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.
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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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 G1BlockOffsetTable* _bot;
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_footer(jlong pause_time_counter);
294
295 void trace_heap(GCWhen::Type when, const GCTracer* tracer);
296
297 void process_weak_jni_handles();
298
299 // These are macros so that, if the assert fires, we get the correct
300 // line number, file, etc.
301
302 #define heap_locking_asserts_params(_extra_message_) \
303 "%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \
304 (_extra_message_), \
305 BOOL_TO_STR(Heap_lock->owned_by_self()), \
306 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \
307 BOOL_TO_STR(Thread::current()->is_VM_thread())
308
309 #define assert_heap_locked() \
310 do { \
311 assert(Heap_lock->owned_by_self(), \
312 heap_locking_asserts_params("should be holding the Heap_lock")); \
313 } while (0)
314
315 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \
316 do { \
317 assert(Heap_lock->owned_by_self() || \
318 (SafepointSynchronize::is_at_safepoint() && \
319 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
320 heap_locking_asserts_params("should be holding the Heap_lock or " \
321 "should be at a safepoint")); \
322 } while (0)
323
324 #define assert_heap_locked_and_not_at_safepoint() \
325 do { \
326 assert(Heap_lock->owned_by_self() && \
327 !SafepointSynchronize::is_at_safepoint(), \
328 heap_locking_asserts_params("should be holding the Heap_lock and " \
329 "should not be at a safepoint")); \
330 } while (0)
331
332 #define assert_heap_not_locked() \
333 do { \
334 assert(!Heap_lock->owned_by_self(), \
335 heap_locking_asserts_params("should not be holding the Heap_lock")); \
336 } while (0)
337
338 #define assert_heap_not_locked_and_not_at_safepoint() \
339 do { \
340 assert(!Heap_lock->owned_by_self() && \
341 !SafepointSynchronize::is_at_safepoint(), \
342 heap_locking_asserts_params("should not be holding the Heap_lock and " \
343 "should not be at a safepoint")); \
344 } while (0)
345
346 #define assert_at_safepoint(_should_be_vm_thread_) \
347 do { \
348 assert(SafepointSynchronize::is_at_safepoint() && \
349 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
350 heap_locking_asserts_params("should be at a safepoint")); \
351 } while (0)
352
353 #define assert_not_at_safepoint() \
354 do { \
355 assert(!SafepointSynchronize::is_at_safepoint(), \
356 heap_locking_asserts_params("should not be at a safepoint")); \
357 } while (0)
358
359 protected:
360
361 // The young region list.
362 YoungList* _young_list;
363
364 // The current policy object for the collector.
365 G1CollectorPolicy* _g1_policy;
366
367 // This is the second level of trying to allocate a new region. If
368 // new_region() didn't find a region on the free_list, this call will
369 // check whether there's anything available on the
370 // secondary_free_list and/or wait for more regions to appear on
371 // that list, if _free_regions_coming is set.
372 HeapRegion* new_region_try_secondary_free_list(bool is_old);
373
374 // Try to allocate a single non-humongous HeapRegion sufficient for
375 // an allocation of the given word_size. If do_expand is true,
376 // attempt to expand the heap if necessary to satisfy the allocation
377 // request. If the region is to be used as an old region or for a
378 // humongous object, set is_old to true. If not, to false.
379 HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
380
381 // Initialize a contiguous set of free regions of length num_regions
382 // and starting at index first so that they appear as a single
383 // humongous region.
384 HeapWord* humongous_obj_allocate_initialize_regions(uint first,
385 uint num_regions,
386 size_t word_size,
387 AllocationContext_t context);
388
389 // Attempt to allocate a humongous object of the given size. Return
390 // NULL if unsuccessful.
391 HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context);
392
393 // The following two methods, allocate_new_tlab() and
394 // mem_allocate(), are the two main entry points from the runtime
395 // into the G1's allocation routines. They have the following
396 // assumptions:
397 //
398 // * They should both be called outside safepoints.
399 //
400 // * They should both be called without holding the Heap_lock.
401 //
402 // * All allocation requests for new TLABs should go to
403 // allocate_new_tlab().
404 //
405 // * All non-TLAB allocation requests should go to mem_allocate().
406 //
407 // * If either call cannot satisfy the allocation request using the
408 // current allocating region, they will try to get a new one. If
409 // this fails, they will attempt to do an evacuation pause and
410 // retry the allocation.
411 //
412 // * If all allocation attempts fail, even after trying to schedule
413 // an evacuation pause, allocate_new_tlab() will return NULL,
414 // whereas mem_allocate() will attempt a heap expansion and/or
415 // schedule a Full GC.
416 //
417 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
418 // should never be called with word_size being humongous. All
419 // humongous allocation requests should go to mem_allocate() which
420 // will satisfy them with a special path.
421
422 virtual HeapWord* allocate_new_tlab(size_t word_size);
423
424 virtual HeapWord* mem_allocate(size_t word_size,
425 bool* gc_overhead_limit_was_exceeded);
426
427 // The following three methods take a gc_count_before_ret
428 // parameter which is used to return the GC count if the method
429 // returns NULL. Given that we are required to read the GC count
430 // while holding the Heap_lock, and these paths will take the
431 // Heap_lock at some point, it's easier to get them to read the GC
432 // count while holding the Heap_lock before they return NULL instead
433 // of the caller (namely: mem_allocate()) having to also take the
434 // Heap_lock just to read the GC count.
435
436 // First-level mutator allocation attempt: try to allocate out of
437 // the mutator alloc region without taking the Heap_lock. This
438 // should only be used for non-humongous allocations.
439 inline HeapWord* attempt_allocation(size_t word_size,
440 uint* gc_count_before_ret,
441 uint* gclocker_retry_count_ret);
442
443 // Second-level mutator allocation attempt: take the Heap_lock and
444 // retry the allocation attempt, potentially scheduling a GC
445 // pause. This should only be used for non-humongous allocations.
446 HeapWord* attempt_allocation_slow(size_t word_size,
447 AllocationContext_t context,
448 uint* gc_count_before_ret,
449 uint* gclocker_retry_count_ret);
450
451 // Takes the Heap_lock and attempts a humongous allocation. It can
452 // potentially schedule a GC pause.
453 HeapWord* attempt_allocation_humongous(size_t word_size,
454 uint* gc_count_before_ret,
455 uint* gclocker_retry_count_ret);
456
457 // Allocation attempt that should be called during safepoints (e.g.,
458 // at the end of a successful GC). expect_null_mutator_alloc_region
459 // specifies whether the mutator alloc region is expected to be NULL
460 // or not.
461 HeapWord* attempt_allocation_at_safepoint(size_t word_size,
462 AllocationContext_t context,
463 bool expect_null_mutator_alloc_region);
464
465 // These methods are the "callbacks" from the G1AllocRegion class.
466
467 // For mutator alloc regions.
468 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
469 void retire_mutator_alloc_region(HeapRegion* alloc_region,
470 size_t allocated_bytes);
471
472 // For GC alloc regions.
473 HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
474 InCSetState dest);
475 void retire_gc_alloc_region(HeapRegion* alloc_region,
476 size_t allocated_bytes, InCSetState dest);
477
478 // - if explicit_gc is true, the GC is for a System.gc() etc,
479 // otherwise it's for a failed allocation.
480 // - if clear_all_soft_refs is true, all soft references should be
481 // cleared during the GC.
482 // - it returns false if it is unable to do the collection due to the
483 // GC locker being active, true otherwise.
484 bool do_full_collection(bool explicit_gc,
485 bool clear_all_soft_refs);
486
487 // Callback from VM_G1CollectFull operation, or collect_as_vm_thread.
488 virtual void do_full_collection(bool clear_all_soft_refs);
489
490 // Resize the heap if necessary after a full collection.
491 void resize_if_necessary_after_full_collection();
492
493 // Callback from VM_G1CollectForAllocation operation.
494 // This function does everything necessary/possible to satisfy a
495 // failed allocation request (including collection, expansion, etc.)
496 HeapWord* satisfy_failed_allocation(size_t word_size,
497 AllocationContext_t context,
498 bool* succeeded);
499 private:
500 // Helper method for satisfy_failed_allocation()
501 HeapWord* satisfy_failed_allocation_helper(size_t word_size,
502 AllocationContext_t context,
503 bool do_gc,
504 bool clear_all_soft_refs,
505 bool expect_null_mutator_alloc_region,
506 bool* gc_succeeded);
507
508 protected:
509 // Attempting to expand the heap sufficiently
510 // to support an allocation of the given "word_size". If
511 // successful, perform the allocation and return the address of the
512 // allocated block, or else "NULL".
513 HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context);
514
515 // Process any reference objects discovered during
516 // an incremental evacuation pause.
517 void process_discovered_references(G1ParScanThreadStateSet* per_thread_states);
518
519 // Enqueue any remaining discovered references
520 // after processing.
521 void enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states);
522
523 public:
524 WorkGang* workers() const { return _workers; }
525
526 G1Allocator* allocator() {
527 return _allocator;
528 }
529
530 G1MonitoringSupport* g1mm() {
531 assert(_g1mm != NULL, "should have been initialized");
532 return _g1mm;
533 }
534
535 // Expand the garbage-first heap by at least the given size (in bytes!).
536 // Returns true if the heap was expanded by the requested amount;
537 // false otherwise.
538 // (Rounds up to a HeapRegion boundary.)
539 bool expand(size_t expand_bytes, double* expand_time_ms = NULL);
540
541 // Returns the PLAB statistics for a given destination.
542 inline G1EvacStats* alloc_buffer_stats(InCSetState dest);
543
544 // Determines PLAB size for a given destination.
545 inline size_t desired_plab_sz(InCSetState dest);
546
547 inline AllocationContextStats& allocation_context_stats();
548
549 // Do anything common to GC's.
550 void gc_prologue(bool full);
551 void gc_epilogue(bool full);
552
553 // Modify the reclaim candidate set and test for presence.
554 // These are only valid for starts_humongous regions.
555 inline void set_humongous_reclaim_candidate(uint region, bool value);
556 inline bool is_humongous_reclaim_candidate(uint region);
557
558 // Remove from the reclaim candidate set. Also remove from the
559 // collection set so that later encounters avoid the slow path.
560 inline void set_humongous_is_live(oop obj);
561
562 // Register the given region to be part of the collection set.
563 inline void register_humongous_region_with_cset(uint index);
564 // Register regions with humongous objects (actually on the start region) in
565 // the in_cset_fast_test table.
566 void register_humongous_regions_with_cset();
567 // We register a region with the fast "in collection set" test. We
568 // simply set to true the array slot corresponding to this region.
569 void register_young_region_with_cset(HeapRegion* r) {
570 _in_cset_fast_test.set_in_young(r->hrm_index());
571 }
572 void register_old_region_with_cset(HeapRegion* r) {
573 _in_cset_fast_test.set_in_old(r->hrm_index());
574 }
575 inline void register_ext_region_with_cset(HeapRegion* r) {
576 _in_cset_fast_test.set_ext(r->hrm_index());
577 }
578 void clear_in_cset(const HeapRegion* hr) {
579 _in_cset_fast_test.clear(hr);
580 }
581
582 void clear_cset_fast_test() {
583 _in_cset_fast_test.clear();
584 }
585
586 bool is_user_requested_concurrent_full_gc(GCCause::Cause cause);
587
588 // This is called at the start of either a concurrent cycle or a Full
589 // GC to update the number of old marking cycles started.
590 void increment_old_marking_cycles_started();
591
592 // This is called at the end of either a concurrent cycle or a Full
593 // GC to update the number of old marking cycles completed. Those two
594 // can happen in a nested fashion, i.e., we start a concurrent
595 // cycle, a Full GC happens half-way through it which ends first,
596 // and then the cycle notices that a Full GC happened and ends
597 // too. The concurrent parameter is a boolean to help us do a bit
598 // tighter consistency checking in the method. If concurrent is
599 // false, the caller is the inner caller in the nesting (i.e., the
600 // Full GC). If concurrent is true, the caller is the outer caller
601 // in this nesting (i.e., the concurrent cycle). Further nesting is
602 // not currently supported. The end of this call also notifies
603 // the FullGCCount_lock in case a Java thread is waiting for a full
604 // GC to happen (e.g., it called System.gc() with
605 // +ExplicitGCInvokesConcurrent).
606 void increment_old_marking_cycles_completed(bool concurrent);
607
608 uint old_marking_cycles_completed() {
609 return _old_marking_cycles_completed;
610 }
611
612 void register_concurrent_cycle_start(const Ticks& start_time);
613 void register_concurrent_cycle_end();
614 void trace_heap_after_concurrent_cycle();
615
616 G1HRPrinter* hr_printer() { return &_hr_printer; }
617
618 // Allocates a new heap region instance.
619 HeapRegion* new_heap_region(uint hrs_index, MemRegion mr);
620
621 // Allocate the highest free region in the reserved heap. This will commit
622 // regions as necessary.
623 HeapRegion* alloc_highest_free_region();
624
625 // Frees a non-humongous region by initializing its contents and
626 // adding it to the free list that's passed as a parameter (this is
627 // usually a local list which will be appended to the master free
628 // list later). The used bytes of freed regions are accumulated in
629 // pre_used. If par is true, the region's RSet will not be freed
630 // up. The assumption is that this will be done later.
631 // The locked parameter indicates if the caller has already taken
632 // care of proper synchronization. This may allow some optimizations.
633 void free_region(HeapRegion* hr,
634 FreeRegionList* free_list,
635 bool par,
636 bool locked = false);
637
638 // It dirties the cards that cover the block so that the post
639 // write barrier never queues anything when updating objects on this
640 // block. It is assumed (and in fact we assert) that the block
641 // belongs to a young region.
642 inline void dirty_young_block(HeapWord* start, size_t word_size);
643
644 // Frees a humongous region by collapsing it into individual regions
645 // and calling free_region() for each of them. The freed regions
646 // will be added to the free list that's passed as a parameter (this
647 // is usually a local list which will be appended to the master free
648 // list later). The used bytes of freed regions are accumulated in
649 // pre_used. If par is true, the region's RSet will not be freed
650 // up. The assumption is that this will be done later.
651 void free_humongous_region(HeapRegion* hr,
652 FreeRegionList* free_list,
653 bool par);
654
655 // Facility for allocating in 'archive' regions in high heap memory and
656 // recording the allocated ranges. These should all be called from the
657 // VM thread at safepoints, without the heap lock held. They can be used
658 // to create and archive a set of heap regions which can be mapped at the
659 // same fixed addresses in a subsequent JVM invocation.
660 void begin_archive_alloc_range();
661
662 // Check if the requested size would be too large for an archive allocation.
663 bool is_archive_alloc_too_large(size_t word_size);
664
665 // Allocate memory of the requested size from the archive region. This will
666 // return NULL if the size is too large or if no memory is available. It
667 // does not trigger a garbage collection.
668 HeapWord* archive_mem_allocate(size_t word_size);
669
670 // Optionally aligns the end address and returns the allocated ranges in
671 // an array of MemRegions in order of ascending addresses.
672 void end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
673 size_t end_alignment_in_bytes = 0);
674
675 // Facility for allocating a fixed range within the heap and marking
676 // the containing regions as 'archive'. For use at JVM init time, when the
677 // caller may mmap archived heap data at the specified range(s).
678 // Verify that the MemRegions specified in the argument array are within the
679 // reserved heap.
680 bool check_archive_addresses(MemRegion* range, size_t count);
681
682 // Commit the appropriate G1 regions containing the specified MemRegions
683 // and mark them as 'archive' regions. The regions in the array must be
684 // non-overlapping and in order of ascending address.
685 bool alloc_archive_regions(MemRegion* range, size_t count);
686
687 // Insert any required filler objects in the G1 regions around the specified
688 // ranges to make the regions parseable. This must be called after
689 // alloc_archive_regions, and after class loading has occurred.
690 void fill_archive_regions(MemRegion* range, size_t count);
691
692 // For each of the specified MemRegions, uncommit the containing G1 regions
693 // which had been allocated by alloc_archive_regions. This should be called
694 // rather than fill_archive_regions at JVM init time if the archive file
695 // mapping failed, with the same non-overlapping and sorted MemRegion array.
696 void dealloc_archive_regions(MemRegion* range, size_t count);
697
698 protected:
699
700 // Shrink the garbage-first heap by at most the given size (in bytes!).
701 // (Rounds down to a HeapRegion boundary.)
702 virtual void shrink(size_t expand_bytes);
703 void shrink_helper(size_t expand_bytes);
704
705 #if TASKQUEUE_STATS
706 static void print_taskqueue_stats_hdr(outputStream* const st);
707 void print_taskqueue_stats() const;
708 void reset_taskqueue_stats();
709 #endif // TASKQUEUE_STATS
710
711 // Schedule the VM operation that will do an evacuation pause to
712 // satisfy an allocation request of word_size. *succeeded will
713 // return whether the VM operation was successful (it did do an
714 // evacuation pause) or not (another thread beat us to it or the GC
715 // locker was active). Given that we should not be holding the
716 // Heap_lock when we enter this method, we will pass the
717 // gc_count_before (i.e., total_collections()) as a parameter since
718 // it has to be read while holding the Heap_lock. Currently, both
719 // methods that call do_collection_pause() release the Heap_lock
720 // before the call, so it's easy to read gc_count_before just before.
721 HeapWord* do_collection_pause(size_t word_size,
722 uint gc_count_before,
723 bool* succeeded,
724 GCCause::Cause gc_cause);
725
726 void wait_for_root_region_scanning();
727
728 // The guts of the incremental collection pause, executed by the vm
729 // thread. It returns false if it is unable to do the collection due
730 // to the GC locker being active, true otherwise
731 bool do_collection_pause_at_safepoint(double target_pause_time_ms);
732
733 // Actually do the work of evacuating the collection set.
734 virtual void evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states);
735
736 void pre_evacuate_collection_set();
737 void post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* pss);
738
739 // Print the header for the per-thread termination statistics.
740 static void print_termination_stats_hdr();
741 // Print actual per-thread termination statistics.
742 void print_termination_stats(uint worker_id,
743 double elapsed_ms,
744 double strong_roots_ms,
745 double term_ms,
746 size_t term_attempts,
747 size_t alloc_buffer_waste,
748 size_t undo_waste) const;
749 // Update object copying statistics.
750 void record_obj_copy_mem_stats();
751
752 // The g1 remembered set of the heap.
753 G1RemSet* _g1_rem_set;
754
755 // A set of cards that cover the objects for which the Rsets should be updated
756 // concurrently after the collection.
757 DirtyCardQueueSet _dirty_card_queue_set;
758
759 // The closure used to refine a single card.
760 RefineCardTableEntryClosure* _refine_cte_cl;
761
762 // After a collection pause, make the regions in the CS into free
763 // regions.
764 void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info, const size_t* surviving_young_words);
765
766 // Abandon the current collection set without recording policy
767 // statistics or updating free lists.
768 void abandon_collection_set(HeapRegion* cs_head);
769
770 // The concurrent marker (and the thread it runs in.)
771 ConcurrentMark* _cm;
772 ConcurrentMarkThread* _cmThread;
773
774 // The concurrent refiner.
775 ConcurrentG1Refine* _cg1r;
776
777 // The parallel task queues
778 RefToScanQueueSet *_task_queues;
779
780 // True iff a evacuation has failed in the current collection.
781 bool _evacuation_failed;
782
783 EvacuationFailedInfo* _evacuation_failed_info_array;
784
785 // Failed evacuations cause some logical from-space objects to have
786 // forwarding pointers to themselves. Reset them.
787 void remove_self_forwarding_pointers();
788
789 // Restore the preserved mark words for objects with self-forwarding pointers.
790 void restore_preserved_marks();
791
792 // Restore the objects in the regions in the collection set after an
793 // evacuation failure.
794 void restore_after_evac_failure();
795
796 // Stores marks with the corresponding oop that we need to preserve during evacuation
797 // failure.
798 OopAndMarkOopStack* _preserved_objs;
799
800 // Preserve the mark of "obj", if necessary, in preparation for its mark
801 // word being overwritten with a self-forwarding-pointer.
802 void preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m);
803
804 #ifndef PRODUCT
805 // Support for forcing evacuation failures. Analogous to
806 // PromotionFailureALot for the other collectors.
807
808 // Records whether G1EvacuationFailureALot should be in effect
809 // for the current GC
810 bool _evacuation_failure_alot_for_current_gc;
811
812 // Used to record the GC number for interval checking when
813 // determining whether G1EvaucationFailureALot is in effect
814 // for the current GC.
815 size_t _evacuation_failure_alot_gc_number;
816
817 // Count of the number of evacuations between failures.
818 volatile size_t _evacuation_failure_alot_count;
819
820 // Set whether G1EvacuationFailureALot should be in effect
821 // for the current GC (based upon the type of GC and which
822 // command line flags are set);
823 inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
824 bool during_initial_mark,
825 bool during_marking);
826
827 inline void set_evacuation_failure_alot_for_current_gc();
828
829 // Return true if it's time to cause an evacuation failure.
830 inline bool evacuation_should_fail();
831
832 // Reset the G1EvacuationFailureALot counters. Should be called at
833 // the end of an evacuation pause in which an evacuation failure occurred.
834 inline void reset_evacuation_should_fail();
835 #endif // !PRODUCT
836
837 // ("Weak") Reference processing support.
838 //
839 // G1 has 2 instances of the reference processor class. One
840 // (_ref_processor_cm) handles reference object discovery
841 // and subsequent processing during concurrent marking cycles.
842 //
843 // The other (_ref_processor_stw) handles reference object
844 // discovery and processing during full GCs and incremental
845 // evacuation pauses.
846 //
847 // During an incremental pause, reference discovery will be
848 // temporarily disabled for _ref_processor_cm and will be
849 // enabled for _ref_processor_stw. At the end of the evacuation
850 // pause references discovered by _ref_processor_stw will be
851 // processed and discovery will be disabled. The previous
852 // setting for reference object discovery for _ref_processor_cm
853 // will be re-instated.
854 //
855 // At the start of marking:
856 // * Discovery by the CM ref processor is verified to be inactive
857 // and it's discovered lists are empty.
858 // * Discovery by the CM ref processor is then enabled.
859 //
860 // At the end of marking:
861 // * Any references on the CM ref processor's discovered
862 // lists are processed (possibly MT).
863 //
864 // At the start of full GC we:
865 // * Disable discovery by the CM ref processor and
866 // empty CM ref processor's discovered lists
867 // (without processing any entries).
868 // * Verify that the STW ref processor is inactive and it's
869 // discovered lists are empty.
870 // * Temporarily set STW ref processor discovery as single threaded.
871 // * Temporarily clear the STW ref processor's _is_alive_non_header
872 // field.
873 // * Finally enable discovery by the STW ref processor.
874 //
875 // The STW ref processor is used to record any discovered
876 // references during the full GC.
877 //
878 // At the end of a full GC we:
879 // * Enqueue any reference objects discovered by the STW ref processor
880 // that have non-live referents. This has the side-effect of
881 // making the STW ref processor inactive by disabling discovery.
882 // * Verify that the CM ref processor is still inactive
883 // and no references have been placed on it's discovered
884 // lists (also checked as a precondition during initial marking).
885
886 // The (stw) reference processor...
887 ReferenceProcessor* _ref_processor_stw;
888
889 STWGCTimer* _gc_timer_stw;
890 ConcurrentGCTimer* _gc_timer_cm;
891
892 G1OldTracer* _gc_tracer_cm;
893 G1NewTracer* _gc_tracer_stw;
894
895 // During reference object discovery, the _is_alive_non_header
896 // closure (if non-null) is applied to the referent object to
897 // determine whether the referent is live. If so then the
898 // reference object does not need to be 'discovered' and can
899 // be treated as a regular oop. This has the benefit of reducing
900 // the number of 'discovered' reference objects that need to
901 // be processed.
902 //
903 // Instance of the is_alive closure for embedding into the
904 // STW reference processor as the _is_alive_non_header field.
905 // Supplying a value for the _is_alive_non_header field is
906 // optional but doing so prevents unnecessary additions to
907 // the discovered lists during reference discovery.
908 G1STWIsAliveClosure _is_alive_closure_stw;
909
910 // The (concurrent marking) reference processor...
911 ReferenceProcessor* _ref_processor_cm;
912
913 // Instance of the concurrent mark is_alive closure for embedding
914 // into the Concurrent Marking reference processor as the
915 // _is_alive_non_header field. Supplying a value for the
916 // _is_alive_non_header field is optional but doing so prevents
917 // unnecessary additions to the discovered lists during reference
918 // discovery.
919 G1CMIsAliveClosure _is_alive_closure_cm;
920
921 // Cache used by G1CollectedHeap::start_cset_region_for_worker().
922 HeapRegion** _worker_cset_start_region;
923
924 // Time stamp to validate the regions recorded in the cache
925 // used by G1CollectedHeap::start_cset_region_for_worker().
926 // The heap region entry for a given worker is valid iff
927 // the associated time stamp value matches the current value
928 // of G1CollectedHeap::_gc_time_stamp.
929 uint* _worker_cset_start_region_time_stamp;
930
931 volatile bool _free_regions_coming;
932
933 public:
934
935 void set_refine_cte_cl_concurrency(bool concurrent);
936
937 RefToScanQueue *task_queue(uint i) const;
938
939 uint num_task_queues() const;
940
941 // A set of cards where updates happened during the GC
942 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
943
944 // Create a G1CollectedHeap with the specified policy.
945 // Must call the initialize method afterwards.
946 // May not return if something goes wrong.
947 G1CollectedHeap(G1CollectorPolicy* policy);
948
949 // Initialize the G1CollectedHeap to have the initial and
950 // maximum sizes and remembered and barrier sets
951 // specified by the policy object.
952 jint initialize();
953
954 virtual void stop();
955
956 // Return the (conservative) maximum heap alignment for any G1 heap
957 static size_t conservative_max_heap_alignment();
958
959 // Does operations required after initialization has been done.
960 void post_initialize();
961
962 // Initialize weak reference processing.
963 void ref_processing_init();
964
965 virtual Name kind() const {
966 return CollectedHeap::G1CollectedHeap;
967 }
968
969 virtual const char* name() const {
970 return "G1";
971 }
972
973 const G1CollectorState* collector_state() const { return &_collector_state; }
974 G1CollectorState* collector_state() { return &_collector_state; }
975
976 // The current policy object for the collector.
977 G1CollectorPolicy* g1_policy() const { return _g1_policy; }
978
979 virtual CollectorPolicy* collector_policy() const;
980
981 // Adaptive size policy. No such thing for g1.
982 virtual AdaptiveSizePolicy* size_policy() { return NULL; }
983
984 // The rem set and barrier set.
985 G1RemSet* g1_rem_set() const { return _g1_rem_set; }
986
987 void scrub_rem_set(BitMap* region_bm, BitMap* card_bm);
988
989 unsigned get_gc_time_stamp() {
990 return _gc_time_stamp;
991 }
992
993 inline void reset_gc_time_stamp();
994
995 void check_gc_time_stamps() PRODUCT_RETURN;
996
997 inline void increment_gc_time_stamp();
998
999 // Reset the given region's GC timestamp. If it's starts humongous,
1000 // also reset the GC timestamp of its corresponding
1001 // continues humongous regions too.
1002 void reset_gc_time_stamps(HeapRegion* hr);
1003
1004 // Apply the given closure on all cards in the Hot Card Cache, emptying it.
1005 void iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i);
1006
1007 // Apply the given closure on all cards in the Dirty Card Queue Set, emptying it.
1008 void iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i);
1009
1010 // The shared block offset table array.
1011 G1BlockOffsetTable* bot() const { return _bot; }
1012
1013 // Reference Processing accessors
1014
1015 // The STW reference processor....
1016 ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1017
1018 G1NewTracer* gc_tracer_stw() const { return _gc_tracer_stw; }
1019
1020 // The Concurrent Marking reference processor...
1021 ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1022
1023 ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1024 G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1025
1026 virtual size_t capacity() const;
1027 virtual size_t used() const;
1028 // This should be called when we're not holding the heap lock. The
1029 // result might be a bit inaccurate.
1030 size_t used_unlocked() const;
1031 size_t recalculate_used() const;
1032
1033 // These virtual functions do the actual allocation.
1034 // Some heaps may offer a contiguous region for shared non-blocking
1035 // allocation, via inlined code (by exporting the address of the top and
1036 // end fields defining the extent of the contiguous allocation region.)
1037 // But G1CollectedHeap doesn't yet support this.
1038
1039 virtual bool is_maximal_no_gc() const {
1040 return _hrm.available() == 0;
1041 }
1042
1043 // The current number of regions in the heap.
1044 uint num_regions() const { return _hrm.length(); }
1045
1046 // The max number of regions in the heap.
1047 uint max_regions() const { return _hrm.max_length(); }
1048
1049 // The number of regions that are completely free.
1050 uint num_free_regions() const { return _hrm.num_free_regions(); }
1051
1052 MemoryUsage get_auxiliary_data_memory_usage() const {
1053 return _hrm.get_auxiliary_data_memory_usage();
1054 }
1055
1056 // The number of regions that are not completely free.
1057 uint num_used_regions() const { return num_regions() - num_free_regions(); }
1058
1059 void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1060 void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1061 void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1062 void verify_dirty_young_regions() PRODUCT_RETURN;
1063
1064 #ifndef PRODUCT
1065 // Make sure that the given bitmap has no marked objects in the
1066 // range [from,limit). If it does, print an error message and return
1067 // false. Otherwise, just return true. bitmap_name should be "prev"
1068 // or "next".
1069 bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
1070 HeapWord* from, HeapWord* limit);
1071
1072 // Verify that the prev / next bitmap range [tams,end) for the given
1073 // region has no marks. Return true if all is well, false if errors
1074 // are detected.
1075 bool verify_bitmaps(const char* caller, HeapRegion* hr);
1076 #endif // PRODUCT
1077
1078 // If G1VerifyBitmaps is set, verify that the marking bitmaps for
1079 // the given region do not have any spurious marks. If errors are
1080 // detected, print appropriate error messages and crash.
1081 void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN;
1082
1083 // If G1VerifyBitmaps is set, verify that the marking bitmaps do not
1084 // have any spurious marks. If errors are detected, print
1085 // appropriate error messages and crash.
1086 void check_bitmaps(const char* caller) PRODUCT_RETURN;
1087
1088 // Do sanity check on the contents of the in-cset fast test table.
1089 bool check_cset_fast_test() PRODUCT_RETURN_( return true; );
1090
1091 // verify_region_sets() performs verification over the region
1092 // lists. It will be compiled in the product code to be used when
1093 // necessary (i.e., during heap verification).
1094 void verify_region_sets();
1095
1096 // verify_region_sets_optional() is planted in the code for
1097 // list verification in non-product builds (and it can be enabled in
1098 // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1).
1099 #if HEAP_REGION_SET_FORCE_VERIFY
1100 void verify_region_sets_optional() {
1101 verify_region_sets();
1102 }
1103 #else // HEAP_REGION_SET_FORCE_VERIFY
1104 void verify_region_sets_optional() { }
1105 #endif // HEAP_REGION_SET_FORCE_VERIFY
1106
1107 #ifdef ASSERT
1108 bool is_on_master_free_list(HeapRegion* hr) {
1109 return _hrm.is_free(hr);
1110 }
1111 #endif // ASSERT
1112
1113 // Wrapper for the region list operations that can be called from
1114 // methods outside this class.
1115
1116 void secondary_free_list_add(FreeRegionList* list) {
1117 _secondary_free_list.add_ordered(list);
1118 }
1119
1120 void append_secondary_free_list() {
1121 _hrm.insert_list_into_free_list(&_secondary_free_list);
1122 }
1123
1124 void append_secondary_free_list_if_not_empty_with_lock() {
1125 // If the secondary free list looks empty there's no reason to
1126 // take the lock and then try to append it.
1127 if (!_secondary_free_list.is_empty()) {
1128 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1129 append_secondary_free_list();
1130 }
1131 }
1132
1133 inline void old_set_add(HeapRegion* hr);
1134 inline void old_set_remove(HeapRegion* hr);
1135
1136 size_t non_young_capacity_bytes() {
1137 return (_old_set.length() + _humongous_set.length()) * HeapRegion::GrainBytes;
1138 }
1139
1140 void set_free_regions_coming();
1141 void reset_free_regions_coming();
1142 bool free_regions_coming() { return _free_regions_coming; }
1143 void wait_while_free_regions_coming();
1144
1145 // Determine whether the given region is one that we are using as an
1146 // old GC alloc region.
1147 bool is_old_gc_alloc_region(HeapRegion* hr);
1148
1149 // Perform a collection of the heap; intended for use in implementing
1150 // "System.gc". This probably implies as full a collection as the
1151 // "CollectedHeap" supports.
1152 virtual void collect(GCCause::Cause cause);
1153
1154 virtual bool copy_allocation_context_stats(const jint* contexts,
1155 jlong* totals,
1156 jbyte* accuracy,
1157 jint len);
1158
1159 // True iff an evacuation has failed in the most-recent collection.
1160 bool evacuation_failed() { return _evacuation_failed; }
1161
1162 void remove_from_old_sets(const uint old_regions_removed, const uint humongous_regions_removed);
1163 void prepend_to_freelist(FreeRegionList* list);
1164 void decrement_summary_bytes(size_t bytes);
1165
1166 virtual bool is_in(const void* p) const;
1167 #ifdef ASSERT
1168 // Returns whether p is in one of the available areas of the heap. Slow but
1169 // extensive version.
1170 bool is_in_exact(const void* p) const;
1171 #endif
1172
1173 // Return "TRUE" iff the given object address is within the collection
1174 // set. Slow implementation.
1175 bool obj_in_cs(oop obj);
1176
1177 inline bool is_in_cset(const HeapRegion *hr);
1178 inline bool is_in_cset(oop obj);
1179
1180 inline bool is_in_cset_or_humongous(const oop obj);
1181
1182 private:
1183 // This array is used for a quick test on whether a reference points into
1184 // the collection set or not. Each of the array's elements denotes whether the
1185 // corresponding region is in the collection set or not.
1186 G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test;
1187
1188 public:
1189
1190 inline InCSetState in_cset_state(const oop obj);
1191
1192 // Return "TRUE" iff the given object address is in the reserved
1193 // region of g1.
1194 bool is_in_g1_reserved(const void* p) const {
1195 return _hrm.reserved().contains(p);
1196 }
1197
1198 // Returns a MemRegion that corresponds to the space that has been
1199 // reserved for the heap
1200 MemRegion g1_reserved() const {
1201 return _hrm.reserved();
1202 }
1203
1204 virtual bool is_in_closed_subset(const void* p) const;
1205
1206 G1SATBCardTableLoggingModRefBS* g1_barrier_set() {
1207 return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set());
1208 }
1209
1210 // This resets the card table to all zeros. It is used after
1211 // a collection pause which used the card table to claim cards.
1212 void cleanUpCardTable();
1213
1214 // Iteration functions.
1215
1216 // Iterate over all objects, calling "cl.do_object" on each.
1217 virtual void object_iterate(ObjectClosure* cl);
1218
1219 virtual void safe_object_iterate(ObjectClosure* cl) {
1220 object_iterate(cl);
1221 }
1222
1223 // Iterate over heap regions, in address order, terminating the
1224 // iteration early if the "doHeapRegion" method returns "true".
1225 void heap_region_iterate(HeapRegionClosure* blk) const;
1226
1227 // Return the region with the given index. It assumes the index is valid.
1228 inline HeapRegion* region_at(uint index) const;
1229
1230 // Return the next region (by index) that is part of the same
1231 // humongous object that hr is part of.
1232 inline HeapRegion* next_region_in_humongous(HeapRegion* hr) const;
1233
1234 // Calculate the region index of the given address. Given address must be
1235 // within the heap.
1236 inline uint addr_to_region(HeapWord* addr) const;
1237
1238 inline HeapWord* bottom_addr_for_region(uint index) const;
1239
1240 // Iterate over the heap regions in parallel. Assumes that this will be called
1241 // in parallel by ParallelGCThreads worker threads with distinct worker ids
1242 // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion"
1243 // to each of the regions, by attempting to claim the region using the
1244 // HeapRegionClaimer and, if successful, applying the closure to the claimed
1245 // region. The concurrent argument should be set to true if iteration is
1246 // performed concurrently, during which no assumptions are made for consistent
1247 // attributes of the heap regions (as they might be modified while iterating).
1248 void heap_region_par_iterate(HeapRegionClosure* cl,
1249 uint worker_id,
1250 HeapRegionClaimer* hrclaimer,
1251 bool concurrent = false) const;
1252
1253 // Clear the cached cset start regions and (more importantly)
1254 // the time stamps. Called when we reset the GC time stamp.
1255 void clear_cset_start_regions();
1256
1257 // Given the id of a worker, obtain or calculate a suitable
1258 // starting region for iterating over the current collection set.
1259 HeapRegion* start_cset_region_for_worker(uint worker_i);
1260
1261 // Iterate over the regions (if any) in the current collection set.
1262 void collection_set_iterate(HeapRegionClosure* blk);
1263
1264 // As above but starting from region r
1265 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1266
1267 HeapRegion* next_compaction_region(const HeapRegion* from) const;
1268
1269 // Returns the HeapRegion that contains addr. addr must not be NULL.
1270 template <class T>
1271 inline HeapRegion* heap_region_containing(const T addr) const;
1272
1273 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1274 // each address in the (reserved) heap is a member of exactly
1275 // one block. The defining characteristic of a block is that it is
1276 // possible to find its size, and thus to progress forward to the next
1277 // block. (Blocks may be of different sizes.) Thus, blocks may
1278 // represent Java objects, or they might be free blocks in a
1279 // free-list-based heap (or subheap), as long as the two kinds are
1280 // distinguishable and the size of each is determinable.
1281
1282 // Returns the address of the start of the "block" that contains the
1283 // address "addr". We say "blocks" instead of "object" since some heaps
1284 // may not pack objects densely; a chunk may either be an object or a
1285 // non-object.
1286 virtual HeapWord* block_start(const void* addr) const;
1287
1288 // Requires "addr" to be the start of a chunk, and returns its size.
1289 // "addr + size" is required to be the start of a new chunk, or the end
1290 // of the active area of the heap.
1291 virtual size_t block_size(const HeapWord* addr) const;
1292
1293 // Requires "addr" to be the start of a block, and returns "TRUE" iff
1294 // the block is an object.
1295 virtual bool block_is_obj(const HeapWord* addr) const;
1296
1297 // Section on thread-local allocation buffers (TLABs)
1298 // See CollectedHeap for semantics.
1299
1300 bool supports_tlab_allocation() const;
1301 size_t tlab_capacity(Thread* ignored) const;
1302 size_t tlab_used(Thread* ignored) const;
1303 size_t max_tlab_size() const;
1304 size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1305
1306 // Can a compiler initialize a new object without store barriers?
1307 // This permission only extends from the creation of a new object
1308 // via a TLAB up to the first subsequent safepoint. If such permission
1309 // is granted for this heap type, the compiler promises to call
1310 // defer_store_barrier() below on any slow path allocation of
1311 // a new object for which such initializing store barriers will
1312 // have been elided. G1, like CMS, allows this, but should be
1313 // ready to provide a compensating write barrier as necessary
1314 // if that storage came out of a non-young region. The efficiency
1315 // of this implementation depends crucially on being able to
1316 // answer very efficiently in constant time whether a piece of
1317 // storage in the heap comes from a young region or not.
1318 // See ReduceInitialCardMarks.
1319 virtual bool can_elide_tlab_store_barriers() const {
1320 return true;
1321 }
1322
1323 virtual bool card_mark_must_follow_store() const {
1324 return true;
1325 }
1326
1327 inline bool is_in_young(const oop obj);
1328
1329 virtual bool is_scavengable(const void* addr);
1330
1331 // We don't need barriers for initializing stores to objects
1332 // in the young gen: for the SATB pre-barrier, there is no
1333 // pre-value that needs to be remembered; for the remembered-set
1334 // update logging post-barrier, we don't maintain remembered set
1335 // information for young gen objects.
1336 virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1337
1338 // Returns "true" iff the given word_size is "very large".
1339 static bool is_humongous(size_t word_size) {
1340 // Note this has to be strictly greater-than as the TLABs
1341 // are capped at the humongous threshold and we want to
1342 // ensure that we don't try to allocate a TLAB as
1343 // humongous and that we don't allocate a humongous
1344 // object in a TLAB.
1345 return word_size > _humongous_object_threshold_in_words;
1346 }
1347
1348 // Returns the humongous threshold for a specific region size
1349 static size_t humongous_threshold_for(size_t region_size) {
1350 return (region_size / 2);
1351 }
1352
1353 // Returns the number of regions the humongous object of the given word size
1354 // requires.
1355 static size_t humongous_obj_size_in_regions(size_t word_size);
1356
1357 // Print the maximum heap capacity.
1358 virtual size_t max_capacity() const;
1359
1360 virtual jlong millis_since_last_gc();
1361
1362
1363 // Convenience function to be used in situations where the heap type can be
1364 // asserted to be this type.
1365 static G1CollectedHeap* heap();
1366
1367 void set_region_short_lived_locked(HeapRegion* hr);
1368 // add appropriate methods for any other surv rate groups
1369
1370 YoungList* young_list() const { return _young_list; }
1371
1372 uint old_regions_count() const { return _old_set.length(); }
1373
1374 uint humongous_regions_count() const { return _humongous_set.length(); }
1375
1376 // debugging
1377 bool check_young_list_well_formed() {
1378 return _young_list->check_list_well_formed();
1379 }
1380
1381 bool check_young_list_empty(bool check_heap,
1382 bool check_sample = true);
1383
1384 // *** Stuff related to concurrent marking. It's not clear to me that so
1385 // many of these need to be public.
1386
1387 // The functions below are helper functions that a subclass of
1388 // "CollectedHeap" can use in the implementation of its virtual
1389 // functions.
1390 // This performs a concurrent marking of the live objects in a
1391 // bitmap off to the side.
1392 void doConcurrentMark();
1393
1394 bool isMarkedPrev(oop obj) const;
1395 bool isMarkedNext(oop obj) const;
1396
1397 // Determine if an object is dead, given the object and also
1398 // the region to which the object belongs. An object is dead
1399 // iff a) it was not allocated since the last mark, b) it
1400 // is not marked, and c) it is not in an archive region.
1401 bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1402 return
1403 !hr->obj_allocated_since_prev_marking(obj) &&
1404 !isMarkedPrev(obj) &&
1405 !hr->is_archive();
1406 }
1407
1408 // This function returns true when an object has been
1409 // around since the previous marking and hasn't yet
1410 // been marked during this marking, and is not in an archive region.
1411 bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1412 return
1413 !hr->obj_allocated_since_next_marking(obj) &&
1414 !isMarkedNext(obj) &&
1415 !hr->is_archive();
1416 }
1417
1418 // Determine if an object is dead, given only the object itself.
1419 // This will find the region to which the object belongs and
1420 // then call the region version of the same function.
1421
1422 // Added if it is NULL it isn't dead.
1423
1424 inline bool is_obj_dead(const oop obj) const;
1425
1426 inline bool is_obj_ill(const oop obj) const;
1427
1428 bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1429 HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1430 bool is_marked(oop obj, VerifyOption vo);
1431 const char* top_at_mark_start_str(VerifyOption vo);
1432
1433 ConcurrentMark* concurrent_mark() const { return _cm; }
1434
1435 // Refinement
1436
1437 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1438
1439 // The dirty cards region list is used to record a subset of regions
1440 // whose cards need clearing. The list if populated during the
1441 // remembered set scanning and drained during the card table
1442 // cleanup. Although the methods are reentrant, population/draining
1443 // phases must not overlap. For synchronization purposes the last
1444 // element on the list points to itself.
1445 HeapRegion* _dirty_cards_region_list;
1446 void push_dirty_cards_region(HeapRegion* hr);
1447 HeapRegion* pop_dirty_cards_region();
1448
1449 // Optimized nmethod scanning support routines
1450
1451 // Register the given nmethod with the G1 heap.
1452 virtual void register_nmethod(nmethod* nm);
1453
1454 // Unregister the given nmethod from the G1 heap.
1455 virtual void unregister_nmethod(nmethod* nm);
1456
1457 // Free up superfluous code root memory.
1458 void purge_code_root_memory();
1459
1460 // Rebuild the strong code root lists for each region
1461 // after a full GC.
1462 void rebuild_strong_code_roots();
1463
1464 // Delete entries for dead interned string and clean up unreferenced symbols
1465 // in symbol table, possibly in parallel.
1466 void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1467
1468 // Parallel phase of unloading/cleaning after G1 concurrent mark.
1469 void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred);
1470
1471 // Redirty logged cards in the refinement queue.
1472 void redirty_logged_cards();
1473 // Verification
1474
1475 // Perform any cleanup actions necessary before allowing a verification.
1476 virtual void prepare_for_verify();
1477
1478 // Perform verification.
1479
1480 // vo == UsePrevMarking -> use "prev" marking information,
1481 // vo == UseNextMarking -> use "next" marking information
1482 // vo == UseMarkWord -> use the mark word in the object header
1483 //
1484 // NOTE: Only the "prev" marking information is guaranteed to be
1485 // consistent most of the time, so most calls to this should use
1486 // vo == UsePrevMarking.
1487 // Currently, there is only one case where this is called with
1488 // vo == UseNextMarking, which is to verify the "next" marking
1489 // information at the end of remark.
1490 // Currently there is only one place where this is called with
1491 // vo == UseMarkWord, which is to verify the marking during a
1492 // full GC.
1493 void verify(VerifyOption vo);
1494
1495 // The methods below are here for convenience and dispatch the
1496 // appropriate method depending on value of the given VerifyOption
1497 // parameter. The values for that parameter, and their meanings,
1498 // are the same as those above.
1499
1500 bool is_obj_dead_cond(const oop obj,
1501 const HeapRegion* hr,
1502 const VerifyOption vo) const;
1503
1504 bool is_obj_dead_cond(const oop obj,
1505 const VerifyOption vo) const;
1506
1507 G1HeapSummary create_g1_heap_summary();
1508 G1EvacSummary create_g1_evac_summary(G1EvacStats* stats);
1509
1510 // Printing
1511
1512 virtual void print_on(outputStream* st) const;
1513 virtual void print_extended_on(outputStream* st) const;
1514 virtual void print_on_error(outputStream* st) const;
1515
1516 virtual void print_gc_threads_on(outputStream* st) const;
1517 virtual void gc_threads_do(ThreadClosure* tc) const;
1518
1519 // Override
1520 void print_tracing_info() const;
1521
1522 // The following two methods are helpful for debugging RSet issues.
1523 void print_cset_rsets() PRODUCT_RETURN;
1524 void print_all_rsets() PRODUCT_RETURN;
1525
1526 public:
1527 size_t pending_card_num();
1528
1529 protected:
1530 size_t _max_heap_capacity;
1531 };
1532
1533 class G1ParEvacuateFollowersClosure : public VoidClosure {
1534 private:
1535 double _start_term;
1536 double _term_time;
1537 size_t _term_attempts;
1538
1539 void start_term_time() { _term_attempts++; _start_term = os::elapsedTime(); }
1540 void end_term_time() { _term_time += os::elapsedTime() - _start_term; }
1541 protected:
1542 G1CollectedHeap* _g1h;
1543 G1ParScanThreadState* _par_scan_state;
1544 RefToScanQueueSet* _queues;
1545 ParallelTaskTerminator* _terminator;
1546
1547 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
1548 RefToScanQueueSet* queues() { return _queues; }
1549 ParallelTaskTerminator* terminator() { return _terminator; }
1550
1551 public:
1552 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
1553 G1ParScanThreadState* par_scan_state,
1554 RefToScanQueueSet* queues,
1555 ParallelTaskTerminator* terminator)
1556 : _g1h(g1h), _par_scan_state(par_scan_state),
1557 _queues(queues), _terminator(terminator),
1558 _start_term(0.0), _term_time(0.0), _term_attempts(0) {}
1559
1560 void do_void();
1561
1562 double term_time() const { return _term_time; }
1563 size_t term_attempts() const { return _term_attempts; }
1564
1565 private:
1566 inline bool offer_termination();
1567 };
1568
1569 #endif // SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP