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_remark_times_ms;
145 TruncatedSeq* _concurrent_mark_cleanup_times_ms;
146
147 Summary* _summary;
148
149 NumberSeq* _all_pause_times_ms;
150 NumberSeq* _all_full_gc_times_ms;
151 double _stop_world_start;
152 NumberSeq* _all_stop_world_times_ms;
153 NumberSeq* _all_yield_times_ms;
154
155 size_t _region_num_young;
156 size_t _region_num_tenured;
157 size_t _prev_region_num_young;
158 size_t _prev_region_num_tenured;
159
160 NumberSeq* _all_mod_union_times_ms;
161
162 int _aux_num;
163 NumberSeq* _all_aux_times_ms;
164 double* _cur_aux_start_times_ms;
165 double* _cur_aux_times_ms;
166 bool* _cur_aux_times_set;
167
168 double* _par_last_gc_worker_start_times_ms;
169 double* _par_last_ext_root_scan_times_ms;
170 double* _par_last_mark_stack_scan_times_ms;
171 double* _par_last_update_rs_times_ms;
172 double* _par_last_update_rs_processed_buffers;
173 double* _par_last_scan_rs_times_ms;
174 double* _par_last_obj_copy_times_ms;
175 double* _par_last_termination_times_ms;
176 double* _par_last_termination_attempts;
177 double* _par_last_gc_worker_end_times_ms;
178 double* _par_last_gc_worker_times_ms;
179
180 // indicates whether we are in full young or partially young GC mode
181 bool _full_young_gcs;
182
183 // if true, then it tries to dynamically adjust the length of the
184 // young list
185 bool _adaptive_young_list_length;
186 size_t _young_list_target_length;
187 size_t _young_list_fixed_length;
188 size_t _prev_eden_capacity; // used for logging
189
190 // The max number of regions we can extend the eden by while the GC
191 // locker is active. This should be >= _young_list_target_length;
192 size_t _young_list_max_length;
193
194 size_t _young_cset_length;
195 bool _last_young_gc_full;
196
197 unsigned _full_young_pause_num;
198 unsigned _partial_young_pause_num;
199
200 bool _during_marking;
201 bool _in_marking_window;
202 bool _in_marking_window_im;
203
204 SurvRateGroup* _short_lived_surv_rate_group;
205 SurvRateGroup* _survivor_surv_rate_group;
206 // add here any more surv rate groups
207
208 double _gc_overhead_perc;
209
210 double _reserve_factor;
211 size_t _reserve_regions;
212
213 bool during_marking() {
214 return _during_marking;
215 }
216
217 // <NEW PREDICTION>
218
219 private:
220 enum PredictionConstants {
221 TruncatedSeqLength = 10
222 };
223
224 TruncatedSeq* _alloc_rate_ms_seq;
225 double _prev_collection_pause_end_ms;
226
227 TruncatedSeq* _pending_card_diff_seq;
228 TruncatedSeq* _rs_length_diff_seq;
229 TruncatedSeq* _cost_per_card_ms_seq;
230 TruncatedSeq* _fully_young_cards_per_entry_ratio_seq;
231 TruncatedSeq* _partially_young_cards_per_entry_ratio_seq;
232 TruncatedSeq* _cost_per_entry_ms_seq;
233 TruncatedSeq* _partially_young_cost_per_entry_ms_seq;
234 TruncatedSeq* _cost_per_byte_ms_seq;
235 TruncatedSeq* _constant_other_time_ms_seq;
236 TruncatedSeq* _young_other_cost_per_region_ms_seq;
237 TruncatedSeq* _non_young_other_cost_per_region_ms_seq;
238
239 TruncatedSeq* _pending_cards_seq;
240 TruncatedSeq* _scanned_cards_seq;
241 TruncatedSeq* _rs_lengths_seq;
242
243 TruncatedSeq* _cost_per_byte_ms_during_cm_seq;
244
245 TruncatedSeq* _young_gc_eff_seq;
246
247 TruncatedSeq* _max_conc_overhead_seq;
248
249 bool _using_new_ratio_calculations;
250 size_t _min_desired_young_length; // as set on the command line or default calculations
251 size_t _max_desired_young_length; // as set on the command line or default calculations
252
253 size_t _recorded_young_regions;
254 size_t _recorded_non_young_regions;
255 size_t _recorded_region_num;
256
257 size_t _free_regions_at_end_of_collection;
258
259 size_t _recorded_rs_lengths;
260 size_t _max_rs_lengths;
261
262 size_t _recorded_marked_bytes;
263 size_t _recorded_young_bytes;
264
265 size_t _predicted_pending_cards;
266 size_t _predicted_cards_scanned;
267 size_t _predicted_rs_lengths;
268 size_t _predicted_bytes_to_copy;
269
270 double _predicted_survival_ratio;
271 double _predicted_rs_update_time_ms;
272 double _predicted_rs_scan_time_ms;
273 double _predicted_object_copy_time_ms;
274 double _predicted_constant_other_time_ms;
275 double _predicted_young_other_time_ms;
276 double _predicted_non_young_other_time_ms;
277 double _predicted_pause_time_ms;
278
279 double _vtime_diff_ms;
280
281 double _recorded_young_free_cset_time_ms;
282 double _recorded_non_young_free_cset_time_ms;
283
284 double _sigma;
285 double _expensive_region_limit_ms;
286
287 size_t _rs_lengths_prediction;
288
289 size_t _known_garbage_bytes;
290 double _known_garbage_ratio;
291
292 double sigma() {
293 return _sigma;
294 }
295
296 // A function that prevents us putting too much stock in small sample
297 // sets. Returns a number between 2.0 and 1.0, depending on the number
298 // of samples. 5 or more samples yields one; fewer scales linearly from
299 // 2.0 at 1 sample to 1.0 at 5.
300 double confidence_factor(int samples) {
301 if (samples > 4) return 1.0;
302 else return 1.0 + sigma() * ((double)(5 - samples))/2.0;
303 }
304
305 double get_new_neg_prediction(TruncatedSeq* seq) {
306 return seq->davg() - sigma() * seq->dsd();
307 }
308
309 #ifndef PRODUCT
310 bool verify_young_ages(HeapRegion* head, SurvRateGroup *surv_rate_group);
311 #endif // PRODUCT
312
313 void adjust_concurrent_refinement(double update_rs_time,
314 double update_rs_processed_buffers,
315 double goal_ms);
316
317 protected:
318 double _pause_time_target_ms;
319 double _recorded_young_cset_choice_time_ms;
320 double _recorded_non_young_cset_choice_time_ms;
321 bool _within_target;
322 size_t _pending_cards;
323 size_t _max_pending_cards;
324
325 public:
326
327 void set_region_short_lived(HeapRegion* hr) {
328 hr->install_surv_rate_group(_short_lived_surv_rate_group);
329 }
330
331 void set_region_survivors(HeapRegion* hr) {
332 hr->install_surv_rate_group(_survivor_surv_rate_group);
333 }
334
335 #ifndef PRODUCT
336 bool verify_young_ages();
337 #endif // PRODUCT
338
339 double get_new_prediction(TruncatedSeq* seq) {
340 return MAX2(seq->davg() + sigma() * seq->dsd(),
341 seq->davg() * confidence_factor(seq->num()));
342 }
343
344 size_t young_cset_length() {
345 return _young_cset_length;
346 }
347
348 void record_max_rs_lengths(size_t rs_lengths) {
349 _max_rs_lengths = rs_lengths;
350 }
351
352 size_t predict_pending_card_diff() {
353 double prediction = get_new_neg_prediction(_pending_card_diff_seq);
354 if (prediction < 0.00001)
355 return 0;
356 else
357 return (size_t) prediction;
358 }
359
360 size_t predict_pending_cards() {
361 size_t max_pending_card_num = _g1->max_pending_card_num();
362 size_t diff = predict_pending_card_diff();
363 size_t prediction;
364 if (diff > max_pending_card_num)
365 prediction = max_pending_card_num;
366 else
367 prediction = max_pending_card_num - diff;
368
369 return prediction;
370 }
371
372 size_t predict_rs_length_diff() {
373 return (size_t) get_new_prediction(_rs_length_diff_seq);
374 }
375
376 double predict_alloc_rate_ms() {
377 return get_new_prediction(_alloc_rate_ms_seq);
378 }
379
380 double predict_cost_per_card_ms() {
381 return get_new_prediction(_cost_per_card_ms_seq);
382 }
383
384 double predict_rs_update_time_ms(size_t pending_cards) {
385 return (double) pending_cards * predict_cost_per_card_ms();
386 }
387
388 double predict_fully_young_cards_per_entry_ratio() {
389 return get_new_prediction(_fully_young_cards_per_entry_ratio_seq);
390 }
391
392 double predict_partially_young_cards_per_entry_ratio() {
393 if (_partially_young_cards_per_entry_ratio_seq->num() < 2)
394 return predict_fully_young_cards_per_entry_ratio();
395 else
396 return get_new_prediction(_partially_young_cards_per_entry_ratio_seq);
397 }
398
399 size_t predict_young_card_num(size_t rs_length) {
400 return (size_t) ((double) rs_length *
401 predict_fully_young_cards_per_entry_ratio());
402 }
403
404 size_t predict_non_young_card_num(size_t rs_length) {
405 return (size_t) ((double) rs_length *
406 predict_partially_young_cards_per_entry_ratio());
407 }
408
409 double predict_rs_scan_time_ms(size_t card_num) {
410 if (full_young_gcs())
411 return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq);
412 else
413 return predict_partially_young_rs_scan_time_ms(card_num);
414 }
415
416 double predict_partially_young_rs_scan_time_ms(size_t card_num) {
417 if (_partially_young_cost_per_entry_ms_seq->num() < 3)
418 return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq);
419 else
420 return (double) card_num *
421 get_new_prediction(_partially_young_cost_per_entry_ms_seq);
422 }
423
424 double predict_object_copy_time_ms_during_cm(size_t bytes_to_copy) {
425 if (_cost_per_byte_ms_during_cm_seq->num() < 3)
426 return 1.1 * (double) bytes_to_copy *
427 get_new_prediction(_cost_per_byte_ms_seq);
428 else
429 return (double) bytes_to_copy *
430 get_new_prediction(_cost_per_byte_ms_during_cm_seq);
431 }
432
433 double predict_object_copy_time_ms(size_t bytes_to_copy) {
434 if (_in_marking_window && !_in_marking_window_im)
435 return predict_object_copy_time_ms_during_cm(bytes_to_copy);
436 else
437 return (double) bytes_to_copy *
438 get_new_prediction(_cost_per_byte_ms_seq);
439 }
440
441 double predict_constant_other_time_ms() {
442 return get_new_prediction(_constant_other_time_ms_seq);
443 }
444
445 double predict_young_other_time_ms(size_t young_num) {
446 return
447 (double) young_num *
448 get_new_prediction(_young_other_cost_per_region_ms_seq);
449 }
450
451 double predict_non_young_other_time_ms(size_t non_young_num) {
452 return
453 (double) non_young_num *
454 get_new_prediction(_non_young_other_cost_per_region_ms_seq);
455 }
456
457 void check_if_region_is_too_expensive(double predicted_time_ms);
458
459 double predict_young_collection_elapsed_time_ms(size_t adjustment);
460 double predict_base_elapsed_time_ms(size_t pending_cards);
461 double predict_base_elapsed_time_ms(size_t pending_cards,
462 size_t scanned_cards);
463 size_t predict_bytes_to_copy(HeapRegion* hr);
464 double predict_region_elapsed_time_ms(HeapRegion* hr, bool young);
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_remark_time_ms() {
528 return get_new_prediction(_concurrent_mark_remark_times_ms);
529 }
530
531 double predict_cleanup_time_ms() {
532 return get_new_prediction(_concurrent_mark_cleanup_times_ms);
533 }
534
535 // Returns an estimate of the survival rate of the region at yg-age
536 // "yg_age".
537 double predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) {
538 TruncatedSeq* seq = surv_rate_group->get_seq(age);
539 if (seq->num() == 0)
540 gclog_or_tty->print("BARF! age is %d", age);
541 guarantee( seq->num() > 0, "invariant" );
542 double pred = get_new_prediction(seq);
543 if (pred > 1.0)
544 pred = 1.0;
545 return pred;
546 }
547
548 double predict_yg_surv_rate(int age) {
549 return predict_yg_surv_rate(age, _short_lived_surv_rate_group);
550 }
551
552 double accum_yg_surv_rate_pred(int age) {
553 return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
554 }
555
556 protected:
557 void print_stats(int level, const char* str, double value);
558 void print_stats(int level, const char* str, int value);
559
560 void print_par_stats(int level, const char* str, double* data);
561 void print_par_sizes(int level, const char* str, double* data);
562
563 void check_other_times(int level,
564 NumberSeq* other_times_ms,
565 NumberSeq* calc_other_times_ms) const;
566
567 void print_summary (PauseSummary* stats) const;
568
569 void print_summary (int level, const char* str, NumberSeq* seq) const;
570 void print_summary_sd (int level, const char* str, NumberSeq* seq) const;
571
572 double avg_value (double* data);
573 double max_value (double* data);
574 double sum_of_values (double* data);
575 double max_sum (double* data1, double* data2);
576
577 int _last_satb_drain_processed_buffers;
578 int _last_update_rs_processed_buffers;
579 double _last_pause_time_ms;
580
581 size_t _bytes_in_collection_set_before_gc;
582 size_t _bytes_copied_during_gc;
583
584 // Used to count used bytes in CS.
585 friend class CountCSClosure;
586
587 // Statistics kept per GC stoppage, pause or full.
588 TruncatedSeq* _recent_prev_end_times_for_all_gcs_sec;
589
590 // We track markings.
591 int _num_markings;
592 double _mark_thread_startup_sec; // Time at startup of marking thread
593
594 // Add a new GC of the given duration and end time to the record.
595 void update_recent_gc_times(double end_time_sec, double elapsed_ms);
596
597 // The head of the list (via "next_in_collection_set()") representing the
598 // current collection set. Set from the incrementally built collection
599 // set at the start of the pause.
600 HeapRegion* _collection_set;
601
602 // The number of regions in the collection set. Set from the incrementally
603 // built collection set at the start of an evacuation pause.
604 size_t _collection_set_size;
605
606 // The number of bytes in the collection set before the pause. Set from
607 // the incrementally built collection set at the start of an evacuation
608 // pause.
609 size_t _collection_set_bytes_used_before;
610
611 // The associated information that is maintained while the incremental
612 // collection set is being built with young regions. Used to populate
613 // the recorded info for the evacuation pause.
614
615 enum CSetBuildType {
616 Active, // We are actively building the collection set
617 Inactive // We are not actively building the collection set
618 };
619
620 CSetBuildType _inc_cset_build_state;
621
622 // The head of the incrementally built collection set.
623 HeapRegion* _inc_cset_head;
624
625 // The tail of the incrementally built collection set.
626 HeapRegion* _inc_cset_tail;
627
628 // The number of regions in the incrementally built collection set.
629 // Used to set _collection_set_size at the start of an evacuation
630 // pause.
631 size_t _inc_cset_size;
632
633 // Used as the index in the surving young words structure
634 // which tracks the amount of space, for each young region,
635 // that survives the pause.
636 size_t _inc_cset_young_index;
637
638 // The number of bytes in the incrementally built collection set.
639 // Used to set _collection_set_bytes_used_before at the start of
640 // an evacuation pause.
641 size_t _inc_cset_bytes_used_before;
642
643 // Used to record the highest end of heap region in collection set
644 HeapWord* _inc_cset_max_finger;
645
646 // The number of recorded used bytes in the young regions
647 // of the collection set. This is the sum of the used() bytes
648 // of retired young regions in the collection set.
649 size_t _inc_cset_recorded_young_bytes;
650
651 // The RSet lengths recorded for regions in the collection set
652 // (updated by the periodic sampling of the regions in the
653 // young list/collection set).
654 size_t _inc_cset_recorded_rs_lengths;
655
656 // The predicted elapsed time it will take to collect the regions
657 // in the collection set (updated by the periodic sampling of the
658 // regions in the young list/collection set).
659 double _inc_cset_predicted_elapsed_time_ms;
660
661 // The predicted bytes to copy for the regions in the collection
662 // set (updated by the periodic sampling of the regions in the
663 // young list/collection set).
664 size_t _inc_cset_predicted_bytes_to_copy;
665
666 // Info about marking.
667 int _n_marks; // Sticky at 2, so we know when we've done at least 2.
668
669 // The number of collection pauses at the end of the last mark.
670 size_t _n_pauses_at_mark_end;
671
672 // Stash a pointer to the g1 heap.
673 G1CollectedHeap* _g1;
674
675 // The average time in ms per collection pause, averaged over recent pauses.
676 double recent_avg_time_for_pauses_ms();
677
678 // The average time in ms for RS scanning, per pause, averaged
679 // over recent pauses. (Note the RS scanning time for a pause
680 // is itself an average of the RS scanning time for each worker
681 // thread.)
682 double recent_avg_time_for_rs_scan_ms();
683
684 // The number of "recent" GCs recorded in the number sequences
685 int number_of_recent_gcs();
686
687 // The average survival ratio, computed by the total number of bytes
688 // suriviving / total number of bytes before collection over the last
689 // several recent pauses.
690 double recent_avg_survival_fraction();
691 // The survival fraction of the most recent pause; if there have been no
692 // pauses, returns 1.0.
693 double last_survival_fraction();
694
695 // Returns a "conservative" estimate of the recent survival rate, i.e.,
696 // one that may be higher than "recent_avg_survival_fraction".
697 // This is conservative in several ways:
698 // If there have been few pauses, it will assume a potential high
699 // variance, and err on the side of caution.
700 // It puts a lower bound (currently 0.1) on the value it will return.
701 // To try to detect phase changes, if the most recent pause ("latest") has a
702 // higher-than average ("avg") survival rate, it returns that rate.
703 // "work" version is a utility function; young is restricted to young regions.
704 double conservative_avg_survival_fraction_work(double avg,
705 double latest);
706
707 // The arguments are the two sequences that keep track of the number of bytes
708 // surviving and the total number of bytes before collection, resp.,
709 // over the last evereal recent pauses
710 // Returns the survival rate for the category in the most recent pause.
711 // If there have been no pauses, returns 1.0.
712 double last_survival_fraction_work(TruncatedSeq* surviving,
713 TruncatedSeq* before);
714
715 // The arguments are the two sequences that keep track of the number of bytes
716 // surviving and the total number of bytes before collection, resp.,
717 // over the last several recent pauses
718 // Returns the average survival ration over the last several recent pauses
719 // If there have been no pauses, return 1.0
720 double recent_avg_survival_fraction_work(TruncatedSeq* surviving,
721 TruncatedSeq* before);
722
723 double conservative_avg_survival_fraction() {
724 double avg = recent_avg_survival_fraction();
725 double latest = last_survival_fraction();
726 return conservative_avg_survival_fraction_work(avg, latest);
727 }
728
729 // The ratio of gc time to elapsed time, computed over recent pauses.
730 double _recent_avg_pause_time_ratio;
731
732 double recent_avg_pause_time_ratio() {
733 return _recent_avg_pause_time_ratio;
734 }
735
736 // Number of pauses between concurrent marking.
737 size_t _pauses_btwn_concurrent_mark;
738
739 size_t _n_marks_since_last_pause;
740
741 // At the end of a pause we check the heap occupancy and we decide
742 // whether we will start a marking cycle during the next pause. If
743 // we decide that we want to do that, we will set this parameter to
744 // true. So, this parameter will stay true between the end of a
745 // pause and the beginning of a subsequent pause (not necessarily
746 // the next one, see the comments on the next field) when we decide
747 // that we will indeed start a marking cycle and do the initial-mark
748 // work.
749 volatile bool _initiate_conc_mark_if_possible;
750
751 // If initiate_conc_mark_if_possible() is set at the beginning of a
752 // pause, it is a suggestion that the pause should start a marking
753 // cycle by doing the initial-mark work. However, it is possible
754 // that the concurrent marking thread is still finishing up the
755 // previous marking cycle (e.g., clearing the next marking
756 // bitmap). If that is the case we cannot start a new cycle and
757 // we'll have to wait for the concurrent marking thread to finish
758 // what it is doing. In this case we will postpone the marking cycle
759 // initiation decision for the next pause. When we eventually decide
760 // to start a cycle, we will set _during_initial_mark_pause which
761 // will stay true until the end of the initial-mark pause and it's
762 // the condition that indicates that a pause is doing the
763 // initial-mark work.
764 volatile bool _during_initial_mark_pause;
765
766 bool _should_revert_to_full_young_gcs;
767 bool _last_full_young_gc;
768
769 // This set of variables tracks the collector efficiency, in order to
770 // determine whether we should initiate a new marking.
771 double _cur_mark_stop_world_time_ms;
772 double _mark_remark_start_sec;
773 double _mark_cleanup_start_sec;
774 double _mark_closure_time_ms;
775
776 // Update the young list target length either by setting it to the
777 // desired fixed value or by calculating it using G1's pause
778 // prediction model. If no rs_lengths parameter is passed, predict
779 // the RS lengths using the prediction model, otherwise use the
780 // given rs_lengths as the prediction.
781 void update_young_list_target_length(size_t rs_lengths = (size_t) -1);
782
783 // Calculate and return the minimum desired young list target
784 // length. This is the minimum desired young list length according
785 // to the user's inputs.
786 size_t calculate_young_list_desired_min_length(size_t base_min_length);
787
788 // Calculate and return the maximum desired young list target
789 // length. This is the maximum desired young list length according
790 // to the user's inputs.
791 size_t calculate_young_list_desired_max_length();
792
793 // Calculate and return the maximum young list target length that
794 // can fit into the pause time goal. The parameters are: rs_lengths
795 // represent the prediction of how large the young RSet lengths will
796 // be, base_min_length is the alreay existing number of regions in
797 // the young list, min_length and max_length are the desired min and
798 // max young list length according to the user's inputs.
799 size_t calculate_young_list_target_length(size_t rs_lengths,
800 size_t base_min_length,
801 size_t desired_min_length,
802 size_t desired_max_length);
803
804 // Check whether a given young length (young_length) fits into the
805 // given target pause time and whether the prediction for the amount
806 // of objects to be copied for the given length will fit into the
807 // given free space (expressed by base_free_regions). It is used by
808 // calculate_young_list_target_length().
809 bool predict_will_fit(size_t young_length, double base_time_ms,
810 size_t base_free_regions, double target_pause_time_ms);
811
812 public:
813
814 G1CollectorPolicy();
815
816 virtual G1CollectorPolicy* as_g1_policy() { return this; }
817
818 virtual CollectorPolicy::Name kind() {
819 return CollectorPolicy::G1CollectorPolicyKind;
820 }
821
822 // Check the current value of the young list RSet lengths and
823 // compare it against the last prediction. If the current value is
824 // higher, recalculate the young list target length prediction.
825 void revise_young_list_target_length_if_necessary();
826
827 size_t bytes_in_collection_set() {
828 return _bytes_in_collection_set_before_gc;
829 }
830
831 unsigned calc_gc_alloc_time_stamp() {
832 return _all_pause_times_ms->num() + 1;
833 }
834
835 // This should be called after the heap is resized.
836 void record_new_heap_size(size_t new_number_of_regions);
837
838 protected:
839
840 // Count the number of bytes used in the CS.
841 void count_CS_bytes_used();
842
843 // Together these do the base cleanup-recording work. Subclasses might
844 // want to put something between them.
845 void record_concurrent_mark_cleanup_end_work1(size_t freed_bytes,
846 size_t max_live_bytes);
847 void record_concurrent_mark_cleanup_end_work2();
848
849 void update_young_list_size_using_newratio(size_t number_of_heap_regions);
850
851 public:
852
853 virtual void init();
854
855 // Create jstat counters for the policy.
856 virtual void initialize_gc_policy_counters();
857
858 virtual HeapWord* mem_allocate_work(size_t size,
859 bool is_tlab,
860 bool* gc_overhead_limit_was_exceeded);
861
862 // This method controls how a collector handles one or more
863 // of its generations being fully allocated.
864 virtual HeapWord* satisfy_failed_allocation(size_t size,
865 bool is_tlab);
866
867 BarrierSet::Name barrier_set_name() { return BarrierSet::G1SATBCTLogging; }
868
869 GenRemSet::Name rem_set_name() { return GenRemSet::CardTable; }
870
871 // The number of collection pauses so far.
872 long n_pauses() const { return _n_pauses; }
873
874 // Update the heuristic info to record a collection pause of the given
875 // start time, where the given number of bytes were used at the start.
876 // This may involve changing the desired size of a collection set.
877
878 virtual void record_stop_world_start();
879
880 virtual void record_collection_pause_start(double start_time_sec,
881 size_t start_used);
882
883 // Must currently be called while the world is stopped.
884 void record_concurrent_mark_init_end(double
885 mark_init_elapsed_time_ms);
886
887 void record_mark_closure_time(double mark_closure_time_ms);
888
889 virtual void record_concurrent_mark_remark_start();
890 virtual void record_concurrent_mark_remark_end();
891
892 virtual void record_concurrent_mark_cleanup_start();
893 virtual void record_concurrent_mark_cleanup_end(size_t freed_bytes,
894 size_t max_live_bytes);
895 virtual void record_concurrent_mark_cleanup_completed();
896
897 virtual void record_concurrent_pause();
898 virtual void record_concurrent_pause_end();
899
900 virtual void record_collection_pause_end();
901 void print_heap_transition();
902
903 // Record the fact that a full collection occurred.
904 virtual void record_full_collection_start();
905 virtual void record_full_collection_end();
906
907 void record_gc_worker_start_time(int worker_i, double ms) {
908 _par_last_gc_worker_start_times_ms[worker_i] = ms;
909 }
910
911 void record_ext_root_scan_time(int worker_i, double ms) {
912 _par_last_ext_root_scan_times_ms[worker_i] = ms;
913 }
914
915 void record_mark_stack_scan_time(int worker_i, double ms) {
916 _par_last_mark_stack_scan_times_ms[worker_i] = ms;
917 }
918
919 void record_satb_drain_time(double ms) {
920 _cur_satb_drain_time_ms = ms;
921 _satb_drain_time_set = true;
922 }
923
924 void record_satb_drain_processed_buffers (int processed_buffers) {
925 _last_satb_drain_processed_buffers = processed_buffers;
926 }
927
928 void record_mod_union_time(double ms) {
929 _all_mod_union_times_ms->add(ms);
930 }
931
932 void record_update_rs_time(int thread, double ms) {
933 _par_last_update_rs_times_ms[thread] = ms;
934 }
935
936 void record_update_rs_processed_buffers (int thread,
937 double processed_buffers) {
938 _par_last_update_rs_processed_buffers[thread] = processed_buffers;
939 }
940
941 void record_scan_rs_time(int thread, double ms) {
942 _par_last_scan_rs_times_ms[thread] = ms;
943 }
944
945 void reset_obj_copy_time(int thread) {
946 _par_last_obj_copy_times_ms[thread] = 0.0;
947 }
948
949 void reset_obj_copy_time() {
950 reset_obj_copy_time(0);
951 }
952
953 void record_obj_copy_time(int thread, double ms) {
954 _par_last_obj_copy_times_ms[thread] += ms;
955 }
956
957 void record_termination(int thread, double ms, size_t attempts) {
958 _par_last_termination_times_ms[thread] = ms;
959 _par_last_termination_attempts[thread] = (double) attempts;
960 }
961
962 void record_gc_worker_end_time(int worker_i, double ms) {
963 _par_last_gc_worker_end_times_ms[worker_i] = ms;
964 }
965
966 void record_pause_time_ms(double ms) {
967 _last_pause_time_ms = ms;
968 }
969
970 void record_clear_ct_time(double ms) {
971 _cur_clear_ct_time_ms = ms;
972 }
973
974 void record_par_time(double ms) {
975 _cur_collection_par_time_ms = ms;
976 }
977
978 void record_aux_start_time(int i) {
979 guarantee(i < _aux_num, "should be within range");
980 _cur_aux_start_times_ms[i] = os::elapsedTime() * 1000.0;
981 }
982
983 void record_aux_end_time(int i) {
984 guarantee(i < _aux_num, "should be within range");
985 double ms = os::elapsedTime() * 1000.0 - _cur_aux_start_times_ms[i];
986 _cur_aux_times_set[i] = true;
987 _cur_aux_times_ms[i] += ms;
988 }
989
990 #ifndef PRODUCT
991 void record_cc_clear_time(double ms) {
992 if (_min_clear_cc_time_ms < 0.0 || ms <= _min_clear_cc_time_ms)
993 _min_clear_cc_time_ms = ms;
994 if (_max_clear_cc_time_ms < 0.0 || ms >= _max_clear_cc_time_ms)
995 _max_clear_cc_time_ms = ms;
996 _cur_clear_cc_time_ms = ms;
997 _cum_clear_cc_time_ms += ms;
998 _num_cc_clears++;
999 }
1000 #endif
1001
1002 // Record how much space we copied during a GC. This is typically
1003 // called when a GC alloc region is being retired.
1004 void record_bytes_copied_during_gc(size_t bytes) {
1005 _bytes_copied_during_gc += bytes;
1006 }
1007
1008 // The amount of space we copied during a GC.
1009 size_t bytes_copied_during_gc() {
1010 return _bytes_copied_during_gc;
1011 }
1012
1013 // Choose a new collection set. Marks the chosen regions as being
1014 // "in_collection_set", and links them together. The head and number of
1015 // the collection set are available via access methods.
1016 virtual void choose_collection_set(double target_pause_time_ms) = 0;
1017
1018 // The head of the list (via "next_in_collection_set()") representing the
1019 // current collection set.
1020 HeapRegion* collection_set() { return _collection_set; }
1021
1022 void clear_collection_set() { _collection_set = NULL; }
1023
1024 // The number of elements in the current collection set.
1025 size_t collection_set_size() { return _collection_set_size; }
1026
1027 // Add "hr" to the CS.
1028 void add_to_collection_set(HeapRegion* hr);
1029
1030 // Incremental CSet Support
1031
1032 // The head of the incrementally built collection set.
1033 HeapRegion* inc_cset_head() { return _inc_cset_head; }
1034
1035 // The tail of the incrementally built collection set.
1036 HeapRegion* inc_set_tail() { return _inc_cset_tail; }
1037
1038 // The number of elements in the incrementally built collection set.
1039 size_t inc_cset_size() { return _inc_cset_size; }
1040
1041 // Initialize incremental collection set info.
1042 void start_incremental_cset_building();
1043
1044 void clear_incremental_cset() {
1045 _inc_cset_head = NULL;
1046 _inc_cset_tail = NULL;
1047 }
1048
1049 // Stop adding regions to the incremental collection set
1050 void stop_incremental_cset_building() { _inc_cset_build_state = Inactive; }
1051
1052 // Add/remove information about hr to the aggregated information
1053 // for the incrementally built collection set.
1054 void add_to_incremental_cset_info(HeapRegion* hr, size_t rs_length);
1055 void remove_from_incremental_cset_info(HeapRegion* hr);
1056
1057 // Update information about hr in the aggregated information for
1058 // the incrementally built collection set.
1059 void update_incremental_cset_info(HeapRegion* hr, size_t new_rs_length);
1060
1061 private:
1062 // Update the incremental cset information when adding a region
1063 // (should not be called directly).
1064 void add_region_to_incremental_cset_common(HeapRegion* hr);
1065
1066 public:
1067 // Add hr to the LHS of the incremental collection set.
1068 void add_region_to_incremental_cset_lhs(HeapRegion* hr);
1069
1070 // Add hr to the RHS of the incremental collection set.
1071 void add_region_to_incremental_cset_rhs(HeapRegion* hr);
1072
1073 #ifndef PRODUCT
1074 void print_collection_set(HeapRegion* list_head, outputStream* st);
1075 #endif // !PRODUCT
1076
1077 bool initiate_conc_mark_if_possible() { return _initiate_conc_mark_if_possible; }
1078 void set_initiate_conc_mark_if_possible() { _initiate_conc_mark_if_possible = true; }
1079 void clear_initiate_conc_mark_if_possible() { _initiate_conc_mark_if_possible = false; }
1080
1081 bool during_initial_mark_pause() { return _during_initial_mark_pause; }
1082 void set_during_initial_mark_pause() { _during_initial_mark_pause = true; }
1083 void clear_during_initial_mark_pause(){ _during_initial_mark_pause = false; }
1084
1085 // This sets the initiate_conc_mark_if_possible() flag to start a
1086 // new cycle, as long as we are not already in one. It's best if it
1087 // is called during a safepoint when the test whether a cycle is in
1088 // progress or not is stable.
1089 bool force_initial_mark_if_outside_cycle();
1090
1091 // This is called at the very beginning of an evacuation pause (it
1092 // has to be the first thing that the pause does). If
1093 // initiate_conc_mark_if_possible() is true, and the concurrent
1094 // marking thread has completed its work during the previous cycle,
1095 // it will set during_initial_mark_pause() to so that the pause does
1096 // the initial-mark work and start a marking cycle.
1097 void decide_on_conc_mark_initiation();
1098
1099 // If an expansion would be appropriate, because recent GC overhead had
1100 // exceeded the desired limit, return an amount to expand by.
1101 virtual size_t expansion_amount();
1102
1103 // note start of mark thread
1104 void note_start_of_mark_thread();
1105
1106 // The marked bytes of the "r" has changed; reclassify it's desirability
1107 // for marking. Also asserts that "r" is eligible for a CS.
1108 virtual void note_change_in_marked_bytes(HeapRegion* r) = 0;
1109
1110 #ifndef PRODUCT
1111 // Check any appropriate marked bytes info, asserting false if
1112 // something's wrong, else returning "true".
1113 virtual bool assertMarkedBytesDataOK() = 0;
1114 #endif
1115
1116 // Print tracing information.
1117 void print_tracing_info() const;
1118
1119 // Print stats on young survival ratio
1120 void print_yg_surv_rate_info() const;
1121
1122 void finished_recalculating_age_indexes(bool is_survivors) {
1123 if (is_survivors) {
1124 _survivor_surv_rate_group->finished_recalculating_age_indexes();
1125 } else {
1126 _short_lived_surv_rate_group->finished_recalculating_age_indexes();
1127 }
1128 // do that for any other surv rate groups
1129 }
1130
1131 bool is_young_list_full() {
1132 size_t young_list_length = _g1->young_list()->length();
1133 size_t young_list_target_length = _young_list_target_length;
1134 return young_list_length >= young_list_target_length;
1135 }
1136
1137 bool can_expand_young_list() {
1138 size_t young_list_length = _g1->young_list()->length();
1139 size_t young_list_max_length = _young_list_max_length;
1140 return young_list_length < young_list_max_length;
1141 }
1142
1143 void update_region_num(bool young);
1144
1145 bool full_young_gcs() {
1146 return _full_young_gcs;
1147 }
1148 void set_full_young_gcs(bool full_young_gcs) {
1149 _full_young_gcs = full_young_gcs;
1150 }
1151
1152 bool adaptive_young_list_length() {
1153 return _adaptive_young_list_length;
1154 }
1155 void set_adaptive_young_list_length(bool adaptive_young_list_length) {
1156 _adaptive_young_list_length = adaptive_young_list_length;
1157 }
1158
1159 inline double get_gc_eff_factor() {
1160 double ratio = _known_garbage_ratio;
1161
1162 double square = ratio * ratio;
1163 // square = square * square;
1164 double ret = square * 9.0 + 1.0;
1165 #if 0
1166 gclog_or_tty->print_cr("ratio = %1.2lf, ret = %1.2lf", ratio, ret);
1167 #endif // 0
1168 guarantee(0.0 <= ret && ret < 10.0, "invariant!");
1169 return ret;
1170 }
1171
1172 //
1173 // Survivor regions policy.
1174 //
1175 protected:
1176
1177 // Current tenuring threshold, set to 0 if the collector reaches the
1178 // maximum amount of suvivors regions.
1179 int _tenuring_threshold;
1180
1181 // The limit on the number of regions allocated for survivors.
1182 size_t _max_survivor_regions;
1183
1184 // For reporting purposes.
1185 size_t _eden_bytes_before_gc;
1186 size_t _survivor_bytes_before_gc;
1187 size_t _capacity_before_gc;
1188
1189 // The amount of survor regions after a collection.
1190 size_t _recorded_survivor_regions;
1191 // List of survivor regions.
1192 HeapRegion* _recorded_survivor_head;
1193 HeapRegion* _recorded_survivor_tail;
1194
1195 ageTable _survivors_age_table;
1196
1197 public:
1198
1199 inline GCAllocPurpose
1200 evacuation_destination(HeapRegion* src_region, int age, size_t word_sz) {
1201 if (age < _tenuring_threshold && src_region->is_young()) {
1202 return GCAllocForSurvived;
1203 } else {
1204 return GCAllocForTenured;
1205 }
1206 }
1207
1208 inline bool track_object_age(GCAllocPurpose purpose) {
1209 return purpose == GCAllocForSurvived;
1210 }
1211
1212 static const size_t REGIONS_UNLIMITED = ~(size_t)0;
1213
1214 size_t max_regions(int purpose);
1215
1216 // The limit on regions for a particular purpose is reached.
1217 void note_alloc_region_limit_reached(int purpose) {
1218 if (purpose == GCAllocForSurvived) {
1219 _tenuring_threshold = 0;
1220 }
1221 }
1222
1223 void note_start_adding_survivor_regions() {
1224 _survivor_surv_rate_group->start_adding_regions();
1225 }
1226
1227 void note_stop_adding_survivor_regions() {
1228 _survivor_surv_rate_group->stop_adding_regions();
1229 }
1230
1231 void record_survivor_regions(size_t regions,
1232 HeapRegion* head,
1233 HeapRegion* tail) {
1234 _recorded_survivor_regions = regions;
1235 _recorded_survivor_head = head;
1236 _recorded_survivor_tail = tail;
1237 }
1238
1239 size_t recorded_survivor_regions() {
1240 return _recorded_survivor_regions;
1241 }
1242
1243 void record_thread_age_table(ageTable* age_table)
1244 {
1245 _survivors_age_table.merge_par(age_table);
1246 }
1247
1248 void update_max_gc_locker_expansion();
1249
1250 // Calculates survivor space parameters.
1251 void update_survivors_policy();
1252
1253 };
1254
1255 // This encapsulates a particular strategy for a g1 Collector.
1256 //
1257 // Start a concurrent mark when our heap size is n bytes
1258 // greater then our heap size was at the last concurrent
1259 // mark. Where n is a function of the CMSTriggerRatio
1260 // and the MinHeapFreeRatio.
1261 //
1262 // Start a g1 collection pause when we have allocated the
1263 // average number of bytes currently being freed in
1264 // a collection, but only if it is at least one region
1265 // full
1266 //
1267 // Resize Heap based on desired
1268 // allocation space, where desired allocation space is
1269 // a function of survival rate and desired future to size.
1270 //
1271 // Choose collection set by first picking all older regions
1272 // which have a survival rate which beats our projected young
1273 // survival rate. Then fill out the number of needed regions
1274 // with young regions.
1275
1276 class G1CollectorPolicy_BestRegionsFirst: public G1CollectorPolicy {
1277 CollectionSetChooser* _collectionSetChooser;
1278 // If the estimated is less then desirable, resize if possible.
1279 void expand_if_possible(size_t numRegions);
1280
1281 virtual void choose_collection_set(double target_pause_time_ms);
1282 virtual void record_collection_pause_start(double start_time_sec,
1283 size_t start_used);
1284 virtual void record_concurrent_mark_cleanup_end(size_t freed_bytes,
1285 size_t max_live_bytes);
1286 virtual void record_full_collection_end();
1287
1288 public:
1289 G1CollectorPolicy_BestRegionsFirst() {
1290 _collectionSetChooser = new CollectionSetChooser();
1291 }
1292 void record_collection_pause_end();
1293 // This is not needed any more, after the CSet choosing code was
1294 // changed to use the pause prediction work. But let's leave the
1295 // hook in just in case.
1296 void note_change_in_marked_bytes(HeapRegion* r) { }
1297 #ifndef PRODUCT
1298 bool assertMarkedBytesDataOK();
1299 #endif
1300 };
1301
1302 // This should move to some place more general...
1303
1304 // If we have "n" measurements, and we've kept track of their "sum" and the
1305 // "sum_of_squares" of the measurements, this returns the variance of the
1306 // sequence.
1307 inline double variance(int n, double sum_of_squares, double sum) {
1308 double n_d = (double)n;
1309 double avg = sum/n_d;
1310 return (sum_of_squares - 2.0 * avg * sum + n_d * avg * avg) / n_d;
1311 }
1312
1313 // Local Variables: ***
1314 // c-indentation-style: gnu ***
1315 // End: ***
1316
1317 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP