1 /*
2 * Copyright (c) 2001, 2016, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
8 *
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
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24
25 #ifndef SHARE_VM_GC_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/g1HeapVerifier.hpp"
38 #include "gc/g1/g1HRPrinter.hpp"
39 #include "gc/g1/g1InCSetState.hpp"
40 #include "gc/g1/g1MonitoringSupport.hpp"
41 #include "gc/g1/g1SATBCardTableModRefBS.hpp"
42 #include "gc/g1/g1SurvivorRegions.hpp"
43 #include "gc/g1/g1YCTypes.hpp"
44 #include "gc/g1/hSpaceCounters.hpp"
45 #include "gc/g1/heapRegionManager.hpp"
46 #include "gc/g1/heapRegionSet.hpp"
47 #include "gc/shared/barrierSet.hpp"
48 #include "gc/shared/collectedHeap.hpp"
49 #include "gc/shared/plab.hpp"
50 #include "gc/shared/preservedMarks.hpp"
51 #include "memory/memRegion.hpp"
52 #include "utilities/stack.hpp"
53
54 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
55 // It uses the "Garbage First" heap organization and algorithm, which
56 // may combine concurrent marking with parallel, incremental compaction of
57 // heap subsets that will yield large amounts of garbage.
58
59 // Forward declarations
60 class HeapRegion;
61 class HRRSCleanupTask;
62 class GenerationSpec;
63 class OopsInHeapRegionClosure;
64 class G1ParScanThreadState;
65 class G1ParScanThreadStateSet;
66 class G1KlassScanClosure;
67 class G1ParScanThreadState;
68 class ObjectClosure;
69 class SpaceClosure;
70 class CompactibleSpaceClosure;
71 class Space;
72 class G1CollectionSet;
73 class G1CollectorPolicy;
74 class G1Policy;
75 class G1HotCardCache;
76 class G1RemSet;
77 class HeapRegionRemSetIterator;
78 class G1ConcurrentMark;
79 class ConcurrentMarkThread;
80 class ConcurrentG1Refine;
81 class GenerationCounters;
82 class STWGCTimer;
83 class G1NewTracer;
84 class EvacuationFailedInfo;
85 class nmethod;
86 class Ticks;
87 class WorkGang;
88 class G1Allocator;
89 class G1ArchiveAllocator;
90 class G1HeapVerifier;
91 class G1HeapSizingPolicy;
92
93 typedef OverflowTaskQueue<StarTask, mtGC> RefToScanQueue;
94 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
95
96 typedef int RegionIdx_t; // needs to hold [ 0..max_regions() )
97 typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion )
98
99 // The G1 STW is alive closure.
100 // An instance is embedded into the G1CH and used as the
101 // (optional) _is_alive_non_header closure in the STW
102 // reference processor. It is also extensively used during
103 // reference processing during STW evacuation pauses.
104 class G1STWIsAliveClosure: public BoolObjectClosure {
105 G1CollectedHeap* _g1;
106 public:
107 G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
108 bool do_object_b(oop p);
109 };
110
111 class RefineCardTableEntryClosure;
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 VM_CollectForMetadataAllocation;
122 friend class VM_G1CollectForAllocation;
123 friend class VM_G1CollectFull;
124 friend class VM_G1IncCollectionPause;
125 friend class VMStructs;
126 friend class MutatorAllocRegion;
127 friend class G1GCAllocRegion;
128 friend class G1HeapVerifier;
129
130 // Closures used in implementation.
131 friend class G1ParScanThreadState;
132 friend class G1ParScanThreadStateSet;
133 friend class G1ParTask;
134 friend class G1PLABAllocator;
135 friend class G1PrepareCompactClosure;
136
137 // Other related classes.
138 friend class HeapRegionClaimer;
139
140 // Testing classes.
141 friend class G1CheckCSetFastTableClosure;
142
143 private:
144 WorkGang* _workers;
145 G1CollectorPolicy* _collector_policy;
146
147 static size_t _humongous_object_threshold_in_words;
148
149 // The secondary free list which contains regions that have been
150 // freed up during the cleanup process. This will be appended to
151 // the master free list when appropriate.
152 FreeRegionList _secondary_free_list;
153
154 // It keeps track of the old regions.
155 HeapRegionSet _old_set;
156
157 // It keeps track of the humongous regions.
158 HeapRegionSet _humongous_set;
159
160 void eagerly_reclaim_humongous_regions();
161
162 // The number of regions we could create by expansion.
163 uint _expansion_regions;
164
165 // The block offset table for the G1 heap.
166 G1BlockOffsetTable* _bot;
167
168 // Tears down the region sets / lists so that they are empty and the
169 // regions on the heap do not belong to a region set / list. The
170 // only exception is the humongous set which we leave unaltered. If
171 // free_list_only is true, it will only tear down the master free
172 // list. It is called before a Full GC (free_list_only == false) or
173 // before heap shrinking (free_list_only == true).
174 void tear_down_region_sets(bool free_list_only);
175
176 // Rebuilds the region sets / lists so that they are repopulated to
177 // reflect the contents of the heap. The only exception is the
178 // humongous set which was not torn down in the first place. If
179 // free_list_only is true, it will only rebuild the master free
180 // list. It is called after a Full GC (free_list_only == false) or
181 // after heap shrinking (free_list_only == true).
182 void rebuild_region_sets(bool free_list_only);
183
184 // Callback for region mapping changed events.
185 G1RegionMappingChangedListener _listener;
186
187 // The sequence of all heap regions in the heap.
188 HeapRegionManager _hrm;
189
190 // Manages all allocations with regions except humongous object allocations.
191 G1Allocator* _allocator;
192
193 // Manages all heap verification.
194 G1HeapVerifier* _verifier;
195
196 // Outside of GC pauses, the number of bytes used in all regions other
197 // than the current allocation region(s).
198 size_t _summary_bytes_used;
199
200 void increase_used(size_t bytes);
201 void decrease_used(size_t bytes);
202
203 void set_used(size_t bytes);
204
205 // Class that handles archive allocation ranges.
206 G1ArchiveAllocator* _archive_allocator;
207
208 // Statistics for each allocation context
209 AllocationContextStats _allocation_context_stats;
210
211 // GC allocation statistics policy for survivors.
212 G1EvacStats _survivor_evac_stats;
213
214 // GC allocation statistics policy for tenured objects.
215 G1EvacStats _old_evac_stats;
216
217 // It specifies whether we should attempt to expand the heap after a
218 // region allocation failure. If heap expansion fails we set this to
219 // false so that we don't re-attempt the heap expansion (it's likely
220 // that subsequent expansion attempts will also fail if one fails).
221 // Currently, it is only consulted during GC and it's reset at the
222 // start of each GC.
223 bool _expand_heap_after_alloc_failure;
224
225 // Helper for monitoring and management support.
226 G1MonitoringSupport* _g1mm;
227
228 // Records whether the region at the given index is (still) a
229 // candidate for eager reclaim. Only valid for humongous start
230 // regions; other regions have unspecified values. Humongous start
231 // regions are initialized at start of collection pause, with
232 // candidates removed from the set as they are found reachable from
233 // roots or the young generation.
234 class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> {
235 protected:
236 bool default_value() const { return false; }
237 public:
238 void clear() { G1BiasedMappedArray<bool>::clear(); }
239 void set_candidate(uint region, bool value) {
240 set_by_index(region, value);
241 }
242 bool is_candidate(uint region) {
243 return get_by_index(region);
244 }
245 };
246
247 HumongousReclaimCandidates _humongous_reclaim_candidates;
248 // Stores whether during humongous object registration we found candidate regions.
249 // If not, we can skip a few steps.
250 bool _has_humongous_reclaim_candidates;
251
252 volatile uint _gc_time_stamp;
253
254 G1HRPrinter _hr_printer;
255
256 // It decides whether an explicit GC should start a concurrent cycle
257 // instead of doing a STW GC. Currently, a concurrent cycle is
258 // explicitly started if:
259 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
260 // (b) cause == _g1_humongous_allocation
261 // (c) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
262 // (d) cause == _dcmd_gc_run and +ExplicitGCInvokesConcurrent.
263 // (e) cause == _update_allocation_context_stats_inc
264 // (f) cause == _wb_conc_mark
265 bool should_do_concurrent_full_gc(GCCause::Cause cause);
266
267 // indicates whether we are in young or mixed GC mode
268 G1CollectorState _collector_state;
269
270 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
271 // concurrent cycles) we have started.
272 volatile uint _old_marking_cycles_started;
273
274 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
275 // concurrent cycles) we have completed.
276 volatile uint _old_marking_cycles_completed;
277
278 // This is a non-product method that is helpful for testing. It is
279 // called at the end of a GC and artificially expands the heap by
280 // allocating a number of dead regions. This way we can induce very
281 // frequent marking cycles and stress the cleanup / concurrent
282 // cleanup code more (as all the regions that will be allocated by
283 // this method will be found dead by the marking cycle).
284 void allocate_dummy_regions() PRODUCT_RETURN;
285
286 // Clear RSets after a compaction. It also resets the GC time stamps.
287 void clear_rsets_post_compaction();
288
289 // If the HR printer is active, dump the state of the regions in the
290 // heap after a compaction.
291 void print_hrm_post_compaction();
292
293 // Create a memory mapper for auxiliary data structures of the given size and
294 // translation factor.
295 static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description,
296 size_t size,
297 size_t translation_factor);
298
299 static G1Policy* create_g1_policy();
300
301 void trace_heap(GCWhen::Type when, const GCTracer* tracer);
302
303 void process_weak_jni_handles();
304
305 // These are macros so that, if the assert fires, we get the correct
306 // line number, file, etc.
307
308 #define heap_locking_asserts_params(_extra_message_) \
309 "%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \
310 (_extra_message_), \
311 BOOL_TO_STR(Heap_lock->owned_by_self()), \
312 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \
313 BOOL_TO_STR(Thread::current()->is_VM_thread())
314
315 #define assert_heap_locked() \
316 do { \
317 assert(Heap_lock->owned_by_self(), \
318 heap_locking_asserts_params("should be holding the Heap_lock")); \
319 } while (0)
320
321 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \
322 do { \
323 assert(Heap_lock->owned_by_self() || \
324 (SafepointSynchronize::is_at_safepoint() && \
325 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
326 heap_locking_asserts_params("should be holding the Heap_lock or " \
327 "should be at a safepoint")); \
328 } while (0)
329
330 #define assert_heap_locked_and_not_at_safepoint() \
331 do { \
332 assert(Heap_lock->owned_by_self() && \
333 !SafepointSynchronize::is_at_safepoint(), \
334 heap_locking_asserts_params("should be holding the Heap_lock and " \
335 "should not be at a safepoint")); \
336 } while (0)
337
338 #define assert_heap_not_locked() \
339 do { \
340 assert(!Heap_lock->owned_by_self(), \
341 heap_locking_asserts_params("should not be holding the Heap_lock")); \
342 } while (0)
343
344 #define assert_heap_not_locked_and_not_at_safepoint() \
345 do { \
346 assert(!Heap_lock->owned_by_self() && \
347 !SafepointSynchronize::is_at_safepoint(), \
348 heap_locking_asserts_params("should not be holding the Heap_lock and " \
349 "should not be at a safepoint")); \
350 } while (0)
351
352 #define assert_at_safepoint(_should_be_vm_thread_) \
353 do { \
354 assert(SafepointSynchronize::is_at_safepoint() && \
355 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
356 heap_locking_asserts_params("should be at a safepoint")); \
357 } while (0)
358
359 #define assert_not_at_safepoint() \
360 do { \
361 assert(!SafepointSynchronize::is_at_safepoint(), \
362 heap_locking_asserts_params("should not be at a safepoint")); \
363 } while (0)
364
365 protected:
366
367 // The young region list.
368 G1EdenRegions _eden;
369 G1SurvivorRegions _survivor;
370
371 // The current policy object for the collector.
372 G1Policy* _g1_policy;
373 G1HeapSizingPolicy* _heap_sizing_policy;
374
375 G1CollectionSet _collection_set;
376
377 // This is the second level of trying to allocate a new region. If
378 // new_region() didn't find a region on the free_list, this call will
379 // check whether there's anything available on the
380 // secondary_free_list and/or wait for more regions to appear on
381 // that list, if _free_regions_coming is set.
382 HeapRegion* new_region_try_secondary_free_list(bool is_old);
383
384 // Try to allocate a single non-humongous HeapRegion sufficient for
385 // an allocation of the given word_size. If do_expand is true,
386 // attempt to expand the heap if necessary to satisfy the allocation
387 // request. If the region is to be used as an old region or for a
388 // humongous object, set is_old to true. If not, to false.
389 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
390
391 // Initialize a contiguous set of free regions of length num_regions
392 // and starting at index first so that they appear as a single
393 // humongous region.
394 HeapWord* humongous_obj_allocate_initialize_regions(uint first,
395 uint num_regions,
396 size_t word_size,
397 AllocationContext_t context);
398
399 // Attempt to allocate a humongous object of the given size. Return
400 // NULL if unsuccessful.
401 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context);
402
403 // The following two methods, allocate_new_tlab() and
404 // mem_allocate(), are the two main entry points from the runtime
405 // into the G1's allocation routines. They have the following
406 // assumptions:
407 //
408 // * They should both be called outside safepoints.
409 //
410 // * They should both be called without holding the Heap_lock.
411 //
412 // * All allocation requests for new TLABs should go to
413 // allocate_new_tlab().
414 //
415 // * All non-TLAB allocation requests should go to mem_allocate().
416 //
417 // * If either call cannot satisfy the allocation request using the
418 // current allocating region, they will try to get a new one. If
419 // this fails, they will attempt to do an evacuation pause and
420 // retry the allocation.
421 //
422 // * If all allocation attempts fail, even after trying to schedule
423 // an evacuation pause, allocate_new_tlab() will return NULL,
424 // whereas mem_allocate() will attempt a heap expansion and/or
425 // schedule a Full GC.
426 //
427 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
428 // should never be called with word_size being humongous. All
429 // humongous allocation requests should go to mem_allocate() which
430 // will satisfy them with a special path.
431
432 virtual HeapWord* allocate_new_tlab(size_t word_size);
433
434 virtual HeapWord* mem_allocate(size_t word_size,
435 bool* gc_overhead_limit_was_exceeded);
436
437 // The following three methods take a gc_count_before_ret
438 // parameter which is used to return the GC count if the method
439 // returns NULL. Given that we are required to read the GC count
440 // while holding the Heap_lock, and these paths will take the
441 // Heap_lock at some point, it's easier to get them to read the GC
442 // count while holding the Heap_lock before they return NULL instead
443 // of the caller (namely: mem_allocate()) having to also take the
444 // Heap_lock just to read the GC count.
445
446 // First-level mutator allocation attempt: try to allocate out of
447 // the mutator alloc region without taking the Heap_lock. This
448 // should only be used for non-humongous allocations.
449 inline HeapWord* attempt_allocation(size_t word_size,
450 uint* gc_count_before_ret,
451 uint* gclocker_retry_count_ret);
452
453 // Second-level mutator allocation attempt: take the Heap_lock and
454 // retry the allocation attempt, potentially scheduling a GC
455 // pause. This should only be used for non-humongous allocations.
456 HeapWord* attempt_allocation_slow(size_t word_size,
457 AllocationContext_t context,
458 uint* gc_count_before_ret,
459 uint* gclocker_retry_count_ret);
460
461 // Takes the Heap_lock and attempts a humongous allocation. It can
462 // potentially schedule a GC pause.
463 HeapWord* attempt_allocation_humongous(size_t word_size,
464 uint* gc_count_before_ret,
465 uint* gclocker_retry_count_ret);
466
467 // Allocation attempt that should be called during safepoints (e.g.,
468 // at the end of a successful GC). expect_null_mutator_alloc_region
469 // specifies whether the mutator alloc region is expected to be NULL
470 // or not.
471 HeapWord* attempt_allocation_at_safepoint(size_t word_size,
472 AllocationContext_t context,
473 bool expect_null_mutator_alloc_region);
474
475 // These methods are the "callbacks" from the G1AllocRegion class.
476
477 // For mutator alloc regions.
478 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
479 void retire_mutator_alloc_region(HeapRegion* alloc_region,
480 size_t allocated_bytes);
481
482 // For GC alloc regions.
483 bool has_more_regions(InCSetState dest);
484 HeapRegion* new_gc_alloc_region(size_t word_size, InCSetState dest);
485 void retire_gc_alloc_region(HeapRegion* alloc_region,
486 size_t allocated_bytes, InCSetState dest);
487
488 // - if explicit_gc is true, the GC is for a System.gc() etc,
489 // otherwise it's for a failed allocation.
490 // - if clear_all_soft_refs is true, all soft references should be
491 // cleared during the GC.
492 // - it returns false if it is unable to do the collection due to the
493 // GC locker being active, true otherwise.
494 bool do_full_collection(bool explicit_gc,
495 bool clear_all_soft_refs);
496
497 // Callback from VM_G1CollectFull operation, or collect_as_vm_thread.
498 virtual void do_full_collection(bool clear_all_soft_refs);
499
500 // Resize the heap if necessary after a full collection.
501 void resize_if_necessary_after_full_collection();
502
503 // Callback from VM_G1CollectForAllocation operation.
504 // This function does everything necessary/possible to satisfy a
505 // failed allocation request (including collection, expansion, etc.)
506 HeapWord* satisfy_failed_allocation(size_t word_size,
507 AllocationContext_t context,
508 bool* succeeded);
509 private:
510 // Helper method for satisfy_failed_allocation()
511 HeapWord* satisfy_failed_allocation_helper(size_t word_size,
512 AllocationContext_t context,
513 bool do_gc,
514 bool clear_all_soft_refs,
515 bool expect_null_mutator_alloc_region,
516 bool* gc_succeeded);
517
518 protected:
519 // Attempting to expand the heap sufficiently
520 // to support an allocation of the given "word_size". If
521 // successful, perform the allocation and return the address of the
522 // allocated block, or else "NULL".
523 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context);
524
525 // Preserve any referents discovered by concurrent marking that have not yet been
526 // copied by the STW pause.
527 void preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states);
528 // Process any reference objects discovered during
529 // an incremental evacuation pause.
530 void process_discovered_references(G1ParScanThreadStateSet* per_thread_states);
531
532 // Enqueue any remaining discovered references
533 // after processing.
534 void enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states);
535
536 // Merges the information gathered on a per-thread basis for all worker threads
537 // during GC into global variables.
538 void merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states);
539 public:
540 WorkGang* workers() const { return _workers; }
541
542 G1Allocator* allocator() {
543 return _allocator;
544 }
545
546 G1HeapVerifier* verifier() {
547 return _verifier;
548 }
549
550 G1MonitoringSupport* g1mm() {
551 assert(_g1mm != NULL, "should have been initialized");
552 return _g1mm;
553 }
554
555 // Expand the garbage-first heap by at least the given size (in bytes!).
556 // Returns true if the heap was expanded by the requested amount;
557 // false otherwise.
558 // (Rounds up to a HeapRegion boundary.)
559 bool expand(size_t expand_bytes, double* expand_time_ms = NULL);
560
561 // Returns the PLAB statistics for a given destination.
562 inline G1EvacStats* alloc_buffer_stats(InCSetState dest);
563
564 // Determines PLAB size for a given destination.
565 inline size_t desired_plab_sz(InCSetState dest);
566
567 inline AllocationContextStats& allocation_context_stats();
568
569 // Do anything common to GC's.
570 void gc_prologue(bool full);
571 void gc_epilogue(bool full);
572
573 // Modify the reclaim candidate set and test for presence.
574 // These are only valid for starts_humongous regions.
575 inline void set_humongous_reclaim_candidate(uint region, bool value);
576 inline bool is_humongous_reclaim_candidate(uint region);
577
578 // Remove from the reclaim candidate set. Also remove from the
579 // collection set so that later encounters avoid the slow path.
580 inline void set_humongous_is_live(oop obj);
581
582 // Register the given region to be part of the collection set.
583 inline void register_humongous_region_with_cset(uint index);
584 // Register regions with humongous objects (actually on the start region) in
585 // the in_cset_fast_test table.
586 void register_humongous_regions_with_cset();
587 // We register a region with the fast "in collection set" test. We
588 // simply set to true the array slot corresponding to this region.
589 void register_young_region_with_cset(HeapRegion* r) {
590 _in_cset_fast_test.set_in_young(r->hrm_index());
591 }
592 void register_old_region_with_cset(HeapRegion* r) {
593 _in_cset_fast_test.set_in_old(r->hrm_index());
594 }
595 inline void register_ext_region_with_cset(HeapRegion* r) {
596 _in_cset_fast_test.set_ext(r->hrm_index());
597 }
598 void clear_in_cset(const HeapRegion* hr) {
599 _in_cset_fast_test.clear(hr);
600 }
601
602 void clear_cset_fast_test() {
603 _in_cset_fast_test.clear();
604 }
605
606 bool is_user_requested_concurrent_full_gc(GCCause::Cause cause);
607
608 // This is called at the start of either a concurrent cycle or a Full
609 // GC to update the number of old marking cycles started.
610 void increment_old_marking_cycles_started();
611
612 // This is called at the end of either a concurrent cycle or a Full
613 // GC to update the number of old marking cycles completed. Those two
614 // can happen in a nested fashion, i.e., we start a concurrent
615 // cycle, a Full GC happens half-way through it which ends first,
616 // and then the cycle notices that a Full GC happened and ends
617 // too. The concurrent parameter is a boolean to help us do a bit
618 // tighter consistency checking in the method. If concurrent is
619 // false, the caller is the inner caller in the nesting (i.e., the
620 // Full GC). If concurrent is true, the caller is the outer caller
621 // in this nesting (i.e., the concurrent cycle). Further nesting is
622 // not currently supported. The end of this call also notifies
623 // the FullGCCount_lock in case a Java thread is waiting for a full
624 // GC to happen (e.g., it called System.gc() with
625 // +ExplicitGCInvokesConcurrent).
626 void increment_old_marking_cycles_completed(bool concurrent);
627
628 uint old_marking_cycles_completed() {
629 return _old_marking_cycles_completed;
630 }
631
632 G1HRPrinter* hr_printer() { return &_hr_printer; }
633
634 // Allocates a new heap region instance.
635 HeapRegion* new_heap_region(uint hrs_index, MemRegion mr);
636
637 // Allocate the highest free region in the reserved heap. This will commit
638 // regions as necessary.
639 HeapRegion* alloc_highest_free_region();
640
641 // Frees a non-humongous region by initializing its contents and
642 // adding it to the free list that's passed as a parameter (this is
643 // usually a local list which will be appended to the master free
644 // list later). The used bytes of freed regions are accumulated in
645 // pre_used. If par is true, the region's RSet will not be freed
646 // up. The assumption is that this will be done later.
647 // The locked parameter indicates if the caller has already taken
648 // care of proper synchronization. This may allow some optimizations.
649 void free_region(HeapRegion* hr,
650 FreeRegionList* free_list,
651 bool par,
652 bool locked = false);
653
654 // It dirties the cards that cover the block so that the post
655 // write barrier never queues anything when updating objects on this
656 // block. It is assumed (and in fact we assert) that the block
657 // belongs to a young region.
658 inline void dirty_young_block(HeapWord* start, size_t word_size);
659
660 // Frees a humongous region by collapsing it into individual regions
661 // and calling free_region() for each of them. The freed regions
662 // will be added to the free list that's passed as a parameter (this
663 // is usually a local list which will be appended to the master free
664 // list later). The used bytes of freed regions are accumulated in
665 // pre_used. If par is true, the region's RSet will not be freed
666 // up. The assumption is that this will be done later.
667 void free_humongous_region(HeapRegion* hr,
668 FreeRegionList* free_list,
669 bool par);
670
671 // Facility for allocating in 'archive' regions in high heap memory and
672 // recording the allocated ranges. These should all be called from the
673 // VM thread at safepoints, without the heap lock held. They can be used
674 // to create and archive a set of heap regions which can be mapped at the
675 // same fixed addresses in a subsequent JVM invocation.
676 void begin_archive_alloc_range();
677
678 // Check if the requested size would be too large for an archive allocation.
679 bool is_archive_alloc_too_large(size_t word_size);
680
681 // Allocate memory of the requested size from the archive region. This will
682 // return NULL if the size is too large or if no memory is available. It
683 // does not trigger a garbage collection.
684 HeapWord* archive_mem_allocate(size_t word_size);
685
686 // Optionally aligns the end address and returns the allocated ranges in
687 // an array of MemRegions in order of ascending addresses.
688 void end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
689 size_t end_alignment_in_bytes = 0);
690
691 // Facility for allocating a fixed range within the heap and marking
692 // the containing regions as 'archive'. For use at JVM init time, when the
693 // caller may mmap archived heap data at the specified range(s).
694 // Verify that the MemRegions specified in the argument array are within the
695 // reserved heap.
696 bool check_archive_addresses(MemRegion* range, size_t count);
697
698 // Commit the appropriate G1 regions containing the specified MemRegions
699 // and mark them as 'archive' regions. The regions in the array must be
700 // non-overlapping and in order of ascending address.
701 bool alloc_archive_regions(MemRegion* range, size_t count);
702
703 // Insert any required filler objects in the G1 regions around the specified
704 // ranges to make the regions parseable. This must be called after
705 // alloc_archive_regions, and after class loading has occurred.
706 void fill_archive_regions(MemRegion* range, size_t count);
707
708 // For each of the specified MemRegions, uncommit the containing G1 regions
709 // which had been allocated by alloc_archive_regions. This should be called
710 // rather than fill_archive_regions at JVM init time if the archive file
711 // mapping failed, with the same non-overlapping and sorted MemRegion array.
712 void dealloc_archive_regions(MemRegion* range, size_t count);
713
714 protected:
715
716 // Shrink the garbage-first heap by at most the given size (in bytes!).
717 // (Rounds down to a HeapRegion boundary.)
718 virtual void shrink(size_t expand_bytes);
719 void shrink_helper(size_t expand_bytes);
720
721 #if TASKQUEUE_STATS
722 static void print_taskqueue_stats_hdr(outputStream* const st);
723 void print_taskqueue_stats() const;
724 void reset_taskqueue_stats();
725 #endif // TASKQUEUE_STATS
726
727 // Schedule the VM operation that will do an evacuation pause to
728 // satisfy an allocation request of word_size. *succeeded will
729 // return whether the VM operation was successful (it did do an
730 // evacuation pause) or not (another thread beat us to it or the GC
731 // locker was active). Given that we should not be holding the
732 // Heap_lock when we enter this method, we will pass the
733 // gc_count_before (i.e., total_collections()) as a parameter since
734 // it has to be read while holding the Heap_lock. Currently, both
735 // methods that call do_collection_pause() release the Heap_lock
736 // before the call, so it's easy to read gc_count_before just before.
737 HeapWord* do_collection_pause(size_t word_size,
738 uint gc_count_before,
739 bool* succeeded,
740 GCCause::Cause gc_cause);
741
742 void wait_for_root_region_scanning();
743
744 // The guts of the incremental collection pause, executed by the vm
745 // thread. It returns false if it is unable to do the collection due
746 // to the GC locker being active, true otherwise
747 bool do_collection_pause_at_safepoint(double target_pause_time_ms);
748
749 // Actually do the work of evacuating the collection set.
750 virtual void evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states);
751
752 void pre_evacuate_collection_set();
753 void post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* pss);
754
755 // Print the header for the per-thread termination statistics.
756 static void print_termination_stats_hdr();
757 // Print actual per-thread termination statistics.
758 void print_termination_stats(uint worker_id,
759 double elapsed_ms,
760 double strong_roots_ms,
761 double term_ms,
762 size_t term_attempts,
763 size_t alloc_buffer_waste,
764 size_t undo_waste) const;
765 // Update object copying statistics.
766 void record_obj_copy_mem_stats();
767
768 // The hot card cache for remembered set insertion optimization.
769 G1HotCardCache* _hot_card_cache;
770
771 // The g1 remembered set of the heap.
772 G1RemSet* _g1_rem_set;
773
774 // A set of cards that cover the objects for which the Rsets should be updated
775 // concurrently after the collection.
776 DirtyCardQueueSet _dirty_card_queue_set;
777
778 // The closure used to refine a single card.
779 RefineCardTableEntryClosure* _refine_cte_cl;
780
781 // After a collection pause, convert the regions in the collection set into free
782 // regions.
783 void free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words);
784
785 // Abandon the current collection set without recording policy
786 // statistics or updating free lists.
787 void abandon_collection_set(G1CollectionSet* collection_set);
788
789 // The concurrent marker (and the thread it runs in.)
790 G1ConcurrentMark* _cm;
791 ConcurrentMarkThread* _cmThread;
792
793 // The concurrent refiner.
794 ConcurrentG1Refine* _cg1r;
795
796 // The parallel task queues
797 RefToScanQueueSet *_task_queues;
798
799 // True iff a evacuation has failed in the current collection.
800 bool _evacuation_failed;
801
802 EvacuationFailedInfo* _evacuation_failed_info_array;
803
804 // Failed evacuations cause some logical from-space objects to have
805 // forwarding pointers to themselves. Reset them.
806 void remove_self_forwarding_pointers();
807
808 // Restore the objects in the regions in the collection set after an
809 // evacuation failure.
810 void restore_after_evac_failure();
811
812 PreservedMarksSet _preserved_marks_set;
813
814 // Preserve the mark of "obj", if necessary, in preparation for its mark
815 // word being overwritten with a self-forwarding-pointer.
816 void preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m);
817
818 #ifndef PRODUCT
819 // Support for forcing evacuation failures. Analogous to
820 // PromotionFailureALot for the other collectors.
821
822 // Records whether G1EvacuationFailureALot should be in effect
823 // for the current GC
824 bool _evacuation_failure_alot_for_current_gc;
825
826 // Used to record the GC number for interval checking when
827 // determining whether G1EvaucationFailureALot is in effect
828 // for the current GC.
829 size_t _evacuation_failure_alot_gc_number;
830
831 // Count of the number of evacuations between failures.
832 volatile size_t _evacuation_failure_alot_count;
833
834 // Set whether G1EvacuationFailureALot should be in effect
835 // for the current GC (based upon the type of GC and which
836 // command line flags are set);
837 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
838 bool during_initial_mark,
839 bool during_marking);
840
841 inline void set_evacuation_failure_alot_for_current_gc();
842
843 // Return true if it's time to cause an evacuation failure.
844 inline bool evacuation_should_fail();
845
846 // Reset the G1EvacuationFailureALot counters. Should be called at
847 // the end of an evacuation pause in which an evacuation failure occurred.
848 inline void reset_evacuation_should_fail();
849 #endif // !PRODUCT
850
851 // ("Weak") Reference processing support.
852 //
853 // G1 has 2 instances of the reference processor class. One
854 // (_ref_processor_cm) handles reference object discovery
855 // and subsequent processing during concurrent marking cycles.
856 //
857 // The other (_ref_processor_stw) handles reference object
858 // discovery and processing during full GCs and incremental
859 // evacuation pauses.
860 //
861 // During an incremental pause, reference discovery will be
862 // temporarily disabled for _ref_processor_cm and will be
863 // enabled for _ref_processor_stw. At the end of the evacuation
864 // pause references discovered by _ref_processor_stw will be
865 // processed and discovery will be disabled. The previous
866 // setting for reference object discovery for _ref_processor_cm
867 // will be re-instated.
868 //
869 // At the start of marking:
870 // * Discovery by the CM ref processor is verified to be inactive
871 // and it's discovered lists are empty.
872 // * Discovery by the CM ref processor is then enabled.
873 //
874 // At the end of marking:
875 // * Any references on the CM ref processor's discovered
876 // lists are processed (possibly MT).
877 //
878 // At the start of full GC we:
879 // * Disable discovery by the CM ref processor and
880 // empty CM ref processor's discovered lists
881 // (without processing any entries).
882 // * Verify that the STW ref processor is inactive and it's
883 // discovered lists are empty.
884 // * Temporarily set STW ref processor discovery as single threaded.
885 // * Temporarily clear the STW ref processor's _is_alive_non_header
886 // field.
887 // * Finally enable discovery by the STW ref processor.
888 //
889 // The STW ref processor is used to record any discovered
890 // references during the full GC.
891 //
892 // At the end of a full GC we:
893 // * Enqueue any reference objects discovered by the STW ref processor
894 // that have non-live referents. This has the side-effect of
895 // making the STW ref processor inactive by disabling discovery.
896 // * Verify that the CM ref processor is still inactive
897 // and no references have been placed on it's discovered
898 // lists (also checked as a precondition during initial marking).
899
900 // The (stw) reference processor...
901 ReferenceProcessor* _ref_processor_stw;
902
903 STWGCTimer* _gc_timer_stw;
904
905 G1NewTracer* _gc_tracer_stw;
906
907 // During reference object discovery, the _is_alive_non_header
908 // closure (if non-null) is applied to the referent object to
909 // determine whether the referent is live. If so then the
910 // reference object does not need to be 'discovered' and can
911 // be treated as a regular oop. This has the benefit of reducing
912 // the number of 'discovered' reference objects that need to
913 // be processed.
914 //
915 // Instance of the is_alive closure for embedding into the
916 // STW reference processor as the _is_alive_non_header field.
917 // Supplying a value for the _is_alive_non_header field is
918 // optional but doing so prevents unnecessary additions to
919 // the discovered lists during reference discovery.
920 G1STWIsAliveClosure _is_alive_closure_stw;
921
922 // The (concurrent marking) reference processor...
923 ReferenceProcessor* _ref_processor_cm;
924
925 // Instance of the concurrent mark is_alive closure for embedding
926 // into the Concurrent Marking reference processor as the
927 // _is_alive_non_header field. Supplying a value for the
928 // _is_alive_non_header field is optional but doing so prevents
929 // unnecessary additions to the discovered lists during reference
930 // discovery.
931 G1CMIsAliveClosure _is_alive_closure_cm;
932
933 volatile bool _free_regions_coming;
934
935 public:
936
937 void set_refine_cte_cl_concurrency(bool concurrent);
938
939 RefToScanQueue *task_queue(uint i) const;
940
941 uint num_task_queues() const;
942
943 // A set of cards where updates happened during the GC
944 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
945
946 // Create a G1CollectedHeap with the specified policy.
947 // Must call the initialize method afterwards.
948 // May not return if something goes wrong.
949 G1CollectedHeap(G1CollectorPolicy* policy);
950
951 // Initialize the G1CollectedHeap to have the initial and
952 // maximum sizes and remembered and barrier sets
953 // specified by the policy object.
954 jint initialize();
955
956 virtual void stop();
957
958 // Return the (conservative) maximum heap alignment for any G1 heap
959 static size_t conservative_max_heap_alignment();
960
961 // Does operations required after initialization has been done.
962 void post_initialize();
963
964 // Initialize weak reference processing.
965 void ref_processing_init();
966
967 virtual Name kind() const {
968 return CollectedHeap::G1CollectedHeap;
969 }
970
971 virtual const char* name() const {
972 return "G1";
973 }
974
975 const G1CollectorState* collector_state() const { return &_collector_state; }
976 G1CollectorState* collector_state() { return &_collector_state; }
977
978 // The current policy object for the collector.
979 G1Policy* g1_policy() const { return _g1_policy; }
980
981 const G1CollectionSet* collection_set() const { return &_collection_set; }
982 G1CollectionSet* collection_set() { return &_collection_set; }
983
984 virtual CollectorPolicy* collector_policy() const;
985
986 // Adaptive size policy. No such thing for g1.
987 virtual AdaptiveSizePolicy* size_policy() { return NULL; }
988
989 // The rem set and barrier set.
990 G1RemSet* g1_rem_set() const { return _g1_rem_set; }
991
992 // Try to minimize the remembered set.
993 void scrub_rem_set();
994
995 uint get_gc_time_stamp() {
996 return _gc_time_stamp;
997 }
998
999 inline void reset_gc_time_stamp();
1000
1001 void check_gc_time_stamps() PRODUCT_RETURN;
1002
1003 inline void increment_gc_time_stamp();
1004
1005 // Reset the given region's GC timestamp. If it's starts humongous,
1006 // also reset the GC timestamp of its corresponding
1007 // continues humongous regions too.
1008 void reset_gc_time_stamps(HeapRegion* hr);
1009
1010 // Apply the given closure on all cards in the Hot Card Cache, emptying it.
1011 void iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i);
1012
1013 // Apply the given closure on all cards in the Dirty Card Queue Set, emptying it.
1014 void iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i);
1015
1016 // The shared block offset table array.
1017 G1BlockOffsetTable* bot() const { return _bot; }
1018
1019 // Reference Processing accessors
1020
1021 // The STW reference processor....
1022 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1023
1024 G1NewTracer* gc_tracer_stw() const { return _gc_tracer_stw; }
1025
1026 // The Concurrent Marking reference processor...
1027 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1028
1029 virtual size_t capacity() const;
1030 virtual size_t used() const;
1031 // This should be called when we're not holding the heap lock. The
1032 // result might be a bit inaccurate.
1033 size_t used_unlocked() const;
1034 size_t recalculate_used() const;
1035
1036 // These virtual functions do the actual allocation.
1037 // Some heaps may offer a contiguous region for shared non-blocking
1038 // allocation, via inlined code (by exporting the address of the top and
1039 // end fields defining the extent of the contiguous allocation region.)
1040 // But G1CollectedHeap doesn't yet support this.
1041
1042 virtual bool is_maximal_no_gc() const {
1043 return _hrm.available() == 0;
1044 }
1045
1046 // The current number of regions in the heap.
1047 uint num_regions() const { return _hrm.length(); }
1048
1049 // The max number of regions in the heap.
1050 uint max_regions() const { return _hrm.max_length(); }
1051
1052 // The number of regions that are completely free.
1053 uint num_free_regions() const { return _hrm.num_free_regions(); }
1054
1055 MemoryUsage get_auxiliary_data_memory_usage() const {
1056 return _hrm.get_auxiliary_data_memory_usage();
1057 }
1058
1059 // The number of regions that are not completely free.
1060 uint num_used_regions() const { return num_regions() - num_free_regions(); }
1061
1062 #ifdef ASSERT
1063 bool is_on_master_free_list(HeapRegion* hr) {
1064 return _hrm.is_free(hr);
1065 }
1066 #endif // ASSERT
1067
1068 // Wrapper for the region list operations that can be called from
1069 // methods outside this class.
1070
1071 void secondary_free_list_add(FreeRegionList* list) {
1072 _secondary_free_list.add_ordered(list);
1073 }
1074
1075 void append_secondary_free_list() {
1076 _hrm.insert_list_into_free_list(&_secondary_free_list);
1077 }
1078
1079 void append_secondary_free_list_if_not_empty_with_lock() {
1080 // If the secondary free list looks empty there's no reason to
1081 // take the lock and then try to append it.
1082 if (!_secondary_free_list.is_empty()) {
1083 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1084 append_secondary_free_list();
1085 }
1086 }
1087
1088 inline void old_set_add(HeapRegion* hr);
1089 inline void old_set_remove(HeapRegion* hr);
1090
1091 size_t non_young_capacity_bytes() {
1092 return (_old_set.length() + _humongous_set.length()) * HeapRegion::GrainBytes;
1093 }
1094
1095 void set_free_regions_coming();
1096 void reset_free_regions_coming();
1097 bool free_regions_coming() { return _free_regions_coming; }
1098 void wait_while_free_regions_coming();
1099
1100 // Determine whether the given region is one that we are using as an
1101 // old GC alloc region.
1102 bool is_old_gc_alloc_region(HeapRegion* hr);
1103
1104 // Perform a collection of the heap; intended for use in implementing
1105 // "System.gc". This probably implies as full a collection as the
1106 // "CollectedHeap" supports.
1107 virtual void collect(GCCause::Cause cause);
1108
1109 virtual bool copy_allocation_context_stats(const jint* contexts,
1110 jlong* totals,
1111 jbyte* accuracy,
1112 jint len);
1113
1114 // True iff an evacuation has failed in the most-recent collection.
1115 bool evacuation_failed() { return _evacuation_failed; }
1116
1117 void remove_from_old_sets(const uint old_regions_removed, const uint humongous_regions_removed);
1118 void prepend_to_freelist(FreeRegionList* list);
1119 void decrement_summary_bytes(size_t bytes);
1120
1121 virtual bool is_in(const void* p) const;
1122 #ifdef ASSERT
1123 // Returns whether p is in one of the available areas of the heap. Slow but
1124 // extensive version.
1125 bool is_in_exact(const void* p) const;
1126 #endif
1127
1128 // Return "TRUE" iff the given object address is within the collection
1129 // set. Slow implementation.
1130 bool obj_in_cs(oop obj);
1131
1132 inline bool is_in_cset(const HeapRegion *hr);
1133 inline bool is_in_cset(oop obj);
1134
1135 inline bool is_in_cset_or_humongous(const oop obj);
1136
1137 private:
1138 // This array is used for a quick test on whether a reference points into
1139 // the collection set or not. Each of the array's elements denotes whether the
1140 // corresponding region is in the collection set or not.
1141 G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test;
1142
1143 public:
1144
1145 inline InCSetState in_cset_state(const oop obj);
1146
1147 // Return "TRUE" iff the given object address is in the reserved
1148 // region of g1.
1149 bool is_in_g1_reserved(const void* p) const {
1150 return _hrm.reserved().contains(p);
1151 }
1152
1153 // Returns a MemRegion that corresponds to the space that has been
1154 // reserved for the heap
1155 MemRegion g1_reserved() const {
1156 return _hrm.reserved();
1157 }
1158
1159 virtual bool is_in_closed_subset(const void* p) const;
1160
1161 G1SATBCardTableLoggingModRefBS* g1_barrier_set() {
1162 return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set());
1163 }
1164
1165 // Iteration functions.
1166
1167 // Iterate over all objects, calling "cl.do_object" on each.
1168 virtual void object_iterate(ObjectClosure* cl);
1169
1170 virtual void safe_object_iterate(ObjectClosure* cl) {
1171 object_iterate(cl);
1172 }
1173
1174 // Iterate over heap regions, in address order, terminating the
1175 // iteration early if the "doHeapRegion" method returns "true".
1176 void heap_region_iterate(HeapRegionClosure* blk) const;
1177
1178 // Return the region with the given index. It assumes the index is valid.
1179 inline HeapRegion* region_at(uint index) const;
1180
1181 // Return the next region (by index) that is part of the same
1182 // humongous object that hr is part of.
1183 inline HeapRegion* next_region_in_humongous(HeapRegion* hr) const;
1184
1185 // Calculate the region index of the given address. Given address must be
1186 // within the heap.
1187 inline uint addr_to_region(HeapWord* addr) const;
1188
1189 inline HeapWord* bottom_addr_for_region(uint index) const;
1190
1191 // Iterate over the heap regions in parallel. Assumes that this will be called
1192 // in parallel by ParallelGCThreads worker threads with distinct worker ids
1193 // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion"
1194 // to each of the regions, by attempting to claim the region using the
1195 // HeapRegionClaimer and, if successful, applying the closure to the claimed
1196 // region. The concurrent argument should be set to true if iteration is
1197 // performed concurrently, during which no assumptions are made for consistent
1198 // attributes of the heap regions (as they might be modified while iterating).
1199 void heap_region_par_iterate(HeapRegionClosure* cl,
1200 uint worker_id,
1201 HeapRegionClaimer* hrclaimer,
1202 bool concurrent = false) const;
1203
1204 // Iterate over the regions (if any) in the current collection set.
1205 void collection_set_iterate(HeapRegionClosure* blk);
1206
1207 // Iterate over the regions (if any) in the current collection set. Starts the
1208 // iteration over the entire collection set so that a given worker id over the
1209 // set of 0..active_workers-1 are distributed across the set of collection set
1210 // regions.
1211 void collection_set_iterate_from(HeapRegionClosure *blk, uint worker_id, uint active_workers);
1212
1213 HeapRegion* next_compaction_region(const HeapRegion* from) const;
1214
1215 // Returns the HeapRegion that contains addr. addr must not be NULL.
1216 template <class T>
1217 inline HeapRegion* heap_region_containing(const T addr) const;
1218
1219 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1220 // each address in the (reserved) heap is a member of exactly
1221 // one block. The defining characteristic of a block is that it is
1222 // possible to find its size, and thus to progress forward to the next
1223 // block. (Blocks may be of different sizes.) Thus, blocks may
1224 // represent Java objects, or they might be free blocks in a
1225 // free-list-based heap (or subheap), as long as the two kinds are
1226 // distinguishable and the size of each is determinable.
1227
1228 // Returns the address of the start of the "block" that contains the
1229 // address "addr". We say "blocks" instead of "object" since some heaps
1230 // may not pack objects densely; a chunk may either be an object or a
1231 // non-object.
1232 virtual HeapWord* block_start(const void* addr) const;
1233
1234 // Requires "addr" to be the start of a chunk, and returns its size.
1235 // "addr + size" is required to be the start of a new chunk, or the end
1236 // of the active area of the heap.
1237 virtual size_t block_size(const HeapWord* addr) const;
1238
1239 // Requires "addr" to be the start of a block, and returns "TRUE" iff
1240 // the block is an object.
1241 virtual bool block_is_obj(const HeapWord* addr) const;
1242
1243 // Section on thread-local allocation buffers (TLABs)
1244 // See CollectedHeap for semantics.
1245
1246 bool supports_tlab_allocation() const;
1247 size_t tlab_capacity(Thread* ignored) const;
1248 size_t tlab_used(Thread* ignored) const;
1249 size_t max_tlab_size() const;
1250 size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1251
1252 // Can a compiler initialize a new object without store barriers?
1253 // This permission only extends from the creation of a new object
1254 // via a TLAB up to the first subsequent safepoint. If such permission
1255 // is granted for this heap type, the compiler promises to call
1256 // defer_store_barrier() below on any slow path allocation of
1257 // a new object for which such initializing store barriers will
1258 // have been elided. G1, like CMS, allows this, but should be
1259 // ready to provide a compensating write barrier as necessary
1260 // if that storage came out of a non-young region. The efficiency
1261 // of this implementation depends crucially on being able to
1262 // answer very efficiently in constant time whether a piece of
1263 // storage in the heap comes from a young region or not.
1264 // See ReduceInitialCardMarks.
1265 virtual bool can_elide_tlab_store_barriers() const {
1266 return true;
1267 }
1268
1269 virtual bool card_mark_must_follow_store() const {
1270 return true;
1271 }
1272
1273 // The reference pending list lock is acquired from from the
1274 // ConcurrentMarkThread.
1275 virtual bool needs_reference_pending_list_locker_thread() const {
1276 return true;
1277 }
1278
1279 inline bool is_in_young(const oop obj);
1280
1281 virtual bool is_scavengable(const void* addr);
1282
1283 // We don't need barriers for initializing stores to objects
1284 // in the young gen: for the SATB pre-barrier, there is no
1285 // pre-value that needs to be remembered; for the remembered-set
1286 // update logging post-barrier, we don't maintain remembered set
1287 // information for young gen objects.
1288 virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1289
1290 // Returns "true" iff the given word_size is "very large".
1291 static bool is_humongous(size_t word_size) {
1292 // Note this has to be strictly greater-than as the TLABs
1293 // are capped at the humongous threshold and we want to
1294 // ensure that we don't try to allocate a TLAB as
1295 // humongous and that we don't allocate a humongous
1296 // object in a TLAB.
1297 return word_size > _humongous_object_threshold_in_words;
1298 }
1299
1300 // Returns the humongous threshold for a specific region size
1301 static size_t humongous_threshold_for(size_t region_size) {
1302 return (region_size / 2);
1303 }
1304
1305 // Returns the number of regions the humongous object of the given word size
1306 // requires.
1307 static size_t humongous_obj_size_in_regions(size_t word_size);
1308
1309 // Print the maximum heap capacity.
1310 virtual size_t max_capacity() const;
1311
1312 virtual jlong millis_since_last_gc();
1313
1314
1315 // Convenience function to be used in situations where the heap type can be
1316 // asserted to be this type.
1317 static G1CollectedHeap* heap();
1318
1319 void set_region_short_lived_locked(HeapRegion* hr);
1320 // add appropriate methods for any other surv rate groups
1321
1322 const G1SurvivorRegions* survivor() const { return &_survivor; }
1323
1324 uint survivor_regions_count() const {
1325 return _survivor.length();
1326 }
1327
1328 uint eden_regions_count() const {
1329 return _eden.length();
1330 }
1331
1332 uint young_regions_count() const {
1333 return _eden.length() + _survivor.length();
1334 }
1335
1336 uint old_regions_count() const { return _old_set.length(); }
1337
1338 uint humongous_regions_count() const { return _humongous_set.length(); }
1339
1340 #ifdef ASSERT
1341 bool check_young_list_empty();
1342 #endif
1343
1344 // *** Stuff related to concurrent marking. It's not clear to me that so
1345 // many of these need to be public.
1346
1347 // The functions below are helper functions that a subclass of
1348 // "CollectedHeap" can use in the implementation of its virtual
1349 // functions.
1350 // This performs a concurrent marking of the live objects in a
1351 // bitmap off to the side.
1352 void doConcurrentMark();
1353
1354 bool isMarkedPrev(oop obj) const;
1355 bool isMarkedNext(oop obj) const;
1356
1357 // Determine if an object is dead, given the object and also
1358 // the region to which the object belongs. An object is dead
1359 // iff a) it was not allocated since the last mark, b) it
1360 // is not marked, and c) it is not in an archive region.
1361 bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1362 return
1363 !hr->obj_allocated_since_prev_marking(obj) &&
1364 !isMarkedPrev(obj) &&
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 // Delete entries for dead interned string and clean up unreferenced symbols
1410 // in symbol table, possibly in parallel.
1411 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1412
1413 // Parallel phase of unloading/cleaning after G1 concurrent mark.
1414 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred);
1415
1416 // Redirty logged cards in the refinement queue.
1417 void redirty_logged_cards();
1418 // Verification
1419
1420 // Perform any cleanup actions necessary before allowing a verification.
1421 virtual void prepare_for_verify();
1422
1423 // Perform verification.
1424
1425 // vo == UsePrevMarking -> use "prev" marking information,
1426 // vo == UseNextMarking -> use "next" marking information
1427 // vo == UseMarkWord -> use the mark word in the object header
1428 //
1429 // NOTE: Only the "prev" marking information is guaranteed to be
1430 // consistent most of the time, so most calls to this should use
1431 // vo == UsePrevMarking.
1432 // Currently, there is only one case where this is called with
1433 // vo == UseNextMarking, which is to verify the "next" marking
1434 // information at the end of remark.
1435 // Currently there is only one place where this is called with
1436 // vo == UseMarkWord, which is to verify the marking during a
1437 // full GC.
1438 void verify(VerifyOption vo);
1439
1440 // The methods below are here for convenience and dispatch the
1441 // appropriate method depending on value of the given VerifyOption
1442 // parameter. The values for that parameter, and their meanings,
1443 // are the same as those above.
1444
1445 bool is_obj_dead_cond(const oop obj,
1446 const HeapRegion* hr,
1447 const VerifyOption vo) const;
1448
1449 bool is_obj_dead_cond(const oop obj,
1450 const VerifyOption vo) const;
1451
1452 G1HeapSummary create_g1_heap_summary();
1453 G1EvacSummary create_g1_evac_summary(G1EvacStats* stats);
1454
1455 // Printing
1456 private:
1457 void print_heap_regions() const;
1458 void print_regions_on(outputStream* st) const;
1459
1460 public:
1461 virtual void print_on(outputStream* st) const;
1462 virtual void print_extended_on(outputStream* st) const;
1463 virtual void print_on_error(outputStream* st) const;
1464
1465 virtual void print_gc_threads_on(outputStream* st) const;
1466 virtual void gc_threads_do(ThreadClosure* tc) const;
1467
1468 // Override
1469 void print_tracing_info() const;
1470
1471 // The following two methods are helpful for debugging RSet issues.
1472 void print_cset_rsets() PRODUCT_RETURN;
1473 void print_all_rsets() PRODUCT_RETURN;
1474
1475 public:
1476 size_t pending_card_num();
1477
1478 protected:
1479 size_t _max_heap_capacity;
1480 };
1481
1482 class G1ParEvacuateFollowersClosure : public VoidClosure {
1483 private:
1484 double _start_term;
1485 double _term_time;
1486 size_t _term_attempts;
1487
1488 void start_term_time() { _term_attempts++; _start_term = os::elapsedTime(); }
1489 void end_term_time() { _term_time += os::elapsedTime() - _start_term; }
1490 protected:
1491 G1CollectedHeap* _g1h;
1492 G1ParScanThreadState* _par_scan_state;
1493 RefToScanQueueSet* _queues;
1494 ParallelTaskTerminator* _terminator;
1495
1496 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
1497 RefToScanQueueSet* queues() { return _queues; }
1498 ParallelTaskTerminator* terminator() { return _terminator; }
1499
1500 public:
1501 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
1502 G1ParScanThreadState* par_scan_state,
1503 RefToScanQueueSet* queues,
1504 ParallelTaskTerminator* terminator)
1505 : _g1h(g1h), _par_scan_state(par_scan_state),
1506 _queues(queues), _terminator(terminator),
1507 _start_term(0.0), _term_time(0.0), _term_attempts(0) {}
1508
1509 void do_void();
1510
1511 double term_time() const { return _term_time; }
1512 size_t term_attempts() const { return _term_attempts; }
1513
1514 private:
1515 inline bool offer_termination();
1516 };
1517
1518 #endif // SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP