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 _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 // Note that the gc time limit test only works for the collections 282 // of the young gen + tenured gen and not for collections of the 283 // permanent gen. That is because the calculation of the space 284 // freed by the collection is the free space in the young gen + 285 // tenured gen. 286 return _gc_cost > (GCTimeLimit / 100.0); 287 } 288 }; 289 290 class AdaptiveSizePolicySpaceOverheadTester: public GCOverheadTester { 291 size_t _eden_live; 292 size_t _max_old_gen_size; 293 size_t _max_eden_size; 294 size_t _promo_size; 295 double _avg_eden_live; 296 double _avg_old_live; 297 298 public: 299 AdaptiveSizePolicySpaceOverheadTester(size_t eden_live, 300 size_t max_old_gen_size, 301 size_t max_eden_size, 302 size_t promo_size, 303 double avg_eden_live, 304 double avg_old_live) : 305 _eden_live(eden_live), 306 _max_old_gen_size(max_old_gen_size), 307 _max_eden_size(max_eden_size), 308 _promo_size(promo_size), 309 _avg_eden_live(avg_eden_live), 310 _avg_old_live(avg_old_live) {} 311 312 bool is_exceeded() { 313 // _max_eden_size is the upper limit on the size of eden based on 314 // the maximum size of the young generation and the sizes 315 // of the survivor space. 316 // The question being asked is whether the space being recovered by 317 // a collection is low. 318 // free_in_eden is the free space in eden after a collection and 319 // free_in_old_gen is the free space in the old generation after 320 // a collection. 321 // 322 // Use the minimum of the current value of the live in eden 323 // or the average of the live in eden. 324 // If the current value drops quickly, that should be taken 325 // into account (i.e., don't trigger if the amount of free 326 // space has suddenly jumped up). If the current is much 327 // higher than the average, use the average since it represents 328 // the longer term behavior. 329 const size_t live_in_eden = 330 MIN2(_eden_live, (size_t)_avg_eden_live); 331 const size_t free_in_eden = _max_eden_size > live_in_eden ? 332 _max_eden_size - live_in_eden : 0; 333 const size_t free_in_old_gen = (size_t)(_max_old_gen_size - _avg_old_live); 334 const size_t total_free_limit = free_in_old_gen + free_in_eden; 335 const size_t total_mem = _max_old_gen_size + _max_eden_size; 336 const double free_limit_ratio = GCHeapFreeLimit / 100.0; 337 const double mem_free_limit = total_mem * free_limit_ratio; 338 const double mem_free_old_limit = _max_old_gen_size * free_limit_ratio; 339 const double mem_free_eden_limit = _max_eden_size * free_limit_ratio; 340 size_t promo_limit = (size_t)(_max_old_gen_size - _avg_old_live); 341 // But don't force a promo size below the current promo size. Otherwise, 342 // the promo size will shrink for no good reason. 343 promo_limit = MAX2(promo_limit, _promo_size); 344 345 log_trace(gc, ergo)( 346 "AdaptiveSizePolicySpaceOverheadTester::is_exceeded:" 347 " promo_limit: " SIZE_FORMAT 348 " max_eden_size: " SIZE_FORMAT 349 " total_free_limit: " SIZE_FORMAT 350 " max_old_gen_size: " SIZE_FORMAT 351 " max_eden_size: " SIZE_FORMAT 352 " mem_free_limit: " SIZE_FORMAT, 353 promo_limit, _max_eden_size, total_free_limit, 354 _max_old_gen_size, _max_eden_size, 355 (size_t)mem_free_limit); 356 357 return free_in_old_gen < (size_t)mem_free_old_limit && 358 free_in_eden < (size_t)mem_free_eden_limit; 359 } 360 }; 361 362 void AdaptiveSizePolicy::check_gc_overhead_limit( 363 size_t eden_live, 364 size_t max_old_gen_size, 365 size_t max_eden_size, 366 bool is_full_gc, 367 GCCause::Cause gc_cause, 368 SoftRefPolicy* soft_ref_policy) { 369 370 AdaptiveSizePolicyTimeOverheadTester time_overhead(gc_cost()); 371 AdaptiveSizePolicySpaceOverheadTester space_overhead(eden_live, 372 max_old_gen_size, 373 max_eden_size, 374 _promo_size, 375 avg_eden_live()->average(), 376 avg_old_live()->average()); 377 _overhead_checker.check_gc_overhead_limit(&time_overhead, 378 &space_overhead, 379 is_full_gc, 380 gc_cause, 381 soft_ref_policy); 382 } 383 // Printing 384 385 bool AdaptiveSizePolicy::print() const { 386 assert(UseAdaptiveSizePolicy, "UseAdaptiveSizePolicy need to be enabled."); 387 388 if (!log_is_enabled(Debug, gc, ergo)) { 389 return false; 390 } 391 392 // Print goal for which action is needed. 393 char* action = NULL; 394 bool change_for_pause = false; 395 if ((change_old_gen_for_maj_pauses() == 396 decrease_old_gen_for_maj_pauses_true) || 397 (change_young_gen_for_min_pauses() == 398 decrease_young_gen_for_min_pauses_true)) { 399 action = (char*) " *** pause time goal ***"; 400 change_for_pause = true; 401 } else if ((change_old_gen_for_throughput() == 402 increase_old_gen_for_throughput_true) || 403 (change_young_gen_for_throughput() == 404 increase_young_gen_for_througput_true)) { 405 action = (char*) " *** throughput goal ***"; 406 } else if (decrease_for_footprint()) { 407 action = (char*) " *** reduced footprint ***"; 408 } else { 409 // No actions were taken. This can legitimately be the 410 // situation if not enough data has been gathered to make 411 // decisions. 412 return false; 413 } 414 415 // Pauses 416 // Currently the size of the old gen is only adjusted to 417 // change the major pause times. 418 char* young_gen_action = NULL; 419 char* tenured_gen_action = NULL; 420 421 char* shrink_msg = (char*) "(attempted to shrink)"; 422 char* grow_msg = (char*) "(attempted to grow)"; 423 char* no_change_msg = (char*) "(no change)"; 424 if (change_young_gen_for_min_pauses() == 425 decrease_young_gen_for_min_pauses_true) { 426 young_gen_action = shrink_msg; 427 } else if (change_for_pause) { 428 young_gen_action = no_change_msg; 429 } 430 431 if (change_old_gen_for_maj_pauses() == decrease_old_gen_for_maj_pauses_true) { 432 tenured_gen_action = shrink_msg; 433 } else if (change_for_pause) { 434 tenured_gen_action = no_change_msg; 435 } 436 437 // Throughput 438 if (change_old_gen_for_throughput() == increase_old_gen_for_throughput_true) { 439 assert(change_young_gen_for_throughput() == 440 increase_young_gen_for_througput_true, 441 "Both generations should be growing"); 442 young_gen_action = grow_msg; 443 tenured_gen_action = grow_msg; 444 } else if (change_young_gen_for_throughput() == 445 increase_young_gen_for_througput_true) { 446 // Only the young generation may grow at start up (before 447 // enough full collections have been done to grow the old generation). 448 young_gen_action = grow_msg; 449 tenured_gen_action = no_change_msg; 450 } 451 452 // Minimum footprint 453 if (decrease_for_footprint() != 0) { 454 young_gen_action = shrink_msg; 455 tenured_gen_action = shrink_msg; 456 } 457 458 log_debug(gc, ergo)("UseAdaptiveSizePolicy actions to meet %s", action); 459 log_debug(gc, ergo)(" GC overhead (%%)"); 460 log_debug(gc, ergo)(" Young generation: %7.2f\t %s", 461 100.0 * avg_minor_gc_cost()->average(), young_gen_action); 462 log_debug(gc, ergo)(" Tenured generation: %7.2f\t %s", 463 100.0 * avg_major_gc_cost()->average(), tenured_gen_action); 464 return true; 465 } 466 467 void AdaptiveSizePolicy::print_tenuring_threshold( uint new_tenuring_threshold_arg) const { 468 // Tenuring threshold 469 if (decrement_tenuring_threshold_for_survivor_limit()) { 470 log_debug(gc, ergo)("Tenuring threshold: (attempted to decrease to avoid survivor space overflow) = %u", new_tenuring_threshold_arg); 471 } else if (decrement_tenuring_threshold_for_gc_cost()) { 472 log_debug(gc, ergo)("Tenuring threshold: (attempted to decrease to balance GC costs) = %u", new_tenuring_threshold_arg); 473 } else if (increment_tenuring_threshold_for_gc_cost()) { 474 log_debug(gc, ergo)("Tenuring threshold: (attempted to increase to balance GC costs) = %u", new_tenuring_threshold_arg); 475 } else { 476 assert(!tenuring_threshold_change(), "(no change was attempted)"); 477 } 478 }