1 /*
2 * Copyright (c) 2001, 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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24
25 #ifndef SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP
26 #define SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP
27
28 #include "gc/g1/evacuationInfo.hpp"
29 #include "gc/g1/g1AllocationContext.hpp"
30 #include "gc/g1/g1BiasedArray.hpp"
31 #include "gc/g1/g1CollectionSet.hpp"
32 #include "gc/g1/g1CollectorState.hpp"
33 #include "gc/g1/g1ConcurrentMark.hpp"
34 #include "gc/g1/g1EdenRegions.hpp"
35 #include "gc/g1/g1EvacFailure.hpp"
36 #include "gc/g1/g1EvacStats.hpp"
37 #include "gc/g1/g1HeapTransition.hpp"
38 #include "gc/g1/g1HeapVerifier.hpp"
39 #include "gc/g1/g1HRPrinter.hpp"
40 #include "gc/g1/g1InCSetState.hpp"
41 #include "gc/g1/g1MonitoringSupport.hpp"
42 #include "gc/g1/g1SATBCardTableModRefBS.hpp"
43 #include "gc/g1/g1SurvivorRegions.hpp"
44 #include "gc/g1/g1YCTypes.hpp"
45 #include "gc/g1/hSpaceCounters.hpp"
46 #include "gc/g1/heapRegionManager.hpp"
47 #include "gc/g1/heapRegionSet.hpp"
48 #include "gc/shared/barrierSet.hpp"
49 #include "gc/shared/collectedHeap.hpp"
50 #include "gc/shared/plab.hpp"
51 #include "gc/shared/preservedMarks.hpp"
52 #include "memory/memRegion.hpp"
53 #include "utilities/stack.hpp"
54
55 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
56 // It uses the "Garbage First" heap organization and algorithm, which
57 // may combine concurrent marking with parallel, incremental compaction of
58 // heap subsets that will yield large amounts of garbage.
59
60 // Forward declarations
61 class HeapRegion;
62 class HRRSCleanupTask;
63 class GenerationSpec;
64 class G1ParScanThreadState;
65 class G1ParScanThreadStateSet;
66 class G1KlassScanClosure;
67 class G1ParScanThreadState;
68 class ObjectClosure;
69 class SpaceClosure;
70 class CompactibleSpaceClosure;
71 class Space;
72 class G1CollectionSet;
73 class G1CollectorPolicy;
74 class G1Policy;
75 class G1HotCardCache;
76 class G1RemSet;
77 class HeapRegionRemSetIterator;
78 class G1ConcurrentMark;
79 class ConcurrentMarkThread;
80 class ConcurrentG1Refine;
81 class GenerationCounters;
82 class STWGCTimer;
83 class G1NewTracer;
84 class EvacuationFailedInfo;
85 class nmethod;
86 class Ticks;
87 class WorkGang;
88 class G1Allocator;
89 class G1ArchiveAllocator;
90 class G1FullGCScope;
91 class G1HeapVerifier;
92 class G1HeapSizingPolicy;
93 class G1HeapSummary;
94 class G1EvacSummary;
95
96 typedef OverflowTaskQueue<StarTask, mtGC> RefToScanQueue;
97 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
98
99 typedef int RegionIdx_t; // needs to hold [ 0..max_regions() )
100 typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion )
101
102 // The G1 STW is alive closure.
103 // An instance is embedded into the G1CH and used as the
104 // (optional) _is_alive_non_header closure in the STW
105 // reference processor. It is also extensively used during
106 // reference processing during STW evacuation pauses.
107 class G1STWIsAliveClosure: public BoolObjectClosure {
108 G1CollectedHeap* _g1;
109 public:
110 G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
111 bool do_object_b(oop p);
112 };
113
114 class G1RefineCardConcurrentlyClosure;
115
116 class G1RegionMappingChangedListener : public G1MappingChangedListener {
117 private:
118 void reset_from_card_cache(uint start_idx, size_t num_regions);
119 public:
120 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
121 };
122
123 class G1CollectedHeap : public CollectedHeap {
124 friend class G1FreeCollectionSetTask;
125 friend class VM_CollectForMetadataAllocation;
126 friend class VM_G1CollectForAllocation;
127 friend class VM_G1CollectFull;
128 friend class VM_G1IncCollectionPause;
129 friend class VMStructs;
130 friend class MutatorAllocRegion;
131 friend class G1GCAllocRegion;
132 friend class G1HeapVerifier;
133
134 // Closures used in implementation.
135 friend class G1ParScanThreadState;
136 friend class G1ParScanThreadStateSet;
137 friend class G1ParTask;
138 friend class G1PLABAllocator;
139 friend class G1PrepareCompactClosure;
140
141 // Other related classes.
142 friend class HeapRegionClaimerBase;
143
144 // Testing classes.
145 friend class G1CheckCSetFastTableClosure;
146
147 private:
148 WorkGang* _workers;
149 G1CollectorPolicy* _collector_policy;
150
151 static size_t _humongous_object_threshold_in_words;
152
153 // The secondary free list which contains regions that have been
154 // freed up during the cleanup process. This will be appended to
155 // the master free list when appropriate.
156 FreeRegionList _secondary_free_list;
157
158 // It keeps track of the old regions.
159 HeapRegionSet _old_set;
160
161 // It keeps track of the humongous regions.
162 HeapRegionSet _humongous_set;
163
164 void eagerly_reclaim_humongous_regions();
165 // Start a new incremental collection set for the next pause.
166 void start_new_collection_set();
167
168 // The number of regions we could create by expansion.
169 uint _expansion_regions;
170
171 // The block offset table for the G1 heap.
172 G1BlockOffsetTable* _bot;
173
174 // Tears down the region sets / lists so that they are empty and the
175 // regions on the heap do not belong to a region set / list. The
176 // only exception is the humongous set which we leave unaltered. If
177 // free_list_only is true, it will only tear down the master free
178 // list. It is called before a Full GC (free_list_only == false) or
179 // before heap shrinking (free_list_only == true).
180 void tear_down_region_sets(bool free_list_only);
181
182 // Rebuilds the region sets / lists so that they are repopulated to
183 // reflect the contents of the heap. The only exception is the
184 // humongous set which was not torn down in the first place. If
185 // free_list_only is true, it will only rebuild the master free
186 // list. It is called after a Full GC (free_list_only == false) or
187 // after heap shrinking (free_list_only == true).
188 void rebuild_region_sets(bool free_list_only);
189
190 // Callback for region mapping changed events.
191 G1RegionMappingChangedListener _listener;
192
193 // The sequence of all heap regions in the heap.
194 HeapRegionManager _hrm;
195
196 // Manages all allocations with regions except humongous object allocations.
197 G1Allocator* _allocator;
198
199 // Manages all heap verification.
200 G1HeapVerifier* _verifier;
201
202 // Outside of GC pauses, the number of bytes used in all regions other
203 // than the current allocation region(s).
204 size_t _summary_bytes_used;
205
206 void increase_used(size_t bytes);
207 void decrease_used(size_t bytes);
208
209 void set_used(size_t bytes);
210
211 // Class that handles archive allocation ranges.
212 G1ArchiveAllocator* _archive_allocator;
213
214 // Statistics for each allocation context
215 AllocationContextStats _allocation_context_stats;
216
217 // GC allocation statistics policy for survivors.
218 G1EvacStats _survivor_evac_stats;
219
220 // GC allocation statistics policy for tenured objects.
221 G1EvacStats _old_evac_stats;
222
223 // It specifies whether we should attempt to expand the heap after a
224 // region allocation failure. If heap expansion fails we set this to
225 // false so that we don't re-attempt the heap expansion (it's likely
226 // that subsequent expansion attempts will also fail if one fails).
227 // Currently, it is only consulted during GC and it's reset at the
228 // start of each GC.
229 bool _expand_heap_after_alloc_failure;
230
231 // Helper for monitoring and management support.
232 G1MonitoringSupport* _g1mm;
233
234 // Records whether the region at the given index is (still) a
235 // candidate for eager reclaim. Only valid for humongous start
236 // regions; other regions have unspecified values. Humongous start
237 // regions are initialized at start of collection pause, with
238 // candidates removed from the set as they are found reachable from
239 // roots or the young generation.
240 class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> {
241 protected:
242 bool default_value() const { return false; }
243 public:
244 void clear() { G1BiasedMappedArray<bool>::clear(); }
245 void set_candidate(uint region, bool value) {
246 set_by_index(region, value);
247 }
248 bool is_candidate(uint region) {
249 return get_by_index(region);
250 }
251 };
252
253 HumongousReclaimCandidates _humongous_reclaim_candidates;
254 // Stores whether during humongous object registration we found candidate regions.
255 // If not, we can skip a few steps.
256 bool _has_humongous_reclaim_candidates;
257
258 volatile uint _gc_time_stamp;
259
260 G1HRPrinter _hr_printer;
261
262 // It decides whether an explicit GC should start a concurrent cycle
263 // instead of doing a STW GC. Currently, a concurrent cycle is
264 // explicitly started if:
265 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
266 // (b) cause == _g1_humongous_allocation
267 // (c) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
268 // (d) cause == _dcmd_gc_run and +ExplicitGCInvokesConcurrent.
269 // (e) cause == _update_allocation_context_stats_inc
270 // (f) cause == _wb_conc_mark
271 bool should_do_concurrent_full_gc(GCCause::Cause cause);
272
273 // indicates whether we are in young or mixed GC mode
274 G1CollectorState _collector_state;
275
276 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
277 // concurrent cycles) we have started.
278 volatile uint _old_marking_cycles_started;
279
280 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
281 // concurrent cycles) we have completed.
282 volatile uint _old_marking_cycles_completed;
283
284 // This is a non-product method that is helpful for testing. It is
285 // called at the end of a GC and artificially expands the heap by
286 // allocating a number of dead regions. This way we can induce very
287 // frequent marking cycles and stress the cleanup / concurrent
288 // cleanup code more (as all the regions that will be allocated by
289 // this method will be found dead by the marking cycle).
290 void allocate_dummy_regions() PRODUCT_RETURN;
291
292 // Clear RSets after a compaction. It also resets the GC time stamps.
293 void clear_rsets_post_compaction();
294
295 // If the HR printer is active, dump the state of the regions in the
296 // heap after a compaction.
297 void print_hrm_post_compaction();
298
299 // Create a memory mapper for auxiliary data structures of the given size and
300 // translation factor.
301 static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description,
302 size_t size,
303 size_t translation_factor);
304
305 static G1Policy* create_g1_policy();
306
307 void trace_heap(GCWhen::Type when, const GCTracer* tracer);
308
309 void process_weak_jni_handles();
310
311 // These are macros so that, if the assert fires, we get the correct
312 // line number, file, etc.
313
314 #define heap_locking_asserts_params(_extra_message_) \
315 "%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \
316 (_extra_message_), \
317 BOOL_TO_STR(Heap_lock->owned_by_self()), \
318 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \
319 BOOL_TO_STR(Thread::current()->is_VM_thread())
320
321 #define assert_heap_locked() \
322 do { \
323 assert(Heap_lock->owned_by_self(), \
324 heap_locking_asserts_params("should be holding the Heap_lock")); \
325 } while (0)
326
327 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \
328 do { \
329 assert(Heap_lock->owned_by_self() || \
330 (SafepointSynchronize::is_at_safepoint() && \
331 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
332 heap_locking_asserts_params("should be holding the Heap_lock or " \
333 "should be at a safepoint")); \
334 } while (0)
335
336 #define assert_heap_locked_and_not_at_safepoint() \
337 do { \
338 assert(Heap_lock->owned_by_self() && \
339 !SafepointSynchronize::is_at_safepoint(), \
340 heap_locking_asserts_params("should be holding the Heap_lock and " \
341 "should not be at a safepoint")); \
342 } while (0)
343
344 #define assert_heap_not_locked() \
345 do { \
346 assert(!Heap_lock->owned_by_self(), \
347 heap_locking_asserts_params("should not be holding the Heap_lock")); \
348 } while (0)
349
350 #define assert_heap_not_locked_and_not_at_safepoint() \
351 do { \
352 assert(!Heap_lock->owned_by_self() && \
353 !SafepointSynchronize::is_at_safepoint(), \
354 heap_locking_asserts_params("should not be holding the Heap_lock and " \
355 "should not be at a safepoint")); \
356 } while (0)
357
358 #define assert_at_safepoint(_should_be_vm_thread_) \
359 do { \
360 assert(SafepointSynchronize::is_at_safepoint() && \
361 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
362 heap_locking_asserts_params("should be at a safepoint")); \
363 } while (0)
364
365 #define assert_not_at_safepoint() \
366 do { \
367 assert(!SafepointSynchronize::is_at_safepoint(), \
368 heap_locking_asserts_params("should not be at a safepoint")); \
369 } while (0)
370
371 protected:
372
373 // The young region list.
374 G1EdenRegions _eden;
375 G1SurvivorRegions _survivor;
376
377 // The current policy object for the collector.
378 G1Policy* _g1_policy;
379 G1HeapSizingPolicy* _heap_sizing_policy;
380
381 G1CollectionSet _collection_set;
382
383 // This is the second level of trying to allocate a new region. If
384 // new_region() didn't find a region on the free_list, this call will
385 // check whether there's anything available on the
386 // secondary_free_list and/or wait for more regions to appear on
387 // that list, if _free_regions_coming is set.
388 HeapRegion* new_region_try_secondary_free_list(bool is_old);
389
390 // Try to allocate a single non-humongous HeapRegion sufficient for
391 // an allocation of the given word_size. If do_expand is true,
392 // attempt to expand the heap if necessary to satisfy the allocation
393 // request. If the region is to be used as an old region or for a
394 // humongous object, set is_old to true. If not, to false.
395 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
396
397 // Initialize a contiguous set of free regions of length num_regions
398 // and starting at index first so that they appear as a single
399 // humongous region.
400 HeapWord* humongous_obj_allocate_initialize_regions(uint first,
401 uint num_regions,
402 size_t word_size,
403 AllocationContext_t context);
404
405 // Attempt to allocate a humongous object of the given size. Return
406 // NULL if unsuccessful.
407 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context);
408
409 // The following two methods, allocate_new_tlab() and
410 // mem_allocate(), are the two main entry points from the runtime
411 // into the G1's allocation routines. They have the following
412 // assumptions:
413 //
414 // * They should both be called outside safepoints.
415 //
416 // * They should both be called without holding the Heap_lock.
417 //
418 // * All allocation requests for new TLABs should go to
419 // allocate_new_tlab().
420 //
421 // * All non-TLAB allocation requests should go to mem_allocate().
422 //
423 // * If either call cannot satisfy the allocation request using the
424 // current allocating region, they will try to get a new one. If
425 // this fails, they will attempt to do an evacuation pause and
426 // retry the allocation.
427 //
428 // * If all allocation attempts fail, even after trying to schedule
429 // an evacuation pause, allocate_new_tlab() will return NULL,
430 // whereas mem_allocate() will attempt a heap expansion and/or
431 // schedule a Full GC.
432 //
433 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
434 // should never be called with word_size being humongous. All
435 // humongous allocation requests should go to mem_allocate() which
436 // will satisfy them with a special path.
437
438 virtual HeapWord* allocate_new_tlab(size_t word_size);
439
440 virtual HeapWord* mem_allocate(size_t word_size,
441 bool* gc_overhead_limit_was_exceeded);
442
443 // The following three methods take a gc_count_before_ret
444 // parameter which is used to return the GC count if the method
445 // returns NULL. Given that we are required to read the GC count
446 // while holding the Heap_lock, and these paths will take the
447 // Heap_lock at some point, it's easier to get them to read the GC
448 // count while holding the Heap_lock before they return NULL instead
449 // of the caller (namely: mem_allocate()) having to also take the
450 // Heap_lock just to read the GC count.
451
452 // First-level mutator allocation attempt: try to allocate out of
453 // the mutator alloc region without taking the Heap_lock. This
454 // should only be used for non-humongous allocations.
455 inline HeapWord* attempt_allocation(size_t word_size,
456 uint* gc_count_before_ret,
457 uint* gclocker_retry_count_ret);
458
459 // Second-level mutator allocation attempt: take the Heap_lock and
460 // retry the allocation attempt, potentially scheduling a GC
461 // pause. This should only be used for non-humongous allocations.
462 HeapWord* attempt_allocation_slow(size_t word_size,
463 AllocationContext_t context,
464 uint* gc_count_before_ret,
465 uint* gclocker_retry_count_ret);
466
467 // Takes the Heap_lock and attempts a humongous allocation. It can
468 // potentially schedule a GC pause.
469 HeapWord* attempt_allocation_humongous(size_t word_size,
470 uint* gc_count_before_ret,
471 uint* gclocker_retry_count_ret);
472
473 // Allocation attempt that should be called during safepoints (e.g.,
474 // at the end of a successful GC). expect_null_mutator_alloc_region
475 // specifies whether the mutator alloc region is expected to be NULL
476 // or not.
477 HeapWord* attempt_allocation_at_safepoint(size_t word_size,
478 AllocationContext_t context,
479 bool expect_null_mutator_alloc_region);
480
481 // These methods are the "callbacks" from the G1AllocRegion class.
482
483 // For mutator alloc regions.
484 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
485 void retire_mutator_alloc_region(HeapRegion* alloc_region,
486 size_t allocated_bytes);
487
488 // For GC alloc regions.
489 bool has_more_regions(InCSetState dest);
490 HeapRegion* new_gc_alloc_region(size_t word_size, InCSetState dest);
491 void retire_gc_alloc_region(HeapRegion* alloc_region,
492 size_t allocated_bytes, InCSetState dest);
493
494 // - if explicit_gc is true, the GC is for a System.gc() etc,
495 // otherwise it's for a failed allocation.
496 // - if clear_all_soft_refs is true, all soft references should be
497 // cleared during the GC.
498 // - it returns false if it is unable to do the collection due to the
499 // GC locker being active, true otherwise.
500 bool do_full_collection(bool explicit_gc,
501 bool clear_all_soft_refs);
502
503 // Callback from VM_G1CollectFull operation, or collect_as_vm_thread.
504 virtual void do_full_collection(bool clear_all_soft_refs);
505
506 // Resize the heap if necessary after a full collection.
507 void resize_if_necessary_after_full_collection();
508
509 // Callback from VM_G1CollectForAllocation operation.
510 // This function does everything necessary/possible to satisfy a
511 // failed allocation request (including collection, expansion, etc.)
512 HeapWord* satisfy_failed_allocation(size_t word_size,
513 AllocationContext_t context,
514 bool* succeeded);
515 private:
516 // Internal helpers used during full GC to split it up to
517 // increase readability.
518 void do_full_collection_inner(G1FullGCScope* scope);
519 void abort_concurrent_cycle();
520 void verify_before_full_collection(bool explicit_gc);
521 void prepare_heap_for_full_collection();
522 void prepare_heap_for_mutators();
523 void abort_refinement();
524 void verify_after_full_collection();
525 void print_heap_after_full_collection(G1HeapTransition* heap_transition);
526
527 // Helper method for satisfy_failed_allocation()
528 HeapWord* satisfy_failed_allocation_helper(size_t word_size,
529 AllocationContext_t context,
530 bool do_gc,
531 bool clear_all_soft_refs,
532 bool expect_null_mutator_alloc_region,
533 bool* gc_succeeded);
534
535 protected:
536 // Attempting to expand the heap sufficiently
537 // to support an allocation of the given "word_size". If
538 // successful, perform the allocation and return the address of the
539 // allocated block, or else "NULL".
540 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context);
541
542 // Preserve any referents discovered by concurrent marking that have not yet been
543 // copied by the STW pause.
544 void preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states);
545 // Process any reference objects discovered during
546 // an incremental evacuation pause.
547 void process_discovered_references(G1ParScanThreadStateSet* per_thread_states);
548
549 // Enqueue any remaining discovered references
550 // after processing.
551 void enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states);
552
553 // Merges the information gathered on a per-thread basis for all worker threads
554 // during GC into global variables.
555 void merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states);
556 public:
557 WorkGang* workers() const { return _workers; }
558
559 G1Allocator* allocator() {
560 return _allocator;
561 }
562
563 G1HeapVerifier* verifier() {
564 return _verifier;
565 }
566
567 G1MonitoringSupport* g1mm() {
568 assert(_g1mm != NULL, "should have been initialized");
569 return _g1mm;
570 }
571
572 // Expand the garbage-first heap by at least the given size (in bytes!).
573 // Returns true if the heap was expanded by the requested amount;
574 // false otherwise.
575 // (Rounds up to a HeapRegion boundary.)
576 bool expand(size_t expand_bytes, WorkGang* pretouch_workers = NULL, double* expand_time_ms = NULL);
577
578 // Returns the PLAB statistics for a given destination.
579 inline G1EvacStats* alloc_buffer_stats(InCSetState dest);
580
581 // Determines PLAB size for a given destination.
582 inline size_t desired_plab_sz(InCSetState dest);
583
584 inline AllocationContextStats& allocation_context_stats();
585
586 // Do anything common to GC's.
587 void gc_prologue(bool full);
588 void gc_epilogue(bool full);
589
590 // Modify the reclaim candidate set and test for presence.
591 // These are only valid for starts_humongous regions.
592 inline void set_humongous_reclaim_candidate(uint region, bool value);
593 inline bool is_humongous_reclaim_candidate(uint region);
594
595 // Remove from the reclaim candidate set. Also remove from the
596 // collection set so that later encounters avoid the slow path.
597 inline void set_humongous_is_live(oop obj);
598
599 // Register the given region to be part of the collection set.
600 inline void register_humongous_region_with_cset(uint index);
601 // Register regions with humongous objects (actually on the start region) in
602 // the in_cset_fast_test table.
603 void register_humongous_regions_with_cset();
604 // We register a region with the fast "in collection set" test. We
605 // simply set to true the array slot corresponding to this region.
606 void register_young_region_with_cset(HeapRegion* r) {
607 _in_cset_fast_test.set_in_young(r->hrm_index());
608 }
609 void register_old_region_with_cset(HeapRegion* r) {
610 _in_cset_fast_test.set_in_old(r->hrm_index());
611 }
612 inline void register_ext_region_with_cset(HeapRegion* r) {
613 _in_cset_fast_test.set_ext(r->hrm_index());
614 }
615 void clear_in_cset(const HeapRegion* hr) {
616 _in_cset_fast_test.clear(hr);
617 }
618
619 void clear_cset_fast_test() {
620 _in_cset_fast_test.clear();
621 }
622
623 bool is_user_requested_concurrent_full_gc(GCCause::Cause cause);
624
625 // This is called at the start of either a concurrent cycle or a Full
626 // GC to update the number of old marking cycles started.
627 void increment_old_marking_cycles_started();
628
629 // This is called at the end of either a concurrent cycle or a Full
630 // GC to update the number of old marking cycles completed. Those two
631 // can happen in a nested fashion, i.e., we start a concurrent
632 // cycle, a Full GC happens half-way through it which ends first,
633 // and then the cycle notices that a Full GC happened and ends
634 // too. The concurrent parameter is a boolean to help us do a bit
635 // tighter consistency checking in the method. If concurrent is
636 // false, the caller is the inner caller in the nesting (i.e., the
637 // Full GC). If concurrent is true, the caller is the outer caller
638 // in this nesting (i.e., the concurrent cycle). Further nesting is
639 // not currently supported. The end of this call also notifies
640 // the FullGCCount_lock in case a Java thread is waiting for a full
641 // GC to happen (e.g., it called System.gc() with
642 // +ExplicitGCInvokesConcurrent).
643 void increment_old_marking_cycles_completed(bool concurrent);
644
645 uint old_marking_cycles_completed() {
646 return _old_marking_cycles_completed;
647 }
648
649 G1HRPrinter* hr_printer() { return &_hr_printer; }
650
651 // Allocates a new heap region instance.
652 HeapRegion* new_heap_region(uint hrs_index, MemRegion mr);
653
654 // Allocate the highest free region in the reserved heap. This will commit
655 // regions as necessary.
656 HeapRegion* alloc_highest_free_region();
657
658 // Frees a non-humongous region by initializing its contents and
659 // adding it to the free list that's passed as a parameter (this is
660 // usually a local list which will be appended to the master free
661 // list later). The used bytes of freed regions are accumulated in
662 // pre_used. If skip_remset is true, the region's RSet will not be freed
663 // up. If skip_hot_card_cache is true, the region's hot card cache will not
664 // be freed up. The assumption is that this will be done later.
665 // The locked parameter indicates if the caller has already taken
666 // care of proper synchronization. This may allow some optimizations.
667 void free_region(HeapRegion* hr,
668 FreeRegionList* free_list,
669 bool skip_remset,
670 bool skip_hot_card_cache = false,
671 bool locked = false);
672
673 // It dirties the cards that cover the block so that the post
674 // write barrier never queues anything when updating objects on this
675 // block. It is assumed (and in fact we assert) that the block
676 // belongs to a young region.
677 inline void dirty_young_block(HeapWord* start, size_t word_size);
678
679 // Frees a humongous region by collapsing it into individual regions
680 // and calling free_region() for each of them. The freed regions
681 // will be added to the free list that's passed as a parameter (this
682 // is usually a local list which will be appended to the master free
683 // list later). The used bytes of freed regions are accumulated in
684 // pre_used. If skip_remset is true, the region's RSet will not be freed
685 // up. The assumption is that this will be done later.
686 void free_humongous_region(HeapRegion* hr,
687 FreeRegionList* free_list,
688 bool skip_remset);
689
690 // Facility for allocating in 'archive' regions in high heap memory and
691 // recording the allocated ranges. These should all be called from the
692 // VM thread at safepoints, without the heap lock held. They can be used
693 // to create and archive a set of heap regions which can be mapped at the
694 // same fixed addresses in a subsequent JVM invocation.
695 void begin_archive_alloc_range();
696
697 // Check if the requested size would be too large for an archive allocation.
698 bool is_archive_alloc_too_large(size_t word_size);
699
700 // Allocate memory of the requested size from the archive region. This will
701 // return NULL if the size is too large or if no memory is available. It
702 // does not trigger a garbage collection.
703 HeapWord* archive_mem_allocate(size_t word_size);
704
705 // Optionally aligns the end address and returns the allocated ranges in
706 // an array of MemRegions in order of ascending addresses.
707 void end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
708 size_t end_alignment_in_bytes = 0);
709
710 // Facility for allocating a fixed range within the heap and marking
711 // the containing regions as 'archive'. For use at JVM init time, when the
712 // caller may mmap archived heap data at the specified range(s).
713 // Verify that the MemRegions specified in the argument array are within the
714 // reserved heap.
715 bool check_archive_addresses(MemRegion* range, size_t count);
716
717 // Commit the appropriate G1 regions containing the specified MemRegions
718 // and mark them as 'archive' regions. The regions in the array must be
719 // non-overlapping and in order of ascending address.
720 bool alloc_archive_regions(MemRegion* range, size_t count);
721
722 // Insert any required filler objects in the G1 regions around the specified
723 // ranges to make the regions parseable. This must be called after
724 // alloc_archive_regions, and after class loading has occurred.
725 void fill_archive_regions(MemRegion* range, size_t count);
726
727 // For each of the specified MemRegions, uncommit the containing G1 regions
728 // which had been allocated by alloc_archive_regions. This should be called
729 // rather than fill_archive_regions at JVM init time if the archive file
730 // mapping failed, with the same non-overlapping and sorted MemRegion array.
731 void dealloc_archive_regions(MemRegion* range, size_t count);
732
733 protected:
734
735 // Shrink the garbage-first heap by at most the given size (in bytes!).
736 // (Rounds down to a HeapRegion boundary.)
737 virtual void shrink(size_t expand_bytes);
738 void shrink_helper(size_t expand_bytes);
739
740 #if TASKQUEUE_STATS
741 static void print_taskqueue_stats_hdr(outputStream* const st);
742 void print_taskqueue_stats() const;
743 void reset_taskqueue_stats();
744 #endif // TASKQUEUE_STATS
745
746 // Schedule the VM operation that will do an evacuation pause to
747 // satisfy an allocation request of word_size. *succeeded will
748 // return whether the VM operation was successful (it did do an
749 // evacuation pause) or not (another thread beat us to it or the GC
750 // locker was active). Given that we should not be holding the
751 // Heap_lock when we enter this method, we will pass the
752 // gc_count_before (i.e., total_collections()) as a parameter since
753 // it has to be read while holding the Heap_lock. Currently, both
754 // methods that call do_collection_pause() release the Heap_lock
755 // before the call, so it's easy to read gc_count_before just before.
756 HeapWord* do_collection_pause(size_t word_size,
757 uint gc_count_before,
758 bool* succeeded,
759 GCCause::Cause gc_cause);
760
761 void wait_for_root_region_scanning();
762
763 // The guts of the incremental collection pause, executed by the vm
764 // thread. It returns false if it is unable to do the collection due
765 // to the GC locker being active, true otherwise
766 bool do_collection_pause_at_safepoint(double target_pause_time_ms);
767
768 // Actually do the work of evacuating the collection set.
769 virtual void evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states);
770
771 void pre_evacuate_collection_set();
772 void post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* pss);
773
774 // Print the header for the per-thread termination statistics.
775 static void print_termination_stats_hdr();
776 // Print actual per-thread termination statistics.
777 void print_termination_stats(uint worker_id,
778 double elapsed_ms,
779 double strong_roots_ms,
780 double term_ms,
781 size_t term_attempts,
782 size_t alloc_buffer_waste,
783 size_t undo_waste) const;
784 // Update object copying statistics.
785 void record_obj_copy_mem_stats();
786
787 // The hot card cache for remembered set insertion optimization.
788 G1HotCardCache* _hot_card_cache;
789
790 // The g1 remembered set of the heap.
791 G1RemSet* _g1_rem_set;
792
793 // A set of cards that cover the objects for which the Rsets should be updated
794 // concurrently after the collection.
795 DirtyCardQueueSet _dirty_card_queue_set;
796
797 // After a collection pause, convert the regions in the collection set into free
798 // regions.
799 void free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words);
800
801 // Abandon the current collection set without recording policy
802 // statistics or updating free lists.
803 void abandon_collection_set(G1CollectionSet* collection_set);
804
805 // The concurrent marker (and the thread it runs in.)
806 G1ConcurrentMark* _cm;
807 ConcurrentMarkThread* _cmThread;
808
809 // The concurrent refiner.
810 ConcurrentG1Refine* _cg1r;
811
812 // The parallel task queues
813 RefToScanQueueSet *_task_queues;
814
815 // True iff a evacuation has failed in the current collection.
816 bool _evacuation_failed;
817
818 EvacuationFailedInfo* _evacuation_failed_info_array;
819
820 // Failed evacuations cause some logical from-space objects to have
821 // forwarding pointers to themselves. Reset them.
822 void remove_self_forwarding_pointers();
823
824 // Restore the objects in the regions in the collection set after an
825 // evacuation failure.
826 void restore_after_evac_failure();
827
828 PreservedMarksSet _preserved_marks_set;
829
830 // Preserve the mark of "obj", if necessary, in preparation for its mark
831 // word being overwritten with a self-forwarding-pointer.
832 void preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m);
833
834 #ifndef PRODUCT
835 // Support for forcing evacuation failures. Analogous to
836 // PromotionFailureALot for the other collectors.
837
838 // Records whether G1EvacuationFailureALot should be in effect
839 // for the current GC
840 bool _evacuation_failure_alot_for_current_gc;
841
842 // Used to record the GC number for interval checking when
843 // determining whether G1EvaucationFailureALot is in effect
844 // for the current GC.
845 size_t _evacuation_failure_alot_gc_number;
846
847 // Count of the number of evacuations between failures.
848 volatile size_t _evacuation_failure_alot_count;
849
850 // Set whether G1EvacuationFailureALot should be in effect
851 // for the current GC (based upon the type of GC and which
852 // command line flags are set);
853 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
854 bool during_initial_mark,
855 bool during_marking);
856
857 inline void set_evacuation_failure_alot_for_current_gc();
858
859 // Return true if it's time to cause an evacuation failure.
860 inline bool evacuation_should_fail();
861
862 // Reset the G1EvacuationFailureALot counters. Should be called at
863 // the end of an evacuation pause in which an evacuation failure occurred.
864 inline void reset_evacuation_should_fail();
865 #endif // !PRODUCT
866
867 // ("Weak") Reference processing support.
868 //
869 // G1 has 2 instances of the reference processor class. One
870 // (_ref_processor_cm) handles reference object discovery
871 // and subsequent processing during concurrent marking cycles.
872 //
873 // The other (_ref_processor_stw) handles reference object
874 // discovery and processing during full GCs and incremental
875 // evacuation pauses.
876 //
877 // During an incremental pause, reference discovery will be
878 // temporarily disabled for _ref_processor_cm and will be
879 // enabled for _ref_processor_stw. At the end of the evacuation
880 // pause references discovered by _ref_processor_stw will be
881 // processed and discovery will be disabled. The previous
882 // setting for reference object discovery for _ref_processor_cm
883 // will be re-instated.
884 //
885 // At the start of marking:
886 // * Discovery by the CM ref processor is verified to be inactive
887 // and it's discovered lists are empty.
888 // * Discovery by the CM ref processor is then enabled.
889 //
890 // At the end of marking:
891 // * Any references on the CM ref processor's discovered
892 // lists are processed (possibly MT).
893 //
894 // At the start of full GC we:
895 // * Disable discovery by the CM ref processor and
896 // empty CM ref processor's discovered lists
897 // (without processing any entries).
898 // * Verify that the STW ref processor is inactive and it's
899 // discovered lists are empty.
900 // * Temporarily set STW ref processor discovery as single threaded.
901 // * Temporarily clear the STW ref processor's _is_alive_non_header
902 // field.
903 // * Finally enable discovery by the STW ref processor.
904 //
905 // The STW ref processor is used to record any discovered
906 // references during the full GC.
907 //
908 // At the end of a full GC we:
909 // * Enqueue any reference objects discovered by the STW ref processor
910 // that have non-live referents. This has the side-effect of
911 // making the STW ref processor inactive by disabling discovery.
912 // * Verify that the CM ref processor is still inactive
913 // and no references have been placed on it's discovered
914 // lists (also checked as a precondition during initial marking).
915
916 // The (stw) reference processor...
917 ReferenceProcessor* _ref_processor_stw;
918
919 STWGCTimer* _gc_timer_stw;
920
921 G1NewTracer* _gc_tracer_stw;
922
923 // During reference object discovery, the _is_alive_non_header
924 // closure (if non-null) is applied to the referent object to
925 // determine whether the referent is live. If so then the
926 // reference object does not need to be 'discovered' and can
927 // be treated as a regular oop. This has the benefit of reducing
928 // the number of 'discovered' reference objects that need to
929 // be processed.
930 //
931 // Instance of the is_alive closure for embedding into the
932 // STW reference processor as the _is_alive_non_header field.
933 // Supplying a value for the _is_alive_non_header field is
934 // optional but doing so prevents unnecessary additions to
935 // the discovered lists during reference discovery.
936 G1STWIsAliveClosure _is_alive_closure_stw;
937
938 // The (concurrent marking) reference processor...
939 ReferenceProcessor* _ref_processor_cm;
940
941 // Instance of the concurrent mark is_alive closure for embedding
942 // into the Concurrent Marking reference processor as the
943 // _is_alive_non_header field. Supplying a value for the
944 // _is_alive_non_header field is optional but doing so prevents
945 // unnecessary additions to the discovered lists during reference
946 // discovery.
947 G1CMIsAliveClosure _is_alive_closure_cm;
948
949 volatile bool _free_regions_coming;
950
951 public:
952
953 RefToScanQueue *task_queue(uint i) const;
954
955 uint num_task_queues() const;
956
957 // A set of cards where updates happened during the GC
958 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
959
960 // Create a G1CollectedHeap with the specified policy.
961 // Must call the initialize method afterwards.
962 // May not return if something goes wrong.
963 G1CollectedHeap(G1CollectorPolicy* policy);
964
965 private:
966 jint initialize_concurrent_refinement();
967 public:
968 // Initialize the G1CollectedHeap to have the initial and
969 // maximum sizes and remembered and barrier sets
970 // specified by the policy object.
971 jint initialize();
972
973 virtual void stop();
974
975 // Return the (conservative) maximum heap alignment for any G1 heap
976 static size_t conservative_max_heap_alignment();
977
978 // Does operations required after initialization has been done.
979 void post_initialize();
980
981 // Initialize weak reference processing.
982 void ref_processing_init();
983
984 virtual Name kind() const {
985 return CollectedHeap::G1CollectedHeap;
986 }
987
988 virtual const char* name() const {
989 return "G1";
990 }
991
992 const G1CollectorState* collector_state() const { return &_collector_state; }
993 G1CollectorState* collector_state() { return &_collector_state; }
994
995 // The current policy object for the collector.
996 G1Policy* g1_policy() const { return _g1_policy; }
997
998 const G1CollectionSet* collection_set() const { return &_collection_set; }
999 G1CollectionSet* collection_set() { return &_collection_set; }
1000
1001 virtual CollectorPolicy* collector_policy() const;
1002
1003 // Adaptive size policy. No such thing for g1.
1004 virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1005
1006 // The rem set and barrier set.
1007 G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1008
1009 // Try to minimize the remembered set.
1010 void scrub_rem_set();
1011
1012 uint get_gc_time_stamp() {
1013 return _gc_time_stamp;
1014 }
1015
1016 inline void reset_gc_time_stamp();
1017
1018 void check_gc_time_stamps() PRODUCT_RETURN;
1019
1020 inline void increment_gc_time_stamp();
1021
1022 // Reset the given region's GC timestamp. If it's starts humongous,
1023 // also reset the GC timestamp of its corresponding
1024 // continues humongous regions too.
1025 void reset_gc_time_stamps(HeapRegion* hr);
1026
1027 // Apply the given closure on all cards in the Hot Card Cache, emptying it.
1028 void iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i);
1029
1030 // Apply the given closure on all cards in the Dirty Card Queue Set, emptying it.
1031 void iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i);
1032
1033 // The shared block offset table array.
1034 G1BlockOffsetTable* bot() const { return _bot; }
1035
1036 // Reference Processing accessors
1037
1038 // The STW reference processor....
1039 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1040
1041 G1NewTracer* gc_tracer_stw() const { return _gc_tracer_stw; }
1042
1043 // The Concurrent Marking reference processor...
1044 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1045
1046 virtual size_t capacity() const;
1047 virtual size_t used() const;
1048 // This should be called when we're not holding the heap lock. The
1049 // result might be a bit inaccurate.
1050 size_t used_unlocked() const;
1051 size_t recalculate_used() const;
1052
1053 // These virtual functions do the actual allocation.
1054 // Some heaps may offer a contiguous region for shared non-blocking
1055 // allocation, via inlined code (by exporting the address of the top and
1056 // end fields defining the extent of the contiguous allocation region.)
1057 // But G1CollectedHeap doesn't yet support this.
1058
1059 virtual bool is_maximal_no_gc() const {
1060 return _hrm.available() == 0;
1061 }
1062
1063 // The current number of regions in the heap.
1064 uint num_regions() const { return _hrm.length(); }
1065
1066 // The max number of regions in the heap.
1067 uint max_regions() const { return _hrm.max_length(); }
1068
1069 // The number of regions that are completely free.
1070 uint num_free_regions() const { return _hrm.num_free_regions(); }
1071
1072 MemoryUsage get_auxiliary_data_memory_usage() const {
1073 return _hrm.get_auxiliary_data_memory_usage();
1074 }
1075
1076 // The number of regions that are not completely free.
1077 uint num_used_regions() const { return num_regions() - num_free_regions(); }
1078
1079 #ifdef ASSERT
1080 bool is_on_master_free_list(HeapRegion* hr) {
1081 return _hrm.is_free(hr);
1082 }
1083 #endif // ASSERT
1084
1085 // Wrapper for the region list operations that can be called from
1086 // methods outside this class.
1087
1088 void secondary_free_list_add(FreeRegionList* list) {
1089 _secondary_free_list.add_ordered(list);
1090 }
1091
1092 void append_secondary_free_list() {
1093 _hrm.insert_list_into_free_list(&_secondary_free_list);
1094 }
1095
1096 void append_secondary_free_list_if_not_empty_with_lock() {
1097 // If the secondary free list looks empty there's no reason to
1098 // take the lock and then try to append it.
1099 if (!_secondary_free_list.is_empty()) {
1100 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1101 append_secondary_free_list();
1102 }
1103 }
1104
1105 inline void old_set_add(HeapRegion* hr);
1106 inline void old_set_remove(HeapRegion* hr);
1107
1108 size_t non_young_capacity_bytes() {
1109 return (_old_set.length() + _humongous_set.length()) * HeapRegion::GrainBytes;
1110 }
1111
1112 void set_free_regions_coming();
1113 void reset_free_regions_coming();
1114 bool free_regions_coming() { return _free_regions_coming; }
1115 void wait_while_free_regions_coming();
1116
1117 // Determine whether the given region is one that we are using as an
1118 // old GC alloc region.
1119 bool is_old_gc_alloc_region(HeapRegion* hr);
1120
1121 // Perform a collection of the heap; intended for use in implementing
1122 // "System.gc". This probably implies as full a collection as the
1123 // "CollectedHeap" supports.
1124 virtual void collect(GCCause::Cause cause);
1125
1126 virtual bool copy_allocation_context_stats(const jint* contexts,
1127 jlong* totals,
1128 jbyte* accuracy,
1129 jint len);
1130
1131 // True iff an evacuation has failed in the most-recent collection.
1132 bool evacuation_failed() { return _evacuation_failed; }
1133
1134 void remove_from_old_sets(const uint old_regions_removed, const uint humongous_regions_removed);
1135 void prepend_to_freelist(FreeRegionList* list);
1136 void decrement_summary_bytes(size_t bytes);
1137
1138 virtual bool is_in(const void* p) const;
1139 #ifdef ASSERT
1140 // Returns whether p is in one of the available areas of the heap. Slow but
1141 // extensive version.
1142 bool is_in_exact(const void* p) const;
1143 #endif
1144
1145 // Return "TRUE" iff the given object address is within the collection
1146 // set. Assumes that the reference points into the heap.
1147 inline bool is_in_cset(const HeapRegion *hr);
1148 inline bool is_in_cset(oop obj);
1149 inline bool is_in_cset(HeapWord* addr);
1150
1151 inline bool is_in_cset_or_humongous(const oop obj);
1152
1153 private:
1154 // This array is used for a quick test on whether a reference points into
1155 // the collection set or not. Each of the array's elements denotes whether the
1156 // corresponding region is in the collection set or not.
1157 G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test;
1158
1159 public:
1160
1161 inline InCSetState in_cset_state(const oop obj);
1162
1163 // Return "TRUE" iff the given object address is in the reserved
1164 // region of g1.
1165 bool is_in_g1_reserved(const void* p) const {
1166 return _hrm.reserved().contains(p);
1167 }
1168
1169 // Returns a MemRegion that corresponds to the space that has been
1170 // reserved for the heap
1171 MemRegion g1_reserved() const {
1172 return _hrm.reserved();
1173 }
1174
1175 virtual bool is_in_closed_subset(const void* p) const;
1176
1177 G1SATBCardTableLoggingModRefBS* g1_barrier_set() {
1178 return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set());
1179 }
1180
1181 // Iteration functions.
1182
1183 // Iterate over all objects, calling "cl.do_object" on each.
1184 virtual void object_iterate(ObjectClosure* cl);
1185
1186 virtual void safe_object_iterate(ObjectClosure* cl) {
1187 object_iterate(cl);
1188 }
1189
1190 // Iterate over heap regions, in address order, terminating the
1191 // iteration early if the "doHeapRegion" method returns "true".
1192 void heap_region_iterate(HeapRegionClosure* blk) const;
1193
1194 // Return the region with the given index. It assumes the index is valid.
1195 inline HeapRegion* region_at(uint index) const;
1196
1197 // Return the next region (by index) that is part of the same
1198 // humongous object that hr is part of.
1199 inline HeapRegion* next_region_in_humongous(HeapRegion* hr) const;
1200
1201 // Calculate the region index of the given address. Given address must be
1202 // within the heap.
1203 inline uint addr_to_region(HeapWord* addr) const;
1204
1205 inline HeapWord* bottom_addr_for_region(uint index) const;
1206
1207 // Iterate over the heap regions in parallel. Assumes that this will be called
1208 // in parallel by a number of worker threads with distinct worker ids
1209 // in the range passed to the HeapRegionClaimer. Applies "blk->doHeapRegion"
1210 // to each of the regions, by attempting to claim the region using the
1211 // HeapRegionClaimer and, if successful, applying the closure to the claimed
1212 // region.
1213 void heap_region_par_iterate(HeapRegionClosure* cl,
1214 uint worker_id,
1215 HeapRegionClaimerBase* hrclaimer) const;
1216
1217 // Iterate over the regions (if any) in the current collection set.
1218 void collection_set_iterate(HeapRegionClosure* blk);
1219
1220 // Iterate over the regions (if any) in the current collection set. Starts the
1221 // iteration over the entire collection set so that the start regions of a given
1222 // worker id over the set active_workers are evenly spread across the set of
1223 // collection set regions.
1224 void collection_set_iterate_from(HeapRegionClosure *blk, uint worker_id);
1225
1226 // Returns the HeapRegion that contains addr. addr must not be NULL.
1227 template <class T>
1228 inline HeapRegion* heap_region_containing(const T addr) const;
1229
1230 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1231 // each address in the (reserved) heap is a member of exactly
1232 // one block. The defining characteristic of a block is that it is
1233 // possible to find its size, and thus to progress forward to the next
1234 // block. (Blocks may be of different sizes.) Thus, blocks may
1235 // represent Java objects, or they might be free blocks in a
1236 // free-list-based heap (or subheap), as long as the two kinds are
1237 // distinguishable and the size of each is determinable.
1238
1239 // Returns the address of the start of the "block" that contains the
1240 // address "addr". We say "blocks" instead of "object" since some heaps
1241 // may not pack objects densely; a chunk may either be an object or a
1242 // non-object.
1243 virtual HeapWord* block_start(const void* addr) const;
1244
1245 // Requires "addr" to be the start of a chunk, and returns its size.
1246 // "addr + size" is required to be the start of a new chunk, or the end
1247 // of the active area of the heap.
1248 virtual size_t block_size(const HeapWord* addr) const;
1249
1250 // Requires "addr" to be the start of a block, and returns "TRUE" iff
1251 // the block is an object.
1252 virtual bool block_is_obj(const HeapWord* addr) const;
1253
1254 // Section on thread-local allocation buffers (TLABs)
1255 // See CollectedHeap for semantics.
1256
1257 bool supports_tlab_allocation() const;
1258 size_t tlab_capacity(Thread* ignored) const;
1259 size_t tlab_used(Thread* ignored) const;
1260 size_t max_tlab_size() const;
1261 size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1262
1263 // Can a compiler initialize a new object without store barriers?
1264 // This permission only extends from the creation of a new object
1265 // via a TLAB up to the first subsequent safepoint. If such permission
1266 // is granted for this heap type, the compiler promises to call
1267 // defer_store_barrier() below on any slow path allocation of
1268 // a new object for which such initializing store barriers will
1269 // have been elided. G1, like CMS, allows this, but should be
1270 // ready to provide a compensating write barrier as necessary
1271 // if that storage came out of a non-young region. The efficiency
1272 // of this implementation depends crucially on being able to
1273 // answer very efficiently in constant time whether a piece of
1274 // storage in the heap comes from a young region or not.
1275 // See ReduceInitialCardMarks.
1276 virtual bool can_elide_tlab_store_barriers() const {
1277 return true;
1278 }
1279
1280 virtual bool card_mark_must_follow_store() const {
1281 return true;
1282 }
1283
1284 inline bool is_in_young(const oop obj);
1285
1286 virtual bool is_scavengable(const void* addr);
1287
1288 // We don't need barriers for initializing stores to objects
1289 // in the young gen: for the SATB pre-barrier, there is no
1290 // pre-value that needs to be remembered; for the remembered-set
1291 // update logging post-barrier, we don't maintain remembered set
1292 // information for young gen objects.
1293 virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1294
1295 // Returns "true" iff the given word_size is "very large".
1296 static bool is_humongous(size_t word_size) {
1297 // Note this has to be strictly greater-than as the TLABs
1298 // are capped at the humongous threshold and we want to
1299 // ensure that we don't try to allocate a TLAB as
1300 // humongous and that we don't allocate a humongous
1301 // object in a TLAB.
1302 return word_size > _humongous_object_threshold_in_words;
1303 }
1304
1305 // Returns the humongous threshold for a specific region size
1306 static size_t humongous_threshold_for(size_t region_size) {
1307 return (region_size / 2);
1308 }
1309
1310 // Returns the number of regions the humongous object of the given word size
1311 // requires.
1312 static size_t humongous_obj_size_in_regions(size_t word_size);
1313
1314 // Print the maximum heap capacity.
1315 virtual size_t max_capacity() const;
1316
1317 virtual jlong millis_since_last_gc();
1318
1319
1320 // Convenience function to be used in situations where the heap type can be
1321 // asserted to be this type.
1322 static G1CollectedHeap* heap();
1323
1324 void set_region_short_lived_locked(HeapRegion* hr);
1325 // add appropriate methods for any other surv rate groups
1326
1327 const G1SurvivorRegions* survivor() const { return &_survivor; }
1328
1329 uint survivor_regions_count() const {
1330 return _survivor.length();
1331 }
1332
1333 uint eden_regions_count() const {
1334 return _eden.length();
1335 }
1336
1337 uint young_regions_count() const {
1338 return _eden.length() + _survivor.length();
1339 }
1340
1341 uint old_regions_count() const { return _old_set.length(); }
1342
1343 uint humongous_regions_count() const { return _humongous_set.length(); }
1344
1345 #ifdef ASSERT
1346 bool check_young_list_empty();
1347 #endif
1348
1349 // *** Stuff related to concurrent marking. It's not clear to me that so
1350 // many of these need to be public.
1351
1352 // The functions below are helper functions that a subclass of
1353 // "CollectedHeap" can use in the implementation of its virtual
1354 // functions.
1355 // This performs a concurrent marking of the live objects in a
1356 // bitmap off to the side.
1357 void doConcurrentMark();
1358
1359 bool isMarkedNext(oop obj) const;
1360
1361 // Determine if an object is dead, given the object and also
1362 // the region to which the object belongs. An object is dead
1363 // iff a) it was not allocated since the last mark, b) it
1364 // is not marked, and c) it is not in an archive region.
1365 bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1366 return
1367 hr->is_obj_dead(obj, _cm->prevMarkBitMap()) &&
1368 !hr->is_archive();
1369 }
1370
1371 // This function returns true when an object has been
1372 // around since the previous marking and hasn't yet
1373 // been marked during this marking, and is not in an archive region.
1374 bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1375 return
1376 !hr->obj_allocated_since_next_marking(obj) &&
1377 !isMarkedNext(obj) &&
1378 !hr->is_archive();
1379 }
1380
1381 // Determine if an object is dead, given only the object itself.
1382 // This will find the region to which the object belongs and
1383 // then call the region version of the same function.
1384
1385 // Added if it is NULL it isn't dead.
1386
1387 inline bool is_obj_dead(const oop obj) const;
1388
1389 inline bool is_obj_ill(const oop obj) const;
1390
1391 G1ConcurrentMark* concurrent_mark() const { return _cm; }
1392
1393 // Refinement
1394
1395 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1396
1397 // Optimized nmethod scanning support routines
1398
1399 // Register the given nmethod with the G1 heap.
1400 virtual void register_nmethod(nmethod* nm);
1401
1402 // Unregister the given nmethod from the G1 heap.
1403 virtual void unregister_nmethod(nmethod* nm);
1404
1405 // Free up superfluous code root memory.
1406 void purge_code_root_memory();
1407
1408 // Rebuild the strong code root lists for each region
1409 // after a full GC.
1410 void rebuild_strong_code_roots();
1411
1412 // Partial cleaning used when class unloading is disabled.
1413 // Let the caller choose what structures to clean out:
1414 // - StringTable
1415 // - SymbolTable
1416 // - StringDeduplication structures
1417 void partial_cleaning(BoolObjectClosure* is_alive, bool unlink_strings, bool unlink_symbols, bool unlink_string_dedup);
1418
1419 // Complete cleaning used when class unloading is enabled.
1420 // Cleans out all structures handled by partial_cleaning and also the CodeCache.
1421 void complete_cleaning(BoolObjectClosure* is_alive, bool class_unloading_occurred);
1422
1423 // Redirty logged cards in the refinement queue.
1424 void redirty_logged_cards();
1425 // Verification
1426
1427 // Perform any cleanup actions necessary before allowing a verification.
1428 virtual void prepare_for_verify();
1429
1430 // Perform verification.
1431
1432 // vo == UsePrevMarking -> use "prev" marking information,
1433 // vo == UseNextMarking -> use "next" marking information
1434 // vo == UseMarkWord -> use the mark word in the object header
1435 //
1436 // NOTE: Only the "prev" marking information is guaranteed to be
1437 // consistent most of the time, so most calls to this should use
1438 // vo == UsePrevMarking.
1439 // Currently, there is only one case where this is called with
1440 // vo == UseNextMarking, which is to verify the "next" marking
1441 // information at the end of remark.
1442 // Currently there is only one place where this is called with
1443 // vo == UseMarkWord, which is to verify the marking during a
1444 // full GC.
1445 void verify(VerifyOption vo);
1446
1447 // WhiteBox testing support.
1448 virtual bool supports_concurrent_phase_control() const;
1449 virtual const char* const* concurrent_phases() const;
1450 virtual bool request_concurrent_phase(const char* phase);
1451
1452 // The methods below are here for convenience and dispatch the
1453 // appropriate method depending on value of the given VerifyOption
1454 // parameter. The values for that parameter, and their meanings,
1455 // are the same as those above.
1456
1457 bool is_obj_dead_cond(const oop obj,
1458 const HeapRegion* hr,
1459 const VerifyOption vo) const;
1460
1461 bool is_obj_dead_cond(const oop obj,
1462 const VerifyOption vo) const;
1463
1464 G1HeapSummary create_g1_heap_summary();
1465 G1EvacSummary create_g1_evac_summary(G1EvacStats* stats);
1466
1467 // Printing
1468 private:
1469 void print_heap_regions() const;
1470 void print_regions_on(outputStream* st) const;
1471
1472 public:
1473 virtual void print_on(outputStream* st) const;
1474 virtual void print_extended_on(outputStream* st) const;
1475 virtual void print_on_error(outputStream* st) const;
1476
1477 virtual void print_gc_threads_on(outputStream* st) const;
1478 virtual void gc_threads_do(ThreadClosure* tc) const;
1479
1480 // Override
1481 void print_tracing_info() const;
1482
1483 // The following two methods are helpful for debugging RSet issues.
1484 void print_cset_rsets() PRODUCT_RETURN;
1485 void print_all_rsets() PRODUCT_RETURN;
1486
1487 public:
1488 size_t pending_card_num();
1489
1490 protected:
1491 size_t _max_heap_capacity;
1492 };
1493
1494 class G1ParEvacuateFollowersClosure : public VoidClosure {
1495 private:
1496 double _start_term;
1497 double _term_time;
1498 size_t _term_attempts;
1499
1500 void start_term_time() { _term_attempts++; _start_term = os::elapsedTime(); }
1501 void end_term_time() { _term_time += os::elapsedTime() - _start_term; }
1502 protected:
1503 G1CollectedHeap* _g1h;
1504 G1ParScanThreadState* _par_scan_state;
1505 RefToScanQueueSet* _queues;
1506 ParallelTaskTerminator* _terminator;
1507
1508 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
1509 RefToScanQueueSet* queues() { return _queues; }
1510 ParallelTaskTerminator* terminator() { return _terminator; }
1511
1512 public:
1513 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
1514 G1ParScanThreadState* par_scan_state,
1515 RefToScanQueueSet* queues,
1516 ParallelTaskTerminator* terminator)
1517 : _g1h(g1h), _par_scan_state(par_scan_state),
1518 _queues(queues), _terminator(terminator),
1519 _start_term(0.0), _term_time(0.0), _term_attempts(0) {}
1520
1521 void do_void();
1522
1523 double term_time() const { return _term_time; }
1524 size_t term_attempts() const { return _term_attempts; }
1525
1526 private:
1527 inline bool offer_termination();
1528 };
1529
1530 #endif // SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP