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