Mon, 31 Aug 2009 05:27:29 -0700
6841313: G1: dirty cards of survivor regions in parallel
Reviewed-by: tonyp, iveresov
1 /*
2 * Copyright 2001-2009 Sun Microsystems, Inc. All Rights Reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
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23 */
25 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
26 // It uses the "Garbage First" heap organization and algorithm, which
27 // may combine concurrent marking with parallel, incremental compaction of
28 // heap subsets that will yield large amounts of garbage.
30 class HeapRegion;
31 class HeapRegionSeq;
32 class PermanentGenerationSpec;
33 class GenerationSpec;
34 class OopsInHeapRegionClosure;
35 class G1ScanHeapEvacClosure;
36 class ObjectClosure;
37 class SpaceClosure;
38 class CompactibleSpaceClosure;
39 class Space;
40 class G1CollectorPolicy;
41 class GenRemSet;
42 class G1RemSet;
43 class HeapRegionRemSetIterator;
44 class ConcurrentMark;
45 class ConcurrentMarkThread;
46 class ConcurrentG1Refine;
47 class ConcurrentZFThread;
49 // If want to accumulate detailed statistics on work queues
50 // turn this on.
51 #define G1_DETAILED_STATS 0
53 #if G1_DETAILED_STATS
54 # define IF_G1_DETAILED_STATS(code) code
55 #else
56 # define IF_G1_DETAILED_STATS(code)
57 #endif
59 typedef GenericTaskQueue<StarTask> RefToScanQueue;
60 typedef GenericTaskQueueSet<StarTask> RefToScanQueueSet;
62 typedef int RegionIdx_t; // needs to hold [ 0..max_regions() )
63 typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion )
65 enum G1GCThreadGroups {
66 G1CRGroup = 0,
67 G1ZFGroup = 1,
68 G1CMGroup = 2,
69 G1CLGroup = 3
70 };
72 enum GCAllocPurpose {
73 GCAllocForTenured,
74 GCAllocForSurvived,
75 GCAllocPurposeCount
76 };
78 class YoungList : public CHeapObj {
79 private:
80 G1CollectedHeap* _g1h;
82 HeapRegion* _head;
84 HeapRegion* _scan_only_head;
85 HeapRegion* _scan_only_tail;
86 size_t _length;
87 size_t _scan_only_length;
89 size_t _last_sampled_rs_lengths;
90 size_t _sampled_rs_lengths;
91 HeapRegion* _curr;
92 HeapRegion* _curr_scan_only;
94 HeapRegion* _survivor_head;
95 HeapRegion* _survivor_tail;
96 size_t _survivor_length;
98 void empty_list(HeapRegion* list);
100 public:
101 YoungList(G1CollectedHeap* g1h);
103 void push_region(HeapRegion* hr);
104 void add_survivor_region(HeapRegion* hr);
105 HeapRegion* pop_region();
106 void empty_list();
107 bool is_empty() { return _length == 0; }
108 size_t length() { return _length; }
109 size_t scan_only_length() { return _scan_only_length; }
110 size_t survivor_length() { return _survivor_length; }
112 void rs_length_sampling_init();
113 bool rs_length_sampling_more();
114 void rs_length_sampling_next();
116 void reset_sampled_info() {
117 _last_sampled_rs_lengths = 0;
118 }
119 size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
121 // for development purposes
122 void reset_auxilary_lists();
123 HeapRegion* first_region() { return _head; }
124 HeapRegion* first_scan_only_region() { return _scan_only_head; }
125 HeapRegion* first_survivor_region() { return _survivor_head; }
126 HeapRegion* last_survivor_region() { return _survivor_tail; }
127 HeapRegion* par_get_next_scan_only_region() {
128 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
129 HeapRegion* ret = _curr_scan_only;
130 if (ret != NULL)
131 _curr_scan_only = ret->get_next_young_region();
132 return ret;
133 }
135 // debugging
136 bool check_list_well_formed();
137 bool check_list_empty(bool ignore_scan_only_list,
138 bool check_sample = true);
139 void print();
140 };
142 class RefineCardTableEntryClosure;
143 class G1CollectedHeap : public SharedHeap {
144 friend class VM_G1CollectForAllocation;
145 friend class VM_GenCollectForPermanentAllocation;
146 friend class VM_G1CollectFull;
147 friend class VM_G1IncCollectionPause;
148 friend class VMStructs;
150 // Closures used in implementation.
151 friend class G1ParCopyHelper;
152 friend class G1IsAliveClosure;
153 friend class G1EvacuateFollowersClosure;
154 friend class G1ParScanThreadState;
155 friend class G1ParScanClosureSuper;
156 friend class G1ParEvacuateFollowersClosure;
157 friend class G1ParTask;
158 friend class G1FreeGarbageRegionClosure;
159 friend class RefineCardTableEntryClosure;
160 friend class G1PrepareCompactClosure;
161 friend class RegionSorter;
162 friend class CountRCClosure;
163 friend class EvacPopObjClosure;
164 friend class G1ParCleanupCTTask;
166 // Other related classes.
167 friend class G1MarkSweep;
169 private:
170 enum SomePrivateConstants {
171 VeryLargeInBytes = HeapRegion::GrainBytes/2,
172 VeryLargeInWords = VeryLargeInBytes/HeapWordSize,
173 MinHeapDeltaBytes = 10 * HeapRegion::GrainBytes, // FIXME
174 NumAPIs = HeapRegion::MaxAge
175 };
177 // The one and only G1CollectedHeap, so static functions can find it.
178 static G1CollectedHeap* _g1h;
180 // Storage for the G1 heap (excludes the permanent generation).
181 VirtualSpace _g1_storage;
182 MemRegion _g1_reserved;
184 // The part of _g1_storage that is currently committed.
185 MemRegion _g1_committed;
187 // The maximum part of _g1_storage that has ever been committed.
188 MemRegion _g1_max_committed;
190 // The number of regions that are completely free.
191 size_t _free_regions;
193 // The number of regions we could create by expansion.
194 size_t _expansion_regions;
196 // Return the number of free regions in the heap (by direct counting.)
197 size_t count_free_regions();
198 // Return the number of free regions on the free and unclean lists.
199 size_t count_free_regions_list();
201 // The block offset table for the G1 heap.
202 G1BlockOffsetSharedArray* _bot_shared;
204 // Move all of the regions off the free lists, then rebuild those free
205 // lists, before and after full GC.
206 void tear_down_region_lists();
207 void rebuild_region_lists();
208 // This sets all non-empty regions to need zero-fill (which they will if
209 // they are empty after full collection.)
210 void set_used_regions_to_need_zero_fill();
212 // The sequence of all heap regions in the heap.
213 HeapRegionSeq* _hrs;
215 // The region from which normal-sized objects are currently being
216 // allocated. May be NULL.
217 HeapRegion* _cur_alloc_region;
219 // Postcondition: cur_alloc_region == NULL.
220 void abandon_cur_alloc_region();
221 void abandon_gc_alloc_regions();
223 // The to-space memory regions into which objects are being copied during
224 // a GC.
225 HeapRegion* _gc_alloc_regions[GCAllocPurposeCount];
226 size_t _gc_alloc_region_counts[GCAllocPurposeCount];
227 // These are the regions, one per GCAllocPurpose, that are half-full
228 // at the end of a collection and that we want to reuse during the
229 // next collection.
230 HeapRegion* _retained_gc_alloc_regions[GCAllocPurposeCount];
231 // This specifies whether we will keep the last half-full region at
232 // the end of a collection so that it can be reused during the next
233 // collection (this is specified per GCAllocPurpose)
234 bool _retain_gc_alloc_region[GCAllocPurposeCount];
236 // A list of the regions that have been set to be alloc regions in the
237 // current collection.
238 HeapRegion* _gc_alloc_region_list;
240 // When called by par thread, require par_alloc_during_gc_lock() to be held.
241 void push_gc_alloc_region(HeapRegion* hr);
243 // This should only be called single-threaded. Undeclares all GC alloc
244 // regions.
245 void forget_alloc_region_list();
247 // Should be used to set an alloc region, because there's other
248 // associated bookkeeping.
249 void set_gc_alloc_region(int purpose, HeapRegion* r);
251 // Check well-formedness of alloc region list.
252 bool check_gc_alloc_regions();
254 // Outside of GC pauses, the number of bytes used in all regions other
255 // than the current allocation region.
256 size_t _summary_bytes_used;
258 // This is used for a quick test on whether a reference points into
259 // the collection set or not. Basically, we have an array, with one
260 // byte per region, and that byte denotes whether the corresponding
261 // region is in the collection set or not. The entry corresponding
262 // the bottom of the heap, i.e., region 0, is pointed to by
263 // _in_cset_fast_test_base. The _in_cset_fast_test field has been
264 // biased so that it actually points to address 0 of the address
265 // space, to make the test as fast as possible (we can simply shift
266 // the address to address into it, instead of having to subtract the
267 // bottom of the heap from the address before shifting it; basically
268 // it works in the same way the card table works).
269 bool* _in_cset_fast_test;
271 // The allocated array used for the fast test on whether a reference
272 // points into the collection set or not. This field is also used to
273 // free the array.
274 bool* _in_cset_fast_test_base;
276 // The length of the _in_cset_fast_test_base array.
277 size_t _in_cset_fast_test_length;
279 volatile unsigned _gc_time_stamp;
281 size_t* _surviving_young_words;
283 void setup_surviving_young_words();
284 void update_surviving_young_words(size_t* surv_young_words);
285 void cleanup_surviving_young_words();
287 protected:
289 // Returns "true" iff none of the gc alloc regions have any allocations
290 // since the last call to "save_marks".
291 bool all_alloc_regions_no_allocs_since_save_marks();
292 // Perform finalization stuff on all allocation regions.
293 void retire_all_alloc_regions();
295 // The number of regions allocated to hold humongous objects.
296 int _num_humongous_regions;
297 YoungList* _young_list;
299 // The current policy object for the collector.
300 G1CollectorPolicy* _g1_policy;
302 // Parallel allocation lock to protect the current allocation region.
303 Mutex _par_alloc_during_gc_lock;
304 Mutex* par_alloc_during_gc_lock() { return &_par_alloc_during_gc_lock; }
306 // If possible/desirable, allocate a new HeapRegion for normal object
307 // allocation sufficient for an allocation of the given "word_size".
308 // If "do_expand" is true, will attempt to expand the heap if necessary
309 // to to satisfy the request. If "zero_filled" is true, requires a
310 // zero-filled region.
311 // (Returning NULL will trigger a GC.)
312 virtual HeapRegion* newAllocRegion_work(size_t word_size,
313 bool do_expand,
314 bool zero_filled);
316 virtual HeapRegion* newAllocRegion(size_t word_size,
317 bool zero_filled = true) {
318 return newAllocRegion_work(word_size, false, zero_filled);
319 }
320 virtual HeapRegion* newAllocRegionWithExpansion(int purpose,
321 size_t word_size,
322 bool zero_filled = true);
324 // Attempt to allocate an object of the given (very large) "word_size".
325 // Returns "NULL" on failure.
326 virtual HeapWord* humongousObjAllocate(size_t word_size);
328 // If possible, allocate a block of the given word_size, else return "NULL".
329 // Returning NULL will trigger GC or heap expansion.
330 // These two methods have rather awkward pre- and
331 // post-conditions. If they are called outside a safepoint, then
332 // they assume that the caller is holding the heap lock. Upon return
333 // they release the heap lock, if they are returning a non-NULL
334 // value. attempt_allocation_slow() also dirties the cards of a
335 // newly-allocated young region after it releases the heap
336 // lock. This change in interface was the neatest way to achieve
337 // this card dirtying without affecting mem_allocate(), which is a
338 // more frequently called method. We tried two or three different
339 // approaches, but they were even more hacky.
340 HeapWord* attempt_allocation(size_t word_size,
341 bool permit_collection_pause = true);
343 HeapWord* attempt_allocation_slow(size_t word_size,
344 bool permit_collection_pause = true);
346 // Allocate blocks during garbage collection. Will ensure an
347 // allocation region, either by picking one or expanding the
348 // heap, and then allocate a block of the given size. The block
349 // may not be a humongous - it must fit into a single heap region.
350 HeapWord* allocate_during_gc(GCAllocPurpose purpose, size_t word_size);
351 HeapWord* par_allocate_during_gc(GCAllocPurpose purpose, size_t word_size);
353 HeapWord* allocate_during_gc_slow(GCAllocPurpose purpose,
354 HeapRegion* alloc_region,
355 bool par,
356 size_t word_size);
358 // Ensure that no further allocations can happen in "r", bearing in mind
359 // that parallel threads might be attempting allocations.
360 void par_allocate_remaining_space(HeapRegion* r);
362 // Retires an allocation region when it is full or at the end of a
363 // GC pause.
364 void retire_alloc_region(HeapRegion* alloc_region, bool par);
366 // Helper function for two callbacks below.
367 // "full", if true, indicates that the GC is for a System.gc() request,
368 // and should collect the entire heap. If "clear_all_soft_refs" is true,
369 // all soft references are cleared during the GC. If "full" is false,
370 // "word_size" describes the allocation that the GC should
371 // attempt (at least) to satisfy.
372 void do_collection(bool full, bool clear_all_soft_refs,
373 size_t word_size);
375 // Callback from VM_G1CollectFull operation.
376 // Perform a full collection.
377 void do_full_collection(bool clear_all_soft_refs);
379 // Resize the heap if necessary after a full collection. If this is
380 // after a collect-for allocation, "word_size" is the allocation size,
381 // and will be considered part of the used portion of the heap.
382 void resize_if_necessary_after_full_collection(size_t word_size);
384 // Callback from VM_G1CollectForAllocation operation.
385 // This function does everything necessary/possible to satisfy a
386 // failed allocation request (including collection, expansion, etc.)
387 HeapWord* satisfy_failed_allocation(size_t word_size);
389 // Attempting to expand the heap sufficiently
390 // to support an allocation of the given "word_size". If
391 // successful, perform the allocation and return the address of the
392 // allocated block, or else "NULL".
393 virtual HeapWord* expand_and_allocate(size_t word_size);
395 public:
396 // Expand the garbage-first heap by at least the given size (in bytes!).
397 // (Rounds up to a HeapRegion boundary.)
398 virtual void expand(size_t expand_bytes);
400 // Do anything common to GC's.
401 virtual void gc_prologue(bool full);
402 virtual void gc_epilogue(bool full);
404 // We register a region with the fast "in collection set" test. We
405 // simply set to true the array slot corresponding to this region.
406 void register_region_with_in_cset_fast_test(HeapRegion* r) {
407 assert(_in_cset_fast_test_base != NULL, "sanity");
408 assert(r->in_collection_set(), "invariant");
409 int index = r->hrs_index();
410 assert(0 <= (size_t) index && (size_t) index < _in_cset_fast_test_length,
411 "invariant");
412 assert(!_in_cset_fast_test_base[index], "invariant");
413 _in_cset_fast_test_base[index] = true;
414 }
416 // This is a fast test on whether a reference points into the
417 // collection set or not. It does not assume that the reference
418 // points into the heap; if it doesn't, it will return false.
419 bool in_cset_fast_test(oop obj) {
420 assert(_in_cset_fast_test != NULL, "sanity");
421 if (_g1_committed.contains((HeapWord*) obj)) {
422 // no need to subtract the bottom of the heap from obj,
423 // _in_cset_fast_test is biased
424 size_t index = ((size_t) obj) >> HeapRegion::LogOfHRGrainBytes;
425 bool ret = _in_cset_fast_test[index];
426 // let's make sure the result is consistent with what the slower
427 // test returns
428 assert( ret || !obj_in_cs(obj), "sanity");
429 assert(!ret || obj_in_cs(obj), "sanity");
430 return ret;
431 } else {
432 return false;
433 }
434 }
436 protected:
438 // Shrink the garbage-first heap by at most the given size (in bytes!).
439 // (Rounds down to a HeapRegion boundary.)
440 virtual void shrink(size_t expand_bytes);
441 void shrink_helper(size_t expand_bytes);
443 // Do an incremental collection: identify a collection set, and evacuate
444 // its live objects elsewhere.
445 virtual void do_collection_pause();
447 // The guts of the incremental collection pause, executed by the vm
448 // thread.
449 virtual void do_collection_pause_at_safepoint();
451 // Actually do the work of evacuating the collection set.
452 virtual void evacuate_collection_set();
454 // If this is an appropriate right time, do a collection pause.
455 // The "word_size" argument, if non-zero, indicates the size of an
456 // allocation request that is prompting this query.
457 void do_collection_pause_if_appropriate(size_t word_size);
459 // The g1 remembered set of the heap.
460 G1RemSet* _g1_rem_set;
461 // And it's mod ref barrier set, used to track updates for the above.
462 ModRefBarrierSet* _mr_bs;
464 // A set of cards that cover the objects for which the Rsets should be updated
465 // concurrently after the collection.
466 DirtyCardQueueSet _dirty_card_queue_set;
468 // The Heap Region Rem Set Iterator.
469 HeapRegionRemSetIterator** _rem_set_iterator;
471 // The closure used to refine a single card.
472 RefineCardTableEntryClosure* _refine_cte_cl;
474 // A function to check the consistency of dirty card logs.
475 void check_ct_logs_at_safepoint();
477 // After a collection pause, make the regions in the CS into free
478 // regions.
479 void free_collection_set(HeapRegion* cs_head);
481 // Applies "scan_non_heap_roots" to roots outside the heap,
482 // "scan_rs" to roots inside the heap (having done "set_region" to
483 // indicate the region in which the root resides), and does "scan_perm"
484 // (setting the generation to the perm generation.) If "scan_rs" is
485 // NULL, then this step is skipped. The "worker_i"
486 // param is for use with parallel roots processing, and should be
487 // the "i" of the calling parallel worker thread's work(i) function.
488 // In the sequential case this param will be ignored.
489 void g1_process_strong_roots(bool collecting_perm_gen,
490 SharedHeap::ScanningOption so,
491 OopClosure* scan_non_heap_roots,
492 OopsInHeapRegionClosure* scan_rs,
493 OopsInHeapRegionClosure* scan_so,
494 OopsInGenClosure* scan_perm,
495 int worker_i);
497 void scan_scan_only_set(OopsInHeapRegionClosure* oc,
498 int worker_i);
499 void scan_scan_only_region(HeapRegion* hr,
500 OopsInHeapRegionClosure* oc,
501 int worker_i);
503 // Apply "blk" to all the weak roots of the system. These include
504 // JNI weak roots, the code cache, system dictionary, symbol table,
505 // string table, and referents of reachable weak refs.
506 void g1_process_weak_roots(OopClosure* root_closure,
507 OopClosure* non_root_closure);
509 // Invoke "save_marks" on all heap regions.
510 void save_marks();
512 // Free a heap region.
513 void free_region(HeapRegion* hr);
514 // A component of "free_region", exposed for 'batching'.
515 // All the params after "hr" are out params: the used bytes of the freed
516 // region(s), the number of H regions cleared, the number of regions
517 // freed, and pointers to the head and tail of a list of freed contig
518 // regions, linked throught the "next_on_unclean_list" field.
519 void free_region_work(HeapRegion* hr,
520 size_t& pre_used,
521 size_t& cleared_h,
522 size_t& freed_regions,
523 UncleanRegionList* list,
524 bool par = false);
527 // The concurrent marker (and the thread it runs in.)
528 ConcurrentMark* _cm;
529 ConcurrentMarkThread* _cmThread;
530 bool _mark_in_progress;
532 // The concurrent refiner.
533 ConcurrentG1Refine* _cg1r;
535 // The concurrent zero-fill thread.
536 ConcurrentZFThread* _czft;
538 // The parallel task queues
539 RefToScanQueueSet *_task_queues;
541 // True iff a evacuation has failed in the current collection.
542 bool _evacuation_failed;
544 // Set the attribute indicating whether evacuation has failed in the
545 // current collection.
546 void set_evacuation_failed(bool b) { _evacuation_failed = b; }
548 // Failed evacuations cause some logical from-space objects to have
549 // forwarding pointers to themselves. Reset them.
550 void remove_self_forwarding_pointers();
552 // When one is non-null, so is the other. Together, they each pair is
553 // an object with a preserved mark, and its mark value.
554 GrowableArray<oop>* _objs_with_preserved_marks;
555 GrowableArray<markOop>* _preserved_marks_of_objs;
557 // Preserve the mark of "obj", if necessary, in preparation for its mark
558 // word being overwritten with a self-forwarding-pointer.
559 void preserve_mark_if_necessary(oop obj, markOop m);
561 // The stack of evac-failure objects left to be scanned.
562 GrowableArray<oop>* _evac_failure_scan_stack;
563 // The closure to apply to evac-failure objects.
565 OopsInHeapRegionClosure* _evac_failure_closure;
566 // Set the field above.
567 void
568 set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
569 _evac_failure_closure = evac_failure_closure;
570 }
572 // Push "obj" on the scan stack.
573 void push_on_evac_failure_scan_stack(oop obj);
574 // Process scan stack entries until the stack is empty.
575 void drain_evac_failure_scan_stack();
576 // True iff an invocation of "drain_scan_stack" is in progress; to
577 // prevent unnecessary recursion.
578 bool _drain_in_progress;
580 // Do any necessary initialization for evacuation-failure handling.
581 // "cl" is the closure that will be used to process evac-failure
582 // objects.
583 void init_for_evac_failure(OopsInHeapRegionClosure* cl);
584 // Do any necessary cleanup for evacuation-failure handling data
585 // structures.
586 void finalize_for_evac_failure();
588 // An attempt to evacuate "obj" has failed; take necessary steps.
589 void handle_evacuation_failure(oop obj);
590 oop handle_evacuation_failure_par(OopsInHeapRegionClosure* cl, oop obj);
591 void handle_evacuation_failure_common(oop obj, markOop m);
594 // Ensure that the relevant gc_alloc regions are set.
595 void get_gc_alloc_regions();
596 // We're done with GC alloc regions. We are going to tear down the
597 // gc alloc list and remove the gc alloc tag from all the regions on
598 // that list. However, we will also retain the last (i.e., the one
599 // that is half-full) GC alloc region, per GCAllocPurpose, for
600 // possible reuse during the next collection, provided
601 // _retain_gc_alloc_region[] indicates that it should be the
602 // case. Said regions are kept in the _retained_gc_alloc_regions[]
603 // array. If the parameter totally is set, we will not retain any
604 // regions, irrespective of what _retain_gc_alloc_region[]
605 // indicates.
606 void release_gc_alloc_regions(bool totally);
607 #ifndef PRODUCT
608 // Useful for debugging.
609 void print_gc_alloc_regions();
610 #endif // !PRODUCT
612 // ("Weak") Reference processing support
613 ReferenceProcessor* _ref_processor;
615 enum G1H_process_strong_roots_tasks {
616 G1H_PS_mark_stack_oops_do,
617 G1H_PS_refProcessor_oops_do,
618 // Leave this one last.
619 G1H_PS_NumElements
620 };
622 SubTasksDone* _process_strong_tasks;
624 // List of regions which require zero filling.
625 UncleanRegionList _unclean_region_list;
626 bool _unclean_regions_coming;
628 public:
629 void set_refine_cte_cl_concurrency(bool concurrent);
631 RefToScanQueue *task_queue(int i);
633 // A set of cards where updates happened during the GC
634 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
636 // Create a G1CollectedHeap with the specified policy.
637 // Must call the initialize method afterwards.
638 // May not return if something goes wrong.
639 G1CollectedHeap(G1CollectorPolicy* policy);
641 // Initialize the G1CollectedHeap to have the initial and
642 // maximum sizes, permanent generation, and remembered and barrier sets
643 // specified by the policy object.
644 jint initialize();
646 void ref_processing_init();
648 void set_par_threads(int t) {
649 SharedHeap::set_par_threads(t);
650 _process_strong_tasks->set_par_threads(t);
651 }
653 virtual CollectedHeap::Name kind() const {
654 return CollectedHeap::G1CollectedHeap;
655 }
657 // The current policy object for the collector.
658 G1CollectorPolicy* g1_policy() const { return _g1_policy; }
660 // Adaptive size policy. No such thing for g1.
661 virtual AdaptiveSizePolicy* size_policy() { return NULL; }
663 // The rem set and barrier set.
664 G1RemSet* g1_rem_set() const { return _g1_rem_set; }
665 ModRefBarrierSet* mr_bs() const { return _mr_bs; }
667 // The rem set iterator.
668 HeapRegionRemSetIterator* rem_set_iterator(int i) {
669 return _rem_set_iterator[i];
670 }
672 HeapRegionRemSetIterator* rem_set_iterator() {
673 return _rem_set_iterator[0];
674 }
676 unsigned get_gc_time_stamp() {
677 return _gc_time_stamp;
678 }
680 void reset_gc_time_stamp() {
681 _gc_time_stamp = 0;
682 OrderAccess::fence();
683 }
685 void increment_gc_time_stamp() {
686 ++_gc_time_stamp;
687 OrderAccess::fence();
688 }
690 void iterate_dirty_card_closure(bool concurrent, int worker_i);
692 // The shared block offset table array.
693 G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
695 // Reference Processing accessor
696 ReferenceProcessor* ref_processor() { return _ref_processor; }
698 // Reserved (g1 only; super method includes perm), capacity and the used
699 // portion in bytes.
700 size_t g1_reserved_obj_bytes() { return _g1_reserved.byte_size(); }
701 virtual size_t capacity() const;
702 virtual size_t used() const;
703 // This should be called when we're not holding the heap lock. The
704 // result might be a bit inaccurate.
705 size_t used_unlocked() const;
706 size_t recalculate_used() const;
707 #ifndef PRODUCT
708 size_t recalculate_used_regions() const;
709 #endif // PRODUCT
711 // These virtual functions do the actual allocation.
712 virtual HeapWord* mem_allocate(size_t word_size,
713 bool is_noref,
714 bool is_tlab,
715 bool* gc_overhead_limit_was_exceeded);
717 // Some heaps may offer a contiguous region for shared non-blocking
718 // allocation, via inlined code (by exporting the address of the top and
719 // end fields defining the extent of the contiguous allocation region.)
720 // But G1CollectedHeap doesn't yet support this.
722 // Return an estimate of the maximum allocation that could be performed
723 // without triggering any collection or expansion activity. In a
724 // generational collector, for example, this is probably the largest
725 // allocation that could be supported (without expansion) in the youngest
726 // generation. It is "unsafe" because no locks are taken; the result
727 // should be treated as an approximation, not a guarantee, for use in
728 // heuristic resizing decisions.
729 virtual size_t unsafe_max_alloc();
731 virtual bool is_maximal_no_gc() const {
732 return _g1_storage.uncommitted_size() == 0;
733 }
735 // The total number of regions in the heap.
736 size_t n_regions();
738 // The number of regions that are completely free.
739 size_t max_regions();
741 // The number of regions that are completely free.
742 size_t free_regions();
744 // The number of regions that are not completely free.
745 size_t used_regions() { return n_regions() - free_regions(); }
747 // True iff the ZF thread should run.
748 bool should_zf();
750 // The number of regions available for "regular" expansion.
751 size_t expansion_regions() { return _expansion_regions; }
753 #ifndef PRODUCT
754 bool regions_accounted_for();
755 bool print_region_accounting_info();
756 void print_region_counts();
757 #endif
759 HeapRegion* alloc_region_from_unclean_list(bool zero_filled);
760 HeapRegion* alloc_region_from_unclean_list_locked(bool zero_filled);
762 void put_region_on_unclean_list(HeapRegion* r);
763 void put_region_on_unclean_list_locked(HeapRegion* r);
765 void prepend_region_list_on_unclean_list(UncleanRegionList* list);
766 void prepend_region_list_on_unclean_list_locked(UncleanRegionList* list);
768 void set_unclean_regions_coming(bool b);
769 void set_unclean_regions_coming_locked(bool b);
770 // Wait for cleanup to be complete.
771 void wait_for_cleanup_complete();
772 // Like above, but assumes that the calling thread owns the Heap_lock.
773 void wait_for_cleanup_complete_locked();
775 // Return the head of the unclean list.
776 HeapRegion* peek_unclean_region_list_locked();
777 // Remove and return the head of the unclean list.
778 HeapRegion* pop_unclean_region_list_locked();
780 // List of regions which are zero filled and ready for allocation.
781 HeapRegion* _free_region_list;
782 // Number of elements on the free list.
783 size_t _free_region_list_size;
785 // If the head of the unclean list is ZeroFilled, move it to the free
786 // list.
787 bool move_cleaned_region_to_free_list_locked();
788 bool move_cleaned_region_to_free_list();
790 void put_free_region_on_list_locked(HeapRegion* r);
791 void put_free_region_on_list(HeapRegion* r);
793 // Remove and return the head element of the free list.
794 HeapRegion* pop_free_region_list_locked();
796 // If "zero_filled" is true, we first try the free list, then we try the
797 // unclean list, zero-filling the result. If "zero_filled" is false, we
798 // first try the unclean list, then the zero-filled list.
799 HeapRegion* alloc_free_region_from_lists(bool zero_filled);
801 // Verify the integrity of the region lists.
802 void remove_allocated_regions_from_lists();
803 bool verify_region_lists();
804 bool verify_region_lists_locked();
805 size_t unclean_region_list_length();
806 size_t free_region_list_length();
808 // Perform a collection of the heap; intended for use in implementing
809 // "System.gc". This probably implies as full a collection as the
810 // "CollectedHeap" supports.
811 virtual void collect(GCCause::Cause cause);
813 // The same as above but assume that the caller holds the Heap_lock.
814 void collect_locked(GCCause::Cause cause);
816 // This interface assumes that it's being called by the
817 // vm thread. It collects the heap assuming that the
818 // heap lock is already held and that we are executing in
819 // the context of the vm thread.
820 virtual void collect_as_vm_thread(GCCause::Cause cause);
822 // True iff a evacuation has failed in the most-recent collection.
823 bool evacuation_failed() { return _evacuation_failed; }
825 // Free a region if it is totally full of garbage. Returns the number of
826 // bytes freed (0 ==> didn't free it).
827 size_t free_region_if_totally_empty(HeapRegion *hr);
828 void free_region_if_totally_empty_work(HeapRegion *hr,
829 size_t& pre_used,
830 size_t& cleared_h_regions,
831 size_t& freed_regions,
832 UncleanRegionList* list,
833 bool par = false);
835 // If we've done free region work that yields the given changes, update
836 // the relevant global variables.
837 void finish_free_region_work(size_t pre_used,
838 size_t cleared_h_regions,
839 size_t freed_regions,
840 UncleanRegionList* list);
843 // Returns "TRUE" iff "p" points into the allocated area of the heap.
844 virtual bool is_in(const void* p) const;
846 // Return "TRUE" iff the given object address is within the collection
847 // set.
848 inline bool obj_in_cs(oop obj);
850 // Return "TRUE" iff the given object address is in the reserved
851 // region of g1 (excluding the permanent generation).
852 bool is_in_g1_reserved(const void* p) const {
853 return _g1_reserved.contains(p);
854 }
856 // Returns a MemRegion that corresponds to the space that has been
857 // committed in the heap
858 MemRegion g1_committed() {
859 return _g1_committed;
860 }
862 NOT_PRODUCT( bool is_in_closed_subset(const void* p) const; )
864 // Dirty card table entries covering a list of young regions.
865 void dirtyCardsForYoungRegions(CardTableModRefBS* ct_bs, HeapRegion* list);
867 // This resets the card table to all zeros. It is used after
868 // a collection pause which used the card table to claim cards.
869 void cleanUpCardTable();
871 // Iteration functions.
873 // Iterate over all the ref-containing fields of all objects, calling
874 // "cl.do_oop" on each.
875 virtual void oop_iterate(OopClosure* cl) {
876 oop_iterate(cl, true);
877 }
878 void oop_iterate(OopClosure* cl, bool do_perm);
880 // Same as above, restricted to a memory region.
881 virtual void oop_iterate(MemRegion mr, OopClosure* cl) {
882 oop_iterate(mr, cl, true);
883 }
884 void oop_iterate(MemRegion mr, OopClosure* cl, bool do_perm);
886 // Iterate over all objects, calling "cl.do_object" on each.
887 virtual void object_iterate(ObjectClosure* cl) {
888 object_iterate(cl, true);
889 }
890 virtual void safe_object_iterate(ObjectClosure* cl) {
891 object_iterate(cl, true);
892 }
893 void object_iterate(ObjectClosure* cl, bool do_perm);
895 // Iterate over all objects allocated since the last collection, calling
896 // "cl.do_object" on each. The heap must have been initialized properly
897 // to support this function, or else this call will fail.
898 virtual void object_iterate_since_last_GC(ObjectClosure* cl);
900 // Iterate over all spaces in use in the heap, in ascending address order.
901 virtual void space_iterate(SpaceClosure* cl);
903 // Iterate over heap regions, in address order, terminating the
904 // iteration early if the "doHeapRegion" method returns "true".
905 void heap_region_iterate(HeapRegionClosure* blk);
907 // Iterate over heap regions starting with r (or the first region if "r"
908 // is NULL), in address order, terminating early if the "doHeapRegion"
909 // method returns "true".
910 void heap_region_iterate_from(HeapRegion* r, HeapRegionClosure* blk);
912 // As above but starting from the region at index idx.
913 void heap_region_iterate_from(int idx, HeapRegionClosure* blk);
915 HeapRegion* region_at(size_t idx);
917 // Divide the heap region sequence into "chunks" of some size (the number
918 // of regions divided by the number of parallel threads times some
919 // overpartition factor, currently 4). Assumes that this will be called
920 // in parallel by ParallelGCThreads worker threads with discinct worker
921 // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel
922 // calls will use the same "claim_value", and that that claim value is
923 // different from the claim_value of any heap region before the start of
924 // the iteration. Applies "blk->doHeapRegion" to each of the regions, by
925 // attempting to claim the first region in each chunk, and, if
926 // successful, applying the closure to each region in the chunk (and
927 // setting the claim value of the second and subsequent regions of the
928 // chunk.) For now requires that "doHeapRegion" always returns "false",
929 // i.e., that a closure never attempt to abort a traversal.
930 void heap_region_par_iterate_chunked(HeapRegionClosure* blk,
931 int worker,
932 jint claim_value);
934 // It resets all the region claim values to the default.
935 void reset_heap_region_claim_values();
937 #ifdef ASSERT
938 bool check_heap_region_claim_values(jint claim_value);
939 #endif // ASSERT
941 // Iterate over the regions (if any) in the current collection set.
942 void collection_set_iterate(HeapRegionClosure* blk);
944 // As above but starting from region r
945 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
947 // Returns the first (lowest address) compactible space in the heap.
948 virtual CompactibleSpace* first_compactible_space();
950 // A CollectedHeap will contain some number of spaces. This finds the
951 // space containing a given address, or else returns NULL.
952 virtual Space* space_containing(const void* addr) const;
954 // A G1CollectedHeap will contain some number of heap regions. This
955 // finds the region containing a given address, or else returns NULL.
956 HeapRegion* heap_region_containing(const void* addr) const;
958 // Like the above, but requires "addr" to be in the heap (to avoid a
959 // null-check), and unlike the above, may return an continuing humongous
960 // region.
961 HeapRegion* heap_region_containing_raw(const void* addr) const;
963 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
964 // each address in the (reserved) heap is a member of exactly
965 // one block. The defining characteristic of a block is that it is
966 // possible to find its size, and thus to progress forward to the next
967 // block. (Blocks may be of different sizes.) Thus, blocks may
968 // represent Java objects, or they might be free blocks in a
969 // free-list-based heap (or subheap), as long as the two kinds are
970 // distinguishable and the size of each is determinable.
972 // Returns the address of the start of the "block" that contains the
973 // address "addr". We say "blocks" instead of "object" since some heaps
974 // may not pack objects densely; a chunk may either be an object or a
975 // non-object.
976 virtual HeapWord* block_start(const void* addr) const;
978 // Requires "addr" to be the start of a chunk, and returns its size.
979 // "addr + size" is required to be the start of a new chunk, or the end
980 // of the active area of the heap.
981 virtual size_t block_size(const HeapWord* addr) const;
983 // Requires "addr" to be the start of a block, and returns "TRUE" iff
984 // the block is an object.
985 virtual bool block_is_obj(const HeapWord* addr) const;
987 // Does this heap support heap inspection? (+PrintClassHistogram)
988 virtual bool supports_heap_inspection() const { return true; }
990 // Section on thread-local allocation buffers (TLABs)
991 // See CollectedHeap for semantics.
993 virtual bool supports_tlab_allocation() const;
994 virtual size_t tlab_capacity(Thread* thr) const;
995 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
996 virtual HeapWord* allocate_new_tlab(size_t size);
998 // Can a compiler initialize a new object without store barriers?
999 // This permission only extends from the creation of a new object
1000 // via a TLAB up to the first subsequent safepoint.
1001 virtual bool can_elide_tlab_store_barriers() const {
1002 // Since G1's TLAB's may, on occasion, come from non-young regions
1003 // as well. (Is there a flag controlling that? XXX)
1004 return false;
1005 }
1007 // Can a compiler elide a store barrier when it writes
1008 // a permanent oop into the heap? Applies when the compiler
1009 // is storing x to the heap, where x->is_perm() is true.
1010 virtual bool can_elide_permanent_oop_store_barriers() const {
1011 // At least until perm gen collection is also G1-ified, at
1012 // which point this should return false.
1013 return true;
1014 }
1016 virtual bool allocs_are_zero_filled();
1018 // The boundary between a "large" and "small" array of primitives, in
1019 // words.
1020 virtual size_t large_typearray_limit();
1022 // Returns "true" iff the given word_size is "very large".
1023 static bool isHumongous(size_t word_size) {
1024 return word_size >= VeryLargeInWords;
1025 }
1027 // Update mod union table with the set of dirty cards.
1028 void updateModUnion();
1030 // Set the mod union bits corresponding to the given memRegion. Note
1031 // that this is always a safe operation, since it doesn't clear any
1032 // bits.
1033 void markModUnionRange(MemRegion mr);
1035 // Records the fact that a marking phase is no longer in progress.
1036 void set_marking_complete() {
1037 _mark_in_progress = false;
1038 }
1039 void set_marking_started() {
1040 _mark_in_progress = true;
1041 }
1042 bool mark_in_progress() {
1043 return _mark_in_progress;
1044 }
1046 // Print the maximum heap capacity.
1047 virtual size_t max_capacity() const;
1049 virtual jlong millis_since_last_gc();
1051 // Perform any cleanup actions necessary before allowing a verification.
1052 virtual void prepare_for_verify();
1054 // Perform verification.
1056 // use_prev_marking == true -> use "prev" marking information,
1057 // use_prev_marking == false -> use "next" marking information
1058 // NOTE: Only the "prev" marking information is guaranteed to be
1059 // consistent most of the time, so most calls to this should use
1060 // use_prev_marking == true. Currently, there is only one case where
1061 // this is called with use_prev_marking == false, which is to verify
1062 // the "next" marking information at the end of remark.
1063 void verify(bool allow_dirty, bool silent, bool use_prev_marking);
1065 // Override; it uses the "prev" marking information
1066 virtual void verify(bool allow_dirty, bool silent);
1067 // Default behavior by calling print(tty);
1068 virtual void print() const;
1069 // This calls print_on(st, PrintHeapAtGCExtended).
1070 virtual void print_on(outputStream* st) const;
1071 // If extended is true, it will print out information for all
1072 // regions in the heap by calling print_on_extended(st).
1073 virtual void print_on(outputStream* st, bool extended) const;
1074 virtual void print_on_extended(outputStream* st) const;
1076 virtual void print_gc_threads_on(outputStream* st) const;
1077 virtual void gc_threads_do(ThreadClosure* tc) const;
1079 // Override
1080 void print_tracing_info() const;
1082 // If "addr" is a pointer into the (reserved?) heap, returns a positive
1083 // number indicating the "arena" within the heap in which "addr" falls.
1084 // Or else returns 0.
1085 virtual int addr_to_arena_id(void* addr) const;
1087 // Convenience function to be used in situations where the heap type can be
1088 // asserted to be this type.
1089 static G1CollectedHeap* heap();
1091 void empty_young_list();
1092 bool should_set_young_locked();
1094 void set_region_short_lived_locked(HeapRegion* hr);
1095 // add appropriate methods for any other surv rate groups
1097 void young_list_rs_length_sampling_init() {
1098 _young_list->rs_length_sampling_init();
1099 }
1100 bool young_list_rs_length_sampling_more() {
1101 return _young_list->rs_length_sampling_more();
1102 }
1103 void young_list_rs_length_sampling_next() {
1104 _young_list->rs_length_sampling_next();
1105 }
1106 size_t young_list_sampled_rs_lengths() {
1107 return _young_list->sampled_rs_lengths();
1108 }
1110 size_t young_list_length() { return _young_list->length(); }
1111 size_t young_list_scan_only_length() {
1112 return _young_list->scan_only_length(); }
1114 HeapRegion* pop_region_from_young_list() {
1115 return _young_list->pop_region();
1116 }
1118 HeapRegion* young_list_first_region() {
1119 return _young_list->first_region();
1120 }
1122 // debugging
1123 bool check_young_list_well_formed() {
1124 return _young_list->check_list_well_formed();
1125 }
1126 bool check_young_list_empty(bool ignore_scan_only_list,
1127 bool check_sample = true);
1129 // *** Stuff related to concurrent marking. It's not clear to me that so
1130 // many of these need to be public.
1132 // The functions below are helper functions that a subclass of
1133 // "CollectedHeap" can use in the implementation of its virtual
1134 // functions.
1135 // This performs a concurrent marking of the live objects in a
1136 // bitmap off to the side.
1137 void doConcurrentMark();
1139 // This is called from the marksweep collector which then does
1140 // a concurrent mark and verifies that the results agree with
1141 // the stop the world marking.
1142 void checkConcurrentMark();
1143 void do_sync_mark();
1145 bool isMarkedPrev(oop obj) const;
1146 bool isMarkedNext(oop obj) const;
1148 // use_prev_marking == true -> use "prev" marking information,
1149 // use_prev_marking == false -> use "next" marking information
1150 bool is_obj_dead_cond(const oop obj,
1151 const HeapRegion* hr,
1152 const bool use_prev_marking) const {
1153 if (use_prev_marking) {
1154 return is_obj_dead(obj, hr);
1155 } else {
1156 return is_obj_ill(obj, hr);
1157 }
1158 }
1160 // Determine if an object is dead, given the object and also
1161 // the region to which the object belongs. An object is dead
1162 // iff a) it was not allocated since the last mark and b) it
1163 // is not marked.
1165 bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1166 return
1167 !hr->obj_allocated_since_prev_marking(obj) &&
1168 !isMarkedPrev(obj);
1169 }
1171 // This is used when copying an object to survivor space.
1172 // If the object is marked live, then we mark the copy live.
1173 // If the object is allocated since the start of this mark
1174 // cycle, then we mark the copy live.
1175 // If the object has been around since the previous mark
1176 // phase, and hasn't been marked yet during this phase,
1177 // then we don't mark it, we just wait for the
1178 // current marking cycle to get to it.
1180 // This function returns true when an object has been
1181 // around since the previous marking and hasn't yet
1182 // been marked during this marking.
1184 bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1185 return
1186 !hr->obj_allocated_since_next_marking(obj) &&
1187 !isMarkedNext(obj);
1188 }
1190 // Determine if an object is dead, given only the object itself.
1191 // This will find the region to which the object belongs and
1192 // then call the region version of the same function.
1194 // Added if it is in permanent gen it isn't dead.
1195 // Added if it is NULL it isn't dead.
1197 // use_prev_marking == true -> use "prev" marking information,
1198 // use_prev_marking == false -> use "next" marking information
1199 bool is_obj_dead_cond(const oop obj,
1200 const bool use_prev_marking) {
1201 if (use_prev_marking) {
1202 return is_obj_dead(obj);
1203 } else {
1204 return is_obj_ill(obj);
1205 }
1206 }
1208 bool is_obj_dead(const oop obj) {
1209 const HeapRegion* hr = heap_region_containing(obj);
1210 if (hr == NULL) {
1211 if (Universe::heap()->is_in_permanent(obj))
1212 return false;
1213 else if (obj == NULL) return false;
1214 else return true;
1215 }
1216 else return is_obj_dead(obj, hr);
1217 }
1219 bool is_obj_ill(const oop obj) {
1220 const HeapRegion* hr = heap_region_containing(obj);
1221 if (hr == NULL) {
1222 if (Universe::heap()->is_in_permanent(obj))
1223 return false;
1224 else if (obj == NULL) return false;
1225 else return true;
1226 }
1227 else return is_obj_ill(obj, hr);
1228 }
1230 // The following is just to alert the verification code
1231 // that a full collection has occurred and that the
1232 // remembered sets are no longer up to date.
1233 bool _full_collection;
1234 void set_full_collection() { _full_collection = true;}
1235 void clear_full_collection() {_full_collection = false;}
1236 bool full_collection() {return _full_collection;}
1238 ConcurrentMark* concurrent_mark() const { return _cm; }
1239 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1241 // The dirty cards region list is used to record a subset of regions
1242 // whose cards need clearing. The list if populated during the
1243 // remembered set scanning and drained during the card table
1244 // cleanup. Although the methods are reentrant, population/draining
1245 // phases must not overlap. For synchronization purposes the last
1246 // element on the list points to itself.
1247 HeapRegion* _dirty_cards_region_list;
1248 void push_dirty_cards_region(HeapRegion* hr);
1249 HeapRegion* pop_dirty_cards_region();
1251 public:
1252 void stop_conc_gc_threads();
1254 // <NEW PREDICTION>
1256 double predict_region_elapsed_time_ms(HeapRegion* hr, bool young);
1257 void check_if_region_is_too_expensive(double predicted_time_ms);
1258 size_t pending_card_num();
1259 size_t max_pending_card_num();
1260 size_t cards_scanned();
1262 // </NEW PREDICTION>
1264 protected:
1265 size_t _max_heap_capacity;
1267 // debug_only(static void check_for_valid_allocation_state();)
1269 public:
1270 // Temporary: call to mark things unimplemented for the G1 heap (e.g.,
1271 // MemoryService). In productization, we can make this assert false
1272 // to catch such places (as well as searching for calls to this...)
1273 static void g1_unimplemented();
1275 };
1277 #define use_local_bitmaps 1
1278 #define verify_local_bitmaps 0
1279 #define oop_buffer_length 256
1281 #ifndef PRODUCT
1282 class GCLabBitMap;
1283 class GCLabBitMapClosure: public BitMapClosure {
1284 private:
1285 ConcurrentMark* _cm;
1286 GCLabBitMap* _bitmap;
1288 public:
1289 GCLabBitMapClosure(ConcurrentMark* cm,
1290 GCLabBitMap* bitmap) {
1291 _cm = cm;
1292 _bitmap = bitmap;
1293 }
1295 virtual bool do_bit(size_t offset);
1296 };
1297 #endif // !PRODUCT
1299 class GCLabBitMap: public BitMap {
1300 private:
1301 ConcurrentMark* _cm;
1303 int _shifter;
1304 size_t _bitmap_word_covers_words;
1306 // beginning of the heap
1307 HeapWord* _heap_start;
1309 // this is the actual start of the GCLab
1310 HeapWord* _real_start_word;
1312 // this is the actual end of the GCLab
1313 HeapWord* _real_end_word;
1315 // this is the first word, possibly located before the actual start
1316 // of the GCLab, that corresponds to the first bit of the bitmap
1317 HeapWord* _start_word;
1319 // size of a GCLab in words
1320 size_t _gclab_word_size;
1322 static int shifter() {
1323 return MinObjAlignment - 1;
1324 }
1326 // how many heap words does a single bitmap word corresponds to?
1327 static size_t bitmap_word_covers_words() {
1328 return BitsPerWord << shifter();
1329 }
1331 static size_t gclab_word_size() {
1332 return G1ParallelGCAllocBufferSize / HeapWordSize;
1333 }
1335 static size_t bitmap_size_in_bits() {
1336 size_t bits_in_bitmap = gclab_word_size() >> shifter();
1337 // We are going to ensure that the beginning of a word in this
1338 // bitmap also corresponds to the beginning of a word in the
1339 // global marking bitmap. To handle the case where a GCLab
1340 // starts from the middle of the bitmap, we need to add enough
1341 // space (i.e. up to a bitmap word) to ensure that we have
1342 // enough bits in the bitmap.
1343 return bits_in_bitmap + BitsPerWord - 1;
1344 }
1345 public:
1346 GCLabBitMap(HeapWord* heap_start)
1347 : BitMap(bitmap_size_in_bits()),
1348 _cm(G1CollectedHeap::heap()->concurrent_mark()),
1349 _shifter(shifter()),
1350 _bitmap_word_covers_words(bitmap_word_covers_words()),
1351 _heap_start(heap_start),
1352 _gclab_word_size(gclab_word_size()),
1353 _real_start_word(NULL),
1354 _real_end_word(NULL),
1355 _start_word(NULL)
1356 {
1357 guarantee( size_in_words() >= bitmap_size_in_words(),
1358 "just making sure");
1359 }
1361 inline unsigned heapWordToOffset(HeapWord* addr) {
1362 unsigned offset = (unsigned) pointer_delta(addr, _start_word) >> _shifter;
1363 assert(offset < size(), "offset should be within bounds");
1364 return offset;
1365 }
1367 inline HeapWord* offsetToHeapWord(size_t offset) {
1368 HeapWord* addr = _start_word + (offset << _shifter);
1369 assert(_real_start_word <= addr && addr < _real_end_word, "invariant");
1370 return addr;
1371 }
1373 bool fields_well_formed() {
1374 bool ret1 = (_real_start_word == NULL) &&
1375 (_real_end_word == NULL) &&
1376 (_start_word == NULL);
1377 if (ret1)
1378 return true;
1380 bool ret2 = _real_start_word >= _start_word &&
1381 _start_word < _real_end_word &&
1382 (_real_start_word + _gclab_word_size) == _real_end_word &&
1383 (_start_word + _gclab_word_size + _bitmap_word_covers_words)
1384 > _real_end_word;
1385 return ret2;
1386 }
1388 inline bool mark(HeapWord* addr) {
1389 guarantee(use_local_bitmaps, "invariant");
1390 assert(fields_well_formed(), "invariant");
1392 if (addr >= _real_start_word && addr < _real_end_word) {
1393 assert(!isMarked(addr), "should not have already been marked");
1395 // first mark it on the bitmap
1396 at_put(heapWordToOffset(addr), true);
1398 return true;
1399 } else {
1400 return false;
1401 }
1402 }
1404 inline bool isMarked(HeapWord* addr) {
1405 guarantee(use_local_bitmaps, "invariant");
1406 assert(fields_well_formed(), "invariant");
1408 return at(heapWordToOffset(addr));
1409 }
1411 void set_buffer(HeapWord* start) {
1412 guarantee(use_local_bitmaps, "invariant");
1413 clear();
1415 assert(start != NULL, "invariant");
1416 _real_start_word = start;
1417 _real_end_word = start + _gclab_word_size;
1419 size_t diff =
1420 pointer_delta(start, _heap_start) % _bitmap_word_covers_words;
1421 _start_word = start - diff;
1423 assert(fields_well_formed(), "invariant");
1424 }
1426 #ifndef PRODUCT
1427 void verify() {
1428 // verify that the marks have been propagated
1429 GCLabBitMapClosure cl(_cm, this);
1430 iterate(&cl);
1431 }
1432 #endif // PRODUCT
1434 void retire() {
1435 guarantee(use_local_bitmaps, "invariant");
1436 assert(fields_well_formed(), "invariant");
1438 if (_start_word != NULL) {
1439 CMBitMap* mark_bitmap = _cm->nextMarkBitMap();
1441 // this means that the bitmap was set up for the GCLab
1442 assert(_real_start_word != NULL && _real_end_word != NULL, "invariant");
1444 mark_bitmap->mostly_disjoint_range_union(this,
1445 0, // always start from the start of the bitmap
1446 _start_word,
1447 size_in_words());
1448 _cm->grayRegionIfNecessary(MemRegion(_real_start_word, _real_end_word));
1450 #ifndef PRODUCT
1451 if (use_local_bitmaps && verify_local_bitmaps)
1452 verify();
1453 #endif // PRODUCT
1454 } else {
1455 assert(_real_start_word == NULL && _real_end_word == NULL, "invariant");
1456 }
1457 }
1459 static size_t bitmap_size_in_words() {
1460 return (bitmap_size_in_bits() + BitsPerWord - 1) / BitsPerWord;
1461 }
1462 };
1464 class G1ParGCAllocBuffer: public ParGCAllocBuffer {
1465 private:
1466 bool _retired;
1467 bool _during_marking;
1468 GCLabBitMap _bitmap;
1470 public:
1471 G1ParGCAllocBuffer() :
1472 ParGCAllocBuffer(G1ParallelGCAllocBufferSize / HeapWordSize),
1473 _during_marking(G1CollectedHeap::heap()->mark_in_progress()),
1474 _bitmap(G1CollectedHeap::heap()->reserved_region().start()),
1475 _retired(false)
1476 { }
1478 inline bool mark(HeapWord* addr) {
1479 guarantee(use_local_bitmaps, "invariant");
1480 assert(_during_marking, "invariant");
1481 return _bitmap.mark(addr);
1482 }
1484 inline void set_buf(HeapWord* buf) {
1485 if (use_local_bitmaps && _during_marking)
1486 _bitmap.set_buffer(buf);
1487 ParGCAllocBuffer::set_buf(buf);
1488 _retired = false;
1489 }
1491 inline void retire(bool end_of_gc, bool retain) {
1492 if (_retired)
1493 return;
1494 if (use_local_bitmaps && _during_marking) {
1495 _bitmap.retire();
1496 }
1497 ParGCAllocBuffer::retire(end_of_gc, retain);
1498 _retired = true;
1499 }
1500 };
1502 class G1ParScanThreadState : public StackObj {
1503 protected:
1504 G1CollectedHeap* _g1h;
1505 RefToScanQueue* _refs;
1506 DirtyCardQueue _dcq;
1507 CardTableModRefBS* _ct_bs;
1508 G1RemSet* _g1_rem;
1510 typedef GrowableArray<StarTask> OverflowQueue;
1511 OverflowQueue* _overflowed_refs;
1513 G1ParGCAllocBuffer _alloc_buffers[GCAllocPurposeCount];
1514 ageTable _age_table;
1516 size_t _alloc_buffer_waste;
1517 size_t _undo_waste;
1519 OopsInHeapRegionClosure* _evac_failure_cl;
1520 G1ParScanHeapEvacClosure* _evac_cl;
1521 G1ParScanPartialArrayClosure* _partial_scan_cl;
1523 int _hash_seed;
1524 int _queue_num;
1526 int _term_attempts;
1527 #if G1_DETAILED_STATS
1528 int _pushes, _pops, _steals, _steal_attempts;
1529 int _overflow_pushes;
1530 #endif
1532 double _start;
1533 double _start_strong_roots;
1534 double _strong_roots_time;
1535 double _start_term;
1536 double _term_time;
1538 // Map from young-age-index (0 == not young, 1 is youngest) to
1539 // surviving words. base is what we get back from the malloc call
1540 size_t* _surviving_young_words_base;
1541 // this points into the array, as we use the first few entries for padding
1542 size_t* _surviving_young_words;
1544 #define PADDING_ELEM_NUM (64 / sizeof(size_t))
1546 void add_to_alloc_buffer_waste(size_t waste) { _alloc_buffer_waste += waste; }
1548 void add_to_undo_waste(size_t waste) { _undo_waste += waste; }
1550 DirtyCardQueue& dirty_card_queue() { return _dcq; }
1551 CardTableModRefBS* ctbs() { return _ct_bs; }
1553 template <class T> void immediate_rs_update(HeapRegion* from, T* p, int tid) {
1554 if (!from->is_survivor()) {
1555 _g1_rem->par_write_ref(from, p, tid);
1556 }
1557 }
1559 template <class T> void deferred_rs_update(HeapRegion* from, T* p, int tid) {
1560 // If the new value of the field points to the same region or
1561 // is the to-space, we don't need to include it in the Rset updates.
1562 if (!from->is_in_reserved(oopDesc::load_decode_heap_oop(p)) && !from->is_survivor()) {
1563 size_t card_index = ctbs()->index_for(p);
1564 // If the card hasn't been added to the buffer, do it.
1565 if (ctbs()->mark_card_deferred(card_index)) {
1566 dirty_card_queue().enqueue((jbyte*)ctbs()->byte_for_index(card_index));
1567 }
1568 }
1569 }
1571 public:
1572 G1ParScanThreadState(G1CollectedHeap* g1h, int queue_num);
1574 ~G1ParScanThreadState() {
1575 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words_base);
1576 }
1578 RefToScanQueue* refs() { return _refs; }
1579 OverflowQueue* overflowed_refs() { return _overflowed_refs; }
1580 ageTable* age_table() { return &_age_table; }
1582 G1ParGCAllocBuffer* alloc_buffer(GCAllocPurpose purpose) {
1583 return &_alloc_buffers[purpose];
1584 }
1586 size_t alloc_buffer_waste() { return _alloc_buffer_waste; }
1587 size_t undo_waste() { return _undo_waste; }
1589 template <class T> void push_on_queue(T* ref) {
1590 assert(ref != NULL, "invariant");
1591 assert(has_partial_array_mask(ref) ||
1592 _g1h->obj_in_cs(oopDesc::load_decode_heap_oop(ref)), "invariant");
1593 #ifdef ASSERT
1594 if (has_partial_array_mask(ref)) {
1595 oop p = clear_partial_array_mask(ref);
1596 // Verify that we point into the CS
1597 assert(_g1h->obj_in_cs(p), "Should be in CS");
1598 }
1599 #endif
1600 if (!refs()->push(ref)) {
1601 overflowed_refs()->push(ref);
1602 IF_G1_DETAILED_STATS(note_overflow_push());
1603 } else {
1604 IF_G1_DETAILED_STATS(note_push());
1605 }
1606 }
1608 void pop_from_queue(StarTask& ref) {
1609 if (refs()->pop_local(ref)) {
1610 assert((oop*)ref != NULL, "pop_local() returned true");
1611 assert(UseCompressedOops || !ref.is_narrow(), "Error");
1612 assert(has_partial_array_mask((oop*)ref) ||
1613 _g1h->obj_in_cs(ref.is_narrow() ? oopDesc::load_decode_heap_oop((narrowOop*)ref)
1614 : oopDesc::load_decode_heap_oop((oop*)ref)),
1615 "invariant");
1616 IF_G1_DETAILED_STATS(note_pop());
1617 } else {
1618 StarTask null_task;
1619 ref = null_task;
1620 }
1621 }
1623 void pop_from_overflow_queue(StarTask& ref) {
1624 StarTask new_ref = overflowed_refs()->pop();
1625 assert((oop*)new_ref != NULL, "pop() from a local non-empty stack");
1626 assert(UseCompressedOops || !new_ref.is_narrow(), "Error");
1627 assert(has_partial_array_mask((oop*)new_ref) ||
1628 _g1h->obj_in_cs(new_ref.is_narrow() ? oopDesc::load_decode_heap_oop((narrowOop*)new_ref)
1629 : oopDesc::load_decode_heap_oop((oop*)new_ref)),
1630 "invariant");
1631 ref = new_ref;
1632 }
1634 int refs_to_scan() { return refs()->size(); }
1635 int overflowed_refs_to_scan() { return overflowed_refs()->length(); }
1637 template <class T> void update_rs(HeapRegion* from, T* p, int tid) {
1638 if (G1DeferredRSUpdate) {
1639 deferred_rs_update(from, p, tid);
1640 } else {
1641 immediate_rs_update(from, p, tid);
1642 }
1643 }
1645 HeapWord* allocate_slow(GCAllocPurpose purpose, size_t word_sz) {
1647 HeapWord* obj = NULL;
1648 if (word_sz * 100 <
1649 (size_t)(G1ParallelGCAllocBufferSize / HeapWordSize) *
1650 ParallelGCBufferWastePct) {
1651 G1ParGCAllocBuffer* alloc_buf = alloc_buffer(purpose);
1652 add_to_alloc_buffer_waste(alloc_buf->words_remaining());
1653 alloc_buf->retire(false, false);
1655 HeapWord* buf =
1656 _g1h->par_allocate_during_gc(purpose, G1ParallelGCAllocBufferSize / HeapWordSize);
1657 if (buf == NULL) return NULL; // Let caller handle allocation failure.
1658 // Otherwise.
1659 alloc_buf->set_buf(buf);
1661 obj = alloc_buf->allocate(word_sz);
1662 assert(obj != NULL, "buffer was definitely big enough...");
1663 } else {
1664 obj = _g1h->par_allocate_during_gc(purpose, word_sz);
1665 }
1666 return obj;
1667 }
1669 HeapWord* allocate(GCAllocPurpose purpose, size_t word_sz) {
1670 HeapWord* obj = alloc_buffer(purpose)->allocate(word_sz);
1671 if (obj != NULL) return obj;
1672 return allocate_slow(purpose, word_sz);
1673 }
1675 void undo_allocation(GCAllocPurpose purpose, HeapWord* obj, size_t word_sz) {
1676 if (alloc_buffer(purpose)->contains(obj)) {
1677 assert(alloc_buffer(purpose)->contains(obj + word_sz - 1),
1678 "should contain whole object");
1679 alloc_buffer(purpose)->undo_allocation(obj, word_sz);
1680 } else {
1681 CollectedHeap::fill_with_object(obj, word_sz);
1682 add_to_undo_waste(word_sz);
1683 }
1684 }
1686 void set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_cl) {
1687 _evac_failure_cl = evac_failure_cl;
1688 }
1689 OopsInHeapRegionClosure* evac_failure_closure() {
1690 return _evac_failure_cl;
1691 }
1693 void set_evac_closure(G1ParScanHeapEvacClosure* evac_cl) {
1694 _evac_cl = evac_cl;
1695 }
1697 void set_partial_scan_closure(G1ParScanPartialArrayClosure* partial_scan_cl) {
1698 _partial_scan_cl = partial_scan_cl;
1699 }
1701 int* hash_seed() { return &_hash_seed; }
1702 int queue_num() { return _queue_num; }
1704 int term_attempts() { return _term_attempts; }
1705 void note_term_attempt() { _term_attempts++; }
1707 #if G1_DETAILED_STATS
1708 int pushes() { return _pushes; }
1709 int pops() { return _pops; }
1710 int steals() { return _steals; }
1711 int steal_attempts() { return _steal_attempts; }
1712 int overflow_pushes() { return _overflow_pushes; }
1714 void note_push() { _pushes++; }
1715 void note_pop() { _pops++; }
1716 void note_steal() { _steals++; }
1717 void note_steal_attempt() { _steal_attempts++; }
1718 void note_overflow_push() { _overflow_pushes++; }
1719 #endif
1721 void start_strong_roots() {
1722 _start_strong_roots = os::elapsedTime();
1723 }
1724 void end_strong_roots() {
1725 _strong_roots_time += (os::elapsedTime() - _start_strong_roots);
1726 }
1727 double strong_roots_time() { return _strong_roots_time; }
1729 void start_term_time() {
1730 note_term_attempt();
1731 _start_term = os::elapsedTime();
1732 }
1733 void end_term_time() {
1734 _term_time += (os::elapsedTime() - _start_term);
1735 }
1736 double term_time() { return _term_time; }
1738 double elapsed() {
1739 return os::elapsedTime() - _start;
1740 }
1742 size_t* surviving_young_words() {
1743 // We add on to hide entry 0 which accumulates surviving words for
1744 // age -1 regions (i.e. non-young ones)
1745 return _surviving_young_words;
1746 }
1748 void retire_alloc_buffers() {
1749 for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
1750 size_t waste = _alloc_buffers[ap].words_remaining();
1751 add_to_alloc_buffer_waste(waste);
1752 _alloc_buffers[ap].retire(true, false);
1753 }
1754 }
1756 private:
1757 template <class T> void deal_with_reference(T* ref_to_scan) {
1758 if (has_partial_array_mask(ref_to_scan)) {
1759 _partial_scan_cl->do_oop_nv(ref_to_scan);
1760 } else {
1761 // Note: we can use "raw" versions of "region_containing" because
1762 // "obj_to_scan" is definitely in the heap, and is not in a
1763 // humongous region.
1764 HeapRegion* r = _g1h->heap_region_containing_raw(ref_to_scan);
1765 _evac_cl->set_region(r);
1766 _evac_cl->do_oop_nv(ref_to_scan);
1767 }
1768 }
1770 public:
1771 void trim_queue() {
1772 // I've replicated the loop twice, first to drain the overflow
1773 // queue, second to drain the task queue. This is better than
1774 // having a single loop, which checks both conditions and, inside
1775 // it, either pops the overflow queue or the task queue, as each
1776 // loop is tighter. Also, the decision to drain the overflow queue
1777 // first is not arbitrary, as the overflow queue is not visible
1778 // to the other workers, whereas the task queue is. So, we want to
1779 // drain the "invisible" entries first, while allowing the other
1780 // workers to potentially steal the "visible" entries.
1782 while (refs_to_scan() > 0 || overflowed_refs_to_scan() > 0) {
1783 while (overflowed_refs_to_scan() > 0) {
1784 StarTask ref_to_scan;
1785 assert((oop*)ref_to_scan == NULL, "Constructed above");
1786 pop_from_overflow_queue(ref_to_scan);
1787 // We shouldn't have pushed it on the queue if it was not
1788 // pointing into the CSet.
1789 assert((oop*)ref_to_scan != NULL, "Follows from inner loop invariant");
1790 if (ref_to_scan.is_narrow()) {
1791 assert(UseCompressedOops, "Error");
1792 narrowOop* p = (narrowOop*)ref_to_scan;
1793 assert(!has_partial_array_mask(p) &&
1794 _g1h->obj_in_cs(oopDesc::load_decode_heap_oop(p)), "sanity");
1795 deal_with_reference(p);
1796 } else {
1797 oop* p = (oop*)ref_to_scan;
1798 assert((has_partial_array_mask(p) && _g1h->obj_in_cs(clear_partial_array_mask(p))) ||
1799 _g1h->obj_in_cs(oopDesc::load_decode_heap_oop(p)), "sanity");
1800 deal_with_reference(p);
1801 }
1802 }
1804 while (refs_to_scan() > 0) {
1805 StarTask ref_to_scan;
1806 assert((oop*)ref_to_scan == NULL, "Constructed above");
1807 pop_from_queue(ref_to_scan);
1808 if ((oop*)ref_to_scan != NULL) {
1809 if (ref_to_scan.is_narrow()) {
1810 assert(UseCompressedOops, "Error");
1811 narrowOop* p = (narrowOop*)ref_to_scan;
1812 assert(!has_partial_array_mask(p) &&
1813 _g1h->obj_in_cs(oopDesc::load_decode_heap_oop(p)), "sanity");
1814 deal_with_reference(p);
1815 } else {
1816 oop* p = (oop*)ref_to_scan;
1817 assert((has_partial_array_mask(p) && _g1h->obj_in_cs(clear_partial_array_mask(p))) ||
1818 _g1h->obj_in_cs(oopDesc::load_decode_heap_oop(p)), "sanity");
1819 deal_with_reference(p);
1820 }
1821 }
1822 }
1823 }
1824 }
1825 };