1 /*
2 * Copyright (c) 2004, 2019, 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 _avg_minor_pause =
57 new AdaptivePaddedAverage(AdaptiveTimeWeight, PausePadding);
58 _avg_minor_interval = new AdaptiveWeightedAverage(AdaptiveTimeWeight);
59 _avg_minor_gc_cost = new AdaptiveWeightedAverage(AdaptiveTimeWeight);
60 _avg_major_gc_cost = new AdaptiveWeightedAverage(AdaptiveTimeWeight);
61
62 _avg_young_live = new AdaptiveWeightedAverage(AdaptiveSizePolicyWeight);
63 _avg_old_live = new AdaptiveWeightedAverage(AdaptiveSizePolicyWeight);
64 _avg_eden_live = new AdaptiveWeightedAverage(AdaptiveSizePolicyWeight);
65
66 _avg_survived = new AdaptivePaddedAverage(AdaptiveSizePolicyWeight,
67 SurvivorPadding);
68 _avg_pretenured = new AdaptivePaddedNoZeroDevAverage(
69 AdaptiveSizePolicyWeight,
70 SurvivorPadding);
71
72 _minor_pause_old_estimator =
73 new LinearLeastSquareFit(AdaptiveSizePolicyWeight);
74 _minor_pause_young_estimator =
75 new LinearLeastSquareFit(AdaptiveSizePolicyWeight);
76 _minor_collection_estimator =
77 new LinearLeastSquareFit(AdaptiveSizePolicyWeight);
78 _major_collection_estimator =
79 new LinearLeastSquareFit(AdaptiveSizePolicyWeight);
80
81 // Start the timers
82 _minor_timer.start();
83
84 _young_gen_policy_is_ready = false;
85 }
86
87 bool AdaptiveSizePolicy::tenuring_threshold_change() const {
88 return decrement_tenuring_threshold_for_gc_cost() ||
89 increment_tenuring_threshold_for_gc_cost() ||
90 decrement_tenuring_threshold_for_survivor_limit();
91 }
92
93 void AdaptiveSizePolicy::minor_collection_begin() {
94 // Update the interval time
95 _minor_timer.stop();
96 // Save most recent collection time
97 _latest_minor_mutator_interval_seconds = _minor_timer.seconds();
98 _minor_timer.reset();
99 _minor_timer.start();
100 }
101
102 void AdaptiveSizePolicy::update_minor_pause_young_estimator(
103 double minor_pause_in_ms) {
104 double eden_size_in_mbytes = ((double)_eden_size)/((double)M);
105 _minor_pause_young_estimator->update(eden_size_in_mbytes,
106 minor_pause_in_ms);
107 }
108
109 void AdaptiveSizePolicy::minor_collection_end(GCCause::Cause gc_cause) {
110 // Update the pause time.
111 _minor_timer.stop();
112
113 if (!GCCause::is_user_requested_gc(gc_cause) ||
114 UseAdaptiveSizePolicyWithSystemGC) {
115 double minor_pause_in_seconds = _minor_timer.seconds();
116 double minor_pause_in_ms = minor_pause_in_seconds * MILLIUNITS;
117
118 // Sample for performance counter
119 _avg_minor_pause->sample(minor_pause_in_seconds);
120
121 // Cost of collection (unit-less)
122 double collection_cost = 0.0;
123 if ((_latest_minor_mutator_interval_seconds > 0.0) &&
124 (minor_pause_in_seconds > 0.0)) {
125 double interval_in_seconds =
126 _latest_minor_mutator_interval_seconds + minor_pause_in_seconds;
127 collection_cost =
128 minor_pause_in_seconds / interval_in_seconds;
129 _avg_minor_gc_cost->sample(collection_cost);
130 // Sample for performance counter
131 _avg_minor_interval->sample(interval_in_seconds);
132 }
133
134 // The policy does not have enough data until at least some
135 // young collections have been done.
136 _young_gen_policy_is_ready =
137 (_avg_minor_gc_cost->count() >= AdaptiveSizePolicyReadyThreshold);
138
139 // Calculate variables used to estimate pause time vs. gen sizes
140 double eden_size_in_mbytes = ((double)_eden_size) / ((double)M);
141 update_minor_pause_young_estimator(minor_pause_in_ms);
142 update_minor_pause_old_estimator(minor_pause_in_ms);
143
144 log_trace(gc, ergo)("AdaptiveSizePolicy::minor_collection_end: minor gc cost: %f average: %f",
145 collection_cost, _avg_minor_gc_cost->average());
146 log_trace(gc, ergo)(" minor pause: %f minor period %f",
147 minor_pause_in_ms, _latest_minor_mutator_interval_seconds * MILLIUNITS);
148
149 // Calculate variable used to estimate collection cost vs. gen sizes
150 assert(collection_cost >= 0.0, "Expected to be non-negative");
151 _minor_collection_estimator->update(eden_size_in_mbytes, collection_cost);
152 }
153
154 // Interval times use this timer to measure the mutator time.
155 // Reset the timer after the GC pause.
156 _minor_timer.reset();
157 _minor_timer.start();
158 }
159
160 size_t AdaptiveSizePolicy::eden_increment(size_t cur_eden, uint percent_change) {
161 size_t eden_heap_delta;
162 eden_heap_delta = cur_eden / 100 * percent_change;
163 return eden_heap_delta;
164 }
165
166 size_t AdaptiveSizePolicy::eden_increment(size_t cur_eden) {
167 return eden_increment(cur_eden, YoungGenerationSizeIncrement);
168 }
169
170 size_t AdaptiveSizePolicy::eden_decrement(size_t cur_eden) {
171 size_t eden_heap_delta = eden_increment(cur_eden) /
172 AdaptiveSizeDecrementScaleFactor;
173 return eden_heap_delta;
174 }
175
176 size_t AdaptiveSizePolicy::promo_increment(size_t cur_promo, uint percent_change) {
177 size_t promo_heap_delta;
178 promo_heap_delta = cur_promo / 100 * percent_change;
179 return promo_heap_delta;
180 }
181
182 size_t AdaptiveSizePolicy::promo_increment(size_t cur_promo) {
183 return promo_increment(cur_promo, TenuredGenerationSizeIncrement);
184 }
185
186 size_t AdaptiveSizePolicy::promo_decrement(size_t cur_promo) {
187 size_t promo_heap_delta = promo_increment(cur_promo);
188 promo_heap_delta = promo_heap_delta / AdaptiveSizeDecrementScaleFactor;
189 return promo_heap_delta;
190 }
191
192 double AdaptiveSizePolicy::time_since_major_gc() const {
193 _major_timer.stop();
194 double result = _major_timer.seconds();
195 _major_timer.start();
196 return result;
197 }
198
199 // Linear decay of major gc cost
200 double AdaptiveSizePolicy::decaying_major_gc_cost() const {
201 double major_interval = major_gc_interval_average_for_decay();
202 double major_gc_cost_average = major_gc_cost();
203 double decayed_major_gc_cost = major_gc_cost_average;
204 if(time_since_major_gc() > 0.0) {
205 decayed_major_gc_cost = major_gc_cost() *
206 (((double) AdaptiveSizeMajorGCDecayTimeScale) * major_interval)
207 / time_since_major_gc();
208 }
209
210 // The decayed cost should always be smaller than the
211 // average cost but the vagaries of finite arithmetic could
212 // produce a larger value in decayed_major_gc_cost so protect
213 // against that.
214 return MIN2(major_gc_cost_average, decayed_major_gc_cost);
215 }
216
217 // Use a value of the major gc cost that has been decayed
218 // by the factor
219 //
220 // average-interval-between-major-gc * AdaptiveSizeMajorGCDecayTimeScale /
221 // time-since-last-major-gc
222 //
223 // if the average-interval-between-major-gc * AdaptiveSizeMajorGCDecayTimeScale
224 // is less than time-since-last-major-gc.
225 //
226 // In cases where there are initial major gc's that
227 // are of a relatively high cost but no later major
228 // gc's, the total gc cost can remain high because
229 // the major gc cost remains unchanged (since there are no major
230 // gc's). In such a situation the value of the unchanging
231 // major gc cost can keep the mutator throughput below
232 // the goal when in fact the major gc cost is becoming diminishingly
233 // small. Use the decaying gc cost only to decide whether to
234 // adjust for throughput. Using it also to determine the adjustment
235 // to be made for throughput also seems reasonable but there is
236 // no test case to use to decide if it is the right thing to do
237 // don't do it yet.
238
239 double AdaptiveSizePolicy::decaying_gc_cost() const {
240 double decayed_major_gc_cost = major_gc_cost();
241 double avg_major_interval = major_gc_interval_average_for_decay();
242 if (UseAdaptiveSizeDecayMajorGCCost &&
243 (AdaptiveSizeMajorGCDecayTimeScale > 0) &&
244 (avg_major_interval > 0.00)) {
245 double time_since_last_major_gc = time_since_major_gc();
246
247 // Decay the major gc cost?
248 if (time_since_last_major_gc >
249 ((double) AdaptiveSizeMajorGCDecayTimeScale) * avg_major_interval) {
250
251 // Decay using the time-since-last-major-gc
252 decayed_major_gc_cost = decaying_major_gc_cost();
253 log_trace(gc, ergo)("decaying_gc_cost: major interval average: %f time since last major gc: %f",
254 avg_major_interval, time_since_last_major_gc);
255 log_trace(gc, ergo)(" major gc cost: %f decayed major gc cost: %f",
256 major_gc_cost(), decayed_major_gc_cost);
257 }
258 }
259 double result = MIN2(1.0, decayed_major_gc_cost + minor_gc_cost());
260 return result;
261 }
262
263
264 void AdaptiveSizePolicy::clear_generation_free_space_flags() {
265 set_change_young_gen_for_min_pauses(0);
266 set_change_old_gen_for_maj_pauses(0);
267
268 set_change_old_gen_for_throughput(0);
269 set_change_young_gen_for_throughput(0);
270 set_decrease_for_footprint(0);
271 set_decide_at_full_gc(0);
272 }
273
274 class AdaptiveSizePolicyTimeOverheadTester: public GCOverheadTester {
275 double _gc_cost;
276
277 public:
278 AdaptiveSizePolicyTimeOverheadTester(double gc_cost) : _gc_cost(gc_cost) {}
279
280 bool is_exceeded() {
281 return _gc_cost > (GCTimeLimit / 100.0);
282 }
283 };
284
285 class AdaptiveSizePolicySpaceOverheadTester: public GCOverheadTester {
286 size_t _eden_live;
287 size_t _max_old_gen_size;
288 size_t _max_eden_size;
289 size_t _promo_size;
290 double _avg_eden_live;
291 double _avg_old_live;
292
293 public:
294 AdaptiveSizePolicySpaceOverheadTester(size_t eden_live,
295 size_t max_old_gen_size,
296 size_t max_eden_size,
297 size_t promo_size,
298 double avg_eden_live,
299 double avg_old_live) :
300 _eden_live(eden_live),
301 _max_old_gen_size(max_old_gen_size),
302 _max_eden_size(max_eden_size),
303 _promo_size(promo_size),
304 _avg_eden_live(avg_eden_live),
305 _avg_old_live(avg_old_live) {}
306
307 bool is_exceeded() {
308 // _max_eden_size is the upper limit on the size of eden based on
309 // the maximum size of the young generation and the sizes
310 // of the survivor space.
311 // The question being asked is whether the space being recovered by
312 // a collection is low.
313 // free_in_eden is the free space in eden after a collection and
314 // free_in_old_gen is the free space in the old generation after
315 // a collection.
316 //
317 // Use the minimum of the current value of the live in eden
318 // or the average of the live in eden.
319 // If the current value drops quickly, that should be taken
320 // into account (i.e., don't trigger if the amount of free
321 // space has suddenly jumped up). If the current is much
322 // higher than the average, use the average since it represents
323 // the longer term behavior.
324 const size_t live_in_eden =
325 MIN2(_eden_live, (size_t)_avg_eden_live);
326 const size_t free_in_eden = _max_eden_size > live_in_eden ?
327 _max_eden_size - live_in_eden : 0;
328 const size_t free_in_old_gen = (size_t)(_max_old_gen_size - _avg_old_live);
329 const size_t total_free_limit = free_in_old_gen + free_in_eden;
330 const size_t total_mem = _max_old_gen_size + _max_eden_size;
331 const double free_limit_ratio = GCHeapFreeLimit / 100.0;
332 const double mem_free_limit = total_mem * free_limit_ratio;
333 const double mem_free_old_limit = _max_old_gen_size * free_limit_ratio;
334 const double mem_free_eden_limit = _max_eden_size * free_limit_ratio;
335 size_t promo_limit = (size_t)(_max_old_gen_size - _avg_old_live);
336 // But don't force a promo size below the current promo size. Otherwise,
337 // the promo size will shrink for no good reason.
338 promo_limit = MAX2(promo_limit, _promo_size);
339
340 log_trace(gc, ergo)(
341 "AdaptiveSizePolicySpaceOverheadTester::is_exceeded:"
342 " promo_limit: " SIZE_FORMAT
343 " max_eden_size: " SIZE_FORMAT
344 " total_free_limit: " SIZE_FORMAT
345 " max_old_gen_size: " SIZE_FORMAT
346 " max_eden_size: " SIZE_FORMAT
347 " mem_free_limit: " SIZE_FORMAT,
348 promo_limit, _max_eden_size, total_free_limit,
349 _max_old_gen_size, _max_eden_size,
350 (size_t)mem_free_limit);
351
352 return free_in_old_gen < (size_t)mem_free_old_limit &&
353 free_in_eden < (size_t)mem_free_eden_limit;
354 }
355 };
356
357 void AdaptiveSizePolicy::check_gc_overhead_limit(
358 size_t eden_live,
359 size_t max_old_gen_size,
360 size_t max_eden_size,
361 bool is_full_gc,
362 GCCause::Cause gc_cause,
363 SoftRefPolicy* soft_ref_policy) {
364
365 AdaptiveSizePolicyTimeOverheadTester time_overhead(gc_cost());
366 AdaptiveSizePolicySpaceOverheadTester space_overhead(eden_live,
367 max_old_gen_size,
368 max_eden_size,
369 _promo_size,
370 avg_eden_live()->average(),
371 avg_old_live()->average());
372 _overhead_checker.check_gc_overhead_limit(&time_overhead,
373 &space_overhead,
374 is_full_gc,
375 gc_cause,
376 soft_ref_policy);
377 }
378 // Printing
379
380 bool AdaptiveSizePolicy::print() const {
381 assert(UseAdaptiveSizePolicy, "UseAdaptiveSizePolicy need to be enabled.");
382
383 if (!log_is_enabled(Debug, gc, ergo)) {
384 return false;
385 }
386
387 // Print goal for which action is needed.
388 char* action = NULL;
389 bool change_for_pause = false;
390 if ((change_old_gen_for_maj_pauses() ==
391 decrease_old_gen_for_maj_pauses_true) ||
392 (change_young_gen_for_min_pauses() ==
393 decrease_young_gen_for_min_pauses_true)) {
394 action = (char*) " *** pause time goal ***";
395 change_for_pause = true;
396 } else if ((change_old_gen_for_throughput() ==
397 increase_old_gen_for_throughput_true) ||
398 (change_young_gen_for_throughput() ==
399 increase_young_gen_for_througput_true)) {
400 action = (char*) " *** throughput goal ***";
401 } else if (decrease_for_footprint()) {
402 action = (char*) " *** reduced footprint ***";
403 } else {
404 // No actions were taken. This can legitimately be the
405 // situation if not enough data has been gathered to make
406 // decisions.
407 return false;
408 }
409
410 // Pauses
411 // Currently the size of the old gen is only adjusted to
412 // change the major pause times.
413 char* young_gen_action = NULL;
414 char* tenured_gen_action = NULL;
415
416 char* shrink_msg = (char*) "(attempted to shrink)";
417 char* grow_msg = (char*) "(attempted to grow)";
418 char* no_change_msg = (char*) "(no change)";
419 if (change_young_gen_for_min_pauses() ==
420 decrease_young_gen_for_min_pauses_true) {
421 young_gen_action = shrink_msg;
422 } else if (change_for_pause) {
423 young_gen_action = no_change_msg;
424 }
425
426 if (change_old_gen_for_maj_pauses() == decrease_old_gen_for_maj_pauses_true) {
427 tenured_gen_action = shrink_msg;
428 } else if (change_for_pause) {
429 tenured_gen_action = no_change_msg;
430 }
431
432 // Throughput
433 if (change_old_gen_for_throughput() == increase_old_gen_for_throughput_true) {
434 assert(change_young_gen_for_throughput() ==
435 increase_young_gen_for_througput_true,
436 "Both generations should be growing");
437 young_gen_action = grow_msg;
438 tenured_gen_action = grow_msg;
439 } else if (change_young_gen_for_throughput() ==
440 increase_young_gen_for_througput_true) {
441 // Only the young generation may grow at start up (before
442 // enough full collections have been done to grow the old generation).
443 young_gen_action = grow_msg;
444 tenured_gen_action = no_change_msg;
445 }
446
447 // Minimum footprint
448 if (decrease_for_footprint() != 0) {
449 young_gen_action = shrink_msg;
450 tenured_gen_action = shrink_msg;
451 }
452
453 log_debug(gc, ergo)("UseAdaptiveSizePolicy actions to meet %s", action);
454 log_debug(gc, ergo)(" GC overhead (%%)");
455 log_debug(gc, ergo)(" Young generation: %7.2f\t %s",
456 100.0 * avg_minor_gc_cost()->average(), young_gen_action);
457 log_debug(gc, ergo)(" Tenured generation: %7.2f\t %s",
458 100.0 * avg_major_gc_cost()->average(), tenured_gen_action);
459 return true;
460 }
461
462 void AdaptiveSizePolicy::print_tenuring_threshold( uint new_tenuring_threshold_arg) const {
463 // Tenuring threshold
464 if (decrement_tenuring_threshold_for_survivor_limit()) {
465 log_debug(gc, ergo)("Tenuring threshold: (attempted to decrease to avoid survivor space overflow) = %u", new_tenuring_threshold_arg);
466 } else if (decrement_tenuring_threshold_for_gc_cost()) {
467 log_debug(gc, ergo)("Tenuring threshold: (attempted to decrease to balance GC costs) = %u", new_tenuring_threshold_arg);
468 } else if (increment_tenuring_threshold_for_gc_cost()) {
469 log_debug(gc, ergo)("Tenuring threshold: (attempted to increase to balance GC costs) = %u", new_tenuring_threshold_arg);
470 } else {
471 assert(!tenuring_threshold_change(), "(no change was attempted)");
472 }
473 }