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annotate src/share/vm/gc_implementation/parallelScavenge/psAdaptiveSizePolicy.hpp @ 1562:dfe27f03244a
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2 * Copyright (c) 2002, 2010, Oracle and/or its affiliates. All rights reserved. |
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
0 | 22 * |
23 */ | |
24 | |
25 // This class keeps statistical information and computes the | |
26 // optimal free space for both the young and old generation | |
27 // based on current application characteristics (based on gc cost | |
28 // and application footprint). | |
29 // | |
30 // It also computes an optimal tenuring threshold between the young | |
31 // and old generations, so as to equalize the cost of collections | |
32 // of those generations, as well as optimial survivor space sizes | |
33 // for the young generation. | |
34 // | |
35 // While this class is specifically intended for a generational system | |
36 // consisting of a young gen (containing an Eden and two semi-spaces) | |
37 // and a tenured gen, as well as a perm gen for reflective data, it | |
38 // makes NO references to specific generations. | |
39 // | |
40 // 05/02/2003 Update | |
41 // The 1.5 policy makes use of data gathered for the costs of GC on | |
42 // specific generations. That data does reference specific | |
43 // generation. Also diagnostics specific to generations have | |
44 // been added. | |
45 | |
46 // Forward decls | |
47 class elapsedTimer; | |
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48 class GenerationSizer; |
0 | 49 |
50 class PSAdaptiveSizePolicy : public AdaptiveSizePolicy { | |
51 friend class PSGCAdaptivePolicyCounters; | |
52 private: | |
53 // These values are used to record decisions made during the | |
54 // policy. For example, if the young generation was decreased | |
55 // to decrease the GC cost of minor collections the value | |
56 // decrease_young_gen_for_throughput_true is used. | |
57 | |
58 // Last calculated sizes, in bytes, and aligned | |
59 // NEEDS_CLEANUP should use sizes.hpp, but it works in ints, not size_t's | |
60 | |
61 // Time statistics | |
62 AdaptivePaddedAverage* _avg_major_pause; | |
63 | |
64 // Footprint statistics | |
65 AdaptiveWeightedAverage* _avg_base_footprint; | |
66 | |
67 // Statistical data gathered for GC | |
68 GCStats _gc_stats; | |
69 | |
70 size_t _survivor_size_limit; // Limit in bytes of survivor size | |
71 const double _collection_cost_margin_fraction; | |
72 | |
73 // Variable for estimating the major and minor pause times. | |
74 // These variables represent linear least-squares fits of | |
75 // the data. | |
76 // major pause time vs. old gen size | |
77 LinearLeastSquareFit* _major_pause_old_estimator; | |
78 // major pause time vs. young gen size | |
79 LinearLeastSquareFit* _major_pause_young_estimator; | |
80 | |
81 | |
82 // These record the most recent collection times. They | |
83 // are available as an alternative to using the averages | |
84 // for making ergonomic decisions. | |
85 double _latest_major_mutator_interval_seconds; | |
86 | |
87 const size_t _intra_generation_alignment; // alignment for eden, survivors | |
88 | |
89 const double _gc_minor_pause_goal_sec; // goal for maximum minor gc pause | |
90 | |
91 // The amount of live data in the heap at the last full GC, used | |
92 // as a baseline to help us determine when we need to perform the | |
93 // next full GC. | |
94 size_t _live_at_last_full_gc; | |
95 | |
96 // decrease/increase the old generation for minor pause time | |
97 int _change_old_gen_for_min_pauses; | |
98 | |
99 // increase/decrease the young generation for major pause time | |
100 int _change_young_gen_for_maj_pauses; | |
101 | |
102 | |
103 // Flag indicating that the adaptive policy is ready to use | |
104 bool _old_gen_policy_is_ready; | |
105 | |
106 // Changing the generation sizing depends on the data that is | |
107 // gathered about the effects of changes on the pause times and | |
108 // throughput. These variable count the number of data points | |
109 // gathered. The policy may use these counters as a threshhold | |
110 // for reliable data. | |
111 julong _young_gen_change_for_major_pause_count; | |
112 | |
113 // To facilitate faster growth at start up, supplement the normal | |
114 // growth percentage for the young gen eden and the | |
115 // old gen space for promotion with these value which decay | |
116 // with increasing collections. | |
117 uint _young_gen_size_increment_supplement; | |
118 uint _old_gen_size_increment_supplement; | |
119 | |
120 // The number of bytes absorbed from eden into the old gen by moving the | |
121 // boundary over live data. | |
122 size_t _bytes_absorbed_from_eden; | |
123 | |
124 private: | |
125 | |
126 // Accessors | |
127 AdaptivePaddedAverage* avg_major_pause() const { return _avg_major_pause; } | |
128 double gc_minor_pause_goal_sec() const { return _gc_minor_pause_goal_sec; } | |
129 | |
130 // Change the young generation size to achieve a minor GC pause time goal | |
131 void adjust_for_minor_pause_time(bool is_full_gc, | |
132 size_t* desired_promo_size_ptr, | |
133 size_t* desired_eden_size_ptr); | |
134 // Change the generation sizes to achieve a GC pause time goal | |
135 // Returned sizes are not necessarily aligned. | |
136 void adjust_for_pause_time(bool is_full_gc, | |
137 size_t* desired_promo_size_ptr, | |
138 size_t* desired_eden_size_ptr); | |
139 // Change the generation sizes to achieve an application throughput goal | |
140 // Returned sizes are not necessarily aligned. | |
141 void adjust_for_throughput(bool is_full_gc, | |
142 size_t* desired_promo_size_ptr, | |
143 size_t* desired_eden_size_ptr); | |
144 // Change the generation sizes to achieve minimum footprint | |
145 // Returned sizes are not aligned. | |
146 size_t adjust_promo_for_footprint(size_t desired_promo_size, | |
147 size_t desired_total); | |
148 size_t adjust_eden_for_footprint(size_t desired_promo_size, | |
149 size_t desired_total); | |
150 | |
151 // Size in bytes for an increment or decrement of eden. | |
152 virtual size_t eden_increment(size_t cur_eden, uint percent_change); | |
153 virtual size_t eden_decrement(size_t cur_eden); | |
154 size_t eden_decrement_aligned_down(size_t cur_eden); | |
155 size_t eden_increment_with_supplement_aligned_up(size_t cur_eden); | |
156 | |
157 // Size in bytes for an increment or decrement of the promotion area | |
158 virtual size_t promo_increment(size_t cur_promo, uint percent_change); | |
159 virtual size_t promo_decrement(size_t cur_promo); | |
160 size_t promo_decrement_aligned_down(size_t cur_promo); | |
161 size_t promo_increment_with_supplement_aligned_up(size_t cur_promo); | |
162 | |
163 // Decay the supplemental growth additive. | |
164 void decay_supplemental_growth(bool is_full_gc); | |
165 | |
166 // Returns a change that has been scaled down. Result | |
167 // is not aligned. (If useful, move to some shared | |
168 // location.) | |
169 size_t scale_down(size_t change, double part, double total); | |
170 | |
171 protected: | |
172 // Time accessors | |
173 | |
174 // Footprint accessors | |
175 size_t live_space() const { | |
176 return (size_t)(avg_base_footprint()->average() + | |
177 avg_young_live()->average() + | |
178 avg_old_live()->average()); | |
179 } | |
180 size_t free_space() const { | |
181 return _eden_size + _promo_size; | |
182 } | |
183 | |
184 void set_promo_size(size_t new_size) { | |
185 _promo_size = new_size; | |
186 } | |
187 void set_survivor_size(size_t new_size) { | |
188 _survivor_size = new_size; | |
189 } | |
190 | |
191 // Update estimators | |
192 void update_minor_pause_old_estimator(double minor_pause_in_ms); | |
193 | |
194 virtual GCPolicyKind kind() const { return _gc_ps_adaptive_size_policy; } | |
195 | |
196 public: | |
197 // Use by ASPSYoungGen and ASPSOldGen to limit boundary moving. | |
198 size_t eden_increment_aligned_up(size_t cur_eden); | |
199 size_t eden_increment_aligned_down(size_t cur_eden); | |
200 size_t promo_increment_aligned_up(size_t cur_promo); | |
201 size_t promo_increment_aligned_down(size_t cur_promo); | |
202 | |
203 virtual size_t eden_increment(size_t cur_eden); | |
204 virtual size_t promo_increment(size_t cur_promo); | |
205 | |
206 // Accessors for use by performance counters | |
207 AdaptivePaddedNoZeroDevAverage* avg_promoted() const { | |
208 return _gc_stats.avg_promoted(); | |
209 } | |
210 AdaptiveWeightedAverage* avg_base_footprint() const { | |
211 return _avg_base_footprint; | |
212 } | |
213 | |
214 // Input arguments are initial free space sizes for young and old | |
215 // generations, the initial survivor space size, the | |
216 // alignment values and the pause & throughput goals. | |
217 // | |
218 // NEEDS_CLEANUP this is a singleton object | |
219 PSAdaptiveSizePolicy(size_t init_eden_size, | |
220 size_t init_promo_size, | |
221 size_t init_survivor_size, | |
222 size_t intra_generation_alignment, | |
223 double gc_pause_goal_sec, | |
224 double gc_minor_pause_goal_sec, | |
225 uint gc_time_ratio); | |
226 | |
227 // Methods indicating events of interest to the adaptive size policy, | |
228 // called by GC algorithms. It is the responsibility of users of this | |
229 // policy to call these methods at the correct times! | |
230 void major_collection_begin(); | |
231 void major_collection_end(size_t amount_live, GCCause::Cause gc_cause); | |
232 | |
233 // | |
234 void tenured_allocation(size_t size) { | |
235 _avg_pretenured->sample(size); | |
236 } | |
237 | |
238 // Accessors | |
239 // NEEDS_CLEANUP should use sizes.hpp | |
240 | |
241 size_t calculated_old_free_size_in_bytes() const { | |
242 return (size_t)(_promo_size + avg_promoted()->padded_average()); | |
243 } | |
244 | |
245 size_t average_old_live_in_bytes() const { | |
246 return (size_t) avg_old_live()->average(); | |
247 } | |
248 | |
249 size_t average_promoted_in_bytes() const { | |
250 return (size_t)avg_promoted()->average(); | |
251 } | |
252 | |
253 size_t padded_average_promoted_in_bytes() const { | |
254 return (size_t)avg_promoted()->padded_average(); | |
255 } | |
256 | |
257 int change_young_gen_for_maj_pauses() { | |
258 return _change_young_gen_for_maj_pauses; | |
259 } | |
260 void set_change_young_gen_for_maj_pauses(int v) { | |
261 _change_young_gen_for_maj_pauses = v; | |
262 } | |
263 | |
264 int change_old_gen_for_min_pauses() { | |
265 return _change_old_gen_for_min_pauses; | |
266 } | |
267 void set_change_old_gen_for_min_pauses(int v) { | |
268 _change_old_gen_for_min_pauses = v; | |
269 } | |
270 | |
271 // Return true if the old generation size was changed | |
272 // to try to reach a pause time goal. | |
273 bool old_gen_changed_for_pauses() { | |
274 bool result = _change_old_gen_for_maj_pauses != 0 || | |
275 _change_old_gen_for_min_pauses != 0; | |
276 return result; | |
277 } | |
278 | |
279 // Return true if the young generation size was changed | |
280 // to try to reach a pause time goal. | |
281 bool young_gen_changed_for_pauses() { | |
282 bool result = _change_young_gen_for_min_pauses != 0 || | |
283 _change_young_gen_for_maj_pauses != 0; | |
284 return result; | |
285 } | |
286 // end flags for pause goal | |
287 | |
288 // Return true if the old generation size was changed | |
289 // to try to reach a throughput goal. | |
290 bool old_gen_changed_for_throughput() { | |
291 bool result = _change_old_gen_for_throughput != 0; | |
292 return result; | |
293 } | |
294 | |
295 // Return true if the young generation size was changed | |
296 // to try to reach a throughput goal. | |
297 bool young_gen_changed_for_throughput() { | |
298 bool result = _change_young_gen_for_throughput != 0; | |
299 return result; | |
300 } | |
301 | |
302 int decrease_for_footprint() { return _decrease_for_footprint; } | |
303 | |
304 | |
305 // Accessors for estimators. The slope of the linear fit is | |
306 // currently all that is used for making decisions. | |
307 | |
308 LinearLeastSquareFit* major_pause_old_estimator() { | |
309 return _major_pause_old_estimator; | |
310 } | |
311 | |
312 LinearLeastSquareFit* major_pause_young_estimator() { | |
313 return _major_pause_young_estimator; | |
314 } | |
315 | |
316 | |
317 virtual void clear_generation_free_space_flags(); | |
318 | |
319 float major_pause_old_slope() { return _major_pause_old_estimator->slope(); } | |
320 float major_pause_young_slope() { | |
321 return _major_pause_young_estimator->slope(); | |
322 } | |
323 float major_collection_slope() { return _major_collection_estimator->slope();} | |
324 | |
325 bool old_gen_policy_is_ready() { return _old_gen_policy_is_ready; } | |
326 | |
327 // Given the amount of live data in the heap, should we | |
328 // perform a Full GC? | |
329 bool should_full_GC(size_t live_in_old_gen); | |
330 | |
331 // Calculates optimial free space sizes for both the old and young | |
332 // generations. Stores results in _eden_size and _promo_size. | |
333 // Takes current used space in all generations as input, as well | |
334 // as an indication if a full gc has just been performed, for use | |
335 // in deciding if an OOM error should be thrown. | |
336 void compute_generation_free_space(size_t young_live, | |
337 size_t eden_live, | |
338 size_t old_live, | |
339 size_t perm_live, | |
340 size_t cur_eden, // current eden in bytes | |
341 size_t max_old_gen_size, | |
342 size_t max_eden_size, | |
343 bool is_full_gc, | |
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344 GCCause::Cause gc_cause, |
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345 CollectorPolicy* collector_policy); |
0 | 346 |
347 // Calculates new survivor space size; returns a new tenuring threshold | |
348 // value. Stores new survivor size in _survivor_size. | |
349 int compute_survivor_space_size_and_threshold(bool is_survivor_overflow, | |
350 int tenuring_threshold, | |
351 size_t survivor_limit); | |
352 | |
353 // Return the maximum size of a survivor space if the young generation were of | |
354 // size gen_size. | |
355 size_t max_survivor_size(size_t gen_size) { | |
356 // Never allow the target survivor size to grow more than MinSurvivorRatio | |
357 // of the young generation size. We cannot grow into a two semi-space | |
358 // system, with Eden zero sized. Even if the survivor space grows, from() | |
359 // might grow by moving the bottom boundary "down" -- so from space will | |
360 // remain almost full anyway (top() will be near end(), but there will be a | |
361 // large filler object at the bottom). | |
362 const size_t sz = gen_size / MinSurvivorRatio; | |
363 const size_t alignment = _intra_generation_alignment; | |
364 return sz > alignment ? align_size_down(sz, alignment) : alignment; | |
365 } | |
366 | |
367 size_t live_at_last_full_gc() { | |
368 return _live_at_last_full_gc; | |
369 } | |
370 | |
371 size_t bytes_absorbed_from_eden() const { return _bytes_absorbed_from_eden; } | |
372 void reset_bytes_absorbed_from_eden() { _bytes_absorbed_from_eden = 0; } | |
373 | |
374 void set_bytes_absorbed_from_eden(size_t val) { | |
375 _bytes_absorbed_from_eden = val; | |
376 } | |
377 | |
378 // Update averages that are always used (even | |
379 // if adaptive sizing is turned off). | |
380 void update_averages(bool is_survivor_overflow, | |
381 size_t survived, | |
382 size_t promoted); | |
383 | |
384 // Printing support | |
385 virtual bool print_adaptive_size_policy_on(outputStream* st) const; | |
386 }; |