Mon, 21 Jul 2014 10:00:31 +0200
8048112: G1 Full GC needs to support the case when the very first region is not available
Summary: Refactor preparation for compaction during Full GC so that it lazily initializes the first compaction point. This also avoids problems later when the first region may not be committed. Also reviewed by K. Barrett.
Reviewed-by: brutisso
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.
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 */
25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
28 #include "gc_implementation/g1/concurrentMark.hpp"
29 #include "gc_implementation/g1/evacuationInfo.hpp"
30 #include "gc_implementation/g1/g1AllocRegion.hpp"
31 #include "gc_implementation/g1/g1BiasedArray.hpp"
32 #include "gc_implementation/g1/g1HRPrinter.hpp"
33 #include "gc_implementation/g1/g1MonitoringSupport.hpp"
34 #include "gc_implementation/g1/g1SATBCardTableModRefBS.hpp"
35 #include "gc_implementation/g1/g1YCTypes.hpp"
36 #include "gc_implementation/g1/heapRegionSeq.hpp"
37 #include "gc_implementation/g1/heapRegionSet.hpp"
38 #include "gc_implementation/shared/hSpaceCounters.hpp"
39 #include "gc_implementation/shared/parGCAllocBuffer.hpp"
40 #include "memory/barrierSet.hpp"
41 #include "memory/memRegion.hpp"
42 #include "memory/sharedHeap.hpp"
43 #include "utilities/stack.hpp"
45 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
46 // It uses the "Garbage First" heap organization and algorithm, which
47 // may combine concurrent marking with parallel, incremental compaction of
48 // heap subsets that will yield large amounts of garbage.
50 // Forward declarations
51 class HeapRegion;
52 class HRRSCleanupTask;
53 class GenerationSpec;
54 class OopsInHeapRegionClosure;
55 class G1KlassScanClosure;
56 class G1ScanHeapEvacClosure;
57 class ObjectClosure;
58 class SpaceClosure;
59 class CompactibleSpaceClosure;
60 class Space;
61 class G1CollectorPolicy;
62 class GenRemSet;
63 class G1RemSet;
64 class HeapRegionRemSetIterator;
65 class ConcurrentMark;
66 class ConcurrentMarkThread;
67 class ConcurrentG1Refine;
68 class ConcurrentGCTimer;
69 class GenerationCounters;
70 class STWGCTimer;
71 class G1NewTracer;
72 class G1OldTracer;
73 class EvacuationFailedInfo;
74 class nmethod;
75 class Ticks;
77 typedef OverflowTaskQueue<StarTask, mtGC> RefToScanQueue;
78 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
80 typedef int RegionIdx_t; // needs to hold [ 0..max_regions() )
81 typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion )
83 enum GCAllocPurpose {
84 GCAllocForTenured,
85 GCAllocForSurvived,
86 GCAllocPurposeCount
87 };
89 class YoungList : public CHeapObj<mtGC> {
90 private:
91 G1CollectedHeap* _g1h;
93 HeapRegion* _head;
95 HeapRegion* _survivor_head;
96 HeapRegion* _survivor_tail;
98 HeapRegion* _curr;
100 uint _length;
101 uint _survivor_length;
103 size_t _last_sampled_rs_lengths;
104 size_t _sampled_rs_lengths;
106 void empty_list(HeapRegion* list);
108 public:
109 YoungList(G1CollectedHeap* g1h);
111 void push_region(HeapRegion* hr);
112 void add_survivor_region(HeapRegion* hr);
114 void empty_list();
115 bool is_empty() { return _length == 0; }
116 uint length() { return _length; }
117 uint survivor_length() { return _survivor_length; }
119 // Currently we do not keep track of the used byte sum for the
120 // young list and the survivors and it'd be quite a lot of work to
121 // do so. When we'll eventually replace the young list with
122 // instances of HeapRegionLinkedList we'll get that for free. So,
123 // we'll report the more accurate information then.
124 size_t eden_used_bytes() {
125 assert(length() >= survivor_length(), "invariant");
126 return (size_t) (length() - survivor_length()) * HeapRegion::GrainBytes;
127 }
128 size_t survivor_used_bytes() {
129 return (size_t) survivor_length() * HeapRegion::GrainBytes;
130 }
132 void rs_length_sampling_init();
133 bool rs_length_sampling_more();
134 void rs_length_sampling_next();
136 void reset_sampled_info() {
137 _last_sampled_rs_lengths = 0;
138 }
139 size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
141 // for development purposes
142 void reset_auxilary_lists();
143 void clear() { _head = NULL; _length = 0; }
145 void clear_survivors() {
146 _survivor_head = NULL;
147 _survivor_tail = NULL;
148 _survivor_length = 0;
149 }
151 HeapRegion* first_region() { return _head; }
152 HeapRegion* first_survivor_region() { return _survivor_head; }
153 HeapRegion* last_survivor_region() { return _survivor_tail; }
155 // debugging
156 bool check_list_well_formed();
157 bool check_list_empty(bool check_sample = true);
158 void print();
159 };
161 class MutatorAllocRegion : public G1AllocRegion {
162 protected:
163 virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
164 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
165 public:
166 MutatorAllocRegion()
167 : G1AllocRegion("Mutator Alloc Region", false /* bot_updates */) { }
168 };
170 class SurvivorGCAllocRegion : public G1AllocRegion {
171 protected:
172 virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
173 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
174 public:
175 SurvivorGCAllocRegion()
176 : G1AllocRegion("Survivor GC Alloc Region", false /* bot_updates */) { }
177 };
179 class OldGCAllocRegion : public G1AllocRegion {
180 protected:
181 virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
182 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
183 public:
184 OldGCAllocRegion()
185 : G1AllocRegion("Old GC Alloc Region", true /* bot_updates */) { }
186 };
188 // The G1 STW is alive closure.
189 // An instance is embedded into the G1CH and used as the
190 // (optional) _is_alive_non_header closure in the STW
191 // reference processor. It is also extensively used during
192 // reference processing during STW evacuation pauses.
193 class G1STWIsAliveClosure: public BoolObjectClosure {
194 G1CollectedHeap* _g1;
195 public:
196 G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
197 bool do_object_b(oop p);
198 };
200 // Instances of this class are used for quick tests on whether a reference points
201 // into the collection set. Each of the array's elements denotes whether the
202 // corresponding region is in the collection set.
203 class G1FastCSetBiasedMappedArray : public G1BiasedMappedArray<bool> {
204 protected:
205 bool default_value() const { return false; }
206 public:
207 void clear() { G1BiasedMappedArray<bool>::clear(); }
208 };
210 class RefineCardTableEntryClosure;
212 class G1CollectedHeap : public SharedHeap {
213 friend class VM_CollectForMetadataAllocation;
214 friend class VM_G1CollectForAllocation;
215 friend class VM_G1CollectFull;
216 friend class VM_G1IncCollectionPause;
217 friend class VMStructs;
218 friend class MutatorAllocRegion;
219 friend class SurvivorGCAllocRegion;
220 friend class OldGCAllocRegion;
222 // Closures used in implementation.
223 template <G1Barrier barrier, G1Mark do_mark_object>
224 friend class G1ParCopyClosure;
225 friend class G1IsAliveClosure;
226 friend class G1EvacuateFollowersClosure;
227 friend class G1ParScanThreadState;
228 friend class G1ParScanClosureSuper;
229 friend class G1ParEvacuateFollowersClosure;
230 friend class G1ParTask;
231 friend class G1FreeGarbageRegionClosure;
232 friend class RefineCardTableEntryClosure;
233 friend class G1PrepareCompactClosure;
234 friend class RegionSorter;
235 friend class RegionResetter;
236 friend class CountRCClosure;
237 friend class EvacPopObjClosure;
238 friend class G1ParCleanupCTTask;
240 // Other related classes.
241 friend class G1MarkSweep;
243 private:
244 // The one and only G1CollectedHeap, so static functions can find it.
245 static G1CollectedHeap* _g1h;
247 static size_t _humongous_object_threshold_in_words;
249 // Storage for the G1 heap.
250 VirtualSpace _g1_storage;
251 MemRegion _g1_reserved;
253 // The part of _g1_storage that is currently committed.
254 MemRegion _g1_committed;
256 // The master free list. It will satisfy all new region allocations.
257 FreeRegionList _free_list;
259 // The secondary free list which contains regions that have been
260 // freed up during the cleanup process. This will be appended to the
261 // master free list when appropriate.
262 FreeRegionList _secondary_free_list;
264 // It keeps track of the old regions.
265 HeapRegionSet _old_set;
267 // It keeps track of the humongous regions.
268 HeapRegionSet _humongous_set;
270 // The number of regions we could create by expansion.
271 uint _expansion_regions;
273 // The block offset table for the G1 heap.
274 G1BlockOffsetSharedArray* _bot_shared;
276 // Tears down the region sets / lists so that they are empty and the
277 // regions on the heap do not belong to a region set / list. The
278 // only exception is the humongous set which we leave unaltered. If
279 // free_list_only is true, it will only tear down the master free
280 // list. It is called before a Full GC (free_list_only == false) or
281 // before heap shrinking (free_list_only == true).
282 void tear_down_region_sets(bool free_list_only);
284 // Rebuilds the region sets / lists so that they are repopulated to
285 // reflect the contents of the heap. The only exception is the
286 // humongous set which was not torn down in the first place. If
287 // free_list_only is true, it will only rebuild the master free
288 // list. It is called after a Full GC (free_list_only == false) or
289 // after heap shrinking (free_list_only == true).
290 void rebuild_region_sets(bool free_list_only);
292 // The sequence of all heap regions in the heap.
293 HeapRegionSeq _hrs;
295 // Alloc region used to satisfy mutator allocation requests.
296 MutatorAllocRegion _mutator_alloc_region;
298 // Alloc region used to satisfy allocation requests by the GC for
299 // survivor objects.
300 SurvivorGCAllocRegion _survivor_gc_alloc_region;
302 // PLAB sizing policy for survivors.
303 PLABStats _survivor_plab_stats;
305 // Alloc region used to satisfy allocation requests by the GC for
306 // old objects.
307 OldGCAllocRegion _old_gc_alloc_region;
309 // PLAB sizing policy for tenured objects.
310 PLABStats _old_plab_stats;
312 PLABStats* stats_for_purpose(GCAllocPurpose purpose) {
313 PLABStats* stats = NULL;
315 switch (purpose) {
316 case GCAllocForSurvived:
317 stats = &_survivor_plab_stats;
318 break;
319 case GCAllocForTenured:
320 stats = &_old_plab_stats;
321 break;
322 default:
323 assert(false, "unrecognized GCAllocPurpose");
324 }
326 return stats;
327 }
329 // The last old region we allocated to during the last GC.
330 // Typically, it is not full so we should re-use it during the next GC.
331 HeapRegion* _retained_old_gc_alloc_region;
333 // It specifies whether we should attempt to expand the heap after a
334 // region allocation failure. If heap expansion fails we set this to
335 // false so that we don't re-attempt the heap expansion (it's likely
336 // that subsequent expansion attempts will also fail if one fails).
337 // Currently, it is only consulted during GC and it's reset at the
338 // start of each GC.
339 bool _expand_heap_after_alloc_failure;
341 // It resets the mutator alloc region before new allocations can take place.
342 void init_mutator_alloc_region();
344 // It releases the mutator alloc region.
345 void release_mutator_alloc_region();
347 // It initializes the GC alloc regions at the start of a GC.
348 void init_gc_alloc_regions(EvacuationInfo& evacuation_info);
350 // Setup the retained old gc alloc region as the currrent old gc alloc region.
351 void use_retained_old_gc_alloc_region(EvacuationInfo& evacuation_info);
353 // It releases the GC alloc regions at the end of a GC.
354 void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info);
356 // It does any cleanup that needs to be done on the GC alloc regions
357 // before a Full GC.
358 void abandon_gc_alloc_regions();
360 // Helper for monitoring and management support.
361 G1MonitoringSupport* _g1mm;
363 // Determines PLAB size for a particular allocation purpose.
364 size_t desired_plab_sz(GCAllocPurpose purpose);
366 // Outside of GC pauses, the number of bytes used in all regions other
367 // than the current allocation region.
368 size_t _summary_bytes_used;
370 // This array is used for a quick test on whether a reference points into
371 // the collection set or not. Each of the array's elements denotes whether the
372 // corresponding region is in the collection set or not.
373 G1FastCSetBiasedMappedArray _in_cset_fast_test;
375 volatile unsigned _gc_time_stamp;
377 size_t* _surviving_young_words;
379 G1HRPrinter _hr_printer;
381 void setup_surviving_young_words();
382 void update_surviving_young_words(size_t* surv_young_words);
383 void cleanup_surviving_young_words();
385 // It decides whether an explicit GC should start a concurrent cycle
386 // instead of doing a STW GC. Currently, a concurrent cycle is
387 // explicitly started if:
388 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
389 // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
390 // (c) cause == _g1_humongous_allocation
391 bool should_do_concurrent_full_gc(GCCause::Cause cause);
393 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
394 // concurrent cycles) we have started.
395 volatile unsigned int _old_marking_cycles_started;
397 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
398 // concurrent cycles) we have completed.
399 volatile unsigned int _old_marking_cycles_completed;
401 bool _concurrent_cycle_started;
403 // This is a non-product method that is helpful for testing. It is
404 // called at the end of a GC and artificially expands the heap by
405 // allocating a number of dead regions. This way we can induce very
406 // frequent marking cycles and stress the cleanup / concurrent
407 // cleanup code more (as all the regions that will be allocated by
408 // this method will be found dead by the marking cycle).
409 void allocate_dummy_regions() PRODUCT_RETURN;
411 // Clear RSets after a compaction. It also resets the GC time stamps.
412 void clear_rsets_post_compaction();
414 // If the HR printer is active, dump the state of the regions in the
415 // heap after a compaction.
416 void print_hrs_post_compaction();
418 double verify(bool guard, const char* msg);
419 void verify_before_gc();
420 void verify_after_gc();
422 void log_gc_header();
423 void log_gc_footer(double pause_time_sec);
425 // These are macros so that, if the assert fires, we get the correct
426 // line number, file, etc.
428 #define heap_locking_asserts_err_msg(_extra_message_) \
429 err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \
430 (_extra_message_), \
431 BOOL_TO_STR(Heap_lock->owned_by_self()), \
432 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \
433 BOOL_TO_STR(Thread::current()->is_VM_thread()))
435 #define assert_heap_locked() \
436 do { \
437 assert(Heap_lock->owned_by_self(), \
438 heap_locking_asserts_err_msg("should be holding the Heap_lock")); \
439 } while (0)
441 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \
442 do { \
443 assert(Heap_lock->owned_by_self() || \
444 (SafepointSynchronize::is_at_safepoint() && \
445 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
446 heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
447 "should be at a safepoint")); \
448 } while (0)
450 #define assert_heap_locked_and_not_at_safepoint() \
451 do { \
452 assert(Heap_lock->owned_by_self() && \
453 !SafepointSynchronize::is_at_safepoint(), \
454 heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
455 "should not be at a safepoint")); \
456 } while (0)
458 #define assert_heap_not_locked() \
459 do { \
460 assert(!Heap_lock->owned_by_self(), \
461 heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
462 } while (0)
464 #define assert_heap_not_locked_and_not_at_safepoint() \
465 do { \
466 assert(!Heap_lock->owned_by_self() && \
467 !SafepointSynchronize::is_at_safepoint(), \
468 heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
469 "should not be at a safepoint")); \
470 } while (0)
472 #define assert_at_safepoint(_should_be_vm_thread_) \
473 do { \
474 assert(SafepointSynchronize::is_at_safepoint() && \
475 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
476 heap_locking_asserts_err_msg("should be at a safepoint")); \
477 } while (0)
479 #define assert_not_at_safepoint() \
480 do { \
481 assert(!SafepointSynchronize::is_at_safepoint(), \
482 heap_locking_asserts_err_msg("should not be at a safepoint")); \
483 } while (0)
485 protected:
487 // The young region list.
488 YoungList* _young_list;
490 // The current policy object for the collector.
491 G1CollectorPolicy* _g1_policy;
493 // This is the second level of trying to allocate a new region. If
494 // new_region() didn't find a region on the free_list, this call will
495 // check whether there's anything available on the
496 // secondary_free_list and/or wait for more regions to appear on
497 // that list, if _free_regions_coming is set.
498 HeapRegion* new_region_try_secondary_free_list(bool is_old);
500 // Try to allocate a single non-humongous HeapRegion sufficient for
501 // an allocation of the given word_size. If do_expand is true,
502 // attempt to expand the heap if necessary to satisfy the allocation
503 // request. If the region is to be used as an old region or for a
504 // humongous object, set is_old to true. If not, to false.
505 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
507 // Attempt to satisfy a humongous allocation request of the given
508 // size by finding a contiguous set of free regions of num_regions
509 // length and remove them from the master free list. Return the
510 // index of the first region or G1_NULL_HRS_INDEX if the search
511 // was unsuccessful.
512 uint humongous_obj_allocate_find_first(uint num_regions,
513 size_t word_size);
515 // Initialize a contiguous set of free regions of length num_regions
516 // and starting at index first so that they appear as a single
517 // humongous region.
518 HeapWord* humongous_obj_allocate_initialize_regions(uint first,
519 uint num_regions,
520 size_t word_size);
522 // Attempt to allocate a humongous object of the given size. Return
523 // NULL if unsuccessful.
524 HeapWord* humongous_obj_allocate(size_t word_size);
526 // The following two methods, allocate_new_tlab() and
527 // mem_allocate(), are the two main entry points from the runtime
528 // into the G1's allocation routines. They have the following
529 // assumptions:
530 //
531 // * They should both be called outside safepoints.
532 //
533 // * They should both be called without holding the Heap_lock.
534 //
535 // * All allocation requests for new TLABs should go to
536 // allocate_new_tlab().
537 //
538 // * All non-TLAB allocation requests should go to mem_allocate().
539 //
540 // * If either call cannot satisfy the allocation request using the
541 // current allocating region, they will try to get a new one. If
542 // this fails, they will attempt to do an evacuation pause and
543 // retry the allocation.
544 //
545 // * If all allocation attempts fail, even after trying to schedule
546 // an evacuation pause, allocate_new_tlab() will return NULL,
547 // whereas mem_allocate() will attempt a heap expansion and/or
548 // schedule a Full GC.
549 //
550 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
551 // should never be called with word_size being humongous. All
552 // humongous allocation requests should go to mem_allocate() which
553 // will satisfy them with a special path.
555 virtual HeapWord* allocate_new_tlab(size_t word_size);
557 virtual HeapWord* mem_allocate(size_t word_size,
558 bool* gc_overhead_limit_was_exceeded);
560 // The following three methods take a gc_count_before_ret
561 // parameter which is used to return the GC count if the method
562 // returns NULL. Given that we are required to read the GC count
563 // while holding the Heap_lock, and these paths will take the
564 // Heap_lock at some point, it's easier to get them to read the GC
565 // count while holding the Heap_lock before they return NULL instead
566 // of the caller (namely: mem_allocate()) having to also take the
567 // Heap_lock just to read the GC count.
569 // First-level mutator allocation attempt: try to allocate out of
570 // the mutator alloc region without taking the Heap_lock. This
571 // should only be used for non-humongous allocations.
572 inline HeapWord* attempt_allocation(size_t word_size,
573 unsigned int* gc_count_before_ret,
574 int* gclocker_retry_count_ret);
576 // Second-level mutator allocation attempt: take the Heap_lock and
577 // retry the allocation attempt, potentially scheduling a GC
578 // pause. This should only be used for non-humongous allocations.
579 HeapWord* attempt_allocation_slow(size_t word_size,
580 unsigned int* gc_count_before_ret,
581 int* gclocker_retry_count_ret);
583 // Takes the Heap_lock and attempts a humongous allocation. It can
584 // potentially schedule a GC pause.
585 HeapWord* attempt_allocation_humongous(size_t word_size,
586 unsigned int* gc_count_before_ret,
587 int* gclocker_retry_count_ret);
589 // Allocation attempt that should be called during safepoints (e.g.,
590 // at the end of a successful GC). expect_null_mutator_alloc_region
591 // specifies whether the mutator alloc region is expected to be NULL
592 // or not.
593 HeapWord* attempt_allocation_at_safepoint(size_t word_size,
594 bool expect_null_mutator_alloc_region);
596 // It dirties the cards that cover the block so that so that the post
597 // write barrier never queues anything when updating objects on this
598 // block. It is assumed (and in fact we assert) that the block
599 // belongs to a young region.
600 inline void dirty_young_block(HeapWord* start, size_t word_size);
602 // Allocate blocks during garbage collection. Will ensure an
603 // allocation region, either by picking one or expanding the
604 // heap, and then allocate a block of the given size. The block
605 // may not be a humongous - it must fit into a single heap region.
606 HeapWord* par_allocate_during_gc(GCAllocPurpose purpose, size_t word_size);
608 HeapWord* allocate_during_gc_slow(GCAllocPurpose purpose,
609 HeapRegion* alloc_region,
610 bool par,
611 size_t word_size);
613 // Ensure that no further allocations can happen in "r", bearing in mind
614 // that parallel threads might be attempting allocations.
615 void par_allocate_remaining_space(HeapRegion* r);
617 // Allocation attempt during GC for a survivor object / PLAB.
618 inline HeapWord* survivor_attempt_allocation(size_t word_size);
620 // Allocation attempt during GC for an old object / PLAB.
621 inline HeapWord* old_attempt_allocation(size_t word_size);
623 // These methods are the "callbacks" from the G1AllocRegion class.
625 // For mutator alloc regions.
626 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
627 void retire_mutator_alloc_region(HeapRegion* alloc_region,
628 size_t allocated_bytes);
630 // For GC alloc regions.
631 HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
632 GCAllocPurpose ap);
633 void retire_gc_alloc_region(HeapRegion* alloc_region,
634 size_t allocated_bytes, GCAllocPurpose ap);
636 // - if explicit_gc is true, the GC is for a System.gc() or a heap
637 // inspection request and should collect the entire heap
638 // - if clear_all_soft_refs is true, all soft references should be
639 // cleared during the GC
640 // - if explicit_gc is false, word_size describes the allocation that
641 // the GC should attempt (at least) to satisfy
642 // - it returns false if it is unable to do the collection due to the
643 // GC locker being active, true otherwise
644 bool do_collection(bool explicit_gc,
645 bool clear_all_soft_refs,
646 size_t word_size);
648 // Callback from VM_G1CollectFull operation.
649 // Perform a full collection.
650 virtual void do_full_collection(bool clear_all_soft_refs);
652 // Resize the heap if necessary after a full collection. If this is
653 // after a collect-for allocation, "word_size" is the allocation size,
654 // and will be considered part of the used portion of the heap.
655 void resize_if_necessary_after_full_collection(size_t word_size);
657 // Callback from VM_G1CollectForAllocation operation.
658 // This function does everything necessary/possible to satisfy a
659 // failed allocation request (including collection, expansion, etc.)
660 HeapWord* satisfy_failed_allocation(size_t word_size, bool* succeeded);
662 // Attempting to expand the heap sufficiently
663 // to support an allocation of the given "word_size". If
664 // successful, perform the allocation and return the address of the
665 // allocated block, or else "NULL".
666 HeapWord* expand_and_allocate(size_t word_size);
668 // Process any reference objects discovered during
669 // an incremental evacuation pause.
670 void process_discovered_references(uint no_of_gc_workers);
672 // Enqueue any remaining discovered references
673 // after processing.
674 void enqueue_discovered_references(uint no_of_gc_workers);
676 public:
678 G1MonitoringSupport* g1mm() {
679 assert(_g1mm != NULL, "should have been initialized");
680 return _g1mm;
681 }
683 // Expand the garbage-first heap by at least the given size (in bytes!).
684 // Returns true if the heap was expanded by the requested amount;
685 // false otherwise.
686 // (Rounds up to a HeapRegion boundary.)
687 bool expand(size_t expand_bytes);
689 // Do anything common to GC's.
690 virtual void gc_prologue(bool full);
691 virtual void gc_epilogue(bool full);
693 // We register a region with the fast "in collection set" test. We
694 // simply set to true the array slot corresponding to this region.
695 void register_region_with_in_cset_fast_test(HeapRegion* r) {
696 _in_cset_fast_test.set_by_index(r->hrs_index(), true);
697 }
699 // This is a fast test on whether a reference points into the
700 // collection set or not. Assume that the reference
701 // points into the heap.
702 inline bool in_cset_fast_test(oop obj);
704 void clear_cset_fast_test() {
705 _in_cset_fast_test.clear();
706 }
708 // This is called at the start of either a concurrent cycle or a Full
709 // GC to update the number of old marking cycles started.
710 void increment_old_marking_cycles_started();
712 // This is called at the end of either a concurrent cycle or a Full
713 // GC to update the number of old marking cycles completed. Those two
714 // can happen in a nested fashion, i.e., we start a concurrent
715 // cycle, a Full GC happens half-way through it which ends first,
716 // and then the cycle notices that a Full GC happened and ends
717 // too. The concurrent parameter is a boolean to help us do a bit
718 // tighter consistency checking in the method. If concurrent is
719 // false, the caller is the inner caller in the nesting (i.e., the
720 // Full GC). If concurrent is true, the caller is the outer caller
721 // in this nesting (i.e., the concurrent cycle). Further nesting is
722 // not currently supported. The end of this call also notifies
723 // the FullGCCount_lock in case a Java thread is waiting for a full
724 // GC to happen (e.g., it called System.gc() with
725 // +ExplicitGCInvokesConcurrent).
726 void increment_old_marking_cycles_completed(bool concurrent);
728 unsigned int old_marking_cycles_completed() {
729 return _old_marking_cycles_completed;
730 }
732 void register_concurrent_cycle_start(const Ticks& start_time);
733 void register_concurrent_cycle_end();
734 void trace_heap_after_concurrent_cycle();
736 G1YCType yc_type();
738 G1HRPrinter* hr_printer() { return &_hr_printer; }
740 // Frees a non-humongous region by initializing its contents and
741 // adding it to the free list that's passed as a parameter (this is
742 // usually a local list which will be appended to the master free
743 // list later). The used bytes of freed regions are accumulated in
744 // pre_used. If par is true, the region's RSet will not be freed
745 // up. The assumption is that this will be done later.
746 // The locked parameter indicates if the caller has already taken
747 // care of proper synchronization. This may allow some optimizations.
748 void free_region(HeapRegion* hr,
749 FreeRegionList* free_list,
750 bool par,
751 bool locked = false);
753 // Frees a humongous region by collapsing it into individual regions
754 // and calling free_region() for each of them. The freed regions
755 // will be added to the free list that's passed as a parameter (this
756 // is usually a local list which will be appended to the master free
757 // list later). The used bytes of freed regions are accumulated in
758 // pre_used. If par is true, the region's RSet will not be freed
759 // up. The assumption is that this will be done later.
760 void free_humongous_region(HeapRegion* hr,
761 FreeRegionList* free_list,
762 bool par);
763 protected:
765 // Shrink the garbage-first heap by at most the given size (in bytes!).
766 // (Rounds down to a HeapRegion boundary.)
767 virtual void shrink(size_t expand_bytes);
768 void shrink_helper(size_t expand_bytes);
770 #if TASKQUEUE_STATS
771 static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
772 void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
773 void reset_taskqueue_stats();
774 #endif // TASKQUEUE_STATS
776 // Schedule the VM operation that will do an evacuation pause to
777 // satisfy an allocation request of word_size. *succeeded will
778 // return whether the VM operation was successful (it did do an
779 // evacuation pause) or not (another thread beat us to it or the GC
780 // locker was active). Given that we should not be holding the
781 // Heap_lock when we enter this method, we will pass the
782 // gc_count_before (i.e., total_collections()) as a parameter since
783 // it has to be read while holding the Heap_lock. Currently, both
784 // methods that call do_collection_pause() release the Heap_lock
785 // before the call, so it's easy to read gc_count_before just before.
786 HeapWord* do_collection_pause(size_t word_size,
787 unsigned int gc_count_before,
788 bool* succeeded,
789 GCCause::Cause gc_cause);
791 // The guts of the incremental collection pause, executed by the vm
792 // thread. It returns false if it is unable to do the collection due
793 // to the GC locker being active, true otherwise
794 bool do_collection_pause_at_safepoint(double target_pause_time_ms);
796 // Actually do the work of evacuating the collection set.
797 void evacuate_collection_set(EvacuationInfo& evacuation_info);
799 // The g1 remembered set of the heap.
800 G1RemSet* _g1_rem_set;
802 // A set of cards that cover the objects for which the Rsets should be updated
803 // concurrently after the collection.
804 DirtyCardQueueSet _dirty_card_queue_set;
806 // The closure used to refine a single card.
807 RefineCardTableEntryClosure* _refine_cte_cl;
809 // A function to check the consistency of dirty card logs.
810 void check_ct_logs_at_safepoint();
812 // A DirtyCardQueueSet that is used to hold cards that contain
813 // references into the current collection set. This is used to
814 // update the remembered sets of the regions in the collection
815 // set in the event of an evacuation failure.
816 DirtyCardQueueSet _into_cset_dirty_card_queue_set;
818 // After a collection pause, make the regions in the CS into free
819 // regions.
820 void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info);
822 // Abandon the current collection set without recording policy
823 // statistics or updating free lists.
824 void abandon_collection_set(HeapRegion* cs_head);
826 // Applies "scan_non_heap_roots" to roots outside the heap,
827 // "scan_rs" to roots inside the heap (having done "set_region" to
828 // indicate the region in which the root resides),
829 // and does "scan_metadata" If "scan_rs" is
830 // NULL, then this step is skipped. The "worker_i"
831 // param is for use with parallel roots processing, and should be
832 // the "i" of the calling parallel worker thread's work(i) function.
833 // In the sequential case this param will be ignored.
834 void g1_process_roots(OopClosure* scan_non_heap_roots,
835 OopClosure* scan_non_heap_weak_roots,
836 OopsInHeapRegionClosure* scan_rs,
837 CLDClosure* scan_strong_clds,
838 CLDClosure* scan_weak_clds,
839 CodeBlobClosure* scan_strong_code,
840 uint worker_i);
842 // Notifies all the necessary spaces that the committed space has
843 // been updated (either expanded or shrunk). It should be called
844 // after _g1_storage is updated.
845 void update_committed_space(HeapWord* old_end, HeapWord* new_end);
847 // The concurrent marker (and the thread it runs in.)
848 ConcurrentMark* _cm;
849 ConcurrentMarkThread* _cmThread;
850 bool _mark_in_progress;
852 // The concurrent refiner.
853 ConcurrentG1Refine* _cg1r;
855 // The parallel task queues
856 RefToScanQueueSet *_task_queues;
858 // True iff a evacuation has failed in the current collection.
859 bool _evacuation_failed;
861 EvacuationFailedInfo* _evacuation_failed_info_array;
863 // Failed evacuations cause some logical from-space objects to have
864 // forwarding pointers to themselves. Reset them.
865 void remove_self_forwarding_pointers();
867 // Together, these store an object with a preserved mark, and its mark value.
868 Stack<oop, mtGC> _objs_with_preserved_marks;
869 Stack<markOop, mtGC> _preserved_marks_of_objs;
871 // Preserve the mark of "obj", if necessary, in preparation for its mark
872 // word being overwritten with a self-forwarding-pointer.
873 void preserve_mark_if_necessary(oop obj, markOop m);
875 // The stack of evac-failure objects left to be scanned.
876 GrowableArray<oop>* _evac_failure_scan_stack;
877 // The closure to apply to evac-failure objects.
879 OopsInHeapRegionClosure* _evac_failure_closure;
880 // Set the field above.
881 void
882 set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
883 _evac_failure_closure = evac_failure_closure;
884 }
886 // Push "obj" on the scan stack.
887 void push_on_evac_failure_scan_stack(oop obj);
888 // Process scan stack entries until the stack is empty.
889 void drain_evac_failure_scan_stack();
890 // True iff an invocation of "drain_scan_stack" is in progress; to
891 // prevent unnecessary recursion.
892 bool _drain_in_progress;
894 // Do any necessary initialization for evacuation-failure handling.
895 // "cl" is the closure that will be used to process evac-failure
896 // objects.
897 void init_for_evac_failure(OopsInHeapRegionClosure* cl);
898 // Do any necessary cleanup for evacuation-failure handling data
899 // structures.
900 void finalize_for_evac_failure();
902 // An attempt to evacuate "obj" has failed; take necessary steps.
903 oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj);
904 void handle_evacuation_failure_common(oop obj, markOop m);
906 #ifndef PRODUCT
907 // Support for forcing evacuation failures. Analogous to
908 // PromotionFailureALot for the other collectors.
910 // Records whether G1EvacuationFailureALot should be in effect
911 // for the current GC
912 bool _evacuation_failure_alot_for_current_gc;
914 // Used to record the GC number for interval checking when
915 // determining whether G1EvaucationFailureALot is in effect
916 // for the current GC.
917 size_t _evacuation_failure_alot_gc_number;
919 // Count of the number of evacuations between failures.
920 volatile size_t _evacuation_failure_alot_count;
922 // Set whether G1EvacuationFailureALot should be in effect
923 // for the current GC (based upon the type of GC and which
924 // command line flags are set);
925 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
926 bool during_initial_mark,
927 bool during_marking);
929 inline void set_evacuation_failure_alot_for_current_gc();
931 // Return true if it's time to cause an evacuation failure.
932 inline bool evacuation_should_fail();
934 // Reset the G1EvacuationFailureALot counters. Should be called at
935 // the end of an evacuation pause in which an evacuation failure occurred.
936 inline void reset_evacuation_should_fail();
937 #endif // !PRODUCT
939 // ("Weak") Reference processing support.
940 //
941 // G1 has 2 instances of the reference processor class. One
942 // (_ref_processor_cm) handles reference object discovery
943 // and subsequent processing during concurrent marking cycles.
944 //
945 // The other (_ref_processor_stw) handles reference object
946 // discovery and processing during full GCs and incremental
947 // evacuation pauses.
948 //
949 // During an incremental pause, reference discovery will be
950 // temporarily disabled for _ref_processor_cm and will be
951 // enabled for _ref_processor_stw. At the end of the evacuation
952 // pause references discovered by _ref_processor_stw will be
953 // processed and discovery will be disabled. The previous
954 // setting for reference object discovery for _ref_processor_cm
955 // will be re-instated.
956 //
957 // At the start of marking:
958 // * Discovery by the CM ref processor is verified to be inactive
959 // and it's discovered lists are empty.
960 // * Discovery by the CM ref processor is then enabled.
961 //
962 // At the end of marking:
963 // * Any references on the CM ref processor's discovered
964 // lists are processed (possibly MT).
965 //
966 // At the start of full GC we:
967 // * Disable discovery by the CM ref processor and
968 // empty CM ref processor's discovered lists
969 // (without processing any entries).
970 // * Verify that the STW ref processor is inactive and it's
971 // discovered lists are empty.
972 // * Temporarily set STW ref processor discovery as single threaded.
973 // * Temporarily clear the STW ref processor's _is_alive_non_header
974 // field.
975 // * Finally enable discovery by the STW ref processor.
976 //
977 // The STW ref processor is used to record any discovered
978 // references during the full GC.
979 //
980 // At the end of a full GC we:
981 // * Enqueue any reference objects discovered by the STW ref processor
982 // that have non-live referents. This has the side-effect of
983 // making the STW ref processor inactive by disabling discovery.
984 // * Verify that the CM ref processor is still inactive
985 // and no references have been placed on it's discovered
986 // lists (also checked as a precondition during initial marking).
988 // The (stw) reference processor...
989 ReferenceProcessor* _ref_processor_stw;
991 STWGCTimer* _gc_timer_stw;
992 ConcurrentGCTimer* _gc_timer_cm;
994 G1OldTracer* _gc_tracer_cm;
995 G1NewTracer* _gc_tracer_stw;
997 // During reference object discovery, the _is_alive_non_header
998 // closure (if non-null) is applied to the referent object to
999 // determine whether the referent is live. If so then the
1000 // reference object does not need to be 'discovered' and can
1001 // be treated as a regular oop. This has the benefit of reducing
1002 // the number of 'discovered' reference objects that need to
1003 // be processed.
1004 //
1005 // Instance of the is_alive closure for embedding into the
1006 // STW reference processor as the _is_alive_non_header field.
1007 // Supplying a value for the _is_alive_non_header field is
1008 // optional but doing so prevents unnecessary additions to
1009 // the discovered lists during reference discovery.
1010 G1STWIsAliveClosure _is_alive_closure_stw;
1012 // The (concurrent marking) reference processor...
1013 ReferenceProcessor* _ref_processor_cm;
1015 // Instance of the concurrent mark is_alive closure for embedding
1016 // into the Concurrent Marking reference processor as the
1017 // _is_alive_non_header field. Supplying a value for the
1018 // _is_alive_non_header field is optional but doing so prevents
1019 // unnecessary additions to the discovered lists during reference
1020 // discovery.
1021 G1CMIsAliveClosure _is_alive_closure_cm;
1023 // Cache used by G1CollectedHeap::start_cset_region_for_worker().
1024 HeapRegion** _worker_cset_start_region;
1026 // Time stamp to validate the regions recorded in the cache
1027 // used by G1CollectedHeap::start_cset_region_for_worker().
1028 // The heap region entry for a given worker is valid iff
1029 // the associated time stamp value matches the current value
1030 // of G1CollectedHeap::_gc_time_stamp.
1031 unsigned int* _worker_cset_start_region_time_stamp;
1033 enum G1H_process_roots_tasks {
1034 G1H_PS_filter_satb_buffers,
1035 G1H_PS_refProcessor_oops_do,
1036 // Leave this one last.
1037 G1H_PS_NumElements
1038 };
1040 SubTasksDone* _process_strong_tasks;
1042 volatile bool _free_regions_coming;
1044 public:
1046 SubTasksDone* process_strong_tasks() { return _process_strong_tasks; }
1048 void set_refine_cte_cl_concurrency(bool concurrent);
1050 RefToScanQueue *task_queue(int i) const;
1052 // A set of cards where updates happened during the GC
1053 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
1055 // A DirtyCardQueueSet that is used to hold cards that contain
1056 // references into the current collection set. This is used to
1057 // update the remembered sets of the regions in the collection
1058 // set in the event of an evacuation failure.
1059 DirtyCardQueueSet& into_cset_dirty_card_queue_set()
1060 { return _into_cset_dirty_card_queue_set; }
1062 // Create a G1CollectedHeap with the specified policy.
1063 // Must call the initialize method afterwards.
1064 // May not return if something goes wrong.
1065 G1CollectedHeap(G1CollectorPolicy* policy);
1067 // Initialize the G1CollectedHeap to have the initial and
1068 // maximum sizes and remembered and barrier sets
1069 // specified by the policy object.
1070 jint initialize();
1072 virtual void stop();
1074 // Return the (conservative) maximum heap alignment for any G1 heap
1075 static size_t conservative_max_heap_alignment();
1077 // Initialize weak reference processing.
1078 virtual void ref_processing_init();
1080 void set_par_threads(uint t) {
1081 SharedHeap::set_par_threads(t);
1082 // Done in SharedHeap but oddly there are
1083 // two _process_strong_tasks's in a G1CollectedHeap
1084 // so do it here too.
1085 _process_strong_tasks->set_n_threads(t);
1086 }
1088 // Set _n_par_threads according to a policy TBD.
1089 void set_par_threads();
1091 void set_n_termination(int t) {
1092 _process_strong_tasks->set_n_threads(t);
1093 }
1095 virtual CollectedHeap::Name kind() const {
1096 return CollectedHeap::G1CollectedHeap;
1097 }
1099 // The current policy object for the collector.
1100 G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1102 virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); }
1104 // Adaptive size policy. No such thing for g1.
1105 virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1107 // The rem set and barrier set.
1108 G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1110 unsigned get_gc_time_stamp() {
1111 return _gc_time_stamp;
1112 }
1114 inline void reset_gc_time_stamp();
1116 void check_gc_time_stamps() PRODUCT_RETURN;
1118 inline void increment_gc_time_stamp();
1120 // Reset the given region's GC timestamp. If it's starts humongous,
1121 // also reset the GC timestamp of its corresponding
1122 // continues humongous regions too.
1123 void reset_gc_time_stamps(HeapRegion* hr);
1125 void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1126 DirtyCardQueue* into_cset_dcq,
1127 bool concurrent, uint worker_i);
1129 // The shared block offset table array.
1130 G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1132 // Reference Processing accessors
1134 // The STW reference processor....
1135 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1137 // The Concurrent Marking reference processor...
1138 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1140 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1141 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1143 virtual size_t capacity() const;
1144 virtual size_t used() const;
1145 // This should be called when we're not holding the heap lock. The
1146 // result might be a bit inaccurate.
1147 size_t used_unlocked() const;
1148 size_t recalculate_used() const;
1150 // These virtual functions do the actual allocation.
1151 // Some heaps may offer a contiguous region for shared non-blocking
1152 // allocation, via inlined code (by exporting the address of the top and
1153 // end fields defining the extent of the contiguous allocation region.)
1154 // But G1CollectedHeap doesn't yet support this.
1156 // Return an estimate of the maximum allocation that could be performed
1157 // without triggering any collection or expansion activity. In a
1158 // generational collector, for example, this is probably the largest
1159 // allocation that could be supported (without expansion) in the youngest
1160 // generation. It is "unsafe" because no locks are taken; the result
1161 // should be treated as an approximation, not a guarantee, for use in
1162 // heuristic resizing decisions.
1163 virtual size_t unsafe_max_alloc();
1165 virtual bool is_maximal_no_gc() const {
1166 return _g1_storage.uncommitted_size() == 0;
1167 }
1169 // The total number of regions in the heap.
1170 uint n_regions() const { return _hrs.length(); }
1172 // The max number of regions in the heap.
1173 uint max_regions() const { return _hrs.max_length(); }
1175 // The number of regions that are completely free.
1176 uint free_regions() const { return _free_list.length(); }
1178 // The number of regions that are not completely free.
1179 uint used_regions() const { return n_regions() - free_regions(); }
1181 // The number of regions available for "regular" expansion.
1182 uint expansion_regions() const { return _expansion_regions; }
1184 // Factory method for HeapRegion instances. It will return NULL if
1185 // the allocation fails.
1186 HeapRegion* new_heap_region(uint hrs_index, HeapWord* bottom);
1188 void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1189 void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1190 void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1191 void verify_dirty_young_regions() PRODUCT_RETURN;
1193 // verify_region_sets() performs verification over the region
1194 // lists. It will be compiled in the product code to be used when
1195 // necessary (i.e., during heap verification).
1196 void verify_region_sets();
1198 // verify_region_sets_optional() is planted in the code for
1199 // list verification in non-product builds (and it can be enabled in
1200 // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1).
1201 #if HEAP_REGION_SET_FORCE_VERIFY
1202 void verify_region_sets_optional() {
1203 verify_region_sets();
1204 }
1205 #else // HEAP_REGION_SET_FORCE_VERIFY
1206 void verify_region_sets_optional() { }
1207 #endif // HEAP_REGION_SET_FORCE_VERIFY
1209 #ifdef ASSERT
1210 bool is_on_master_free_list(HeapRegion* hr) {
1211 return hr->containing_set() == &_free_list;
1212 }
1213 #endif // ASSERT
1215 // Wrapper for the region list operations that can be called from
1216 // methods outside this class.
1218 void secondary_free_list_add(FreeRegionList* list) {
1219 _secondary_free_list.add_ordered(list);
1220 }
1222 void append_secondary_free_list() {
1223 _free_list.add_ordered(&_secondary_free_list);
1224 }
1226 void append_secondary_free_list_if_not_empty_with_lock() {
1227 // If the secondary free list looks empty there's no reason to
1228 // take the lock and then try to append it.
1229 if (!_secondary_free_list.is_empty()) {
1230 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1231 append_secondary_free_list();
1232 }
1233 }
1235 inline void old_set_remove(HeapRegion* hr);
1237 size_t non_young_capacity_bytes() {
1238 return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1239 }
1241 void set_free_regions_coming();
1242 void reset_free_regions_coming();
1243 bool free_regions_coming() { return _free_regions_coming; }
1244 void wait_while_free_regions_coming();
1246 // Determine whether the given region is one that we are using as an
1247 // old GC alloc region.
1248 bool is_old_gc_alloc_region(HeapRegion* hr) {
1249 return hr == _retained_old_gc_alloc_region;
1250 }
1252 // Perform a collection of the heap; intended for use in implementing
1253 // "System.gc". This probably implies as full a collection as the
1254 // "CollectedHeap" supports.
1255 virtual void collect(GCCause::Cause cause);
1257 // The same as above but assume that the caller holds the Heap_lock.
1258 void collect_locked(GCCause::Cause cause);
1260 // True iff an evacuation has failed in the most-recent collection.
1261 bool evacuation_failed() { return _evacuation_failed; }
1263 void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed);
1264 void prepend_to_freelist(FreeRegionList* list);
1265 void decrement_summary_bytes(size_t bytes);
1267 // Returns "TRUE" iff "p" points into the committed areas of the heap.
1268 virtual bool is_in(const void* p) const;
1270 // Return "TRUE" iff the given object address is within the collection
1271 // set.
1272 inline bool obj_in_cs(oop obj);
1274 // Return "TRUE" iff the given object address is in the reserved
1275 // region of g1.
1276 bool is_in_g1_reserved(const void* p) const {
1277 return _g1_reserved.contains(p);
1278 }
1280 // Returns a MemRegion that corresponds to the space that has been
1281 // reserved for the heap
1282 MemRegion g1_reserved() {
1283 return _g1_reserved;
1284 }
1286 // Returns a MemRegion that corresponds to the space that has been
1287 // committed in the heap
1288 MemRegion g1_committed() {
1289 return _g1_committed;
1290 }
1292 virtual bool is_in_closed_subset(const void* p) const;
1294 G1SATBCardTableModRefBS* g1_barrier_set() {
1295 return (G1SATBCardTableModRefBS*) barrier_set();
1296 }
1298 // This resets the card table to all zeros. It is used after
1299 // a collection pause which used the card table to claim cards.
1300 void cleanUpCardTable();
1302 // Iteration functions.
1304 // Iterate over all the ref-containing fields of all objects, calling
1305 // "cl.do_oop" on each.
1306 virtual void oop_iterate(ExtendedOopClosure* cl);
1308 // Same as above, restricted to a memory region.
1309 void oop_iterate(MemRegion mr, ExtendedOopClosure* cl);
1311 // Iterate over all objects, calling "cl.do_object" on each.
1312 virtual void object_iterate(ObjectClosure* cl);
1314 virtual void safe_object_iterate(ObjectClosure* cl) {
1315 object_iterate(cl);
1316 }
1318 // Iterate over all spaces in use in the heap, in ascending address order.
1319 virtual void space_iterate(SpaceClosure* cl);
1321 // Iterate over heap regions, in address order, terminating the
1322 // iteration early if the "doHeapRegion" method returns "true".
1323 void heap_region_iterate(HeapRegionClosure* blk) const;
1325 // Return the region with the given index. It assumes the index is valid.
1326 inline HeapRegion* region_at(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* blk,
1342 uint worker,
1343 uint no_of_par_workers,
1344 jint claim_value);
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 // This is a convenience method that is used by the
1370 // HeapRegionIterator classes to calculate the starting region for
1371 // each worker so that they do not all start from the same region.
1372 HeapRegion* start_region_for_worker(uint worker_i, uint no_of_par_workers);
1374 // Iterate over the regions (if any) in the current collection set.
1375 void collection_set_iterate(HeapRegionClosure* blk);
1377 // As above but starting from region r
1378 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1380 HeapRegion* next_compaction_region(const HeapRegion* from) const;
1382 // A CollectedHeap will contain some number of spaces. This finds the
1383 // space containing a given address, or else returns NULL.
1384 virtual Space* space_containing(const void* addr) const;
1386 // A G1CollectedHeap will contain some number of heap regions. This
1387 // finds the region containing a given address, or else returns NULL.
1388 template <class T>
1389 inline HeapRegion* heap_region_containing(const T addr) const;
1391 // Like the above, but requires "addr" to be in the heap (to avoid a
1392 // null-check), and unlike the above, may return an continuing humongous
1393 // region.
1394 template <class T>
1395 inline HeapRegion* heap_region_containing_raw(const T addr) const;
1397 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1398 // each address in the (reserved) heap is a member of exactly
1399 // one block. The defining characteristic of a block is that it is
1400 // possible to find its size, and thus to progress forward to the next
1401 // block. (Blocks may be of different sizes.) Thus, blocks may
1402 // represent Java objects, or they might be free blocks in a
1403 // free-list-based heap (or subheap), as long as the two kinds are
1404 // distinguishable and the size of each is determinable.
1406 // Returns the address of the start of the "block" that contains the
1407 // address "addr". We say "blocks" instead of "object" since some heaps
1408 // may not pack objects densely; a chunk may either be an object or a
1409 // non-object.
1410 virtual HeapWord* block_start(const void* addr) const;
1412 // Requires "addr" to be the start of a chunk, and returns its size.
1413 // "addr + size" is required to be the start of a new chunk, or the end
1414 // of the active area of the heap.
1415 virtual size_t block_size(const HeapWord* addr) const;
1417 // Requires "addr" to be the start of a block, and returns "TRUE" iff
1418 // the block is an object.
1419 virtual bool block_is_obj(const HeapWord* addr) const;
1421 // Does this heap support heap inspection? (+PrintClassHistogram)
1422 virtual bool supports_heap_inspection() const { return true; }
1424 // Section on thread-local allocation buffers (TLABs)
1425 // See CollectedHeap for semantics.
1427 bool supports_tlab_allocation() const;
1428 size_t tlab_capacity(Thread* ignored) const;
1429 size_t tlab_used(Thread* ignored) const;
1430 size_t max_tlab_size() const;
1431 size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1433 // Can a compiler initialize a new object without store barriers?
1434 // This permission only extends from the creation of a new object
1435 // via a TLAB up to the first subsequent safepoint. If such permission
1436 // is granted for this heap type, the compiler promises to call
1437 // defer_store_barrier() below on any slow path allocation of
1438 // a new object for which such initializing store barriers will
1439 // have been elided. G1, like CMS, allows this, but should be
1440 // ready to provide a compensating write barrier as necessary
1441 // if that storage came out of a non-young region. The efficiency
1442 // of this implementation depends crucially on being able to
1443 // answer very efficiently in constant time whether a piece of
1444 // storage in the heap comes from a young region or not.
1445 // See ReduceInitialCardMarks.
1446 virtual bool can_elide_tlab_store_barriers() const {
1447 return true;
1448 }
1450 virtual bool card_mark_must_follow_store() const {
1451 return true;
1452 }
1454 inline bool is_in_young(const oop obj);
1456 #ifdef ASSERT
1457 virtual bool is_in_partial_collection(const void* p);
1458 #endif
1460 virtual bool is_scavengable(const void* addr);
1462 // We don't need barriers for initializing stores to objects
1463 // in the young gen: for the SATB pre-barrier, there is no
1464 // pre-value that needs to be remembered; for the remembered-set
1465 // update logging post-barrier, we don't maintain remembered set
1466 // information for young gen objects.
1467 virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1469 // Returns "true" iff the given word_size is "very large".
1470 static bool isHumongous(size_t word_size) {
1471 // Note this has to be strictly greater-than as the TLABs
1472 // are capped at the humongous thresold and we want to
1473 // ensure that we don't try to allocate a TLAB as
1474 // humongous and that we don't allocate a humongous
1475 // object in a TLAB.
1476 return word_size > _humongous_object_threshold_in_words;
1477 }
1479 // Update mod union table with the set of dirty cards.
1480 void updateModUnion();
1482 // Set the mod union bits corresponding to the given memRegion. Note
1483 // that this is always a safe operation, since it doesn't clear any
1484 // bits.
1485 void markModUnionRange(MemRegion mr);
1487 // Records the fact that a marking phase is no longer in progress.
1488 void set_marking_complete() {
1489 _mark_in_progress = false;
1490 }
1491 void set_marking_started() {
1492 _mark_in_progress = true;
1493 }
1494 bool mark_in_progress() {
1495 return _mark_in_progress;
1496 }
1498 // Print the maximum heap capacity.
1499 virtual size_t max_capacity() const;
1501 virtual jlong millis_since_last_gc();
1504 // Convenience function to be used in situations where the heap type can be
1505 // asserted to be this type.
1506 static G1CollectedHeap* heap();
1508 void set_region_short_lived_locked(HeapRegion* hr);
1509 // add appropriate methods for any other surv rate groups
1511 YoungList* young_list() const { return _young_list; }
1513 // debugging
1514 bool check_young_list_well_formed() {
1515 return _young_list->check_list_well_formed();
1516 }
1518 bool check_young_list_empty(bool check_heap,
1519 bool check_sample = true);
1521 // *** Stuff related to concurrent marking. It's not clear to me that so
1522 // many of these need to be public.
1524 // The functions below are helper functions that a subclass of
1525 // "CollectedHeap" can use in the implementation of its virtual
1526 // functions.
1527 // This performs a concurrent marking of the live objects in a
1528 // bitmap off to the side.
1529 void doConcurrentMark();
1531 bool isMarkedPrev(oop obj) const;
1532 bool isMarkedNext(oop obj) const;
1534 // Determine if an object is dead, given the object and also
1535 // the region to which the object belongs. An object is dead
1536 // iff a) it was not allocated since the last mark and b) it
1537 // is not marked.
1539 bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1540 return
1541 !hr->obj_allocated_since_prev_marking(obj) &&
1542 !isMarkedPrev(obj);
1543 }
1545 // This function returns true when an object has been
1546 // around since the previous marking and hasn't yet
1547 // been marked during this marking.
1549 bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1550 return
1551 !hr->obj_allocated_since_next_marking(obj) &&
1552 !isMarkedNext(obj);
1553 }
1555 // Determine if an object is dead, given only the object itself.
1556 // This will find the region to which the object belongs and
1557 // then call the region version of the same function.
1559 // Added if it is NULL it isn't dead.
1561 inline bool is_obj_dead(const oop obj) const;
1563 inline bool is_obj_ill(const oop obj) const;
1565 bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1566 HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1567 bool is_marked(oop obj, VerifyOption vo);
1568 const char* top_at_mark_start_str(VerifyOption vo);
1570 ConcurrentMark* concurrent_mark() const { return _cm; }
1572 // Refinement
1574 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1576 // The dirty cards region list is used to record a subset of regions
1577 // whose cards need clearing. The list if populated during the
1578 // remembered set scanning and drained during the card table
1579 // cleanup. Although the methods are reentrant, population/draining
1580 // phases must not overlap. For synchronization purposes the last
1581 // element on the list points to itself.
1582 HeapRegion* _dirty_cards_region_list;
1583 void push_dirty_cards_region(HeapRegion* hr);
1584 HeapRegion* pop_dirty_cards_region();
1586 // Optimized nmethod scanning support routines
1588 // Register the given nmethod with the G1 heap
1589 virtual void register_nmethod(nmethod* nm);
1591 // Unregister the given nmethod from the G1 heap
1592 virtual void unregister_nmethod(nmethod* nm);
1594 // Migrate the nmethods in the code root lists of the regions
1595 // in the collection set to regions in to-space. In the event
1596 // of an evacuation failure, nmethods that reference objects
1597 // that were not successfullly evacuated are not migrated.
1598 void migrate_strong_code_roots();
1600 // Free up superfluous code root memory.
1601 void purge_code_root_memory();
1603 // Rebuild the stong code root lists for each region
1604 // after a full GC
1605 void rebuild_strong_code_roots();
1607 // Delete entries for dead interned string and clean up unreferenced symbols
1608 // in symbol table, possibly in parallel.
1609 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1611 // Parallel phase of unloading/cleaning after G1 concurrent mark.
1612 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred);
1614 // Redirty logged cards in the refinement queue.
1615 void redirty_logged_cards();
1616 // Verification
1618 // The following is just to alert the verification code
1619 // that a full collection has occurred and that the
1620 // remembered sets are no longer up to date.
1621 bool _full_collection;
1622 void set_full_collection() { _full_collection = true;}
1623 void clear_full_collection() {_full_collection = false;}
1624 bool full_collection() {return _full_collection;}
1626 // Perform any cleanup actions necessary before allowing a verification.
1627 virtual void prepare_for_verify();
1629 // Perform verification.
1631 // vo == UsePrevMarking -> use "prev" marking information,
1632 // vo == UseNextMarking -> use "next" marking information
1633 // vo == UseMarkWord -> use the mark word in the object header
1634 //
1635 // NOTE: Only the "prev" marking information is guaranteed to be
1636 // consistent most of the time, so most calls to this should use
1637 // vo == UsePrevMarking.
1638 // Currently, there is only one case where this is called with
1639 // vo == UseNextMarking, which is to verify the "next" marking
1640 // information at the end of remark.
1641 // Currently there is only one place where this is called with
1642 // vo == UseMarkWord, which is to verify the marking during a
1643 // full GC.
1644 void verify(bool silent, VerifyOption vo);
1646 // Override; it uses the "prev" marking information
1647 virtual void verify(bool silent);
1649 // The methods below are here for convenience and dispatch the
1650 // appropriate method depending on value of the given VerifyOption
1651 // parameter. The values for that parameter, and their meanings,
1652 // are the same as those above.
1654 bool is_obj_dead_cond(const oop obj,
1655 const HeapRegion* hr,
1656 const VerifyOption vo) const;
1658 bool is_obj_dead_cond(const oop obj,
1659 const VerifyOption vo) const;
1661 // Printing
1663 virtual void print_on(outputStream* st) const;
1664 virtual void print_extended_on(outputStream* st) const;
1665 virtual void print_on_error(outputStream* st) const;
1667 virtual void print_gc_threads_on(outputStream* st) const;
1668 virtual void gc_threads_do(ThreadClosure* tc) const;
1670 // Override
1671 void print_tracing_info() const;
1673 // The following two methods are helpful for debugging RSet issues.
1674 void print_cset_rsets() PRODUCT_RETURN;
1675 void print_all_rsets() PRODUCT_RETURN;
1677 public:
1678 size_t pending_card_num();
1679 size_t cards_scanned();
1681 protected:
1682 size_t _max_heap_capacity;
1683 };
1685 class G1ParGCAllocBuffer: public ParGCAllocBuffer {
1686 private:
1687 bool _retired;
1689 public:
1690 G1ParGCAllocBuffer(size_t gclab_word_size);
1691 virtual ~G1ParGCAllocBuffer() {
1692 guarantee(_retired, "Allocation buffer has not been retired");
1693 }
1695 virtual void set_buf(HeapWord* buf) {
1696 ParGCAllocBuffer::set_buf(buf);
1697 _retired = false;
1698 }
1700 virtual void retire(bool end_of_gc, bool retain) {
1701 if (_retired) {
1702 return;
1703 }
1704 ParGCAllocBuffer::retire(end_of_gc, retain);
1705 _retired = true;
1706 }
1707 };
1709 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP