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