Wed, 02 Nov 2011 08:04:23 +0100
7106751: G1: gc/gctests/nativeGC03 crashes VM with SIGSEGV
Summary: _cset_rs_update_cl[] was indexed with values beyond what it is set up to handle.
Reviewed-by: ysr, jmasa, johnc
1 /*
2 * Copyright (c) 2001, 2011, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
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23 */
25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP
28 #include "gc_implementation/g1/collectionSetChooser.hpp"
29 #include "gc_implementation/g1/g1MMUTracker.hpp"
30 #include "memory/collectorPolicy.hpp"
32 // A G1CollectorPolicy makes policy decisions that determine the
33 // characteristics of the collector. Examples include:
34 // * choice of collection set.
35 // * when to collect.
37 class HeapRegion;
38 class CollectionSetChooser;
40 // Yes, this is a bit unpleasant... but it saves replicating the same thing
41 // over and over again and introducing subtle problems through small typos and
42 // cutting and pasting mistakes. The macros below introduces a number
43 // sequnce into the following two classes and the methods that access it.
45 #define define_num_seq(name) \
46 private: \
47 NumberSeq _all_##name##_times_ms; \
48 public: \
49 void record_##name##_time_ms(double ms) { \
50 _all_##name##_times_ms.add(ms); \
51 } \
52 NumberSeq* get_##name##_seq() { \
53 return &_all_##name##_times_ms; \
54 }
56 class MainBodySummary;
58 class PauseSummary: public CHeapObj {
59 define_num_seq(total)
60 define_num_seq(other)
62 public:
63 virtual MainBodySummary* main_body_summary() { return NULL; }
64 };
66 class MainBodySummary: public CHeapObj {
67 define_num_seq(satb_drain) // optional
68 define_num_seq(parallel) // parallel only
69 define_num_seq(ext_root_scan)
70 define_num_seq(mark_stack_scan)
71 define_num_seq(update_rs)
72 define_num_seq(scan_rs)
73 define_num_seq(obj_copy)
74 define_num_seq(termination) // parallel only
75 define_num_seq(parallel_other) // parallel only
76 define_num_seq(mark_closure)
77 define_num_seq(clear_ct)
78 };
80 class Summary: public PauseSummary,
81 public MainBodySummary {
82 public:
83 virtual MainBodySummary* main_body_summary() { return this; }
84 };
86 class G1CollectorPolicy: public CollectorPolicy {
87 private:
88 // The number of pauses during the execution.
89 long _n_pauses;
91 // either equal to the number of parallel threads, if ParallelGCThreads
92 // has been set, or 1 otherwise
93 int _parallel_gc_threads;
95 enum SomePrivateConstants {
96 NumPrevPausesForHeuristics = 10
97 };
99 G1MMUTracker* _mmu_tracker;
101 void initialize_flags();
103 void initialize_all() {
104 initialize_flags();
105 initialize_size_info();
106 initialize_perm_generation(PermGen::MarkSweepCompact);
107 }
109 CollectionSetChooser* _collectionSetChooser;
111 double _cur_collection_start_sec;
112 size_t _cur_collection_pause_used_at_start_bytes;
113 size_t _cur_collection_pause_used_regions_at_start;
114 size_t _prev_collection_pause_used_at_end_bytes;
115 double _cur_collection_par_time_ms;
116 double _cur_satb_drain_time_ms;
117 double _cur_clear_ct_time_ms;
118 double _cur_ref_proc_time_ms;
119 double _cur_ref_enq_time_ms;
121 #ifndef PRODUCT
122 // Card Table Count Cache stats
123 double _min_clear_cc_time_ms; // min
124 double _max_clear_cc_time_ms; // max
125 double _cur_clear_cc_time_ms; // clearing time during current pause
126 double _cum_clear_cc_time_ms; // cummulative clearing time
127 jlong _num_cc_clears; // number of times the card count cache has been cleared
128 #endif
130 // Statistics for recent GC pauses. See below for how indexed.
131 TruncatedSeq* _recent_rs_scan_times_ms;
133 // These exclude marking times.
134 TruncatedSeq* _recent_pause_times_ms;
135 TruncatedSeq* _recent_gc_times_ms;
137 TruncatedSeq* _recent_CS_bytes_used_before;
138 TruncatedSeq* _recent_CS_bytes_surviving;
140 TruncatedSeq* _recent_rs_sizes;
142 TruncatedSeq* _concurrent_mark_remark_times_ms;
143 TruncatedSeq* _concurrent_mark_cleanup_times_ms;
145 Summary* _summary;
147 NumberSeq* _all_pause_times_ms;
148 NumberSeq* _all_full_gc_times_ms;
149 double _stop_world_start;
150 NumberSeq* _all_stop_world_times_ms;
151 NumberSeq* _all_yield_times_ms;
153 size_t _region_num_young;
154 size_t _region_num_tenured;
155 size_t _prev_region_num_young;
156 size_t _prev_region_num_tenured;
158 NumberSeq* _all_mod_union_times_ms;
160 int _aux_num;
161 NumberSeq* _all_aux_times_ms;
162 double* _cur_aux_start_times_ms;
163 double* _cur_aux_times_ms;
164 bool* _cur_aux_times_set;
166 double* _par_last_gc_worker_start_times_ms;
167 double* _par_last_ext_root_scan_times_ms;
168 double* _par_last_mark_stack_scan_times_ms;
169 double* _par_last_update_rs_times_ms;
170 double* _par_last_update_rs_processed_buffers;
171 double* _par_last_scan_rs_times_ms;
172 double* _par_last_obj_copy_times_ms;
173 double* _par_last_termination_times_ms;
174 double* _par_last_termination_attempts;
175 double* _par_last_gc_worker_end_times_ms;
176 double* _par_last_gc_worker_times_ms;
178 // Each workers 'other' time i.e. the elapsed time of the parallel
179 // phase of the pause minus the sum of the individual sub-phase
180 // times for a given worker thread.
181 double* _par_last_gc_worker_other_times_ms;
183 // indicates whether we are in full young or partially young GC mode
184 bool _full_young_gcs;
186 // if true, then it tries to dynamically adjust the length of the
187 // young list
188 bool _adaptive_young_list_length;
189 size_t _young_list_target_length;
190 size_t _young_list_fixed_length;
191 size_t _prev_eden_capacity; // used for logging
193 // The max number of regions we can extend the eden by while the GC
194 // locker is active. This should be >= _young_list_target_length;
195 size_t _young_list_max_length;
197 size_t _young_cset_length;
198 bool _last_young_gc_full;
200 unsigned _full_young_pause_num;
201 unsigned _partial_young_pause_num;
203 bool _during_marking;
204 bool _in_marking_window;
205 bool _in_marking_window_im;
207 SurvRateGroup* _short_lived_surv_rate_group;
208 SurvRateGroup* _survivor_surv_rate_group;
209 // add here any more surv rate groups
211 double _gc_overhead_perc;
213 double _reserve_factor;
214 size_t _reserve_regions;
216 bool during_marking() {
217 return _during_marking;
218 }
220 // <NEW PREDICTION>
222 private:
223 enum PredictionConstants {
224 TruncatedSeqLength = 10
225 };
227 TruncatedSeq* _alloc_rate_ms_seq;
228 double _prev_collection_pause_end_ms;
230 TruncatedSeq* _pending_card_diff_seq;
231 TruncatedSeq* _rs_length_diff_seq;
232 TruncatedSeq* _cost_per_card_ms_seq;
233 TruncatedSeq* _fully_young_cards_per_entry_ratio_seq;
234 TruncatedSeq* _partially_young_cards_per_entry_ratio_seq;
235 TruncatedSeq* _cost_per_entry_ms_seq;
236 TruncatedSeq* _partially_young_cost_per_entry_ms_seq;
237 TruncatedSeq* _cost_per_byte_ms_seq;
238 TruncatedSeq* _constant_other_time_ms_seq;
239 TruncatedSeq* _young_other_cost_per_region_ms_seq;
240 TruncatedSeq* _non_young_other_cost_per_region_ms_seq;
242 TruncatedSeq* _pending_cards_seq;
243 TruncatedSeq* _scanned_cards_seq;
244 TruncatedSeq* _rs_lengths_seq;
246 TruncatedSeq* _cost_per_byte_ms_during_cm_seq;
248 TruncatedSeq* _young_gc_eff_seq;
250 TruncatedSeq* _max_conc_overhead_seq;
252 bool _using_new_ratio_calculations;
253 size_t _min_desired_young_length; // as set on the command line or default calculations
254 size_t _max_desired_young_length; // as set on the command line or default calculations
256 size_t _recorded_young_regions;
257 size_t _recorded_non_young_regions;
258 size_t _recorded_region_num;
260 size_t _free_regions_at_end_of_collection;
262 size_t _recorded_rs_lengths;
263 size_t _max_rs_lengths;
265 size_t _recorded_marked_bytes;
266 size_t _recorded_young_bytes;
268 size_t _predicted_pending_cards;
269 size_t _predicted_cards_scanned;
270 size_t _predicted_rs_lengths;
271 size_t _predicted_bytes_to_copy;
273 double _predicted_survival_ratio;
274 double _predicted_rs_update_time_ms;
275 double _predicted_rs_scan_time_ms;
276 double _predicted_object_copy_time_ms;
277 double _predicted_constant_other_time_ms;
278 double _predicted_young_other_time_ms;
279 double _predicted_non_young_other_time_ms;
280 double _predicted_pause_time_ms;
282 double _vtime_diff_ms;
284 double _recorded_young_free_cset_time_ms;
285 double _recorded_non_young_free_cset_time_ms;
287 double _sigma;
288 double _expensive_region_limit_ms;
290 size_t _rs_lengths_prediction;
292 size_t _known_garbage_bytes;
293 double _known_garbage_ratio;
295 double sigma() {
296 return _sigma;
297 }
299 // A function that prevents us putting too much stock in small sample
300 // sets. Returns a number between 2.0 and 1.0, depending on the number
301 // of samples. 5 or more samples yields one; fewer scales linearly from
302 // 2.0 at 1 sample to 1.0 at 5.
303 double confidence_factor(int samples) {
304 if (samples > 4) return 1.0;
305 else return 1.0 + sigma() * ((double)(5 - samples))/2.0;
306 }
308 double get_new_neg_prediction(TruncatedSeq* seq) {
309 return seq->davg() - sigma() * seq->dsd();
310 }
312 #ifndef PRODUCT
313 bool verify_young_ages(HeapRegion* head, SurvRateGroup *surv_rate_group);
314 #endif // PRODUCT
316 void adjust_concurrent_refinement(double update_rs_time,
317 double update_rs_processed_buffers,
318 double goal_ms);
320 double _pause_time_target_ms;
321 double _recorded_young_cset_choice_time_ms;
322 double _recorded_non_young_cset_choice_time_ms;
323 bool _within_target;
324 size_t _pending_cards;
325 size_t _max_pending_cards;
327 public:
329 void set_region_short_lived(HeapRegion* hr) {
330 hr->install_surv_rate_group(_short_lived_surv_rate_group);
331 }
333 void set_region_survivors(HeapRegion* hr) {
334 hr->install_surv_rate_group(_survivor_surv_rate_group);
335 }
337 #ifndef PRODUCT
338 bool verify_young_ages();
339 #endif // PRODUCT
341 double get_new_prediction(TruncatedSeq* seq) {
342 return MAX2(seq->davg() + sigma() * seq->dsd(),
343 seq->davg() * confidence_factor(seq->num()));
344 }
346 size_t young_cset_length() {
347 return _young_cset_length;
348 }
350 void record_max_rs_lengths(size_t rs_lengths) {
351 _max_rs_lengths = rs_lengths;
352 }
354 size_t predict_pending_card_diff() {
355 double prediction = get_new_neg_prediction(_pending_card_diff_seq);
356 if (prediction < 0.00001)
357 return 0;
358 else
359 return (size_t) prediction;
360 }
362 size_t predict_pending_cards() {
363 size_t max_pending_card_num = _g1->max_pending_card_num();
364 size_t diff = predict_pending_card_diff();
365 size_t prediction;
366 if (diff > max_pending_card_num)
367 prediction = max_pending_card_num;
368 else
369 prediction = max_pending_card_num - diff;
371 return prediction;
372 }
374 size_t predict_rs_length_diff() {
375 return (size_t) get_new_prediction(_rs_length_diff_seq);
376 }
378 double predict_alloc_rate_ms() {
379 return get_new_prediction(_alloc_rate_ms_seq);
380 }
382 double predict_cost_per_card_ms() {
383 return get_new_prediction(_cost_per_card_ms_seq);
384 }
386 double predict_rs_update_time_ms(size_t pending_cards) {
387 return (double) pending_cards * predict_cost_per_card_ms();
388 }
390 double predict_fully_young_cards_per_entry_ratio() {
391 return get_new_prediction(_fully_young_cards_per_entry_ratio_seq);
392 }
394 double predict_partially_young_cards_per_entry_ratio() {
395 if (_partially_young_cards_per_entry_ratio_seq->num() < 2)
396 return predict_fully_young_cards_per_entry_ratio();
397 else
398 return get_new_prediction(_partially_young_cards_per_entry_ratio_seq);
399 }
401 size_t predict_young_card_num(size_t rs_length) {
402 return (size_t) ((double) rs_length *
403 predict_fully_young_cards_per_entry_ratio());
404 }
406 size_t predict_non_young_card_num(size_t rs_length) {
407 return (size_t) ((double) rs_length *
408 predict_partially_young_cards_per_entry_ratio());
409 }
411 double predict_rs_scan_time_ms(size_t card_num) {
412 if (full_young_gcs())
413 return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq);
414 else
415 return predict_partially_young_rs_scan_time_ms(card_num);
416 }
418 double predict_partially_young_rs_scan_time_ms(size_t card_num) {
419 if (_partially_young_cost_per_entry_ms_seq->num() < 3)
420 return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq);
421 else
422 return (double) card_num *
423 get_new_prediction(_partially_young_cost_per_entry_ms_seq);
424 }
426 double predict_object_copy_time_ms_during_cm(size_t bytes_to_copy) {
427 if (_cost_per_byte_ms_during_cm_seq->num() < 3)
428 return 1.1 * (double) bytes_to_copy *
429 get_new_prediction(_cost_per_byte_ms_seq);
430 else
431 return (double) bytes_to_copy *
432 get_new_prediction(_cost_per_byte_ms_during_cm_seq);
433 }
435 double predict_object_copy_time_ms(size_t bytes_to_copy) {
436 if (_in_marking_window && !_in_marking_window_im)
437 return predict_object_copy_time_ms_during_cm(bytes_to_copy);
438 else
439 return (double) bytes_to_copy *
440 get_new_prediction(_cost_per_byte_ms_seq);
441 }
443 double predict_constant_other_time_ms() {
444 return get_new_prediction(_constant_other_time_ms_seq);
445 }
447 double predict_young_other_time_ms(size_t young_num) {
448 return
449 (double) young_num *
450 get_new_prediction(_young_other_cost_per_region_ms_seq);
451 }
453 double predict_non_young_other_time_ms(size_t non_young_num) {
454 return
455 (double) non_young_num *
456 get_new_prediction(_non_young_other_cost_per_region_ms_seq);
457 }
459 void check_if_region_is_too_expensive(double predicted_time_ms);
461 double predict_young_collection_elapsed_time_ms(size_t adjustment);
462 double predict_base_elapsed_time_ms(size_t pending_cards);
463 double predict_base_elapsed_time_ms(size_t pending_cards,
464 size_t scanned_cards);
465 size_t predict_bytes_to_copy(HeapRegion* hr);
466 double predict_region_elapsed_time_ms(HeapRegion* hr, bool young);
468 void start_recording_regions();
469 void record_cset_region_info(HeapRegion* hr, bool young);
470 void record_non_young_cset_region(HeapRegion* hr);
472 void set_recorded_young_regions(size_t n_regions);
473 void set_recorded_young_bytes(size_t bytes);
474 void set_recorded_rs_lengths(size_t rs_lengths);
475 void set_predicted_bytes_to_copy(size_t bytes);
477 void end_recording_regions();
479 void record_vtime_diff_ms(double vtime_diff_ms) {
480 _vtime_diff_ms = vtime_diff_ms;
481 }
483 void record_young_free_cset_time_ms(double time_ms) {
484 _recorded_young_free_cset_time_ms = time_ms;
485 }
487 void record_non_young_free_cset_time_ms(double time_ms) {
488 _recorded_non_young_free_cset_time_ms = time_ms;
489 }
491 double predict_young_gc_eff() {
492 return get_new_neg_prediction(_young_gc_eff_seq);
493 }
495 double predict_survivor_regions_evac_time();
497 // </NEW PREDICTION>
499 void cset_regions_freed() {
500 bool propagate = _last_young_gc_full && !_in_marking_window;
501 _short_lived_surv_rate_group->all_surviving_words_recorded(propagate);
502 _survivor_surv_rate_group->all_surviving_words_recorded(propagate);
503 // also call it on any more surv rate groups
504 }
506 void set_known_garbage_bytes(size_t known_garbage_bytes) {
507 _known_garbage_bytes = known_garbage_bytes;
508 size_t heap_bytes = _g1->capacity();
509 _known_garbage_ratio = (double) _known_garbage_bytes / (double) heap_bytes;
510 }
512 void decrease_known_garbage_bytes(size_t known_garbage_bytes) {
513 guarantee( _known_garbage_bytes >= known_garbage_bytes, "invariant" );
515 _known_garbage_bytes -= known_garbage_bytes;
516 size_t heap_bytes = _g1->capacity();
517 _known_garbage_ratio = (double) _known_garbage_bytes / (double) heap_bytes;
518 }
520 G1MMUTracker* mmu_tracker() {
521 return _mmu_tracker;
522 }
524 double max_pause_time_ms() {
525 return _mmu_tracker->max_gc_time() * 1000.0;
526 }
528 double predict_remark_time_ms() {
529 return get_new_prediction(_concurrent_mark_remark_times_ms);
530 }
532 double predict_cleanup_time_ms() {
533 return get_new_prediction(_concurrent_mark_cleanup_times_ms);
534 }
536 // Returns an estimate of the survival rate of the region at yg-age
537 // "yg_age".
538 double predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) {
539 TruncatedSeq* seq = surv_rate_group->get_seq(age);
540 if (seq->num() == 0)
541 gclog_or_tty->print("BARF! age is %d", age);
542 guarantee( seq->num() > 0, "invariant" );
543 double pred = get_new_prediction(seq);
544 if (pred > 1.0)
545 pred = 1.0;
546 return pred;
547 }
549 double predict_yg_surv_rate(int age) {
550 return predict_yg_surv_rate(age, _short_lived_surv_rate_group);
551 }
553 double accum_yg_surv_rate_pred(int age) {
554 return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
555 }
557 private:
558 void print_stats(int level, const char* str, double value);
559 void print_stats(int level, const char* str, int value);
561 void print_par_stats(int level, const char* str, double* data);
562 void print_par_sizes(int level, const char* str, double* data);
564 void check_other_times(int level,
565 NumberSeq* other_times_ms,
566 NumberSeq* calc_other_times_ms) const;
568 void print_summary (PauseSummary* stats) const;
570 void print_summary (int level, const char* str, NumberSeq* seq) const;
571 void print_summary_sd (int level, const char* str, NumberSeq* seq) const;
573 double avg_value (double* data);
574 double max_value (double* data);
575 double sum_of_values (double* data);
576 double max_sum (double* data1, double* data2);
578 int _last_satb_drain_processed_buffers;
579 int _last_update_rs_processed_buffers;
580 double _last_pause_time_ms;
582 size_t _bytes_in_collection_set_before_gc;
583 size_t _bytes_copied_during_gc;
585 // Used to count used bytes in CS.
586 friend class CountCSClosure;
588 // Statistics kept per GC stoppage, pause or full.
589 TruncatedSeq* _recent_prev_end_times_for_all_gcs_sec;
591 // Add a new GC of the given duration and end time to the record.
592 void update_recent_gc_times(double end_time_sec, double elapsed_ms);
594 // The head of the list (via "next_in_collection_set()") representing the
595 // current collection set. Set from the incrementally built collection
596 // set at the start of the pause.
597 HeapRegion* _collection_set;
599 // The number of regions in the collection set. Set from the incrementally
600 // built collection set at the start of an evacuation pause.
601 size_t _collection_set_size;
603 // The number of bytes in the collection set before the pause. Set from
604 // the incrementally built collection set at the start of an evacuation
605 // pause.
606 size_t _collection_set_bytes_used_before;
608 // The associated information that is maintained while the incremental
609 // collection set is being built with young regions. Used to populate
610 // the recorded info for the evacuation pause.
612 enum CSetBuildType {
613 Active, // We are actively building the collection set
614 Inactive // We are not actively building the collection set
615 };
617 CSetBuildType _inc_cset_build_state;
619 // The head of the incrementally built collection set.
620 HeapRegion* _inc_cset_head;
622 // The tail of the incrementally built collection set.
623 HeapRegion* _inc_cset_tail;
625 // The number of regions in the incrementally built collection set.
626 // Used to set _collection_set_size at the start of an evacuation
627 // pause.
628 size_t _inc_cset_size;
630 // Used as the index in the surving young words structure
631 // which tracks the amount of space, for each young region,
632 // that survives the pause.
633 size_t _inc_cset_young_index;
635 // The number of bytes in the incrementally built collection set.
636 // Used to set _collection_set_bytes_used_before at the start of
637 // an evacuation pause.
638 size_t _inc_cset_bytes_used_before;
640 // Used to record the highest end of heap region in collection set
641 HeapWord* _inc_cset_max_finger;
643 // The number of recorded used bytes in the young regions
644 // of the collection set. This is the sum of the used() bytes
645 // of retired young regions in the collection set.
646 size_t _inc_cset_recorded_young_bytes;
648 // The RSet lengths recorded for regions in the collection set
649 // (updated by the periodic sampling of the regions in the
650 // young list/collection set).
651 size_t _inc_cset_recorded_rs_lengths;
653 // The predicted elapsed time it will take to collect the regions
654 // in the collection set (updated by the periodic sampling of the
655 // regions in the young list/collection set).
656 double _inc_cset_predicted_elapsed_time_ms;
658 // The predicted bytes to copy for the regions in the collection
659 // set (updated by the periodic sampling of the regions in the
660 // young list/collection set).
661 size_t _inc_cset_predicted_bytes_to_copy;
663 // Stash a pointer to the g1 heap.
664 G1CollectedHeap* _g1;
666 // The average time in ms per collection pause, averaged over recent pauses.
667 double recent_avg_time_for_pauses_ms();
669 // The average time in ms for RS scanning, per pause, averaged
670 // over recent pauses. (Note the RS scanning time for a pause
671 // is itself an average of the RS scanning time for each worker
672 // thread.)
673 double recent_avg_time_for_rs_scan_ms();
675 // The number of "recent" GCs recorded in the number sequences
676 int number_of_recent_gcs();
678 // The average survival ratio, computed by the total number of bytes
679 // suriviving / total number of bytes before collection over the last
680 // several recent pauses.
681 double recent_avg_survival_fraction();
682 // The survival fraction of the most recent pause; if there have been no
683 // pauses, returns 1.0.
684 double last_survival_fraction();
686 // Returns a "conservative" estimate of the recent survival rate, i.e.,
687 // one that may be higher than "recent_avg_survival_fraction".
688 // This is conservative in several ways:
689 // If there have been few pauses, it will assume a potential high
690 // variance, and err on the side of caution.
691 // It puts a lower bound (currently 0.1) on the value it will return.
692 // To try to detect phase changes, if the most recent pause ("latest") has a
693 // higher-than average ("avg") survival rate, it returns that rate.
694 // "work" version is a utility function; young is restricted to young regions.
695 double conservative_avg_survival_fraction_work(double avg,
696 double latest);
698 // The arguments are the two sequences that keep track of the number of bytes
699 // surviving and the total number of bytes before collection, resp.,
700 // over the last evereal recent pauses
701 // Returns the survival rate for the category in the most recent pause.
702 // If there have been no pauses, returns 1.0.
703 double last_survival_fraction_work(TruncatedSeq* surviving,
704 TruncatedSeq* before);
706 // The arguments are the two sequences that keep track of the number of bytes
707 // surviving and the total number of bytes before collection, resp.,
708 // over the last several recent pauses
709 // Returns the average survival ration over the last several recent pauses
710 // If there have been no pauses, return 1.0
711 double recent_avg_survival_fraction_work(TruncatedSeq* surviving,
712 TruncatedSeq* before);
714 double conservative_avg_survival_fraction() {
715 double avg = recent_avg_survival_fraction();
716 double latest = last_survival_fraction();
717 return conservative_avg_survival_fraction_work(avg, latest);
718 }
720 // The ratio of gc time to elapsed time, computed over recent pauses.
721 double _recent_avg_pause_time_ratio;
723 double recent_avg_pause_time_ratio() {
724 return _recent_avg_pause_time_ratio;
725 }
727 // Number of pauses between concurrent marking.
728 size_t _pauses_btwn_concurrent_mark;
730 // At the end of a pause we check the heap occupancy and we decide
731 // whether we will start a marking cycle during the next pause. If
732 // we decide that we want to do that, we will set this parameter to
733 // true. So, this parameter will stay true between the end of a
734 // pause and the beginning of a subsequent pause (not necessarily
735 // the next one, see the comments on the next field) when we decide
736 // that we will indeed start a marking cycle and do the initial-mark
737 // work.
738 volatile bool _initiate_conc_mark_if_possible;
740 // If initiate_conc_mark_if_possible() is set at the beginning of a
741 // pause, it is a suggestion that the pause should start a marking
742 // cycle by doing the initial-mark work. However, it is possible
743 // that the concurrent marking thread is still finishing up the
744 // previous marking cycle (e.g., clearing the next marking
745 // bitmap). If that is the case we cannot start a new cycle and
746 // we'll have to wait for the concurrent marking thread to finish
747 // what it is doing. In this case we will postpone the marking cycle
748 // initiation decision for the next pause. When we eventually decide
749 // to start a cycle, we will set _during_initial_mark_pause which
750 // will stay true until the end of the initial-mark pause and it's
751 // the condition that indicates that a pause is doing the
752 // initial-mark work.
753 volatile bool _during_initial_mark_pause;
755 bool _should_revert_to_full_young_gcs;
756 bool _last_full_young_gc;
758 // This set of variables tracks the collector efficiency, in order to
759 // determine whether we should initiate a new marking.
760 double _cur_mark_stop_world_time_ms;
761 double _mark_remark_start_sec;
762 double _mark_cleanup_start_sec;
763 double _mark_closure_time_ms;
765 // Update the young list target length either by setting it to the
766 // desired fixed value or by calculating it using G1's pause
767 // prediction model. If no rs_lengths parameter is passed, predict
768 // the RS lengths using the prediction model, otherwise use the
769 // given rs_lengths as the prediction.
770 void update_young_list_target_length(size_t rs_lengths = (size_t) -1);
772 // Calculate and return the minimum desired young list target
773 // length. This is the minimum desired young list length according
774 // to the user's inputs.
775 size_t calculate_young_list_desired_min_length(size_t base_min_length);
777 // Calculate and return the maximum desired young list target
778 // length. This is the maximum desired young list length according
779 // to the user's inputs.
780 size_t calculate_young_list_desired_max_length();
782 // Calculate and return the maximum young list target length that
783 // can fit into the pause time goal. The parameters are: rs_lengths
784 // represent the prediction of how large the young RSet lengths will
785 // be, base_min_length is the alreay existing number of regions in
786 // the young list, min_length and max_length are the desired min and
787 // max young list length according to the user's inputs.
788 size_t calculate_young_list_target_length(size_t rs_lengths,
789 size_t base_min_length,
790 size_t desired_min_length,
791 size_t desired_max_length);
793 // Check whether a given young length (young_length) fits into the
794 // given target pause time and whether the prediction for the amount
795 // of objects to be copied for the given length will fit into the
796 // given free space (expressed by base_free_regions). It is used by
797 // calculate_young_list_target_length().
798 bool predict_will_fit(size_t young_length, double base_time_ms,
799 size_t base_free_regions, double target_pause_time_ms);
801 // Count the number of bytes used in the CS.
802 void count_CS_bytes_used();
804 void update_young_list_size_using_newratio(size_t number_of_heap_regions);
806 public:
808 G1CollectorPolicy();
810 virtual G1CollectorPolicy* as_g1_policy() { return this; }
812 virtual CollectorPolicy::Name kind() {
813 return CollectorPolicy::G1CollectorPolicyKind;
814 }
816 // Check the current value of the young list RSet lengths and
817 // compare it against the last prediction. If the current value is
818 // higher, recalculate the young list target length prediction.
819 void revise_young_list_target_length_if_necessary();
821 size_t bytes_in_collection_set() {
822 return _bytes_in_collection_set_before_gc;
823 }
825 unsigned calc_gc_alloc_time_stamp() {
826 return _all_pause_times_ms->num() + 1;
827 }
829 // This should be called after the heap is resized.
830 void record_new_heap_size(size_t new_number_of_regions);
832 public:
834 void init();
836 // Create jstat counters for the policy.
837 virtual void initialize_gc_policy_counters();
839 virtual HeapWord* mem_allocate_work(size_t size,
840 bool is_tlab,
841 bool* gc_overhead_limit_was_exceeded);
843 // This method controls how a collector handles one or more
844 // of its generations being fully allocated.
845 virtual HeapWord* satisfy_failed_allocation(size_t size,
846 bool is_tlab);
848 BarrierSet::Name barrier_set_name() { return BarrierSet::G1SATBCTLogging; }
850 GenRemSet::Name rem_set_name() { return GenRemSet::CardTable; }
852 // The number of collection pauses so far.
853 long n_pauses() const { return _n_pauses; }
855 // Update the heuristic info to record a collection pause of the given
856 // start time, where the given number of bytes were used at the start.
857 // This may involve changing the desired size of a collection set.
859 void record_stop_world_start();
861 void record_collection_pause_start(double start_time_sec, size_t start_used);
863 // Must currently be called while the world is stopped.
864 void record_concurrent_mark_init_end(double
865 mark_init_elapsed_time_ms);
867 void record_mark_closure_time(double mark_closure_time_ms);
869 void record_concurrent_mark_remark_start();
870 void record_concurrent_mark_remark_end();
872 void record_concurrent_mark_cleanup_start();
873 void record_concurrent_mark_cleanup_end();
874 void record_concurrent_mark_cleanup_completed();
876 void record_concurrent_pause();
877 void record_concurrent_pause_end();
879 void record_collection_pause_end();
880 void print_heap_transition();
882 // Record the fact that a full collection occurred.
883 void record_full_collection_start();
884 void record_full_collection_end();
886 void record_gc_worker_start_time(int worker_i, double ms) {
887 _par_last_gc_worker_start_times_ms[worker_i] = ms;
888 }
890 void record_ext_root_scan_time(int worker_i, double ms) {
891 _par_last_ext_root_scan_times_ms[worker_i] = ms;
892 }
894 void record_mark_stack_scan_time(int worker_i, double ms) {
895 _par_last_mark_stack_scan_times_ms[worker_i] = ms;
896 }
898 void record_satb_drain_time(double ms) {
899 assert(_g1->mark_in_progress(), "shouldn't be here otherwise");
900 _cur_satb_drain_time_ms = ms;
901 }
903 void record_satb_drain_processed_buffers(int processed_buffers) {
904 assert(_g1->mark_in_progress(), "shouldn't be here otherwise");
905 _last_satb_drain_processed_buffers = processed_buffers;
906 }
908 void record_mod_union_time(double ms) {
909 _all_mod_union_times_ms->add(ms);
910 }
912 void record_update_rs_time(int thread, double ms) {
913 _par_last_update_rs_times_ms[thread] = ms;
914 }
916 void record_update_rs_processed_buffers (int thread,
917 double processed_buffers) {
918 _par_last_update_rs_processed_buffers[thread] = processed_buffers;
919 }
921 void record_scan_rs_time(int thread, double ms) {
922 _par_last_scan_rs_times_ms[thread] = ms;
923 }
925 void reset_obj_copy_time(int thread) {
926 _par_last_obj_copy_times_ms[thread] = 0.0;
927 }
929 void reset_obj_copy_time() {
930 reset_obj_copy_time(0);
931 }
933 void record_obj_copy_time(int thread, double ms) {
934 _par_last_obj_copy_times_ms[thread] += ms;
935 }
937 void record_termination(int thread, double ms, size_t attempts) {
938 _par_last_termination_times_ms[thread] = ms;
939 _par_last_termination_attempts[thread] = (double) attempts;
940 }
942 void record_gc_worker_end_time(int worker_i, double ms) {
943 _par_last_gc_worker_end_times_ms[worker_i] = ms;
944 }
946 void record_pause_time_ms(double ms) {
947 _last_pause_time_ms = ms;
948 }
950 void record_clear_ct_time(double ms) {
951 _cur_clear_ct_time_ms = ms;
952 }
954 void record_par_time(double ms) {
955 _cur_collection_par_time_ms = ms;
956 }
958 void record_aux_start_time(int i) {
959 guarantee(i < _aux_num, "should be within range");
960 _cur_aux_start_times_ms[i] = os::elapsedTime() * 1000.0;
961 }
963 void record_aux_end_time(int i) {
964 guarantee(i < _aux_num, "should be within range");
965 double ms = os::elapsedTime() * 1000.0 - _cur_aux_start_times_ms[i];
966 _cur_aux_times_set[i] = true;
967 _cur_aux_times_ms[i] += ms;
968 }
970 void record_ref_proc_time(double ms) {
971 _cur_ref_proc_time_ms = ms;
972 }
974 void record_ref_enq_time(double ms) {
975 _cur_ref_enq_time_ms = ms;
976 }
978 #ifndef PRODUCT
979 void record_cc_clear_time(double ms) {
980 if (_min_clear_cc_time_ms < 0.0 || ms <= _min_clear_cc_time_ms)
981 _min_clear_cc_time_ms = ms;
982 if (_max_clear_cc_time_ms < 0.0 || ms >= _max_clear_cc_time_ms)
983 _max_clear_cc_time_ms = ms;
984 _cur_clear_cc_time_ms = ms;
985 _cum_clear_cc_time_ms += ms;
986 _num_cc_clears++;
987 }
988 #endif
990 // Record how much space we copied during a GC. This is typically
991 // called when a GC alloc region is being retired.
992 void record_bytes_copied_during_gc(size_t bytes) {
993 _bytes_copied_during_gc += bytes;
994 }
996 // The amount of space we copied during a GC.
997 size_t bytes_copied_during_gc() {
998 return _bytes_copied_during_gc;
999 }
1001 // Choose a new collection set. Marks the chosen regions as being
1002 // "in_collection_set", and links them together. The head and number of
1003 // the collection set are available via access methods.
1004 void choose_collection_set(double target_pause_time_ms);
1006 // The head of the list (via "next_in_collection_set()") representing the
1007 // current collection set.
1008 HeapRegion* collection_set() { return _collection_set; }
1010 void clear_collection_set() { _collection_set = NULL; }
1012 // The number of elements in the current collection set.
1013 size_t collection_set_size() { return _collection_set_size; }
1015 // Add "hr" to the CS.
1016 void add_to_collection_set(HeapRegion* hr);
1018 // Incremental CSet Support
1020 // The head of the incrementally built collection set.
1021 HeapRegion* inc_cset_head() { return _inc_cset_head; }
1023 // The tail of the incrementally built collection set.
1024 HeapRegion* inc_set_tail() { return _inc_cset_tail; }
1026 // The number of elements in the incrementally built collection set.
1027 size_t inc_cset_size() { return _inc_cset_size; }
1029 // Initialize incremental collection set info.
1030 void start_incremental_cset_building();
1032 void clear_incremental_cset() {
1033 _inc_cset_head = NULL;
1034 _inc_cset_tail = NULL;
1035 }
1037 // Stop adding regions to the incremental collection set
1038 void stop_incremental_cset_building() { _inc_cset_build_state = Inactive; }
1040 // Add/remove information about hr to the aggregated information
1041 // for the incrementally built collection set.
1042 void add_to_incremental_cset_info(HeapRegion* hr, size_t rs_length);
1043 void remove_from_incremental_cset_info(HeapRegion* hr);
1045 // Update information about hr in the aggregated information for
1046 // the incrementally built collection set.
1047 void update_incremental_cset_info(HeapRegion* hr, size_t new_rs_length);
1049 private:
1050 // Update the incremental cset information when adding a region
1051 // (should not be called directly).
1052 void add_region_to_incremental_cset_common(HeapRegion* hr);
1054 public:
1055 // Add hr to the LHS of the incremental collection set.
1056 void add_region_to_incremental_cset_lhs(HeapRegion* hr);
1058 // Add hr to the RHS of the incremental collection set.
1059 void add_region_to_incremental_cset_rhs(HeapRegion* hr);
1061 #ifndef PRODUCT
1062 void print_collection_set(HeapRegion* list_head, outputStream* st);
1063 #endif // !PRODUCT
1065 bool initiate_conc_mark_if_possible() { return _initiate_conc_mark_if_possible; }
1066 void set_initiate_conc_mark_if_possible() { _initiate_conc_mark_if_possible = true; }
1067 void clear_initiate_conc_mark_if_possible() { _initiate_conc_mark_if_possible = false; }
1069 bool during_initial_mark_pause() { return _during_initial_mark_pause; }
1070 void set_during_initial_mark_pause() { _during_initial_mark_pause = true; }
1071 void clear_during_initial_mark_pause(){ _during_initial_mark_pause = false; }
1073 // This sets the initiate_conc_mark_if_possible() flag to start a
1074 // new cycle, as long as we are not already in one. It's best if it
1075 // is called during a safepoint when the test whether a cycle is in
1076 // progress or not is stable.
1077 bool force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause);
1079 // This is called at the very beginning of an evacuation pause (it
1080 // has to be the first thing that the pause does). If
1081 // initiate_conc_mark_if_possible() is true, and the concurrent
1082 // marking thread has completed its work during the previous cycle,
1083 // it will set during_initial_mark_pause() to so that the pause does
1084 // the initial-mark work and start a marking cycle.
1085 void decide_on_conc_mark_initiation();
1087 // If an expansion would be appropriate, because recent GC overhead had
1088 // exceeded the desired limit, return an amount to expand by.
1089 size_t expansion_amount();
1091 #ifndef PRODUCT
1092 // Check any appropriate marked bytes info, asserting false if
1093 // something's wrong, else returning "true".
1094 bool assertMarkedBytesDataOK();
1095 #endif
1097 // Print tracing information.
1098 void print_tracing_info() const;
1100 // Print stats on young survival ratio
1101 void print_yg_surv_rate_info() const;
1103 void finished_recalculating_age_indexes(bool is_survivors) {
1104 if (is_survivors) {
1105 _survivor_surv_rate_group->finished_recalculating_age_indexes();
1106 } else {
1107 _short_lived_surv_rate_group->finished_recalculating_age_indexes();
1108 }
1109 // do that for any other surv rate groups
1110 }
1112 bool is_young_list_full() {
1113 size_t young_list_length = _g1->young_list()->length();
1114 size_t young_list_target_length = _young_list_target_length;
1115 return young_list_length >= young_list_target_length;
1116 }
1118 bool can_expand_young_list() {
1119 size_t young_list_length = _g1->young_list()->length();
1120 size_t young_list_max_length = _young_list_max_length;
1121 return young_list_length < young_list_max_length;
1122 }
1124 size_t young_list_max_length() {
1125 return _young_list_max_length;
1126 }
1128 void update_region_num(bool young);
1130 bool full_young_gcs() {
1131 return _full_young_gcs;
1132 }
1133 void set_full_young_gcs(bool full_young_gcs) {
1134 _full_young_gcs = full_young_gcs;
1135 }
1137 bool adaptive_young_list_length() {
1138 return _adaptive_young_list_length;
1139 }
1140 void set_adaptive_young_list_length(bool adaptive_young_list_length) {
1141 _adaptive_young_list_length = adaptive_young_list_length;
1142 }
1144 inline double get_gc_eff_factor() {
1145 double ratio = _known_garbage_ratio;
1147 double square = ratio * ratio;
1148 // square = square * square;
1149 double ret = square * 9.0 + 1.0;
1150 #if 0
1151 gclog_or_tty->print_cr("ratio = %1.2lf, ret = %1.2lf", ratio, ret);
1152 #endif // 0
1153 guarantee(0.0 <= ret && ret < 10.0, "invariant!");
1154 return ret;
1155 }
1157 private:
1158 //
1159 // Survivor regions policy.
1160 //
1162 // Current tenuring threshold, set to 0 if the collector reaches the
1163 // maximum amount of suvivors regions.
1164 int _tenuring_threshold;
1166 // The limit on the number of regions allocated for survivors.
1167 size_t _max_survivor_regions;
1169 // For reporting purposes.
1170 size_t _eden_bytes_before_gc;
1171 size_t _survivor_bytes_before_gc;
1172 size_t _capacity_before_gc;
1174 // The amount of survor regions after a collection.
1175 size_t _recorded_survivor_regions;
1176 // List of survivor regions.
1177 HeapRegion* _recorded_survivor_head;
1178 HeapRegion* _recorded_survivor_tail;
1180 ageTable _survivors_age_table;
1182 public:
1184 inline GCAllocPurpose
1185 evacuation_destination(HeapRegion* src_region, int age, size_t word_sz) {
1186 if (age < _tenuring_threshold && src_region->is_young()) {
1187 return GCAllocForSurvived;
1188 } else {
1189 return GCAllocForTenured;
1190 }
1191 }
1193 inline bool track_object_age(GCAllocPurpose purpose) {
1194 return purpose == GCAllocForSurvived;
1195 }
1197 static const size_t REGIONS_UNLIMITED = ~(size_t)0;
1199 size_t max_regions(int purpose);
1201 // The limit on regions for a particular purpose is reached.
1202 void note_alloc_region_limit_reached(int purpose) {
1203 if (purpose == GCAllocForSurvived) {
1204 _tenuring_threshold = 0;
1205 }
1206 }
1208 void note_start_adding_survivor_regions() {
1209 _survivor_surv_rate_group->start_adding_regions();
1210 }
1212 void note_stop_adding_survivor_regions() {
1213 _survivor_surv_rate_group->stop_adding_regions();
1214 }
1216 void record_survivor_regions(size_t regions,
1217 HeapRegion* head,
1218 HeapRegion* tail) {
1219 _recorded_survivor_regions = regions;
1220 _recorded_survivor_head = head;
1221 _recorded_survivor_tail = tail;
1222 }
1224 size_t recorded_survivor_regions() {
1225 return _recorded_survivor_regions;
1226 }
1228 void record_thread_age_table(ageTable* age_table)
1229 {
1230 _survivors_age_table.merge_par(age_table);
1231 }
1233 void update_max_gc_locker_expansion();
1235 // Calculates survivor space parameters.
1236 void update_survivors_policy();
1238 };
1240 // This should move to some place more general...
1242 // If we have "n" measurements, and we've kept track of their "sum" and the
1243 // "sum_of_squares" of the measurements, this returns the variance of the
1244 // sequence.
1245 inline double variance(int n, double sum_of_squares, double sum) {
1246 double n_d = (double)n;
1247 double avg = sum/n_d;
1248 return (sum_of_squares - 2.0 * avg * sum + n_d * avg * avg) / n_d;
1249 }
1251 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP