Wed, 23 Mar 2011 14:12:51 +0100
6948149: G1: Imbalance in termination times
Summary: Changed default value of WorkStealingYieldsBeforeSleep from 1000 to 5000. Added more information to G1 pause logging.
Reviewed-by: jwilhelm, tonyp, jmasa
1 /*
2 * Copyright (c) 2001, 2010, 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 *
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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,
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18 *
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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) // parallel only
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 protected:
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 virtual size_t default_init_heap_size() {
110 // Pick some reasonable default.
111 return 8*M;
112 }
114 double _cur_collection_start_sec;
115 size_t _cur_collection_pause_used_at_start_bytes;
116 size_t _cur_collection_pause_used_regions_at_start;
117 size_t _prev_collection_pause_used_at_end_bytes;
118 double _cur_collection_par_time_ms;
119 double _cur_satb_drain_time_ms;
120 double _cur_clear_ct_time_ms;
121 bool _satb_drain_time_set;
123 #ifndef PRODUCT
124 // Card Table Count Cache stats
125 double _min_clear_cc_time_ms; // min
126 double _max_clear_cc_time_ms; // max
127 double _cur_clear_cc_time_ms; // clearing time during current pause
128 double _cum_clear_cc_time_ms; // cummulative clearing time
129 jlong _num_cc_clears; // number of times the card count cache has been cleared
130 #endif
132 double _cur_CH_strong_roots_end_sec;
133 double _cur_CH_strong_roots_dur_ms;
134 double _cur_G1_strong_roots_end_sec;
135 double _cur_G1_strong_roots_dur_ms;
137 // Statistics for recent GC pauses. See below for how indexed.
138 TruncatedSeq* _recent_CH_strong_roots_times_ms;
139 TruncatedSeq* _recent_G1_strong_roots_times_ms;
140 TruncatedSeq* _recent_evac_times_ms;
141 // These exclude marking times.
142 TruncatedSeq* _recent_pause_times_ms;
143 TruncatedSeq* _recent_gc_times_ms;
145 TruncatedSeq* _recent_CS_bytes_used_before;
146 TruncatedSeq* _recent_CS_bytes_surviving;
148 TruncatedSeq* _recent_rs_sizes;
150 TruncatedSeq* _concurrent_mark_init_times_ms;
151 TruncatedSeq* _concurrent_mark_remark_times_ms;
152 TruncatedSeq* _concurrent_mark_cleanup_times_ms;
154 Summary* _summary;
156 NumberSeq* _all_pause_times_ms;
157 NumberSeq* _all_full_gc_times_ms;
158 double _stop_world_start;
159 NumberSeq* _all_stop_world_times_ms;
160 NumberSeq* _all_yield_times_ms;
162 size_t _region_num_young;
163 size_t _region_num_tenured;
164 size_t _prev_region_num_young;
165 size_t _prev_region_num_tenured;
167 NumberSeq* _all_mod_union_times_ms;
169 int _aux_num;
170 NumberSeq* _all_aux_times_ms;
171 double* _cur_aux_start_times_ms;
172 double* _cur_aux_times_ms;
173 bool* _cur_aux_times_set;
175 double* _par_last_gc_worker_start_times_ms;
176 double* _par_last_ext_root_scan_times_ms;
177 double* _par_last_mark_stack_scan_times_ms;
178 double* _par_last_update_rs_times_ms;
179 double* _par_last_update_rs_processed_buffers;
180 double* _par_last_scan_rs_times_ms;
181 double* _par_last_obj_copy_times_ms;
182 double* _par_last_termination_times_ms;
183 double* _par_last_termination_attempts;
184 double* _par_last_gc_worker_end_times_ms;
185 double* _par_last_gc_worker_times_ms;
187 // indicates that we are in young GC mode
188 bool _in_young_gc_mode;
190 // indicates whether we are in full young or partially young GC mode
191 bool _full_young_gcs;
193 // if true, then it tries to dynamically adjust the length of the
194 // young list
195 bool _adaptive_young_list_length;
196 size_t _young_list_min_length;
197 size_t _young_list_target_length;
198 size_t _young_list_fixed_length;
200 // The max number of regions we can extend the eden by while the GC
201 // locker is active. This should be >= _young_list_target_length;
202 size_t _young_list_max_length;
204 size_t _young_cset_length;
205 bool _last_young_gc_full;
207 unsigned _full_young_pause_num;
208 unsigned _partial_young_pause_num;
210 bool _during_marking;
211 bool _in_marking_window;
212 bool _in_marking_window_im;
214 SurvRateGroup* _short_lived_surv_rate_group;
215 SurvRateGroup* _survivor_surv_rate_group;
216 // add here any more surv rate groups
218 double _gc_overhead_perc;
220 bool during_marking() {
221 return _during_marking;
222 }
224 // <NEW PREDICTION>
226 private:
227 enum PredictionConstants {
228 TruncatedSeqLength = 10
229 };
231 TruncatedSeq* _alloc_rate_ms_seq;
232 double _prev_collection_pause_end_ms;
234 TruncatedSeq* _pending_card_diff_seq;
235 TruncatedSeq* _rs_length_diff_seq;
236 TruncatedSeq* _cost_per_card_ms_seq;
237 TruncatedSeq* _fully_young_cards_per_entry_ratio_seq;
238 TruncatedSeq* _partially_young_cards_per_entry_ratio_seq;
239 TruncatedSeq* _cost_per_entry_ms_seq;
240 TruncatedSeq* _partially_young_cost_per_entry_ms_seq;
241 TruncatedSeq* _cost_per_byte_ms_seq;
242 TruncatedSeq* _constant_other_time_ms_seq;
243 TruncatedSeq* _young_other_cost_per_region_ms_seq;
244 TruncatedSeq* _non_young_other_cost_per_region_ms_seq;
246 TruncatedSeq* _pending_cards_seq;
247 TruncatedSeq* _scanned_cards_seq;
248 TruncatedSeq* _rs_lengths_seq;
250 TruncatedSeq* _cost_per_byte_ms_during_cm_seq;
252 TruncatedSeq* _young_gc_eff_seq;
254 TruncatedSeq* _max_conc_overhead_seq;
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 protected:
321 double _pause_time_target_ms;
322 double _recorded_young_cset_choice_time_ms;
323 double _recorded_non_young_cset_choice_time_ms;
324 bool _within_target;
325 size_t _pending_cards;
326 size_t _max_pending_cards;
328 public:
330 void set_region_short_lived(HeapRegion* hr) {
331 hr->install_surv_rate_group(_short_lived_surv_rate_group);
332 }
334 void set_region_survivors(HeapRegion* hr) {
335 hr->install_surv_rate_group(_survivor_surv_rate_group);
336 }
338 #ifndef PRODUCT
339 bool verify_young_ages();
340 #endif // PRODUCT
342 double get_new_prediction(TruncatedSeq* seq) {
343 return MAX2(seq->davg() + sigma() * seq->dsd(),
344 seq->davg() * confidence_factor(seq->num()));
345 }
347 size_t young_cset_length() {
348 return _young_cset_length;
349 }
351 void record_max_rs_lengths(size_t rs_lengths) {
352 _max_rs_lengths = rs_lengths;
353 }
355 size_t predict_pending_card_diff() {
356 double prediction = get_new_neg_prediction(_pending_card_diff_seq);
357 if (prediction < 0.00001)
358 return 0;
359 else
360 return (size_t) prediction;
361 }
363 size_t predict_pending_cards() {
364 size_t max_pending_card_num = _g1->max_pending_card_num();
365 size_t diff = predict_pending_card_diff();
366 size_t prediction;
367 if (diff > max_pending_card_num)
368 prediction = max_pending_card_num;
369 else
370 prediction = max_pending_card_num - diff;
372 return prediction;
373 }
375 size_t predict_rs_length_diff() {
376 return (size_t) get_new_prediction(_rs_length_diff_seq);
377 }
379 double predict_alloc_rate_ms() {
380 return get_new_prediction(_alloc_rate_ms_seq);
381 }
383 double predict_cost_per_card_ms() {
384 return get_new_prediction(_cost_per_card_ms_seq);
385 }
387 double predict_rs_update_time_ms(size_t pending_cards) {
388 return (double) pending_cards * predict_cost_per_card_ms();
389 }
391 double predict_fully_young_cards_per_entry_ratio() {
392 return get_new_prediction(_fully_young_cards_per_entry_ratio_seq);
393 }
395 double predict_partially_young_cards_per_entry_ratio() {
396 if (_partially_young_cards_per_entry_ratio_seq->num() < 2)
397 return predict_fully_young_cards_per_entry_ratio();
398 else
399 return get_new_prediction(_partially_young_cards_per_entry_ratio_seq);
400 }
402 size_t predict_young_card_num(size_t rs_length) {
403 return (size_t) ((double) rs_length *
404 predict_fully_young_cards_per_entry_ratio());
405 }
407 size_t predict_non_young_card_num(size_t rs_length) {
408 return (size_t) ((double) rs_length *
409 predict_partially_young_cards_per_entry_ratio());
410 }
412 double predict_rs_scan_time_ms(size_t card_num) {
413 if (full_young_gcs())
414 return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq);
415 else
416 return predict_partially_young_rs_scan_time_ms(card_num);
417 }
419 double predict_partially_young_rs_scan_time_ms(size_t card_num) {
420 if (_partially_young_cost_per_entry_ms_seq->num() < 3)
421 return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq);
422 else
423 return (double) card_num *
424 get_new_prediction(_partially_young_cost_per_entry_ms_seq);
425 }
427 double predict_object_copy_time_ms_during_cm(size_t bytes_to_copy) {
428 if (_cost_per_byte_ms_during_cm_seq->num() < 3)
429 return 1.1 * (double) bytes_to_copy *
430 get_new_prediction(_cost_per_byte_ms_seq);
431 else
432 return (double) bytes_to_copy *
433 get_new_prediction(_cost_per_byte_ms_during_cm_seq);
434 }
436 double predict_object_copy_time_ms(size_t bytes_to_copy) {
437 if (_in_marking_window && !_in_marking_window_im)
438 return predict_object_copy_time_ms_during_cm(bytes_to_copy);
439 else
440 return (double) bytes_to_copy *
441 get_new_prediction(_cost_per_byte_ms_seq);
442 }
444 double predict_constant_other_time_ms() {
445 return get_new_prediction(_constant_other_time_ms_seq);
446 }
448 double predict_young_other_time_ms(size_t young_num) {
449 return
450 (double) young_num *
451 get_new_prediction(_young_other_cost_per_region_ms_seq);
452 }
454 double predict_non_young_other_time_ms(size_t non_young_num) {
455 return
456 (double) non_young_num *
457 get_new_prediction(_non_young_other_cost_per_region_ms_seq);
458 }
460 void check_if_region_is_too_expensive(double predicted_time_ms);
462 double predict_young_collection_elapsed_time_ms(size_t adjustment);
463 double predict_base_elapsed_time_ms(size_t pending_cards);
464 double predict_base_elapsed_time_ms(size_t pending_cards,
465 size_t scanned_cards);
466 size_t predict_bytes_to_copy(HeapRegion* hr);
467 double predict_region_elapsed_time_ms(HeapRegion* hr, bool young);
469 // for use by: calculate_young_list_target_length(rs_length)
470 bool predict_will_fit(size_t young_region_num,
471 double base_time_ms,
472 size_t init_free_regions,
473 double target_pause_time_ms);
475 void start_recording_regions();
476 void record_cset_region_info(HeapRegion* hr, bool young);
477 void record_non_young_cset_region(HeapRegion* hr);
479 void set_recorded_young_regions(size_t n_regions);
480 void set_recorded_young_bytes(size_t bytes);
481 void set_recorded_rs_lengths(size_t rs_lengths);
482 void set_predicted_bytes_to_copy(size_t bytes);
484 void end_recording_regions();
486 void record_vtime_diff_ms(double vtime_diff_ms) {
487 _vtime_diff_ms = vtime_diff_ms;
488 }
490 void record_young_free_cset_time_ms(double time_ms) {
491 _recorded_young_free_cset_time_ms = time_ms;
492 }
494 void record_non_young_free_cset_time_ms(double time_ms) {
495 _recorded_non_young_free_cset_time_ms = time_ms;
496 }
498 double predict_young_gc_eff() {
499 return get_new_neg_prediction(_young_gc_eff_seq);
500 }
502 double predict_survivor_regions_evac_time();
504 // </NEW PREDICTION>
506 public:
507 void cset_regions_freed() {
508 bool propagate = _last_young_gc_full && !_in_marking_window;
509 _short_lived_surv_rate_group->all_surviving_words_recorded(propagate);
510 _survivor_surv_rate_group->all_surviving_words_recorded(propagate);
511 // also call it on any more surv rate groups
512 }
514 void set_known_garbage_bytes(size_t known_garbage_bytes) {
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 void decrease_known_garbage_bytes(size_t known_garbage_bytes) {
521 guarantee( _known_garbage_bytes >= known_garbage_bytes, "invariant" );
523 _known_garbage_bytes -= known_garbage_bytes;
524 size_t heap_bytes = _g1->capacity();
525 _known_garbage_ratio = (double) _known_garbage_bytes / (double) heap_bytes;
526 }
528 G1MMUTracker* mmu_tracker() {
529 return _mmu_tracker;
530 }
532 double max_pause_time_ms() {
533 return _mmu_tracker->max_gc_time() * 1000.0;
534 }
536 double predict_init_time_ms() {
537 return get_new_prediction(_concurrent_mark_init_times_ms);
538 }
540 double predict_remark_time_ms() {
541 return get_new_prediction(_concurrent_mark_remark_times_ms);
542 }
544 double predict_cleanup_time_ms() {
545 return get_new_prediction(_concurrent_mark_cleanup_times_ms);
546 }
548 // Returns an estimate of the survival rate of the region at yg-age
549 // "yg_age".
550 double predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) {
551 TruncatedSeq* seq = surv_rate_group->get_seq(age);
552 if (seq->num() == 0)
553 gclog_or_tty->print("BARF! age is %d", age);
554 guarantee( seq->num() > 0, "invariant" );
555 double pred = get_new_prediction(seq);
556 if (pred > 1.0)
557 pred = 1.0;
558 return pred;
559 }
561 double predict_yg_surv_rate(int age) {
562 return predict_yg_surv_rate(age, _short_lived_surv_rate_group);
563 }
565 double accum_yg_surv_rate_pred(int age) {
566 return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
567 }
569 protected:
570 void print_stats(int level, const char* str, double value);
571 void print_stats(int level, const char* str, int value);
573 void print_par_stats(int level, const char* str, double* data);
574 void print_par_sizes(int level, const char* str, double* data);
576 void check_other_times(int level,
577 NumberSeq* other_times_ms,
578 NumberSeq* calc_other_times_ms) const;
580 void print_summary (PauseSummary* stats) const;
582 void print_summary (int level, const char* str, NumberSeq* seq) const;
583 void print_summary_sd (int level, const char* str, NumberSeq* seq) const;
585 double avg_value (double* data);
586 double max_value (double* data);
587 double sum_of_values (double* data);
588 double max_sum (double* data1, double* data2);
590 int _last_satb_drain_processed_buffers;
591 int _last_update_rs_processed_buffers;
592 double _last_pause_time_ms;
594 size_t _bytes_in_to_space_before_gc;
595 size_t _bytes_in_to_space_after_gc;
596 size_t bytes_in_to_space_during_gc() {
597 return
598 _bytes_in_to_space_after_gc - _bytes_in_to_space_before_gc;
599 }
600 size_t _bytes_in_collection_set_before_gc;
601 // Used to count used bytes in CS.
602 friend class CountCSClosure;
604 // Statistics kept per GC stoppage, pause or full.
605 TruncatedSeq* _recent_prev_end_times_for_all_gcs_sec;
607 // We track markings.
608 int _num_markings;
609 double _mark_thread_startup_sec; // Time at startup of marking thread
611 // Add a new GC of the given duration and end time to the record.
612 void update_recent_gc_times(double end_time_sec, double elapsed_ms);
614 // The head of the list (via "next_in_collection_set()") representing the
615 // current collection set. Set from the incrementally built collection
616 // set at the start of the pause.
617 HeapRegion* _collection_set;
619 // The number of regions in the collection set. Set from the incrementally
620 // built collection set at the start of an evacuation pause.
621 size_t _collection_set_size;
623 // The number of bytes in the collection set before the pause. Set from
624 // the incrementally built collection set at the start of an evacuation
625 // pause.
626 size_t _collection_set_bytes_used_before;
628 // The associated information that is maintained while the incremental
629 // collection set is being built with young regions. Used to populate
630 // the recorded info for the evacuation pause.
632 enum CSetBuildType {
633 Active, // We are actively building the collection set
634 Inactive // We are not actively building the collection set
635 };
637 CSetBuildType _inc_cset_build_state;
639 // The head of the incrementally built collection set.
640 HeapRegion* _inc_cset_head;
642 // The tail of the incrementally built collection set.
643 HeapRegion* _inc_cset_tail;
645 // The number of regions in the incrementally built collection set.
646 // Used to set _collection_set_size at the start of an evacuation
647 // pause.
648 size_t _inc_cset_size;
650 // Used as the index in the surving young words structure
651 // which tracks the amount of space, for each young region,
652 // that survives the pause.
653 size_t _inc_cset_young_index;
655 // The number of bytes in the incrementally built collection set.
656 // Used to set _collection_set_bytes_used_before at the start of
657 // an evacuation pause.
658 size_t _inc_cset_bytes_used_before;
660 // Used to record the highest end of heap region in collection set
661 HeapWord* _inc_cset_max_finger;
663 // The number of recorded used bytes in the young regions
664 // of the collection set. This is the sum of the used() bytes
665 // of retired young regions in the collection set.
666 size_t _inc_cset_recorded_young_bytes;
668 // The RSet lengths recorded for regions in the collection set
669 // (updated by the periodic sampling of the regions in the
670 // young list/collection set).
671 size_t _inc_cset_recorded_rs_lengths;
673 // The predicted elapsed time it will take to collect the regions
674 // in the collection set (updated by the periodic sampling of the
675 // regions in the young list/collection set).
676 double _inc_cset_predicted_elapsed_time_ms;
678 // The predicted bytes to copy for the regions in the collection
679 // set (updated by the periodic sampling of the regions in the
680 // young list/collection set).
681 size_t _inc_cset_predicted_bytes_to_copy;
683 // Info about marking.
684 int _n_marks; // Sticky at 2, so we know when we've done at least 2.
686 // The number of collection pauses at the end of the last mark.
687 size_t _n_pauses_at_mark_end;
689 // Stash a pointer to the g1 heap.
690 G1CollectedHeap* _g1;
692 // The average time in ms per collection pause, averaged over recent pauses.
693 double recent_avg_time_for_pauses_ms();
695 // The average time in ms for processing CollectedHeap strong roots, per
696 // collection pause, averaged over recent pauses.
697 double recent_avg_time_for_CH_strong_ms();
699 // The average time in ms for processing the G1 remembered set, per
700 // pause, averaged over recent pauses.
701 double recent_avg_time_for_G1_strong_ms();
703 // The average time in ms for "evacuating followers", per pause, averaged
704 // over recent pauses.
705 double recent_avg_time_for_evac_ms();
707 // The number of "recent" GCs recorded in the number sequences
708 int number_of_recent_gcs();
710 // The average survival ratio, computed by the total number of bytes
711 // suriviving / total number of bytes before collection over the last
712 // several recent pauses.
713 double recent_avg_survival_fraction();
714 // The survival fraction of the most recent pause; if there have been no
715 // pauses, returns 1.0.
716 double last_survival_fraction();
718 // Returns a "conservative" estimate of the recent survival rate, i.e.,
719 // one that may be higher than "recent_avg_survival_fraction".
720 // This is conservative in several ways:
721 // If there have been few pauses, it will assume a potential high
722 // variance, and err on the side of caution.
723 // It puts a lower bound (currently 0.1) on the value it will return.
724 // To try to detect phase changes, if the most recent pause ("latest") has a
725 // higher-than average ("avg") survival rate, it returns that rate.
726 // "work" version is a utility function; young is restricted to young regions.
727 double conservative_avg_survival_fraction_work(double avg,
728 double latest);
730 // The arguments are the two sequences that keep track of the number of bytes
731 // surviving and the total number of bytes before collection, resp.,
732 // over the last evereal recent pauses
733 // Returns the survival rate for the category in the most recent pause.
734 // If there have been no pauses, returns 1.0.
735 double last_survival_fraction_work(TruncatedSeq* surviving,
736 TruncatedSeq* before);
738 // The arguments are the two sequences that keep track of the number of bytes
739 // surviving and the total number of bytes before collection, resp.,
740 // over the last several recent pauses
741 // Returns the average survival ration over the last several recent pauses
742 // If there have been no pauses, return 1.0
743 double recent_avg_survival_fraction_work(TruncatedSeq* surviving,
744 TruncatedSeq* before);
746 double conservative_avg_survival_fraction() {
747 double avg = recent_avg_survival_fraction();
748 double latest = last_survival_fraction();
749 return conservative_avg_survival_fraction_work(avg, latest);
750 }
752 // The ratio of gc time to elapsed time, computed over recent pauses.
753 double _recent_avg_pause_time_ratio;
755 double recent_avg_pause_time_ratio() {
756 return _recent_avg_pause_time_ratio;
757 }
759 // Number of pauses between concurrent marking.
760 size_t _pauses_btwn_concurrent_mark;
762 size_t _n_marks_since_last_pause;
764 // At the end of a pause we check the heap occupancy and we decide
765 // whether we will start a marking cycle during the next pause. If
766 // we decide that we want to do that, we will set this parameter to
767 // true. So, this parameter will stay true between the end of a
768 // pause and the beginning of a subsequent pause (not necessarily
769 // the next one, see the comments on the next field) when we decide
770 // that we will indeed start a marking cycle and do the initial-mark
771 // work.
772 volatile bool _initiate_conc_mark_if_possible;
774 // If initiate_conc_mark_if_possible() is set at the beginning of a
775 // pause, it is a suggestion that the pause should start a marking
776 // cycle by doing the initial-mark work. However, it is possible
777 // that the concurrent marking thread is still finishing up the
778 // previous marking cycle (e.g., clearing the next marking
779 // bitmap). If that is the case we cannot start a new cycle and
780 // we'll have to wait for the concurrent marking thread to finish
781 // what it is doing. In this case we will postpone the marking cycle
782 // initiation decision for the next pause. When we eventually decide
783 // to start a cycle, we will set _during_initial_mark_pause which
784 // will stay true until the end of the initial-mark pause and it's
785 // the condition that indicates that a pause is doing the
786 // initial-mark work.
787 volatile bool _during_initial_mark_pause;
789 bool _should_revert_to_full_young_gcs;
790 bool _last_full_young_gc;
792 // This set of variables tracks the collector efficiency, in order to
793 // determine whether we should initiate a new marking.
794 double _cur_mark_stop_world_time_ms;
795 double _mark_init_start_sec;
796 double _mark_remark_start_sec;
797 double _mark_cleanup_start_sec;
798 double _mark_closure_time_ms;
800 void calculate_young_list_min_length();
801 void calculate_young_list_target_length();
802 void calculate_young_list_target_length(size_t rs_lengths);
804 public:
806 G1CollectorPolicy();
808 virtual G1CollectorPolicy* as_g1_policy() { return this; }
810 virtual CollectorPolicy::Name kind() {
811 return CollectorPolicy::G1CollectorPolicyKind;
812 }
814 void check_prediction_validity();
816 size_t bytes_in_collection_set() {
817 return _bytes_in_collection_set_before_gc;
818 }
820 size_t bytes_in_to_space() {
821 return bytes_in_to_space_during_gc();
822 }
824 unsigned calc_gc_alloc_time_stamp() {
825 return _all_pause_times_ms->num() + 1;
826 }
828 protected:
830 // Count the number of bytes used in the CS.
831 void count_CS_bytes_used();
833 // Together these do the base cleanup-recording work. Subclasses might
834 // want to put something between them.
835 void record_concurrent_mark_cleanup_end_work1(size_t freed_bytes,
836 size_t max_live_bytes);
837 void record_concurrent_mark_cleanup_end_work2();
839 public:
841 virtual void init();
843 // Create jstat counters for the policy.
844 virtual void initialize_gc_policy_counters();
846 virtual HeapWord* mem_allocate_work(size_t size,
847 bool is_tlab,
848 bool* gc_overhead_limit_was_exceeded);
850 // This method controls how a collector handles one or more
851 // of its generations being fully allocated.
852 virtual HeapWord* satisfy_failed_allocation(size_t size,
853 bool is_tlab);
855 BarrierSet::Name barrier_set_name() { return BarrierSet::G1SATBCTLogging; }
857 GenRemSet::Name rem_set_name() { return GenRemSet::CardTable; }
859 // The number of collection pauses so far.
860 long n_pauses() const { return _n_pauses; }
862 // Update the heuristic info to record a collection pause of the given
863 // start time, where the given number of bytes were used at the start.
864 // This may involve changing the desired size of a collection set.
866 virtual void record_stop_world_start();
868 virtual void record_collection_pause_start(double start_time_sec,
869 size_t start_used);
871 // Must currently be called while the world is stopped.
872 virtual void record_concurrent_mark_init_start();
873 virtual void record_concurrent_mark_init_end();
874 void record_concurrent_mark_init_end_pre(double
875 mark_init_elapsed_time_ms);
877 void record_mark_closure_time(double mark_closure_time_ms);
879 virtual void record_concurrent_mark_remark_start();
880 virtual void record_concurrent_mark_remark_end();
882 virtual void record_concurrent_mark_cleanup_start();
883 virtual void record_concurrent_mark_cleanup_end(size_t freed_bytes,
884 size_t max_live_bytes);
885 virtual void record_concurrent_mark_cleanup_completed();
887 virtual void record_concurrent_pause();
888 virtual void record_concurrent_pause_end();
890 virtual void record_collection_pause_end_CH_strong_roots();
891 virtual void record_collection_pause_end_G1_strong_roots();
893 virtual void record_collection_pause_end();
895 // Record the fact that a full collection occurred.
896 virtual void record_full_collection_start();
897 virtual void record_full_collection_end();
899 void record_gc_worker_start_time(int worker_i, double ms) {
900 _par_last_gc_worker_start_times_ms[worker_i] = ms;
901 }
903 void record_ext_root_scan_time(int worker_i, double ms) {
904 _par_last_ext_root_scan_times_ms[worker_i] = ms;
905 }
907 void record_mark_stack_scan_time(int worker_i, double ms) {
908 _par_last_mark_stack_scan_times_ms[worker_i] = ms;
909 }
911 void record_satb_drain_time(double ms) {
912 _cur_satb_drain_time_ms = ms;
913 _satb_drain_time_set = true;
914 }
916 void record_satb_drain_processed_buffers (int processed_buffers) {
917 _last_satb_drain_processed_buffers = processed_buffers;
918 }
920 void record_mod_union_time(double ms) {
921 _all_mod_union_times_ms->add(ms);
922 }
924 void record_update_rs_time(int thread, double ms) {
925 _par_last_update_rs_times_ms[thread] = ms;
926 }
928 void record_update_rs_processed_buffers (int thread,
929 double processed_buffers) {
930 _par_last_update_rs_processed_buffers[thread] = processed_buffers;
931 }
933 void record_scan_rs_time(int thread, double ms) {
934 _par_last_scan_rs_times_ms[thread] = ms;
935 }
937 void reset_obj_copy_time(int thread) {
938 _par_last_obj_copy_times_ms[thread] = 0.0;
939 }
941 void reset_obj_copy_time() {
942 reset_obj_copy_time(0);
943 }
945 void record_obj_copy_time(int thread, double ms) {
946 _par_last_obj_copy_times_ms[thread] += ms;
947 }
949 void record_termination(int thread, double ms, size_t attempts) {
950 _par_last_termination_times_ms[thread] = ms;
951 _par_last_termination_attempts[thread] = (double) attempts;
952 }
954 void record_gc_worker_end_time(int worker_i, double ms) {
955 _par_last_gc_worker_end_times_ms[worker_i] = ms;
956 }
958 void record_pause_time_ms(double ms) {
959 _last_pause_time_ms = ms;
960 }
962 void record_clear_ct_time(double ms) {
963 _cur_clear_ct_time_ms = ms;
964 }
966 void record_par_time(double ms) {
967 _cur_collection_par_time_ms = ms;
968 }
970 void record_aux_start_time(int i) {
971 guarantee(i < _aux_num, "should be within range");
972 _cur_aux_start_times_ms[i] = os::elapsedTime() * 1000.0;
973 }
975 void record_aux_end_time(int i) {
976 guarantee(i < _aux_num, "should be within range");
977 double ms = os::elapsedTime() * 1000.0 - _cur_aux_start_times_ms[i];
978 _cur_aux_times_set[i] = true;
979 _cur_aux_times_ms[i] += ms;
980 }
982 #ifndef PRODUCT
983 void record_cc_clear_time(double ms) {
984 if (_min_clear_cc_time_ms < 0.0 || ms <= _min_clear_cc_time_ms)
985 _min_clear_cc_time_ms = ms;
986 if (_max_clear_cc_time_ms < 0.0 || ms >= _max_clear_cc_time_ms)
987 _max_clear_cc_time_ms = ms;
988 _cur_clear_cc_time_ms = ms;
989 _cum_clear_cc_time_ms += ms;
990 _num_cc_clears++;
991 }
992 #endif
994 // Record the fact that "bytes" bytes allocated in a region.
995 void record_before_bytes(size_t bytes);
996 void record_after_bytes(size_t bytes);
998 // Choose a new collection set. Marks the chosen regions as being
999 // "in_collection_set", and links them together. The head and number of
1000 // the collection set are available via access methods.
1001 virtual void choose_collection_set(double target_pause_time_ms) = 0;
1003 // The head of the list (via "next_in_collection_set()") representing the
1004 // current collection set.
1005 HeapRegion* collection_set() { return _collection_set; }
1007 void clear_collection_set() { _collection_set = NULL; }
1009 // The number of elements in the current collection set.
1010 size_t collection_set_size() { return _collection_set_size; }
1012 // Add "hr" to the CS.
1013 void add_to_collection_set(HeapRegion* hr);
1015 // Incremental CSet Support
1017 // The head of the incrementally built collection set.
1018 HeapRegion* inc_cset_head() { return _inc_cset_head; }
1020 // The tail of the incrementally built collection set.
1021 HeapRegion* inc_set_tail() { return _inc_cset_tail; }
1023 // The number of elements in the incrementally built collection set.
1024 size_t inc_cset_size() { return _inc_cset_size; }
1026 // Initialize incremental collection set info.
1027 void start_incremental_cset_building();
1029 void clear_incremental_cset() {
1030 _inc_cset_head = NULL;
1031 _inc_cset_tail = NULL;
1032 }
1034 // Stop adding regions to the incremental collection set
1035 void stop_incremental_cset_building() { _inc_cset_build_state = Inactive; }
1037 // Add/remove information about hr to the aggregated information
1038 // for the incrementally built collection set.
1039 void add_to_incremental_cset_info(HeapRegion* hr, size_t rs_length);
1040 void remove_from_incremental_cset_info(HeapRegion* hr);
1042 // Update information about hr in the aggregated information for
1043 // the incrementally built collection set.
1044 void update_incremental_cset_info(HeapRegion* hr, size_t new_rs_length);
1046 private:
1047 // Update the incremental cset information when adding a region
1048 // (should not be called directly).
1049 void add_region_to_incremental_cset_common(HeapRegion* hr);
1051 public:
1052 // Add hr to the LHS of the incremental collection set.
1053 void add_region_to_incremental_cset_lhs(HeapRegion* hr);
1055 // Add hr to the RHS of the incremental collection set.
1056 void add_region_to_incremental_cset_rhs(HeapRegion* hr);
1058 #ifndef PRODUCT
1059 void print_collection_set(HeapRegion* list_head, outputStream* st);
1060 #endif // !PRODUCT
1062 bool initiate_conc_mark_if_possible() { return _initiate_conc_mark_if_possible; }
1063 void set_initiate_conc_mark_if_possible() { _initiate_conc_mark_if_possible = true; }
1064 void clear_initiate_conc_mark_if_possible() { _initiate_conc_mark_if_possible = false; }
1066 bool during_initial_mark_pause() { return _during_initial_mark_pause; }
1067 void set_during_initial_mark_pause() { _during_initial_mark_pause = true; }
1068 void clear_during_initial_mark_pause(){ _during_initial_mark_pause = false; }
1070 // This sets the initiate_conc_mark_if_possible() flag to start a
1071 // new cycle, as long as we are not already in one. It's best if it
1072 // is called during a safepoint when the test whether a cycle is in
1073 // progress or not is stable.
1074 bool force_initial_mark_if_outside_cycle();
1076 // This is called at the very beginning of an evacuation pause (it
1077 // has to be the first thing that the pause does). If
1078 // initiate_conc_mark_if_possible() is true, and the concurrent
1079 // marking thread has completed its work during the previous cycle,
1080 // it will set during_initial_mark_pause() to so that the pause does
1081 // the initial-mark work and start a marking cycle.
1082 void decide_on_conc_mark_initiation();
1084 // If an expansion would be appropriate, because recent GC overhead had
1085 // exceeded the desired limit, return an amount to expand by.
1086 virtual size_t expansion_amount();
1088 // note start of mark thread
1089 void note_start_of_mark_thread();
1091 // The marked bytes of the "r" has changed; reclassify it's desirability
1092 // for marking. Also asserts that "r" is eligible for a CS.
1093 virtual void note_change_in_marked_bytes(HeapRegion* r) = 0;
1095 #ifndef PRODUCT
1096 // Check any appropriate marked bytes info, asserting false if
1097 // something's wrong, else returning "true".
1098 virtual bool assertMarkedBytesDataOK() = 0;
1099 #endif
1101 // Print tracing information.
1102 void print_tracing_info() const;
1104 // Print stats on young survival ratio
1105 void print_yg_surv_rate_info() const;
1107 void finished_recalculating_age_indexes(bool is_survivors) {
1108 if (is_survivors) {
1109 _survivor_surv_rate_group->finished_recalculating_age_indexes();
1110 } else {
1111 _short_lived_surv_rate_group->finished_recalculating_age_indexes();
1112 }
1113 // do that for any other surv rate groups
1114 }
1116 bool is_young_list_full() {
1117 size_t young_list_length = _g1->young_list()->length();
1118 size_t young_list_target_length = _young_list_target_length;
1119 if (G1FixedEdenSize) {
1120 young_list_target_length -= _max_survivor_regions;
1121 }
1122 return young_list_length >= young_list_target_length;
1123 }
1125 bool can_expand_young_list() {
1126 size_t young_list_length = _g1->young_list()->length();
1127 size_t young_list_max_length = _young_list_max_length;
1128 if (G1FixedEdenSize) {
1129 young_list_max_length -= _max_survivor_regions;
1130 }
1131 return young_list_length < young_list_max_length;
1132 }
1134 void update_region_num(bool young);
1136 bool in_young_gc_mode() {
1137 return _in_young_gc_mode;
1138 }
1139 void set_in_young_gc_mode(bool in_young_gc_mode) {
1140 _in_young_gc_mode = in_young_gc_mode;
1141 }
1143 bool full_young_gcs() {
1144 return _full_young_gcs;
1145 }
1146 void set_full_young_gcs(bool full_young_gcs) {
1147 _full_young_gcs = full_young_gcs;
1148 }
1150 bool adaptive_young_list_length() {
1151 return _adaptive_young_list_length;
1152 }
1153 void set_adaptive_young_list_length(bool adaptive_young_list_length) {
1154 _adaptive_young_list_length = adaptive_young_list_length;
1155 }
1157 inline double get_gc_eff_factor() {
1158 double ratio = _known_garbage_ratio;
1160 double square = ratio * ratio;
1161 // square = square * square;
1162 double ret = square * 9.0 + 1.0;
1163 #if 0
1164 gclog_or_tty->print_cr("ratio = %1.2lf, ret = %1.2lf", ratio, ret);
1165 #endif // 0
1166 guarantee(0.0 <= ret && ret < 10.0, "invariant!");
1167 return ret;
1168 }
1170 //
1171 // Survivor regions policy.
1172 //
1173 protected:
1175 // Current tenuring threshold, set to 0 if the collector reaches the
1176 // maximum amount of suvivors regions.
1177 int _tenuring_threshold;
1179 // The limit on the number of regions allocated for survivors.
1180 size_t _max_survivor_regions;
1182 // The amount of survor regions after a collection.
1183 size_t _recorded_survivor_regions;
1184 // List of survivor regions.
1185 HeapRegion* _recorded_survivor_head;
1186 HeapRegion* _recorded_survivor_tail;
1188 ageTable _survivors_age_table;
1190 public:
1192 inline GCAllocPurpose
1193 evacuation_destination(HeapRegion* src_region, int age, size_t word_sz) {
1194 if (age < _tenuring_threshold && src_region->is_young()) {
1195 return GCAllocForSurvived;
1196 } else {
1197 return GCAllocForTenured;
1198 }
1199 }
1201 inline bool track_object_age(GCAllocPurpose purpose) {
1202 return purpose == GCAllocForSurvived;
1203 }
1205 inline GCAllocPurpose alternative_purpose(int purpose) {
1206 return GCAllocForTenured;
1207 }
1209 static const size_t REGIONS_UNLIMITED = ~(size_t)0;
1211 size_t max_regions(int purpose);
1213 // The limit on regions for a particular purpose is reached.
1214 void note_alloc_region_limit_reached(int purpose) {
1215 if (purpose == GCAllocForSurvived) {
1216 _tenuring_threshold = 0;
1217 }
1218 }
1220 void note_start_adding_survivor_regions() {
1221 _survivor_surv_rate_group->start_adding_regions();
1222 }
1224 void note_stop_adding_survivor_regions() {
1225 _survivor_surv_rate_group->stop_adding_regions();
1226 }
1228 void record_survivor_regions(size_t regions,
1229 HeapRegion* head,
1230 HeapRegion* tail) {
1231 _recorded_survivor_regions = regions;
1232 _recorded_survivor_head = head;
1233 _recorded_survivor_tail = tail;
1234 }
1236 size_t recorded_survivor_regions() {
1237 return _recorded_survivor_regions;
1238 }
1240 void record_thread_age_table(ageTable* age_table)
1241 {
1242 _survivors_age_table.merge_par(age_table);
1243 }
1245 void calculate_max_gc_locker_expansion();
1247 // Calculates survivor space parameters.
1248 void calculate_survivors_policy();
1250 };
1252 // This encapsulates a particular strategy for a g1 Collector.
1253 //
1254 // Start a concurrent mark when our heap size is n bytes
1255 // greater then our heap size was at the last concurrent
1256 // mark. Where n is a function of the CMSTriggerRatio
1257 // and the MinHeapFreeRatio.
1258 //
1259 // Start a g1 collection pause when we have allocated the
1260 // average number of bytes currently being freed in
1261 // a collection, but only if it is at least one region
1262 // full
1263 //
1264 // Resize Heap based on desired
1265 // allocation space, where desired allocation space is
1266 // a function of survival rate and desired future to size.
1267 //
1268 // Choose collection set by first picking all older regions
1269 // which have a survival rate which beats our projected young
1270 // survival rate. Then fill out the number of needed regions
1271 // with young regions.
1273 class G1CollectorPolicy_BestRegionsFirst: public G1CollectorPolicy {
1274 CollectionSetChooser* _collectionSetChooser;
1275 // If the estimated is less then desirable, resize if possible.
1276 void expand_if_possible(size_t numRegions);
1278 virtual void choose_collection_set(double target_pause_time_ms);
1279 virtual void record_collection_pause_start(double start_time_sec,
1280 size_t start_used);
1281 virtual void record_concurrent_mark_cleanup_end(size_t freed_bytes,
1282 size_t max_live_bytes);
1283 virtual void record_full_collection_end();
1285 public:
1286 G1CollectorPolicy_BestRegionsFirst() {
1287 _collectionSetChooser = new CollectionSetChooser();
1288 }
1289 void record_collection_pause_end();
1290 // This is not needed any more, after the CSet choosing code was
1291 // changed to use the pause prediction work. But let's leave the
1292 // hook in just in case.
1293 void note_change_in_marked_bytes(HeapRegion* r) { }
1294 #ifndef PRODUCT
1295 bool assertMarkedBytesDataOK();
1296 #endif
1297 };
1299 // This should move to some place more general...
1301 // If we have "n" measurements, and we've kept track of their "sum" and the
1302 // "sum_of_squares" of the measurements, this returns the variance of the
1303 // sequence.
1304 inline double variance(int n, double sum_of_squares, double sum) {
1305 double n_d = (double)n;
1306 double avg = sum/n_d;
1307 return (sum_of_squares - 2.0 * avg * sum + n_d * avg * avg) / n_d;
1308 }
1310 // Local Variables: ***
1311 // c-indentation-style: gnu ***
1312 // End: ***
1314 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP