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rev 3486 : 7185699: G1: Prediction model discrepancies
Summary: Correct the result value of G1CollectedHeap::pending_card_num(). Change the code that calculates the GC efficiency of a non-young heap region to use historical data from mixed GCs and the actual number of live bytes when predicting how long it would take to collect the region.
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--- old/src/share/vm/gc_implementation/g1/g1CollectorPolicy.hpp
+++ new/src/share/vm/gc_implementation/g1/g1CollectorPolicy.hpp
1 1 /*
2 2 * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved.
3 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 4 *
5 5 * This code is free software; you can redistribute it and/or modify it
6 6 * under the terms of the GNU General Public License version 2 only, as
7 7 * published by the Free Software Foundation.
8 8 *
9 9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 12 * version 2 for more details (a copy is included in the LICENSE file that
13 13 * accompanied this code).
14 14 *
15 15 * You should have received a copy of the GNU General Public License version
16 16 * 2 along with this work; if not, write to the Free Software Foundation,
17 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 18 *
19 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 20 * or visit www.oracle.com if you need additional information or have any
21 21 * questions.
22 22 *
23 23 */
24 24
25 25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP
26 26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP
27 27
28 28 #include "gc_implementation/g1/collectionSetChooser.hpp"
29 29 #include "gc_implementation/g1/g1MMUTracker.hpp"
30 30 #include "memory/collectorPolicy.hpp"
31 31
32 32 // A G1CollectorPolicy makes policy decisions that determine the
33 33 // characteristics of the collector. Examples include:
34 34 // * choice of collection set.
35 35 // * when to collect.
36 36
37 37 class HeapRegion;
38 38 class CollectionSetChooser;
39 39 class G1GCPhaseTimes;
40 40
41 41 // TraceGen0Time collects data on _both_ young and mixed evacuation pauses
42 42 // (the latter may contain non-young regions - i.e. regions that are
43 43 // technically in Gen1) while TraceGen1Time collects data about full GCs.
44 44 class TraceGen0TimeData : public CHeapObj<mtGC> {
45 45 private:
46 46 unsigned _young_pause_num;
47 47 unsigned _mixed_pause_num;
48 48
49 49 NumberSeq _all_stop_world_times_ms;
50 50 NumberSeq _all_yield_times_ms;
51 51
52 52 NumberSeq _total;
53 53 NumberSeq _other;
54 54 NumberSeq _root_region_scan_wait;
55 55 NumberSeq _parallel;
56 56 NumberSeq _ext_root_scan;
57 57 NumberSeq _satb_filtering;
58 58 NumberSeq _update_rs;
59 59 NumberSeq _scan_rs;
60 60 NumberSeq _obj_copy;
61 61 NumberSeq _termination;
62 62 NumberSeq _parallel_other;
63 63 NumberSeq _clear_ct;
64 64
65 65 void print_summary(const char* str, const NumberSeq* seq) const;
66 66 void print_summary_sd(const char* str, const NumberSeq* seq) const;
67 67
68 68 public:
69 69 TraceGen0TimeData() : _young_pause_num(0), _mixed_pause_num(0) {};
70 70 void record_start_collection(double time_to_stop_the_world_ms);
71 71 void record_yield_time(double yield_time_ms);
72 72 void record_end_collection(double pause_time_ms, G1GCPhaseTimes* phase_times);
73 73 void increment_young_collection_count();
74 74 void increment_mixed_collection_count();
75 75 void print() const;
76 76 };
77 77
78 78 class TraceGen1TimeData : public CHeapObj<mtGC> {
79 79 private:
80 80 NumberSeq _all_full_gc_times;
81 81
82 82 public:
83 83 void record_full_collection(double full_gc_time_ms);
84 84 void print() const;
85 85 };
86 86
87 87 // There are three command line options related to the young gen size:
88 88 // NewSize, MaxNewSize and NewRatio (There is also -Xmn, but that is
89 89 // just a short form for NewSize==MaxNewSize). G1 will use its internal
90 90 // heuristics to calculate the actual young gen size, so these options
91 91 // basically only limit the range within which G1 can pick a young gen
92 92 // size. Also, these are general options taking byte sizes. G1 will
93 93 // internally work with a number of regions instead. So, some rounding
94 94 // will occur.
95 95 //
96 96 // If nothing related to the the young gen size is set on the command
97 97 // line we should allow the young gen to be between
98 98 // G1DefaultMinNewGenPercent and G1DefaultMaxNewGenPercent of the
99 99 // heap size. This means that every time the heap size changes the
100 100 // limits for the young gen size will be updated.
101 101 //
102 102 // If only -XX:NewSize is set we should use the specified value as the
103 103 // minimum size for young gen. Still using G1DefaultMaxNewGenPercent
104 104 // of the heap as maximum.
105 105 //
106 106 // If only -XX:MaxNewSize is set we should use the specified value as the
107 107 // maximum size for young gen. Still using G1DefaultMinNewGenPercent
108 108 // of the heap as minimum.
109 109 //
110 110 // If -XX:NewSize and -XX:MaxNewSize are both specified we use these values.
111 111 // No updates when the heap size changes. There is a special case when
112 112 // NewSize==MaxNewSize. This is interpreted as "fixed" and will use a
113 113 // different heuristic for calculating the collection set when we do mixed
114 114 // collection.
115 115 //
116 116 // If only -XX:NewRatio is set we should use the specified ratio of the heap
117 117 // as both min and max. This will be interpreted as "fixed" just like the
118 118 // NewSize==MaxNewSize case above. But we will update the min and max
119 119 // everytime the heap size changes.
120 120 //
121 121 // NewSize and MaxNewSize override NewRatio. So, NewRatio is ignored if it is
122 122 // combined with either NewSize or MaxNewSize. (A warning message is printed.)
123 123 class G1YoungGenSizer : public CHeapObj<mtGC> {
124 124 private:
125 125 enum SizerKind {
126 126 SizerDefaults,
127 127 SizerNewSizeOnly,
128 128 SizerMaxNewSizeOnly,
129 129 SizerMaxAndNewSize,
130 130 SizerNewRatio
131 131 };
132 132 SizerKind _sizer_kind;
133 133 uint _min_desired_young_length;
134 134 uint _max_desired_young_length;
135 135 bool _adaptive_size;
136 136 uint calculate_default_min_length(uint new_number_of_heap_regions);
137 137 uint calculate_default_max_length(uint new_number_of_heap_regions);
138 138
139 139 public:
140 140 G1YoungGenSizer();
141 141 void heap_size_changed(uint new_number_of_heap_regions);
142 142 uint min_desired_young_length() {
143 143 return _min_desired_young_length;
144 144 }
145 145 uint max_desired_young_length() {
146 146 return _max_desired_young_length;
147 147 }
148 148 bool adaptive_young_list_length() {
149 149 return _adaptive_size;
150 150 }
151 151 };
152 152
153 153 class G1CollectorPolicy: public CollectorPolicy {
154 154 private:
155 155 // either equal to the number of parallel threads, if ParallelGCThreads
156 156 // has been set, or 1 otherwise
157 157 int _parallel_gc_threads;
158 158
159 159 // The number of GC threads currently active.
160 160 uintx _no_of_gc_threads;
161 161
162 162 enum SomePrivateConstants {
163 163 NumPrevPausesForHeuristics = 10
164 164 };
165 165
166 166 G1MMUTracker* _mmu_tracker;
167 167
168 168 void initialize_flags();
169 169
170 170 void initialize_all() {
171 171 initialize_flags();
172 172 initialize_size_info();
173 173 initialize_perm_generation(PermGen::MarkSweepCompact);
174 174 }
175 175
176 176 CollectionSetChooser* _collectionSetChooser;
177 177
178 178 double _full_collection_start_sec;
179 179 size_t _cur_collection_pause_used_at_start_bytes;
180 180 uint _cur_collection_pause_used_regions_at_start;
181 181
182 182 // These exclude marking times.
183 183 TruncatedSeq* _recent_gc_times_ms;
184 184
185 185 TruncatedSeq* _concurrent_mark_remark_times_ms;
186 186 TruncatedSeq* _concurrent_mark_cleanup_times_ms;
187 187
188 188 TraceGen0TimeData _trace_gen0_time_data;
189 189 TraceGen1TimeData _trace_gen1_time_data;
190 190
191 191 double _stop_world_start;
192 192
193 193 // indicates whether we are in young or mixed GC mode
194 194 bool _gcs_are_young;
195 195
196 196 uint _young_list_target_length;
197 197 uint _young_list_fixed_length;
198 198 size_t _prev_eden_capacity; // used for logging
199 199
200 200 // The max number of regions we can extend the eden by while the GC
201 201 // locker is active. This should be >= _young_list_target_length;
202 202 uint _young_list_max_length;
203 203
204 204 bool _last_gc_was_young;
205 205
206 206 bool _during_marking;
207 207 bool _in_marking_window;
208 208 bool _in_marking_window_im;
209 209
210 210 SurvRateGroup* _short_lived_surv_rate_group;
211 211 SurvRateGroup* _survivor_surv_rate_group;
212 212 // add here any more surv rate groups
213 213
214 214 double _gc_overhead_perc;
215 215
216 216 double _reserve_factor;
217 217 uint _reserve_regions;
218 218
219 219 bool during_marking() {
220 220 return _during_marking;
221 221 }
222 222
223 223 private:
224 224 enum PredictionConstants {
225 225 TruncatedSeqLength = 10
226 226 };
227 227
228 228 TruncatedSeq* _alloc_rate_ms_seq;
229 229 double _prev_collection_pause_end_ms;
230 230
231 231 TruncatedSeq* _pending_card_diff_seq;
232 232 TruncatedSeq* _rs_length_diff_seq;
233 233 TruncatedSeq* _cost_per_card_ms_seq;
234 234 TruncatedSeq* _young_cards_per_entry_ratio_seq;
235 235 TruncatedSeq* _mixed_cards_per_entry_ratio_seq;
236 236 TruncatedSeq* _cost_per_entry_ms_seq;
237 237 TruncatedSeq* _mixed_cost_per_entry_ms_seq;
238 238 TruncatedSeq* _cost_per_byte_ms_seq;
239 239 TruncatedSeq* _constant_other_time_ms_seq;
240 240 TruncatedSeq* _young_other_cost_per_region_ms_seq;
241 241 TruncatedSeq* _non_young_other_cost_per_region_ms_seq;
242 242
243 243 TruncatedSeq* _pending_cards_seq;
244 244 TruncatedSeq* _rs_lengths_seq;
245 245
246 246 TruncatedSeq* _cost_per_byte_ms_during_cm_seq;
247 247
248 248 G1YoungGenSizer* _young_gen_sizer;
249 249
250 250 uint _eden_cset_region_length;
251 251 uint _survivor_cset_region_length;
252 252 uint _old_cset_region_length;
253 253
254 254 void init_cset_region_lengths(uint eden_cset_region_length,
255 255 uint survivor_cset_region_length);
256 256
257 257 uint eden_cset_region_length() { return _eden_cset_region_length; }
258 258 uint survivor_cset_region_length() { return _survivor_cset_region_length; }
259 259 uint old_cset_region_length() { return _old_cset_region_length; }
260 260
261 261 uint _free_regions_at_end_of_collection;
262 262
263 263 size_t _recorded_rs_lengths;
264 264 size_t _max_rs_lengths;
265 265 double _sigma;
266 266
267 267 size_t _rs_lengths_prediction;
268 268
269 269 double sigma() { return _sigma; }
270 270
271 271 // A function that prevents us putting too much stock in small sample
272 272 // sets. Returns a number between 2.0 and 1.0, depending on the number
273 273 // of samples. 5 or more samples yields one; fewer scales linearly from
274 274 // 2.0 at 1 sample to 1.0 at 5.
275 275 double confidence_factor(int samples) {
276 276 if (samples > 4) return 1.0;
277 277 else return 1.0 + sigma() * ((double)(5 - samples))/2.0;
278 278 }
279 279
280 280 double get_new_neg_prediction(TruncatedSeq* seq) {
281 281 return seq->davg() - sigma() * seq->dsd();
282 282 }
283 283
284 284 #ifndef PRODUCT
285 285 bool verify_young_ages(HeapRegion* head, SurvRateGroup *surv_rate_group);
286 286 #endif // PRODUCT
287 287
288 288 void adjust_concurrent_refinement(double update_rs_time,
289 289 double update_rs_processed_buffers,
290 290 double goal_ms);
291 291
292 292 uintx no_of_gc_threads() { return _no_of_gc_threads; }
293 293 void set_no_of_gc_threads(uintx v) { _no_of_gc_threads = v; }
294 294
295 295 double _pause_time_target_ms;
296 296
297 297 size_t _pending_cards;
298 298 size_t _max_pending_cards;
299 299
300 300 public:
301 301 // Accessors
302 302
303 303 void set_region_eden(HeapRegion* hr, int young_index_in_cset) {
304 304 hr->set_young();
305 305 hr->install_surv_rate_group(_short_lived_surv_rate_group);
306 306 hr->set_young_index_in_cset(young_index_in_cset);
307 307 }
308 308
309 309 void set_region_survivor(HeapRegion* hr, int young_index_in_cset) {
310 310 assert(hr->is_young() && hr->is_survivor(), "pre-condition");
311 311 hr->install_surv_rate_group(_survivor_surv_rate_group);
312 312 hr->set_young_index_in_cset(young_index_in_cset);
313 313 }
314 314
315 315 #ifndef PRODUCT
316 316 bool verify_young_ages();
317 317 #endif // PRODUCT
318 318
319 319 double get_new_prediction(TruncatedSeq* seq) {
320 320 return MAX2(seq->davg() + sigma() * seq->dsd(),
321 321 seq->davg() * confidence_factor(seq->num()));
322 322 }
323 323
324 324 void record_max_rs_lengths(size_t rs_lengths) {
325 325 _max_rs_lengths = rs_lengths;
326 326 }
327 327
328 328 size_t predict_pending_card_diff() {
329 329 double prediction = get_new_neg_prediction(_pending_card_diff_seq);
330 330 if (prediction < 0.00001) {
331 331 return 0;
332 332 } else {
333 333 return (size_t) prediction;
334 334 }
335 335 }
336 336
337 337 size_t predict_pending_cards() {
338 338 size_t max_pending_card_num = _g1->max_pending_card_num();
339 339 size_t diff = predict_pending_card_diff();
340 340 size_t prediction;
341 341 if (diff > max_pending_card_num) {
342 342 prediction = max_pending_card_num;
343 343 } else {
344 344 prediction = max_pending_card_num - diff;
345 345 }
346 346
347 347 return prediction;
348 348 }
349 349
350 350 size_t predict_rs_length_diff() {
351 351 return (size_t) get_new_prediction(_rs_length_diff_seq);
352 352 }
353 353
354 354 double predict_alloc_rate_ms() {
355 355 return get_new_prediction(_alloc_rate_ms_seq);
356 356 }
357 357
358 358 double predict_cost_per_card_ms() {
359 359 return get_new_prediction(_cost_per_card_ms_seq);
360 360 }
361 361
362 362 double predict_rs_update_time_ms(size_t pending_cards) {
363 363 return (double) pending_cards * predict_cost_per_card_ms();
364 364 }
365 365
366 366 double predict_young_cards_per_entry_ratio() {
367 367 return get_new_prediction(_young_cards_per_entry_ratio_seq);
368 368 }
369 369
370 370 double predict_mixed_cards_per_entry_ratio() {
371 371 if (_mixed_cards_per_entry_ratio_seq->num() < 2) {
372 372 return predict_young_cards_per_entry_ratio();
373 373 } else {
374 374 return get_new_prediction(_mixed_cards_per_entry_ratio_seq);
375 375 }
376 376 }
377 377
378 378 size_t predict_young_card_num(size_t rs_length) {
379 379 return (size_t) ((double) rs_length *
380 380 predict_young_cards_per_entry_ratio());
381 381 }
382 382
383 383 size_t predict_non_young_card_num(size_t rs_length) {
384 384 return (size_t) ((double) rs_length *
385 385 predict_mixed_cards_per_entry_ratio());
386 386 }
387 387
388 388 double predict_rs_scan_time_ms(size_t card_num) {
389 389 if (gcs_are_young()) {
390 390 return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq);
391 391 } else {
392 392 return predict_mixed_rs_scan_time_ms(card_num);
393 393 }
394 394 }
395 395
396 396 double predict_mixed_rs_scan_time_ms(size_t card_num) {
397 397 if (_mixed_cost_per_entry_ms_seq->num() < 3) {
398 398 return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq);
399 399 } else {
400 400 return (double) (card_num *
401 401 get_new_prediction(_mixed_cost_per_entry_ms_seq));
402 402 }
403 403 }
404 404
405 405 double predict_object_copy_time_ms_during_cm(size_t bytes_to_copy) {
406 406 if (_cost_per_byte_ms_during_cm_seq->num() < 3) {
407 407 return (1.1 * (double) bytes_to_copy) *
408 408 get_new_prediction(_cost_per_byte_ms_seq);
409 409 } else {
410 410 return (double) bytes_to_copy *
411 411 get_new_prediction(_cost_per_byte_ms_during_cm_seq);
412 412 }
413 413 }
414 414
415 415 double predict_object_copy_time_ms(size_t bytes_to_copy) {
416 416 if (_in_marking_window && !_in_marking_window_im) {
417 417 return predict_object_copy_time_ms_during_cm(bytes_to_copy);
418 418 } else {
419 419 return (double) bytes_to_copy *
420 420 get_new_prediction(_cost_per_byte_ms_seq);
421 421 }
422 422 }
423 423
424 424 double predict_constant_other_time_ms() {
425 425 return get_new_prediction(_constant_other_time_ms_seq);
426 426 }
427 427
428 428 double predict_young_other_time_ms(size_t young_num) {
429 429 return (double) young_num *
430 430 get_new_prediction(_young_other_cost_per_region_ms_seq);
431 431 }
432 432
433 433 double predict_non_young_other_time_ms(size_t non_young_num) {
434 434 return (double) non_young_num *
435 435 get_new_prediction(_non_young_other_cost_per_region_ms_seq);
436 436 }
437 437
438 438 double predict_base_elapsed_time_ms(size_t pending_cards);
439 439 double predict_base_elapsed_time_ms(size_t pending_cards,
440 440 size_t scanned_cards);
441 441 size_t predict_bytes_to_copy(HeapRegion* hr);
442 442 double predict_region_elapsed_time_ms(HeapRegion* hr, bool young);
443 443
444 444 void set_recorded_rs_lengths(size_t rs_lengths);
445 445
446 446 uint cset_region_length() { return young_cset_region_length() +
447 447 old_cset_region_length(); }
448 448 uint young_cset_region_length() { return eden_cset_region_length() +
449 449 survivor_cset_region_length(); }
450 450
451 451 double predict_survivor_regions_evac_time();
452 452
453 453 void cset_regions_freed() {
454 454 bool propagate = _last_gc_was_young && !_in_marking_window;
455 455 _short_lived_surv_rate_group->all_surviving_words_recorded(propagate);
456 456 _survivor_surv_rate_group->all_surviving_words_recorded(propagate);
457 457 // also call it on any more surv rate groups
458 458 }
459 459
460 460 G1MMUTracker* mmu_tracker() {
461 461 return _mmu_tracker;
462 462 }
463 463
464 464 double max_pause_time_ms() {
465 465 return _mmu_tracker->max_gc_time() * 1000.0;
466 466 }
467 467
468 468 double predict_remark_time_ms() {
469 469 return get_new_prediction(_concurrent_mark_remark_times_ms);
470 470 }
471 471
472 472 double predict_cleanup_time_ms() {
473 473 return get_new_prediction(_concurrent_mark_cleanup_times_ms);
474 474 }
475 475
476 476 // Returns an estimate of the survival rate of the region at yg-age
477 477 // "yg_age".
478 478 double predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) {
479 479 TruncatedSeq* seq = surv_rate_group->get_seq(age);
480 480 if (seq->num() == 0)
481 481 gclog_or_tty->print("BARF! age is %d", age);
482 482 guarantee( seq->num() > 0, "invariant" );
483 483 double pred = get_new_prediction(seq);
484 484 if (pred > 1.0)
485 485 pred = 1.0;
486 486 return pred;
487 487 }
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488 488
489 489 double predict_yg_surv_rate(int age) {
490 490 return predict_yg_surv_rate(age, _short_lived_surv_rate_group);
491 491 }
492 492
493 493 double accum_yg_surv_rate_pred(int age) {
494 494 return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
495 495 }
496 496
497 497 private:
498 - size_t _bytes_in_collection_set_before_gc;
499 - size_t _bytes_copied_during_gc;
500 -
501 - // Used to count used bytes in CS.
502 - friend class CountCSClosure;
503 -
504 498 // Statistics kept per GC stoppage, pause or full.
505 499 TruncatedSeq* _recent_prev_end_times_for_all_gcs_sec;
506 500
507 501 // Add a new GC of the given duration and end time to the record.
508 502 void update_recent_gc_times(double end_time_sec, double elapsed_ms);
509 503
510 504 // The head of the list (via "next_in_collection_set()") representing the
511 505 // current collection set. Set from the incrementally built collection
512 506 // set at the start of the pause.
513 507 HeapRegion* _collection_set;
514 508
515 509 // The number of bytes in the collection set before the pause. Set from
516 510 // the incrementally built collection set at the start of an evacuation
517 - // pause.
511 + // pause, and incremented in finalize_cset() when adding old regions
512 + // (if any) to the collection set.
518 513 size_t _collection_set_bytes_used_before;
519 514
515 + // The number of bytes copied during the GC.
516 + size_t _bytes_copied_during_gc;
517 +
520 518 // The associated information that is maintained while the incremental
521 519 // collection set is being built with young regions. Used to populate
522 520 // the recorded info for the evacuation pause.
523 521
524 522 enum CSetBuildType {
525 523 Active, // We are actively building the collection set
526 524 Inactive // We are not actively building the collection set
527 525 };
528 526
529 527 CSetBuildType _inc_cset_build_state;
530 528
531 529 // The head of the incrementally built collection set.
532 530 HeapRegion* _inc_cset_head;
533 531
534 532 // The tail of the incrementally built collection set.
535 533 HeapRegion* _inc_cset_tail;
536 534
537 535 // The number of bytes in the incrementally built collection set.
538 536 // Used to set _collection_set_bytes_used_before at the start of
539 537 // an evacuation pause.
540 538 size_t _inc_cset_bytes_used_before;
541 539
542 540 // Used to record the highest end of heap region in collection set
543 541 HeapWord* _inc_cset_max_finger;
544 542
545 543 // The RSet lengths recorded for regions in the CSet. It is updated
546 544 // by the thread that adds a new region to the CSet. We assume that
547 545 // only one thread can be allocating a new CSet region (currently,
548 546 // it does so after taking the Heap_lock) hence no need to
549 547 // synchronize updates to this field.
550 548 size_t _inc_cset_recorded_rs_lengths;
551 549
552 550 // A concurrent refinement thread periodcially samples the young
553 551 // region RSets and needs to update _inc_cset_recorded_rs_lengths as
554 552 // the RSets grow. Instead of having to syncronize updates to that
555 553 // field we accumulate them in this field and add it to
556 554 // _inc_cset_recorded_rs_lengths_diffs at the start of a GC.
557 555 ssize_t _inc_cset_recorded_rs_lengths_diffs;
558 556
559 557 // The predicted elapsed time it will take to collect the regions in
560 558 // the CSet. This is updated by the thread that adds a new region to
561 559 // the CSet. See the comment for _inc_cset_recorded_rs_lengths about
562 560 // MT-safety assumptions.
563 561 double _inc_cset_predicted_elapsed_time_ms;
564 562
565 563 // See the comment for _inc_cset_recorded_rs_lengths_diffs.
566 564 double _inc_cset_predicted_elapsed_time_ms_diffs;
567 565
568 566 // Stash a pointer to the g1 heap.
569 567 G1CollectedHeap* _g1;
570 568
571 569 G1GCPhaseTimes* _phase_times;
572 570
573 571 // The ratio of gc time to elapsed time, computed over recent pauses.
574 572 double _recent_avg_pause_time_ratio;
575 573
576 574 double recent_avg_pause_time_ratio() {
577 575 return _recent_avg_pause_time_ratio;
578 576 }
579 577
580 578 // At the end of a pause we check the heap occupancy and we decide
581 579 // whether we will start a marking cycle during the next pause. If
582 580 // we decide that we want to do that, we will set this parameter to
583 581 // true. So, this parameter will stay true between the end of a
584 582 // pause and the beginning of a subsequent pause (not necessarily
585 583 // the next one, see the comments on the next field) when we decide
586 584 // that we will indeed start a marking cycle and do the initial-mark
587 585 // work.
588 586 volatile bool _initiate_conc_mark_if_possible;
589 587
590 588 // If initiate_conc_mark_if_possible() is set at the beginning of a
591 589 // pause, it is a suggestion that the pause should start a marking
592 590 // cycle by doing the initial-mark work. However, it is possible
593 591 // that the concurrent marking thread is still finishing up the
594 592 // previous marking cycle (e.g., clearing the next marking
595 593 // bitmap). If that is the case we cannot start a new cycle and
596 594 // we'll have to wait for the concurrent marking thread to finish
597 595 // what it is doing. In this case we will postpone the marking cycle
598 596 // initiation decision for the next pause. When we eventually decide
599 597 // to start a cycle, we will set _during_initial_mark_pause which
600 598 // will stay true until the end of the initial-mark pause and it's
601 599 // the condition that indicates that a pause is doing the
602 600 // initial-mark work.
603 601 volatile bool _during_initial_mark_pause;
604 602
605 603 bool _last_young_gc;
606 604
607 605 // This set of variables tracks the collector efficiency, in order to
608 606 // determine whether we should initiate a new marking.
609 607 double _cur_mark_stop_world_time_ms;
610 608 double _mark_remark_start_sec;
611 609 double _mark_cleanup_start_sec;
612 610
613 611 // Update the young list target length either by setting it to the
614 612 // desired fixed value or by calculating it using G1's pause
615 613 // prediction model. If no rs_lengths parameter is passed, predict
616 614 // the RS lengths using the prediction model, otherwise use the
617 615 // given rs_lengths as the prediction.
618 616 void update_young_list_target_length(size_t rs_lengths = (size_t) -1);
619 617
620 618 // Calculate and return the minimum desired young list target
621 619 // length. This is the minimum desired young list length according
622 620 // to the user's inputs.
623 621 uint calculate_young_list_desired_min_length(uint base_min_length);
624 622
625 623 // Calculate and return the maximum desired young list target
626 624 // length. This is the maximum desired young list length according
627 625 // to the user's inputs.
628 626 uint calculate_young_list_desired_max_length();
629 627
630 628 // Calculate and return the maximum young list target length that
631 629 // can fit into the pause time goal. The parameters are: rs_lengths
632 630 // represent the prediction of how large the young RSet lengths will
633 631 // be, base_min_length is the alreay existing number of regions in
634 632 // the young list, min_length and max_length are the desired min and
635 633 // max young list length according to the user's inputs.
636 634 uint calculate_young_list_target_length(size_t rs_lengths,
637 635 uint base_min_length,
638 636 uint desired_min_length,
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639 637 uint desired_max_length);
640 638
641 639 // Check whether a given young length (young_length) fits into the
642 640 // given target pause time and whether the prediction for the amount
643 641 // of objects to be copied for the given length will fit into the
644 642 // given free space (expressed by base_free_regions). It is used by
645 643 // calculate_young_list_target_length().
646 644 bool predict_will_fit(uint young_length, double base_time_ms,
647 645 uint base_free_regions, double target_pause_time_ms);
648 646
649 - // Count the number of bytes used in the CS.
650 - void count_CS_bytes_used();
651 -
652 647 public:
653 648
654 649 G1CollectorPolicy();
655 650
656 651 virtual G1CollectorPolicy* as_g1_policy() { return this; }
657 652
658 653 virtual CollectorPolicy::Name kind() {
659 654 return CollectorPolicy::G1CollectorPolicyKind;
660 655 }
661 656
662 657 G1GCPhaseTimes* phase_times() const { return _phase_times; }
663 658
664 659 // Check the current value of the young list RSet lengths and
665 660 // compare it against the last prediction. If the current value is
666 661 // higher, recalculate the young list target length prediction.
667 662 void revise_young_list_target_length_if_necessary();
668 663
669 - size_t bytes_in_collection_set() {
670 - return _bytes_in_collection_set_before_gc;
671 - }
672 -
673 664 // This should be called after the heap is resized.
674 665 void record_new_heap_size(uint new_number_of_regions);
675 666
676 667 void init();
677 668
678 669 // Create jstat counters for the policy.
679 670 virtual void initialize_gc_policy_counters();
680 671
681 672 virtual HeapWord* mem_allocate_work(size_t size,
682 673 bool is_tlab,
683 674 bool* gc_overhead_limit_was_exceeded);
684 675
685 676 // This method controls how a collector handles one or more
686 677 // of its generations being fully allocated.
687 678 virtual HeapWord* satisfy_failed_allocation(size_t size,
688 679 bool is_tlab);
689 680
690 681 BarrierSet::Name barrier_set_name() { return BarrierSet::G1SATBCTLogging; }
691 682
692 683 GenRemSet::Name rem_set_name() { return GenRemSet::CardTable; }
693 684
694 685 bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0);
695 686
696 687 // Update the heuristic info to record a collection pause of the given
697 688 // start time, where the given number of bytes were used at the start.
698 689 // This may involve changing the desired size of a collection set.
699 690
700 691 void record_stop_world_start();
701 692
702 693 void record_collection_pause_start(double start_time_sec, size_t start_used);
703 694
704 695 // Must currently be called while the world is stopped.
705 696 void record_concurrent_mark_init_end(double
706 697 mark_init_elapsed_time_ms);
707 698
708 699 void record_concurrent_mark_remark_start();
709 700 void record_concurrent_mark_remark_end();
710 701
711 702 void record_concurrent_mark_cleanup_start();
712 703 void record_concurrent_mark_cleanup_end(int no_of_gc_threads);
713 704 void record_concurrent_mark_cleanup_completed();
714 705
715 706 void record_concurrent_pause();
716 707
717 708 void record_collection_pause_end(double pause_time);
718 709 void print_heap_transition();
719 710
720 711 // Record the fact that a full collection occurred.
721 712 void record_full_collection_start();
722 713 void record_full_collection_end();
723 714
724 715 // Record how much space we copied during a GC. This is typically
725 716 // called when a GC alloc region is being retired.
726 717 void record_bytes_copied_during_gc(size_t bytes) {
727 718 _bytes_copied_during_gc += bytes;
728 719 }
729 720
730 721 // The amount of space we copied during a GC.
731 722 size_t bytes_copied_during_gc() {
732 723 return _bytes_copied_during_gc;
733 724 }
734 725
735 726 // Determine whether there are candidate regions so that the
736 727 // next GC should be mixed. The two action strings are used
737 728 // in the ergo output when the method returns true or false.
738 729 bool next_gc_should_be_mixed(const char* true_action_str,
739 730 const char* false_action_str);
740 731
741 732 // Choose a new collection set. Marks the chosen regions as being
742 733 // "in_collection_set", and links them together. The head and number of
743 734 // the collection set are available via access methods.
744 735 void finalize_cset(double target_pause_time_ms);
745 736
746 737 // The head of the list (via "next_in_collection_set()") representing the
747 738 // current collection set.
748 739 HeapRegion* collection_set() { return _collection_set; }
749 740
750 741 void clear_collection_set() { _collection_set = NULL; }
751 742
752 743 // Add old region "hr" to the CSet.
753 744 void add_old_region_to_cset(HeapRegion* hr);
754 745
755 746 // Incremental CSet Support
756 747
757 748 // The head of the incrementally built collection set.
758 749 HeapRegion* inc_cset_head() { return _inc_cset_head; }
759 750
760 751 // The tail of the incrementally built collection set.
761 752 HeapRegion* inc_set_tail() { return _inc_cset_tail; }
762 753
763 754 // Initialize incremental collection set info.
764 755 void start_incremental_cset_building();
765 756
766 757 // Perform any final calculations on the incremental CSet fields
767 758 // before we can use them.
768 759 void finalize_incremental_cset_building();
769 760
770 761 void clear_incremental_cset() {
771 762 _inc_cset_head = NULL;
772 763 _inc_cset_tail = NULL;
773 764 }
774 765
775 766 // Stop adding regions to the incremental collection set
776 767 void stop_incremental_cset_building() { _inc_cset_build_state = Inactive; }
777 768
778 769 // Add information about hr to the aggregated information for the
779 770 // incrementally built collection set.
780 771 void add_to_incremental_cset_info(HeapRegion* hr, size_t rs_length);
781 772
782 773 // Update information about hr in the aggregated information for
783 774 // the incrementally built collection set.
784 775 void update_incremental_cset_info(HeapRegion* hr, size_t new_rs_length);
785 776
786 777 private:
787 778 // Update the incremental cset information when adding a region
788 779 // (should not be called directly).
789 780 void add_region_to_incremental_cset_common(HeapRegion* hr);
790 781
791 782 public:
792 783 // Add hr to the LHS of the incremental collection set.
793 784 void add_region_to_incremental_cset_lhs(HeapRegion* hr);
794 785
795 786 // Add hr to the RHS of the incremental collection set.
796 787 void add_region_to_incremental_cset_rhs(HeapRegion* hr);
797 788
798 789 #ifndef PRODUCT
799 790 void print_collection_set(HeapRegion* list_head, outputStream* st);
800 791 #endif // !PRODUCT
801 792
802 793 bool initiate_conc_mark_if_possible() { return _initiate_conc_mark_if_possible; }
803 794 void set_initiate_conc_mark_if_possible() { _initiate_conc_mark_if_possible = true; }
804 795 void clear_initiate_conc_mark_if_possible() { _initiate_conc_mark_if_possible = false; }
805 796
806 797 bool during_initial_mark_pause() { return _during_initial_mark_pause; }
807 798 void set_during_initial_mark_pause() { _during_initial_mark_pause = true; }
808 799 void clear_during_initial_mark_pause(){ _during_initial_mark_pause = false; }
809 800
810 801 // This sets the initiate_conc_mark_if_possible() flag to start a
811 802 // new cycle, as long as we are not already in one. It's best if it
812 803 // is called during a safepoint when the test whether a cycle is in
813 804 // progress or not is stable.
814 805 bool force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause);
815 806
816 807 // This is called at the very beginning of an evacuation pause (it
817 808 // has to be the first thing that the pause does). If
818 809 // initiate_conc_mark_if_possible() is true, and the concurrent
819 810 // marking thread has completed its work during the previous cycle,
820 811 // it will set during_initial_mark_pause() to so that the pause does
821 812 // the initial-mark work and start a marking cycle.
822 813 void decide_on_conc_mark_initiation();
823 814
824 815 // If an expansion would be appropriate, because recent GC overhead had
825 816 // exceeded the desired limit, return an amount to expand by.
826 817 size_t expansion_amount();
827 818
828 819 // Print tracing information.
829 820 void print_tracing_info() const;
830 821
831 822 // Print stats on young survival ratio
832 823 void print_yg_surv_rate_info() const;
833 824
834 825 void finished_recalculating_age_indexes(bool is_survivors) {
835 826 if (is_survivors) {
836 827 _survivor_surv_rate_group->finished_recalculating_age_indexes();
837 828 } else {
838 829 _short_lived_surv_rate_group->finished_recalculating_age_indexes();
839 830 }
840 831 // do that for any other surv rate groups
841 832 }
842 833
843 834 bool is_young_list_full() {
844 835 uint young_list_length = _g1->young_list()->length();
845 836 uint young_list_target_length = _young_list_target_length;
846 837 return young_list_length >= young_list_target_length;
847 838 }
848 839
849 840 bool can_expand_young_list() {
850 841 uint young_list_length = _g1->young_list()->length();
851 842 uint young_list_max_length = _young_list_max_length;
852 843 return young_list_length < young_list_max_length;
853 844 }
854 845
855 846 uint young_list_max_length() {
856 847 return _young_list_max_length;
857 848 }
858 849
859 850 bool gcs_are_young() {
860 851 return _gcs_are_young;
861 852 }
862 853 void set_gcs_are_young(bool gcs_are_young) {
863 854 _gcs_are_young = gcs_are_young;
864 855 }
865 856
866 857 bool adaptive_young_list_length() {
867 858 return _young_gen_sizer->adaptive_young_list_length();
868 859 }
869 860
870 861 private:
871 862 //
872 863 // Survivor regions policy.
873 864 //
874 865
875 866 // Current tenuring threshold, set to 0 if the collector reaches the
876 867 // maximum amount of suvivors regions.
877 868 int _tenuring_threshold;
878 869
879 870 // The limit on the number of regions allocated for survivors.
880 871 uint _max_survivor_regions;
881 872
882 873 // For reporting purposes.
883 874 size_t _eden_bytes_before_gc;
884 875 size_t _survivor_bytes_before_gc;
885 876 size_t _capacity_before_gc;
886 877
887 878 // The amount of survor regions after a collection.
888 879 uint _recorded_survivor_regions;
889 880 // List of survivor regions.
890 881 HeapRegion* _recorded_survivor_head;
891 882 HeapRegion* _recorded_survivor_tail;
892 883
893 884 ageTable _survivors_age_table;
894 885
895 886 public:
896 887
897 888 inline GCAllocPurpose
898 889 evacuation_destination(HeapRegion* src_region, int age, size_t word_sz) {
899 890 if (age < _tenuring_threshold && src_region->is_young()) {
900 891 return GCAllocForSurvived;
901 892 } else {
902 893 return GCAllocForTenured;
903 894 }
904 895 }
905 896
906 897 inline bool track_object_age(GCAllocPurpose purpose) {
907 898 return purpose == GCAllocForSurvived;
908 899 }
909 900
910 901 static const uint REGIONS_UNLIMITED = (uint) -1;
911 902
912 903 uint max_regions(int purpose);
913 904
914 905 // The limit on regions for a particular purpose is reached.
915 906 void note_alloc_region_limit_reached(int purpose) {
916 907 if (purpose == GCAllocForSurvived) {
917 908 _tenuring_threshold = 0;
918 909 }
919 910 }
920 911
921 912 void note_start_adding_survivor_regions() {
922 913 _survivor_surv_rate_group->start_adding_regions();
923 914 }
924 915
925 916 void note_stop_adding_survivor_regions() {
926 917 _survivor_surv_rate_group->stop_adding_regions();
927 918 }
928 919
929 920 void record_survivor_regions(uint regions,
930 921 HeapRegion* head,
931 922 HeapRegion* tail) {
932 923 _recorded_survivor_regions = regions;
933 924 _recorded_survivor_head = head;
934 925 _recorded_survivor_tail = tail;
935 926 }
936 927
937 928 uint recorded_survivor_regions() {
938 929 return _recorded_survivor_regions;
939 930 }
940 931
941 932 void record_thread_age_table(ageTable* age_table) {
942 933 _survivors_age_table.merge_par(age_table);
943 934 }
944 935
945 936 void update_max_gc_locker_expansion();
946 937
947 938 // Calculates survivor space parameters.
948 939 void update_survivors_policy();
949 940
950 941 };
951 942
952 943 // This should move to some place more general...
953 944
954 945 // If we have "n" measurements, and we've kept track of their "sum" and the
955 946 // "sum_of_squares" of the measurements, this returns the variance of the
956 947 // sequence.
957 948 inline double variance(int n, double sum_of_squares, double sum) {
958 949 double n_d = (double)n;
959 950 double avg = sum/n_d;
960 951 return (sum_of_squares - 2.0 * avg * sum + n_d * avg * avg) / n_d;
961 952 }
962 953
963 954 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP
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