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 double _cur_ref_proc_time_ms;
123 double _cur_ref_enq_time_ms;
124
125 #ifndef PRODUCT
126 // Card Table Count Cache stats
127 double _min_clear_cc_time_ms; // min
128 double _max_clear_cc_time_ms; // max
129 double _cur_clear_cc_time_ms; // clearing time during current pause
130 double _cum_clear_cc_time_ms; // cummulative clearing time
131 jlong _num_cc_clears; // number of times the card count cache has been cleared
132 #endif
133
134 // Statistics for recent GC pauses. See below for how indexed.
135 TruncatedSeq* _recent_rs_scan_times_ms;
136
137 // These exclude marking times.
138 TruncatedSeq* _recent_pause_times_ms;
139 TruncatedSeq* _recent_gc_times_ms;
140
141 TruncatedSeq* _recent_CS_bytes_used_before;
142 TruncatedSeq* _recent_CS_bytes_surviving;
143
144 TruncatedSeq* _recent_rs_sizes;
145
146 TruncatedSeq* _concurrent_mark_remark_times_ms;
147 TruncatedSeq* _concurrent_mark_cleanup_times_ms;
148
149 Summary* _summary;
150
151 NumberSeq* _all_pause_times_ms;
152 NumberSeq* _all_full_gc_times_ms;
153 double _stop_world_start;
154 NumberSeq* _all_stop_world_times_ms;
155 NumberSeq* _all_yield_times_ms;
156
157 size_t _region_num_young;
158 size_t _region_num_tenured;
159 size_t _prev_region_num_young;
160 size_t _prev_region_num_tenured;
161
162 NumberSeq* _all_mod_union_times_ms;
163
164 int _aux_num;
165 NumberSeq* _all_aux_times_ms;
166 double* _cur_aux_start_times_ms;
167 double* _cur_aux_times_ms;
168 bool* _cur_aux_times_set;
169
170 double* _par_last_gc_worker_start_times_ms;
171 double* _par_last_ext_root_scan_times_ms;
172 double* _par_last_mark_stack_scan_times_ms;
173 double* _par_last_update_rs_times_ms;
174 double* _par_last_update_rs_processed_buffers;
175 double* _par_last_scan_rs_times_ms;
176 double* _par_last_obj_copy_times_ms;
177 double* _par_last_termination_times_ms;
178 double* _par_last_termination_attempts;
179 double* _par_last_gc_worker_end_times_ms;
180 double* _par_last_gc_worker_times_ms;
181
182 // indicates whether we are in full young or partially young GC mode
183 bool _full_young_gcs;
184
185 // if true, then it tries to dynamically adjust the length of the
186 // young list
187 bool _adaptive_young_list_length;
188 size_t _young_list_target_length;
189 size_t _young_list_fixed_length;
190 size_t _prev_eden_capacity; // used for logging
191
192 // The max number of regions we can extend the eden by while the GC
193 // locker is active. This should be >= _young_list_target_length;
194 size_t _young_list_max_length;
195
196 size_t _young_cset_length;
197 bool _last_young_gc_full;
198
199 unsigned _full_young_pause_num;
200 unsigned _partial_young_pause_num;
201
202 bool _during_marking;
203 bool _in_marking_window;
204 bool _in_marking_window_im;
205
206 SurvRateGroup* _short_lived_surv_rate_group;
207 SurvRateGroup* _survivor_surv_rate_group;
208 // add here any more surv rate groups
209
210 double _gc_overhead_perc;
211
212 double _reserve_factor;
213 size_t _reserve_regions;
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 bool _using_new_ratio_calculations;
252 size_t _min_desired_young_length; // as set on the command line or default calculations
253 size_t _max_desired_young_length; // as set on the command line or default calculations
254
255 size_t _recorded_young_regions;
256 size_t _recorded_non_young_regions;
257 size_t _recorded_region_num;
258
259 size_t _free_regions_at_end_of_collection;
260
261 size_t _recorded_rs_lengths;
262 size_t _max_rs_lengths;
263
264 size_t _recorded_marked_bytes;
265 size_t _recorded_young_bytes;
266
267 size_t _predicted_pending_cards;
268 size_t _predicted_cards_scanned;
269 size_t _predicted_rs_lengths;
270 size_t _predicted_bytes_to_copy;
271
272 double _predicted_survival_ratio;
273 double _predicted_rs_update_time_ms;
274 double _predicted_rs_scan_time_ms;
275 double _predicted_object_copy_time_ms;
276 double _predicted_constant_other_time_ms;
277 double _predicted_young_other_time_ms;
278 double _predicted_non_young_other_time_ms;
279 double _predicted_pause_time_ms;
280
281 double _vtime_diff_ms;
282
283 double _recorded_young_free_cset_time_ms;
284 double _recorded_non_young_free_cset_time_ms;
285
286 double _sigma;
287 double _expensive_region_limit_ms;
288
289 size_t _rs_lengths_prediction;
290
291 size_t _known_garbage_bytes;
292 double _known_garbage_ratio;
293
294 double sigma() {
295 return _sigma;
296 }
297
298 // A function that prevents us putting too much stock in small sample
299 // sets. Returns a number between 2.0 and 1.0, depending on the number
300 // of samples. 5 or more samples yields one; fewer scales linearly from
301 // 2.0 at 1 sample to 1.0 at 5.
302 double confidence_factor(int samples) {
303 if (samples > 4) return 1.0;
304 else return 1.0 + sigma() * ((double)(5 - samples))/2.0;
305 }
306
307 double get_new_neg_prediction(TruncatedSeq* seq) {
308 return seq->davg() - sigma() * seq->dsd();
309 }
310
311 #ifndef PRODUCT
312 bool verify_young_ages(HeapRegion* head, SurvRateGroup *surv_rate_group);
313 #endif // PRODUCT
314
315 void adjust_concurrent_refinement(double update_rs_time,
316 double update_rs_processed_buffers,
317 double goal_ms);
318
319 protected:
320 double _pause_time_target_ms;
321 double _recorded_young_cset_choice_time_ms;
322 double _recorded_non_young_cset_choice_time_ms;
323 bool _within_target;
324 size_t _pending_cards;
325 size_t _max_pending_cards;
326
327 public:
328
329 void set_region_short_lived(HeapRegion* hr) {
330 hr->install_surv_rate_group(_short_lived_surv_rate_group);
331 }
332
333 void set_region_survivors(HeapRegion* hr) {
334 hr->install_surv_rate_group(_survivor_surv_rate_group);
335 }
336
337 #ifndef PRODUCT
338 bool verify_young_ages();
339 #endif // PRODUCT
340
341 double get_new_prediction(TruncatedSeq* seq) {
342 return MAX2(seq->davg() + sigma() * seq->dsd(),
343 seq->davg() * confidence_factor(seq->num()));
344 }
345
346 size_t young_cset_length() {
347 return _young_cset_length;
348 }
349
350 void record_max_rs_lengths(size_t rs_lengths) {
351 _max_rs_lengths = rs_lengths;
352 }
353
354 size_t predict_pending_card_diff() {
355 double prediction = get_new_neg_prediction(_pending_card_diff_seq);
356 if (prediction < 0.00001)
357 return 0;
358 else
359 return (size_t) prediction;
360 }
361
362 size_t predict_pending_cards() {
363 size_t max_pending_card_num = _g1->max_pending_card_num();
364 size_t diff = predict_pending_card_diff();
365 size_t prediction;
366 if (diff > max_pending_card_num)
367 prediction = max_pending_card_num;
368 else
369 prediction = max_pending_card_num - diff;
370
371 return prediction;
372 }
373
374 size_t predict_rs_length_diff() {
375 return (size_t) get_new_prediction(_rs_length_diff_seq);
376 }
377
378 double predict_alloc_rate_ms() {
379 return get_new_prediction(_alloc_rate_ms_seq);
380 }
381
382 double predict_cost_per_card_ms() {
383 return get_new_prediction(_cost_per_card_ms_seq);
384 }
385
386 double predict_rs_update_time_ms(size_t pending_cards) {
387 return (double) pending_cards * predict_cost_per_card_ms();
388 }
389
390 double predict_fully_young_cards_per_entry_ratio() {
391 return get_new_prediction(_fully_young_cards_per_entry_ratio_seq);
392 }
393
394 double predict_partially_young_cards_per_entry_ratio() {
395 if (_partially_young_cards_per_entry_ratio_seq->num() < 2)
396 return predict_fully_young_cards_per_entry_ratio();
397 else
398 return get_new_prediction(_partially_young_cards_per_entry_ratio_seq);
399 }
400
401 size_t predict_young_card_num(size_t rs_length) {
402 return (size_t) ((double) rs_length *
403 predict_fully_young_cards_per_entry_ratio());
404 }
405
406 size_t predict_non_young_card_num(size_t rs_length) {
407 return (size_t) ((double) rs_length *
408 predict_partially_young_cards_per_entry_ratio());
409 }
410
411 double predict_rs_scan_time_ms(size_t card_num) {
412 if (full_young_gcs())
413 return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq);
414 else
415 return predict_partially_young_rs_scan_time_ms(card_num);
416 }
417
418 double predict_partially_young_rs_scan_time_ms(size_t card_num) {
419 if (_partially_young_cost_per_entry_ms_seq->num() < 3)
420 return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq);
421 else
422 return (double) card_num *
423 get_new_prediction(_partially_young_cost_per_entry_ms_seq);
424 }
425
426 double predict_object_copy_time_ms_during_cm(size_t bytes_to_copy) {
427 if (_cost_per_byte_ms_during_cm_seq->num() < 3)
428 return 1.1 * (double) bytes_to_copy *
429 get_new_prediction(_cost_per_byte_ms_seq);
430 else
431 return (double) bytes_to_copy *
432 get_new_prediction(_cost_per_byte_ms_during_cm_seq);
433 }
434
435 double predict_object_copy_time_ms(size_t bytes_to_copy) {
436 if (_in_marking_window && !_in_marking_window_im)
437 return predict_object_copy_time_ms_during_cm(bytes_to_copy);
438 else
439 return (double) bytes_to_copy *
440 get_new_prediction(_cost_per_byte_ms_seq);
441 }
442
443 double predict_constant_other_time_ms() {
444 return get_new_prediction(_constant_other_time_ms_seq);
445 }
446
447 double predict_young_other_time_ms(size_t young_num) {
448 return
449 (double) young_num *
450 get_new_prediction(_young_other_cost_per_region_ms_seq);
451 }
452
453 double predict_non_young_other_time_ms(size_t non_young_num) {
454 return
455 (double) non_young_num *
456 get_new_prediction(_non_young_other_cost_per_region_ms_seq);
457 }
458
459 void check_if_region_is_too_expensive(double predicted_time_ms);
460
461 double predict_young_collection_elapsed_time_ms(size_t adjustment);
462 double predict_base_elapsed_time_ms(size_t pending_cards);
463 double predict_base_elapsed_time_ms(size_t pending_cards,
464 size_t scanned_cards);
465 size_t predict_bytes_to_copy(HeapRegion* hr);
466 double predict_region_elapsed_time_ms(HeapRegion* hr, bool young);
467
468 void start_recording_regions();
469 void record_cset_region_info(HeapRegion* hr, bool young);
470 void record_non_young_cset_region(HeapRegion* hr);
471
472 void set_recorded_young_regions(size_t n_regions);
473 void set_recorded_young_bytes(size_t bytes);
474 void set_recorded_rs_lengths(size_t rs_lengths);
475 void set_predicted_bytes_to_copy(size_t bytes);
476
477 void end_recording_regions();
478
479 void record_vtime_diff_ms(double vtime_diff_ms) {
480 _vtime_diff_ms = vtime_diff_ms;
481 }
482
483 void record_young_free_cset_time_ms(double time_ms) {
484 _recorded_young_free_cset_time_ms = time_ms;
485 }
486
487 void record_non_young_free_cset_time_ms(double time_ms) {
488 _recorded_non_young_free_cset_time_ms = time_ms;
489 }
490
491 double predict_young_gc_eff() {
492 return get_new_neg_prediction(_young_gc_eff_seq);
493 }
494
495 double predict_survivor_regions_evac_time();
496
497 // </NEW PREDICTION>
498
499 void cset_regions_freed() {
500 bool propagate = _last_young_gc_full && !_in_marking_window;
501 _short_lived_surv_rate_group->all_surviving_words_recorded(propagate);
502 _survivor_surv_rate_group->all_surviving_words_recorded(propagate);
503 // also call it on any more surv rate groups
504 }
505
506 void set_known_garbage_bytes(size_t known_garbage_bytes) {
507 _known_garbage_bytes = known_garbage_bytes;
508 size_t heap_bytes = _g1->capacity();
509 _known_garbage_ratio = (double) _known_garbage_bytes / (double) heap_bytes;
510 }
511
512 void decrease_known_garbage_bytes(size_t known_garbage_bytes) {
513 guarantee( _known_garbage_bytes >= known_garbage_bytes, "invariant" );
514
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 }
519
520 G1MMUTracker* mmu_tracker() {
521 return _mmu_tracker;
522 }
523
524 double max_pause_time_ms() {
525 return _mmu_tracker->max_gc_time() * 1000.0;
526 }
527
528 double predict_remark_time_ms() {
529 return get_new_prediction(_concurrent_mark_remark_times_ms);
530 }
531
532 double predict_cleanup_time_ms() {
533 return get_new_prediction(_concurrent_mark_cleanup_times_ms);
534 }
535
536 // Returns an estimate of the survival rate of the region at yg-age
537 // "yg_age".
538 double predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) {
539 TruncatedSeq* seq = surv_rate_group->get_seq(age);
540 if (seq->num() == 0)
541 gclog_or_tty->print("BARF! age is %d", age);
542 guarantee( seq->num() > 0, "invariant" );
543 double pred = get_new_prediction(seq);
544 if (pred > 1.0)
545 pred = 1.0;
546 return pred;
547 }
548
549 double predict_yg_surv_rate(int age) {
550 return predict_yg_surv_rate(age, _short_lived_surv_rate_group);
551 }
552
553 double accum_yg_surv_rate_pred(int age) {
554 return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
555 }
556
557 protected:
558 void print_stats(int level, const char* str, double value);
559 void print_stats(int level, const char* str, int value);
560
561 void print_par_stats(int level, const char* str, double* data);
562 void print_par_sizes(int level, const char* str, double* data);
563
564 void check_other_times(int level,
565 NumberSeq* other_times_ms,
566 NumberSeq* calc_other_times_ms) const;
567
568 void print_summary (PauseSummary* stats) const;
569
570 void print_summary (int level, const char* str, NumberSeq* seq) const;
571 void print_summary_sd (int level, const char* str, NumberSeq* seq) const;
572
573 double avg_value (double* data);
574 double max_value (double* data);
575 double sum_of_values (double* data);
576 double max_sum (double* data1, double* data2);
577
578 int _last_satb_drain_processed_buffers;
579 int _last_update_rs_processed_buffers;
580 double _last_pause_time_ms;
581
582 size_t _bytes_in_collection_set_before_gc;
583 size_t _bytes_copied_during_gc;
584
585 // Used to count used bytes in CS.
586 friend class CountCSClosure;
587
588 // Statistics kept per GC stoppage, pause or full.
589 TruncatedSeq* _recent_prev_end_times_for_all_gcs_sec;
590
591 // We track markings.
592 int _num_markings;
593 double _mark_thread_startup_sec; // Time at startup of marking thread
594
595 // Add a new GC of the given duration and end time to the record.
596 void update_recent_gc_times(double end_time_sec, double elapsed_ms);
597
598 // The head of the list (via "next_in_collection_set()") representing the
599 // current collection set. Set from the incrementally built collection
600 // set at the start of the pause.
601 HeapRegion* _collection_set;
602
603 // The number of regions in the collection set. Set from the incrementally
604 // built collection set at the start of an evacuation pause.
605 size_t _collection_set_size;
606
607 // The number of bytes in the collection set before the pause. Set from
608 // the incrementally built collection set at the start of an evacuation
609 // pause.
610 size_t _collection_set_bytes_used_before;
611
612 // The associated information that is maintained while the incremental
613 // collection set is being built with young regions. Used to populate
614 // the recorded info for the evacuation pause.
615
616 enum CSetBuildType {
617 Active, // We are actively building the collection set
618 Inactive // We are not actively building the collection set
619 };
620
621 CSetBuildType _inc_cset_build_state;
622
623 // The head of the incrementally built collection set.
624 HeapRegion* _inc_cset_head;
625
626 // The tail of the incrementally built collection set.
627 HeapRegion* _inc_cset_tail;
628
629 // The number of regions in the incrementally built collection set.
630 // Used to set _collection_set_size at the start of an evacuation
631 // pause.
632 size_t _inc_cset_size;
633
634 // Used as the index in the surving young words structure
635 // which tracks the amount of space, for each young region,
636 // that survives the pause.
637 size_t _inc_cset_young_index;
638
639 // The number of bytes in the incrementally built collection set.
640 // Used to set _collection_set_bytes_used_before at the start of
641 // an evacuation pause.
642 size_t _inc_cset_bytes_used_before;
643
644 // Used to record the highest end of heap region in collection set
645 HeapWord* _inc_cset_max_finger;
646
647 // The number of recorded used bytes in the young regions
648 // of the collection set. This is the sum of the used() bytes
649 // of retired young regions in the collection set.
650 size_t _inc_cset_recorded_young_bytes;
651
652 // The RSet lengths recorded for regions in the collection set
653 // (updated by the periodic sampling of the regions in the
654 // young list/collection set).
655 size_t _inc_cset_recorded_rs_lengths;
656
657 // The predicted elapsed time it will take to collect the regions
658 // in the collection set (updated by the periodic sampling of the
659 // regions in the young list/collection set).
660 double _inc_cset_predicted_elapsed_time_ms;
661
662 // The predicted bytes to copy for the regions in the collection
663 // set (updated by the periodic sampling of the regions in the
664 // young list/collection set).
665 size_t _inc_cset_predicted_bytes_to_copy;
666
667 // Info about marking.
668 int _n_marks; // Sticky at 2, so we know when we've done at least 2.
669
670 // The number of collection pauses at the end of the last mark.
671 size_t _n_pauses_at_mark_end;
672
673 // Stash a pointer to the g1 heap.
674 G1CollectedHeap* _g1;
675
676 // The average time in ms per collection pause, averaged over recent pauses.
677 double recent_avg_time_for_pauses_ms();
678
679 // The average time in ms for RS scanning, per pause, averaged
680 // over recent pauses. (Note the RS scanning time for a pause
681 // is itself an average of the RS scanning time for each worker
682 // thread.)
683 double recent_avg_time_for_rs_scan_ms();
684
685 // The number of "recent" GCs recorded in the number sequences
686 int number_of_recent_gcs();
687
688 // The average survival ratio, computed by the total number of bytes
689 // suriviving / total number of bytes before collection over the last
690 // several recent pauses.
691 double recent_avg_survival_fraction();
692 // The survival fraction of the most recent pause; if there have been no
693 // pauses, returns 1.0.
694 double last_survival_fraction();
695
696 // Returns a "conservative" estimate of the recent survival rate, i.e.,
697 // one that may be higher than "recent_avg_survival_fraction".
698 // This is conservative in several ways:
699 // If there have been few pauses, it will assume a potential high
700 // variance, and err on the side of caution.
701 // It puts a lower bound (currently 0.1) on the value it will return.
702 // To try to detect phase changes, if the most recent pause ("latest") has a
703 // higher-than average ("avg") survival rate, it returns that rate.
704 // "work" version is a utility function; young is restricted to young regions.
705 double conservative_avg_survival_fraction_work(double avg,
706 double latest);
707
708 // The arguments are the two sequences that keep track of the number of bytes
709 // surviving and the total number of bytes before collection, resp.,
710 // over the last evereal recent pauses
711 // Returns the survival rate for the category in the most recent pause.
712 // If there have been no pauses, returns 1.0.
713 double last_survival_fraction_work(TruncatedSeq* surviving,
714 TruncatedSeq* before);
715
716 // The arguments are the two sequences that keep track of the number of bytes
717 // surviving and the total number of bytes before collection, resp.,
718 // over the last several recent pauses
719 // Returns the average survival ration over the last several recent pauses
720 // If there have been no pauses, return 1.0
721 double recent_avg_survival_fraction_work(TruncatedSeq* surviving,
722 TruncatedSeq* before);
723
724 double conservative_avg_survival_fraction() {
725 double avg = recent_avg_survival_fraction();
726 double latest = last_survival_fraction();
727 return conservative_avg_survival_fraction_work(avg, latest);
728 }
729
730 // The ratio of gc time to elapsed time, computed over recent pauses.
731 double _recent_avg_pause_time_ratio;
732
733 double recent_avg_pause_time_ratio() {
734 return _recent_avg_pause_time_ratio;
735 }
736
737 // Number of pauses between concurrent marking.
738 size_t _pauses_btwn_concurrent_mark;
739
740 size_t _n_marks_since_last_pause;
741
742 // At the end of a pause we check the heap occupancy and we decide
743 // whether we will start a marking cycle during the next pause. If
744 // we decide that we want to do that, we will set this parameter to
745 // true. So, this parameter will stay true between the end of a
746 // pause and the beginning of a subsequent pause (not necessarily
747 // the next one, see the comments on the next field) when we decide
748 // that we will indeed start a marking cycle and do the initial-mark
749 // work.
750 volatile bool _initiate_conc_mark_if_possible;
751
752 // If initiate_conc_mark_if_possible() is set at the beginning of a
753 // pause, it is a suggestion that the pause should start a marking
754 // cycle by doing the initial-mark work. However, it is possible
755 // that the concurrent marking thread is still finishing up the
756 // previous marking cycle (e.g., clearing the next marking
757 // bitmap). If that is the case we cannot start a new cycle and
758 // we'll have to wait for the concurrent marking thread to finish
759 // what it is doing. In this case we will postpone the marking cycle
760 // initiation decision for the next pause. When we eventually decide
761 // to start a cycle, we will set _during_initial_mark_pause which
762 // will stay true until the end of the initial-mark pause and it's
763 // the condition that indicates that a pause is doing the
764 // initial-mark work.
765 volatile bool _during_initial_mark_pause;
766
767 bool _should_revert_to_full_young_gcs;
768 bool _last_full_young_gc;
769
770 // This set of variables tracks the collector efficiency, in order to
771 // determine whether we should initiate a new marking.
772 double _cur_mark_stop_world_time_ms;
773 double _mark_remark_start_sec;
774 double _mark_cleanup_start_sec;
775 double _mark_closure_time_ms;
776
777 // Update the young list target length either by setting it to the
778 // desired fixed value or by calculating it using G1's pause
779 // prediction model. If no rs_lengths parameter is passed, predict
780 // the RS lengths using the prediction model, otherwise use the
781 // given rs_lengths as the prediction.
782 void update_young_list_target_length(size_t rs_lengths = (size_t) -1);
783
784 // Calculate and return the minimum desired young list target
785 // length. This is the minimum desired young list length according
786 // to the user's inputs.
787 size_t calculate_young_list_desired_min_length(size_t base_min_length);
788
789 // Calculate and return the maximum desired young list target
790 // length. This is the maximum desired young list length according
791 // to the user's inputs.
792 size_t calculate_young_list_desired_max_length();
793
794 // Calculate and return the maximum young list target length that
795 // can fit into the pause time goal. The parameters are: rs_lengths
796 // represent the prediction of how large the young RSet lengths will
797 // be, base_min_length is the alreay existing number of regions in
798 // the young list, min_length and max_length are the desired min and
799 // max young list length according to the user's inputs.
800 size_t calculate_young_list_target_length(size_t rs_lengths,
801 size_t base_min_length,
802 size_t desired_min_length,
803 size_t desired_max_length);
804
805 // Check whether a given young length (young_length) fits into the
806 // given target pause time and whether the prediction for the amount
807 // of objects to be copied for the given length will fit into the
808 // given free space (expressed by base_free_regions). It is used by
809 // calculate_young_list_target_length().
810 bool predict_will_fit(size_t young_length, double base_time_ms,
811 size_t base_free_regions, double target_pause_time_ms);
812
813 public:
814
815 G1CollectorPolicy();
816
817 virtual G1CollectorPolicy* as_g1_policy() { return this; }
818
819 virtual CollectorPolicy::Name kind() {
820 return CollectorPolicy::G1CollectorPolicyKind;
821 }
822
823 // Check the current value of the young list RSet lengths and
824 // compare it against the last prediction. If the current value is
825 // higher, recalculate the young list target length prediction.
826 void revise_young_list_target_length_if_necessary();
827
828 size_t bytes_in_collection_set() {
829 return _bytes_in_collection_set_before_gc;
830 }
831
832 unsigned calc_gc_alloc_time_stamp() {
833 return _all_pause_times_ms->num() + 1;
834 }
835
836 // This should be called after the heap is resized.
837 void record_new_heap_size(size_t new_number_of_regions);
838
839 protected:
840
841 // Count the number of bytes used in the CS.
842 void count_CS_bytes_used();
843
844 // Together these do the base cleanup-recording work. Subclasses might
845 // want to put something between them.
846 void record_concurrent_mark_cleanup_end_work1(size_t freed_bytes,
847 size_t max_live_bytes);
848 void record_concurrent_mark_cleanup_end_work2();
849
850 void update_young_list_size_using_newratio(size_t number_of_heap_regions);
851
852 public:
853
854 virtual void init();
855
856 // Create jstat counters for the policy.
857 virtual void initialize_gc_policy_counters();
858
859 virtual HeapWord* mem_allocate_work(size_t size,
860 bool is_tlab,
861 bool* gc_overhead_limit_was_exceeded);
862
863 // This method controls how a collector handles one or more
864 // of its generations being fully allocated.
865 virtual HeapWord* satisfy_failed_allocation(size_t size,
866 bool is_tlab);
867
868 BarrierSet::Name barrier_set_name() { return BarrierSet::G1SATBCTLogging; }
869
870 GenRemSet::Name rem_set_name() { return GenRemSet::CardTable; }
871
872 // The number of collection pauses so far.
873 long n_pauses() const { return _n_pauses; }
874
875 // Update the heuristic info to record a collection pause of the given
876 // start time, where the given number of bytes were used at the start.
877 // This may involve changing the desired size of a collection set.
878
879 virtual void record_stop_world_start();
880
881 virtual void record_collection_pause_start(double start_time_sec,
882 size_t start_used);
883
884 // Must currently be called while the world is stopped.
885 void record_concurrent_mark_init_end(double
886 mark_init_elapsed_time_ms);
887
888 void record_mark_closure_time(double mark_closure_time_ms);
889
890 virtual void record_concurrent_mark_remark_start();
891 virtual void record_concurrent_mark_remark_end();
892
893 virtual void record_concurrent_mark_cleanup_start();
894 virtual void record_concurrent_mark_cleanup_end(size_t freed_bytes,
895 size_t max_live_bytes);
896 virtual void record_concurrent_mark_cleanup_completed();
897
898 virtual void record_concurrent_pause();
899 virtual void record_concurrent_pause_end();
900
901 virtual void record_collection_pause_end();
902 void print_heap_transition();
903
904 // Record the fact that a full collection occurred.
905 virtual void record_full_collection_start();
906 virtual void record_full_collection_end();
907
908 void record_gc_worker_start_time(int worker_i, double ms) {
909 _par_last_gc_worker_start_times_ms[worker_i] = ms;
910 }
911
912 void record_ext_root_scan_time(int worker_i, double ms) {
913 _par_last_ext_root_scan_times_ms[worker_i] = ms;
914 }
915
916 void record_mark_stack_scan_time(int worker_i, double ms) {
917 _par_last_mark_stack_scan_times_ms[worker_i] = ms;
918 }
919
920 void record_satb_drain_time(double ms) {
921 _cur_satb_drain_time_ms = ms;
922 _satb_drain_time_set = true;
923 }
924
925 void record_satb_drain_processed_buffers (int processed_buffers) {
926 _last_satb_drain_processed_buffers = processed_buffers;
927 }
928
929 void record_mod_union_time(double ms) {
930 _all_mod_union_times_ms->add(ms);
931 }
932
933 void record_update_rs_time(int thread, double ms) {
934 _par_last_update_rs_times_ms[thread] = ms;
935 }
936
937 void record_update_rs_processed_buffers (int thread,
938 double processed_buffers) {
939 _par_last_update_rs_processed_buffers[thread] = processed_buffers;
940 }
941
942 void record_scan_rs_time(int thread, double ms) {
943 _par_last_scan_rs_times_ms[thread] = ms;
944 }
945
946 void reset_obj_copy_time(int thread) {
947 _par_last_obj_copy_times_ms[thread] = 0.0;
948 }
949
950 void reset_obj_copy_time() {
951 reset_obj_copy_time(0);
952 }
953
954 void record_obj_copy_time(int thread, double ms) {
955 _par_last_obj_copy_times_ms[thread] += ms;
956 }
957
958 void record_termination(int thread, double ms, size_t attempts) {
959 _par_last_termination_times_ms[thread] = ms;
960 _par_last_termination_attempts[thread] = (double) attempts;
961 }
962
963 void record_gc_worker_end_time(int worker_i, double ms) {
964 _par_last_gc_worker_end_times_ms[worker_i] = ms;
965 }
966
967 void record_pause_time_ms(double ms) {
968 _last_pause_time_ms = ms;
969 }
970
971 void record_clear_ct_time(double ms) {
972 _cur_clear_ct_time_ms = ms;
973 }
974
975 void record_par_time(double ms) {
976 _cur_collection_par_time_ms = ms;
977 }
978
979 void record_aux_start_time(int i) {
980 guarantee(i < _aux_num, "should be within range");
981 _cur_aux_start_times_ms[i] = os::elapsedTime() * 1000.0;
982 }
983
984 void record_aux_end_time(int i) {
985 guarantee(i < _aux_num, "should be within range");
986 double ms = os::elapsedTime() * 1000.0 - _cur_aux_start_times_ms[i];
987 _cur_aux_times_set[i] = true;
988 _cur_aux_times_ms[i] += ms;
989 }
990
991 void record_ref_proc_time(double ms) {
992 _cur_ref_proc_time_ms = ms;
993 }
994
995 void record_ref_enq_time(double ms) {
996 _cur_ref_enq_time_ms = ms;
997 }
998
999 #ifndef PRODUCT
1000 void record_cc_clear_time(double ms) {
1001 if (_min_clear_cc_time_ms < 0.0 || ms <= _min_clear_cc_time_ms)
1002 _min_clear_cc_time_ms = ms;
1003 if (_max_clear_cc_time_ms < 0.0 || ms >= _max_clear_cc_time_ms)
1004 _max_clear_cc_time_ms = ms;
1005 _cur_clear_cc_time_ms = ms;
1006 _cum_clear_cc_time_ms += ms;
1007 _num_cc_clears++;
1008 }
1009 #endif
1010
1011 // Record how much space we copied during a GC. This is typically
1012 // called when a GC alloc region is being retired.
1013 void record_bytes_copied_during_gc(size_t bytes) {
1014 _bytes_copied_during_gc += bytes;
1015 }
1016
1017 // The amount of space we copied during a GC.
1018 size_t bytes_copied_during_gc() {
1019 return _bytes_copied_during_gc;
1020 }
1021
1022 // Choose a new collection set. Marks the chosen regions as being
1023 // "in_collection_set", and links them together. The head and number of
1024 // the collection set are available via access methods.
1025 virtual void choose_collection_set(double target_pause_time_ms) = 0;
1026
1027 // The head of the list (via "next_in_collection_set()") representing the
1028 // current collection set.
1029 HeapRegion* collection_set() { return _collection_set; }
1030
1031 void clear_collection_set() { _collection_set = NULL; }
1032
1033 // The number of elements in the current collection set.
1034 size_t collection_set_size() { return _collection_set_size; }
1035
1036 // Add "hr" to the CS.
1037 void add_to_collection_set(HeapRegion* hr);
1038
1039 // Incremental CSet Support
1040
1041 // The head of the incrementally built collection set.
1042 HeapRegion* inc_cset_head() { return _inc_cset_head; }
1043
1044 // The tail of the incrementally built collection set.
1045 HeapRegion* inc_set_tail() { return _inc_cset_tail; }
1046
1047 // The number of elements in the incrementally built collection set.
1048 size_t inc_cset_size() { return _inc_cset_size; }
1049
1050 // Initialize incremental collection set info.
1051 void start_incremental_cset_building();
1052
1053 void clear_incremental_cset() {
1054 _inc_cset_head = NULL;
1055 _inc_cset_tail = NULL;
1056 }
1057
1058 // Stop adding regions to the incremental collection set
1059 void stop_incremental_cset_building() { _inc_cset_build_state = Inactive; }
1060
1061 // Add/remove information about hr to the aggregated information
1062 // for the incrementally built collection set.
1063 void add_to_incremental_cset_info(HeapRegion* hr, size_t rs_length);
1064 void remove_from_incremental_cset_info(HeapRegion* hr);
1065
1066 // Update information about hr in the aggregated information for
1067 // the incrementally built collection set.
1068 void update_incremental_cset_info(HeapRegion* hr, size_t new_rs_length);
1069
1070 private:
1071 // Update the incremental cset information when adding a region
1072 // (should not be called directly).
1073 void add_region_to_incremental_cset_common(HeapRegion* hr);
1074
1075 public:
1076 // Add hr to the LHS of the incremental collection set.
1077 void add_region_to_incremental_cset_lhs(HeapRegion* hr);
1078
1079 // Add hr to the RHS of the incremental collection set.
1080 void add_region_to_incremental_cset_rhs(HeapRegion* hr);
1081
1082 #ifndef PRODUCT
1083 void print_collection_set(HeapRegion* list_head, outputStream* st);
1084 #endif // !PRODUCT
1085
1086 bool initiate_conc_mark_if_possible() { return _initiate_conc_mark_if_possible; }
1087 void set_initiate_conc_mark_if_possible() { _initiate_conc_mark_if_possible = true; }
1088 void clear_initiate_conc_mark_if_possible() { _initiate_conc_mark_if_possible = false; }
1089
1090 bool during_initial_mark_pause() { return _during_initial_mark_pause; }
1091 void set_during_initial_mark_pause() { _during_initial_mark_pause = true; }
1092 void clear_during_initial_mark_pause(){ _during_initial_mark_pause = false; }
1093
1094 // This sets the initiate_conc_mark_if_possible() flag to start a
1095 // new cycle, as long as we are not already in one. It's best if it
1096 // is called during a safepoint when the test whether a cycle is in
1097 // progress or not is stable.
1098 bool force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause);
1099
1100 // This is called at the very beginning of an evacuation pause (it
1101 // has to be the first thing that the pause does). If
1102 // initiate_conc_mark_if_possible() is true, and the concurrent
1103 // marking thread has completed its work during the previous cycle,
1104 // it will set during_initial_mark_pause() to so that the pause does
1105 // the initial-mark work and start a marking cycle.
1106 void decide_on_conc_mark_initiation();
1107
1108 // If an expansion would be appropriate, because recent GC overhead had
1109 // exceeded the desired limit, return an amount to expand by.
1110 virtual size_t expansion_amount();
1111
1112 // note start of mark thread
1113 void note_start_of_mark_thread();
1114
1115 // The marked bytes of the "r" has changed; reclassify it's desirability
1116 // for marking. Also asserts that "r" is eligible for a CS.
1117 virtual void note_change_in_marked_bytes(HeapRegion* r) = 0;
1118
1119 #ifndef PRODUCT
1120 // Check any appropriate marked bytes info, asserting false if
1121 // something's wrong, else returning "true".
1122 virtual bool assertMarkedBytesDataOK() = 0;
1123 #endif
1124
1125 // Print tracing information.
1126 void print_tracing_info() const;
1127
1128 // Print stats on young survival ratio
1129 void print_yg_surv_rate_info() const;
1130
1131 void finished_recalculating_age_indexes(bool is_survivors) {
1132 if (is_survivors) {
1133 _survivor_surv_rate_group->finished_recalculating_age_indexes();
1134 } else {
1135 _short_lived_surv_rate_group->finished_recalculating_age_indexes();
1136 }
1137 // do that for any other surv rate groups
1138 }
1139
1140 bool is_young_list_full() {
1141 size_t young_list_length = _g1->young_list()->length();
1142 size_t young_list_target_length = _young_list_target_length;
1143 return young_list_length >= young_list_target_length;
1144 }
1145
1146 bool can_expand_young_list() {
1147 size_t young_list_length = _g1->young_list()->length();
1148 size_t young_list_max_length = _young_list_max_length;
1149 return young_list_length < young_list_max_length;
1150 }
1151
1152 void update_region_num(bool young);
1153
1154 bool full_young_gcs() {
1155 return _full_young_gcs;
1156 }
1157 void set_full_young_gcs(bool full_young_gcs) {
1158 _full_young_gcs = full_young_gcs;
1159 }
1160
1161 bool adaptive_young_list_length() {
1162 return _adaptive_young_list_length;
1163 }
1164 void set_adaptive_young_list_length(bool adaptive_young_list_length) {
1165 _adaptive_young_list_length = adaptive_young_list_length;
1166 }
1167
1168 inline double get_gc_eff_factor() {
1169 double ratio = _known_garbage_ratio;
1170
1171 double square = ratio * ratio;
1172 // square = square * square;
1173 double ret = square * 9.0 + 1.0;
1174 #if 0
1175 gclog_or_tty->print_cr("ratio = %1.2lf, ret = %1.2lf", ratio, ret);
1176 #endif // 0
1177 guarantee(0.0 <= ret && ret < 10.0, "invariant!");
1178 return ret;
1179 }
1180
1181 //
1182 // Survivor regions policy.
1183 //
1184 protected:
1185
1186 // Current tenuring threshold, set to 0 if the collector reaches the
1187 // maximum amount of suvivors regions.
1188 int _tenuring_threshold;
1189
1190 // The limit on the number of regions allocated for survivors.
1191 size_t _max_survivor_regions;
1192
1193 // For reporting purposes.
1194 size_t _eden_bytes_before_gc;
1195 size_t _survivor_bytes_before_gc;
1196 size_t _capacity_before_gc;
1197
1198 // The amount of survor regions after a collection.
1199 size_t _recorded_survivor_regions;
1200 // List of survivor regions.
1201 HeapRegion* _recorded_survivor_head;
1202 HeapRegion* _recorded_survivor_tail;
1203
1204 ageTable _survivors_age_table;
1205
1206 public:
1207
1208 inline GCAllocPurpose
1209 evacuation_destination(HeapRegion* src_region, int age, size_t word_sz) {
1210 if (age < _tenuring_threshold && src_region->is_young()) {
1211 return GCAllocForSurvived;
1212 } else {
1213 return GCAllocForTenured;
1214 }
1215 }
1216
1217 inline bool track_object_age(GCAllocPurpose purpose) {
1218 return purpose == GCAllocForSurvived;
1219 }
1220
1221 static const size_t REGIONS_UNLIMITED = ~(size_t)0;
1222
1223 size_t max_regions(int purpose);
1224
1225 // The limit on regions for a particular purpose is reached.
1226 void note_alloc_region_limit_reached(int purpose) {
1227 if (purpose == GCAllocForSurvived) {
1228 _tenuring_threshold = 0;
1229 }
1230 }
1231
1232 void note_start_adding_survivor_regions() {
1233 _survivor_surv_rate_group->start_adding_regions();
1234 }
1235
1236 void note_stop_adding_survivor_regions() {
1237 _survivor_surv_rate_group->stop_adding_regions();
1238 }
1239
1240 void record_survivor_regions(size_t regions,
1241 HeapRegion* head,
1242 HeapRegion* tail) {
1243 _recorded_survivor_regions = regions;
1244 _recorded_survivor_head = head;
1245 _recorded_survivor_tail = tail;
1246 }
1247
1248 size_t recorded_survivor_regions() {
1249 return _recorded_survivor_regions;
1250 }
1251
1252 void record_thread_age_table(ageTable* age_table)
1253 {
1254 _survivors_age_table.merge_par(age_table);
1255 }
1256
1257 void update_max_gc_locker_expansion();
1258
1259 // Calculates survivor space parameters.
1260 void update_survivors_policy();
1261
1262 };
1263
1264 // This encapsulates a particular strategy for a g1 Collector.
1265 //
1266 // Start a concurrent mark when our heap size is n bytes
1267 // greater then our heap size was at the last concurrent
1268 // mark. Where n is a function of the CMSTriggerRatio
1269 // and the MinHeapFreeRatio.
1270 //
1271 // Start a g1 collection pause when we have allocated the
1272 // average number of bytes currently being freed in
1273 // a collection, but only if it is at least one region
1274 // full
1275 //
1276 // Resize Heap based on desired
1277 // allocation space, where desired allocation space is
1278 // a function of survival rate and desired future to size.
1279 //
1280 // Choose collection set by first picking all older regions
1281 // which have a survival rate which beats our projected young
1282 // survival rate. Then fill out the number of needed regions
1283 // with young regions.
1284
1285 class G1CollectorPolicy_BestRegionsFirst: public G1CollectorPolicy {
1286 CollectionSetChooser* _collectionSetChooser;
1287
1288 virtual void choose_collection_set(double target_pause_time_ms);
1289 virtual void record_collection_pause_start(double start_time_sec,
1290 size_t start_used);
1291 virtual void record_concurrent_mark_cleanup_end(size_t freed_bytes,
1292 size_t max_live_bytes);
1293 virtual void record_full_collection_end();
1294
1295 public:
1296 G1CollectorPolicy_BestRegionsFirst() {
1297 _collectionSetChooser = new CollectionSetChooser();
1298 }
1299 void record_collection_pause_end();
1300 // This is not needed any more, after the CSet choosing code was
1301 // changed to use the pause prediction work. But let's leave the
1302 // hook in just in case.
1303 void note_change_in_marked_bytes(HeapRegion* r) { }
1304 #ifndef PRODUCT
1305 bool assertMarkedBytesDataOK();
1306 #endif
1307 };
1308
1309 // This should move to some place more general...
1310
1311 // If we have "n" measurements, and we've kept track of their "sum" and the
1312 // "sum_of_squares" of the measurements, this returns the variance of the
1313 // sequence.
1314 inline double variance(int n, double sum_of_squares, double sum) {
1315 double n_d = (double)n;
1316 double avg = sum/n_d;
1317 return (sum_of_squares - 2.0 * avg * sum + n_d * avg * avg) / n_d;
1318 }
1319
1320 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP