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 *
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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/g1HRPrinter.hpp"
32 #include "gc_implementation/g1/g1MonitoringSupport.hpp"
33 #include "gc_implementation/g1/g1RemSet.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_G1CollectForAllocation;
204 friend class VM_G1CollectFull;
205 friend class VM_G1IncCollectionPause;
206 friend class VMStructs;
207 friend class MutatorAllocRegion;
208 friend class SurvivorGCAllocRegion;
209 friend class OldGCAllocRegion;
210
211 // Closures used in implementation.
212 template <G1Barrier barrier, bool do_mark_object>
213 friend class G1ParCopyClosure;
214 friend class G1IsAliveClosure;
215 friend class G1EvacuateFollowersClosure;
216 friend class G1ParScanThreadState;
217 friend class G1ParScanClosureSuper;
218 friend class G1ParEvacuateFollowersClosure;
219 friend class G1ParTask;
220 friend class G1FreeGarbageRegionClosure;
221 friend class RefineCardTableEntryClosure;
222 friend class G1PrepareCompactClosure;
223 friend class RegionSorter;
224 friend class RegionResetter;
225 friend class CountRCClosure;
226 friend class EvacPopObjClosure;
227 friend class G1ParCleanupCTTask;
228
229 // Other related classes.
230 friend class G1MarkSweep;
231
232 private:
233 // The one and only G1CollectedHeap, so static functions can find it.
234 static G1CollectedHeap* _g1h;
235
236 static size_t _humongous_object_threshold_in_words;
237
238 // Storage for the G1 heap.
239 VirtualSpace _g1_storage;
240 MemRegion _g1_reserved;
241
242 // The part of _g1_storage that is currently committed.
243 MemRegion _g1_committed;
244
245 // The master free list. It will satisfy all new region allocations.
246 FreeRegionList _free_list;
247
248 // The secondary free list which contains regions that have been
249 // freed up during the cleanup process. This will be appended to the
250 // master free list when appropriate.
251 FreeRegionList _secondary_free_list;
252
253 // It keeps track of the old regions.
254 HeapRegionSet _old_set;
255
256 // It keeps track of the humongous regions.
257 HeapRegionSet _humongous_set;
258
259 // The number of regions we could create by expansion.
260 uint _expansion_regions;
261
262 // The block offset table for the G1 heap.
263 G1BlockOffsetSharedArray* _bot_shared;
264
265 // Tears down the region sets / lists so that they are empty and the
266 // regions on the heap do not belong to a region set / list. The
267 // only exception is the humongous set which we leave unaltered. If
268 // free_list_only is true, it will only tear down the master free
269 // list. It is called before a Full GC (free_list_only == false) or
270 // before heap shrinking (free_list_only == true).
271 void tear_down_region_sets(bool free_list_only);
272
273 // Rebuilds the region sets / lists so that they are repopulated to
274 // reflect the contents of the heap. The only exception is the
275 // humongous set which was not torn down in the first place. If
276 // free_list_only is true, it will only rebuild the master free
277 // list. It is called after a Full GC (free_list_only == false) or
278 // after heap shrinking (free_list_only == true).
279 void rebuild_region_sets(bool free_list_only);
280
281 // The sequence of all heap regions in the heap.
282 HeapRegionSeq _hrs;
283
284 // Alloc region used to satisfy mutator allocation requests.
285 MutatorAllocRegion _mutator_alloc_region;
286
287 // Alloc region used to satisfy allocation requests by the GC for
288 // survivor objects.
289 SurvivorGCAllocRegion _survivor_gc_alloc_region;
290
291 // PLAB sizing policy for survivors.
292 PLABStats _survivor_plab_stats;
293
294 // Alloc region used to satisfy allocation requests by the GC for
295 // old objects.
296 OldGCAllocRegion _old_gc_alloc_region;
297
298 // PLAB sizing policy for tenured objects.
299 PLABStats _old_plab_stats;
300
301 PLABStats* stats_for_purpose(GCAllocPurpose purpose) {
302 PLABStats* stats = NULL;
303
304 switch (purpose) {
305 case GCAllocForSurvived:
306 stats = &_survivor_plab_stats;
307 break;
308 case GCAllocForTenured:
309 stats = &_old_plab_stats;
310 break;
311 default:
312 assert(false, "unrecognized GCAllocPurpose");
313 }
314
315 return stats;
316 }
317
318 // The last old region we allocated to during the last GC.
319 // Typically, it is not full so we should re-use it during the next GC.
320 HeapRegion* _retained_old_gc_alloc_region;
321
322 // It specifies whether we should attempt to expand the heap after a
323 // region allocation failure. If heap expansion fails we set this to
324 // false so that we don't re-attempt the heap expansion (it's likely
325 // that subsequent expansion attempts will also fail if one fails).
326 // Currently, it is only consulted during GC and it's reset at the
327 // start of each GC.
328 bool _expand_heap_after_alloc_failure;
329
330 // It resets the mutator alloc region before new allocations can take place.
331 void init_mutator_alloc_region();
332
333 // It releases the mutator alloc region.
334 void release_mutator_alloc_region();
335
336 // It initializes the GC alloc regions at the start of a GC.
337 void init_gc_alloc_regions(EvacuationInfo& evacuation_info);
338
339 // It releases the GC alloc regions at the end of a GC.
340 void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info);
341
342 // It does any cleanup that needs to be done on the GC alloc regions
343 // before a Full GC.
344 void abandon_gc_alloc_regions();
345
346 // Helper for monitoring and management support.
347 G1MonitoringSupport* _g1mm;
348
349 // Determines PLAB size for a particular allocation purpose.
350 size_t desired_plab_sz(GCAllocPurpose purpose);
351
352 // Outside of GC pauses, the number of bytes used in all regions other
353 // than the current allocation region.
354 size_t _summary_bytes_used;
355
356 // This is used for a quick test on whether a reference points into
357 // the collection set or not. Basically, we have an array, with one
358 // byte per region, and that byte denotes whether the corresponding
359 // region is in the collection set or not. The entry corresponding
360 // the bottom of the heap, i.e., region 0, is pointed to by
361 // _in_cset_fast_test_base. The _in_cset_fast_test field has been
362 // biased so that it actually points to address 0 of the address
363 // space, to make the test as fast as possible (we can simply shift
364 // the address to address into it, instead of having to subtract the
365 // bottom of the heap from the address before shifting it; basically
366 // it works in the same way the card table works).
367 bool* _in_cset_fast_test;
368
369 // The allocated array used for the fast test on whether a reference
370 // points into the collection set or not. This field is also used to
371 // free the array.
372 bool* _in_cset_fast_test_base;
373
374 // The length of the _in_cset_fast_test_base array.
375 uint _in_cset_fast_test_length;
376
377 volatile unsigned _gc_time_stamp;
378
379 size_t* _surviving_young_words;
380
381 G1HRPrinter _hr_printer;
382
383 void setup_surviving_young_words();
384 void update_surviving_young_words(size_t* surv_young_words);
385 void cleanup_surviving_young_words();
386
387 // It decides whether an explicit GC should start a concurrent cycle
388 // instead of doing a STW GC. Currently, a concurrent cycle is
389 // explicitly started if:
390 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
391 // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
392 // (c) cause == _g1_humongous_allocation
393 bool should_do_concurrent_full_gc(GCCause::Cause cause);
394
395 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
396 // concurrent cycles) we have started.
397 volatile unsigned int _old_marking_cycles_started;
398
399 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
400 // concurrent cycles) we have completed.
401 volatile unsigned int _old_marking_cycles_completed;
402
403 bool _concurrent_cycle_started;
404
405 // This is a non-product method that is helpful for testing. It is
406 // called at the end of a GC and artificially expands the heap by
407 // allocating a number of dead regions. This way we can induce very
408 // frequent marking cycles and stress the cleanup / concurrent
409 // cleanup code more (as all the regions that will be allocated by
410 // this method will be found dead by the marking cycle).
411 void allocate_dummy_regions() PRODUCT_RETURN;
412
413 // Clear RSets after a compaction. It also resets the GC time stamps.
414 void clear_rsets_post_compaction();
415
416 // If the HR printer is active, dump the state of the regions in the
417 // heap after a compaction.
418 void print_hrs_post_compaction();
419
420 double verify(bool guard, const char* msg);
421 void verify_before_gc();
422 void verify_after_gc();
423
424 void log_gc_header();
425 void log_gc_footer(double pause_time_sec);
426
427 // These are macros so that, if the assert fires, we get the correct
428 // line number, file, etc.
429
430 #define heap_locking_asserts_err_msg(_extra_message_) \
431 err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \
432 (_extra_message_), \
433 BOOL_TO_STR(Heap_lock->owned_by_self()), \
434 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \
435 BOOL_TO_STR(Thread::current()->is_VM_thread()))
436
437 #define assert_heap_locked() \
438 do { \
439 assert(Heap_lock->owned_by_self(), \
440 heap_locking_asserts_err_msg("should be holding the Heap_lock")); \
441 } while (0)
442
443 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \
444 do { \
445 assert(Heap_lock->owned_by_self() || \
446 (SafepointSynchronize::is_at_safepoint() && \
447 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
448 heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
449 "should be at a safepoint")); \
450 } while (0)
451
452 #define assert_heap_locked_and_not_at_safepoint() \
453 do { \
454 assert(Heap_lock->owned_by_self() && \
455 !SafepointSynchronize::is_at_safepoint(), \
456 heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
457 "should not be at a safepoint")); \
458 } while (0)
459
460 #define assert_heap_not_locked() \
461 do { \
462 assert(!Heap_lock->owned_by_self(), \
463 heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
464 } while (0)
465
466 #define assert_heap_not_locked_and_not_at_safepoint() \
467 do { \
468 assert(!Heap_lock->owned_by_self() && \
469 !SafepointSynchronize::is_at_safepoint(), \
470 heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
471 "should not be at a safepoint")); \
472 } while (0)
473
474 #define assert_at_safepoint(_should_be_vm_thread_) \
475 do { \
476 assert(SafepointSynchronize::is_at_safepoint() && \
477 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
478 heap_locking_asserts_err_msg("should be at a safepoint")); \
479 } while (0)
480
481 #define assert_not_at_safepoint() \
482 do { \
483 assert(!SafepointSynchronize::is_at_safepoint(), \
484 heap_locking_asserts_err_msg("should not be at a safepoint")); \
485 } while (0)
486
487 protected:
488
489 // The young region list.
490 YoungList* _young_list;
491
492 // The current policy object for the collector.
493 G1CollectorPolicy* _g1_policy;
494
495 // This is the second level of trying to allocate a new region. If
496 // new_region() didn't find a region on the free_list, this call will
497 // check whether there's anything available on the
498 // secondary_free_list and/or wait for more regions to appear on
499 // that list, if _free_regions_coming is set.
500 HeapRegion* new_region_try_secondary_free_list(bool is_old);
501
502 // Try to allocate a single non-humongous HeapRegion sufficient for
503 // an allocation of the given word_size. If do_expand is true,
504 // attempt to expand the heap if necessary to satisfy the allocation
505 // request. If the region is to be used as an old region or for a
506 // humongous object, set is_old to true. If not, to false.
507 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
508
509 // Attempt to satisfy a humongous allocation request of the given
510 // size by finding a contiguous set of free regions of num_regions
511 // length and remove them from the master free list. Return the
512 // index of the first region or G1_NULL_HRS_INDEX if the search
513 // was unsuccessful.
514 uint humongous_obj_allocate_find_first(uint num_regions,
515 size_t word_size);
516
517 // Initialize a contiguous set of free regions of length num_regions
518 // and starting at index first so that they appear as a single
519 // humongous region.
520 HeapWord* humongous_obj_allocate_initialize_regions(uint first,
521 uint num_regions,
522 size_t word_size);
523
524 // Attempt to allocate a humongous object of the given size. Return
525 // NULL if unsuccessful.
526 HeapWord* humongous_obj_allocate(size_t word_size);
527
528 // The following two methods, allocate_new_tlab() and
529 // mem_allocate(), are the two main entry points from the runtime
530 // into the G1's allocation routines. They have the following
531 // assumptions:
532 //
533 // * They should both be called outside safepoints.
534 //
535 // * They should both be called without holding the Heap_lock.
536 //
537 // * All allocation requests for new TLABs should go to
538 // allocate_new_tlab().
539 //
540 // * All non-TLAB allocation requests should go to mem_allocate().
541 //
542 // * If either call cannot satisfy the allocation request using the
543 // current allocating region, they will try to get a new one. If
544 // this fails, they will attempt to do an evacuation pause and
545 // retry the allocation.
546 //
547 // * If all allocation attempts fail, even after trying to schedule
548 // an evacuation pause, allocate_new_tlab() will return NULL,
549 // whereas mem_allocate() will attempt a heap expansion and/or
550 // schedule a Full GC.
551 //
552 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
553 // should never be called with word_size being humongous. All
554 // humongous allocation requests should go to mem_allocate() which
555 // will satisfy them with a special path.
556
557 virtual HeapWord* allocate_new_tlab(size_t word_size);
558
559 virtual HeapWord* mem_allocate(size_t word_size,
560 bool* gc_overhead_limit_was_exceeded);
561
562 // The following three methods take a gc_count_before_ret
563 // parameter which is used to return the GC count if the method
564 // returns NULL. Given that we are required to read the GC count
565 // while holding the Heap_lock, and these paths will take the
566 // Heap_lock at some point, it's easier to get them to read the GC
567 // count while holding the Heap_lock before they return NULL instead
568 // of the caller (namely: mem_allocate()) having to also take the
569 // Heap_lock just to read the GC count.
570
571 // First-level mutator allocation attempt: try to allocate out of
572 // the mutator alloc region without taking the Heap_lock. This
573 // should only be used for non-humongous allocations.
574 inline HeapWord* attempt_allocation(size_t word_size,
575 unsigned int* gc_count_before_ret,
576 int* gclocker_retry_count_ret);
577
578 // Second-level mutator allocation attempt: take the Heap_lock and
579 // retry the allocation attempt, potentially scheduling a GC
580 // pause. This should only be used for non-humongous allocations.
581 HeapWord* attempt_allocation_slow(size_t word_size,
582 unsigned int* gc_count_before_ret,
583 int* gclocker_retry_count_ret);
584
585 // Takes the Heap_lock and attempts a humongous allocation. It can
586 // potentially schedule a GC pause.
587 HeapWord* attempt_allocation_humongous(size_t word_size,
588 unsigned int* gc_count_before_ret,
589 int* gclocker_retry_count_ret);
590
591 // Allocation attempt that should be called during safepoints (e.g.,
592 // at the end of a successful GC). expect_null_mutator_alloc_region
593 // specifies whether the mutator alloc region is expected to be NULL
594 // or not.
595 HeapWord* attempt_allocation_at_safepoint(size_t word_size,
596 bool expect_null_mutator_alloc_region);
597
598 // It dirties the cards that cover the block so that so that the post
599 // write barrier never queues anything when updating objects on this
600 // block. It is assumed (and in fact we assert) that the block
601 // belongs to a young region.
602 inline void dirty_young_block(HeapWord* start, size_t word_size);
603
604 // Allocate blocks during garbage collection. Will ensure an
605 // allocation region, either by picking one or expanding the
606 // heap, and then allocate a block of the given size. The block
607 // may not be a humongous - it must fit into a single heap region.
608 HeapWord* par_allocate_during_gc(GCAllocPurpose purpose, size_t word_size);
609
610 HeapWord* allocate_during_gc_slow(GCAllocPurpose purpose,
611 HeapRegion* alloc_region,
612 bool par,
613 size_t word_size);
614
615 // Ensure that no further allocations can happen in "r", bearing in mind
616 // that parallel threads might be attempting allocations.
617 void par_allocate_remaining_space(HeapRegion* r);
618
619 // Allocation attempt during GC for a survivor object / PLAB.
620 inline HeapWord* survivor_attempt_allocation(size_t word_size);
621
622 // Allocation attempt during GC for an old object / PLAB.
623 inline HeapWord* old_attempt_allocation(size_t word_size);
624
625 // These methods are the "callbacks" from the G1AllocRegion class.
626
627 // For mutator alloc regions.
628 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
629 void retire_mutator_alloc_region(HeapRegion* alloc_region,
630 size_t allocated_bytes);
631
632 // For GC alloc regions.
633 HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
634 GCAllocPurpose ap);
635 void retire_gc_alloc_region(HeapRegion* alloc_region,
636 size_t allocated_bytes, GCAllocPurpose ap);
637
638 // - if explicit_gc is true, the GC is for a System.gc() or a heap
639 // inspection request and should collect the entire heap
640 // - if clear_all_soft_refs is true, all soft references should be
641 // cleared during the GC
642 // - if explicit_gc is false, word_size describes the allocation that
643 // the GC should attempt (at least) to satisfy
644 // - it returns false if it is unable to do the collection due to the
645 // GC locker being active, true otherwise
646 bool do_collection(bool explicit_gc,
647 bool clear_all_soft_refs,
648 size_t word_size);
649
650 // Callback from VM_G1CollectFull operation.
651 // Perform a full collection.
652 virtual void do_full_collection(bool clear_all_soft_refs);
653
654 // Resize the heap if necessary after a full collection. If this is
655 // after a collect-for allocation, "word_size" is the allocation size,
656 // and will be considered part of the used portion of the heap.
657 void resize_if_necessary_after_full_collection(size_t word_size);
658
659 // Callback from VM_G1CollectForAllocation operation.
660 // This function does everything necessary/possible to satisfy a
661 // failed allocation request (including collection, expansion, etc.)
662 HeapWord* satisfy_failed_allocation(size_t word_size, bool* succeeded);
663
664 // Attempting to expand the heap sufficiently
665 // to support an allocation of the given "word_size". If
666 // successful, perform the allocation and return the address of the
667 // allocated block, or else "NULL".
668 HeapWord* expand_and_allocate(size_t word_size);
669
670 // Process any reference objects discovered during
671 // an incremental evacuation pause.
672 void process_discovered_references(uint no_of_gc_workers);
673
674 // Enqueue any remaining discovered references
675 // after processing.
676 void enqueue_discovered_references(uint no_of_gc_workers);
677
678 public:
679
680 G1MonitoringSupport* g1mm() {
681 assert(_g1mm != NULL, "should have been initialized");
682 return _g1mm;
683 }
684
685 // Expand the garbage-first heap by at least the given size (in bytes!).
686 // Returns true if the heap was expanded by the requested amount;
687 // false otherwise.
688 // (Rounds up to a HeapRegion boundary.)
689 bool expand(size_t expand_bytes);
690
691 // Do anything common to GC's.
692 virtual void gc_prologue(bool full);
693 virtual void gc_epilogue(bool full);
694
695 // We register a region with the fast "in collection set" test. We
696 // simply set to true the array slot corresponding to this region.
697 void register_region_with_in_cset_fast_test(HeapRegion* r) {
698 assert(_in_cset_fast_test_base != NULL, "sanity");
699 assert(r->in_collection_set(), "invariant");
700 uint index = r->hrs_index();
701 assert(index < _in_cset_fast_test_length, "invariant");
702 assert(!_in_cset_fast_test_base[index], "invariant");
703 _in_cset_fast_test_base[index] = true;
704 }
705
706 // This is a fast test on whether a reference points into the
707 // collection set or not. Assume that the reference
708 // points into the heap.
709 bool in_cset_fast_test(oop obj) {
710 assert(_in_cset_fast_test != NULL, "sanity");
711 assert(_g1_committed.contains((HeapWord*) obj), err_msg("Given reference outside of heap, is "PTR_FORMAT, (HeapWord*)obj));
712 // no need to subtract the bottom of the heap from obj,
713 // _in_cset_fast_test is biased
714 uintx index = cast_from_oop<uintx>(obj) >> HeapRegion::LogOfHRGrainBytes;
715 bool ret = _in_cset_fast_test[index];
716 // let's make sure the result is consistent with what the slower
717 // test returns
718 assert( ret || !obj_in_cs(obj), "sanity");
719 assert(!ret || obj_in_cs(obj), "sanity");
720 return ret;
721 }
722
723 void clear_cset_fast_test() {
724 assert(_in_cset_fast_test_base != NULL, "sanity");
725 memset(_in_cset_fast_test_base, false,
726 (size_t) _in_cset_fast_test_length * sizeof(bool));
727 }
728
729 // This is called at the start of either a concurrent cycle or a Full
730 // GC to update the number of old marking cycles started.
731 void increment_old_marking_cycles_started();
732
733 // This is called at the end of either a concurrent cycle or a Full
734 // GC to update the number of old marking cycles completed. Those two
735 // can happen in a nested fashion, i.e., we start a concurrent
736 // cycle, a Full GC happens half-way through it which ends first,
737 // and then the cycle notices that a Full GC happened and ends
738 // too. The concurrent parameter is a boolean to help us do a bit
739 // tighter consistency checking in the method. If concurrent is
740 // false, the caller is the inner caller in the nesting (i.e., the
741 // Full GC). If concurrent is true, the caller is the outer caller
742 // in this nesting (i.e., the concurrent cycle). Further nesting is
743 // not currently supported. The end of this call also notifies
744 // the FullGCCount_lock in case a Java thread is waiting for a full
745 // GC to happen (e.g., it called System.gc() with
746 // +ExplicitGCInvokesConcurrent).
747 void increment_old_marking_cycles_completed(bool concurrent);
748
749 unsigned int old_marking_cycles_completed() {
750 return _old_marking_cycles_completed;
751 }
752
753 void register_concurrent_cycle_start(const Ticks& start_time);
754 void register_concurrent_cycle_end();
755 void trace_heap_after_concurrent_cycle();
756
757 G1YCType yc_type();
758
759 G1HRPrinter* hr_printer() { return &_hr_printer; }
760
761 // Frees a non-humongous region by initializing its contents and
762 // adding it to the free list that's passed as a parameter (this is
763 // usually a local list which will be appended to the master free
764 // list later). The used bytes of freed regions are accumulated in
765 // pre_used. If par is true, the region's RSet will not be freed
766 // up. The assumption is that this will be done later.
767 // The locked parameter indicates if the caller has already taken
768 // care of proper synchronization. This may allow some optimizations.
769 void free_region(HeapRegion* hr,
770 FreeRegionList* free_list,
771 bool par,
772 bool locked = false);
773
774 // Frees a humongous region by collapsing it into individual regions
775 // and calling free_region() for each of them. The freed regions
776 // will be added to the free list that's passed as a parameter (this
777 // is usually a local list which will be appended to the master free
778 // list later). The used bytes of freed regions are accumulated in
779 // pre_used. If par is true, the region's RSet will not be freed
780 // up. The assumption is that this will be done later.
781 void free_humongous_region(HeapRegion* hr,
782 FreeRegionList* free_list,
783 bool par);
784 protected:
785
786 // Shrink the garbage-first heap by at most the given size (in bytes!).
787 // (Rounds down to a HeapRegion boundary.)
788 virtual void shrink(size_t expand_bytes);
789 void shrink_helper(size_t expand_bytes);
790
791 #if TASKQUEUE_STATS
792 static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
793 void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
794 void reset_taskqueue_stats();
795 #endif // TASKQUEUE_STATS
796
797 // Schedule the VM operation that will do an evacuation pause to
798 // satisfy an allocation request of word_size. *succeeded will
799 // return whether the VM operation was successful (it did do an
800 // evacuation pause) or not (another thread beat us to it or the GC
801 // locker was active). Given that we should not be holding the
802 // Heap_lock when we enter this method, we will pass the
803 // gc_count_before (i.e., total_collections()) as a parameter since
804 // it has to be read while holding the Heap_lock. Currently, both
805 // methods that call do_collection_pause() release the Heap_lock
806 // before the call, so it's easy to read gc_count_before just before.
807 HeapWord* do_collection_pause(size_t word_size,
808 unsigned int gc_count_before,
809 bool* succeeded,
810 GCCause::Cause gc_cause);
811
812 // The guts of the incremental collection pause, executed by the vm
813 // thread. It returns false if it is unable to do the collection due
814 // to the GC locker being active, true otherwise
815 bool do_collection_pause_at_safepoint(double target_pause_time_ms);
816
817 // Actually do the work of evacuating the collection set.
818 void evacuate_collection_set(EvacuationInfo& evacuation_info);
819
820 // The g1 remembered set of the heap.
821 G1RemSet* _g1_rem_set;
822
823 // A set of cards that cover the objects for which the Rsets should be updated
824 // concurrently after the collection.
825 DirtyCardQueueSet _dirty_card_queue_set;
826
827 // The closure used to refine a single card.
828 RefineCardTableEntryClosure* _refine_cte_cl;
829
830 // A function to check the consistency of dirty card logs.
831 void check_ct_logs_at_safepoint();
832
833 // A DirtyCardQueueSet that is used to hold cards that contain
834 // references into the current collection set. This is used to
835 // update the remembered sets of the regions in the collection
836 // set in the event of an evacuation failure.
837 DirtyCardQueueSet _into_cset_dirty_card_queue_set;
838
839 // After a collection pause, make the regions in the CS into free
840 // regions.
841 void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info);
842
843 // Abandon the current collection set without recording policy
844 // statistics or updating free lists.
845 void abandon_collection_set(HeapRegion* cs_head);
846
847 // Applies "scan_non_heap_roots" to roots outside the heap,
848 // "scan_rs" to roots inside the heap (having done "set_region" to
849 // indicate the region in which the root resides),
850 // and does "scan_metadata" If "scan_rs" is
851 // NULL, then this step is skipped. The "worker_i"
852 // param is for use with parallel roots processing, and should be
853 // the "i" of the calling parallel worker thread's work(i) function.
854 // In the sequential case this param will be ignored.
855 void g1_process_strong_roots(bool is_scavenging,
856 ScanningOption so,
857 OopClosure* scan_non_heap_roots,
858 OopsInHeapRegionClosure* scan_rs,
859 G1KlassScanClosure* scan_klasses,
860 int worker_i);
861
862 // Notifies all the necessary spaces that the committed space has
863 // been updated (either expanded or shrunk). It should be called
864 // after _g1_storage is updated.
865 void update_committed_space(HeapWord* old_end, HeapWord* new_end);
866
867 // The concurrent marker (and the thread it runs in.)
868 ConcurrentMark* _cm;
869 ConcurrentMarkThread* _cmThread;
870 bool _mark_in_progress;
871
872 // The concurrent refiner.
873 ConcurrentG1Refine* _cg1r;
874
875 // The parallel task queues
876 RefToScanQueueSet *_task_queues;
877
878 // True iff a evacuation has failed in the current collection.
879 bool _evacuation_failed;
880
881 EvacuationFailedInfo* _evacuation_failed_info_array;
882
883 // Failed evacuations cause some logical from-space objects to have
884 // forwarding pointers to themselves. Reset them.
885 void remove_self_forwarding_pointers();
886
887 // Together, these store an object with a preserved mark, and its mark value.
888 Stack<oop, mtGC> _objs_with_preserved_marks;
889 Stack<markOop, mtGC> _preserved_marks_of_objs;
890
891 // Preserve the mark of "obj", if necessary, in preparation for its mark
892 // word being overwritten with a self-forwarding-pointer.
893 void preserve_mark_if_necessary(oop obj, markOop m);
894
895 // The stack of evac-failure objects left to be scanned.
896 GrowableArray<oop>* _evac_failure_scan_stack;
897 // The closure to apply to evac-failure objects.
898
899 OopsInHeapRegionClosure* _evac_failure_closure;
900 // Set the field above.
901 void
902 set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
903 _evac_failure_closure = evac_failure_closure;
904 }
905
906 // Push "obj" on the scan stack.
907 void push_on_evac_failure_scan_stack(oop obj);
908 // Process scan stack entries until the stack is empty.
909 void drain_evac_failure_scan_stack();
910 // True iff an invocation of "drain_scan_stack" is in progress; to
911 // prevent unnecessary recursion.
912 bool _drain_in_progress;
913
914 // Do any necessary initialization for evacuation-failure handling.
915 // "cl" is the closure that will be used to process evac-failure
916 // objects.
917 void init_for_evac_failure(OopsInHeapRegionClosure* cl);
918 // Do any necessary cleanup for evacuation-failure handling data
919 // structures.
920 void finalize_for_evac_failure();
921
922 // An attempt to evacuate "obj" has failed; take necessary steps.
923 oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj);
924 void handle_evacuation_failure_common(oop obj, markOop m);
925
926 #ifndef PRODUCT
927 // Support for forcing evacuation failures. Analogous to
928 // PromotionFailureALot for the other collectors.
929
930 // Records whether G1EvacuationFailureALot should be in effect
931 // for the current GC
932 bool _evacuation_failure_alot_for_current_gc;
933
934 // Used to record the GC number for interval checking when
935 // determining whether G1EvaucationFailureALot is in effect
936 // for the current GC.
937 size_t _evacuation_failure_alot_gc_number;
938
939 // Count of the number of evacuations between failures.
940 volatile size_t _evacuation_failure_alot_count;
941
942 // Set whether G1EvacuationFailureALot should be in effect
943 // for the current GC (based upon the type of GC and which
944 // command line flags are set);
945 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
946 bool during_initial_mark,
947 bool during_marking);
948
949 inline void set_evacuation_failure_alot_for_current_gc();
950
951 // Return true if it's time to cause an evacuation failure.
952 inline bool evacuation_should_fail();
953
954 // Reset the G1EvacuationFailureALot counters. Should be called at
955 // the end of an evacuation pause in which an evacuation failure occurred.
956 inline void reset_evacuation_should_fail();
957 #endif // !PRODUCT
958
959 // ("Weak") Reference processing support.
960 //
961 // G1 has 2 instances of the reference processor class. One
962 // (_ref_processor_cm) handles reference object discovery
963 // and subsequent processing during concurrent marking cycles.
964 //
965 // The other (_ref_processor_stw) handles reference object
966 // discovery and processing during full GCs and incremental
967 // evacuation pauses.
968 //
969 // During an incremental pause, reference discovery will be
970 // temporarily disabled for _ref_processor_cm and will be
971 // enabled for _ref_processor_stw. At the end of the evacuation
972 // pause references discovered by _ref_processor_stw will be
973 // processed and discovery will be disabled. The previous
974 // setting for reference object discovery for _ref_processor_cm
975 // will be re-instated.
976 //
977 // At the start of marking:
978 // * Discovery by the CM ref processor is verified to be inactive
979 // and it's discovered lists are empty.
980 // * Discovery by the CM ref processor is then enabled.
981 //
982 // At the end of marking:
983 // * Any references on the CM ref processor's discovered
984 // lists are processed (possibly MT).
985 //
986 // At the start of full GC we:
987 // * Disable discovery by the CM ref processor and
988 // empty CM ref processor's discovered lists
989 // (without processing any entries).
990 // * Verify that the STW ref processor is inactive and it's
991 // discovered lists are empty.
992 // * Temporarily set STW ref processor discovery as single threaded.
993 // * Temporarily clear the STW ref processor's _is_alive_non_header
994 // field.
995 // * Finally enable discovery by the STW ref processor.
996 //
997 // The STW ref processor is used to record any discovered
998 // references during the full GC.
999 //
1000 // At the end of a full GC we:
1001 // * Enqueue any reference objects discovered by the STW ref processor
1002 // that have non-live referents. This has the side-effect of
1003 // making the STW ref processor inactive by disabling discovery.
1004 // * Verify that the CM ref processor is still inactive
1005 // and no references have been placed on it's discovered
1006 // lists (also checked as a precondition during initial marking).
1007
1008 // The (stw) reference processor...
1009 ReferenceProcessor* _ref_processor_stw;
1010
1011 STWGCTimer* _gc_timer_stw;
1012 ConcurrentGCTimer* _gc_timer_cm;
1013
1014 G1OldTracer* _gc_tracer_cm;
1015 G1NewTracer* _gc_tracer_stw;
1016
1017 // During reference object discovery, the _is_alive_non_header
1018 // closure (if non-null) is applied to the referent object to
1019 // determine whether the referent is live. If so then the
1020 // reference object does not need to be 'discovered' and can
1021 // be treated as a regular oop. This has the benefit of reducing
1022 // the number of 'discovered' reference objects that need to
1023 // be processed.
1024 //
1025 // Instance of the is_alive closure for embedding into the
1026 // STW reference processor as the _is_alive_non_header field.
1027 // Supplying a value for the _is_alive_non_header field is
1028 // optional but doing so prevents unnecessary additions to
1029 // the discovered lists during reference discovery.
1030 G1STWIsAliveClosure _is_alive_closure_stw;
1031
1032 // The (concurrent marking) reference processor...
1033 ReferenceProcessor* _ref_processor_cm;
1034
1035 // Instance of the concurrent mark is_alive closure for embedding
1036 // into the Concurrent Marking reference processor as the
1037 // _is_alive_non_header field. Supplying a value for the
1038 // _is_alive_non_header field is optional but doing so prevents
1039 // unnecessary additions to the discovered lists during reference
1040 // discovery.
1041 G1CMIsAliveClosure _is_alive_closure_cm;
1042
1043 // Cache used by G1CollectedHeap::start_cset_region_for_worker().
1044 HeapRegion** _worker_cset_start_region;
1045
1046 // Time stamp to validate the regions recorded in the cache
1047 // used by G1CollectedHeap::start_cset_region_for_worker().
1048 // The heap region entry for a given worker is valid iff
1049 // the associated time stamp value matches the current value
1050 // of G1CollectedHeap::_gc_time_stamp.
1051 unsigned int* _worker_cset_start_region_time_stamp;
1052
1053 enum G1H_process_strong_roots_tasks {
1054 G1H_PS_filter_satb_buffers,
1055 G1H_PS_refProcessor_oops_do,
1056 // Leave this one last.
1057 G1H_PS_NumElements
1058 };
1059
1060 SubTasksDone* _process_strong_tasks;
1061
1062 volatile bool _free_regions_coming;
1063
1064 public:
1065
1066 SubTasksDone* process_strong_tasks() { return _process_strong_tasks; }
1067
1068 void set_refine_cte_cl_concurrency(bool concurrent);
1069
1070 RefToScanQueue *task_queue(int i) const;
1071
1072 // A set of cards where updates happened during the GC
1073 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
1074
1075 // A DirtyCardQueueSet that is used to hold cards that contain
1076 // references into the current collection set. This is used to
1077 // update the remembered sets of the regions in the collection
1078 // set in the event of an evacuation failure.
1079 DirtyCardQueueSet& into_cset_dirty_card_queue_set()
1080 { return _into_cset_dirty_card_queue_set; }
1081
1082 // Create a G1CollectedHeap with the specified policy.
1083 // Must call the initialize method afterwards.
1084 // May not return if something goes wrong.
1085 G1CollectedHeap(G1CollectorPolicy* policy);
1086
1087 // Initialize the G1CollectedHeap to have the initial and
1088 // maximum sizes and remembered and barrier sets
1089 // specified by the policy object.
1090 jint initialize();
1091
1092 // Return the (conservative) maximum heap alignment for any G1 heap
1093 static size_t conservative_max_heap_alignment();
1094
1095 // Initialize weak reference processing.
1096 virtual void ref_processing_init();
1097
1098 void set_par_threads(uint t) {
1099 SharedHeap::set_par_threads(t);
1100 // Done in SharedHeap but oddly there are
1101 // two _process_strong_tasks's in a G1CollectedHeap
1102 // so do it here too.
1103 _process_strong_tasks->set_n_threads(t);
1104 }
1105
1106 // Set _n_par_threads according to a policy TBD.
1107 void set_par_threads();
1108
1109 void set_n_termination(int t) {
1110 _process_strong_tasks->set_n_threads(t);
1111 }
1112
1113 virtual CollectedHeap::Name kind() const {
1114 return CollectedHeap::G1CollectedHeap;
1115 }
1116
1117 // The current policy object for the collector.
1118 G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1119
1120 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); }
1121
1122 // Adaptive size policy. No such thing for g1.
1123 virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1124
1125 // The rem set and barrier set.
1126 G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1127
1128 unsigned get_gc_time_stamp() {
1129 return _gc_time_stamp;
1130 }
1131
1132 void reset_gc_time_stamp() {
1133 _gc_time_stamp = 0;
1134 OrderAccess::fence();
1135 // Clear the cached CSet starting regions and time stamps.
1136 // Their validity is dependent on the GC timestamp.
1137 clear_cset_start_regions();
1138 }
1139
1140 void check_gc_time_stamps() PRODUCT_RETURN;
1141
1142 void increment_gc_time_stamp() {
1143 ++_gc_time_stamp;
1144 OrderAccess::fence();
1145 }
1146
1147 // Reset the given region's GC timestamp. If it's starts humongous,
1148 // also reset the GC timestamp of its corresponding
1149 // continues humongous regions too.
1150 void reset_gc_time_stamps(HeapRegion* hr);
1151
1152 void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1153 DirtyCardQueue* into_cset_dcq,
1154 bool concurrent, int worker_i);
1155
1156 // The shared block offset table array.
1157 G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1158
1159 // Reference Processing accessors
1160
1161 // The STW reference processor....
1162 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1163
1164 // The Concurrent Marking reference processor...
1165 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1166
1167 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1168 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1169
1170 virtual size_t capacity() const;
1171 virtual size_t used() const;
1172 // This should be called when we're not holding the heap lock. The
1173 // result might be a bit inaccurate.
1174 size_t used_unlocked() const;
1175 size_t recalculate_used() const;
1176
1177 // These virtual functions do the actual allocation.
1178 // Some heaps may offer a contiguous region for shared non-blocking
1179 // allocation, via inlined code (by exporting the address of the top and
1180 // end fields defining the extent of the contiguous allocation region.)
1181 // But G1CollectedHeap doesn't yet support this.
1182
1183 virtual bool is_maximal_no_gc() const {
1184 return _g1_storage.uncommitted_size() == 0;
1185 }
1186
1187 // The total number of regions in the heap.
1188 uint n_regions() { return _hrs.length(); }
1189
1190 // The max number of regions in the heap.
1191 uint max_regions() { return _hrs.max_length(); }
1192
1193 // The number of regions that are completely free.
1194 uint free_regions() { return _free_list.length(); }
1195
1196 // The number of regions that are not completely free.
1197 uint used_regions() { return n_regions() - free_regions(); }
1198
1199 // The number of regions available for "regular" expansion.
1200 uint expansion_regions() { return _expansion_regions; }
1201
1202 // Factory method for HeapRegion instances. It will return NULL if
1203 // the allocation fails.
1204 HeapRegion* new_heap_region(uint hrs_index, HeapWord* bottom);
1205
1206 void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1207 void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1208 void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1209 void verify_dirty_young_regions() PRODUCT_RETURN;
1210
1211 // verify_region_sets() performs verification over the region
1212 // lists. It will be compiled in the product code to be used when
1213 // necessary (i.e., during heap verification).
1214 void verify_region_sets();
1215
1216 // verify_region_sets_optional() is planted in the code for
1217 // list verification in non-product builds (and it can be enabled in
1218 // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1).
1219 #if HEAP_REGION_SET_FORCE_VERIFY
1220 void verify_region_sets_optional() {
1221 verify_region_sets();
1222 }
1223 #else // HEAP_REGION_SET_FORCE_VERIFY
1224 void verify_region_sets_optional() { }
1225 #endif // HEAP_REGION_SET_FORCE_VERIFY
1226
1227 #ifdef ASSERT
1228 bool is_on_master_free_list(HeapRegion* hr) {
1229 return hr->containing_set() == &_free_list;
1230 }
1231 #endif // ASSERT
1232
1233 // Wrapper for the region list operations that can be called from
1234 // methods outside this class.
1235
1236 void secondary_free_list_add(FreeRegionList* list) {
1237 _secondary_free_list.add_ordered(list);
1238 }
1239
1240 void append_secondary_free_list() {
1241 _free_list.add_ordered(&_secondary_free_list);
1242 }
1243
1244 void append_secondary_free_list_if_not_empty_with_lock() {
1245 // If the secondary free list looks empty there's no reason to
1246 // take the lock and then try to append it.
1247 if (!_secondary_free_list.is_empty()) {
1248 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1249 append_secondary_free_list();
1250 }
1251 }
1252
1253 void old_set_remove(HeapRegion* hr) {
1254 _old_set.remove(hr);
1255 }
1256
1257 size_t non_young_capacity_bytes() {
1258 return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1259 }
1260
1261 void set_free_regions_coming();
1262 void reset_free_regions_coming();
1263 bool free_regions_coming() { return _free_regions_coming; }
1264 void wait_while_free_regions_coming();
1265
1266 // Determine whether the given region is one that we are using as an
1267 // old GC alloc region.
1268 bool is_old_gc_alloc_region(HeapRegion* hr) {
1269 return hr == _retained_old_gc_alloc_region;
1270 }
1271
1272 // Perform a collection of the heap; intended for use in implementing
1273 // "System.gc". This probably implies as full a collection as the
1274 // "CollectedHeap" supports.
1275 virtual void collect(GCCause::Cause cause);
1276
1277 // The same as above but assume that the caller holds the Heap_lock.
1278 void collect_locked(GCCause::Cause cause);
1279
1280 // True iff an evacuation has failed in the most-recent collection.
1281 bool evacuation_failed() { return _evacuation_failed; }
1282
1283 void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed);
1284 void prepend_to_freelist(FreeRegionList* list);
1285 void decrement_summary_bytes(size_t bytes);
1286
1287 // Returns "TRUE" iff "p" points into the committed areas of the heap.
1288 virtual bool is_in(const void* p) const;
1289
1290 // Return "TRUE" iff the given object address is within the collection
1291 // set.
1292 inline bool obj_in_cs(oop obj);
1293
1294 // Return "TRUE" iff the given object address is in the reserved
1295 // region of g1.
1296 bool is_in_g1_reserved(const void* p) const {
1297 return _g1_reserved.contains(p);
1298 }
1299
1300 // Returns a MemRegion that corresponds to the space that has been
1301 // reserved for the heap
1302 MemRegion g1_reserved() {
1303 return _g1_reserved;
1304 }
1305
1306 // Returns a MemRegion that corresponds to the space that has been
1307 // committed in the heap
1308 MemRegion g1_committed() {
1309 return _g1_committed;
1310 }
1311
1312 virtual bool is_in_closed_subset(const void* p) const;
1313
1314 G1SATBCardTableModRefBS* g1_barrier_set() {
1315 return (G1SATBCardTableModRefBS*) barrier_set();
1316 }
1317
1318 // This resets the card table to all zeros. It is used after
1319 // a collection pause which used the card table to claim cards.
1320 void cleanUpCardTable();
1321
1322 // Iteration functions.
1323
1324 // Iterate over all the ref-containing fields of all objects, calling
1325 // "cl.do_oop" on each.
1326 virtual void oop_iterate(ExtendedOopClosure* cl);
1327
1328 // Same as above, restricted to a memory region.
1329 void oop_iterate(MemRegion mr, ExtendedOopClosure* cl);
1330
1331 // Iterate over all objects, calling "cl.do_object" on each.
1332 virtual void object_iterate(ObjectClosure* cl);
1333
1334 virtual void safe_object_iterate(ObjectClosure* cl) {
1335 object_iterate(cl);
1336 }
1337
1338 // Iterate over all spaces in use in the heap, in ascending address order.
1339 virtual void space_iterate(SpaceClosure* cl);
1340
1341 // Iterate over heap regions, in address order, terminating the
1342 // iteration early if the "doHeapRegion" method returns "true".
1343 void heap_region_iterate(HeapRegionClosure* blk) const;
1344
1345 // Return the region with the given index. It assumes the index is valid.
1346 HeapRegion* region_at(uint index) const { return _hrs.at(index); }
1347
1348 // Divide the heap region sequence into "chunks" of some size (the number
1349 // of regions divided by the number of parallel threads times some
1350 // overpartition factor, currently 4). Assumes that this will be called
1351 // in parallel by ParallelGCThreads worker threads with distinct worker
1352 // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel
1353 // calls will use the same "claim_value", and that that claim value is
1354 // different from the claim_value of any heap region before the start of
1355 // the iteration. Applies "blk->doHeapRegion" to each of the regions, by
1356 // attempting to claim the first region in each chunk, and, if
1357 // successful, applying the closure to each region in the chunk (and
1358 // setting the claim value of the second and subsequent regions of the
1359 // chunk.) For now requires that "doHeapRegion" always returns "false",
1360 // i.e., that a closure never attempt to abort a traversal.
1361 void heap_region_par_iterate_chunked(HeapRegionClosure* blk,
1362 uint worker,
1363 uint no_of_par_workers,
1364 jint claim_value);
1365
1366 // It resets all the region claim values to the default.
1367 void reset_heap_region_claim_values();
1368
1369 // Resets the claim values of regions in the current
1370 // collection set to the default.
1371 void reset_cset_heap_region_claim_values();
1372
1373 #ifdef ASSERT
1374 bool check_heap_region_claim_values(jint claim_value);
1375
1376 // Same as the routine above but only checks regions in the
1377 // current collection set.
1378 bool check_cset_heap_region_claim_values(jint claim_value);
1379 #endif // ASSERT
1380
1381 // Clear the cached cset start regions and (more importantly)
1382 // the time stamps. Called when we reset the GC time stamp.
1383 void clear_cset_start_regions();
1384
1385 // Given the id of a worker, obtain or calculate a suitable
1386 // starting region for iterating over the current collection set.
1387 HeapRegion* start_cset_region_for_worker(int worker_i);
1388
1389 // This is a convenience method that is used by the
1390 // HeapRegionIterator classes to calculate the starting region for
1391 // each worker so that they do not all start from the same region.
1392 HeapRegion* start_region_for_worker(uint worker_i, uint no_of_par_workers);
1393
1394 // Iterate over the regions (if any) in the current collection set.
1395 void collection_set_iterate(HeapRegionClosure* blk);
1396
1397 // As above but starting from region r
1398 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1399
1400 // Returns the first (lowest address) compactible space in the heap.
1401 virtual CompactibleSpace* first_compactible_space();
1402
1403 // A CollectedHeap will contain some number of spaces. This finds the
1404 // space containing a given address, or else returns NULL.
1405 virtual Space* space_containing(const void* addr) const;
1406
1407 // A G1CollectedHeap will contain some number of heap regions. This
1408 // finds the region containing a given address, or else returns NULL.
1409 template <class T>
1410 inline HeapRegion* heap_region_containing(const T addr) const;
1411
1412 // Like the above, but requires "addr" to be in the heap (to avoid a
1413 // null-check), and unlike the above, may return an continuing humongous
1414 // region.
1415 template <class T>
1416 inline HeapRegion* heap_region_containing_raw(const T addr) const;
1417
1418 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1419 // each address in the (reserved) heap is a member of exactly
1420 // one block. The defining characteristic of a block is that it is
1421 // possible to find its size, and thus to progress forward to the next
1422 // block. (Blocks may be of different sizes.) Thus, blocks may
1423 // represent Java objects, or they might be free blocks in a
1424 // free-list-based heap (or subheap), as long as the two kinds are
1425 // distinguishable and the size of each is determinable.
1426
1427 // Returns the address of the start of the "block" that contains the
1428 // address "addr". We say "blocks" instead of "object" since some heaps
1429 // may not pack objects densely; a chunk may either be an object or a
1430 // non-object.
1431 virtual HeapWord* block_start(const void* addr) const;
1432
1433 // Requires "addr" to be the start of a chunk, and returns its size.
1434 // "addr + size" is required to be the start of a new chunk, or the end
1435 // of the active area of the heap.
1436 virtual size_t block_size(const HeapWord* addr) const;
1437
1438 // Requires "addr" to be the start of a block, and returns "TRUE" iff
1439 // the block is an object.
1440 virtual bool block_is_obj(const HeapWord* addr) const;
1441
1442 // Does this heap support heap inspection? (+PrintClassHistogram)
1443 virtual bool supports_heap_inspection() const { return true; }
1444
1445 // Section on thread-local allocation buffers (TLABs)
1446 // See CollectedHeap for semantics.
1447
1448 bool supports_tlab_allocation() const;
1449 size_t tlab_capacity(Thread* ignored) const;
1450 size_t tlab_used(Thread* ignored) const;
1451 size_t max_tlab_size() const;
1452 size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1453
1454 // Can a compiler initialize a new object without store barriers?
1455 // This permission only extends from the creation of a new object
1456 // via a TLAB up to the first subsequent safepoint. If such permission
1457 // is granted for this heap type, the compiler promises to call
1458 // defer_store_barrier() below on any slow path allocation of
1459 // a new object for which such initializing store barriers will
1460 // have been elided. G1, like CMS, allows this, but should be
1461 // ready to provide a compensating write barrier as necessary
1462 // if that storage came out of a non-young region. The efficiency
1463 // of this implementation depends crucially on being able to
1464 // answer very efficiently in constant time whether a piece of
1465 // storage in the heap comes from a young region or not.
1466 // See ReduceInitialCardMarks.
1467 virtual bool can_elide_tlab_store_barriers() const {
1468 return true;
1469 }
1470
1471 virtual bool card_mark_must_follow_store() const {
1472 return true;
1473 }
1474
1475 bool is_in_young(const oop obj) {
1476 HeapRegion* hr = heap_region_containing(obj);
1477 return hr != NULL && hr->is_young();
1478 }
1479
1480 #ifdef ASSERT
1481 virtual bool is_in_partial_collection(const void* p);
1482 #endif
1483
1484 virtual bool is_scavengable(const void* addr);
1485
1486 // We don't need barriers for initializing stores to objects
1487 // in the young gen: for the SATB pre-barrier, there is no
1488 // pre-value that needs to be remembered; for the remembered-set
1489 // update logging post-barrier, we don't maintain remembered set
1490 // information for young gen objects.
1491 virtual bool can_elide_initializing_store_barrier(oop new_obj) {
1492 return is_in_young(new_obj);
1493 }
1494
1495 // Returns "true" iff the given word_size is "very large".
1496 static bool isHumongous(size_t word_size) {
1497 // Note this has to be strictly greater-than as the TLABs
1498 // are capped at the humongous threshold and we want to
1499 // ensure that we don't try to allocate a TLAB as
1500 // humongous and that we don't allocate a humongous
1501 // object in a TLAB.
1502 return word_size > _humongous_object_threshold_in_words;
1503 }
1504
1505 // Update mod union table with the set of dirty cards.
1506 void updateModUnion();
1507
1508 // Set the mod union bits corresponding to the given memRegion. Note
1509 // that this is always a safe operation, since it doesn't clear any
1510 // bits.
1511 void markModUnionRange(MemRegion mr);
1512
1513 // Records the fact that a marking phase is no longer in progress.
1514 void set_marking_complete() {
1515 _mark_in_progress = false;
1516 }
1517 void set_marking_started() {
1518 _mark_in_progress = true;
1519 }
1520 bool mark_in_progress() {
1521 return _mark_in_progress;
1522 }
1523
1524 // Print the maximum heap capacity.
1525 virtual size_t max_capacity() const;
1526
1527 virtual jlong millis_since_last_gc();
1528
1529
1530 // Convenience function to be used in situations where the heap type can be
1531 // asserted to be this type.
1532 static G1CollectedHeap* heap();
1533
1534 void set_region_short_lived_locked(HeapRegion* hr);
1535 // add appropriate methods for any other surv rate groups
1536
1537 YoungList* young_list() const { return _young_list; }
1538
1539 // debugging
1540 bool check_young_list_well_formed() {
1541 return _young_list->check_list_well_formed();
1542 }
1543
1544 bool check_young_list_empty(bool check_heap,
1545 bool check_sample = true);
1546
1547 // *** Stuff related to concurrent marking. It's not clear to me that so
1548 // many of these need to be public.
1549
1550 // The functions below are helper functions that a subclass of
1551 // "CollectedHeap" can use in the implementation of its virtual
1552 // functions.
1553 // This performs a concurrent marking of the live objects in a
1554 // bitmap off to the side.
1555 void doConcurrentMark();
1556
1557 bool isMarkedPrev(oop obj) const;
1558 bool isMarkedNext(oop obj) const;
1559
1560 // Determine if an object is dead, given the object and also
1561 // the region to which the object belongs. An object is dead
1562 // iff a) it was not allocated since the last mark and b) it
1563 // is not marked.
1564
1565 bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1566 return
1567 !hr->obj_allocated_since_prev_marking(obj) &&
1568 !isMarkedPrev(obj);
1569 }
1570
1571 // This function returns true when an object has been
1572 // around since the previous marking and hasn't yet
1573 // been marked during this marking.
1574
1575 bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1576 return
1577 !hr->obj_allocated_since_next_marking(obj) &&
1578 !isMarkedNext(obj);
1579 }
1580
1581 // Determine if an object is dead, given only the object itself.
1582 // This will find the region to which the object belongs and
1583 // then call the region version of the same function.
1584
1585 // Added if it is NULL it isn't dead.
1586
1587 bool is_obj_dead(const oop obj) const {
1588 const HeapRegion* hr = heap_region_containing(obj);
1589 if (hr == NULL) {
1590 if (obj == NULL) return false;
1591 else return true;
1592 }
1593 else return is_obj_dead(obj, hr);
1594 }
1595
1596 bool is_obj_ill(const oop obj) const {
1597 const HeapRegion* hr = heap_region_containing(obj);
1598 if (hr == NULL) {
1599 if (obj == NULL) return false;
1600 else return true;
1601 }
1602 else return is_obj_ill(obj, hr);
1603 }
1604
1605 bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1606 HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1607 bool is_marked(oop obj, VerifyOption vo);
1608 const char* top_at_mark_start_str(VerifyOption vo);
1609
1610 ConcurrentMark* concurrent_mark() const { return _cm; }
1611
1612 // Refinement
1613
1614 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1615
1616 // The dirty cards region list is used to record a subset of regions
1617 // whose cards need clearing. The list if populated during the
1618 // remembered set scanning and drained during the card table
1619 // cleanup. Although the methods are reentrant, population/draining
1620 // phases must not overlap. For synchronization purposes the last
1621 // element on the list points to itself.
1622 HeapRegion* _dirty_cards_region_list;
1623 void push_dirty_cards_region(HeapRegion* hr);
1624 HeapRegion* pop_dirty_cards_region();
1625
1626 // Optimized nmethod scanning support routines
1627
1628 // Register the given nmethod with the G1 heap.
1629 virtual void register_nmethod(nmethod* nm);
1630
1631 // Unregister the given nmethod from the G1 heap.
1632 virtual void unregister_nmethod(nmethod* nm);
1633
1634 // Migrate the nmethods in the code root lists of the regions
1635 // in the collection set to regions in to-space. In the event
1636 // of an evacuation failure, nmethods that reference objects
1637 // that were not successfully evacuated are not migrated.
1638 void migrate_strong_code_roots();
1639
1640 // Free up superfluous code root memory.
1641 void purge_code_root_memory();
1642
1643 // During an initial mark pause, mark all the code roots that
1644 // point into regions *not* in the collection set.
1645 void mark_strong_code_roots(uint worker_id);
1646
1647 // Rebuild the strong code root lists for each region
1648 // after a full GC.
1649 void rebuild_strong_code_roots();
1650
1651 // Delete entries for dead interned string and clean up unreferenced symbols
1652 // in symbol table, possibly in parallel.
1653 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1654
1655 // Redirty logged cards in the refinement queue.
1656 void redirty_logged_cards();
1657 // Verification
1658
1659 // The following is just to alert the verification code
1660 // that a full collection has occurred and that the
1661 // remembered sets are no longer up to date.
1662 bool _full_collection;
1663 void set_full_collection() { _full_collection = true;}
1664 void clear_full_collection() {_full_collection = false;}
1665 bool full_collection() {return _full_collection;}
1666
1667 // Perform any cleanup actions necessary before allowing a verification.
1668 virtual void prepare_for_verify();
1669
1670 // Perform verification.
1671
1672 // vo == UsePrevMarking -> use "prev" marking information,
1673 // vo == UseNextMarking -> use "next" marking information
1674 // vo == UseMarkWord -> use the mark word in the object header
1675 //
1676 // NOTE: Only the "prev" marking information is guaranteed to be
1677 // consistent most of the time, so most calls to this should use
1678 // vo == UsePrevMarking.
1679 // Currently, there is only one case where this is called with
1680 // vo == UseNextMarking, which is to verify the "next" marking
1681 // information at the end of remark.
1682 // Currently there is only one place where this is called with
1683 // vo == UseMarkWord, which is to verify the marking during a
1684 // full GC.
1685 void verify(bool silent, VerifyOption vo);
1686
1687 // Override; it uses the "prev" marking information
1688 virtual void verify(bool silent);
1689
1690 // The methods below are here for convenience and dispatch the
1691 // appropriate method depending on value of the given VerifyOption
1692 // parameter. The values for that parameter, and their meanings,
1693 // are the same as those above.
1694
1695 bool is_obj_dead_cond(const oop obj,
1696 const HeapRegion* hr,
1697 const VerifyOption vo) const {
1698 switch (vo) {
1699 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
1700 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
1701 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
1702 default: ShouldNotReachHere();
1703 }
1704 return false; // keep some compilers happy
1705 }
1706
1707 bool is_obj_dead_cond(const oop obj,
1708 const VerifyOption vo) const {
1709 switch (vo) {
1710 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
1711 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
1712 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
1713 default: ShouldNotReachHere();
1714 }
1715 return false; // keep some compilers happy
1716 }
1717
1718 // Printing
1719
1720 virtual void print_on(outputStream* st) const;
1721 virtual void print_extended_on(outputStream* st) const;
1722 virtual void print_on_error(outputStream* st) const;
1723
1724 virtual void print_gc_threads_on(outputStream* st) const;
1725 virtual void gc_threads_do(ThreadClosure* tc) const;
1726
1727 // Override
1728 void print_tracing_info() const;
1729
1730 // The following two methods are helpful for debugging RSet issues.
1731 void print_cset_rsets() PRODUCT_RETURN;
1732 void print_all_rsets() PRODUCT_RETURN;
1733
1734 public:
1735 void stop_conc_gc_threads();
1736
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
1751 void set_buf(HeapWord* buf) {
1752 ParGCAllocBuffer::set_buf(buf);
1753 _retired = false;
1754 }
1755
1756 void retire(bool end_of_gc, bool retain) {
1757 if (_retired)
1758 return;
1759 ParGCAllocBuffer::retire(end_of_gc, retain);
1760 _retired = true;
1761 }
1762 };
1763
1764 class G1ParScanThreadState : public StackObj {
1765 protected:
1766 G1CollectedHeap* _g1h;
1767 RefToScanQueue* _refs;
1768 DirtyCardQueue _dcq;
1769 G1SATBCardTableModRefBS* _ct_bs;
1770 G1RemSet* _g1_rem;
1771
1772 G1ParGCAllocBuffer _surviving_alloc_buffer;
1773 G1ParGCAllocBuffer _tenured_alloc_buffer;
1774 G1ParGCAllocBuffer* _alloc_buffers[GCAllocPurposeCount];
1775 ageTable _age_table;
1776
1777 G1ParScanClosure _scanner;
1778
1779 size_t _alloc_buffer_waste;
1780 size_t _undo_waste;
1781
1782 OopsInHeapRegionClosure* _evac_failure_cl;
1783
1784 int _hash_seed;
1785 uint _queue_num;
1786
1787 size_t _term_attempts;
1788
1789 double _start;
1790 double _start_strong_roots;
1791 double _strong_roots_time;
1792 double _start_term;
1793 double _term_time;
1794
1795 // Map from young-age-index (0 == not young, 1 is youngest) to
1796 // surviving words. base is what we get back from the malloc call
1797 size_t* _surviving_young_words_base;
1798 // this points into the array, as we use the first few entries for padding
1799 size_t* _surviving_young_words;
1800
1801 #define PADDING_ELEM_NUM (DEFAULT_CACHE_LINE_SIZE / sizeof(size_t))
1802
1803 void add_to_alloc_buffer_waste(size_t waste) { _alloc_buffer_waste += waste; }
1804
1805 void add_to_undo_waste(size_t waste) { _undo_waste += waste; }
1806
1807 DirtyCardQueue& dirty_card_queue() { return _dcq; }
1808 G1SATBCardTableModRefBS* ctbs() { return _ct_bs; }
1809
1810 template <class T> void immediate_rs_update(HeapRegion* from, T* p, int tid) {
1811 if (!from->is_survivor()) {
1812 _g1_rem->par_write_ref(from, p, tid);
1813 }
1814 }
1815
1816 template <class T> void deferred_rs_update(HeapRegion* from, T* p, int tid) {
1817 // If the new value of the field points to the same region or
1818 // is the to-space, we don't need to include it in the Rset updates.
1819 if (!from->is_in_reserved(oopDesc::load_decode_heap_oop(p)) && !from->is_survivor()) {
1820 size_t card_index = ctbs()->index_for(p);
1821 // If the card hasn't been added to the buffer, do it.
1822 if (ctbs()->mark_card_deferred(card_index)) {
1823 dirty_card_queue().enqueue((jbyte*)ctbs()->byte_for_index(card_index));
1824 }
1825 }
1826 }
1827
1828 public:
1829 G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num, ReferenceProcessor* rp);
1830
1831 ~G1ParScanThreadState() {
1832 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words_base, mtGC);
1833 }
1834
1835 RefToScanQueue* refs() { return _refs; }
1836 ageTable* age_table() { return &_age_table; }
1837
1838 G1ParGCAllocBuffer* alloc_buffer(GCAllocPurpose purpose) {
1839 return _alloc_buffers[purpose];
1840 }
1841
1842 size_t alloc_buffer_waste() const { return _alloc_buffer_waste; }
1843 size_t undo_waste() const { return _undo_waste; }
1844
1845 #ifdef ASSERT
1846 bool verify_ref(narrowOop* ref) const;
1847 bool verify_ref(oop* ref) const;
1848 bool verify_task(StarTask ref) const;
1849 #endif // ASSERT
1850
1851 template <class T> void push_on_queue(T* ref) {
1852 assert(verify_ref(ref), "sanity");
1853 refs()->push(ref);
1854 }
1855
1856 template <class T> void update_rs(HeapRegion* from, T* p, int tid) {
1857 if (G1DeferredRSUpdate) {
1858 deferred_rs_update(from, p, tid);
1859 } else {
1860 immediate_rs_update(from, p, tid);
1861 }
1862 }
1863
1864 HeapWord* allocate_slow(GCAllocPurpose purpose, size_t word_sz) {
1865 HeapWord* obj = NULL;
1866 size_t gclab_word_size = _g1h->desired_plab_sz(purpose);
1867 if (word_sz * 100 < gclab_word_size * ParallelGCBufferWastePct) {
1868 G1ParGCAllocBuffer* alloc_buf = alloc_buffer(purpose);
1869 add_to_alloc_buffer_waste(alloc_buf->words_remaining());
1870 alloc_buf->retire(false /* end_of_gc */, false /* retain */);
1871
1872 HeapWord* buf = _g1h->par_allocate_during_gc(purpose, gclab_word_size);
1873 if (buf == NULL) return NULL; // Let caller handle allocation failure.
1874 // Otherwise.
1875 alloc_buf->set_word_size(gclab_word_size);
1876 alloc_buf->set_buf(buf);
1877
1878 obj = alloc_buf->allocate(word_sz);
1879 assert(obj != NULL, "buffer was definitely big enough...");
1880 } else {
1881 obj = _g1h->par_allocate_during_gc(purpose, word_sz);
1882 }
1883 return obj;
1884 }
1885
1886 HeapWord* allocate(GCAllocPurpose purpose, size_t word_sz) {
1887 HeapWord* obj = alloc_buffer(purpose)->allocate(word_sz);
1888 if (obj != NULL) return obj;
1889 return allocate_slow(purpose, word_sz);
1890 }
1891
1892 void undo_allocation(GCAllocPurpose purpose, HeapWord* obj, size_t word_sz) {
1893 if (alloc_buffer(purpose)->contains(obj)) {
1894 assert(alloc_buffer(purpose)->contains(obj + word_sz - 1),
1895 "should contain whole object");
1896 alloc_buffer(purpose)->undo_allocation(obj, word_sz);
1897 } else {
1898 CollectedHeap::fill_with_object(obj, word_sz);
1899 add_to_undo_waste(word_sz);
1900 }
1901 }
1902
1903 void set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_cl) {
1904 _evac_failure_cl = evac_failure_cl;
1905 }
1906 OopsInHeapRegionClosure* evac_failure_closure() {
1907 return _evac_failure_cl;
1908 }
1909
1910 int* hash_seed() { return &_hash_seed; }
1911 uint queue_num() { return _queue_num; }
1912
1913 size_t term_attempts() const { return _term_attempts; }
1914 void note_term_attempt() { _term_attempts++; }
1915
1916 void start_strong_roots() {
1917 _start_strong_roots = os::elapsedTime();
1918 }
1919 void end_strong_roots() {
1920 _strong_roots_time += (os::elapsedTime() - _start_strong_roots);
1921 }
1922 double strong_roots_time() const { return _strong_roots_time; }
1923
1924 void start_term_time() {
1925 note_term_attempt();
1926 _start_term = os::elapsedTime();
1927 }
1928 void end_term_time() {
1929 _term_time += (os::elapsedTime() - _start_term);
1930 }
1931 double term_time() const { return _term_time; }
1932
1933 double elapsed_time() const {
1934 return os::elapsedTime() - _start;
1935 }
1936
1937 static void
1938 print_termination_stats_hdr(outputStream* const st = gclog_or_tty);
1939 void
1940 print_termination_stats(int i, outputStream* const st = gclog_or_tty) const;
1941
1942 size_t* surviving_young_words() {
1943 // We add on to hide entry 0 which accumulates surviving words for
1944 // age -1 regions (i.e. non-young ones)
1945 return _surviving_young_words;
1946 }
1947
1948 void retire_alloc_buffers() {
1949 for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
1950 size_t waste = _alloc_buffers[ap]->words_remaining();
1951 add_to_alloc_buffer_waste(waste);
1952 _alloc_buffers[ap]->flush_stats_and_retire(_g1h->stats_for_purpose((GCAllocPurpose)ap),
1953 true /* end_of_gc */,
1954 false /* retain */);
1955 }
1956 }
1957 private:
1958 #define G1_PARTIAL_ARRAY_MASK 0x2
1959
1960 inline bool has_partial_array_mask(oop* ref) const {
1961 return ((uintptr_t)ref & G1_PARTIAL_ARRAY_MASK) == G1_PARTIAL_ARRAY_MASK;
1962 }
1963
1964 // We never encode partial array oops as narrowOop*, so return false immediately.
1965 // This allows the compiler to create optimized code when popping references from
1966 // the work queue.
1967 inline bool has_partial_array_mask(narrowOop* ref) const {
1968 assert(((uintptr_t)ref & G1_PARTIAL_ARRAY_MASK) != G1_PARTIAL_ARRAY_MASK, "Partial array oop reference encoded as narrowOop*");
1969 return false;
1970 }
1971
1972 // Only implement set_partial_array_mask() for regular oops, not for narrowOops.
1973 // We always encode partial arrays as regular oop, to allow the
1974 // specialization for has_partial_array_mask() for narrowOops above.
1975 // This means that unintentional use of this method with narrowOops are caught
1976 // by the compiler.
1977 inline oop* set_partial_array_mask(oop obj) const {
1978 assert(((uintptr_t)(void *)obj & G1_PARTIAL_ARRAY_MASK) == 0, "Information loss!");
1979 return (oop*) ((uintptr_t)(void *)obj | G1_PARTIAL_ARRAY_MASK);
1980 }
1981
1982 inline oop clear_partial_array_mask(oop* ref) const {
1983 return cast_to_oop((intptr_t)ref & ~G1_PARTIAL_ARRAY_MASK);
1984 }
1985
1986 void do_oop_partial_array(oop* p) {
1987 assert(has_partial_array_mask(p), "invariant");
1988 oop from_obj = clear_partial_array_mask(p);
1989
1990 assert(Universe::heap()->is_in_reserved(from_obj), "must be in heap.");
1991 assert(from_obj->is_objArray(), "must be obj array");
1992 objArrayOop from_obj_array = objArrayOop(from_obj);
1993 // The from-space object contains the real length.
1994 int length = from_obj_array->length();
1995
1996 assert(from_obj->is_forwarded(), "must be forwarded");
1997 oop to_obj = from_obj->forwardee();
1998 assert(from_obj != to_obj, "should not be chunking self-forwarded objects");
1999 objArrayOop to_obj_array = objArrayOop(to_obj);
2000 // We keep track of the next start index in the length field of the
2001 // to-space object.
2002 int next_index = to_obj_array->length();
2003 assert(0 <= next_index && next_index < length,
2004 err_msg("invariant, next index: %d, length: %d", next_index, length));
2005
2006 int start = next_index;
2007 int end = length;
2008 int remainder = end - start;
2009 // We'll try not to push a range that's smaller than ParGCArrayScanChunk.
2010 if (remainder > 2 * ParGCArrayScanChunk) {
2011 end = start + ParGCArrayScanChunk;
2012 to_obj_array->set_length(end);
2013 // Push the remainder before we process the range in case another
2014 // worker has run out of things to do and can steal it.
2015 oop* from_obj_p = set_partial_array_mask(from_obj);
2016 push_on_queue(from_obj_p);
2017 } else {
2018 assert(length == end, "sanity");
2019 // We'll process the final range for this object. Restore the length
2020 // so that the heap remains parsable in case of evacuation failure.
2021 to_obj_array->set_length(end);
2022 }
2023 _scanner.set_region(_g1h->heap_region_containing_raw(to_obj));
2024 // Process indexes [start,end). It will also process the header
2025 // along with the first chunk (i.e., the chunk with start == 0).
2026 // Note that at this point the length field of to_obj_array is not
2027 // correct given that we are using it to keep track of the next
2028 // start index. oop_iterate_range() (thankfully!) ignores the length
2029 // field and only relies on the start / end parameters. It does
2030 // however return the size of the object which will be incorrect. So
2031 // we have to ignore it even if we wanted to use it.
2032 to_obj_array->oop_iterate_range(&_scanner, start, end);
2033 }
2034
2035 // This method is applied to the fields of the objects that have just been copied.
2036 template <class T> void do_oop_evac(T* p, HeapRegion* from) {
2037 assert(!oopDesc::is_null(oopDesc::load_decode_heap_oop(p)),
2038 "Reference should not be NULL here as such are never pushed to the task queue.");
2039 oop obj = oopDesc::load_decode_heap_oop_not_null(p);
2040
2041 // Although we never intentionally push references outside of the collection
2042 // set, due to (benign) races in the claim mechanism during RSet scanning more
2043 // than one thread might claim the same card. So the same card may be
2044 // processed multiple times. So redo this check.
2045 if (_g1h->in_cset_fast_test(obj)) {
2046 oop forwardee;
2047 if (obj->is_forwarded()) {
2048 forwardee = obj->forwardee();
2049 } else {
2050 forwardee = copy_to_survivor_space(obj);
2051 }
2052 assert(forwardee != NULL, "forwardee should not be NULL");
2053 oopDesc::encode_store_heap_oop(p, forwardee);
2054 }
2055
2056 assert(obj != NULL, "Must be");
2057 update_rs(from, p, queue_num());
2058 }
2059 public:
2060
2061 oop copy_to_survivor_space(oop const obj);
2062
2063 template <class T> void deal_with_reference(T* ref_to_scan) {
2064 if (!has_partial_array_mask(ref_to_scan)) {
2065 // Note: we can use "raw" versions of "region_containing" because
2066 // "obj_to_scan" is definitely in the heap, and is not in a
2067 // humongous region.
2068 HeapRegion* r = _g1h->heap_region_containing_raw(ref_to_scan);
2069 do_oop_evac(ref_to_scan, r);
2070 } else {
2071 do_oop_partial_array((oop*)ref_to_scan);
2072 }
2073 }
2074
2075 void deal_with_reference(StarTask ref) {
2076 assert(verify_task(ref), "sanity");
2077 if (ref.is_narrow()) {
2078 deal_with_reference((narrowOop*)ref);
2079 } else {
2080 deal_with_reference((oop*)ref);
2081 }
2082 }
2083
2084 public:
2085 void trim_queue();
2086 };
2087
2088 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP