1 /*
2 * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
8 *
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
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24
25 #ifndef SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP
26 #define SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP
27
28 #include "gc/g1/concurrentMark.hpp"
29 #include "gc/g1/evacuationInfo.hpp"
30 #include "gc/g1/g1AllocationContext.hpp"
31 #include "gc/g1/g1BiasedArray.hpp"
32 #include "gc/g1/g1CollectorState.hpp"
33 #include "gc/g1/g1HRPrinter.hpp"
34 #include "gc/g1/g1InCSetState.hpp"
35 #include "gc/g1/g1MonitoringSupport.hpp"
36 #include "gc/g1/g1EvacFailure.hpp"
37 #include "gc/g1/g1EvacStats.hpp"
38 #include "gc/g1/g1SATBCardTableModRefBS.hpp"
39 #include "gc/g1/g1YCTypes.hpp"
40 #include "gc/g1/hSpaceCounters.hpp"
41 #include "gc/g1/heapRegionManager.hpp"
42 #include "gc/g1/heapRegionSet.hpp"
43 #include "gc/g1/youngList.hpp"
44 #include "gc/shared/barrierSet.hpp"
45 #include "gc/shared/collectedHeap.hpp"
46 #include "gc/shared/plab.hpp"
47 #include "memory/memRegion.hpp"
48 #include "utilities/stack.hpp"
49
50 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
51 // It uses the "Garbage First" heap organization and algorithm, which
52 // may combine concurrent marking with parallel, incremental compaction of
53 // heap subsets that will yield large amounts of garbage.
54
55 // Forward declarations
56 class HeapRegion;
57 class HRRSCleanupTask;
58 class GenerationSpec;
59 class OopsInHeapRegionClosure;
60 class G1ParScanThreadState;
61 class G1ParScanThreadStateSet;
62 class G1KlassScanClosure;
63 class G1ParScanThreadState;
64 class ObjectClosure;
65 class SpaceClosure;
66 class CompactibleSpaceClosure;
67 class Space;
68 class G1CollectorPolicy;
69 class G1RemSet;
70 class HeapRegionRemSetIterator;
71 class ConcurrentMark;
72 class ConcurrentMarkThread;
73 class ConcurrentG1Refine;
74 class ConcurrentGCTimer;
75 class GenerationCounters;
76 class STWGCTimer;
77 class G1NewTracer;
78 class G1OldTracer;
79 class EvacuationFailedInfo;
80 class nmethod;
81 class Ticks;
82 class WorkGang;
83 class G1Allocator;
84 class G1ArchiveAllocator;
85
86 typedef OverflowTaskQueue<StarTask, mtGC> RefToScanQueue;
87 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
88
89 typedef int RegionIdx_t; // needs to hold [ 0..max_regions() )
90 typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion )
91
92 // The G1 STW is alive closure.
93 // An instance is embedded into the G1CH and used as the
94 // (optional) _is_alive_non_header closure in the STW
95 // reference processor. It is also extensively used during
96 // reference processing during STW evacuation pauses.
97 class G1STWIsAliveClosure: public BoolObjectClosure {
98 G1CollectedHeap* _g1;
99 public:
100 G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
101 bool do_object_b(oop p);
102 };
103
104 class RefineCardTableEntryClosure;
105
106 class G1RegionMappingChangedListener : public G1MappingChangedListener {
107 private:
108 void reset_from_card_cache(uint start_idx, size_t num_regions);
109 public:
110 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
111 };
112
113 class G1CollectedHeap : public CollectedHeap {
114 friend class VM_CollectForMetadataAllocation;
115 friend class VM_G1CollectForAllocation;
116 friend class VM_G1CollectFull;
117 friend class VM_G1IncCollectionPause;
118 friend class VMStructs;
119 friend class MutatorAllocRegion;
120 friend class G1GCAllocRegion;
121
122 // Closures used in implementation.
123 friend class G1ParScanThreadState;
124 friend class G1ParScanThreadStateSet;
125 friend class G1ParTask;
126 friend class G1PLABAllocator;
127 friend class G1PrepareCompactClosure;
128
129 // Other related classes.
130 friend class HeapRegionClaimer;
131
132 // Testing classes.
133 friend class G1CheckCSetFastTableClosure;
134
135 private:
136 WorkGang* _workers;
137
138 static size_t _humongous_object_threshold_in_words;
139
140 // The secondary free list which contains regions that have been
141 // freed up during the cleanup process. This will be appended to
142 // the master free list when appropriate.
143 FreeRegionList _secondary_free_list;
144
145 // It keeps track of the old regions.
146 HeapRegionSet _old_set;
147
148 // It keeps track of the humongous regions.
149 HeapRegionSet _humongous_set;
150
151 void eagerly_reclaim_humongous_regions();
152
153 // The number of regions we could create by expansion.
154 uint _expansion_regions;
155
156 // The block offset table for the G1 heap.
157 G1BlockOffsetSharedArray* _bot_shared;
158
159 // Tears down the region sets / lists so that they are empty and the
160 // regions on the heap do not belong to a region set / list. The
161 // only exception is the humongous set which we leave unaltered. If
162 // free_list_only is true, it will only tear down the master free
163 // list. It is called before a Full GC (free_list_only == false) or
164 // before heap shrinking (free_list_only == true).
165 void tear_down_region_sets(bool free_list_only);
166
167 // Rebuilds the region sets / lists so that they are repopulated to
168 // reflect the contents of the heap. The only exception is the
169 // humongous set which was not torn down in the first place. If
170 // free_list_only is true, it will only rebuild the master free
171 // list. It is called after a Full GC (free_list_only == false) or
172 // after heap shrinking (free_list_only == true).
173 void rebuild_region_sets(bool free_list_only);
174
175 // Callback for region mapping changed events.
176 G1RegionMappingChangedListener _listener;
177
178 // The sequence of all heap regions in the heap.
179 HeapRegionManager _hrm;
180
181 // Manages all allocations with regions except humongous object allocations.
182 G1Allocator* _allocator;
183
184 // Outside of GC pauses, the number of bytes used in all regions other
185 // than the current allocation region(s).
186 size_t _summary_bytes_used;
187
188 void increase_used(size_t bytes);
189 void decrease_used(size_t bytes);
190
191 void set_used(size_t bytes);
192
193 // Class that handles archive allocation ranges.
194 G1ArchiveAllocator* _archive_allocator;
195
196 // Statistics for each allocation context
197 AllocationContextStats _allocation_context_stats;
198
199 // GC allocation statistics policy for survivors.
200 G1EvacStats _survivor_evac_stats;
201
202 // GC allocation statistics policy for tenured objects.
203 G1EvacStats _old_evac_stats;
204
205 // It specifies whether we should attempt to expand the heap after a
206 // region allocation failure. If heap expansion fails we set this to
207 // false so that we don't re-attempt the heap expansion (it's likely
208 // that subsequent expansion attempts will also fail if one fails).
209 // Currently, it is only consulted during GC and it's reset at the
210 // start of each GC.
211 bool _expand_heap_after_alloc_failure;
212
213 // Helper for monitoring and management support.
214 G1MonitoringSupport* _g1mm;
215
216 // Records whether the region at the given index is (still) a
217 // candidate for eager reclaim. Only valid for humongous start
218 // regions; other regions have unspecified values. Humongous start
219 // regions are initialized at start of collection pause, with
220 // candidates removed from the set as they are found reachable from
221 // roots or the young generation.
222 class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> {
223 protected:
224 bool default_value() const { return false; }
225 public:
226 void clear() { G1BiasedMappedArray<bool>::clear(); }
227 void set_candidate(uint region, bool value) {
228 set_by_index(region, value);
229 }
230 bool is_candidate(uint region) {
231 return get_by_index(region);
232 }
233 };
234
235 HumongousReclaimCandidates _humongous_reclaim_candidates;
236 // Stores whether during humongous object registration we found candidate regions.
237 // If not, we can skip a few steps.
238 bool _has_humongous_reclaim_candidates;
239
240 volatile unsigned _gc_time_stamp;
241
242 G1HRPrinter _hr_printer;
243
244 // It decides whether an explicit GC should start a concurrent cycle
245 // instead of doing a STW GC. Currently, a concurrent cycle is
246 // explicitly started if:
247 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
248 // (b) cause == _g1_humongous_allocation
249 // (c) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
250 // (d) cause == _dcmd_gc_run and +ExplicitGCInvokesConcurrent.
251 // (e) cause == _update_allocation_context_stats_inc
252 // (f) cause == _wb_conc_mark
253 bool should_do_concurrent_full_gc(GCCause::Cause cause);
254
255 // indicates whether we are in young or mixed GC mode
256 G1CollectorState _collector_state;
257
258 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
259 // concurrent cycles) we have started.
260 volatile uint _old_marking_cycles_started;
261
262 // Keeps track of how many "old marking cycles" (i.e., Full GCs or
263 // concurrent cycles) we have completed.
264 volatile uint _old_marking_cycles_completed;
265
266 bool _heap_summary_sent;
267
268 // This is a non-product method that is helpful for testing. It is
269 // called at the end of a GC and artificially expands the heap by
270 // allocating a number of dead regions. This way we can induce very
271 // frequent marking cycles and stress the cleanup / concurrent
272 // cleanup code more (as all the regions that will be allocated by
273 // this method will be found dead by the marking cycle).
274 void allocate_dummy_regions() PRODUCT_RETURN;
275
276 // Clear RSets after a compaction. It also resets the GC time stamps.
277 void clear_rsets_post_compaction();
278
279 // If the HR printer is active, dump the state of the regions in the
280 // heap after a compaction.
281 void print_hrm_post_compaction();
282
283 // Create a memory mapper for auxiliary data structures of the given size and
284 // translation factor.
285 static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description,
286 size_t size,
287 size_t translation_factor);
288
289 double verify(bool guard, const char* msg);
290 void verify_before_gc();
291 void verify_after_gc();
292
293 void log_gc_header();
294 void log_gc_footer(double pause_time_sec);
295
296 void trace_heap(GCWhen::Type when, const GCTracer* tracer);
297
298 void process_weak_jni_handles();
299
300 // These are macros so that, if the assert fires, we get the correct
301 // line number, file, etc.
302
303 #define heap_locking_asserts_params(_extra_message_) \
304 "%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \
305 (_extra_message_), \
306 BOOL_TO_STR(Heap_lock->owned_by_self()), \
307 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \
308 BOOL_TO_STR(Thread::current()->is_VM_thread())
309
310 #define assert_heap_locked() \
311 do { \
312 assert(Heap_lock->owned_by_self(), \
313 heap_locking_asserts_params("should be holding the Heap_lock")); \
314 } while (0)
315
316 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \
317 do { \
318 assert(Heap_lock->owned_by_self() || \
319 (SafepointSynchronize::is_at_safepoint() && \
320 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
321 heap_locking_asserts_params("should be holding the Heap_lock or " \
322 "should be at a safepoint")); \
323 } while (0)
324
325 #define assert_heap_locked_and_not_at_safepoint() \
326 do { \
327 assert(Heap_lock->owned_by_self() && \
328 !SafepointSynchronize::is_at_safepoint(), \
329 heap_locking_asserts_params("should be holding the Heap_lock and " \
330 "should not be at a safepoint")); \
331 } while (0)
332
333 #define assert_heap_not_locked() \
334 do { \
335 assert(!Heap_lock->owned_by_self(), \
336 heap_locking_asserts_params("should not be holding the Heap_lock")); \
337 } while (0)
338
339 #define assert_heap_not_locked_and_not_at_safepoint() \
340 do { \
341 assert(!Heap_lock->owned_by_self() && \
342 !SafepointSynchronize::is_at_safepoint(), \
343 heap_locking_asserts_params("should not be holding the Heap_lock and " \
344 "should not be at a safepoint")); \
345 } while (0)
346
347 #define assert_at_safepoint(_should_be_vm_thread_) \
348 do { \
349 assert(SafepointSynchronize::is_at_safepoint() && \
350 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
351 heap_locking_asserts_params("should be at a safepoint")); \
352 } while (0)
353
354 #define assert_not_at_safepoint() \
355 do { \
356 assert(!SafepointSynchronize::is_at_safepoint(), \
357 heap_locking_asserts_params("should not be at a safepoint")); \
358 } while (0)
359
360 protected:
361
362 // The young region list.
363 YoungList* _young_list;
364
365 // The current policy object for the collector.
366 G1CollectorPolicy* _g1_policy;
367
368 // This is the second level of trying to allocate a new region. If
369 // new_region() didn't find a region on the free_list, this call will
370 // check whether there's anything available on the
371 // secondary_free_list and/or wait for more regions to appear on
372 // that list, if _free_regions_coming is set.
373 HeapRegion* new_region_try_secondary_free_list(bool is_old);
374
375 // Try to allocate a single non-humongous HeapRegion sufficient for
376 // an allocation of the given word_size. If do_expand is true,
377 // attempt to expand the heap if necessary to satisfy the allocation
378 // request. If the region is to be used as an old region or for a
379 // humongous object, set is_old to true. If not, to false.
380 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
381
382 // Initialize a contiguous set of free regions of length num_regions
383 // and starting at index first so that they appear as a single
384 // humongous region.
385 HeapWord* humongous_obj_allocate_initialize_regions(uint first,
386 uint num_regions,
387 size_t word_size,
388 AllocationContext_t context);
389
390 // Attempt to allocate a humongous object of the given size. Return
391 // NULL if unsuccessful.
392 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context);
393
394 // The following two methods, allocate_new_tlab() and
395 // mem_allocate(), are the two main entry points from the runtime
396 // into the G1's allocation routines. They have the following
397 // assumptions:
398 //
399 // * They should both be called outside safepoints.
400 //
401 // * They should both be called without holding the Heap_lock.
402 //
403 // * All allocation requests for new TLABs should go to
404 // allocate_new_tlab().
405 //
406 // * All non-TLAB allocation requests should go to mem_allocate().
407 //
408 // * If either call cannot satisfy the allocation request using the
409 // current allocating region, they will try to get a new one. If
410 // this fails, they will attempt to do an evacuation pause and
411 // retry the allocation.
412 //
413 // * If all allocation attempts fail, even after trying to schedule
414 // an evacuation pause, allocate_new_tlab() will return NULL,
415 // whereas mem_allocate() will attempt a heap expansion and/or
416 // schedule a Full GC.
417 //
418 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
419 // should never be called with word_size being humongous. All
420 // humongous allocation requests should go to mem_allocate() which
421 // will satisfy them with a special path.
422
423 virtual HeapWord* allocate_new_tlab(size_t word_size);
424
425 virtual HeapWord* mem_allocate(size_t word_size,
426 bool* gc_overhead_limit_was_exceeded);
427
428 // The following three methods take a gc_count_before_ret
429 // parameter which is used to return the GC count if the method
430 // returns NULL. Given that we are required to read the GC count
431 // while holding the Heap_lock, and these paths will take the
432 // Heap_lock at some point, it's easier to get them to read the GC
433 // count while holding the Heap_lock before they return NULL instead
434 // of the caller (namely: mem_allocate()) having to also take the
435 // Heap_lock just to read the GC count.
436
437 // First-level mutator allocation attempt: try to allocate out of
438 // the mutator alloc region without taking the Heap_lock. This
439 // should only be used for non-humongous allocations.
440 inline HeapWord* attempt_allocation(size_t word_size,
441 uint* gc_count_before_ret,
442 uint* gclocker_retry_count_ret);
443
444 // Second-level mutator allocation attempt: take the Heap_lock and
445 // retry the allocation attempt, potentially scheduling a GC
446 // pause. This should only be used for non-humongous allocations.
447 HeapWord* attempt_allocation_slow(size_t word_size,
448 AllocationContext_t context,
449 uint* gc_count_before_ret,
450 uint* gclocker_retry_count_ret);
451
452 // Takes the Heap_lock and attempts a humongous allocation. It can
453 // potentially schedule a GC pause.
454 HeapWord* attempt_allocation_humongous(size_t word_size,
455 uint* gc_count_before_ret,
456 uint* gclocker_retry_count_ret);
457
458 // Allocation attempt that should be called during safepoints (e.g.,
459 // at the end of a successful GC). expect_null_mutator_alloc_region
460 // specifies whether the mutator alloc region is expected to be NULL
461 // or not.
462 HeapWord* attempt_allocation_at_safepoint(size_t word_size,
463 AllocationContext_t context,
464 bool expect_null_mutator_alloc_region);
465
466 // These methods are the "callbacks" from the G1AllocRegion class.
467
468 // For mutator alloc regions.
469 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
470 void retire_mutator_alloc_region(HeapRegion* alloc_region,
471 size_t allocated_bytes);
472
473 // For GC alloc regions.
474 HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
475 InCSetState dest);
476 void retire_gc_alloc_region(HeapRegion* alloc_region,
477 size_t allocated_bytes, InCSetState dest);
478
479 // - if explicit_gc is true, the GC is for a System.gc() etc,
480 // otherwise it's for a failed allocation.
481 // - if clear_all_soft_refs is true, all soft references should be
482 // cleared during the GC.
483 // - it returns false if it is unable to do the collection due to the
484 // GC locker being active, true otherwise.
485 bool do_full_collection(bool explicit_gc,
486 bool clear_all_soft_refs);
487
488 // Callback from VM_G1CollectFull operation, or collect_as_vm_thread.
489 virtual void do_full_collection(bool clear_all_soft_refs);
490
491 // Resize the heap if necessary after a full collection.
492 void resize_if_necessary_after_full_collection();
493
494 // Callback from VM_G1CollectForAllocation operation.
495 // This function does everything necessary/possible to satisfy a
496 // failed allocation request (including collection, expansion, etc.)
497 HeapWord* satisfy_failed_allocation(size_t word_size,
498 AllocationContext_t context,
499 bool* succeeded);
500 private:
501 // Helper method for satisfy_failed_allocation()
502 HeapWord* satisfy_failed_allocation_helper(size_t word_size,
503 AllocationContext_t context,
504 bool do_gc,
505 bool clear_all_soft_refs,
506 bool expect_null_mutator_alloc_region,
507 bool* gc_succeeded);
508
509 protected:
510 // Attempting to expand the heap sufficiently
511 // to support an allocation of the given "word_size". If
512 // successful, perform the allocation and return the address of the
513 // allocated block, or else "NULL".
514 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context);
515
516 // Process any reference objects discovered during
517 // an incremental evacuation pause.
518 void process_discovered_references(G1ParScanThreadStateSet* per_thread_states);
519
520 // Enqueue any remaining discovered references
521 // after processing.
522 void enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states);
523
524 public:
525 WorkGang* workers() const { return _workers; }
526
527 G1Allocator* allocator() {
528 return _allocator;
529 }
530
531 G1MonitoringSupport* g1mm() {
532 assert(_g1mm != NULL, "should have been initialized");
533 return _g1mm;
534 }
535
536 // Expand the garbage-first heap by at least the given size (in bytes!).
537 // Returns true if the heap was expanded by the requested amount;
538 // false otherwise.
539 // (Rounds up to a HeapRegion boundary.)
540 bool expand(size_t expand_bytes, double* expand_time_ms = NULL);
541
542 // Returns the PLAB statistics for a given destination.
543 inline G1EvacStats* alloc_buffer_stats(InCSetState dest);
544
545 // Determines PLAB size for a given destination.
546 inline size_t desired_plab_sz(InCSetState dest);
547
548 inline AllocationContextStats& allocation_context_stats();
549
550 // Do anything common to GC's.
551 void gc_prologue(bool full);
552 void gc_epilogue(bool full);
553
554 // Modify the reclaim candidate set and test for presence.
555 // These are only valid for starts_humongous regions.
556 inline void set_humongous_reclaim_candidate(uint region, bool value);
557 inline bool is_humongous_reclaim_candidate(uint region);
558
559 // Remove from the reclaim candidate set. Also remove from the
560 // collection set so that later encounters avoid the slow path.
561 inline void set_humongous_is_live(oop obj);
562
563 // Register the given region to be part of the collection set.
564 inline void register_humongous_region_with_cset(uint index);
565 // Register regions with humongous objects (actually on the start region) in
566 // the in_cset_fast_test table.
567 void register_humongous_regions_with_cset();
568 // We register a region with the fast "in collection set" test. We
569 // simply set to true the array slot corresponding to this region.
570 void register_young_region_with_cset(HeapRegion* r) {
571 _in_cset_fast_test.set_in_young(r->hrm_index());
572 }
573 void register_old_region_with_cset(HeapRegion* r) {
574 _in_cset_fast_test.set_in_old(r->hrm_index());
575 }
576 inline void register_ext_region_with_cset(HeapRegion* r) {
577 _in_cset_fast_test.set_ext(r->hrm_index());
578 }
579 void clear_in_cset(const HeapRegion* hr) {
580 _in_cset_fast_test.clear(hr);
581 }
582
583 void clear_cset_fast_test() {
584 _in_cset_fast_test.clear();
585 }
586
587 bool is_user_requested_concurrent_full_gc(GCCause::Cause cause);
588
589 // This is called at the start of either a concurrent cycle or a Full
590 // GC to update the number of old marking cycles started.
591 void increment_old_marking_cycles_started();
592
593 // This is called at the end of either a concurrent cycle or a Full
594 // GC to update the number of old marking cycles completed. Those two
595 // can happen in a nested fashion, i.e., we start a concurrent
596 // cycle, a Full GC happens half-way through it which ends first,
597 // and then the cycle notices that a Full GC happened and ends
598 // too. The concurrent parameter is a boolean to help us do a bit
599 // tighter consistency checking in the method. If concurrent is
600 // false, the caller is the inner caller in the nesting (i.e., the
601 // Full GC). If concurrent is true, the caller is the outer caller
602 // in this nesting (i.e., the concurrent cycle). Further nesting is
603 // not currently supported. The end of this call also notifies
604 // the FullGCCount_lock in case a Java thread is waiting for a full
605 // GC to happen (e.g., it called System.gc() with
606 // +ExplicitGCInvokesConcurrent).
607 void increment_old_marking_cycles_completed(bool concurrent);
608
609 uint old_marking_cycles_completed() {
610 return _old_marking_cycles_completed;
611 }
612
613 void register_concurrent_cycle_start(const Ticks& start_time);
614 void register_concurrent_cycle_end();
615 void trace_heap_after_concurrent_cycle();
616
617 G1HRPrinter* hr_printer() { return &_hr_printer; }
618
619 // Allocates a new heap region instance.
620 HeapRegion* new_heap_region(uint hrs_index, MemRegion mr);
621
622 // Allocate the highest free region in the reserved heap. This will commit
623 // regions as necessary.
624 HeapRegion* alloc_highest_free_region();
625
626 // Frees a non-humongous region by initializing its contents and
627 // adding it to the free list that's passed as a parameter (this is
628 // usually a local list which will be appended to the master free
629 // list later). The used bytes of freed regions are accumulated in
630 // pre_used. If par is true, the region's RSet will not be freed
631 // up. The assumption is that this will be done later.
632 // The locked parameter indicates if the caller has already taken
633 // care of proper synchronization. This may allow some optimizations.
634 void free_region(HeapRegion* hr,
635 FreeRegionList* free_list,
636 bool par,
637 bool locked = false);
638
639 // It dirties the cards that cover the block so that the post
640 // write barrier never queues anything when updating objects on this
641 // block. It is assumed (and in fact we assert) that the block
642 // belongs to a young region.
643 inline void dirty_young_block(HeapWord* start, size_t word_size);
644
645 // Frees a humongous region by collapsing it into individual regions
646 // and calling free_region() for each of them. The freed regions
647 // will be added to the free list that's passed as a parameter (this
648 // is usually a local list which will be appended to the master free
649 // list later). The used bytes of freed regions are accumulated in
650 // pre_used. If par is true, the region's RSet will not be freed
651 // up. The assumption is that this will be done later.
652 void free_humongous_region(HeapRegion* hr,
653 FreeRegionList* free_list,
654 bool par);
655
656 // Facility for allocating in 'archive' regions in high heap memory and
657 // recording the allocated ranges. These should all be called from the
658 // VM thread at safepoints, without the heap lock held. They can be used
659 // to create and archive a set of heap regions which can be mapped at the
660 // same fixed addresses in a subsequent JVM invocation.
661 void begin_archive_alloc_range();
662
663 // Check if the requested size would be too large for an archive allocation.
664 bool is_archive_alloc_too_large(size_t word_size);
665
666 // Allocate memory of the requested size from the archive region. This will
667 // return NULL if the size is too large or if no memory is available. It
668 // does not trigger a garbage collection.
669 HeapWord* archive_mem_allocate(size_t word_size);
670
671 // Optionally aligns the end address and returns the allocated ranges in
672 // an array of MemRegions in order of ascending addresses.
673 void end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
674 size_t end_alignment_in_bytes = 0);
675
676 // Facility for allocating a fixed range within the heap and marking
677 // the containing regions as 'archive'. For use at JVM init time, when the
678 // caller may mmap archived heap data at the specified range(s).
679 // Verify that the MemRegions specified in the argument array are within the
680 // reserved heap.
681 bool check_archive_addresses(MemRegion* range, size_t count);
682
683 // Commit the appropriate G1 regions containing the specified MemRegions
684 // and mark them as 'archive' regions. The regions in the array must be
685 // non-overlapping and in order of ascending address.
686 bool alloc_archive_regions(MemRegion* range, size_t count);
687
688 // Insert any required filler objects in the G1 regions around the specified
689 // ranges to make the regions parseable. This must be called after
690 // alloc_archive_regions, and after class loading has occurred.
691 void fill_archive_regions(MemRegion* range, size_t count);
692
693 // For each of the specified MemRegions, uncommit the containing G1 regions
694 // which had been allocated by alloc_archive_regions. This should be called
695 // rather than fill_archive_regions at JVM init time if the archive file
696 // mapping failed, with the same non-overlapping and sorted MemRegion array.
697 void dealloc_archive_regions(MemRegion* range, size_t count);
698
699 protected:
700
701 // Shrink the garbage-first heap by at most the given size (in bytes!).
702 // (Rounds down to a HeapRegion boundary.)
703 virtual void shrink(size_t expand_bytes);
704 void shrink_helper(size_t expand_bytes);
705
706 #if TASKQUEUE_STATS
707 static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
708 void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
709 void reset_taskqueue_stats();
710 #endif // TASKQUEUE_STATS
711
712 // Schedule the VM operation that will do an evacuation pause to
713 // satisfy an allocation request of word_size. *succeeded will
714 // return whether the VM operation was successful (it did do an
715 // evacuation pause) or not (another thread beat us to it or the GC
716 // locker was active). Given that we should not be holding the
717 // Heap_lock when we enter this method, we will pass the
718 // gc_count_before (i.e., total_collections()) as a parameter since
719 // it has to be read while holding the Heap_lock. Currently, both
720 // methods that call do_collection_pause() release the Heap_lock
721 // before the call, so it's easy to read gc_count_before just before.
722 HeapWord* do_collection_pause(size_t word_size,
723 uint gc_count_before,
724 bool* succeeded,
725 GCCause::Cause gc_cause);
726
727 void wait_for_root_region_scanning();
728
729 // The guts of the incremental collection pause, executed by the vm
730 // thread. It returns false if it is unable to do the collection due
731 // to the GC locker being active, true otherwise
732 bool do_collection_pause_at_safepoint(double target_pause_time_ms);
733
734 // Actually do the work of evacuating the collection set.
735 virtual void evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states);
736
737 void pre_evacuate_collection_set();
738 void post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* pss);
739
740 // Print the header for the per-thread termination statistics.
741 static void print_termination_stats_hdr(outputStream* const st);
742 // Print actual per-thread termination statistics.
743 void print_termination_stats(outputStream* const st,
744 uint worker_id,
745 double elapsed_ms,
746 double strong_roots_ms,
747 double term_ms,
748 size_t term_attempts,
749 size_t alloc_buffer_waste,
750 size_t undo_waste) const;
751 // Update object copying statistics.
752 void record_obj_copy_mem_stats();
753
754 // The g1 remembered set of the heap.
755 G1RemSet* _g1_rem_set;
756
757 // A set of cards that cover the objects for which the Rsets should be updated
758 // concurrently after the collection.
759 DirtyCardQueueSet _dirty_card_queue_set;
760
761 // The closure used to refine a single card.
762 RefineCardTableEntryClosure* _refine_cte_cl;
763
764 // After a collection pause, make the regions in the CS into free
765 // regions.
766 void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info, const size_t* surviving_young_words);
767
768 // Abandon the current collection set without recording policy
769 // statistics or updating free lists.
770 void abandon_collection_set(HeapRegion* cs_head);
771
772 // The concurrent marker (and the thread it runs in.)
773 ConcurrentMark* _cm;
774 ConcurrentMarkThread* _cmThread;
775
776 // The concurrent refiner.
777 ConcurrentG1Refine* _cg1r;
778
779 // The parallel task queues
780 RefToScanQueueSet *_task_queues;
781
782 // True iff a evacuation has failed in the current collection.
783 bool _evacuation_failed;
784
785 EvacuationFailedInfo* _evacuation_failed_info_array;
786
787 // Failed evacuations cause some logical from-space objects to have
788 // forwarding pointers to themselves. Reset them.
789 void remove_self_forwarding_pointers();
790
791 // Restore the preserved mark words for objects with self-forwarding pointers.
792 void restore_preserved_marks();
793
794 // Restore the objects in the regions in the collection set after an
795 // evacuation failure.
796 void restore_after_evac_failure();
797
798 // Stores marks with the corresponding oop that we need to preserve during evacuation
799 // failure.
800 OopAndMarkOopStack* _preserved_objs;
801
802 // Preserve the mark of "obj", if necessary, in preparation for its mark
803 // word being overwritten with a self-forwarding-pointer.
804 void preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m);
805
806 #ifndef PRODUCT
807 // Support for forcing evacuation failures. Analogous to
808 // PromotionFailureALot for the other collectors.
809
810 // Records whether G1EvacuationFailureALot should be in effect
811 // for the current GC
812 bool _evacuation_failure_alot_for_current_gc;
813
814 // Used to record the GC number for interval checking when
815 // determining whether G1EvaucationFailureALot is in effect
816 // for the current GC.
817 size_t _evacuation_failure_alot_gc_number;
818
819 // Count of the number of evacuations between failures.
820 volatile size_t _evacuation_failure_alot_count;
821
822 // Set whether G1EvacuationFailureALot should be in effect
823 // for the current GC (based upon the type of GC and which
824 // command line flags are set);
825 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
826 bool during_initial_mark,
827 bool during_marking);
828
829 inline void set_evacuation_failure_alot_for_current_gc();
830
831 // Return true if it's time to cause an evacuation failure.
832 inline bool evacuation_should_fail();
833
834 // Reset the G1EvacuationFailureALot counters. Should be called at
835 // the end of an evacuation pause in which an evacuation failure occurred.
836 inline void reset_evacuation_should_fail();
837 #endif // !PRODUCT
838
839 // ("Weak") Reference processing support.
840 //
841 // G1 has 2 instances of the reference processor class. One
842 // (_ref_processor_cm) handles reference object discovery
843 // and subsequent processing during concurrent marking cycles.
844 //
845 // The other (_ref_processor_stw) handles reference object
846 // discovery and processing during full GCs and incremental
847 // evacuation pauses.
848 //
849 // During an incremental pause, reference discovery will be
850 // temporarily disabled for _ref_processor_cm and will be
851 // enabled for _ref_processor_stw. At the end of the evacuation
852 // pause references discovered by _ref_processor_stw will be
853 // processed and discovery will be disabled. The previous
854 // setting for reference object discovery for _ref_processor_cm
855 // will be re-instated.
856 //
857 // At the start of marking:
858 // * Discovery by the CM ref processor is verified to be inactive
859 // and it's discovered lists are empty.
860 // * Discovery by the CM ref processor is then enabled.
861 //
862 // At the end of marking:
863 // * Any references on the CM ref processor's discovered
864 // lists are processed (possibly MT).
865 //
866 // At the start of full GC we:
867 // * Disable discovery by the CM ref processor and
868 // empty CM ref processor's discovered lists
869 // (without processing any entries).
870 // * Verify that the STW ref processor is inactive and it's
871 // discovered lists are empty.
872 // * Temporarily set STW ref processor discovery as single threaded.
873 // * Temporarily clear the STW ref processor's _is_alive_non_header
874 // field.
875 // * Finally enable discovery by the STW ref processor.
876 //
877 // The STW ref processor is used to record any discovered
878 // references during the full GC.
879 //
880 // At the end of a full GC we:
881 // * Enqueue any reference objects discovered by the STW ref processor
882 // that have non-live referents. This has the side-effect of
883 // making the STW ref processor inactive by disabling discovery.
884 // * Verify that the CM ref processor is still inactive
885 // and no references have been placed on it's discovered
886 // lists (also checked as a precondition during initial marking).
887
888 // The (stw) reference processor...
889 ReferenceProcessor* _ref_processor_stw;
890
891 STWGCTimer* _gc_timer_stw;
892 ConcurrentGCTimer* _gc_timer_cm;
893
894 G1OldTracer* _gc_tracer_cm;
895 G1NewTracer* _gc_tracer_stw;
896
897 // During reference object discovery, the _is_alive_non_header
898 // closure (if non-null) is applied to the referent object to
899 // determine whether the referent is live. If so then the
900 // reference object does not need to be 'discovered' and can
901 // be treated as a regular oop. This has the benefit of reducing
902 // the number of 'discovered' reference objects that need to
903 // be processed.
904 //
905 // Instance of the is_alive closure for embedding into the
906 // STW reference processor as the _is_alive_non_header field.
907 // Supplying a value for the _is_alive_non_header field is
908 // optional but doing so prevents unnecessary additions to
909 // the discovered lists during reference discovery.
910 G1STWIsAliveClosure _is_alive_closure_stw;
911
912 // The (concurrent marking) reference processor...
913 ReferenceProcessor* _ref_processor_cm;
914
915 // Instance of the concurrent mark is_alive closure for embedding
916 // into the Concurrent Marking reference processor as the
917 // _is_alive_non_header field. Supplying a value for the
918 // _is_alive_non_header field is optional but doing so prevents
919 // unnecessary additions to the discovered lists during reference
920 // discovery.
921 G1CMIsAliveClosure _is_alive_closure_cm;
922
923 // Cache used by G1CollectedHeap::start_cset_region_for_worker().
924 HeapRegion** _worker_cset_start_region;
925
926 // Time stamp to validate the regions recorded in the cache
927 // used by G1CollectedHeap::start_cset_region_for_worker().
928 // The heap region entry for a given worker is valid iff
929 // the associated time stamp value matches the current value
930 // of G1CollectedHeap::_gc_time_stamp.
931 uint* _worker_cset_start_region_time_stamp;
932
933 volatile bool _free_regions_coming;
934
935 public:
936
937 void set_refine_cte_cl_concurrency(bool concurrent);
938
939 RefToScanQueue *task_queue(uint i) const;
940
941 uint num_task_queues() const;
942
943 // A set of cards where updates happened during the GC
944 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
945
946 // Create a G1CollectedHeap with the specified policy.
947 // Must call the initialize method afterwards.
948 // May not return if something goes wrong.
949 G1CollectedHeap(G1CollectorPolicy* policy);
950
951 // Initialize the G1CollectedHeap to have the initial and
952 // maximum sizes and remembered and barrier sets
953 // specified by the policy object.
954 jint initialize();
955
956 virtual void stop();
957
958 // Return the (conservative) maximum heap alignment for any G1 heap
959 static size_t conservative_max_heap_alignment();
960
961 // Does operations required after initialization has been done.
962 void post_initialize();
963
964 // Initialize weak reference processing.
965 void ref_processing_init();
966
967 virtual Name kind() const {
968 return CollectedHeap::G1CollectedHeap;
969 }
970
971 const G1CollectorState* collector_state() const { return &_collector_state; }
972 G1CollectorState* collector_state() { return &_collector_state; }
973
974 // The current policy object for the collector.
975 G1CollectorPolicy* g1_policy() const { return _g1_policy; }
976
977 virtual CollectorPolicy* collector_policy() const;
978
979 // Adaptive size policy. No such thing for g1.
980 virtual AdaptiveSizePolicy* size_policy() { return NULL; }
981
982 // The rem set and barrier set.
983 G1RemSet* g1_rem_set() const { return _g1_rem_set; }
984
985 unsigned get_gc_time_stamp() {
986 return _gc_time_stamp;
987 }
988
989 inline void reset_gc_time_stamp();
990
991 void check_gc_time_stamps() PRODUCT_RETURN;
992
993 inline void increment_gc_time_stamp();
994
995 // Reset the given region's GC timestamp. If it's starts humongous,
996 // also reset the GC timestamp of its corresponding
997 // continues humongous regions too.
998 void reset_gc_time_stamps(HeapRegion* hr);
999
1000 // Apply the given closure on all cards in the Hot Card Cache, emptying it.
1001 void iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i);
1002
1003 // Apply the given closure on all cards in the Dirty Card Queue Set, emptying it.
1004 void iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i);
1005
1006 // The shared block offset table array.
1007 G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1008
1009 // Reference Processing accessors
1010
1011 // The STW reference processor....
1012 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1013
1014 G1NewTracer* gc_tracer_stw() const { return _gc_tracer_stw; }
1015
1016 // The Concurrent Marking reference processor...
1017 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1018
1019 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1020 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1021
1022 virtual size_t capacity() const;
1023 virtual size_t used() const;
1024 // This should be called when we're not holding the heap lock. The
1025 // result might be a bit inaccurate.
1026 size_t used_unlocked() const;
1027 size_t recalculate_used() const;
1028
1029 // These virtual functions do the actual allocation.
1030 // Some heaps may offer a contiguous region for shared non-blocking
1031 // allocation, via inlined code (by exporting the address of the top and
1032 // end fields defining the extent of the contiguous allocation region.)
1033 // But G1CollectedHeap doesn't yet support this.
1034
1035 virtual bool is_maximal_no_gc() const {
1036 return _hrm.available() == 0;
1037 }
1038
1039 // The current number of regions in the heap.
1040 uint num_regions() const { return _hrm.length(); }
1041
1042 // The max number of regions in the heap.
1043 uint max_regions() const { return _hrm.max_length(); }
1044
1045 // The number of regions that are completely free.
1046 uint num_free_regions() const { return _hrm.num_free_regions(); }
1047
1048 MemoryUsage get_auxiliary_data_memory_usage() const {
1049 return _hrm.get_auxiliary_data_memory_usage();
1050 }
1051
1052 // The number of regions that are not completely free.
1053 uint num_used_regions() const { return num_regions() - num_free_regions(); }
1054
1055 void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1056 void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1057 void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1058 void verify_dirty_young_regions() PRODUCT_RETURN;
1059
1060 #ifndef PRODUCT
1061 // Make sure that the given bitmap has no marked objects in the
1062 // range [from,limit). If it does, print an error message and return
1063 // false. Otherwise, just return true. bitmap_name should be "prev"
1064 // or "next".
1065 bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
1066 HeapWord* from, HeapWord* limit);
1067
1068 // Verify that the prev / next bitmap range [tams,end) for the given
1069 // region has no marks. Return true if all is well, false if errors
1070 // are detected.
1071 bool verify_bitmaps(const char* caller, HeapRegion* hr);
1072 #endif // PRODUCT
1073
1074 // If G1VerifyBitmaps is set, verify that the marking bitmaps for
1075 // the given region do not have any spurious marks. If errors are
1076 // detected, print appropriate error messages and crash.
1077 void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN;
1078
1079 // If G1VerifyBitmaps is set, verify that the marking bitmaps do not
1080 // have any spurious marks. If errors are detected, print
1081 // appropriate error messages and crash.
1082 void check_bitmaps(const char* caller) PRODUCT_RETURN;
1083
1084 // Do sanity check on the contents of the in-cset fast test table.
1085 bool check_cset_fast_test() PRODUCT_RETURN_( return true; );
1086
1087 // verify_region_sets() performs verification over the region
1088 // lists. It will be compiled in the product code to be used when
1089 // necessary (i.e., during heap verification).
1090 void verify_region_sets();
1091
1092 // verify_region_sets_optional() is planted in the code for
1093 // list verification in non-product builds (and it can be enabled in
1094 // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1).
1095 #if HEAP_REGION_SET_FORCE_VERIFY
1096 void verify_region_sets_optional() {
1097 verify_region_sets();
1098 }
1099 #else // HEAP_REGION_SET_FORCE_VERIFY
1100 void verify_region_sets_optional() { }
1101 #endif // HEAP_REGION_SET_FORCE_VERIFY
1102
1103 #ifdef ASSERT
1104 bool is_on_master_free_list(HeapRegion* hr) {
1105 return _hrm.is_free(hr);
1106 }
1107 #endif // ASSERT
1108
1109 // Wrapper for the region list operations that can be called from
1110 // methods outside this class.
1111
1112 void secondary_free_list_add(FreeRegionList* list) {
1113 _secondary_free_list.add_ordered(list);
1114 }
1115
1116 void append_secondary_free_list() {
1117 _hrm.insert_list_into_free_list(&_secondary_free_list);
1118 }
1119
1120 void append_secondary_free_list_if_not_empty_with_lock() {
1121 // If the secondary free list looks empty there's no reason to
1122 // take the lock and then try to append it.
1123 if (!_secondary_free_list.is_empty()) {
1124 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1125 append_secondary_free_list();
1126 }
1127 }
1128
1129 inline void old_set_add(HeapRegion* hr);
1130 inline void old_set_remove(HeapRegion* hr);
1131
1132 size_t non_young_capacity_bytes() {
1133 return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1134 }
1135
1136 void set_free_regions_coming();
1137 void reset_free_regions_coming();
1138 bool free_regions_coming() { return _free_regions_coming; }
1139 void wait_while_free_regions_coming();
1140
1141 // Determine whether the given region is one that we are using as an
1142 // old GC alloc region.
1143 bool is_old_gc_alloc_region(HeapRegion* hr);
1144
1145 // Perform a collection of the heap; intended for use in implementing
1146 // "System.gc". This probably implies as full a collection as the
1147 // "CollectedHeap" supports.
1148 virtual void collect(GCCause::Cause cause);
1149
1150 virtual bool copy_allocation_context_stats(const jint* contexts,
1151 jlong* totals,
1152 jbyte* accuracy,
1153 jint len);
1154
1155 // True iff an evacuation has failed in the most-recent collection.
1156 bool evacuation_failed() { return _evacuation_failed; }
1157
1158 void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed);
1159 void prepend_to_freelist(FreeRegionList* list);
1160 void decrement_summary_bytes(size_t bytes);
1161
1162 virtual bool is_in(const void* p) const;
1163 #ifdef ASSERT
1164 // Returns whether p is in one of the available areas of the heap. Slow but
1165 // extensive version.
1166 bool is_in_exact(const void* p) const;
1167 #endif
1168
1169 // Return "TRUE" iff the given object address is within the collection
1170 // set. Slow implementation.
1171 bool obj_in_cs(oop obj);
1172
1173 inline bool is_in_cset(const HeapRegion *hr);
1174 inline bool is_in_cset(oop obj);
1175
1176 inline bool is_in_cset_or_humongous(const oop obj);
1177
1178 private:
1179 // This array is used for a quick test on whether a reference points into
1180 // the collection set or not. Each of the array's elements denotes whether the
1181 // corresponding region is in the collection set or not.
1182 G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test;
1183
1184 public:
1185
1186 inline InCSetState in_cset_state(const oop obj);
1187
1188 // Return "TRUE" iff the given object address is in the reserved
1189 // region of g1.
1190 bool is_in_g1_reserved(const void* p) const {
1191 return _hrm.reserved().contains(p);
1192 }
1193
1194 // Returns a MemRegion that corresponds to the space that has been
1195 // reserved for the heap
1196 MemRegion g1_reserved() const {
1197 return _hrm.reserved();
1198 }
1199
1200 virtual bool is_in_closed_subset(const void* p) const;
1201
1202 G1SATBCardTableLoggingModRefBS* g1_barrier_set() {
1203 return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set());
1204 }
1205
1206 // This resets the card table to all zeros. It is used after
1207 // a collection pause which used the card table to claim cards.
1208 void cleanUpCardTable();
1209
1210 // Iteration functions.
1211
1212 // Iterate over all objects, calling "cl.do_object" on each.
1213 virtual void object_iterate(ObjectClosure* cl);
1214
1215 virtual void safe_object_iterate(ObjectClosure* cl) {
1216 object_iterate(cl);
1217 }
1218
1219 // Iterate over heap regions, in address order, terminating the
1220 // iteration early if the "doHeapRegion" method returns "true".
1221 void heap_region_iterate(HeapRegionClosure* blk) const;
1222
1223 // Return the region with the given index. It assumes the index is valid.
1224 inline HeapRegion* region_at(uint index) const;
1225
1226 // Return the next region (by index) that is part of the same
1227 // humongous object that hr is part of.
1228 inline HeapRegion* next_region_in_humongous(HeapRegion* hr) const;
1229
1230 // Calculate the region index of the given address. Given address must be
1231 // within the heap.
1232 inline uint addr_to_region(HeapWord* addr) const;
1233
1234 inline HeapWord* bottom_addr_for_region(uint index) const;
1235
1236 // Iterate over the heap regions in parallel. Assumes that this will be called
1237 // in parallel by ParallelGCThreads worker threads with distinct worker ids
1238 // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion"
1239 // to each of the regions, by attempting to claim the region using the
1240 // HeapRegionClaimer and, if successful, applying the closure to the claimed
1241 // region. The concurrent argument should be set to true if iteration is
1242 // performed concurrently, during which no assumptions are made for consistent
1243 // attributes of the heap regions (as they might be modified while iterating).
1244 void heap_region_par_iterate(HeapRegionClosure* cl,
1245 uint worker_id,
1246 HeapRegionClaimer* hrclaimer,
1247 bool concurrent = false) const;
1248
1249 // Clear the cached cset start regions and (more importantly)
1250 // the time stamps. Called when we reset the GC time stamp.
1251 void clear_cset_start_regions();
1252
1253 // Given the id of a worker, obtain or calculate a suitable
1254 // starting region for iterating over the current collection set.
1255 HeapRegion* start_cset_region_for_worker(uint worker_i);
1256
1257 // Iterate over the regions (if any) in the current collection set.
1258 void collection_set_iterate(HeapRegionClosure* blk);
1259
1260 // As above but starting from region r
1261 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1262
1263 HeapRegion* next_compaction_region(const HeapRegion* from) const;
1264
1265 // Returns the HeapRegion that contains addr. addr must not be NULL.
1266 template <class T>
1267 inline HeapRegion* heap_region_containing(const T addr) const;
1268
1269 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1270 // each address in the (reserved) heap is a member of exactly
1271 // one block. The defining characteristic of a block is that it is
1272 // possible to find its size, and thus to progress forward to the next
1273 // block. (Blocks may be of different sizes.) Thus, blocks may
1274 // represent Java objects, or they might be free blocks in a
1275 // free-list-based heap (or subheap), as long as the two kinds are
1276 // distinguishable and the size of each is determinable.
1277
1278 // Returns the address of the start of the "block" that contains the
1279 // address "addr". We say "blocks" instead of "object" since some heaps
1280 // may not pack objects densely; a chunk may either be an object or a
1281 // non-object.
1282 virtual HeapWord* block_start(const void* addr) const;
1283
1284 // Requires "addr" to be the start of a chunk, and returns its size.
1285 // "addr + size" is required to be the start of a new chunk, or the end
1286 // of the active area of the heap.
1287 virtual size_t block_size(const HeapWord* addr) const;
1288
1289 // Requires "addr" to be the start of a block, and returns "TRUE" iff
1290 // the block is an object.
1291 virtual bool block_is_obj(const HeapWord* addr) const;
1292
1293 // Section on thread-local allocation buffers (TLABs)
1294 // See CollectedHeap for semantics.
1295
1296 bool supports_tlab_allocation() const;
1297 size_t tlab_capacity(Thread* ignored) const;
1298 size_t tlab_used(Thread* ignored) const;
1299 size_t max_tlab_size() const;
1300 size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1301
1302 // Can a compiler initialize a new object without store barriers?
1303 // This permission only extends from the creation of a new object
1304 // via a TLAB up to the first subsequent safepoint. If such permission
1305 // is granted for this heap type, the compiler promises to call
1306 // defer_store_barrier() below on any slow path allocation of
1307 // a new object for which such initializing store barriers will
1308 // have been elided. G1, like CMS, allows this, but should be
1309 // ready to provide a compensating write barrier as necessary
1310 // if that storage came out of a non-young region. The efficiency
1311 // of this implementation depends crucially on being able to
1312 // answer very efficiently in constant time whether a piece of
1313 // storage in the heap comes from a young region or not.
1314 // See ReduceInitialCardMarks.
1315 virtual bool can_elide_tlab_store_barriers() const {
1316 return true;
1317 }
1318
1319 virtual bool card_mark_must_follow_store() const {
1320 return true;
1321 }
1322
1323 inline bool is_in_young(const oop obj);
1324
1325 virtual bool is_scavengable(const void* addr);
1326
1327 // We don't need barriers for initializing stores to objects
1328 // in the young gen: for the SATB pre-barrier, there is no
1329 // pre-value that needs to be remembered; for the remembered-set
1330 // update logging post-barrier, we don't maintain remembered set
1331 // information for young gen objects.
1332 virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1333
1334 // Returns "true" iff the given word_size is "very large".
1335 static bool is_humongous(size_t word_size) {
1336 // Note this has to be strictly greater-than as the TLABs
1337 // are capped at the humongous threshold and we want to
1338 // ensure that we don't try to allocate a TLAB as
1339 // humongous and that we don't allocate a humongous
1340 // object in a TLAB.
1341 return word_size > _humongous_object_threshold_in_words;
1342 }
1343
1344 // Returns the humongous threshold for a specific region size
1345 static size_t humongous_threshold_for(size_t region_size) {
1346 return (region_size / 2);
1347 }
1348
1349 // Returns the number of regions the humongous object of the given word size
1350 // requires.
1351 static size_t humongous_obj_size_in_regions(size_t word_size);
1352
1353 // Print the maximum heap capacity.
1354 virtual size_t max_capacity() const;
1355
1356 virtual jlong millis_since_last_gc();
1357
1358
1359 // Convenience function to be used in situations where the heap type can be
1360 // asserted to be this type.
1361 static G1CollectedHeap* heap();
1362
1363 void set_region_short_lived_locked(HeapRegion* hr);
1364 // add appropriate methods for any other surv rate groups
1365
1366 YoungList* young_list() const { return _young_list; }
1367
1368 // debugging
1369 bool check_young_list_well_formed() {
1370 return _young_list->check_list_well_formed();
1371 }
1372
1373 bool check_young_list_empty(bool check_heap,
1374 bool check_sample = true);
1375
1376 // *** Stuff related to concurrent marking. It's not clear to me that so
1377 // many of these need to be public.
1378
1379 // The functions below are helper functions that a subclass of
1380 // "CollectedHeap" can use in the implementation of its virtual
1381 // functions.
1382 // This performs a concurrent marking of the live objects in a
1383 // bitmap off to the side.
1384 void doConcurrentMark();
1385
1386 bool isMarkedPrev(oop obj) const;
1387 bool isMarkedNext(oop obj) const;
1388
1389 // Determine if an object is dead, given the object and also
1390 // the region to which the object belongs. An object is dead
1391 // iff a) it was not allocated since the last mark, b) it
1392 // is not marked, and c) it is not in an archive region.
1393 bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1394 return
1395 !hr->obj_allocated_since_prev_marking(obj) &&
1396 !isMarkedPrev(obj) &&
1397 !hr->is_archive();
1398 }
1399
1400 // This function returns true when an object has been
1401 // around since the previous marking and hasn't yet
1402 // been marked during this marking, and is not in an archive region.
1403 bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1404 return
1405 !hr->obj_allocated_since_next_marking(obj) &&
1406 !isMarkedNext(obj) &&
1407 !hr->is_archive();
1408 }
1409
1410 // Determine if an object is dead, given only the object itself.
1411 // This will find the region to which the object belongs and
1412 // then call the region version of the same function.
1413
1414 // Added if it is NULL it isn't dead.
1415
1416 inline bool is_obj_dead(const oop obj) const;
1417
1418 inline bool is_obj_ill(const oop obj) const;
1419
1420 bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1421 HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1422 bool is_marked(oop obj, VerifyOption vo);
1423 const char* top_at_mark_start_str(VerifyOption vo);
1424
1425 ConcurrentMark* concurrent_mark() const { return _cm; }
1426
1427 // Refinement
1428
1429 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1430
1431 // The dirty cards region list is used to record a subset of regions
1432 // whose cards need clearing. The list if populated during the
1433 // remembered set scanning and drained during the card table
1434 // cleanup. Although the methods are reentrant, population/draining
1435 // phases must not overlap. For synchronization purposes the last
1436 // element on the list points to itself.
1437 HeapRegion* _dirty_cards_region_list;
1438 void push_dirty_cards_region(HeapRegion* hr);
1439 HeapRegion* pop_dirty_cards_region();
1440
1441 // Optimized nmethod scanning support routines
1442
1443 // Register the given nmethod with the G1 heap.
1444 virtual void register_nmethod(nmethod* nm);
1445
1446 // Unregister the given nmethod from the G1 heap.
1447 virtual void unregister_nmethod(nmethod* nm);
1448
1449 // Free up superfluous code root memory.
1450 void purge_code_root_memory();
1451
1452 // Rebuild the strong code root lists for each region
1453 // after a full GC.
1454 void rebuild_strong_code_roots();
1455
1456 // Delete entries for dead interned string and clean up unreferenced symbols
1457 // in symbol table, possibly in parallel.
1458 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1459
1460 // Parallel phase of unloading/cleaning after G1 concurrent mark.
1461 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred);
1462
1463 // Redirty logged cards in the refinement queue.
1464 void redirty_logged_cards();
1465 // Verification
1466
1467 // Perform any cleanup actions necessary before allowing a verification.
1468 virtual void prepare_for_verify();
1469
1470 // Perform verification.
1471
1472 // vo == UsePrevMarking -> use "prev" marking information,
1473 // vo == UseNextMarking -> use "next" marking information
1474 // vo == UseMarkWord -> use the mark word in the object header
1475 //
1476 // NOTE: Only the "prev" marking information is guaranteed to be
1477 // consistent most of the time, so most calls to this should use
1478 // vo == UsePrevMarking.
1479 // Currently, there is only one case where this is called with
1480 // vo == UseNextMarking, which is to verify the "next" marking
1481 // information at the end of remark.
1482 // Currently there is only one place where this is called with
1483 // vo == UseMarkWord, which is to verify the marking during a
1484 // full GC.
1485 void verify(bool silent, VerifyOption vo);
1486
1487 // Override; it uses the "prev" marking information
1488 virtual void verify(bool silent);
1489
1490 // The methods below are here for convenience and dispatch the
1491 // appropriate method depending on value of the given VerifyOption
1492 // parameter. The values for that parameter, and their meanings,
1493 // are the same as those above.
1494
1495 bool is_obj_dead_cond(const oop obj,
1496 const HeapRegion* hr,
1497 const VerifyOption vo) const;
1498
1499 bool is_obj_dead_cond(const oop obj,
1500 const VerifyOption vo) const;
1501
1502 G1HeapSummary create_g1_heap_summary();
1503 G1EvacSummary create_g1_evac_summary(G1EvacStats* stats);
1504
1505 // Printing
1506
1507 virtual void print_on(outputStream* st) const;
1508 virtual void print_extended_on(outputStream* st) const;
1509 virtual void print_on_error(outputStream* st) const;
1510
1511 virtual void print_gc_threads_on(outputStream* st) const;
1512 virtual void gc_threads_do(ThreadClosure* tc) const;
1513
1514 // Override
1515 void print_tracing_info() const;
1516
1517 // The following two methods are helpful for debugging RSet issues.
1518 void print_cset_rsets() PRODUCT_RETURN;
1519 void print_all_rsets() PRODUCT_RETURN;
1520
1521 public:
1522 size_t pending_card_num();
1523
1524 protected:
1525 size_t _max_heap_capacity;
1526 };
1527
1528 class G1ParEvacuateFollowersClosure : public VoidClosure {
1529 private:
1530 double _start_term;
1531 double _term_time;
1532 size_t _term_attempts;
1533
1534 void start_term_time() { _term_attempts++; _start_term = os::elapsedTime(); }
1535 void end_term_time() { _term_time += os::elapsedTime() - _start_term; }
1536 protected:
1537 G1CollectedHeap* _g1h;
1538 G1ParScanThreadState* _par_scan_state;
1539 RefToScanQueueSet* _queues;
1540 ParallelTaskTerminator* _terminator;
1541
1542 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
1543 RefToScanQueueSet* queues() { return _queues; }
1544 ParallelTaskTerminator* terminator() { return _terminator; }
1545
1546 public:
1547 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
1548 G1ParScanThreadState* par_scan_state,
1549 RefToScanQueueSet* queues,
1550 ParallelTaskTerminator* terminator)
1551 : _g1h(g1h), _par_scan_state(par_scan_state),
1552 _queues(queues), _terminator(terminator),
1553 _start_term(0.0), _term_time(0.0), _term_attempts(0) {}
1554
1555 void do_void();
1556
1557 double term_time() const { return _term_time; }
1558 size_t term_attempts() const { return _term_attempts; }
1559
1560 private:
1561 inline bool offer_termination();
1562 };
1563
1564 #endif // SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP