1 /*
2 * Copyright (c) 2004, 2006, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
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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).
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23 */
24
25 // This class keeps statistical information and computes the
26 // size of the heap for the concurrent mark sweep collector.
27 //
28 // Cost for garbage collector include cost for
29 // minor collection
30 // concurrent collection
31 // stop-the-world component
32 // concurrent component
33 // major compacting collection
34 // uses decaying cost
35
36 // Forward decls
37 class elapsedTimer;
38
39 class CMSAdaptiveSizePolicy : public AdaptiveSizePolicy {
40 friend class CMSGCAdaptivePolicyCounters;
41 friend class CMSCollector;
42 private:
43
44 // Total number of processors available
45 int _processor_count;
46 // Number of processors used by the concurrent phases of GC
47 // This number is assumed to be the same for all concurrent
48 // phases.
49 int _concurrent_processor_count;
50
51 // Time that the mutators run exclusive of a particular
52 // phase. For example, the time the mutators run excluding
53 // the time during which the cms collector runs concurrently
54 // with the mutators.
55 // Between end of most recent cms reset and start of initial mark
56 // This may be redundant
57 double _latest_cms_reset_end_to_initial_mark_start_secs;
58 // Between end of the most recent initial mark and start of remark
59 double _latest_cms_initial_mark_end_to_remark_start_secs;
60 // Between end of most recent collection and start of
61 // a concurrent collection
62 double _latest_cms_collection_end_to_collection_start_secs;
63 // Times of the concurrent phases of the most recent
64 // concurrent collection
65 double _latest_cms_concurrent_marking_time_secs;
66 double _latest_cms_concurrent_precleaning_time_secs;
67 double _latest_cms_concurrent_sweeping_time_secs;
68 // Between end of most recent STW MSC and start of next STW MSC
69 double _latest_cms_msc_end_to_msc_start_time_secs;
70 // Between end of most recent MS and start of next MS
71 // This does not include any time spent during a concurrent
72 // collection.
73 double _latest_cms_ms_end_to_ms_start;
74 // Between start and end of the initial mark of the most recent
75 // concurrent collection.
76 double _latest_cms_initial_mark_start_to_end_time_secs;
77 // Between start and end of the remark phase of the most recent
78 // concurrent collection
79 double _latest_cms_remark_start_to_end_time_secs;
80 // Between start and end of the most recent MS STW marking phase
81 double _latest_cms_ms_marking_start_to_end_time_secs;
82
83 // Pause time timers
84 static elapsedTimer _STW_timer;
85 // Concurrent collection timer. Used for total of all concurrent phases
86 // during 1 collection cycle.
87 static elapsedTimer _concurrent_timer;
88
89 // When the size of the generation is changed, the size
90 // of the change will rounded up or down (depending on the
91 // type of change) by this value.
92 size_t _generation_alignment;
93
94 // If this variable is true, the size of the young generation
95 // may be changed in order to reduce the pause(s) of the
96 // collection of the tenured generation in order to meet the
97 // pause time goal. It is common to change the size of the
98 // tenured generation in order to meet the pause time goal
99 // for the tenured generation. With the CMS collector for
100 // the tenured generation, the size of the young generation
101 // can have an significant affect on the pause times for collecting the
102 // tenured generation.
103 // This is a duplicate of a variable in PSAdaptiveSizePolicy. It
104 // is duplicated because it is not clear that it is general enough
105 // to go into AdaptiveSizePolicy.
106 int _change_young_gen_for_maj_pauses;
107
108 // Variable that is set to true after a collection.
109 bool _first_after_collection;
110
111 // Fraction of collections that are of each type
112 double concurrent_fraction() const;
113 double STW_msc_fraction() const;
114 double STW_ms_fraction() const;
115
116 // This call cannot be put into the epilogue as long as some
117 // of the counters can be set during concurrent phases.
118 virtual void clear_generation_free_space_flags();
119
120 void set_first_after_collection() { _first_after_collection = true; }
121
122 protected:
123 // Average of the sum of the concurrent times for
124 // one collection in seconds.
125 AdaptiveWeightedAverage* _avg_concurrent_time;
126 // Average time between concurrent collections in seconds.
127 AdaptiveWeightedAverage* _avg_concurrent_interval;
128 // Average cost of the concurrent part of a collection
129 // in seconds.
130 AdaptiveWeightedAverage* _avg_concurrent_gc_cost;
131
132 // Average of the initial pause of a concurrent collection in seconds.
133 AdaptivePaddedAverage* _avg_initial_pause;
134 // Average of the remark pause of a concurrent collection in seconds.
135 AdaptivePaddedAverage* _avg_remark_pause;
136
137 // Average of the stop-the-world (STW) (initial mark + remark)
138 // times in seconds for concurrent collections.
139 AdaptiveWeightedAverage* _avg_cms_STW_time;
140 // Average of the STW collection cost for concurrent collections.
141 AdaptiveWeightedAverage* _avg_cms_STW_gc_cost;
142
143 // Average of the bytes free at the start of the sweep.
144 AdaptiveWeightedAverage* _avg_cms_free_at_sweep;
145 // Average of the bytes free at the end of the collection.
146 AdaptiveWeightedAverage* _avg_cms_free;
147 // Average of the bytes promoted between cms collections.
148 AdaptiveWeightedAverage* _avg_cms_promo;
149
150 // stop-the-world (STW) mark-sweep-compact
151 // Average of the pause time in seconds for STW mark-sweep-compact
152 // collections.
153 AdaptiveWeightedAverage* _avg_msc_pause;
154 // Average of the interval in seconds between STW mark-sweep-compact
155 // collections.
156 AdaptiveWeightedAverage* _avg_msc_interval;
157 // Average of the collection costs for STW mark-sweep-compact
158 // collections.
159 AdaptiveWeightedAverage* _avg_msc_gc_cost;
160
161 // Averages for mark-sweep collections.
162 // The collection may have started as a background collection
163 // that completes in a stop-the-world (STW) collection.
164 // Average of the pause time in seconds for mark-sweep
165 // collections.
166 AdaptiveWeightedAverage* _avg_ms_pause;
167 // Average of the interval in seconds between mark-sweep
168 // collections.
169 AdaptiveWeightedAverage* _avg_ms_interval;
170 // Average of the collection costs for mark-sweep
171 // collections.
172 AdaptiveWeightedAverage* _avg_ms_gc_cost;
173
174 // These variables contain a linear fit of
175 // a generation size as the independent variable
176 // and a pause time as the dependent variable.
177 // For example _remark_pause_old_estimator
178 // is a fit of the old generation size as the
179 // independent variable and the remark pause
180 // as the dependent variable.
181 // remark pause time vs. cms gen size
182 LinearLeastSquareFit* _remark_pause_old_estimator;
183 // initial pause time vs. cms gen size
184 LinearLeastSquareFit* _initial_pause_old_estimator;
185 // remark pause time vs. young gen size
186 LinearLeastSquareFit* _remark_pause_young_estimator;
187 // initial pause time vs. young gen size
188 LinearLeastSquareFit* _initial_pause_young_estimator;
189
190 // Accessors
191 int processor_count() const { return _processor_count; }
192 int concurrent_processor_count() const { return _concurrent_processor_count; }
193
194 AdaptiveWeightedAverage* avg_concurrent_time() const {
195 return _avg_concurrent_time;
196 }
197
198 AdaptiveWeightedAverage* avg_concurrent_interval() const {
199 return _avg_concurrent_interval;
200 }
201
202 AdaptiveWeightedAverage* avg_concurrent_gc_cost() const {
203 return _avg_concurrent_gc_cost;
204 }
205
206 AdaptiveWeightedAverage* avg_cms_STW_time() const {
207 return _avg_cms_STW_time;
208 }
209
210 AdaptiveWeightedAverage* avg_cms_STW_gc_cost() const {
211 return _avg_cms_STW_gc_cost;
212 }
213
214 AdaptivePaddedAverage* avg_initial_pause() const {
215 return _avg_initial_pause;
216 }
217
218 AdaptivePaddedAverage* avg_remark_pause() const {
219 return _avg_remark_pause;
220 }
221
222 AdaptiveWeightedAverage* avg_cms_free() const {
223 return _avg_cms_free;
224 }
225
226 AdaptiveWeightedAverage* avg_cms_free_at_sweep() const {
227 return _avg_cms_free_at_sweep;
228 }
229
230 AdaptiveWeightedAverage* avg_msc_pause() const {
231 return _avg_msc_pause;
232 }
233
234 AdaptiveWeightedAverage* avg_msc_interval() const {
235 return _avg_msc_interval;
236 }
237
238 AdaptiveWeightedAverage* avg_msc_gc_cost() const {
239 return _avg_msc_gc_cost;
240 }
241
242 AdaptiveWeightedAverage* avg_ms_pause() const {
243 return _avg_ms_pause;
244 }
245
246 AdaptiveWeightedAverage* avg_ms_interval() const {
247 return _avg_ms_interval;
248 }
249
250 AdaptiveWeightedAverage* avg_ms_gc_cost() const {
251 return _avg_ms_gc_cost;
252 }
253
254 LinearLeastSquareFit* remark_pause_old_estimator() {
255 return _remark_pause_old_estimator;
256 }
257 LinearLeastSquareFit* initial_pause_old_estimator() {
258 return _initial_pause_old_estimator;
259 }
260 LinearLeastSquareFit* remark_pause_young_estimator() {
261 return _remark_pause_young_estimator;
262 }
263 LinearLeastSquareFit* initial_pause_young_estimator() {
264 return _initial_pause_young_estimator;
265 }
266
267 // These *slope() methods return the slope
268 // m for the linear fit of an independent
269 // variable vs. a dependent variable. For
270 // example
271 // remark_pause = m * old_generation_size + c
272 // These may be used to determine if an
273 // adjustment should be made to achieve a goal.
274 // For example, if remark_pause_old_slope() is
275 // positive, a reduction of the old generation
276 // size has on average resulted in the reduction
277 // of the remark pause.
278 float remark_pause_old_slope() {
279 return _remark_pause_old_estimator->slope();
280 }
281
282 float initial_pause_old_slope() {
283 return _initial_pause_old_estimator->slope();
284 }
285
286 float remark_pause_young_slope() {
287 return _remark_pause_young_estimator->slope();
288 }
289
290 float initial_pause_young_slope() {
291 return _initial_pause_young_estimator->slope();
292 }
293
294 // Update estimators
295 void update_minor_pause_old_estimator(double minor_pause_in_ms);
296
297 // Fraction of processors used by the concurrent phases.
298 double concurrent_processor_fraction();
299
300 // Returns the total times for the concurrent part of the
301 // latest collection in seconds.
302 double concurrent_collection_time();
303
304 // Return the total times for the concurrent part of the
305 // latest collection in seconds where the times of the various
306 // concurrent phases are scaled by the processor fraction used
307 // during the phase.
308 double scaled_concurrent_collection_time();
309
310 // Dimensionless concurrent GC cost for all the concurrent phases.
311 double concurrent_collection_cost(double interval_in_seconds);
312
313 // Dimensionless GC cost
314 double collection_cost(double pause_in_seconds, double interval_in_seconds);
315
316 virtual GCPolicyKind kind() const { return _gc_cms_adaptive_size_policy; }
317
318 virtual double time_since_major_gc() const;
319
320 // This returns the maximum average for the concurrent, ms, and
321 // msc collections. This is meant to be used for the calculation
322 // of the decayed major gc cost and is not in general the
323 // average of all the different types of major collections.
324 virtual double major_gc_interval_average_for_decay() const;
325
326 public:
327 CMSAdaptiveSizePolicy(size_t init_eden_size,
328 size_t init_promo_size,
329 size_t init_survivor_size,
330 double max_gc_minor_pause_sec,
331 double max_gc_pause_sec,
332 uint gc_cost_ratio);
333
334 // The timers for the stop-the-world phases measure a total
335 // stop-the-world time. The timer is started and stopped
336 // for each phase but is only reset after the final checkpoint.
337 void checkpoint_roots_initial_begin();
338 void checkpoint_roots_initial_end(GCCause::Cause gc_cause);
339 void checkpoint_roots_final_begin();
340 void checkpoint_roots_final_end(GCCause::Cause gc_cause);
341
342 // Methods for gathering information about the
343 // concurrent marking phase of the collection.
344 // Records the mutator times and
345 // resets the concurrent timer.
346 void concurrent_marking_begin();
347 // Resets concurrent phase timer in the begin methods and
348 // saves the time for a phase in the end methods.
349 void concurrent_marking_end();
350 void concurrent_sweeping_begin();
351 void concurrent_sweeping_end();
352 // Similar to the above (e.g., concurrent_marking_end()) and
353 // is used for both the precleaning an abortable precleaing
354 // phases.
355 void concurrent_precleaning_begin();
356 void concurrent_precleaning_end();
357 // Stops the concurrent phases time. Gathers
358 // information and resets the timer.
359 void concurrent_phases_end(GCCause::Cause gc_cause,
360 size_t cur_eden,
361 size_t cur_promo);
362
363 // Methods for gather information about STW Mark-Sweep-Compact
364 void msc_collection_begin();
365 void msc_collection_end(GCCause::Cause gc_cause);
366
367 // Methods for gather information about Mark-Sweep done
368 // in the foreground.
369 void ms_collection_begin();
370 void ms_collection_end(GCCause::Cause gc_cause);
371
372 // Cost for a mark-sweep tenured gen collection done in the foreground
373 double ms_gc_cost() const {
374 return MAX2(0.0F, _avg_ms_gc_cost->average());
375 }
376
377 // Cost of collecting the tenured generation. Includes
378 // concurrent collection and STW collection costs
379 double cms_gc_cost() const;
380
381 // Cost of STW mark-sweep-compact tenured gen collection.
382 double msc_gc_cost() const {
383 return MAX2(0.0F, _avg_msc_gc_cost->average());
384 }
385
386 //
387 double compacting_gc_cost() const {
388 double result = MIN2(1.0, minor_gc_cost() + msc_gc_cost());
389 assert(result >= 0.0, "Both minor and major costs are non-negative");
390 return result;
391 }
392
393 // Restarts the concurrent phases timer.
394 void concurrent_phases_resume();
395
396 // Time beginning and end of the marking phase for
397 // a synchronous MS collection. A MS collection
398 // that finishes in the foreground can have started
399 // in the background. These methods capture the
400 // completion of the marking (after the initial
401 // marking) that is done in the foreground.
402 void ms_collection_marking_begin();
403 void ms_collection_marking_end(GCCause::Cause gc_cause);
404
405 static elapsedTimer* concurrent_timer_ptr() {
406 return &_concurrent_timer;
407 }
408
409 AdaptiveWeightedAverage* avg_cms_promo() const {
410 return _avg_cms_promo;
411 }
412
413 int change_young_gen_for_maj_pauses() {
414 return _change_young_gen_for_maj_pauses;
415 }
416 void set_change_young_gen_for_maj_pauses(int v) {
417 _change_young_gen_for_maj_pauses = v;
418 }
419
420 void clear_internal_time_intervals();
421
422
423 // Either calculated_promo_size_in_bytes() or promo_size()
424 // should be deleted.
425 size_t promo_size() { return _promo_size; }
426 void set_promo_size(size_t v) { _promo_size = v; }
427
428 // Cost of GC for all types of collections.
429 virtual double gc_cost() const;
430
431 size_t generation_alignment() { return _generation_alignment; }
432
433 virtual void compute_young_generation_free_space(size_t cur_eden,
434 size_t max_eden_size);
435 // Calculates new survivor space size; returns a new tenuring threshold
436 // value. Stores new survivor size in _survivor_size.
437 virtual int compute_survivor_space_size_and_threshold(
438 bool is_survivor_overflow,
439 int tenuring_threshold,
440 size_t survivor_limit);
441
442 virtual void compute_tenured_generation_free_space(size_t cur_tenured_free,
443 size_t max_tenured_available,
444 size_t cur_eden);
445
446 size_t eden_decrement_aligned_down(size_t cur_eden);
447 size_t eden_increment_aligned_up(size_t cur_eden);
448
449 size_t adjust_eden_for_pause_time(size_t cur_eden);
450 size_t adjust_eden_for_throughput(size_t cur_eden);
451 size_t adjust_eden_for_footprint(size_t cur_eden);
452
453 size_t promo_decrement_aligned_down(size_t cur_promo);
454 size_t promo_increment_aligned_up(size_t cur_promo);
455
456 size_t adjust_promo_for_pause_time(size_t cur_promo);
457 size_t adjust_promo_for_throughput(size_t cur_promo);
458 size_t adjust_promo_for_footprint(size_t cur_promo, size_t cur_eden);
459
460 // Scale down the input size by the ratio of the cost to collect the
461 // generation to the total GC cost.
462 size_t scale_by_gen_gc_cost(size_t base_change, double gen_gc_cost);
463
464 // Return the value and clear it.
465 bool get_and_clear_first_after_collection();
466
467 // Printing support
468 virtual bool print_adaptive_size_policy_on(outputStream* st) const;
469 };