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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13 * accompanied this code).
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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 survivor_length() { return _survivor_length; }
114
115 // Currently we do not keep track of the used byte sum for the
116 // young list and the survivors and it'd be quite a lot of work to
117 // do so. When we'll eventually replace the young list with
118 // instances of HeapRegionLinkedList we'll get that for free. So,
119 // we'll report the more accurate information then.
120 size_t eden_used_bytes() {
121 assert(length() >= survivor_length(), "invariant");
122 return (size_t) (length() - survivor_length()) * HeapRegion::GrainBytes;
123 }
124 size_t survivor_used_bytes() {
125 return (size_t) survivor_length() * HeapRegion::GrainBytes;
126 }
127
128 void rs_length_sampling_init();
129 bool rs_length_sampling_more();
130 void rs_length_sampling_next();
131
132 void reset_sampled_info() {
133 _last_sampled_rs_lengths = 0;
134 }
135 size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
136
137 // for development purposes
138 void reset_auxilary_lists();
139 void clear() { _head = NULL; _length = 0; }
140
141 void clear_survivors() {
142 _survivor_head = NULL;
143 _survivor_tail = NULL;
144 _survivor_length = 0;
145 }
146
147 HeapRegion* first_region() { return _head; }
148 HeapRegion* first_survivor_region() { return _survivor_head; }
149 HeapRegion* last_survivor_region() { return _survivor_tail; }
150
151 // debugging
152 bool check_list_well_formed();
153 bool check_list_empty(bool check_sample = true);
154 void print();
155 };
156
157 // The G1 STW is alive closure.
158 // An instance is embedded into the G1CH and used as the
159 // (optional) _is_alive_non_header closure in the STW
160 // reference processor. It is also extensively used during
161 // reference processing during STW evacuation pauses.
162 class G1STWIsAliveClosure: public BoolObjectClosure {
163 G1CollectedHeap* _g1;
164 public:
165 G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
166 bool do_object_b(oop p);
167 };
168
169 class RefineCardTableEntryClosure;
170
171 class G1RegionMappingChangedListener : public G1MappingChangedListener {
172 private:
173 void reset_from_card_cache(uint start_idx, size_t num_regions);
174 public:
175 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
176 };
177
178 class G1CollectedHeap : public SharedHeap {
179 friend class VM_CollectForMetadataAllocation;
180 friend class VM_G1CollectForAllocation;
181 friend class VM_G1CollectFull;
182 friend class VM_G1IncCollectionPause;
183 friend class VMStructs;
184 friend class MutatorAllocRegion;
185 friend class SurvivorGCAllocRegion;
186 friend class OldGCAllocRegion;
187 friend class G1Allocator;
188
189 // Closures used in implementation.
190 friend class G1ParScanThreadState;
191 friend class G1ParTask;
192 friend class G1ParGCAllocator;
193 friend class G1PrepareCompactClosure;
194
195 // Other related classes.
196 friend class HeapRegionClaimer;
197
198 // Testing classes.
199 friend class G1CheckCSetFastTableClosure;
200
201 private:
202 // The one and only G1CollectedHeap, so static functions can find it.
203 static G1CollectedHeap* _g1h;
204
205 static size_t _humongous_object_threshold_in_words;
206
207 // The secondary free list which contains regions that have been
208 // freed up during the cleanup process. This will be appended to
209 // the master free list when appropriate.
210 FreeRegionList _secondary_free_list;
211
212 // It keeps track of the old regions.
213 HeapRegionSet _old_set;
214
215 // It keeps track of the humongous regions.
216 HeapRegionSet _humongous_set;
217
218 void clear_humongous_is_live_table();
219 void eagerly_reclaim_humongous_regions();
220
221 // The number of regions we could create by expansion.
222 uint _expansion_regions;
223
224 // The block offset table for the G1 heap.
225 G1BlockOffsetSharedArray* _bot_shared;
226
227 // Tears down the region sets / lists so that they are empty and the
228 // regions on the heap do not belong to a region set / list. The
229 // only exception is the humongous set which we leave unaltered. If
230 // free_list_only is true, it will only tear down the master free
231 // list. It is called before a Full GC (free_list_only == false) or
232 // before heap shrinking (free_list_only == true).
233 void tear_down_region_sets(bool free_list_only);
234
235 // Rebuilds the region sets / lists so that they are repopulated to
236 // reflect the contents of the heap. The only exception is the
237 // humongous set which was not torn down in the first place. If
238 // free_list_only is true, it will only rebuild the master free
239 // list. It is called after a Full GC (free_list_only == false) or
240 // after heap shrinking (free_list_only == true).
241 void rebuild_region_sets(bool free_list_only);
242
243 // Callback for region mapping changed events.
244 G1RegionMappingChangedListener _listener;
245
246 // The sequence of all heap regions in the heap.
247 HeapRegionManager _hrm;
248
249 // Class that handles the different kinds of allocations.
250 G1Allocator* _allocator;
251
252 // Statistics for each allocation context
253 AllocationContextStats _allocation_context_stats;
254
255 // PLAB sizing policy for survivors.
256 PLABStats _survivor_plab_stats;
257
258 // PLAB sizing policy for tenured objects.
259 PLABStats _old_plab_stats;
260
261 // It specifies whether we should attempt to expand the heap after a
262 // region allocation failure. If heap expansion fails we set this to
263 // false so that we don't re-attempt the heap expansion (it's likely
264 // that subsequent expansion attempts will also fail if one fails).
265 // Currently, it is only consulted during GC and it's reset at the
266 // start of each GC.
267 bool _expand_heap_after_alloc_failure;
268
269 // It resets the mutator alloc region before new allocations can take place.
270 void init_mutator_alloc_region();
271
272 // It releases the mutator alloc region.
273 void release_mutator_alloc_region();
274
275 // It initializes the GC alloc regions at the start of a GC.
276 void init_gc_alloc_regions(EvacuationInfo& evacuation_info);
277
278 // It releases the GC alloc regions at the end of a GC.
279 void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info);
280
281 // It does any cleanup that needs to be done on the GC alloc regions
282 // before a Full GC.
283 void abandon_gc_alloc_regions();
284
285 // Helper for monitoring and management support.
286 G1MonitoringSupport* _g1mm;
287
288 // Records whether the region at the given index is kept live by roots or
289 // references from the young generation.
290 class HumongousIsLiveBiasedMappedArray : public G1BiasedMappedArray<bool> {
291 protected:
292 bool default_value() const { return false; }
293 public:
294 void clear() { G1BiasedMappedArray<bool>::clear(); }
295 void set_live(uint region) {
296 set_by_index(region, true);
297 }
298 bool is_live(uint region) {
299 return get_by_index(region);
300 }
301 };
302
303 HumongousIsLiveBiasedMappedArray _humongous_is_live;
304 // Stores whether during humongous object registration we found candidate regions.
305 // If not, we can skip a few steps.
306 bool _has_humongous_reclaim_candidates;
307
308 volatile unsigned _gc_time_stamp;
309
310 size_t* _surviving_young_words;
311
312 G1HRPrinter _hr_printer;
313
314 void setup_surviving_young_words();
315 void update_surviving_young_words(size_t* surv_young_words);
316 void cleanup_surviving_young_words();
317
318 // It decides whether an explicit GC should start a concurrent cycle
319 // instead of doing a STW GC. Currently, a concurrent cycle is
320 // explicitly started if:
321 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
322 // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
323 // (c) cause == _g1_humongous_allocation
324 bool should_do_concurrent_full_gc(GCCause::Cause cause);
325
326 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
327 // concurrent cycles) we have started.
328 volatile uint _old_marking_cycles_started;
329
330 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
331 // concurrent cycles) we have completed.
332 volatile uint _old_marking_cycles_completed;
333
334 bool _concurrent_cycle_started;
335 bool _heap_summary_sent;
336
337 // This is a non-product method that is helpful for testing. It is
338 // called at the end of a GC and artificially expands the heap by
339 // allocating a number of dead regions. This way we can induce very
340 // frequent marking cycles and stress the cleanup / concurrent
341 // cleanup code more (as all the regions that will be allocated by
342 // this method will be found dead by the marking cycle).
343 void allocate_dummy_regions() PRODUCT_RETURN;
344
345 // Clear RSets after a compaction. It also resets the GC time stamps.
346 void clear_rsets_post_compaction();
347
348 // If the HR printer is active, dump the state of the regions in the
349 // heap after a compaction.
350 void print_hrm_post_compaction();
351
352 double verify(bool guard, const char* msg);
353 void verify_before_gc();
354 void verify_after_gc();
355
356 void log_gc_header();
357 void log_gc_footer(double pause_time_sec);
358
359 // These are macros so that, if the assert fires, we get the correct
360 // line number, file, etc.
361
362 #define heap_locking_asserts_err_msg(_extra_message_) \
363 err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \
364 (_extra_message_), \
365 BOOL_TO_STR(Heap_lock->owned_by_self()), \
366 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \
367 BOOL_TO_STR(Thread::current()->is_VM_thread()))
368
369 #define assert_heap_locked() \
370 do { \
371 assert(Heap_lock->owned_by_self(), \
372 heap_locking_asserts_err_msg("should be holding the Heap_lock")); \
373 } while (0)
374
375 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \
376 do { \
377 assert(Heap_lock->owned_by_self() || \
378 (SafepointSynchronize::is_at_safepoint() && \
379 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
380 heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
381 "should be at a safepoint")); \
382 } while (0)
383
384 #define assert_heap_locked_and_not_at_safepoint() \
385 do { \
386 assert(Heap_lock->owned_by_self() && \
387 !SafepointSynchronize::is_at_safepoint(), \
388 heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
389 "should not be at a safepoint")); \
390 } while (0)
391
392 #define assert_heap_not_locked() \
393 do { \
394 assert(!Heap_lock->owned_by_self(), \
395 heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
396 } while (0)
397
398 #define assert_heap_not_locked_and_not_at_safepoint() \
399 do { \
400 assert(!Heap_lock->owned_by_self() && \
401 !SafepointSynchronize::is_at_safepoint(), \
402 heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
403 "should not be at a safepoint")); \
404 } while (0)
405
406 #define assert_at_safepoint(_should_be_vm_thread_) \
407 do { \
408 assert(SafepointSynchronize::is_at_safepoint() && \
409 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
410 heap_locking_asserts_err_msg("should be at a safepoint")); \
411 } while (0)
412
413 #define assert_not_at_safepoint() \
414 do { \
415 assert(!SafepointSynchronize::is_at_safepoint(), \
416 heap_locking_asserts_err_msg("should not be at a safepoint")); \
417 } while (0)
418
419 protected:
420
421 // The young region list.
422 YoungList* _young_list;
423
424 // The current policy object for the collector.
425 G1CollectorPolicy* _g1_policy;
426
427 // This is the second level of trying to allocate a new region. If
428 // new_region() didn't find a region on the free_list, this call will
429 // check whether there's anything available on the
430 // secondary_free_list and/or wait for more regions to appear on
431 // that list, if _free_regions_coming is set.
432 HeapRegion* new_region_try_secondary_free_list(bool is_old);
433
434 // Try to allocate a single non-humongous HeapRegion sufficient for
435 // an allocation of the given word_size. If do_expand is true,
436 // attempt to expand the heap if necessary to satisfy the allocation
437 // request. If the region is to be used as an old region or for a
438 // humongous object, set is_old to true. If not, to false.
439 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
440
441 // Initialize a contiguous set of free regions of length num_regions
442 // and starting at index first so that they appear as a single
443 // humongous region.
444 HeapWord* humongous_obj_allocate_initialize_regions(uint first,
445 uint num_regions,
446 size_t word_size,
447 AllocationContext_t context);
448
449 // Attempt to allocate a humongous object of the given size. Return
450 // NULL if unsuccessful.
451 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context);
452
453 // The following two methods, allocate_new_tlab() and
454 // mem_allocate(), are the two main entry points from the runtime
455 // into the G1's allocation routines. They have the following
456 // assumptions:
457 //
458 // * They should both be called outside safepoints.
459 //
460 // * They should both be called without holding the Heap_lock.
461 //
462 // * All allocation requests for new TLABs should go to
463 // allocate_new_tlab().
464 //
465 // * All non-TLAB allocation requests should go to mem_allocate().
466 //
467 // * If either call cannot satisfy the allocation request using the
468 // current allocating region, they will try to get a new one. If
469 // this fails, they will attempt to do an evacuation pause and
470 // retry the allocation.
471 //
472 // * If all allocation attempts fail, even after trying to schedule
473 // an evacuation pause, allocate_new_tlab() will return NULL,
474 // whereas mem_allocate() will attempt a heap expansion and/or
475 // schedule a Full GC.
476 //
477 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
478 // should never be called with word_size being humongous. All
479 // humongous allocation requests should go to mem_allocate() which
480 // will satisfy them with a special path.
481
482 virtual HeapWord* allocate_new_tlab(size_t word_size);
483
484 virtual HeapWord* mem_allocate(size_t word_size,
485 bool* gc_overhead_limit_was_exceeded);
486
487 // The following three methods take a gc_count_before_ret
488 // parameter which is used to return the GC count if the method
489 // returns NULL. Given that we are required to read the GC count
490 // while holding the Heap_lock, and these paths will take the
491 // Heap_lock at some point, it's easier to get them to read the GC
492 // count while holding the Heap_lock before they return NULL instead
493 // of the caller (namely: mem_allocate()) having to also take the
494 // Heap_lock just to read the GC count.
495
496 // First-level mutator allocation attempt: try to allocate out of
497 // the mutator alloc region without taking the Heap_lock. This
498 // should only be used for non-humongous allocations.
499 inline HeapWord* attempt_allocation(size_t word_size,
500 uint* gc_count_before_ret,
501 uint* gclocker_retry_count_ret);
502
503 // Second-level mutator allocation attempt: take the Heap_lock and
504 // retry the allocation attempt, potentially scheduling a GC
505 // pause. This should only be used for non-humongous allocations.
506 HeapWord* attempt_allocation_slow(size_t word_size,
507 AllocationContext_t context,
508 uint* gc_count_before_ret,
509 uint* gclocker_retry_count_ret);
510
511 // Takes the Heap_lock and attempts a humongous allocation. It can
512 // potentially schedule a GC pause.
513 HeapWord* attempt_allocation_humongous(size_t word_size,
514 uint* gc_count_before_ret,
515 uint* gclocker_retry_count_ret);
516
517 // Allocation attempt that should be called during safepoints (e.g.,
518 // at the end of a successful GC). expect_null_mutator_alloc_region
519 // specifies whether the mutator alloc region is expected to be NULL
520 // or not.
521 HeapWord* attempt_allocation_at_safepoint(size_t word_size,
522 AllocationContext_t context,
523 bool expect_null_mutator_alloc_region);
524
525 // It dirties the cards that cover the block so that so that the post
526 // write barrier never queues anything when updating objects on this
527 // block. It is assumed (and in fact we assert) that the block
528 // belongs to a young region.
529 inline void dirty_young_block(HeapWord* start, size_t word_size);
530
531 // Allocate blocks during garbage collection. Will ensure an
532 // allocation region, either by picking one or expanding the
533 // heap, and then allocate a block of the given size. The block
534 // may not be a humongous - it must fit into a single heap region.
535 inline HeapWord* par_allocate_during_gc(InCSetState dest,
536 size_t word_size,
537 AllocationContext_t context);
538 // Ensure that no further allocations can happen in "r", bearing in mind
539 // that parallel threads might be attempting allocations.
540 void par_allocate_remaining_space(HeapRegion* r);
541
542 // Allocation attempt during GC for a survivor object / PLAB.
543 inline HeapWord* survivor_attempt_allocation(size_t word_size,
544 AllocationContext_t context);
545
546 // Allocation attempt during GC for an old object / PLAB.
547 inline HeapWord* old_attempt_allocation(size_t word_size,
548 AllocationContext_t context);
549
550 // These methods are the "callbacks" from the G1AllocRegion class.
551
552 // For mutator alloc regions.
553 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
554 void retire_mutator_alloc_region(HeapRegion* alloc_region,
555 size_t allocated_bytes);
556
557 // For GC alloc regions.
558 HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
559 InCSetState dest);
560 void retire_gc_alloc_region(HeapRegion* alloc_region,
561 size_t allocated_bytes, InCSetState dest);
562
563 // - if explicit_gc is true, the GC is for a System.gc() or a heap
564 // inspection request and should collect the entire heap
565 // - if clear_all_soft_refs is true, all soft references should be
566 // cleared during the GC
567 // - if explicit_gc is false, word_size describes the allocation that
568 // the GC should attempt (at least) to satisfy
569 // - it returns false if it is unable to do the collection due to the
570 // GC locker being active, true otherwise
571 bool do_collection(bool explicit_gc,
572 bool clear_all_soft_refs,
573 size_t word_size);
574
575 // Callback from VM_G1CollectFull operation.
576 // Perform a full collection.
577 virtual void do_full_collection(bool clear_all_soft_refs);
578
579 // Resize the heap if necessary after a full collection. If this is
580 // after a collect-for allocation, "word_size" is the allocation size,
581 // and will be considered part of the used portion of the heap.
582 void resize_if_necessary_after_full_collection(size_t word_size);
583
584 // Callback from VM_G1CollectForAllocation operation.
585 // This function does everything necessary/possible to satisfy a
586 // failed allocation request (including collection, expansion, etc.)
587 HeapWord* satisfy_failed_allocation(size_t word_size,
588 AllocationContext_t context,
589 bool* succeeded);
590
591 // Attempting to expand the heap sufficiently
592 // to support an allocation of the given "word_size". If
593 // successful, perform the allocation and return the address of the
594 // allocated block, or else "NULL".
595 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context);
596
597 // Process any reference objects discovered during
598 // an incremental evacuation pause.
599 void process_discovered_references(uint no_of_gc_workers);
600
601 // Enqueue any remaining discovered references
602 // after processing.
603 void enqueue_discovered_references(uint no_of_gc_workers);
604
605 public:
606
607 G1Allocator* allocator() {
608 return _allocator;
609 }
610
611 G1MonitoringSupport* g1mm() {
612 assert(_g1mm != NULL, "should have been initialized");
613 return _g1mm;
614 }
615
616 // Expand the garbage-first heap by at least the given size (in bytes!).
617 // Returns true if the heap was expanded by the requested amount;
618 // false otherwise.
619 // (Rounds up to a HeapRegion boundary.)
620 bool expand(size_t expand_bytes);
621
622 // Returns the PLAB statistics for a given destination.
623 inline PLABStats* alloc_buffer_stats(InCSetState dest);
624
625 // Determines PLAB size for a given destination.
626 inline size_t desired_plab_sz(InCSetState dest);
627
628 inline AllocationContextStats& allocation_context_stats();
629
630 // Do anything common to GC's.
631 virtual void gc_prologue(bool full);
632 virtual void gc_epilogue(bool full);
633
634 inline void set_humongous_is_live(oop obj);
635
636 bool humongous_is_live(uint region) {
637 return _humongous_is_live.is_live(region);
638 }
639
640 // Returns whether the given region (which must be a humongous (start) region)
641 // is to be considered conservatively live regardless of any other conditions.
642 bool humongous_region_is_always_live(uint index);
643 // Returns whether the given region (which must be a humongous (start) region)
644 // is considered a candidate for eager reclamation.
645 bool humongous_region_is_candidate(uint index);
646 // Register the given region to be part of the collection set.
647 inline void register_humongous_region_with_in_cset_fast_test(uint index);
648 // Register regions with humongous objects (actually on the start region) in
649 // the in_cset_fast_test table.
650 void register_humongous_regions_with_in_cset_fast_test();
651 // We register a region with the fast "in collection set" test. We
652 // simply set to true the array slot corresponding to this region.
653 void register_young_region_with_in_cset_fast_test(HeapRegion* r) {
654 _in_cset_fast_test.set_in_young(r->hrm_index());
655 }
656 void register_old_region_with_in_cset_fast_test(HeapRegion* r) {
657 _in_cset_fast_test.set_in_old(r->hrm_index());
658 }
659
660 // This is a fast test on whether a reference points into the
661 // collection set or not. Assume that the reference
662 // points into the heap.
663 inline bool in_cset_fast_test(oop obj);
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 // Applies "scan_non_heap_roots" to roots outside the heap,
785 // "scan_rs" to roots inside the heap (having done "set_region" to
786 // indicate the region in which the root resides),
787 // and does "scan_metadata" If "scan_rs" is
788 // NULL, then this step is skipped. The "worker_i"
789 // param is for use with parallel roots processing, and should be
790 // the "i" of the calling parallel worker thread's work(i) function.
791 // In the sequential case this param will be ignored.
792 void g1_process_roots(OopClosure* scan_non_heap_roots,
793 OopClosure* scan_non_heap_weak_roots,
794 G1ParPushHeapRSClosure* scan_rs,
795 CLDClosure* scan_strong_clds,
796 CLDClosure* scan_weak_clds,
797 CodeBlobClosure* scan_strong_code,
798 uint worker_i);
799
800 // The concurrent marker (and the thread it runs in.)
801 ConcurrentMark* _cm;
802 ConcurrentMarkThread* _cmThread;
803 bool _mark_in_progress;
804
805 // The concurrent refiner.
806 ConcurrentG1Refine* _cg1r;
807
808 // The parallel task queues
809 RefToScanQueueSet *_task_queues;
810
811 // True iff a evacuation has failed in the current collection.
812 bool _evacuation_failed;
813
814 EvacuationFailedInfo* _evacuation_failed_info_array;
815
816 // Failed evacuations cause some logical from-space objects to have
817 // forwarding pointers to themselves. Reset them.
818 void remove_self_forwarding_pointers();
819
820 // Together, these store an object with a preserved mark, and its mark value.
821 Stack<oop, mtGC> _objs_with_preserved_marks;
822 Stack<markOop, mtGC> _preserved_marks_of_objs;
823
824 // Preserve the mark of "obj", if necessary, in preparation for its mark
825 // word being overwritten with a self-forwarding-pointer.
826 void preserve_mark_if_necessary(oop obj, markOop m);
827
828 // The stack of evac-failure objects left to be scanned.
829 GrowableArray<oop>* _evac_failure_scan_stack;
830 // The closure to apply to evac-failure objects.
831
832 OopsInHeapRegionClosure* _evac_failure_closure;
833 // Set the field above.
834 void
835 set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
836 _evac_failure_closure = evac_failure_closure;
837 }
838
839 // Push "obj" on the scan stack.
840 void push_on_evac_failure_scan_stack(oop obj);
841 // Process scan stack entries until the stack is empty.
842 void drain_evac_failure_scan_stack();
843 // True iff an invocation of "drain_scan_stack" is in progress; to
844 // prevent unnecessary recursion.
845 bool _drain_in_progress;
846
847 // Do any necessary initialization for evacuation-failure handling.
848 // "cl" is the closure that will be used to process evac-failure
849 // objects.
850 void init_for_evac_failure(OopsInHeapRegionClosure* cl);
851 // Do any necessary cleanup for evacuation-failure handling data
852 // structures.
853 void finalize_for_evac_failure();
854
855 // An attempt to evacuate "obj" has failed; take necessary steps.
856 oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj);
857 void handle_evacuation_failure_common(oop obj, markOop m);
858
859 #ifndef PRODUCT
860 // Support for forcing evacuation failures. Analogous to
861 // PromotionFailureALot for the other collectors.
862
863 // Records whether G1EvacuationFailureALot should be in effect
864 // for the current GC
865 bool _evacuation_failure_alot_for_current_gc;
866
867 // Used to record the GC number for interval checking when
868 // determining whether G1EvaucationFailureALot is in effect
869 // for the current GC.
870 size_t _evacuation_failure_alot_gc_number;
871
872 // Count of the number of evacuations between failures.
873 volatile size_t _evacuation_failure_alot_count;
874
875 // Set whether G1EvacuationFailureALot should be in effect
876 // for the current GC (based upon the type of GC and which
877 // command line flags are set);
878 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
879 bool during_initial_mark,
880 bool during_marking);
881
882 inline void set_evacuation_failure_alot_for_current_gc();
883
884 // Return true if it's time to cause an evacuation failure.
885 inline bool evacuation_should_fail();
886
887 // Reset the G1EvacuationFailureALot counters. Should be called at
888 // the end of an evacuation pause in which an evacuation failure occurred.
889 inline void reset_evacuation_should_fail();
890 #endif // !PRODUCT
891
892 // ("Weak") Reference processing support.
893 //
894 // G1 has 2 instances of the reference processor class. One
895 // (_ref_processor_cm) handles reference object discovery
896 // and subsequent processing during concurrent marking cycles.
897 //
898 // The other (_ref_processor_stw) handles reference object
899 // discovery and processing during full GCs and incremental
900 // evacuation pauses.
901 //
902 // During an incremental pause, reference discovery will be
903 // temporarily disabled for _ref_processor_cm and will be
904 // enabled for _ref_processor_stw. At the end of the evacuation
905 // pause references discovered by _ref_processor_stw will be
906 // processed and discovery will be disabled. The previous
907 // setting for reference object discovery for _ref_processor_cm
908 // will be re-instated.
909 //
910 // At the start of marking:
911 // * Discovery by the CM ref processor is verified to be inactive
912 // and it's discovered lists are empty.
913 // * Discovery by the CM ref processor is then enabled.
914 //
915 // At the end of marking:
916 // * Any references on the CM ref processor's discovered
917 // lists are processed (possibly MT).
918 //
919 // At the start of full GC we:
920 // * Disable discovery by the CM ref processor and
921 // empty CM ref processor's discovered lists
922 // (without processing any entries).
923 // * Verify that the STW ref processor is inactive and it's
924 // discovered lists are empty.
925 // * Temporarily set STW ref processor discovery as single threaded.
926 // * Temporarily clear the STW ref processor's _is_alive_non_header
927 // field.
928 // * Finally enable discovery by the STW ref processor.
929 //
930 // The STW ref processor is used to record any discovered
931 // references during the full GC.
932 //
933 // At the end of a full GC we:
934 // * Enqueue any reference objects discovered by the STW ref processor
935 // that have non-live referents. This has the side-effect of
936 // making the STW ref processor inactive by disabling discovery.
937 // * Verify that the CM ref processor is still inactive
938 // and no references have been placed on it's discovered
939 // lists (also checked as a precondition during initial marking).
940
941 // The (stw) reference processor...
942 ReferenceProcessor* _ref_processor_stw;
943
944 STWGCTimer* _gc_timer_stw;
945 ConcurrentGCTimer* _gc_timer_cm;
946
947 G1OldTracer* _gc_tracer_cm;
948 G1NewTracer* _gc_tracer_stw;
949
950 // During reference object discovery, the _is_alive_non_header
951 // closure (if non-null) is applied to the referent object to
952 // determine whether the referent is live. If so then the
953 // reference object does not need to be 'discovered' and can
954 // be treated as a regular oop. This has the benefit of reducing
955 // the number of 'discovered' reference objects that need to
956 // be processed.
957 //
958 // Instance of the is_alive closure for embedding into the
959 // STW reference processor as the _is_alive_non_header field.
960 // Supplying a value for the _is_alive_non_header field is
961 // optional but doing so prevents unnecessary additions to
962 // the discovered lists during reference discovery.
963 G1STWIsAliveClosure _is_alive_closure_stw;
964
965 // The (concurrent marking) reference processor...
966 ReferenceProcessor* _ref_processor_cm;
967
968 // Instance of the concurrent mark is_alive closure for embedding
969 // into the Concurrent Marking reference processor as the
970 // _is_alive_non_header field. Supplying a value for the
971 // _is_alive_non_header field is optional but doing so prevents
972 // unnecessary additions to the discovered lists during reference
973 // discovery.
974 G1CMIsAliveClosure _is_alive_closure_cm;
975
976 // Cache used by G1CollectedHeap::start_cset_region_for_worker().
977 HeapRegion** _worker_cset_start_region;
978
979 // Time stamp to validate the regions recorded in the cache
980 // used by G1CollectedHeap::start_cset_region_for_worker().
981 // The heap region entry for a given worker is valid iff
982 // the associated time stamp value matches the current value
983 // of G1CollectedHeap::_gc_time_stamp.
984 uint* _worker_cset_start_region_time_stamp;
985
986 enum G1H_process_roots_tasks {
987 G1H_PS_filter_satb_buffers,
988 G1H_PS_refProcessor_oops_do,
989 // Leave this one last.
990 G1H_PS_NumElements
991 };
992
993 SubTasksDone* _process_strong_tasks;
994
995 volatile bool _free_regions_coming;
996
997 public:
998
999 SubTasksDone* process_strong_tasks() { return _process_strong_tasks; }
1000
1001 void set_refine_cte_cl_concurrency(bool concurrent);
1002
1003 RefToScanQueue *task_queue(int i) const;
1004
1005 // A set of cards where updates happened during the GC
1006 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
1007
1008 // A DirtyCardQueueSet that is used to hold cards that contain
1009 // references into the current collection set. This is used to
1010 // update the remembered sets of the regions in the collection
1011 // set in the event of an evacuation failure.
1012 DirtyCardQueueSet& into_cset_dirty_card_queue_set()
1013 { return _into_cset_dirty_card_queue_set; }
1014
1015 // Create a G1CollectedHeap with the specified policy.
1016 // Must call the initialize method afterwards.
1017 // May not return if something goes wrong.
1018 G1CollectedHeap(G1CollectorPolicy* policy);
1019
1020 // Initialize the G1CollectedHeap to have the initial and
1021 // maximum sizes and remembered and barrier sets
1022 // specified by the policy object.
1023 jint initialize();
1024
1025 virtual void stop();
1026
1027 // Return the (conservative) maximum heap alignment for any G1 heap
1028 static size_t conservative_max_heap_alignment();
1029
1030 // Initialize weak reference processing.
1031 virtual void ref_processing_init();
1032
1033 void set_par_threads(uint t) {
1034 SharedHeap::set_par_threads(t);
1035 // Done in SharedHeap but oddly there are
1036 // two _process_strong_tasks's in a G1CollectedHeap
1037 // so do it here too.
1038 _process_strong_tasks->set_n_threads(t);
1039 }
1040
1041 // Set _n_par_threads according to a policy TBD.
1042 void set_par_threads();
1043
1044 void set_n_termination(int t) {
1045 _process_strong_tasks->set_n_threads(t);
1046 }
1047
1048 virtual CollectedHeap::Name kind() const {
1049 return CollectedHeap::G1CollectedHeap;
1050 }
1051
1052 // The current policy object for the collector.
1053 G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1054
1055 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); }
1056
1057 // Adaptive size policy. No such thing for g1.
1058 virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1059
1060 // The rem set and barrier set.
1061 G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1062
1063 unsigned get_gc_time_stamp() {
1064 return _gc_time_stamp;
1065 }
1066
1067 inline void reset_gc_time_stamp();
1068
1069 void check_gc_time_stamps() PRODUCT_RETURN;
1070
1071 inline void increment_gc_time_stamp();
1072
1073 // Reset the given region's GC timestamp. If it's starts humongous,
1074 // also reset the GC timestamp of its corresponding
1075 // continues humongous regions too.
1076 void reset_gc_time_stamps(HeapRegion* hr);
1077
1078 void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1079 DirtyCardQueue* into_cset_dcq,
1080 bool concurrent, uint worker_i);
1081
1082 // The shared block offset table array.
1083 G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1084
1085 // Reference Processing accessors
1086
1087 // The STW reference processor....
1088 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1089
1090 // The Concurrent Marking reference processor...
1091 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1092
1093 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1094 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1095
1096 virtual size_t capacity() const;
1097 virtual size_t used() const;
1098 // This should be called when we're not holding the heap lock. The
1099 // result might be a bit inaccurate.
1100 size_t used_unlocked() const;
1101 size_t recalculate_used() const;
1102
1103 // These virtual functions do the actual allocation.
1104 // Some heaps may offer a contiguous region for shared non-blocking
1105 // allocation, via inlined code (by exporting the address of the top and
1106 // end fields defining the extent of the contiguous allocation region.)
1107 // But G1CollectedHeap doesn't yet support this.
1108
1109 virtual bool is_maximal_no_gc() const {
1110 return _hrm.available() == 0;
1111 }
1112
1113 // The current number of regions in the heap.
1114 uint num_regions() const { return _hrm.length(); }
1115
1116 // The max number of regions in the heap.
1117 uint max_regions() const { return _hrm.max_length(); }
1118
1119 // The number of regions that are completely free.
1120 uint num_free_regions() const { return _hrm.num_free_regions(); }
1121
1122 // The number of regions that are not completely free.
1123 uint num_used_regions() const { return num_regions() - num_free_regions(); }
1124
1125 void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1126 void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1127 void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1128 void verify_dirty_young_regions() PRODUCT_RETURN;
1129
1130 #ifndef PRODUCT
1131 // Make sure that the given bitmap has no marked objects in the
1132 // range [from,limit). If it does, print an error message and return
1133 // false. Otherwise, just return true. bitmap_name should be "prev"
1134 // or "next".
1135 bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
1136 HeapWord* from, HeapWord* limit);
1137
1138 // Verify that the prev / next bitmap range [tams,end) for the given
1139 // region has no marks. Return true if all is well, false if errors
1140 // are detected.
1141 bool verify_bitmaps(const char* caller, HeapRegion* hr);
1142 #endif // PRODUCT
1143
1144 // If G1VerifyBitmaps is set, verify that the marking bitmaps for
1145 // the given region do not have any spurious marks. If errors are
1146 // detected, print appropriate error messages and crash.
1147 void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN;
1148
1149 // If G1VerifyBitmaps is set, verify that the marking bitmaps do not
1150 // have any spurious marks. If errors are detected, print
1151 // appropriate error messages and crash.
1152 void check_bitmaps(const char* caller) PRODUCT_RETURN;
1153
1154 // Do sanity check on the contents of the in-cset fast test table.
1155 bool check_cset_fast_test() PRODUCT_RETURN_( return true; );
1156
1157 // verify_region_sets() performs verification over the region
1158 // lists. It will be compiled in the product code to be used when
1159 // necessary (i.e., during heap verification).
1160 void verify_region_sets();
1161
1162 // verify_region_sets_optional() is planted in the code for
1163 // list verification in non-product builds (and it can be enabled in
1164 // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1).
1165 #if HEAP_REGION_SET_FORCE_VERIFY
1166 void verify_region_sets_optional() {
1167 verify_region_sets();
1168 }
1169 #else // HEAP_REGION_SET_FORCE_VERIFY
1170 void verify_region_sets_optional() { }
1171 #endif // HEAP_REGION_SET_FORCE_VERIFY
1172
1173 #ifdef ASSERT
1174 bool is_on_master_free_list(HeapRegion* hr) {
1175 return _hrm.is_free(hr);
1176 }
1177 #endif // ASSERT
1178
1179 // Wrapper for the region list operations that can be called from
1180 // methods outside this class.
1181
1182 void secondary_free_list_add(FreeRegionList* list) {
1183 _secondary_free_list.add_ordered(list);
1184 }
1185
1186 void append_secondary_free_list() {
1187 _hrm.insert_list_into_free_list(&_secondary_free_list);
1188 }
1189
1190 void append_secondary_free_list_if_not_empty_with_lock() {
1191 // If the secondary free list looks empty there's no reason to
1192 // take the lock and then try to append it.
1193 if (!_secondary_free_list.is_empty()) {
1194 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1195 append_secondary_free_list();
1196 }
1197 }
1198
1199 inline void old_set_remove(HeapRegion* hr);
1200
1201 size_t non_young_capacity_bytes() {
1202 return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1203 }
1204
1205 void set_free_regions_coming();
1206 void reset_free_regions_coming();
1207 bool free_regions_coming() { return _free_regions_coming; }
1208 void wait_while_free_regions_coming();
1209
1210 // Determine whether the given region is one that we are using as an
1211 // old GC alloc region.
1212 bool is_old_gc_alloc_region(HeapRegion* hr) {
1213 return _allocator->is_retained_old_region(hr);
1214 }
1215
1216 // Perform a collection of the heap; intended for use in implementing
1217 // "System.gc". This probably implies as full a collection as the
1218 // "CollectedHeap" supports.
1219 virtual void collect(GCCause::Cause cause);
1220
1221 // The same as above but assume that the caller holds the Heap_lock.
1222 void collect_locked(GCCause::Cause cause);
1223
1224 virtual bool copy_allocation_context_stats(const jint* contexts,
1225 jlong* totals,
1226 jbyte* accuracy,
1227 jint len);
1228
1229 // True iff an evacuation has failed in the most-recent collection.
1230 bool evacuation_failed() { return _evacuation_failed; }
1231
1232 void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed);
1233 void prepend_to_freelist(FreeRegionList* list);
1234 void decrement_summary_bytes(size_t bytes);
1235
1236 // Returns "TRUE" iff "p" points into the committed areas of the heap.
1237 virtual bool is_in(const void* p) const;
1238 #ifdef ASSERT
1239 // Returns whether p is in one of the available areas of the heap. Slow but
1240 // extensive version.
1241 bool is_in_exact(const void* p) const;
1242 #endif
1243
1244 // Return "TRUE" iff the given object address is within the collection
1245 // set. Slow implementation.
1246 inline bool obj_in_cs(oop obj);
1247
1248 inline bool is_in_cset(oop obj);
1249
1250 inline bool is_in_cset_or_humongous(const oop obj);
1251
1252 private:
1253 // This array is used for a quick test on whether a reference points into
1254 // the collection set or not. Each of the array's elements denotes whether the
1255 // corresponding region is in the collection set or not.
1256 G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test;
1257
1258 public:
1259
1260 inline InCSetState in_cset_state(const oop obj);
1261
1262 // Return "TRUE" iff the given object address is in the reserved
1263 // region of g1.
1264 bool is_in_g1_reserved(const void* p) const {
1265 return _hrm.reserved().contains(p);
1266 }
1267
1268 // Returns a MemRegion that corresponds to the space that has been
1269 // reserved for the heap
1270 MemRegion g1_reserved() const {
1271 return _hrm.reserved();
1272 }
1273
1274 virtual bool is_in_closed_subset(const void* p) const;
1275
1276 G1SATBCardTableLoggingModRefBS* g1_barrier_set() {
1277 return (G1SATBCardTableLoggingModRefBS*) barrier_set();
1278 }
1279
1280 // This resets the card table to all zeros. It is used after
1281 // a collection pause which used the card table to claim cards.
1282 void cleanUpCardTable();
1283
1284 // Iteration functions.
1285
1286 // Iterate over all the ref-containing fields of all objects, calling
1287 // "cl.do_oop" on each.
1288 virtual void oop_iterate(ExtendedOopClosure* cl);
1289
1290 // Iterate over all objects, calling "cl.do_object" on each.
1291 virtual void object_iterate(ObjectClosure* cl);
1292
1293 virtual void safe_object_iterate(ObjectClosure* cl) {
1294 object_iterate(cl);
1295 }
1296
1297 // Iterate over all spaces in use in the heap, in ascending address order.
1298 virtual void space_iterate(SpaceClosure* cl);
1299
1300 // Iterate over heap regions, in address order, terminating the
1301 // iteration early if the "doHeapRegion" method returns "true".
1302 void heap_region_iterate(HeapRegionClosure* blk) const;
1303
1304 // Return the region with the given index. It assumes the index is valid.
1305 inline HeapRegion* region_at(uint index) const;
1306
1307 // Calculate the region index of the given address. Given address must be
1308 // within the heap.
1309 inline uint addr_to_region(HeapWord* addr) const;
1310
1311 inline HeapWord* bottom_addr_for_region(uint index) const;
1312
1313 // Iterate over the heap regions in parallel. Assumes that this will be called
1314 // in parallel by ParallelGCThreads worker threads with distinct worker ids
1315 // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion"
1316 // to each of the regions, by attempting to claim the region using the
1317 // HeapRegionClaimer and, if successful, applying the closure to the claimed
1318 // region. The concurrent argument should be set to true if iteration is
1319 // performed concurrently, during which no assumptions are made for consistent
1320 // attributes of the heap regions (as they might be modified while iterating).
1321 void heap_region_par_iterate(HeapRegionClosure* cl,
1322 uint worker_id,
1323 HeapRegionClaimer* hrclaimer,
1324 bool concurrent = false) const;
1325
1326 // Clear the cached cset start regions and (more importantly)
1327 // the time stamps. Called when we reset the GC time stamp.
1328 void clear_cset_start_regions();
1329
1330 // Given the id of a worker, obtain or calculate a suitable
1331 // starting region for iterating over the current collection set.
1332 HeapRegion* start_cset_region_for_worker(uint worker_i);
1333
1334 // Iterate over the regions (if any) in the current collection set.
1335 void collection_set_iterate(HeapRegionClosure* blk);
1336
1337 // As above but starting from region r
1338 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1339
1340 HeapRegion* next_compaction_region(const HeapRegion* from) const;
1341
1342 // A CollectedHeap will contain some number of spaces. This finds the
1343 // space containing a given address, or else returns NULL.
1344 virtual Space* space_containing(const void* addr) const;
1345
1346 // Returns the HeapRegion that contains addr. addr must not be NULL.
1347 template <class T>
1348 inline HeapRegion* heap_region_containing_raw(const T addr) const;
1349
1350 // Returns the HeapRegion that contains addr. addr must not be NULL.
1351 // If addr is within a humongous continues region, it returns its humongous start region.
1352 template <class T>
1353 inline HeapRegion* heap_region_containing(const T addr) const;
1354
1355 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1356 // each address in the (reserved) heap is a member of exactly
1357 // one block. The defining characteristic of a block is that it is
1358 // possible to find its size, and thus to progress forward to the next
1359 // block. (Blocks may be of different sizes.) Thus, blocks may
1360 // represent Java objects, or they might be free blocks in a
1361 // free-list-based heap (or subheap), as long as the two kinds are
1362 // distinguishable and the size of each is determinable.
1363
1364 // Returns the address of the start of the "block" that contains the
1365 // address "addr". We say "blocks" instead of "object" since some heaps
1366 // may not pack objects densely; a chunk may either be an object or a
1367 // non-object.
1368 virtual HeapWord* block_start(const void* addr) const;
1369
1370 // Requires "addr" to be the start of a chunk, and returns its size.
1371 // "addr + size" is required to be the start of a new chunk, or the end
1372 // of the active area of the heap.
1373 virtual size_t block_size(const HeapWord* addr) const;
1374
1375 // Requires "addr" to be the start of a block, and returns "TRUE" iff
1376 // the block is an object.
1377 virtual bool block_is_obj(const HeapWord* addr) const;
1378
1379 // Does this heap support heap inspection? (+PrintClassHistogram)
1380 virtual bool supports_heap_inspection() const { return true; }
1381
1382 // Section on thread-local allocation buffers (TLABs)
1383 // See CollectedHeap for semantics.
1384
1385 bool supports_tlab_allocation() const;
1386 size_t tlab_capacity(Thread* ignored) const;
1387 size_t tlab_used(Thread* ignored) const;
1388 size_t max_tlab_size() const;
1389 size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1390
1391 // Can a compiler initialize a new object without store barriers?
1392 // This permission only extends from the creation of a new object
1393 // via a TLAB up to the first subsequent safepoint. If such permission
1394 // is granted for this heap type, the compiler promises to call
1395 // defer_store_barrier() below on any slow path allocation of
1396 // a new object for which such initializing store barriers will
1397 // have been elided. G1, like CMS, allows this, but should be
1398 // ready to provide a compensating write barrier as necessary
1399 // if that storage came out of a non-young region. The efficiency
1400 // of this implementation depends crucially on being able to
1401 // answer very efficiently in constant time whether a piece of
1402 // storage in the heap comes from a young region or not.
1403 // See ReduceInitialCardMarks.
1404 virtual bool can_elide_tlab_store_barriers() const {
1405 return true;
1406 }
1407
1408 virtual bool card_mark_must_follow_store() const {
1409 return true;
1410 }
1411
1412 inline bool is_in_young(const oop obj);
1413
1414 #ifdef ASSERT
1415 virtual bool is_in_partial_collection(const void* p);
1416 #endif
1417
1418 virtual bool is_scavengable(const void* addr);
1419
1420 // We don't need barriers for initializing stores to objects
1421 // in the young gen: for the SATB pre-barrier, there is no
1422 // pre-value that needs to be remembered; for the remembered-set
1423 // update logging post-barrier, we don't maintain remembered set
1424 // information for young gen objects.
1425 virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1426
1427 // Returns "true" iff the given word_size is "very large".
1428 static bool is_humongous(size_t word_size) {
1429 // Note this has to be strictly greater-than as the TLABs
1430 // are capped at the humongous threshold and we want to
1431 // ensure that we don't try to allocate a TLAB as
1432 // humongous and that we don't allocate a humongous
1433 // object in a TLAB.
1434 return word_size > _humongous_object_threshold_in_words;
1435 }
1436
1437 // Update mod union table with the set of dirty cards.
1438 void updateModUnion();
1439
1440 // Set the mod union bits corresponding to the given memRegion. Note
1441 // that this is always a safe operation, since it doesn't clear any
1442 // bits.
1443 void markModUnionRange(MemRegion mr);
1444
1445 // Records the fact that a marking phase is no longer in progress.
1446 void set_marking_complete() {
1447 _mark_in_progress = false;
1448 }
1449 void set_marking_started() {
1450 _mark_in_progress = true;
1451 }
1452 bool mark_in_progress() {
1453 return _mark_in_progress;
1454 }
1455
1456 // Print the maximum heap capacity.
1457 virtual size_t max_capacity() const;
1458
1459 virtual jlong millis_since_last_gc();
1460
1461
1462 // Convenience function to be used in situations where the heap type can be
1463 // asserted to be this type.
1464 static G1CollectedHeap* heap();
1465
1466 void set_region_short_lived_locked(HeapRegion* hr);
1467 // add appropriate methods for any other surv rate groups
1468
1469 YoungList* young_list() const { return _young_list; }
1470
1471 // debugging
1472 bool check_young_list_well_formed() {
1473 return _young_list->check_list_well_formed();
1474 }
1475
1476 bool check_young_list_empty(bool check_heap,
1477 bool check_sample = true);
1478
1479 // *** Stuff related to concurrent marking. It's not clear to me that so
1480 // many of these need to be public.
1481
1482 // The functions below are helper functions that a subclass of
1483 // "CollectedHeap" can use in the implementation of its virtual
1484 // functions.
1485 // This performs a concurrent marking of the live objects in a
1486 // bitmap off to the side.
1487 void doConcurrentMark();
1488
1489 bool isMarkedPrev(oop obj) const;
1490 bool isMarkedNext(oop obj) const;
1491
1492 // Determine if an object is dead, given the object and also
1493 // the region to which the object belongs. An object is dead
1494 // iff a) it was not allocated since the last mark and b) it
1495 // is not marked.
1496 bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1497 return
1498 !hr->obj_allocated_since_prev_marking(obj) &&
1499 !isMarkedPrev(obj);
1500 }
1501
1502 // This function returns true when an object has been
1503 // around since the previous marking and hasn't yet
1504 // been marked during this marking.
1505 bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1506 return
1507 !hr->obj_allocated_since_next_marking(obj) &&
1508 !isMarkedNext(obj);
1509 }
1510
1511 // Determine if an object is dead, given only the object itself.
1512 // This will find the region to which the object belongs and
1513 // then call the region version of the same function.
1514
1515 // Added if it is NULL it isn't dead.
1516
1517 inline bool is_obj_dead(const oop obj) const;
1518
1519 inline bool is_obj_ill(const oop obj) const;
1520
1521 bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1522 HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1523 bool is_marked(oop obj, VerifyOption vo);
1524 const char* top_at_mark_start_str(VerifyOption vo);
1525
1526 ConcurrentMark* concurrent_mark() const { return _cm; }
1527
1528 // Refinement
1529
1530 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1531
1532 // The dirty cards region list is used to record a subset of regions
1533 // whose cards need clearing. The list if populated during the
1534 // remembered set scanning and drained during the card table
1535 // cleanup. Although the methods are reentrant, population/draining
1536 // phases must not overlap. For synchronization purposes the last
1537 // element on the list points to itself.
1538 HeapRegion* _dirty_cards_region_list;
1539 void push_dirty_cards_region(HeapRegion* hr);
1540 HeapRegion* pop_dirty_cards_region();
1541
1542 // Optimized nmethod scanning support routines
1543
1544 // Register the given nmethod with the G1 heap.
1545 virtual void register_nmethod(nmethod* nm);
1546
1547 // Unregister the given nmethod from the G1 heap.
1548 virtual void unregister_nmethod(nmethod* nm);
1549
1550 // Free up superfluous code root memory.
1551 void purge_code_root_memory();
1552
1553 // Rebuild the strong code root lists for each region
1554 // after a full GC.
1555 void rebuild_strong_code_roots();
1556
1557 // Delete entries for dead interned string and clean up unreferenced symbols
1558 // in symbol table, possibly in parallel.
1559 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1560
1561 // Parallel phase of unloading/cleaning after G1 concurrent mark.
1562 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred);
1563
1564 // Redirty logged cards in the refinement queue.
1565 void redirty_logged_cards();
1566 // Verification
1567
1568 // The following is just to alert the verification code
1569 // that a full collection has occurred and that the
1570 // remembered sets are no longer up to date.
1571 bool _full_collection;
1572 void set_full_collection() { _full_collection = true;}
1573 void clear_full_collection() {_full_collection = false;}
1574 bool full_collection() {return _full_collection;}
1575
1576 // Perform any cleanup actions necessary before allowing a verification.
1577 virtual void prepare_for_verify();
1578
1579 // Perform verification.
1580
1581 // vo == UsePrevMarking -> use "prev" marking information,
1582 // vo == UseNextMarking -> use "next" marking information
1583 // vo == UseMarkWord -> use the mark word in the object header
1584 //
1585 // NOTE: Only the "prev" marking information is guaranteed to be
1586 // consistent most of the time, so most calls to this should use
1587 // vo == UsePrevMarking.
1588 // Currently, there is only one case where this is called with
1589 // vo == UseNextMarking, which is to verify the "next" marking
1590 // information at the end of remark.
1591 // Currently there is only one place where this is called with
1592 // vo == UseMarkWord, which is to verify the marking during a
1593 // full GC.
1594 void verify(bool silent, VerifyOption vo);
1595
1596 // Override; it uses the "prev" marking information
1597 virtual void verify(bool silent);
1598
1599 // The methods below are here for convenience and dispatch the
1600 // appropriate method depending on value of the given VerifyOption
1601 // parameter. The values for that parameter, and their meanings,
1602 // are the same as those above.
1603
1604 bool is_obj_dead_cond(const oop obj,
1605 const HeapRegion* hr,
1606 const VerifyOption vo) const;
1607
1608 bool is_obj_dead_cond(const oop obj,
1609 const VerifyOption vo) const;
1610
1611 // Printing
1612
1613 virtual void print_on(outputStream* st) const;
1614 virtual void print_extended_on(outputStream* st) const;
1615 virtual void print_on_error(outputStream* st) const;
1616
1617 virtual void print_gc_threads_on(outputStream* st) const;
1618 virtual void gc_threads_do(ThreadClosure* tc) const;
1619
1620 // Override
1621 void print_tracing_info() const;
1622
1623 // The following two methods are helpful for debugging RSet issues.
1624 void print_cset_rsets() PRODUCT_RETURN;
1625 void print_all_rsets() PRODUCT_RETURN;
1626
1627 public:
1628 size_t pending_card_num();
1629 size_t cards_scanned();
1630
1631 protected:
1632 size_t _max_heap_capacity;
1633 };
1634
1635 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP