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 *
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.
22 *
23 */
24
25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP
27
28 #include "gc_implementation/g1/collectionSetChooser.hpp"
29 #include "gc_implementation/g1/g1MMUTracker.hpp"
30 #include "memory/collectorPolicy.hpp"
31
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.
36
37 class HeapRegion;
38 class CollectionSetChooser;
39
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.
44
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 }
55
56 class MainBodySummary;
57
58 class PauseSummary: public CHeapObj {
59 define_num_seq(total)
60 define_num_seq(other)
61
62 public:
63 virtual MainBodySummary* main_body_summary() { return NULL; }
64 };
65
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 };
79
80 class Summary: public PauseSummary,
81 public MainBodySummary {
82 public:
83 virtual MainBodySummary* main_body_summary() { return this; }
84 };
85
86 class G1CollectorPolicy: public CollectorPolicy {
87 protected:
88 // The number of pauses during the execution.
89 long _n_pauses;
90
91 // either equal to the number of parallel threads, if ParallelGCThreads
92 // has been set, or 1 otherwise
93 int _parallel_gc_threads;
94
95 enum SomePrivateConstants {
96 NumPrevPausesForHeuristics = 10
97 };
98
99 G1MMUTracker* _mmu_tracker;
100
101 void initialize_flags();
102
103 void initialize_all() {
104 initialize_flags();
105 initialize_size_info();
106 initialize_perm_generation(PermGen::MarkSweepCompact);
107 }
108
109 virtual size_t default_init_heap_size() {
110 // Pick some reasonable default.
111 return 8*M;
112 }
113
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;
122
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
131
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;
136
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;
144
145 TruncatedSeq* _recent_CS_bytes_used_before;
146 TruncatedSeq* _recent_CS_bytes_surviving;
147
148 TruncatedSeq* _recent_rs_sizes;
149
150 TruncatedSeq* _concurrent_mark_init_times_ms;
151 TruncatedSeq* _concurrent_mark_remark_times_ms;
152 TruncatedSeq* _concurrent_mark_cleanup_times_ms;
153
154 Summary* _summary;
155
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;
161
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;
166
167 NumberSeq* _all_mod_union_times_ms;
168
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;
174
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
186 // indicates that we are in young GC mode
187 bool _in_young_gc_mode;
188
189 // indicates whether we are in full young or partially young GC mode
190 bool _full_young_gcs;
191
192 // if true, then it tries to dynamically adjust the length of the
193 // young list
194 bool _adaptive_young_list_length;
195 size_t _young_list_min_length;
196 size_t _young_list_target_length;
197 size_t _young_list_fixed_length;
198
199 size_t _young_cset_length;
200 bool _last_young_gc_full;
201
202 unsigned _full_young_pause_num;
203 unsigned _partial_young_pause_num;
204
205 bool _during_marking;
206 bool _in_marking_window;
207 bool _in_marking_window_im;
208
209 SurvRateGroup* _short_lived_surv_rate_group;
210 SurvRateGroup* _survivor_surv_rate_group;
211 // add here any more surv rate groups
212
213 double _gc_overhead_perc;
214
215 bool during_marking() {
216 return _during_marking;
217 }
218
219 // <NEW PREDICTION>
220
221 private:
222 enum PredictionConstants {
223 TruncatedSeqLength = 10
224 };
225
226 TruncatedSeq* _alloc_rate_ms_seq;
227 double _prev_collection_pause_end_ms;
228
229 TruncatedSeq* _pending_card_diff_seq;
230 TruncatedSeq* _rs_length_diff_seq;
231 TruncatedSeq* _cost_per_card_ms_seq;
232 TruncatedSeq* _fully_young_cards_per_entry_ratio_seq;
233 TruncatedSeq* _partially_young_cards_per_entry_ratio_seq;
234 TruncatedSeq* _cost_per_entry_ms_seq;
235 TruncatedSeq* _partially_young_cost_per_entry_ms_seq;
236 TruncatedSeq* _cost_per_byte_ms_seq;
237 TruncatedSeq* _constant_other_time_ms_seq;
238 TruncatedSeq* _young_other_cost_per_region_ms_seq;
239 TruncatedSeq* _non_young_other_cost_per_region_ms_seq;
240
241 TruncatedSeq* _pending_cards_seq;
242 TruncatedSeq* _scanned_cards_seq;
243 TruncatedSeq* _rs_lengths_seq;
244
245 TruncatedSeq* _cost_per_byte_ms_during_cm_seq;
246
247 TruncatedSeq* _young_gc_eff_seq;
248
249 TruncatedSeq* _max_conc_overhead_seq;
250
251 size_t _recorded_young_regions;
252 size_t _recorded_non_young_regions;
253 size_t _recorded_region_num;
254
255 size_t _free_regions_at_end_of_collection;
256
257 size_t _recorded_rs_lengths;
258 size_t _max_rs_lengths;
259
260 size_t _recorded_marked_bytes;
261 size_t _recorded_young_bytes;
262
263 size_t _predicted_pending_cards;
264 size_t _predicted_cards_scanned;
265 size_t _predicted_rs_lengths;
266 size_t _predicted_bytes_to_copy;
267
268 double _predicted_survival_ratio;
269 double _predicted_rs_update_time_ms;
270 double _predicted_rs_scan_time_ms;
271 double _predicted_object_copy_time_ms;
272 double _predicted_constant_other_time_ms;
273 double _predicted_young_other_time_ms;
274 double _predicted_non_young_other_time_ms;
275 double _predicted_pause_time_ms;
276
277 double _vtime_diff_ms;
278
279 double _recorded_young_free_cset_time_ms;
280 double _recorded_non_young_free_cset_time_ms;
281
282 double _sigma;
283 double _expensive_region_limit_ms;
284
285 size_t _rs_lengths_prediction;
286
287 size_t _known_garbage_bytes;
288 double _known_garbage_ratio;
289
290 double sigma() {
291 return _sigma;
292 }
293
294 // A function that prevents us putting too much stock in small sample
295 // sets. Returns a number between 2.0 and 1.0, depending on the number
296 // of samples. 5 or more samples yields one; fewer scales linearly from
297 // 2.0 at 1 sample to 1.0 at 5.
298 double confidence_factor(int samples) {
299 if (samples > 4) return 1.0;
300 else return 1.0 + sigma() * ((double)(5 - samples))/2.0;
301 }
302
303 double get_new_neg_prediction(TruncatedSeq* seq) {
304 return seq->davg() - sigma() * seq->dsd();
305 }
306
307 #ifndef PRODUCT
308 bool verify_young_ages(HeapRegion* head, SurvRateGroup *surv_rate_group);
309 #endif // PRODUCT
310
311 void adjust_concurrent_refinement(double update_rs_time,
312 double update_rs_processed_buffers,
313 double goal_ms);
314
315 protected:
316 double _pause_time_target_ms;
317 double _recorded_young_cset_choice_time_ms;
318 double _recorded_non_young_cset_choice_time_ms;
319 bool _within_target;
320 size_t _pending_cards;
321 size_t _max_pending_cards;
322
323 public:
324
325 void set_region_short_lived(HeapRegion* hr) {
326 hr->install_surv_rate_group(_short_lived_surv_rate_group);
327 }
328
329 void set_region_survivors(HeapRegion* hr) {
330 hr->install_surv_rate_group(_survivor_surv_rate_group);
331 }
332
333 #ifndef PRODUCT
334 bool verify_young_ages();
335 #endif // PRODUCT
336
337 double get_new_prediction(TruncatedSeq* seq) {
338 return MAX2(seq->davg() + sigma() * seq->dsd(),
339 seq->davg() * confidence_factor(seq->num()));
340 }
341
342 size_t young_cset_length() {
343 return _young_cset_length;
344 }
345
346 void record_max_rs_lengths(size_t rs_lengths) {
347 _max_rs_lengths = rs_lengths;
348 }
349
350 size_t predict_pending_card_diff() {
351 double prediction = get_new_neg_prediction(_pending_card_diff_seq);
352 if (prediction < 0.00001)
353 return 0;
354 else
355 return (size_t) prediction;
356 }
357
358 size_t predict_pending_cards() {
359 size_t max_pending_card_num = _g1->max_pending_card_num();
360 size_t diff = predict_pending_card_diff();
361 size_t prediction;
362 if (diff > max_pending_card_num)
363 prediction = max_pending_card_num;
364 else
365 prediction = max_pending_card_num - diff;
366
367 return prediction;
368 }
369
370 size_t predict_rs_length_diff() {
371 return (size_t) get_new_prediction(_rs_length_diff_seq);
372 }
373
374 double predict_alloc_rate_ms() {
375 return get_new_prediction(_alloc_rate_ms_seq);
376 }
377
378 double predict_cost_per_card_ms() {
379 return get_new_prediction(_cost_per_card_ms_seq);
380 }
381
382 double predict_rs_update_time_ms(size_t pending_cards) {
383 return (double) pending_cards * predict_cost_per_card_ms();
384 }
385
386 double predict_fully_young_cards_per_entry_ratio() {
387 return get_new_prediction(_fully_young_cards_per_entry_ratio_seq);
388 }
389
390 double predict_partially_young_cards_per_entry_ratio() {
391 if (_partially_young_cards_per_entry_ratio_seq->num() < 2)
392 return predict_fully_young_cards_per_entry_ratio();
393 else
394 return get_new_prediction(_partially_young_cards_per_entry_ratio_seq);
395 }
396
397 size_t predict_young_card_num(size_t rs_length) {
398 return (size_t) ((double) rs_length *
399 predict_fully_young_cards_per_entry_ratio());
400 }
401
402 size_t predict_non_young_card_num(size_t rs_length) {
403 return (size_t) ((double) rs_length *
404 predict_partially_young_cards_per_entry_ratio());
405 }
406
407 double predict_rs_scan_time_ms(size_t card_num) {
408 if (full_young_gcs())
409 return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq);
410 else
411 return predict_partially_young_rs_scan_time_ms(card_num);
412 }
413
414 double predict_partially_young_rs_scan_time_ms(size_t card_num) {
415 if (_partially_young_cost_per_entry_ms_seq->num() < 3)
416 return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq);
417 else
418 return (double) card_num *
419 get_new_prediction(_partially_young_cost_per_entry_ms_seq);
420 }
421
422 double predict_object_copy_time_ms_during_cm(size_t bytes_to_copy) {
423 if (_cost_per_byte_ms_during_cm_seq->num() < 3)
424 return 1.1 * (double) bytes_to_copy *
425 get_new_prediction(_cost_per_byte_ms_seq);
426 else
427 return (double) bytes_to_copy *
428 get_new_prediction(_cost_per_byte_ms_during_cm_seq);
429 }
430
431 double predict_object_copy_time_ms(size_t bytes_to_copy) {
432 if (_in_marking_window && !_in_marking_window_im)
433 return predict_object_copy_time_ms_during_cm(bytes_to_copy);
434 else
435 return (double) bytes_to_copy *
436 get_new_prediction(_cost_per_byte_ms_seq);
437 }
438
439 double predict_constant_other_time_ms() {
440 return get_new_prediction(_constant_other_time_ms_seq);
441 }
442
443 double predict_young_other_time_ms(size_t young_num) {
444 return
445 (double) young_num *
446 get_new_prediction(_young_other_cost_per_region_ms_seq);
447 }
448
449 double predict_non_young_other_time_ms(size_t non_young_num) {
450 return
451 (double) non_young_num *
452 get_new_prediction(_non_young_other_cost_per_region_ms_seq);
453 }
454
455 void check_if_region_is_too_expensive(double predicted_time_ms);
456
457 double predict_young_collection_elapsed_time_ms(size_t adjustment);
458 double predict_base_elapsed_time_ms(size_t pending_cards);
459 double predict_base_elapsed_time_ms(size_t pending_cards,
460 size_t scanned_cards);
461 size_t predict_bytes_to_copy(HeapRegion* hr);
462 double predict_region_elapsed_time_ms(HeapRegion* hr, bool young);
463
464 // for use by: calculate_young_list_target_length(rs_length)
465 bool predict_will_fit(size_t young_region_num,
466 double base_time_ms,
467 size_t init_free_regions,
468 double target_pause_time_ms);
469
470 void start_recording_regions();
471 void record_cset_region_info(HeapRegion* hr, bool young);
472 void record_non_young_cset_region(HeapRegion* hr);
473
474 void set_recorded_young_regions(size_t n_regions);
475 void set_recorded_young_bytes(size_t bytes);
476 void set_recorded_rs_lengths(size_t rs_lengths);
477 void set_predicted_bytes_to_copy(size_t bytes);
478
479 void end_recording_regions();
480
481 void record_vtime_diff_ms(double vtime_diff_ms) {
482 _vtime_diff_ms = vtime_diff_ms;
483 }
484
485 void record_young_free_cset_time_ms(double time_ms) {
486 _recorded_young_free_cset_time_ms = time_ms;
487 }
488
489 void record_non_young_free_cset_time_ms(double time_ms) {
490 _recorded_non_young_free_cset_time_ms = time_ms;
491 }
492
493 double predict_young_gc_eff() {
494 return get_new_neg_prediction(_young_gc_eff_seq);
495 }
496
497 double predict_survivor_regions_evac_time();
498
499 // </NEW PREDICTION>
500
501 public:
502 void cset_regions_freed() {
503 bool propagate = _last_young_gc_full && !_in_marking_window;
504 _short_lived_surv_rate_group->all_surviving_words_recorded(propagate);
505 _survivor_surv_rate_group->all_surviving_words_recorded(propagate);
506 // also call it on any more surv rate groups
507 }
508
509 void set_known_garbage_bytes(size_t known_garbage_bytes) {
510 _known_garbage_bytes = known_garbage_bytes;
511 size_t heap_bytes = _g1->capacity();
512 _known_garbage_ratio = (double) _known_garbage_bytes / (double) heap_bytes;
513 }
514
515 void decrease_known_garbage_bytes(size_t known_garbage_bytes) {
516 guarantee( _known_garbage_bytes >= known_garbage_bytes, "invariant" );
517
518 _known_garbage_bytes -= known_garbage_bytes;
519 size_t heap_bytes = _g1->capacity();
520 _known_garbage_ratio = (double) _known_garbage_bytes / (double) heap_bytes;
521 }
522
523 G1MMUTracker* mmu_tracker() {
524 return _mmu_tracker;
525 }
526
527 double max_pause_time_ms() {
528 return _mmu_tracker->max_gc_time() * 1000.0;
529 }
530
531 double predict_init_time_ms() {
532 return get_new_prediction(_concurrent_mark_init_times_ms);
533 }
534
535 double predict_remark_time_ms() {
536 return get_new_prediction(_concurrent_mark_remark_times_ms);
537 }
538
539 double predict_cleanup_time_ms() {
540 return get_new_prediction(_concurrent_mark_cleanup_times_ms);
541 }
542
543 // Returns an estimate of the survival rate of the region at yg-age
544 // "yg_age".
545 double predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) {
546 TruncatedSeq* seq = surv_rate_group->get_seq(age);
547 if (seq->num() == 0)
548 gclog_or_tty->print("BARF! age is %d", age);
549 guarantee( seq->num() > 0, "invariant" );
550 double pred = get_new_prediction(seq);
551 if (pred > 1.0)
552 pred = 1.0;
553 return pred;
554 }
555
556 double predict_yg_surv_rate(int age) {
557 return predict_yg_surv_rate(age, _short_lived_surv_rate_group);
558 }
559
560 double accum_yg_surv_rate_pred(int age) {
561 return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
562 }
563
564 protected:
565 void print_stats(int level, const char* str, double value);
566 void print_stats(int level, const char* str, int value);
567
568 void print_par_stats(int level, const char* str, double* data) {
569 print_par_stats(level, str, data, true);
570 }
571 void print_par_stats(int level, const char* str, double* data, bool summary);
572 void print_par_sizes(int level, const char* str, double* data, bool summary);
573
574 void check_other_times(int level,
575 NumberSeq* other_times_ms,
576 NumberSeq* calc_other_times_ms) const;
577
578 void print_summary (PauseSummary* stats) const;
579
580 void print_summary (int level, const char* str, NumberSeq* seq) const;
581 void print_summary_sd (int level, const char* str, NumberSeq* seq) const;
582
583 double avg_value (double* data);
584 double max_value (double* data);
585 double sum_of_values (double* data);
586 double max_sum (double* data1, double* data2);
587
588 int _last_satb_drain_processed_buffers;
589 int _last_update_rs_processed_buffers;
590 double _last_pause_time_ms;
591
592 size_t _bytes_in_to_space_before_gc;
593 size_t _bytes_in_to_space_after_gc;
594 size_t bytes_in_to_space_during_gc() {
595 return
596 _bytes_in_to_space_after_gc - _bytes_in_to_space_before_gc;
597 }
598 size_t _bytes_in_collection_set_before_gc;
599 // Used to count used bytes in CS.
600 friend class CountCSClosure;
601
602 // Statistics kept per GC stoppage, pause or full.
603 TruncatedSeq* _recent_prev_end_times_for_all_gcs_sec;
604
605 // We track markings.
606 int _num_markings;
607 double _mark_thread_startup_sec; // Time at startup of marking thread
608
609 // Add a new GC of the given duration and end time to the record.
610 void update_recent_gc_times(double end_time_sec, double elapsed_ms);
611
612 // The head of the list (via "next_in_collection_set()") representing the
613 // current collection set. Set from the incrementally built collection
614 // set at the start of the pause.
615 HeapRegion* _collection_set;
616
617 // The number of regions in the collection set. Set from the incrementally
618 // built collection set at the start of an evacuation pause.
619 size_t _collection_set_size;
620
621 // The number of bytes in the collection set before the pause. Set from
622 // the incrementally built collection set at the start of an evacuation
623 // pause.
624 size_t _collection_set_bytes_used_before;
625
626 // The associated information that is maintained while the incremental
627 // collection set is being built with young regions. Used to populate
628 // the recorded info for the evacuation pause.
629
630 enum CSetBuildType {
631 Active, // We are actively building the collection set
632 Inactive // We are not actively building the collection set
633 };
634
635 CSetBuildType _inc_cset_build_state;
636
637 // The head of the incrementally built collection set.
638 HeapRegion* _inc_cset_head;
639
640 // The tail of the incrementally built collection set.
641 HeapRegion* _inc_cset_tail;
642
643 // The number of regions in the incrementally built collection set.
644 // Used to set _collection_set_size at the start of an evacuation
645 // pause.
646 size_t _inc_cset_size;
647
648 // Used as the index in the surving young words structure
649 // which tracks the amount of space, for each young region,
650 // that survives the pause.
651 size_t _inc_cset_young_index;
652
653 // The number of bytes in the incrementally built collection set.
654 // Used to set _collection_set_bytes_used_before at the start of
655 // an evacuation pause.
656 size_t _inc_cset_bytes_used_before;
657
658 // Used to record the highest end of heap region in collection set
659 HeapWord* _inc_cset_max_finger;
660
661 // The number of recorded used bytes in the young regions
662 // of the collection set. This is the sum of the used() bytes
663 // of retired young regions in the collection set.
664 size_t _inc_cset_recorded_young_bytes;
665
666 // The RSet lengths recorded for regions in the collection set
667 // (updated by the periodic sampling of the regions in the
668 // young list/collection set).
669 size_t _inc_cset_recorded_rs_lengths;
670
671 // The predicted elapsed time it will take to collect the regions
672 // in the collection set (updated by the periodic sampling of the
673 // regions in the young list/collection set).
674 double _inc_cset_predicted_elapsed_time_ms;
675
676 // The predicted bytes to copy for the regions in the collection
677 // set (updated by the periodic sampling of the regions in the
678 // young list/collection set).
679 size_t _inc_cset_predicted_bytes_to_copy;
680
681 // Info about marking.
682 int _n_marks; // Sticky at 2, so we know when we've done at least 2.
683
684 // The number of collection pauses at the end of the last mark.
685 size_t _n_pauses_at_mark_end;
686
687 // Stash a pointer to the g1 heap.
688 G1CollectedHeap* _g1;
689
690 // The average time in ms per collection pause, averaged over recent pauses.
691 double recent_avg_time_for_pauses_ms();
692
693 // The average time in ms for processing CollectedHeap strong roots, per
694 // collection pause, averaged over recent pauses.
695 double recent_avg_time_for_CH_strong_ms();
696
697 // The average time in ms for processing the G1 remembered set, per
698 // pause, averaged over recent pauses.
699 double recent_avg_time_for_G1_strong_ms();
700
701 // The average time in ms for "evacuating followers", per pause, averaged
702 // over recent pauses.
703 double recent_avg_time_for_evac_ms();
704
705 // The number of "recent" GCs recorded in the number sequences
706 int number_of_recent_gcs();
707
708 // The average survival ratio, computed by the total number of bytes
709 // suriviving / total number of bytes before collection over the last
710 // several recent pauses.
711 double recent_avg_survival_fraction();
712 // The survival fraction of the most recent pause; if there have been no
713 // pauses, returns 1.0.
714 double last_survival_fraction();
715
716 // Returns a "conservative" estimate of the recent survival rate, i.e.,
717 // one that may be higher than "recent_avg_survival_fraction".
718 // This is conservative in several ways:
719 // If there have been few pauses, it will assume a potential high
720 // variance, and err on the side of caution.
721 // It puts a lower bound (currently 0.1) on the value it will return.
722 // To try to detect phase changes, if the most recent pause ("latest") has a
723 // higher-than average ("avg") survival rate, it returns that rate.
724 // "work" version is a utility function; young is restricted to young regions.
725 double conservative_avg_survival_fraction_work(double avg,
726 double latest);
727
728 // The arguments are the two sequences that keep track of the number of bytes
729 // surviving and the total number of bytes before collection, resp.,
730 // over the last evereal recent pauses
731 // Returns the survival rate for the category in the most recent pause.
732 // If there have been no pauses, returns 1.0.
733 double last_survival_fraction_work(TruncatedSeq* surviving,
734 TruncatedSeq* before);
735
736 // The arguments are the two sequences that keep track of the number of bytes
737 // surviving and the total number of bytes before collection, resp.,
738 // over the last several recent pauses
739 // Returns the average survival ration over the last several recent pauses
740 // If there have been no pauses, return 1.0
741 double recent_avg_survival_fraction_work(TruncatedSeq* surviving,
742 TruncatedSeq* before);
743
744 double conservative_avg_survival_fraction() {
745 double avg = recent_avg_survival_fraction();
746 double latest = last_survival_fraction();
747 return conservative_avg_survival_fraction_work(avg, latest);
748 }
749
750 // The ratio of gc time to elapsed time, computed over recent pauses.
751 double _recent_avg_pause_time_ratio;
752
753 double recent_avg_pause_time_ratio() {
754 return _recent_avg_pause_time_ratio;
755 }
756
757 // Number of pauses between concurrent marking.
758 size_t _pauses_btwn_concurrent_mark;
759
760 size_t _n_marks_since_last_pause;
761
762 // At the end of a pause we check the heap occupancy and we decide
763 // whether we will start a marking cycle during the next pause. If
764 // we decide that we want to do that, we will set this parameter to
765 // true. So, this parameter will stay true between the end of a
766 // pause and the beginning of a subsequent pause (not necessarily
767 // the next one, see the comments on the next field) when we decide
768 // that we will indeed start a marking cycle and do the initial-mark
769 // work.
770 volatile bool _initiate_conc_mark_if_possible;
771
772 // If initiate_conc_mark_if_possible() is set at the beginning of a
773 // pause, it is a suggestion that the pause should start a marking
774 // cycle by doing the initial-mark work. However, it is possible
775 // that the concurrent marking thread is still finishing up the
776 // previous marking cycle (e.g., clearing the next marking
777 // bitmap). If that is the case we cannot start a new cycle and
778 // we'll have to wait for the concurrent marking thread to finish
779 // what it is doing. In this case we will postpone the marking cycle
780 // initiation decision for the next pause. When we eventually decide
781 // to start a cycle, we will set _during_initial_mark_pause which
782 // will stay true until the end of the initial-mark pause and it's
783 // the condition that indicates that a pause is doing the
784 // initial-mark work.
785 volatile bool _during_initial_mark_pause;
786
787 bool _should_revert_to_full_young_gcs;
788 bool _last_full_young_gc;
789
790 // This set of variables tracks the collector efficiency, in order to
791 // determine whether we should initiate a new marking.
792 double _cur_mark_stop_world_time_ms;
793 double _mark_init_start_sec;
794 double _mark_remark_start_sec;
795 double _mark_cleanup_start_sec;
796 double _mark_closure_time_ms;
797
798 void calculate_young_list_min_length();
799 void calculate_young_list_target_length();
800 void calculate_young_list_target_length(size_t rs_lengths);
801
802 public:
803
804 G1CollectorPolicy();
805
806 virtual G1CollectorPolicy* as_g1_policy() { return this; }
807
808 virtual CollectorPolicy::Name kind() {
809 return CollectorPolicy::G1CollectorPolicyKind;
810 }
811
812 void check_prediction_validity();
813
814 size_t bytes_in_collection_set() {
815 return _bytes_in_collection_set_before_gc;
816 }
817
818 size_t bytes_in_to_space() {
819 return bytes_in_to_space_during_gc();
820 }
821
822 unsigned calc_gc_alloc_time_stamp() {
823 return _all_pause_times_ms->num() + 1;
824 }
825
826 protected:
827
828 // Count the number of bytes used in the CS.
829 void count_CS_bytes_used();
830
831 // Together these do the base cleanup-recording work. Subclasses might
832 // want to put something between them.
833 void record_concurrent_mark_cleanup_end_work1(size_t freed_bytes,
834 size_t max_live_bytes);
835 void record_concurrent_mark_cleanup_end_work2();
836
837 public:
838
839 virtual void init();
840
841 // Create jstat counters for the policy.
842 virtual void initialize_gc_policy_counters();
843
844 virtual HeapWord* mem_allocate_work(size_t size,
845 bool is_tlab,
846 bool* gc_overhead_limit_was_exceeded);
847
848 // This method controls how a collector handles one or more
849 // of its generations being fully allocated.
850 virtual HeapWord* satisfy_failed_allocation(size_t size,
851 bool is_tlab);
852
853 BarrierSet::Name barrier_set_name() { return BarrierSet::G1SATBCTLogging; }
854
855 GenRemSet::Name rem_set_name() { return GenRemSet::CardTable; }
856
857 // The number of collection pauses so far.
858 long n_pauses() const { return _n_pauses; }
859
860 // Update the heuristic info to record a collection pause of the given
861 // start time, where the given number of bytes were used at the start.
862 // This may involve changing the desired size of a collection set.
863
864 virtual void record_stop_world_start();
865
866 virtual void record_collection_pause_start(double start_time_sec,
867 size_t start_used);
868
869 // Must currently be called while the world is stopped.
870 virtual void record_concurrent_mark_init_start();
871 virtual void record_concurrent_mark_init_end();
872 void record_concurrent_mark_init_end_pre(double
873 mark_init_elapsed_time_ms);
874
875 void record_mark_closure_time(double mark_closure_time_ms);
876
877 virtual void record_concurrent_mark_remark_start();
878 virtual void record_concurrent_mark_remark_end();
879
880 virtual void record_concurrent_mark_cleanup_start();
881 virtual void record_concurrent_mark_cleanup_end(size_t freed_bytes,
882 size_t max_live_bytes);
883 virtual void record_concurrent_mark_cleanup_completed();
884
885 virtual void record_concurrent_pause();
886 virtual void record_concurrent_pause_end();
887
888 virtual void record_collection_pause_end_CH_strong_roots();
889 virtual void record_collection_pause_end_G1_strong_roots();
890
891 virtual void record_collection_pause_end();
892
893 // Record the fact that a full collection occurred.
894 virtual void record_full_collection_start();
895 virtual void record_full_collection_end();
896
897 void record_gc_worker_start_time(int worker_i, double ms) {
898 _par_last_gc_worker_start_times_ms[worker_i] = ms;
899 }
900
901 void record_ext_root_scan_time(int worker_i, double ms) {
902 _par_last_ext_root_scan_times_ms[worker_i] = ms;
903 }
904
905 void record_mark_stack_scan_time(int worker_i, double ms) {
906 _par_last_mark_stack_scan_times_ms[worker_i] = ms;
907 }
908
909 void record_satb_drain_time(double ms) {
910 _cur_satb_drain_time_ms = ms;
911 _satb_drain_time_set = true;
912 }
913
914 void record_satb_drain_processed_buffers (int processed_buffers) {
915 _last_satb_drain_processed_buffers = processed_buffers;
916 }
917
918 void record_mod_union_time(double ms) {
919 _all_mod_union_times_ms->add(ms);
920 }
921
922 void record_update_rs_time(int thread, double ms) {
923 _par_last_update_rs_times_ms[thread] = ms;
924 }
925
926 void record_update_rs_processed_buffers (int thread,
927 double processed_buffers) {
928 _par_last_update_rs_processed_buffers[thread] = processed_buffers;
929 }
930
931 void record_scan_rs_time(int thread, double ms) {
932 _par_last_scan_rs_times_ms[thread] = ms;
933 }
934
935 void reset_obj_copy_time(int thread) {
936 _par_last_obj_copy_times_ms[thread] = 0.0;
937 }
938
939 void reset_obj_copy_time() {
940 reset_obj_copy_time(0);
941 }
942
943 void record_obj_copy_time(int thread, double ms) {
944 _par_last_obj_copy_times_ms[thread] += ms;
945 }
946
947 void record_termination(int thread, double ms, size_t attempts) {
948 _par_last_termination_times_ms[thread] = ms;
949 _par_last_termination_attempts[thread] = (double) attempts;
950 }
951
952 void record_gc_worker_end_time(int worker_i, double ms) {
953 _par_last_gc_worker_end_times_ms[worker_i] = ms;
954 }
955
956 void record_pause_time_ms(double ms) {
957 _last_pause_time_ms = ms;
958 }
959
960 void record_clear_ct_time(double ms) {
961 _cur_clear_ct_time_ms = ms;
962 }
963
964 void record_par_time(double ms) {
965 _cur_collection_par_time_ms = ms;
966 }
967
968 void record_aux_start_time(int i) {
969 guarantee(i < _aux_num, "should be within range");
970 _cur_aux_start_times_ms[i] = os::elapsedTime() * 1000.0;
971 }
972
973 void record_aux_end_time(int i) {
974 guarantee(i < _aux_num, "should be within range");
975 double ms = os::elapsedTime() * 1000.0 - _cur_aux_start_times_ms[i];
976 _cur_aux_times_set[i] = true;
977 _cur_aux_times_ms[i] += ms;
978 }
979
980 #ifndef PRODUCT
981 void record_cc_clear_time(double ms) {
982 if (_min_clear_cc_time_ms < 0.0 || ms <= _min_clear_cc_time_ms)
983 _min_clear_cc_time_ms = ms;
984 if (_max_clear_cc_time_ms < 0.0 || ms >= _max_clear_cc_time_ms)
985 _max_clear_cc_time_ms = ms;
986 _cur_clear_cc_time_ms = ms;
987 _cum_clear_cc_time_ms += ms;
988 _num_cc_clears++;
989 }
990 #endif
991
992 // Record the fact that "bytes" bytes allocated in a region.
993 void record_before_bytes(size_t bytes);
994 void record_after_bytes(size_t bytes);
995
996 // Returns "true" if this is a good time to do a collection pause.
997 // The "word_size" argument, if non-zero, indicates the size of an
998 // allocation request that is prompting this query.
999 virtual bool should_do_collection_pause(size_t word_size) = 0;
1000
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 virtual void choose_collection_set(double target_pause_time_ms) = 0;
1005
1006 // The head of the list (via "next_in_collection_set()") representing the
1007 // current collection set.
1008 HeapRegion* collection_set() { return _collection_set; }
1009
1010 void clear_collection_set() { _collection_set = NULL; }
1011
1012 // The number of elements in the current collection set.
1013 size_t collection_set_size() { return _collection_set_size; }
1014
1015 // Add "hr" to the CS.
1016 void add_to_collection_set(HeapRegion* hr);
1017
1018 // Incremental CSet Support
1019
1020 // The head of the incrementally built collection set.
1021 HeapRegion* inc_cset_head() { return _inc_cset_head; }
1022
1023 // The tail of the incrementally built collection set.
1024 HeapRegion* inc_set_tail() { return _inc_cset_tail; }
1025
1026 // The number of elements in the incrementally built collection set.
1027 size_t inc_cset_size() { return _inc_cset_size; }
1028
1029 // Initialize incremental collection set info.
1030 void start_incremental_cset_building();
1031
1032 void clear_incremental_cset() {
1033 _inc_cset_head = NULL;
1034 _inc_cset_tail = NULL;
1035 }
1036
1037 // Stop adding regions to the incremental collection set
1038 void stop_incremental_cset_building() { _inc_cset_build_state = Inactive; }
1039
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);
1044
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);
1048
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);
1053
1054 public:
1055 // Add hr to the LHS of the incremental collection set.
1056 void add_region_to_incremental_cset_lhs(HeapRegion* hr);
1057
1058 // Add hr to the RHS of the incremental collection set.
1059 void add_region_to_incremental_cset_rhs(HeapRegion* hr);
1060
1061 #ifndef PRODUCT
1062 void print_collection_set(HeapRegion* list_head, outputStream* st);
1063 #endif // !PRODUCT
1064
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; }
1068
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; }
1072
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();
1078
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();
1086
1087 // If an expansion would be appropriate, because recent GC overhead had
1088 // exceeded the desired limit, return an amount to expand by.
1089 virtual size_t expansion_amount();
1090
1091 // note start of mark thread
1092 void note_start_of_mark_thread();
1093
1094 // The marked bytes of the "r" has changed; reclassify it's desirability
1095 // for marking. Also asserts that "r" is eligible for a CS.
1096 virtual void note_change_in_marked_bytes(HeapRegion* r) = 0;
1097
1098 #ifndef PRODUCT
1099 // Check any appropriate marked bytes info, asserting false if
1100 // something's wrong, else returning "true".
1101 virtual bool assertMarkedBytesDataOK() = 0;
1102 #endif
1103
1104 // Print tracing information.
1105 void print_tracing_info() const;
1106
1107 // Print stats on young survival ratio
1108 void print_yg_surv_rate_info() const;
1109
1110 void finished_recalculating_age_indexes(bool is_survivors) {
1111 if (is_survivors) {
1112 _survivor_surv_rate_group->finished_recalculating_age_indexes();
1113 } else {
1114 _short_lived_surv_rate_group->finished_recalculating_age_indexes();
1115 }
1116 // do that for any other surv rate groups
1117 }
1118
1119 bool should_add_next_region_to_young_list();
1120
1121 bool in_young_gc_mode() {
1122 return _in_young_gc_mode;
1123 }
1124 void set_in_young_gc_mode(bool in_young_gc_mode) {
1125 _in_young_gc_mode = in_young_gc_mode;
1126 }
1127
1128 bool full_young_gcs() {
1129 return _full_young_gcs;
1130 }
1131 void set_full_young_gcs(bool full_young_gcs) {
1132 _full_young_gcs = full_young_gcs;
1133 }
1134
1135 bool adaptive_young_list_length() {
1136 return _adaptive_young_list_length;
1137 }
1138 void set_adaptive_young_list_length(bool adaptive_young_list_length) {
1139 _adaptive_young_list_length = adaptive_young_list_length;
1140 }
1141
1142 inline double get_gc_eff_factor() {
1143 double ratio = _known_garbage_ratio;
1144
1145 double square = ratio * ratio;
1146 // square = square * square;
1147 double ret = square * 9.0 + 1.0;
1148 #if 0
1149 gclog_or_tty->print_cr("ratio = %1.2lf, ret = %1.2lf", ratio, ret);
1150 #endif // 0
1151 guarantee(0.0 <= ret && ret < 10.0, "invariant!");
1152 return ret;
1153 }
1154
1155 //
1156 // Survivor regions policy.
1157 //
1158 protected:
1159
1160 // Current tenuring threshold, set to 0 if the collector reaches the
1161 // maximum amount of suvivors regions.
1162 int _tenuring_threshold;
1163
1164 // The limit on the number of regions allocated for survivors.
1165 size_t _max_survivor_regions;
1166
1167 // The amount of survor regions after a collection.
1168 size_t _recorded_survivor_regions;
1169 // List of survivor regions.
1170 HeapRegion* _recorded_survivor_head;
1171 HeapRegion* _recorded_survivor_tail;
1172
1173 ageTable _survivors_age_table;
1174
1175 public:
1176
1177 inline GCAllocPurpose
1178 evacuation_destination(HeapRegion* src_region, int age, size_t word_sz) {
1179 if (age < _tenuring_threshold && src_region->is_young()) {
1180 return GCAllocForSurvived;
1181 } else {
1182 return GCAllocForTenured;
1183 }
1184 }
1185
1186 inline bool track_object_age(GCAllocPurpose purpose) {
1187 return purpose == GCAllocForSurvived;
1188 }
1189
1190 inline GCAllocPurpose alternative_purpose(int purpose) {
1191 return GCAllocForTenured;
1192 }
1193
1194 static const size_t REGIONS_UNLIMITED = ~(size_t)0;
1195
1196 size_t max_regions(int purpose);
1197
1198 // The limit on regions for a particular purpose is reached.
1199 void note_alloc_region_limit_reached(int purpose) {
1200 if (purpose == GCAllocForSurvived) {
1201 _tenuring_threshold = 0;
1202 }
1203 }
1204
1205 void note_start_adding_survivor_regions() {
1206 _survivor_surv_rate_group->start_adding_regions();
1207 }
1208
1209 void note_stop_adding_survivor_regions() {
1210 _survivor_surv_rate_group->stop_adding_regions();
1211 }
1212
1213 void record_survivor_regions(size_t regions,
1214 HeapRegion* head,
1215 HeapRegion* tail) {
1216 _recorded_survivor_regions = regions;
1217 _recorded_survivor_head = head;
1218 _recorded_survivor_tail = tail;
1219 }
1220
1221 size_t recorded_survivor_regions() {
1222 return _recorded_survivor_regions;
1223 }
1224
1225 void record_thread_age_table(ageTable* age_table)
1226 {
1227 _survivors_age_table.merge_par(age_table);
1228 }
1229
1230 // Calculates survivor space parameters.
1231 void calculate_survivors_policy();
1232
1233 };
1234
1235 // This encapsulates a particular strategy for a g1 Collector.
1236 //
1237 // Start a concurrent mark when our heap size is n bytes
1238 // greater then our heap size was at the last concurrent
1239 // mark. Where n is a function of the CMSTriggerRatio
1240 // and the MinHeapFreeRatio.
1241 //
1242 // Start a g1 collection pause when we have allocated the
1243 // average number of bytes currently being freed in
1244 // a collection, but only if it is at least one region
1245 // full
1246 //
1247 // Resize Heap based on desired
1248 // allocation space, where desired allocation space is
1249 // a function of survival rate and desired future to size.
1250 //
1251 // Choose collection set by first picking all older regions
1252 // which have a survival rate which beats our projected young
1253 // survival rate. Then fill out the number of needed regions
1254 // with young regions.
1255
1256 class G1CollectorPolicy_BestRegionsFirst: public G1CollectorPolicy {
1257 CollectionSetChooser* _collectionSetChooser;
1258 // If the estimated is less then desirable, resize if possible.
1259 void expand_if_possible(size_t numRegions);
1260
1261 virtual void choose_collection_set(double target_pause_time_ms);
1262 virtual void record_collection_pause_start(double start_time_sec,
1263 size_t start_used);
1264 virtual void record_concurrent_mark_cleanup_end(size_t freed_bytes,
1265 size_t max_live_bytes);
1266 virtual void record_full_collection_end();
1267
1268 public:
1269 G1CollectorPolicy_BestRegionsFirst() {
1270 _collectionSetChooser = new CollectionSetChooser();
1271 }
1272 void record_collection_pause_end();
1273 bool should_do_collection_pause(size_t word_size);
1274 // This is not needed any more, after the CSet choosing code was
1275 // changed to use the pause prediction work. But let's leave the
1276 // hook in just in case.
1277 void note_change_in_marked_bytes(HeapRegion* r) { }
1278 #ifndef PRODUCT
1279 bool assertMarkedBytesDataOK();
1280 #endif
1281 };
1282
1283 // This should move to some place more general...
1284
1285 // If we have "n" measurements, and we've kept track of their "sum" and the
1286 // "sum_of_squares" of the measurements, this returns the variance of the
1287 // sequence.
1288 inline double variance(int n, double sum_of_squares, double sum) {
1289 double n_d = (double)n;
1290 double avg = sum/n_d;
1291 return (sum_of_squares - 2.0 * avg * sum + n_d * avg * avg) / n_d;
1292 }
1293
1294 // Local Variables: ***
1295 // c-indentation-style: gnu ***
1296 // End: ***
1297
1298 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP