1 /*
2 * Copyright (c) 2001, 2012, 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.
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23 */
24
25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP
27
28 #include "gc_implementation/g1/collectionSetChooser.hpp"
29 #include "gc_implementation/g1/g1MMUTracker.hpp"
30 #include "memory/collectorPolicy.hpp"
31
32 // A G1CollectorPolicy makes policy decisions that determine the
33 // characteristics of the collector. Examples include:
34 // * choice of collection set.
35 // * when to collect.
36
37 class HeapRegion;
38 class CollectionSetChooser;
39
40 class TraceGen0TimeData : public CHeapObj {
41 private:
42 unsigned _young_pause_num;
43 unsigned _mixed_pause_num;
44
45 NumberSeq _all_stop_world_times_ms;
46 NumberSeq _all_yield_times_ms;
47
48 NumberSeq _total;
49 NumberSeq _other;
50 NumberSeq _root_region_scan_wait;
51 NumberSeq _parallel;
52 NumberSeq _ext_root_scan;
53 NumberSeq _satb_filtering;
54 NumberSeq _update_rs;
55 NumberSeq _scan_rs;
56 NumberSeq _obj_copy;
57 NumberSeq _termination;
58 NumberSeq _parallel_other;
59 NumberSeq _clear_ct;
60
61 void print_summary (int level, const char* str, const NumberSeq* seq) const;
62 void print_summary_sd (int level, const char* str, const NumberSeq* seq) const;
63
64 public:
65 TraceGen0TimeData() : _young_pause_num(0), _mixed_pause_num(0) {};
66 void record_start_collection(double time_to_stop_the_world_ms);
67 void record_yield_time(double yield_time_ms);
68 void record_end_collection(
69 double total_ms,
70 double other_ms,
71 double root_region_scan_wait_ms,
72 double parallel_ms,
73 double ext_root_scan_ms,
74 double satb_filtering_ms,
75 double update_rs_ms,
76 double scan_rs_ms,
77 double obj_copy_ms,
78 double termination_ms,
79 double parallel_other_ms,
80 double clear_ct_ms);
81 void increment_collection_count(bool mixed);
82 void print() const;
83 };
84
85 class TraceGen1TimeData : public CHeapObj {
86 private:
87 NumberSeq _all_full_gc_times;
88
89 public:
90 void record_full_collection(double full_gc_time_ms);
91 void print() const;
92 };
93
94 // There are three command line options related to the young gen size:
95 // NewSize, MaxNewSize and NewRatio (There is also -Xmn, but that is
96 // just a short form for NewSize==MaxNewSize). G1 will use its internal
97 // heuristics to calculate the actual young gen size, so these options
98 // basically only limit the range within which G1 can pick a young gen
99 // size. Also, these are general options taking byte sizes. G1 will
100 // internally work with a number of regions instead. So, some rounding
101 // will occur.
102 //
103 // If nothing related to the the young gen size is set on the command
104 // line we should allow the young gen to be between
105 // G1DefaultMinNewGenPercent and G1DefaultMaxNewGenPercent of the
106 // heap size. This means that every time the heap size changes the
107 // limits for the young gen size will be updated.
108 //
109 // If only -XX:NewSize is set we should use the specified value as the
110 // minimum size for young gen. Still using G1DefaultMaxNewGenPercent
111 // of the heap as maximum.
112 //
113 // If only -XX:MaxNewSize is set we should use the specified value as the
114 // maximum size for young gen. Still using G1DefaultMinNewGenPercent
115 // of the heap as minimum.
116 //
117 // If -XX:NewSize and -XX:MaxNewSize are both specified we use these values.
118 // No updates when the heap size changes. There is a special case when
119 // NewSize==MaxNewSize. This is interpreted as "fixed" and will use a
120 // different heuristic for calculating the collection set when we do mixed
121 // collection.
122 //
123 // If only -XX:NewRatio is set we should use the specified ratio of the heap
124 // as both min and max. This will be interpreted as "fixed" just like the
125 // NewSize==MaxNewSize case above. But we will update the min and max
126 // everytime the heap size changes.
127 //
128 // NewSize and MaxNewSize override NewRatio. So, NewRatio is ignored if it is
129 // combined with either NewSize or MaxNewSize. (A warning message is printed.)
130 class G1YoungGenSizer : public CHeapObj {
131 private:
132 enum SizerKind {
133 SizerDefaults,
134 SizerNewSizeOnly,
135 SizerMaxNewSizeOnly,
136 SizerMaxAndNewSize,
137 SizerNewRatio
138 };
139 SizerKind _sizer_kind;
140 uint _min_desired_young_length;
141 uint _max_desired_young_length;
142 bool _adaptive_size;
143 uint calculate_default_min_length(uint new_number_of_heap_regions);
144 uint calculate_default_max_length(uint new_number_of_heap_regions);
145
146 public:
147 G1YoungGenSizer();
148 void heap_size_changed(uint new_number_of_heap_regions);
149 uint min_desired_young_length() {
150 return _min_desired_young_length;
151 }
152 uint max_desired_young_length() {
153 return _max_desired_young_length;
154 }
155 bool adaptive_young_list_length() {
156 return _adaptive_size;
157 }
158 };
159
160 class G1CollectorPolicy: public CollectorPolicy {
161 private:
162 // either equal to the number of parallel threads, if ParallelGCThreads
163 // has been set, or 1 otherwise
164 int _parallel_gc_threads;
165
166 // The number of GC threads currently active.
167 uintx _no_of_gc_threads;
168
169 enum SomePrivateConstants {
170 NumPrevPausesForHeuristics = 10
171 };
172
173 G1MMUTracker* _mmu_tracker;
174
175 void initialize_flags();
176
177 void initialize_all() {
178 initialize_flags();
179 initialize_size_info();
180 initialize_perm_generation(PermGen::MarkSweepCompact);
181 }
182
183 CollectionSetChooser* _collectionSetChooser;
184
185 double _cur_collection_start_sec;
186 size_t _cur_collection_pause_used_at_start_bytes;
187 uint _cur_collection_pause_used_regions_at_start;
188 double _cur_collection_par_time_ms;
189
190 double _cur_collection_code_root_fixup_time_ms;
191
192 double _cur_clear_ct_time_ms;
193 double _cur_ref_proc_time_ms;
194 double _cur_ref_enq_time_ms;
195
196 #ifndef PRODUCT
197 // Card Table Count Cache stats
198 double _min_clear_cc_time_ms; // min
199 double _max_clear_cc_time_ms; // max
200 double _cur_clear_cc_time_ms; // clearing time during current pause
201 double _cum_clear_cc_time_ms; // cummulative clearing time
202 jlong _num_cc_clears; // number of times the card count cache has been cleared
203 #endif
204
205 // These exclude marking times.
206 TruncatedSeq* _recent_gc_times_ms;
207
208 TruncatedSeq* _concurrent_mark_remark_times_ms;
209 TruncatedSeq* _concurrent_mark_cleanup_times_ms;
210
211 TraceGen0TimeData _trace_gen0_time_data;
212 TraceGen1TimeData _trace_gen1_time_data;
213
214 double _stop_world_start;
215
216 double* _par_last_gc_worker_start_times_ms;
217 double* _par_last_ext_root_scan_times_ms;
218 double* _par_last_satb_filtering_times_ms;
219 double* _par_last_update_rs_times_ms;
220 double* _par_last_update_rs_processed_buffers;
221 double* _par_last_scan_rs_times_ms;
222 double* _par_last_obj_copy_times_ms;
223 double* _par_last_termination_times_ms;
224 double* _par_last_termination_attempts;
225 double* _par_last_gc_worker_end_times_ms;
226 double* _par_last_gc_worker_times_ms;
227
228 // Each workers 'other' time i.e. the elapsed time of the parallel
229 // code executed by a worker minus the sum of the individual sub-phase
230 // times for that worker thread.
231 double* _par_last_gc_worker_other_times_ms;
232
233 // indicates whether we are in young or mixed GC mode
234 bool _gcs_are_young;
235
236 uint _young_list_target_length;
237 uint _young_list_fixed_length;
238 size_t _prev_eden_capacity; // used for logging
239
240 // The max number of regions we can extend the eden by while the GC
241 // locker is active. This should be >= _young_list_target_length;
242 uint _young_list_max_length;
243
244 bool _last_gc_was_young;
245
246 unsigned _young_pause_num;
247 unsigned _mixed_pause_num;
248
249 bool _during_marking;
250 bool _in_marking_window;
251 bool _in_marking_window_im;
252
253 SurvRateGroup* _short_lived_surv_rate_group;
254 SurvRateGroup* _survivor_surv_rate_group;
255 // add here any more surv rate groups
256
257 double _gc_overhead_perc;
258
259 double _reserve_factor;
260 uint _reserve_regions;
261
262 bool during_marking() {
263 return _during_marking;
264 }
265
266 private:
267 enum PredictionConstants {
268 TruncatedSeqLength = 10
269 };
270
271 TruncatedSeq* _alloc_rate_ms_seq;
272 double _prev_collection_pause_end_ms;
273
274 TruncatedSeq* _pending_card_diff_seq;
275 TruncatedSeq* _rs_length_diff_seq;
276 TruncatedSeq* _cost_per_card_ms_seq;
277 TruncatedSeq* _young_cards_per_entry_ratio_seq;
278 TruncatedSeq* _mixed_cards_per_entry_ratio_seq;
279 TruncatedSeq* _cost_per_entry_ms_seq;
280 TruncatedSeq* _mixed_cost_per_entry_ms_seq;
281 TruncatedSeq* _cost_per_byte_ms_seq;
282 TruncatedSeq* _constant_other_time_ms_seq;
283 TruncatedSeq* _young_other_cost_per_region_ms_seq;
284 TruncatedSeq* _non_young_other_cost_per_region_ms_seq;
285
286 TruncatedSeq* _pending_cards_seq;
287 TruncatedSeq* _rs_lengths_seq;
288
289 TruncatedSeq* _cost_per_byte_ms_during_cm_seq;
290
291 G1YoungGenSizer* _young_gen_sizer;
292
293 uint _eden_cset_region_length;
294 uint _survivor_cset_region_length;
295 uint _old_cset_region_length;
296
297 void init_cset_region_lengths(uint eden_cset_region_length,
298 uint survivor_cset_region_length);
299
300 uint eden_cset_region_length() { return _eden_cset_region_length; }
301 uint survivor_cset_region_length() { return _survivor_cset_region_length; }
302 uint old_cset_region_length() { return _old_cset_region_length; }
303
304 uint _free_regions_at_end_of_collection;
305
306 size_t _recorded_rs_lengths;
307 size_t _max_rs_lengths;
308
309 double _recorded_young_free_cset_time_ms;
310 double _recorded_non_young_free_cset_time_ms;
311
312 double _sigma;
313
314 size_t _rs_lengths_prediction;
315
316 double sigma() { return _sigma; }
317
318 // A function that prevents us putting too much stock in small sample
319 // sets. Returns a number between 2.0 and 1.0, depending on the number
320 // of samples. 5 or more samples yields one; fewer scales linearly from
321 // 2.0 at 1 sample to 1.0 at 5.
322 double confidence_factor(int samples) {
323 if (samples > 4) return 1.0;
324 else return 1.0 + sigma() * ((double)(5 - samples))/2.0;
325 }
326
327 double get_new_neg_prediction(TruncatedSeq* seq) {
328 return seq->davg() - sigma() * seq->dsd();
329 }
330
331 #ifndef PRODUCT
332 bool verify_young_ages(HeapRegion* head, SurvRateGroup *surv_rate_group);
333 #endif // PRODUCT
334
335 void adjust_concurrent_refinement(double update_rs_time,
336 double update_rs_processed_buffers,
337 double goal_ms);
338
339 uintx no_of_gc_threads() { return _no_of_gc_threads; }
340 void set_no_of_gc_threads(uintx v) { _no_of_gc_threads = v; }
341
342 double _pause_time_target_ms;
343 double _recorded_young_cset_choice_time_ms;
344 double _recorded_non_young_cset_choice_time_ms;
345 size_t _pending_cards;
346 size_t _max_pending_cards;
347
348 public:
349 // Accessors
350
351 void set_region_eden(HeapRegion* hr, int young_index_in_cset) {
352 hr->set_young();
353 hr->install_surv_rate_group(_short_lived_surv_rate_group);
354 hr->set_young_index_in_cset(young_index_in_cset);
355 }
356
357 void set_region_survivor(HeapRegion* hr, int young_index_in_cset) {
358 assert(hr->is_young() && hr->is_survivor(), "pre-condition");
359 hr->install_surv_rate_group(_survivor_surv_rate_group);
360 hr->set_young_index_in_cset(young_index_in_cset);
361 }
362
363 #ifndef PRODUCT
364 bool verify_young_ages();
365 #endif // PRODUCT
366
367 double get_new_prediction(TruncatedSeq* seq) {
368 return MAX2(seq->davg() + sigma() * seq->dsd(),
369 seq->davg() * confidence_factor(seq->num()));
370 }
371
372 void record_max_rs_lengths(size_t rs_lengths) {
373 _max_rs_lengths = rs_lengths;
374 }
375
376 size_t predict_pending_card_diff() {
377 double prediction = get_new_neg_prediction(_pending_card_diff_seq);
378 if (prediction < 0.00001) {
379 return 0;
380 } else {
381 return (size_t) prediction;
382 }
383 }
384
385 size_t predict_pending_cards() {
386 size_t max_pending_card_num = _g1->max_pending_card_num();
387 size_t diff = predict_pending_card_diff();
388 size_t prediction;
389 if (diff > max_pending_card_num) {
390 prediction = max_pending_card_num;
391 } else {
392 prediction = max_pending_card_num - diff;
393 }
394
395 return prediction;
396 }
397
398 size_t predict_rs_length_diff() {
399 return (size_t) get_new_prediction(_rs_length_diff_seq);
400 }
401
402 double predict_alloc_rate_ms() {
403 return get_new_prediction(_alloc_rate_ms_seq);
404 }
405
406 double predict_cost_per_card_ms() {
407 return get_new_prediction(_cost_per_card_ms_seq);
408 }
409
410 double predict_rs_update_time_ms(size_t pending_cards) {
411 return (double) pending_cards * predict_cost_per_card_ms();
412 }
413
414 double predict_young_cards_per_entry_ratio() {
415 return get_new_prediction(_young_cards_per_entry_ratio_seq);
416 }
417
418 double predict_mixed_cards_per_entry_ratio() {
419 if (_mixed_cards_per_entry_ratio_seq->num() < 2) {
420 return predict_young_cards_per_entry_ratio();
421 } else {
422 return get_new_prediction(_mixed_cards_per_entry_ratio_seq);
423 }
424 }
425
426 size_t predict_young_card_num(size_t rs_length) {
427 return (size_t) ((double) rs_length *
428 predict_young_cards_per_entry_ratio());
429 }
430
431 size_t predict_non_young_card_num(size_t rs_length) {
432 return (size_t) ((double) rs_length *
433 predict_mixed_cards_per_entry_ratio());
434 }
435
436 double predict_rs_scan_time_ms(size_t card_num) {
437 if (gcs_are_young()) {
438 return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq);
439 } else {
440 return predict_mixed_rs_scan_time_ms(card_num);
441 }
442 }
443
444 double predict_mixed_rs_scan_time_ms(size_t card_num) {
445 if (_mixed_cost_per_entry_ms_seq->num() < 3) {
446 return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq);
447 } else {
448 return (double) (card_num *
449 get_new_prediction(_mixed_cost_per_entry_ms_seq));
450 }
451 }
452
453 double predict_object_copy_time_ms_during_cm(size_t bytes_to_copy) {
454 if (_cost_per_byte_ms_during_cm_seq->num() < 3) {
455 return (1.1 * (double) bytes_to_copy) *
456 get_new_prediction(_cost_per_byte_ms_seq);
457 } else {
458 return (double) bytes_to_copy *
459 get_new_prediction(_cost_per_byte_ms_during_cm_seq);
460 }
461 }
462
463 double predict_object_copy_time_ms(size_t bytes_to_copy) {
464 if (_in_marking_window && !_in_marking_window_im) {
465 return predict_object_copy_time_ms_during_cm(bytes_to_copy);
466 } else {
467 return (double) bytes_to_copy *
468 get_new_prediction(_cost_per_byte_ms_seq);
469 }
470 }
471
472 double predict_constant_other_time_ms() {
473 return get_new_prediction(_constant_other_time_ms_seq);
474 }
475
476 double predict_young_other_time_ms(size_t young_num) {
477 return (double) young_num *
478 get_new_prediction(_young_other_cost_per_region_ms_seq);
479 }
480
481 double predict_non_young_other_time_ms(size_t non_young_num) {
482 return (double) non_young_num *
483 get_new_prediction(_non_young_other_cost_per_region_ms_seq);
484 }
485
486 double predict_base_elapsed_time_ms(size_t pending_cards);
487 double predict_base_elapsed_time_ms(size_t pending_cards,
488 size_t scanned_cards);
489 size_t predict_bytes_to_copy(HeapRegion* hr);
490 double predict_region_elapsed_time_ms(HeapRegion* hr, bool young);
491
492 void set_recorded_rs_lengths(size_t rs_lengths);
493
494 uint cset_region_length() { return young_cset_region_length() +
495 old_cset_region_length(); }
496 uint young_cset_region_length() { return eden_cset_region_length() +
497 survivor_cset_region_length(); }
498
499 void record_young_free_cset_time_ms(double time_ms) {
500 _recorded_young_free_cset_time_ms = time_ms;
501 }
502
503 void record_non_young_free_cset_time_ms(double time_ms) {
504 _recorded_non_young_free_cset_time_ms = time_ms;
505 }
506
507 double predict_survivor_regions_evac_time();
508
509 void cset_regions_freed() {
510 bool propagate = _last_gc_was_young && !_in_marking_window;
511 _short_lived_surv_rate_group->all_surviving_words_recorded(propagate);
512 _survivor_surv_rate_group->all_surviving_words_recorded(propagate);
513 // also call it on any more surv rate groups
514 }
515
516 G1MMUTracker* mmu_tracker() {
517 return _mmu_tracker;
518 }
519
520 double max_pause_time_ms() {
521 return _mmu_tracker->max_gc_time() * 1000.0;
522 }
523
524 double predict_remark_time_ms() {
525 return get_new_prediction(_concurrent_mark_remark_times_ms);
526 }
527
528 double predict_cleanup_time_ms() {
529 return get_new_prediction(_concurrent_mark_cleanup_times_ms);
530 }
531
532 // Returns an estimate of the survival rate of the region at yg-age
533 // "yg_age".
534 double predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) {
535 TruncatedSeq* seq = surv_rate_group->get_seq(age);
536 if (seq->num() == 0)
537 gclog_or_tty->print("BARF! age is %d", age);
538 guarantee( seq->num() > 0, "invariant" );
539 double pred = get_new_prediction(seq);
540 if (pred > 1.0)
541 pred = 1.0;
542 return pred;
543 }
544
545 double predict_yg_surv_rate(int age) {
546 return predict_yg_surv_rate(age, _short_lived_surv_rate_group);
547 }
548
549 double accum_yg_surv_rate_pred(int age) {
550 return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
551 }
552
553 private:
554 void print_stats(int level, const char* str, double value);
555 void print_stats(int level, const char* str, double value, int workers);
556 void print_stats(int level, const char* str, int value);
557
558 void print_par_stats(int level, const char* str, double* data, bool showDecimals = true);
559
560 double avg_value (double* data);
561 double max_value (double* data);
562 double sum_of_values (double* data);
563 double max_sum (double* data1, double* data2);
564
565 double _last_pause_time_ms;
566
567 size_t _bytes_in_collection_set_before_gc;
568 size_t _bytes_copied_during_gc;
569
570 // Used to count used bytes in CS.
571 friend class CountCSClosure;
572
573 // Statistics kept per GC stoppage, pause or full.
574 TruncatedSeq* _recent_prev_end_times_for_all_gcs_sec;
575
576 // Add a new GC of the given duration and end time to the record.
577 void update_recent_gc_times(double end_time_sec, double elapsed_ms);
578
579 // The head of the list (via "next_in_collection_set()") representing the
580 // current collection set. Set from the incrementally built collection
581 // set at the start of the pause.
582 HeapRegion* _collection_set;
583
584 // The number of bytes in the collection set before the pause. Set from
585 // the incrementally built collection set at the start of an evacuation
586 // pause.
587 size_t _collection_set_bytes_used_before;
588
589 // The associated information that is maintained while the incremental
590 // collection set is being built with young regions. Used to populate
591 // the recorded info for the evacuation pause.
592
593 enum CSetBuildType {
594 Active, // We are actively building the collection set
595 Inactive // We are not actively building the collection set
596 };
597
598 CSetBuildType _inc_cset_build_state;
599
600 // The head of the incrementally built collection set.
601 HeapRegion* _inc_cset_head;
602
603 // The tail of the incrementally built collection set.
604 HeapRegion* _inc_cset_tail;
605
606 // The number of bytes in the incrementally built collection set.
607 // Used to set _collection_set_bytes_used_before at the start of
608 // an evacuation pause.
609 size_t _inc_cset_bytes_used_before;
610
611 // Used to record the highest end of heap region in collection set
612 HeapWord* _inc_cset_max_finger;
613
614 // The RSet lengths recorded for regions in the CSet. It is updated
615 // by the thread that adds a new region to the CSet. We assume that
616 // only one thread can be allocating a new CSet region (currently,
617 // it does so after taking the Heap_lock) hence no need to
618 // synchronize updates to this field.
619 size_t _inc_cset_recorded_rs_lengths;
620
621 // A concurrent refinement thread periodcially samples the young
622 // region RSets and needs to update _inc_cset_recorded_rs_lengths as
623 // the RSets grow. Instead of having to syncronize updates to that
624 // field we accumulate them in this field and add it to
625 // _inc_cset_recorded_rs_lengths_diffs at the start of a GC.
626 ssize_t _inc_cset_recorded_rs_lengths_diffs;
627
628 // The predicted elapsed time it will take to collect the regions in
629 // the CSet. This is updated by the thread that adds a new region to
630 // the CSet. See the comment for _inc_cset_recorded_rs_lengths about
631 // MT-safety assumptions.
632 double _inc_cset_predicted_elapsed_time_ms;
633
634 // See the comment for _inc_cset_recorded_rs_lengths_diffs.
635 double _inc_cset_predicted_elapsed_time_ms_diffs;
636
637 // Stash a pointer to the g1 heap.
638 G1CollectedHeap* _g1;
639
640 // The ratio of gc time to elapsed time, computed over recent pauses.
641 double _recent_avg_pause_time_ratio;
642
643 double recent_avg_pause_time_ratio() {
644 return _recent_avg_pause_time_ratio;
645 }
646
647 // At the end of a pause we check the heap occupancy and we decide
648 // whether we will start a marking cycle during the next pause. If
649 // we decide that we want to do that, we will set this parameter to
650 // true. So, this parameter will stay true between the end of a
651 // pause and the beginning of a subsequent pause (not necessarily
652 // the next one, see the comments on the next field) when we decide
653 // that we will indeed start a marking cycle and do the initial-mark
654 // work.
655 volatile bool _initiate_conc_mark_if_possible;
656
657 // If initiate_conc_mark_if_possible() is set at the beginning of a
658 // pause, it is a suggestion that the pause should start a marking
659 // cycle by doing the initial-mark work. However, it is possible
660 // that the concurrent marking thread is still finishing up the
661 // previous marking cycle (e.g., clearing the next marking
662 // bitmap). If that is the case we cannot start a new cycle and
663 // we'll have to wait for the concurrent marking thread to finish
664 // what it is doing. In this case we will postpone the marking cycle
665 // initiation decision for the next pause. When we eventually decide
666 // to start a cycle, we will set _during_initial_mark_pause which
667 // will stay true until the end of the initial-mark pause and it's
668 // the condition that indicates that a pause is doing the
669 // initial-mark work.
670 volatile bool _during_initial_mark_pause;
671
672 bool _last_young_gc;
673
674 // This set of variables tracks the collector efficiency, in order to
675 // determine whether we should initiate a new marking.
676 double _cur_mark_stop_world_time_ms;
677 double _mark_remark_start_sec;
678 double _mark_cleanup_start_sec;
679 double _root_region_scan_wait_time_ms;
680
681 // Update the young list target length either by setting it to the
682 // desired fixed value or by calculating it using G1's pause
683 // prediction model. If no rs_lengths parameter is passed, predict
684 // the RS lengths using the prediction model, otherwise use the
685 // given rs_lengths as the prediction.
686 void update_young_list_target_length(size_t rs_lengths = (size_t) -1);
687
688 // Calculate and return the minimum desired young list target
689 // length. This is the minimum desired young list length according
690 // to the user's inputs.
691 uint calculate_young_list_desired_min_length(uint base_min_length);
692
693 // Calculate and return the maximum desired young list target
694 // length. This is the maximum desired young list length according
695 // to the user's inputs.
696 uint calculate_young_list_desired_max_length();
697
698 // Calculate and return the maximum young list target length that
699 // can fit into the pause time goal. The parameters are: rs_lengths
700 // represent the prediction of how large the young RSet lengths will
701 // be, base_min_length is the alreay existing number of regions in
702 // the young list, min_length and max_length are the desired min and
703 // max young list length according to the user's inputs.
704 uint calculate_young_list_target_length(size_t rs_lengths,
705 uint base_min_length,
706 uint desired_min_length,
707 uint desired_max_length);
708
709 // Check whether a given young length (young_length) fits into the
710 // given target pause time and whether the prediction for the amount
711 // of objects to be copied for the given length will fit into the
712 // given free space (expressed by base_free_regions). It is used by
713 // calculate_young_list_target_length().
714 bool predict_will_fit(uint young_length, double base_time_ms,
715 uint base_free_regions, double target_pause_time_ms);
716
717 // Count the number of bytes used in the CS.
718 void count_CS_bytes_used();
719
720 public:
721
722 G1CollectorPolicy();
723
724 virtual G1CollectorPolicy* as_g1_policy() { return this; }
725
726 virtual CollectorPolicy::Name kind() {
727 return CollectorPolicy::G1CollectorPolicyKind;
728 }
729
730 // Check the current value of the young list RSet lengths and
731 // compare it against the last prediction. If the current value is
732 // higher, recalculate the young list target length prediction.
733 void revise_young_list_target_length_if_necessary();
734
735 size_t bytes_in_collection_set() {
736 return _bytes_in_collection_set_before_gc;
737 }
738
739 // This should be called after the heap is resized.
740 void record_new_heap_size(uint new_number_of_regions);
741
742 void init();
743
744 // Create jstat counters for the policy.
745 virtual void initialize_gc_policy_counters();
746
747 virtual HeapWord* mem_allocate_work(size_t size,
748 bool is_tlab,
749 bool* gc_overhead_limit_was_exceeded);
750
751 // This method controls how a collector handles one or more
752 // of its generations being fully allocated.
753 virtual HeapWord* satisfy_failed_allocation(size_t size,
754 bool is_tlab);
755
756 BarrierSet::Name barrier_set_name() { return BarrierSet::G1SATBCTLogging; }
757
758 GenRemSet::Name rem_set_name() { return GenRemSet::CardTable; }
759
760 bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0);
761
762 // Update the heuristic info to record a collection pause of the given
763 // start time, where the given number of bytes were used at the start.
764 // This may involve changing the desired size of a collection set.
765
766 void record_stop_world_start();
767
768 void record_collection_pause_start(double start_time_sec, size_t start_used);
769
770 // Must currently be called while the world is stopped.
771 void record_concurrent_mark_init_end(double
772 mark_init_elapsed_time_ms);
773
774 void record_root_region_scan_wait_time(double time_ms) {
775 _root_region_scan_wait_time_ms = time_ms;
776 }
777
778 void record_concurrent_mark_remark_start();
779 void record_concurrent_mark_remark_end();
780
781 void record_concurrent_mark_cleanup_start();
782 void record_concurrent_mark_cleanup_end(int no_of_gc_threads);
783 void record_concurrent_mark_cleanup_completed();
784
785 void record_concurrent_pause();
786 void record_concurrent_pause_end();
787
788 void record_collection_pause_end(int no_of_gc_threads);
789 void print_heap_transition();
790
791 // Record the fact that a full collection occurred.
792 void record_full_collection_start();
793 void record_full_collection_end();
794
795 void record_gc_worker_start_time(int worker_i, double ms) {
796 _par_last_gc_worker_start_times_ms[worker_i] = ms;
797 }
798
799 void record_ext_root_scan_time(int worker_i, double ms) {
800 _par_last_ext_root_scan_times_ms[worker_i] = ms;
801 }
802
803 void record_satb_filtering_time(int worker_i, double ms) {
804 _par_last_satb_filtering_times_ms[worker_i] = ms;
805 }
806
807 void record_update_rs_time(int thread, double ms) {
808 _par_last_update_rs_times_ms[thread] = ms;
809 }
810
811 void record_update_rs_processed_buffers (int thread,
812 double processed_buffers) {
813 _par_last_update_rs_processed_buffers[thread] = processed_buffers;
814 }
815
816 void record_scan_rs_time(int thread, double ms) {
817 _par_last_scan_rs_times_ms[thread] = ms;
818 }
819
820 void reset_obj_copy_time(int thread) {
821 _par_last_obj_copy_times_ms[thread] = 0.0;
822 }
823
824 void reset_obj_copy_time() {
825 reset_obj_copy_time(0);
826 }
827
828 void record_obj_copy_time(int thread, double ms) {
829 _par_last_obj_copy_times_ms[thread] += ms;
830 }
831
832 void record_termination(int thread, double ms, size_t attempts) {
833 _par_last_termination_times_ms[thread] = ms;
834 _par_last_termination_attempts[thread] = (double) attempts;
835 }
836
837 void record_gc_worker_end_time(int worker_i, double ms) {
838 _par_last_gc_worker_end_times_ms[worker_i] = ms;
839 }
840
841 void record_pause_time_ms(double ms) {
842 _last_pause_time_ms = ms;
843 }
844
845 void record_clear_ct_time(double ms) {
846 _cur_clear_ct_time_ms = ms;
847 }
848
849 void record_par_time(double ms) {
850 _cur_collection_par_time_ms = ms;
851 }
852
853 void record_code_root_fixup_time(double ms) {
854 _cur_collection_code_root_fixup_time_ms = ms;
855 }
856
857 void record_ref_proc_time(double ms) {
858 _cur_ref_proc_time_ms = ms;
859 }
860
861 void record_ref_enq_time(double ms) {
862 _cur_ref_enq_time_ms = ms;
863 }
864
865 #ifndef PRODUCT
866 void record_cc_clear_time(double ms) {
867 if (_min_clear_cc_time_ms < 0.0 || ms <= _min_clear_cc_time_ms)
868 _min_clear_cc_time_ms = ms;
869 if (_max_clear_cc_time_ms < 0.0 || ms >= _max_clear_cc_time_ms)
870 _max_clear_cc_time_ms = ms;
871 _cur_clear_cc_time_ms = ms;
872 _cum_clear_cc_time_ms += ms;
873 _num_cc_clears++;
874 }
875 #endif
876
877 // Record how much space we copied during a GC. This is typically
878 // called when a GC alloc region is being retired.
879 void record_bytes_copied_during_gc(size_t bytes) {
880 _bytes_copied_during_gc += bytes;
881 }
882
883 // The amount of space we copied during a GC.
884 size_t bytes_copied_during_gc() {
885 return _bytes_copied_during_gc;
886 }
887
888 // Determine whether there are candidate regions so that the
889 // next GC should be mixed. The two action strings are used
890 // in the ergo output when the method returns true or false.
891 bool next_gc_should_be_mixed(const char* true_action_str,
892 const char* false_action_str);
893
894 // Choose a new collection set. Marks the chosen regions as being
895 // "in_collection_set", and links them together. The head and number of
896 // the collection set are available via access methods.
897 void finalize_cset(double target_pause_time_ms);
898
899 // The head of the list (via "next_in_collection_set()") representing the
900 // current collection set.
901 HeapRegion* collection_set() { return _collection_set; }
902
903 void clear_collection_set() { _collection_set = NULL; }
904
905 // Add old region "hr" to the CSet.
906 void add_old_region_to_cset(HeapRegion* hr);
907
908 // Incremental CSet Support
909
910 // The head of the incrementally built collection set.
911 HeapRegion* inc_cset_head() { return _inc_cset_head; }
912
913 // The tail of the incrementally built collection set.
914 HeapRegion* inc_set_tail() { return _inc_cset_tail; }
915
916 // Initialize incremental collection set info.
917 void start_incremental_cset_building();
918
919 // Perform any final calculations on the incremental CSet fields
920 // before we can use them.
921 void finalize_incremental_cset_building();
922
923 void clear_incremental_cset() {
924 _inc_cset_head = NULL;
925 _inc_cset_tail = NULL;
926 }
927
928 // Stop adding regions to the incremental collection set
929 void stop_incremental_cset_building() { _inc_cset_build_state = Inactive; }
930
931 // Add information about hr to the aggregated information for the
932 // incrementally built collection set.
933 void add_to_incremental_cset_info(HeapRegion* hr, size_t rs_length);
934
935 // Update information about hr in the aggregated information for
936 // the incrementally built collection set.
937 void update_incremental_cset_info(HeapRegion* hr, size_t new_rs_length);
938
939 private:
940 // Update the incremental cset information when adding a region
941 // (should not be called directly).
942 void add_region_to_incremental_cset_common(HeapRegion* hr);
943
944 public:
945 // Add hr to the LHS of the incremental collection set.
946 void add_region_to_incremental_cset_lhs(HeapRegion* hr);
947
948 // Add hr to the RHS of the incremental collection set.
949 void add_region_to_incremental_cset_rhs(HeapRegion* hr);
950
951 #ifndef PRODUCT
952 void print_collection_set(HeapRegion* list_head, outputStream* st);
953 #endif // !PRODUCT
954
955 bool initiate_conc_mark_if_possible() { return _initiate_conc_mark_if_possible; }
956 void set_initiate_conc_mark_if_possible() { _initiate_conc_mark_if_possible = true; }
957 void clear_initiate_conc_mark_if_possible() { _initiate_conc_mark_if_possible = false; }
958
959 bool during_initial_mark_pause() { return _during_initial_mark_pause; }
960 void set_during_initial_mark_pause() { _during_initial_mark_pause = true; }
961 void clear_during_initial_mark_pause(){ _during_initial_mark_pause = false; }
962
963 // This sets the initiate_conc_mark_if_possible() flag to start a
964 // new cycle, as long as we are not already in one. It's best if it
965 // is called during a safepoint when the test whether a cycle is in
966 // progress or not is stable.
967 bool force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause);
968
969 // This is called at the very beginning of an evacuation pause (it
970 // has to be the first thing that the pause does). If
971 // initiate_conc_mark_if_possible() is true, and the concurrent
972 // marking thread has completed its work during the previous cycle,
973 // it will set during_initial_mark_pause() to so that the pause does
974 // the initial-mark work and start a marking cycle.
975 void decide_on_conc_mark_initiation();
976
977 // If an expansion would be appropriate, because recent GC overhead had
978 // exceeded the desired limit, return an amount to expand by.
979 size_t expansion_amount();
980
981 // Print tracing information.
982 void print_tracing_info() const;
983
984 // Print stats on young survival ratio
985 void print_yg_surv_rate_info() const;
986
987 void finished_recalculating_age_indexes(bool is_survivors) {
988 if (is_survivors) {
989 _survivor_surv_rate_group->finished_recalculating_age_indexes();
990 } else {
991 _short_lived_surv_rate_group->finished_recalculating_age_indexes();
992 }
993 // do that for any other surv rate groups
994 }
995
996 bool is_young_list_full() {
997 uint young_list_length = _g1->young_list()->length();
998 uint young_list_target_length = _young_list_target_length;
999 return young_list_length >= young_list_target_length;
1000 }
1001
1002 bool can_expand_young_list() {
1003 uint young_list_length = _g1->young_list()->length();
1004 uint young_list_max_length = _young_list_max_length;
1005 return young_list_length < young_list_max_length;
1006 }
1007
1008 uint young_list_max_length() {
1009 return _young_list_max_length;
1010 }
1011
1012 bool gcs_are_young() {
1013 return _gcs_are_young;
1014 }
1015 void set_gcs_are_young(bool gcs_are_young) {
1016 _gcs_are_young = gcs_are_young;
1017 }
1018
1019 bool adaptive_young_list_length() {
1020 return _young_gen_sizer->adaptive_young_list_length();
1021 }
1022
1023 private:
1024 //
1025 // Survivor regions policy.
1026 //
1027
1028 // Current tenuring threshold, set to 0 if the collector reaches the
1029 // maximum amount of suvivors regions.
1030 int _tenuring_threshold;
1031
1032 // The limit on the number of regions allocated for survivors.
1033 uint _max_survivor_regions;
1034
1035 // For reporting purposes.
1036 size_t _eden_bytes_before_gc;
1037 size_t _survivor_bytes_before_gc;
1038 size_t _capacity_before_gc;
1039
1040 // The amount of survor regions after a collection.
1041 uint _recorded_survivor_regions;
1042 // List of survivor regions.
1043 HeapRegion* _recorded_survivor_head;
1044 HeapRegion* _recorded_survivor_tail;
1045
1046 ageTable _survivors_age_table;
1047
1048 public:
1049
1050 inline GCAllocPurpose
1051 evacuation_destination(HeapRegion* src_region, int age, size_t word_sz) {
1052 if (age < _tenuring_threshold && src_region->is_young()) {
1053 return GCAllocForSurvived;
1054 } else {
1055 return GCAllocForTenured;
1056 }
1057 }
1058
1059 inline bool track_object_age(GCAllocPurpose purpose) {
1060 return purpose == GCAllocForSurvived;
1061 }
1062
1063 static const uint REGIONS_UNLIMITED = (uint) -1;
1064
1065 uint max_regions(int purpose);
1066
1067 // The limit on regions for a particular purpose is reached.
1068 void note_alloc_region_limit_reached(int purpose) {
1069 if (purpose == GCAllocForSurvived) {
1070 _tenuring_threshold = 0;
1071 }
1072 }
1073
1074 void note_start_adding_survivor_regions() {
1075 _survivor_surv_rate_group->start_adding_regions();
1076 }
1077
1078 void note_stop_adding_survivor_regions() {
1079 _survivor_surv_rate_group->stop_adding_regions();
1080 }
1081
1082 void record_survivor_regions(uint regions,
1083 HeapRegion* head,
1084 HeapRegion* tail) {
1085 _recorded_survivor_regions = regions;
1086 _recorded_survivor_head = head;
1087 _recorded_survivor_tail = tail;
1088 }
1089
1090 uint recorded_survivor_regions() {
1091 return _recorded_survivor_regions;
1092 }
1093
1094 void record_thread_age_table(ageTable* age_table) {
1095 _survivors_age_table.merge_par(age_table);
1096 }
1097
1098 void update_max_gc_locker_expansion();
1099
1100 // Calculates survivor space parameters.
1101 void update_survivors_policy();
1102
1103 };
1104
1105 // This should move to some place more general...
1106
1107 // If we have "n" measurements, and we've kept track of their "sum" and the
1108 // "sum_of_squares" of the measurements, this returns the variance of the
1109 // sequence.
1110 inline double variance(int n, double sum_of_squares, double sum) {
1111 double n_d = (double)n;
1112 double avg = sum/n_d;
1113 return (sum_of_squares - 2.0 * avg * sum + n_d * avg * avg) / n_d;
1114 }
1115
1116 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP