Fri, 19 Dec 2014 09:21:06 +0100
8060025: Object copy time regressions after JDK-8031323 and JDK-8057536
Summary: Evaluate and improve object copy time by micro-optimizations and splitting out slow and fast paths aggressively.
Reviewed-by: kbarrett, mgerdin, jmasa
Contributed-by: Tony Printezis <tprintezis@twitter.com>, Thomas Schatzl <thomas.schatzl@oracle.com>
1 /*
2 * Copyright (c) 2001, 2014, 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.
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23 */
25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
28 #include "gc_implementation/g1/g1AllocationContext.hpp"
29 #include "gc_implementation/g1/g1Allocator.hpp"
30 #include "gc_implementation/g1/concurrentMark.hpp"
31 #include "gc_implementation/g1/evacuationInfo.hpp"
32 #include "gc_implementation/g1/g1AllocRegion.hpp"
33 #include "gc_implementation/g1/g1BiasedArray.hpp"
34 #include "gc_implementation/g1/g1HRPrinter.hpp"
35 #include "gc_implementation/g1/g1InCSetState.hpp"
36 #include "gc_implementation/g1/g1MonitoringSupport.hpp"
37 #include "gc_implementation/g1/g1SATBCardTableModRefBS.hpp"
38 #include "gc_implementation/g1/g1YCTypes.hpp"
39 #include "gc_implementation/g1/heapRegionManager.hpp"
40 #include "gc_implementation/g1/heapRegionSet.hpp"
41 #include "gc_implementation/shared/hSpaceCounters.hpp"
42 #include "gc_implementation/shared/parGCAllocBuffer.hpp"
43 #include "memory/barrierSet.hpp"
44 #include "memory/memRegion.hpp"
45 #include "memory/sharedHeap.hpp"
46 #include "utilities/stack.hpp"
48 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
49 // It uses the "Garbage First" heap organization and algorithm, which
50 // may combine concurrent marking with parallel, incremental compaction of
51 // heap subsets that will yield large amounts of garbage.
53 // Forward declarations
54 class HeapRegion;
55 class HRRSCleanupTask;
56 class GenerationSpec;
57 class OopsInHeapRegionClosure;
58 class G1KlassScanClosure;
59 class G1ScanHeapEvacClosure;
60 class ObjectClosure;
61 class SpaceClosure;
62 class CompactibleSpaceClosure;
63 class Space;
64 class G1CollectorPolicy;
65 class GenRemSet;
66 class G1RemSet;
67 class HeapRegionRemSetIterator;
68 class ConcurrentMark;
69 class ConcurrentMarkThread;
70 class ConcurrentG1Refine;
71 class ConcurrentGCTimer;
72 class GenerationCounters;
73 class STWGCTimer;
74 class G1NewTracer;
75 class G1OldTracer;
76 class EvacuationFailedInfo;
77 class nmethod;
78 class Ticks;
80 typedef OverflowTaskQueue<StarTask, mtGC> RefToScanQueue;
81 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
83 typedef int RegionIdx_t; // needs to hold [ 0..max_regions() )
84 typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion )
86 class YoungList : public CHeapObj<mtGC> {
87 private:
88 G1CollectedHeap* _g1h;
90 HeapRegion* _head;
92 HeapRegion* _survivor_head;
93 HeapRegion* _survivor_tail;
95 HeapRegion* _curr;
97 uint _length;
98 uint _survivor_length;
100 size_t _last_sampled_rs_lengths;
101 size_t _sampled_rs_lengths;
103 void empty_list(HeapRegion* list);
105 public:
106 YoungList(G1CollectedHeap* g1h);
108 void push_region(HeapRegion* hr);
109 void add_survivor_region(HeapRegion* hr);
111 void empty_list();
112 bool is_empty() { return _length == 0; }
113 uint length() { return _length; }
114 uint survivor_length() { return _survivor_length; }
116 // Currently we do not keep track of the used byte sum for the
117 // young list and the survivors and it'd be quite a lot of work to
118 // do so. When we'll eventually replace the young list with
119 // instances of HeapRegionLinkedList we'll get that for free. So,
120 // we'll report the more accurate information then.
121 size_t eden_used_bytes() {
122 assert(length() >= survivor_length(), "invariant");
123 return (size_t) (length() - survivor_length()) * HeapRegion::GrainBytes;
124 }
125 size_t survivor_used_bytes() {
126 return (size_t) survivor_length() * HeapRegion::GrainBytes;
127 }
129 void rs_length_sampling_init();
130 bool rs_length_sampling_more();
131 void rs_length_sampling_next();
133 void reset_sampled_info() {
134 _last_sampled_rs_lengths = 0;
135 }
136 size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
138 // for development purposes
139 void reset_auxilary_lists();
140 void clear() { _head = NULL; _length = 0; }
142 void clear_survivors() {
143 _survivor_head = NULL;
144 _survivor_tail = NULL;
145 _survivor_length = 0;
146 }
148 HeapRegion* first_region() { return _head; }
149 HeapRegion* first_survivor_region() { return _survivor_head; }
150 HeapRegion* last_survivor_region() { return _survivor_tail; }
152 // debugging
153 bool check_list_well_formed();
154 bool check_list_empty(bool check_sample = true);
155 void print();
156 };
158 // The G1 STW is alive closure.
159 // An instance is embedded into the G1CH and used as the
160 // (optional) _is_alive_non_header closure in the STW
161 // reference processor. It is also extensively used during
162 // reference processing during STW evacuation pauses.
163 class G1STWIsAliveClosure: public BoolObjectClosure {
164 G1CollectedHeap* _g1;
165 public:
166 G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
167 bool do_object_b(oop p);
168 };
170 class RefineCardTableEntryClosure;
172 class G1RegionMappingChangedListener : public G1MappingChangedListener {
173 private:
174 void reset_from_card_cache(uint start_idx, size_t num_regions);
175 public:
176 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
177 };
179 class G1CollectedHeap : public SharedHeap {
180 friend class VM_CollectForMetadataAllocation;
181 friend class VM_G1CollectForAllocation;
182 friend class VM_G1CollectFull;
183 friend class VM_G1IncCollectionPause;
184 friend class VMStructs;
185 friend class MutatorAllocRegion;
186 friend class SurvivorGCAllocRegion;
187 friend class OldGCAllocRegion;
188 friend class G1Allocator;
189 friend class G1DefaultAllocator;
190 friend class G1ResManAllocator;
192 // Closures used in implementation.
193 template <G1Barrier barrier, G1Mark do_mark_object>
194 friend class G1ParCopyClosure;
195 friend class G1IsAliveClosure;
196 friend class G1EvacuateFollowersClosure;
197 friend class G1ParScanThreadState;
198 friend class G1ParScanClosureSuper;
199 friend class G1ParEvacuateFollowersClosure;
200 friend class G1ParTask;
201 friend class G1ParGCAllocator;
202 friend class G1DefaultParGCAllocator;
203 friend class G1FreeGarbageRegionClosure;
204 friend class RefineCardTableEntryClosure;
205 friend class G1PrepareCompactClosure;
206 friend class RegionSorter;
207 friend class RegionResetter;
208 friend class CountRCClosure;
209 friend class EvacPopObjClosure;
210 friend class G1ParCleanupCTTask;
212 friend class G1FreeHumongousRegionClosure;
213 // Other related classes.
214 friend class G1MarkSweep;
216 private:
217 // The one and only G1CollectedHeap, so static functions can find it.
218 static G1CollectedHeap* _g1h;
220 static size_t _humongous_object_threshold_in_words;
222 // The secondary free list which contains regions that have been
223 // freed up during the cleanup process. This will be appended to
224 // the master free list when appropriate.
225 FreeRegionList _secondary_free_list;
227 // It keeps track of the old regions.
228 HeapRegionSet _old_set;
230 // It keeps track of the humongous regions.
231 HeapRegionSet _humongous_set;
233 void clear_humongous_is_live_table();
234 void eagerly_reclaim_humongous_regions();
236 // The number of regions we could create by expansion.
237 uint _expansion_regions;
239 // The block offset table for the G1 heap.
240 G1BlockOffsetSharedArray* _bot_shared;
242 // Tears down the region sets / lists so that they are empty and the
243 // regions on the heap do not belong to a region set / list. The
244 // only exception is the humongous set which we leave unaltered. If
245 // free_list_only is true, it will only tear down the master free
246 // list. It is called before a Full GC (free_list_only == false) or
247 // before heap shrinking (free_list_only == true).
248 void tear_down_region_sets(bool free_list_only);
250 // Rebuilds the region sets / lists so that they are repopulated to
251 // reflect the contents of the heap. The only exception is the
252 // humongous set which was not torn down in the first place. If
253 // free_list_only is true, it will only rebuild the master free
254 // list. It is called after a Full GC (free_list_only == false) or
255 // after heap shrinking (free_list_only == true).
256 void rebuild_region_sets(bool free_list_only);
258 // Callback for region mapping changed events.
259 G1RegionMappingChangedListener _listener;
261 // The sequence of all heap regions in the heap.
262 HeapRegionManager _hrm;
264 // Class that handles the different kinds of allocations.
265 G1Allocator* _allocator;
267 // Statistics for each allocation context
268 AllocationContextStats _allocation_context_stats;
270 // PLAB sizing policy for survivors.
271 PLABStats _survivor_plab_stats;
273 // PLAB sizing policy for tenured objects.
274 PLABStats _old_plab_stats;
276 // It specifies whether we should attempt to expand the heap after a
277 // region allocation failure. If heap expansion fails we set this to
278 // false so that we don't re-attempt the heap expansion (it's likely
279 // that subsequent expansion attempts will also fail if one fails).
280 // Currently, it is only consulted during GC and it's reset at the
281 // start of each GC.
282 bool _expand_heap_after_alloc_failure;
284 // It resets the mutator alloc region before new allocations can take place.
285 void init_mutator_alloc_region();
287 // It releases the mutator alloc region.
288 void release_mutator_alloc_region();
290 // It initializes the GC alloc regions at the start of a GC.
291 void init_gc_alloc_regions(EvacuationInfo& evacuation_info);
293 // It releases the GC alloc regions at the end of a GC.
294 void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info);
296 // It does any cleanup that needs to be done on the GC alloc regions
297 // before a Full GC.
298 void abandon_gc_alloc_regions();
300 // Helper for monitoring and management support.
301 G1MonitoringSupport* _g1mm;
303 // Records whether the region at the given index is kept live by roots or
304 // references from the young generation.
305 class HumongousIsLiveBiasedMappedArray : public G1BiasedMappedArray<bool> {
306 protected:
307 bool default_value() const { return false; }
308 public:
309 void clear() { G1BiasedMappedArray<bool>::clear(); }
310 void set_live(uint region) {
311 set_by_index(region, true);
312 }
313 bool is_live(uint region) {
314 return get_by_index(region);
315 }
316 };
318 HumongousIsLiveBiasedMappedArray _humongous_is_live;
319 // Stores whether during humongous object registration we found candidate regions.
320 // If not, we can skip a few steps.
321 bool _has_humongous_reclaim_candidates;
323 volatile unsigned _gc_time_stamp;
325 size_t* _surviving_young_words;
327 G1HRPrinter _hr_printer;
329 void setup_surviving_young_words();
330 void update_surviving_young_words(size_t* surv_young_words);
331 void cleanup_surviving_young_words();
333 // It decides whether an explicit GC should start a concurrent cycle
334 // instead of doing a STW GC. Currently, a concurrent cycle is
335 // explicitly started if:
336 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
337 // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
338 // (c) cause == _g1_humongous_allocation
339 bool should_do_concurrent_full_gc(GCCause::Cause cause);
341 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
342 // concurrent cycles) we have started.
343 volatile unsigned int _old_marking_cycles_started;
345 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
346 // concurrent cycles) we have completed.
347 volatile unsigned int _old_marking_cycles_completed;
349 bool _concurrent_cycle_started;
350 bool _heap_summary_sent;
352 // This is a non-product method that is helpful for testing. It is
353 // called at the end of a GC and artificially expands the heap by
354 // allocating a number of dead regions. This way we can induce very
355 // frequent marking cycles and stress the cleanup / concurrent
356 // cleanup code more (as all the regions that will be allocated by
357 // this method will be found dead by the marking cycle).
358 void allocate_dummy_regions() PRODUCT_RETURN;
360 // Clear RSets after a compaction. It also resets the GC time stamps.
361 void clear_rsets_post_compaction();
363 // If the HR printer is active, dump the state of the regions in the
364 // heap after a compaction.
365 void print_hrm_post_compaction();
367 double verify(bool guard, const char* msg);
368 void verify_before_gc();
369 void verify_after_gc();
371 void log_gc_header();
372 void log_gc_footer(double pause_time_sec);
374 // These are macros so that, if the assert fires, we get the correct
375 // line number, file, etc.
377 #define heap_locking_asserts_err_msg(_extra_message_) \
378 err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \
379 (_extra_message_), \
380 BOOL_TO_STR(Heap_lock->owned_by_self()), \
381 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \
382 BOOL_TO_STR(Thread::current()->is_VM_thread()))
384 #define assert_heap_locked() \
385 do { \
386 assert(Heap_lock->owned_by_self(), \
387 heap_locking_asserts_err_msg("should be holding the Heap_lock")); \
388 } while (0)
390 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \
391 do { \
392 assert(Heap_lock->owned_by_self() || \
393 (SafepointSynchronize::is_at_safepoint() && \
394 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
395 heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
396 "should be at a safepoint")); \
397 } while (0)
399 #define assert_heap_locked_and_not_at_safepoint() \
400 do { \
401 assert(Heap_lock->owned_by_self() && \
402 !SafepointSynchronize::is_at_safepoint(), \
403 heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
404 "should not be at a safepoint")); \
405 } while (0)
407 #define assert_heap_not_locked() \
408 do { \
409 assert(!Heap_lock->owned_by_self(), \
410 heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
411 } while (0)
413 #define assert_heap_not_locked_and_not_at_safepoint() \
414 do { \
415 assert(!Heap_lock->owned_by_self() && \
416 !SafepointSynchronize::is_at_safepoint(), \
417 heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
418 "should not be at a safepoint")); \
419 } while (0)
421 #define assert_at_safepoint(_should_be_vm_thread_) \
422 do { \
423 assert(SafepointSynchronize::is_at_safepoint() && \
424 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
425 heap_locking_asserts_err_msg("should be at a safepoint")); \
426 } while (0)
428 #define assert_not_at_safepoint() \
429 do { \
430 assert(!SafepointSynchronize::is_at_safepoint(), \
431 heap_locking_asserts_err_msg("should not be at a safepoint")); \
432 } while (0)
434 protected:
436 // The young region list.
437 YoungList* _young_list;
439 // The current policy object for the collector.
440 G1CollectorPolicy* _g1_policy;
442 // This is the second level of trying to allocate a new region. If
443 // new_region() didn't find a region on the free_list, this call will
444 // check whether there's anything available on the
445 // secondary_free_list and/or wait for more regions to appear on
446 // that list, if _free_regions_coming is set.
447 HeapRegion* new_region_try_secondary_free_list(bool is_old);
449 // Try to allocate a single non-humongous HeapRegion sufficient for
450 // an allocation of the given word_size. If do_expand is true,
451 // attempt to expand the heap if necessary to satisfy the allocation
452 // request. If the region is to be used as an old region or for a
453 // humongous object, set is_old to true. If not, to false.
454 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
456 // Initialize a contiguous set of free regions of length num_regions
457 // and starting at index first so that they appear as a single
458 // humongous region.
459 HeapWord* humongous_obj_allocate_initialize_regions(uint first,
460 uint num_regions,
461 size_t word_size,
462 AllocationContext_t context);
464 // Attempt to allocate a humongous object of the given size. Return
465 // NULL if unsuccessful.
466 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context);
468 // The following two methods, allocate_new_tlab() and
469 // mem_allocate(), are the two main entry points from the runtime
470 // into the G1's allocation routines. They have the following
471 // assumptions:
472 //
473 // * They should both be called outside safepoints.
474 //
475 // * They should both be called without holding the Heap_lock.
476 //
477 // * All allocation requests for new TLABs should go to
478 // allocate_new_tlab().
479 //
480 // * All non-TLAB allocation requests should go to mem_allocate().
481 //
482 // * If either call cannot satisfy the allocation request using the
483 // current allocating region, they will try to get a new one. If
484 // this fails, they will attempt to do an evacuation pause and
485 // retry the allocation.
486 //
487 // * If all allocation attempts fail, even after trying to schedule
488 // an evacuation pause, allocate_new_tlab() will return NULL,
489 // whereas mem_allocate() will attempt a heap expansion and/or
490 // schedule a Full GC.
491 //
492 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
493 // should never be called with word_size being humongous. All
494 // humongous allocation requests should go to mem_allocate() which
495 // will satisfy them with a special path.
497 virtual HeapWord* allocate_new_tlab(size_t word_size);
499 virtual HeapWord* mem_allocate(size_t word_size,
500 bool* gc_overhead_limit_was_exceeded);
502 // The following three methods take a gc_count_before_ret
503 // parameter which is used to return the GC count if the method
504 // returns NULL. Given that we are required to read the GC count
505 // while holding the Heap_lock, and these paths will take the
506 // Heap_lock at some point, it's easier to get them to read the GC
507 // count while holding the Heap_lock before they return NULL instead
508 // of the caller (namely: mem_allocate()) having to also take the
509 // Heap_lock just to read the GC count.
511 // First-level mutator allocation attempt: try to allocate out of
512 // the mutator alloc region without taking the Heap_lock. This
513 // should only be used for non-humongous allocations.
514 inline HeapWord* attempt_allocation(size_t word_size,
515 unsigned int* gc_count_before_ret,
516 int* gclocker_retry_count_ret);
518 // Second-level mutator allocation attempt: take the Heap_lock and
519 // retry the allocation attempt, potentially scheduling a GC
520 // pause. This should only be used for non-humongous allocations.
521 HeapWord* attempt_allocation_slow(size_t word_size,
522 AllocationContext_t context,
523 unsigned int* gc_count_before_ret,
524 int* gclocker_retry_count_ret);
526 // Takes the Heap_lock and attempts a humongous allocation. It can
527 // potentially schedule a GC pause.
528 HeapWord* attempt_allocation_humongous(size_t word_size,
529 unsigned int* gc_count_before_ret,
530 int* gclocker_retry_count_ret);
532 // Allocation attempt that should be called during safepoints (e.g.,
533 // at the end of a successful GC). expect_null_mutator_alloc_region
534 // specifies whether the mutator alloc region is expected to be NULL
535 // or not.
536 HeapWord* attempt_allocation_at_safepoint(size_t word_size,
537 AllocationContext_t context,
538 bool expect_null_mutator_alloc_region);
540 // It dirties the cards that cover the block so that so that the post
541 // write barrier never queues anything when updating objects on this
542 // block. It is assumed (and in fact we assert) that the block
543 // belongs to a young region.
544 inline void dirty_young_block(HeapWord* start, size_t word_size);
546 // Allocate blocks during garbage collection. Will ensure an
547 // allocation region, either by picking one or expanding the
548 // heap, and then allocate a block of the given size. The block
549 // may not be a humongous - it must fit into a single heap region.
550 inline HeapWord* par_allocate_during_gc(InCSetState dest,
551 size_t word_size,
552 AllocationContext_t context);
553 // Ensure that no further allocations can happen in "r", bearing in mind
554 // that parallel threads might be attempting allocations.
555 void par_allocate_remaining_space(HeapRegion* r);
557 // Allocation attempt during GC for a survivor object / PLAB.
558 inline HeapWord* survivor_attempt_allocation(size_t word_size,
559 AllocationContext_t context);
561 // Allocation attempt during GC for an old object / PLAB.
562 inline HeapWord* old_attempt_allocation(size_t word_size,
563 AllocationContext_t context);
565 // These methods are the "callbacks" from the G1AllocRegion class.
567 // For mutator alloc regions.
568 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
569 void retire_mutator_alloc_region(HeapRegion* alloc_region,
570 size_t allocated_bytes);
572 // For GC alloc regions.
573 HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
574 InCSetState dest);
575 void retire_gc_alloc_region(HeapRegion* alloc_region,
576 size_t allocated_bytes, InCSetState dest);
578 // - if explicit_gc is true, the GC is for a System.gc() or a heap
579 // inspection request and should collect the entire heap
580 // - if clear_all_soft_refs is true, all soft references should be
581 // cleared during the GC
582 // - if explicit_gc is false, word_size describes the allocation that
583 // the GC should attempt (at least) to satisfy
584 // - it returns false if it is unable to do the collection due to the
585 // GC locker being active, true otherwise
586 bool do_collection(bool explicit_gc,
587 bool clear_all_soft_refs,
588 size_t word_size);
590 // Callback from VM_G1CollectFull operation.
591 // Perform a full collection.
592 virtual void do_full_collection(bool clear_all_soft_refs);
594 // Resize the heap if necessary after a full collection. If this is
595 // after a collect-for allocation, "word_size" is the allocation size,
596 // and will be considered part of the used portion of the heap.
597 void resize_if_necessary_after_full_collection(size_t word_size);
599 // Callback from VM_G1CollectForAllocation operation.
600 // This function does everything necessary/possible to satisfy a
601 // failed allocation request (including collection, expansion, etc.)
602 HeapWord* satisfy_failed_allocation(size_t word_size,
603 AllocationContext_t context,
604 bool* succeeded);
606 // Attempting to expand the heap sufficiently
607 // to support an allocation of the given "word_size". If
608 // successful, perform the allocation and return the address of the
609 // allocated block, or else "NULL".
610 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context);
612 // Process any reference objects discovered during
613 // an incremental evacuation pause.
614 void process_discovered_references(uint no_of_gc_workers);
616 // Enqueue any remaining discovered references
617 // after processing.
618 void enqueue_discovered_references(uint no_of_gc_workers);
620 public:
622 G1Allocator* allocator() {
623 return _allocator;
624 }
626 G1MonitoringSupport* g1mm() {
627 assert(_g1mm != NULL, "should have been initialized");
628 return _g1mm;
629 }
631 // Expand the garbage-first heap by at least the given size (in bytes!).
632 // Returns true if the heap was expanded by the requested amount;
633 // false otherwise.
634 // (Rounds up to a HeapRegion boundary.)
635 bool expand(size_t expand_bytes);
637 // Returns the PLAB statistics for a given destination.
638 inline PLABStats* alloc_buffer_stats(InCSetState dest);
640 // Determines PLAB size for a given destination.
641 inline size_t desired_plab_sz(InCSetState dest);
643 inline AllocationContextStats& allocation_context_stats();
645 // Do anything common to GC's.
646 virtual void gc_prologue(bool full);
647 virtual void gc_epilogue(bool full);
649 inline void set_humongous_is_live(oop obj);
651 bool humongous_is_live(uint region) {
652 return _humongous_is_live.is_live(region);
653 }
655 // Returns whether the given region (which must be a humongous (start) region)
656 // is to be considered conservatively live regardless of any other conditions.
657 bool humongous_region_is_always_live(uint index);
658 // Register the given region to be part of the collection set.
659 inline void register_humongous_region_with_in_cset_fast_test(uint index);
660 // Register regions with humongous objects (actually on the start region) in
661 // the in_cset_fast_test table.
662 void register_humongous_regions_with_in_cset_fast_test();
663 // We register a region with the fast "in collection set" test. We
664 // simply set to true the array slot corresponding to this region.
665 void register_young_region_with_in_cset_fast_test(HeapRegion* r) {
666 _in_cset_fast_test.set_in_young(r->hrm_index());
667 }
668 void register_old_region_with_in_cset_fast_test(HeapRegion* r) {
669 _in_cset_fast_test.set_in_old(r->hrm_index());
670 }
672 // This is a fast test on whether a reference points into the
673 // collection set or not. Assume that the reference
674 // points into the heap.
675 inline bool in_cset_fast_test(oop obj);
677 void clear_cset_fast_test() {
678 _in_cset_fast_test.clear();
679 }
681 // This is called at the start of either a concurrent cycle or a Full
682 // GC to update the number of old marking cycles started.
683 void increment_old_marking_cycles_started();
685 // This is called at the end of either a concurrent cycle or a Full
686 // GC to update the number of old marking cycles completed. Those two
687 // can happen in a nested fashion, i.e., we start a concurrent
688 // cycle, a Full GC happens half-way through it which ends first,
689 // and then the cycle notices that a Full GC happened and ends
690 // too. The concurrent parameter is a boolean to help us do a bit
691 // tighter consistency checking in the method. If concurrent is
692 // false, the caller is the inner caller in the nesting (i.e., the
693 // Full GC). If concurrent is true, the caller is the outer caller
694 // in this nesting (i.e., the concurrent cycle). Further nesting is
695 // not currently supported. The end of this call also notifies
696 // the FullGCCount_lock in case a Java thread is waiting for a full
697 // GC to happen (e.g., it called System.gc() with
698 // +ExplicitGCInvokesConcurrent).
699 void increment_old_marking_cycles_completed(bool concurrent);
701 unsigned int old_marking_cycles_completed() {
702 return _old_marking_cycles_completed;
703 }
705 void register_concurrent_cycle_start(const Ticks& start_time);
706 void register_concurrent_cycle_end();
707 void trace_heap_after_concurrent_cycle();
709 G1YCType yc_type();
711 G1HRPrinter* hr_printer() { return &_hr_printer; }
713 // Frees a non-humongous region by initializing its contents and
714 // adding it to the free list that's passed as a parameter (this is
715 // usually a local list which will be appended to the master free
716 // list later). The used bytes of freed regions are accumulated in
717 // pre_used. If par is true, the region's RSet will not be freed
718 // up. The assumption is that this will be done later.
719 // The locked parameter indicates if the caller has already taken
720 // care of proper synchronization. This may allow some optimizations.
721 void free_region(HeapRegion* hr,
722 FreeRegionList* free_list,
723 bool par,
724 bool locked = false);
726 // Frees a humongous region by collapsing it into individual regions
727 // and calling free_region() for each of them. The freed regions
728 // will be added to the free list that's passed as a parameter (this
729 // is usually a local list which will be appended to the master free
730 // list later). The used bytes of freed regions are accumulated in
731 // pre_used. If par is true, the region's RSet will not be freed
732 // up. The assumption is that this will be done later.
733 void free_humongous_region(HeapRegion* hr,
734 FreeRegionList* free_list,
735 bool par);
736 protected:
738 // Shrink the garbage-first heap by at most the given size (in bytes!).
739 // (Rounds down to a HeapRegion boundary.)
740 virtual void shrink(size_t expand_bytes);
741 void shrink_helper(size_t expand_bytes);
743 #if TASKQUEUE_STATS
744 static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
745 void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
746 void reset_taskqueue_stats();
747 #endif // TASKQUEUE_STATS
749 // Schedule the VM operation that will do an evacuation pause to
750 // satisfy an allocation request of word_size. *succeeded will
751 // return whether the VM operation was successful (it did do an
752 // evacuation pause) or not (another thread beat us to it or the GC
753 // locker was active). Given that we should not be holding the
754 // Heap_lock when we enter this method, we will pass the
755 // gc_count_before (i.e., total_collections()) as a parameter since
756 // it has to be read while holding the Heap_lock. Currently, both
757 // methods that call do_collection_pause() release the Heap_lock
758 // before the call, so it's easy to read gc_count_before just before.
759 HeapWord* do_collection_pause(size_t word_size,
760 unsigned int gc_count_before,
761 bool* succeeded,
762 GCCause::Cause gc_cause);
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);
769 // Actually do the work of evacuating the collection set.
770 void evacuate_collection_set(EvacuationInfo& evacuation_info);
772 // The g1 remembered set of the heap.
773 G1RemSet* _g1_rem_set;
775 // A set of cards that cover the objects for which the Rsets should be updated
776 // concurrently after the collection.
777 DirtyCardQueueSet _dirty_card_queue_set;
779 // The closure used to refine a single card.
780 RefineCardTableEntryClosure* _refine_cte_cl;
782 // A function to check the consistency of dirty card logs.
783 void check_ct_logs_at_safepoint();
785 // A DirtyCardQueueSet that is used to hold cards that contain
786 // references into the current collection set. This is used to
787 // update the remembered sets of the regions in the collection
788 // set in the event of an evacuation failure.
789 DirtyCardQueueSet _into_cset_dirty_card_queue_set;
791 // After a collection pause, make the regions in the CS into free
792 // regions.
793 void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info);
795 // Abandon the current collection set without recording policy
796 // statistics or updating free lists.
797 void abandon_collection_set(HeapRegion* cs_head);
799 // Applies "scan_non_heap_roots" to roots outside the heap,
800 // "scan_rs" to roots inside the heap (having done "set_region" to
801 // indicate the region in which the root resides),
802 // and does "scan_metadata" If "scan_rs" is
803 // NULL, then this step is skipped. The "worker_i"
804 // param is for use with parallel roots processing, and should be
805 // the "i" of the calling parallel worker thread's work(i) function.
806 // In the sequential case this param will be ignored.
807 void g1_process_roots(OopClosure* scan_non_heap_roots,
808 OopClosure* scan_non_heap_weak_roots,
809 OopsInHeapRegionClosure* scan_rs,
810 CLDClosure* scan_strong_clds,
811 CLDClosure* scan_weak_clds,
812 CodeBlobClosure* scan_strong_code,
813 uint worker_i);
815 // The concurrent marker (and the thread it runs in.)
816 ConcurrentMark* _cm;
817 ConcurrentMarkThread* _cmThread;
818 bool _mark_in_progress;
820 // The concurrent refiner.
821 ConcurrentG1Refine* _cg1r;
823 // The parallel task queues
824 RefToScanQueueSet *_task_queues;
826 // True iff a evacuation has failed in the current collection.
827 bool _evacuation_failed;
829 EvacuationFailedInfo* _evacuation_failed_info_array;
831 // Failed evacuations cause some logical from-space objects to have
832 // forwarding pointers to themselves. Reset them.
833 void remove_self_forwarding_pointers();
835 // Together, these store an object with a preserved mark, and its mark value.
836 Stack<oop, mtGC> _objs_with_preserved_marks;
837 Stack<markOop, mtGC> _preserved_marks_of_objs;
839 // Preserve the mark of "obj", if necessary, in preparation for its mark
840 // word being overwritten with a self-forwarding-pointer.
841 void preserve_mark_if_necessary(oop obj, markOop m);
843 // The stack of evac-failure objects left to be scanned.
844 GrowableArray<oop>* _evac_failure_scan_stack;
845 // The closure to apply to evac-failure objects.
847 OopsInHeapRegionClosure* _evac_failure_closure;
848 // Set the field above.
849 void
850 set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
851 _evac_failure_closure = evac_failure_closure;
852 }
854 // Push "obj" on the scan stack.
855 void push_on_evac_failure_scan_stack(oop obj);
856 // Process scan stack entries until the stack is empty.
857 void drain_evac_failure_scan_stack();
858 // True iff an invocation of "drain_scan_stack" is in progress; to
859 // prevent unnecessary recursion.
860 bool _drain_in_progress;
862 // Do any necessary initialization for evacuation-failure handling.
863 // "cl" is the closure that will be used to process evac-failure
864 // objects.
865 void init_for_evac_failure(OopsInHeapRegionClosure* cl);
866 // Do any necessary cleanup for evacuation-failure handling data
867 // structures.
868 void finalize_for_evac_failure();
870 // An attempt to evacuate "obj" has failed; take necessary steps.
871 oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj);
872 void handle_evacuation_failure_common(oop obj, markOop m);
874 #ifndef PRODUCT
875 // Support for forcing evacuation failures. Analogous to
876 // PromotionFailureALot for the other collectors.
878 // Records whether G1EvacuationFailureALot should be in effect
879 // for the current GC
880 bool _evacuation_failure_alot_for_current_gc;
882 // Used to record the GC number for interval checking when
883 // determining whether G1EvaucationFailureALot is in effect
884 // for the current GC.
885 size_t _evacuation_failure_alot_gc_number;
887 // Count of the number of evacuations between failures.
888 volatile size_t _evacuation_failure_alot_count;
890 // Set whether G1EvacuationFailureALot should be in effect
891 // for the current GC (based upon the type of GC and which
892 // command line flags are set);
893 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
894 bool during_initial_mark,
895 bool during_marking);
897 inline void set_evacuation_failure_alot_for_current_gc();
899 // Return true if it's time to cause an evacuation failure.
900 inline bool evacuation_should_fail();
902 // Reset the G1EvacuationFailureALot counters. Should be called at
903 // the end of an evacuation pause in which an evacuation failure occurred.
904 inline void reset_evacuation_should_fail();
905 #endif // !PRODUCT
907 // ("Weak") Reference processing support.
908 //
909 // G1 has 2 instances of the reference processor class. One
910 // (_ref_processor_cm) handles reference object discovery
911 // and subsequent processing during concurrent marking cycles.
912 //
913 // The other (_ref_processor_stw) handles reference object
914 // discovery and processing during full GCs and incremental
915 // evacuation pauses.
916 //
917 // During an incremental pause, reference discovery will be
918 // temporarily disabled for _ref_processor_cm and will be
919 // enabled for _ref_processor_stw. At the end of the evacuation
920 // pause references discovered by _ref_processor_stw will be
921 // processed and discovery will be disabled. The previous
922 // setting for reference object discovery for _ref_processor_cm
923 // will be re-instated.
924 //
925 // At the start of marking:
926 // * Discovery by the CM ref processor is verified to be inactive
927 // and it's discovered lists are empty.
928 // * Discovery by the CM ref processor is then enabled.
929 //
930 // At the end of marking:
931 // * Any references on the CM ref processor's discovered
932 // lists are processed (possibly MT).
933 //
934 // At the start of full GC we:
935 // * Disable discovery by the CM ref processor and
936 // empty CM ref processor's discovered lists
937 // (without processing any entries).
938 // * Verify that the STW ref processor is inactive and it's
939 // discovered lists are empty.
940 // * Temporarily set STW ref processor discovery as single threaded.
941 // * Temporarily clear the STW ref processor's _is_alive_non_header
942 // field.
943 // * Finally enable discovery by the STW ref processor.
944 //
945 // The STW ref processor is used to record any discovered
946 // references during the full GC.
947 //
948 // At the end of a full GC we:
949 // * Enqueue any reference objects discovered by the STW ref processor
950 // that have non-live referents. This has the side-effect of
951 // making the STW ref processor inactive by disabling discovery.
952 // * Verify that the CM ref processor is still inactive
953 // and no references have been placed on it's discovered
954 // lists (also checked as a precondition during initial marking).
956 // The (stw) reference processor...
957 ReferenceProcessor* _ref_processor_stw;
959 STWGCTimer* _gc_timer_stw;
960 ConcurrentGCTimer* _gc_timer_cm;
962 G1OldTracer* _gc_tracer_cm;
963 G1NewTracer* _gc_tracer_stw;
965 // During reference object discovery, the _is_alive_non_header
966 // closure (if non-null) is applied to the referent object to
967 // determine whether the referent is live. If so then the
968 // reference object does not need to be 'discovered' and can
969 // be treated as a regular oop. This has the benefit of reducing
970 // the number of 'discovered' reference objects that need to
971 // be processed.
972 //
973 // Instance of the is_alive closure for embedding into the
974 // STW reference processor as the _is_alive_non_header field.
975 // Supplying a value for the _is_alive_non_header field is
976 // optional but doing so prevents unnecessary additions to
977 // the discovered lists during reference discovery.
978 G1STWIsAliveClosure _is_alive_closure_stw;
980 // The (concurrent marking) reference processor...
981 ReferenceProcessor* _ref_processor_cm;
983 // Instance of the concurrent mark is_alive closure for embedding
984 // into the Concurrent Marking reference processor as the
985 // _is_alive_non_header field. Supplying a value for the
986 // _is_alive_non_header field is optional but doing so prevents
987 // unnecessary additions to the discovered lists during reference
988 // discovery.
989 G1CMIsAliveClosure _is_alive_closure_cm;
991 // Cache used by G1CollectedHeap::start_cset_region_for_worker().
992 HeapRegion** _worker_cset_start_region;
994 // Time stamp to validate the regions recorded in the cache
995 // used by G1CollectedHeap::start_cset_region_for_worker().
996 // The heap region entry for a given worker is valid iff
997 // the associated time stamp value matches the current value
998 // of G1CollectedHeap::_gc_time_stamp.
999 unsigned int* _worker_cset_start_region_time_stamp;
1001 enum G1H_process_roots_tasks {
1002 G1H_PS_filter_satb_buffers,
1003 G1H_PS_refProcessor_oops_do,
1004 // Leave this one last.
1005 G1H_PS_NumElements
1006 };
1008 SubTasksDone* _process_strong_tasks;
1010 volatile bool _free_regions_coming;
1012 public:
1014 SubTasksDone* process_strong_tasks() { return _process_strong_tasks; }
1016 void set_refine_cte_cl_concurrency(bool concurrent);
1018 RefToScanQueue *task_queue(int i) const;
1020 // A set of cards where updates happened during the GC
1021 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
1023 // A DirtyCardQueueSet that is used to hold cards that contain
1024 // references into the current collection set. This is used to
1025 // update the remembered sets of the regions in the collection
1026 // set in the event of an evacuation failure.
1027 DirtyCardQueueSet& into_cset_dirty_card_queue_set()
1028 { return _into_cset_dirty_card_queue_set; }
1030 // Create a G1CollectedHeap with the specified policy.
1031 // Must call the initialize method afterwards.
1032 // May not return if something goes wrong.
1033 G1CollectedHeap(G1CollectorPolicy* policy);
1035 // Initialize the G1CollectedHeap to have the initial and
1036 // maximum sizes and remembered and barrier sets
1037 // specified by the policy object.
1038 jint initialize();
1040 virtual void stop();
1042 // Return the (conservative) maximum heap alignment for any G1 heap
1043 static size_t conservative_max_heap_alignment();
1045 // Initialize weak reference processing.
1046 virtual void ref_processing_init();
1048 void set_par_threads(uint t) {
1049 SharedHeap::set_par_threads(t);
1050 // Done in SharedHeap but oddly there are
1051 // two _process_strong_tasks's in a G1CollectedHeap
1052 // so do it here too.
1053 _process_strong_tasks->set_n_threads(t);
1054 }
1056 // Set _n_par_threads according to a policy TBD.
1057 void set_par_threads();
1059 void set_n_termination(int t) {
1060 _process_strong_tasks->set_n_threads(t);
1061 }
1063 virtual CollectedHeap::Name kind() const {
1064 return CollectedHeap::G1CollectedHeap;
1065 }
1067 // The current policy object for the collector.
1068 G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1070 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); }
1072 // Adaptive size policy. No such thing for g1.
1073 virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1075 // The rem set and barrier set.
1076 G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1078 unsigned get_gc_time_stamp() {
1079 return _gc_time_stamp;
1080 }
1082 inline void reset_gc_time_stamp();
1084 void check_gc_time_stamps() PRODUCT_RETURN;
1086 inline void increment_gc_time_stamp();
1088 // Reset the given region's GC timestamp. If it's starts humongous,
1089 // also reset the GC timestamp of its corresponding
1090 // continues humongous regions too.
1091 void reset_gc_time_stamps(HeapRegion* hr);
1093 void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1094 DirtyCardQueue* into_cset_dcq,
1095 bool concurrent, uint worker_i);
1097 // The shared block offset table array.
1098 G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1100 // Reference Processing accessors
1102 // The STW reference processor....
1103 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1105 // The Concurrent Marking reference processor...
1106 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1108 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1109 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1111 virtual size_t capacity() const;
1112 virtual size_t used() const;
1113 // This should be called when we're not holding the heap lock. The
1114 // result might be a bit inaccurate.
1115 size_t used_unlocked() const;
1116 size_t recalculate_used() const;
1118 // These virtual functions do the actual allocation.
1119 // Some heaps may offer a contiguous region for shared non-blocking
1120 // allocation, via inlined code (by exporting the address of the top and
1121 // end fields defining the extent of the contiguous allocation region.)
1122 // But G1CollectedHeap doesn't yet support this.
1124 virtual bool is_maximal_no_gc() const {
1125 return _hrm.available() == 0;
1126 }
1128 // The current number of regions in the heap.
1129 uint num_regions() const { return _hrm.length(); }
1131 // The max number of regions in the heap.
1132 uint max_regions() const { return _hrm.max_length(); }
1134 // The number of regions that are completely free.
1135 uint num_free_regions() const { return _hrm.num_free_regions(); }
1137 // The number of regions that are not completely free.
1138 uint num_used_regions() const { return num_regions() - num_free_regions(); }
1140 void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1141 void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1142 void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1143 void verify_dirty_young_regions() PRODUCT_RETURN;
1145 #ifndef PRODUCT
1146 // Make sure that the given bitmap has no marked objects in the
1147 // range [from,limit). If it does, print an error message and return
1148 // false. Otherwise, just return true. bitmap_name should be "prev"
1149 // or "next".
1150 bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
1151 HeapWord* from, HeapWord* limit);
1153 // Verify that the prev / next bitmap range [tams,end) for the given
1154 // region has no marks. Return true if all is well, false if errors
1155 // are detected.
1156 bool verify_bitmaps(const char* caller, HeapRegion* hr);
1157 #endif // PRODUCT
1159 // If G1VerifyBitmaps is set, verify that the marking bitmaps for
1160 // the given region do not have any spurious marks. If errors are
1161 // detected, print appropriate error messages and crash.
1162 void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN;
1164 // If G1VerifyBitmaps is set, verify that the marking bitmaps do not
1165 // have any spurious marks. If errors are detected, print
1166 // appropriate error messages and crash.
1167 void check_bitmaps(const char* caller) PRODUCT_RETURN;
1169 // Do sanity check on the contents of the in-cset fast test table.
1170 bool check_cset_fast_test() PRODUCT_RETURN_( return true; );
1172 // verify_region_sets() performs verification over the region
1173 // lists. It will be compiled in the product code to be used when
1174 // necessary (i.e., during heap verification).
1175 void verify_region_sets();
1177 // verify_region_sets_optional() is planted in the code for
1178 // list verification in non-product builds (and it can be enabled in
1179 // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1).
1180 #if HEAP_REGION_SET_FORCE_VERIFY
1181 void verify_region_sets_optional() {
1182 verify_region_sets();
1183 }
1184 #else // HEAP_REGION_SET_FORCE_VERIFY
1185 void verify_region_sets_optional() { }
1186 #endif // HEAP_REGION_SET_FORCE_VERIFY
1188 #ifdef ASSERT
1189 bool is_on_master_free_list(HeapRegion* hr) {
1190 return _hrm.is_free(hr);
1191 }
1192 #endif // ASSERT
1194 // Wrapper for the region list operations that can be called from
1195 // methods outside this class.
1197 void secondary_free_list_add(FreeRegionList* list) {
1198 _secondary_free_list.add_ordered(list);
1199 }
1201 void append_secondary_free_list() {
1202 _hrm.insert_list_into_free_list(&_secondary_free_list);
1203 }
1205 void append_secondary_free_list_if_not_empty_with_lock() {
1206 // If the secondary free list looks empty there's no reason to
1207 // take the lock and then try to append it.
1208 if (!_secondary_free_list.is_empty()) {
1209 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1210 append_secondary_free_list();
1211 }
1212 }
1214 inline void old_set_remove(HeapRegion* hr);
1216 size_t non_young_capacity_bytes() {
1217 return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1218 }
1220 void set_free_regions_coming();
1221 void reset_free_regions_coming();
1222 bool free_regions_coming() { return _free_regions_coming; }
1223 void wait_while_free_regions_coming();
1225 // Determine whether the given region is one that we are using as an
1226 // old GC alloc region.
1227 bool is_old_gc_alloc_region(HeapRegion* hr) {
1228 return _allocator->is_retained_old_region(hr);
1229 }
1231 // Perform a collection of the heap; intended for use in implementing
1232 // "System.gc". This probably implies as full a collection as the
1233 // "CollectedHeap" supports.
1234 virtual void collect(GCCause::Cause cause);
1236 // The same as above but assume that the caller holds the Heap_lock.
1237 void collect_locked(GCCause::Cause cause);
1239 virtual bool copy_allocation_context_stats(const jint* contexts,
1240 jlong* totals,
1241 jbyte* accuracy,
1242 jint len);
1244 // True iff an evacuation has failed in the most-recent collection.
1245 bool evacuation_failed() { return _evacuation_failed; }
1247 void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed);
1248 void prepend_to_freelist(FreeRegionList* list);
1249 void decrement_summary_bytes(size_t bytes);
1251 // Returns "TRUE" iff "p" points into the committed areas of the heap.
1252 virtual bool is_in(const void* p) const;
1253 #ifdef ASSERT
1254 // Returns whether p is in one of the available areas of the heap. Slow but
1255 // extensive version.
1256 bool is_in_exact(const void* p) const;
1257 #endif
1259 // Return "TRUE" iff the given object address is within the collection
1260 // set. Slow implementation.
1261 inline bool obj_in_cs(oop obj);
1263 inline bool is_in_cset(oop obj);
1265 inline bool is_in_cset_or_humongous(const oop obj);
1267 private:
1268 // This array is used for a quick test on whether a reference points into
1269 // the collection set or not. Each of the array's elements denotes whether the
1270 // corresponding region is in the collection set or not.
1271 G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test;
1273 public:
1275 inline InCSetState in_cset_state(const oop obj);
1277 // Return "TRUE" iff the given object address is in the reserved
1278 // region of g1.
1279 bool is_in_g1_reserved(const void* p) const {
1280 return _hrm.reserved().contains(p);
1281 }
1283 // Returns a MemRegion that corresponds to the space that has been
1284 // reserved for the heap
1285 MemRegion g1_reserved() const {
1286 return _hrm.reserved();
1287 }
1289 virtual bool is_in_closed_subset(const void* p) const;
1291 G1SATBCardTableLoggingModRefBS* g1_barrier_set() {
1292 return (G1SATBCardTableLoggingModRefBS*) barrier_set();
1293 }
1295 // This resets the card table to all zeros. It is used after
1296 // a collection pause which used the card table to claim cards.
1297 void cleanUpCardTable();
1299 // Iteration functions.
1301 // Iterate over all the ref-containing fields of all objects, calling
1302 // "cl.do_oop" on each.
1303 virtual void oop_iterate(ExtendedOopClosure* cl);
1305 // Iterate over all objects, calling "cl.do_object" on each.
1306 virtual void object_iterate(ObjectClosure* cl);
1308 virtual void safe_object_iterate(ObjectClosure* cl) {
1309 object_iterate(cl);
1310 }
1312 // Iterate over all spaces in use in the heap, in ascending address order.
1313 virtual void space_iterate(SpaceClosure* cl);
1315 // Iterate over heap regions, in address order, terminating the
1316 // iteration early if the "doHeapRegion" method returns "true".
1317 void heap_region_iterate(HeapRegionClosure* blk) const;
1319 // Return the region with the given index. It assumes the index is valid.
1320 inline HeapRegion* region_at(uint index) const;
1322 // Calculate the region index of the given address. Given address must be
1323 // within the heap.
1324 inline uint addr_to_region(HeapWord* addr) const;
1326 inline HeapWord* bottom_addr_for_region(uint index) const;
1328 // Divide the heap region sequence into "chunks" of some size (the number
1329 // of regions divided by the number of parallel threads times some
1330 // overpartition factor, currently 4). Assumes that this will be called
1331 // in parallel by ParallelGCThreads worker threads with discinct worker
1332 // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel
1333 // calls will use the same "claim_value", and that that claim value is
1334 // different from the claim_value of any heap region before the start of
1335 // the iteration. Applies "blk->doHeapRegion" to each of the regions, by
1336 // attempting to claim the first region in each chunk, and, if
1337 // successful, applying the closure to each region in the chunk (and
1338 // setting the claim value of the second and subsequent regions of the
1339 // chunk.) For now requires that "doHeapRegion" always returns "false",
1340 // i.e., that a closure never attempt to abort a traversal.
1341 void heap_region_par_iterate_chunked(HeapRegionClosure* cl,
1342 uint worker_id,
1343 uint num_workers,
1344 jint claim_value) const;
1346 // It resets all the region claim values to the default.
1347 void reset_heap_region_claim_values();
1349 // Resets the claim values of regions in the current
1350 // collection set to the default.
1351 void reset_cset_heap_region_claim_values();
1353 #ifdef ASSERT
1354 bool check_heap_region_claim_values(jint claim_value);
1356 // Same as the routine above but only checks regions in the
1357 // current collection set.
1358 bool check_cset_heap_region_claim_values(jint claim_value);
1359 #endif // ASSERT
1361 // Clear the cached cset start regions and (more importantly)
1362 // the time stamps. Called when we reset the GC time stamp.
1363 void clear_cset_start_regions();
1365 // Given the id of a worker, obtain or calculate a suitable
1366 // starting region for iterating over the current collection set.
1367 HeapRegion* start_cset_region_for_worker(uint worker_i);
1369 // Iterate over the regions (if any) in the current collection set.
1370 void collection_set_iterate(HeapRegionClosure* blk);
1372 // As above but starting from region r
1373 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1375 HeapRegion* next_compaction_region(const HeapRegion* from) const;
1377 // A CollectedHeap will contain some number of spaces. This finds the
1378 // space containing a given address, or else returns NULL.
1379 virtual Space* space_containing(const void* addr) const;
1381 // Returns the HeapRegion that contains addr. addr must not be NULL.
1382 template <class T>
1383 inline HeapRegion* heap_region_containing_raw(const T addr) const;
1385 // Returns the HeapRegion that contains addr. addr must not be NULL.
1386 // If addr is within a humongous continues region, it returns its humongous start region.
1387 template <class T>
1388 inline HeapRegion* heap_region_containing(const T addr) const;
1390 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1391 // each address in the (reserved) heap is a member of exactly
1392 // one block. The defining characteristic of a block is that it is
1393 // possible to find its size, and thus to progress forward to the next
1394 // block. (Blocks may be of different sizes.) Thus, blocks may
1395 // represent Java objects, or they might be free blocks in a
1396 // free-list-based heap (or subheap), as long as the two kinds are
1397 // distinguishable and the size of each is determinable.
1399 // Returns the address of the start of the "block" that contains the
1400 // address "addr". We say "blocks" instead of "object" since some heaps
1401 // may not pack objects densely; a chunk may either be an object or a
1402 // non-object.
1403 virtual HeapWord* block_start(const void* addr) const;
1405 // Requires "addr" to be the start of a chunk, and returns its size.
1406 // "addr + size" is required to be the start of a new chunk, or the end
1407 // of the active area of the heap.
1408 virtual size_t block_size(const HeapWord* addr) const;
1410 // Requires "addr" to be the start of a block, and returns "TRUE" iff
1411 // the block is an object.
1412 virtual bool block_is_obj(const HeapWord* addr) const;
1414 // Does this heap support heap inspection? (+PrintClassHistogram)
1415 virtual bool supports_heap_inspection() const { return true; }
1417 // Section on thread-local allocation buffers (TLABs)
1418 // See CollectedHeap for semantics.
1420 bool supports_tlab_allocation() const;
1421 size_t tlab_capacity(Thread* ignored) const;
1422 size_t tlab_used(Thread* ignored) const;
1423 size_t max_tlab_size() const;
1424 size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1426 // Can a compiler initialize a new object without store barriers?
1427 // This permission only extends from the creation of a new object
1428 // via a TLAB up to the first subsequent safepoint. If such permission
1429 // is granted for this heap type, the compiler promises to call
1430 // defer_store_barrier() below on any slow path allocation of
1431 // a new object for which such initializing store barriers will
1432 // have been elided. G1, like CMS, allows this, but should be
1433 // ready to provide a compensating write barrier as necessary
1434 // if that storage came out of a non-young region. The efficiency
1435 // of this implementation depends crucially on being able to
1436 // answer very efficiently in constant time whether a piece of
1437 // storage in the heap comes from a young region or not.
1438 // See ReduceInitialCardMarks.
1439 virtual bool can_elide_tlab_store_barriers() const {
1440 return true;
1441 }
1443 virtual bool card_mark_must_follow_store() const {
1444 return true;
1445 }
1447 inline bool is_in_young(const oop obj);
1449 #ifdef ASSERT
1450 virtual bool is_in_partial_collection(const void* p);
1451 #endif
1453 virtual bool is_scavengable(const void* addr);
1455 // We don't need barriers for initializing stores to objects
1456 // in the young gen: for the SATB pre-barrier, there is no
1457 // pre-value that needs to be remembered; for the remembered-set
1458 // update logging post-barrier, we don't maintain remembered set
1459 // information for young gen objects.
1460 virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1462 // Returns "true" iff the given word_size is "very large".
1463 static bool isHumongous(size_t word_size) {
1464 // Note this has to be strictly greater-than as the TLABs
1465 // are capped at the humongous thresold and we want to
1466 // ensure that we don't try to allocate a TLAB as
1467 // humongous and that we don't allocate a humongous
1468 // object in a TLAB.
1469 return word_size > _humongous_object_threshold_in_words;
1470 }
1472 // Update mod union table with the set of dirty cards.
1473 void updateModUnion();
1475 // Set the mod union bits corresponding to the given memRegion. Note
1476 // that this is always a safe operation, since it doesn't clear any
1477 // bits.
1478 void markModUnionRange(MemRegion mr);
1480 // Records the fact that a marking phase is no longer in progress.
1481 void set_marking_complete() {
1482 _mark_in_progress = false;
1483 }
1484 void set_marking_started() {
1485 _mark_in_progress = true;
1486 }
1487 bool mark_in_progress() {
1488 return _mark_in_progress;
1489 }
1491 // Print the maximum heap capacity.
1492 virtual size_t max_capacity() const;
1494 virtual jlong millis_since_last_gc();
1497 // Convenience function to be used in situations where the heap type can be
1498 // asserted to be this type.
1499 static G1CollectedHeap* heap();
1501 void set_region_short_lived_locked(HeapRegion* hr);
1502 // add appropriate methods for any other surv rate groups
1504 YoungList* young_list() const { return _young_list; }
1506 // debugging
1507 bool check_young_list_well_formed() {
1508 return _young_list->check_list_well_formed();
1509 }
1511 bool check_young_list_empty(bool check_heap,
1512 bool check_sample = true);
1514 // *** Stuff related to concurrent marking. It's not clear to me that so
1515 // many of these need to be public.
1517 // The functions below are helper functions that a subclass of
1518 // "CollectedHeap" can use in the implementation of its virtual
1519 // functions.
1520 // This performs a concurrent marking of the live objects in a
1521 // bitmap off to the side.
1522 void doConcurrentMark();
1524 bool isMarkedPrev(oop obj) const;
1525 bool isMarkedNext(oop obj) const;
1527 // Determine if an object is dead, given the object and also
1528 // the region to which the object belongs. An object is dead
1529 // iff a) it was not allocated since the last mark and b) it
1530 // is not marked.
1531 bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1532 return
1533 !hr->obj_allocated_since_prev_marking(obj) &&
1534 !isMarkedPrev(obj);
1535 }
1537 // This function returns true when an object has been
1538 // around since the previous marking and hasn't yet
1539 // been marked during this marking.
1540 bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1541 return
1542 !hr->obj_allocated_since_next_marking(obj) &&
1543 !isMarkedNext(obj);
1544 }
1546 // Determine if an object is dead, given only the object itself.
1547 // This will find the region to which the object belongs and
1548 // then call the region version of the same function.
1550 // Added if it is NULL it isn't dead.
1552 inline bool is_obj_dead(const oop obj) const;
1554 inline bool is_obj_ill(const oop obj) const;
1556 bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1557 HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1558 bool is_marked(oop obj, VerifyOption vo);
1559 const char* top_at_mark_start_str(VerifyOption vo);
1561 ConcurrentMark* concurrent_mark() const { return _cm; }
1563 // Refinement
1565 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1567 // The dirty cards region list is used to record a subset of regions
1568 // whose cards need clearing. The list if populated during the
1569 // remembered set scanning and drained during the card table
1570 // cleanup. Although the methods are reentrant, population/draining
1571 // phases must not overlap. For synchronization purposes the last
1572 // element on the list points to itself.
1573 HeapRegion* _dirty_cards_region_list;
1574 void push_dirty_cards_region(HeapRegion* hr);
1575 HeapRegion* pop_dirty_cards_region();
1577 // Optimized nmethod scanning support routines
1579 // Register the given nmethod with the G1 heap
1580 virtual void register_nmethod(nmethod* nm);
1582 // Unregister the given nmethod from the G1 heap
1583 virtual void unregister_nmethod(nmethod* nm);
1585 // Free up superfluous code root memory.
1586 void purge_code_root_memory();
1588 // Rebuild the stong code root lists for each region
1589 // after a full GC
1590 void rebuild_strong_code_roots();
1592 // Delete entries for dead interned string and clean up unreferenced symbols
1593 // in symbol table, possibly in parallel.
1594 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1596 // Parallel phase of unloading/cleaning after G1 concurrent mark.
1597 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred);
1599 // Redirty logged cards in the refinement queue.
1600 void redirty_logged_cards();
1601 // Verification
1603 // The following is just to alert the verification code
1604 // that a full collection has occurred and that the
1605 // remembered sets are no longer up to date.
1606 bool _full_collection;
1607 void set_full_collection() { _full_collection = true;}
1608 void clear_full_collection() {_full_collection = false;}
1609 bool full_collection() {return _full_collection;}
1611 // Perform any cleanup actions necessary before allowing a verification.
1612 virtual void prepare_for_verify();
1614 // Perform verification.
1616 // vo == UsePrevMarking -> use "prev" marking information,
1617 // vo == UseNextMarking -> use "next" marking information
1618 // vo == UseMarkWord -> use the mark word in the object header
1619 //
1620 // NOTE: Only the "prev" marking information is guaranteed to be
1621 // consistent most of the time, so most calls to this should use
1622 // vo == UsePrevMarking.
1623 // Currently, there is only one case where this is called with
1624 // vo == UseNextMarking, which is to verify the "next" marking
1625 // information at the end of remark.
1626 // Currently there is only one place where this is called with
1627 // vo == UseMarkWord, which is to verify the marking during a
1628 // full GC.
1629 void verify(bool silent, VerifyOption vo);
1631 // Override; it uses the "prev" marking information
1632 virtual void verify(bool silent);
1634 // The methods below are here for convenience and dispatch the
1635 // appropriate method depending on value of the given VerifyOption
1636 // parameter. The values for that parameter, and their meanings,
1637 // are the same as those above.
1639 bool is_obj_dead_cond(const oop obj,
1640 const HeapRegion* hr,
1641 const VerifyOption vo) const;
1643 bool is_obj_dead_cond(const oop obj,
1644 const VerifyOption vo) const;
1646 // Printing
1648 virtual void print_on(outputStream* st) const;
1649 virtual void print_extended_on(outputStream* st) const;
1650 virtual void print_on_error(outputStream* st) const;
1652 virtual void print_gc_threads_on(outputStream* st) const;
1653 virtual void gc_threads_do(ThreadClosure* tc) const;
1655 // Override
1656 void print_tracing_info() const;
1658 // The following two methods are helpful for debugging RSet issues.
1659 void print_cset_rsets() PRODUCT_RETURN;
1660 void print_all_rsets() PRODUCT_RETURN;
1662 public:
1663 size_t pending_card_num();
1664 size_t cards_scanned();
1666 protected:
1667 size_t _max_heap_capacity;
1668 };
1670 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP