Thu, 15 Apr 2010 18:45:30 -0400
6939027: G1: assertion failure during the concurrent phase of cleanup
Summary: The outgoing region map is not maintained properly and it's causing an assert failure. Given that we don't actually use it, I'm removing it. I'm piggy-backing a small change on this which removes a message that it's printed before a Full GC when DisableExplicitGC is set.
Reviewed-by: apetrusenko, ysr
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 double _gc_overhead_perc;
220 bool during_marking() {
221 return _during_marking;
222 }
224 // <NEW PREDICTION>
226 private:
227 enum PredictionConstants {
228 TruncatedSeqLength = 10
229 };
231 TruncatedSeq* _alloc_rate_ms_seq;
232 double _prev_collection_pause_end_ms;
234 TruncatedSeq* _pending_card_diff_seq;
235 TruncatedSeq* _rs_length_diff_seq;
236 TruncatedSeq* _cost_per_card_ms_seq;
237 TruncatedSeq* _cost_per_scan_only_region_ms_seq;
238 TruncatedSeq* _fully_young_cards_per_entry_ratio_seq;
239 TruncatedSeq* _partially_young_cards_per_entry_ratio_seq;
240 TruncatedSeq* _cost_per_entry_ms_seq;
241 TruncatedSeq* _partially_young_cost_per_entry_ms_seq;
242 TruncatedSeq* _cost_per_byte_ms_seq;
243 TruncatedSeq* _constant_other_time_ms_seq;
244 TruncatedSeq* _young_other_cost_per_region_ms_seq;
245 TruncatedSeq* _non_young_other_cost_per_region_ms_seq;
247 TruncatedSeq* _pending_cards_seq;
248 TruncatedSeq* _scanned_cards_seq;
249 TruncatedSeq* _rs_lengths_seq;
251 TruncatedSeq* _cost_per_byte_ms_during_cm_seq;
252 TruncatedSeq* _cost_per_scan_only_region_ms_during_cm_seq;
254 TruncatedSeq* _young_gc_eff_seq;
256 TruncatedSeq* _max_conc_overhead_seq;
258 size_t _recorded_young_regions;
259 size_t _recorded_scan_only_regions;
260 size_t _recorded_non_young_regions;
261 size_t _recorded_region_num;
263 size_t _free_regions_at_end_of_collection;
264 size_t _scan_only_regions_at_end_of_collection;
266 size_t _recorded_rs_lengths;
267 size_t _max_rs_lengths;
269 size_t _recorded_marked_bytes;
270 size_t _recorded_young_bytes;
272 size_t _predicted_pending_cards;
273 size_t _predicted_cards_scanned;
274 size_t _predicted_rs_lengths;
275 size_t _predicted_bytes_to_copy;
277 double _predicted_survival_ratio;
278 double _predicted_rs_update_time_ms;
279 double _predicted_rs_scan_time_ms;
280 double _predicted_scan_only_scan_time_ms;
281 double _predicted_object_copy_time_ms;
282 double _predicted_constant_other_time_ms;
283 double _predicted_young_other_time_ms;
284 double _predicted_non_young_other_time_ms;
285 double _predicted_pause_time_ms;
287 double _vtime_diff_ms;
289 double _recorded_young_free_cset_time_ms;
290 double _recorded_non_young_free_cset_time_ms;
292 double _sigma;
293 double _expensive_region_limit_ms;
295 size_t _rs_lengths_prediction;
297 size_t _known_garbage_bytes;
298 double _known_garbage_ratio;
300 double sigma() {
301 return _sigma;
302 }
304 // A function that prevents us putting too much stock in small sample
305 // sets. Returns a number between 2.0 and 1.0, depending on the number
306 // of samples. 5 or more samples yields one; fewer scales linearly from
307 // 2.0 at 1 sample to 1.0 at 5.
308 double confidence_factor(int samples) {
309 if (samples > 4) return 1.0;
310 else return 1.0 + sigma() * ((double)(5 - samples))/2.0;
311 }
313 double get_new_neg_prediction(TruncatedSeq* seq) {
314 return seq->davg() - sigma() * seq->dsd();
315 }
317 #ifndef PRODUCT
318 bool verify_young_ages(HeapRegion* head, SurvRateGroup *surv_rate_group);
319 #endif // PRODUCT
321 void adjust_concurrent_refinement(double update_rs_time,
322 double update_rs_processed_buffers,
323 double goal_ms);
325 protected:
326 double _pause_time_target_ms;
327 double _recorded_young_cset_choice_time_ms;
328 double _recorded_non_young_cset_choice_time_ms;
329 bool _within_target;
330 size_t _pending_cards;
331 size_t _max_pending_cards;
333 public:
335 void set_region_short_lived(HeapRegion* hr) {
336 hr->install_surv_rate_group(_short_lived_surv_rate_group);
337 }
339 void set_region_survivors(HeapRegion* hr) {
340 hr->install_surv_rate_group(_survivor_surv_rate_group);
341 }
343 #ifndef PRODUCT
344 bool verify_young_ages();
345 #endif // PRODUCT
347 void tag_scan_only(size_t short_lived_scan_only_length);
349 double get_new_prediction(TruncatedSeq* seq) {
350 return MAX2(seq->davg() + sigma() * seq->dsd(),
351 seq->davg() * confidence_factor(seq->num()));
352 }
354 size_t young_cset_length() {
355 return _young_cset_length;
356 }
358 void record_max_rs_lengths(size_t rs_lengths) {
359 _max_rs_lengths = rs_lengths;
360 }
362 size_t predict_pending_card_diff() {
363 double prediction = get_new_neg_prediction(_pending_card_diff_seq);
364 if (prediction < 0.00001)
365 return 0;
366 else
367 return (size_t) prediction;
368 }
370 size_t predict_pending_cards() {
371 size_t max_pending_card_num = _g1->max_pending_card_num();
372 size_t diff = predict_pending_card_diff();
373 size_t prediction;
374 if (diff > max_pending_card_num)
375 prediction = max_pending_card_num;
376 else
377 prediction = max_pending_card_num - diff;
379 return prediction;
380 }
382 size_t predict_rs_length_diff() {
383 return (size_t) get_new_prediction(_rs_length_diff_seq);
384 }
386 double predict_alloc_rate_ms() {
387 return get_new_prediction(_alloc_rate_ms_seq);
388 }
390 double predict_cost_per_card_ms() {
391 return get_new_prediction(_cost_per_card_ms_seq);
392 }
394 double predict_rs_update_time_ms(size_t pending_cards) {
395 return (double) pending_cards * predict_cost_per_card_ms();
396 }
398 double predict_fully_young_cards_per_entry_ratio() {
399 return get_new_prediction(_fully_young_cards_per_entry_ratio_seq);
400 }
402 double predict_partially_young_cards_per_entry_ratio() {
403 if (_partially_young_cards_per_entry_ratio_seq->num() < 2)
404 return predict_fully_young_cards_per_entry_ratio();
405 else
406 return get_new_prediction(_partially_young_cards_per_entry_ratio_seq);
407 }
409 size_t predict_young_card_num(size_t rs_length) {
410 return (size_t) ((double) rs_length *
411 predict_fully_young_cards_per_entry_ratio());
412 }
414 size_t predict_non_young_card_num(size_t rs_length) {
415 return (size_t) ((double) rs_length *
416 predict_partially_young_cards_per_entry_ratio());
417 }
419 double predict_rs_scan_time_ms(size_t card_num) {
420 if (full_young_gcs())
421 return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq);
422 else
423 return predict_partially_young_rs_scan_time_ms(card_num);
424 }
426 double predict_partially_young_rs_scan_time_ms(size_t card_num) {
427 if (_partially_young_cost_per_entry_ms_seq->num() < 3)
428 return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq);
429 else
430 return (double) card_num *
431 get_new_prediction(_partially_young_cost_per_entry_ms_seq);
432 }
434 double predict_scan_only_time_ms_during_cm(size_t scan_only_region_num) {
435 if (_cost_per_scan_only_region_ms_during_cm_seq->num() < 3)
436 return 1.5 * (double) scan_only_region_num *
437 get_new_prediction(_cost_per_scan_only_region_ms_seq);
438 else
439 return (double) scan_only_region_num *
440 get_new_prediction(_cost_per_scan_only_region_ms_during_cm_seq);
441 }
443 double predict_scan_only_time_ms(size_t scan_only_region_num) {
444 if (_in_marking_window_im)
445 return predict_scan_only_time_ms_during_cm(scan_only_region_num);
446 else
447 return (double) scan_only_region_num *
448 get_new_prediction(_cost_per_scan_only_region_ms_seq);
449 }
451 double predict_object_copy_time_ms_during_cm(size_t bytes_to_copy) {
452 if (_cost_per_byte_ms_during_cm_seq->num() < 3)
453 return 1.1 * (double) bytes_to_copy *
454 get_new_prediction(_cost_per_byte_ms_seq);
455 else
456 return (double) bytes_to_copy *
457 get_new_prediction(_cost_per_byte_ms_during_cm_seq);
458 }
460 double predict_object_copy_time_ms(size_t bytes_to_copy) {
461 if (_in_marking_window && !_in_marking_window_im)
462 return predict_object_copy_time_ms_during_cm(bytes_to_copy);
463 else
464 return (double) bytes_to_copy *
465 get_new_prediction(_cost_per_byte_ms_seq);
466 }
468 double predict_constant_other_time_ms() {
469 return get_new_prediction(_constant_other_time_ms_seq);
470 }
472 double predict_young_other_time_ms(size_t young_num) {
473 return
474 (double) young_num *
475 get_new_prediction(_young_other_cost_per_region_ms_seq);
476 }
478 double predict_non_young_other_time_ms(size_t non_young_num) {
479 return
480 (double) non_young_num *
481 get_new_prediction(_non_young_other_cost_per_region_ms_seq);
482 }
484 void check_if_region_is_too_expensive(double predicted_time_ms);
486 double predict_young_collection_elapsed_time_ms(size_t adjustment);
487 double predict_base_elapsed_time_ms(size_t pending_cards);
488 double predict_base_elapsed_time_ms(size_t pending_cards,
489 size_t scanned_cards);
490 size_t predict_bytes_to_copy(HeapRegion* hr);
491 double predict_region_elapsed_time_ms(HeapRegion* hr, bool young);
493 // for use by: calculate_optimal_so_length(length)
494 void predict_gc_eff(size_t young_region_num,
495 size_t so_length,
496 double base_time_ms,
497 double *gc_eff,
498 double *pause_time_ms);
500 // for use by: calculate_young_list_target_config(rs_length)
501 bool predict_gc_eff(size_t young_region_num,
502 size_t so_length,
503 double base_time_with_so_ms,
504 size_t init_free_regions,
505 double target_pause_time_ms,
506 double* gc_eff);
508 void start_recording_regions();
509 void record_cset_region(HeapRegion* hr, bool young);
510 void record_scan_only_regions(size_t scan_only_length);
511 void end_recording_regions();
513 void record_vtime_diff_ms(double vtime_diff_ms) {
514 _vtime_diff_ms = vtime_diff_ms;
515 }
517 void record_young_free_cset_time_ms(double time_ms) {
518 _recorded_young_free_cset_time_ms = time_ms;
519 }
521 void record_non_young_free_cset_time_ms(double time_ms) {
522 _recorded_non_young_free_cset_time_ms = time_ms;
523 }
525 double predict_young_gc_eff() {
526 return get_new_neg_prediction(_young_gc_eff_seq);
527 }
529 double predict_survivor_regions_evac_time();
531 // </NEW PREDICTION>
533 public:
534 void cset_regions_freed() {
535 bool propagate = _last_young_gc_full && !_in_marking_window;
536 _short_lived_surv_rate_group->all_surviving_words_recorded(propagate);
537 _survivor_surv_rate_group->all_surviving_words_recorded(propagate);
538 // also call it on any more surv rate groups
539 }
541 void set_known_garbage_bytes(size_t known_garbage_bytes) {
542 _known_garbage_bytes = known_garbage_bytes;
543 size_t heap_bytes = _g1->capacity();
544 _known_garbage_ratio = (double) _known_garbage_bytes / (double) heap_bytes;
545 }
547 void decrease_known_garbage_bytes(size_t known_garbage_bytes) {
548 guarantee( _known_garbage_bytes >= known_garbage_bytes, "invariant" );
550 _known_garbage_bytes -= known_garbage_bytes;
551 size_t heap_bytes = _g1->capacity();
552 _known_garbage_ratio = (double) _known_garbage_bytes / (double) heap_bytes;
553 }
555 G1MMUTracker* mmu_tracker() {
556 return _mmu_tracker;
557 }
559 double predict_init_time_ms() {
560 return get_new_prediction(_concurrent_mark_init_times_ms);
561 }
563 double predict_remark_time_ms() {
564 return get_new_prediction(_concurrent_mark_remark_times_ms);
565 }
567 double predict_cleanup_time_ms() {
568 return get_new_prediction(_concurrent_mark_cleanup_times_ms);
569 }
571 // Returns an estimate of the survival rate of the region at yg-age
572 // "yg_age".
573 double predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) {
574 TruncatedSeq* seq = surv_rate_group->get_seq(age);
575 if (seq->num() == 0)
576 gclog_or_tty->print("BARF! age is %d", age);
577 guarantee( seq->num() > 0, "invariant" );
578 double pred = get_new_prediction(seq);
579 if (pred > 1.0)
580 pred = 1.0;
581 return pred;
582 }
584 double predict_yg_surv_rate(int age) {
585 return predict_yg_surv_rate(age, _short_lived_surv_rate_group);
586 }
588 double accum_yg_surv_rate_pred(int age) {
589 return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
590 }
592 protected:
593 void print_stats (int level, const char* str, double value);
594 void print_stats (int level, const char* str, int value);
595 void print_par_stats (int level, const char* str, double* data) {
596 print_par_stats(level, str, data, true);
597 }
598 void print_par_stats (int level, const char* str, double* data, bool summary);
599 void print_par_buffers (int level, const char* str, double* data, bool summary);
601 void check_other_times(int level,
602 NumberSeq* other_times_ms,
603 NumberSeq* calc_other_times_ms) const;
605 void print_summary (PauseSummary* stats) const;
606 void print_abandoned_summary(PauseSummary* summary) const;
608 void print_summary (int level, const char* str, NumberSeq* seq) const;
609 void print_summary_sd (int level, const char* str, NumberSeq* seq) const;
611 double avg_value (double* data);
612 double max_value (double* data);
613 double sum_of_values (double* data);
614 double max_sum (double* data1, double* data2);
616 int _last_satb_drain_processed_buffers;
617 int _last_update_rs_processed_buffers;
618 double _last_pause_time_ms;
620 size_t _bytes_in_to_space_before_gc;
621 size_t _bytes_in_to_space_after_gc;
622 size_t bytes_in_to_space_during_gc() {
623 return
624 _bytes_in_to_space_after_gc - _bytes_in_to_space_before_gc;
625 }
626 size_t _bytes_in_collection_set_before_gc;
627 // Used to count used bytes in CS.
628 friend class CountCSClosure;
630 // Statistics kept per GC stoppage, pause or full.
631 TruncatedSeq* _recent_prev_end_times_for_all_gcs_sec;
633 // We track markings.
634 int _num_markings;
635 double _mark_thread_startup_sec; // Time at startup of marking thread
637 // Add a new GC of the given duration and end time to the record.
638 void update_recent_gc_times(double end_time_sec, double elapsed_ms);
640 // The head of the list (via "next_in_collection_set()") representing the
641 // current collection set.
642 HeapRegion* _collection_set;
643 size_t _collection_set_size;
644 size_t _collection_set_bytes_used_before;
646 // Info about marking.
647 int _n_marks; // Sticky at 2, so we know when we've done at least 2.
649 // The number of collection pauses at the end of the last mark.
650 size_t _n_pauses_at_mark_end;
652 // Stash a pointer to the g1 heap.
653 G1CollectedHeap* _g1;
655 // The average time in ms per collection pause, averaged over recent pauses.
656 double recent_avg_time_for_pauses_ms();
658 // The average time in ms for processing CollectedHeap strong roots, per
659 // collection pause, averaged over recent pauses.
660 double recent_avg_time_for_CH_strong_ms();
662 // The average time in ms for processing the G1 remembered set, per
663 // pause, averaged over recent pauses.
664 double recent_avg_time_for_G1_strong_ms();
666 // The average time in ms for "evacuating followers", per pause, averaged
667 // over recent pauses.
668 double recent_avg_time_for_evac_ms();
670 // The number of "recent" GCs recorded in the number sequences
671 int number_of_recent_gcs();
673 // The average survival ratio, computed by the total number of bytes
674 // suriviving / total number of bytes before collection over the last
675 // several recent pauses.
676 double recent_avg_survival_fraction();
677 // The survival fraction of the most recent pause; if there have been no
678 // pauses, returns 1.0.
679 double last_survival_fraction();
681 // Returns a "conservative" estimate of the recent survival rate, i.e.,
682 // one that may be higher than "recent_avg_survival_fraction".
683 // This is conservative in several ways:
684 // If there have been few pauses, it will assume a potential high
685 // variance, and err on the side of caution.
686 // It puts a lower bound (currently 0.1) on the value it will return.
687 // To try to detect phase changes, if the most recent pause ("latest") has a
688 // higher-than average ("avg") survival rate, it returns that rate.
689 // "work" version is a utility function; young is restricted to young regions.
690 double conservative_avg_survival_fraction_work(double avg,
691 double latest);
693 // The arguments are the two sequences that keep track of the number of bytes
694 // surviving and the total number of bytes before collection, resp.,
695 // over the last evereal recent pauses
696 // Returns the survival rate for the category in the most recent pause.
697 // If there have been no pauses, returns 1.0.
698 double last_survival_fraction_work(TruncatedSeq* surviving,
699 TruncatedSeq* before);
701 // The arguments are the two sequences that keep track of the number of bytes
702 // surviving and the total number of bytes before collection, resp.,
703 // over the last several recent pauses
704 // Returns the average survival ration over the last several recent pauses
705 // If there have been no pauses, return 1.0
706 double recent_avg_survival_fraction_work(TruncatedSeq* surviving,
707 TruncatedSeq* before);
709 double conservative_avg_survival_fraction() {
710 double avg = recent_avg_survival_fraction();
711 double latest = last_survival_fraction();
712 return conservative_avg_survival_fraction_work(avg, latest);
713 }
715 // The ratio of gc time to elapsed time, computed over recent pauses.
716 double _recent_avg_pause_time_ratio;
718 double recent_avg_pause_time_ratio() {
719 return _recent_avg_pause_time_ratio;
720 }
722 // Number of pauses between concurrent marking.
723 size_t _pauses_btwn_concurrent_mark;
725 size_t _n_marks_since_last_pause;
727 // At the end of a pause we check the heap occupancy and we decide
728 // whether we will start a marking cycle during the next pause. If
729 // we decide that we want to do that, we will set this parameter to
730 // true. So, this parameter will stay true between the end of a
731 // pause and the beginning of a subsequent pause (not necessarily
732 // the next one, see the comments on the next field) when we decide
733 // that we will indeed start a marking cycle and do the initial-mark
734 // work.
735 volatile bool _initiate_conc_mark_if_possible;
737 // If initiate_conc_mark_if_possible() is set at the beginning of a
738 // pause, it is a suggestion that the pause should start a marking
739 // cycle by doing the initial-mark work. However, it is possible
740 // that the concurrent marking thread is still finishing up the
741 // previous marking cycle (e.g., clearing the next marking
742 // bitmap). If that is the case we cannot start a new cycle and
743 // we'll have to wait for the concurrent marking thread to finish
744 // what it is doing. In this case we will postpone the marking cycle
745 // initiation decision for the next pause. When we eventually decide
746 // to start a cycle, we will set _during_initial_mark_pause which
747 // will stay true until the end of the initial-mark pause and it's
748 // the condition that indicates that a pause is doing the
749 // initial-mark work.
750 volatile bool _during_initial_mark_pause;
752 bool _should_revert_to_full_young_gcs;
753 bool _last_full_young_gc;
755 // This set of variables tracks the collector efficiency, in order to
756 // determine whether we should initiate a new marking.
757 double _cur_mark_stop_world_time_ms;
758 double _mark_init_start_sec;
759 double _mark_remark_start_sec;
760 double _mark_cleanup_start_sec;
761 double _mark_closure_time_ms;
763 void calculate_young_list_min_length();
764 void calculate_young_list_target_config();
765 void calculate_young_list_target_config(size_t rs_lengths);
766 size_t calculate_optimal_so_length(size_t young_list_length);
768 public:
770 G1CollectorPolicy();
772 virtual G1CollectorPolicy* as_g1_policy() { return this; }
774 virtual CollectorPolicy::Name kind() {
775 return CollectorPolicy::G1CollectorPolicyKind;
776 }
778 void check_prediction_validity();
780 size_t bytes_in_collection_set() {
781 return _bytes_in_collection_set_before_gc;
782 }
784 size_t bytes_in_to_space() {
785 return bytes_in_to_space_during_gc();
786 }
788 unsigned calc_gc_alloc_time_stamp() {
789 return _all_pause_times_ms->num() + 1;
790 }
792 protected:
794 // Count the number of bytes used in the CS.
795 void count_CS_bytes_used();
797 // Together these do the base cleanup-recording work. Subclasses might
798 // want to put something between them.
799 void record_concurrent_mark_cleanup_end_work1(size_t freed_bytes,
800 size_t max_live_bytes);
801 void record_concurrent_mark_cleanup_end_work2();
803 public:
805 virtual void init();
807 // Create jstat counters for the policy.
808 virtual void initialize_gc_policy_counters();
810 virtual HeapWord* mem_allocate_work(size_t size,
811 bool is_tlab,
812 bool* gc_overhead_limit_was_exceeded);
814 // This method controls how a collector handles one or more
815 // of its generations being fully allocated.
816 virtual HeapWord* satisfy_failed_allocation(size_t size,
817 bool is_tlab);
819 BarrierSet::Name barrier_set_name() { return BarrierSet::G1SATBCTLogging; }
821 GenRemSet::Name rem_set_name() { return GenRemSet::CardTable; }
823 // The number of collection pauses so far.
824 long n_pauses() const { return _n_pauses; }
826 // Update the heuristic info to record a collection pause of the given
827 // start time, where the given number of bytes were used at the start.
828 // This may involve changing the desired size of a collection set.
830 virtual void record_stop_world_start();
832 virtual void record_collection_pause_start(double start_time_sec,
833 size_t start_used);
835 // Must currently be called while the world is stopped.
836 virtual void record_concurrent_mark_init_start();
837 virtual void record_concurrent_mark_init_end();
838 void record_concurrent_mark_init_end_pre(double
839 mark_init_elapsed_time_ms);
841 void record_mark_closure_time(double mark_closure_time_ms);
843 virtual void record_concurrent_mark_remark_start();
844 virtual void record_concurrent_mark_remark_end();
846 virtual void record_concurrent_mark_cleanup_start();
847 virtual void record_concurrent_mark_cleanup_end(size_t freed_bytes,
848 size_t max_live_bytes);
849 virtual void record_concurrent_mark_cleanup_completed();
851 virtual void record_concurrent_pause();
852 virtual void record_concurrent_pause_end();
854 virtual void record_collection_pause_end_CH_strong_roots();
855 virtual void record_collection_pause_end_G1_strong_roots();
857 virtual void record_collection_pause_end(bool abandoned);
859 // Record the fact that a full collection occurred.
860 virtual void record_full_collection_start();
861 virtual void record_full_collection_end();
863 void record_ext_root_scan_time(int worker_i, double ms) {
864 _par_last_ext_root_scan_times_ms[worker_i] = ms;
865 }
867 void record_mark_stack_scan_time(int worker_i, double ms) {
868 _par_last_mark_stack_scan_times_ms[worker_i] = ms;
869 }
871 void record_scan_only_time(int worker_i, double ms, int n) {
872 _par_last_scan_only_times_ms[worker_i] = ms;
873 _par_last_scan_only_regions_scanned[worker_i] = (double) n;
874 }
876 void record_satb_drain_time(double ms) {
877 _cur_satb_drain_time_ms = ms;
878 _satb_drain_time_set = true;
879 }
881 void record_satb_drain_processed_buffers (int processed_buffers) {
882 _last_satb_drain_processed_buffers = processed_buffers;
883 }
885 void record_mod_union_time(double ms) {
886 _all_mod_union_times_ms->add(ms);
887 }
889 void record_update_rs_start_time(int thread, double ms) {
890 _par_last_update_rs_start_times_ms[thread] = ms;
891 }
893 void record_update_rs_time(int thread, double ms) {
894 _par_last_update_rs_times_ms[thread] = ms;
895 }
897 void record_update_rs_processed_buffers (int thread,
898 double processed_buffers) {
899 _par_last_update_rs_processed_buffers[thread] = processed_buffers;
900 }
902 void record_scan_rs_start_time(int thread, double ms) {
903 _par_last_scan_rs_start_times_ms[thread] = ms;
904 }
906 void record_scan_rs_time(int thread, double ms) {
907 _par_last_scan_rs_times_ms[thread] = ms;
908 }
910 void record_scan_new_refs_time(int thread, double ms) {
911 _par_last_scan_new_refs_times_ms[thread] = ms;
912 }
914 double get_scan_new_refs_time(int thread) {
915 return _par_last_scan_new_refs_times_ms[thread];
916 }
918 void reset_obj_copy_time(int thread) {
919 _par_last_obj_copy_times_ms[thread] = 0.0;
920 }
922 void reset_obj_copy_time() {
923 reset_obj_copy_time(0);
924 }
926 void record_obj_copy_time(int thread, double ms) {
927 _par_last_obj_copy_times_ms[thread] += ms;
928 }
930 void record_obj_copy_time(double ms) {
931 record_obj_copy_time(0, ms);
932 }
934 void record_termination_time(int thread, double ms) {
935 _par_last_termination_times_ms[thread] = ms;
936 }
938 void record_termination_time(double ms) {
939 record_termination_time(0, ms);
940 }
942 void record_pause_time_ms(double ms) {
943 _last_pause_time_ms = ms;
944 }
946 void record_clear_ct_time(double ms) {
947 _cur_clear_ct_time_ms = ms;
948 }
950 void record_par_time(double ms) {
951 _cur_collection_par_time_ms = ms;
952 }
954 void record_aux_start_time(int i) {
955 guarantee(i < _aux_num, "should be within range");
956 _cur_aux_start_times_ms[i] = os::elapsedTime() * 1000.0;
957 }
959 void record_aux_end_time(int i) {
960 guarantee(i < _aux_num, "should be within range");
961 double ms = os::elapsedTime() * 1000.0 - _cur_aux_start_times_ms[i];
962 _cur_aux_times_set[i] = true;
963 _cur_aux_times_ms[i] += ms;
964 }
966 #ifndef PRODUCT
967 void record_cc_clear_time(double ms) {
968 if (_min_clear_cc_time_ms < 0.0 || ms <= _min_clear_cc_time_ms)
969 _min_clear_cc_time_ms = ms;
970 if (_max_clear_cc_time_ms < 0.0 || ms >= _max_clear_cc_time_ms)
971 _max_clear_cc_time_ms = ms;
972 _cur_clear_cc_time_ms = ms;
973 _cum_clear_cc_time_ms += ms;
974 _num_cc_clears++;
975 }
976 #endif
978 // Record the fact that "bytes" bytes allocated in a region.
979 void record_before_bytes(size_t bytes);
980 void record_after_bytes(size_t bytes);
982 // Returns "true" if this is a good time to do a collection pause.
983 // The "word_size" argument, if non-zero, indicates the size of an
984 // allocation request that is prompting this query.
985 virtual bool should_do_collection_pause(size_t word_size) = 0;
987 // Choose a new collection set. Marks the chosen regions as being
988 // "in_collection_set", and links them together. The head and number of
989 // the collection set are available via access methods.
990 virtual void choose_collection_set() = 0;
992 void clear_collection_set() { _collection_set = NULL; }
994 // The head of the list (via "next_in_collection_set()") representing the
995 // current collection set.
996 HeapRegion* collection_set() { return _collection_set; }
998 // The number of elements in the current collection set.
999 size_t collection_set_size() { return _collection_set_size; }
1001 // Add "hr" to the CS.
1002 void add_to_collection_set(HeapRegion* hr);
1004 bool initiate_conc_mark_if_possible() { return _initiate_conc_mark_if_possible; }
1005 void set_initiate_conc_mark_if_possible() { _initiate_conc_mark_if_possible = true; }
1006 void clear_initiate_conc_mark_if_possible() { _initiate_conc_mark_if_possible = false; }
1008 bool during_initial_mark_pause() { return _during_initial_mark_pause; }
1009 void set_during_initial_mark_pause() { _during_initial_mark_pause = true; }
1010 void clear_during_initial_mark_pause(){ _during_initial_mark_pause = false; }
1012 // This is called at the very beginning of an evacuation pause (it
1013 // has to be the first thing that the pause does). If
1014 // initiate_conc_mark_if_possible() is true, and the concurrent
1015 // marking thread has completed its work during the previous cycle,
1016 // it will set during_initial_mark_pause() to so that the pause does
1017 // the initial-mark work and start a marking cycle.
1018 void decide_on_conc_mark_initiation();
1020 // If an expansion would be appropriate, because recent GC overhead had
1021 // exceeded the desired limit, return an amount to expand by.
1022 virtual size_t expansion_amount();
1024 // note start of mark thread
1025 void note_start_of_mark_thread();
1027 // The marked bytes of the "r" has changed; reclassify it's desirability
1028 // for marking. Also asserts that "r" is eligible for a CS.
1029 virtual void note_change_in_marked_bytes(HeapRegion* r) = 0;
1031 #ifndef PRODUCT
1032 // Check any appropriate marked bytes info, asserting false if
1033 // something's wrong, else returning "true".
1034 virtual bool assertMarkedBytesDataOK() = 0;
1035 #endif
1037 // Print tracing information.
1038 void print_tracing_info() const;
1040 // Print stats on young survival ratio
1041 void print_yg_surv_rate_info() const;
1043 void finished_recalculating_age_indexes(bool is_survivors) {
1044 if (is_survivors) {
1045 _survivor_surv_rate_group->finished_recalculating_age_indexes();
1046 } else {
1047 _short_lived_surv_rate_group->finished_recalculating_age_indexes();
1048 }
1049 // do that for any other surv rate groups
1050 }
1052 bool should_add_next_region_to_young_list();
1054 bool in_young_gc_mode() {
1055 return _in_young_gc_mode;
1056 }
1057 void set_in_young_gc_mode(bool in_young_gc_mode) {
1058 _in_young_gc_mode = in_young_gc_mode;
1059 }
1061 bool full_young_gcs() {
1062 return _full_young_gcs;
1063 }
1064 void set_full_young_gcs(bool full_young_gcs) {
1065 _full_young_gcs = full_young_gcs;
1066 }
1068 bool adaptive_young_list_length() {
1069 return _adaptive_young_list_length;
1070 }
1071 void set_adaptive_young_list_length(bool adaptive_young_list_length) {
1072 _adaptive_young_list_length = adaptive_young_list_length;
1073 }
1075 inline double get_gc_eff_factor() {
1076 double ratio = _known_garbage_ratio;
1078 double square = ratio * ratio;
1079 // square = square * square;
1080 double ret = square * 9.0 + 1.0;
1081 #if 0
1082 gclog_or_tty->print_cr("ratio = %1.2lf, ret = %1.2lf", ratio, ret);
1083 #endif // 0
1084 guarantee(0.0 <= ret && ret < 10.0, "invariant!");
1085 return ret;
1086 }
1088 //
1089 // Survivor regions policy.
1090 //
1091 protected:
1093 // Current tenuring threshold, set to 0 if the collector reaches the
1094 // maximum amount of suvivors regions.
1095 int _tenuring_threshold;
1097 // The limit on the number of regions allocated for survivors.
1098 size_t _max_survivor_regions;
1100 // The amount of survor regions after a collection.
1101 size_t _recorded_survivor_regions;
1102 // List of survivor regions.
1103 HeapRegion* _recorded_survivor_head;
1104 HeapRegion* _recorded_survivor_tail;
1106 ageTable _survivors_age_table;
1108 public:
1110 inline GCAllocPurpose
1111 evacuation_destination(HeapRegion* src_region, int age, size_t word_sz) {
1112 if (age < _tenuring_threshold && src_region->is_young()) {
1113 return GCAllocForSurvived;
1114 } else {
1115 return GCAllocForTenured;
1116 }
1117 }
1119 inline bool track_object_age(GCAllocPurpose purpose) {
1120 return purpose == GCAllocForSurvived;
1121 }
1123 inline GCAllocPurpose alternative_purpose(int purpose) {
1124 return GCAllocForTenured;
1125 }
1127 static const size_t REGIONS_UNLIMITED = ~(size_t)0;
1129 size_t max_regions(int purpose);
1131 // The limit on regions for a particular purpose is reached.
1132 void note_alloc_region_limit_reached(int purpose) {
1133 if (purpose == GCAllocForSurvived) {
1134 _tenuring_threshold = 0;
1135 }
1136 }
1138 void note_start_adding_survivor_regions() {
1139 _survivor_surv_rate_group->start_adding_regions();
1140 }
1142 void note_stop_adding_survivor_regions() {
1143 _survivor_surv_rate_group->stop_adding_regions();
1144 }
1146 void record_survivor_regions(size_t regions,
1147 HeapRegion* head,
1148 HeapRegion* tail) {
1149 _recorded_survivor_regions = regions;
1150 _recorded_survivor_head = head;
1151 _recorded_survivor_tail = tail;
1152 }
1154 size_t recorded_survivor_regions() {
1155 return _recorded_survivor_regions;
1156 }
1158 void record_thread_age_table(ageTable* age_table)
1159 {
1160 _survivors_age_table.merge_par(age_table);
1161 }
1163 // Calculates survivor space parameters.
1164 void calculate_survivors_policy();
1166 };
1168 // This encapsulates a particular strategy for a g1 Collector.
1169 //
1170 // Start a concurrent mark when our heap size is n bytes
1171 // greater then our heap size was at the last concurrent
1172 // mark. Where n is a function of the CMSTriggerRatio
1173 // and the MinHeapFreeRatio.
1174 //
1175 // Start a g1 collection pause when we have allocated the
1176 // average number of bytes currently being freed in
1177 // a collection, but only if it is at least one region
1178 // full
1179 //
1180 // Resize Heap based on desired
1181 // allocation space, where desired allocation space is
1182 // a function of survival rate and desired future to size.
1183 //
1184 // Choose collection set by first picking all older regions
1185 // which have a survival rate which beats our projected young
1186 // survival rate. Then fill out the number of needed regions
1187 // with young regions.
1189 class G1CollectorPolicy_BestRegionsFirst: public G1CollectorPolicy {
1190 CollectionSetChooser* _collectionSetChooser;
1191 // If the estimated is less then desirable, resize if possible.
1192 void expand_if_possible(size_t numRegions);
1194 virtual void choose_collection_set();
1195 virtual void record_collection_pause_start(double start_time_sec,
1196 size_t start_used);
1197 virtual void record_concurrent_mark_cleanup_end(size_t freed_bytes,
1198 size_t max_live_bytes);
1199 virtual void record_full_collection_end();
1201 public:
1202 G1CollectorPolicy_BestRegionsFirst() {
1203 _collectionSetChooser = new CollectionSetChooser();
1204 }
1205 void record_collection_pause_end(bool abandoned);
1206 bool should_do_collection_pause(size_t word_size);
1207 // This is not needed any more, after the CSet choosing code was
1208 // changed to use the pause prediction work. But let's leave the
1209 // hook in just in case.
1210 void note_change_in_marked_bytes(HeapRegion* r) { }
1211 #ifndef PRODUCT
1212 bool assertMarkedBytesDataOK();
1213 #endif
1214 };
1216 // This should move to some place more general...
1218 // If we have "n" measurements, and we've kept track of their "sum" and the
1219 // "sum_of_squares" of the measurements, this returns the variance of the
1220 // sequence.
1221 inline double variance(int n, double sum_of_squares, double sum) {
1222 double n_d = (double)n;
1223 double avg = sum/n_d;
1224 return (sum_of_squares - 2.0 * avg * sum + n_d * avg * avg) / n_d;
1225 }
1227 // Local Variables: ***
1228 // c-indentation-style: gnu ***
1229 // End: ***