1 /*
2 * Copyright (c) 2004, 2018, 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/shared/adaptiveSizePolicy.hpp"
27 #include "gc/shared/gcCause.hpp"
28 #include "gc/shared/gcUtil.inline.hpp"
29 #include "logging/log.hpp"
30 #include "runtime/timer.hpp"
31
32 elapsedTimer AdaptiveSizePolicy::_minor_timer;
33 elapsedTimer AdaptiveSizePolicy::_major_timer;
34
35 // The throughput goal is implemented as
36 // _throughput_goal = 1 - ( 1 / (1 + gc_cost_ratio))
37 // gc_cost_ratio is the ratio
38 // application cost / gc cost
39 // For example a gc_cost_ratio of 4 translates into a
40 // throughput goal of .80
41
42 AdaptiveSizePolicy::AdaptiveSizePolicy(size_t init_eden_size,
43 size_t init_promo_size,
44 size_t init_survivor_size,
45 double gc_pause_goal_sec,
46 uint gc_cost_ratio) :
47 _throughput_goal(1.0 - double(1.0 / (1.0 + (double) gc_cost_ratio))),
48 _eden_size(init_eden_size),
49 _promo_size(init_promo_size),
50 _survivor_size(init_survivor_size),
51 _latest_minor_mutator_interval_seconds(0),
52 _threshold_tolerance_percent(1.0 + ThresholdTolerance/100.0),
53 _gc_pause_goal_sec(gc_pause_goal_sec),
54 _young_gen_change_for_minor_throughput(0),
55 _old_gen_change_for_major_throughput(0) {
56 assert(AdaptiveSizePolicyGCTimeLimitThreshold > 0,
57 "No opportunity to clear SoftReferences before GC overhead limit");
58 _avg_minor_pause =
59 new AdaptivePaddedAverage(AdaptiveTimeWeight, PausePadding);
60 _avg_minor_interval = new AdaptiveWeightedAverage(AdaptiveTimeWeight);
61 _avg_minor_gc_cost = new AdaptiveWeightedAverage(AdaptiveTimeWeight);
62 _avg_major_gc_cost = new AdaptiveWeightedAverage(AdaptiveTimeWeight);
63
64 _avg_young_live = new AdaptiveWeightedAverage(AdaptiveSizePolicyWeight);
65 _avg_old_live = new AdaptiveWeightedAverage(AdaptiveSizePolicyWeight);
66 _avg_eden_live = new AdaptiveWeightedAverage(AdaptiveSizePolicyWeight);
67
68 _avg_survived = new AdaptivePaddedAverage(AdaptiveSizePolicyWeight,
69 SurvivorPadding);
70 _avg_pretenured = new AdaptivePaddedNoZeroDevAverage(
71 AdaptiveSizePolicyWeight,
72 SurvivorPadding);
73
74 _minor_pause_old_estimator =
75 new LinearLeastSquareFit(AdaptiveSizePolicyWeight);
76 _minor_pause_young_estimator =
77 new LinearLeastSquareFit(AdaptiveSizePolicyWeight);
78 _minor_collection_estimator =
79 new LinearLeastSquareFit(AdaptiveSizePolicyWeight);
80 _major_collection_estimator =
81 new LinearLeastSquareFit(AdaptiveSizePolicyWeight);
82
83 // Start the timers
84 _minor_timer.start();
85
86 _young_gen_policy_is_ready = false;
87 }
88
89 bool AdaptiveSizePolicy::tenuring_threshold_change() const {
90 return decrement_tenuring_threshold_for_gc_cost() ||
91 increment_tenuring_threshold_for_gc_cost() ||
92 decrement_tenuring_threshold_for_survivor_limit();
93 }
94
95 void AdaptiveSizePolicy::minor_collection_begin() {
96 // Update the interval time
97 _minor_timer.stop();
98 // Save most recent collection time
99 _latest_minor_mutator_interval_seconds = _minor_timer.seconds();
100 _minor_timer.reset();
101 _minor_timer.start();
102 }
103
104 void AdaptiveSizePolicy::update_minor_pause_young_estimator(
105 double minor_pause_in_ms) {
106 double eden_size_in_mbytes = ((double)_eden_size)/((double)M);
107 _minor_pause_young_estimator->update(eden_size_in_mbytes,
108 minor_pause_in_ms);
109 }
110
111 void AdaptiveSizePolicy::minor_collection_end(GCCause::Cause gc_cause) {
112 // Update the pause time.
113 _minor_timer.stop();
114
115 if (!GCCause::is_user_requested_gc(gc_cause) ||
116 UseAdaptiveSizePolicyWithSystemGC) {
117 double minor_pause_in_seconds = _minor_timer.seconds();
118 double minor_pause_in_ms = minor_pause_in_seconds * MILLIUNITS;
119
120 // Sample for performance counter
121 _avg_minor_pause->sample(minor_pause_in_seconds);
122
123 // Cost of collection (unit-less)
124 double collection_cost = 0.0;
125 if ((_latest_minor_mutator_interval_seconds > 0.0) &&
126 (minor_pause_in_seconds > 0.0)) {
127 double interval_in_seconds =
128 _latest_minor_mutator_interval_seconds + minor_pause_in_seconds;
129 collection_cost =
130 minor_pause_in_seconds / interval_in_seconds;
131 _avg_minor_gc_cost->sample(collection_cost);
132 // Sample for performance counter
133 _avg_minor_interval->sample(interval_in_seconds);
134 }
135
136 // The policy does not have enough data until at least some
137 // young collections have been done.
138 _young_gen_policy_is_ready =
139 (_avg_minor_gc_cost->count() >= AdaptiveSizePolicyReadyThreshold);
140
141 // Calculate variables used to estimate pause time vs. gen sizes
142 double eden_size_in_mbytes = ((double)_eden_size) / ((double)M);
143 update_minor_pause_young_estimator(minor_pause_in_ms);
144 update_minor_pause_old_estimator(minor_pause_in_ms);
145
146 log_trace(gc, ergo)("AdaptiveSizePolicy::minor_collection_end: minor gc cost: %f average: %f",
147 collection_cost, _avg_minor_gc_cost->average());
148 log_trace(gc, ergo)(" minor pause: %f minor period %f",
149 minor_pause_in_ms, _latest_minor_mutator_interval_seconds * MILLIUNITS);
150
151 // Calculate variable used to estimate collection cost vs. gen sizes
152 assert(collection_cost >= 0.0, "Expected to be non-negative");
153 _minor_collection_estimator->update(eden_size_in_mbytes, collection_cost);
154 }
155
156 // Interval times use this timer to measure the mutator time.
157 // Reset the timer after the GC pause.
158 _minor_timer.reset();
159 _minor_timer.start();
160 }
161
162 size_t AdaptiveSizePolicy::eden_increment(size_t cur_eden, uint percent_change) {
163 size_t eden_heap_delta;
164 eden_heap_delta = cur_eden / 100 * percent_change;
165 return eden_heap_delta;
166 }
167
168 size_t AdaptiveSizePolicy::eden_increment(size_t cur_eden) {
169 return eden_increment(cur_eden, YoungGenerationSizeIncrement);
170 }
171
172 size_t AdaptiveSizePolicy::eden_decrement(size_t cur_eden) {
173 size_t eden_heap_delta = eden_increment(cur_eden) /
174 AdaptiveSizeDecrementScaleFactor;
175 return eden_heap_delta;
176 }
177
178 size_t AdaptiveSizePolicy::promo_increment(size_t cur_promo, uint percent_change) {
179 size_t promo_heap_delta;
180 promo_heap_delta = cur_promo / 100 * percent_change;
181 return promo_heap_delta;
182 }
183
184 size_t AdaptiveSizePolicy::promo_increment(size_t cur_promo) {
185 return promo_increment(cur_promo, TenuredGenerationSizeIncrement);
186 }
187
188 size_t AdaptiveSizePolicy::promo_decrement(size_t cur_promo) {
189 size_t promo_heap_delta = promo_increment(cur_promo);
190 promo_heap_delta = promo_heap_delta / AdaptiveSizeDecrementScaleFactor;
191 return promo_heap_delta;
192 }
193
194 double AdaptiveSizePolicy::time_since_major_gc() const {
195 _major_timer.stop();
196 double result = _major_timer.seconds();
197 _major_timer.start();
198 return result;
199 }
200
201 // Linear decay of major gc cost
202 double AdaptiveSizePolicy::decaying_major_gc_cost() const {
203 double major_interval = major_gc_interval_average_for_decay();
204 double major_gc_cost_average = major_gc_cost();
205 double decayed_major_gc_cost = major_gc_cost_average;
206 if(time_since_major_gc() > 0.0) {
207 decayed_major_gc_cost = major_gc_cost() *
208 (((double) AdaptiveSizeMajorGCDecayTimeScale) * major_interval)
209 / time_since_major_gc();
210 }
211
212 // The decayed cost should always be smaller than the
213 // average cost but the vagaries of finite arithmetic could
214 // produce a larger value in decayed_major_gc_cost so protect
215 // against that.
216 return MIN2(major_gc_cost_average, decayed_major_gc_cost);
217 }
218
219 // Use a value of the major gc cost that has been decayed
220 // by the factor
221 //
222 // average-interval-between-major-gc * AdaptiveSizeMajorGCDecayTimeScale /
223 // time-since-last-major-gc
224 //
225 // if the average-interval-between-major-gc * AdaptiveSizeMajorGCDecayTimeScale
226 // is less than time-since-last-major-gc.
227 //
228 // In cases where there are initial major gc's that
229 // are of a relatively high cost but no later major
230 // gc's, the total gc cost can remain high because
231 // the major gc cost remains unchanged (since there are no major
232 // gc's). In such a situation the value of the unchanging
233 // major gc cost can keep the mutator throughput below
234 // the goal when in fact the major gc cost is becoming diminishingly
235 // small. Use the decaying gc cost only to decide whether to
236 // adjust for throughput. Using it also to determine the adjustment
237 // to be made for throughput also seems reasonable but there is
238 // no test case to use to decide if it is the right thing to do
239 // don't do it yet.
240
241 double AdaptiveSizePolicy::decaying_gc_cost() const {
242 double decayed_major_gc_cost = major_gc_cost();
243 double avg_major_interval = major_gc_interval_average_for_decay();
244 if (UseAdaptiveSizeDecayMajorGCCost &&
245 (AdaptiveSizeMajorGCDecayTimeScale > 0) &&
246 (avg_major_interval > 0.00)) {
247 double time_since_last_major_gc = time_since_major_gc();
248
249 // Decay the major gc cost?
250 if (time_since_last_major_gc >
251 ((double) AdaptiveSizeMajorGCDecayTimeScale) * avg_major_interval) {
252
253 // Decay using the time-since-last-major-gc
254 decayed_major_gc_cost = decaying_major_gc_cost();
255 log_trace(gc, ergo)("decaying_gc_cost: major interval average: %f time since last major gc: %f",
256 avg_major_interval, time_since_last_major_gc);
257 log_trace(gc, ergo)(" major gc cost: %f decayed major gc cost: %f",
258 major_gc_cost(), decayed_major_gc_cost);
259 }
260 }
261 double result = MIN2(1.0, decayed_major_gc_cost + minor_gc_cost());
262 return result;
263 }
264
265
266 void AdaptiveSizePolicy::clear_generation_free_space_flags() {
267 set_change_young_gen_for_min_pauses(0);
268 set_change_old_gen_for_maj_pauses(0);
269
270 set_change_old_gen_for_throughput(0);
271 set_change_young_gen_for_throughput(0);
272 set_decrease_for_footprint(0);
273 set_decide_at_full_gc(0);
274 }
275
276 class AdaptiveSizePolicyTimeOverheadTester: public OverheadTester {
277 double _gc_cost;
278
279 public:
280 AdaptiveSizePolicyTimeOverheadTester(double gc_cost) : _gc_cost(gc_cost) {}
281
282 bool is_exceeded() {
283 // Note that the gc time limit test only works for the collections
284 // of the young gen + tenured gen and not for collections of the
285 // permanent gen. That is because the calculation of the space
286 // freed by the collection is the free space in the young gen +
287 // tenured gen.
288 return _gc_cost > (GCTimeLimit / 100.0);
289 }
290 };
291
292 class AdaptiveSizePolicySpaceOverheadTester: public OverheadTester {
293 size_t _eden_live;
294 size_t _max_old_gen_size;
295 size_t _max_eden_size;
296 size_t _promo_size;
297 double _avg_eden_live;
298 double _avg_old_live;
299
300 public:
301 AdaptiveSizePolicySpaceOverheadTester(size_t eden_live,
302 size_t max_old_gen_size,
303 size_t max_eden_size,
304 size_t promo_size,
305 double avg_eden_live,
306 double avg_old_live) :
307 _eden_live(eden_live),
308 _max_old_gen_size(max_old_gen_size),
309 _max_eden_size(max_eden_size),
310 _promo_size(promo_size),
311 _avg_eden_live(avg_eden_live),
312 _avg_old_live(avg_old_live) {}
313
314 bool is_exceeded() {
315 // _max_eden_size is the upper limit on the size of eden based on
316 // the maximum size of the young generation and the sizes
317 // of the survivor space.
318 // The question being asked is whether the space being recovered by
319 // a collection is low.
320 // free_in_eden is the free space in eden after a collection and
321 // free_in_old_gen is the free space in the old generation after
322 // a collection.
323 //
324 // Use the minimum of the current value of the live in eden
325 // or the average of the live in eden.
326 // If the current value drops quickly, that should be taken
327 // into account (i.e., don't trigger if the amount of free
328 // space has suddenly jumped up). If the current is much
329 // higher than the average, use the average since it represents
330 // the longer term behavior.
331 const size_t live_in_eden =
332 MIN2(_eden_live, (size_t)_avg_eden_live);
333 const size_t free_in_eden = _max_eden_size > live_in_eden ?
334 _max_eden_size - live_in_eden : 0;
335 const size_t free_in_old_gen = (size_t)(_max_old_gen_size - _avg_old_live);
336 const size_t total_free_limit = free_in_old_gen + free_in_eden;
337 const size_t total_mem = _max_old_gen_size + _max_eden_size;
338 const double free_limit_ratio = GCHeapFreeLimit / 100.0;
339 const double mem_free_limit = total_mem * free_limit_ratio;
340 const double mem_free_old_limit = _max_old_gen_size * free_limit_ratio;
341 const double mem_free_eden_limit = _max_eden_size * free_limit_ratio;
342 size_t promo_limit = (size_t)(_max_old_gen_size - _avg_old_live);
343 // But don't force a promo size below the current promo size. Otherwise,
344 // the promo size will shrink for no good reason.
345 promo_limit = MAX2(promo_limit, _promo_size);
346
347 log_trace(gc, ergo)(
348 "AdaptiveSizePolicySpaceOverheadTester::is_exceeded:"
349 " promo_limit: " SIZE_FORMAT
350 " max_eden_size: " SIZE_FORMAT
351 " total_free_limit: " SIZE_FORMAT
352 " max_old_gen_size: " SIZE_FORMAT
353 " max_eden_size: " SIZE_FORMAT
354 " mem_free_limit: " SIZE_FORMAT,
355 promo_limit, _max_eden_size, total_free_limit,
356 _max_old_gen_size, _max_eden_size,
357 (size_t)mem_free_limit);
358
359 return free_in_old_gen < (size_t)mem_free_old_limit &&
360 free_in_eden < (size_t)mem_free_eden_limit;
361 }
362
363 };
364
365 void AdaptiveSizePolicy::check_gc_overhead_limit(
366 size_t eden_live,
367 size_t max_old_gen_size,
368 size_t max_eden_size,
369 bool is_full_gc,
370 GCCause::Cause gc_cause,
371 SoftRefPolicy* soft_ref_policy) {
372
373 AdaptiveSizePolicyTimeOverheadTester time_overhead(gc_cost());
374 AdaptiveSizePolicySpaceOverheadTester space_overhead(eden_live,
375 max_old_gen_size,
376 max_eden_size,
377 _promo_size,
378 avg_eden_live()->average(),
379 avg_old_live()->average());
380 _overhead_checker.check_gc_overhead_limit(&time_overhead,
381 &space_overhead,
382 is_full_gc,
383 gc_cause,
384 soft_ref_policy);
385 }
386 // Printing
387
388 bool AdaptiveSizePolicy::print() const {
389 assert(UseAdaptiveSizePolicy, "UseAdaptiveSizePolicy need to be enabled.");
390
391 if (!log_is_enabled(Debug, gc, ergo)) {
392 return false;
393 }
394
395 // Print goal for which action is needed.
396 char* action = NULL;
397 bool change_for_pause = false;
398 if ((change_old_gen_for_maj_pauses() ==
399 decrease_old_gen_for_maj_pauses_true) ||
400 (change_young_gen_for_min_pauses() ==
401 decrease_young_gen_for_min_pauses_true)) {
402 action = (char*) " *** pause time goal ***";
403 change_for_pause = true;
404 } else if ((change_old_gen_for_throughput() ==
405 increase_old_gen_for_throughput_true) ||
406 (change_young_gen_for_throughput() ==
407 increase_young_gen_for_througput_true)) {
408 action = (char*) " *** throughput goal ***";
409 } else if (decrease_for_footprint()) {
410 action = (char*) " *** reduced footprint ***";
411 } else {
412 // No actions were taken. This can legitimately be the
413 // situation if not enough data has been gathered to make
414 // decisions.
415 return false;
416 }
417
418 // Pauses
419 // Currently the size of the old gen is only adjusted to
420 // change the major pause times.
421 char* young_gen_action = NULL;
422 char* tenured_gen_action = NULL;
423
424 char* shrink_msg = (char*) "(attempted to shrink)";
425 char* grow_msg = (char*) "(attempted to grow)";
426 char* no_change_msg = (char*) "(no change)";
427 if (change_young_gen_for_min_pauses() ==
428 decrease_young_gen_for_min_pauses_true) {
429 young_gen_action = shrink_msg;
430 } else if (change_for_pause) {
431 young_gen_action = no_change_msg;
432 }
433
434 if (change_old_gen_for_maj_pauses() == decrease_old_gen_for_maj_pauses_true) {
435 tenured_gen_action = shrink_msg;
436 } else if (change_for_pause) {
437 tenured_gen_action = no_change_msg;
438 }
439
440 // Throughput
441 if (change_old_gen_for_throughput() == increase_old_gen_for_throughput_true) {
442 assert(change_young_gen_for_throughput() ==
443 increase_young_gen_for_througput_true,
444 "Both generations should be growing");
445 young_gen_action = grow_msg;
446 tenured_gen_action = grow_msg;
447 } else if (change_young_gen_for_throughput() ==
448 increase_young_gen_for_througput_true) {
449 // Only the young generation may grow at start up (before
450 // enough full collections have been done to grow the old generation).
451 young_gen_action = grow_msg;
452 tenured_gen_action = no_change_msg;
453 }
454
455 // Minimum footprint
456 if (decrease_for_footprint() != 0) {
457 young_gen_action = shrink_msg;
458 tenured_gen_action = shrink_msg;
459 }
460
461 log_debug(gc, ergo)("UseAdaptiveSizePolicy actions to meet %s", action);
462 log_debug(gc, ergo)(" GC overhead (%%)");
463 log_debug(gc, ergo)(" Young generation: %7.2f\t %s",
464 100.0 * avg_minor_gc_cost()->average(), young_gen_action);
465 log_debug(gc, ergo)(" Tenured generation: %7.2f\t %s",
466 100.0 * avg_major_gc_cost()->average(), tenured_gen_action);
467 return true;
468 }
469
470 void AdaptiveSizePolicy::print_tenuring_threshold( uint new_tenuring_threshold_arg) const {
471 // Tenuring threshold
472 if (decrement_tenuring_threshold_for_survivor_limit()) {
473 log_debug(gc, ergo)("Tenuring threshold: (attempted to decrease to avoid survivor space overflow) = %u", new_tenuring_threshold_arg);
474 } else if (decrement_tenuring_threshold_for_gc_cost()) {
475 log_debug(gc, ergo)("Tenuring threshold: (attempted to decrease to balance GC costs) = %u", new_tenuring_threshold_arg);
476 } else if (increment_tenuring_threshold_for_gc_cost()) {
477 log_debug(gc, ergo)("Tenuring threshold: (attempted to increase to balance GC costs) = %u", new_tenuring_threshold_arg);
478 } else {
479 assert(!tenuring_threshold_change(), "(no change was attempted)");
480 }
481 }