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