Thu, 30 Jul 2009 16:22:58 -0400
6819085: G1: use larger and/or user settable region size
Summary: Instead of the region size being hard-coded, allow the user to set it.
Reviewed-by: jmasa, johnc, apetrusenko
1 /*
2 * Copyright 2001-2009 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
25 // A G1CollectorPolicy makes policy decisions that determine the
26 // characteristics of the collector. Examples include:
27 // * choice of collection set.
28 // * when to collect.
30 class HeapRegion;
31 class CollectionSetChooser;
33 // Yes, this is a bit unpleasant... but it saves replicating the same thing
34 // over and over again and introducing subtle problems through small typos and
35 // cutting and pasting mistakes. The macros below introduces a number
36 // sequnce into the following two classes and the methods that access it.
38 #define define_num_seq(name) \
39 private: \
40 NumberSeq _all_##name##_times_ms; \
41 public: \
42 void record_##name##_time_ms(double ms) { \
43 _all_##name##_times_ms.add(ms); \
44 } \
45 NumberSeq* get_##name##_seq() { \
46 return &_all_##name##_times_ms; \
47 }
49 class MainBodySummary;
51 class PauseSummary: public CHeapObj {
52 define_num_seq(total)
53 define_num_seq(other)
55 public:
56 virtual MainBodySummary* main_body_summary() { return NULL; }
57 };
59 class MainBodySummary: public CHeapObj {
60 define_num_seq(satb_drain) // optional
61 define_num_seq(parallel) // parallel only
62 define_num_seq(ext_root_scan)
63 define_num_seq(mark_stack_scan)
64 define_num_seq(scan_only)
65 define_num_seq(update_rs)
66 define_num_seq(scan_rs)
67 define_num_seq(scan_new_refs) // Only for temp use; added to
68 // in parallel case.
69 define_num_seq(obj_copy)
70 define_num_seq(termination) // parallel only
71 define_num_seq(parallel_other) // parallel only
72 define_num_seq(mark_closure)
73 define_num_seq(clear_ct) // parallel only
74 };
76 class Summary: public PauseSummary,
77 public MainBodySummary {
78 public:
79 virtual MainBodySummary* main_body_summary() { return this; }
80 };
82 class AbandonedSummary: public PauseSummary {
83 };
85 class G1CollectorPolicy: public CollectorPolicy {
86 protected:
87 // The number of pauses during the execution.
88 long _n_pauses;
90 // either equal to the number of parallel threads, if ParallelGCThreads
91 // has been set, or 1 otherwise
92 int _parallel_gc_threads;
94 enum SomePrivateConstants {
95 NumPrevPausesForHeuristics = 10
96 };
98 G1MMUTracker* _mmu_tracker;
100 void initialize_flags();
102 void initialize_all() {
103 initialize_flags();
104 initialize_size_info();
105 initialize_perm_generation(PermGen::MarkSweepCompact);
106 }
108 virtual size_t default_init_heap_size() {
109 // Pick some reasonable default.
110 return 8*M;
111 }
113 double _cur_collection_start_sec;
114 size_t _cur_collection_pause_used_at_start_bytes;
115 size_t _cur_collection_pause_used_regions_at_start;
116 size_t _prev_collection_pause_used_at_end_bytes;
117 double _cur_collection_par_time_ms;
118 double _cur_satb_drain_time_ms;
119 double _cur_clear_ct_time_ms;
120 bool _satb_drain_time_set;
122 #ifndef PRODUCT
123 // Card Table Count Cache stats
124 double _min_clear_cc_time_ms; // min
125 double _max_clear_cc_time_ms; // max
126 double _cur_clear_cc_time_ms; // clearing time during current pause
127 double _cum_clear_cc_time_ms; // cummulative clearing time
128 jlong _num_cc_clears; // number of times the card count cache has been cleared
129 #endif
131 double _cur_CH_strong_roots_end_sec;
132 double _cur_CH_strong_roots_dur_ms;
133 double _cur_G1_strong_roots_end_sec;
134 double _cur_G1_strong_roots_dur_ms;
136 // Statistics for recent GC pauses. See below for how indexed.
137 TruncatedSeq* _recent_CH_strong_roots_times_ms;
138 TruncatedSeq* _recent_G1_strong_roots_times_ms;
139 TruncatedSeq* _recent_evac_times_ms;
140 // These exclude marking times.
141 TruncatedSeq* _recent_pause_times_ms;
142 TruncatedSeq* _recent_gc_times_ms;
144 TruncatedSeq* _recent_CS_bytes_used_before;
145 TruncatedSeq* _recent_CS_bytes_surviving;
147 TruncatedSeq* _recent_rs_sizes;
149 TruncatedSeq* _concurrent_mark_init_times_ms;
150 TruncatedSeq* _concurrent_mark_remark_times_ms;
151 TruncatedSeq* _concurrent_mark_cleanup_times_ms;
153 Summary* _summary;
154 AbandonedSummary* _abandoned_summary;
156 NumberSeq* _all_pause_times_ms;
157 NumberSeq* _all_full_gc_times_ms;
158 double _stop_world_start;
159 NumberSeq* _all_stop_world_times_ms;
160 NumberSeq* _all_yield_times_ms;
162 size_t _region_num_young;
163 size_t _region_num_tenured;
164 size_t _prev_region_num_young;
165 size_t _prev_region_num_tenured;
167 NumberSeq* _all_mod_union_times_ms;
169 int _aux_num;
170 NumberSeq* _all_aux_times_ms;
171 double* _cur_aux_start_times_ms;
172 double* _cur_aux_times_ms;
173 bool* _cur_aux_times_set;
175 double* _par_last_ext_root_scan_times_ms;
176 double* _par_last_mark_stack_scan_times_ms;
177 double* _par_last_scan_only_times_ms;
178 double* _par_last_scan_only_regions_scanned;
179 double* _par_last_update_rs_start_times_ms;
180 double* _par_last_update_rs_times_ms;
181 double* _par_last_update_rs_processed_buffers;
182 double* _par_last_scan_rs_start_times_ms;
183 double* _par_last_scan_rs_times_ms;
184 double* _par_last_scan_new_refs_times_ms;
185 double* _par_last_obj_copy_times_ms;
186 double* _par_last_termination_times_ms;
188 // indicates that we are in young GC mode
189 bool _in_young_gc_mode;
191 // indicates whether we are in full young or partially young GC mode
192 bool _full_young_gcs;
194 // if true, then it tries to dynamically adjust the length of the
195 // young list
196 bool _adaptive_young_list_length;
197 size_t _young_list_min_length;
198 size_t _young_list_target_length;
199 size_t _young_list_so_prefix_length;
200 size_t _young_list_fixed_length;
202 size_t _young_cset_length;
203 bool _last_young_gc_full;
205 double _target_pause_time_ms;
207 unsigned _full_young_pause_num;
208 unsigned _partial_young_pause_num;
210 bool _during_marking;
211 bool _in_marking_window;
212 bool _in_marking_window_im;
214 SurvRateGroup* _short_lived_surv_rate_group;
215 SurvRateGroup* _survivor_surv_rate_group;
216 // add here any more surv rate groups
218 bool during_marking() {
219 return _during_marking;
220 }
222 // <NEW PREDICTION>
224 private:
225 enum PredictionConstants {
226 TruncatedSeqLength = 10
227 };
229 TruncatedSeq* _alloc_rate_ms_seq;
230 double _prev_collection_pause_end_ms;
232 TruncatedSeq* _pending_card_diff_seq;
233 TruncatedSeq* _rs_length_diff_seq;
234 TruncatedSeq* _cost_per_card_ms_seq;
235 TruncatedSeq* _cost_per_scan_only_region_ms_seq;
236 TruncatedSeq* _fully_young_cards_per_entry_ratio_seq;
237 TruncatedSeq* _partially_young_cards_per_entry_ratio_seq;
238 TruncatedSeq* _cost_per_entry_ms_seq;
239 TruncatedSeq* _partially_young_cost_per_entry_ms_seq;
240 TruncatedSeq* _cost_per_byte_ms_seq;
241 TruncatedSeq* _constant_other_time_ms_seq;
242 TruncatedSeq* _young_other_cost_per_region_ms_seq;
243 TruncatedSeq* _non_young_other_cost_per_region_ms_seq;
245 TruncatedSeq* _pending_cards_seq;
246 TruncatedSeq* _scanned_cards_seq;
247 TruncatedSeq* _rs_lengths_seq;
249 TruncatedSeq* _cost_per_byte_ms_during_cm_seq;
250 TruncatedSeq* _cost_per_scan_only_region_ms_during_cm_seq;
252 TruncatedSeq* _young_gc_eff_seq;
254 TruncatedSeq* _max_conc_overhead_seq;
256 size_t _recorded_young_regions;
257 size_t _recorded_scan_only_regions;
258 size_t _recorded_non_young_regions;
259 size_t _recorded_region_num;
261 size_t _free_regions_at_end_of_collection;
262 size_t _scan_only_regions_at_end_of_collection;
264 size_t _recorded_rs_lengths;
265 size_t _max_rs_lengths;
267 size_t _recorded_marked_bytes;
268 size_t _recorded_young_bytes;
270 size_t _predicted_pending_cards;
271 size_t _predicted_cards_scanned;
272 size_t _predicted_rs_lengths;
273 size_t _predicted_bytes_to_copy;
275 double _predicted_survival_ratio;
276 double _predicted_rs_update_time_ms;
277 double _predicted_rs_scan_time_ms;
278 double _predicted_scan_only_scan_time_ms;
279 double _predicted_object_copy_time_ms;
280 double _predicted_constant_other_time_ms;
281 double _predicted_young_other_time_ms;
282 double _predicted_non_young_other_time_ms;
283 double _predicted_pause_time_ms;
285 double _vtime_diff_ms;
287 double _recorded_young_free_cset_time_ms;
288 double _recorded_non_young_free_cset_time_ms;
290 double _sigma;
291 double _expensive_region_limit_ms;
293 size_t _rs_lengths_prediction;
295 size_t _known_garbage_bytes;
296 double _known_garbage_ratio;
298 double sigma() {
299 return _sigma;
300 }
302 // A function that prevents us putting too much stock in small sample
303 // sets. Returns a number between 2.0 and 1.0, depending on the number
304 // of samples. 5 or more samples yields one; fewer scales linearly from
305 // 2.0 at 1 sample to 1.0 at 5.
306 double confidence_factor(int samples) {
307 if (samples > 4) return 1.0;
308 else return 1.0 + sigma() * ((double)(5 - samples))/2.0;
309 }
311 double get_new_neg_prediction(TruncatedSeq* seq) {
312 return seq->davg() - sigma() * seq->dsd();
313 }
315 #ifndef PRODUCT
316 bool verify_young_ages(HeapRegion* head, SurvRateGroup *surv_rate_group);
317 #endif // PRODUCT
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;
327 public:
329 void set_region_short_lived(HeapRegion* hr) {
330 hr->install_surv_rate_group(_short_lived_surv_rate_group);
331 }
333 void set_region_survivors(HeapRegion* hr) {
334 hr->install_surv_rate_group(_survivor_surv_rate_group);
335 }
337 #ifndef PRODUCT
338 bool verify_young_ages();
339 #endif // PRODUCT
341 void tag_scan_only(size_t short_lived_scan_only_length);
343 double get_new_prediction(TruncatedSeq* seq) {
344 return MAX2(seq->davg() + sigma() * seq->dsd(),
345 seq->davg() * confidence_factor(seq->num()));
346 }
348 size_t young_cset_length() {
349 return _young_cset_length;
350 }
352 void record_max_rs_lengths(size_t rs_lengths) {
353 _max_rs_lengths = rs_lengths;
354 }
356 size_t predict_pending_card_diff() {
357 double prediction = get_new_neg_prediction(_pending_card_diff_seq);
358 if (prediction < 0.00001)
359 return 0;
360 else
361 return (size_t) prediction;
362 }
364 size_t predict_pending_cards() {
365 size_t max_pending_card_num = _g1->max_pending_card_num();
366 size_t diff = predict_pending_card_diff();
367 size_t prediction;
368 if (diff > max_pending_card_num)
369 prediction = max_pending_card_num;
370 else
371 prediction = max_pending_card_num - diff;
373 return prediction;
374 }
376 size_t predict_rs_length_diff() {
377 return (size_t) get_new_prediction(_rs_length_diff_seq);
378 }
380 double predict_alloc_rate_ms() {
381 return get_new_prediction(_alloc_rate_ms_seq);
382 }
384 double predict_cost_per_card_ms() {
385 return get_new_prediction(_cost_per_card_ms_seq);
386 }
388 double predict_rs_update_time_ms(size_t pending_cards) {
389 return (double) pending_cards * predict_cost_per_card_ms();
390 }
392 double predict_fully_young_cards_per_entry_ratio() {
393 return get_new_prediction(_fully_young_cards_per_entry_ratio_seq);
394 }
396 double predict_partially_young_cards_per_entry_ratio() {
397 if (_partially_young_cards_per_entry_ratio_seq->num() < 2)
398 return predict_fully_young_cards_per_entry_ratio();
399 else
400 return get_new_prediction(_partially_young_cards_per_entry_ratio_seq);
401 }
403 size_t predict_young_card_num(size_t rs_length) {
404 return (size_t) ((double) rs_length *
405 predict_fully_young_cards_per_entry_ratio());
406 }
408 size_t predict_non_young_card_num(size_t rs_length) {
409 return (size_t) ((double) rs_length *
410 predict_partially_young_cards_per_entry_ratio());
411 }
413 double predict_rs_scan_time_ms(size_t card_num) {
414 if (full_young_gcs())
415 return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq);
416 else
417 return predict_partially_young_rs_scan_time_ms(card_num);
418 }
420 double predict_partially_young_rs_scan_time_ms(size_t card_num) {
421 if (_partially_young_cost_per_entry_ms_seq->num() < 3)
422 return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq);
423 else
424 return (double) card_num *
425 get_new_prediction(_partially_young_cost_per_entry_ms_seq);
426 }
428 double predict_scan_only_time_ms_during_cm(size_t scan_only_region_num) {
429 if (_cost_per_scan_only_region_ms_during_cm_seq->num() < 3)
430 return 1.5 * (double) scan_only_region_num *
431 get_new_prediction(_cost_per_scan_only_region_ms_seq);
432 else
433 return (double) scan_only_region_num *
434 get_new_prediction(_cost_per_scan_only_region_ms_during_cm_seq);
435 }
437 double predict_scan_only_time_ms(size_t scan_only_region_num) {
438 if (_in_marking_window_im)
439 return predict_scan_only_time_ms_during_cm(scan_only_region_num);
440 else
441 return (double) scan_only_region_num *
442 get_new_prediction(_cost_per_scan_only_region_ms_seq);
443 }
445 double predict_object_copy_time_ms_during_cm(size_t bytes_to_copy) {
446 if (_cost_per_byte_ms_during_cm_seq->num() < 3)
447 return 1.1 * (double) bytes_to_copy *
448 get_new_prediction(_cost_per_byte_ms_seq);
449 else
450 return (double) bytes_to_copy *
451 get_new_prediction(_cost_per_byte_ms_during_cm_seq);
452 }
454 double predict_object_copy_time_ms(size_t bytes_to_copy) {
455 if (_in_marking_window && !_in_marking_window_im)
456 return predict_object_copy_time_ms_during_cm(bytes_to_copy);
457 else
458 return (double) bytes_to_copy *
459 get_new_prediction(_cost_per_byte_ms_seq);
460 }
462 double predict_constant_other_time_ms() {
463 return get_new_prediction(_constant_other_time_ms_seq);
464 }
466 double predict_young_other_time_ms(size_t young_num) {
467 return
468 (double) young_num *
469 get_new_prediction(_young_other_cost_per_region_ms_seq);
470 }
472 double predict_non_young_other_time_ms(size_t non_young_num) {
473 return
474 (double) non_young_num *
475 get_new_prediction(_non_young_other_cost_per_region_ms_seq);
476 }
478 void check_if_region_is_too_expensive(double predicted_time_ms);
480 double predict_young_collection_elapsed_time_ms(size_t adjustment);
481 double predict_base_elapsed_time_ms(size_t pending_cards);
482 double predict_base_elapsed_time_ms(size_t pending_cards,
483 size_t scanned_cards);
484 size_t predict_bytes_to_copy(HeapRegion* hr);
485 double predict_region_elapsed_time_ms(HeapRegion* hr, bool young);
487 // for use by: calculate_optimal_so_length(length)
488 void predict_gc_eff(size_t young_region_num,
489 size_t so_length,
490 double base_time_ms,
491 double *gc_eff,
492 double *pause_time_ms);
494 // for use by: calculate_young_list_target_config(rs_length)
495 bool predict_gc_eff(size_t young_region_num,
496 size_t so_length,
497 double base_time_with_so_ms,
498 size_t init_free_regions,
499 double target_pause_time_ms,
500 double* gc_eff);
502 void start_recording_regions();
503 void record_cset_region(HeapRegion* hr, bool young);
504 void record_scan_only_regions(size_t scan_only_length);
505 void end_recording_regions();
507 void record_vtime_diff_ms(double vtime_diff_ms) {
508 _vtime_diff_ms = vtime_diff_ms;
509 }
511 void record_young_free_cset_time_ms(double time_ms) {
512 _recorded_young_free_cset_time_ms = time_ms;
513 }
515 void record_non_young_free_cset_time_ms(double time_ms) {
516 _recorded_non_young_free_cset_time_ms = time_ms;
517 }
519 double predict_young_gc_eff() {
520 return get_new_neg_prediction(_young_gc_eff_seq);
521 }
523 double predict_survivor_regions_evac_time();
525 // </NEW PREDICTION>
527 public:
528 void cset_regions_freed() {
529 bool propagate = _last_young_gc_full && !_in_marking_window;
530 _short_lived_surv_rate_group->all_surviving_words_recorded(propagate);
531 _survivor_surv_rate_group->all_surviving_words_recorded(propagate);
532 // also call it on any more surv rate groups
533 }
535 void set_known_garbage_bytes(size_t known_garbage_bytes) {
536 _known_garbage_bytes = known_garbage_bytes;
537 size_t heap_bytes = _g1->capacity();
538 _known_garbage_ratio = (double) _known_garbage_bytes / (double) heap_bytes;
539 }
541 void decrease_known_garbage_bytes(size_t known_garbage_bytes) {
542 guarantee( _known_garbage_bytes >= known_garbage_bytes, "invariant" );
544 _known_garbage_bytes -= known_garbage_bytes;
545 size_t heap_bytes = _g1->capacity();
546 _known_garbage_ratio = (double) _known_garbage_bytes / (double) heap_bytes;
547 }
549 G1MMUTracker* mmu_tracker() {
550 return _mmu_tracker;
551 }
553 double predict_init_time_ms() {
554 return get_new_prediction(_concurrent_mark_init_times_ms);
555 }
557 double predict_remark_time_ms() {
558 return get_new_prediction(_concurrent_mark_remark_times_ms);
559 }
561 double predict_cleanup_time_ms() {
562 return get_new_prediction(_concurrent_mark_cleanup_times_ms);
563 }
565 // Returns an estimate of the survival rate of the region at yg-age
566 // "yg_age".
567 double predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) {
568 TruncatedSeq* seq = surv_rate_group->get_seq(age);
569 if (seq->num() == 0)
570 gclog_or_tty->print("BARF! age is %d", age);
571 guarantee( seq->num() > 0, "invariant" );
572 double pred = get_new_prediction(seq);
573 if (pred > 1.0)
574 pred = 1.0;
575 return pred;
576 }
578 double predict_yg_surv_rate(int age) {
579 return predict_yg_surv_rate(age, _short_lived_surv_rate_group);
580 }
582 double accum_yg_surv_rate_pred(int age) {
583 return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
584 }
586 protected:
587 void print_stats (int level, const char* str, double value);
588 void print_stats (int level, const char* str, int value);
589 void print_par_stats (int level, const char* str, double* data) {
590 print_par_stats(level, str, data, true);
591 }
592 void print_par_stats (int level, const char* str, double* data, bool summary);
593 void print_par_buffers (int level, const char* str, double* data, bool summary);
595 void check_other_times(int level,
596 NumberSeq* other_times_ms,
597 NumberSeq* calc_other_times_ms) const;
599 void print_summary (PauseSummary* stats) const;
600 void print_abandoned_summary(PauseSummary* summary) const;
602 void print_summary (int level, const char* str, NumberSeq* seq) const;
603 void print_summary_sd (int level, const char* str, NumberSeq* seq) const;
605 double avg_value (double* data);
606 double max_value (double* data);
607 double sum_of_values (double* data);
608 double max_sum (double* data1, double* data2);
610 int _last_satb_drain_processed_buffers;
611 int _last_update_rs_processed_buffers;
612 double _last_pause_time_ms;
614 size_t _bytes_in_to_space_before_gc;
615 size_t _bytes_in_to_space_after_gc;
616 size_t bytes_in_to_space_during_gc() {
617 return
618 _bytes_in_to_space_after_gc - _bytes_in_to_space_before_gc;
619 }
620 size_t _bytes_in_collection_set_before_gc;
621 // Used to count used bytes in CS.
622 friend class CountCSClosure;
624 // Statistics kept per GC stoppage, pause or full.
625 TruncatedSeq* _recent_prev_end_times_for_all_gcs_sec;
627 // We track markings.
628 int _num_markings;
629 double _mark_thread_startup_sec; // Time at startup of marking thread
631 // Add a new GC of the given duration and end time to the record.
632 void update_recent_gc_times(double end_time_sec, double elapsed_ms);
634 // The head of the list (via "next_in_collection_set()") representing the
635 // current collection set.
636 HeapRegion* _collection_set;
637 size_t _collection_set_size;
638 size_t _collection_set_bytes_used_before;
640 // Info about marking.
641 int _n_marks; // Sticky at 2, so we know when we've done at least 2.
643 // The number of collection pauses at the end of the last mark.
644 size_t _n_pauses_at_mark_end;
646 // Stash a pointer to the g1 heap.
647 G1CollectedHeap* _g1;
649 // The average time in ms per collection pause, averaged over recent pauses.
650 double recent_avg_time_for_pauses_ms();
652 // The average time in ms for processing CollectedHeap strong roots, per
653 // collection pause, averaged over recent pauses.
654 double recent_avg_time_for_CH_strong_ms();
656 // The average time in ms for processing the G1 remembered set, per
657 // pause, averaged over recent pauses.
658 double recent_avg_time_for_G1_strong_ms();
660 // The average time in ms for "evacuating followers", per pause, averaged
661 // over recent pauses.
662 double recent_avg_time_for_evac_ms();
664 // The number of "recent" GCs recorded in the number sequences
665 int number_of_recent_gcs();
667 // The average survival ratio, computed by the total number of bytes
668 // suriviving / total number of bytes before collection over the last
669 // several recent pauses.
670 double recent_avg_survival_fraction();
671 // The survival fraction of the most recent pause; if there have been no
672 // pauses, returns 1.0.
673 double last_survival_fraction();
675 // Returns a "conservative" estimate of the recent survival rate, i.e.,
676 // one that may be higher than "recent_avg_survival_fraction".
677 // This is conservative in several ways:
678 // If there have been few pauses, it will assume a potential high
679 // variance, and err on the side of caution.
680 // It puts a lower bound (currently 0.1) on the value it will return.
681 // To try to detect phase changes, if the most recent pause ("latest") has a
682 // higher-than average ("avg") survival rate, it returns that rate.
683 // "work" version is a utility function; young is restricted to young regions.
684 double conservative_avg_survival_fraction_work(double avg,
685 double latest);
687 // The arguments are the two sequences that keep track of the number of bytes
688 // surviving and the total number of bytes before collection, resp.,
689 // over the last evereal recent pauses
690 // Returns the survival rate for the category in the most recent pause.
691 // If there have been no pauses, returns 1.0.
692 double last_survival_fraction_work(TruncatedSeq* surviving,
693 TruncatedSeq* before);
695 // The arguments are the two sequences that keep track of the number of bytes
696 // surviving and the total number of bytes before collection, resp.,
697 // over the last several recent pauses
698 // Returns the average survival ration over the last several recent pauses
699 // If there have been no pauses, return 1.0
700 double recent_avg_survival_fraction_work(TruncatedSeq* surviving,
701 TruncatedSeq* before);
703 double conservative_avg_survival_fraction() {
704 double avg = recent_avg_survival_fraction();
705 double latest = last_survival_fraction();
706 return conservative_avg_survival_fraction_work(avg, latest);
707 }
709 // The ratio of gc time to elapsed time, computed over recent pauses.
710 double _recent_avg_pause_time_ratio;
712 double recent_avg_pause_time_ratio() {
713 return _recent_avg_pause_time_ratio;
714 }
716 // Number of pauses between concurrent marking.
717 size_t _pauses_btwn_concurrent_mark;
719 size_t _n_marks_since_last_pause;
721 // True iff CM has been initiated.
722 bool _conc_mark_initiated;
724 // True iff CM should be initiated
725 bool _should_initiate_conc_mark;
726 bool _should_revert_to_full_young_gcs;
727 bool _last_full_young_gc;
729 // This set of variables tracks the collector efficiency, in order to
730 // determine whether we should initiate a new marking.
731 double _cur_mark_stop_world_time_ms;
732 double _mark_init_start_sec;
733 double _mark_remark_start_sec;
734 double _mark_cleanup_start_sec;
735 double _mark_closure_time_ms;
737 void calculate_young_list_min_length();
738 void calculate_young_list_target_config();
739 void calculate_young_list_target_config(size_t rs_lengths);
740 size_t calculate_optimal_so_length(size_t young_list_length);
742 public:
744 G1CollectorPolicy();
746 virtual G1CollectorPolicy* as_g1_policy() { return this; }
748 virtual CollectorPolicy::Name kind() {
749 return CollectorPolicy::G1CollectorPolicyKind;
750 }
752 void check_prediction_validity();
754 size_t bytes_in_collection_set() {
755 return _bytes_in_collection_set_before_gc;
756 }
758 size_t bytes_in_to_space() {
759 return bytes_in_to_space_during_gc();
760 }
762 unsigned calc_gc_alloc_time_stamp() {
763 return _all_pause_times_ms->num() + 1;
764 }
766 protected:
768 // Count the number of bytes used in the CS.
769 void count_CS_bytes_used();
771 // Together these do the base cleanup-recording work. Subclasses might
772 // want to put something between them.
773 void record_concurrent_mark_cleanup_end_work1(size_t freed_bytes,
774 size_t max_live_bytes);
775 void record_concurrent_mark_cleanup_end_work2();
777 public:
779 virtual void init();
781 // Create jstat counters for the policy.
782 virtual void initialize_gc_policy_counters();
784 virtual HeapWord* mem_allocate_work(size_t size,
785 bool is_tlab,
786 bool* gc_overhead_limit_was_exceeded);
788 // This method controls how a collector handles one or more
789 // of its generations being fully allocated.
790 virtual HeapWord* satisfy_failed_allocation(size_t size,
791 bool is_tlab);
793 BarrierSet::Name barrier_set_name() { return BarrierSet::G1SATBCTLogging; }
795 GenRemSet::Name rem_set_name() { return GenRemSet::CardTable; }
797 // The number of collection pauses so far.
798 long n_pauses() const { return _n_pauses; }
800 // Update the heuristic info to record a collection pause of the given
801 // start time, where the given number of bytes were used at the start.
802 // This may involve changing the desired size of a collection set.
804 virtual void record_stop_world_start();
806 virtual void record_collection_pause_start(double start_time_sec,
807 size_t start_used);
809 // Must currently be called while the world is stopped.
810 virtual void record_concurrent_mark_init_start();
811 virtual void record_concurrent_mark_init_end();
812 void record_concurrent_mark_init_end_pre(double
813 mark_init_elapsed_time_ms);
815 void record_mark_closure_time(double mark_closure_time_ms);
817 virtual void record_concurrent_mark_remark_start();
818 virtual void record_concurrent_mark_remark_end();
820 virtual void record_concurrent_mark_cleanup_start();
821 virtual void record_concurrent_mark_cleanup_end(size_t freed_bytes,
822 size_t max_live_bytes);
823 virtual void record_concurrent_mark_cleanup_completed();
825 virtual void record_concurrent_pause();
826 virtual void record_concurrent_pause_end();
828 virtual void record_collection_pause_end_CH_strong_roots();
829 virtual void record_collection_pause_end_G1_strong_roots();
831 virtual void record_collection_pause_end(bool abandoned);
833 // Record the fact that a full collection occurred.
834 virtual void record_full_collection_start();
835 virtual void record_full_collection_end();
837 void record_ext_root_scan_time(int worker_i, double ms) {
838 _par_last_ext_root_scan_times_ms[worker_i] = ms;
839 }
841 void record_mark_stack_scan_time(int worker_i, double ms) {
842 _par_last_mark_stack_scan_times_ms[worker_i] = ms;
843 }
845 void record_scan_only_time(int worker_i, double ms, int n) {
846 _par_last_scan_only_times_ms[worker_i] = ms;
847 _par_last_scan_only_regions_scanned[worker_i] = (double) n;
848 }
850 void record_satb_drain_time(double ms) {
851 _cur_satb_drain_time_ms = ms;
852 _satb_drain_time_set = true;
853 }
855 void record_satb_drain_processed_buffers (int processed_buffers) {
856 _last_satb_drain_processed_buffers = processed_buffers;
857 }
859 void record_mod_union_time(double ms) {
860 _all_mod_union_times_ms->add(ms);
861 }
863 void record_update_rs_start_time(int thread, double ms) {
864 _par_last_update_rs_start_times_ms[thread] = ms;
865 }
867 void record_update_rs_time(int thread, double ms) {
868 _par_last_update_rs_times_ms[thread] = ms;
869 }
871 void record_update_rs_processed_buffers (int thread,
872 double processed_buffers) {
873 _par_last_update_rs_processed_buffers[thread] = processed_buffers;
874 }
876 void record_scan_rs_start_time(int thread, double ms) {
877 _par_last_scan_rs_start_times_ms[thread] = ms;
878 }
880 void record_scan_rs_time(int thread, double ms) {
881 _par_last_scan_rs_times_ms[thread] = ms;
882 }
884 void record_scan_new_refs_time(int thread, double ms) {
885 _par_last_scan_new_refs_times_ms[thread] = ms;
886 }
888 double get_scan_new_refs_time(int thread) {
889 return _par_last_scan_new_refs_times_ms[thread];
890 }
892 void reset_obj_copy_time(int thread) {
893 _par_last_obj_copy_times_ms[thread] = 0.0;
894 }
896 void reset_obj_copy_time() {
897 reset_obj_copy_time(0);
898 }
900 void record_obj_copy_time(int thread, double ms) {
901 _par_last_obj_copy_times_ms[thread] += ms;
902 }
904 void record_obj_copy_time(double ms) {
905 record_obj_copy_time(0, ms);
906 }
908 void record_termination_time(int thread, double ms) {
909 _par_last_termination_times_ms[thread] = ms;
910 }
912 void record_termination_time(double ms) {
913 record_termination_time(0, ms);
914 }
916 void record_pause_time_ms(double ms) {
917 _last_pause_time_ms = ms;
918 }
920 void record_clear_ct_time(double ms) {
921 _cur_clear_ct_time_ms = ms;
922 }
924 void record_par_time(double ms) {
925 _cur_collection_par_time_ms = ms;
926 }
928 void record_aux_start_time(int i) {
929 guarantee(i < _aux_num, "should be within range");
930 _cur_aux_start_times_ms[i] = os::elapsedTime() * 1000.0;
931 }
933 void record_aux_end_time(int i) {
934 guarantee(i < _aux_num, "should be within range");
935 double ms = os::elapsedTime() * 1000.0 - _cur_aux_start_times_ms[i];
936 _cur_aux_times_set[i] = true;
937 _cur_aux_times_ms[i] += ms;
938 }
940 #ifndef PRODUCT
941 void record_cc_clear_time(double ms) {
942 if (_min_clear_cc_time_ms < 0.0 || ms <= _min_clear_cc_time_ms)
943 _min_clear_cc_time_ms = ms;
944 if (_max_clear_cc_time_ms < 0.0 || ms >= _max_clear_cc_time_ms)
945 _max_clear_cc_time_ms = ms;
946 _cur_clear_cc_time_ms = ms;
947 _cum_clear_cc_time_ms += ms;
948 _num_cc_clears++;
949 }
950 #endif
952 // Record the fact that "bytes" bytes allocated in a region.
953 void record_before_bytes(size_t bytes);
954 void record_after_bytes(size_t bytes);
956 // Returns "true" if this is a good time to do a collection pause.
957 // The "word_size" argument, if non-zero, indicates the size of an
958 // allocation request that is prompting this query.
959 virtual bool should_do_collection_pause(size_t word_size) = 0;
961 // Choose a new collection set. Marks the chosen regions as being
962 // "in_collection_set", and links them together. The head and number of
963 // the collection set are available via access methods.
964 virtual void choose_collection_set() = 0;
966 void clear_collection_set() { _collection_set = NULL; }
968 // The head of the list (via "next_in_collection_set()") representing the
969 // current collection set.
970 HeapRegion* collection_set() { return _collection_set; }
972 // The number of elements in the current collection set.
973 size_t collection_set_size() { return _collection_set_size; }
975 // Add "hr" to the CS.
976 void add_to_collection_set(HeapRegion* hr);
978 bool should_initiate_conc_mark() { return _should_initiate_conc_mark; }
979 void set_should_initiate_conc_mark() { _should_initiate_conc_mark = true; }
980 void unset_should_initiate_conc_mark(){ _should_initiate_conc_mark = false; }
982 // If an expansion would be appropriate, because recent GC overhead had
983 // exceeded the desired limit, return an amount to expand by.
984 virtual size_t expansion_amount();
986 // note start of mark thread
987 void note_start_of_mark_thread();
989 // The marked bytes of the "r" has changed; reclassify it's desirability
990 // for marking. Also asserts that "r" is eligible for a CS.
991 virtual void note_change_in_marked_bytes(HeapRegion* r) = 0;
993 #ifndef PRODUCT
994 // Check any appropriate marked bytes info, asserting false if
995 // something's wrong, else returning "true".
996 virtual bool assertMarkedBytesDataOK() = 0;
997 #endif
999 // Print tracing information.
1000 void print_tracing_info() const;
1002 // Print stats on young survival ratio
1003 void print_yg_surv_rate_info() const;
1005 void finished_recalculating_age_indexes(bool is_survivors) {
1006 if (is_survivors) {
1007 _survivor_surv_rate_group->finished_recalculating_age_indexes();
1008 } else {
1009 _short_lived_surv_rate_group->finished_recalculating_age_indexes();
1010 }
1011 // do that for any other surv rate groups
1012 }
1014 bool should_add_next_region_to_young_list();
1016 bool in_young_gc_mode() {
1017 return _in_young_gc_mode;
1018 }
1019 void set_in_young_gc_mode(bool in_young_gc_mode) {
1020 _in_young_gc_mode = in_young_gc_mode;
1021 }
1023 bool full_young_gcs() {
1024 return _full_young_gcs;
1025 }
1026 void set_full_young_gcs(bool full_young_gcs) {
1027 _full_young_gcs = full_young_gcs;
1028 }
1030 bool adaptive_young_list_length() {
1031 return _adaptive_young_list_length;
1032 }
1033 void set_adaptive_young_list_length(bool adaptive_young_list_length) {
1034 _adaptive_young_list_length = adaptive_young_list_length;
1035 }
1037 inline double get_gc_eff_factor() {
1038 double ratio = _known_garbage_ratio;
1040 double square = ratio * ratio;
1041 // square = square * square;
1042 double ret = square * 9.0 + 1.0;
1043 #if 0
1044 gclog_or_tty->print_cr("ratio = %1.2lf, ret = %1.2lf", ratio, ret);
1045 #endif // 0
1046 guarantee(0.0 <= ret && ret < 10.0, "invariant!");
1047 return ret;
1048 }
1050 //
1051 // Survivor regions policy.
1052 //
1053 protected:
1055 // Current tenuring threshold, set to 0 if the collector reaches the
1056 // maximum amount of suvivors regions.
1057 int _tenuring_threshold;
1059 // The limit on the number of regions allocated for survivors.
1060 size_t _max_survivor_regions;
1062 // The amount of survor regions after a collection.
1063 size_t _recorded_survivor_regions;
1064 // List of survivor regions.
1065 HeapRegion* _recorded_survivor_head;
1066 HeapRegion* _recorded_survivor_tail;
1068 ageTable _survivors_age_table;
1070 public:
1072 inline GCAllocPurpose
1073 evacuation_destination(HeapRegion* src_region, int age, size_t word_sz) {
1074 if (age < _tenuring_threshold && src_region->is_young()) {
1075 return GCAllocForSurvived;
1076 } else {
1077 return GCAllocForTenured;
1078 }
1079 }
1081 inline bool track_object_age(GCAllocPurpose purpose) {
1082 return purpose == GCAllocForSurvived;
1083 }
1085 inline GCAllocPurpose alternative_purpose(int purpose) {
1086 return GCAllocForTenured;
1087 }
1089 static const size_t REGIONS_UNLIMITED = ~(size_t)0;
1091 size_t max_regions(int purpose);
1093 // The limit on regions for a particular purpose is reached.
1094 void note_alloc_region_limit_reached(int purpose) {
1095 if (purpose == GCAllocForSurvived) {
1096 _tenuring_threshold = 0;
1097 }
1098 }
1100 void note_start_adding_survivor_regions() {
1101 _survivor_surv_rate_group->start_adding_regions();
1102 }
1104 void note_stop_adding_survivor_regions() {
1105 _survivor_surv_rate_group->stop_adding_regions();
1106 }
1108 void record_survivor_regions(size_t regions,
1109 HeapRegion* head,
1110 HeapRegion* tail) {
1111 _recorded_survivor_regions = regions;
1112 _recorded_survivor_head = head;
1113 _recorded_survivor_tail = tail;
1114 }
1116 size_t recorded_survivor_regions() {
1117 return _recorded_survivor_regions;
1118 }
1120 void record_thread_age_table(ageTable* age_table)
1121 {
1122 _survivors_age_table.merge_par(age_table);
1123 }
1125 // Calculates survivor space parameters.
1126 void calculate_survivors_policy();
1128 };
1130 // This encapsulates a particular strategy for a g1 Collector.
1131 //
1132 // Start a concurrent mark when our heap size is n bytes
1133 // greater then our heap size was at the last concurrent
1134 // mark. Where n is a function of the CMSTriggerRatio
1135 // and the MinHeapFreeRatio.
1136 //
1137 // Start a g1 collection pause when we have allocated the
1138 // average number of bytes currently being freed in
1139 // a collection, but only if it is at least one region
1140 // full
1141 //
1142 // Resize Heap based on desired
1143 // allocation space, where desired allocation space is
1144 // a function of survival rate and desired future to size.
1145 //
1146 // Choose collection set by first picking all older regions
1147 // which have a survival rate which beats our projected young
1148 // survival rate. Then fill out the number of needed regions
1149 // with young regions.
1151 class G1CollectorPolicy_BestRegionsFirst: public G1CollectorPolicy {
1152 CollectionSetChooser* _collectionSetChooser;
1153 // If the estimated is less then desirable, resize if possible.
1154 void expand_if_possible(size_t numRegions);
1156 virtual void choose_collection_set();
1157 virtual void record_collection_pause_start(double start_time_sec,
1158 size_t start_used);
1159 virtual void record_concurrent_mark_cleanup_end(size_t freed_bytes,
1160 size_t max_live_bytes);
1161 virtual void record_full_collection_end();
1163 public:
1164 G1CollectorPolicy_BestRegionsFirst() {
1165 _collectionSetChooser = new CollectionSetChooser();
1166 }
1167 void record_collection_pause_end(bool abandoned);
1168 bool should_do_collection_pause(size_t word_size);
1169 // This is not needed any more, after the CSet choosing code was
1170 // changed to use the pause prediction work. But let's leave the
1171 // hook in just in case.
1172 void note_change_in_marked_bytes(HeapRegion* r) { }
1173 #ifndef PRODUCT
1174 bool assertMarkedBytesDataOK();
1175 #endif
1176 };
1178 // This should move to some place more general...
1180 // If we have "n" measurements, and we've kept track of their "sum" and the
1181 // "sum_of_squares" of the measurements, this returns the variance of the
1182 // sequence.
1183 inline double variance(int n, double sum_of_squares, double sum) {
1184 double n_d = (double)n;
1185 double avg = sum/n_d;
1186 return (sum_of_squares - 2.0 * avg * sum + n_d * avg * avg) / n_d;
1187 }
1189 // Local Variables: ***
1190 // c-indentation-style: gnu ***
1191 // End: ***