1 /*
2 * Copyright (c) 2002, 2010, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
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).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "gc_implementation/parallelScavenge/generationSizer.hpp"
27 #include "gc_implementation/parallelScavenge/psAdaptiveSizePolicy.hpp"
28 #include "gc_implementation/parallelScavenge/psGCAdaptivePolicyCounters.hpp"
29 #include "gc_implementation/parallelScavenge/psScavenge.hpp"
30 #include "gc_implementation/shared/gcPolicyCounters.hpp"
31 #include "gc_interface/gcCause.hpp"
32 #include "memory/collectorPolicy.hpp"
33 #include "runtime/timer.hpp"
34 #include "utilities/top.hpp"
35
36 #include <math.h>
37
38 PSAdaptiveSizePolicy::PSAdaptiveSizePolicy(size_t init_eden_size,
39 size_t init_promo_size,
40 size_t init_survivor_size,
41 size_t intra_generation_alignment,
42 double gc_pause_goal_sec,
43 double gc_minor_pause_goal_sec,
44 uint gc_cost_ratio) :
45 AdaptiveSizePolicy(init_eden_size,
46 init_promo_size,
47 init_survivor_size,
48 gc_pause_goal_sec,
49 gc_cost_ratio),
50 _collection_cost_margin_fraction(AdaptiveSizePolicyCollectionCostMargin/
51 100.0),
52 _intra_generation_alignment(intra_generation_alignment),
53 _live_at_last_full_gc(init_promo_size),
54 _gc_minor_pause_goal_sec(gc_minor_pause_goal_sec),
55 _latest_major_mutator_interval_seconds(0),
56 _young_gen_change_for_major_pause_count(0)
57 {
58 // Sizing policy statistics
59 _avg_major_pause =
60 new AdaptivePaddedAverage(AdaptiveTimeWeight, PausePadding);
61 _avg_minor_interval = new AdaptiveWeightedAverage(AdaptiveTimeWeight);
62 _avg_major_interval = new AdaptiveWeightedAverage(AdaptiveTimeWeight);
63
64 _avg_base_footprint = new AdaptiveWeightedAverage(AdaptiveSizePolicyWeight);
65 _major_pause_old_estimator =
66 new LinearLeastSquareFit(AdaptiveSizePolicyWeight);
67 _major_pause_young_estimator =
68 new LinearLeastSquareFit(AdaptiveSizePolicyWeight);
69 _major_collection_estimator =
70 new LinearLeastSquareFit(AdaptiveSizePolicyWeight);
71
72 _young_gen_size_increment_supplement = YoungGenerationSizeSupplement;
73 _old_gen_size_increment_supplement = TenuredGenerationSizeSupplement;
74
75 // Start the timers
76 _major_timer.start();
77
78 _old_gen_policy_is_ready = false;
79 }
80
81 void PSAdaptiveSizePolicy::major_collection_begin() {
82 // Update the interval time
83 _major_timer.stop();
84 // Save most recent collection time
85 _latest_major_mutator_interval_seconds = _major_timer.seconds();
86 _major_timer.reset();
87 _major_timer.start();
88 }
89
90 void PSAdaptiveSizePolicy::update_minor_pause_old_estimator(
91 double minor_pause_in_ms) {
92 double promo_size_in_mbytes = ((double)_promo_size)/((double)M);
93 _minor_pause_old_estimator->update(promo_size_in_mbytes,
94 minor_pause_in_ms);
95 }
96
97 void PSAdaptiveSizePolicy::major_collection_end(size_t amount_live,
98 GCCause::Cause gc_cause) {
99 // Update the pause time.
100 _major_timer.stop();
101
102 if (gc_cause != GCCause::_java_lang_system_gc ||
103 UseAdaptiveSizePolicyWithSystemGC) {
104 double major_pause_in_seconds = _major_timer.seconds();
105 double major_pause_in_ms = major_pause_in_seconds * MILLIUNITS;
106
107 // Sample for performance counter
108 _avg_major_pause->sample(major_pause_in_seconds);
109
110 // Cost of collection (unit-less)
111 double collection_cost = 0.0;
112 if ((_latest_major_mutator_interval_seconds > 0.0) &&
113 (major_pause_in_seconds > 0.0)) {
114 double interval_in_seconds =
115 _latest_major_mutator_interval_seconds + major_pause_in_seconds;
116 collection_cost =
117 major_pause_in_seconds / interval_in_seconds;
118 avg_major_gc_cost()->sample(collection_cost);
119
120 // Sample for performance counter
121 _avg_major_interval->sample(interval_in_seconds);
122 }
123
124 // Calculate variables used to estimate pause time vs. gen sizes
125 double eden_size_in_mbytes = ((double)_eden_size)/((double)M);
126 double promo_size_in_mbytes = ((double)_promo_size)/((double)M);
127 _major_pause_old_estimator->update(promo_size_in_mbytes,
128 major_pause_in_ms);
129 _major_pause_young_estimator->update(eden_size_in_mbytes,
130 major_pause_in_ms);
131
132 if (PrintAdaptiveSizePolicy && Verbose) {
133 gclog_or_tty->print("psAdaptiveSizePolicy::major_collection_end: "
134 "major gc cost: %f average: %f", collection_cost,
135 avg_major_gc_cost()->average());
136 gclog_or_tty->print_cr(" major pause: %f major period %f",
137 major_pause_in_ms,
138 _latest_major_mutator_interval_seconds * MILLIUNITS);
139 }
140
141 // Calculate variable used to estimate collection cost vs. gen sizes
142 assert(collection_cost >= 0.0, "Expected to be non-negative");
143 _major_collection_estimator->update(promo_size_in_mbytes,
144 collection_cost);
145 }
146
147 // Update the amount live at the end of a full GC
148 _live_at_last_full_gc = amount_live;
149
150 // The policy does not have enough data until at least some major collections
151 // have been done.
152 if (_avg_major_pause->count() >= AdaptiveSizePolicyReadyThreshold) {
153 _old_gen_policy_is_ready = true;
154 }
155
156 // Interval times use this timer to measure the interval that
157 // the mutator runs. Reset after the GC pause has been measured.
158 _major_timer.reset();
159 _major_timer.start();
160 }
161
162 // If the remaining free space in the old generation is less that
163 // that expected to be needed by the next collection, do a full
164 // collection now.
165 bool PSAdaptiveSizePolicy::should_full_GC(size_t old_free_in_bytes) {
166
167 // A similar test is done in the scavenge's should_attempt_scavenge(). If
168 // this is changed, decide if that test should also be changed.
169 bool result = padded_average_promoted_in_bytes() > (float) old_free_in_bytes;
170 if (PrintGCDetails && Verbose) {
171 if (result) {
172 gclog_or_tty->print(" full after scavenge: ");
173 } else {
174 gclog_or_tty->print(" no full after scavenge: ");
175 }
176 gclog_or_tty->print_cr(" average_promoted " SIZE_FORMAT
177 " padded_average_promoted " SIZE_FORMAT
178 " free in old gen " SIZE_FORMAT,
179 (size_t) average_promoted_in_bytes(),
180 (size_t) padded_average_promoted_in_bytes(),
181 old_free_in_bytes);
182 }
183 return result;
184 }
185
186 void PSAdaptiveSizePolicy::clear_generation_free_space_flags() {
187
188 AdaptiveSizePolicy::clear_generation_free_space_flags();
189
190 set_change_old_gen_for_min_pauses(0);
191
192 set_change_young_gen_for_maj_pauses(0);
193 }
194
195 // If this is not a full GC, only test and modify the young generation.
196
197 void PSAdaptiveSizePolicy::compute_generation_free_space(
198 size_t young_live,
199 size_t eden_live,
200 size_t old_live,
201 size_t perm_live,
202 size_t cur_eden,
203 size_t max_old_gen_size,
204 size_t max_eden_size,
205 bool is_full_gc,
206 GCCause::Cause gc_cause,
207 CollectorPolicy* collector_policy) {
208
209 // Update statistics
210 // Time statistics are updated as we go, update footprint stats here
211 _avg_base_footprint->sample(BaseFootPrintEstimate + perm_live);
212 avg_young_live()->sample(young_live);
213 avg_eden_live()->sample(eden_live);
214 if (is_full_gc) {
215 // old_live is only accurate after a full gc
216 avg_old_live()->sample(old_live);
217 }
218
219 // This code used to return if the policy was not ready , i.e.,
220 // policy_is_ready() returning false. The intent was that
221 // decisions below needed major collection times and so could
222 // not be made before two major collections. A consequence was
223 // adjustments to the young generation were not done until after
224 // two major collections even if the minor collections times
225 // exceeded the requested goals. Now let the young generation
226 // adjust for the minor collection times. Major collection times
227 // will be zero for the first collection and will naturally be
228 // ignored. Tenured generation adjustments are only made at the
229 // full collections so until the second major collection has
230 // been reached, no tenured generation adjustments will be made.
231
232 // Until we know better, desired promotion size uses the last calculation
233 size_t desired_promo_size = _promo_size;
234
235 // Start eden at the current value. The desired value that is stored
236 // in _eden_size is not bounded by constraints of the heap and can
237 // run away.
238 //
239 // As expected setting desired_eden_size to the current
240 // value of desired_eden_size as a starting point
241 // caused desired_eden_size to grow way too large and caused
242 // an overflow down stream. It may have improved performance in
243 // some case but is dangerous.
244 size_t desired_eden_size = cur_eden;
245
246 #ifdef ASSERT
247 size_t original_promo_size = desired_promo_size;
248 size_t original_eden_size = desired_eden_size;
249 #endif
250
251 // Cache some values. There's a bit of work getting these, so
252 // we might save a little time.
253 const double major_cost = major_gc_cost();
254 const double minor_cost = minor_gc_cost();
255
256 // Used for diagnostics
257 clear_generation_free_space_flags();
258
259 // Limits on our growth
260 size_t promo_limit = (size_t)(max_old_gen_size - avg_old_live()->average());
261
262 // This method sets the desired eden size. That plus the
263 // desired survivor space sizes sets the desired young generation
264 // size. This methods does not know what the desired survivor
265 // size is but expects that other policy will attempt to make
266 // the survivor sizes compatible with the live data in the
267 // young generation. This limit is an estimate of the space left
268 // in the young generation after the survivor spaces have been
269 // subtracted out.
270 size_t eden_limit = max_eden_size;
271
272 // But don't force a promo size below the current promo size. Otherwise,
273 // the promo size will shrink for no good reason.
274 promo_limit = MAX2(promo_limit, _promo_size);
275
276 const double gc_cost_limit = GCTimeLimit/100.0;
277
278 // Which way should we go?
279 // if pause requirement is not met
280 // adjust size of any generation with average paus exceeding
281 // the pause limit. Adjust one pause at a time (the larger)
282 // and only make adjustments for the major pause at full collections.
283 // else if throughput requirement not met
284 // adjust the size of the generation with larger gc time. Only
285 // adjust one generation at a time.
286 // else
287 // adjust down the total heap size. Adjust down the larger of the
288 // generations.
289
290 // Add some checks for a threshhold for a change. For example,
291 // a change less than the necessary alignment is probably not worth
292 // attempting.
293
294
295 if ((_avg_minor_pause->padded_average() > gc_pause_goal_sec()) ||
296 (_avg_major_pause->padded_average() > gc_pause_goal_sec())) {
297 //
298 // Check pauses
299 //
300 // Make changes only to affect one of the pauses (the larger)
301 // at a time.
302 adjust_for_pause_time(is_full_gc, &desired_promo_size, &desired_eden_size);
303
304 } else if (_avg_minor_pause->padded_average() > gc_minor_pause_goal_sec()) {
305 // Adjust only for the minor pause time goal
306 adjust_for_minor_pause_time(is_full_gc, &desired_promo_size, &desired_eden_size);
307
308 } else if(adjusted_mutator_cost() < _throughput_goal) {
309 // This branch used to require that (mutator_cost() > 0.0 in 1.4.2.
310 // This sometimes resulted in skipping to the minimize footprint
311 // code. Change this to try and reduce GC time if mutator time is
312 // negative for whatever reason. Or for future consideration,
313 // bail out of the code if mutator time is negative.
314 //
315 // Throughput
316 //
317 assert(major_cost >= 0.0, "major cost is < 0.0");
318 assert(minor_cost >= 0.0, "minor cost is < 0.0");
319 // Try to reduce the GC times.
320 adjust_for_throughput(is_full_gc, &desired_promo_size, &desired_eden_size);
321
322 } else {
323
324 // Be conservative about reducing the footprint.
325 // Do a minimum number of major collections first.
326 // Have reasonable averages for major and minor collections costs.
327 if (UseAdaptiveSizePolicyFootprintGoal &&
328 young_gen_policy_is_ready() &&
329 avg_major_gc_cost()->average() >= 0.0 &&
330 avg_minor_gc_cost()->average() >= 0.0) {
331 size_t desired_sum = desired_eden_size + desired_promo_size;
332 desired_eden_size = adjust_eden_for_footprint(desired_eden_size,
333 desired_sum);
334 if (is_full_gc) {
335 set_decide_at_full_gc(decide_at_full_gc_true);
336 desired_promo_size = adjust_promo_for_footprint(desired_promo_size,
337 desired_sum);
338 }
339 }
340 }
341
342 // Note we make the same tests as in the code block below; the code
343 // seems a little easier to read with the printing in another block.
344 if (PrintAdaptiveSizePolicy) {
345 if (desired_promo_size > promo_limit) {
346 // "free_in_old_gen" was the original value for used for promo_limit
347 size_t free_in_old_gen = (size_t)(max_old_gen_size - avg_old_live()->average());
348 gclog_or_tty->print_cr(
349 "PSAdaptiveSizePolicy::compute_generation_free_space limits:"
350 " desired_promo_size: " SIZE_FORMAT
351 " promo_limit: " SIZE_FORMAT
352 " free_in_old_gen: " SIZE_FORMAT
353 " max_old_gen_size: " SIZE_FORMAT
354 " avg_old_live: " SIZE_FORMAT,
355 desired_promo_size, promo_limit, free_in_old_gen,
356 max_old_gen_size, (size_t) avg_old_live()->average());
357 }
358 if (desired_eden_size > eden_limit) {
359 gclog_or_tty->print_cr(
360 "AdaptiveSizePolicy::compute_generation_free_space limits:"
361 " desired_eden_size: " SIZE_FORMAT
362 " old_eden_size: " SIZE_FORMAT
363 " eden_limit: " SIZE_FORMAT
364 " cur_eden: " SIZE_FORMAT
365 " max_eden_size: " SIZE_FORMAT
366 " avg_young_live: " SIZE_FORMAT,
367 desired_eden_size, _eden_size, eden_limit, cur_eden,
368 max_eden_size, (size_t)avg_young_live()->average());
369 }
370 if (gc_cost() > gc_cost_limit) {
371 gclog_or_tty->print_cr(
372 "AdaptiveSizePolicy::compute_generation_free_space: gc time limit"
373 " gc_cost: %f "
374 " GCTimeLimit: %d",
375 gc_cost(), GCTimeLimit);
376 }
377 }
378
379 // Align everything and make a final limit check
380 const size_t alignment = _intra_generation_alignment;
381 desired_eden_size = align_size_up(desired_eden_size, alignment);
382 desired_eden_size = MAX2(desired_eden_size, alignment);
383 desired_promo_size = align_size_up(desired_promo_size, alignment);
384 desired_promo_size = MAX2(desired_promo_size, alignment);
385
386 eden_limit = align_size_down(eden_limit, alignment);
387 promo_limit = align_size_down(promo_limit, alignment);
388
389 // Is too much time being spent in GC?
390 // Is the heap trying to grow beyond it's limits?
391
392 const size_t free_in_old_gen =
393 (size_t)(max_old_gen_size - avg_old_live()->average());
394 if (desired_promo_size > free_in_old_gen && desired_eden_size > eden_limit) {
395 check_gc_overhead_limit(young_live,
396 eden_live,
397 max_old_gen_size,
398 max_eden_size,
399 is_full_gc,
400 gc_cause,
401 collector_policy);
402 }
403
404
405 // And one last limit check, now that we've aligned things.
406 if (desired_eden_size > eden_limit) {
407 // If the policy says to get a larger eden but
408 // is hitting the limit, don't decrease eden.
409 // This can lead to a general drifting down of the
410 // eden size. Let the tenuring calculation push more
411 // into the old gen.
412 desired_eden_size = MAX2(eden_limit, cur_eden);
413 }
414 desired_promo_size = MIN2(desired_promo_size, promo_limit);
415
416
417 if (PrintAdaptiveSizePolicy) {
418 // Timing stats
419 gclog_or_tty->print(
420 "PSAdaptiveSizePolicy::compute_generation_free_space: costs"
421 " minor_time: %f"
422 " major_cost: %f"
423 " mutator_cost: %f"
424 " throughput_goal: %f",
425 minor_gc_cost(), major_gc_cost(), mutator_cost(),
426 _throughput_goal);
427
428 // We give more details if Verbose is set
429 if (Verbose) {
430 gclog_or_tty->print( " minor_pause: %f"
431 " major_pause: %f"
432 " minor_interval: %f"
433 " major_interval: %f"
434 " pause_goal: %f",
435 _avg_minor_pause->padded_average(),
436 _avg_major_pause->padded_average(),
437 _avg_minor_interval->average(),
438 _avg_major_interval->average(),
439 gc_pause_goal_sec());
440 }
441
442 // Footprint stats
443 gclog_or_tty->print( " live_space: " SIZE_FORMAT
444 " free_space: " SIZE_FORMAT,
445 live_space(), free_space());
446 // More detail
447 if (Verbose) {
448 gclog_or_tty->print( " base_footprint: " SIZE_FORMAT
449 " avg_young_live: " SIZE_FORMAT
450 " avg_old_live: " SIZE_FORMAT,
451 (size_t)_avg_base_footprint->average(),
452 (size_t)avg_young_live()->average(),
453 (size_t)avg_old_live()->average());
454 }
455
456 // And finally, our old and new sizes.
457 gclog_or_tty->print(" old_promo_size: " SIZE_FORMAT
458 " old_eden_size: " SIZE_FORMAT
459 " desired_promo_size: " SIZE_FORMAT
460 " desired_eden_size: " SIZE_FORMAT,
461 _promo_size, _eden_size,
462 desired_promo_size, desired_eden_size);
463 gclog_or_tty->cr();
464 }
465
466 decay_supplemental_growth(is_full_gc);
467
468 set_promo_size(desired_promo_size);
469 set_eden_size(desired_eden_size);
470 };
471
472 void PSAdaptiveSizePolicy::decay_supplemental_growth(bool is_full_gc) {
473 // Decay the supplemental increment? Decay the supplement growth
474 // factor even if it is not used. It is only meant to give a boost
475 // to the initial growth and if it is not used, then it was not
476 // needed.
477 if (is_full_gc) {
478 // Don't wait for the threshold value for the major collections. If
479 // here, the supplemental growth term was used and should decay.
480 if ((_avg_major_pause->count() % TenuredGenerationSizeSupplementDecay)
481 == 0) {
482 _old_gen_size_increment_supplement =
483 _old_gen_size_increment_supplement >> 1;
484 }
485 } else {
486 if ((_avg_minor_pause->count() >= AdaptiveSizePolicyReadyThreshold) &&
487 (_avg_minor_pause->count() % YoungGenerationSizeSupplementDecay) == 0) {
488 _young_gen_size_increment_supplement =
489 _young_gen_size_increment_supplement >> 1;
490 }
491 }
492 }
493
494 void PSAdaptiveSizePolicy::adjust_for_minor_pause_time(bool is_full_gc,
495 size_t* desired_promo_size_ptr, size_t* desired_eden_size_ptr) {
496
497 // Adjust the young generation size to reduce pause time of
498 // of collections.
499 //
500 // The AdaptiveSizePolicyInitializingSteps test is not used
501 // here. It has not seemed to be needed but perhaps should
502 // be added for consistency.
503 if (minor_pause_young_estimator()->decrement_will_decrease()) {
504 // reduce eden size
505 set_change_young_gen_for_min_pauses(
506 decrease_young_gen_for_min_pauses_true);
507 *desired_eden_size_ptr = *desired_eden_size_ptr -
508 eden_decrement_aligned_down(*desired_eden_size_ptr);
509 } else {
510 // EXPERIMENTAL ADJUSTMENT
511 // Only record that the estimator indicated such an action.
512 // *desired_eden_size_ptr = *desired_eden_size_ptr + eden_heap_delta;
513 set_change_young_gen_for_min_pauses(
514 increase_young_gen_for_min_pauses_true);
515 }
516 if (PSAdjustTenuredGenForMinorPause) {
517 // If the desired eden size is as small as it will get,
518 // try to adjust the old gen size.
519 if (*desired_eden_size_ptr <= _intra_generation_alignment) {
520 // Vary the old gen size to reduce the young gen pause. This
521 // may not be a good idea. This is just a test.
522 if (minor_pause_old_estimator()->decrement_will_decrease()) {
523 set_change_old_gen_for_min_pauses(
524 decrease_old_gen_for_min_pauses_true);
525 *desired_promo_size_ptr =
526 _promo_size - promo_decrement_aligned_down(*desired_promo_size_ptr);
527 } else {
528 set_change_old_gen_for_min_pauses(
529 increase_old_gen_for_min_pauses_true);
530 size_t promo_heap_delta =
531 promo_increment_with_supplement_aligned_up(*desired_promo_size_ptr);
532 if ((*desired_promo_size_ptr + promo_heap_delta) >
533 *desired_promo_size_ptr) {
534 *desired_promo_size_ptr =
535 _promo_size + promo_heap_delta;
536 }
537 }
538 }
539 }
540 }
541
542 void PSAdaptiveSizePolicy::adjust_for_pause_time(bool is_full_gc,
543 size_t* desired_promo_size_ptr,
544 size_t* desired_eden_size_ptr) {
545
546 size_t promo_heap_delta = 0;
547 size_t eden_heap_delta = 0;
548 // Add some checks for a threshhold for a change. For example,
549 // a change less than the required alignment is probably not worth
550 // attempting.
551 if (is_full_gc) {
552 set_decide_at_full_gc(decide_at_full_gc_true);
553 }
554
555 if (_avg_minor_pause->padded_average() > _avg_major_pause->padded_average()) {
556 adjust_for_minor_pause_time(is_full_gc,
557 desired_promo_size_ptr,
558 desired_eden_size_ptr);
559 // major pause adjustments
560 } else if (is_full_gc) {
561 // Adjust for the major pause time only at full gc's because the
562 // affects of a change can only be seen at full gc's.
563
564 // Reduce old generation size to reduce pause?
565 if (major_pause_old_estimator()->decrement_will_decrease()) {
566 // reduce old generation size
567 set_change_old_gen_for_maj_pauses(decrease_old_gen_for_maj_pauses_true);
568 promo_heap_delta = promo_decrement_aligned_down(*desired_promo_size_ptr);
569 *desired_promo_size_ptr = _promo_size - promo_heap_delta;
570 } else {
571 // EXPERIMENTAL ADJUSTMENT
572 // Only record that the estimator indicated such an action.
573 // *desired_promo_size_ptr = _promo_size +
574 // promo_increment_aligned_up(*desired_promo_size_ptr);
575 set_change_old_gen_for_maj_pauses(increase_old_gen_for_maj_pauses_true);
576 }
577 if (PSAdjustYoungGenForMajorPause) {
578 // If the promo size is at the minimum (i.e., the old gen
579 // size will not actually decrease), consider changing the
580 // young gen size.
581 if (*desired_promo_size_ptr < _intra_generation_alignment) {
582 // If increasing the young generation will decrease the old gen
583 // pause, do it.
584 // During startup there is noise in the statistics for deciding
585 // on whether to increase or decrease the young gen size. For
586 // some number of iterations, just try to increase the young
587 // gen size if the major pause is too long to try and establish
588 // good statistics for later decisions.
589 if (major_pause_young_estimator()->increment_will_decrease() ||
590 (_young_gen_change_for_major_pause_count
591 <= AdaptiveSizePolicyInitializingSteps)) {
592 set_change_young_gen_for_maj_pauses(
593 increase_young_gen_for_maj_pauses_true);
594 eden_heap_delta = eden_increment_aligned_up(*desired_eden_size_ptr);
595 *desired_eden_size_ptr = _eden_size + eden_heap_delta;
596 _young_gen_change_for_major_pause_count++;
597 } else {
598 // Record that decreasing the young gen size would decrease
599 // the major pause
600 set_change_young_gen_for_maj_pauses(
601 decrease_young_gen_for_maj_pauses_true);
602 eden_heap_delta = eden_decrement_aligned_down(*desired_eden_size_ptr);
603 *desired_eden_size_ptr = _eden_size - eden_heap_delta;
604 }
605 }
606 }
607 }
608
609 if (PrintAdaptiveSizePolicy && Verbose) {
610 gclog_or_tty->print_cr(
611 "AdaptiveSizePolicy::compute_generation_free_space "
612 "adjusting gen sizes for major pause (avg %f goal %f). "
613 "desired_promo_size " SIZE_FORMAT "desired_eden_size "
614 SIZE_FORMAT
615 " promo delta " SIZE_FORMAT " eden delta " SIZE_FORMAT,
616 _avg_major_pause->average(), gc_pause_goal_sec(),
617 *desired_promo_size_ptr, *desired_eden_size_ptr,
618 promo_heap_delta, eden_heap_delta);
619 }
620 }
621
622 void PSAdaptiveSizePolicy::adjust_for_throughput(bool is_full_gc,
623 size_t* desired_promo_size_ptr,
624 size_t* desired_eden_size_ptr) {
625
626 // Add some checks for a threshhold for a change. For example,
627 // a change less than the required alignment is probably not worth
628 // attempting.
629 if (is_full_gc) {
630 set_decide_at_full_gc(decide_at_full_gc_true);
631 }
632
633 if ((gc_cost() + mutator_cost()) == 0.0) {
634 return;
635 }
636
637 if (PrintAdaptiveSizePolicy && Verbose) {
638 gclog_or_tty->print("\nPSAdaptiveSizePolicy::adjust_for_throughput("
639 "is_full: %d, promo: " SIZE_FORMAT ", cur_eden: " SIZE_FORMAT "): ",
640 is_full_gc, *desired_promo_size_ptr, *desired_eden_size_ptr);
641 gclog_or_tty->print_cr("mutator_cost %f major_gc_cost %f "
642 "minor_gc_cost %f", mutator_cost(), major_gc_cost(), minor_gc_cost());
643 }
644
645 // Tenured generation
646 if (is_full_gc) {
647
648 // Calculate the change to use for the tenured gen.
649 size_t scaled_promo_heap_delta = 0;
650 // Can the increment to the generation be scaled?
651 if (gc_cost() >= 0.0 && major_gc_cost() >= 0.0) {
652 size_t promo_heap_delta =
653 promo_increment_with_supplement_aligned_up(*desired_promo_size_ptr);
654 double scale_by_ratio = major_gc_cost() / gc_cost();
655 scaled_promo_heap_delta =
656 (size_t) (scale_by_ratio * (double) promo_heap_delta);
657 if (PrintAdaptiveSizePolicy && Verbose) {
658 gclog_or_tty->print_cr(
659 "Scaled tenured increment: " SIZE_FORMAT " by %f down to "
660 SIZE_FORMAT,
661 promo_heap_delta, scale_by_ratio, scaled_promo_heap_delta);
662 }
663 } else if (major_gc_cost() >= 0.0) {
664 // Scaling is not going to work. If the major gc time is the
665 // larger, give it a full increment.
666 if (major_gc_cost() >= minor_gc_cost()) {
667 scaled_promo_heap_delta =
668 promo_increment_with_supplement_aligned_up(*desired_promo_size_ptr);
669 }
670 } else {
671 // Don't expect to get here but it's ok if it does
672 // in the product build since the delta will be 0
673 // and nothing will change.
674 assert(false, "Unexpected value for gc costs");
675 }
676
677 switch (AdaptiveSizeThroughPutPolicy) {
678 case 1:
679 // Early in the run the statistics might not be good. Until
680 // a specific number of collections have been, use the heuristic
681 // that a larger generation size means lower collection costs.
682 if (major_collection_estimator()->increment_will_decrease() ||
683 (_old_gen_change_for_major_throughput
684 <= AdaptiveSizePolicyInitializingSteps)) {
685 // Increase tenured generation size to reduce major collection cost
686 if ((*desired_promo_size_ptr + scaled_promo_heap_delta) >
687 *desired_promo_size_ptr) {
688 *desired_promo_size_ptr = _promo_size + scaled_promo_heap_delta;
689 }
690 set_change_old_gen_for_throughput(
691 increase_old_gen_for_throughput_true);
692 _old_gen_change_for_major_throughput++;
693 } else {
694 // EXPERIMENTAL ADJUSTMENT
695 // Record that decreasing the old gen size would decrease
696 // the major collection cost but don't do it.
697 // *desired_promo_size_ptr = _promo_size -
698 // promo_decrement_aligned_down(*desired_promo_size_ptr);
699 set_change_old_gen_for_throughput(
700 decrease_old_gen_for_throughput_true);
701 }
702
703 break;
704 default:
705 // Simplest strategy
706 if ((*desired_promo_size_ptr + scaled_promo_heap_delta) >
707 *desired_promo_size_ptr) {
708 *desired_promo_size_ptr = *desired_promo_size_ptr +
709 scaled_promo_heap_delta;
710 }
711 set_change_old_gen_for_throughput(
712 increase_old_gen_for_throughput_true);
713 _old_gen_change_for_major_throughput++;
714 }
715
716 if (PrintAdaptiveSizePolicy && Verbose) {
717 gclog_or_tty->print_cr(
718 "adjusting tenured gen for throughput (avg %f goal %f). "
719 "desired_promo_size " SIZE_FORMAT " promo_delta " SIZE_FORMAT ,
720 mutator_cost(), _throughput_goal,
721 *desired_promo_size_ptr, scaled_promo_heap_delta);
722 }
723 }
724
725 // Young generation
726 size_t scaled_eden_heap_delta = 0;
727 // Can the increment to the generation be scaled?
728 if (gc_cost() >= 0.0 && minor_gc_cost() >= 0.0) {
729 size_t eden_heap_delta =
730 eden_increment_with_supplement_aligned_up(*desired_eden_size_ptr);
731 double scale_by_ratio = minor_gc_cost() / gc_cost();
732 assert(scale_by_ratio <= 1.0 && scale_by_ratio >= 0.0, "Scaling is wrong");
733 scaled_eden_heap_delta =
734 (size_t) (scale_by_ratio * (double) eden_heap_delta);
735 if (PrintAdaptiveSizePolicy && Verbose) {
736 gclog_or_tty->print_cr(
737 "Scaled eden increment: " SIZE_FORMAT " by %f down to "
738 SIZE_FORMAT,
739 eden_heap_delta, scale_by_ratio, scaled_eden_heap_delta);
740 }
741 } else if (minor_gc_cost() >= 0.0) {
742 // Scaling is not going to work. If the minor gc time is the
743 // larger, give it a full increment.
744 if (minor_gc_cost() > major_gc_cost()) {
745 scaled_eden_heap_delta =
746 eden_increment_with_supplement_aligned_up(*desired_eden_size_ptr);
747 }
748 } else {
749 // Don't expect to get here but it's ok if it does
750 // in the product build since the delta will be 0
751 // and nothing will change.
752 assert(false, "Unexpected value for gc costs");
753 }
754
755 // Use a heuristic for some number of collections to give
756 // the averages time to settle down.
757 switch (AdaptiveSizeThroughPutPolicy) {
758 case 1:
759 if (minor_collection_estimator()->increment_will_decrease() ||
760 (_young_gen_change_for_minor_throughput
761 <= AdaptiveSizePolicyInitializingSteps)) {
762 // Expand young generation size to reduce frequency of
763 // of collections.
764 if ((*desired_eden_size_ptr + scaled_eden_heap_delta) >
765 *desired_eden_size_ptr) {
766 *desired_eden_size_ptr =
767 *desired_eden_size_ptr + scaled_eden_heap_delta;
768 }
769 set_change_young_gen_for_throughput(
770 increase_young_gen_for_througput_true);
771 _young_gen_change_for_minor_throughput++;
772 } else {
773 // EXPERIMENTAL ADJUSTMENT
774 // Record that decreasing the young gen size would decrease
775 // the minor collection cost but don't do it.
776 // *desired_eden_size_ptr = _eden_size -
777 // eden_decrement_aligned_down(*desired_eden_size_ptr);
778 set_change_young_gen_for_throughput(
779 decrease_young_gen_for_througput_true);
780 }
781 break;
782 default:
783 if ((*desired_eden_size_ptr + scaled_eden_heap_delta) >
784 *desired_eden_size_ptr) {
785 *desired_eden_size_ptr =
786 *desired_eden_size_ptr + scaled_eden_heap_delta;
787 }
788 set_change_young_gen_for_throughput(
789 increase_young_gen_for_througput_true);
790 _young_gen_change_for_minor_throughput++;
791 }
792
793 if (PrintAdaptiveSizePolicy && Verbose) {
794 gclog_or_tty->print_cr(
795 "adjusting eden for throughput (avg %f goal %f). desired_eden_size "
796 SIZE_FORMAT " eden delta " SIZE_FORMAT "\n",
797 mutator_cost(), _throughput_goal,
798 *desired_eden_size_ptr, scaled_eden_heap_delta);
799 }
800 }
801
802 size_t PSAdaptiveSizePolicy::adjust_promo_for_footprint(
803 size_t desired_promo_size, size_t desired_sum) {
804 assert(desired_promo_size <= desired_sum, "Inconsistent parameters");
805 set_decrease_for_footprint(decrease_old_gen_for_footprint_true);
806
807 size_t change = promo_decrement(desired_promo_size);
808 change = scale_down(change, desired_promo_size, desired_sum);
809
810 size_t reduced_size = desired_promo_size - change;
811
812 if (PrintAdaptiveSizePolicy && Verbose) {
813 gclog_or_tty->print_cr(
814 "AdaptiveSizePolicy::compute_generation_free_space "
815 "adjusting tenured gen for footprint. "
816 "starting promo size " SIZE_FORMAT
817 " reduced promo size " SIZE_FORMAT,
818 " promo delta " SIZE_FORMAT,
819 desired_promo_size, reduced_size, change );
820 }
821
822 assert(reduced_size <= desired_promo_size, "Inconsistent result");
823 return reduced_size;
824 }
825
826 size_t PSAdaptiveSizePolicy::adjust_eden_for_footprint(
827 size_t desired_eden_size, size_t desired_sum) {
828 assert(desired_eden_size <= desired_sum, "Inconsistent parameters");
829 set_decrease_for_footprint(decrease_young_gen_for_footprint_true);
830
831 size_t change = eden_decrement(desired_eden_size);
832 change = scale_down(change, desired_eden_size, desired_sum);
833
834 size_t reduced_size = desired_eden_size - change;
835
836 if (PrintAdaptiveSizePolicy && Verbose) {
837 gclog_or_tty->print_cr(
838 "AdaptiveSizePolicy::compute_generation_free_space "
839 "adjusting eden for footprint. "
840 " starting eden size " SIZE_FORMAT
841 " reduced eden size " SIZE_FORMAT
842 " eden delta " SIZE_FORMAT,
843 desired_eden_size, reduced_size, change);
844 }
845
846 assert(reduced_size <= desired_eden_size, "Inconsistent result");
847 return reduced_size;
848 }
849
850 // Scale down "change" by the factor
851 // part / total
852 // Don't align the results.
853
854 size_t PSAdaptiveSizePolicy::scale_down(size_t change,
855 double part,
856 double total) {
857 assert(part <= total, "Inconsistent input");
858 size_t reduced_change = change;
859 if (total > 0) {
860 double fraction = part / total;
861 reduced_change = (size_t) (fraction * (double) change);
862 }
863 assert(reduced_change <= change, "Inconsistent result");
864 return reduced_change;
865 }
866
867 size_t PSAdaptiveSizePolicy::eden_increment(size_t cur_eden,
868 uint percent_change) {
869 size_t eden_heap_delta;
870 eden_heap_delta = cur_eden / 100 * percent_change;
871 return eden_heap_delta;
872 }
873
874 size_t PSAdaptiveSizePolicy::eden_increment(size_t cur_eden) {
875 return eden_increment(cur_eden, YoungGenerationSizeIncrement);
876 }
877
878 size_t PSAdaptiveSizePolicy::eden_increment_aligned_up(size_t cur_eden) {
879 size_t result = eden_increment(cur_eden, YoungGenerationSizeIncrement);
880 return align_size_up(result, _intra_generation_alignment);
881 }
882
883 size_t PSAdaptiveSizePolicy::eden_increment_aligned_down(size_t cur_eden) {
884 size_t result = eden_increment(cur_eden);
885 return align_size_down(result, _intra_generation_alignment);
886 }
887
888 size_t PSAdaptiveSizePolicy::eden_increment_with_supplement_aligned_up(
889 size_t cur_eden) {
890 size_t result = eden_increment(cur_eden,
891 YoungGenerationSizeIncrement + _young_gen_size_increment_supplement);
892 return align_size_up(result, _intra_generation_alignment);
893 }
894
895 size_t PSAdaptiveSizePolicy::eden_decrement_aligned_down(size_t cur_eden) {
896 size_t eden_heap_delta = eden_decrement(cur_eden);
897 return align_size_down(eden_heap_delta, _intra_generation_alignment);
898 }
899
900 size_t PSAdaptiveSizePolicy::eden_decrement(size_t cur_eden) {
901 size_t eden_heap_delta = eden_increment(cur_eden) /
902 AdaptiveSizeDecrementScaleFactor;
903 return eden_heap_delta;
904 }
905
906 size_t PSAdaptiveSizePolicy::promo_increment(size_t cur_promo,
907 uint percent_change) {
908 size_t promo_heap_delta;
909 promo_heap_delta = cur_promo / 100 * percent_change;
910 return promo_heap_delta;
911 }
912
913 size_t PSAdaptiveSizePolicy::promo_increment(size_t cur_promo) {
914 return promo_increment(cur_promo, TenuredGenerationSizeIncrement);
915 }
916
917 size_t PSAdaptiveSizePolicy::promo_increment_aligned_up(size_t cur_promo) {
918 size_t result = promo_increment(cur_promo, TenuredGenerationSizeIncrement);
919 return align_size_up(result, _intra_generation_alignment);
920 }
921
922 size_t PSAdaptiveSizePolicy::promo_increment_aligned_down(size_t cur_promo) {
923 size_t result = promo_increment(cur_promo, TenuredGenerationSizeIncrement);
924 return align_size_down(result, _intra_generation_alignment);
925 }
926
927 size_t PSAdaptiveSizePolicy::promo_increment_with_supplement_aligned_up(
928 size_t cur_promo) {
929 size_t result = promo_increment(cur_promo,
930 TenuredGenerationSizeIncrement + _old_gen_size_increment_supplement);
931 return align_size_up(result, _intra_generation_alignment);
932 }
933
934 size_t PSAdaptiveSizePolicy::promo_decrement_aligned_down(size_t cur_promo) {
935 size_t promo_heap_delta = promo_decrement(cur_promo);
936 return align_size_down(promo_heap_delta, _intra_generation_alignment);
937 }
938
939 size_t PSAdaptiveSizePolicy::promo_decrement(size_t cur_promo) {
940 size_t promo_heap_delta = promo_increment(cur_promo);
941 promo_heap_delta = promo_heap_delta / AdaptiveSizeDecrementScaleFactor;
942 return promo_heap_delta;
943 }
944
945 int PSAdaptiveSizePolicy::compute_survivor_space_size_and_threshold(
946 bool is_survivor_overflow,
947 int tenuring_threshold,
948 size_t survivor_limit) {
949 assert(survivor_limit >= _intra_generation_alignment,
950 "survivor_limit too small");
951 assert((size_t)align_size_down(survivor_limit, _intra_generation_alignment)
952 == survivor_limit, "survivor_limit not aligned");
953
954 // This method is called even if the tenuring threshold and survivor
955 // spaces are not adjusted so that the averages are sampled above.
956 if (!UsePSAdaptiveSurvivorSizePolicy ||
957 !young_gen_policy_is_ready()) {
958 return tenuring_threshold;
959 }
960
961 // We'll decide whether to increase or decrease the tenuring
962 // threshold based partly on the newly computed survivor size
963 // (if we hit the maximum limit allowed, we'll always choose to
964 // decrement the threshold).
965 bool incr_tenuring_threshold = false;
966 bool decr_tenuring_threshold = false;
967
968 set_decrement_tenuring_threshold_for_gc_cost(false);
969 set_increment_tenuring_threshold_for_gc_cost(false);
970 set_decrement_tenuring_threshold_for_survivor_limit(false);
971
972 if (!is_survivor_overflow) {
973 // Keep running averages on how much survived
974
975 // We use the tenuring threshold to equalize the cost of major
976 // and minor collections.
977 // ThresholdTolerance is used to indicate how sensitive the
978 // tenuring threshold is to differences in cost betweent the
979 // collection types.
980
981 // Get the times of interest. This involves a little work, so
982 // we cache the values here.
983 const double major_cost = major_gc_cost();
984 const double minor_cost = minor_gc_cost();
985
986 if (minor_cost > major_cost * _threshold_tolerance_percent) {
987 // Minor times are getting too long; lower the threshold so
988 // less survives and more is promoted.
989 decr_tenuring_threshold = true;
990 set_decrement_tenuring_threshold_for_gc_cost(true);
991 } else if (major_cost > minor_cost * _threshold_tolerance_percent) {
992 // Major times are too long, so we want less promotion.
993 incr_tenuring_threshold = true;
994 set_increment_tenuring_threshold_for_gc_cost(true);
995 }
996
997 } else {
998 // Survivor space overflow occurred, so promoted and survived are
999 // not accurate. We'll make our best guess by combining survived
1000 // and promoted and count them as survivors.
1001 //
1002 // We'll lower the tenuring threshold to see if we can correct
1003 // things. Also, set the survivor size conservatively. We're
1004 // trying to avoid many overflows from occurring if defnew size
1005 // is just too small.
1006
1007 decr_tenuring_threshold = true;
1008 }
1009
1010 // The padded average also maintains a deviation from the average;
1011 // we use this to see how good of an estimate we have of what survived.
1012 // We're trying to pad the survivor size as little as possible without
1013 // overflowing the survivor spaces.
1014 size_t target_size = align_size_up((size_t)_avg_survived->padded_average(),
1015 _intra_generation_alignment);
1016 target_size = MAX2(target_size, _intra_generation_alignment);
1017
1018 if (target_size > survivor_limit) {
1019 // Target size is bigger than we can handle. Let's also reduce
1020 // the tenuring threshold.
1021 target_size = survivor_limit;
1022 decr_tenuring_threshold = true;
1023 set_decrement_tenuring_threshold_for_survivor_limit(true);
1024 }
1025
1026 // Finally, increment or decrement the tenuring threshold, as decided above.
1027 // We test for decrementing first, as we might have hit the target size
1028 // limit.
1029 if (decr_tenuring_threshold && !(AlwaysTenure || NeverTenure)) {
1030 if (tenuring_threshold > 1) {
1031 tenuring_threshold--;
1032 }
1033 } else if (incr_tenuring_threshold && !(AlwaysTenure || NeverTenure)) {
1034 if (tenuring_threshold < MaxTenuringThreshold) {
1035 tenuring_threshold++;
1036 }
1037 }
1038
1039 // We keep a running average of the amount promoted which is used
1040 // to decide when we should collect the old generation (when
1041 // the amount of old gen free space is less than what we expect to
1042 // promote).
1043
1044 if (PrintAdaptiveSizePolicy) {
1045 // A little more detail if Verbose is on
1046 if (Verbose) {
1047 gclog_or_tty->print( " avg_survived: %f"
1048 " avg_deviation: %f",
1049 _avg_survived->average(),
1050 _avg_survived->deviation());
1051 }
1052
1053 gclog_or_tty->print( " avg_survived_padded_avg: %f",
1054 _avg_survived->padded_average());
1055
1056 if (Verbose) {
1057 gclog_or_tty->print( " avg_promoted_avg: %f"
1058 " avg_promoted_dev: %f",
1059 avg_promoted()->average(),
1060 avg_promoted()->deviation());
1061 }
1062
1063 gclog_or_tty->print( " avg_promoted_padded_avg: %f"
1064 " avg_pretenured_padded_avg: %f"
1065 " tenuring_thresh: %d"
1066 " target_size: " SIZE_FORMAT,
1067 avg_promoted()->padded_average(),
1068 _avg_pretenured->padded_average(),
1069 tenuring_threshold, target_size);
1070 tty->cr();
1071 }
1072
1073 set_survivor_size(target_size);
1074
1075 return tenuring_threshold;
1076 }
1077
1078 void PSAdaptiveSizePolicy::update_averages(bool is_survivor_overflow,
1079 size_t survived,
1080 size_t promoted) {
1081 // Update averages
1082 if (!is_survivor_overflow) {
1083 // Keep running averages on how much survived
1084 _avg_survived->sample(survived);
1085 } else {
1086 size_t survived_guess = survived + promoted;
1087 _avg_survived->sample(survived_guess);
1088 }
1089 avg_promoted()->sample(promoted + _avg_pretenured->padded_average());
1090
1091 if (PrintAdaptiveSizePolicy) {
1092 gclog_or_tty->print(
1093 "AdaptiveSizePolicy::compute_survivor_space_size_and_thresh:"
1094 " survived: " SIZE_FORMAT
1095 " promoted: " SIZE_FORMAT
1096 " overflow: %s",
1097 survived, promoted, is_survivor_overflow ? "true" : "false");
1098 }
1099 }
1100
1101 bool PSAdaptiveSizePolicy::print_adaptive_size_policy_on(outputStream* st)
1102 const {
1103
1104 if (!UseAdaptiveSizePolicy) return false;
1105
1106 return AdaptiveSizePolicy::print_adaptive_size_policy_on(
1107 st,
1108 PSScavenge::tenuring_threshold());
1109 }