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.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #ifndef SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP
26 #define SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP
27
28 #include "gc/g1/evacuationInfo.hpp"
29 #include "gc/g1/g1AllocationContext.hpp"
30 #include "gc/g1/g1BiasedArray.hpp"
31 #include "gc/g1/g1CollectionSet.hpp"
32 #include "gc/g1/g1CollectorState.hpp"
33 #include "gc/g1/g1ConcurrentMark.hpp"
34 #include "gc/g1/g1EdenRegions.hpp"
35 #include "gc/g1/g1EvacFailure.hpp"
36 #include "gc/g1/g1EvacStats.hpp"
37 #include "gc/g1/g1HeapTransition.hpp"
38 #include "gc/g1/g1HeapVerifier.hpp"
39 #include "gc/g1/g1HRPrinter.hpp"
40 #include "gc/g1/g1InCSetState.hpp"
41 #include "gc/g1/g1MonitoringSupport.hpp"
42 #include "gc/g1/g1SATBCardTableModRefBS.hpp"
43 #include "gc/g1/g1SurvivorRegions.hpp"
44 #include "gc/g1/g1YCTypes.hpp"
45 #include "gc/g1/hSpaceCounters.hpp"
46 #include "gc/g1/heapRegionManager.hpp"
47 #include "gc/g1/heapRegionSet.hpp"
48 #include "gc/shared/barrierSet.hpp"
49 #include "gc/shared/collectedHeap.hpp"
50 #include "gc/shared/plab.hpp"
51 #include "gc/shared/preservedMarks.hpp"
52 #include "memory/memRegion.hpp"
53 #include "utilities/stack.hpp"
54
55 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
56 // It uses the "Garbage First" heap organization and algorithm, which
57 // may combine concurrent marking with parallel, incremental compaction of
58 // heap subsets that will yield large amounts of garbage.
59
60 // Forward declarations
61 class HeapRegion;
62 class HRRSCleanupTask;
63 class GenerationSpec;
64 class G1ParScanThreadState;
65 class G1ParScanThreadStateSet;
66 class G1ParScanThreadState;
67 class ObjectClosure;
68 class SpaceClosure;
69 class CompactibleSpaceClosure;
70 class Space;
71 class G1CollectionSet;
72 class G1CollectorPolicy;
73 class G1Policy;
74 class G1HotCardCache;
75 class G1RemSet;
76 class HeapRegionRemSetIterator;
77 class G1ConcurrentMark;
78 class ConcurrentMarkThread;
79 class ConcurrentG1Refine;
80 class GenerationCounters;
81 class STWGCTimer;
82 class G1NewTracer;
83 class EvacuationFailedInfo;
84 class nmethod;
85 class Ticks;
86 class WorkGang;
87 class G1Allocator;
88 class G1ArchiveAllocator;
89 class G1FullGCScope;
90 class G1HeapVerifier;
91 class G1HeapSizingPolicy;
92 class G1HeapSummary;
93 class G1EvacSummary;
94
95 typedef OverflowTaskQueue<StarTask, mtGC> RefToScanQueue;
96 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
97
98 typedef int RegionIdx_t; // needs to hold [ 0..max_regions() )
99 typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion )
100
101 // The G1 STW is alive closure.
102 // An instance is embedded into the G1CH and used as the
103 // (optional) _is_alive_non_header closure in the STW
104 // reference processor. It is also extensively used during
105 // reference processing during STW evacuation pauses.
106 class G1STWIsAliveClosure: public BoolObjectClosure {
107 G1CollectedHeap* _g1;
108 public:
109 G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
110 bool do_object_b(oop p);
111 };
112
113 class G1RegionMappingChangedListener : public G1MappingChangedListener {
114 private:
115 void reset_from_card_cache(uint start_idx, size_t num_regions);
116 public:
117 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
118 };
119
120 class G1CollectedHeap : public CollectedHeap {
121 friend class G1FreeCollectionSetTask;
122 friend class VM_CollectForMetadataAllocation;
123 friend class VM_G1CollectForAllocation;
124 friend class VM_G1CollectFull;
125 friend class VM_G1IncCollectionPause;
126 friend class VMStructs;
127 friend class MutatorAllocRegion;
128 friend class G1GCAllocRegion;
129 friend class G1HeapVerifier;
130
131 // Closures used in implementation.
132 friend class G1ParScanThreadState;
133 friend class G1ParScanThreadStateSet;
134 friend class G1ParTask;
135 friend class G1PLABAllocator;
136 friend class G1PrepareCompactClosure;
137
138 // Other related classes.
139 friend class HeapRegionClaimer;
140
141 // Testing classes.
142 friend class G1CheckCSetFastTableClosure;
143
144 private:
145 WorkGang* _workers;
146 G1CollectorPolicy* _collector_policy;
147
148 static size_t _humongous_object_threshold_in_words;
149
150 // The secondary free list which contains regions that have been
151 // freed up during the cleanup process. This will be appended to
152 // the master free list when appropriate.
153 FreeRegionList _secondary_free_list;
154
155 // It keeps track of the old regions.
156 HeapRegionSet _old_set;
157
158 // It keeps track of the humongous regions.
159 HeapRegionSet _humongous_set;
160
161 void eagerly_reclaim_humongous_regions();
162 // Start a new incremental collection set for the next pause.
163 void start_new_collection_set();
164
165 // The number of regions we could create by expansion.
166 uint _expansion_regions;
167
168 // The block offset table for the G1 heap.
169 G1BlockOffsetTable* _bot;
170
171 // Tears down the region sets / lists so that they are empty and the
172 // regions on the heap do not belong to a region set / list. The
173 // only exception is the humongous set which we leave unaltered. If
174 // free_list_only is true, it will only tear down the master free
175 // list. It is called before a Full GC (free_list_only == false) or
176 // before heap shrinking (free_list_only == true).
177 void tear_down_region_sets(bool free_list_only);
178
179 // Rebuilds the region sets / lists so that they are repopulated to
180 // reflect the contents of the heap. The only exception is the
181 // humongous set which was not torn down in the first place. If
182 // free_list_only is true, it will only rebuild the master free
183 // list. It is called after a Full GC (free_list_only == false) or
184 // after heap shrinking (free_list_only == true).
185 void rebuild_region_sets(bool free_list_only);
186
187 // Callback for region mapping changed events.
188 G1RegionMappingChangedListener _listener;
189
190 // The sequence of all heap regions in the heap.
191 HeapRegionManager _hrm;
192
193 // Manages all allocations with regions except humongous object allocations.
194 G1Allocator* _allocator;
195
196 // Manages all heap verification.
197 G1HeapVerifier* _verifier;
198
199 // Outside of GC pauses, the number of bytes used in all regions other
200 // than the current allocation region(s).
201 size_t _summary_bytes_used;
202
203 void increase_used(size_t bytes);
204 void decrease_used(size_t bytes);
205
206 void set_used(size_t bytes);
207
208 // Class that handles archive allocation ranges.
209 G1ArchiveAllocator* _archive_allocator;
210
211 // Statistics for each allocation context
212 AllocationContextStats _allocation_context_stats;
213
214 // GC allocation statistics policy for survivors.
215 G1EvacStats _survivor_evac_stats;
216
217 // GC allocation statistics policy for tenured objects.
218 G1EvacStats _old_evac_stats;
219
220 // It specifies whether we should attempt to expand the heap after a
221 // region allocation failure. If heap expansion fails we set this to
222 // false so that we don't re-attempt the heap expansion (it's likely
223 // that subsequent expansion attempts will also fail if one fails).
224 // Currently, it is only consulted during GC and it's reset at the
225 // start of each GC.
226 bool _expand_heap_after_alloc_failure;
227
228 // Helper for monitoring and management support.
229 G1MonitoringSupport* _g1mm;
230
231 // Records whether the region at the given index is (still) a
232 // candidate for eager reclaim. Only valid for humongous start
233 // regions; other regions have unspecified values. Humongous start
234 // regions are initialized at start of collection pause, with
235 // candidates removed from the set as they are found reachable from
236 // roots or the young generation.
237 class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> {
238 protected:
239 bool default_value() const { return false; }
240 public:
241 void clear() { G1BiasedMappedArray<bool>::clear(); }
242 void set_candidate(uint region, bool value) {
243 set_by_index(region, value);
244 }
245 bool is_candidate(uint region) {
246 return get_by_index(region);
247 }
248 };
249
250 HumongousReclaimCandidates _humongous_reclaim_candidates;
251 // Stores whether during humongous object registration we found candidate regions.
252 // If not, we can skip a few steps.
253 bool _has_humongous_reclaim_candidates;
254
255 volatile uint _gc_time_stamp;
256
257 G1HRPrinter _hr_printer;
258
259 // It decides whether an explicit GC should start a concurrent cycle
260 // instead of doing a STW GC. Currently, a concurrent cycle is
261 // explicitly started if:
262 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
263 // (b) cause == _g1_humongous_allocation
264 // (c) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
265 // (d) cause == _dcmd_gc_run and +ExplicitGCInvokesConcurrent.
266 // (e) cause == _update_allocation_context_stats_inc
267 // (f) cause == _wb_conc_mark
268 bool should_do_concurrent_full_gc(GCCause::Cause cause);
269
270 // indicates whether we are in young or mixed GC mode
271 G1CollectorState _collector_state;
272
273 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
274 // concurrent cycles) we have started.
275 volatile uint _old_marking_cycles_started;
276
277 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
278 // concurrent cycles) we have completed.
279 volatile uint _old_marking_cycles_completed;
280
281 // This is a non-product method that is helpful for testing. It is
282 // called at the end of a GC and artificially expands the heap by
283 // allocating a number of dead regions. This way we can induce very
284 // frequent marking cycles and stress the cleanup / concurrent
285 // cleanup code more (as all the regions that will be allocated by
286 // this method will be found dead by the marking cycle).
287 void allocate_dummy_regions() PRODUCT_RETURN;
288
289 // Clear RSets after a compaction. It also resets the GC time stamps.
290 void clear_rsets_post_compaction();
291
292 // If the HR printer is active, dump the state of the regions in the
293 // heap after a compaction.
294 void print_hrm_post_compaction();
295
296 // Create a memory mapper for auxiliary data structures of the given size and
297 // translation factor.
298 static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description,
299 size_t size,
300 size_t translation_factor);
301
302 static G1Policy* create_g1_policy(STWGCTimer* gc_timer);
303
304 void trace_heap(GCWhen::Type when, const GCTracer* tracer);
305
306 void process_weak_jni_handles();
307
308 // These are macros so that, if the assert fires, we get the correct
309 // line number, file, etc.
310
311 #define heap_locking_asserts_params(_extra_message_) \
312 "%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \
313 (_extra_message_), \
314 BOOL_TO_STR(Heap_lock->owned_by_self()), \
315 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \
316 BOOL_TO_STR(Thread::current()->is_VM_thread())
317
318 #define assert_heap_locked() \
319 do { \
320 assert(Heap_lock->owned_by_self(), \
321 heap_locking_asserts_params("should be holding the Heap_lock")); \
322 } while (0)
323
324 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \
325 do { \
326 assert(Heap_lock->owned_by_self() || \
327 (SafepointSynchronize::is_at_safepoint() && \
328 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
329 heap_locking_asserts_params("should be holding the Heap_lock or " \
330 "should be at a safepoint")); \
331 } while (0)
332
333 #define assert_heap_locked_and_not_at_safepoint() \
334 do { \
335 assert(Heap_lock->owned_by_self() && \
336 !SafepointSynchronize::is_at_safepoint(), \
337 heap_locking_asserts_params("should be holding the Heap_lock and " \
338 "should not be at a safepoint")); \
339 } while (0)
340
341 #define assert_heap_not_locked() \
342 do { \
343 assert(!Heap_lock->owned_by_self(), \
344 heap_locking_asserts_params("should not be holding the Heap_lock")); \
345 } while (0)
346
347 #define assert_heap_not_locked_and_not_at_safepoint() \
348 do { \
349 assert(!Heap_lock->owned_by_self() && \
350 !SafepointSynchronize::is_at_safepoint(), \
351 heap_locking_asserts_params("should not be holding the Heap_lock and " \
352 "should not be at a safepoint")); \
353 } while (0)
354
355 #define assert_at_safepoint(_should_be_vm_thread_) \
356 do { \
357 assert(SafepointSynchronize::is_at_safepoint() && \
358 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
359 heap_locking_asserts_params("should be at a safepoint")); \
360 } while (0)
361
362 #define assert_not_at_safepoint() \
363 do { \
364 assert(!SafepointSynchronize::is_at_safepoint(), \
365 heap_locking_asserts_params("should not be at a safepoint")); \
366 } while (0)
367
368 protected:
369
370 // The young region list.
371 G1EdenRegions _eden;
372 G1SurvivorRegions _survivor;
373
374 STWGCTimer* _gc_timer_stw;
375
376 G1NewTracer* _gc_tracer_stw;
377
378 // The current policy object for the collector.
379 G1Policy* _g1_policy;
380 G1HeapSizingPolicy* _heap_sizing_policy;
381
382 G1CollectionSet _collection_set;
383
384 // This is the second level of trying to allocate a new region. If
385 // new_region() didn't find a region on the free_list, this call will
386 // check whether there's anything available on the
387 // secondary_free_list and/or wait for more regions to appear on
388 // that list, if _free_regions_coming is set.
389 HeapRegion* new_region_try_secondary_free_list(bool is_old);
390
391 // Try to allocate a single non-humongous HeapRegion sufficient for
392 // an allocation of the given word_size. If do_expand is true,
393 // attempt to expand the heap if necessary to satisfy the allocation
394 // request. If the region is to be used as an old region or for a
395 // humongous object, set is_old to true. If not, to false.
396 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
397
398 // Initialize a contiguous set of free regions of length num_regions
399 // and starting at index first so that they appear as a single
400 // humongous region.
401 HeapWord* humongous_obj_allocate_initialize_regions(uint first,
402 uint num_regions,
403 size_t word_size,
404 AllocationContext_t context);
405
406 // Attempt to allocate a humongous object of the given size. Return
407 // NULL if unsuccessful.
408 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context);
409
410 // The following two methods, allocate_new_tlab() and
411 // mem_allocate(), are the two main entry points from the runtime
412 // into the G1's allocation routines. They have the following
413 // assumptions:
414 //
415 // * They should both be called outside safepoints.
416 //
417 // * They should both be called without holding the Heap_lock.
418 //
419 // * All allocation requests for new TLABs should go to
420 // allocate_new_tlab().
421 //
422 // * All non-TLAB allocation requests should go to mem_allocate().
423 //
424 // * If either call cannot satisfy the allocation request using the
425 // current allocating region, they will try to get a new one. If
426 // this fails, they will attempt to do an evacuation pause and
427 // retry the allocation.
428 //
429 // * If all allocation attempts fail, even after trying to schedule
430 // an evacuation pause, allocate_new_tlab() will return NULL,
431 // whereas mem_allocate() will attempt a heap expansion and/or
432 // schedule a Full GC.
433 //
434 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
435 // should never be called with word_size being humongous. All
436 // humongous allocation requests should go to mem_allocate() which
437 // will satisfy them with a special path.
438
439 virtual HeapWord* allocate_new_tlab(size_t word_size);
440
441 virtual HeapWord* mem_allocate(size_t word_size,
442 bool* gc_overhead_limit_was_exceeded);
443
444 // The following three methods take a gc_count_before_ret
445 // parameter which is used to return the GC count if the method
446 // returns NULL. Given that we are required to read the GC count
447 // while holding the Heap_lock, and these paths will take the
448 // Heap_lock at some point, it's easier to get them to read the GC
449 // count while holding the Heap_lock before they return NULL instead
450 // of the caller (namely: mem_allocate()) having to also take the
451 // Heap_lock just to read the GC count.
452
453 // First-level mutator allocation attempt: try to allocate out of
454 // the mutator alloc region without taking the Heap_lock. This
455 // should only be used for non-humongous allocations.
456 inline HeapWord* attempt_allocation(size_t word_size,
457 uint* gc_count_before_ret,
458 uint* gclocker_retry_count_ret);
459
460 // Second-level mutator allocation attempt: take the Heap_lock and
461 // retry the allocation attempt, potentially scheduling a GC
462 // pause. This should only be used for non-humongous allocations.
463 HeapWord* attempt_allocation_slow(size_t word_size,
464 AllocationContext_t context,
465 uint* gc_count_before_ret,
466 uint* gclocker_retry_count_ret);
467
468 // Takes the Heap_lock and attempts a humongous allocation. It can
469 // potentially schedule a GC pause.
470 HeapWord* attempt_allocation_humongous(size_t word_size,
471 uint* gc_count_before_ret,
472 uint* gclocker_retry_count_ret);
473
474 // Allocation attempt that should be called during safepoints (e.g.,
475 // at the end of a successful GC). expect_null_mutator_alloc_region
476 // specifies whether the mutator alloc region is expected to be NULL
477 // or not.
478 HeapWord* attempt_allocation_at_safepoint(size_t word_size,
479 AllocationContext_t context,
480 bool expect_null_mutator_alloc_region);
481
482 // These methods are the "callbacks" from the G1AllocRegion class.
483
484 // For mutator alloc regions.
485 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
486 void retire_mutator_alloc_region(HeapRegion* alloc_region,
487 size_t allocated_bytes);
488
489 // For GC alloc regions.
490 bool has_more_regions(InCSetState dest);
491 HeapRegion* new_gc_alloc_region(size_t word_size, InCSetState dest);
492 void retire_gc_alloc_region(HeapRegion* alloc_region,
493 size_t allocated_bytes, InCSetState dest);
494
495 // - if explicit_gc is true, the GC is for a System.gc() etc,
496 // otherwise it's for a failed allocation.
497 // - if clear_all_soft_refs is true, all soft references should be
498 // cleared during the GC.
499 // - it returns false if it is unable to do the collection due to the
500 // GC locker being active, true otherwise.
501 bool do_full_collection(bool explicit_gc,
502 bool clear_all_soft_refs);
503
504 // Callback from VM_G1CollectFull operation, or collect_as_vm_thread.
505 virtual void do_full_collection(bool clear_all_soft_refs);
506
507 // Resize the heap if necessary after a full collection.
508 void resize_if_necessary_after_full_collection();
509
510 // Callback from VM_G1CollectForAllocation operation.
511 // This function does everything necessary/possible to satisfy a
512 // failed allocation request (including collection, expansion, etc.)
513 HeapWord* satisfy_failed_allocation(size_t word_size,
514 AllocationContext_t context,
515 bool* succeeded);
516 private:
517 // Internal helpers used during full GC to split it up to
518 // increase readability.
519 void do_full_collection_inner(G1FullGCScope* scope);
520 void abort_concurrent_cycle();
521 void verify_before_full_collection(bool explicit_gc);
522 void prepare_heap_for_full_collection();
523 void prepare_heap_for_mutators();
524 void abort_refinement();
525 void verify_after_full_collection();
526 void print_heap_after_full_collection(G1HeapTransition* heap_transition);
527
528 // Helper method for satisfy_failed_allocation()
529 HeapWord* satisfy_failed_allocation_helper(size_t word_size,
530 AllocationContext_t context,
531 bool do_gc,
532 bool clear_all_soft_refs,
533 bool expect_null_mutator_alloc_region,
534 bool* gc_succeeded);
535
536 protected:
537 // Attempting to expand the heap sufficiently
538 // to support an allocation of the given "word_size". If
539 // successful, perform the allocation and return the address of the
540 // allocated block, or else "NULL".
541 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context);
542
543 // Preserve any referents discovered by concurrent marking that have not yet been
544 // copied by the STW pause.
545 void preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states);
546 // Process any reference objects discovered during
547 // an incremental evacuation pause.
548 void process_discovered_references(G1ParScanThreadStateSet* per_thread_states);
549
550 // Enqueue any remaining discovered references
551 // after processing.
552 void enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states);
553
554 // Merges the information gathered on a per-thread basis for all worker threads
555 // during GC into global variables.
556 void merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states);
557 public:
558 WorkGang* workers() const { return _workers; }
559
560 G1Allocator* allocator() {
561 return _allocator;
562 }
563
564 G1HeapVerifier* verifier() {
565 return _verifier;
566 }
567
568 G1MonitoringSupport* g1mm() {
569 assert(_g1mm != NULL, "should have been initialized");
570 return _g1mm;
571 }
572
573 // Expand the garbage-first heap by at least the given size (in bytes!).
574 // Returns true if the heap was expanded by the requested amount;
575 // false otherwise.
576 // (Rounds up to a HeapRegion boundary.)
577 bool expand(size_t expand_bytes, WorkGang* pretouch_workers = NULL, double* expand_time_ms = NULL);
578
579 // Returns the PLAB statistics for a given destination.
580 inline G1EvacStats* alloc_buffer_stats(InCSetState dest);
581
582 // Determines PLAB size for a given destination.
583 inline size_t desired_plab_sz(InCSetState dest);
584
585 inline AllocationContextStats& allocation_context_stats();
586
587 // Do anything common to GC's.
588 void gc_prologue(bool full);
589 void gc_epilogue(bool full);
590
591 // Modify the reclaim candidate set and test for presence.
592 // These are only valid for starts_humongous regions.
593 inline void set_humongous_reclaim_candidate(uint region, bool value);
594 inline bool is_humongous_reclaim_candidate(uint region);
595
596 // Remove from the reclaim candidate set. Also remove from the
597 // collection set so that later encounters avoid the slow path.
598 inline void set_humongous_is_live(oop obj);
599
600 // Register the given region to be part of the collection set.
601 inline void register_humongous_region_with_cset(uint index);
602 // Register regions with humongous objects (actually on the start region) in
603 // the in_cset_fast_test table.
604 void register_humongous_regions_with_cset();
605 // We register a region with the fast "in collection set" test. We
606 // simply set to true the array slot corresponding to this region.
607 void register_young_region_with_cset(HeapRegion* r) {
608 _in_cset_fast_test.set_in_young(r->hrm_index());
609 }
610 void register_old_region_with_cset(HeapRegion* r) {
611 _in_cset_fast_test.set_in_old(r->hrm_index());
612 }
613 inline void register_ext_region_with_cset(HeapRegion* r) {
614 _in_cset_fast_test.set_ext(r->hrm_index());
615 }
616 void clear_in_cset(const HeapRegion* hr) {
617 _in_cset_fast_test.clear(hr);
618 }
619
620 void clear_cset_fast_test() {
621 _in_cset_fast_test.clear();
622 }
623
624 bool is_user_requested_concurrent_full_gc(GCCause::Cause cause);
625
626 // This is called at the start of either a concurrent cycle or a Full
627 // GC to update the number of old marking cycles started.
628 void increment_old_marking_cycles_started();
629
630 // This is called at the end of either a concurrent cycle or a Full
631 // GC to update the number of old marking cycles completed. Those two
632 // can happen in a nested fashion, i.e., we start a concurrent
633 // cycle, a Full GC happens half-way through it which ends first,
634 // and then the cycle notices that a Full GC happened and ends
635 // too. The concurrent parameter is a boolean to help us do a bit
636 // tighter consistency checking in the method. If concurrent is
637 // false, the caller is the inner caller in the nesting (i.e., the
638 // Full GC). If concurrent is true, the caller is the outer caller
639 // in this nesting (i.e., the concurrent cycle). Further nesting is
640 // not currently supported. The end of this call also notifies
641 // the FullGCCount_lock in case a Java thread is waiting for a full
642 // GC to happen (e.g., it called System.gc() with
643 // +ExplicitGCInvokesConcurrent).
644 void increment_old_marking_cycles_completed(bool concurrent);
645
646 uint old_marking_cycles_completed() {
647 return _old_marking_cycles_completed;
648 }
649
650 G1HRPrinter* hr_printer() { return &_hr_printer; }
651
652 // Allocates a new heap region instance.
653 HeapRegion* new_heap_region(uint hrs_index, MemRegion mr);
654
655 // Allocate the highest free region in the reserved heap. This will commit
656 // regions as necessary.
657 HeapRegion* alloc_highest_free_region();
658
659 // Frees a non-humongous region by initializing its contents and
660 // adding it to the free list that's passed as a parameter (this is
661 // usually a local list which will be appended to the master free
662 // list later). The used bytes of freed regions are accumulated in
663 // pre_used. If skip_remset is true, the region's RSet will not be freed
664 // up. If skip_hot_card_cache is true, the region's hot card cache will not
665 // be freed up. The assumption is that this will be done later.
666 // The locked parameter indicates if the caller has already taken
667 // care of proper synchronization. This may allow some optimizations.
668 void free_region(HeapRegion* hr,
669 FreeRegionList* free_list,
670 bool skip_remset,
671 bool skip_hot_card_cache = false,
672 bool locked = false);
673
674 // It dirties the cards that cover the block so that the post
675 // write barrier never queues anything when updating objects on this
676 // block. It is assumed (and in fact we assert) that the block
677 // belongs to a young region.
678 inline void dirty_young_block(HeapWord* start, size_t word_size);
679
680 // Frees a humongous region by collapsing it into individual regions
681 // and calling free_region() for each of them. The freed regions
682 // will be added to the free list that's passed as a parameter (this
683 // is usually a local list which will be appended to the master free
684 // list later). The used bytes of freed regions are accumulated in
685 // pre_used. If skip_remset is true, the region's RSet will not be freed
686 // up. The assumption is that this will be done later.
687 void free_humongous_region(HeapRegion* hr,
688 FreeRegionList* free_list,
689 bool skip_remset);
690
691 // Facility for allocating in 'archive' regions in high heap memory and
692 // recording the allocated ranges. These should all be called from the
693 // VM thread at safepoints, without the heap lock held. They can be used
694 // to create and archive a set of heap regions which can be mapped at the
695 // same fixed addresses in a subsequent JVM invocation.
696 void begin_archive_alloc_range(bool open = false);
697
698 // Check if the requested size would be too large for an archive allocation.
699 bool is_archive_alloc_too_large(size_t word_size);
700
701 // Allocate memory of the requested size from the archive region. This will
702 // return NULL if the size is too large or if no memory is available. It
703 // does not trigger a garbage collection.
704 HeapWord* archive_mem_allocate(size_t word_size);
705
706 // Optionally aligns the end address and returns the allocated ranges in
707 // an array of MemRegions in order of ascending addresses.
708 void end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
709 size_t end_alignment_in_bytes = 0);
710
711 // Facility for allocating a fixed range within the heap and marking
712 // the containing regions as 'archive'. For use at JVM init time, when the
713 // caller may mmap archived heap data at the specified range(s).
714 // Verify that the MemRegions specified in the argument array are within the
715 // reserved heap.
716 bool check_archive_addresses(MemRegion* range, size_t count);
717
718 // Commit the appropriate G1 regions containing the specified MemRegions
719 // and mark them as 'archive' regions. The regions in the array must be
720 // non-overlapping and in order of ascending address.
721 bool alloc_archive_regions(MemRegion* range, size_t count, bool open);
722
723 // Insert any required filler objects in the G1 regions around the specified
724 // ranges to make the regions parseable. This must be called after
725 // alloc_archive_regions, and after class loading has occurred.
726 void fill_archive_regions(MemRegion* range, size_t count);
727
728 // For each of the specified MemRegions, uncommit the containing G1 regions
729 // which had been allocated by alloc_archive_regions. This should be called
730 // rather than fill_archive_regions at JVM init time if the archive file
731 // mapping failed, with the same non-overlapping and sorted MemRegion array.
732 void dealloc_archive_regions(MemRegion* range, size_t count);
733
734 protected:
735
736 // Shrink the garbage-first heap by at most the given size (in bytes!).
737 // (Rounds down to a HeapRegion boundary.)
738 virtual void shrink(size_t expand_bytes);
739 void shrink_helper(size_t expand_bytes);
740
741 #if TASKQUEUE_STATS
742 static void print_taskqueue_stats_hdr(outputStream* const st);
743 void print_taskqueue_stats() const;
744 void reset_taskqueue_stats();
745 #endif // TASKQUEUE_STATS
746
747 // Schedule the VM operation that will do an evacuation pause to
748 // satisfy an allocation request of word_size. *succeeded will
749 // return whether the VM operation was successful (it did do an
750 // evacuation pause) or not (another thread beat us to it or the GC
751 // locker was active). Given that we should not be holding the
752 // Heap_lock when we enter this method, we will pass the
753 // gc_count_before (i.e., total_collections()) as a parameter since
754 // it has to be read while holding the Heap_lock. Currently, both
755 // methods that call do_collection_pause() release the Heap_lock
756 // before the call, so it's easy to read gc_count_before just before.
757 HeapWord* do_collection_pause(size_t word_size,
758 uint gc_count_before,
759 bool* succeeded,
760 GCCause::Cause gc_cause);
761
762 void wait_for_root_region_scanning();
763
764 // The guts of the incremental collection pause, executed by the vm
765 // thread. It returns false if it is unable to do the collection due
766 // to the GC locker being active, true otherwise
767 bool do_collection_pause_at_safepoint(double target_pause_time_ms);
768
769 // Actually do the work of evacuating the collection set.
770 virtual void evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states);
771
772 void pre_evacuate_collection_set();
773 void post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* pss);
774
775 // Print the header for the per-thread termination statistics.
776 static void print_termination_stats_hdr();
777 // Print actual per-thread termination statistics.
778 void print_termination_stats(uint worker_id,
779 double elapsed_ms,
780 double strong_roots_ms,
781 double term_ms,
782 size_t term_attempts,
783 size_t alloc_buffer_waste,
784 size_t undo_waste) const;
785 // Update object copying statistics.
786 void record_obj_copy_mem_stats();
787
788 // The hot card cache for remembered set insertion optimization.
789 G1HotCardCache* _hot_card_cache;
790
791 // The g1 remembered set of the heap.
792 G1RemSet* _g1_rem_set;
793
794 // A set of cards that cover the objects for which the Rsets should be updated
795 // concurrently after the collection.
796 DirtyCardQueueSet _dirty_card_queue_set;
797
798 // After a collection pause, convert the regions in the collection set into free
799 // regions.
800 void free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words);
801
802 // Abandon the current collection set without recording policy
803 // statistics or updating free lists.
804 void abandon_collection_set(G1CollectionSet* collection_set);
805
806 // The concurrent marker (and the thread it runs in.)
807 G1ConcurrentMark* _cm;
808 ConcurrentMarkThread* _cmThread;
809
810 // The concurrent refiner.
811 ConcurrentG1Refine* _cg1r;
812
813 // The parallel task queues
814 RefToScanQueueSet *_task_queues;
815
816 // True iff a evacuation has failed in the current collection.
817 bool _evacuation_failed;
818
819 EvacuationFailedInfo* _evacuation_failed_info_array;
820
821 // Failed evacuations cause some logical from-space objects to have
822 // forwarding pointers to themselves. Reset them.
823 void remove_self_forwarding_pointers();
824
825 // Restore the objects in the regions in the collection set after an
826 // evacuation failure.
827 void restore_after_evac_failure();
828
829 PreservedMarksSet _preserved_marks_set;
830
831 // Preserve the mark of "obj", if necessary, in preparation for its mark
832 // word being overwritten with a self-forwarding-pointer.
833 void preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m);
834
835 #ifndef PRODUCT
836 // Support for forcing evacuation failures. Analogous to
837 // PromotionFailureALot for the other collectors.
838
839 // Records whether G1EvacuationFailureALot should be in effect
840 // for the current GC
841 bool _evacuation_failure_alot_for_current_gc;
842
843 // Used to record the GC number for interval checking when
844 // determining whether G1EvaucationFailureALot is in effect
845 // for the current GC.
846 size_t _evacuation_failure_alot_gc_number;
847
848 // Count of the number of evacuations between failures.
849 volatile size_t _evacuation_failure_alot_count;
850
851 // Set whether G1EvacuationFailureALot should be in effect
852 // for the current GC (based upon the type of GC and which
853 // command line flags are set);
854 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
855 bool during_initial_mark,
856 bool during_marking);
857
858 inline void set_evacuation_failure_alot_for_current_gc();
859
860 // Return true if it's time to cause an evacuation failure.
861 inline bool evacuation_should_fail();
862
863 // Reset the G1EvacuationFailureALot counters. Should be called at
864 // the end of an evacuation pause in which an evacuation failure occurred.
865 inline void reset_evacuation_should_fail();
866 #endif // !PRODUCT
867
868 // ("Weak") Reference processing support.
869 //
870 // G1 has 2 instances of the reference processor class. One
871 // (_ref_processor_cm) handles reference object discovery
872 // and subsequent processing during concurrent marking cycles.
873 //
874 // The other (_ref_processor_stw) handles reference object
875 // discovery and processing during full GCs and incremental
876 // evacuation pauses.
877 //
878 // During an incremental pause, reference discovery will be
879 // temporarily disabled for _ref_processor_cm and will be
880 // enabled for _ref_processor_stw. At the end of the evacuation
881 // pause references discovered by _ref_processor_stw will be
882 // processed and discovery will be disabled. The previous
883 // setting for reference object discovery for _ref_processor_cm
884 // will be re-instated.
885 //
886 // At the start of marking:
887 // * Discovery by the CM ref processor is verified to be inactive
888 // and it's discovered lists are empty.
889 // * Discovery by the CM ref processor is then enabled.
890 //
891 // At the end of marking:
892 // * Any references on the CM ref processor's discovered
893 // lists are processed (possibly MT).
894 //
895 // At the start of full GC we:
896 // * Disable discovery by the CM ref processor and
897 // empty CM ref processor's discovered lists
898 // (without processing any entries).
899 // * Verify that the STW ref processor is inactive and it's
900 // discovered lists are empty.
901 // * Temporarily set STW ref processor discovery as single threaded.
902 // * Temporarily clear the STW ref processor's _is_alive_non_header
903 // field.
904 // * Finally enable discovery by the STW ref processor.
905 //
906 // The STW ref processor is used to record any discovered
907 // references during the full GC.
908 //
909 // At the end of a full GC we:
910 // * Enqueue any reference objects discovered by the STW ref processor
911 // that have non-live referents. This has the side-effect of
912 // making the STW ref processor inactive by disabling discovery.
913 // * Verify that the CM ref processor is still inactive
914 // and no references have been placed on it's discovered
915 // lists (also checked as a precondition during initial marking).
916
917 // The (stw) reference processor...
918 ReferenceProcessor* _ref_processor_stw;
919
920 // During reference object discovery, the _is_alive_non_header
921 // closure (if non-null) is applied to the referent object to
922 // determine whether the referent is live. If so then the
923 // reference object does not need to be 'discovered' and can
924 // be treated as a regular oop. This has the benefit of reducing
925 // the number of 'discovered' reference objects that need to
926 // be processed.
927 //
928 // Instance of the is_alive closure for embedding into the
929 // STW reference processor as the _is_alive_non_header field.
930 // Supplying a value for the _is_alive_non_header field is
931 // optional but doing so prevents unnecessary additions to
932 // the discovered lists during reference discovery.
933 G1STWIsAliveClosure _is_alive_closure_stw;
934
935 // The (concurrent marking) reference processor...
936 ReferenceProcessor* _ref_processor_cm;
937
938 // Instance of the concurrent mark is_alive closure for embedding
939 // into the Concurrent Marking reference processor as the
940 // _is_alive_non_header field. Supplying a value for the
941 // _is_alive_non_header field is optional but doing so prevents
942 // unnecessary additions to the discovered lists during reference
943 // discovery.
944 G1CMIsAliveClosure _is_alive_closure_cm;
945
946 volatile bool _free_regions_coming;
947
948 public:
949
950 RefToScanQueue *task_queue(uint i) const;
951
952 uint num_task_queues() const;
953
954 // A set of cards where updates happened during the GC
955 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
956
957 // Create a G1CollectedHeap with the specified policy.
958 // Must call the initialize method afterwards.
959 // May not return if something goes wrong.
960 G1CollectedHeap(G1CollectorPolicy* policy);
961
962 private:
963 jint initialize_concurrent_refinement();
964 public:
965 // Initialize the G1CollectedHeap to have the initial and
966 // maximum sizes and remembered and barrier sets
967 // specified by the policy object.
968 jint initialize();
969
970 virtual void stop();
971
972 // Return the (conservative) maximum heap alignment for any G1 heap
973 static size_t conservative_max_heap_alignment();
974
975 // Does operations required after initialization has been done.
976 void post_initialize();
977
978 // Initialize weak reference processing.
979 void ref_processing_init();
980
981 virtual Name kind() const {
982 return CollectedHeap::G1CollectedHeap;
983 }
984
985 virtual const char* name() const {
986 return "G1";
987 }
988
989 const G1CollectorState* collector_state() const { return &_collector_state; }
990 G1CollectorState* collector_state() { return &_collector_state; }
991
992 // The current policy object for the collector.
993 G1Policy* g1_policy() const { return _g1_policy; }
994
995 const G1CollectionSet* collection_set() const { return &_collection_set; }
996 G1CollectionSet* collection_set() { return &_collection_set; }
997
998 virtual CollectorPolicy* collector_policy() const;
999
1000 // Adaptive size policy. No such thing for g1.
1001 virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1002
1003 // The rem set and barrier set.
1004 G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1005
1006 // Try to minimize the remembered set.
1007 void scrub_rem_set();
1008
1009 uint get_gc_time_stamp() {
1010 return _gc_time_stamp;
1011 }
1012
1013 inline void reset_gc_time_stamp();
1014
1015 void check_gc_time_stamps() PRODUCT_RETURN;
1016
1017 inline void increment_gc_time_stamp();
1018
1019 // Reset the given region's GC timestamp. If it's starts humongous,
1020 // also reset the GC timestamp of its corresponding
1021 // continues humongous regions too.
1022 void reset_gc_time_stamps(HeapRegion* hr);
1023
1024 // Apply the given closure on all cards in the Hot Card Cache, emptying it.
1025 void iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i);
1026
1027 // Apply the given closure on all cards in the Dirty Card Queue Set, emptying it.
1028 void iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i);
1029
1030 // The shared block offset table array.
1031 G1BlockOffsetTable* bot() const { return _bot; }
1032
1033 // Reference Processing accessors
1034
1035 // The STW reference processor....
1036 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1037
1038 G1NewTracer* gc_tracer_stw() const { return _gc_tracer_stw; }
1039
1040 // The Concurrent Marking reference processor...
1041 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1042
1043 virtual size_t capacity() const;
1044 virtual size_t used() const;
1045 // This should be called when we're not holding the heap lock. The
1046 // result might be a bit inaccurate.
1047 size_t used_unlocked() const;
1048 size_t recalculate_used() const;
1049
1050 // These virtual functions do the actual allocation.
1051 // Some heaps may offer a contiguous region for shared non-blocking
1052 // allocation, via inlined code (by exporting the address of the top and
1053 // end fields defining the extent of the contiguous allocation region.)
1054 // But G1CollectedHeap doesn't yet support this.
1055
1056 virtual bool is_maximal_no_gc() const {
1057 return _hrm.available() == 0;
1058 }
1059
1060 // The current number of regions in the heap.
1061 uint num_regions() const { return _hrm.length(); }
1062
1063 // The max number of regions in the heap.
1064 uint max_regions() const { return _hrm.max_length(); }
1065
1066 // The number of regions that are completely free.
1067 uint num_free_regions() const { return _hrm.num_free_regions(); }
1068
1069 MemoryUsage get_auxiliary_data_memory_usage() const {
1070 return _hrm.get_auxiliary_data_memory_usage();
1071 }
1072
1073 // The number of regions that are not completely free.
1074 uint num_used_regions() const { return num_regions() - num_free_regions(); }
1075
1076 #ifdef ASSERT
1077 bool is_on_master_free_list(HeapRegion* hr) {
1078 return _hrm.is_free(hr);
1079 }
1080 #endif // ASSERT
1081
1082 // Wrapper for the region list operations that can be called from
1083 // methods outside this class.
1084
1085 void secondary_free_list_add(FreeRegionList* list) {
1086 _secondary_free_list.add_ordered(list);
1087 }
1088
1089 void append_secondary_free_list() {
1090 _hrm.insert_list_into_free_list(&_secondary_free_list);
1091 }
1092
1093 void append_secondary_free_list_if_not_empty_with_lock() {
1094 // If the secondary free list looks empty there's no reason to
1095 // take the lock and then try to append it.
1096 if (!_secondary_free_list.is_empty()) {
1097 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1098 append_secondary_free_list();
1099 }
1100 }
1101
1102 inline void old_set_add(HeapRegion* hr);
1103 inline void old_set_remove(HeapRegion* hr);
1104
1105 size_t non_young_capacity_bytes() {
1106 return (_old_set.length() + _humongous_set.length()) * HeapRegion::GrainBytes;
1107 }
1108
1109 void set_free_regions_coming();
1110 void reset_free_regions_coming();
1111 bool free_regions_coming() { return _free_regions_coming; }
1112 void wait_while_free_regions_coming();
1113
1114 // Determine whether the given region is one that we are using as an
1115 // old GC alloc region.
1116 bool is_old_gc_alloc_region(HeapRegion* hr);
1117
1118 // Perform a collection of the heap; intended for use in implementing
1119 // "System.gc". This probably implies as full a collection as the
1120 // "CollectedHeap" supports.
1121 virtual void collect(GCCause::Cause cause);
1122
1123 virtual bool copy_allocation_context_stats(const jint* contexts,
1124 jlong* totals,
1125 jbyte* accuracy,
1126 jint len);
1127
1128 // True iff an evacuation has failed in the most-recent collection.
1129 bool evacuation_failed() { return _evacuation_failed; }
1130
1131 void remove_from_old_sets(const uint old_regions_removed, const uint humongous_regions_removed);
1132 void prepend_to_freelist(FreeRegionList* list);
1133 void decrement_summary_bytes(size_t bytes);
1134
1135 virtual bool is_in(const void* p) const;
1136 #ifdef ASSERT
1137 // Returns whether p is in one of the available areas of the heap. Slow but
1138 // extensive version.
1139 bool is_in_exact(const void* p) const;
1140 #endif
1141
1142 // Return "TRUE" iff the given object address is within the collection
1143 // set. Assumes that the reference points into the heap.
1144 inline bool is_in_cset(const HeapRegion *hr);
1145 inline bool is_in_cset(oop obj);
1146 inline bool is_in_cset(HeapWord* addr);
1147
1148 inline bool is_in_cset_or_humongous(const oop obj);
1149
1150 private:
1151 // This array is used for a quick test on whether a reference points into
1152 // the collection set or not. Each of the array's elements denotes whether the
1153 // corresponding region is in the collection set or not.
1154 G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test;
1155
1156 public:
1157
1158 inline InCSetState in_cset_state(const oop obj);
1159
1160 // Return "TRUE" iff the given object address is in the reserved
1161 // region of g1.
1162 bool is_in_g1_reserved(const void* p) const {
1163 return _hrm.reserved().contains(p);
1164 }
1165
1166 // Returns a MemRegion that corresponds to the space that has been
1167 // reserved for the heap
1168 MemRegion g1_reserved() const {
1169 return _hrm.reserved();
1170 }
1171
1172 virtual bool is_in_closed_subset(const void* p) const;
1173
1174 G1SATBCardTableLoggingModRefBS* g1_barrier_set() {
1175 return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set());
1176 }
1177
1178 // Iteration functions.
1179
1180 // Iterate over all objects, calling "cl.do_object" on each.
1181 virtual void object_iterate(ObjectClosure* cl);
1182
1183 virtual void safe_object_iterate(ObjectClosure* cl) {
1184 object_iterate(cl);
1185 }
1186
1187 // Iterate over heap regions, in address order, terminating the
1188 // iteration early if the "doHeapRegion" method returns "true".
1189 void heap_region_iterate(HeapRegionClosure* blk) const;
1190
1191 // Return the region with the given index. It assumes the index is valid.
1192 inline HeapRegion* region_at(uint index) const;
1193
1194 // Return the next region (by index) that is part of the same
1195 // humongous object that hr is part of.
1196 inline HeapRegion* next_region_in_humongous(HeapRegion* hr) const;
1197
1198 // Calculate the region index of the given address. Given address must be
1199 // within the heap.
1200 inline uint addr_to_region(HeapWord* addr) const;
1201
1202 inline HeapWord* bottom_addr_for_region(uint index) const;
1203
1204 // Iterate over the heap regions in parallel. Assumes that this will be called
1205 // in parallel by a number of worker threads with distinct worker ids
1206 // in the range passed to the HeapRegionClaimer. Applies "blk->doHeapRegion"
1207 // to each of the regions, by attempting to claim the region using the
1208 // HeapRegionClaimer and, if successful, applying the closure to the claimed
1209 // region.
1210 void heap_region_par_iterate(HeapRegionClosure* cl,
1211 uint worker_id,
1212 HeapRegionClaimer* hrclaimer) const;
1213
1214 // Iterate over the regions (if any) in the current collection set.
1215 void collection_set_iterate(HeapRegionClosure* blk);
1216
1217 // Iterate over the regions (if any) in the current collection set. Starts the
1218 // iteration over the entire collection set so that the start regions of a given
1219 // worker id over the set active_workers are evenly spread across the set of
1220 // collection set regions.
1221 void collection_set_iterate_from(HeapRegionClosure *blk, uint worker_id);
1222
1223 HeapRegion* next_compaction_region(const HeapRegion* from) const;
1224
1225 // Returns the HeapRegion that contains addr. addr must not be NULL.
1226 template <class T>
1227 inline HeapRegion* heap_region_containing(const T addr) const;
1228
1229 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1230 // each address in the (reserved) heap is a member of exactly
1231 // one block. The defining characteristic of a block is that it is
1232 // possible to find its size, and thus to progress forward to the next
1233 // block. (Blocks may be of different sizes.) Thus, blocks may
1234 // represent Java objects, or they might be free blocks in a
1235 // free-list-based heap (or subheap), as long as the two kinds are
1236 // distinguishable and the size of each is determinable.
1237
1238 // Returns the address of the start of the "block" that contains the
1239 // address "addr". We say "blocks" instead of "object" since some heaps
1240 // may not pack objects densely; a chunk may either be an object or a
1241 // non-object.
1242 virtual HeapWord* block_start(const void* addr) const;
1243
1244 // Requires "addr" to be the start of a chunk, and returns its size.
1245 // "addr + size" is required to be the start of a new chunk, or the end
1246 // of the active area of the heap.
1247 virtual size_t block_size(const HeapWord* addr) const;
1248
1249 // Requires "addr" to be the start of a block, and returns "TRUE" iff
1250 // the block is an object.
1251 virtual bool block_is_obj(const HeapWord* addr) const;
1252
1253 // Section on thread-local allocation buffers (TLABs)
1254 // See CollectedHeap for semantics.
1255
1256 bool supports_tlab_allocation() const;
1257 size_t tlab_capacity(Thread* ignored) const;
1258 size_t tlab_used(Thread* ignored) const;
1259 size_t max_tlab_size() const;
1260 size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1261
1262 // Can a compiler initialize a new object without store barriers?
1263 // This permission only extends from the creation of a new object
1264 // via a TLAB up to the first subsequent safepoint. If such permission
1265 // is granted for this heap type, the compiler promises to call
1266 // defer_store_barrier() below on any slow path allocation of
1267 // a new object for which such initializing store barriers will
1268 // have been elided. G1, like CMS, allows this, but should be
1269 // ready to provide a compensating write barrier as necessary
1270 // if that storage came out of a non-young region. The efficiency
1271 // of this implementation depends crucially on being able to
1272 // answer very efficiently in constant time whether a piece of
1273 // storage in the heap comes from a young region or not.
1274 // See ReduceInitialCardMarks.
1275 virtual bool can_elide_tlab_store_barriers() const {
1276 return true;
1277 }
1278
1279 virtual bool card_mark_must_follow_store() const {
1280 return true;
1281 }
1282
1283 inline bool is_in_young(const oop obj);
1284
1285 virtual bool is_scavengable(const void* addr);
1286
1287 // We don't need barriers for initializing stores to objects
1288 // in the young gen: for the SATB pre-barrier, there is no
1289 // pre-value that needs to be remembered; for the remembered-set
1290 // update logging post-barrier, we don't maintain remembered set
1291 // information for young gen objects.
1292 virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1293
1294 // Returns "true" iff the given word_size is "very large".
1295 static bool is_humongous(size_t word_size) {
1296 // Note this has to be strictly greater-than as the TLABs
1297 // are capped at the humongous threshold and we want to
1298 // ensure that we don't try to allocate a TLAB as
1299 // humongous and that we don't allocate a humongous
1300 // object in a TLAB.
1301 return word_size > _humongous_object_threshold_in_words;
1302 }
1303
1304 // Returns the humongous threshold for a specific region size
1305 static size_t humongous_threshold_for(size_t region_size) {
1306 return (region_size / 2);
1307 }
1308
1309 // Returns the number of regions the humongous object of the given word size
1310 // requires.
1311 static size_t humongous_obj_size_in_regions(size_t word_size);
1312
1313 // Print the maximum heap capacity.
1314 virtual size_t max_capacity() const;
1315
1316 virtual jlong millis_since_last_gc();
1317
1318
1319 // Convenience function to be used in situations where the heap type can be
1320 // asserted to be this type.
1321 static G1CollectedHeap* heap();
1322
1323 void set_region_short_lived_locked(HeapRegion* hr);
1324 // add appropriate methods for any other surv rate groups
1325
1326 const G1SurvivorRegions* survivor() const { return &_survivor; }
1327
1328 uint survivor_regions_count() const {
1329 return _survivor.length();
1330 }
1331
1332 uint eden_regions_count() const {
1333 return _eden.length();
1334 }
1335
1336 uint young_regions_count() const {
1337 return _eden.length() + _survivor.length();
1338 }
1339
1340 uint old_regions_count() const { return _old_set.length(); }
1341
1342 uint humongous_regions_count() const { return _humongous_set.length(); }
1343
1344 #ifdef ASSERT
1345 bool check_young_list_empty();
1346 #endif
1347
1348 // *** Stuff related to concurrent marking. It's not clear to me that so
1349 // many of these need to be public.
1350
1351 // The functions below are helper functions that a subclass of
1352 // "CollectedHeap" can use in the implementation of its virtual
1353 // functions.
1354 // This performs a concurrent marking of the live objects in a
1355 // bitmap off to the side.
1356 void doConcurrentMark();
1357
1358 bool isMarkedNext(oop obj) const;
1359
1360 // Determine if an object is dead, given the object and also
1361 // the region to which the object belongs. An object is dead
1362 // iff a) it was not allocated since the last mark, b) it
1363 // is not marked, and c) it is not in an archive region.
1364 bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1365 return
1366 hr->is_obj_dead(obj, _cm->prevMarkBitMap()) &&
1367 !hr->is_archive();
1368 }
1369
1370 // This function returns true when an object has been
1371 // around since the previous marking and hasn't yet
1372 // been marked during this marking, and is not in an archive region.
1373 bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1374 return
1375 !hr->obj_allocated_since_next_marking(obj) &&
1376 !isMarkedNext(obj) &&
1377 !hr->is_archive();
1378 }
1379
1380 // Determine if an object is dead, given only the object itself.
1381 // This will find the region to which the object belongs and
1382 // then call the region version of the same function.
1383
1384 // Added if it is NULL it isn't dead.
1385
1386 inline bool is_obj_dead(const oop obj) const;
1387
1388 inline bool is_obj_ill(const oop obj) const;
1389
1390 G1ConcurrentMark* concurrent_mark() const { return _cm; }
1391
1392 // Refinement
1393
1394 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1395
1396 // Optimized nmethod scanning support routines
1397
1398 // Register the given nmethod with the G1 heap.
1399 virtual void register_nmethod(nmethod* nm);
1400
1401 // Unregister the given nmethod from the G1 heap.
1402 virtual void unregister_nmethod(nmethod* nm);
1403
1404 // Free up superfluous code root memory.
1405 void purge_code_root_memory();
1406
1407 // Rebuild the strong code root lists for each region
1408 // after a full GC.
1409 void rebuild_strong_code_roots();
1410
1411 // Partial cleaning used when class unloading is disabled.
1412 // Let the caller choose what structures to clean out:
1413 // - StringTable
1414 // - SymbolTable
1415 // - StringDeduplication structures
1416 void partial_cleaning(BoolObjectClosure* is_alive, bool unlink_strings, bool unlink_symbols, bool unlink_string_dedup);
1417
1418 // Complete cleaning used when class unloading is enabled.
1419 // Cleans out all structures handled by partial_cleaning and also the CodeCache.
1420 void complete_cleaning(BoolObjectClosure* is_alive, bool class_unloading_occurred);
1421
1422 // Redirty logged cards in the refinement queue.
1423 void redirty_logged_cards();
1424 // Verification
1425
1426 // Perform any cleanup actions necessary before allowing a verification.
1427 virtual void prepare_for_verify();
1428
1429 // Perform verification.
1430
1431 // vo == UsePrevMarking -> use "prev" marking information,
1432 // vo == UseNextMarking -> use "next" marking information
1433 // vo == UseMarkWord -> use the mark word in the object header
1434 //
1435 // NOTE: Only the "prev" marking information is guaranteed to be
1436 // consistent most of the time, so most calls to this should use
1437 // vo == UsePrevMarking.
1438 // Currently, there is only one case where this is called with
1439 // vo == UseNextMarking, which is to verify the "next" marking
1440 // information at the end of remark.
1441 // Currently there is only one place where this is called with
1442 // vo == UseMarkWord, which is to verify the marking during a
1443 // full GC.
1444 void verify(VerifyOption vo);
1445
1446 // WhiteBox testing support.
1447 virtual bool supports_concurrent_phase_control() const;
1448 virtual const char* const* concurrent_phases() const;
1449 virtual bool request_concurrent_phase(const char* phase);
1450
1451 // The methods below are here for convenience and dispatch the
1452 // appropriate method depending on value of the given VerifyOption
1453 // parameter. The values for that parameter, and their meanings,
1454 // are the same as those above.
1455
1456 bool is_obj_dead_cond(const oop obj,
1457 const HeapRegion* hr,
1458 const VerifyOption vo) const;
1459
1460 bool is_obj_dead_cond(const oop obj,
1461 const VerifyOption vo) const;
1462
1463 G1HeapSummary create_g1_heap_summary();
1464 G1EvacSummary create_g1_evac_summary(G1EvacStats* stats);
1465
1466 // Printing
1467 private:
1468 void print_heap_regions() const;
1469 void print_regions_on(outputStream* st) const;
1470
1471 public:
1472 virtual void print_on(outputStream* st) const;
1473 virtual void print_extended_on(outputStream* st) const;
1474 virtual void print_on_error(outputStream* st) const;
1475
1476 virtual void print_gc_threads_on(outputStream* st) const;
1477 virtual void gc_threads_do(ThreadClosure* tc) const;
1478
1479 // Override
1480 void print_tracing_info() const;
1481
1482 // The following two methods are helpful for debugging RSet issues.
1483 void print_cset_rsets() PRODUCT_RETURN;
1484 void print_all_rsets() PRODUCT_RETURN;
1485
1486 public:
1487 size_t pending_card_num();
1488
1489 protected:
1490 size_t _max_heap_capacity;
1491 };
1492
1493 class G1ParEvacuateFollowersClosure : public VoidClosure {
1494 private:
1495 double _start_term;
1496 double _term_time;
1497 size_t _term_attempts;
1498
1499 void start_term_time() { _term_attempts++; _start_term = os::elapsedTime(); }
1500 void end_term_time() { _term_time += os::elapsedTime() - _start_term; }
1501 protected:
1502 G1CollectedHeap* _g1h;
1503 G1ParScanThreadState* _par_scan_state;
1504 RefToScanQueueSet* _queues;
1505 ParallelTaskTerminator* _terminator;
1506
1507 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
1508 RefToScanQueueSet* queues() { return _queues; }
1509 ParallelTaskTerminator* terminator() { return _terminator; }
1510
1511 public:
1512 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
1513 G1ParScanThreadState* par_scan_state,
1514 RefToScanQueueSet* queues,
1515 ParallelTaskTerminator* terminator)
1516 : _g1h(g1h), _par_scan_state(par_scan_state),
1517 _queues(queues), _terminator(terminator),
1518 _start_term(0.0), _term_time(0.0), _term_attempts(0) {}
1519
1520 void do_void();
1521
1522 double term_time() const { return _term_time; }
1523 size_t term_attempts() const { return _term_attempts; }
1524
1525 private:
1526 inline bool offer_termination();
1527 };
1528
1529 #endif // SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP