cycle).
345 void allocate_dummy_regions() PRODUCT_RETURN;
346
347 // Clear RSets after a compaction. It also resets the GC time stamps.
348 void clear_rsets_post_compaction();
349
350 // If the HR printer is active, dump the state of the regions in the
351 // heap after a compaction.
352 void print_hrm_post_compaction();
353
354 double verify(bool guard, const char* msg);
355 void verify_before_gc();
356 void verify_after_gc();
357
358 void log_gc_header();
359 void log_gc_footer(double pause_time_sec);
360
361 // These are macros so that, if the assert fires, we get the correct
362 // line number, file, etc.
363
364 #define heap_locking_asserts_err_msg(_extra_message_) \
365 err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \
366 (_extra_message_), \
367 BOOL_TO_STR(Heap_lock->owned_by_self()), \
368 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \
369 BOOL_TO_STR(Thread::current()->is_VM_thread()))
370
371 #define assert_heap_locked() \
372 do { \
373 assert(Heap_lock->owned_by_self(), \
374 heap_locking_asserts_err_msg("should be holding the Heap_lock")); \
375 } while (0)
376
377 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \
378 do { \
379 assert(Heap_lock->owned_by_self() || \
380 (SafepointSynchronize::is_at_safepoint() && \
381 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
382 heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
383 "should be at a safepoint")); \
384 } while (0)
385
386 #define assert_heap_locked_and_not_at_safepoint() \
387 do { \
388 assert(Heap_lock->owned_by_self() && \
389 !SafepointSynchronize::is_at_safepoint(), \
390 heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
391 "should not be at a safepoint")); \
392 } while (0)
393
394 #define assert_heap_not_locked() \
395 do { \
396 assert(!Heap_lock->owned_by_self(), \
397 heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
398 } while (0)
399
400 #define assert_heap_not_locked_and_not_at_safepoint() \
401 do { \
402 assert(!Heap_lock->owned_by_self() && \
403 !SafepointSynchronize::is_at_safepoint(), \
404 heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
405 "should not be at a safepoint")); \
406 } while (0)
407
408 #define assert_at_safepoint(_should_be_vm_thread_) \
409 do { \
410 assert(SafepointSynchronize::is_at_safepoint() && \
411 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
412 heap_locking_asserts_err_msg("should be at a safepoint")); \
413 } while (0)
414
415 #define assert_not_at_safepoint() \
416 do { \
417 assert(!SafepointSynchronize::is_at_safepoint(), \
418 heap_locking_asserts_err_msg("should not be at a safepoint")); \
419 } while (0)
420
421 protected:
422
423 // The young region list.
424 YoungList* _young_list;
425
426 // The current policy object for the collector.
427 G1CollectorPolicy* _g1_policy;
428
429 // This is the second level of trying to allocate a new region. If
430 // new_region() didn't find a region on the free_list, this call will
431 // check whether there's anything available on the
432 // secondary_free_list and/or wait for more regions to appear on
433 // that list, if _free_regions_coming is set.
434 HeapRegion* new_region_try_secondary_free_list(bool is_old);
435
436 // Try to allocate a single non-humongous HeapRegion sufficient for
437 // an allocation of the given word_size. If do_expand is true,
438 // attempt to expand the heap if necessary to satisfy the allocation
439 // request. If the region is to be used as an old region or for a
440 // humongous object, set is_old to true. If not, to false.
441 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
442
443 // Initialize a contiguous set of free regions of length num_regions
444 // and starting at index first so that they appear as a single
445 // humongous region.
446 HeapWord* humongous_obj_allocate_initialize_regions(uint first,
447 uint num_regions,
448 size_t word_size,
449 AllocationContext_t context);
450
451 // Attempt to allocate a humongous object of the given size. Return
452 // NULL if unsuccessful.
453 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context);
454
455 // The following two methods, allocate_new_tlab() and
456 // mem_allocate(), are the two main entry points from the runtime
457 // into the G1's allocation routines. They have the following
458 // assumptions:
459 //
460 // * They should both be called outside safepoints.
461 //
462 // * They should both be called without holding the Heap_lock.
463 //
464 // * All allocation requests for new TLABs should go to
465 // allocate_new_tlab().
466 //
467 // * All non-TLAB allocation requests should go to mem_allocate().
468 //
469 // * If either call cannot satisfy the allocation request using the
470 // current allocating region, they will try to get a new one. If
471 // this fails, they will attempt to do an evacuation pause and
472 // retry the allocation.
473 //
474 // * If all allocation attempts fail, even after trying to schedule
475 // an evacuation pause, allocate_new_tlab() will return NULL,
476 // whereas mem_allocate() will attempt a heap expansion and/or
477 // schedule a Full GC.
478 //
479 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
480 // should never be called with word_size being humongous. All
481 // humongous allocation requests should go to mem_allocate() which
482 // will satisfy them with a special path.
483
484 virtual HeapWord* allocate_new_tlab(size_t word_size);
485
486 virtual HeapWord* mem_allocate(size_t word_size,
487 bool* gc_overhead_limit_was_exceeded);
488
489 // The following three methods take a gc_count_before_ret
490 // parameter which is used to return the GC count if the method
491 // returns NULL. Given that we are required to read the GC count
492 // while holding the Heap_lock, and these paths will take the
493 // Heap_lock at some point, it's easier to get them to read the GC
494 // count while holding the Heap_lock before they return NULL instead
495 // of the caller (namely: mem_allocate()) having to also take the
496 // Heap_lock just to read the GC count.
497
498 // First-level mutator allocation attempt: try to allocate out of
499 // the mutator alloc region without taking the Heap_lock. This
500 // should only be used for non-humongous allocations.
501 inline HeapWord* attempt_allocation(size_t word_size,
502 uint* gc_count_before_ret,
503 uint* gclocker_retry_count_ret);
504
505 // Second-level mutator allocation attempt: take the Heap_lock and
506 // retry the allocation attempt, potentially scheduling a GC
507 // pause. This should only be used for non-humongous allocations.
508 HeapWord* attempt_allocation_slow(size_t word_size,
509 AllocationContext_t context,
510 uint* gc_count_before_ret,
511 uint* gclocker_retry_count_ret);
512
513 // Takes the Heap_lock and attempts a humongous allocation. It can
514 // potentially schedule a GC pause.
515 HeapWord* attempt_allocation_humongous(size_t word_size,
516 uint* gc_count_before_ret,
517 uint* gclocker_retry_count_ret);
518
519 // Allocation attempt that should be called during safepoints (e.g.,
520 // at the end of a successful GC). expect_null_mutator_alloc_region
521 // specifies whether the mutator alloc region is expected to be NULL
522 // or not.
523 HeapWord* attempt_allocation_at_safepoint(size_t word_size,
524 AllocationContext_t context,
525 bool expect_null_mutator_alloc_region);
526
527 // It dirties the cards that cover the block so that so that the post
528 // write barrier never queues anything when updating objects on this
529 // block. It is assumed (and in fact we assert) that the block
530 // belongs to a young region.
531 inline void dirty_young_block(HeapWord* start, size_t word_size);
532
533 // Allocate blocks during garbage collection. Will ensure an
534 // allocation region, either by picking one or expanding the
535 // heap, and then allocate a block of the given size. The block
536 // may not be a humongous - it must fit into a single heap region.
537 inline HeapWord* par_allocate_during_gc(InCSetState dest,
538 size_t word_size,
539 AllocationContext_t context);
540 // Ensure that no further allocations can happen in "r", bearing in mind
541 // that parallel threads might be attempting allocations.
542 void par_allocate_remaining_space(HeapRegion* r);
543
544 // Allocation attempt during GC for a survivor object / PLAB.
545 inline HeapWord* survivor_attempt_allocation(size_t word_size,
546 AllocationContext_t context);
547
548 // Allocation attempt during GC for an old object / PLAB.
549 inline HeapWord* old_attempt_allocation(size_t word_size,
550 AllocationContext_t context);
551
552 // These methods are the "callbacks" from the G1AllocRegion class.
553
554 // For mutator alloc regions.
555 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
556 void retire_mutator_alloc_region(HeapRegion* alloc_region,
557 size_t allocated_bytes);
558
559 // For GC alloc regions.
560 HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
561 InCSetState dest);
562 void retire_gc_alloc_region(HeapRegion* alloc_region,
563 size_t allocated_bytes, InCSetState dest);
564
565 // - if explicit_gc is true, the GC is for a System.gc() or a heap
566 // inspection request and should collect the entire heap
567 // - if clear_all_soft_refs is true, all soft references should be
568 // cleared during the GC
569 // - if explicit_gc is false, word_size describes the allocation that
570 // the GC should attempt (at least) to satisfy
571 // - it returns false if it is unable to do the collection due to the
572 // GC locker being active, true otherwise
573 bool do_collection(bool explicit_gc,
574 bool clear_all_soft_refs,
575 size_t word_size);
576
577 // Callback from VM_G1CollectFull operation.
578 // Perform a full collection.
579 virtual void do_full_collection(bool clear_all_soft_refs);
580
581 // Resize the heap if necessary after a full collection. If this is
582 // after a collect-for allocation, "word_size" is the allocation size,
583 // and will be considered part of the used portion of the heap.
584 void resize_if_necessary_after_full_collection(size_t word_size);
585
586 // Callback from VM_G1CollectForAllocation operation.
587 // This function does everything necessary/possible to satisfy a
588 // failed allocation request (including collection, expansion, etc.)
589 HeapWord* satisfy_failed_allocation(size_t word_size,
590 AllocationContext_t context,
591 bool* succeeded);
592
593 // Attempting to expand the heap sufficiently
594 // to support an allocation of the given "word_size". If
595 // successful, perform the allocation and return the address of the
596 // allocated block, or else "NULL".
597 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context);
598
599 // Process any reference objects discovered during
600 // an incremental evacuation pause.
601 void process_discovered_references(uint no_of_gc_workers);
602
603 // Enqueue any remaining discovered references
604 // after processing.
605 void enqueue_discovered_references(uint no_of_gc_workers);
606
607 public:
608
609 G1Allocator* allocator() {
610 return _allocator;
611 }
612
613 G1MonitoringSupport* g1mm() {
614 assert(_g1mm != NULL, "should have been initialized");
615 return _g1mm;
616 }
617
618 // Expand the garbage-first heap by at least the given size (in bytes!).
619 // Returns true if the heap was expanded by the requested amount;
620 // false otherwise.
621 // (Rounds up to a HeapRegion boundary.)
622 bool expand(size_t expand_bytes);
623
624 // Returns the PLAB statistics for a given destination.
625 inline PLABStats* alloc_buffer_stats(InCSetState dest);
626
627 // Determines PLAB size for a given destination.
628 inline size_t desired_plab_sz(InCSetState dest);
629
630 inline AllocationContextStats& allocation_context_stats();
631
632 // Do anything common to GC's.
633 virtual void gc_prologue(bool full);
634 virtual void gc_epilogue(bool full);
635
636 inline void set_humongous_is_live(oop obj);
637
638 bool humongous_is_live(uint region) {
639 return _humongous_is_live.is_live(region);
640 }
641
642 // Returns whether the given region (which must be a humongous (start) region)
643 // is to be considered conservatively live regardless of any other conditions.
644 bool humongous_region_is_always_live(uint index);
645 // Returns whether the given region (which must be a humongous (start) region)
646 // is considered a candidate for eager reclamation.
647 bool humongous_region_is_candidate(uint index);
648 // Register the given region to be part of the collection set.
649 inline void register_humongous_region_with_cset(uint index);
650 // Register regions with humongous objects (actually on the start region) in
651 // the in_cset_fast_test table.
652 void register_humongous_regions_with_cset();
653 // We register a region with the fast "in collection set" test. We
654 // simply set to true the array slot corresponding to this region.
655 void register_young_region_with_cset(HeapRegion* r) {
656 _in_cset_fast_test.set_in_young(r->hrm_index());
657 }
658 void register_old_region_with_cset(HeapRegion* r) {
659 _in_cset_fast_test.set_in_old(r->hrm_index());
660 }
661 void clear_in_cset(const HeapRegion* hr) {
662 _in_cset_fast_test.clear(hr);
663 }
664
665 void clear_cset_fast_test() {
666 _in_cset_fast_test.clear();
667 }
668
669 // This is called at the start of either a concurrent cycle or a Full
670 // GC to update the number of old marking cycles started.
671 void increment_old_marking_cycles_started();
672
673 // This is called at the end of either a concurrent cycle or a Full
674 // GC to update the number of old marking cycles completed. Those two
675 // can happen in a nested fashion, i.e., we start a concurrent
676 // cycle, a Full GC happens half-way through it which ends first,
677 // and then the cycle notices that a Full GC happened and ends
678 // too. The concurrent parameter is a boolean to help us do a bit
679 // tighter consistency checking in the method. If concurrent is
680 // false, the caller is the inner caller in the nesting (i.e., the
681 // Full GC). If concurrent is true, the caller is the outer caller
682 // in this nesting (i.e., the concurrent cycle). Further nesting is
683 // not currently supported. The end of this call also notifies
684 // the FullGCCount_lock in case a Java thread is waiting for a full
685 // GC to happen (e.g., it called System.gc() with
686 // +ExplicitGCInvokesConcurrent).
687 void increment_old_marking_cycles_completed(bool concurrent);
688
689 uint old_marking_cycles_completed() {
690 return _old_marking_cycles_completed;
691 }
692
693 void register_concurrent_cycle_start(const Ticks& start_time);
694 void register_concurrent_cycle_end();
695 void trace_heap_after_concurrent_cycle();
696
697 G1YCType yc_type();
698
699 G1HRPrinter* hr_printer() { return &_hr_printer; }
700
701 // Frees a non-humongous region by initializing its contents and
702 // adding it to the free list that's passed as a parameter (this is
703 // usually a local list which will be appended to the master free
704 // list later). The used bytes of freed regions are accumulated in
705 // pre_used. If par is true, the region's RSet will not be freed
706 // up. The assumption is that this will be done later.
707 // The locked parameter indicates if the caller has already taken
708 // care of proper synchronization. This may allow some optimizations.
709 void free_region(HeapRegion* hr,
710 FreeRegionList* free_list,
711 bool par,
712 bool locked = false);
713
714 // Frees a humongous region by collapsing it into individual regions
715 // and calling free_region() for each of them. The freed regions
716 // will be added to the free list that's passed as a parameter (this
717 // is usually a local list which will be appended to the master free
718 // list later). The used bytes of freed regions are accumulated in
719 // pre_used. If par is true, the region's RSet will not be freed
720 // up. The assumption is that this will be done later.
721 void free_humongous_region(HeapRegion* hr,
722 FreeRegionList* free_list,
723 bool par);
724 protected:
725
726 // Shrink the garbage-first heap by at most the given size (in bytes!).
727 // (Rounds down to a HeapRegion boundary.)
728 virtual void shrink(size_t expand_bytes);
729 void shrink_helper(size_t expand_bytes);
730
731 #if TASKQUEUE_STATS
732 static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
733 void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
734 void reset_taskqueue_stats();
735 #endif // TASKQUEUE_STATS
736
737 // Schedule the VM operation that will do an evacuation pause to
738 // satisfy an allocation request of word_size. *succeeded will
739 // return whether the VM operation was successful (it did do an
740 // evacuation pause) or not (another thread beat us to it or the GC
741 // locker was active). Given that we should not be holding the
742 // Heap_lock when we enter this method, we will pass the
743 // gc_count_before (i.e., total_collections()) as a parameter since
744 // it has to be read while holding the Heap_lock. Currently, both
745 // methods that call do_collection_pause() release the Heap_lock
746 // before the call, so it's easy to read gc_count_before just before.
747 HeapWord* do_collection_pause(size_t word_size,
748 uint gc_count_before,
749 bool* succeeded,
750 GCCause::Cause gc_cause);
751
752 // The guts of the incremental collection pause, executed by the vm
753 // thread. It returns false if it is unable to do the collection due
754 // to the GC locker being active, true otherwise
755 bool do_collection_pause_at_safepoint(double target_pause_time_ms);
756
757 // Actually do the work of evacuating the collection set.
758 void evacuate_collection_set(EvacuationInfo& evacuation_info);
759
760 // The g1 remembered set of the heap.
761 G1RemSet* _g1_rem_set;
762
763 // A set of cards that cover the objects for which the Rsets should be updated
764 // concurrently after the collection.
765 DirtyCardQueueSet _dirty_card_queue_set;
766
767 // The closure used to refine a single card.
768 RefineCardTableEntryClosure* _refine_cte_cl;
769
770 // A DirtyCardQueueSet that is used to hold cards that contain
771 // references into the current collection set. This is used to
772 // update the remembered sets of the regions in the collection
773 // set in the event of an evacuation failure.
774 DirtyCardQueueSet _into_cset_dirty_card_queue_set;
775
776 // After a collection pause, make the regions in the CS into free
777 // regions.
778 void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info);
779
780 // Abandon the current collection set without recording policy
781 // statistics or updating free lists.
782 void abandon_collection_set(HeapRegion* cs_head);
783
784 // The concurrent marker (and the thread it runs in.)
785 ConcurrentMark* _cm;
786 ConcurrentMarkThread* _cmThread;
787 bool _mark_in_progress;
788
789 // The concurrent refiner.
790 ConcurrentG1Refine* _cg1r;
791
792 // The parallel task queues
793 RefToScanQueueSet *_task_queues;
794
795 // True iff a evacuation has failed in the current collection.
796 bool _evacuation_failed;
797
798 EvacuationFailedInfo* _evacuation_failed_info_array;
799
800 // Failed evacuations cause some logical from-space objects to have
801 // forwarding pointers to themselves. Reset them.
802 void remove_self_forwarding_pointers();
803
804 // Together, these store an object with a preserved mark, and its mark value.
805 Stack<oop, mtGC> _objs_with_preserved_marks;
806 Stack<markOop, mtGC> _preserved_marks_of_objs;
807
808 // Preserve the mark of "obj", if necessary, in preparation for its mark
809 // word being overwritten with a self-forwarding-pointer.
810 void preserve_mark_if_necessary(oop obj, markOop m);
811
812 // The stack of evac-failure objects left to be scanned.
813 GrowableArray<oop>* _evac_failure_scan_stack;
814 // The closure to apply to evac-failure objects.
815
816 OopsInHeapRegionClosure* _evac_failure_closure;
817 // Set the field above.
818 void
819 set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
820 _evac_failure_closure = evac_failure_closure;
821 }
822
823 // Push "obj" on the scan stack.
824 void push_on_evac_failure_scan_stack(oop obj);
825 // Process scan stack entries until the stack is empty.
826 void drain_evac_failure_scan_stack();
827 // True iff an invocation of "drain_scan_stack" is in progress; to
828 // prevent unnecessary recursion.
829 bool _drain_in_progress;
830
831 // Do any necessary initialization for evacuation-failure handling.
832 // "cl" is the closure that will be used to process evac-failure
833 // objects.
834 void init_for_evac_failure(OopsInHeapRegionClosure* cl);
835 // Do any necessary cleanup for evacuation-failure handling data
836 // structures.
837 void finalize_for_evac_failure();
838
839 // An attempt to evacuate "obj" has failed; take necessary steps.
840 oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj);
841 void handle_evacuation_failure_common(oop obj, markOop m);
842
843 #ifndef PRODUCT
844 // Support for forcing evacuation failures. Analogous to
845 // PromotionFailureALot for the other collectors.
846
847 // Records whether G1EvacuationFailureALot should be in effect
848 // for the current GC
849 bool _evacuation_failure_alot_for_current_gc;
850
851 // Used to record the GC number for interval checking when
852 // determining whether G1EvaucationFailureALot is in effect
853 // for the current GC.
854 size_t _evacuation_failure_alot_gc_number;
855
856 // Count of the number of evacuations between failures.
857 volatile size_t _evacuation_failure_alot_count;
858
859 // Set whether G1EvacuationFailureALot should be in effect
860 // for the current GC (based upon the type of GC and which
861 // command line flags are set);
862 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
863 bool during_initial_mark,
864 bool during_marking);
865
866 inline void set_evacuation_failure_alot_for_current_gc();
867
868 // Return true if it's time to cause an evacuation failure.
869 inline bool evacuation_should_fail();
870
871 // Reset the G1EvacuationFailureALot counters. Should be called at
872 // the end of an evacuation pause in which an evacuation failure occurred.
873 inline void reset_evacuation_should_fail();
874 #endif // !PRODUCT
875
876 // ("Weak") Reference processing support.
877 //
878 // G1 has 2 instances of the reference processor class. One
879 // (_ref_processor_cm) handles reference object discovery
880 // and subsequent processing during concurrent marking cycles.
881 //
882 // The other (_ref_processor_stw) handles reference object
883 // discovery and processing during full GCs and incremental
884 // evacuation pauses.
885 //
886 // During an incremental pause, reference discovery will be
887 // temporarily disabled for _ref_processor_cm and will be
888 // enabled for _ref_processor_stw. At the end of the evacuation
889 // pause references discovered by _ref_processor_stw will be
890 // processed and discovery will be disabled. The previous
891 // setting for reference object discovery for _ref_processor_cm
892 // will be re-instated.
893 //
894 // At the start of marking:
895 // * Discovery by the CM ref processor is verified to be inactive
896 // and it's discovered lists are empty.
897 // * Discovery by the CM ref processor is then enabled.
898 //
899 // At the end of marking:
900 // * Any references on the CM ref processor's discovered
901 // lists are processed (possibly MT).
902 //
903 // At the start of full GC we:
904 // * Disable discovery by the CM ref processor and
905 // empty CM ref processor's discovered lists
906 // (without processing any entries).
907 // * Verify that the STW ref processor is inactive and it's
908 // discovered lists are empty.
909 // * Temporarily set STW ref processor discovery as single threaded.
910 // * Temporarily clear the STW ref processor's _is_alive_non_header
911 // field.
912 // * Finally enable discovery by the STW ref processor.
913 //
914 // The STW ref processor is used to record any discovered
915 // references during the full GC.
916 //
917 // At the end of a full GC we:
918 // * Enqueue any reference objects discovered by the STW ref processor
919 // that have non-live referents. This has the side-effect of
920 // making the STW ref processor inactive by disabling discovery.
921 // * Verify that the CM ref processor is still inactive
922 // and no references have been placed on it's discovered
923 // lists (also checked as a precondition during initial marking).
924
925 // The (stw) reference processor...
926 ReferenceProcessor* _ref_processor_stw;
927
928 STWGCTimer* _gc_timer_stw;
929 ConcurrentGCTimer* _gc_timer_cm;
930
931 G1OldTracer* _gc_tracer_cm;
932 G1NewTracer* _gc_tracer_stw;
933
934 // During reference object discovery, the _is_alive_non_header
935 // closure (if non-null) is applied to the referent object to
936 // determine whether the referent is live. If so then the
937 // reference object does not need to be 'discovered' and can
938 // be treated as a regular oop. This has the benefit of reducing
939 // the number of 'discovered' reference objects that need to
940 // be processed.
941 //
942 // Instance of the is_alive closure for embedding into the
943 // STW reference processor as the _is_alive_non_header field.
944 // Supplying a value for the _is_alive_non_header field is
945 // optional but doing so prevents unnecessary additions to
946 // the discovered lists during reference discovery.
947 G1STWIsAliveClosure _is_alive_closure_stw;
948
949 // The (concurrent marking) reference processor...
950 ReferenceProcessor* _ref_processor_cm;
951
952 // Instance of the concurrent mark is_alive closure for embedding
953 // into the Concurrent Marking reference processor as the
954 // _is_alive_non_header field. Supplying a value for the
955 // _is_alive_non_header field is optional but doing so prevents
956 // unnecessary additions to the discovered lists during reference
957 // discovery.
958 G1CMIsAliveClosure _is_alive_closure_cm;
959
960 // Cache used by G1CollectedHeap::start_cset_region_for_worker().
961 HeapRegion** _worker_cset_start_region;
962
963 // Time stamp to validate the regions recorded in the cache
964 // used by G1CollectedHeap::start_cset_region_for_worker().
965 // The heap region entry for a given worker is valid iff
966 // the associated time stamp value matches the current value
967 // of G1CollectedHeap::_gc_time_stamp.
968 uint* _worker_cset_start_region_time_stamp;
969
970 volatile bool _free_regions_coming;
971
972 public:
973
974 void set_refine_cte_cl_concurrency(bool concurrent);
975
976 RefToScanQueue *task_queue(int i) const;
977
978 // A set of cards where updates happened during the GC
979 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
980
981 // A DirtyCardQueueSet that is used to hold cards that contain
982 // references into the current collection set. This is used to
983 // update the remembered sets of the regions in the collection
984 // set in the event of an evacuation failure.
985 DirtyCardQueueSet& into_cset_dirty_card_queue_set()
986 { return _into_cset_dirty_card_queue_set; }
987
988 // Create a G1CollectedHeap with the specified policy.
989 // Must call the initialize method afterwards.
990 // May not return if something goes wrong.
991 G1CollectedHeap(G1CollectorPolicy* policy);
992
993 // Initialize the G1CollectedHeap to have the initial and
994 // maximum sizes and remembered and barrier sets
995 // specified by the policy object.
996 jint initialize();
997
998 virtual void stop();
999
1000 // Return the (conservative) maximum heap alignment for any G1 heap
1001 static size_t conservative_max_heap_alignment();
1002
1003 // Initialize weak reference processing.
1004 virtual void ref_processing_init();
1005
1006 // Explicitly import set_par_threads into this scope
1007 using SharedHeap::set_par_threads;
1008 // Set _n_par_threads according to a policy TBD.
1009 void set_par_threads();
1010
1011 virtual CollectedHeap::Name kind() const {
1012 return CollectedHeap::G1CollectedHeap;
1013 }
1014
1015 // The current policy object for the collector.
1016 G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1017
1018 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); }
1019
1020 // Adaptive size policy. No such thing for g1.
1021 virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1022
1023 // The rem set and barrier set.
1024 G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1025
1026 unsigned get_gc_time_stamp() {
1027 return _gc_time_stamp;
1028 }
1029
1030 inline void reset_gc_time_stamp();
1031
1032 void check_gc_time_stamps() PRODUCT_RETURN;
1033
1034 inline void increment_gc_time_stamp();
1035
1036 // Reset the given region's GC timestamp. If it's starts humongous,
1037 // also reset the GC timestamp of its corresponding
1038 // continues humongous regions too.
1039 void reset_gc_time_stamps(HeapRegion* hr);
1040
1041 void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1042 DirtyCardQueue* into_cset_dcq,
1043 bool concurrent, uint worker_i);
1044
1045 // The shared block offset table array.
1046 G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1047
1048 // Reference Processing accessors
1049
1050 // The STW reference processor....
1051 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1052
1053 // The Concurrent Marking reference processor...
1054 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1055
1056 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1057 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1058
1059 virtual size_t capacity() const;
1060 virtual size_t used() const;
1061 // This should be called when we're not holding the heap lock. The
1062 // result might be a bit inaccurate.
1063 size_t used_unlocked() const;
1064 size_t recalculate_used() const;
1065
1066 // These virtual functions do the actual allocation.
1067 // Some heaps may offer a contiguous region for shared non-blocking
1068 // allocation, via inlined code (by exporting the address of the top and
1069 // end fields defining the extent of the contiguous allocation region.)
1070 // But G1CollectedHeap doesn't yet support this.
1071
1072 virtual bool is_maximal_no_gc() const {
1073 return _hrm.available() == 0;
1074 }
1075
1076 // The current number of regions in the heap.
1077 uint num_regions() const { return _hrm.length(); }
1078
1079 // The max number of regions in the heap.
1080 uint max_regions() const { return _hrm.max_length(); }
1081
1082 // The number of regions that are completely free.
1083 uint num_free_regions() const { return _hrm.num_free_regions(); }
1084
1085 MemoryUsage get_auxiliary_data_memory_usage() const {
1086 return _hrm.get_auxiliary_data_memory_usage();
1087 }
1088
1089 // The number of regions that are not completely free.
1090 uint num_used_regions() const { return num_regions() - num_free_regions(); }
1091
1092 void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1093 void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1094 void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1095 void verify_dirty_young_regions() PRODUCT_RETURN;
1096
1097 #ifndef PRODUCT
1098 // Make sure that the given bitmap has no marked objects in the
1099 // range [from,limit). If it does, print an error message and return
1100 // false. Otherwise, just return true. bitmap_name should be "prev"
1101 // or "next".
1102 bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
1103 HeapWord* from, HeapWord* limit);
1104
1105 // Verify that the prev / next bitmap range [tams,end) for the given
1106 // region has no marks. Return true if all is well, false if errors
1107 // are detected.
1108 bool verify_bitmaps(const char* caller, HeapRegion* hr);
1109 #endif // PRODUCT
1110
1111 // If G1VerifyBitmaps is set, verify that the marking bitmaps for
1112 // the given region do not have any spurious marks. If errors are
1113 // detected, print appropriate error messages and crash.
1114 void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN;
1115
1116 // If G1VerifyBitmaps is set, verify that the marking bitmaps do not
1117 // have any spurious marks. If errors are detected, print
1118 // appropriate error messages and crash.
1119 void check_bitmaps(const char* caller) PRODUCT_RETURN;
1120
1121 // Do sanity check on the contents of the in-cset fast test table.
1122 bool check_cset_fast_test() PRODUCT_RETURN_( return true; );
1123
1124 // verify_region_sets() performs verification over the region
1125 // lists. It will be compiled in the product code to be used when
1126 // necessary (i.e., during heap verification).
1127 void verify_region_sets();
1128
1129 // verify_region_sets_optional() is planted in the code for
1130 // list verification in non-product builds (and it can be enabled in
1131 // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1).
1132 #if HEAP_REGION_SET_FORCE_VERIFY
1133 void verify_region_sets_optional() {
1134 verify_region_sets();
1135 }
1136 #else // HEAP_REGION_SET_FORCE_VERIFY
1137 void verify_region_sets_optional() { }
1138 #endif // HEAP_REGION_SET_FORCE_VERIFY
1139
1140 #ifdef ASSERT
1141 bool is_on_master_free_list(HeapRegion* hr) {
1142 return _hrm.is_free(hr);
1143 }
1144 #endif // ASSERT
1145
1146 // Wrapper for the region list operations that can be called from
1147 // methods outside this class.
1148
1149 void secondary_free_list_add(FreeRegionList* list) {
1150 _secondary_free_list.add_ordered(list);
1151 }
1152
1153 void append_secondary_free_list() {
1154 _hrm.insert_list_into_free_list(&_secondary_free_list);
1155 }
1156
1157 void append_secondary_free_list_if_not_empty_with_lock() {
1158 // If the secondary free list looks empty there's no reason to
1159 // take the lock and then try to append it.
1160 if (!_secondary_free_list.is_empty()) {
1161 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1162 append_secondary_free_list();
1163 }
1164 }
1165
1166 inline void old_set_remove(HeapRegion* hr);
1167
1168 size_t non_young_capacity_bytes() {
1169 return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1170 }
1171
1172 void set_free_regions_coming();
1173 void reset_free_regions_coming();
1174 bool free_regions_coming() { return _free_regions_coming; }
1175 void wait_while_free_regions_coming();
1176
1177 // Determine whether the given region is one that we are using as an
1178 // old GC alloc region.
1179 bool is_old_gc_alloc_region(HeapRegion* hr) {
1180 return _allocator->is_retained_old_region(hr);
1181 }
1182
1183 // Perform a collection of the heap; intended for use in implementing
1184 // "System.gc". This probably implies as full a collection as the
1185 // "CollectedHeap" supports.
1186 virtual void collect(GCCause::Cause cause);
1187
1188 // The same as above but assume that the caller holds the Heap_lock.
1189 void collect_locked(GCCause::Cause cause);
1190
1191 virtual bool copy_allocation_context_stats(const jint* contexts,
1192 jlong* totals,
1193 jbyte* accuracy,
1194 jint len);
1195
1196 // True iff an evacuation has failed in the most-recent collection.
1197 bool evacuation_failed() { return _evacuation_failed; }
1198
1199 void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed);
1200 void prepend_to_freelist(FreeRegionList* list);
1201 void decrement_summary_bytes(size_t bytes);
1202
1203 // Returns "TRUE" iff "p" points into the committed areas of the heap.
1204 virtual bool is_in(const void* p) const;
1205 #ifdef ASSERT
1206 // Returns whether p is in one of the available areas of the heap. Slow but
1207 // extensive version.
1208 bool is_in_exact(const void* p) const;
1209 #endif
1210
1211 // Return "TRUE" iff the given object address is within the collection
1212 // set. Slow implementation.
1213 inline bool obj_in_cs(oop obj);
1214
1215 inline bool is_in_cset(const HeapRegion *hr);
1216 inline bool is_in_cset(oop obj);
1217
1218 inline bool is_in_cset_or_humongous(const oop obj);
1219
1220 private:
1221 // This array is used for a quick test on whether a reference points into
1222 // the collection set or not. Each of the array's elements denotes whether the
1223 // corresponding region is in the collection set or not.
1224 G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test;
1225
1226 public:
1227
1228 inline InCSetState in_cset_state(const oop obj);
1229
1230 // Return "TRUE" iff the given object address is in the reserved
1231 // region of g1.
1232 bool is_in_g1_reserved(const void* p) const {
1233 return _hrm.reserved().contains(p);
1234 }
1235
1236 // Returns a MemRegion that corresponds to the space that has been
1237 // reserved for the heap
1238 MemRegion g1_reserved() const {
1239 return _hrm.reserved();
1240 }
1241
1242 virtual bool is_in_closed_subset(const void* p) const;
1243
1244 G1SATBCardTableLoggingModRefBS* g1_barrier_set() {
1245 return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set());
1246 }
1247
1248 // This resets the card table to all zeros. It is used after
1249 // a collection pause which used the card table to claim cards.
1250 void cleanUpCardTable();
1251
1252 // Iteration functions.
1253
1254 // Iterate over all the ref-containing fields of all objects, calling
1255 // "cl.do_oop" on each.
1256 virtual void oop_iterate(ExtendedOopClosure* cl);
1257
1258 // Iterate over all objects, calling "cl.do_object" on each.
1259 virtual void object_iterate(ObjectClosure* cl);
1260
1261 virtual void safe_object_iterate(ObjectClosure* cl) {
1262 object_iterate(cl);
1263 }
1264
1265 // Iterate over all spaces in use in the heap, in ascending address order.
1266 virtual void space_iterate(SpaceClosure* cl);
1267
1268 // Iterate over heap regions, in address order, terminating the
1269 // iteration early if the "doHeapRegion" method returns "true".
1270 void heap_region_iterate(HeapRegionClosure* blk) const;
1271
1272 // Return the region with the given index. It assumes the index is valid.
1273 inline HeapRegion* region_at(uint index) const;
1274
1275 // Calculate the region index of the given address. Given address must be
1276 // within the heap.
1277 inline uint addr_to_region(HeapWord* addr) const;
1278
1279 inline HeapWord* bottom_addr_for_region(uint index) const;
1280
1281 // Iterate over the heap regions in parallel. Assumes that this will be called
1282 // in parallel by ParallelGCThreads worker threads with distinct worker ids
1283 // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion"
1284 // to each of the regions, by attempting to claim the region using the
1285 // HeapRegionClaimer and, if successful, applying the closure to the claimed
1286 // region. The concurrent argument should be set to true if iteration is
1287 // performed concurrently, during which no assumptions are made for consistent
1288 // attributes of the heap regions (as they might be modified while iterating).
1289 void heap_region_par_iterate(HeapRegionClosure* cl,
1290 uint worker_id,
1291 HeapRegionClaimer* hrclaimer,
1292 bool concurrent = false) const;
1293
1294 // Clear the cached cset start regions and (more importantly)
1295 // the time stamps. Called when we reset the GC time stamp.
1296 void clear_cset_start_regions();
1297
1298 // Given the id of a worker, obtain or calculate a suitable
1299 // starting region for iterating over the current collection set.
1300 HeapRegion* start_cset_region_for_worker(uint worker_i);
1301
1302 // Iterate over the regions (if any) in the current collection set.
1303 void collection_set_iterate(HeapRegionClosure* blk);
1304
1305 // As above but starting from region r
1306 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1307
1308 HeapRegion* next_compaction_region(const HeapRegion* from) const;
1309
1310 // A CollectedHeap will contain some number of spaces. This finds the
1311 // space containing a given address, or else returns NULL.
1312 virtual Space* space_containing(const void* addr) const;
1313
1314 // Returns the HeapRegion that contains addr. addr must not be NULL.
1315 template <class T>
1316 inline HeapRegion* heap_region_containing_raw(const T addr) const;
1317
1318 // Returns the HeapRegion that contains addr. addr must not be NULL.
1319 // If addr is within a humongous continues region, it returns its humongous start region.
1320 template <class T>
1321 inline HeapRegion* heap_region_containing(const T addr) const;
1322
1323 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1324 // each address in the (reserved) heap is a member of exactly
1325 // one block. The defining characteristic of a block is that it is
1326 // possible to find its size, and thus to progress forward to the next
1327 // block. (Blocks may be of different sizes.) Thus, blocks may
1328 // represent Java objects, or they might be free blocks in a
1329 // free-list-based heap (or subheap), as long as the two kinds are
1330 // distinguishable and the size of each is determinable.
1331
1332 // Returns the address of the start of the "block" that contains the
1333 // address "addr". We say "blocks" instead of "object" since some heaps
1334 // may not pack objects densely; a chunk may either be an object or a
1335 // non-object.
1336 virtual HeapWord* block_start(const void* addr) const;
1337
1338 // Requires "addr" to be the start of a chunk, and returns its size.
1339 // "addr + size" is required to be the start of a new chunk, or the end
1340 // of the active area of the heap.
1341 virtual size_t block_size(const HeapWord* addr) const;
1342
1343 // Requires "addr" to be the start of a block, and returns "TRUE" iff
1344 // the block is an object.
1345 virtual bool block_is_obj(const HeapWord* addr) const;
1346
1347 // Does this heap support heap inspection? (+PrintClassHistogram)
1348 virtual bool supports_heap_inspection() const { return true; }
1349
1350 // Section on thread-local allocation buffers (TLABs)
1351 // See CollectedHeap for semantics.
1352
1353 bool supports_tlab_allocation() const;
1354 size_t tlab_capacity(Thread* ignored) const;
1355 size_t tlab_used(Thread* ignored) const;
1356 size_t max_tlab_size() const;
1357 size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1358
1359 // Can a compiler initialize a new object without store barriers?
1360 // This permission only extends from the creation of a new object
1361 // via a TLAB up to the first subsequent safepoint. If such permission
1362 // is granted for this heap type, the compiler promises to call
1363 // defer_store_barrier() below on any slow path allocation of
1364 // a new object for which such initializing store barriers will
1365 // have been elided. G1, like CMS, allows this, but should be
1366 // ready to provide a compensating write barrier as necessary
1367 // if that storage came out of a non-young region. The efficiency
1368 // of this implementation depends crucially on being able to
1369 // answer very efficiently in constant time whether a piece of
1370 // storage in the heap comes from a young region or not.
1371 // See ReduceInitialCardMarks.
1372 virtual bool can_elide_tlab_store_barriers() const {
1373 return true;
1374 }
1375
1376 virtual bool card_mark_must_follow_store() const {
1377 return true;
1378 }
1379
1380 inline bool is_in_young(const oop obj);
1381
1382 #ifdef ASSERT
1383 virtual bool is_in_partial_collection(const void* p);
1384 #endif
1385
1386 virtual bool is_scavengable(const void* addr);
1387
1388 // We don't need barriers for initializing stores to objects
1389 // in the young gen: for the SATB pre-barrier, there is no
1390 // pre-value that needs to be remembered; for the remembered-set
1391 // update logging post-barrier, we don't maintain remembered set
1392 // information for young gen objects.
1393 virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1394
1395 // Returns "true" iff the given word_size is "very large".
1396 static bool is_humongous(size_t word_size) {
1397 // Note this has to be strictly greater-than as the TLABs
1398 // are capped at the humongous threshold and we want to
1399 // ensure that we don't try to allocate a TLAB as
1400 // humongous and that we don't allocate a humongous
1401 // object in a TLAB.
1402 return word_size > _humongous_object_threshold_in_words;
1403 }
1404
1405 // Update mod union table with the set of dirty cards.
1406 void updateModUnion();
1407
1408 // Set the mod union bits corresponding to the given memRegion. Note
1409 // that this is always a safe operation, since it doesn't clear any
1410 // bits.
1411 void markModUnionRange(MemRegion mr);
1412
1413 // Records the fact that a marking phase is no longer in progress.
1414 void set_marking_complete() {
1415 _mark_in_progress = false;
1416 }
1417 void set_marking_started() {
1418 _mark_in_progress = true;
1419 }
1420 bool mark_in_progress() {
1421 return _mark_in_progress;
1422 }
1423
1424 // Print the maximum heap capacity.
1425 virtual size_t max_capacity() const;
1426
1427 virtual jlong millis_since_last_gc();
1428
1429
1430 // Convenience function to be used in situations where the heap type can be
1431 // asserted to be this type.
1432 static G1CollectedHeap* heap();
1433
1434 void set_region_short_lived_locked(HeapRegion* hr);
1435 // add appropriate methods for any other surv rate groups
1436
1437 YoungList* young_list() const { return _young_list; }
1438
1439 // debugging
1440 bool check_young_list_well_formed() {
1441 return _young_list->check_list_well_formed();
1442 }
1443
1444 bool check_young_list_empty(bool check_heap,
1445 bool check_sample = true);
1446
1447 // *** Stuff related to concurrent marking. It's not clear to me that so
1448 // many of these need to be public.
1449
1450 // The functions below are helper functions that a subclass of
1451 // "CollectedHeap" can use in the implementation of its virtual
1452 // functions.
1453 // This performs a concurrent marking of the live objects in a
1454 // bitmap off to the side.
1455 void doConcurrentMark();
1456
1457 bool isMarkedPrev(oop obj) const;
1458 bool isMarkedNext(oop obj) const;
1459
1460 // Determine if an object is dead, given the object and also
1461 // the region to which the object belongs. An object is dead
1462 // iff a) it was not allocated since the last mark and b) it
1463 // is not marked.
1464 bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1465 return
1466 !hr->obj_allocated_since_prev_marking(obj) &&
1467 !isMarkedPrev(obj);
1468 }
1469
1470 // This function returns true when an object has been
1471 // around since the previous marking and hasn't yet
1472 // been marked during this marking.
1473 bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1474 return
1475 !hr->obj_allocated_since_next_marking(obj) &&
1476 !isMarkedNext(obj);
1477 }
1478
1479 // Determine if an object is dead, given only the object itself.
1480 // This will find the region to which the object belongs and
1481 // then call the region version of the same function.
1482
1483 // Added if it is NULL it isn't dead.
1484
1485 inline bool is_obj_dead(const oop obj) const;
1486
1487 inline bool is_obj_ill(const oop obj) const;
1488
1489 bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1490 HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1491 bool is_marked(oop obj, VerifyOption vo);
1492 const char* top_at_mark_start_str(VerifyOption vo);
1493
1494 ConcurrentMark* concurrent_mark() const { return _cm; }
1495
1496 // Refinement
1497
1498 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1499
1500 // The dirty cards region list is used to record a subset of regions
1501 // whose cards need clearing. The list if populated during the
1502 // remembered set scanning and drained during the card table
1503 // cleanup. Although the methods are reentrant, population/draining
1504 // phases must not overlap. For synchronization purposes the last
1505 // element on the list points to itself.
1506 HeapRegion* _dirty_cards_region_list;
1507 void push_dirty_cards_region(HeapRegion* hr);
1508 HeapRegion* pop_dirty_cards_region();
1509
1510 // Optimized nmethod scanning support routines
1511
1512 // Register the given nmethod with the G1 heap.
1513 virtual void register_nmethod(nmethod* nm);
1514
1515 // Unregister the given nmethod from the G1 heap.
1516 virtual void unregister_nmethod(nmethod* nm);
1517
1518 // Free up superfluous code root memory.
1519 void purge_code_root_memory();
1520
1521 // Rebuild the strong code root lists for each region
1522 // after a full GC.
1523 void rebuild_strong_code_roots();
1524
1525 // Delete entries for dead interned string and clean up unreferenced symbols
1526 // in symbol table, possibly in parallel.
1527 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1528
1529 // Parallel phase of unloading/cleaning after G1 concurrent mark.
1530 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred);
1531
1532 // Redirty logged cards in the refinement queue.
1533 void redirty_logged_cards();
1534 // Verification
1535
1536 // The following is just to alert the verification code
1537 // that a full collection has occurred and that the
1538 // remembered sets are no longer up to date.
1539 bool _full_collection;
1540 void set_full_collection() { _full_collection = true;}
1541 void clear_full_collection() {_full_collection = false;}
1542 bool full_collection() {return _full_collection;}
1543
1544 // Perform any cleanup actions necessary before allowing a verification.
1545 virtual void prepare_for_verify();
1546
1547 // Perform verification.
1548
1549 // vo == UsePrevMarking -> use "prev" marking information,
1550 // vo == UseNextMarking -> use "next" marking information
1551 // vo == UseMarkWord -> use the mark word in the object header
1552 //
1553 // NOTE: Only the "prev" marking information is guaranteed to be
1554 // consistent most of the time, so most calls to this should use
1555 // vo == UsePrevMarking.
1556 // Currently, there is only one case where this is called with
1557 // vo == UseNextMarking, which is to verify the "next" marking
1558 // information at the end of remark.
1559 // Currently there is only one place where this is called with
1560 // vo == UseMarkWord, which is to verify the marking during a
1561 // full GC.
1562 void verify(bool silent, VerifyOption vo);
1563
1564 // Override; it uses the "prev" marking information
1565 virtual void verify(bool silent);
1566
1567 // The methods below are here for convenience and dispatch the
1568 // appropriate method depending on value of the given VerifyOption
1569 // parameter. The values for that parameter, and their meanings,
1570 // are the same as those above.
1571
1572 bool is_obj_dead_cond(const oop obj,
1573 const HeapRegion* hr,
1574 const VerifyOption vo) const;
1575
1576 bool is_obj_dead_cond(const oop obj,
1577 const VerifyOption vo) const;
1578
1579 // Printing
1580
1581 virtual void print_on(outputStream* st) const;
1582 virtual void print_extended_on(outputStream* st) const;
1583 virtual void print_on_error(outputStream* st) const;
1584
1585 virtual void print_gc_threads_on(outputStream* st) const;
1586 virtual void gc_threads_do(ThreadClosure* tc) const;
1587
1588 // Override
1589 void print_tracing_info() const;
1590
1591 // The following two methods are helpful for debugging RSet issues.
1592 void print_cset_rsets() PRODUCT_RETURN;
1593 void print_all_rsets() PRODUCT_RETURN;
1594
1595 public:
1596 size_t pending_card_num();
1597 size_t cards_scanned();
1598
1599 protected:
1600 size_t _max_heap_capacity;
1601 };
1602
1603 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP