1 /*
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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;
48 class GenerationSizer;
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,
344 GCCause::Cause gc_cause,
345 CollectorPolicy* collector_policy);
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 };