1 /*
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24
25 #ifndef SHARE_VM_GC_IMPLEMENTATION_PARALLELSCAVENGE_PSADAPTIVESIZEPOLICY_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_PARALLELSCAVENGE_PSADAPTIVESIZEPOLICY_HPP
27
28 #include "gc_implementation/shared/adaptiveSizePolicy.hpp"
29 #include "gc_implementation/shared/gcStats.hpp"
30 #include "gc_implementation/shared/gcUtil.hpp"
31 #include "gc_interface/gcCause.hpp"
32
33 // This class keeps statistical information and computes the
34 // optimal free space for both the young and old generation
35 // based on current application characteristics (based on gc cost
36 // and application footprint).
37 //
38 // It also computes an optimal tenuring threshold between the young
39 // and old generations, so as to equalize the cost of collections
40 // of those generations, as well as optimal survivor space sizes
41 // for the young generation.
42 //
43 // While this class is specifically intended for a generational system
44 // consisting of a young gen (containing an Eden and two semi-spaces)
45 // and a tenured gen, as well as a perm gen for reflective data, it
46 // makes NO references to specific generations.
47 //
48 // 05/02/2003 Update
49 // The 1.5 policy makes use of data gathered for the costs of GC on
50 // specific generations. That data does reference specific
51 // generation. Also diagnostics specific to generations have
52 // been added.
53
54 // Forward decls
55 class elapsedTimer;
56
57 class PSAdaptiveSizePolicy : public AdaptiveSizePolicy {
58 friend class PSGCAdaptivePolicyCounters;
59 private:
60 // These values are used to record decisions made during the
61 // policy. For example, if the young generation was decreased
62 // to decrease the GC cost of minor collections the value
63 // decrease_young_gen_for_throughput_true is used.
64
65 // Last calculated sizes, in bytes, and aligned
66 // NEEDS_CLEANUP should use sizes.hpp, but it works in ints, not size_t's
67
68 // Time statistics
69 AdaptivePaddedAverage* _avg_major_pause;
70
71 // Footprint statistics
72 AdaptiveWeightedAverage* _avg_base_footprint;
73
74 // Statistical data gathered for GC
75 GCStats _gc_stats;
76
77 size_t _survivor_size_limit; // Limit in bytes of survivor size
78 const double _collection_cost_margin_fraction;
79
80 // Variable for estimating the major and minor pause times.
81 // These variables represent linear least-squares fits of
82 // the data.
83 // major pause time vs. old gen size
84 LinearLeastSquareFit* _major_pause_old_estimator;
85 // major pause time vs. young gen size
86 LinearLeastSquareFit* _major_pause_young_estimator;
87
88
89 // These record the most recent collection times. They
90 // are available as an alternative to using the averages
91 // for making ergonomic decisions.
92 double _latest_major_mutator_interval_seconds;
93
94 const size_t _space_alignment; // alignment for eden, survivors
95
96 const double _gc_minor_pause_goal_sec; // goal for maximum minor gc pause
97
98 // The amount of live data in the heap at the last full GC, used
99 // as a baseline to help us determine when we need to perform the
100 // next full GC.
101 size_t _live_at_last_full_gc;
102
103 // decrease/increase the old generation for minor pause time
104 int _change_old_gen_for_min_pauses;
105
106 // increase/decrease the young generation for major pause time
107 int _change_young_gen_for_maj_pauses;
108
109
110 // Flag indicating that the adaptive policy is ready to use
111 bool _old_gen_policy_is_ready;
112
113 // Changing the generation sizing depends on the data that is
114 // gathered about the effects of changes on the pause times and
115 // throughput. These variable count the number of data points
116 // gathered. The policy may use these counters as a threshold
117 // for reliable data.
118 julong _young_gen_change_for_major_pause_count;
119
120 // To facilitate faster growth at start up, supplement the normal
121 // growth percentage for the young gen eden and the
122 // old gen space for promotion with these value which decay
123 // with increasing collections.
124 uint _young_gen_size_increment_supplement;
125 uint _old_gen_size_increment_supplement;
126
127 // The number of bytes absorbed from eden into the old gen by moving the
128 // boundary over live data.
129 size_t _bytes_absorbed_from_eden;
130
131 private:
132
133 // Accessors
134 AdaptivePaddedAverage* avg_major_pause() const { return _avg_major_pause; }
135 double gc_minor_pause_goal_sec() const { return _gc_minor_pause_goal_sec; }
136
137 // Change the young generation size to achieve a minor GC pause time goal
138 void adjust_promo_for_minor_pause_time(bool is_full_gc,
139 size_t* desired_promo_size_ptr,
140 size_t* desired_eden_size_ptr);
141 void adjust_eden_for_minor_pause_time(bool is_full_gc,
142 size_t* desired_eden_size_ptr);
143 // Change the generation sizes to achieve a GC pause time goal
144 // Returned sizes are not necessarily aligned.
145 void adjust_promo_for_pause_time(bool is_full_gc,
146 size_t* desired_promo_size_ptr,
147 size_t* desired_eden_size_ptr);
148 void adjust_eden_for_pause_time(bool is_full_gc,
149 size_t* desired_promo_size_ptr,
150 size_t* desired_eden_size_ptr);
151 // Change the generation sizes to achieve an application throughput goal
152 // Returned sizes are not necessarily aligned.
153 void adjust_promo_for_throughput(bool is_full_gc,
154 size_t* desired_promo_size_ptr);
155 void adjust_eden_for_throughput(bool is_full_gc,
156 size_t* desired_eden_size_ptr);
157 // Change the generation sizes to achieve minimum footprint
158 // Returned sizes are not aligned.
159 size_t adjust_promo_for_footprint(size_t desired_promo_size,
160 size_t desired_total);
161 size_t adjust_eden_for_footprint(size_t desired_promo_size,
162 size_t desired_total);
163
164 // Size in bytes for an increment or decrement of eden.
165 virtual size_t eden_increment(size_t cur_eden, uint percent_change);
166 virtual size_t eden_decrement(size_t cur_eden);
167 size_t eden_decrement_aligned_down(size_t cur_eden);
168 size_t eden_increment_with_supplement_aligned_up(size_t cur_eden);
169
170 // Size in bytes for an increment or decrement of the promotion area
171 virtual size_t promo_increment(size_t cur_promo, uint percent_change);
172 virtual size_t promo_decrement(size_t cur_promo);
173 size_t promo_decrement_aligned_down(size_t cur_promo);
174 size_t promo_increment_with_supplement_aligned_up(size_t cur_promo);
175
176 // Returns a change that has been scaled down. Result
177 // is not aligned. (If useful, move to some shared
178 // location.)
179 size_t scale_down(size_t change, double part, double total);
180
181 protected:
182 // Time accessors
183
184 // Footprint accessors
185 size_t live_space() const {
186 return (size_t)(avg_base_footprint()->average() +
187 avg_young_live()->average() +
188 avg_old_live()->average());
189 }
190 size_t free_space() const {
191 return _eden_size + _promo_size;
192 }
193
194 void set_promo_size(size_t new_size) {
195 _promo_size = new_size;
196 }
197 void set_survivor_size(size_t new_size) {
198 _survivor_size = new_size;
199 }
200
201 // Update estimators
202 void update_minor_pause_old_estimator(double minor_pause_in_ms);
203
204 virtual GCPolicyKind kind() const { return _gc_ps_adaptive_size_policy; }
205
206 public:
207 // Use by ASPSYoungGen and ASPSOldGen to limit boundary moving.
208 size_t eden_increment_aligned_up(size_t cur_eden);
209 size_t eden_increment_aligned_down(size_t cur_eden);
210 size_t promo_increment_aligned_up(size_t cur_promo);
211 size_t promo_increment_aligned_down(size_t cur_promo);
212
213 virtual size_t eden_increment(size_t cur_eden);
214 virtual size_t promo_increment(size_t cur_promo);
215
216 // Accessors for use by performance counters
217 AdaptivePaddedNoZeroDevAverage* avg_promoted() const {
218 return _gc_stats.avg_promoted();
219 }
220 AdaptiveWeightedAverage* avg_base_footprint() const {
221 return _avg_base_footprint;
222 }
223
224 // Input arguments are initial free space sizes for young and old
225 // generations, the initial survivor space size, the
226 // alignment values and the pause & throughput goals.
227 //
228 // NEEDS_CLEANUP this is a singleton object
229 PSAdaptiveSizePolicy(size_t init_eden_size,
230 size_t init_promo_size,
231 size_t init_survivor_size,
232 size_t space_alignment,
233 double gc_pause_goal_sec,
234 double gc_minor_pause_goal_sec,
235 uint gc_time_ratio);
236
237 // Methods indicating events of interest to the adaptive size policy,
238 // called by GC algorithms. It is the responsibility of users of this
239 // policy to call these methods at the correct times!
240 void major_collection_begin();
241 void major_collection_end(size_t amount_live, GCCause::Cause gc_cause);
242
243 void tenured_allocation(size_t size) {
244 _avg_pretenured->sample(size);
245 }
246
247 // Accessors
248 // NEEDS_CLEANUP should use sizes.hpp
249
250 static size_t calculate_free_based_on_live(size_t live, uintx ratio_as_percentage);
251
252 size_t calculated_old_free_size_in_bytes() const;
253
254 size_t average_old_live_in_bytes() const {
255 return (size_t) avg_old_live()->average();
256 }
257
258 size_t average_promoted_in_bytes() const {
259 return (size_t)avg_promoted()->average();
260 }
261
262 size_t padded_average_promoted_in_bytes() const {
263 return (size_t)avg_promoted()->padded_average();
264 }
265
266 int change_young_gen_for_maj_pauses() {
267 return _change_young_gen_for_maj_pauses;
268 }
269 void set_change_young_gen_for_maj_pauses(int v) {
270 _change_young_gen_for_maj_pauses = v;
271 }
272
273 int change_old_gen_for_min_pauses() {
274 return _change_old_gen_for_min_pauses;
275 }
276 void set_change_old_gen_for_min_pauses(int v) {
277 _change_old_gen_for_min_pauses = v;
278 }
279
280 // Return true if the old generation size was changed
281 // to try to reach a pause time goal.
282 bool old_gen_changed_for_pauses() {
283 bool result = _change_old_gen_for_maj_pauses != 0 ||
284 _change_old_gen_for_min_pauses != 0;
285 return result;
286 }
287
288 // Return true if the young generation size was changed
289 // to try to reach a pause time goal.
290 bool young_gen_changed_for_pauses() {
291 bool result = _change_young_gen_for_min_pauses != 0 ||
292 _change_young_gen_for_maj_pauses != 0;
293 return result;
294 }
295 // end flags for pause goal
296
297 // Return true if the old generation size was changed
298 // to try to reach a throughput goal.
299 bool old_gen_changed_for_throughput() {
300 bool result = _change_old_gen_for_throughput != 0;
301 return result;
302 }
303
304 // Return true if the young generation size was changed
305 // to try to reach a throughput goal.
306 bool young_gen_changed_for_throughput() {
307 bool result = _change_young_gen_for_throughput != 0;
308 return result;
309 }
310
311 int decrease_for_footprint() { return _decrease_for_footprint; }
312
313
314 // Accessors for estimators. The slope of the linear fit is
315 // currently all that is used for making decisions.
316
317 LinearLeastSquareFit* major_pause_old_estimator() {
318 return _major_pause_old_estimator;
319 }
320
321 LinearLeastSquareFit* major_pause_young_estimator() {
322 return _major_pause_young_estimator;
323 }
324
325
326 virtual void clear_generation_free_space_flags();
327
328 float major_pause_old_slope() { return _major_pause_old_estimator->slope(); }
329 float major_pause_young_slope() {
330 return _major_pause_young_estimator->slope();
331 }
332 float major_collection_slope() { return _major_collection_estimator->slope();}
333
334 bool old_gen_policy_is_ready() { return _old_gen_policy_is_ready; }
335
336 // Given the amount of live data in the heap, should we
337 // perform a Full GC?
338 bool should_full_GC(size_t live_in_old_gen);
339
340 // Calculates optimal (free) space sizes for both the young and old
341 // generations. Stores results in _eden_size and _promo_size.
342 // Takes current used space in all generations as input, as well
343 // as an indication if a full gc has just been performed, for use
344 // in deciding if an OOM error should be thrown.
345 void compute_generations_free_space(size_t young_live,
346 size_t eden_live,
347 size_t old_live,
348 size_t cur_eden, // current eden in bytes
349 size_t max_old_gen_size,
350 size_t max_eden_size,
351 bool is_full_gc);
352
353 void compute_eden_space_size(size_t young_live,
354 size_t eden_live,
355 size_t cur_eden, // current eden in bytes
356 size_t max_eden_size,
357 bool is_full_gc);
358
359 void compute_old_gen_free_space(size_t old_live,
360 size_t cur_eden, // current eden in bytes
361 size_t max_old_gen_size,
362 bool is_full_gc);
363
364 // Calculates new survivor space size; returns a new tenuring threshold
365 // value. Stores new survivor size in _survivor_size.
366 uint compute_survivor_space_size_and_threshold(bool is_survivor_overflow,
367 uint tenuring_threshold,
368 size_t survivor_limit);
369
370 // Return the maximum size of a survivor space if the young generation were of
371 // size gen_size.
372 size_t max_survivor_size(size_t gen_size) {
373 // Never allow the target survivor size to grow more than MinSurvivorRatio
374 // of the young generation size. We cannot grow into a two semi-space
375 // system, with Eden zero sized. Even if the survivor space grows, from()
376 // might grow by moving the bottom boundary "down" -- so from space will
377 // remain almost full anyway (top() will be near end(), but there will be a
378 // large filler object at the bottom).
379 const size_t sz = gen_size / MinSurvivorRatio;
380 const size_t alignment = _space_alignment;
381 return sz > alignment ? align_size_down(sz, alignment) : alignment;
382 }
383
384 size_t live_at_last_full_gc() {
385 return _live_at_last_full_gc;
386 }
387
388 size_t bytes_absorbed_from_eden() const { return _bytes_absorbed_from_eden; }
389 void reset_bytes_absorbed_from_eden() { _bytes_absorbed_from_eden = 0; }
390
391 void set_bytes_absorbed_from_eden(size_t val) {
392 _bytes_absorbed_from_eden = val;
393 }
394
395 // Update averages that are always used (even
396 // if adaptive sizing is turned off).
397 void update_averages(bool is_survivor_overflow,
398 size_t survived,
399 size_t promoted);
400
401 // Printing support
402 virtual bool print_adaptive_size_policy_on(outputStream* st) const;
403
404 // Decay the supplemental growth additive.
405 void decay_supplemental_growth(bool is_full_gc);
406 };
407
408 #endif // SHARE_VM_GC_IMPLEMENTATION_PARALLELSCAVENGE_PSADAPTIVESIZEPOLICY_HPP