Tue, 20 Sep 2011 09:59:59 -0400
7059019: G1: add G1 support to the SA
Summary: Extend the SA to recognize the G1CollectedHeap and implement any code that's needed by our serviceability tools (jmap, jinfo, jstack, etc.) that depend on the SA.
Reviewed-by: never, poonam, johnc
1 /*
2 * Copyright (c) 2001, 2011, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
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23 */
25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP
28 #include "gc_implementation/g1/collectionSetChooser.hpp"
29 #include "gc_implementation/g1/g1MMUTracker.hpp"
30 #include "memory/collectorPolicy.hpp"
32 // A G1CollectorPolicy makes policy decisions that determine the
33 // characteristics of the collector. Examples include:
34 // * choice of collection set.
35 // * when to collect.
37 class HeapRegion;
38 class CollectionSetChooser;
40 // Yes, this is a bit unpleasant... but it saves replicating the same thing
41 // over and over again and introducing subtle problems through small typos and
42 // cutting and pasting mistakes. The macros below introduces a number
43 // sequnce into the following two classes and the methods that access it.
45 #define define_num_seq(name) \
46 private: \
47 NumberSeq _all_##name##_times_ms; \
48 public: \
49 void record_##name##_time_ms(double ms) { \
50 _all_##name##_times_ms.add(ms); \
51 } \
52 NumberSeq* get_##name##_seq() { \
53 return &_all_##name##_times_ms; \
54 }
56 class MainBodySummary;
58 class PauseSummary: public CHeapObj {
59 define_num_seq(total)
60 define_num_seq(other)
62 public:
63 virtual MainBodySummary* main_body_summary() { return NULL; }
64 };
66 class MainBodySummary: public CHeapObj {
67 define_num_seq(satb_drain) // optional
68 define_num_seq(parallel) // parallel only
69 define_num_seq(ext_root_scan)
70 define_num_seq(mark_stack_scan)
71 define_num_seq(update_rs)
72 define_num_seq(scan_rs)
73 define_num_seq(obj_copy)
74 define_num_seq(termination) // parallel only
75 define_num_seq(parallel_other) // parallel only
76 define_num_seq(mark_closure)
77 define_num_seq(clear_ct) // parallel only
78 };
80 class Summary: public PauseSummary,
81 public MainBodySummary {
82 public:
83 virtual MainBodySummary* main_body_summary() { return this; }
84 };
86 class G1CollectorPolicy: public CollectorPolicy {
87 protected:
88 // The number of pauses during the execution.
89 long _n_pauses;
91 // either equal to the number of parallel threads, if ParallelGCThreads
92 // has been set, or 1 otherwise
93 int _parallel_gc_threads;
95 enum SomePrivateConstants {
96 NumPrevPausesForHeuristics = 10
97 };
99 G1MMUTracker* _mmu_tracker;
101 void initialize_flags();
103 void initialize_all() {
104 initialize_flags();
105 initialize_size_info();
106 initialize_perm_generation(PermGen::MarkSweepCompact);
107 }
109 virtual size_t default_init_heap_size() {
110 // Pick some reasonable default.
111 return 8*M;
112 }
114 double _cur_collection_start_sec;
115 size_t _cur_collection_pause_used_at_start_bytes;
116 size_t _cur_collection_pause_used_regions_at_start;
117 size_t _prev_collection_pause_used_at_end_bytes;
118 double _cur_collection_par_time_ms;
119 double _cur_satb_drain_time_ms;
120 double _cur_clear_ct_time_ms;
121 bool _satb_drain_time_set;
123 #ifndef PRODUCT
124 // Card Table Count Cache stats
125 double _min_clear_cc_time_ms; // min
126 double _max_clear_cc_time_ms; // max
127 double _cur_clear_cc_time_ms; // clearing time during current pause
128 double _cum_clear_cc_time_ms; // cummulative clearing time
129 jlong _num_cc_clears; // number of times the card count cache has been cleared
130 #endif
132 // Statistics for recent GC pauses. See below for how indexed.
133 TruncatedSeq* _recent_rs_scan_times_ms;
135 // These exclude marking times.
136 TruncatedSeq* _recent_pause_times_ms;
137 TruncatedSeq* _recent_gc_times_ms;
139 TruncatedSeq* _recent_CS_bytes_used_before;
140 TruncatedSeq* _recent_CS_bytes_surviving;
142 TruncatedSeq* _recent_rs_sizes;
144 TruncatedSeq* _concurrent_mark_remark_times_ms;
145 TruncatedSeq* _concurrent_mark_cleanup_times_ms;
147 Summary* _summary;
149 NumberSeq* _all_pause_times_ms;
150 NumberSeq* _all_full_gc_times_ms;
151 double _stop_world_start;
152 NumberSeq* _all_stop_world_times_ms;
153 NumberSeq* _all_yield_times_ms;
155 size_t _region_num_young;
156 size_t _region_num_tenured;
157 size_t _prev_region_num_young;
158 size_t _prev_region_num_tenured;
160 NumberSeq* _all_mod_union_times_ms;
162 int _aux_num;
163 NumberSeq* _all_aux_times_ms;
164 double* _cur_aux_start_times_ms;
165 double* _cur_aux_times_ms;
166 bool* _cur_aux_times_set;
168 double* _par_last_gc_worker_start_times_ms;
169 double* _par_last_ext_root_scan_times_ms;
170 double* _par_last_mark_stack_scan_times_ms;
171 double* _par_last_update_rs_times_ms;
172 double* _par_last_update_rs_processed_buffers;
173 double* _par_last_scan_rs_times_ms;
174 double* _par_last_obj_copy_times_ms;
175 double* _par_last_termination_times_ms;
176 double* _par_last_termination_attempts;
177 double* _par_last_gc_worker_end_times_ms;
178 double* _par_last_gc_worker_times_ms;
180 // indicates whether we are in full young or partially young GC mode
181 bool _full_young_gcs;
183 // if true, then it tries to dynamically adjust the length of the
184 // young list
185 bool _adaptive_young_list_length;
186 size_t _young_list_target_length;
187 size_t _young_list_fixed_length;
188 size_t _prev_eden_capacity; // used for logging
190 // The max number of regions we can extend the eden by while the GC
191 // locker is active. This should be >= _young_list_target_length;
192 size_t _young_list_max_length;
194 size_t _young_cset_length;
195 bool _last_young_gc_full;
197 unsigned _full_young_pause_num;
198 unsigned _partial_young_pause_num;
200 bool _during_marking;
201 bool _in_marking_window;
202 bool _in_marking_window_im;
204 SurvRateGroup* _short_lived_surv_rate_group;
205 SurvRateGroup* _survivor_surv_rate_group;
206 // add here any more surv rate groups
208 double _gc_overhead_perc;
210 double _reserve_factor;
211 size_t _reserve_regions;
213 bool during_marking() {
214 return _during_marking;
215 }
217 // <NEW PREDICTION>
219 private:
220 enum PredictionConstants {
221 TruncatedSeqLength = 10
222 };
224 TruncatedSeq* _alloc_rate_ms_seq;
225 double _prev_collection_pause_end_ms;
227 TruncatedSeq* _pending_card_diff_seq;
228 TruncatedSeq* _rs_length_diff_seq;
229 TruncatedSeq* _cost_per_card_ms_seq;
230 TruncatedSeq* _fully_young_cards_per_entry_ratio_seq;
231 TruncatedSeq* _partially_young_cards_per_entry_ratio_seq;
232 TruncatedSeq* _cost_per_entry_ms_seq;
233 TruncatedSeq* _partially_young_cost_per_entry_ms_seq;
234 TruncatedSeq* _cost_per_byte_ms_seq;
235 TruncatedSeq* _constant_other_time_ms_seq;
236 TruncatedSeq* _young_other_cost_per_region_ms_seq;
237 TruncatedSeq* _non_young_other_cost_per_region_ms_seq;
239 TruncatedSeq* _pending_cards_seq;
240 TruncatedSeq* _scanned_cards_seq;
241 TruncatedSeq* _rs_lengths_seq;
243 TruncatedSeq* _cost_per_byte_ms_during_cm_seq;
245 TruncatedSeq* _young_gc_eff_seq;
247 TruncatedSeq* _max_conc_overhead_seq;
249 bool _using_new_ratio_calculations;
250 size_t _min_desired_young_length; // as set on the command line or default calculations
251 size_t _max_desired_young_length; // as set on the command line or default calculations
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 void start_recording_regions();
467 void record_cset_region_info(HeapRegion* hr, bool young);
468 void record_non_young_cset_region(HeapRegion* hr);
470 void set_recorded_young_regions(size_t n_regions);
471 void set_recorded_young_bytes(size_t bytes);
472 void set_recorded_rs_lengths(size_t rs_lengths);
473 void set_predicted_bytes_to_copy(size_t bytes);
475 void end_recording_regions();
477 void record_vtime_diff_ms(double vtime_diff_ms) {
478 _vtime_diff_ms = vtime_diff_ms;
479 }
481 void record_young_free_cset_time_ms(double time_ms) {
482 _recorded_young_free_cset_time_ms = time_ms;
483 }
485 void record_non_young_free_cset_time_ms(double time_ms) {
486 _recorded_non_young_free_cset_time_ms = time_ms;
487 }
489 double predict_young_gc_eff() {
490 return get_new_neg_prediction(_young_gc_eff_seq);
491 }
493 double predict_survivor_regions_evac_time();
495 // </NEW PREDICTION>
497 void cset_regions_freed() {
498 bool propagate = _last_young_gc_full && !_in_marking_window;
499 _short_lived_surv_rate_group->all_surviving_words_recorded(propagate);
500 _survivor_surv_rate_group->all_surviving_words_recorded(propagate);
501 // also call it on any more surv rate groups
502 }
504 void set_known_garbage_bytes(size_t known_garbage_bytes) {
505 _known_garbage_bytes = known_garbage_bytes;
506 size_t heap_bytes = _g1->capacity();
507 _known_garbage_ratio = (double) _known_garbage_bytes / (double) heap_bytes;
508 }
510 void decrease_known_garbage_bytes(size_t known_garbage_bytes) {
511 guarantee( _known_garbage_bytes >= known_garbage_bytes, "invariant" );
513 _known_garbage_bytes -= known_garbage_bytes;
514 size_t heap_bytes = _g1->capacity();
515 _known_garbage_ratio = (double) _known_garbage_bytes / (double) heap_bytes;
516 }
518 G1MMUTracker* mmu_tracker() {
519 return _mmu_tracker;
520 }
522 double max_pause_time_ms() {
523 return _mmu_tracker->max_gc_time() * 1000.0;
524 }
526 double predict_remark_time_ms() {
527 return get_new_prediction(_concurrent_mark_remark_times_ms);
528 }
530 double predict_cleanup_time_ms() {
531 return get_new_prediction(_concurrent_mark_cleanup_times_ms);
532 }
534 // Returns an estimate of the survival rate of the region at yg-age
535 // "yg_age".
536 double predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) {
537 TruncatedSeq* seq = surv_rate_group->get_seq(age);
538 if (seq->num() == 0)
539 gclog_or_tty->print("BARF! age is %d", age);
540 guarantee( seq->num() > 0, "invariant" );
541 double pred = get_new_prediction(seq);
542 if (pred > 1.0)
543 pred = 1.0;
544 return pred;
545 }
547 double predict_yg_surv_rate(int age) {
548 return predict_yg_surv_rate(age, _short_lived_surv_rate_group);
549 }
551 double accum_yg_surv_rate_pred(int age) {
552 return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
553 }
555 protected:
556 void print_stats(int level, const char* str, double value);
557 void print_stats(int level, const char* str, int value);
559 void print_par_stats(int level, const char* str, double* data);
560 void print_par_sizes(int level, const char* str, double* data);
562 void check_other_times(int level,
563 NumberSeq* other_times_ms,
564 NumberSeq* calc_other_times_ms) const;
566 void print_summary (PauseSummary* stats) const;
568 void print_summary (int level, const char* str, NumberSeq* seq) const;
569 void print_summary_sd (int level, const char* str, NumberSeq* seq) const;
571 double avg_value (double* data);
572 double max_value (double* data);
573 double sum_of_values (double* data);
574 double max_sum (double* data1, double* data2);
576 int _last_satb_drain_processed_buffers;
577 int _last_update_rs_processed_buffers;
578 double _last_pause_time_ms;
580 size_t _bytes_in_collection_set_before_gc;
581 size_t _bytes_copied_during_gc;
583 // Used to count used bytes in CS.
584 friend class CountCSClosure;
586 // Statistics kept per GC stoppage, pause or full.
587 TruncatedSeq* _recent_prev_end_times_for_all_gcs_sec;
589 // We track markings.
590 int _num_markings;
591 double _mark_thread_startup_sec; // Time at startup of marking thread
593 // Add a new GC of the given duration and end time to the record.
594 void update_recent_gc_times(double end_time_sec, double elapsed_ms);
596 // The head of the list (via "next_in_collection_set()") representing the
597 // current collection set. Set from the incrementally built collection
598 // set at the start of the pause.
599 HeapRegion* _collection_set;
601 // The number of regions in the collection set. Set from the incrementally
602 // built collection set at the start of an evacuation pause.
603 size_t _collection_set_size;
605 // The number of bytes in the collection set before the pause. Set from
606 // the incrementally built collection set at the start of an evacuation
607 // pause.
608 size_t _collection_set_bytes_used_before;
610 // The associated information that is maintained while the incremental
611 // collection set is being built with young regions. Used to populate
612 // the recorded info for the evacuation pause.
614 enum CSetBuildType {
615 Active, // We are actively building the collection set
616 Inactive // We are not actively building the collection set
617 };
619 CSetBuildType _inc_cset_build_state;
621 // The head of the incrementally built collection set.
622 HeapRegion* _inc_cset_head;
624 // The tail of the incrementally built collection set.
625 HeapRegion* _inc_cset_tail;
627 // The number of regions in the incrementally built collection set.
628 // Used to set _collection_set_size at the start of an evacuation
629 // pause.
630 size_t _inc_cset_size;
632 // Used as the index in the surving young words structure
633 // which tracks the amount of space, for each young region,
634 // that survives the pause.
635 size_t _inc_cset_young_index;
637 // The number of bytes in the incrementally built collection set.
638 // Used to set _collection_set_bytes_used_before at the start of
639 // an evacuation pause.
640 size_t _inc_cset_bytes_used_before;
642 // Used to record the highest end of heap region in collection set
643 HeapWord* _inc_cset_max_finger;
645 // The number of recorded used bytes in the young regions
646 // of the collection set. This is the sum of the used() bytes
647 // of retired young regions in the collection set.
648 size_t _inc_cset_recorded_young_bytes;
650 // The RSet lengths recorded for regions in the collection set
651 // (updated by the periodic sampling of the regions in the
652 // young list/collection set).
653 size_t _inc_cset_recorded_rs_lengths;
655 // The predicted elapsed time it will take to collect the regions
656 // in the collection set (updated by the periodic sampling of the
657 // regions in the young list/collection set).
658 double _inc_cset_predicted_elapsed_time_ms;
660 // The predicted bytes to copy for the regions in the collection
661 // set (updated by the periodic sampling of the regions in the
662 // young list/collection set).
663 size_t _inc_cset_predicted_bytes_to_copy;
665 // Info about marking.
666 int _n_marks; // Sticky at 2, so we know when we've done at least 2.
668 // The number of collection pauses at the end of the last mark.
669 size_t _n_pauses_at_mark_end;
671 // Stash a pointer to the g1 heap.
672 G1CollectedHeap* _g1;
674 // The average time in ms per collection pause, averaged over recent pauses.
675 double recent_avg_time_for_pauses_ms();
677 // The average time in ms for RS scanning, per pause, averaged
678 // over recent pauses. (Note the RS scanning time for a pause
679 // is itself an average of the RS scanning time for each worker
680 // thread.)
681 double recent_avg_time_for_rs_scan_ms();
683 // The number of "recent" GCs recorded in the number sequences
684 int number_of_recent_gcs();
686 // The average survival ratio, computed by the total number of bytes
687 // suriviving / total number of bytes before collection over the last
688 // several recent pauses.
689 double recent_avg_survival_fraction();
690 // The survival fraction of the most recent pause; if there have been no
691 // pauses, returns 1.0.
692 double last_survival_fraction();
694 // Returns a "conservative" estimate of the recent survival rate, i.e.,
695 // one that may be higher than "recent_avg_survival_fraction".
696 // This is conservative in several ways:
697 // If there have been few pauses, it will assume a potential high
698 // variance, and err on the side of caution.
699 // It puts a lower bound (currently 0.1) on the value it will return.
700 // To try to detect phase changes, if the most recent pause ("latest") has a
701 // higher-than average ("avg") survival rate, it returns that rate.
702 // "work" version is a utility function; young is restricted to young regions.
703 double conservative_avg_survival_fraction_work(double avg,
704 double latest);
706 // The arguments are the two sequences that keep track of the number of bytes
707 // surviving and the total number of bytes before collection, resp.,
708 // over the last evereal recent pauses
709 // Returns the survival rate for the category in the most recent pause.
710 // If there have been no pauses, returns 1.0.
711 double last_survival_fraction_work(TruncatedSeq* surviving,
712 TruncatedSeq* before);
714 // The arguments are the two sequences that keep track of the number of bytes
715 // surviving and the total number of bytes before collection, resp.,
716 // over the last several recent pauses
717 // Returns the average survival ration over the last several recent pauses
718 // If there have been no pauses, return 1.0
719 double recent_avg_survival_fraction_work(TruncatedSeq* surviving,
720 TruncatedSeq* before);
722 double conservative_avg_survival_fraction() {
723 double avg = recent_avg_survival_fraction();
724 double latest = last_survival_fraction();
725 return conservative_avg_survival_fraction_work(avg, latest);
726 }
728 // The ratio of gc time to elapsed time, computed over recent pauses.
729 double _recent_avg_pause_time_ratio;
731 double recent_avg_pause_time_ratio() {
732 return _recent_avg_pause_time_ratio;
733 }
735 // Number of pauses between concurrent marking.
736 size_t _pauses_btwn_concurrent_mark;
738 size_t _n_marks_since_last_pause;
740 // At the end of a pause we check the heap occupancy and we decide
741 // whether we will start a marking cycle during the next pause. If
742 // we decide that we want to do that, we will set this parameter to
743 // true. So, this parameter will stay true between the end of a
744 // pause and the beginning of a subsequent pause (not necessarily
745 // the next one, see the comments on the next field) when we decide
746 // that we will indeed start a marking cycle and do the initial-mark
747 // work.
748 volatile bool _initiate_conc_mark_if_possible;
750 // If initiate_conc_mark_if_possible() is set at the beginning of a
751 // pause, it is a suggestion that the pause should start a marking
752 // cycle by doing the initial-mark work. However, it is possible
753 // that the concurrent marking thread is still finishing up the
754 // previous marking cycle (e.g., clearing the next marking
755 // bitmap). If that is the case we cannot start a new cycle and
756 // we'll have to wait for the concurrent marking thread to finish
757 // what it is doing. In this case we will postpone the marking cycle
758 // initiation decision for the next pause. When we eventually decide
759 // to start a cycle, we will set _during_initial_mark_pause which
760 // will stay true until the end of the initial-mark pause and it's
761 // the condition that indicates that a pause is doing the
762 // initial-mark work.
763 volatile bool _during_initial_mark_pause;
765 bool _should_revert_to_full_young_gcs;
766 bool _last_full_young_gc;
768 // This set of variables tracks the collector efficiency, in order to
769 // determine whether we should initiate a new marking.
770 double _cur_mark_stop_world_time_ms;
771 double _mark_remark_start_sec;
772 double _mark_cleanup_start_sec;
773 double _mark_closure_time_ms;
775 // Update the young list target length either by setting it to the
776 // desired fixed value or by calculating it using G1's pause
777 // prediction model. If no rs_lengths parameter is passed, predict
778 // the RS lengths using the prediction model, otherwise use the
779 // given rs_lengths as the prediction.
780 void update_young_list_target_length(size_t rs_lengths = (size_t) -1);
782 // Calculate and return the minimum desired young list target
783 // length. This is the minimum desired young list length according
784 // to the user's inputs.
785 size_t calculate_young_list_desired_min_length(size_t base_min_length);
787 // Calculate and return the maximum desired young list target
788 // length. This is the maximum desired young list length according
789 // to the user's inputs.
790 size_t calculate_young_list_desired_max_length();
792 // Calculate and return the maximum young list target length that
793 // can fit into the pause time goal. The parameters are: rs_lengths
794 // represent the prediction of how large the young RSet lengths will
795 // be, base_min_length is the alreay existing number of regions in
796 // the young list, min_length and max_length are the desired min and
797 // max young list length according to the user's inputs.
798 size_t calculate_young_list_target_length(size_t rs_lengths,
799 size_t base_min_length,
800 size_t desired_min_length,
801 size_t desired_max_length);
803 // Check whether a given young length (young_length) fits into the
804 // given target pause time and whether the prediction for the amount
805 // of objects to be copied for the given length will fit into the
806 // given free space (expressed by base_free_regions). It is used by
807 // calculate_young_list_target_length().
808 bool predict_will_fit(size_t young_length, double base_time_ms,
809 size_t base_free_regions, double target_pause_time_ms);
811 public:
813 G1CollectorPolicy();
815 virtual G1CollectorPolicy* as_g1_policy() { return this; }
817 virtual CollectorPolicy::Name kind() {
818 return CollectorPolicy::G1CollectorPolicyKind;
819 }
821 // Check the current value of the young list RSet lengths and
822 // compare it against the last prediction. If the current value is
823 // higher, recalculate the young list target length prediction.
824 void revise_young_list_target_length_if_necessary();
826 size_t bytes_in_collection_set() {
827 return _bytes_in_collection_set_before_gc;
828 }
830 unsigned calc_gc_alloc_time_stamp() {
831 return _all_pause_times_ms->num() + 1;
832 }
834 // This should be called after the heap is resized.
835 void record_new_heap_size(size_t new_number_of_regions);
837 protected:
839 // Count the number of bytes used in the CS.
840 void count_CS_bytes_used();
842 // Together these do the base cleanup-recording work. Subclasses might
843 // want to put something between them.
844 void record_concurrent_mark_cleanup_end_work1(size_t freed_bytes,
845 size_t max_live_bytes);
846 void record_concurrent_mark_cleanup_end_work2();
848 void update_young_list_size_using_newratio(size_t number_of_heap_regions);
850 public:
852 virtual void init();
854 // Create jstat counters for the policy.
855 virtual void initialize_gc_policy_counters();
857 virtual HeapWord* mem_allocate_work(size_t size,
858 bool is_tlab,
859 bool* gc_overhead_limit_was_exceeded);
861 // This method controls how a collector handles one or more
862 // of its generations being fully allocated.
863 virtual HeapWord* satisfy_failed_allocation(size_t size,
864 bool is_tlab);
866 BarrierSet::Name barrier_set_name() { return BarrierSet::G1SATBCTLogging; }
868 GenRemSet::Name rem_set_name() { return GenRemSet::CardTable; }
870 // The number of collection pauses so far.
871 long n_pauses() const { return _n_pauses; }
873 // Update the heuristic info to record a collection pause of the given
874 // start time, where the given number of bytes were used at the start.
875 // This may involve changing the desired size of a collection set.
877 virtual void record_stop_world_start();
879 virtual void record_collection_pause_start(double start_time_sec,
880 size_t start_used);
882 // Must currently be called while the world is stopped.
883 void record_concurrent_mark_init_end(double
884 mark_init_elapsed_time_ms);
886 void record_mark_closure_time(double mark_closure_time_ms);
888 virtual void record_concurrent_mark_remark_start();
889 virtual void record_concurrent_mark_remark_end();
891 virtual void record_concurrent_mark_cleanup_start();
892 virtual void record_concurrent_mark_cleanup_end(size_t freed_bytes,
893 size_t max_live_bytes);
894 virtual void record_concurrent_mark_cleanup_completed();
896 virtual void record_concurrent_pause();
897 virtual void record_concurrent_pause_end();
899 virtual void record_collection_pause_end();
900 void print_heap_transition();
902 // Record the fact that a full collection occurred.
903 virtual void record_full_collection_start();
904 virtual void record_full_collection_end();
906 void record_gc_worker_start_time(int worker_i, double ms) {
907 _par_last_gc_worker_start_times_ms[worker_i] = ms;
908 }
910 void record_ext_root_scan_time(int worker_i, double ms) {
911 _par_last_ext_root_scan_times_ms[worker_i] = ms;
912 }
914 void record_mark_stack_scan_time(int worker_i, double ms) {
915 _par_last_mark_stack_scan_times_ms[worker_i] = ms;
916 }
918 void record_satb_drain_time(double ms) {
919 _cur_satb_drain_time_ms = ms;
920 _satb_drain_time_set = true;
921 }
923 void record_satb_drain_processed_buffers (int processed_buffers) {
924 _last_satb_drain_processed_buffers = processed_buffers;
925 }
927 void record_mod_union_time(double ms) {
928 _all_mod_union_times_ms->add(ms);
929 }
931 void record_update_rs_time(int thread, double ms) {
932 _par_last_update_rs_times_ms[thread] = ms;
933 }
935 void record_update_rs_processed_buffers (int thread,
936 double processed_buffers) {
937 _par_last_update_rs_processed_buffers[thread] = processed_buffers;
938 }
940 void record_scan_rs_time(int thread, double ms) {
941 _par_last_scan_rs_times_ms[thread] = ms;
942 }
944 void reset_obj_copy_time(int thread) {
945 _par_last_obj_copy_times_ms[thread] = 0.0;
946 }
948 void reset_obj_copy_time() {
949 reset_obj_copy_time(0);
950 }
952 void record_obj_copy_time(int thread, double ms) {
953 _par_last_obj_copy_times_ms[thread] += ms;
954 }
956 void record_termination(int thread, double ms, size_t attempts) {
957 _par_last_termination_times_ms[thread] = ms;
958 _par_last_termination_attempts[thread] = (double) attempts;
959 }
961 void record_gc_worker_end_time(int worker_i, double ms) {
962 _par_last_gc_worker_end_times_ms[worker_i] = ms;
963 }
965 void record_pause_time_ms(double ms) {
966 _last_pause_time_ms = ms;
967 }
969 void record_clear_ct_time(double ms) {
970 _cur_clear_ct_time_ms = ms;
971 }
973 void record_par_time(double ms) {
974 _cur_collection_par_time_ms = ms;
975 }
977 void record_aux_start_time(int i) {
978 guarantee(i < _aux_num, "should be within range");
979 _cur_aux_start_times_ms[i] = os::elapsedTime() * 1000.0;
980 }
982 void record_aux_end_time(int i) {
983 guarantee(i < _aux_num, "should be within range");
984 double ms = os::elapsedTime() * 1000.0 - _cur_aux_start_times_ms[i];
985 _cur_aux_times_set[i] = true;
986 _cur_aux_times_ms[i] += ms;
987 }
989 #ifndef PRODUCT
990 void record_cc_clear_time(double ms) {
991 if (_min_clear_cc_time_ms < 0.0 || ms <= _min_clear_cc_time_ms)
992 _min_clear_cc_time_ms = ms;
993 if (_max_clear_cc_time_ms < 0.0 || ms >= _max_clear_cc_time_ms)
994 _max_clear_cc_time_ms = ms;
995 _cur_clear_cc_time_ms = ms;
996 _cum_clear_cc_time_ms += ms;
997 _num_cc_clears++;
998 }
999 #endif
1001 // Record how much space we copied during a GC. This is typically
1002 // called when a GC alloc region is being retired.
1003 void record_bytes_copied_during_gc(size_t bytes) {
1004 _bytes_copied_during_gc += bytes;
1005 }
1007 // The amount of space we copied during a GC.
1008 size_t bytes_copied_during_gc() {
1009 return _bytes_copied_during_gc;
1010 }
1012 // Choose a new collection set. Marks the chosen regions as being
1013 // "in_collection_set", and links them together. The head and number of
1014 // the collection set are available via access methods.
1015 virtual void choose_collection_set(double target_pause_time_ms) = 0;
1017 // The head of the list (via "next_in_collection_set()") representing the
1018 // current collection set.
1019 HeapRegion* collection_set() { return _collection_set; }
1021 void clear_collection_set() { _collection_set = NULL; }
1023 // The number of elements in the current collection set.
1024 size_t collection_set_size() { return _collection_set_size; }
1026 // Add "hr" to the CS.
1027 void add_to_collection_set(HeapRegion* hr);
1029 // Incremental CSet Support
1031 // The head of the incrementally built collection set.
1032 HeapRegion* inc_cset_head() { return _inc_cset_head; }
1034 // The tail of the incrementally built collection set.
1035 HeapRegion* inc_set_tail() { return _inc_cset_tail; }
1037 // The number of elements in the incrementally built collection set.
1038 size_t inc_cset_size() { return _inc_cset_size; }
1040 // Initialize incremental collection set info.
1041 void start_incremental_cset_building();
1043 void clear_incremental_cset() {
1044 _inc_cset_head = NULL;
1045 _inc_cset_tail = NULL;
1046 }
1048 // Stop adding regions to the incremental collection set
1049 void stop_incremental_cset_building() { _inc_cset_build_state = Inactive; }
1051 // Add/remove information about hr to the aggregated information
1052 // for the incrementally built collection set.
1053 void add_to_incremental_cset_info(HeapRegion* hr, size_t rs_length);
1054 void remove_from_incremental_cset_info(HeapRegion* hr);
1056 // Update information about hr in the aggregated information for
1057 // the incrementally built collection set.
1058 void update_incremental_cset_info(HeapRegion* hr, size_t new_rs_length);
1060 private:
1061 // Update the incremental cset information when adding a region
1062 // (should not be called directly).
1063 void add_region_to_incremental_cset_common(HeapRegion* hr);
1065 public:
1066 // Add hr to the LHS of the incremental collection set.
1067 void add_region_to_incremental_cset_lhs(HeapRegion* hr);
1069 // Add hr to the RHS of the incremental collection set.
1070 void add_region_to_incremental_cset_rhs(HeapRegion* hr);
1072 #ifndef PRODUCT
1073 void print_collection_set(HeapRegion* list_head, outputStream* st);
1074 #endif // !PRODUCT
1076 bool initiate_conc_mark_if_possible() { return _initiate_conc_mark_if_possible; }
1077 void set_initiate_conc_mark_if_possible() { _initiate_conc_mark_if_possible = true; }
1078 void clear_initiate_conc_mark_if_possible() { _initiate_conc_mark_if_possible = false; }
1080 bool during_initial_mark_pause() { return _during_initial_mark_pause; }
1081 void set_during_initial_mark_pause() { _during_initial_mark_pause = true; }
1082 void clear_during_initial_mark_pause(){ _during_initial_mark_pause = false; }
1084 // This sets the initiate_conc_mark_if_possible() flag to start a
1085 // new cycle, as long as we are not already in one. It's best if it
1086 // is called during a safepoint when the test whether a cycle is in
1087 // progress or not is stable.
1088 bool force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause);
1090 // This is called at the very beginning of an evacuation pause (it
1091 // has to be the first thing that the pause does). If
1092 // initiate_conc_mark_if_possible() is true, and the concurrent
1093 // marking thread has completed its work during the previous cycle,
1094 // it will set during_initial_mark_pause() to so that the pause does
1095 // the initial-mark work and start a marking cycle.
1096 void decide_on_conc_mark_initiation();
1098 // If an expansion would be appropriate, because recent GC overhead had
1099 // exceeded the desired limit, return an amount to expand by.
1100 virtual size_t expansion_amount();
1102 // note start of mark thread
1103 void note_start_of_mark_thread();
1105 // The marked bytes of the "r" has changed; reclassify it's desirability
1106 // for marking. Also asserts that "r" is eligible for a CS.
1107 virtual void note_change_in_marked_bytes(HeapRegion* r) = 0;
1109 #ifndef PRODUCT
1110 // Check any appropriate marked bytes info, asserting false if
1111 // something's wrong, else returning "true".
1112 virtual bool assertMarkedBytesDataOK() = 0;
1113 #endif
1115 // Print tracing information.
1116 void print_tracing_info() const;
1118 // Print stats on young survival ratio
1119 void print_yg_surv_rate_info() const;
1121 void finished_recalculating_age_indexes(bool is_survivors) {
1122 if (is_survivors) {
1123 _survivor_surv_rate_group->finished_recalculating_age_indexes();
1124 } else {
1125 _short_lived_surv_rate_group->finished_recalculating_age_indexes();
1126 }
1127 // do that for any other surv rate groups
1128 }
1130 bool is_young_list_full() {
1131 size_t young_list_length = _g1->young_list()->length();
1132 size_t young_list_target_length = _young_list_target_length;
1133 return young_list_length >= young_list_target_length;
1134 }
1136 bool can_expand_young_list() {
1137 size_t young_list_length = _g1->young_list()->length();
1138 size_t young_list_max_length = _young_list_max_length;
1139 return young_list_length < young_list_max_length;
1140 }
1142 void update_region_num(bool young);
1144 bool full_young_gcs() {
1145 return _full_young_gcs;
1146 }
1147 void set_full_young_gcs(bool full_young_gcs) {
1148 _full_young_gcs = full_young_gcs;
1149 }
1151 bool adaptive_young_list_length() {
1152 return _adaptive_young_list_length;
1153 }
1154 void set_adaptive_young_list_length(bool adaptive_young_list_length) {
1155 _adaptive_young_list_length = adaptive_young_list_length;
1156 }
1158 inline double get_gc_eff_factor() {
1159 double ratio = _known_garbage_ratio;
1161 double square = ratio * ratio;
1162 // square = square * square;
1163 double ret = square * 9.0 + 1.0;
1164 #if 0
1165 gclog_or_tty->print_cr("ratio = %1.2lf, ret = %1.2lf", ratio, ret);
1166 #endif // 0
1167 guarantee(0.0 <= ret && ret < 10.0, "invariant!");
1168 return ret;
1169 }
1171 //
1172 // Survivor regions policy.
1173 //
1174 protected:
1176 // Current tenuring threshold, set to 0 if the collector reaches the
1177 // maximum amount of suvivors regions.
1178 int _tenuring_threshold;
1180 // The limit on the number of regions allocated for survivors.
1181 size_t _max_survivor_regions;
1183 // For reporting purposes.
1184 size_t _eden_bytes_before_gc;
1185 size_t _survivor_bytes_before_gc;
1186 size_t _capacity_before_gc;
1188 // The amount of survor regions after a collection.
1189 size_t _recorded_survivor_regions;
1190 // List of survivor regions.
1191 HeapRegion* _recorded_survivor_head;
1192 HeapRegion* _recorded_survivor_tail;
1194 ageTable _survivors_age_table;
1196 public:
1198 inline GCAllocPurpose
1199 evacuation_destination(HeapRegion* src_region, int age, size_t word_sz) {
1200 if (age < _tenuring_threshold && src_region->is_young()) {
1201 return GCAllocForSurvived;
1202 } else {
1203 return GCAllocForTenured;
1204 }
1205 }
1207 inline bool track_object_age(GCAllocPurpose purpose) {
1208 return purpose == GCAllocForSurvived;
1209 }
1211 static const size_t REGIONS_UNLIMITED = ~(size_t)0;
1213 size_t max_regions(int purpose);
1215 // The limit on regions for a particular purpose is reached.
1216 void note_alloc_region_limit_reached(int purpose) {
1217 if (purpose == GCAllocForSurvived) {
1218 _tenuring_threshold = 0;
1219 }
1220 }
1222 void note_start_adding_survivor_regions() {
1223 _survivor_surv_rate_group->start_adding_regions();
1224 }
1226 void note_stop_adding_survivor_regions() {
1227 _survivor_surv_rate_group->stop_adding_regions();
1228 }
1230 void record_survivor_regions(size_t regions,
1231 HeapRegion* head,
1232 HeapRegion* tail) {
1233 _recorded_survivor_regions = regions;
1234 _recorded_survivor_head = head;
1235 _recorded_survivor_tail = tail;
1236 }
1238 size_t recorded_survivor_regions() {
1239 return _recorded_survivor_regions;
1240 }
1242 void record_thread_age_table(ageTable* age_table)
1243 {
1244 _survivors_age_table.merge_par(age_table);
1245 }
1247 void update_max_gc_locker_expansion();
1249 // Calculates survivor space parameters.
1250 void update_survivors_policy();
1252 };
1254 // This encapsulates a particular strategy for a g1 Collector.
1255 //
1256 // Start a concurrent mark when our heap size is n bytes
1257 // greater then our heap size was at the last concurrent
1258 // mark. Where n is a function of the CMSTriggerRatio
1259 // and the MinHeapFreeRatio.
1260 //
1261 // Start a g1 collection pause when we have allocated the
1262 // average number of bytes currently being freed in
1263 // a collection, but only if it is at least one region
1264 // full
1265 //
1266 // Resize Heap based on desired
1267 // allocation space, where desired allocation space is
1268 // a function of survival rate and desired future to size.
1269 //
1270 // Choose collection set by first picking all older regions
1271 // which have a survival rate which beats our projected young
1272 // survival rate. Then fill out the number of needed regions
1273 // with young regions.
1275 class G1CollectorPolicy_BestRegionsFirst: public G1CollectorPolicy {
1276 CollectionSetChooser* _collectionSetChooser;
1278 virtual void choose_collection_set(double target_pause_time_ms);
1279 virtual void record_collection_pause_start(double start_time_sec,
1280 size_t start_used);
1281 virtual void record_concurrent_mark_cleanup_end(size_t freed_bytes,
1282 size_t max_live_bytes);
1283 virtual void record_full_collection_end();
1285 public:
1286 G1CollectorPolicy_BestRegionsFirst() {
1287 _collectionSetChooser = new CollectionSetChooser();
1288 }
1289 void record_collection_pause_end();
1290 // This is not needed any more, after the CSet choosing code was
1291 // changed to use the pause prediction work. But let's leave the
1292 // hook in just in case.
1293 void note_change_in_marked_bytes(HeapRegion* r) { }
1294 #ifndef PRODUCT
1295 bool assertMarkedBytesDataOK();
1296 #endif
1297 };
1299 // This should move to some place more general...
1301 // If we have "n" measurements, and we've kept track of their "sum" and the
1302 // "sum_of_squares" of the measurements, this returns the variance of the
1303 // sequence.
1304 inline double variance(int n, double sum_of_squares, double sum) {
1305 double n_d = (double)n;
1306 double avg = sum/n_d;
1307 return (sum_of_squares - 2.0 * avg * sum + n_d * avg * avg) / n_d;
1308 }
1310 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP