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 G1YoungRemSetSamplingThread;
77 class HeapRegionRemSetIterator;
78 class G1ConcurrentMark;
79 class ConcurrentMarkThread;
80 class G1ConcurrentRefine;
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 G1RegionMappingChangedListener : public G1MappingChangedListener {
115 private:
116 void reset_from_card_cache(uint start_idx, size_t num_regions);
117 public:
118 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
119 };
120
121 class G1CollectedHeap : public CollectedHeap {
122 friend class G1FreeCollectionSetTask;
123 friend class VM_CollectForMetadataAllocation;
124 friend class VM_G1CollectForAllocation;
125 friend class VM_G1CollectFull;
126 friend class VM_G1IncCollectionPause;
127 friend class VMStructs;
128 friend class MutatorAllocRegion;
129 friend class G1GCAllocRegion;
130 friend class G1HeapVerifier;
131
132 // Closures used in implementation.
133 friend class G1ParScanThreadState;
134 friend class G1ParScanThreadStateSet;
135 friend class G1ParTask;
136 friend class G1PLABAllocator;
137 friend class G1PrepareCompactClosure;
138
139 // Other related classes.
140 friend class HeapRegionClaimer;
141
142 // Testing classes.
143 friend class G1CheckCSetFastTableClosure;
144
145 private:
146 G1YoungRemSetSamplingThread* _young_gen_sampling_thread;
147
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 virtual GCServicabilitySupport* create_servicability_support();
207
208 void increase_used(size_t bytes);
209 void decrease_used(size_t bytes);
210
211 void set_used(size_t bytes);
212
213 // Class that handles archive allocation ranges.
214 G1ArchiveAllocator* _archive_allocator;
215
216 // Statistics for each allocation context
217 AllocationContextStats _allocation_context_stats;
218
219 // GC allocation statistics policy for survivors.
220 G1EvacStats _survivor_evac_stats;
221
222 // GC allocation statistics policy for tenured objects.
223 G1EvacStats _old_evac_stats;
224
225 // It specifies whether we should attempt to expand the heap after a
226 // region allocation failure. If heap expansion fails we set this to
227 // false so that we don't re-attempt the heap expansion (it's likely
228 // that subsequent expansion attempts will also fail if one fails).
229 // Currently, it is only consulted during GC and it's reset at the
230 // start of each GC.
231 bool _expand_heap_after_alloc_failure;
232
233 // Helper for monitoring and management support.
234 G1MonitoringSupport* _g1mm;
235
236 // Records whether the region at the given index is (still) a
237 // candidate for eager reclaim. Only valid for humongous start
238 // regions; other regions have unspecified values. Humongous start
239 // regions are initialized at start of collection pause, with
240 // candidates removed from the set as they are found reachable from
241 // roots or the young generation.
242 class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> {
243 protected:
244 bool default_value() const { return false; }
245 public:
246 void clear() { G1BiasedMappedArray<bool>::clear(); }
247 void set_candidate(uint region, bool value) {
248 set_by_index(region, value);
249 }
250 bool is_candidate(uint region) {
251 return get_by_index(region);
252 }
253 };
254
255 HumongousReclaimCandidates _humongous_reclaim_candidates;
256 // Stores whether during humongous object registration we found candidate regions.
257 // If not, we can skip a few steps.
258 bool _has_humongous_reclaim_candidates;
259
260 volatile uint _gc_time_stamp;
261
262 G1HRPrinter _hr_printer;
263
264 // It decides whether an explicit GC should start a concurrent cycle
265 // instead of doing a STW GC. Currently, a concurrent cycle is
266 // explicitly started if:
267 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
268 // (b) cause == _g1_humongous_allocation
269 // (c) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
270 // (d) cause == _dcmd_gc_run and +ExplicitGCInvokesConcurrent.
271 // (e) cause == _update_allocation_context_stats_inc
272 // (f) cause == _wb_conc_mark
273 bool should_do_concurrent_full_gc(GCCause::Cause cause);
274
275 // indicates whether we are in young or mixed GC mode
276 G1CollectorState _collector_state;
277
278 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
279 // concurrent cycles) we have started.
280 volatile uint _old_marking_cycles_started;
281
282 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
283 // concurrent cycles) we have completed.
284 volatile uint _old_marking_cycles_completed;
285
286 // This is a non-product method that is helpful for testing. It is
287 // called at the end of a GC and artificially expands the heap by
288 // allocating a number of dead regions. This way we can induce very
289 // frequent marking cycles and stress the cleanup / concurrent
290 // cleanup code more (as all the regions that will be allocated by
291 // this method will be found dead by the marking cycle).
292 void allocate_dummy_regions() PRODUCT_RETURN;
293
294 // Clear RSets after a compaction. It also resets the GC time stamps.
295 void clear_rsets_post_compaction();
296
297 // If the HR printer is active, dump the state of the regions in the
298 // heap after a compaction.
299 void print_hrm_post_compaction();
300
301 // Create a memory mapper for auxiliary data structures of the given size and
302 // translation factor.
303 static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description,
304 size_t size,
305 size_t translation_factor);
306
307 static G1Policy* create_g1_policy(STWGCTimer* gc_timer);
308
309 void trace_heap(GCWhen::Type when, const GCTracer* tracer);
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 STWGCTimer* _gc_timer_stw;
378
379 G1NewTracer* _gc_tracer_stw;
380
381 // The current policy object for the collector.
382 G1Policy* _g1_policy;
383 G1HeapSizingPolicy* _heap_sizing_policy;
384
385 G1CollectionSet _collection_set;
386
387 // This is the second level of trying to allocate a new region. If
388 // new_region() didn't find a region on the free_list, this call will
389 // check whether there's anything available on the
390 // secondary_free_list and/or wait for more regions to appear on
391 // that list, if _free_regions_coming is set.
392 HeapRegion* new_region_try_secondary_free_list(bool is_old);
393
394 // Try to allocate a single non-humongous HeapRegion sufficient for
395 // an allocation of the given word_size. If do_expand is true,
396 // attempt to expand the heap if necessary to satisfy the allocation
397 // request. If the region is to be used as an old region or for a
398 // humongous object, set is_old to true. If not, to false.
399 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
400
401 // Initialize a contiguous set of free regions of length num_regions
402 // and starting at index first so that they appear as a single
403 // humongous region.
404 HeapWord* humongous_obj_allocate_initialize_regions(uint first,
405 uint num_regions,
406 size_t word_size,
407 AllocationContext_t context);
408
409 // Attempt to allocate a humongous object of the given size. Return
410 // NULL if unsuccessful.
411 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context);
412
413 // The following two methods, allocate_new_tlab() and
414 // mem_allocate(), are the two main entry points from the runtime
415 // into the G1's allocation routines. They have the following
416 // assumptions:
417 //
418 // * They should both be called outside safepoints.
419 //
420 // * They should both be called without holding the Heap_lock.
421 //
422 // * All allocation requests for new TLABs should go to
423 // allocate_new_tlab().
424 //
425 // * All non-TLAB allocation requests should go to mem_allocate().
426 //
427 // * If either call cannot satisfy the allocation request using the
428 // current allocating region, they will try to get a new one. If
429 // this fails, they will attempt to do an evacuation pause and
430 // retry the allocation.
431 //
432 // * If all allocation attempts fail, even after trying to schedule
433 // an evacuation pause, allocate_new_tlab() will return NULL,
434 // whereas mem_allocate() will attempt a heap expansion and/or
435 // schedule a Full GC.
436 //
437 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
438 // should never be called with word_size being humongous. All
439 // humongous allocation requests should go to mem_allocate() which
440 // will satisfy them with a special path.
441
442 virtual HeapWord* allocate_new_tlab(size_t word_size);
443
444 virtual HeapWord* mem_allocate(size_t word_size,
445 bool* gc_overhead_limit_was_exceeded);
446
447 // The following three methods take a gc_count_before_ret
448 // parameter which is used to return the GC count if the method
449 // returns NULL. Given that we are required to read the GC count
450 // while holding the Heap_lock, and these paths will take the
451 // Heap_lock at some point, it's easier to get them to read the GC
452 // count while holding the Heap_lock before they return NULL instead
453 // of the caller (namely: mem_allocate()) having to also take the
454 // Heap_lock just to read the GC count.
455
456 // First-level mutator allocation attempt: try to allocate out of
457 // the mutator alloc region without taking the Heap_lock. This
458 // should only be used for non-humongous allocations.
459 inline HeapWord* attempt_allocation(size_t word_size,
460 uint* gc_count_before_ret,
461 uint* gclocker_retry_count_ret);
462
463 // Second-level mutator allocation attempt: take the Heap_lock and
464 // retry the allocation attempt, potentially scheduling a GC
465 // pause. This should only be used for non-humongous allocations.
466 HeapWord* attempt_allocation_slow(size_t word_size,
467 AllocationContext_t context,
468 uint* gc_count_before_ret,
469 uint* gclocker_retry_count_ret);
470
471 // Takes the Heap_lock and attempts a humongous allocation. It can
472 // potentially schedule a GC pause.
473 HeapWord* attempt_allocation_humongous(size_t word_size,
474 uint* gc_count_before_ret,
475 uint* gclocker_retry_count_ret);
476
477 // Allocation attempt that should be called during safepoints (e.g.,
478 // at the end of a successful GC). expect_null_mutator_alloc_region
479 // specifies whether the mutator alloc region is expected to be NULL
480 // or not.
481 HeapWord* attempt_allocation_at_safepoint(size_t word_size,
482 AllocationContext_t context,
483 bool expect_null_mutator_alloc_region);
484
485 // These methods are the "callbacks" from the G1AllocRegion class.
486
487 // For mutator alloc regions.
488 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
489 void retire_mutator_alloc_region(HeapRegion* alloc_region,
490 size_t allocated_bytes);
491
492 // For GC alloc regions.
493 bool has_more_regions(InCSetState dest);
494 HeapRegion* new_gc_alloc_region(size_t word_size, InCSetState dest);
495 void retire_gc_alloc_region(HeapRegion* alloc_region,
496 size_t allocated_bytes, InCSetState dest);
497
498 // - if explicit_gc is true, the GC is for a System.gc() etc,
499 // otherwise it's for a failed allocation.
500 // - if clear_all_soft_refs is true, all soft references should be
501 // cleared during the GC.
502 // - it returns false if it is unable to do the collection due to the
503 // GC locker being active, true otherwise.
504 bool do_full_collection(bool explicit_gc,
505 bool clear_all_soft_refs);
506
507 // Callback from VM_G1CollectFull operation, or collect_as_vm_thread.
508 virtual void do_full_collection(bool clear_all_soft_refs);
509
510 // Resize the heap if necessary after a full collection.
511 void resize_if_necessary_after_full_collection();
512
513 // Callback from VM_G1CollectForAllocation operation.
514 // This function does everything necessary/possible to satisfy a
515 // failed allocation request (including collection, expansion, etc.)
516 HeapWord* satisfy_failed_allocation(size_t word_size,
517 AllocationContext_t context,
518 bool* succeeded);
519 private:
520 // Internal helpers used during full GC to split it up to
521 // increase readability.
522 void do_full_collection_inner(G1FullGCScope* scope);
523 void abort_concurrent_cycle();
524 void verify_before_full_collection(bool explicit_gc);
525 void prepare_heap_for_full_collection();
526 void prepare_heap_for_mutators();
527 void abort_refinement();
528 void verify_after_full_collection();
529 void print_heap_after_full_collection(G1HeapTransition* heap_transition);
530
531 // Helper method for satisfy_failed_allocation()
532 HeapWord* satisfy_failed_allocation_helper(size_t word_size,
533 AllocationContext_t context,
534 bool do_gc,
535 bool clear_all_soft_refs,
536 bool expect_null_mutator_alloc_region,
537 bool* gc_succeeded);
538
539 protected:
540 // Attempting to expand the heap sufficiently
541 // to support an allocation of the given "word_size". If
542 // successful, perform the allocation and return the address of the
543 // allocated block, or else "NULL".
544 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context);
545
546 // Preserve any referents discovered by concurrent marking that have not yet been
547 // copied by the STW pause.
548 void preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states);
549 // Process any reference objects discovered during
550 // an incremental evacuation pause.
551 void process_discovered_references(G1ParScanThreadStateSet* per_thread_states);
552
553 // Enqueue any remaining discovered references
554 // after processing.
555 void enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states);
556
557 // Merges the information gathered on a per-thread basis for all worker threads
558 // during GC into global variables.
559 void merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states);
560 public:
561 G1YoungRemSetSamplingThread* sampling_thread() const { return _young_gen_sampling_thread; }
562
563 WorkGang* workers() const { return _workers; }
564
565 G1Allocator* allocator() {
566 return _allocator;
567 }
568
569 G1HeapVerifier* verifier() {
570 return _verifier;
571 }
572
573 G1MonitoringSupport* g1mm() {
574 assert(_g1mm != NULL, "should have been initialized");
575 return _g1mm;
576 }
577
578 // Expand the garbage-first heap by at least the given size (in bytes!).
579 // Returns true if the heap was expanded by the requested amount;
580 // false otherwise.
581 // (Rounds up to a HeapRegion boundary.)
582 bool expand(size_t expand_bytes, WorkGang* pretouch_workers = NULL, double* expand_time_ms = NULL);
583
584 // Returns the PLAB statistics for a given destination.
585 inline G1EvacStats* alloc_buffer_stats(InCSetState dest);
586
587 // Determines PLAB size for a given destination.
588 inline size_t desired_plab_sz(InCSetState dest);
589
590 inline AllocationContextStats& allocation_context_stats();
591
592 // Do anything common to GC's.
593 void gc_prologue(bool full);
594 void gc_epilogue(bool full);
595
596 // Modify the reclaim candidate set and test for presence.
597 // These are only valid for starts_humongous regions.
598 inline void set_humongous_reclaim_candidate(uint region, bool value);
599 inline bool is_humongous_reclaim_candidate(uint region);
600
601 // Remove from the reclaim candidate set. Also remove from the
602 // collection set so that later encounters avoid the slow path.
603 inline void set_humongous_is_live(oop obj);
604
605 // Register the given region to be part of the collection set.
606 inline void register_humongous_region_with_cset(uint index);
607 // Register regions with humongous objects (actually on the start region) in
608 // the in_cset_fast_test table.
609 void register_humongous_regions_with_cset();
610 // We register a region with the fast "in collection set" test. We
611 // simply set to true the array slot corresponding to this region.
612 void register_young_region_with_cset(HeapRegion* r) {
613 _in_cset_fast_test.set_in_young(r->hrm_index());
614 }
615 void register_old_region_with_cset(HeapRegion* r) {
616 _in_cset_fast_test.set_in_old(r->hrm_index());
617 }
618 inline void register_ext_region_with_cset(HeapRegion* r) {
619 _in_cset_fast_test.set_ext(r->hrm_index());
620 }
621 void clear_in_cset(const HeapRegion* hr) {
622 _in_cset_fast_test.clear(hr);
623 }
624
625 void clear_cset_fast_test() {
626 _in_cset_fast_test.clear();
627 }
628
629 bool is_user_requested_concurrent_full_gc(GCCause::Cause cause);
630
631 // This is called at the start of either a concurrent cycle or a Full
632 // GC to update the number of old marking cycles started.
633 void increment_old_marking_cycles_started();
634
635 // This is called at the end of either a concurrent cycle or a Full
636 // GC to update the number of old marking cycles completed. Those two
637 // can happen in a nested fashion, i.e., we start a concurrent
638 // cycle, a Full GC happens half-way through it which ends first,
639 // and then the cycle notices that a Full GC happened and ends
640 // too. The concurrent parameter is a boolean to help us do a bit
641 // tighter consistency checking in the method. If concurrent is
642 // false, the caller is the inner caller in the nesting (i.e., the
643 // Full GC). If concurrent is true, the caller is the outer caller
644 // in this nesting (i.e., the concurrent cycle). Further nesting is
645 // not currently supported. The end of this call also notifies
646 // the FullGCCount_lock in case a Java thread is waiting for a full
647 // GC to happen (e.g., it called System.gc() with
648 // +ExplicitGCInvokesConcurrent).
649 void increment_old_marking_cycles_completed(bool concurrent);
650
651 uint old_marking_cycles_completed() {
652 return _old_marking_cycles_completed;
653 }
654
655 G1HRPrinter* hr_printer() { return &_hr_printer; }
656
657 // Allocates a new heap region instance.
658 HeapRegion* new_heap_region(uint hrs_index, MemRegion mr);
659
660 // Allocate the highest free region in the reserved heap. This will commit
661 // regions as necessary.
662 HeapRegion* alloc_highest_free_region();
663
664 // Frees a non-humongous region by initializing its contents and
665 // adding it to the free list that's passed as a parameter (this is
666 // usually a local list which will be appended to the master free
667 // list later). The used bytes of freed regions are accumulated in
668 // pre_used. If skip_remset is true, the region's RSet will not be freed
669 // up. If skip_hot_card_cache is true, the region's hot card cache will not
670 // be freed up. The assumption is that this will be done later.
671 // The locked parameter indicates if the caller has already taken
672 // care of proper synchronization. This may allow some optimizations.
673 void free_region(HeapRegion* hr,
674 FreeRegionList* free_list,
675 bool skip_remset,
676 bool skip_hot_card_cache = false,
677 bool locked = false);
678
679 // It dirties the cards that cover the block so that the post
680 // write barrier never queues anything when updating objects on this
681 // block. It is assumed (and in fact we assert) that the block
682 // belongs to a young region.
683 inline void dirty_young_block(HeapWord* start, size_t word_size);
684
685 // Frees a humongous region by collapsing it into individual regions
686 // and calling free_region() for each of them. The freed regions
687 // will be added to the free list that's passed as a parameter (this
688 // is usually a local list which will be appended to the master free
689 // list later). The used bytes of freed regions are accumulated in
690 // pre_used. If skip_remset is true, the region's RSet will not be freed
691 // up. The assumption is that this will be done later.
692 void free_humongous_region(HeapRegion* hr,
693 FreeRegionList* free_list,
694 bool skip_remset);
695
696 // Facility for allocating in 'archive' regions in high heap memory and
697 // recording the allocated ranges. These should all be called from the
698 // VM thread at safepoints, without the heap lock held. They can be used
699 // to create and archive a set of heap regions which can be mapped at the
700 // same fixed addresses in a subsequent JVM invocation.
701 void begin_archive_alloc_range(bool open = false);
702
703 // Check if the requested size would be too large for an archive allocation.
704 bool is_archive_alloc_too_large(size_t word_size);
705
706 // Allocate memory of the requested size from the archive region. This will
707 // return NULL if the size is too large or if no memory is available. It
708 // does not trigger a garbage collection.
709 HeapWord* archive_mem_allocate(size_t word_size);
710
711 // Optionally aligns the end address and returns the allocated ranges in
712 // an array of MemRegions in order of ascending addresses.
713 void end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
714 size_t end_alignment_in_bytes = 0);
715
716 // Facility for allocating a fixed range within the heap and marking
717 // the containing regions as 'archive'. For use at JVM init time, when the
718 // caller may mmap archived heap data at the specified range(s).
719 // Verify that the MemRegions specified in the argument array are within the
720 // reserved heap.
721 bool check_archive_addresses(MemRegion* range, size_t count);
722
723 // Commit the appropriate G1 regions containing the specified MemRegions
724 // and mark them as 'archive' regions. The regions in the array must be
725 // non-overlapping and in order of ascending address.
726 bool alloc_archive_regions(MemRegion* range, size_t count, bool open);
727
728 // Insert any required filler objects in the G1 regions around the specified
729 // ranges to make the regions parseable. This must be called after
730 // alloc_archive_regions, and after class loading has occurred.
731 void fill_archive_regions(MemRegion* range, size_t count);
732
733 // For each of the specified MemRegions, uncommit the containing G1 regions
734 // which had been allocated by alloc_archive_regions. This should be called
735 // rather than fill_archive_regions at JVM init time if the archive file
736 // mapping failed, with the same non-overlapping and sorted MemRegion array.
737 void dealloc_archive_regions(MemRegion* range, size_t count);
738
739 protected:
740
741 // Shrink the garbage-first heap by at most the given size (in bytes!).
742 // (Rounds down to a HeapRegion boundary.)
743 virtual void shrink(size_t expand_bytes);
744 void shrink_helper(size_t expand_bytes);
745
746 #if TASKQUEUE_STATS
747 static void print_taskqueue_stats_hdr(outputStream* const st);
748 void print_taskqueue_stats() const;
749 void reset_taskqueue_stats();
750 #endif // TASKQUEUE_STATS
751
752 // Schedule the VM operation that will do an evacuation pause to
753 // satisfy an allocation request of word_size. *succeeded will
754 // return whether the VM operation was successful (it did do an
755 // evacuation pause) or not (another thread beat us to it or the GC
756 // locker was active). Given that we should not be holding the
757 // Heap_lock when we enter this method, we will pass the
758 // gc_count_before (i.e., total_collections()) as a parameter since
759 // it has to be read while holding the Heap_lock. Currently, both
760 // methods that call do_collection_pause() release the Heap_lock
761 // before the call, so it's easy to read gc_count_before just before.
762 HeapWord* do_collection_pause(size_t word_size,
763 uint gc_count_before,
764 bool* succeeded,
765 GCCause::Cause gc_cause);
766
767 void wait_for_root_region_scanning();
768
769 // The guts of the incremental collection pause, executed by the vm
770 // thread. It returns false if it is unable to do the collection due
771 // to the GC locker being active, true otherwise
772 bool do_collection_pause_at_safepoint(double target_pause_time_ms);
773
774 // Actually do the work of evacuating the collection set.
775 virtual void evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states);
776
777 void pre_evacuate_collection_set();
778 void post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* pss);
779
780 // Print the header for the per-thread termination statistics.
781 static void print_termination_stats_hdr();
782 // Print actual per-thread termination statistics.
783 void print_termination_stats(uint worker_id,
784 double elapsed_ms,
785 double strong_roots_ms,
786 double term_ms,
787 size_t term_attempts,
788 size_t alloc_buffer_waste,
789 size_t undo_waste) const;
790 // Update object copying statistics.
791 void record_obj_copy_mem_stats();
792
793 // The hot card cache for remembered set insertion optimization.
794 G1HotCardCache* _hot_card_cache;
795
796 // The g1 remembered set of the heap.
797 G1RemSet* _g1_rem_set;
798
799 // A set of cards that cover the objects for which the Rsets should be updated
800 // concurrently after the collection.
801 DirtyCardQueueSet _dirty_card_queue_set;
802
803 // After a collection pause, convert the regions in the collection set into free
804 // regions.
805 void free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words);
806
807 // Abandon the current collection set without recording policy
808 // statistics or updating free lists.
809 void abandon_collection_set(G1CollectionSet* collection_set);
810
811 // The concurrent marker (and the thread it runs in.)
812 G1ConcurrentMark* _cm;
813 ConcurrentMarkThread* _cmThread;
814
815 // The concurrent refiner.
816 G1ConcurrentRefine* _cr;
817
818 // The parallel task queues
819 RefToScanQueueSet *_task_queues;
820
821 // True iff a evacuation has failed in the current collection.
822 bool _evacuation_failed;
823
824 EvacuationFailedInfo* _evacuation_failed_info_array;
825
826 // Failed evacuations cause some logical from-space objects to have
827 // forwarding pointers to themselves. Reset them.
828 void remove_self_forwarding_pointers();
829
830 // Restore the objects in the regions in the collection set after an
831 // evacuation failure.
832 void restore_after_evac_failure();
833
834 PreservedMarksSet _preserved_marks_set;
835
836 // Preserve the mark of "obj", if necessary, in preparation for its mark
837 // word being overwritten with a self-forwarding-pointer.
838 void preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m);
839
840 #ifndef PRODUCT
841 // Support for forcing evacuation failures. Analogous to
842 // PromotionFailureALot for the other collectors.
843
844 // Records whether G1EvacuationFailureALot should be in effect
845 // for the current GC
846 bool _evacuation_failure_alot_for_current_gc;
847
848 // Used to record the GC number for interval checking when
849 // determining whether G1EvaucationFailureALot is in effect
850 // for the current GC.
851 size_t _evacuation_failure_alot_gc_number;
852
853 // Count of the number of evacuations between failures.
854 volatile size_t _evacuation_failure_alot_count;
855
856 // Set whether G1EvacuationFailureALot should be in effect
857 // for the current GC (based upon the type of GC and which
858 // command line flags are set);
859 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
860 bool during_initial_mark,
861 bool during_marking);
862
863 inline void set_evacuation_failure_alot_for_current_gc();
864
865 // Return true if it's time to cause an evacuation failure.
866 inline bool evacuation_should_fail();
867
868 // Reset the G1EvacuationFailureALot counters. Should be called at
869 // the end of an evacuation pause in which an evacuation failure occurred.
870 inline void reset_evacuation_should_fail();
871 #endif // !PRODUCT
872
873 // ("Weak") Reference processing support.
874 //
875 // G1 has 2 instances of the reference processor class. One
876 // (_ref_processor_cm) handles reference object discovery
877 // and subsequent processing during concurrent marking cycles.
878 //
879 // The other (_ref_processor_stw) handles reference object
880 // discovery and processing during full GCs and incremental
881 // evacuation pauses.
882 //
883 // During an incremental pause, reference discovery will be
884 // temporarily disabled for _ref_processor_cm and will be
885 // enabled for _ref_processor_stw. At the end of the evacuation
886 // pause references discovered by _ref_processor_stw will be
887 // processed and discovery will be disabled. The previous
888 // setting for reference object discovery for _ref_processor_cm
889 // will be re-instated.
890 //
891 // At the start of marking:
892 // * Discovery by the CM ref processor is verified to be inactive
893 // and it's discovered lists are empty.
894 // * Discovery by the CM ref processor is then enabled.
895 //
896 // At the end of marking:
897 // * Any references on the CM ref processor's discovered
898 // lists are processed (possibly MT).
899 //
900 // At the start of full GC we:
901 // * Disable discovery by the CM ref processor and
902 // empty CM ref processor's discovered lists
903 // (without processing any entries).
904 // * Verify that the STW ref processor is inactive and it's
905 // discovered lists are empty.
906 // * Temporarily set STW ref processor discovery as single threaded.
907 // * Temporarily clear the STW ref processor's _is_alive_non_header
908 // field.
909 // * Finally enable discovery by the STW ref processor.
910 //
911 // The STW ref processor is used to record any discovered
912 // references during the full GC.
913 //
914 // At the end of a full GC we:
915 // * Enqueue any reference objects discovered by the STW ref processor
916 // that have non-live referents. This has the side-effect of
917 // making the STW ref processor inactive by disabling discovery.
918 // * Verify that the CM ref processor is still inactive
919 // and no references have been placed on it's discovered
920 // lists (also checked as a precondition during initial marking).
921
922 // The (stw) reference processor...
923 ReferenceProcessor* _ref_processor_stw;
924
925 // During reference object discovery, the _is_alive_non_header
926 // closure (if non-null) is applied to the referent object to
927 // determine whether the referent is live. If so then the
928 // reference object does not need to be 'discovered' and can
929 // be treated as a regular oop. This has the benefit of reducing
930 // the number of 'discovered' reference objects that need to
931 // be processed.
932 //
933 // Instance of the is_alive closure for embedding into the
934 // STW reference processor as the _is_alive_non_header field.
935 // Supplying a value for the _is_alive_non_header field is
936 // optional but doing so prevents unnecessary additions to
937 // the discovered lists during reference discovery.
938 G1STWIsAliveClosure _is_alive_closure_stw;
939
940 // The (concurrent marking) reference processor...
941 ReferenceProcessor* _ref_processor_cm;
942
943 // Instance of the concurrent mark is_alive closure for embedding
944 // into the Concurrent Marking reference processor as the
945 // _is_alive_non_header field. Supplying a value for the
946 // _is_alive_non_header field is optional but doing so prevents
947 // unnecessary additions to the discovered lists during reference
948 // discovery.
949 G1CMIsAliveClosure _is_alive_closure_cm;
950
951 volatile bool _free_regions_coming;
952
953 public:
954
955 RefToScanQueue *task_queue(uint i) const;
956
957 uint num_task_queues() const;
958
959 // A set of cards where updates happened during the GC
960 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
961
962 // Create a G1CollectedHeap with the specified policy.
963 // Must call the initialize method afterwards.
964 // May not return if something goes wrong.
965 G1CollectedHeap(G1CollectorPolicy* policy);
966
967 private:
968 jint initialize_concurrent_refinement();
969 jint initialize_young_gen_sampling_thread();
970 public:
971 // Initialize the G1CollectedHeap to have the initial and
972 // maximum sizes and remembered and barrier sets
973 // specified by the policy object.
974 jint initialize();
975
976 virtual void stop();
977 virtual void safepoint_synchronize_begin();
978 virtual void safepoint_synchronize_end();
979
980 // Return the (conservative) maximum heap alignment for any G1 heap
981 static size_t conservative_max_heap_alignment();
982
983 // Does operations required after initialization has been done.
984 void post_initialize();
985
986 // Initialize weak reference processing.
987 void ref_processing_init();
988
989 virtual Name kind() const {
990 return CollectedHeap::G1CollectedHeap;
991 }
992
993 virtual const char* name() const {
994 return "G1";
995 }
996
997 const G1CollectorState* collector_state() const { return &_collector_state; }
998 G1CollectorState* collector_state() { return &_collector_state; }
999
1000 // The current policy object for the collector.
1001 G1Policy* g1_policy() const { return _g1_policy; }
1002
1003 const G1CollectionSet* collection_set() const { return &_collection_set; }
1004 G1CollectionSet* collection_set() { return &_collection_set; }
1005
1006 virtual CollectorPolicy* collector_policy() const;
1007
1008 // Adaptive size policy. No such thing for g1.
1009 virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1010
1011 // The rem set and barrier set.
1012 G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1013
1014 // Try to minimize the remembered set.
1015 void scrub_rem_set();
1016
1017 uint get_gc_time_stamp() {
1018 return _gc_time_stamp;
1019 }
1020
1021 inline void reset_gc_time_stamp();
1022
1023 void check_gc_time_stamps() PRODUCT_RETURN;
1024
1025 inline void increment_gc_time_stamp();
1026
1027 // Reset the given region's GC timestamp. If it's starts humongous,
1028 // also reset the GC timestamp of its corresponding
1029 // continues humongous regions too.
1030 void reset_gc_time_stamps(HeapRegion* hr);
1031
1032 // Apply the given closure on all cards in the Hot Card Cache, emptying it.
1033 void iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i);
1034
1035 // Apply the given closure on all cards in the Dirty Card Queue Set, emptying it.
1036 void iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i);
1037
1038 // The shared block offset table array.
1039 G1BlockOffsetTable* bot() const { return _bot; }
1040
1041 // Reference Processing accessors
1042
1043 // The STW reference processor....
1044 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1045
1046 G1NewTracer* gc_tracer_stw() const { return _gc_tracer_stw; }
1047
1048 // The Concurrent Marking reference processor...
1049 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1050
1051 size_t unused_committed_regions_in_bytes() const;
1052 virtual size_t capacity() const;
1053 virtual size_t used() const;
1054 // This should be called when we're not holding the heap lock. The
1055 // result might be a bit inaccurate.
1056 size_t used_unlocked() const;
1057 size_t recalculate_used() const;
1058
1059 // These virtual functions do the actual allocation.
1060 // Some heaps may offer a contiguous region for shared non-blocking
1061 // allocation, via inlined code (by exporting the address of the top and
1062 // end fields defining the extent of the contiguous allocation region.)
1063 // But G1CollectedHeap doesn't yet support this.
1064
1065 virtual bool is_maximal_no_gc() const {
1066 return _hrm.available() == 0;
1067 }
1068
1069 // The current number of regions in the heap.
1070 uint num_regions() const { return _hrm.length(); }
1071
1072 // The max number of regions in the heap.
1073 uint max_regions() const { return _hrm.max_length(); }
1074
1075 // The number of regions that are completely free.
1076 uint num_free_regions() const { return _hrm.num_free_regions(); }
1077
1078 MemoryUsage get_auxiliary_data_memory_usage() const {
1079 return _hrm.get_auxiliary_data_memory_usage();
1080 }
1081
1082 // The number of regions that are not completely free.
1083 uint num_used_regions() const { return num_regions() - num_free_regions(); }
1084
1085 #ifdef ASSERT
1086 bool is_on_master_free_list(HeapRegion* hr) {
1087 return _hrm.is_free(hr);
1088 }
1089 #endif // ASSERT
1090
1091 // Wrapper for the region list operations that can be called from
1092 // methods outside this class.
1093
1094 void secondary_free_list_add(FreeRegionList* list) {
1095 _secondary_free_list.add_ordered(list);
1096 }
1097
1098 void append_secondary_free_list() {
1099 _hrm.insert_list_into_free_list(&_secondary_free_list);
1100 }
1101
1102 void append_secondary_free_list_if_not_empty_with_lock() {
1103 // If the secondary free list looks empty there's no reason to
1104 // take the lock and then try to append it.
1105 if (!_secondary_free_list.is_empty()) {
1106 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1107 append_secondary_free_list();
1108 }
1109 }
1110
1111 inline void old_set_add(HeapRegion* hr);
1112 inline void old_set_remove(HeapRegion* hr);
1113
1114 size_t non_young_capacity_bytes() {
1115 return (_old_set.length() + _humongous_set.length()) * HeapRegion::GrainBytes;
1116 }
1117
1118 void set_free_regions_coming();
1119 void reset_free_regions_coming();
1120 bool free_regions_coming() { return _free_regions_coming; }
1121 void wait_while_free_regions_coming();
1122
1123 // Determine whether the given region is one that we are using as an
1124 // old GC alloc region.
1125 bool is_old_gc_alloc_region(HeapRegion* hr);
1126
1127 // Perform a collection of the heap; intended for use in implementing
1128 // "System.gc". This probably implies as full a collection as the
1129 // "CollectedHeap" supports.
1130 virtual void collect(GCCause::Cause cause);
1131
1132 virtual bool copy_allocation_context_stats(const jint* contexts,
1133 jlong* totals,
1134 jbyte* accuracy,
1135 jint len);
1136
1137 // True iff an evacuation has failed in the most-recent collection.
1138 bool evacuation_failed() { return _evacuation_failed; }
1139
1140 void remove_from_old_sets(const uint old_regions_removed, const uint humongous_regions_removed);
1141 void prepend_to_freelist(FreeRegionList* list);
1142 void decrement_summary_bytes(size_t bytes);
1143
1144 virtual bool is_in(const void* p) const;
1145 #ifdef ASSERT
1146 // Returns whether p is in one of the available areas of the heap. Slow but
1147 // extensive version.
1148 bool is_in_exact(const void* p) const;
1149 #endif
1150
1151 // Return "TRUE" iff the given object address is within the collection
1152 // set. Assumes that the reference points into the heap.
1153 inline bool is_in_cset(const HeapRegion *hr);
1154 inline bool is_in_cset(oop obj);
1155 inline bool is_in_cset(HeapWord* addr);
1156
1157 inline bool is_in_cset_or_humongous(const oop obj);
1158
1159 private:
1160 // This array is used for a quick test on whether a reference points into
1161 // the collection set or not. Each of the array's elements denotes whether the
1162 // corresponding region is in the collection set or not.
1163 G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test;
1164
1165 public:
1166
1167 inline InCSetState in_cset_state(const oop obj);
1168
1169 // Return "TRUE" iff the given object address is in the reserved
1170 // region of g1.
1171 bool is_in_g1_reserved(const void* p) const {
1172 return _hrm.reserved().contains(p);
1173 }
1174
1175 // Returns a MemRegion that corresponds to the space that has been
1176 // reserved for the heap
1177 MemRegion g1_reserved() const {
1178 return _hrm.reserved();
1179 }
1180
1181 virtual bool is_in_closed_subset(const void* p) const;
1182
1183 G1SATBCardTableLoggingModRefBS* g1_barrier_set() {
1184 return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set());
1185 }
1186
1187 G1HotCardCache* g1_hot_card_cache() const { return _hot_card_cache; }
1188
1189 // Iteration functions.
1190
1191 // Iterate over all objects, calling "cl.do_object" on each.
1192 virtual void object_iterate(ObjectClosure* cl);
1193
1194 virtual void safe_object_iterate(ObjectClosure* cl) {
1195 object_iterate(cl);
1196 }
1197
1198 // Iterate over heap regions, in address order, terminating the
1199 // iteration early if the "doHeapRegion" method returns "true".
1200 void heap_region_iterate(HeapRegionClosure* blk) const;
1201
1202 // Return the region with the given index. It assumes the index is valid.
1203 inline HeapRegion* region_at(uint index) const;
1204
1205 // Return the next region (by index) that is part of the same
1206 // humongous object that hr is part of.
1207 inline HeapRegion* next_region_in_humongous(HeapRegion* hr) const;
1208
1209 // Calculate the region index of the given address. Given address must be
1210 // within the heap.
1211 inline uint addr_to_region(HeapWord* addr) const;
1212
1213 inline HeapWord* bottom_addr_for_region(uint index) const;
1214
1215 // Two functions to iterate over the heap regions in parallel. Threads
1216 // compete using the HeapRegionClaimer to claim the regions before
1217 // applying the closure on them.
1218 // The _from_worker_offset version uses the HeapRegionClaimer and
1219 // the worker id to calculate a start offset to prevent all workers to
1220 // start from the point.
1221 void heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
1222 HeapRegionClaimer* hrclaimer,
1223 uint worker_id) const;
1224
1225 void heap_region_par_iterate_from_start(HeapRegionClosure* cl,
1226 HeapRegionClaimer* hrclaimer) const;
1227
1228 // Iterate over the regions (if any) in the current collection set.
1229 void collection_set_iterate(HeapRegionClosure* blk);
1230
1231 // Iterate over the regions (if any) in the current collection set. Starts the
1232 // iteration over the entire collection set so that the start regions of a given
1233 // worker id over the set active_workers are evenly spread across the set of
1234 // collection set regions.
1235 void collection_set_iterate_from(HeapRegionClosure *blk, uint worker_id);
1236
1237 // Returns the HeapRegion that contains addr. addr must not be NULL.
1238 template <class T>
1239 inline HeapRegion* heap_region_containing(const T addr) const;
1240
1241 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1242 // each address in the (reserved) heap is a member of exactly
1243 // one block. The defining characteristic of a block is that it is
1244 // possible to find its size, and thus to progress forward to the next
1245 // block. (Blocks may be of different sizes.) Thus, blocks may
1246 // represent Java objects, or they might be free blocks in a
1247 // free-list-based heap (or subheap), as long as the two kinds are
1248 // distinguishable and the size of each is determinable.
1249
1250 // Returns the address of the start of the "block" that contains the
1251 // address "addr". We say "blocks" instead of "object" since some heaps
1252 // may not pack objects densely; a chunk may either be an object or a
1253 // non-object.
1254 virtual HeapWord* block_start(const void* addr) const;
1255
1256 // Requires "addr" to be the start of a chunk, and returns its size.
1257 // "addr + size" is required to be the start of a new chunk, or the end
1258 // of the active area of the heap.
1259 virtual size_t block_size(const HeapWord* addr) const;
1260
1261 // Requires "addr" to be the start of a block, and returns "TRUE" iff
1262 // the block is an object.
1263 virtual bool block_is_obj(const HeapWord* addr) const;
1264
1265 // Section on thread-local allocation buffers (TLABs)
1266 // See CollectedHeap for semantics.
1267
1268 bool supports_tlab_allocation() const;
1269 size_t tlab_capacity(Thread* ignored) const;
1270 size_t tlab_used(Thread* ignored) const;
1271 size_t max_tlab_size() const;
1272 size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1273
1274 // Can a compiler initialize a new object without store barriers?
1275 // This permission only extends from the creation of a new object
1276 // via a TLAB up to the first subsequent safepoint. If such permission
1277 // is granted for this heap type, the compiler promises to call
1278 // defer_store_barrier() below on any slow path allocation of
1279 // a new object for which such initializing store barriers will
1280 // have been elided. G1, like CMS, allows this, but should be
1281 // ready to provide a compensating write barrier as necessary
1282 // if that storage came out of a non-young region. The efficiency
1283 // of this implementation depends crucially on being able to
1284 // answer very efficiently in constant time whether a piece of
1285 // storage in the heap comes from a young region or not.
1286 // See ReduceInitialCardMarks.
1287 virtual bool can_elide_tlab_store_barriers() const {
1288 return true;
1289 }
1290
1291 virtual bool card_mark_must_follow_store() const {
1292 return true;
1293 }
1294
1295 inline bool is_in_young(const oop obj);
1296
1297 // We don't need barriers for initializing stores to objects
1298 // in the young gen: for the SATB pre-barrier, there is no
1299 // pre-value that needs to be remembered; for the remembered-set
1300 // update logging post-barrier, we don't maintain remembered set
1301 // information for young gen objects.
1302 virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1303
1304 // Returns "true" iff the given word_size is "very large".
1305 static bool is_humongous(size_t word_size) {
1306 // Note this has to be strictly greater-than as the TLABs
1307 // are capped at the humongous threshold and we want to
1308 // ensure that we don't try to allocate a TLAB as
1309 // humongous and that we don't allocate a humongous
1310 // object in a TLAB.
1311 return word_size > _humongous_object_threshold_in_words;
1312 }
1313
1314 // Returns the humongous threshold for a specific region size
1315 static size_t humongous_threshold_for(size_t region_size) {
1316 return (region_size / 2);
1317 }
1318
1319 // Returns the number of regions the humongous object of the given word size
1320 // requires.
1321 static size_t humongous_obj_size_in_regions(size_t word_size);
1322
1323 // Print the maximum heap capacity.
1324 virtual size_t max_capacity() const;
1325
1326 virtual jlong millis_since_last_gc();
1327
1328
1329 // Convenience function to be used in situations where the heap type can be
1330 // asserted to be this type.
1331 static G1CollectedHeap* heap();
1332
1333 void set_region_short_lived_locked(HeapRegion* hr);
1334 // add appropriate methods for any other surv rate groups
1335
1336 const G1SurvivorRegions* survivor() const { return &_survivor; }
1337
1338 uint survivor_regions_count() const {
1339 return _survivor.length();
1340 }
1341
1342 uint eden_regions_count() const {
1343 return _eden.length();
1344 }
1345
1346 uint young_regions_count() const {
1347 return _eden.length() + _survivor.length();
1348 }
1349
1350 uint old_regions_count() const { return _old_set.length(); }
1351
1352 uint humongous_regions_count() const { return _humongous_set.length(); }
1353
1354 #ifdef ASSERT
1355 bool check_young_list_empty();
1356 #endif
1357
1358 // *** Stuff related to concurrent marking. It's not clear to me that so
1359 // many of these need to be public.
1360
1361 // The functions below are helper functions that a subclass of
1362 // "CollectedHeap" can use in the implementation of its virtual
1363 // functions.
1364 // This performs a concurrent marking of the live objects in a
1365 // bitmap off to the side.
1366 void doConcurrentMark();
1367
1368 bool isMarkedNext(oop obj) const;
1369
1370 // Determine if an object is dead, given the object and also
1371 // the region to which the object belongs. An object is dead
1372 // iff a) it was not allocated since the last mark, b) it
1373 // is not marked, and c) it is not in an archive region.
1374 bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1375 return
1376 hr->is_obj_dead(obj, _cm->prev_mark_bitmap()) &&
1377 !hr->is_archive();
1378 }
1379
1380 // This function returns true when an object has been
1381 // around since the previous marking and hasn't yet
1382 // been marked during this marking, and is not in an archive region.
1383 bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1384 return
1385 !hr->obj_allocated_since_next_marking(obj) &&
1386 !isMarkedNext(obj) &&
1387 !hr->is_archive();
1388 }
1389
1390 // Determine if an object is dead, given only the object itself.
1391 // This will find the region to which the object belongs and
1392 // then call the region version of the same function.
1393
1394 // Added if it is NULL it isn't dead.
1395
1396 inline bool is_obj_dead(const oop obj) const;
1397
1398 inline bool is_obj_ill(const oop obj) const;
1399
1400 inline bool is_obj_dead_full(const oop obj, const HeapRegion* hr) const;
1401 inline bool is_obj_dead_full(const oop obj) const;
1402
1403 G1ConcurrentMark* concurrent_mark() const { return _cm; }
1404
1405 // Refinement
1406
1407 G1ConcurrentRefine* concurrent_refine() const { return _cr; }
1408
1409 // Optimized nmethod scanning support routines
1410
1411 // Is an oop scavengeable
1412 virtual bool is_scavengable(oop obj);
1413
1414 // Register the given nmethod with the G1 heap.
1415 virtual void register_nmethod(nmethod* nm);
1416
1417 // Unregister the given nmethod from the G1 heap.
1418 virtual void unregister_nmethod(nmethod* nm);
1419
1420 // Free up superfluous code root memory.
1421 void purge_code_root_memory();
1422
1423 // Rebuild the strong code root lists for each region
1424 // after a full GC.
1425 void rebuild_strong_code_roots();
1426
1427 // Partial cleaning used when class unloading is disabled.
1428 // Let the caller choose what structures to clean out:
1429 // - StringTable
1430 // - SymbolTable
1431 // - StringDeduplication structures
1432 void partial_cleaning(BoolObjectClosure* is_alive, bool unlink_strings, bool unlink_symbols, bool unlink_string_dedup);
1433
1434 // Complete cleaning used when class unloading is enabled.
1435 // Cleans out all structures handled by partial_cleaning and also the CodeCache.
1436 void complete_cleaning(BoolObjectClosure* is_alive, bool class_unloading_occurred);
1437
1438 // Redirty logged cards in the refinement queue.
1439 void redirty_logged_cards();
1440 // Verification
1441
1442 // Perform any cleanup actions necessary before allowing a verification.
1443 virtual void prepare_for_verify();
1444
1445 // Perform verification.
1446
1447 // vo == UsePrevMarking -> use "prev" marking information,
1448 // vo == UseNextMarking -> use "next" marking information
1449 // vo == UseFullMarking -> use "next" marking bitmap but no TAMS
1450 //
1451 // NOTE: Only the "prev" marking information is guaranteed to be
1452 // consistent most of the time, so most calls to this should use
1453 // vo == UsePrevMarking.
1454 // Currently, there is only one case where this is called with
1455 // vo == UseNextMarking, which is to verify the "next" marking
1456 // information at the end of remark.
1457 // Currently there is only one place where this is called with
1458 // vo == UseFullMarking, which is to verify the marking during a
1459 // full GC.
1460 void verify(VerifyOption vo);
1461
1462 // WhiteBox testing support.
1463 virtual bool supports_concurrent_phase_control() const;
1464 virtual const char* const* concurrent_phases() const;
1465 virtual bool request_concurrent_phase(const char* phase);
1466
1467 // The methods below are here for convenience and dispatch the
1468 // appropriate method depending on value of the given VerifyOption
1469 // parameter. The values for that parameter, and their meanings,
1470 // are the same as those above.
1471
1472 bool is_obj_dead_cond(const oop obj,
1473 const HeapRegion* hr,
1474 const VerifyOption vo) const;
1475
1476 bool is_obj_dead_cond(const oop obj,
1477 const VerifyOption vo) const;
1478
1479 G1HeapSummary create_g1_heap_summary();
1480 G1EvacSummary create_g1_evac_summary(G1EvacStats* stats);
1481
1482 // Printing
1483 private:
1484 void print_heap_regions() const;
1485 void print_regions_on(outputStream* st) const;
1486
1487 public:
1488 virtual void print_on(outputStream* st) const;
1489 virtual void print_extended_on(outputStream* st) const;
1490 virtual void print_on_error(outputStream* st) const;
1491
1492 virtual void print_gc_threads_on(outputStream* st) const;
1493 virtual void gc_threads_do(ThreadClosure* tc) const;
1494
1495 // Override
1496 void print_tracing_info() const;
1497
1498 // The following two methods are helpful for debugging RSet issues.
1499 void print_cset_rsets() PRODUCT_RETURN;
1500 void print_all_rsets() PRODUCT_RETURN;
1501
1502 public:
1503 size_t pending_card_num();
1504
1505 protected:
1506 size_t _max_heap_capacity;
1507 };
1508
1509 class G1ParEvacuateFollowersClosure : public VoidClosure {
1510 private:
1511 double _start_term;
1512 double _term_time;
1513 size_t _term_attempts;
1514
1515 void start_term_time() { _term_attempts++; _start_term = os::elapsedTime(); }
1516 void end_term_time() { _term_time += os::elapsedTime() - _start_term; }
1517 protected:
1518 G1CollectedHeap* _g1h;
1519 G1ParScanThreadState* _par_scan_state;
1520 RefToScanQueueSet* _queues;
1521 ParallelTaskTerminator* _terminator;
1522
1523 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
1524 RefToScanQueueSet* queues() { return _queues; }
1525 ParallelTaskTerminator* terminator() { return _terminator; }
1526
1527 public:
1528 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
1529 G1ParScanThreadState* par_scan_state,
1530 RefToScanQueueSet* queues,
1531 ParallelTaskTerminator* terminator)
1532 : _g1h(g1h), _par_scan_state(par_scan_state),
1533 _queues(queues), _terminator(terminator),
1534 _start_term(0.0), _term_time(0.0), _term_attempts(0) {}
1535
1536 void do_void();
1537
1538 double term_time() const { return _term_time; }
1539 size_t term_attempts() const { return _term_attempts; }
1540
1541 private:
1542 inline bool offer_termination();
1543 };
1544
1545 #endif // SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP