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