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.
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 // Statistics for recent GC pauses. See below for how indexed.
133 TruncatedSeq* _recent_rs_scan_times_ms;
134
135 // These exclude marking times.
136 TruncatedSeq* _recent_pause_times_ms;
137 TruncatedSeq* _recent_gc_times_ms;
138
139 TruncatedSeq* _recent_CS_bytes_used_before;
140 TruncatedSeq* _recent_CS_bytes_surviving;
141
142 TruncatedSeq* _recent_rs_sizes;
143
144 TruncatedSeq* _concurrent_mark_init_times_ms;
145 TruncatedSeq* _concurrent_mark_remark_times_ms;
146 TruncatedSeq* _concurrent_mark_cleanup_times_ms;
147
148 Summary* _summary;
149
150 NumberSeq* _all_pause_times_ms;
151 NumberSeq* _all_full_gc_times_ms;
152 double _stop_world_start;
153 NumberSeq* _all_stop_world_times_ms;
154 NumberSeq* _all_yield_times_ms;
155
156 size_t _region_num_young;
157 size_t _region_num_tenured;
158 size_t _prev_region_num_young;
159 size_t _prev_region_num_tenured;
160
161 NumberSeq* _all_mod_union_times_ms;
162
163 int _aux_num;
164 NumberSeq* _all_aux_times_ms;
165 double* _cur_aux_start_times_ms;
166 double* _cur_aux_times_ms;
167 bool* _cur_aux_times_set;
168
169 double* _par_last_gc_worker_start_times_ms;
170 double* _par_last_ext_root_scan_times_ms;
171 double* _par_last_mark_stack_scan_times_ms;
172 double* _par_last_update_rs_times_ms;
173 double* _par_last_update_rs_processed_buffers;
174 double* _par_last_scan_rs_times_ms;
175 double* _par_last_obj_copy_times_ms;
176 double* _par_last_termination_times_ms;
177 double* _par_last_termination_attempts;
178 double* _par_last_gc_worker_end_times_ms;
179 double* _par_last_gc_worker_times_ms;
180
181 // indicates whether we are in full young or partially young GC mode
182 bool _full_young_gcs;
183
184 // if true, then it tries to dynamically adjust the length of the
185 // young list
186 bool _adaptive_young_list_length;
187 size_t _young_list_min_length;
188 size_t _young_list_target_length;
189 size_t _young_list_fixed_length;
190
191 // The max number of regions we can extend the eden by while the GC
192 // locker is active. This should be >= _young_list_target_length;
193 size_t _young_list_max_length;
194
195 size_t _young_cset_length;
196 bool _last_young_gc_full;
197
198 unsigned _full_young_pause_num;
199 unsigned _partial_young_pause_num;
200
201 bool _during_marking;
202 bool _in_marking_window;
203 bool _in_marking_window_im;
204
205 SurvRateGroup* _short_lived_surv_rate_group;
206 SurvRateGroup* _survivor_surv_rate_group;
207 // add here any more surv rate groups
208
209 double _gc_overhead_perc;
210
211 bool during_marking() {
212 return _during_marking;
213 }
214
215 // <NEW PREDICTION>
216
217 private:
218 enum PredictionConstants {
219 TruncatedSeqLength = 10
220 };
221
222 TruncatedSeq* _alloc_rate_ms_seq;
223 double _prev_collection_pause_end_ms;
224
225 TruncatedSeq* _pending_card_diff_seq;
226 TruncatedSeq* _rs_length_diff_seq;
227 TruncatedSeq* _cost_per_card_ms_seq;
228 TruncatedSeq* _fully_young_cards_per_entry_ratio_seq;
229 TruncatedSeq* _partially_young_cards_per_entry_ratio_seq;
230 TruncatedSeq* _cost_per_entry_ms_seq;
231 TruncatedSeq* _partially_young_cost_per_entry_ms_seq;
232 TruncatedSeq* _cost_per_byte_ms_seq;
233 TruncatedSeq* _constant_other_time_ms_seq;
234 TruncatedSeq* _young_other_cost_per_region_ms_seq;
235 TruncatedSeq* _non_young_other_cost_per_region_ms_seq;
236
237 TruncatedSeq* _pending_cards_seq;
238 TruncatedSeq* _scanned_cards_seq;
239 TruncatedSeq* _rs_lengths_seq;
240
241 TruncatedSeq* _cost_per_byte_ms_during_cm_seq;
242
243 TruncatedSeq* _young_gc_eff_seq;
244
245 TruncatedSeq* _max_conc_overhead_seq;
246
247 size_t _recorded_young_regions;
248 size_t _recorded_non_young_regions;
249 size_t _recorded_region_num;
250
251 size_t _free_regions_at_end_of_collection;
252
253 size_t _recorded_rs_lengths;
254 size_t _max_rs_lengths;
255
256 size_t _recorded_marked_bytes;
257 size_t _recorded_young_bytes;
258
259 size_t _predicted_pending_cards;
260 size_t _predicted_cards_scanned;
261 size_t _predicted_rs_lengths;
262 size_t _predicted_bytes_to_copy;
263
264 double _predicted_survival_ratio;
265 double _predicted_rs_update_time_ms;
266 double _predicted_rs_scan_time_ms;
267 double _predicted_object_copy_time_ms;
268 double _predicted_constant_other_time_ms;
269 double _predicted_young_other_time_ms;
270 double _predicted_non_young_other_time_ms;
271 double _predicted_pause_time_ms;
272
273 double _vtime_diff_ms;
274
275 double _recorded_young_free_cset_time_ms;
276 double _recorded_non_young_free_cset_time_ms;
277
278 double _sigma;
279 double _expensive_region_limit_ms;
280
281 size_t _rs_lengths_prediction;
282
283 size_t _known_garbage_bytes;
284 double _known_garbage_ratio;
285
286 double sigma() {
287 return _sigma;
288 }
289
290 // A function that prevents us putting too much stock in small sample
291 // sets. Returns a number between 2.0 and 1.0, depending on the number
292 // of samples. 5 or more samples yields one; fewer scales linearly from
293 // 2.0 at 1 sample to 1.0 at 5.
294 double confidence_factor(int samples) {
295 if (samples > 4) return 1.0;
296 else return 1.0 + sigma() * ((double)(5 - samples))/2.0;
297 }
298
299 double get_new_neg_prediction(TruncatedSeq* seq) {
300 return seq->davg() - sigma() * seq->dsd();
301 }
302
303 #ifndef PRODUCT
304 bool verify_young_ages(HeapRegion* head, SurvRateGroup *surv_rate_group);
305 #endif // PRODUCT
306
307 void adjust_concurrent_refinement(double update_rs_time,
308 double update_rs_processed_buffers,
309 double goal_ms);
310
311 protected:
312 double _pause_time_target_ms;
313 double _recorded_young_cset_choice_time_ms;
314 double _recorded_non_young_cset_choice_time_ms;
315 bool _within_target;
316 size_t _pending_cards;
317 size_t _max_pending_cards;
318
319 public:
320
321 void set_region_short_lived(HeapRegion* hr) {
322 hr->install_surv_rate_group(_short_lived_surv_rate_group);
323 }
324
325 void set_region_survivors(HeapRegion* hr) {
326 hr->install_surv_rate_group(_survivor_surv_rate_group);
327 }
328
329 #ifndef PRODUCT
330 bool verify_young_ages();
331 #endif // PRODUCT
332
333 double get_new_prediction(TruncatedSeq* seq) {
334 return MAX2(seq->davg() + sigma() * seq->dsd(),
335 seq->davg() * confidence_factor(seq->num()));
336 }
337
338 size_t young_cset_length() {
339 return _young_cset_length;
340 }
341
342 void record_max_rs_lengths(size_t rs_lengths) {
343 _max_rs_lengths = rs_lengths;
344 }
345
346 size_t predict_pending_card_diff() {
347 double prediction = get_new_neg_prediction(_pending_card_diff_seq);
348 if (prediction < 0.00001)
349 return 0;
350 else
351 return (size_t) prediction;
352 }
353
354 size_t predict_pending_cards() {
355 size_t max_pending_card_num = _g1->max_pending_card_num();
356 size_t diff = predict_pending_card_diff();
357 size_t prediction;
358 if (diff > max_pending_card_num)
359 prediction = max_pending_card_num;
360 else
361 prediction = max_pending_card_num - diff;
362
363 return prediction;
364 }
365
366 size_t predict_rs_length_diff() {
367 return (size_t) get_new_prediction(_rs_length_diff_seq);
368 }
369
370 double predict_alloc_rate_ms() {
371 return get_new_prediction(_alloc_rate_ms_seq);
372 }
373
374 double predict_cost_per_card_ms() {
375 return get_new_prediction(_cost_per_card_ms_seq);
376 }
377
378 double predict_rs_update_time_ms(size_t pending_cards) {
379 return (double) pending_cards * predict_cost_per_card_ms();
380 }
381
382 double predict_fully_young_cards_per_entry_ratio() {
383 return get_new_prediction(_fully_young_cards_per_entry_ratio_seq);
384 }
385
386 double predict_partially_young_cards_per_entry_ratio() {
387 if (_partially_young_cards_per_entry_ratio_seq->num() < 2)
388 return predict_fully_young_cards_per_entry_ratio();
389 else
390 return get_new_prediction(_partially_young_cards_per_entry_ratio_seq);
391 }
392
393 size_t predict_young_card_num(size_t rs_length) {
394 return (size_t) ((double) rs_length *
395 predict_fully_young_cards_per_entry_ratio());
396 }
397
398 size_t predict_non_young_card_num(size_t rs_length) {
399 return (size_t) ((double) rs_length *
400 predict_partially_young_cards_per_entry_ratio());
401 }
402
403 double predict_rs_scan_time_ms(size_t card_num) {
404 if (full_young_gcs())
405 return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq);
406 else
407 return predict_partially_young_rs_scan_time_ms(card_num);
408 }
409
410 double predict_partially_young_rs_scan_time_ms(size_t card_num) {
411 if (_partially_young_cost_per_entry_ms_seq->num() < 3)
412 return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq);
413 else
414 return (double) card_num *
415 get_new_prediction(_partially_young_cost_per_entry_ms_seq);
416 }
417
418 double predict_object_copy_time_ms_during_cm(size_t bytes_to_copy) {
419 if (_cost_per_byte_ms_during_cm_seq->num() < 3)
420 return 1.1 * (double) bytes_to_copy *
421 get_new_prediction(_cost_per_byte_ms_seq);
422 else
423 return (double) bytes_to_copy *
424 get_new_prediction(_cost_per_byte_ms_during_cm_seq);
425 }
426
427 double predict_object_copy_time_ms(size_t bytes_to_copy) {
428 if (_in_marking_window && !_in_marking_window_im)
429 return predict_object_copy_time_ms_during_cm(bytes_to_copy);
430 else
431 return (double) bytes_to_copy *
432 get_new_prediction(_cost_per_byte_ms_seq);
433 }
434
435 double predict_constant_other_time_ms() {
436 return get_new_prediction(_constant_other_time_ms_seq);
437 }
438
439 double predict_young_other_time_ms(size_t young_num) {
440 return
441 (double) young_num *
442 get_new_prediction(_young_other_cost_per_region_ms_seq);
443 }
444
445 double predict_non_young_other_time_ms(size_t non_young_num) {
446 return
447 (double) non_young_num *
448 get_new_prediction(_non_young_other_cost_per_region_ms_seq);
449 }
450
451 void check_if_region_is_too_expensive(double predicted_time_ms);
452
453 double predict_young_collection_elapsed_time_ms(size_t adjustment);
454 double predict_base_elapsed_time_ms(size_t pending_cards);
455 double predict_base_elapsed_time_ms(size_t pending_cards,
456 size_t scanned_cards);
457 size_t predict_bytes_to_copy(HeapRegion* hr);
458 double predict_region_elapsed_time_ms(HeapRegion* hr, bool young);
459
460 // for use by: calculate_young_list_target_length(rs_length)
461 bool predict_will_fit(size_t young_region_num,
462 double base_time_ms,
463 size_t init_free_regions,
464 double target_pause_time_ms);
465
466 void start_recording_regions();
467 void record_cset_region_info(HeapRegion* hr, bool young);
468 void record_non_young_cset_region(HeapRegion* hr);
469
470 void set_recorded_young_regions(size_t n_regions);
471 void set_recorded_young_bytes(size_t bytes);
472 void set_recorded_rs_lengths(size_t rs_lengths);
473 void set_predicted_bytes_to_copy(size_t bytes);
474
475 void end_recording_regions();
476
477 void record_vtime_diff_ms(double vtime_diff_ms) {
478 _vtime_diff_ms = vtime_diff_ms;
479 }
480
481 void record_young_free_cset_time_ms(double time_ms) {
482 _recorded_young_free_cset_time_ms = time_ms;
483 }
484
485 void record_non_young_free_cset_time_ms(double time_ms) {
486 _recorded_non_young_free_cset_time_ms = time_ms;
487 }
488
489 double predict_young_gc_eff() {
490 return get_new_neg_prediction(_young_gc_eff_seq);
491 }
492
493 double predict_survivor_regions_evac_time();
494
495 // </NEW PREDICTION>
496
497 public:
498 void cset_regions_freed() {
499 bool propagate = _last_young_gc_full && !_in_marking_window;
500 _short_lived_surv_rate_group->all_surviving_words_recorded(propagate);
501 _survivor_surv_rate_group->all_surviving_words_recorded(propagate);
502 // also call it on any more surv rate groups
503 }
504
505 void set_known_garbage_bytes(size_t known_garbage_bytes) {
506 _known_garbage_bytes = known_garbage_bytes;
507 size_t heap_bytes = _g1->capacity();
508 _known_garbage_ratio = (double) _known_garbage_bytes / (double) heap_bytes;
509 }
510
511 void decrease_known_garbage_bytes(size_t known_garbage_bytes) {
512 guarantee( _known_garbage_bytes >= known_garbage_bytes, "invariant" );
513
514 _known_garbage_bytes -= known_garbage_bytes;
515 size_t heap_bytes = _g1->capacity();
516 _known_garbage_ratio = (double) _known_garbage_bytes / (double) heap_bytes;
517 }
518
519 G1MMUTracker* mmu_tracker() {
520 return _mmu_tracker;
521 }
522
523 double max_pause_time_ms() {
524 return _mmu_tracker->max_gc_time() * 1000.0;
525 }
526
527 double predict_init_time_ms() {
528 return get_new_prediction(_concurrent_mark_init_times_ms);
529 }
530
531 double predict_remark_time_ms() {
532 return get_new_prediction(_concurrent_mark_remark_times_ms);
533 }
534
535 double predict_cleanup_time_ms() {
536 return get_new_prediction(_concurrent_mark_cleanup_times_ms);
537 }
538
539 // Returns an estimate of the survival rate of the region at yg-age
540 // "yg_age".
541 double predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) {
542 TruncatedSeq* seq = surv_rate_group->get_seq(age);
543 if (seq->num() == 0)
544 gclog_or_tty->print("BARF! age is %d", age);
545 guarantee( seq->num() > 0, "invariant" );
546 double pred = get_new_prediction(seq);
547 if (pred > 1.0)
548 pred = 1.0;
549 return pred;
550 }
551
552 double predict_yg_surv_rate(int age) {
553 return predict_yg_surv_rate(age, _short_lived_surv_rate_group);
554 }
555
556 double accum_yg_surv_rate_pred(int age) {
557 return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
558 }
559
560 protected:
561 void print_stats(int level, const char* str, double value);
562 void print_stats(int level, const char* str, int value);
563
564 void print_par_stats(int level, const char* str, double* data);
565 void print_par_sizes(int level, const char* str, double* data);
566
567 void check_other_times(int level,
568 NumberSeq* other_times_ms,
569 NumberSeq* calc_other_times_ms) const;
570
571 void print_summary (PauseSummary* stats) const;
572
573 void print_summary (int level, const char* str, NumberSeq* seq) const;
574 void print_summary_sd (int level, const char* str, NumberSeq* seq) const;
575
576 double avg_value (double* data);
577 double max_value (double* data);
578 double sum_of_values (double* data);
579 double max_sum (double* data1, double* data2);
580
581 int _last_satb_drain_processed_buffers;
582 int _last_update_rs_processed_buffers;
583 double _last_pause_time_ms;
584
585 size_t _bytes_in_collection_set_before_gc;
586 size_t _bytes_copied_during_gc;
587
588 // Used to count used bytes in CS.
589 friend class CountCSClosure;
590
591 // Statistics kept per GC stoppage, pause or full.
592 TruncatedSeq* _recent_prev_end_times_for_all_gcs_sec;
593
594 // We track markings.
595 int _num_markings;
596 double _mark_thread_startup_sec; // Time at startup of marking thread
597
598 // Add a new GC of the given duration and end time to the record.
599 void update_recent_gc_times(double end_time_sec, double elapsed_ms);
600
601 // The head of the list (via "next_in_collection_set()") representing the
602 // current collection set. Set from the incrementally built collection
603 // set at the start of the pause.
604 HeapRegion* _collection_set;
605
606 // The number of regions in the collection set. Set from the incrementally
607 // built collection set at the start of an evacuation pause.
608 size_t _collection_set_size;
609
610 // The number of bytes in the collection set before the pause. Set from
611 // the incrementally built collection set at the start of an evacuation
612 // pause.
613 size_t _collection_set_bytes_used_before;
614
615 // The associated information that is maintained while the incremental
616 // collection set is being built with young regions. Used to populate
617 // the recorded info for the evacuation pause.
618
619 enum CSetBuildType {
620 Active, // We are actively building the collection set
621 Inactive // We are not actively building the collection set
622 };
623
624 CSetBuildType _inc_cset_build_state;
625
626 // The head of the incrementally built collection set.
627 HeapRegion* _inc_cset_head;
628
629 // The tail of the incrementally built collection set.
630 HeapRegion* _inc_cset_tail;
631
632 // The number of regions in the incrementally built collection set.
633 // Used to set _collection_set_size at the start of an evacuation
634 // pause.
635 size_t _inc_cset_size;
636
637 // Used as the index in the surving young words structure
638 // which tracks the amount of space, for each young region,
639 // that survives the pause.
640 size_t _inc_cset_young_index;
641
642 // The number of bytes in the incrementally built collection set.
643 // Used to set _collection_set_bytes_used_before at the start of
644 // an evacuation pause.
645 size_t _inc_cset_bytes_used_before;
646
647 // Used to record the highest end of heap region in collection set
648 HeapWord* _inc_cset_max_finger;
649
650 // The number of recorded used bytes in the young regions
651 // of the collection set. This is the sum of the used() bytes
652 // of retired young regions in the collection set.
653 size_t _inc_cset_recorded_young_bytes;
654
655 // The RSet lengths recorded for regions in the collection set
656 // (updated by the periodic sampling of the regions in the
657 // young list/collection set).
658 size_t _inc_cset_recorded_rs_lengths;
659
660 // The predicted elapsed time it will take to collect the regions
661 // in the collection set (updated by the periodic sampling of the
662 // regions in the young list/collection set).
663 double _inc_cset_predicted_elapsed_time_ms;
664
665 // The predicted bytes to copy for the regions in the collection
666 // set (updated by the periodic sampling of the regions in the
667 // young list/collection set).
668 size_t _inc_cset_predicted_bytes_to_copy;
669
670 // Info about marking.
671 int _n_marks; // Sticky at 2, so we know when we've done at least 2.
672
673 // The number of collection pauses at the end of the last mark.
674 size_t _n_pauses_at_mark_end;
675
676 // Stash a pointer to the g1 heap.
677 G1CollectedHeap* _g1;
678
679 // The average time in ms per collection pause, averaged over recent pauses.
680 double recent_avg_time_for_pauses_ms();
681
682 // The average time in ms for RS scanning, per pause, averaged
683 // over recent pauses. (Note the RS scanning time for a pause
684 // is itself an average of the RS scanning time for each worker
685 // thread.)
686 double recent_avg_time_for_rs_scan_ms();
687
688 // The number of "recent" GCs recorded in the number sequences
689 int number_of_recent_gcs();
690
691 // The average survival ratio, computed by the total number of bytes
692 // suriviving / total number of bytes before collection over the last
693 // several recent pauses.
694 double recent_avg_survival_fraction();
695 // The survival fraction of the most recent pause; if there have been no
696 // pauses, returns 1.0.
697 double last_survival_fraction();
698
699 // Returns a "conservative" estimate of the recent survival rate, i.e.,
700 // one that may be higher than "recent_avg_survival_fraction".
701 // This is conservative in several ways:
702 // If there have been few pauses, it will assume a potential high
703 // variance, and err on the side of caution.
704 // It puts a lower bound (currently 0.1) on the value it will return.
705 // To try to detect phase changes, if the most recent pause ("latest") has a
706 // higher-than average ("avg") survival rate, it returns that rate.
707 // "work" version is a utility function; young is restricted to young regions.
708 double conservative_avg_survival_fraction_work(double avg,
709 double latest);
710
711 // The arguments are the two sequences that keep track of the number of bytes
712 // surviving and the total number of bytes before collection, resp.,
713 // over the last evereal recent pauses
714 // Returns the survival rate for the category in the most recent pause.
715 // If there have been no pauses, returns 1.0.
716 double last_survival_fraction_work(TruncatedSeq* surviving,
717 TruncatedSeq* before);
718
719 // The arguments are the two sequences that keep track of the number of bytes
720 // surviving and the total number of bytes before collection, resp.,
721 // over the last several recent pauses
722 // Returns the average survival ration over the last several recent pauses
723 // If there have been no pauses, return 1.0
724 double recent_avg_survival_fraction_work(TruncatedSeq* surviving,
725 TruncatedSeq* before);
726
727 double conservative_avg_survival_fraction() {
728 double avg = recent_avg_survival_fraction();
729 double latest = last_survival_fraction();
730 return conservative_avg_survival_fraction_work(avg, latest);
731 }
732
733 // The ratio of gc time to elapsed time, computed over recent pauses.
734 double _recent_avg_pause_time_ratio;
735
736 double recent_avg_pause_time_ratio() {
737 return _recent_avg_pause_time_ratio;
738 }
739
740 // Number of pauses between concurrent marking.
741 size_t _pauses_btwn_concurrent_mark;
742
743 size_t _n_marks_since_last_pause;
744
745 // At the end of a pause we check the heap occupancy and we decide
746 // whether we will start a marking cycle during the next pause. If
747 // we decide that we want to do that, we will set this parameter to
748 // true. So, this parameter will stay true between the end of a
749 // pause and the beginning of a subsequent pause (not necessarily
750 // the next one, see the comments on the next field) when we decide
751 // that we will indeed start a marking cycle and do the initial-mark
752 // work.
753 volatile bool _initiate_conc_mark_if_possible;
754
755 // If initiate_conc_mark_if_possible() is set at the beginning of a
756 // pause, it is a suggestion that the pause should start a marking
757 // cycle by doing the initial-mark work. However, it is possible
758 // that the concurrent marking thread is still finishing up the
759 // previous marking cycle (e.g., clearing the next marking
760 // bitmap). If that is the case we cannot start a new cycle and
761 // we'll have to wait for the concurrent marking thread to finish
762 // what it is doing. In this case we will postpone the marking cycle
763 // initiation decision for the next pause. When we eventually decide
764 // to start a cycle, we will set _during_initial_mark_pause which
765 // will stay true until the end of the initial-mark pause and it's
766 // the condition that indicates that a pause is doing the
767 // initial-mark work.
768 volatile bool _during_initial_mark_pause;
769
770 bool _should_revert_to_full_young_gcs;
771 bool _last_full_young_gc;
772
773 // This set of variables tracks the collector efficiency, in order to
774 // determine whether we should initiate a new marking.
775 double _cur_mark_stop_world_time_ms;
776 double _mark_init_start_sec;
777 double _mark_remark_start_sec;
778 double _mark_cleanup_start_sec;
779 double _mark_closure_time_ms;
780
781 void calculate_young_list_min_length();
782 void calculate_young_list_target_length();
783 void calculate_young_list_target_length(size_t rs_lengths);
784
785 public:
786
787 G1CollectorPolicy();
788
789 virtual G1CollectorPolicy* as_g1_policy() { return this; }
790
791 virtual CollectorPolicy::Name kind() {
792 return CollectorPolicy::G1CollectorPolicyKind;
793 }
794
795 void check_prediction_validity();
796
797 size_t bytes_in_collection_set() {
798 return _bytes_in_collection_set_before_gc;
799 }
800
801 unsigned calc_gc_alloc_time_stamp() {
802 return _all_pause_times_ms->num() + 1;
803 }
804
805 protected:
806
807 // Count the number of bytes used in the CS.
808 void count_CS_bytes_used();
809
810 // Together these do the base cleanup-recording work. Subclasses might
811 // want to put something between them.
812 void record_concurrent_mark_cleanup_end_work1(size_t freed_bytes,
813 size_t max_live_bytes);
814 void record_concurrent_mark_cleanup_end_work2();
815
816 public:
817
818 virtual void init();
819
820 // Create jstat counters for the policy.
821 virtual void initialize_gc_policy_counters();
822
823 virtual HeapWord* mem_allocate_work(size_t size,
824 bool is_tlab,
825 bool* gc_overhead_limit_was_exceeded);
826
827 // This method controls how a collector handles one or more
828 // of its generations being fully allocated.
829 virtual HeapWord* satisfy_failed_allocation(size_t size,
830 bool is_tlab);
831
832 BarrierSet::Name barrier_set_name() { return BarrierSet::G1SATBCTLogging; }
833
834 GenRemSet::Name rem_set_name() { return GenRemSet::CardTable; }
835
836 // The number of collection pauses so far.
837 long n_pauses() const { return _n_pauses; }
838
839 // Update the heuristic info to record a collection pause of the given
840 // start time, where the given number of bytes were used at the start.
841 // This may involve changing the desired size of a collection set.
842
843 virtual void record_stop_world_start();
844
845 virtual void record_collection_pause_start(double start_time_sec,
846 size_t start_used);
847
848 // Must currently be called while the world is stopped.
849 virtual void record_concurrent_mark_init_start();
850 virtual void record_concurrent_mark_init_end();
851 void record_concurrent_mark_init_end_pre(double
852 mark_init_elapsed_time_ms);
853
854 void record_mark_closure_time(double mark_closure_time_ms);
855
856 virtual void record_concurrent_mark_remark_start();
857 virtual void record_concurrent_mark_remark_end();
858
859 virtual void record_concurrent_mark_cleanup_start();
860 virtual void record_concurrent_mark_cleanup_end(size_t freed_bytes,
861 size_t max_live_bytes);
862 virtual void record_concurrent_mark_cleanup_completed();
863
864 virtual void record_concurrent_pause();
865 virtual void record_concurrent_pause_end();
866
867 virtual void record_collection_pause_end();
868 void print_heap_transition();
869
870 // Record the fact that a full collection occurred.
871 virtual void record_full_collection_start();
872 virtual void record_full_collection_end();
873
874 void record_gc_worker_start_time(int worker_i, double ms) {
875 _par_last_gc_worker_start_times_ms[worker_i] = ms;
876 }
877
878 void record_ext_root_scan_time(int worker_i, double ms) {
879 _par_last_ext_root_scan_times_ms[worker_i] = ms;
880 }
881
882 void record_mark_stack_scan_time(int worker_i, double ms) {
883 _par_last_mark_stack_scan_times_ms[worker_i] = ms;
884 }
885
886 void record_satb_drain_time(double ms) {
887 _cur_satb_drain_time_ms = ms;
888 _satb_drain_time_set = true;
889 }
890
891 void record_satb_drain_processed_buffers (int processed_buffers) {
892 _last_satb_drain_processed_buffers = processed_buffers;
893 }
894
895 void record_mod_union_time(double ms) {
896 _all_mod_union_times_ms->add(ms);
897 }
898
899 void record_update_rs_time(int thread, double ms) {
900 _par_last_update_rs_times_ms[thread] = ms;
901 }
902
903 void record_update_rs_processed_buffers (int thread,
904 double processed_buffers) {
905 _par_last_update_rs_processed_buffers[thread] = processed_buffers;
906 }
907
908 void record_scan_rs_time(int thread, double ms) {
909 _par_last_scan_rs_times_ms[thread] = ms;
910 }
911
912 void reset_obj_copy_time(int thread) {
913 _par_last_obj_copy_times_ms[thread] = 0.0;
914 }
915
916 void reset_obj_copy_time() {
917 reset_obj_copy_time(0);
918 }
919
920 void record_obj_copy_time(int thread, double ms) {
921 _par_last_obj_copy_times_ms[thread] += ms;
922 }
923
924 void record_termination(int thread, double ms, size_t attempts) {
925 _par_last_termination_times_ms[thread] = ms;
926 _par_last_termination_attempts[thread] = (double) attempts;
927 }
928
929 void record_gc_worker_end_time(int worker_i, double ms) {
930 _par_last_gc_worker_end_times_ms[worker_i] = ms;
931 }
932
933 void record_pause_time_ms(double ms) {
934 _last_pause_time_ms = ms;
935 }
936
937 void record_clear_ct_time(double ms) {
938 _cur_clear_ct_time_ms = ms;
939 }
940
941 void record_par_time(double ms) {
942 _cur_collection_par_time_ms = ms;
943 }
944
945 void record_aux_start_time(int i) {
946 guarantee(i < _aux_num, "should be within range");
947 _cur_aux_start_times_ms[i] = os::elapsedTime() * 1000.0;
948 }
949
950 void record_aux_end_time(int i) {
951 guarantee(i < _aux_num, "should be within range");
952 double ms = os::elapsedTime() * 1000.0 - _cur_aux_start_times_ms[i];
953 _cur_aux_times_set[i] = true;
954 _cur_aux_times_ms[i] += ms;
955 }
956
957 #ifndef PRODUCT
958 void record_cc_clear_time(double ms) {
959 if (_min_clear_cc_time_ms < 0.0 || ms <= _min_clear_cc_time_ms)
960 _min_clear_cc_time_ms = ms;
961 if (_max_clear_cc_time_ms < 0.0 || ms >= _max_clear_cc_time_ms)
962 _max_clear_cc_time_ms = ms;
963 _cur_clear_cc_time_ms = ms;
964 _cum_clear_cc_time_ms += ms;
965 _num_cc_clears++;
966 }
967 #endif
968
969 // Record how much space we copied during a GC. This is typically
970 // called when a GC alloc region is being retired.
971 void record_bytes_copied_during_gc(size_t bytes) {
972 _bytes_copied_during_gc += bytes;
973 }
974
975 // The amount of space we copied during a GC.
976 size_t bytes_copied_during_gc() {
977 return _bytes_copied_during_gc;
978 }
979
980 // Choose a new collection set. Marks the chosen regions as being
981 // "in_collection_set", and links them together. The head and number of
982 // the collection set are available via access methods.
983 virtual void choose_collection_set(double target_pause_time_ms) = 0;
984
985 // The head of the list (via "next_in_collection_set()") representing the
986 // current collection set.
987 HeapRegion* collection_set() { return _collection_set; }
988
989 void clear_collection_set() { _collection_set = NULL; }
990
991 // The number of elements in the current collection set.
992 size_t collection_set_size() { return _collection_set_size; }
993
994 // Add "hr" to the CS.
995 void add_to_collection_set(HeapRegion* hr);
996
997 // Incremental CSet Support
998
999 // The head of the incrementally built collection set.
1000 HeapRegion* inc_cset_head() { return _inc_cset_head; }
1001
1002 // The tail of the incrementally built collection set.
1003 HeapRegion* inc_set_tail() { return _inc_cset_tail; }
1004
1005 // The number of elements in the incrementally built collection set.
1006 size_t inc_cset_size() { return _inc_cset_size; }
1007
1008 // Initialize incremental collection set info.
1009 void start_incremental_cset_building();
1010
1011 void clear_incremental_cset() {
1012 _inc_cset_head = NULL;
1013 _inc_cset_tail = NULL;
1014 }
1015
1016 // Stop adding regions to the incremental collection set
1017 void stop_incremental_cset_building() { _inc_cset_build_state = Inactive; }
1018
1019 // Add/remove information about hr to the aggregated information
1020 // for the incrementally built collection set.
1021 void add_to_incremental_cset_info(HeapRegion* hr, size_t rs_length);
1022 void remove_from_incremental_cset_info(HeapRegion* hr);
1023
1024 // Update information about hr in the aggregated information for
1025 // the incrementally built collection set.
1026 void update_incremental_cset_info(HeapRegion* hr, size_t new_rs_length);
1027
1028 private:
1029 // Update the incremental cset information when adding a region
1030 // (should not be called directly).
1031 void add_region_to_incremental_cset_common(HeapRegion* hr);
1032
1033 public:
1034 // Add hr to the LHS of the incremental collection set.
1035 void add_region_to_incremental_cset_lhs(HeapRegion* hr);
1036
1037 // Add hr to the RHS of the incremental collection set.
1038 void add_region_to_incremental_cset_rhs(HeapRegion* hr);
1039
1040 #ifndef PRODUCT
1041 void print_collection_set(HeapRegion* list_head, outputStream* st);
1042 #endif // !PRODUCT
1043
1044 bool initiate_conc_mark_if_possible() { return _initiate_conc_mark_if_possible; }
1045 void set_initiate_conc_mark_if_possible() { _initiate_conc_mark_if_possible = true; }
1046 void clear_initiate_conc_mark_if_possible() { _initiate_conc_mark_if_possible = false; }
1047
1048 bool during_initial_mark_pause() { return _during_initial_mark_pause; }
1049 void set_during_initial_mark_pause() { _during_initial_mark_pause = true; }
1050 void clear_during_initial_mark_pause(){ _during_initial_mark_pause = false; }
1051
1052 // This sets the initiate_conc_mark_if_possible() flag to start a
1053 // new cycle, as long as we are not already in one. It's best if it
1054 // is called during a safepoint when the test whether a cycle is in
1055 // progress or not is stable.
1056 bool force_initial_mark_if_outside_cycle();
1057
1058 // This is called at the very beginning of an evacuation pause (it
1059 // has to be the first thing that the pause does). If
1060 // initiate_conc_mark_if_possible() is true, and the concurrent
1061 // marking thread has completed its work during the previous cycle,
1062 // it will set during_initial_mark_pause() to so that the pause does
1063 // the initial-mark work and start a marking cycle.
1064 void decide_on_conc_mark_initiation();
1065
1066 // If an expansion would be appropriate, because recent GC overhead had
1067 // exceeded the desired limit, return an amount to expand by.
1068 virtual size_t expansion_amount();
1069
1070 // note start of mark thread
1071 void note_start_of_mark_thread();
1072
1073 // The marked bytes of the "r" has changed; reclassify it's desirability
1074 // for marking. Also asserts that "r" is eligible for a CS.
1075 virtual void note_change_in_marked_bytes(HeapRegion* r) = 0;
1076
1077 #ifndef PRODUCT
1078 // Check any appropriate marked bytes info, asserting false if
1079 // something's wrong, else returning "true".
1080 virtual bool assertMarkedBytesDataOK() = 0;
1081 #endif
1082
1083 // Print tracing information.
1084 void print_tracing_info() const;
1085
1086 // Print stats on young survival ratio
1087 void print_yg_surv_rate_info() const;
1088
1089 void finished_recalculating_age_indexes(bool is_survivors) {
1090 if (is_survivors) {
1091 _survivor_surv_rate_group->finished_recalculating_age_indexes();
1092 } else {
1093 _short_lived_surv_rate_group->finished_recalculating_age_indexes();
1094 }
1095 // do that for any other surv rate groups
1096 }
1097
1098 bool is_young_list_full() {
1099 size_t young_list_length = _g1->young_list()->length();
1100 size_t young_list_target_length = _young_list_target_length;
1101 if (G1FixedEdenSize) {
1102 young_list_target_length -= _max_survivor_regions;
1103 }
1104 return young_list_length >= young_list_target_length;
1105 }
1106
1107 bool can_expand_young_list() {
1108 size_t young_list_length = _g1->young_list()->length();
1109 size_t young_list_max_length = _young_list_max_length;
1110 if (G1FixedEdenSize) {
1111 young_list_max_length -= _max_survivor_regions;
1112 }
1113 return young_list_length < young_list_max_length;
1114 }
1115
1116 void update_region_num(bool young);
1117
1118 bool full_young_gcs() {
1119 return _full_young_gcs;
1120 }
1121 void set_full_young_gcs(bool full_young_gcs) {
1122 _full_young_gcs = full_young_gcs;
1123 }
1124
1125 bool adaptive_young_list_length() {
1126 return _adaptive_young_list_length;
1127 }
1128 void set_adaptive_young_list_length(bool adaptive_young_list_length) {
1129 _adaptive_young_list_length = adaptive_young_list_length;
1130 }
1131
1132 inline double get_gc_eff_factor() {
1133 double ratio = _known_garbage_ratio;
1134
1135 double square = ratio * ratio;
1136 // square = square * square;
1137 double ret = square * 9.0 + 1.0;
1138 #if 0
1139 gclog_or_tty->print_cr("ratio = %1.2lf, ret = %1.2lf", ratio, ret);
1140 #endif // 0
1141 guarantee(0.0 <= ret && ret < 10.0, "invariant!");
1142 return ret;
1143 }
1144
1145 //
1146 // Survivor regions policy.
1147 //
1148 protected:
1149
1150 // Current tenuring threshold, set to 0 if the collector reaches the
1151 // maximum amount of suvivors regions.
1152 int _tenuring_threshold;
1153
1154 // The limit on the number of regions allocated for survivors.
1155 size_t _max_survivor_regions;
1156
1157 // For reporting purposes.
1158 size_t _eden_bytes_before_gc;
1159 size_t _survivor_bytes_before_gc;
1160 size_t _capacity_before_gc;
1161
1162 // The amount of survor regions after a collection.
1163 size_t _recorded_survivor_regions;
1164 // List of survivor regions.
1165 HeapRegion* _recorded_survivor_head;
1166 HeapRegion* _recorded_survivor_tail;
1167
1168 ageTable _survivors_age_table;
1169
1170 public:
1171
1172 inline GCAllocPurpose
1173 evacuation_destination(HeapRegion* src_region, int age, size_t word_sz) {
1174 if (age < _tenuring_threshold && src_region->is_young()) {
1175 return GCAllocForSurvived;
1176 } else {
1177 return GCAllocForTenured;
1178 }
1179 }
1180
1181 inline bool track_object_age(GCAllocPurpose purpose) {
1182 return purpose == GCAllocForSurvived;
1183 }
1184
1185 static const size_t REGIONS_UNLIMITED = ~(size_t)0;
1186
1187 size_t max_regions(int purpose);
1188
1189 // The limit on regions for a particular purpose is reached.
1190 void note_alloc_region_limit_reached(int purpose) {
1191 if (purpose == GCAllocForSurvived) {
1192 _tenuring_threshold = 0;
1193 }
1194 }
1195
1196 void note_start_adding_survivor_regions() {
1197 _survivor_surv_rate_group->start_adding_regions();
1198 }
1199
1200 void note_stop_adding_survivor_regions() {
1201 _survivor_surv_rate_group->stop_adding_regions();
1202 }
1203
1204 void record_survivor_regions(size_t regions,
1205 HeapRegion* head,
1206 HeapRegion* tail) {
1207 _recorded_survivor_regions = regions;
1208 _recorded_survivor_head = head;
1209 _recorded_survivor_tail = tail;
1210 }
1211
1212 size_t recorded_survivor_regions() {
1213 return _recorded_survivor_regions;
1214 }
1215
1216 void record_thread_age_table(ageTable* age_table)
1217 {
1218 _survivors_age_table.merge_par(age_table);
1219 }
1220
1221 void calculate_max_gc_locker_expansion();
1222
1223 // Calculates survivor space parameters.
1224 void calculate_survivors_policy();
1225
1226 };
1227
1228 // This encapsulates a particular strategy for a g1 Collector.
1229 //
1230 // Start a concurrent mark when our heap size is n bytes
1231 // greater then our heap size was at the last concurrent
1232 // mark. Where n is a function of the CMSTriggerRatio
1233 // and the MinHeapFreeRatio.
1234 //
1235 // Start a g1 collection pause when we have allocated the
1236 // average number of bytes currently being freed in
1237 // a collection, but only if it is at least one region
1238 // full
1239 //
1240 // Resize Heap based on desired
1241 // allocation space, where desired allocation space is
1242 // a function of survival rate and desired future to size.
1243 //
1244 // Choose collection set by first picking all older regions
1245 // which have a survival rate which beats our projected young
1246 // survival rate. Then fill out the number of needed regions
1247 // with young regions.
1248
1249 class G1CollectorPolicy_BestRegionsFirst: public G1CollectorPolicy {
1250 CollectionSetChooser* _collectionSetChooser;
1251 // If the estimated is less then desirable, resize if possible.
1252 void expand_if_possible(size_t numRegions);
1253
1254 virtual void choose_collection_set(double target_pause_time_ms);
1255 virtual void record_collection_pause_start(double start_time_sec,
1256 size_t start_used);
1257 virtual void record_concurrent_mark_cleanup_end(size_t freed_bytes,
1258 size_t max_live_bytes);
1259 virtual void record_full_collection_end();
1260
1261 public:
1262 G1CollectorPolicy_BestRegionsFirst() {
1263 _collectionSetChooser = new CollectionSetChooser();
1264 }
1265 void record_collection_pause_end();
1266 // This is not needed any more, after the CSet choosing code was
1267 // changed to use the pause prediction work. But let's leave the
1268 // hook in just in case.
1269 void note_change_in_marked_bytes(HeapRegion* r) { }
1270 #ifndef PRODUCT
1271 bool assertMarkedBytesDataOK();
1272 #endif
1273 };
1274
1275 // This should move to some place more general...
1276
1277 // If we have "n" measurements, and we've kept track of their "sum" and the
1278 // "sum_of_squares" of the measurements, this returns the variance of the
1279 // sequence.
1280 inline double variance(int n, double sum_of_squares, double sum) {
1281 double n_d = (double)n;
1282 double avg = sum/n_d;
1283 return (sum_of_squares - 2.0 * avg * sum + n_d * avg * avg) / n_d;
1284 }
1285
1286 // Local Variables: ***
1287 // c-indentation-style: gnu ***
1288 // End: ***
1289
1290 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP