1 /*
2 * Copyright (c) 2001, 2014, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
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/concurrentMark.hpp"
29 #include "gc_implementation/g1/evacuationInfo.hpp"
30 #include "gc_implementation/g1/g1AllocRegion.hpp"
31 #include "gc_implementation/g1/g1BiasedArray.hpp"
32 #include "gc_implementation/g1/g1HRPrinter.hpp"
33 #include "gc_implementation/g1/g1MonitoringSupport.hpp"
34 #include "gc_implementation/g1/g1SATBCardTableModRefBS.hpp"
35 #include "gc_implementation/g1/g1YCTypes.hpp"
36 #include "gc_implementation/g1/heapRegionSeq.hpp"
37 #include "gc_implementation/g1/heapRegionSet.hpp"
38 #include "gc_implementation/shared/hSpaceCounters.hpp"
39 #include "gc_implementation/shared/parGCAllocBuffer.hpp"
40 #include "memory/barrierSet.hpp"
41 #include "memory/memRegion.hpp"
42 #include "memory/sharedHeap.hpp"
43 #include "utilities/stack.hpp"
44
45 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
46 // It uses the "Garbage First" heap organization and algorithm, which
47 // may combine concurrent marking with parallel, incremental compaction of
48 // heap subsets that will yield large amounts of garbage.
49
50 // Forward declarations
51 class HeapRegion;
52 class HRRSCleanupTask;
53 class GenerationSpec;
54 class OopsInHeapRegionClosure;
55 class G1KlassScanClosure;
56 class G1ScanHeapEvacClosure;
57 class ObjectClosure;
58 class SpaceClosure;
59 class CompactibleSpaceClosure;
60 class Space;
61 class G1CollectorPolicy;
62 class GenRemSet;
63 class G1RemSet;
64 class HeapRegionRemSetIterator;
65 class ConcurrentMark;
66 class ConcurrentMarkThread;
67 class ConcurrentG1Refine;
68 class ConcurrentGCTimer;
69 class GenerationCounters;
70 class STWGCTimer;
71 class G1NewTracer;
72 class G1OldTracer;
73 class EvacuationFailedInfo;
74 class nmethod;
75 class Ticks;
76
77 typedef OverflowTaskQueue<StarTask, mtGC> RefToScanQueue;
78 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
79
80 typedef int RegionIdx_t; // needs to hold [ 0..max_regions() )
81 typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion )
82
83 enum GCAllocPurpose {
84 GCAllocForTenured,
85 GCAllocForSurvived,
86 GCAllocPurposeCount
87 };
88
89 class YoungList : public CHeapObj<mtGC> {
90 private:
91 G1CollectedHeap* _g1h;
92
93 HeapRegion* _head;
94
95 HeapRegion* _survivor_head;
96 HeapRegion* _survivor_tail;
97
98 HeapRegion* _curr;
99
100 uint _length;
101 uint _survivor_length;
102
103 size_t _last_sampled_rs_lengths;
104 size_t _sampled_rs_lengths;
105
106 void empty_list(HeapRegion* list);
107
108 public:
109 YoungList(G1CollectedHeap* g1h);
110
111 void push_region(HeapRegion* hr);
112 void add_survivor_region(HeapRegion* hr);
113
114 void empty_list();
115 bool is_empty() { return _length == 0; }
116 uint length() { return _length; }
117 uint survivor_length() { return _survivor_length; }
118
119 // Currently we do not keep track of the used byte sum for the
120 // young list and the survivors and it'd be quite a lot of work to
121 // do so. When we'll eventually replace the young list with
122 // instances of HeapRegionLinkedList we'll get that for free. So,
123 // we'll report the more accurate information then.
124 size_t eden_used_bytes() {
125 assert(length() >= survivor_length(), "invariant");
126 return (size_t) (length() - survivor_length()) * HeapRegion::GrainBytes;
127 }
128 size_t survivor_used_bytes() {
129 return (size_t) survivor_length() * HeapRegion::GrainBytes;
130 }
131
132 void rs_length_sampling_init();
133 bool rs_length_sampling_more();
134 void rs_length_sampling_next();
135
136 void reset_sampled_info() {
137 _last_sampled_rs_lengths = 0;
138 }
139 size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
140
141 // for development purposes
142 void reset_auxilary_lists();
143 void clear() { _head = NULL; _length = 0; }
144
145 void clear_survivors() {
146 _survivor_head = NULL;
147 _survivor_tail = NULL;
148 _survivor_length = 0;
149 }
150
151 HeapRegion* first_region() { return _head; }
152 HeapRegion* first_survivor_region() { return _survivor_head; }
153 HeapRegion* last_survivor_region() { return _survivor_tail; }
154
155 // debugging
156 bool check_list_well_formed();
157 bool check_list_empty(bool check_sample = true);
158 void print();
159 };
160
161 class MutatorAllocRegion : public G1AllocRegion {
162 protected:
163 virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
164 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
165 public:
166 MutatorAllocRegion()
167 : G1AllocRegion("Mutator Alloc Region", false /* bot_updates */) { }
168 };
169
170 class SurvivorGCAllocRegion : public G1AllocRegion {
171 protected:
172 virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
173 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
174 public:
175 SurvivorGCAllocRegion()
176 : G1AllocRegion("Survivor GC Alloc Region", false /* bot_updates */) { }
177 };
178
179 class OldGCAllocRegion : public G1AllocRegion {
180 protected:
181 virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
182 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
183 public:
184 OldGCAllocRegion()
185 : G1AllocRegion("Old GC Alloc Region", true /* bot_updates */) { }
186 };
187
188 // The G1 STW is alive closure.
189 // An instance is embedded into the G1CH and used as the
190 // (optional) _is_alive_non_header closure in the STW
191 // reference processor. It is also extensively used during
192 // reference processing during STW evacuation pauses.
193 class G1STWIsAliveClosure: public BoolObjectClosure {
194 G1CollectedHeap* _g1;
195 public:
196 G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
197 bool do_object_b(oop p);
198 };
199
200 class RefineCardTableEntryClosure;
201
202 class G1CollectedHeap : public SharedHeap {
203 friend class VM_CollectForMetadataAllocation;
204 friend class VM_G1CollectForAllocation;
205 friend class VM_G1CollectFull;
206 friend class VM_G1IncCollectionPause;
207 friend class VMStructs;
208 friend class MutatorAllocRegion;
209 friend class SurvivorGCAllocRegion;
210 friend class OldGCAllocRegion;
211
212 // Closures used in implementation.
213 template <G1Barrier barrier, G1Mark do_mark_object>
214 friend class G1ParCopyClosure;
215 friend class G1IsAliveClosure;
216 friend class G1EvacuateFollowersClosure;
217 friend class G1ParScanThreadState;
218 friend class G1ParScanClosureSuper;
219 friend class G1ParEvacuateFollowersClosure;
220 friend class G1ParTask;
221 friend class G1FreeGarbageRegionClosure;
222 friend class RefineCardTableEntryClosure;
223 friend class G1PrepareCompactClosure;
224 friend class RegionSorter;
225 friend class RegionResetter;
226 friend class CountRCClosure;
227 friend class EvacPopObjClosure;
228 friend class G1ParCleanupCTTask;
229
230 friend class G1FreeHumongousRegionClosure;
231 // Other related classes.
232 friend class G1MarkSweep;
233
234 private:
235 // The one and only G1CollectedHeap, so static functions can find it.
236 static G1CollectedHeap* _g1h;
237
238 static size_t _humongous_object_threshold_in_words;
239
240 // The secondary free list which contains regions that have been
241 // freed up during the cleanup process. This will be appended to
242 // the master free list when appropriate.
243 FreeRegionList _secondary_free_list;
244
245 // It keeps track of the old regions.
246 HeapRegionSet _old_set;
247
248 // It keeps track of the humongous regions.
249 HeapRegionSet _humongous_set;
250
251 void clear_humongous_is_live_table();
252 void eagerly_reclaim_humongous_regions();
253
254 // The number of regions we could create by expansion.
255 uint _expansion_regions;
256
257 // The block offset table for the G1 heap.
258 G1BlockOffsetSharedArray* _bot_shared;
259
260 // Tears down the region sets / lists so that they are empty and the
261 // regions on the heap do not belong to a region set / list. The
262 // only exception is the humongous set which we leave unaltered. If
263 // free_list_only is true, it will only tear down the master free
264 // list. It is called before a Full GC (free_list_only == false) or
265 // before heap shrinking (free_list_only == true).
266 void tear_down_region_sets(bool free_list_only);
267
268 // Rebuilds the region sets / lists so that they are repopulated to
269 // reflect the contents of the heap. The only exception is the
270 // humongous set which was not torn down in the first place. If
271 // free_list_only is true, it will only rebuild the master free
272 // list. It is called after a Full GC (free_list_only == false) or
273 // after heap shrinking (free_list_only == true).
274 void rebuild_region_sets(bool free_list_only);
275
276 // The sequence of all heap regions in the heap.
277 HeapRegionSeq _hrs;
278
279 // Alloc region used to satisfy mutator allocation requests.
280 MutatorAllocRegion _mutator_alloc_region;
281
282 // Alloc region used to satisfy allocation requests by the GC for
283 // survivor objects.
284 SurvivorGCAllocRegion _survivor_gc_alloc_region;
285
286 // PLAB sizing policy for survivors.
287 PLABStats _survivor_plab_stats;
288
289 // Alloc region used to satisfy allocation requests by the GC for
290 // old objects.
291 OldGCAllocRegion _old_gc_alloc_region;
292
293 // PLAB sizing policy for tenured objects.
294 PLABStats _old_plab_stats;
295
296 PLABStats* stats_for_purpose(GCAllocPurpose purpose) {
297 PLABStats* stats = NULL;
298
299 switch (purpose) {
300 case GCAllocForSurvived:
301 stats = &_survivor_plab_stats;
302 break;
303 case GCAllocForTenured:
304 stats = &_old_plab_stats;
305 break;
306 default:
307 assert(false, "unrecognized GCAllocPurpose");
308 }
309
310 return stats;
311 }
312
313 // The last old region we allocated to during the last GC.
314 // Typically, it is not full so we should re-use it during the next GC.
315 HeapRegion* _retained_old_gc_alloc_region;
316
317 // It specifies whether we should attempt to expand the heap after a
318 // region allocation failure. If heap expansion fails we set this to
319 // false so that we don't re-attempt the heap expansion (it's likely
320 // that subsequent expansion attempts will also fail if one fails).
321 // Currently, it is only consulted during GC and it's reset at the
322 // start of each GC.
323 bool _expand_heap_after_alloc_failure;
324
325 // It resets the mutator alloc region before new allocations can take place.
326 void init_mutator_alloc_region();
327
328 // It releases the mutator alloc region.
329 void release_mutator_alloc_region();
330
331 // It initializes the GC alloc regions at the start of a GC.
332 void init_gc_alloc_regions(EvacuationInfo& evacuation_info);
333
334 // Setup the retained old gc alloc region as the currrent old gc alloc region.
335 void use_retained_old_gc_alloc_region(EvacuationInfo& evacuation_info);
336
337 // It releases the GC alloc regions at the end of a GC.
338 void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info);
339
340 // It does any cleanup that needs to be done on the GC alloc regions
341 // before a Full GC.
342 void abandon_gc_alloc_regions();
343
344 // Helper for monitoring and management support.
345 G1MonitoringSupport* _g1mm;
346
347 // Determines PLAB size for a particular allocation purpose.
348 size_t desired_plab_sz(GCAllocPurpose purpose);
349
350 // Outside of GC pauses, the number of bytes used in all regions other
351 // than the current allocation region.
352 size_t _summary_bytes_used;
353
354 // Records whether the region at the given index is kept live by roots or
355 // references from the young generation.
356 class HumongousIsLiveBiasedMappedArray : public G1BiasedMappedArray<bool> {
357 protected:
358 bool default_value() const { return false; }
359 public:
360 void clear() { G1BiasedMappedArray<bool>::clear(); }
361 void set_live(uint region) {
362 set_by_index(region, true);
363 }
364 bool is_live(uint region) {
365 return get_by_index(region);
366 }
367 };
368
369 HumongousIsLiveBiasedMappedArray _humongous_is_live;
370 // Stores whether during humongous object registration we found candidate regions.
371 // If not, we can skip a few steps.
372 bool _has_humongous_reclaim_candidates;
373
374 volatile unsigned _gc_time_stamp;
375
376 size_t* _surviving_young_words;
377
378 G1HRPrinter _hr_printer;
379
380 void setup_surviving_young_words();
381 void update_surviving_young_words(size_t* surv_young_words);
382 void cleanup_surviving_young_words();
383
384 // It decides whether an explicit GC should start a concurrent cycle
385 // instead of doing a STW GC. Currently, a concurrent cycle is
386 // explicitly started if:
387 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
388 // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
389 // (c) cause == _g1_humongous_allocation
390 bool should_do_concurrent_full_gc(GCCause::Cause cause);
391
392 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
393 // concurrent cycles) we have started.
394 volatile unsigned int _old_marking_cycles_started;
395
396 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
397 // concurrent cycles) we have completed.
398 volatile unsigned int _old_marking_cycles_completed;
399
400 bool _concurrent_cycle_started;
401
402 // This is a non-product method that is helpful for testing. It is
403 // called at the end of a GC and artificially expands the heap by
404 // allocating a number of dead regions. This way we can induce very
405 // frequent marking cycles and stress the cleanup / concurrent
406 // cleanup code more (as all the regions that will be allocated by
407 // this method will be found dead by the marking cycle).
408 void allocate_dummy_regions() PRODUCT_RETURN;
409
410 // Clear RSets after a compaction. It also resets the GC time stamps.
411 void clear_rsets_post_compaction();
412
413 // If the HR printer is active, dump the state of the regions in the
414 // heap after a compaction.
415 void print_hrs_post_compaction();
416
417 double verify(bool guard, const char* msg);
418 void verify_before_gc();
419 void verify_after_gc();
420
421 void log_gc_header();
422 void log_gc_footer(double pause_time_sec);
423
424 // These are macros so that, if the assert fires, we get the correct
425 // line number, file, etc.
426
427 #define heap_locking_asserts_err_msg(_extra_message_) \
428 err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \
429 (_extra_message_), \
430 BOOL_TO_STR(Heap_lock->owned_by_self()), \
431 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \
432 BOOL_TO_STR(Thread::current()->is_VM_thread()))
433
434 #define assert_heap_locked() \
435 do { \
436 assert(Heap_lock->owned_by_self(), \
437 heap_locking_asserts_err_msg("should be holding the Heap_lock")); \
438 } while (0)
439
440 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \
441 do { \
442 assert(Heap_lock->owned_by_self() || \
443 (SafepointSynchronize::is_at_safepoint() && \
444 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
445 heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
446 "should be at a safepoint")); \
447 } while (0)
448
449 #define assert_heap_locked_and_not_at_safepoint() \
450 do { \
451 assert(Heap_lock->owned_by_self() && \
452 !SafepointSynchronize::is_at_safepoint(), \
453 heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
454 "should not be at a safepoint")); \
455 } while (0)
456
457 #define assert_heap_not_locked() \
458 do { \
459 assert(!Heap_lock->owned_by_self(), \
460 heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
461 } while (0)
462
463 #define assert_heap_not_locked_and_not_at_safepoint() \
464 do { \
465 assert(!Heap_lock->owned_by_self() && \
466 !SafepointSynchronize::is_at_safepoint(), \
467 heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
468 "should not be at a safepoint")); \
469 } while (0)
470
471 #define assert_at_safepoint(_should_be_vm_thread_) \
472 do { \
473 assert(SafepointSynchronize::is_at_safepoint() && \
474 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
475 heap_locking_asserts_err_msg("should be at a safepoint")); \
476 } while (0)
477
478 #define assert_not_at_safepoint() \
479 do { \
480 assert(!SafepointSynchronize::is_at_safepoint(), \
481 heap_locking_asserts_err_msg("should not be at a safepoint")); \
482 } while (0)
483
484 protected:
485
486 // The young region list.
487 YoungList* _young_list;
488
489 // The current policy object for the collector.
490 G1CollectorPolicy* _g1_policy;
491
492 // This is the second level of trying to allocate a new region. If
493 // new_region() didn't find a region on the free_list, this call will
494 // check whether there's anything available on the
495 // secondary_free_list and/or wait for more regions to appear on
496 // that list, if _free_regions_coming is set.
497 HeapRegion* new_region_try_secondary_free_list(bool is_old);
498
499 // Try to allocate a single non-humongous HeapRegion sufficient for
500 // an allocation of the given word_size. If do_expand is true,
501 // attempt to expand the heap if necessary to satisfy the allocation
502 // request. If the region is to be used as an old region or for a
503 // humongous object, set is_old to true. If not, to false.
504 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
505
506 // Initialize a contiguous set of free regions of length num_regions
507 // and starting at index first so that they appear as a single
508 // humongous region.
509 HeapWord* humongous_obj_allocate_initialize_regions(uint first,
510 uint num_regions,
511 size_t word_size);
512
513 // Attempt to allocate a humongous object of the given size. Return
514 // NULL if unsuccessful.
515 HeapWord* humongous_obj_allocate(size_t word_size);
516
517 // The following two methods, allocate_new_tlab() and
518 // mem_allocate(), are the two main entry points from the runtime
519 // into the G1's allocation routines. They have the following
520 // assumptions:
521 //
522 // * They should both be called outside safepoints.
523 //
524 // * They should both be called without holding the Heap_lock.
525 //
526 // * All allocation requests for new TLABs should go to
527 // allocate_new_tlab().
528 //
529 // * All non-TLAB allocation requests should go to mem_allocate().
530 //
531 // * If either call cannot satisfy the allocation request using the
532 // current allocating region, they will try to get a new one. If
533 // this fails, they will attempt to do an evacuation pause and
534 // retry the allocation.
535 //
536 // * If all allocation attempts fail, even after trying to schedule
537 // an evacuation pause, allocate_new_tlab() will return NULL,
538 // whereas mem_allocate() will attempt a heap expansion and/or
539 // schedule a Full GC.
540 //
541 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
542 // should never be called with word_size being humongous. All
543 // humongous allocation requests should go to mem_allocate() which
544 // will satisfy them with a special path.
545
546 virtual HeapWord* allocate_new_tlab(size_t word_size);
547
548 virtual HeapWord* mem_allocate(size_t word_size,
549 bool* gc_overhead_limit_was_exceeded);
550
551 // The following three methods take a gc_count_before_ret
552 // parameter which is used to return the GC count if the method
553 // returns NULL. Given that we are required to read the GC count
554 // while holding the Heap_lock, and these paths will take the
555 // Heap_lock at some point, it's easier to get them to read the GC
556 // count while holding the Heap_lock before they return NULL instead
557 // of the caller (namely: mem_allocate()) having to also take the
558 // Heap_lock just to read the GC count.
559
560 // First-level mutator allocation attempt: try to allocate out of
561 // the mutator alloc region without taking the Heap_lock. This
562 // should only be used for non-humongous allocations.
563 inline HeapWord* attempt_allocation(size_t word_size,
564 unsigned int* gc_count_before_ret,
565 int* gclocker_retry_count_ret);
566
567 // Second-level mutator allocation attempt: take the Heap_lock and
568 // retry the allocation attempt, potentially scheduling a GC
569 // pause. This should only be used for non-humongous allocations.
570 HeapWord* attempt_allocation_slow(size_t word_size,
571 unsigned int* gc_count_before_ret,
572 int* gclocker_retry_count_ret);
573
574 // Takes the Heap_lock and attempts a humongous allocation. It can
575 // potentially schedule a GC pause.
576 HeapWord* attempt_allocation_humongous(size_t word_size,
577 unsigned int* gc_count_before_ret,
578 int* gclocker_retry_count_ret);
579
580 // Allocation attempt that should be called during safepoints (e.g.,
581 // at the end of a successful GC). expect_null_mutator_alloc_region
582 // specifies whether the mutator alloc region is expected to be NULL
583 // or not.
584 HeapWord* attempt_allocation_at_safepoint(size_t word_size,
585 bool expect_null_mutator_alloc_region);
586
587 // It dirties the cards that cover the block so that so that the post
588 // write barrier never queues anything when updating objects on this
589 // block. It is assumed (and in fact we assert) that the block
590 // belongs to a young region.
591 inline void dirty_young_block(HeapWord* start, size_t word_size);
592
593 // Allocate blocks during garbage collection. Will ensure an
594 // allocation region, either by picking one or expanding the
595 // heap, and then allocate a block of the given size. The block
596 // may not be a humongous - it must fit into a single heap region.
597 HeapWord* par_allocate_during_gc(GCAllocPurpose purpose, size_t word_size);
598
599 HeapWord* allocate_during_gc_slow(GCAllocPurpose purpose,
600 HeapRegion* alloc_region,
601 bool par,
602 size_t word_size);
603
604 // Ensure that no further allocations can happen in "r", bearing in mind
605 // that parallel threads might be attempting allocations.
606 void par_allocate_remaining_space(HeapRegion* r);
607
608 // Allocation attempt during GC for a survivor object / PLAB.
609 inline HeapWord* survivor_attempt_allocation(size_t word_size);
610
611 // Allocation attempt during GC for an old object / PLAB.
612 inline HeapWord* old_attempt_allocation(size_t word_size);
613
614 // These methods are the "callbacks" from the G1AllocRegion class.
615
616 // For mutator alloc regions.
617 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
618 void retire_mutator_alloc_region(HeapRegion* alloc_region,
619 size_t allocated_bytes);
620
621 // For GC alloc regions.
622 HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
623 GCAllocPurpose ap);
624 void retire_gc_alloc_region(HeapRegion* alloc_region,
625 size_t allocated_bytes, GCAllocPurpose ap);
626
627 // - if explicit_gc is true, the GC is for a System.gc() or a heap
628 // inspection request and should collect the entire heap
629 // - if clear_all_soft_refs is true, all soft references should be
630 // cleared during the GC
631 // - if explicit_gc is false, word_size describes the allocation that
632 // the GC should attempt (at least) to satisfy
633 // - it returns false if it is unable to do the collection due to the
634 // GC locker being active, true otherwise
635 bool do_collection(bool explicit_gc,
636 bool clear_all_soft_refs,
637 size_t word_size);
638
639 // Callback from VM_G1CollectFull operation.
640 // Perform a full collection.
641 virtual void do_full_collection(bool clear_all_soft_refs);
642
643 // Resize the heap if necessary after a full collection. If this is
644 // after a collect-for allocation, "word_size" is the allocation size,
645 // and will be considered part of the used portion of the heap.
646 void resize_if_necessary_after_full_collection(size_t word_size);
647
648 // Callback from VM_G1CollectForAllocation operation.
649 // This function does everything necessary/possible to satisfy a
650 // failed allocation request (including collection, expansion, etc.)
651 HeapWord* satisfy_failed_allocation(size_t word_size, bool* succeeded);
652
653 // Attempting to expand the heap sufficiently
654 // to support an allocation of the given "word_size". If
655 // successful, perform the allocation and return the address of the
656 // allocated block, or else "NULL".
657 HeapWord* expand_and_allocate(size_t word_size);
658
659 // Process any reference objects discovered during
660 // an incremental evacuation pause.
661 void process_discovered_references(uint no_of_gc_workers);
662
663 // Enqueue any remaining discovered references
664 // after processing.
665 void enqueue_discovered_references(uint no_of_gc_workers);
666
667 public:
668
669 G1MonitoringSupport* g1mm() {
670 assert(_g1mm != NULL, "should have been initialized");
671 return _g1mm;
672 }
673
674 // Expand the garbage-first heap by at least the given size (in bytes!).
675 // Returns true if the heap was expanded by the requested amount;
676 // false otherwise.
677 // (Rounds up to a HeapRegion boundary.)
678 bool expand(size_t expand_bytes);
679
680 // Do anything common to GC's.
681 virtual void gc_prologue(bool full);
682 virtual void gc_epilogue(bool full);
683
684 inline void set_humongous_is_live(oop obj);
685
686 bool humongous_is_live(uint region) {
687 return _humongous_is_live.is_live(region);
688 }
689
690 // Returns whether the given region (which must be a humongous (start) region)
691 // is to be considered conservatively live regardless of any other conditions.
692 bool humongous_region_is_always_live(uint index);
693 // Register the given region to be part of the collection set.
694 inline void register_humongous_region_with_in_cset_fast_test(uint index);
695 // Register regions with humongous objects (actually on the start region) in
696 // the in_cset_fast_test table.
697 void register_humongous_regions_with_in_cset_fast_test();
698 // We register a region with the fast "in collection set" test. We
699 // simply set to true the array slot corresponding to this region.
700 void register_region_with_in_cset_fast_test(HeapRegion* r) {
701 _in_cset_fast_test.set_in_cset(r->hrs_index());
702 }
703
704 // This is a fast test on whether a reference points into the
705 // collection set or not. Assume that the reference
706 // points into the heap.
707 inline bool in_cset_fast_test(oop obj);
708
709 void clear_cset_fast_test() {
710 _in_cset_fast_test.clear();
711 }
712
713 // This is called at the start of either a concurrent cycle or a Full
714 // GC to update the number of old marking cycles started.
715 void increment_old_marking_cycles_started();
716
717 // This is called at the end of either a concurrent cycle or a Full
718 // GC to update the number of old marking cycles completed. Those two
719 // can happen in a nested fashion, i.e., we start a concurrent
720 // cycle, a Full GC happens half-way through it which ends first,
721 // and then the cycle notices that a Full GC happened and ends
722 // too. The concurrent parameter is a boolean to help us do a bit
723 // tighter consistency checking in the method. If concurrent is
724 // false, the caller is the inner caller in the nesting (i.e., the
725 // Full GC). If concurrent is true, the caller is the outer caller
726 // in this nesting (i.e., the concurrent cycle). Further nesting is
727 // not currently supported. The end of this call also notifies
728 // the FullGCCount_lock in case a Java thread is waiting for a full
729 // GC to happen (e.g., it called System.gc() with
730 // +ExplicitGCInvokesConcurrent).
731 void increment_old_marking_cycles_completed(bool concurrent);
732
733 unsigned int old_marking_cycles_completed() {
734 return _old_marking_cycles_completed;
735 }
736
737 void register_concurrent_cycle_start(const Ticks& start_time);
738 void register_concurrent_cycle_end();
739 void trace_heap_after_concurrent_cycle();
740
741 G1YCType yc_type();
742
743 G1HRPrinter* hr_printer() { return &_hr_printer; }
744
745 // Frees a non-humongous region by initializing its contents and
746 // adding it to the free list that's passed as a parameter (this is
747 // usually a local list which will be appended to the master free
748 // list later). The used bytes of freed regions are accumulated in
749 // pre_used. If par is true, the region's RSet will not be freed
750 // up. The assumption is that this will be done later.
751 // The locked parameter indicates if the caller has already taken
752 // care of proper synchronization. This may allow some optimizations.
753 void free_region(HeapRegion* hr,
754 FreeRegionList* free_list,
755 bool par,
756 bool locked = false);
757
758 // Frees a humongous region by collapsing it into individual regions
759 // and calling free_region() for each of them. The freed regions
760 // will be added to the free list that's passed as a parameter (this
761 // is usually a local list which will be appended to the master free
762 // list later). The used bytes of freed regions are accumulated in
763 // pre_used. If par is true, the region's RSet will not be freed
764 // up. The assumption is that this will be done later.
765 void free_humongous_region(HeapRegion* hr,
766 FreeRegionList* free_list,
767 bool par);
768 protected:
769
770 // Shrink the garbage-first heap by at most the given size (in bytes!).
771 // (Rounds down to a HeapRegion boundary.)
772 virtual void shrink(size_t expand_bytes);
773 void shrink_helper(size_t expand_bytes);
774
775 #if TASKQUEUE_STATS
776 static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
777 void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
778 void reset_taskqueue_stats();
779 #endif // TASKQUEUE_STATS
780
781 // Schedule the VM operation that will do an evacuation pause to
782 // satisfy an allocation request of word_size. *succeeded will
783 // return whether the VM operation was successful (it did do an
784 // evacuation pause) or not (another thread beat us to it or the GC
785 // locker was active). Given that we should not be holding the
786 // Heap_lock when we enter this method, we will pass the
787 // gc_count_before (i.e., total_collections()) as a parameter since
788 // it has to be read while holding the Heap_lock. Currently, both
789 // methods that call do_collection_pause() release the Heap_lock
790 // before the call, so it's easy to read gc_count_before just before.
791 HeapWord* do_collection_pause(size_t word_size,
792 unsigned int gc_count_before,
793 bool* succeeded,
794 GCCause::Cause gc_cause);
795
796 // The guts of the incremental collection pause, executed by the vm
797 // thread. It returns false if it is unable to do the collection due
798 // to the GC locker being active, true otherwise
799 bool do_collection_pause_at_safepoint(double target_pause_time_ms);
800
801 // Actually do the work of evacuating the collection set.
802 void evacuate_collection_set(EvacuationInfo& evacuation_info);
803
804 // The g1 remembered set of the heap.
805 G1RemSet* _g1_rem_set;
806
807 // A set of cards that cover the objects for which the Rsets should be updated
808 // concurrently after the collection.
809 DirtyCardQueueSet _dirty_card_queue_set;
810
811 // The closure used to refine a single card.
812 RefineCardTableEntryClosure* _refine_cte_cl;
813
814 // A function to check the consistency of dirty card logs.
815 void check_ct_logs_at_safepoint();
816
817 // A DirtyCardQueueSet that is used to hold cards that contain
818 // references into the current collection set. This is used to
819 // update the remembered sets of the regions in the collection
820 // set in the event of an evacuation failure.
821 DirtyCardQueueSet _into_cset_dirty_card_queue_set;
822
823 // After a collection pause, make the regions in the CS into free
824 // regions.
825 void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info);
826
827 // Abandon the current collection set without recording policy
828 // statistics or updating free lists.
829 void abandon_collection_set(HeapRegion* cs_head);
830
831 // Applies "scan_non_heap_roots" to roots outside the heap,
832 // "scan_rs" to roots inside the heap (having done "set_region" to
833 // indicate the region in which the root resides),
834 // and does "scan_metadata" If "scan_rs" is
835 // NULL, then this step is skipped. The "worker_i"
836 // param is for use with parallel roots processing, and should be
837 // the "i" of the calling parallel worker thread's work(i) function.
838 // In the sequential case this param will be ignored.
839 void g1_process_roots(OopClosure* scan_non_heap_roots,
840 OopClosure* scan_non_heap_weak_roots,
841 OopsInHeapRegionClosure* scan_rs,
842 CLDClosure* scan_strong_clds,
843 CLDClosure* scan_weak_clds,
844 CodeBlobClosure* scan_strong_code,
845 uint worker_i);
846
847 // Notifies all the necessary spaces that the committed space has
848 // been updated (either expanded or shrunk). It should be called
849 // after _g1_storage is updated.
850 void update_committed_space(HeapWord* old_end, HeapWord* new_end);
851
852 // The concurrent marker (and the thread it runs in.)
853 ConcurrentMark* _cm;
854 ConcurrentMarkThread* _cmThread;
855 bool _mark_in_progress;
856
857 // The concurrent refiner.
858 ConcurrentG1Refine* _cg1r;
859
860 // The parallel task queues
861 RefToScanQueueSet *_task_queues;
862
863 // True iff a evacuation has failed in the current collection.
864 bool _evacuation_failed;
865
866 EvacuationFailedInfo* _evacuation_failed_info_array;
867
868 // Failed evacuations cause some logical from-space objects to have
869 // forwarding pointers to themselves. Reset them.
870 void remove_self_forwarding_pointers();
871
872 // Together, these store an object with a preserved mark, and its mark value.
873 Stack<oop, mtGC> _objs_with_preserved_marks;
874 Stack<markOop, mtGC> _preserved_marks_of_objs;
875
876 // Preserve the mark of "obj", if necessary, in preparation for its mark
877 // word being overwritten with a self-forwarding-pointer.
878 void preserve_mark_if_necessary(oop obj, markOop m);
879
880 // The stack of evac-failure objects left to be scanned.
881 GrowableArray<oop>* _evac_failure_scan_stack;
882 // The closure to apply to evac-failure objects.
883
884 OopsInHeapRegionClosure* _evac_failure_closure;
885 // Set the field above.
886 void
887 set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
888 _evac_failure_closure = evac_failure_closure;
889 }
890
891 // Push "obj" on the scan stack.
892 void push_on_evac_failure_scan_stack(oop obj);
893 // Process scan stack entries until the stack is empty.
894 void drain_evac_failure_scan_stack();
895 // True iff an invocation of "drain_scan_stack" is in progress; to
896 // prevent unnecessary recursion.
897 bool _drain_in_progress;
898
899 // Do any necessary initialization for evacuation-failure handling.
900 // "cl" is the closure that will be used to process evac-failure
901 // objects.
902 void init_for_evac_failure(OopsInHeapRegionClosure* cl);
903 // Do any necessary cleanup for evacuation-failure handling data
904 // structures.
905 void finalize_for_evac_failure();
906
907 // An attempt to evacuate "obj" has failed; take necessary steps.
908 oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj);
909 void handle_evacuation_failure_common(oop obj, markOop m);
910
911 #ifndef PRODUCT
912 // Support for forcing evacuation failures. Analogous to
913 // PromotionFailureALot for the other collectors.
914
915 // Records whether G1EvacuationFailureALot should be in effect
916 // for the current GC
917 bool _evacuation_failure_alot_for_current_gc;
918
919 // Used to record the GC number for interval checking when
920 // determining whether G1EvaucationFailureALot is in effect
921 // for the current GC.
922 size_t _evacuation_failure_alot_gc_number;
923
924 // Count of the number of evacuations between failures.
925 volatile size_t _evacuation_failure_alot_count;
926
927 // Set whether G1EvacuationFailureALot should be in effect
928 // for the current GC (based upon the type of GC and which
929 // command line flags are set);
930 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
931 bool during_initial_mark,
932 bool during_marking);
933
934 inline void set_evacuation_failure_alot_for_current_gc();
935
936 // Return true if it's time to cause an evacuation failure.
937 inline bool evacuation_should_fail();
938
939 // Reset the G1EvacuationFailureALot counters. Should be called at
940 // the end of an evacuation pause in which an evacuation failure occurred.
941 inline void reset_evacuation_should_fail();
942 #endif // !PRODUCT
943
944 // ("Weak") Reference processing support.
945 //
946 // G1 has 2 instances of the reference processor class. One
947 // (_ref_processor_cm) handles reference object discovery
948 // and subsequent processing during concurrent marking cycles.
949 //
950 // The other (_ref_processor_stw) handles reference object
951 // discovery and processing during full GCs and incremental
952 // evacuation pauses.
953 //
954 // During an incremental pause, reference discovery will be
955 // temporarily disabled for _ref_processor_cm and will be
956 // enabled for _ref_processor_stw. At the end of the evacuation
957 // pause references discovered by _ref_processor_stw will be
958 // processed and discovery will be disabled. The previous
959 // setting for reference object discovery for _ref_processor_cm
960 // will be re-instated.
961 //
962 // At the start of marking:
963 // * Discovery by the CM ref processor is verified to be inactive
964 // and it's discovered lists are empty.
965 // * Discovery by the CM ref processor is then enabled.
966 //
967 // At the end of marking:
968 // * Any references on the CM ref processor's discovered
969 // lists are processed (possibly MT).
970 //
971 // At the start of full GC we:
972 // * Disable discovery by the CM ref processor and
973 // empty CM ref processor's discovered lists
974 // (without processing any entries).
975 // * Verify that the STW ref processor is inactive and it's
976 // discovered lists are empty.
977 // * Temporarily set STW ref processor discovery as single threaded.
978 // * Temporarily clear the STW ref processor's _is_alive_non_header
979 // field.
980 // * Finally enable discovery by the STW ref processor.
981 //
982 // The STW ref processor is used to record any discovered
983 // references during the full GC.
984 //
985 // At the end of a full GC we:
986 // * Enqueue any reference objects discovered by the STW ref processor
987 // that have non-live referents. This has the side-effect of
988 // making the STW ref processor inactive by disabling discovery.
989 // * Verify that the CM ref processor is still inactive
990 // and no references have been placed on it's discovered
991 // lists (also checked as a precondition during initial marking).
992
993 // The (stw) reference processor...
994 ReferenceProcessor* _ref_processor_stw;
995
996 STWGCTimer* _gc_timer_stw;
997 ConcurrentGCTimer* _gc_timer_cm;
998
999 G1OldTracer* _gc_tracer_cm;
1000 G1NewTracer* _gc_tracer_stw;
1001
1002 // During reference object discovery, the _is_alive_non_header
1003 // closure (if non-null) is applied to the referent object to
1004 // determine whether the referent is live. If so then the
1005 // reference object does not need to be 'discovered' and can
1006 // be treated as a regular oop. This has the benefit of reducing
1007 // the number of 'discovered' reference objects that need to
1008 // be processed.
1009 //
1010 // Instance of the is_alive closure for embedding into the
1011 // STW reference processor as the _is_alive_non_header field.
1012 // Supplying a value for the _is_alive_non_header field is
1013 // optional but doing so prevents unnecessary additions to
1014 // the discovered lists during reference discovery.
1015 G1STWIsAliveClosure _is_alive_closure_stw;
1016
1017 // The (concurrent marking) reference processor...
1018 ReferenceProcessor* _ref_processor_cm;
1019
1020 // Instance of the concurrent mark is_alive closure for embedding
1021 // into the Concurrent Marking reference processor as the
1022 // _is_alive_non_header field. Supplying a value for the
1023 // _is_alive_non_header field is optional but doing so prevents
1024 // unnecessary additions to the discovered lists during reference
1025 // discovery.
1026 G1CMIsAliveClosure _is_alive_closure_cm;
1027
1028 // Cache used by G1CollectedHeap::start_cset_region_for_worker().
1029 HeapRegion** _worker_cset_start_region;
1030
1031 // Time stamp to validate the regions recorded in the cache
1032 // used by G1CollectedHeap::start_cset_region_for_worker().
1033 // The heap region entry for a given worker is valid iff
1034 // the associated time stamp value matches the current value
1035 // of G1CollectedHeap::_gc_time_stamp.
1036 unsigned int* _worker_cset_start_region_time_stamp;
1037
1038 enum G1H_process_roots_tasks {
1039 G1H_PS_filter_satb_buffers,
1040 G1H_PS_refProcessor_oops_do,
1041 // Leave this one last.
1042 G1H_PS_NumElements
1043 };
1044
1045 SubTasksDone* _process_strong_tasks;
1046
1047 volatile bool _free_regions_coming;
1048
1049 public:
1050
1051 SubTasksDone* process_strong_tasks() { return _process_strong_tasks; }
1052
1053 void set_refine_cte_cl_concurrency(bool concurrent);
1054
1055 RefToScanQueue *task_queue(int i) const;
1056
1057 // A set of cards where updates happened during the GC
1058 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
1059
1060 // A DirtyCardQueueSet that is used to hold cards that contain
1061 // references into the current collection set. This is used to
1062 // update the remembered sets of the regions in the collection
1063 // set in the event of an evacuation failure.
1064 DirtyCardQueueSet& into_cset_dirty_card_queue_set()
1065 { return _into_cset_dirty_card_queue_set; }
1066
1067 // Create a G1CollectedHeap with the specified policy.
1068 // Must call the initialize method afterwards.
1069 // May not return if something goes wrong.
1070 G1CollectedHeap(G1CollectorPolicy* policy);
1071
1072 // Initialize the G1CollectedHeap to have the initial and
1073 // maximum sizes and remembered and barrier sets
1074 // specified by the policy object.
1075 jint initialize();
1076
1077 virtual void stop();
1078
1079 // Return the (conservative) maximum heap alignment for any G1 heap
1080 static size_t conservative_max_heap_alignment();
1081
1082 // Initialize weak reference processing.
1083 virtual void ref_processing_init();
1084
1085 void set_par_threads(uint t) {
1086 SharedHeap::set_par_threads(t);
1087 // Done in SharedHeap but oddly there are
1088 // two _process_strong_tasks's in a G1CollectedHeap
1089 // so do it here too.
1090 _process_strong_tasks->set_n_threads(t);
1091 }
1092
1093 // Set _n_par_threads according to a policy TBD.
1094 void set_par_threads();
1095
1096 void set_n_termination(int t) {
1097 _process_strong_tasks->set_n_threads(t);
1098 }
1099
1100 virtual CollectedHeap::Name kind() const {
1101 return CollectedHeap::G1CollectedHeap;
1102 }
1103
1104 // The current policy object for the collector.
1105 G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1106
1107 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); }
1108
1109 // Adaptive size policy. No such thing for g1.
1110 virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1111
1112 // The rem set and barrier set.
1113 G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1114
1115 unsigned get_gc_time_stamp() {
1116 return _gc_time_stamp;
1117 }
1118
1119 inline void reset_gc_time_stamp();
1120
1121 void check_gc_time_stamps() PRODUCT_RETURN;
1122
1123 inline void increment_gc_time_stamp();
1124
1125 // Reset the given region's GC timestamp. If it's starts humongous,
1126 // also reset the GC timestamp of its corresponding
1127 // continues humongous regions too.
1128 void reset_gc_time_stamps(HeapRegion* hr);
1129
1130 void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1131 DirtyCardQueue* into_cset_dcq,
1132 bool concurrent, uint worker_i);
1133
1134 // The shared block offset table array.
1135 G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1136
1137 // Reference Processing accessors
1138
1139 // The STW reference processor....
1140 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1141
1142 // The Concurrent Marking reference processor...
1143 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1144
1145 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1146 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1147
1148 virtual size_t capacity() const;
1149 virtual size_t used() const;
1150 // This should be called when we're not holding the heap lock. The
1151 // result might be a bit inaccurate.
1152 size_t used_unlocked() const;
1153 size_t recalculate_used() const;
1154
1155 // These virtual functions do the actual allocation.
1156 // Some heaps may offer a contiguous region for shared non-blocking
1157 // allocation, via inlined code (by exporting the address of the top and
1158 // end fields defining the extent of the contiguous allocation region.)
1159 // But G1CollectedHeap doesn't yet support this.
1160
1161 virtual bool is_maximal_no_gc() const {
1162 return _hrs.available() == 0;
1163 }
1164
1165 // The current number of regions in the heap.
1166 uint num_regions() const { return _hrs.length(); }
1167
1168 // The max number of regions in the heap.
1169 uint max_regions() const { return _hrs.max_length(); }
1170
1171 // The number of regions that are completely free.
1172 uint num_free_regions() const { return _hrs.num_free_regions(); }
1173
1174 // The number of regions that are not completely free.
1175 uint num_used_regions() const { return num_regions() - num_free_regions(); }
1176
1177 void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1178 void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1179 void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1180 void verify_dirty_young_regions() PRODUCT_RETURN;
1181
1182 #ifndef PRODUCT
1183 // Make sure that the given bitmap has no marked objects in the
1184 // range [from,limit). If it does, print an error message and return
1185 // false. Otherwise, just return true. bitmap_name should be "prev"
1186 // or "next".
1187 bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
1188 HeapWord* from, HeapWord* limit);
1189
1190 // Verify that the prev / next bitmap range [tams,end) for the given
1191 // region has no marks. Return true if all is well, false if errors
1192 // are detected.
1193 bool verify_bitmaps(const char* caller, HeapRegion* hr);
1194 #endif // PRODUCT
1195
1196 // If G1VerifyBitmaps is set, verify that the marking bitmaps for
1197 // the given region do not have any spurious marks. If errors are
1198 // detected, print appropriate error messages and crash.
1199 void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN;
1200
1201 // If G1VerifyBitmaps is set, verify that the marking bitmaps do not
1202 // have any spurious marks. If errors are detected, print
1203 // appropriate error messages and crash.
1204 void check_bitmaps(const char* caller) PRODUCT_RETURN;
1205
1206 // verify_region_sets() performs verification over the region
1207 // lists. It will be compiled in the product code to be used when
1208 // necessary (i.e., during heap verification).
1209 void verify_region_sets();
1210
1211 // verify_region_sets_optional() is planted in the code for
1212 // list verification in non-product builds (and it can be enabled in
1213 // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1).
1214 #if HEAP_REGION_SET_FORCE_VERIFY
1215 void verify_region_sets_optional() {
1216 verify_region_sets();
1217 }
1218 #else // HEAP_REGION_SET_FORCE_VERIFY
1219 void verify_region_sets_optional() { }
1220 #endif // HEAP_REGION_SET_FORCE_VERIFY
1221
1222 #ifdef ASSERT
1223 bool is_on_master_free_list(HeapRegion* hr) {
1224 return _hrs.is_free(hr);
1225 }
1226 #endif // ASSERT
1227
1228 // Wrapper for the region list operations that can be called from
1229 // methods outside this class.
1230
1231 void secondary_free_list_add(FreeRegionList* list) {
1232 _secondary_free_list.add_ordered(list);
1233 }
1234
1235 void append_secondary_free_list() {
1236 _hrs.insert_list_into_free_list(&_secondary_free_list);
1237 }
1238
1239 void append_secondary_free_list_if_not_empty_with_lock() {
1240 // If the secondary free list looks empty there's no reason to
1241 // take the lock and then try to append it.
1242 if (!_secondary_free_list.is_empty()) {
1243 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1244 append_secondary_free_list();
1245 }
1246 }
1247
1248 inline void old_set_remove(HeapRegion* hr);
1249
1250 size_t non_young_capacity_bytes() {
1251 return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1252 }
1253
1254 void set_free_regions_coming();
1255 void reset_free_regions_coming();
1256 bool free_regions_coming() { return _free_regions_coming; }
1257 void wait_while_free_regions_coming();
1258
1259 // Determine whether the given region is one that we are using as an
1260 // old GC alloc region.
1261 bool is_old_gc_alloc_region(HeapRegion* hr) {
1262 return hr == _retained_old_gc_alloc_region;
1263 }
1264
1265 // Perform a collection of the heap; intended for use in implementing
1266 // "System.gc". This probably implies as full a collection as the
1267 // "CollectedHeap" supports.
1268 virtual void collect(GCCause::Cause cause);
1269
1270 // The same as above but assume that the caller holds the Heap_lock.
1271 void collect_locked(GCCause::Cause cause);
1272
1273 // True iff an evacuation has failed in the most-recent collection.
1274 bool evacuation_failed() { return _evacuation_failed; }
1275
1276 void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed);
1277 void prepend_to_freelist(FreeRegionList* list);
1278 void decrement_summary_bytes(size_t bytes);
1279
1280 // Returns "TRUE" iff "p" points into the committed areas of the heap.
1281 virtual bool is_in(const void* p) const;
1282
1283 // Return "TRUE" iff the given object address is within the collection
1284 // set. Slow implementation.
1285 inline bool obj_in_cs(oop obj);
1286
1287 inline bool is_in_cset(oop obj);
1288
1289 inline bool is_in_cset_or_humongous(const oop obj);
1290
1291 enum in_cset_state_t {
1292 InNeither, // neither in collection set nor humongous
1293 InCSet, // region is in collection set only
1294 IsHumongous // region is a humongous start region
1295 };
1296 private:
1297 // Instances of this class are used for quick tests on whether a reference points
1298 // into the collection set or is a humongous object (points into a humongous
1299 // object).
1300 // Each of the array's elements denotes whether the corresponding region is in
1301 // the collection set or a humongous region.
1302 // We use this to quickly reclaim humongous objects: by making a humongous region
1303 // succeed this test, we sort-of add it to the collection set. During the reference
1304 // iteration closures, when we see a humongous region, we simply mark it as
1305 // referenced, i.e. live.
1306 class G1FastCSetBiasedMappedArray : public G1BiasedMappedArray<char> {
1307 protected:
1308 char default_value() const { return G1CollectedHeap::InNeither; }
1309 public:
1310 void set_humongous(uintptr_t index) {
1311 assert(get_by_index(index) != InCSet, "Should not overwrite InCSet values");
1312 set_by_index(index, G1CollectedHeap::IsHumongous);
1313 }
1314
1315 void clear_humongous(uintptr_t index) {
1316 set_by_index(index, G1CollectedHeap::InNeither);
1317 }
1318
1319 void set_in_cset(uintptr_t index) {
1320 assert(get_by_index(index) != G1CollectedHeap::IsHumongous, "Should not overwrite IsHumongous value");
1321 set_by_index(index, G1CollectedHeap::InCSet);
1322 }
1323
1324 bool is_in_cset_or_humongous(HeapWord* addr) const { return get_by_address(addr) != G1CollectedHeap::InNeither; }
1325 bool is_in_cset(HeapWord* addr) const { return get_by_address(addr) == G1CollectedHeap::InCSet; }
1326 G1CollectedHeap::in_cset_state_t at(HeapWord* addr) const { return (G1CollectedHeap::in_cset_state_t)get_by_address(addr); }
1327 void clear() { G1BiasedMappedArray<char>::clear(); }
1328 };
1329
1330 // This array is used for a quick test on whether a reference points into
1331 // the collection set or not. Each of the array's elements denotes whether the
1332 // corresponding region is in the collection set or not.
1333 G1FastCSetBiasedMappedArray _in_cset_fast_test;
1334
1335 public:
1336
1337 inline in_cset_state_t in_cset_state(const oop obj);
1338
1339 // Return "TRUE" iff the given object address is in the reserved
1340 // region of g1.
1341 bool is_in_g1_reserved(const void* p) const {
1342 return _hrs.reserved().contains(p);
1343 }
1344
1345 // Returns a MemRegion that corresponds to the space that has been
1346 // reserved for the heap
1347 MemRegion g1_reserved() const {
1348 return _hrs.reserved();
1349 }
1350
1351 // Returns a MemRegion that corresponds to the space that has been
1352 // committed in the heap
1353 MemRegion g1_committed() {
1354 return _hrs.committed();
1355 }
1356
1357 virtual bool is_in_closed_subset(const void* p) const;
1358
1359 G1SATBCardTableModRefBS* g1_barrier_set() {
1360 return (G1SATBCardTableModRefBS*) barrier_set();
1361 }
1362
1363 // This resets the card table to all zeros. It is used after
1364 // a collection pause which used the card table to claim cards.
1365 void cleanUpCardTable();
1366
1367 // Iteration functions.
1368
1369 // Iterate over all the ref-containing fields of all objects, calling
1370 // "cl.do_oop" on each.
1371 virtual void oop_iterate(ExtendedOopClosure* cl);
1372
1373 // Iterate over all objects, calling "cl.do_object" on each.
1374 virtual void object_iterate(ObjectClosure* cl);
1375
1376 virtual void safe_object_iterate(ObjectClosure* cl) {
1377 object_iterate(cl);
1378 }
1379
1380 // Iterate over all spaces in use in the heap, in ascending address order.
1381 virtual void space_iterate(SpaceClosure* cl);
1382
1383 // Iterate over heap regions, in address order, terminating the
1384 // iteration early if the "doHeapRegion" method returns "true".
1385 void heap_region_iterate(HeapRegionClosure* blk) const;
1386
1387 // Return the region with the given index. It assumes the index is valid.
1388 inline HeapRegion* region_at(uint index) const;
1389
1390 // Calculate the region index of the given address. Given address must be
1391 // within the heap.
1392 inline uint addr_to_region(HeapWord* addr) const;
1393
1394 inline HeapWord* bottom_addr_for_region(uint index) const;
1395
1396 // Divide the heap region sequence into "chunks" of some size (the number
1397 // of regions divided by the number of parallel threads times some
1398 // overpartition factor, currently 4). Assumes that this will be called
1399 // in parallel by ParallelGCThreads worker threads with distinct worker
1400 // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel
1401 // calls will use the same "claim_value", and that that claim value is
1402 // different from the claim_value of any heap region before the start of
1403 // the iteration. Applies "blk->doHeapRegion" to each of the regions, by
1404 // attempting to claim the first region in each chunk, and, if
1405 // successful, applying the closure to each region in the chunk (and
1406 // setting the claim value of the second and subsequent regions of the
1407 // chunk.) For now requires that "doHeapRegion" always returns "false",
1408 // i.e., that a closure never attempt to abort a traversal.
1409 void heap_region_par_iterate_chunked(HeapRegionClosure* cl,
1410 uint worker_id,
1411 uint num_workers,
1412 jint claim_value) const;
1413
1414 // It resets all the region claim values to the default.
1415 void reset_heap_region_claim_values();
1416
1417 // Resets the claim values of regions in the current
1418 // collection set to the default.
1419 void reset_cset_heap_region_claim_values();
1420
1421 #ifdef ASSERT
1422 bool check_heap_region_claim_values(jint claim_value);
1423
1424 // Same as the routine above but only checks regions in the
1425 // current collection set.
1426 bool check_cset_heap_region_claim_values(jint claim_value);
1427 #endif // ASSERT
1428
1429 // Clear the cached cset start regions and (more importantly)
1430 // the time stamps. Called when we reset the GC time stamp.
1431 void clear_cset_start_regions();
1432
1433 // Given the id of a worker, obtain or calculate a suitable
1434 // starting region for iterating over the current collection set.
1435 HeapRegion* start_cset_region_for_worker(uint worker_i);
1436
1437 // Iterate over the regions (if any) in the current collection set.
1438 void collection_set_iterate(HeapRegionClosure* blk);
1439
1440 // As above but starting from region r
1441 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1442
1443 HeapRegion* next_compaction_region(const HeapRegion* from) const;
1444
1445 // A CollectedHeap will contain some number of spaces. This finds the
1446 // space containing a given address, or else returns NULL.
1447 virtual Space* space_containing(const void* addr) const;
1448
1449 // Returns the HeapRegion that contains addr. addr must not be NULL.
1450 template <class T>
1451 inline HeapRegion* heap_region_containing_raw(const T addr) const;
1452
1453 // Returns the HeapRegion that contains addr. addr must not be NULL.
1454 // If addr is within a humongous continues region, it returns its humongous start region.
1455 template <class T>
1456 inline HeapRegion* heap_region_containing(const T addr) const;
1457
1458 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1459 // each address in the (reserved) heap is a member of exactly
1460 // one block. The defining characteristic of a block is that it is
1461 // possible to find its size, and thus to progress forward to the next
1462 // block. (Blocks may be of different sizes.) Thus, blocks may
1463 // represent Java objects, or they might be free blocks in a
1464 // free-list-based heap (or subheap), as long as the two kinds are
1465 // distinguishable and the size of each is determinable.
1466
1467 // Returns the address of the start of the "block" that contains the
1468 // address "addr". We say "blocks" instead of "object" since some heaps
1469 // may not pack objects densely; a chunk may either be an object or a
1470 // non-object.
1471 virtual HeapWord* block_start(const void* addr) const;
1472
1473 // Requires "addr" to be the start of a chunk, and returns its size.
1474 // "addr + size" is required to be the start of a new chunk, or the end
1475 // of the active area of the heap.
1476 virtual size_t block_size(const HeapWord* addr) const;
1477
1478 // Requires "addr" to be the start of a block, and returns "TRUE" iff
1479 // the block is an object.
1480 virtual bool block_is_obj(const HeapWord* addr) const;
1481
1482 // Does this heap support heap inspection? (+PrintClassHistogram)
1483 virtual bool supports_heap_inspection() const { return true; }
1484
1485 // Section on thread-local allocation buffers (TLABs)
1486 // See CollectedHeap for semantics.
1487
1488 bool supports_tlab_allocation() const;
1489 size_t tlab_capacity(Thread* ignored) const;
1490 size_t tlab_used(Thread* ignored) const;
1491 size_t max_tlab_size() const;
1492 size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1493
1494 // Can a compiler initialize a new object without store barriers?
1495 // This permission only extends from the creation of a new object
1496 // via a TLAB up to the first subsequent safepoint. If such permission
1497 // is granted for this heap type, the compiler promises to call
1498 // defer_store_barrier() below on any slow path allocation of
1499 // a new object for which such initializing store barriers will
1500 // have been elided. G1, like CMS, allows this, but should be
1501 // ready to provide a compensating write barrier as necessary
1502 // if that storage came out of a non-young region. The efficiency
1503 // of this implementation depends crucially on being able to
1504 // answer very efficiently in constant time whether a piece of
1505 // storage in the heap comes from a young region or not.
1506 // See ReduceInitialCardMarks.
1507 virtual bool can_elide_tlab_store_barriers() const {
1508 return true;
1509 }
1510
1511 virtual bool card_mark_must_follow_store() const {
1512 return true;
1513 }
1514
1515 inline bool is_in_young(const oop obj);
1516
1517 #ifdef ASSERT
1518 virtual bool is_in_partial_collection(const void* p);
1519 #endif
1520
1521 virtual bool is_scavengable(const void* addr);
1522
1523 // We don't need barriers for initializing stores to objects
1524 // in the young gen: for the SATB pre-barrier, there is no
1525 // pre-value that needs to be remembered; for the remembered-set
1526 // update logging post-barrier, we don't maintain remembered set
1527 // information for young gen objects.
1528 virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1529
1530 // Returns "true" iff the given word_size is "very large".
1531 static bool isHumongous(size_t word_size) {
1532 // Note this has to be strictly greater-than as the TLABs
1533 // are capped at the humongous threshold and we want to
1534 // ensure that we don't try to allocate a TLAB as
1535 // humongous and that we don't allocate a humongous
1536 // object in a TLAB.
1537 return word_size > _humongous_object_threshold_in_words;
1538 }
1539
1540 // Update mod union table with the set of dirty cards.
1541 void updateModUnion();
1542
1543 // Set the mod union bits corresponding to the given memRegion. Note
1544 // that this is always a safe operation, since it doesn't clear any
1545 // bits.
1546 void markModUnionRange(MemRegion mr);
1547
1548 // Records the fact that a marking phase is no longer in progress.
1549 void set_marking_complete() {
1550 _mark_in_progress = false;
1551 }
1552 void set_marking_started() {
1553 _mark_in_progress = true;
1554 }
1555 bool mark_in_progress() {
1556 return _mark_in_progress;
1557 }
1558
1559 // Print the maximum heap capacity.
1560 virtual size_t max_capacity() const;
1561
1562 virtual jlong millis_since_last_gc();
1563
1564
1565 // Convenience function to be used in situations where the heap type can be
1566 // asserted to be this type.
1567 static G1CollectedHeap* heap();
1568
1569 void set_region_short_lived_locked(HeapRegion* hr);
1570 // add appropriate methods for any other surv rate groups
1571
1572 YoungList* young_list() const { return _young_list; }
1573
1574 // debugging
1575 bool check_young_list_well_formed() {
1576 return _young_list->check_list_well_formed();
1577 }
1578
1579 bool check_young_list_empty(bool check_heap,
1580 bool check_sample = true);
1581
1582 // *** Stuff related to concurrent marking. It's not clear to me that so
1583 // many of these need to be public.
1584
1585 // The functions below are helper functions that a subclass of
1586 // "CollectedHeap" can use in the implementation of its virtual
1587 // functions.
1588 // This performs a concurrent marking of the live objects in a
1589 // bitmap off to the side.
1590 void doConcurrentMark();
1591
1592 bool isMarkedPrev(oop obj) const;
1593 bool isMarkedNext(oop obj) const;
1594
1595 // Determine if an object is dead, given the object and also
1596 // the region to which the object belongs. An object is dead
1597 // iff a) it was not allocated since the last mark and b) it
1598 // is not marked.
1599 bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1600 return
1601 !hr->obj_allocated_since_prev_marking(obj) &&
1602 !isMarkedPrev(obj);
1603 }
1604
1605 // This function returns true when an object has been
1606 // around since the previous marking and hasn't yet
1607 // been marked during this marking.
1608 bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1609 return
1610 !hr->obj_allocated_since_next_marking(obj) &&
1611 !isMarkedNext(obj);
1612 }
1613
1614 // Determine if an object is dead, given only the object itself.
1615 // This will find the region to which the object belongs and
1616 // then call the region version of the same function.
1617
1618 // Added if it is NULL it isn't dead.
1619
1620 inline bool is_obj_dead(const oop obj) const;
1621
1622 inline bool is_obj_ill(const oop obj) const;
1623
1624 bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1625 HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1626 bool is_marked(oop obj, VerifyOption vo);
1627 const char* top_at_mark_start_str(VerifyOption vo);
1628
1629 ConcurrentMark* concurrent_mark() const { return _cm; }
1630
1631 // Refinement
1632
1633 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1634
1635 // The dirty cards region list is used to record a subset of regions
1636 // whose cards need clearing. The list if populated during the
1637 // remembered set scanning and drained during the card table
1638 // cleanup. Although the methods are reentrant, population/draining
1639 // phases must not overlap. For synchronization purposes the last
1640 // element on the list points to itself.
1641 HeapRegion* _dirty_cards_region_list;
1642 void push_dirty_cards_region(HeapRegion* hr);
1643 HeapRegion* pop_dirty_cards_region();
1644
1645 // Optimized nmethod scanning support routines
1646
1647 // Register the given nmethod with the G1 heap.
1648 virtual void register_nmethod(nmethod* nm);
1649
1650 // Unregister the given nmethod from the G1 heap.
1651 virtual void unregister_nmethod(nmethod* nm);
1652
1653 // Migrate the nmethods in the code root lists of the regions
1654 // in the collection set to regions in to-space. In the event
1655 // of an evacuation failure, nmethods that reference objects
1656 // that were not successfully evacuated are not migrated.
1657 void migrate_strong_code_roots();
1658
1659 // Free up superfluous code root memory.
1660 void purge_code_root_memory();
1661
1662 // Rebuild the strong code root lists for each region
1663 // after a full GC.
1664 void rebuild_strong_code_roots();
1665
1666 // Delete entries for dead interned string and clean up unreferenced symbols
1667 // in symbol table, possibly in parallel.
1668 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1669
1670 // Parallel phase of unloading/cleaning after G1 concurrent mark.
1671 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred);
1672
1673 // Redirty logged cards in the refinement queue.
1674 void redirty_logged_cards();
1675 // Verification
1676
1677 // The following is just to alert the verification code
1678 // that a full collection has occurred and that the
1679 // remembered sets are no longer up to date.
1680 bool _full_collection;
1681 void set_full_collection() { _full_collection = true;}
1682 void clear_full_collection() {_full_collection = false;}
1683 bool full_collection() {return _full_collection;}
1684
1685 // Perform any cleanup actions necessary before allowing a verification.
1686 virtual void prepare_for_verify();
1687
1688 // Perform verification.
1689
1690 // vo == UsePrevMarking -> use "prev" marking information,
1691 // vo == UseNextMarking -> use "next" marking information
1692 // vo == UseMarkWord -> use the mark word in the object header
1693 //
1694 // NOTE: Only the "prev" marking information is guaranteed to be
1695 // consistent most of the time, so most calls to this should use
1696 // vo == UsePrevMarking.
1697 // Currently, there is only one case where this is called with
1698 // vo == UseNextMarking, which is to verify the "next" marking
1699 // information at the end of remark.
1700 // Currently there is only one place where this is called with
1701 // vo == UseMarkWord, which is to verify the marking during a
1702 // full GC.
1703 void verify(bool silent, VerifyOption vo);
1704
1705 // Override; it uses the "prev" marking information
1706 virtual void verify(bool silent);
1707
1708 // The methods below are here for convenience and dispatch the
1709 // appropriate method depending on value of the given VerifyOption
1710 // parameter. The values for that parameter, and their meanings,
1711 // are the same as those above.
1712
1713 bool is_obj_dead_cond(const oop obj,
1714 const HeapRegion* hr,
1715 const VerifyOption vo) const;
1716
1717 bool is_obj_dead_cond(const oop obj,
1718 const VerifyOption vo) const;
1719
1720 // Printing
1721
1722 virtual void print_on(outputStream* st) const;
1723 virtual void print_extended_on(outputStream* st) const;
1724 virtual void print_on_error(outputStream* st) const;
1725
1726 virtual void print_gc_threads_on(outputStream* st) const;
1727 virtual void gc_threads_do(ThreadClosure* tc) const;
1728
1729 // Override
1730 void print_tracing_info() const;
1731
1732 // The following two methods are helpful for debugging RSet issues.
1733 void print_cset_rsets() PRODUCT_RETURN;
1734 void print_all_rsets() PRODUCT_RETURN;
1735
1736 public:
1737 size_t pending_card_num();
1738 size_t cards_scanned();
1739
1740 protected:
1741 size_t _max_heap_capacity;
1742 };
1743
1744 class G1ParGCAllocBuffer: public ParGCAllocBuffer {
1745 private:
1746 bool _retired;
1747
1748 public:
1749 G1ParGCAllocBuffer(size_t gclab_word_size);
1750 virtual ~G1ParGCAllocBuffer() {
1751 guarantee(_retired, "Allocation buffer has not been retired");
1752 }
1753
1754 virtual void set_buf(HeapWord* buf) {
1755 ParGCAllocBuffer::set_buf(buf);
1756 _retired = false;
1757 }
1758
1759 virtual void retire(bool end_of_gc, bool retain) {
1760 if (_retired) {
1761 return;
1762 }
1763 ParGCAllocBuffer::retire(end_of_gc, retain);
1764 _retired = true;
1765 }
1766 };
1767
1768 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP