Thu, 22 Apr 2010 15:20:16 -0400
6946048: G1: improvements to +PrintGCDetails output
Summary: Small improvements to G1's PrintGCDetails output. It also includes minor formatting details.
Reviewed-by: ysr, johnc
1 /*
2 * Copyright (c) 2001, 2010, 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 */
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(update_rs)
65 define_num_seq(scan_rs)
66 define_num_seq(scan_new_refs) // Only for temp use; added to
67 // in parallel case.
68 define_num_seq(obj_copy)
69 define_num_seq(termination) // parallel only
70 define_num_seq(parallel_other) // parallel only
71 define_num_seq(mark_closure)
72 define_num_seq(clear_ct) // parallel only
73 };
75 class Summary: public PauseSummary,
76 public MainBodySummary {
77 public:
78 virtual MainBodySummary* main_body_summary() { return this; }
79 };
81 class AbandonedSummary: public PauseSummary {
82 };
84 class G1CollectorPolicy: public CollectorPolicy {
85 protected:
86 // The number of pauses during the execution.
87 long _n_pauses;
89 // either equal to the number of parallel threads, if ParallelGCThreads
90 // has been set, or 1 otherwise
91 int _parallel_gc_threads;
93 enum SomePrivateConstants {
94 NumPrevPausesForHeuristics = 10
95 };
97 G1MMUTracker* _mmu_tracker;
99 void initialize_flags();
101 void initialize_all() {
102 initialize_flags();
103 initialize_size_info();
104 initialize_perm_generation(PermGen::MarkSweepCompact);
105 }
107 virtual size_t default_init_heap_size() {
108 // Pick some reasonable default.
109 return 8*M;
110 }
112 double _cur_collection_start_sec;
113 size_t _cur_collection_pause_used_at_start_bytes;
114 size_t _cur_collection_pause_used_regions_at_start;
115 size_t _prev_collection_pause_used_at_end_bytes;
116 double _cur_collection_par_time_ms;
117 double _cur_satb_drain_time_ms;
118 double _cur_clear_ct_time_ms;
119 bool _satb_drain_time_set;
121 #ifndef PRODUCT
122 // Card Table Count Cache stats
123 double _min_clear_cc_time_ms; // min
124 double _max_clear_cc_time_ms; // max
125 double _cur_clear_cc_time_ms; // clearing time during current pause
126 double _cum_clear_cc_time_ms; // cummulative clearing time
127 jlong _num_cc_clears; // number of times the card count cache has been cleared
128 #endif
130 double _cur_CH_strong_roots_end_sec;
131 double _cur_CH_strong_roots_dur_ms;
132 double _cur_G1_strong_roots_end_sec;
133 double _cur_G1_strong_roots_dur_ms;
135 // Statistics for recent GC pauses. See below for how indexed.
136 TruncatedSeq* _recent_CH_strong_roots_times_ms;
137 TruncatedSeq* _recent_G1_strong_roots_times_ms;
138 TruncatedSeq* _recent_evac_times_ms;
139 // These exclude marking times.
140 TruncatedSeq* _recent_pause_times_ms;
141 TruncatedSeq* _recent_gc_times_ms;
143 TruncatedSeq* _recent_CS_bytes_used_before;
144 TruncatedSeq* _recent_CS_bytes_surviving;
146 TruncatedSeq* _recent_rs_sizes;
148 TruncatedSeq* _concurrent_mark_init_times_ms;
149 TruncatedSeq* _concurrent_mark_remark_times_ms;
150 TruncatedSeq* _concurrent_mark_cleanup_times_ms;
152 Summary* _summary;
153 AbandonedSummary* _abandoned_summary;
155 NumberSeq* _all_pause_times_ms;
156 NumberSeq* _all_full_gc_times_ms;
157 double _stop_world_start;
158 NumberSeq* _all_stop_world_times_ms;
159 NumberSeq* _all_yield_times_ms;
161 size_t _region_num_young;
162 size_t _region_num_tenured;
163 size_t _prev_region_num_young;
164 size_t _prev_region_num_tenured;
166 NumberSeq* _all_mod_union_times_ms;
168 int _aux_num;
169 NumberSeq* _all_aux_times_ms;
170 double* _cur_aux_start_times_ms;
171 double* _cur_aux_times_ms;
172 bool* _cur_aux_times_set;
174 double* _par_last_gc_worker_start_times_ms;
175 double* _par_last_ext_root_scan_times_ms;
176 double* _par_last_mark_stack_scan_times_ms;
177 double* _par_last_update_rs_times_ms;
178 double* _par_last_update_rs_processed_buffers;
179 double* _par_last_scan_rs_times_ms;
180 double* _par_last_scan_new_refs_times_ms;
181 double* _par_last_obj_copy_times_ms;
182 double* _par_last_termination_times_ms;
183 double* _par_last_termination_attempts;
184 double* _par_last_gc_worker_end_times_ms;
186 // indicates that we are in young GC mode
187 bool _in_young_gc_mode;
189 // indicates whether we are in full young or partially young GC mode
190 bool _full_young_gcs;
192 // if true, then it tries to dynamically adjust the length of the
193 // young list
194 bool _adaptive_young_list_length;
195 size_t _young_list_min_length;
196 size_t _young_list_target_length;
197 size_t _young_list_fixed_length;
199 size_t _young_cset_length;
200 bool _last_young_gc_full;
202 double _target_pause_time_ms;
204 unsigned _full_young_pause_num;
205 unsigned _partial_young_pause_num;
207 bool _during_marking;
208 bool _in_marking_window;
209 bool _in_marking_window_im;
211 SurvRateGroup* _short_lived_surv_rate_group;
212 SurvRateGroup* _survivor_surv_rate_group;
213 // add here any more surv rate groups
215 double _gc_overhead_perc;
217 bool during_marking() {
218 return _during_marking;
219 }
221 // <NEW PREDICTION>
223 private:
224 enum PredictionConstants {
225 TruncatedSeqLength = 10
226 };
228 TruncatedSeq* _alloc_rate_ms_seq;
229 double _prev_collection_pause_end_ms;
231 TruncatedSeq* _pending_card_diff_seq;
232 TruncatedSeq* _rs_length_diff_seq;
233 TruncatedSeq* _cost_per_card_ms_seq;
234 TruncatedSeq* _fully_young_cards_per_entry_ratio_seq;
235 TruncatedSeq* _partially_young_cards_per_entry_ratio_seq;
236 TruncatedSeq* _cost_per_entry_ms_seq;
237 TruncatedSeq* _partially_young_cost_per_entry_ms_seq;
238 TruncatedSeq* _cost_per_byte_ms_seq;
239 TruncatedSeq* _constant_other_time_ms_seq;
240 TruncatedSeq* _young_other_cost_per_region_ms_seq;
241 TruncatedSeq* _non_young_other_cost_per_region_ms_seq;
243 TruncatedSeq* _pending_cards_seq;
244 TruncatedSeq* _scanned_cards_seq;
245 TruncatedSeq* _rs_lengths_seq;
247 TruncatedSeq* _cost_per_byte_ms_during_cm_seq;
249 TruncatedSeq* _young_gc_eff_seq;
251 TruncatedSeq* _max_conc_overhead_seq;
253 size_t _recorded_young_regions;
254 size_t _recorded_non_young_regions;
255 size_t _recorded_region_num;
257 size_t _free_regions_at_end_of_collection;
259 size_t _recorded_rs_lengths;
260 size_t _max_rs_lengths;
262 size_t _recorded_marked_bytes;
263 size_t _recorded_young_bytes;
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;
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;
279 double _vtime_diff_ms;
281 double _recorded_young_free_cset_time_ms;
282 double _recorded_non_young_free_cset_time_ms;
284 double _sigma;
285 double _expensive_region_limit_ms;
287 size_t _rs_lengths_prediction;
289 size_t _known_garbage_bytes;
290 double _known_garbage_ratio;
292 double sigma() {
293 return _sigma;
294 }
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 }
305 double get_new_neg_prediction(TruncatedSeq* seq) {
306 return seq->davg() - sigma() * seq->dsd();
307 }
309 #ifndef PRODUCT
310 bool verify_young_ages(HeapRegion* head, SurvRateGroup *surv_rate_group);
311 #endif // PRODUCT
313 void adjust_concurrent_refinement(double update_rs_time,
314 double update_rs_processed_buffers,
315 double goal_ms);
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;
325 public:
327 void set_region_short_lived(HeapRegion* hr) {
328 hr->install_surv_rate_group(_short_lived_surv_rate_group);
329 }
331 void set_region_survivors(HeapRegion* hr) {
332 hr->install_surv_rate_group(_survivor_surv_rate_group);
333 }
335 #ifndef PRODUCT
336 bool verify_young_ages();
337 #endif // PRODUCT
339 double get_new_prediction(TruncatedSeq* seq) {
340 return MAX2(seq->davg() + sigma() * seq->dsd(),
341 seq->davg() * confidence_factor(seq->num()));
342 }
344 size_t young_cset_length() {
345 return _young_cset_length;
346 }
348 void record_max_rs_lengths(size_t rs_lengths) {
349 _max_rs_lengths = rs_lengths;
350 }
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 }
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;
369 return prediction;
370 }
372 size_t predict_rs_length_diff() {
373 return (size_t) get_new_prediction(_rs_length_diff_seq);
374 }
376 double predict_alloc_rate_ms() {
377 return get_new_prediction(_alloc_rate_ms_seq);
378 }
380 double predict_cost_per_card_ms() {
381 return get_new_prediction(_cost_per_card_ms_seq);
382 }
384 double predict_rs_update_time_ms(size_t pending_cards) {
385 return (double) pending_cards * predict_cost_per_card_ms();
386 }
388 double predict_fully_young_cards_per_entry_ratio() {
389 return get_new_prediction(_fully_young_cards_per_entry_ratio_seq);
390 }
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 }
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 }
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 }
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 }
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 }
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 }
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 }
441 double predict_constant_other_time_ms() {
442 return get_new_prediction(_constant_other_time_ms_seq);
443 }
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 }
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 }
457 void check_if_region_is_too_expensive(double predicted_time_ms);
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);
466 // for use by: calculate_young_list_target_length(rs_length)
467 bool predict_will_fit(size_t young_region_num,
468 double base_time_ms,
469 size_t init_free_regions,
470 double target_pause_time_ms);
472 void start_recording_regions();
473 void record_cset_region_info(HeapRegion* hr, bool young);
474 void record_non_young_cset_region(HeapRegion* hr);
476 void set_recorded_young_regions(size_t n_regions);
477 void set_recorded_young_bytes(size_t bytes);
478 void set_recorded_rs_lengths(size_t rs_lengths);
479 void set_predicted_bytes_to_copy(size_t bytes);
481 void end_recording_regions();
483 void record_vtime_diff_ms(double vtime_diff_ms) {
484 _vtime_diff_ms = vtime_diff_ms;
485 }
487 void record_young_free_cset_time_ms(double time_ms) {
488 _recorded_young_free_cset_time_ms = time_ms;
489 }
491 void record_non_young_free_cset_time_ms(double time_ms) {
492 _recorded_non_young_free_cset_time_ms = time_ms;
493 }
495 double predict_young_gc_eff() {
496 return get_new_neg_prediction(_young_gc_eff_seq);
497 }
499 double predict_survivor_regions_evac_time();
501 // </NEW PREDICTION>
503 public:
504 void cset_regions_freed() {
505 bool propagate = _last_young_gc_full && !_in_marking_window;
506 _short_lived_surv_rate_group->all_surviving_words_recorded(propagate);
507 _survivor_surv_rate_group->all_surviving_words_recorded(propagate);
508 // also call it on any more surv rate groups
509 }
511 void set_known_garbage_bytes(size_t known_garbage_bytes) {
512 _known_garbage_bytes = known_garbage_bytes;
513 size_t heap_bytes = _g1->capacity();
514 _known_garbage_ratio = (double) _known_garbage_bytes / (double) heap_bytes;
515 }
517 void decrease_known_garbage_bytes(size_t known_garbage_bytes) {
518 guarantee( _known_garbage_bytes >= known_garbage_bytes, "invariant" );
520 _known_garbage_bytes -= known_garbage_bytes;
521 size_t heap_bytes = _g1->capacity();
522 _known_garbage_ratio = (double) _known_garbage_bytes / (double) heap_bytes;
523 }
525 G1MMUTracker* mmu_tracker() {
526 return _mmu_tracker;
527 }
529 double predict_init_time_ms() {
530 return get_new_prediction(_concurrent_mark_init_times_ms);
531 }
533 double predict_remark_time_ms() {
534 return get_new_prediction(_concurrent_mark_remark_times_ms);
535 }
537 double predict_cleanup_time_ms() {
538 return get_new_prediction(_concurrent_mark_cleanup_times_ms);
539 }
541 // Returns an estimate of the survival rate of the region at yg-age
542 // "yg_age".
543 double predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) {
544 TruncatedSeq* seq = surv_rate_group->get_seq(age);
545 if (seq->num() == 0)
546 gclog_or_tty->print("BARF! age is %d", age);
547 guarantee( seq->num() > 0, "invariant" );
548 double pred = get_new_prediction(seq);
549 if (pred > 1.0)
550 pred = 1.0;
551 return pred;
552 }
554 double predict_yg_surv_rate(int age) {
555 return predict_yg_surv_rate(age, _short_lived_surv_rate_group);
556 }
558 double accum_yg_surv_rate_pred(int age) {
559 return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
560 }
562 protected:
563 void print_stats(int level, const char* str, double value);
564 void print_stats(int level, const char* str, int value);
566 void print_par_stats(int level, const char* str, double* data) {
567 print_par_stats(level, str, data, true);
568 }
569 void print_par_stats(int level, const char* str, double* data, bool summary);
570 void print_par_sizes(int level, const char* str, double* data, bool summary);
572 void check_other_times(int level,
573 NumberSeq* other_times_ms,
574 NumberSeq* calc_other_times_ms) const;
576 void print_summary (PauseSummary* stats) const;
577 void print_abandoned_summary(PauseSummary* summary) const;
579 void print_summary (int level, const char* str, NumberSeq* seq) const;
580 void print_summary_sd (int level, const char* str, NumberSeq* seq) const;
582 double avg_value (double* data);
583 double max_value (double* data);
584 double sum_of_values (double* data);
585 double max_sum (double* data1, double* data2);
587 int _last_satb_drain_processed_buffers;
588 int _last_update_rs_processed_buffers;
589 double _last_pause_time_ms;
591 size_t _bytes_in_to_space_before_gc;
592 size_t _bytes_in_to_space_after_gc;
593 size_t bytes_in_to_space_during_gc() {
594 return
595 _bytes_in_to_space_after_gc - _bytes_in_to_space_before_gc;
596 }
597 size_t _bytes_in_collection_set_before_gc;
598 // Used to count used bytes in CS.
599 friend class CountCSClosure;
601 // Statistics kept per GC stoppage, pause or full.
602 TruncatedSeq* _recent_prev_end_times_for_all_gcs_sec;
604 // We track markings.
605 int _num_markings;
606 double _mark_thread_startup_sec; // Time at startup of marking thread
608 // Add a new GC of the given duration and end time to the record.
609 void update_recent_gc_times(double end_time_sec, double elapsed_ms);
611 // The head of the list (via "next_in_collection_set()") representing the
612 // current collection set. Set from the incrementally built collection
613 // set at the start of the pause.
614 HeapRegion* _collection_set;
616 // The number of regions in the collection set. Set from the incrementally
617 // built collection set at the start of an evacuation pause.
618 size_t _collection_set_size;
620 // The number of bytes in the collection set before the pause. Set from
621 // the incrementally built collection set at the start of an evacuation
622 // pause.
623 size_t _collection_set_bytes_used_before;
625 // The associated information that is maintained while the incremental
626 // collection set is being built with young regions. Used to populate
627 // the recorded info for the evacuation pause.
629 enum CSetBuildType {
630 Active, // We are actively building the collection set
631 Inactive // We are not actively building the collection set
632 };
634 CSetBuildType _inc_cset_build_state;
636 // The head of the incrementally built collection set.
637 HeapRegion* _inc_cset_head;
639 // The tail of the incrementally built collection set.
640 HeapRegion* _inc_cset_tail;
642 // The number of regions in the incrementally built collection set.
643 // Used to set _collection_set_size at the start of an evacuation
644 // pause.
645 size_t _inc_cset_size;
647 // Used as the index in the surving young words structure
648 // which tracks the amount of space, for each young region,
649 // that survives the pause.
650 size_t _inc_cset_young_index;
652 // The number of bytes in the incrementally built collection set.
653 // Used to set _collection_set_bytes_used_before at the start of
654 // an evacuation pause.
655 size_t _inc_cset_bytes_used_before;
657 // Used to record the highest end of heap region in collection set
658 HeapWord* _inc_cset_max_finger;
660 // The number of recorded used bytes in the young regions
661 // of the collection set. This is the sum of the used() bytes
662 // of retired young regions in the collection set.
663 size_t _inc_cset_recorded_young_bytes;
665 // The RSet lengths recorded for regions in the collection set
666 // (updated by the periodic sampling of the regions in the
667 // young list/collection set).
668 size_t _inc_cset_recorded_rs_lengths;
670 // The predicted elapsed time it will take to collect the regions
671 // in the collection set (updated by the periodic sampling of the
672 // regions in the young list/collection set).
673 double _inc_cset_predicted_elapsed_time_ms;
675 // The predicted bytes to copy for the regions in the collection
676 // set (updated by the periodic sampling of the regions in the
677 // young list/collection set).
678 size_t _inc_cset_predicted_bytes_to_copy;
680 // Info about marking.
681 int _n_marks; // Sticky at 2, so we know when we've done at least 2.
683 // The number of collection pauses at the end of the last mark.
684 size_t _n_pauses_at_mark_end;
686 // Stash a pointer to the g1 heap.
687 G1CollectedHeap* _g1;
689 // The average time in ms per collection pause, averaged over recent pauses.
690 double recent_avg_time_for_pauses_ms();
692 // The average time in ms for processing CollectedHeap strong roots, per
693 // collection pause, averaged over recent pauses.
694 double recent_avg_time_for_CH_strong_ms();
696 // The average time in ms for processing the G1 remembered set, per
697 // pause, averaged over recent pauses.
698 double recent_avg_time_for_G1_strong_ms();
700 // The average time in ms for "evacuating followers", per pause, averaged
701 // over recent pauses.
702 double recent_avg_time_for_evac_ms();
704 // The number of "recent" GCs recorded in the number sequences
705 int number_of_recent_gcs();
707 // The average survival ratio, computed by the total number of bytes
708 // suriviving / total number of bytes before collection over the last
709 // several recent pauses.
710 double recent_avg_survival_fraction();
711 // The survival fraction of the most recent pause; if there have been no
712 // pauses, returns 1.0.
713 double last_survival_fraction();
715 // Returns a "conservative" estimate of the recent survival rate, i.e.,
716 // one that may be higher than "recent_avg_survival_fraction".
717 // This is conservative in several ways:
718 // If there have been few pauses, it will assume a potential high
719 // variance, and err on the side of caution.
720 // It puts a lower bound (currently 0.1) on the value it will return.
721 // To try to detect phase changes, if the most recent pause ("latest") has a
722 // higher-than average ("avg") survival rate, it returns that rate.
723 // "work" version is a utility function; young is restricted to young regions.
724 double conservative_avg_survival_fraction_work(double avg,
725 double latest);
727 // The arguments are the two sequences that keep track of the number of bytes
728 // surviving and the total number of bytes before collection, resp.,
729 // over the last evereal recent pauses
730 // Returns the survival rate for the category in the most recent pause.
731 // If there have been no pauses, returns 1.0.
732 double last_survival_fraction_work(TruncatedSeq* surviving,
733 TruncatedSeq* before);
735 // The arguments are the two sequences that keep track of the number of bytes
736 // surviving and the total number of bytes before collection, resp.,
737 // over the last several recent pauses
738 // Returns the average survival ration over the last several recent pauses
739 // If there have been no pauses, return 1.0
740 double recent_avg_survival_fraction_work(TruncatedSeq* surviving,
741 TruncatedSeq* before);
743 double conservative_avg_survival_fraction() {
744 double avg = recent_avg_survival_fraction();
745 double latest = last_survival_fraction();
746 return conservative_avg_survival_fraction_work(avg, latest);
747 }
749 // The ratio of gc time to elapsed time, computed over recent pauses.
750 double _recent_avg_pause_time_ratio;
752 double recent_avg_pause_time_ratio() {
753 return _recent_avg_pause_time_ratio;
754 }
756 // Number of pauses between concurrent marking.
757 size_t _pauses_btwn_concurrent_mark;
759 size_t _n_marks_since_last_pause;
761 // At the end of a pause we check the heap occupancy and we decide
762 // whether we will start a marking cycle during the next pause. If
763 // we decide that we want to do that, we will set this parameter to
764 // true. So, this parameter will stay true between the end of a
765 // pause and the beginning of a subsequent pause (not necessarily
766 // the next one, see the comments on the next field) when we decide
767 // that we will indeed start a marking cycle and do the initial-mark
768 // work.
769 volatile bool _initiate_conc_mark_if_possible;
771 // If initiate_conc_mark_if_possible() is set at the beginning of a
772 // pause, it is a suggestion that the pause should start a marking
773 // cycle by doing the initial-mark work. However, it is possible
774 // that the concurrent marking thread is still finishing up the
775 // previous marking cycle (e.g., clearing the next marking
776 // bitmap). If that is the case we cannot start a new cycle and
777 // we'll have to wait for the concurrent marking thread to finish
778 // what it is doing. In this case we will postpone the marking cycle
779 // initiation decision for the next pause. When we eventually decide
780 // to start a cycle, we will set _during_initial_mark_pause which
781 // will stay true until the end of the initial-mark pause and it's
782 // the condition that indicates that a pause is doing the
783 // initial-mark work.
784 volatile bool _during_initial_mark_pause;
786 bool _should_revert_to_full_young_gcs;
787 bool _last_full_young_gc;
789 // This set of variables tracks the collector efficiency, in order to
790 // determine whether we should initiate a new marking.
791 double _cur_mark_stop_world_time_ms;
792 double _mark_init_start_sec;
793 double _mark_remark_start_sec;
794 double _mark_cleanup_start_sec;
795 double _mark_closure_time_ms;
797 void calculate_young_list_min_length();
798 void calculate_young_list_target_length();
799 void calculate_young_list_target_length(size_t rs_lengths);
801 public:
803 G1CollectorPolicy();
805 virtual G1CollectorPolicy* as_g1_policy() { return this; }
807 virtual CollectorPolicy::Name kind() {
808 return CollectorPolicy::G1CollectorPolicyKind;
809 }
811 void check_prediction_validity();
813 size_t bytes_in_collection_set() {
814 return _bytes_in_collection_set_before_gc;
815 }
817 size_t bytes_in_to_space() {
818 return bytes_in_to_space_during_gc();
819 }
821 unsigned calc_gc_alloc_time_stamp() {
822 return _all_pause_times_ms->num() + 1;
823 }
825 protected:
827 // Count the number of bytes used in the CS.
828 void count_CS_bytes_used();
830 // Together these do the base cleanup-recording work. Subclasses might
831 // want to put something between them.
832 void record_concurrent_mark_cleanup_end_work1(size_t freed_bytes,
833 size_t max_live_bytes);
834 void record_concurrent_mark_cleanup_end_work2();
836 public:
838 virtual void init();
840 // Create jstat counters for the policy.
841 virtual void initialize_gc_policy_counters();
843 virtual HeapWord* mem_allocate_work(size_t size,
844 bool is_tlab,
845 bool* gc_overhead_limit_was_exceeded);
847 // This method controls how a collector handles one or more
848 // of its generations being fully allocated.
849 virtual HeapWord* satisfy_failed_allocation(size_t size,
850 bool is_tlab);
852 BarrierSet::Name barrier_set_name() { return BarrierSet::G1SATBCTLogging; }
854 GenRemSet::Name rem_set_name() { return GenRemSet::CardTable; }
856 // The number of collection pauses so far.
857 long n_pauses() const { return _n_pauses; }
859 // Update the heuristic info to record a collection pause of the given
860 // start time, where the given number of bytes were used at the start.
861 // This may involve changing the desired size of a collection set.
863 virtual void record_stop_world_start();
865 virtual void record_collection_pause_start(double start_time_sec,
866 size_t start_used);
868 // Must currently be called while the world is stopped.
869 virtual void record_concurrent_mark_init_start();
870 virtual void record_concurrent_mark_init_end();
871 void record_concurrent_mark_init_end_pre(double
872 mark_init_elapsed_time_ms);
874 void record_mark_closure_time(double mark_closure_time_ms);
876 virtual void record_concurrent_mark_remark_start();
877 virtual void record_concurrent_mark_remark_end();
879 virtual void record_concurrent_mark_cleanup_start();
880 virtual void record_concurrent_mark_cleanup_end(size_t freed_bytes,
881 size_t max_live_bytes);
882 virtual void record_concurrent_mark_cleanup_completed();
884 virtual void record_concurrent_pause();
885 virtual void record_concurrent_pause_end();
887 virtual void record_collection_pause_end_CH_strong_roots();
888 virtual void record_collection_pause_end_G1_strong_roots();
890 virtual void record_collection_pause_end(bool abandoned);
892 // Record the fact that a full collection occurred.
893 virtual void record_full_collection_start();
894 virtual void record_full_collection_end();
896 void record_gc_worker_start_time(int worker_i, double ms) {
897 _par_last_gc_worker_start_times_ms[worker_i] = ms;
898 }
900 void record_ext_root_scan_time(int worker_i, double ms) {
901 _par_last_ext_root_scan_times_ms[worker_i] = ms;
902 }
904 void record_mark_stack_scan_time(int worker_i, double ms) {
905 _par_last_mark_stack_scan_times_ms[worker_i] = ms;
906 }
908 void record_satb_drain_time(double ms) {
909 _cur_satb_drain_time_ms = ms;
910 _satb_drain_time_set = true;
911 }
913 void record_satb_drain_processed_buffers (int processed_buffers) {
914 _last_satb_drain_processed_buffers = processed_buffers;
915 }
917 void record_mod_union_time(double ms) {
918 _all_mod_union_times_ms->add(ms);
919 }
921 void record_update_rs_time(int thread, double ms) {
922 _par_last_update_rs_times_ms[thread] = ms;
923 }
925 void record_update_rs_processed_buffers (int thread,
926 double processed_buffers) {
927 _par_last_update_rs_processed_buffers[thread] = processed_buffers;
928 }
930 void record_scan_rs_time(int thread, double ms) {
931 _par_last_scan_rs_times_ms[thread] = ms;
932 }
934 void record_scan_new_refs_time(int thread, double ms) {
935 _par_last_scan_new_refs_times_ms[thread] = ms;
936 }
938 double get_scan_new_refs_time(int thread) {
939 return _par_last_scan_new_refs_times_ms[thread];
940 }
942 void reset_obj_copy_time(int thread) {
943 _par_last_obj_copy_times_ms[thread] = 0.0;
944 }
946 void reset_obj_copy_time() {
947 reset_obj_copy_time(0);
948 }
950 void record_obj_copy_time(int thread, double ms) {
951 _par_last_obj_copy_times_ms[thread] += ms;
952 }
954 void record_termination(int thread, double ms, size_t attempts) {
955 _par_last_termination_times_ms[thread] = ms;
956 _par_last_termination_attempts[thread] = (double) attempts;
957 }
959 void record_gc_worker_end_time(int worker_i, double ms) {
960 _par_last_gc_worker_end_times_ms[worker_i] = ms;
961 }
963 void record_pause_time_ms(double ms) {
964 _last_pause_time_ms = ms;
965 }
967 void record_clear_ct_time(double ms) {
968 _cur_clear_ct_time_ms = ms;
969 }
971 void record_par_time(double ms) {
972 _cur_collection_par_time_ms = ms;
973 }
975 void record_aux_start_time(int i) {
976 guarantee(i < _aux_num, "should be within range");
977 _cur_aux_start_times_ms[i] = os::elapsedTime() * 1000.0;
978 }
980 void record_aux_end_time(int i) {
981 guarantee(i < _aux_num, "should be within range");
982 double ms = os::elapsedTime() * 1000.0 - _cur_aux_start_times_ms[i];
983 _cur_aux_times_set[i] = true;
984 _cur_aux_times_ms[i] += ms;
985 }
987 #ifndef PRODUCT
988 void record_cc_clear_time(double ms) {
989 if (_min_clear_cc_time_ms < 0.0 || ms <= _min_clear_cc_time_ms)
990 _min_clear_cc_time_ms = ms;
991 if (_max_clear_cc_time_ms < 0.0 || ms >= _max_clear_cc_time_ms)
992 _max_clear_cc_time_ms = ms;
993 _cur_clear_cc_time_ms = ms;
994 _cum_clear_cc_time_ms += ms;
995 _num_cc_clears++;
996 }
997 #endif
999 // Record the fact that "bytes" bytes allocated in a region.
1000 void record_before_bytes(size_t bytes);
1001 void record_after_bytes(size_t bytes);
1003 // Returns "true" if this is a good time to do a collection pause.
1004 // The "word_size" argument, if non-zero, indicates the size of an
1005 // allocation request that is prompting this query.
1006 virtual bool should_do_collection_pause(size_t word_size) = 0;
1008 // Choose a new collection set. Marks the chosen regions as being
1009 // "in_collection_set", and links them together. The head and number of
1010 // the collection set are available via access methods.
1011 virtual bool choose_collection_set() = 0;
1013 // The head of the list (via "next_in_collection_set()") representing the
1014 // current collection set.
1015 HeapRegion* collection_set() { return _collection_set; }
1017 void clear_collection_set() { _collection_set = NULL; }
1019 // The number of elements in the current collection set.
1020 size_t collection_set_size() { return _collection_set_size; }
1022 // Add "hr" to the CS.
1023 void add_to_collection_set(HeapRegion* hr);
1025 // Incremental CSet Support
1027 // The head of the incrementally built collection set.
1028 HeapRegion* inc_cset_head() { return _inc_cset_head; }
1030 // The tail of the incrementally built collection set.
1031 HeapRegion* inc_set_tail() { return _inc_cset_tail; }
1033 // The number of elements in the incrementally built collection set.
1034 size_t inc_cset_size() { return _inc_cset_size; }
1036 // Initialize incremental collection set info.
1037 void start_incremental_cset_building();
1039 void clear_incremental_cset() {
1040 _inc_cset_head = NULL;
1041 _inc_cset_tail = NULL;
1042 }
1044 // Stop adding regions to the incremental collection set
1045 void stop_incremental_cset_building() { _inc_cset_build_state = Inactive; }
1047 // Add/remove information about hr to the aggregated information
1048 // for the incrementally built collection set.
1049 void add_to_incremental_cset_info(HeapRegion* hr, size_t rs_length);
1050 void remove_from_incremental_cset_info(HeapRegion* hr);
1052 // Update information about hr in the aggregated information for
1053 // the incrementally built collection set.
1054 void update_incremental_cset_info(HeapRegion* hr, size_t new_rs_length);
1056 private:
1057 // Update the incremental cset information when adding a region
1058 // (should not be called directly).
1059 void add_region_to_incremental_cset_common(HeapRegion* hr);
1061 public:
1062 // Add hr to the LHS of the incremental collection set.
1063 void add_region_to_incremental_cset_lhs(HeapRegion* hr);
1065 // Add hr to the RHS of the incremental collection set.
1066 void add_region_to_incremental_cset_rhs(HeapRegion* hr);
1068 #ifndef PRODUCT
1069 void print_collection_set(HeapRegion* list_head, outputStream* st);
1070 #endif // !PRODUCT
1072 bool initiate_conc_mark_if_possible() { return _initiate_conc_mark_if_possible; }
1073 void set_initiate_conc_mark_if_possible() { _initiate_conc_mark_if_possible = true; }
1074 void clear_initiate_conc_mark_if_possible() { _initiate_conc_mark_if_possible = false; }
1076 bool during_initial_mark_pause() { return _during_initial_mark_pause; }
1077 void set_during_initial_mark_pause() { _during_initial_mark_pause = true; }
1078 void clear_during_initial_mark_pause(){ _during_initial_mark_pause = false; }
1080 // This is called at the very beginning of an evacuation pause (it
1081 // has to be the first thing that the pause does). If
1082 // initiate_conc_mark_if_possible() is true, and the concurrent
1083 // marking thread has completed its work during the previous cycle,
1084 // it will set during_initial_mark_pause() to so that the pause does
1085 // the initial-mark work and start a marking cycle.
1086 void decide_on_conc_mark_initiation();
1088 // If an expansion would be appropriate, because recent GC overhead had
1089 // exceeded the desired limit, return an amount to expand by.
1090 virtual size_t expansion_amount();
1092 // note start of mark thread
1093 void note_start_of_mark_thread();
1095 // The marked bytes of the "r" has changed; reclassify it's desirability
1096 // for marking. Also asserts that "r" is eligible for a CS.
1097 virtual void note_change_in_marked_bytes(HeapRegion* r) = 0;
1099 #ifndef PRODUCT
1100 // Check any appropriate marked bytes info, asserting false if
1101 // something's wrong, else returning "true".
1102 virtual bool assertMarkedBytesDataOK() = 0;
1103 #endif
1105 // Print tracing information.
1106 void print_tracing_info() const;
1108 // Print stats on young survival ratio
1109 void print_yg_surv_rate_info() const;
1111 void finished_recalculating_age_indexes(bool is_survivors) {
1112 if (is_survivors) {
1113 _survivor_surv_rate_group->finished_recalculating_age_indexes();
1114 } else {
1115 _short_lived_surv_rate_group->finished_recalculating_age_indexes();
1116 }
1117 // do that for any other surv rate groups
1118 }
1120 bool should_add_next_region_to_young_list();
1122 bool in_young_gc_mode() {
1123 return _in_young_gc_mode;
1124 }
1125 void set_in_young_gc_mode(bool in_young_gc_mode) {
1126 _in_young_gc_mode = in_young_gc_mode;
1127 }
1129 bool full_young_gcs() {
1130 return _full_young_gcs;
1131 }
1132 void set_full_young_gcs(bool full_young_gcs) {
1133 _full_young_gcs = full_young_gcs;
1134 }
1136 bool adaptive_young_list_length() {
1137 return _adaptive_young_list_length;
1138 }
1139 void set_adaptive_young_list_length(bool adaptive_young_list_length) {
1140 _adaptive_young_list_length = adaptive_young_list_length;
1141 }
1143 inline double get_gc_eff_factor() {
1144 double ratio = _known_garbage_ratio;
1146 double square = ratio * ratio;
1147 // square = square * square;
1148 double ret = square * 9.0 + 1.0;
1149 #if 0
1150 gclog_or_tty->print_cr("ratio = %1.2lf, ret = %1.2lf", ratio, ret);
1151 #endif // 0
1152 guarantee(0.0 <= ret && ret < 10.0, "invariant!");
1153 return ret;
1154 }
1156 //
1157 // Survivor regions policy.
1158 //
1159 protected:
1161 // Current tenuring threshold, set to 0 if the collector reaches the
1162 // maximum amount of suvivors regions.
1163 int _tenuring_threshold;
1165 // The limit on the number of regions allocated for survivors.
1166 size_t _max_survivor_regions;
1168 // The amount of survor regions after a collection.
1169 size_t _recorded_survivor_regions;
1170 // List of survivor regions.
1171 HeapRegion* _recorded_survivor_head;
1172 HeapRegion* _recorded_survivor_tail;
1174 ageTable _survivors_age_table;
1176 public:
1178 inline GCAllocPurpose
1179 evacuation_destination(HeapRegion* src_region, int age, size_t word_sz) {
1180 if (age < _tenuring_threshold && src_region->is_young()) {
1181 return GCAllocForSurvived;
1182 } else {
1183 return GCAllocForTenured;
1184 }
1185 }
1187 inline bool track_object_age(GCAllocPurpose purpose) {
1188 return purpose == GCAllocForSurvived;
1189 }
1191 inline GCAllocPurpose alternative_purpose(int purpose) {
1192 return GCAllocForTenured;
1193 }
1195 static const size_t REGIONS_UNLIMITED = ~(size_t)0;
1197 size_t max_regions(int purpose);
1199 // The limit on regions for a particular purpose is reached.
1200 void note_alloc_region_limit_reached(int purpose) {
1201 if (purpose == GCAllocForSurvived) {
1202 _tenuring_threshold = 0;
1203 }
1204 }
1206 void note_start_adding_survivor_regions() {
1207 _survivor_surv_rate_group->start_adding_regions();
1208 }
1210 void note_stop_adding_survivor_regions() {
1211 _survivor_surv_rate_group->stop_adding_regions();
1212 }
1214 void record_survivor_regions(size_t regions,
1215 HeapRegion* head,
1216 HeapRegion* tail) {
1217 _recorded_survivor_regions = regions;
1218 _recorded_survivor_head = head;
1219 _recorded_survivor_tail = tail;
1220 }
1222 size_t recorded_survivor_regions() {
1223 return _recorded_survivor_regions;
1224 }
1226 void record_thread_age_table(ageTable* age_table)
1227 {
1228 _survivors_age_table.merge_par(age_table);
1229 }
1231 // Calculates survivor space parameters.
1232 void calculate_survivors_policy();
1234 };
1236 // This encapsulates a particular strategy for a g1 Collector.
1237 //
1238 // Start a concurrent mark when our heap size is n bytes
1239 // greater then our heap size was at the last concurrent
1240 // mark. Where n is a function of the CMSTriggerRatio
1241 // and the MinHeapFreeRatio.
1242 //
1243 // Start a g1 collection pause when we have allocated the
1244 // average number of bytes currently being freed in
1245 // a collection, but only if it is at least one region
1246 // full
1247 //
1248 // Resize Heap based on desired
1249 // allocation space, where desired allocation space is
1250 // a function of survival rate and desired future to size.
1251 //
1252 // Choose collection set by first picking all older regions
1253 // which have a survival rate which beats our projected young
1254 // survival rate. Then fill out the number of needed regions
1255 // with young regions.
1257 class G1CollectorPolicy_BestRegionsFirst: public G1CollectorPolicy {
1258 CollectionSetChooser* _collectionSetChooser;
1259 // If the estimated is less then desirable, resize if possible.
1260 void expand_if_possible(size_t numRegions);
1262 virtual bool choose_collection_set();
1263 virtual void record_collection_pause_start(double start_time_sec,
1264 size_t start_used);
1265 virtual void record_concurrent_mark_cleanup_end(size_t freed_bytes,
1266 size_t max_live_bytes);
1267 virtual void record_full_collection_end();
1269 public:
1270 G1CollectorPolicy_BestRegionsFirst() {
1271 _collectionSetChooser = new CollectionSetChooser();
1272 }
1273 void record_collection_pause_end(bool abandoned);
1274 bool should_do_collection_pause(size_t word_size);
1275 // This is not needed any more, after the CSet choosing code was
1276 // changed to use the pause prediction work. But let's leave the
1277 // hook in just in case.
1278 void note_change_in_marked_bytes(HeapRegion* r) { }
1279 #ifndef PRODUCT
1280 bool assertMarkedBytesDataOK();
1281 #endif
1282 };
1284 // This should move to some place more general...
1286 // If we have "n" measurements, and we've kept track of their "sum" and the
1287 // "sum_of_squares" of the measurements, this returns the variance of the
1288 // sequence.
1289 inline double variance(int n, double sum_of_squares, double sum) {
1290 double n_d = (double)n;
1291 double avg = sum/n_d;
1292 return (sum_of_squares - 2.0 * avg * sum + n_d * avg * avg) / n_d;
1293 }
1295 // Local Variables: ***
1296 // c-indentation-style: gnu ***
1297 // End: ***